Solid-state battery unicorn accused of using ‘shell-swapping’ trick

At CES 2026 in January in Las Vegas (USA), Marko Lehtimäki, CEO of Donut Lab, attracted attention when he confirmed the successful development of solid-state batteries. According to advertising, the battery reaches an ultra-high energy density of 400 Wh/kg, has a lifespan of 100,000 charging cycles and takes less than 10 minutes to fully charge. This achievement is considered to surpass the battery industry’s giants, helping Donut Lab’s valuation quickly reach the 1.25 billion USD mark.

However, on June 8, Ryan Inis Hughes, owner of the YouTube channel Ziroth, announced the results of an investigation he conducted in collaboration with more than 20 battery experts from the Fraunhofer Research Institute and many major universities, which confirmed that Donut Lab’s solid-state battery actually has a regular lithium-ion core.

Theo The VergeDonut Lab once provided test results from VTT Research Center (Finland). However, experts analyzed the data and noticed two suspicious signs. First, during the charging process, Donut Lab’s battery maintains a stable voltage level at 3.7-3.8V – the typical operating range of lithium-ion using NCM chemistry with high nickel content. Next, when charging to 50-70%, the battery shows a fracture on the elasticity graph due to the ions rearranging at the anode – a phenomenon that occurs on regular lithium-ion batteries.

Besides, the actual energy density measured by experts reached a maximum of 298 Wh/kg, reaching the upper limit of current battery technology and far below the 400 Wh/kg level announced by the company.

Donut Lab is said to buy the batteries from German company CT Coatings. Despite promising to supply Donut Lab with sodium-based solid-state batteries using screen printing technology, CT Coatings only delivered one batch of lithium-ion batteries. Leaked emails show that Donut Lab repeatedly asked partners to provide technology proof but received no response. However, the Finnish startup continues to advertise falsely.

Donut Lab representatives have not yet spoken, while the Finnish financial management agency and police are investigating.

Theo CNetbefore Hughes, a number of sites specializing in tracking the electric vehicle and battery sectors also expressed skepticism, such as Electrek. In April, this page posted accusations that Donut Lab was a scam. They also published an article in January with the headline that in a few months CEO Marko Lehtimäki will be proven to be “a world changer or a fool”.

Instead of using liquid electrolytes like traditional batteries, solid-state batteries use solid or gel electrolytes, providing higher energy density, meaning greater capacity in the same physical area, as well as superior longevity and greater safety. While lithium-ion batteries degrade after 300-500 charging cycles, the solid-state battery models being tested retain 80% of their capacity after 1,000 charges.

Many large companies are pursuing this technology, such as Toyota, Samsung, Honda, Nissan… but most set a roadmap for deployment in 2027-2029. The reason is that the battery works well in the lab, but producing millions of identical battery cells will require more testing time.