Donut Lab hits 409 Wh/kg in battery lab test, but credibility is gone

Donut Lab has published a new independent test claiming its battery reached an energy density of 409 Wh/kg and 805 Wh/L, the first energy-density figure the company has put on record after months of scrutiny.

But the number lands against a promise the company has already broken: that this “solid-state” cell was in production and ready to power a production EV by the end of Q1 2026. It isn’t, and it wasn’t.

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