# Donut Lab solid-state battery testing

> Live situation record from CLSTR: https://clstr.news/situations/donut-lab-solid-state-battery-testing
> Updated: 2026-09-05T07:00:00.000Z. Sources: 4. Developments: 2.

Donut Lab released independent test results from the Finnish research center VTT regarding its solid-state battery technology. The tests on a single pouch cell, designated as ‘Donut Battery V1.5’ or DL6, reported a gravimetric energy density of 409.3 Wh/kg and a volumetric energy density of 804.7 Wh/l.

CEO Marko Lehtimäki stated that the results demonstrate the potential of their technology, and the company is now focusing on manufacturing next-generation cells to scale production to an industrial level. 

However, the findings have drawn skepticism from battery experts. Critics noted that the test utilized an optimized scenario with a low discharge rate of 0.1 C, which favors higher readings. Additionally, experts questioned the consistency of the testing methodology, pointing out that the V1.5 cell tested differs from those used in previous measurements.

## Timeline

### 2026-09-05: Donut Lab reports 409 Wh/kg energy density for solid-state battery

Donut Lab reported a 409 Wh/kg energy density for its solid-state battery via VTT testing, though experts express skepticism regarding the consistency of the tested cell versions.

2 sources. https://clstr.news/cluster/donut-lab-reports-409-whkg-energy-density-for-solid-state-battery

### 2026-09-02: Donut Lab reports 409 Wh/kg energy density in independent battery test

Finnish company Donut Lab reported that its DL6 battery cell achieved an energy density of 409.3 Wh/kg in independent testing by VTT, though questions remain regarding mass-production readiness.

2 sources. https://clstr.news/cluster/donut-lab-reports-409-whkg-energy-density-in-independent-battery-test

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Cite as: Donut Lab solid-state battery testing. CLSTR, https://clstr.news/situations/donut-lab-solid-state-battery-testing