| Document And Entity Information | Feb. 27, 2023 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Feb. 27, 2023 |
| Entity Registrant Name | QuantumScape Corporation |
| Entity Central Index Key | 0001811414 |
| Entity Emerging Growth Company | false |
| Securities Act File Number | 001-39345 |
| Entity Incorporation, State or Country Code | DE |
| 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 |
| Entity Information, Former Legal or Registered Name | Not applicable |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Class A Common Stock, par value $0.0001 per share |
| Trading Symbol | QS |
| Security Exchange Name | NYSE |
