Donut Lab claims a solid-state battery breakthrough, but experts remain sceptical

Startup says its batteries will enter production this year, but experts doubt some of the claimed specifications

Finnish start-up Donut Lab has announced what it calls a breakthrough in solid-state batteries - often described as the “holy grail” of battery technology because of their high energy density, long service life and potential for rapid charging. Donut Lab, a spin-off from Verge Motorcycles, says its batteries will move into production as early as this year.

Why specialists remain sceptical about Donut Lab’s solid-state batteries

Industry observers and researchers have questioned the claims, largely because the company does not have a widely recognised research base and has not published scientific data. Even so, Donut Lab has released the results of independent testing carried out by Finland’s leading state research and technology organisation (VTT Technical Research Centre of Finland). According to those tests, the batteries meet the stated performance figures: an energy density of 400 Wh/kg, charging in 5 minutes, a lifespan of up to 100,000 cycles, and tolerance of temperatures from -30 to 100 °C. The batteries are also said to contain no rare-earth elements and no flammable liquid electrolytes.

Open questions: chemistry, density and longevity

Despite the test results, several critical parameters - including the precise chemistry, the claimed density and the promised lifespan - are still viewed as unproven. During thermal testing, Donut Lab’s cells reportedly suffered issues with vacuum sealing, raising doubts about how robust the approach is in practice. Experts, including those in the scientific community, also point out a long-standing challenge for solid-state batteries: dendrite formation - metallic cracks that can trigger a short circuit.

China’s parallel push towards solid-state battery production

While Donut Lab says it is continuing work to address shortcomings, solid-state battery development is also accelerating in China. CATL has recently filed a patent for batteries with an energy density of 500 Wh/kg and says it intends to begin small-scale production in 2027. Other Chinese companies, including FAW, have likewise stated they are ready to integrate their batteries into electric cars.

Donut Lab argues that “its technology poses a threat to major market players”. The company’s chief executive, Marko Lehtimäki, said that resistance from the industry would only intensify, even in the face of proof. Donut Lab has also announced a second version of the battery that it describes as more production-ready, with deliveries to customers set to begin at the end of the year.