Idemitsu Kosan is constructing a lithium sulphide plant in Japan to produce the intermediate raw material for solid-state battery electrolytes. The plant should be operational in June 2027. While the Japanese energy company is cooperating with Toyota to develop solid-state batteries, it also aims to also supply “various customers” in mass production.
The plant will be located within Idemitsu Kosan’s existing Chiba Complex and will be referred to as a “Li2S large-scale facility.” The company currently has two small-scale verification facilities in operation. The expansion has been approved and partially funded by the Japanese Ministry of Economy, Trade and Industry. The total project cost is approximately 21.3 billion yen, while the government grant is 7.1 billion yen (approximately 45 million euros).
Idemitsu Kosan says it will establish an integrated value chain from raw materials to intermediate materials and products, expanding its production capacity of lithium sulphide to “world-class levels (equivalent to 3 GWh/year of storage batteries)”. The aim is to “meet the needs of automakers and battery manufacturers” and commercialize all-solid-state batteries from 2027 to 2028, accelerating the commercialization of solid electrolytes.
While Idemitsu Kosan is cooperating with Toyota to develop solid-state batteries, Idemitsu says it aims to supply high-performance solid electrolytes on a large scale “to various customers.” Three technology paths are emerging for solid-state batteries: with metal oxides, metal sulphides or polymers as the solid electrolyte. Some major players, such as CATL and BYD, are similarly pursuing the sulphide route. BYD’s battery CTO Sun Huajun recently announced that the company was focusing on sulphide electrolytes, driven by “cost and process stability considerations.”
In addition to the Li2S large-scale facility, Idemitsu Kosan also plans to build a large pilot facility for solid electrolytes to further process materials. The Lithium hydroxide and a sulphur component will be processed with ultrafine particle handling technology in the Li2S facility, after which high-purity manufacturing technology is to be used in the large pilot facility to make all-solid-state batteries that can be reused and recycled.
For its sulphur compounds, Idemitsu will use by-products from petroleum products. “Idemitsu was one of the first to discover the usefulness of the sulphur component and developed a technology for the mass production of lithium sulphide in 1994,” the company says. The company aims to leverage the know-how gained through years of handling sulfur components and its proprietary technology to produce high-purity lithium sulfide. This is to be mass-produced in the Li2S large-scale facility.
