Donut Lab has released independent test results demonstrating that its solid-state battery can operate at extreme temperatures [1].
The results aim to validate the company's claims of a production-ready battery after significant industry skepticism followed its announcements at CES 2026 [2]. Proving the safety and performance of solid-state technology is a critical hurdle for the electric vehicle industry, which seeks alternatives to volatile liquid electrolytes.
Data from independent labs, including VTT in Finland, show the 26-Ah cell [3] can discharge at temperatures up to 100°C [1]. According to the reports, the battery actually gained capacity during this high-temperature process [1].
Further tests focused on charge retention over time. Donut Lab said the data shows its battery retains 97.7% [4] of its charge after 10 days, representing a loss of only 2.3% [4]. These figures are intended to address doubts regarding the stability of the company's chemical architecture.
Despite these releases, some industry analysts remain cautious. While the company has provided data on safety and heat, it has not yet provided proof regarding energy density or cycle life [5]. This lack of transparency has led some to describe the company's position as being on the defensive [2].
Donut Lab said the company claimed a commercial breakthrough that has eluded the industry [6]. The company continues to release results over several weeks to counter the narrative that its claims are unsubstantiated [2].
“The battery actually gained capacity in the process of discharging at 100°C.”
The release of safety data from VTT provides a necessary baseline of credibility for Donut Lab, but it does not solve the company's primary problem. In the battery industry, safety and thermal stability are essential, but energy density and cycle life are the metrics that determine commercial viability. Until Donut Lab provides verified data on how much energy the cells hold and how many times they can be charged before degrading, the industry will likely view these safety wins as incomplete evidence of a breakthrough.
