Idemitsu Kosan Builds World’s First Sulfide Solid-State Electrolyte Plant to Support Toyota’s 2027 Mass Production of All-Solid-State Battery EVs

Japanese petroleum giant Idemitsu Kosan has recently begun construction of the world’s first large-scale pilot plant for sulfide-based solid-state electrolytes in Chiba Prefecture. The project, with a total investment of approximately 21.3 billion yen, is expected to commence operations by the end of 2027 and achieve an annual production capacity of several hundred tons. The facility will supply critical materials for Toyota’s all-solid-state battery electric vehicles slated for launch between 2027 and 2028. Toyota and Idemitsu have collaborated on sulfide electrolyte research since 2013. In 2023, they officially launched joint development efforts aimed at mass production, having already validated the technology through two small-scale demonstration plants. The sulfide-based approach is considered a leading candidate for commercialization due to its excellent flexibility, strong adhesion to electrodes, and ionic conductivity approaching that of liquid electrolytes. Idemitsu leverages sulfur—a byproduct of petroleum refining—as a raw material, giving it a significant cost advantage. Toyota’s all-solid-state batteries have achieved a laboratory-level energy density of 450 Wh/kg—two to three times that of conventional lithium-ion batteries—enabling over 1,200 kilometers of driving range, 80% fast charging in just 10 minutes, and enhanced safety with no flammable liquid electrolyte, passing nail penetration tests without ignition. Toyota aims to achieve price parity between solid-state and conventional liquid-electrolyte batteries by 2027–2028.