Donut Lab's 'solid-state' battery exposed as regular li-ion in damning investigation
Electrek
Last updated: June 9, 2026
An extensive investigation by battery researcher Ziroth, involving over 20 independent experts, has concluded that Donut Lab’s claimed "miracle" solid-state battery is, in fact, a standard lithium-ion cell. The company had raised approximately $25 million from over 1,300 investors based on these unproven assertions.
- The investigation traces Donut Lab’s technology to a German company, CT Coatings, and reveals a complex network of entities operating under strict non-disclosure agreements. Electrochemical data, including voltage curves and cell expansion patterns, conclusively identifies the tested cell as lithium-ion, contradicting Donut Lab's claims of revolutionary sodium-ion solid-state chemistry.
- Key evidence includes voltage curves matching high-nickel lithium-ion cells (NCM chemistry) and cell expansion data exhibiting a characteristic "kink" around 50-70% state of charge, a signature of a graphite anode used in lithium-ion batteries. This kink is impossible with sodium ions, which are too large for graphite layers.
- The identified energy density is approximately 298 Wh/kg, consistent with good lithium-ion cells, not the 400 Wh/kg claimed. The technology originated from CT Coatings, which promised a screen-printed sodium-ion solid-state battery but delivered a lithium-ion pouch cell.
- Donut Lab also made misleading claims about vehicle production, presenting pre-production vehicles as customer-ready and admitting the cells used were not the promised 400 Wh/kg ones. The company raised funds from numerous small investors, potentially by circumventing the rigorous technical scrutiny expected from venture capital firms. Finnish financial and criminal authorities are reportedly investigating.
