Idemitsu Kosan Co.,Ltd. (Tokyo) has decided to construct a large-scale production facility for lithium-sulfide (Li2S), a material used in all-solid-state lithium-ion rechargeable batteries. The company will expand production capacity of lithium sulfide, an important intermediate raw material for solid electrolytes, to the world’s top class level (equivalent to 3 GWh/year of storage batteries) and establish an integrated value chain from raw materials to intermediate materials and products. Idemitsu will steadily meet the needs of automakers and battery manufacturers, aiming to
commercialize all-solid-state batteries in 2027 and 2028, and work to accelerate the commercialization of solid electrolytes.
The planned construction site for the Li2S large-scale facility is within the premises of the compant’s Chiba Complex (Ichihara City, Chiba Prefecture), with construction scheduled to be completed in June 2027. This initiative has been approved by the Ministry of Economy, Trade and Industry as a “plan for
ensuring supply of storage batteries,” and of the total project cost of approximately 21.3 billion yen, approximately 7.1 billion yen is planned as the maximum grant amount.
Idemitsu will accelerate mass production of solid electrolytes with lithium sulfide produced by this facility as the base material and widely deliver high-performance solid electrolytes to various customers. This will contribute to the government’s policy of strengthening the storage battery supply chain and improving the competitiveness of Japan’s storage battery industry.
Rendering of the new Li2S facility (Source: Idemitsu Kosan)
Compared to conventional liquid batteries, all-solid-state batteries have a solid electrolyte, which allows ions to move faster. EVs equipped with all-solid-state batteries are expected to have the potential to further reduce charging time and increase power output. In addition, because they are resistant to high voltage and high temperature, all-solid-state batteries are expected to improve energy density and lengthen service life. With a view to the commercialization of all-solid-state batteries in 2027 to 28, Idemitsu is promoting the development of solid electrolytes, an essential material for all-solid-state batteries, and the establishment of a mass production system. Currently, two small-scale verification facilities are in operation, and following these, the basic design of a large pilot facility was started in October 2024.
Lithium sulfide is an important intermediate raw material for solid electrolytes, which are produced from sulfur components generated as a byproduct in the manufacturing process of petroleum products. Among the first to discover the usefulness of the sulfur component, Idemitsu established mass production technology for lithium sulfide in 1994. Taking advantage of know-how gained through years of handling sulfur components, which are difficult to handle, and a proprietary technology for producing high-purity lithium sulfide, the company plans to conduct world-scale
mass production at the new Li2S facility.
The mass production of lithium sulfide is a major step toward commercializing solid electrolytes.