In early 2026, Finnish startup Donut Lab claimed at the CES exhibition to have launched the world’s first mass-producible all-solid-state battery, touting an energy density of 400 Wh/kg, 80% charge in five minutes, a cycle life of 100,000 cycles, and a cost lower than that of liquid electrolyte batteries. However, five months later, multiple independent tests conducted by VTT Technical Research Centre of Finland revealed that the actual measured energy density was only 298 Wh/kg, and the demonstrated product was confirmed to be a conventional lithium-ion battery—not an all-solid-state battery. Finnish financial regulators and criminal investigation authorities have now fully launched an investigation. The company's shareholder structure shows that over 900 of its more than 1,300 investors are retail investors, each investing between $3,000 and $23,000, mostly lured by promises of up to 10x returns within 12 to 18 months. CEO Marko Lehtimäki repeatedly assured investors, “It’s not too late to get in now.” The investigation also uncovered that Donut Lab’s purported contract manufacturer, Germany-based CT Coatings, primarily produces screen-printed paving stones and menu holders and lacks any capability for solid-state battery R&D or manufacturing. Industry experts had questioned the company’s technical claims from the outset, with executives from established battery firms pointing out clear contradictions in the data that violate fundamental electrochemical principles. Meanwhile, numerous global companies continue advancing solid-state battery development: CATL plans to begin pilot production of all-solid-state batteries in Q3 2026; BYD’s sulfide-based all-solid-state battery has already passed China Automotive Technology & Research Center (CATARC) automotive-grade validation; Gotion High-Tech has unveiled its “Golden Stone” all-solid-state battery with an energy density exceeding 420 Wh/kg; Toyota aims to achieve mass production in 2026; and U.S.-based Factorial Energy went public on Nasdaq in June 2026, backed by investments from multiple automakers. Currently, mainstream solid-state battery technologies—including sulfide, oxide, and polymer electrolytes—all face technical hurdles such as material instability, interfacial impedance, or operating temperature constraints. Core materials like lithium sulfide remain prohibitively expensive, and industrialization is still transitioning from laboratory research to pilot-scale production.