Finnish startup Donut Lab has released new test results demonstrating its solid-state battery’s exceptional performance under extreme heat conditions. Conducted by VTT Technical Research Centre of Finland, the tests show the battery not only functions at temperatures up to 100°C (212°F) but increases in capacity as temperatures rise. This contrasts sharply with conventional lithium-ion batteries, which degrade or even catch fire under similar conditions.
Heat Tolerance: A Key Advantage
The tests compared the battery’s performance at room temperature (20°C), 80°C (“high heat”), and 100°C (“extreme heat”). The 3.6V/26 Amp-hour solid-state cell delivered 24.9Ah at room temperature. However, at 80°C, it outputted 27.5Ah—a 110.5% improvement—and at 100°C, it reached 27.6Ah (107.1% of room temperature performance). While the outer pouch lost its vacuum seal due to the heat, the battery remained functional and rechargeable.
This is a significant development. Traditional lithium-ion batteries rely on liquid electrolytes, which become unstable and flammable at high temperatures. This instability leads to “thermal runaway,” a dangerous chain reaction that can result in fires. Solid-state batteries, by contrast, use a “dry” conductive material that eliminates this risk.
The Promise of Solid-State Technology
Solid-state batteries have long been considered the “holy grail” of battery technology. They offer several advantages over liquid-based lithium-ion: faster charging, improved performance in extreme temperatures, and greater energy density. This could translate to electric vehicles with longer ranges, quicker refueling times, and enhanced safety.
The key is the solid electrolyte. As temperatures rise, the solid material’s internal resistance decreases, allowing ions to move more freely, thus increasing capacity. This is precisely what VTT’s tests demonstrated.
Remaining Questions and Future Tests
While these results are promising, some questions remain. VTT did not independently verify Donut Lab’s battery chemistry, taking it at face value. Additionally, the tests did not address the “dendrite issue” — microscopic growths within the battery that can cause electrical shorts over time.
Donut Lab has acknowledged these concerns and is planning further independent testing to address them, as part of its ongoing “I Donut Believe” series. The next phase of testing will be critical in establishing the long-term reliability and scalability of this technology.
Ultimately, Donut Lab’s latest findings underscore the potential of solid-state batteries to overcome the limitations of current lithium-ion technology, but further verification is needed before widespread adoption.
