Idemitsu Kosan : ［Delayed］Development of mass production technology for solid electrolytes approved by METI as a 'plan for ensuring supply of storage batteries'

Press Release

Company Name: Idemitsu Kosan Co.,Ltd.

June 30, 2025

Representative Director & President: Noriaki Sakai (Company Code: 5019, TSE Prime Market) Contact person: Daisuke Mogi, General Manager,

Investor Relations Office, Finance & Accounting Department (TEL: [phone])

Development of mass production technology for solid electrolytes (all-solid-state battery materials) approved by METI as a "plan for ensuring supply of storage batteries"

Idemitsu Kosan Co.,Ltd. (Head Office: Chiyoda-ku, Tokyo; Representative Director, President: Noriaki Sakai; hereinafter referred to as "Idemitsu") is planning to increase the capacity of its Plant 2 (located in Sodegaura City, Chiba Prefecture, on the premises of Idemitsu's Advanced Technology Research Laboratories; hereinafter referred to as "Plant 2"), a small verification facility for developing mass production technology for sulfide-based solid electrolytes used in all-solid-state lithium-ion rechargeable batteries (hereinafter referred to as "all solid-state batteries"). This plan has been approved by the Ministry of Economy, Trade and Industry as a "plan for ensuring supply of storage batteries." Idemitsu will increase the sample production capacity of solid electrolytes to a ten-ton or more scale (annual production) and accelerate the development of mass production technology. By the end of the subsidized project, a decision will be made on capital investment on a scale equivalent to 3 GWh/year or more of storage batteries, taking into account the market environment and the status of technological development.

• Outline of the Plan for Ensuring a Supply of Storage Batteries approved by METI

Item	Sulfide-based solid electrolytes
Details of initiative	Introduction, development, and refinement of production technology
Amount of investment	Approx. 1.1 billion yen
Amount of subsidy	Approx. 600 million yen (maximum)

Idemitsu is developing solid electrolytes, an essential material for all-solid-state batteries, which contribute to the evolution of electric vehicles (EVs) and the creation of a resource-recycling society, as well as building a mass production system. At Plant 2, we are developing mass production technology for a different type of sulfide-based solid electrolyte than the "large pilot facility," the start of basic design of which was announced in October 2024. By conducting technical verification for investment decisions on the next stage of mass production facilities, we will contribute to the government's policy of strengthening the storage battery supply chain and improving the competitiveness of the Japanese storage battery industry.

[Project Roadmap]

[Reference]

Ministry of Economy, Trade and Industry "Ensuring a Stable Supply of Storage Batteries" (Japanese Only)

https://www.meti.go.jp/policy/economy/economic_security/battery/index.html

Press Release: Completed construction to increase capacity of Plant 1, small pilot facilities for mass production of solid electrolytes (all-solid-state battery materials) (April 21, 2025) https://www.idemitsu.com/jp/news/2025/250421_en.pdf

Press Release: Idemitsu has decided to construct a large-scale production facility for lithium sulfide, an intermediate raw material for the mass production of all-solid-state battery materials (hereinafter referred to as "solid electrolytes"). (February 27, 2025) https://www.idemitsu.com/jp/news/2024/250227_en.pdf

Press release: Basic Design of Large Pilot Facility Begins for Commercialization of solid electrolytes for All-Solid-State Batteries in 2027-2028 (October 28, 2024) https://www.idemitsu.com/jp/news/2024/241028_en.pdf

Press Release: Decision made to increase supply capacity of solid electrolytes for next-generation batteries (all-solid lithium battery) (June 19, 2023) https://www.idemitsu.com/en/news/2023/230619_2.html