Solid Power (SLDP) 10-K 28 Feb 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Feb. 26, 2024	Jun. 30, 2023
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2023
Entity File Number	001-40284
Entity Registrant Name	SOLID POWER, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	86-1888095
Entity Address, Address Line One	486 S. Pierce Ave., Suite E
Entity Address, City or Town	Louisville
Entity Address State Or Province	CO
Entity Address, Postal Zip Code	80027
City Area Code	303
Local Phone Number	219-0720
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 421.4
Entity Common Stock, Shares Outstanding		181,091,826
Entity Central Index Key	0001844862
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false
ICFR Auditor Attestation Flag	false
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	Denver, Colorado
Common stock
Title of 12(b) Security	Common stock, par value $0.0001 per share
Trading Symbol	SLDP
Security Exchange Name	NASDAQ
Warrants, each whole warrant exercisable for one share of common stock at an exercise price of $11.50
Title of 12(b) Security	Warrants, each whole warrant exercisablefor one share of common stock at an
Trading Symbol	SLDPW
Security Exchange Name	NASDAQ

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current Assets
Cash and cash equivalents	$ 34,537	$ 50,123
Marketable securities	141,505	272,957
Contract receivables	1,553	1,521
Contract receivables from related parties		319
Prepaid expenses and other current assets	5,523	2,888
Total current assets	183,118	327,808
Property, Plant and Equipment, net	99,156	82,761
Right-Of-Use Operating Lease Assets, net	7,154	7,725
Right-Of-Use Finance Lease Assets, net	1,088	922
Other Assets	1,060	1,148
Long-term Investments	239,566	172,974
Intangible Assets, net	1,650	1,108
Total assets	532,792	594,446
Current Liabilities
Accounts payable and other accrued liabilities	6,455	11,326
Current portion of long-term debt		7
Deferred revenue	1	50
Deferred revenue from related parties	828	4,000
Accrued compensation	7,590	4,528
Operating lease liabilities, short-term	626	549
Finance lease liabilities, short-term	379	273
Total current liabilities	15,879	20,733
Warrant Liabilities	4,227	9,117
Operating Lease Liabilities, Long-Term	7,996	8,622
Finance Lease Liabilities, Long-Term	552	602
Other Long-Term Liabilities	803
Total liabilities	29,457	39,074
Stockholders' Equity
Common Stock, $0.0001 par value; 2,000,000,000 shares authorized; 179,010,884 and 176,007,184 shares issued and outstanding as of December 31, 2023 and December 31, 2022, respectively	18	18
Additional paid-in capital	588,515	577,603
Accumulated deficit	(84,639)	(19,090)
Accumulated other comprehensive loss	(559)	(3,159)
Total stockholders' equity	503,335	555,372
Total liabilities and stockholders' equity	$ 532,792	$ 594,446

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Consolidated Balance Sheets
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	2,000,000,000	2,000,000,000
Common stock, shares issued	179,010,884	176,007,184
Common stock, shares outstanding	179,010,884	176,007,184

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Consolidated Statements of Operations
Revenue	$ 17,410	$ 11,789
Operating Expenses
Direct costs	27,731	9,592
Research and development	54,749	38,592
Selling, general and administrative	25,550	22,724
Total operating expenses	108,030	70,908
Operating Loss	(90,620)	(59,119)
Nonoperating Income and Expense
Interest income	20,265	8,476
Change in fair value of warrant liabilities	4,890	40,903
Interest expense	(84)	(42)
Total nonoperating income and expense	25,071	49,337
Pretax Loss	(65,549)	(9,782)
Income tax benefit	2	(227)
Net Loss Attributable to Common Stockholders	(65,549)	(9,555)
Other Comprehensive Income (Loss)	2,600	(3,159)
Comprehensive Loss Attributable to Common Stockholders	$ (62,949)	$ (12,714)
Basic loss per share	$ (0.37)	$ (0.05)
Diluted loss per share	$ (0.37)	$ (0.05)
Weighted average shares outstanding - Basic	178,006,919	174,374,386
Weighted average shares outstanding - Diluted	178,006,919	174,374,386

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated OCI	Total
Balance at the beginning at Dec. 31, 2021	$ 17	$ 568,183	$ (9,535)		$ 558,665
Balance at the beginning (in shares) at Dec. 31, 2021	167,557,988
Changes in stockholder's equity
Net Income (Loss)			(9,555)		(9,555)
Withholding of employee taxes related to stock-based compensation		(58)			(58)
Shares of common stock issued for vested RSUs (in shares)	20,672
Stock options exercised	$ 1	818			819
Stock options exercised (in shares)	8,428,524
Transaction fees		(12)			(12)
Unrealized gain(loss) on marketable securities				$ (3,159)	(3,159)
Stock-based compensation expense		8,672			8,672
Balance at the end at Dec. 31, 2022	$ 18	577,603	(19,090)	(3,159)	555,372
Balance at the end (in shares) at Dec. 31, 2022	176,007,184
Changes in stockholder's equity
Net Income (Loss)			(65,549)		(65,549)
Withholding of employee taxes related to stock-based compensation		(112)			(112)
Shares of common stock issued under ESPP		434			434
Shares of common stock issued under ESPP (in shares)	287,224
Shares of common stock issued for vested RSUs (in shares)	226,201
Stock options exercised		220			220
Stock options exercised (in shares)	2,490,275
Unrealized gain(loss) on marketable securities				2,600	2,600
Stock-based compensation expense		10,370			10,370
Balance at the end at Dec. 31, 2023	$ 18	$ 588,515	$ (84,639)	$ (559)	$ 503,335
Balance at the end (in shares) at Dec. 31, 2023	179,010,884

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash Flows from Operating Activities
Net Income (Loss)	$ (65,549)	$ (9,555)
Adjustments to reconcile net loss to net cash and cash equivalents from operating activities:
Depreciation and amortization	11,962	5,176
Amortization of right-of-use assets	768	745
Loss on sale of property, plant and equipment		11
Stock-based compensation expense	10,370	8,672
Deferred taxes		(227)
Change in fair value of warrant liabilities	(4,890)	(40,903)
Accretion of discounts on other long-term liabilities	174
Amortization of premiums and accretion of discounts on marketable securities	(10,975)	(3,118)
Change in operating assets and liabilities that provided (used) cash and cash equivalents:
Contract receivables	(31)	(692)
Contract receivables from related parties	319	(319)
Prepaid expenses and other assets	(1,510)	2,687
Accounts payable and other accrued liabilities	1,814	(1,108)
Deferred revenue	(50)	(450)
Deferred revenue from related parties	(3,172)	4,000
Accrued compensation	3,058	1,658
Operating and Finance lease liabilities, short-term	(549)	(401)
Net cash and cash equivalents used in operating activities	(58,261)	(33,824)
Cash Flows from Investing Activities
Purchases of property, plant and equipment	(34,512)	(58,296)
Purchases of marketable securities and long-term investments	(327,591)	(561,565)
Proceeds from sales of marketable securities	405,161	190,374
Purchases of intangible assets	(556)	(498)
Net cash and cash equivalents provided by (used in) investing activities	42,502	(429,985)
Cash Flows from Financing Activities
Payments of debt	(7)	(121)
Proceeds from exercise of stock options	220	818
Proceeds from issuance of shares of common stock under ESPP	434
Cash paid for withholding of employee taxes related to stock-based compensation	(112)	(58)
Payments on finance lease liabilities	(362)	(142)
Transaction costs		(12)
Net cash and cash equivalents provided by financing activities	173	485
Net decrease in cash and cash equivalents	(15,586)	(463,324)
Cash and cash equivalents at beginning of period	50,123	513,447
Cash and cash equivalents at end of period	34,537	50,123
Supplemental information
Cash paid for interest	84	42
Accrued capital expenditures	$ 814	$ 7,561

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2023
Nature of Business
Nature of Business	Note 1 – Nature of Business Solid Power is developing solid-state battery technology for the EV and other markets. The Company’s planned business model is to sell its electrolyte and to license its cell designs and manufacturing processes. For the years ended December 31, 2023 and 2022, the Company has not derived material revenue from its principal business activities.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Significant Accounting Policies
Significant Accounting Policies	Note 2 – Significant Accounting Policies Basis of Presentation and Principles of Consolidation The Consolidated Financial Statements of the Company have been prepared on the basis of GAAP. The preparation of Consolidated Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect amounts reported in the Consolidated Financial Statements. Actual results could differ from those estimates. All amounts presented in the footnotes are in thousands, except share and per share amounts. The Consolidated Financial Statements include accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The accompanying Consolidated Financial Statements have been prepared assuming that the Company will continue as a going concern. Segment Reporting The Company’s CODM is its Chief Executive Officer. The Company has determined that it operates in one operating segment and one reportable segment, as the CODM reviews financial information presented as a single entity for purposes of making operating decisions, allocating resources, and evaluating financial performance. Use of Estimates The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and contingencies at the date of the financial statements as well as reported amounts of revenues and expenses during the reporting periods. Estimates made by the Company include, but are not limited to, those related to the valuation of stock warrants, and useful lives of long-term assets, among others. The Company bases these estimates on historical experience and other assumptions that it believes are reasonable under the circumstances. Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. As of December 31, 2023 and periodically throughout the year, the Company’s cash accounts exceeded federally insured limits. Marketable Securities The Company’s investment policy is consistent with the definition of available-for-sale securities. The Company does not buy and hold securities principally for the purpose of selling them in the near future. The Company’s policy is focused on the preservation of capital, liquidity, and return. From time to time, the Company may sell certain securities, but the objectives are not to generate profits on short-term differences in price. These securities are carried at estimated fair value with unrealized holding gains and losses included in other comprehensive income (loss) in stockholders’ deficit until realized. Gains and losses on marketable security transactions are reported on the specific-identification method. Dividend and interest income are recognized when earned. Contract Receivables Contract receivables consist of amounts due from government entities and commercial contractors. Management considers all contract receivables collectible, and therefore, an allowance for doubtful accounts has not been recorded as of December 31, 2023 and 2022. Included within contract receivables are amounts for work performed but not billed as of December 31, 2023 and 2022, shown below. ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Contract receivables not billed ​ $ 302 ​ $ 1,083 ​ Credit Risk and Major Customers Financial instruments that potentially subject the Company to credit risk consist principally of cash and cash equivalents, marketable securities, and long-term investments. The Company seeks to mitigate its credit risk with respect to cash and cash equivalents, marketable securities, and long-term investments by making deposits with large, reputable financial institutions and investing in high credit rated instruments. The Company grants credit in the normal course of business to government entities and commercial contractors in the United States. The Company periodically monitors the financial condition of its customers to reduce credit risk, but generally does not require collateral to support contract receivables. ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Years Ended December 31, ​ 2023 2022 Revenue Concentration ​ ​ ​ Number of Customers ​ 2 4 Related Total Revenue Percentage 89 % 82 % Contract Receivable Concentration Number of Customers 3 2 Related Contract Receivables Percentage 97 % 40 % ​ Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist primarily of security deposits, prepaid insurance, and other minor miscellaneous expenses paid in advance. Property and Equipment Property and equipment are recorded at cost. The Company capitalizes property and equipment with useful lives exceeding one year. Assets are depreciated over their estimated useful lives. The straight-line method is used for computing depreciation. Depreciation expenses are recorded within Direct costs and Research and development line items in the Consolidated Statements of Operations. Cost of maintenance and repairs are charged to expense when incurred. Construction in progress related to specialized equipment will be reclassified as Property and equipment and depreciated, once placed in service. ​ ​ ​ ​ ​ Depreciable Life - Years Commercial production equipment ​ 5 years Laboratory equipment ​ 5 years Furniture and Computer Equipment 3-7 years Leasehold improvements Lesser of asset life or lease term ​ Long-Term Investments The Company considers all investments with an original maturity of twelve months or more when purchased to be long-term investments. Intangible Assets Intangible assets consist of licenses and costs incurred for pending patents and trademarks. Licenses consist of rights to use patents and are amortized over their estimated useful life of three Deferred Rent Prior to the adoption of ASU No. 2016-02, Leases (Topic 842) on January 1, 2022, the Company had entered into operating lease agreements for each of its two facilities, each of which contain provisions for future rent increases or periods in which rent payments are reduced. The Company records monthly rent expense equal to the total of the payments due over the lease term, divided by the number of months of the lease term. The difference between rent expense recorded and the amount paid is credited or charged to deferred rent, which is reflected in Other Long-term Liabilities in the accompanying Consolidated Balance Sheets. Deferred rent also includes the unamortized portion of landlord-financed tenant improvement allowances, which are amortized on a straight-line basis over the lease term as a reduction in rent expense. Leases The Company accounts for its leases under ASU No. 2016-02, Leases (Topic 842). Under this guidance, the Company classifies contracts meeting the definition of a lease as operating or financing leases, and leases are recorded on the condensed consolidated balance sheet as both a right-of-use asset and lease liability, calculated by discounting fixed lease payments over the lease term at the rate implicit in the lease or the Company’s incremental borrowing rate. Lease liabilities are increased by interest and reduced by payments each period, and the right-of-use asset is amortized over the lease term. For operating leases, interest on the lease liability and the amortization of the right-of-use asset result in straight-line rent expense over the lease term. For finance leases, interest on the lease liability and the amortization of the right-of-use asset results in front-loaded expense over the lease term. Variable lease expenses, including common maintenance fees, insurance and property tax, are recorded when incurred. In calculating the right-of-use asset and lease liability, the Company elects to combine lease and non-lease components for all classes of assets. The Company excludes short-term leases having initial terms of 12 months or less as an accounting policy election, and instead recognizes rent expense on a straight-line basis over the lease term. Stock-based Compensation The Company recognizes expenses for employee services received in exchange for stock-based compensation based on the grant date fair value of the awards. The determination of the estimated fair value of stock-based payment awards on the date of grant is calculated using the Black-Scholes option-pricing model and is affected by the Company’s stock price, as well as assumptions regarding risk-free rate, dividend yield, and the historical volatility of comparable entities. Stock-based compensation is recorded as an expense only for those awards that are expected to vest. Compensation cost is recognized on a straight-line basis over the requisite vesting service period and is allocated ratably within Operating Expenses in the Consolidated Statements of Operations. Revenue The Company records the elements of its JDAs in accordance with ASC Topic 808, Collaborative Arrangements. Accordingly, the elements of the JDAs that represent activities in which both parties are active participants and are exposed to the significant risks and rewards that are dependent on the commercial success of the activities are recorded as collaborative arrangements. The Company considers the guidance in ASC 606-10-15, Revenue from Contracts with Customers – Scope and Scope Exceptions, in determining the appropriate treatment for the transactions between the Company and its partners or third parties. Generally, the classification of transactions under the JDAs is determined based on the nature and contractual terms of the arrangement along with the nature of the operations of the participants. The Company recognizes collaborative revenue from cost contracts on the basis of costs incurred during the period and for cost plus fixed-fee contracts on the basis of costs incurred during the period plus the fee earned. Contract costs include all direct labor, subcontract, material, and indirect costs related to the contract performance that are allowable under contract provisions. Deferred revenue represents billings in advance of revenue recognized. ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Deferred revenue ​ $ 1 ​ $ 50 Deferred revenue from related parties ​ $ 828 ​ $ 4,000 ​ Warrant Liabilities The Company accounts for warrants as liability-classified instruments based on an assessment of the warrant’s specific terms and applicable authoritative guidance in ASC 480 and ASC 815. Warrants recorded as liabilities are recorded at their fair value, within Warrant Liabilities on the Consolidated Balance Sheets and are remeasured on each reporting date with changes recorded in Change in fair value of warrant liabilities on the Company’s Consolidated Statements of Operations. Fair Value Measurements The Company applies fair value accounting for selected financial assets and liabilities measured on a recurring and nonrecurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. The accounting guidance ASC Topic 820 Fair Value Measurement established a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, used to determine the fair value of its financial instruments. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Level 1 – inputs include quoted market prices in an active market for identical assets or liabilities. Level 2 – inputs are market data, other than Level 1, that are observable either directly or indirectly. Level 2 inputs include quoted market prices for similar assets or liabilities, quoted market prices in an inactive market, and other observable information that can be corroborated by market data. Level 3 – inputs are unobservable and corroborated by little or no market data. Research and Development Our research and development activities focus on making improvements to our electrolyte and cell technology with the ultimate goal of commercializing technology that outperforms conventional lithium-ion. ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Research and development expenditures ​ $ 54,749 ​ $ 38,592 ​ Income Taxes The Company recognizes deferred tax liabilities and assets for the expected future tax consequences of events that have been included in the Consolidated Financial Statements or tax returns. Deferred tax liabilities and assets are determined based on the differences between the Consolidated Financial Statements and tax basis of assets and liabilities using the enacted tax rates in effect for the year in which the differences are expected to reverse. The measurement of deferred tax assets is reduced, if necessary, by the amount of any uncertain tax positions or tax benefits that are not expected to be realized based on available evidence. The Company records deferred tax assets and associated valuation allowances, when appropriate, to reflect amounts more likely than not to be realized based upon Company analysis. The Company’s temporary differences result primarily from capitalization of certain qualifying research and development expenses, accruals and reserves, depreciation of property and equipment, stock compensation expense, capitalization of operating or financing leases, and net operating loss carryovers. The Company accounts for any uncertainty in income taxes by recognizing the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The Company measures the tax benefits recognized in the Consolidated Financial Statements from such a position based on the largest benefit that has a greater than 50 percent likelihood of being realized upon ultimate resolution. Interest and penalties associated with tax positions are recorded in the period assessed as General and administrative on the Consolidated Statement of Operations. No interest or penalties have been assessed during the years ended December 31, 2023 and 2022. Net Loss per Share of Common Stock Basic net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted loss per share adjusts basic loss per share for the potentially dilutive impact of stock options and warrants. The Company reported a net loss in 2023 and 2022. As such, all potentially dilutive securities, including options and warrants, are antidilutive and, accordingly, basic net loss per share equals diluted loss per share. Recent Accounting Pronouncements Income taxes In December 2023, the FASB issued ASU No. 2023-09 Income Taxes (Topic 740) Improvements to Income Tax Disclosures. ASU 2023-09 requires companies to disclose, on an annual basis, specific categories in the effective tax rate reconciliation and provide additional information for reconciling items that meet a quantitative threshold. In addition, ASU 2023-09 requires companies to disclose additional information about income taxes paid. ASU 2023-09 will be effective for annual periods beginning January 1, 2025 and will be applied on a prospective basis with the option to apply the standard retrospectively. We are evaluating the disclosure impact of ASU 2023-09. Segment Reporting In November 2023, the FASB issued ASU No. 2023-07 Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. Among other new disclosure requirements, ASC 2023-07 requires companies to disclose significant segment expenses that are regularly provided to the CODM. ASU 2023-07 will be effective for annual periods beginning on January 1, 2024 and interim periods beginning on January 1, 2025. ASU 2023-07 must be applied retrospectively to all prior periods presented in the financial statements. We are evaluating the disclosure impact of ASU 2023-07.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment
Property, Plant and Equipment	Note 3 – Property, Plant and Equipment Property, plant and equipment at December 31 are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Commercial production equipment ​ $ 36,086 ​ $ 21,595 Laboratory equipment ​ ​ 9,910 ​ ​ 3,278 Leasehold improvements ​ 59,109 ​ 27,996 Furniture and computer equipment ​ 3,915 ​ 1,482 Construction in progress ​ 13,650 ​ 40,036 Total cost ​ 122,670 ​ 94,387 Accumulated depreciation ​ (23,514) ​ (11,626) Net property and equipment ​ $ 99,156 ​ $ 82,761 ​ Depreciation expenses for dedicated laboratory equipment and commercial production equipment are charged to research and development; other depreciation expenses are included in the Company’s overhead and are allocated across operating expenses on the accompanying Consolidated Statements of Operations based on Company personnel costs incurred. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2023 2022 Depreciation expense ​ $ 11,947 ​ $ 5,167 ​ ​ In 2023, the Company expanded its electrolyte production to produce larger quantities of electrolyte material required to feed cell-production lines and continue research and development efforts. The Company began producing electrolyte from this facility in 2023. ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Construction in progress ​ ​ SP1 – 2 nd ​ $ 773 ​ $ 2,010 SP1 – Other capital projects ​ 1,525 ​ 2,206 SP2 – Increased scale electrolyte production ​ 11,352 ​ 35,820 ​

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2023
Intangible Assets
Intangible Assets	Note 4 – Intangible Assets Intangible assets of the Company at December 31 are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 ​ ​ Gross Carrying ​ Accumulated ​ Gross Carrying ​ Accumulated ​ ​ Amount Amortization Amount Amortization Intangible assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Licenses ​ $ 149 ​ $ (61) ​ $ 149 ​ $ (51) Patents ​ ​ 92 ​ ​ (5) ​ ​ — ​ ​ — Patents pending ​ ​ 1,444 ​ — ​ 984 ​ — Trademarks ​ ​ 13 ​ ​ — ​ ​ 9 ​ ​ — Trademarks pending ​ ​ 18 ​ — ​ 17 ​ — Total amortized intangible assets ​ $ 1,716 ​ $ (66) ​ $ 1,159 ​ $ (51) ​ Amortization expense for intangible assets at December 31 are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Amortization expense ​ $ 15 ​ $ 9 ​ ​ Useful lives of intangible assets range from three

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2023
Fair Value Measurements
Fair Value Measurements	Note 5 – Fair Value Measurements The Company considers all highly liquid instruments with original maturities of less than 90 days to be cash equivalents. As of December 31, 2023, there were no long-term marketable securities. The carrying amounts of certain financial instruments, such as cash equivalents, short-term investments, accounts receivable, accounts payable, and accrued liabilities, approximate fair value due to their relatively short maturities. Assets and Liabilities Measured and Recorded at Fair Value on a Recurring Basis At December 31, the Company’s financial assets and liabilities measured and recorded at fair value on a recurring basis were classified within the fair value hierarchy as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ Level 1 Level 2 Level 3 Total Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commercial Paper ​ $ 84,909 ​ $ — ​ $ — ​ $ 84,909 Corporate Bonds ​ $ 239,473 ​ $ — ​ $ — ​ $ 239,473 Government Bonds ​ $ 56,689 ​ $ — ​ $ — ​ $ 56,689 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Public Warrants ​ $ 2,505 ​ $ — ​ $ — ​ $ 2,505 Private Placement Warrants ​ $ — ​ $ 1,722 ​ $ — ​ $ 1,722 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ Level 1 Level 2 Level 3 Total Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commercial Paper ​ $ 165,179 ​ $ — ​ $ — ​ $ 165,179 Corporate Bonds ​ $ 227,957 ​ $ — ​ $ — ​ $ 227,957 Government Bonds ​ $ 42,865 ​ $ — ​ $ — ​ $ 42,865 U.S. Treasuries ​ 9,930 ​ ​ — ​ ​ — ​ 9,930 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Public Warrants ​ $ 4,900 ​ $ — ​ $ — ​ $ 4,900 Private Placement Warrants ​ $ — ​ $ 4,217 ​ $ — ​ $ 4,217 ​ The change in fair value of the Company’s marketable securities is included in other comprehensive income (loss). There were no transfers in and out of Level 3 fair value hierarchy during the years ended December 31, 2023 and 2022. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 2022 Marketable securities and long-term investments purchased ​ $ 327,591 ​ $ 561,565 ​ Fair Value of Warrants The fair value of the Private Placement Warrants have been estimated using a Black-Scholes model as of December 31, 2023 and 2022 Consolidated Balance Sheet dates. The estimated fair value of the Private Placement Warrants is determined using Level 2 directly or indirectly observable inputs. Inherent in a Black-Scholes model are assumptions related to expected stock-price volatility, expected life, risk-free interest rate, and dividend yield. Material increases (or decreases) in any of those inputs may result in a significantly higher (or lower) fair value measurement. The Company estimates the volatility of its Private Placement Warrants based on implied volatility from the Company’s Public Warrants and from historical volatility of select peer companies’ common stock that matches the expected remaining life of the Warrants. The risk-free interest rate is based on the U.S. Treasury zero-coupon yield curve for a maturity similar to the expected remaining life of the Warrants. The dividend yield is based on the historical rate, which the Company anticipates remaining at zero. The fair value of the Public Warrants has been measured based on the quoted price of such warrants on the Nasdaq Stock Market, a Level 1 input. The following table provides quantitative information regarding Level 2 inputs used in the recurring valuation of the Private Placement Warrants as of their measurement dates: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Exercise price ​ $ 11.50 ​ $ 11.50 ​ Stock price ​ $ 1.45 ​ $ 2.54 ​ Volatility ​ 95.0 % 71.3 % Term (years) ​ 2.94 ​ 3.94 ​ Risk-free rate ​ 3.94 % 4.03 % ​ The following table provides a reconciliation of the Public Warrants measured at fair value using Level 1 inputs and Private Placement Warrants measured at fair value using Level 2 inputs: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Public Warrants ​ Private Placement Warrants ​ Level 1 Fair Value Level 2 Fair Value December 31, 2022 ​ $ 0.42 ​ $ 0.55 Change in fair value ​ $ (0.23) ​ $ (0.27) December 31, 2023 ​ $ 0.19 ​ $ 0.28 ​ ​ The following table provides a reconciliation of the change in fair value for the Public and Private Placement Warrants at December 31. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Twelve Months Change in ​ ​ Warrant Class Level Warrants December 31, 2022 Fair Value December 31, 2023 Public Warrants 1 13,182,501 ​ $ 4,900 ​ $ (2,395) ​ $ 2,505 Private Placement Warrants 2 6,150,802 ​ $ 4,217 ​ $ (2,495) ​ $ 1,722 Total 19,333,303 ​ $ 9,117 ​ $ (4,890) ​ $ 4,227 ​

Warrant Liabilities

Warrant Liabilities	12 Months Ended
	Dec. 31, 2023
Warrant Liabilities.
Warrant Liabilities	Note 6 –Warrant Liabilities ​ The table below provides a summary of the outstanding Public and Private Placement Warrants at December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Public Warrants ​ ​ 13,182,501 ​ ​ 11,666,636 Private Placement Warrants ​ ​ 6,150,802 ​ ​ 7,666,667 ​ Each whole Warrant entitles the holder thereof to purchase one share of common stock at a price of $11.50 per share, subject to customary adjustments. Only whole Warrants are exercisable. The Warrants became exercisable on January 7, 2022 and will expire on December 8, 2026. Redemption of Public Warrants when the price per share of common stock equals or exceeds $18.00 The Company may redeem all of the outstanding Public Warrants: ● in whole and not in part; ● upon at least 30 days ’ prior written notice; ● at a price of $0.01 per Public Warrant; and ● if the last sale price of the Company’s Common Stock equals or exceeds $18.00 per share, subject to customary adjustments, for any 20 trading days within a 30 -trading day period ending on the third trading day prior to the date on which notice of the redemption is given. Redemption of Public Warrants when the price per share of common stock equals or exceeds $10.00 The Company may redeem all of the outstanding Public Warrants: ● in whole and not in part; ● upon at least 30 days ’ prior written notice; ● at a price of $0.10 per Public Warrant, provided that holders will be able to exercise their Warrants on a cashless basis prior to redemption and receive a number of shares of the Company’s common stock determined in part by the redemption date and the “fair market value” of the common stock; and ● if the last sale price of the Company’s common stock equals or exceeds $10.00 per share, subject to customary adjustments, on the trading day prior to the date on which notice of redemption is given. The “fair market value” of the Company’s common stock means the average reported last sale price of the Company’s common stock for the ten None of the Private Placement Warrants are redeemable by the Company so long as they are held by the initial purchasers of the Private Placement Warrants or their permitted transferees. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2023 2022 Fair value of warrant liabilities ​ $ 4,227 ​ $ 9,117 ​ The table below provides the Company’s recognized gain(loss) recognized in connection with the changes in fair value of warrant liabilities at December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2023 2022 Gain recognized associated with warrant liabilities ​ $ 4,890 ​ $ 40,903 ​

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2023
Stockholders' Equity
Stockholders' Equity	Note 7 – Stockholders’ Equity Common Stock Stock options exercised for common stock, stock issued under the ESPP, and shares of common stock issued upon vesting of RSUs for the years ended December 31, 2023 and 2022 are summarized in the table below: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2023 2022 ​ Stock options exercised ​ 2,490,275 ​ 8,428,524 ​ Shares of common stock issued under ESPP ​ 287,224 ​ — ​ Shares of common stock issued for vested RSUs ​ 226,201 ​ 20,672 ​ ​ ​ ​ ​ The table below presents the cash received associated with common stock related activities at December 31. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 2022 Cash received from stock options exercised ​ $ 220 ​ $ 818 Cash received from shares of common stock issued under ESPP ​ ​ 434 ​ ​ — ​

Stock Based Compensation

Stock Based Compensation	12 Months Ended
	Dec. 31, 2023
Stock Based Compensation
Stock Based Compensation	Note 8 – Stock-Based Compensation 2014 Plan and 2021 Plan Options granted under the 2014 Plan had a ten-year term and vest as to 1/4 balance Options granted under the 2021 Plan during 2022 have a ten-year term and vest as to 1/4 1/4 Effective April 1, 2022, the Company began granting RSUs in accordance with the terms of the 2021 Plan. The grant date fair value of RSUs awarded are determined based on the Company’s closing common share price on the NASDAQ on the trading day preceding the grant date. RSU awards for employees granted during 2022 generally vest 25% per year commencing on the first anniversary of the grant date. RSU awards for employees granted during 2023 generally vest 25% on the first anniversary of the grant date then 6.25% per quarter thereafter. RSU awards upon initial service as a director vest in 12 equal quarterly installments. For initial service grants, vested RSUs are settled in common stock upon the earlier of the director no longer serving on the board of directors or the date the RSU has fully vested. Annual RSU awards to directors generally fully vest on the one-year anniversary of the grant date. Upon vesting, granted RSUs entitle the grantee to receive one share of common stock of the Company at no additional cost. Holders of unvested RSUs do not have voting or dividend rights. At December 31, 2023 and 2022, the Company had 24,264,016 and 24,766,176 shares of common stock underlying stock options outstanding under the 2014 Plan, respectively. No additional grants under the 2014 Plan are permitted. Beginning on January 1, 2022, the number of shares of common stock available for issuance under the 2021 Plan shall increase by an amount equal to the lesser of (i) 18,900,000 shares of common stock, (ii) five percent (5%) of the total number of shares of common stock outstanding on the last day of the immediately preceding fiscal year, or (iii) a number of shares of common stock determined by the administrator no later than the last day of the immediately preceding fiscal year. On January 1, 2022, the number of shares of common stock available for issuance under the 2021 Plan increased by 8,377,899 shares of common stock. As of December 31, 2023, the 2021 Plan permitted the Company to grant up to 21,711,885 shares of common stock to its employees, directors, and consultants, as designated by the board of directors. As of December 31, 2023, the Company had 22,048,584 shares of common stock underlying options awards and RSU awards outstanding under the 2021Plan, respectively. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 2022 Option awards granted under 2021 Plan ​ ​ 5,176,889 ​ ​ 1,730,564 RSU awards granted under 2021 Plan ​ ​ 4,663,079 ​ ​ 1,292,429 ​ Compensation Expense for Stock-Based Compensation The fair value of stock options and RSUs issued to employees and directors is recognized as compensation expense over the period of service that generally coincides with the vesting period of the award. When calculating the amount of annual compensation expense, the Company has elected not to estimate forfeitures and instead accounts for forfeitures as they occur. For the years ended December 31, 2023 and 2022, the Company recognized compensation costs totaling: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2023 2022 Equity-based compensation costs related to RSUs ​ $ 3,427 ​ $ 1,567 Equity-based compensation costs related to stock options ​ 6,774 ​ 7,076 Equity-based compensation costs related to ESPP ​ ​ 169 ​ ​ 29 Total equity-based compensation costs ​ $ 10,370 ​ $ 8,672 Unrecognized future compensation cost as of: ​ ​ 23,922 ​ ​ 25,531 ​ The fair value of stock options and other equity-based compensation issued to employees is recognized as compensation expense over the period of service that generally coincides with the vesting period of the award. The Company allocated compensation ratably across Operating Expenses within the following financial statement lines: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2023 2022 Direct Costs ​ $ 3,751 ​ $ 1,580 Research and Development ​ ​ 4,826 ​ ​ 4,474 Selling, general and administrative ​ ​ 1,793 ​ ​ 2,618 Total equity-based compensation cost ​ $ 10,370 ​ $ 8,672 ​ Stock Options The fair value for purposes of determining the compensation cost of each option award is estimated on the date of grant using a Black-Scholes option valuation model that uses the weighted-average assumptions noted in the following table. Expected volatilities are based on historical volatility of comparable companies. The Company uses historical data to estimate option exercise and employee termination within the valuation model. The risk-free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant. The fair value of each option grant during the years ended December 31, 2023 and 2022 was estimated on the grant date using the Black-Scholes option pricing model with the following weighted-average assumptions used: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Approximate risk‑free rate ​ ​ 4.17 % ​ 2.84 % Volatility ​ ​ 46.91 % ​ 44.69 % Average expected life (years) ​ ​ 6 years ​ ​ 6 years ​ Dividend yield ​ ​ 0 % ​ 0 % Weighted‑average grant date fair value ​ $ 2.80 ​ $ 7.26 ​ Estimated fair value of total stock options granted ​ $ 7,815 ​ $ 5,659 ​ ​ When calculating the amount of annual compensation expense, the Company has elected not to estimate forfeitures and instead accounts for forfeitures as they occur. A summary of option activity under the 2014 Plan and 2021 Plan for the years ended December 31, 2023 and 2022 is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average ​ ​ ​ ​ ​ ​ ​ Remaining ​ ​ Number of ​ Weighted-average ​ Contractual Term Options Shares Exercise Price (in years) Outstanding at January 1, 2022 ​ 34,407,949 ​ $ 1.86 ​ 6.98 Granted 1,730,564 ​ $ 7.19 ​ Exercised ​ (8,428,524) ​ $ 0.10 ​ ​ Forfeited or expired (1,711,817) ​ $ 4.64 ​ Outstanding at December 31, 2022 ​ 25,998,172 ​ $ 2.60 ​ 6.31 ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at January 1, 2023 ​ 25,998,172 ​ $ 2.60 ​ 6.31 Granted ​ 5,176,889 ​ $ 2.75 ​ ​ Exercised ​ (2,490,275) ​ $ 0.09 ​ ​ Forfeited or expired ​ (4,420,770) ​ $ 3.38 ​ ​ Outstanding at December 31, 2023 ​ 24,264,016 ​ $ 2.53 ​ 7.03 ​ ​ ​ ​ ​ ​ ​ ​ Exercisable at December 31, 2022 ​ 18,202,064 ​ $ 1.19 ​ 5.14 Exercisable at December 31, 2023 ​ 16,662,487 ​ $ 1.99 ​ 4.87 ​ Cash received from options exercised under the 2014 Plan for December 31, 2023 and 2022 was $220 and $818, respectively. The aggregate intrinsic value of exercisable options at December 31, 2023 was $14,121. The aggregate intrinsic value of exercised options at December 31, 2023 was $70,115. Restricted Stock Units The following table summarizes non-vested RSUs at December 31, 2023 and the changes for the period ended December 31, 2023: ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Weighted-average ​ ​ Shares ​ Grant Date Fair Value Balance at December 31, 2022 ​ 1,057,980 ​ 7.06 Granted ​ 4,663,079 ​ ​ 2.56 Vested or Exercised ​ (278,606) ​ ​ 7.34 Forfeited ​ (969,437) ​ ​ 3.87 Balance at December 31, 2023 ​ 4,473,016 ​ ​ 3.30 ​ The vested RSUs had no intrinsic value as of December 31, 2023. ESPP The ESPP originated with 3,778,000 shares of common stock available for issuance. Beginning on January 1, 2022, the number of shares of common stock available for issuance under the ESPP shall increase by an amount equal to the lesser of (i) 3,778,000 shares of common stock (ii) one percent (1%) of the total number of shares of common stock outstanding on the last day of the immediately preceding fiscal year or (iii) a number of shares of common stock determined by the administrator no later than the last day of the immediately preceding fiscal year. On January 1, 2022, the number of shares of common stock available for issuance under the ESPP increased by 1,685,579 shares of common stock. As of December 31, 2023, 5,748,573 shares remained available for issuance. As of December 31, 2023, the ESPP permitted the Company to issue up to 5,748,573 shares of common stock. The ESPP is intended to qualify as an “employee stock purchase plan” under Section 423 of the Internal Revenue Code. Substantially all employees are eligible to participate and, through payroll deductions, can purchase shares on dates determined by the administrator. However, with respect to the Section 423 Component, an employee may not be granted rights to purchase stock under the ESPP if the employee, immediately after the grant, would own (directly or through attribution) stock possessing 5% or more of the total combined voting power or value of all classes of the Company’s common stock. The purchase price per share sold pursuant to the ESPP will be the lower of (i) 85% of the fair market value of common stock on the enrollment or (ii) 85% of the fair market value on the exercise date. Each offering period will span up to six months. Purchases may be up to 15% of qualified compensation, with an annual limit of $25,000.

Basic and Diluted Loss Per Shar

Basic and Diluted Loss Per Share	12 Months Ended
	Dec. 31, 2023
Basic and Diluted Loss Per Share
Basic and Diluted Loss Per Share	Note 9 – Basic and Diluted Loss Per Share The table below reconciles basic weighted average common shares outstanding to diluted weighted average shares outstanding for December 31, 2023 and 2022. Basic loss per share is based on the weighted average number of common shares outstanding for the period. Basic loss per share represents net loss attributable to common stock divided by the basic weighted average number of common shares outstanding during the period. Diluted loss per share also includes the dilutive effect of additional potential common shares issuable from stock-based awards and are determined using the treasury stock method. Diluted loss per share represents net loss divided by diluted weighted average number of common shares, which includes the average dilutive effect of all potentially dilutive securities that are outstanding during the period. The unvested stock awards, warrants, and options are included in the number of shares outstanding for diluted earnings per share calculations, unless a net loss is reported, in which situation unvested stock awards, warrants, and options are excluded from the number of shares outstanding for diluted earnings per share calculations. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2023 ​ 2022 ​ Net loss attributable to common stockholders ​ $ (65,549) ​ $ (9,555) ​ Weighted average shares outstanding – basic and diluted ​ ​ 178,006,919 ​ ​ 174,374,386 ​ Basic and diluted loss per share ​ $ (0.37) ​ $ (0.05) ​ ​ Due to the net loss to common stockholders in 2023 and 2022 presented above, diluted loss per share was computed without consideration of potentially dilutive instruments as their inclusion would have been anti-dilutive. As of December 31, 2023 and 2022, potentially dilutive securities excluded from the diluted earnings (loss) per share calculation are as follows (in shares): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Warrants ​ 19,333,303 19,333,303 ​ 2014 Plan & 2021 Plan - Stock Options ​ 25,877,631 26,328,279 ​ 2021 Plan - RSUs ​ 3,477,809 710,385 ​ ESPP - Common Stock ​ 67,724 ​ 26,589 ​ Contingently Issued Shares of Common Stock ​ - ​ 5,399 ​ Total potentially dilutive securities ​ 48,756,467 ​ 46,403,955 ​ ​

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2023
Related Party Transactions
Related Party Transactions	Note 11 – Related Party Transactions During 2022, the Company amended our JDA with BMW to provide a research and development-only license to certain of the Company’s intellectual property relating to cell manufacturing. The license allows, among other things, BMW to install a solid- state prototype cell manufacturing line based upon the Company’s proprietary information. The license is limited to BMW’s research and development activities and may not be used for commercial battery cell production. We expect to negotiate a non-exclusive electrolyte supply agreement to supply BMW with our electrolyte material following commissioning of BMW’s prototype cell manufacturing line. Before BMW’s installation of their cell manufacturing line, the Company and BMW have agreed to joint development and manufacturing activities at Solid Power’s facilities. Any intellectual property developed jointly by the Company and BMW at the Company’s facilities will be solely owned by Solid Power. To the extent intellectual property is jointly conceived elsewhere, the Company and BMW will jointly own such intellectual property. The intellectual property developed by us or BMW individually will be owned by such party. Both parties will have the right to utilize the other party’s technical improvements for research and development purposes only. Solid Power, with certain limitations, has the right to cause BMW to license BMW’s technical improvements to the Company for commercial purposes. BMW will pay the Company $20,000 between December 2022 and June 2024, subject to the Company achieving certain milestones. For the year ended December 31, 2023, the Company recognized $12,700 of revenue from BMW and recorded $828 of deferred revenue related to cash paid from BMW in advance of services provided. For the year ended December 31, 2022, the Company recognized $2,000 of revenue from BMW and recorded $4,000 of deferred revenue related to cash paid from BMW in advance of services provided.

Retirement plans

Retirement plans	12 Months Ended
	Dec. 31, 2023
Retirement Plans
Retirement Plans	Note 12 – Retirement Plans ​ The Company sponsors a 401(k) plan for all employees. The plan provides for the Company to make a discretionary matching contribution. Contributions to the plan totaled $977 and $802 for the years ended December 31, 2023 and 2022, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Taxes
Income Taxes	Note 13 – Income Taxes The Company provides deferred U.S. federal, state, or foreign income tax benefits for periods presented. The Company has also provided a valuation allowance on the net deferred tax asset because of uncertainty regarding realizability. Realization of deferred tax assets is dependent on generating sufficient taxable income prior to the expiration of loss carryforwards. Deferred tax assets and liabilities arise primarily from net operating loss carryforwards and temporary differences arising from the amortization of intangible assets, depreciation on property and equipment, and various accrued liabilities. Income taxes included in the Consolidated Statements of Operations for the years ended December 31, 2023 and 2022 are detailed below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Years Ended December 31, ​ 2023 2022 Current income tax (benefit) expense: ​ ​ ​ ​ ​ ​ ​ Federal ​ $ — ​ $ — ​ State ​ ​ 2 ​ ​ — ​ Deferred income tax (benefit) expense: ​ ​ ​ ​ ​ ​ ​ Federal ​ ​ — ​ ​ (195) ​ State ​ ​ — ​ (32) ​ Total income tax (benefit) expense ​ $ 2 ​ $ (227) ​ ​ ​ ​ The tables below represent a reconciliation of the statutory federal income tax expense to income tax: ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2023 2022 Income tax expense at the federal statutory rate ​ 21.00 % 21.00 % State income benefits ​ 1.42 % 13.07 % Permanent Differences ​ (1.07) % (3.14) % Permanent Differences – Fair Value Adjustments– Warrant Liability ​ 1.63 % 66.21 % Permanent Differences – Fair Value Adjustments– Marketable Securities ​ — % (5.13) % Prior year provision to return ​ (0.26) % 0.03 % Net change in valuation allowance ​ (25.54) % (104.28) % Research and Development ​ 2.62 % 13.65 % Other ​ 0.20 % 0.33 % Total income tax (benefit) ​ — % 1.75 % ​ For the years ended December 31, 2023 and 2022, the effective tax rate was approximately 0.00% and 1.75%, respectively. Differences between the statutory rate and the Company’s effective tax rate resulted from changes in valuation allowance and permanent differences for tax purposes in the treatment of certain nondeductible expenses. The tax effects of temporary differences that give rise to significant portions of the deferred income tax assets and liabilities are presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2023 2022 Deferred tax assets: ​ ​ ​ ​ Net operating loss ​ $ 30,534 ​ $ 17,962 R&D Credit ​ ​ 3,557 ​ ​ 1,908 Stock compensation ​ ​ 3,333 ​ ​ 1,991 Section 174 Capitalization ​ ​ 9,406 ​ ​ 5,731 ROU Lease Liability ​ ​ 2,332 ​ ​ 2,459 MTM Market Equities ​ ​ 125 ​ ​ — Other ​ 1,204 ​ 748 Total income tax expense (benefit) ​ 50,491 ​ 30,799 Valuation allowance ​ (44,109) ​ (28,030) Net deferred tax assets: ​ 6,382 ​ 2,769 Deferred tax liabilities: ​ ​ Intangibles (non-goodwill) ​ $ (1) ​ $ (1) Property and equipment ​ (797) ​ (652) Accretion ​ ​ (3,351) ​ ​ — ROU Asset ​ ​ (2,233) ​ ​ (2,116) Total deferred tax liabilities ​ (6,382) ​ (2,769) Total net deferred tax liability ​ $ — ​ $ — ​ The ultimate realization of deferred tax assets is dependent upon the existence, or generation, of taxable income in the periods when those temporary differences and net operating loss carryovers are deductible. Management considers the scheduled reversal of deferred tax liabilities, taxes paid in carryover years, projected future taxable income, available tax planning strategies, and other factors in making this assessment. Based on available evidence, management does not believe it is more likely than not that all of the deferred tax assets will be realized. Accordingly, the Company has established a valuation allowance equal to the net realizable deferred tax assets. The valuation allowance increased by $16,079 in 2023. At December 31, 2023 and 2022, the Company had total domestic Federal net operating loss carryovers of approximately $129,729 and $73,367, respectively. Federal net operating losses generated on or prior to December 31, 2017 expire in 2037. Federal net operating losses generated on or after January 1, 2018 have an indefinite carryforward and are only available to offset 80% taxable income beginning in 2021. The determination of state net operating loss carryforwards is dependent upon apportionment percentages and state laws that can change from year to year and that can thereby impact the amount of such carryforwards. The majority of the state net operating losses have an indefinite carryforward. Accounting for uncertainty in income taxes is based on a recognition threshold and measurement attribute for the Consolidated Financial Statements recognition and measurement of a tax position taken or expected to be taken in a tax return. The Company recognizes in its Consolidated Financial Statements only those tax positions that are more-likely-than-not to be sustained as of the adoption date, based on the technical merits of the position. Each year the Company performs a comprehensive review of its material tax positions. The Company’s policy is to recognize interest and penalties related to uncertain tax benefits in income tax expense. As the Company had no uncertain tax benefits before the year ending December 31, 2023, there is no accrual of interest or penalties related to uncertain tax positions. The following table summarizes the Company’s unrecognized tax benefits: ​ ​ ​ ​ ​ ​ December 31, 2023 Balance, beginning of year ​ $ 636 Gross increases related to prior period tax position ​ 212 Gross increases related to current period tax position ​ 338 Gross decreases related to prior period tax position ​ — Balance, end of year ​ $ 1,186 ​ Included in the balance of unrecognized tax benefits at December 31, 2023 are potential benefits of $1,186 that if recognized would affect the effective tax rate. The 2019 through 2022 tax years remain open to examination by the Internal Revenue Service and, with few exceptions, various other state tax agencies. These taxing authorities have the authority to examine those tax years until the applicable statutes of limitations expire.

Contingencies

Contingencies	12 Months Ended
	Dec. 31, 2023
Contingencies
Contingencies	Note 14 – Contingencies In the normal course of business, the Company may be party to litigation from time to time. The Company maintains insurance to cover certain actions and believes that resolution of such litigation will not have a material adverse effect on the Company.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2023
Subsequent Events
Subsequent Events	Note 15 – Subsequent Events Agreements with SK On On January 10, 2024, the Company entered into several agreements with SK On to include the R&D License Agreement, the Electrolyte Supply Agreement, and the Line Installation Agreement. The R&D License Agreement granted SK On a research and development license of the Company’s intellectual property related to cell designs and manufacturing processes allowing for the installation and operation of the SK On Line. The license may not be used for commercial battery cell production under the current terms of this agreement. In consideration of the license and the other obligations of the parties in this agreement, SK On will pay the Company $20,000 between June 2024 and July 2027, subject to the Company achieving certain milestones. Under the Electrolyte Supply Agreement, SK On has agreed to purchase the Company’s electrolyte for use on the SK On Line. SK On will initially purchase electrolyte to validate the new pilot line. After validation, SK On is required to purchase at least eight metric tons of electrolyte from the Company by December 31, 2028. The Company expects to receive at least $10,000 in revenue from these electrolyte sales. The Line Installation Agreement provides that the Company will, or will cause a subcontractor to, design, procure, and install the SK On Line in exchange for approximately $22,300 to be paid in three installments. The new line will be modeled after the Company’s pilot cell production line in Colorado, which is capable of producing cells between 60 and 100 Ah, and will produce EV cells utilizing the Company’s electrolyte technology. Construction of the line will begin in 2024 and is expected to be complete in 2025. Stock Repurchase Program On January 23, 2024, the Company announced that its Board of Directors approved a stock repurchase program authorizing the Company to purchase up to $50,000 of the Company’s outstanding common stock. Under the repurchase program, the Company may purchase shares of its common stock from time to time until the repurchase program expires on December 31, 2025.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Significant Accounting Policies
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The Consolidated Financial Statements of the Company have been prepared on the basis of GAAP. The preparation of Consolidated Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect amounts reported in the Consolidated Financial Statements. Actual results could differ from those estimates. All amounts presented in the footnotes are in thousands, except share and per share amounts. The Consolidated Financial Statements include accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The accompanying Consolidated Financial Statements have been prepared assuming that the Company will continue as a going concern.
Segment Reporting	Segment Reporting The Company’s CODM is its Chief Executive Officer. The Company has determined that it operates in one operating segment and one reportable segment, as the CODM reviews financial information presented as a single entity for purposes of making operating decisions, allocating resources, and evaluating financial performance.
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and contingencies at the date of the financial statements as well as reported amounts of revenues and expenses during the reporting periods. Estimates made by the Company include, but are not limited to, those related to the valuation of stock warrants, and useful lives of long-term assets, among others. The Company bases these estimates on historical experience and other assumptions that it believes are reasonable under the circumstances.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. As of December 31, 2023 and periodically throughout the year, the Company’s cash accounts exceeded federally insured limits.
Marketable Securities	Marketable Securities The Company’s investment policy is consistent with the definition of available-for-sale securities. The Company does not buy and hold securities principally for the purpose of selling them in the near future. The Company’s policy is focused on the preservation of capital, liquidity, and return. From time to time, the Company may sell certain securities, but the objectives are not to generate profits on short-term differences in price. These securities are carried at estimated fair value with unrealized holding gains and losses included in other comprehensive income (loss) in stockholders’ deficit until realized. Gains and losses on marketable security transactions are reported on the specific-identification method. Dividend and interest income are recognized when earned.
Contract Receivables	Contract Receivables Contract receivables consist of amounts due from government entities and commercial contractors. Management considers all contract receivables collectible, and therefore, an allowance for doubtful accounts has not been recorded as of December 31, 2023 and 2022. Included within contract receivables are amounts for work performed but not billed as of December 31, 2023 and 2022, shown below. ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Contract receivables not billed ​ $ 302 ​ $ 1,083
Credit Risk and Major Customers	Credit Risk and Major Customers Financial instruments that potentially subject the Company to credit risk consist principally of cash and cash equivalents, marketable securities, and long-term investments. The Company seeks to mitigate its credit risk with respect to cash and cash equivalents, marketable securities, and long-term investments by making deposits with large, reputable financial institutions and investing in high credit rated instruments. The Company grants credit in the normal course of business to government entities and commercial contractors in the United States. The Company periodically monitors the financial condition of its customers to reduce credit risk, but generally does not require collateral to support contract receivables. ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Years Ended December 31, ​ 2023 2022 Revenue Concentration ​ ​ ​ Number of Customers ​ 2 4 Related Total Revenue Percentage 89 % 82 % Contract Receivable Concentration Number of Customers 3 2 Related Contract Receivables Percentage 97 % 40 %
Prepaid Expenses and Other Current Assets	Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist primarily of security deposits, prepaid insurance, and other minor miscellaneous expenses paid in advance.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost. The Company capitalizes property and equipment with useful lives exceeding one year. Assets are depreciated over their estimated useful lives. The straight-line method is used for computing depreciation. Depreciation expenses are recorded within Direct costs and Research and development line items in the Consolidated Statements of Operations. Cost of maintenance and repairs are charged to expense when incurred. Construction in progress related to specialized equipment will be reclassified as Property and equipment and depreciated, once placed in service. ​ ​ ​ ​ ​ Depreciable Life - Years Commercial production equipment ​ 5 years Laboratory equipment ​ 5 years Furniture and Computer Equipment 3-7 years Leasehold improvements Lesser of asset life or lease term
Long-Term Investments	Long-Term Investments The Company considers all investments with an original maturity of twelve months or more when purchased to be long-term investments.
Intangible Assets	Intangible Assets Intangible assets consist of licenses and costs incurred for pending patents and trademarks. Licenses consist of rights to use patents and are amortized over their estimated useful life of three
Deferred Rent	Deferred Rent Prior to the adoption of ASU No. 2016-02, Leases (Topic 842) on January 1, 2022, the Company had entered into operating lease agreements for each of its two facilities, each of which contain provisions for future rent increases or periods in which rent payments are reduced. The Company records monthly rent expense equal to the total of the payments due over the lease term, divided by the number of months of the lease term. The difference between rent expense recorded and the amount paid is credited or charged to deferred rent, which is reflected in Other Long-term Liabilities in the accompanying Consolidated Balance Sheets. Deferred rent also includes the unamortized portion of landlord-financed tenant improvement allowances, which are amortized on a straight-line basis over the lease term as a reduction in rent expense.
Leases	Leases The Company accounts for its leases under ASU No. 2016-02, Leases (Topic 842). Under this guidance, the Company classifies contracts meeting the definition of a lease as operating or financing leases, and leases are recorded on the condensed consolidated balance sheet as both a right-of-use asset and lease liability, calculated by discounting fixed lease payments over the lease term at the rate implicit in the lease or the Company’s incremental borrowing rate. Lease liabilities are increased by interest and reduced by payments each period, and the right-of-use asset is amortized over the lease term. For operating leases, interest on the lease liability and the amortization of the right-of-use asset result in straight-line rent expense over the lease term. For finance leases, interest on the lease liability and the amortization of the right-of-use asset results in front-loaded expense over the lease term. Variable lease expenses, including common maintenance fees, insurance and property tax, are recorded when incurred. In calculating the right-of-use asset and lease liability, the Company elects to combine lease and non-lease components for all classes of assets. The Company excludes short-term leases having initial terms of 12 months or less as an accounting policy election, and instead recognizes rent expense on a straight-line basis over the lease term.
Stock-based Compensation	Stock-based Compensation The Company recognizes expenses for employee services received in exchange for stock-based compensation based on the grant date fair value of the awards. The determination of the estimated fair value of stock-based payment awards on the date of grant is calculated using the Black-Scholes option-pricing model and is affected by the Company’s stock price, as well as assumptions regarding risk-free rate, dividend yield, and the historical volatility of comparable entities. Stock-based compensation is recorded as an expense only for those awards that are expected to vest. Compensation cost is recognized on a straight-line basis over the requisite vesting service period and is allocated ratably within Operating Expenses in the Consolidated Statements of Operations.
Revenue	Revenue The Company records the elements of its JDAs in accordance with ASC Topic 808, Collaborative Arrangements. Accordingly, the elements of the JDAs that represent activities in which both parties are active participants and are exposed to the significant risks and rewards that are dependent on the commercial success of the activities are recorded as collaborative arrangements. The Company considers the guidance in ASC 606-10-15, Revenue from Contracts with Customers – Scope and Scope Exceptions, in determining the appropriate treatment for the transactions between the Company and its partners or third parties. Generally, the classification of transactions under the JDAs is determined based on the nature and contractual terms of the arrangement along with the nature of the operations of the participants. The Company recognizes collaborative revenue from cost contracts on the basis of costs incurred during the period and for cost plus fixed-fee contracts on the basis of costs incurred during the period plus the fee earned. Contract costs include all direct labor, subcontract, material, and indirect costs related to the contract performance that are allowable under contract provisions. Deferred revenue represents billings in advance of revenue recognized. ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Deferred revenue ​ $ 1 ​ $ 50 Deferred revenue from related parties ​ $ 828 ​ $ 4,000
Warrant Liabilities	Warrant Liabilities The Company accounts for warrants as liability-classified instruments based on an assessment of the warrant’s specific terms and applicable authoritative guidance in ASC 480 and ASC 815. Warrants recorded as liabilities are recorded at their fair value, within Warrant Liabilities on the Consolidated Balance Sheets and are remeasured on each reporting date with changes recorded in Change in fair value of warrant liabilities on the Company’s Consolidated Statements of Operations.
Fair Value Measurements	Fair Value Measurements The Company applies fair value accounting for selected financial assets and liabilities measured on a recurring and nonrecurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. The accounting guidance ASC Topic 820 Fair Value Measurement established a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, used to determine the fair value of its financial instruments. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Level 1 – inputs include quoted market prices in an active market for identical assets or liabilities. Level 2 – inputs are market data, other than Level 1, that are observable either directly or indirectly. Level 2 inputs include quoted market prices for similar assets or liabilities, quoted market prices in an inactive market, and other observable information that can be corroborated by market data. Level 3 – inputs are unobservable and corroborated by little or no market data.
Research and Development	Research and Development Our research and development activities focus on making improvements to our electrolyte and cell technology with the ultimate goal of commercializing technology that outperforms conventional lithium-ion. ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Research and development expenditures ​ $ 54,749 ​ $ 38,592
Income Taxes	Income Taxes The Company recognizes deferred tax liabilities and assets for the expected future tax consequences of events that have been included in the Consolidated Financial Statements or tax returns. Deferred tax liabilities and assets are determined based on the differences between the Consolidated Financial Statements and tax basis of assets and liabilities using the enacted tax rates in effect for the year in which the differences are expected to reverse. The measurement of deferred tax assets is reduced, if necessary, by the amount of any uncertain tax positions or tax benefits that are not expected to be realized based on available evidence. The Company records deferred tax assets and associated valuation allowances, when appropriate, to reflect amounts more likely than not to be realized based upon Company analysis. The Company’s temporary differences result primarily from capitalization of certain qualifying research and development expenses, accruals and reserves, depreciation of property and equipment, stock compensation expense, capitalization of operating or financing leases, and net operating loss carryovers. The Company accounts for any uncertainty in income taxes by recognizing the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The Company measures the tax benefits recognized in the Consolidated Financial Statements from such a position based on the largest benefit that has a greater than 50 percent likelihood of being realized upon ultimate resolution. Interest and penalties associated with tax positions are recorded in the period assessed as General and administrative on the Consolidated Statement of Operations. No interest or penalties have been assessed during the years ended December 31, 2023 and 2022.
Net Loss per Share of Common Stock	Net Loss per Share of Common Stock Basic net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted loss per share adjusts basic loss per share for the potentially dilutive impact of stock options and warrants. The Company reported a net loss in 2023 and 2022. As such, all potentially dilutive securities, including options and warrants, are antidilutive and, accordingly, basic net loss per share equals diluted loss per share.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Income taxes In December 2023, the FASB issued ASU No. 2023-09 Income Taxes (Topic 740) Improvements to Income Tax Disclosures. ASU 2023-09 requires companies to disclose, on an annual basis, specific categories in the effective tax rate reconciliation and provide additional information for reconciling items that meet a quantitative threshold. In addition, ASU 2023-09 requires companies to disclose additional information about income taxes paid. ASU 2023-09 will be effective for annual periods beginning January 1, 2025 and will be applied on a prospective basis with the option to apply the standard retrospectively. We are evaluating the disclosure impact of ASU 2023-09. Segment Reporting In November 2023, the FASB issued ASU No. 2023-07 Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. Among other new disclosure requirements, ASC 2023-07 requires companies to disclose significant segment expenses that are regularly provided to the CODM. ASU 2023-07 will be effective for annual periods beginning on January 1, 2024 and interim periods beginning on January 1, 2025. ASU 2023-07 must be applied retrospectively to all prior periods presented in the financial statements. We are evaluating the disclosure impact of ASU 2023-07.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Significant Accounting Policies
Schedule of contract receivables	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Contract receivables not billed ​ $ 302 ​ $ 1,083
Schedule of credit risk and major customers	​ ​ ​ ​ ​ ​ ​ ​ ​ For the Years Ended December 31, ​ 2023 2022 Revenue Concentration ​ ​ ​ Number of Customers ​ 2 4 Related Total Revenue Percentage 89 % 82 % Contract Receivable Concentration Number of Customers 3 2 Related Contract Receivables Percentage 97 % 40 %
Summary of estimated useful life of property, plant and equipment	​ ​ ​ ​ ​ Depreciable Life - Years Commercial production equipment ​ 5 years Laboratory equipment ​ 5 years Furniture and Computer Equipment 3-7 years Leasehold improvements Lesser of asset life or lease term
Schedule of deferred revenue	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Deferred revenue ​ $ 1 ​ $ 50 Deferred revenue from related parties ​ $ 828 ​ $ 4,000
Schedule of research and development	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Research and development expenditures ​ $ 54,749 ​ $ 38,592

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment
Schedule of property and equipment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Commercial production equipment ​ $ 36,086 ​ $ 21,595 Laboratory equipment ​ ​ 9,910 ​ ​ 3,278 Leasehold improvements ​ 59,109 ​ 27,996 Furniture and computer equipment ​ 3,915 ​ 1,482 Construction in progress ​ 13,650 ​ 40,036 Total cost ​ 122,670 ​ 94,387 Accumulated depreciation ​ (23,514) ​ (11,626) Net property and equipment ​ $ 99,156 ​ $ 82,761
Schedule of depreciation and amortization expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2023 2022 Depreciation expense ​ $ 11,947 ​ $ 5,167 ​
Schedule of construction in progress	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Construction in progress ​ ​ SP1 – 2 nd ​ $ 773 ​ $ 2,010 SP1 – Other capital projects ​ 1,525 ​ 2,206 SP2 – Increased scale electrolyte production ​ 11,352 ​ 35,820 ​

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Intangible Assets
Schedule of intangible assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 ​ ​ Gross Carrying ​ Accumulated ​ Gross Carrying ​ Accumulated ​ ​ Amount Amortization Amount Amortization Intangible assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Licenses ​ $ 149 ​ $ (61) ​ $ 149 ​ $ (51) Patents ​ ​ 92 ​ ​ (5) ​ ​ — ​ ​ — Patents pending ​ ​ 1,444 ​ — ​ 984 ​ — Trademarks ​ ​ 13 ​ ​ — ​ ​ 9 ​ ​ — Trademarks pending ​ ​ 18 ​ — ​ 17 ​ — Total amortized intangible assets ​ $ 1,716 ​ $ (66) ​ $ 1,159 ​ $ (51)
Schedule of amortization expense for intangible assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Amortization expense ​ $ 15 ​ $ 9 ​

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Measurements
Schedule of financial assets and liabilities measured and recorded at fair value on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ Level 1 Level 2 Level 3 Total Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commercial Paper ​ $ 84,909 ​ $ — ​ $ — ​ $ 84,909 Corporate Bonds ​ $ 239,473 ​ $ — ​ $ — ​ $ 239,473 Government Bonds ​ $ 56,689 ​ $ — ​ $ — ​ $ 56,689 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Public Warrants ​ $ 2,505 ​ $ — ​ $ — ​ $ 2,505 Private Placement Warrants ​ $ — ​ $ 1,722 ​ $ — ​ $ 1,722 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ Level 1 Level 2 Level 3 Total Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commercial Paper ​ $ 165,179 ​ $ — ​ $ — ​ $ 165,179 Corporate Bonds ​ $ 227,957 ​ $ — ​ $ — ​ $ 227,957 Government Bonds ​ $ 42,865 ​ $ — ​ $ — ​ $ 42,865 U.S. Treasuries ​ 9,930 ​ ​ — ​ ​ — ​ 9,930 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Public Warrants ​ $ 4,900 ​ $ — ​ $ — ​ $ 4,900 Private Placement Warrants ​ $ — ​ $ 4,217 ​ $ — ​ $ 4,217
Schedule of marketable securities and long-term investments purchased	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 2022 Marketable securities and long-term investments purchased ​ $ 327,591 ​ $ 561,565
Schedule of Level 2 inputs used in the recurring valuation of the Private Placement Warrants	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Exercise price ​ $ 11.50 ​ $ 11.50 ​ Stock price ​ $ 1.45 ​ $ 2.54 ​ Volatility ​ 95.0 % 71.3 % Term (years) ​ 2.94 ​ 3.94 ​ Risk-free rate ​ 3.94 % 4.03 %
Schedule of reconciliation of warrants measured at fair value	The following table provides a reconciliation of the Public Warrants measured at fair value using Level 1 inputs and Private Placement Warrants measured at fair value using Level 2 inputs: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Public Warrants ​ Private Placement Warrants ​ Level 1 Fair Value Level 2 Fair Value December 31, 2022 ​ $ 0.42 ​ $ 0.55 Change in fair value ​ $ (0.23) ​ $ (0.27) December 31, 2023 ​ $ 0.19 ​ $ 0.28 ​
Fair value of warrant liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Twelve Months Change in ​ ​ Warrant Class Level Warrants December 31, 2022 Fair Value December 31, 2023 Public Warrants 1 13,182,501 ​ $ 4,900 ​ $ (2,395) ​ $ 2,505 Private Placement Warrants 2 6,150,802 ​ $ 4,217 ​ $ (2,495) ​ $ 1,722 Total 19,333,303 ​ $ 9,117 ​ $ (4,890) ​ $ 4,227 ​

Warrant Liabilities (Tables)

Warrant Liabilities (Tables)	12 Months Ended
	Dec. 31, 2023
Warrant Liabilities.
Summary of the outstanding Public and Private Placement Warrants	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Public Warrants ​ ​ 13,182,501 ​ ​ 11,666,636 Private Placement Warrants ​ ​ 6,150,802 ​ ​ 7,666,667
Schedule of fair value of warrant liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2023 2022 Fair value of warrant liabilities ​ $ 4,227 ​ $ 9,117
Schedule of gain (loss) from changes in fair value of Warrant Liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2023 2022 Gain recognized associated with warrant liabilities ​ $ 4,890 ​ $ 40,903 ​

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2023
Stockholders' Equity
Schedule of stock options exercised	​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2023 2022 ​ Stock options exercised ​ 2,490,275 ​ 8,428,524 ​ Shares of common stock issued under ESPP ​ 287,224 ​ — ​ Shares of common stock issued for vested RSUs ​ 226,201 ​ 20,672 ​
Schedule of cash received associated with common stock related activities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 2022 Cash received from stock options exercised ​ $ 220 ​ $ 818 Cash received from shares of common stock issued under ESPP ​ ​ 434 ​ ​ — ​

Stock Based Compensation (Table

Stock Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2023
Stock Based Compensation
Schedule of option activity under the Plan	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average ​ ​ ​ ​ ​ ​ ​ Remaining ​ ​ Number of ​ Weighted-average ​ Contractual Term Options Shares Exercise Price (in years) Outstanding at January 1, 2022 ​ 34,407,949 ​ $ 1.86 ​ 6.98 Granted 1,730,564 ​ $ 7.19 ​ Exercised ​ (8,428,524) ​ $ 0.10 ​ ​ Forfeited or expired (1,711,817) ​ $ 4.64 ​ Outstanding at December 31, 2022 ​ 25,998,172 ​ $ 2.60 ​ 6.31 ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at January 1, 2023 ​ 25,998,172 ​ $ 2.60 ​ 6.31 Granted ​ 5,176,889 ​ $ 2.75 ​ ​ Exercised ​ (2,490,275) ​ $ 0.09 ​ ​ Forfeited or expired ​ (4,420,770) ​ $ 3.38 ​ ​ Outstanding at December 31, 2023 ​ 24,264,016 ​ $ 2.53 ​ 7.03 ​ ​ ​ ​ ​ ​ ​ ​ Exercisable at December 31, 2022 ​ 18,202,064 ​ $ 1.19 ​ 5.14 Exercisable at December 31, 2023 ​ 16,662,487 ​ $ 1.99 ​ 4.87 ​
Schedule of recognized & allocated compensation costs	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2023 2022 Equity-based compensation costs related to RSUs ​ $ 3,427 ​ $ 1,567 Equity-based compensation costs related to stock options ​ 6,774 ​ 7,076 Equity-based compensation costs related to ESPP ​ ​ 169 ​ ​ 29 Total equity-based compensation costs ​ $ 10,370 ​ $ 8,672 Unrecognized future compensation cost as of: ​ ​ 23,922 ​ ​ 25,531 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2023 2022 Direct Costs ​ $ 3,751 ​ $ 1,580 Research and Development ​ ​ 4,826 ​ ​ 4,474 Selling, general and administrative ​ ​ 1,793 ​ ​ 2,618 Total equity-based compensation cost ​ $ 10,370 ​ $ 8,672
Schedule of fair value of each option using the Black-Scholes option pricing model	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Approximate risk‑free rate ​ ​ 4.17 % ​ 2.84 % Volatility ​ ​ 46.91 % ​ 44.69 % Average expected life (years) ​ ​ 6 years ​ ​ 6 years ​ Dividend yield ​ ​ 0 % ​ 0 % Weighted‑average grant date fair value ​ $ 2.80 ​ $ 7.26 ​ Estimated fair value of total stock options granted ​ $ 7,815 ​ $ 5,659 ​
Schedule of non-vested Restricted stock units	​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Weighted-average ​ ​ Shares ​ Grant Date Fair Value Balance at December 31, 2022 ​ 1,057,980 ​ 7.06 Granted ​ 4,663,079 ​ ​ 2.56 Vested or Exercised ​ (278,606) ​ ​ 7.34 Forfeited ​ (969,437) ​ ​ 3.87 Balance at December 31, 2023 ​ 4,473,016 ​ ​ 3.30
2021 Equity Incentive Plan
Stock Based Compensation
Schedule of option activity under the Plan	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2023 2022 Option awards granted under 2021 Plan ​ ​ 5,176,889 ​ ​ 1,730,564 RSU awards granted under 2021 Plan ​ ​ 4,663,079 ​ ​ 1,292,429

Basic and Diluted Loss Per Sh_2

Basic and Diluted Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2023
Basic and Diluted Loss Per Share
Schedule of reconciliation of basic weighted average common shares outstanding to diluted weighted average shares outstanding	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2023 ​ 2022 ​ Net loss attributable to common stockholders ​ $ (65,549) ​ $ (9,555) ​ Weighted average shares outstanding – basic and diluted ​ ​ 178,006,919 ​ ​ 174,374,386 ​ Basic and diluted loss per share ​ $ (0.37) ​ $ (0.05) ​ ​
Schedule of potentially dilutive securities excluded from the diluted earnings per share calculation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Warrants ​ 19,333,303 19,333,303 ​ 2014 Plan & 2021 Plan - Stock Options ​ 25,877,631 26,328,279 ​ 2021 Plan - RSUs ​ 3,477,809 710,385 ​ ESPP - Common Stock ​ 67,724 ​ 26,589 ​ Contingently Issued Shares of Common Stock ​ - ​ 5,399 ​ Total potentially dilutive securities ​ 48,756,467 ​ 46,403,955 ​ ​

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases
Schedule of components of lease related expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 Finance lease costs: ​ ​ ​ Amortization of right-of-use assets ​ $ 197 ​ $ 92 Interest on lease liabilities ​ 53 ​ 28 Operating lease costs ​ 1,160 ​ 850 Total lease expense ​ $ 1,410 ​ $ 970
Schedule of components of cash flow information related to leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 December 31, 2022 ​ Operating outgoing cash flows – finance leases ​ $ 54 ​ $ 24 ​ Financing outgoing cash flows – finance leases ​ 308 ​ 142 ​ Operating outgoing cash flows – operating leases ​ 1,138 ​ 568 ​ Right-of-use assets obtained in exchange for new finance lease liabilities: ​ ​ 345 ​ ​ 1,014 ​ Right-of-use assets obtained in exchange for new operating lease liabilities: ​ ​ — ​ ​ 8,947 ​
Schedule of remaining weighted-average lease term and weighted-average discount rate	​ ​ ​ ​ ​ ​ December 31, 2023 Finance lease ​ Weighted-average remaining lease term – finance leases (in years) 2.84 ​ Weighted-average discount rate – finance leases 6.5 % Operating lease ​ ​ Weighted-average remaining lease term – operating leases (in years) 9.22 ​ Weighted-average discount rate – operating leases 6.9 %
Schedule of future minimum payments under operating lease	​ ​ ​ ​ ​ ​ ​ ​ Fiscal year Finance Lease Operating Lease 2024 ​ $ 425 ​ $ 1,173 2025 ​ ​ 310 ​ ​ 1,210 2026 ​ ​ 179 ​ ​ 1,248 2027 ​ ​ 85 ​ ​ 1,288 2028 ​ ​ 16 ​ ​ 1,329 Thereafter ​ ​ - ​ ​ 5,242 Total ​ ​ 1,015 ​ ​ 11,490 Less present value discount ​ ​ 85 ​ ​ 2,868 Total lease liabilities ​ $ 930 ​ $ 8,622 Click or tap here to enter text.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Taxes
Schedule of income taxes	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Years Ended December 31, ​ 2023 2022 Current income tax (benefit) expense: ​ ​ ​ ​ ​ ​ ​ Federal ​ $ — ​ $ — ​ State ​ ​ 2 ​ ​ — ​ Deferred income tax (benefit) expense: ​ ​ ​ ​ ​ ​ ​ Federal ​ ​ — ​ ​ (195) ​ State ​ ​ — ​ (32) ​ Total income tax (benefit) expense ​ $ 2 ​ $ (227) ​
Schedule of reconciliation of the statutory federal income tax expense to income tax	​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2023 2022 Income tax expense at the federal statutory rate ​ 21.00 % 21.00 % State income benefits ​ 1.42 % 13.07 % Permanent Differences ​ (1.07) % (3.14) % Permanent Differences – Fair Value Adjustments– Warrant Liability ​ 1.63 % 66.21 % Permanent Differences – Fair Value Adjustments– Marketable Securities ​ — % (5.13) % Prior year provision to return ​ (0.26) % 0.03 % Net change in valuation allowance ​ (25.54) % (104.28) % Research and Development ​ 2.62 % 13.65 % Other ​ 0.20 % 0.33 % Total income tax (benefit) ​ — % 1.75 % ​
Schedule of tax effects of temporary differences that give rise to significant portions of the deferred income tax assets and liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2023 2022 Deferred tax assets: ​ ​ ​ ​ Net operating loss ​ $ 30,534 ​ $ 17,962 R&D Credit ​ ​ 3,557 ​ ​ 1,908 Stock compensation ​ ​ 3,333 ​ ​ 1,991 Section 174 Capitalization ​ ​ 9,406 ​ ​ 5,731 ROU Lease Liability ​ ​ 2,332 ​ ​ 2,459 MTM Market Equities ​ ​ 125 ​ ​ — Other ​ 1,204 ​ 748 Total income tax expense (benefit) ​ 50,491 ​ 30,799 Valuation allowance ​ (44,109) ​ (28,030) Net deferred tax assets: ​ 6,382 ​ 2,769 Deferred tax liabilities: ​ ​ Intangibles (non-goodwill) ​ $ (1) ​ $ (1) Property and equipment ​ (797) ​ (652) Accretion ​ ​ (3,351) ​ ​ — ROU Asset ​ ​ (2,233) ​ ​ (2,116) Total deferred tax liabilities ​ (6,382) ​ (2,769) Total net deferred tax liability ​ $ — ​ $ —
Schedule of unrecognized tax benefits	​ ​ ​ ​ ​ ​ December 31, 2023 Balance, beginning of year ​ $ 636 Gross increases related to prior period tax position ​ 212 Gross increases related to current period tax position ​ 338 Gross decreases related to prior period tax position ​ — Balance, end of year ​ $ 1,186

Significant Accounting Polici_4

Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)
Segment Reporting
Number of operating segment	1
Number of reportable segment	1
Contract Receivables
Contract receivables not billed | $	$ 302	$ 1,083

Significant Accounting Polici_5

Significant Accounting Policies - Credit Risk and Major Customers (Details) - Customer concentration - customer	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenue | Four customers
Concentration risk
Number of customers	2	4
Concentration risk percentage	89%	82%
Contract receivables | Two customers
Concentration risk
Number of customers	3	2
Concentration risk percentage	97%	40%

Significant Accounting Polici_6

Significant Accounting Policies - Property and Equipment (Details)	Dec. 31, 2023
Commercial production equipment
Property and Equipment
Estimated useful lives	5 years
Laboratory equipment
Property and Equipment
Estimated useful lives	5 years
Furniture And Computer Equipment | Minimum
Property and Equipment
Estimated useful lives	3 years

Significant Accounting Polici_7

Significant Accounting Policies - Intangible Assets (Details)	Dec. 31, 2023
Minimum
Intangible Assets
Estimated useful life of intangible assets	3 years
Maximum
Intangible Assets
Estimated useful life of intangible assets	20 years

Significant Accounting Polici_8

Significant Accounting Policies -Deferred revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Significant Accounting Policies
Deferred revenue	$ 1	$ 50
Deferred revenue from related parties	$ 828	$ 4,000

Significant Accounting Polici_9

Significant Accounting Policies - Research and Development (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Significant Accounting Policies
Deferred revenue	$ 1	$ 50
Deferred revenue from related parties	828	4,000
Research and development expenditures	$ 54,749	$ 38,592

Significant Accounting Polic_10

Significant Accounting Policies - Additional information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Taxes
Interest or penalties	$ 0	$ 0

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property and Equipment
Gross property and equipment	$ 122,670	$ 94,387
Accumulated depreciation	(23,514)	(11,626)
Net property and equipment	99,156	82,761
Commercial production equipment
Property and Equipment
Gross property and equipment	36,086	21,595
Laboratory equipment
Property and Equipment
Gross property and equipment	9,910	3,278
Leasehold improvements
Property and Equipment
Gross property and equipment	59,109	27,996
Furniture and computer equipment
Property and Equipment
Gross property and equipment	3,915	1,482
Construction in progress
Property and Equipment
Gross property and equipment	$ 13,650	$ 40,036

Property, Plant and Equipment -

Property, Plant and Equipment - Depreciation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Property and Equipment
Depreciation expense	$ 11,962	$ 5,176
Property, Plant and Equipment
Property and Equipment
Depreciation expense	$ 11,947	$ 5,167

Property, Plant and Equipment_2

Property, Plant and Equipment - Construction in progress (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
SP1 - 2nd cell pilot line
Property, Plant and Equipment
Construction in progress	$ 773	$ 2,010
SP1 - Other capital projects
Property, Plant and Equipment
Construction in progress	1,525	2,206
SP2 - Increased scale electrolyte production
Property, Plant and Equipment
Construction in progress	$ 11,352	$ 35,820

Intangible Assets (Details)

Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Intangible assets:
Gross Carrying Amount	$ 1,716	$ 1,159
Accumulated Amortization	(66)	(51)
Amortization expense	$ 15	9
Minimum
Intangible assets:
Useful lives of intangible assets	3 years
Maximum
Intangible assets:
Useful lives of intangible assets	20 years
Licenses
Intangible assets:
Gross Carrying Amount	$ 149	149
Accumulated Amortization	(61)	(51)
Patents
Intangible assets:
Gross Carrying Amount	92
Accumulated Amortization	(5)
Patents pending
Intangible assets:
Gross Carrying Amount	1,444	984
Trademarks
Intangible assets:
Gross Carrying Amount	13	9
Trademarks pending
Intangible assets:
Gross Carrying Amount	$ 18	$ 17

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured and Recorded at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Liabilities
Long term marketable securities	$ 0
Marketable securities and long-term investments purchased	327,591	$ 561,565
Recurring | Public Warrants
Liabilities
Liabilities	2,505	4,900
Recurring | Private Placement Warrants
Liabilities
Liabilities	1,722	4,217
Recurring | Level 1 | Public Warrants
Liabilities
Liabilities	2,505	4,900
Recurring | Level 2 | Private Placement Warrants
Liabilities
Liabilities	1,722	4,217
Recurring | Level 3
Liabilities
Transfers in or out of Level 3	0	0
Recurring | Commercial Paper
Assets
Assets	84,909	165,179
Recurring | Commercial Paper | Level 1
Assets
Assets	84,909	165,179
Recurring | Corporate Bonds
Assets
Assets	239,473	227,957
Recurring | Corporate Bonds | Level 1
Assets
Assets	239,473	227,957
Recurring | Government Bonds
Assets
Assets	56,689	42,865
Recurring | Government Bonds | Level 1
Assets
Assets	$ 56,689	42,865
Recurring | U.S. Treasuries
Assets
Assets		9,930
Recurring | U.S. Treasuries | Level 1
Assets
Assets		$ 9,930

Fair Value Measurements - Measu

Fair Value Measurements - Measurement inputs (Details) - Recurring - Level 2 - Private Placement Warrants	Dec. 31, 2023 $ / shares Y	Dec. 31, 2022 $ / shares Y
Exercise Price
Fair Value Measurements
Measurement input, warrants	11.50	11.50
Stock Price
Fair Value Measurements
Measurement input, warrants	1.45	2.54
Volatility
Fair Value Measurements
Measurement input, warrants	0.950	0.713
Term
Fair Value Measurements
Measurement input, warrants | Y	2.94	3.94
Risk-free rate
Fair Value Measurements
Measurement input, warrants	0.0394	0.0403

Fair Value Measurements - Publi

Fair Value Measurements - Public Warrants measured at fair value using Level 1 directly observable inputs and Private Placement Warrants (Details) - Recurring	12 Months Ended
	Dec. 31, 2023 $ / shares
Public Warrants | Level 1
Reconciliation
Beginning balance, per share	$ 0.42
Change in fair value	(0.23)
Ending balance, per share	0.19
Private Placement Warrants | Level 2
Reconciliation
Beginning balance, per share	0.55
Change in fair value	(0.27)
Ending balance, per share	$ 0.28

Fair Value Measurements - Fair

Fair Value Measurements - Fair value for the Public Warrants and Private Placement Warrants (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value Measurements
Number of warrants outstanding	6,150,802	7,666,667
Reconciliation
Balance at the beginning	$ 9,117
Balance at the end	$ 4,227
Fair Value, Recurring
Fair Value Measurements
Number of warrants outstanding	19,333,303
Reconciliation
Balance at the beginning	$ 9,117
Change in fair value	(4,890)
Balance at the end	$ 4,227
Public Warrants
Fair Value Measurements
Number of warrants outstanding	13,182,501	11,666,636
Public Warrants | Level 1
Fair Value Measurements
Number of warrants outstanding	13,182,501
Reconciliation
Balance at the beginning	$ 4,900
Change in fair value	(2,395)
Balance at the end	$ 2,505
Private Placement Warrants | Level 2
Fair Value Measurements
Number of warrants outstanding	6,150,802
Reconciliation
Balance at the beginning	$ 4,217
Change in fair value	(2,495)
Balance at the end	$ 1,722

Warrant Liabilities (Details)

Warrant Liabilities (Details) - shares	Dec. 31, 2023	Dec. 31, 2022
Warrant Liabilities
Number of warrants outstanding	6,150,802	7,666,667
Public Warrants
Warrant Liabilities
Number of warrants outstanding	13,182,501	11,666,636

Warrant Liabilities - Additiona

Warrant Liabilities - Additional information (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Warrant Liabilities
Trading days considered in the calculation of fair market value	10 days
Redemption of Public Warrants when the price per share of Common Stock equals or exceeds $18.00
Warrant Liabilities
Stock price trigger for redemption of public warrants (in dollars per share)	$ 18
Sale Price Of Common Stock Equal Or Exceeds To 18.00 Per Share
Warrant Liabilities
Class of warrant or right minimum threshold written notice period for redemption of warrants	30 days
Sale Price Of Common Stock Equal Or Exceeds To 10.00 Per Share
Warrant Liabilities
Class of warrant or right minimum threshold written notice period for redemption of warrants	30 days
Warrants
Warrant Liabilities
Class of warrant or right, number of securities called by each warrant or right	1	1
Exercise price of warrants	$ 11.50	$ 11.50
Warrants | Sale Price Of Common Stock Equal Or Exceeds To 18.00 Per Share
Warrant Liabilities
Redeemable price per warrant	0.01
Trigger price	$ 18
Threshold trading days for which the entity sends notice of redemption	20 days
Threshold consecutive trading days for which the entity sends notice of redemption	30 days
Warrants | Sale Price Of Common Stock Equal Or Exceeds To 10.00 Per Share
Warrant Liabilities
Redeemable price per warrant	$ 0.10
Trigger price	10
Public Warrants | Redemption of Public Warrants when the price per share of Common Stock equals or exceeds $10.00
Warrant Liabilities
Stock price trigger for redemption of public warrants (in dollars per share)	$ 10

Warrant Liabilities - Fair valu

Warrant Liabilities - Fair value of warrant liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Warrant Liabilities.
Fair value of warrant liabilities	$ 4,227	$ 9,117

Warrant Liabilities - Changes i

Warrant Liabilities - Changes in fair value of warrant liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Warrant Liabilities.
Gain recognized associated with warrant liabilities	$ 4,890	$ 40,903

Stockholders' Equity - Stock op

Stockholders' Equity - Stock options exercised (Details) - Common Stock - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Stockholders' Equity
Stock options exercised (in shares)	2,490,275	8,428,524
Shares of common stock issued under ESPP (in shares)	287,224
Shares issued upon vesting of RSUs (in shares)	226,201	20,672

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Stockholders' Equity
Cash received from options exercised	$ 220	$ 818
Cash received from shares of common stock issued under ESPP	$ 434

Stock Based Compensation - 2014

Stock Based Compensation - 2014 Equity Incentive Plan and 2021 Equity Incentive Plan (Details)		12 Months Ended
	Jan. 01, 2022 shares	Dec. 31, 2023 installment shares	Dec. 31, 2022 shares
Employee Stock Option
Stock Based Compensation
Options outstanding		3.30	7.06
Awards granted under 2021 Plan		2.56
Restricted stock units (RSUs)
Stock Based Compensation
Number of common shares for each RSU upon vesting		1
Awards granted under 2021 Plan		4,663,079	1,292,429
Restricted stock units (RSUs) | Vesting after year one
Stock Based Compensation
Number of successive equal number of installments of remaining vesting shares, vested | installment		12
Restricted stock units (RSUs) | Share Based Payment Arrangement Employee
Stock Based Compensation
Vesting percentage		25%	25%
Percentage per quarter thereafter		6.25%
2014 Plan
Stock Based Compensation
Options terms		10 years
Vesting percentage		75%
Options outstanding		24,264,016	24,766,176
2014 Plan | Vesting after year one
Stock Based Compensation
Vesting percentage		25%
2014 Plan | Vesting after year two
Stock Based Compensation
Number of successive equal number of installments of remaining vesting shares, vested | installment		36
2021 Equity Incentive Plan
Stock Based Compensation
Number of additional shares	18,900,000
Percentage on shares outstanding added to shares available for issuance	5%
Options outstanding	8,377,899	21,711,885
Awards granted under 2021 Plan		5,176,889	1,730,564
2021 Equity Incentive Plan | Share Based Payment Arrangement Employee | Vesting after year one
Stock Based Compensation
Percentage per quarter thereafter		6.25%
2021 Equity Incentive Plan | Employee Stock Option
Stock Based Compensation
Options terms		10 years	10 years
2021 Equity Incentive Plan | Employee Stock Option | Vesting after year one
Stock Based Compensation
Vesting percentage		25%	25%
2021 Equity Incentive Plan | Restricted stock units (RSUs)
Stock Based Compensation
Options outstanding		22,048,584

Stock Based Compensation - Comp

Stock Based Compensation - Compensation costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Compensation costs
Equity-based compensation cost	$ 10,370	$ 8,672
Unrecognized compensation costs related to restricted stock units	23,922	25,531
Restricted stock units (RSUs)
Compensation costs
Equity-based compensation cost	3,427	1,567
Employee Stock Option
Compensation costs
Equity-based compensation cost	6,774	7,076
ESPP
Compensation costs
Equity-based compensation cost	$ 169	$ 29

Stock Based Compensation - Allo

Stock Based Compensation - Allocated compensation costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Stock Based Compensation
Equity-based compensation cost	$ 10,370	$ 8,672
Direct Costs
Stock Based Compensation
Equity-based compensation cost	3,751	1,580
Research and Development
Stock Based Compensation
Equity-based compensation cost	4,826	4,474
Sales and Marketing
Stock Based Compensation
Equity-based compensation cost	$ 1,793	$ 2,618

Stock Based Compensation - Fair

Stock Based Compensation - Fair value of options granted (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Stock Based Compensation
Approximate risk-free rate	4.17%	2.84%
Volatility	46.91%	44.69%
Average expected life (years)	6 years	6 years
Dividend yield	0%	0%
Weighted-average grant date fair value	$ 2.80	$ 7.26
Estimated fair value of total stock options granted (in thousands)	$ 7,815	$ 5,659

Stock Based Compensation - Stoc

Stock Based Compensation - Stock options and Restricted stock units (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Restricted stock units (RSUs)
Restricted Stock Units.
Outstanding at beginning of period	1,057,980
Granted	4,663,079
Vested	(278,606)
Forfeited	(969,437)
Outstanding at end of period	4,473,016	1,057,980
Number of Shares
Granted	4,663,079	1,292,429
Intrinsic value	$ 0
Employee Stock Option
Number of Shares
Outstanding at beginning of period	7.06
Granted	2.56
Stock options exercised (in shares)	7.34
Forfeited or expired	3.87
Outstanding at end of period	3.30	7.06

Stock Based Compensation - 2021

Stock Based Compensation - 2021 Employee Stock Purchase Plan (Details) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 08, 2021
Stock Based Compensation
Compensation costs		$ 10,370	$ 8,672
2021 ESPP
Stock Based Compensation
Common Stock available for issuance	1,685,579	5,748,573		3,778,000
Number of shares permitted to deliver		5,748,573
Percentage limit on commons stock shares outstanding	1%
Threshold percentage of the combined voting power		5%
Threshold percentage on the fair market value		85%
Maximum percentage of the qualified compensation		15%
Annual limit		$ 25,000
Number of additional shares	3,778,000

Stock Based Compensation - Summ

Stock Based Compensation - Summary of option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Weighted-average Remaining Contractual Term (in years)
Cash received from options exercised	$ 220	$ 818
Aggregate intrinsic value of exercisable option	14,121
Aggregate intrinsic value of exercised options	$ 70,115
2014 and 2021 Equity Incentive Plan
Number of Shares
Outstanding at beginning of period	25,998,172	34,407,949
Granted	5,176,889	1,730,564
Exercised	(2,490,275)	(8,428,524)
Forfeited or expired	(4,420,770)	(1,711,817)
Outstanding at end of period	24,264,016	25,998,172	34,407,949
Exercisable	16,662,487	18,202,064
Weighted-average Exercise Price
Outstanding at beginning of period	$ 2.60	$ 1.86
Granted	2.75	7.19
Exercised	0.09	0.10
Forfeited or expired	3.38	4.64
Outstanding at end of period	2.53	2.60	$ 1.86
Exercisable	$ 1.99	$ 1.19
Weighted-average Remaining Contractual Term (in years)
Weighted average remaining contractual term	7 years 10 days	6 years 3 months 21 days	6 years 11 months 23 days
Exercisable	4 years 10 months 13 days	5 years 1 month 20 days
2014 Plan
Number of Shares
Outstanding at beginning of period	24,766,176
Outstanding at end of period	24,264,016	24,766,176
Weighted-average Remaining Contractual Term (in years)
Cash received from options exercised	$ 220		$ 818

Basic and Diluted Loss Per Sh_3

Basic and Diluted Loss Per Share - Schedule of reconciliation of basic weighted average common shares outstanding to diluted weighted average shares outstanding (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Basic and Diluted Loss Per Share
Net income (loss) attributable to common stockholders	$ (65,549)	$ (9,555)
Weighted average shares outstanding - basic	178,006,919	174,374,386
Weighted average shares outstanding - diluted	178,006,919	174,374,386
Basic loss per share	$ (0.37)	$ (0.05)
Diluted loss per share	$ (0.37)	$ (0.05)

Basic and Diluted Loss Per Sh_4

Basic and Diluted Loss Per Share - Schedule of potentially dilutive securities excluded from the diluted loss per share calculation (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Earnings (Loss) Per Share
Total potentially dilutive securities	48,756,467	46,403,955
Warrants
Earnings (Loss) Per Share
Total potentially dilutive securities	19,333,303	19,333,303
2014 Plan & 2021 Plan - Stock Options
Earnings (Loss) Per Share
Total potentially dilutive securities	25,877,631	26,328,279
2021 Plan - RSUs
Earnings (Loss) Per Share
Total potentially dilutive securities	3,477,809	710,385
ESPP - Common Stock
Earnings (Loss) Per Share
Total potentially dilutive securities	67,724	26,589
Contingently Issued Shares of Common Stock
Earnings (Loss) Per Share
Total potentially dilutive securities		5,399

Leases - Components of lease (D

Leases - Components of lease (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Sep. 01, 2021
Leases
Operating lease renewal term (in years)		5 years	5 years
Finance lease costs:
Amortization of right-of-use assets	$ 197	$ 92
Interest on lease liabilities	53	28
Operating lease costs	1,160	850
Total lease expense	$ 1,410	$ 970

Leases - Components of suppleme

Leases - Components of supplemental cash flow information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Leases
Operating outgoing cash flows - finance lease	$ 54	$ 24
Financing outgoing cash flows - finance lease	308	142
Operating outgoing cash flows - operating lease	1,138	568
Right-of-use assets obtained in exchange for new finance lease liabilities:	$ 345	1,014
Right-of-use assets obtained in exchange for new operating lease liabilities:		$ 8,947

Leases - Lease term and discoun

Leases - Lease term and discount rate (Details)	Dec. 31, 2023
Leases
Weighted-average remaining lease term - finance lease (in years)	2 years 10 months 2 days
Weighted-average discount rate - finance lease	6.50%
Weighted-average remaining lease term - operating lease (in years)	9 years 2 months 19 days
Weighted-average discount rate - operating lease	6.90%

Leases - Schedule of future min

Leases - Schedule of future minimum payments (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Finance Lease
2024	$ 425
2025	310
2026	179
2027	85
2028	16
Total	1,015
Less present value discount	85
Total lease liabilities	930
Operating Lease
2024	1,173
2025	1,210
2026	1,248
2027	1,288
2028	1,329
Thereafter	5,242
Total	11,490
Less present value discount	2,868
Total lease liabilities	$ 8,622

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Related Party Transactions
Revenue from Related Parties	$ 17,410	$ 11,789
Deferred revenue	1	50
BMW
Related Party Transactions
Revenue subject to achieving certain milestones	20,000
Revenue from Related Parties	12,700	2,000
Deferred revenue	$ 828	$ 4,000

Retirement Plans (Details)

Retirement Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Retirement Plans
Contributions to the plan	$ 977	$ 802

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Current income tax (benefit) expense:
State	$ 2
Deferred income tax (benefit) expense:
Federal		$ (195)
State		(32)
Total income tax (benefit) expense	$ 2	$ (227)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of the statutory federal income tax expense (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Effective Tax Rate
Income tax expense at the federal statutory rate	21%	21%
State income taxes - net of federal income tax benefits	1.42%	13.07%
Permanent Differences	(1.07%)	(3.14%)
Permanent Differences - Fair Value Adjustments- Warrant Liability	1.63%	66.21%
Permanent Differences - Fair Value Adjustments- Marketable Securities		(5.13%)
Prior year provision to return	(0.26%)	0.03%
Net change in valuation allowance	(25.54%)	(104.28%)
Research and Development	2.62%	13.65%
Other	0.20%	0.33%
Total income tax (benefit)	0%	1.75%

Income Taxes - Deferred income

Income Taxes - Deferred income tax assets and liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss	$ 30,534	$ 17,962
R&D Credit	3,557	1,908
Stock compensation	3,333	1,991
Section 174 Capitalization	9,406	5,731
ROU Lease Liability	2,332	2,459
Other	1,204	748
Total income tax expense (benefit)	50,491	30,799
Valuation allowance	(44,109)	(28,030)
Net deferred tax assets:	6,382	2,769
Deferred tax liabilities:
Intangibles (non-goodwill)	(1)	(1)
Property and equipment	(797)	(652)
ROU Asset	(2,233)	(2,116)
Total deferred tax liabilities	$ (6,382)	$ (2,769)

Income Taxes- Additional inform

Income Taxes- Additional information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 30, 2023
Income Taxes
Increase in valuation allowance	$ 16,079
Federal net operating loss carryovers	$ 129,729	$ 73,367
Percentage of offset on taxable income for Federal net operating loss carryovers	80%
Uncertain tax benefits	$ 1,186	$ 636	$ 0
Accrued interest or penalties related to uncertain tax positions	$ 0
Effective tax rate	0%	1.75%

Income Taxes - Unrecognized tax

Income Taxes - Unrecognized tax benefits (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Unrecognized tax benefits
Balance, beginning of year	$ 636
Gross increases related to prior period tax position	212
Gross increases related to current period tax position	338
Balance, end of year	$ 1,186

Subsequent Events (Details) (Im

Subsequent Events (Details) (Imported) $ in Thousands		12 Months Ended
	Jan. 10, 2024 USD ($) item installment T	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Jan. 23, 2024 USD ($)
Subsequent Events
Revenue		$ 17,410	$ 11,789
Subsequent Event [Member]
Subsequent Events
Amount of common stock repurchased				$ 50,000
Subsequent Event [Member] | Related Party | SK On Co., Ltd. | Electrolyte Supply Agreement
Subsequent Events
Revenue subject to achieving certain milestones	$ 20,000
Subsequent Event [Member] | Related Party | SK On Co., Ltd. | Line Installation Agreement
Subsequent Events
Collaboration arrangement payments to be received	$ 22,300
Number of installments | installment	3
Subsequent Event [Member] | Related Party | SK On Co., Ltd. | Minimum | Electrolyte Supply Agreement | Electrolyte
Subsequent Events
No of metric tons | T	8
Subsequent Event [Member] | Related Party | SK On Co., Ltd. | Minimum | Line Installation Agreement
Subsequent Events
Pilot cell production line capable of producing cells (in Ah) | item	60
Subsequent Event [Member] | Related Party | SK On Co., Ltd. | Maximum | Line Installation Agreement
Subsequent Events
Pilot cell production line capable of producing cells (in Ah) | item	100
Subsequent Event [Member] | Related Party | SK On Co., Ltd. | Forecast | Minimum | Electrolyte Supply Agreement | Electrolyte
Subsequent Events
Revenue	$ 10,000

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pay vs Performance Disclosure
Net Income (Loss)	$ (65,549)	$ (9,555)

Insider Trading Arrangements

Insider Trading Arrangements - Derek Johnson	3 Months Ended
	Dec. 31, 2023 shares
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	During the quarter ended December 31, 2023, the following directors or officers (as defined in Rule 16a-1(f) of the Exchange Act) adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” each as defined in Item 408(c) of Regulation S-K: ​ ​ ​ ​ ​ ​ ​ Trading Arrangement Aggregate Number ​ ​ ​ Date of Rule Non-Rule of Securities to be Expiration Name and Title Action Action 10b5-1 (1) 10b5-1 Purchased or Sold Date Derek Johnson Chief Operating Officer Termination 11/21/2023 ☒ ☐ Up to 954,594 shares of common stock to be sold 8/30/2024 ​ (1)
Name	Derek Johnson
Title	Chief Operating Officer
Rule 10b5-1 Arrangement Terminated	true
Non-Rule 10b5-1 Arrangement Terminated	false
Termination Date	11/21/2023
Aggregate Available	954,594
Expiration Date	8/30/2024