Donut Lab Just Turned Up the Heat on Solid-State Battery Expectations, and the Results are Surprising

Donut Lab, a Finnish company, recently released some impressive test data demonstrating how their solid-state battery handles extreme temperatures that conventional lithium-ion cells would struggle to deal with. The test results come from a series of measurements conducted by the VTT Technical Research Centre of Finland, a respected, government-backed research organization. They needed to figure out precisely how high the heat could reach before this Donut Lab cell, rated at 3.6 volts and 26 amp-hours, blew up in smoke (or some other way), so they decided to put it through its paces.

The engineers first established a baseline at a comfortable 20°C, at which point the cell delivered 24.9 amp-hours of capacity during a standard 1C discharge (or, to put it another way, the cell was chucking out a whopping 24 amps in one hour), but then they ramped up the temperature to 80°C, or ‘high heat’ to you and me, and discharged the cell again at the same rate. To their surprise, the cell managed to muster 27.5 amp-hours, which is around 110.5% of what it could manage at ambient temperature, and then outperformed that at 100°C (though at a lower 0.5C rate of 12 amps to keep things stable). There, the cell produced 27.6 amp-hours, or 107.1% of the beginning amount.

The clear upshot of all of this is that when the temperature increased, the internal resistance in the solid electrolyte decreased, allowing the ions to move about more freely, which increased the battery’s useful energy output significantly. After both high discharges, they returned the cell to ambient temperature and recharged it normally; fortunately, no permanent damage was discovered from the electrical angle. Not so good news: at 100°C, the pouch cell lost its vacuum seal, most likely owing to gas buildup or material weakening, although it still functioned properly.

Conventional lithium-ion batteries use liquid electrolytes that become wobbly when temperatures rise above 60-70°C, causing a variety of problems such as vaporisation, swelling, rapid degradation, and, in the worst-case scenario, the dreaded thermal runaway, in which the cell becomes so hot that it is essentially a fire waiting to happen. Solid-state designs replace the liquid with a non-flammable solid, which, for obvious reasons, eliminates the source of all the problems. Donut Lab’s version appears to be capitalising on this advantage, transforming what would be a major issue for other batteries into a little but significant benefit.

This test adds to the evidence Donut Lab is using to support the claim that their battery technology is suitable for use in the real world. Donut Lab unveiled their Donut Battery as the first all-solid-state battery pack ready for cars at CES 2026, and it wasn’t just a pipe dream, as they claimed some pretty impressive numbers, including 400 watt-hours per kilogram energy density, full charges in 5 minutes, and a mind-boggling 100,000 cycles with almost no fade. The cells are really powering various Verge Motorcycles models that will hit the road this quarter, with the boast that they can hold more than 99% of capacity from -30°C to 100°C.