Donut Lab has released the first independent measurement results for its serially producible solid-state battery, confirming rapid charging performance under challenging conditions. The tests, conducted by the Technology Research Centre VTT, assessed charging speed and thermal behavior in a worst-case scenario without active temperature control. (VTT validation report, PDF)
Two passive cooling setups were evaluated: one using two lightly compressed aluminum cooling plates around the cell, and another with a single bottom plate. After an initial discharge capacity test at a standard 1C rate, the team performed rapid charging at 5C (equivalent to a full charge in roughly 12 minutes) and 11C (approximately a 5–6 minute full charge). By comparison, conventional lithium-ion batteries typically rely on active cooling and charge between 1C and 3C.
At the 5C rate, the Donut Battery reached 80% state of charge in about 9.5 minutes and fully charged in just over 12 minutes. Post-charge discharge tests confirmed 100% of the stored capacity was recoverable. For the more aggressive 11C rate, the cell achieved 80% charge in 4.5 minutes and 100% in just over seven minutes, with 98.4% to 99.6% capacity available upon discharge.
Although these tests did not replicate the exact conditions inside a complete battery pack, the results highlight key advantages for pack integration. The cell’s tolerance for high charging rates without active cooling or high compressive forces can simplify pack architecture and reduce system complexity.
Donut Lab CTO Ville Piippo noted that, unlike other solid state designs requiring significant compression and experiencing large volume changes during cycling, the Donut Battery operates effectively with minimal external pressure and passive cooling. He added that this configuration supports more cost-efficient pack structures while delivering higher energy and power density than traditional lithium-ion cells.
The full measurement report is available on Donut Lab’s I Donut Believe website.
