| Document and Entity Information | Nov. 16, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | QuantumScape Corp |
| Amendment Flag | false |
| Entity Central Index Key | 0001811414 |
| Document Type | 8-K |
| Document Period End Date | Nov. 16, 2021 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-39345 |
| Entity Tax Identification Number | 85-0796578 |
| Entity Address, Address Line One | 1730 Technology Drive |
| Entity Address, City or Town | San Jose |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 95110 |
| City Area Code | (408) |
| Local Phone Number | 452-2000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Class A common stock, par value $0.0001 per share |
| Trading Symbol | QS |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
