Donut Lab reports 409 Wh/kg energy density for solid-state battery

Donut Lab has released results from a measurement test conducted by VTT regarding its solid-state battery. The test identified an energy density of 409 Wh/kg for the pouch cell, designated as DL6 or Donut Battery V1.5. This figure aligns with claims previously made by the company at the CES 2026 event.

CEO Marko Lehtimäki stated that these results demonstrate the potential of their technology and that the company is now focused on manufacturing next-generation cells to scale production to an industrial level. The company also noted previous testing by Intertek regarding the bipolar structure of its batteries.

However, the results have met with skepticism from battery experts. Critics have pointed out that the cell tested (V1.5) is different from those used in previous spring measurements. Some experts have questioned the consistency of the testing methodology, comparing the situation to measuring a car's top speed with one vehicle while measuring fuel consumption and crash safety with others.