Idemitsu Kosan, a Japanese energy and chemicals company, has announced the construction of a lithium sulfide (Li₂S) plant , an important material for the manufacture of all-solid-state batteries. This new facility will be located at its Chiba Complex in Ichihara City, Chiba Prefecture, and is expected to be completed in June 2027.
Lithium sulfide plant technology
The company aims to strengthen the storage battery supply chain, with a production capacity equivalent to 3 GWh/year. This will position Idemitsu among the world leaders in lithium sulfide production, enabling it to supply high-performance solid electrolytes to automotive and battery manufacturers.
The project has been approved by Japan’s Ministry of Economy, Trade and Industry under the “plan to ensure the supply of storage batteries.” The total investment will be 21.3 billion yen, of which up to 7.1 billion yen will come from government subsidies. With this infrastructure, Idemitsu aims to accelerate the mass production of solid electrolytes, which will facilitate the commercialization of all-solid-state batteries in the 2027-2028 period.
Solid-state batteries represent a significant evolution from lithium-ion batteries , as they use solid electrolytes instead of liquids , allowing for faster ion transfer rates. This translates into shorter charging times, higher power output, and extended lifespan. Additionally, by being more resistant to high voltages and temperatures , they improve safety and energy efficiency in electric vehicles.
Idemitsu has a long-standing expertise in the production of high-purity lithium sulfide , a technology it began developing in 1994. By utilizing sulfur compounds generated as byproducts in oil refining, the company has perfected a proprietary production process that enables it to manufacture this key material on a large scale.
The company already operates two small-scale verification facilities and has started the design of a pilot plant, the basic development of which began in October 2024. The decision to build this new facility responds to the need to scale up production to ensure a stable supply of solid electrolytes.
With this investment, Idemitsu reaffirms its commitment to innovation and the development of next-generation batteries. The company seeks to accelerate the transition towards more sustainable mobility and strengthen the competitiveness of the Japanese industry in the storage battery sector.
As the commercialization of solid-state batteries approaches, Idemitsu will continue to expand its production capacity, establishing an integrated value chain spanning from raw materials to finished products.
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Source and photo: Idemitsu
