VTT test confirms Donut Lab cells hit 110% capacity in extreme heat

Finnish startup Donut Lab has released independent test results from the VTT Technical Research Centre of Finland, demonstrating that its solid-state battery performs exceptionally well under extreme heat conditions. Unlike traditional lithium-ion batteries, which typically degrade or face safety risks above 60–70°C (140–158°F), Donut Lab’s battery maintained high capacity and efficiency at 80°C (176°F) and 100°C (212°F). Specifically, the battery delivered about 110% of its rated capacity at 176°F and around 107% at 212°F, with no visible damage and stable recharge performance. This resilience is attributed to the battery’s design, which excludes flammable liquid electrolytes, allowing for a higher maximum operating temperature and enhanced safety. These results come amid skepticism from industry experts and competitors who questioned Donut Lab’s earlier claims of breakthrough performance and production readiness, with some labeling the technology as potentially overstated. In response, Donut Lab has shifted its approach by commissioning and publicly