Finland's VTT research institute recently released independent test results for a solid-state battery developed by Donut Lab [1, 2].

These results are critical because solid-state technology promises to replace liquid electrolytes, potentially solving safety and range issues for electric vehicles. However, the data from VTT has raised questions regarding the battery's actual performance and the validity of the company's claims [1, 2].

According to the testing data, the battery achieves an energy density of 400 Wh/kg [1]. This metric is a primary indicator of how much energy a battery can hold relative to its weight. The tests also indicated that the battery can charge fully in five minutes [1, 2].

Further testing focused on the battery's ability to hold a charge over time. The battery demonstrated 97.7% retention over a period of 10 days during self-discharge testing [3]. This suggests a high level of stability when the battery is not in use.

Despite these figures, the independent verification by VTT, Finland's largest research institute, has prompted a closer look at the technology [1, 2]. While the numbers appear promising, the discrepancy between lab results and real-world application often creates skepticism in the energy sector. Donut Lab has not provided a detailed response to the specific concerns raised by the data released this month [1, 2].

Industry experts continue to monitor the development of these cells as they move toward potential commercialization. The ability to maintain high energy density while reducing charge time remains the central goal for the next generation of transport [1].

“The battery achieves an energy density of 400 Wh/kg.”

The gap between laboratory benchmarks and mass-market viability is the primary hurdle for solid-state batteries. While 400 Wh/kg and five-minute charging are industry-leading figures, the scrutiny from VTT suggests that achieving these metrics consistently at scale remains unproven. If Donut Lab cannot reconcile these test results with sustainable manufacturing, the technology may remain a prototype rather than a commercial reality.