Finnish startup Donut Lab just silenced its critics. The company released independent test results proving its controversial solid-state battery is exactly what it claims to be - not a supercapacitor masquerading as breakthrough energy storage. The validation, conducted by state-owned research firm VTT, comes months after skeptics questioned whether Donut Lab's ultra-fast charging technology was actually a fundamentally different, less powerful storage device. For a startup trying to crack the notoriously difficult solid-state battery market, the results couldn't come at a better time.
Donut Lab is fighting back against skeptics with hard data. The Finnish battery startup just published independent test results from VTT, Finland's state-owned technical research center, that definitively prove its solid-state battery isn't actually a supercapacitor in disguise. The distinction matters enormously - and not just for Donut Lab's credibility.
When the company first announced its solid-state battery technology earlier this year, the claims raised eyebrows across the energy storage industry. Ultra-fast charging times that seemed too good to be true sparked immediate speculation on YouTube and in industry circles that Donut Lab might have accidentally - or intentionally - conflated supercapacitor technology with battery chemistry. The two technologies share some superficial similarities, particularly around rapid charge and discharge cycles, but they're fundamentally different animals.
Supercapacitors excel at delivering quick bursts of power and can charge in seconds, but they store dramatically less energy than batteries and lose their charge relatively quickly. Batteries, especially solid-state versions, promise much higher energy density and can maintain their charge for extended periods - exactly what electric vehicles and grid storage applications desperately need. If Donut Lab's technology was actually a supercapacitor, it would be essentially useless for the applications the startup is targeting.
The VTT testing protocol specifically examined the electrochemical behavior of Donut Lab's cells to distinguish between capacitive and battery storage mechanisms. According to the technical report, the Finnish research institute analyzed charge-discharge curves, impedance spectroscopy data, and long-term energy retention characteristics. The results show energy storage behavior consistent with lithium-ion battery chemistry, not the rapid voltage decay and low energy density typical of supercapacitors.
