Idemitsu Kosan constructs electrolyte pilot facility in Japan; Chiyoda awarded EPC contract for lithium sulphide plant

Japan’s Idemitsu Kosan Co Ltd says it has completed construction to increase the capacity of its Plant 1 (located on the premises of Idemitsu’s Chiba Complex in Ichihara City, Chiba Prefecture), a small pilot facility for the mass production of solid electrolytes used in all-solid-state lithium-ion rechargeable batteries.

With this capacity increase, it has expanded its solid electrolyte sample supply capacity from several tonnes per year to more than a dozen tonnes per year. It also has facilities for mass production technology development.

Idemitsu says it will accelerate technological verification to establish mass production technology in a large pilot facility as the next stage, aiming for practical application of all-solid-state batteries in 2027 to 2028, and commercialisation of solid electrolytes.

Two small pilot facilities are currently in operation, of which the capacity increase work started in FY2023 at the Plant 1 has been completed.

The basic design of the pilot facility was started in October 2024. And as with Plant 1, it is scheduled to be constructed within the Chiba Complex.

In February 2025, the firm also announced its decision to construct a large-scale production facility for lithium sulphide (Li2S, an important intermediate raw material for solid electrolytes, for which Chiyoda Corporation has been awarded a joint Engineering, Procurement, and Construction (EPC) contract

Chiyoda, as project leader, has formed a joint venture with Kobelco to execute EPC contract at Chiba. This strategic facility is set to support the growing demand for next-generation battery materials, particularly for solid-state lithium batteries, which are gaining momentum in the global electric vehicle (EV) and energy storage markets.

The project will be delivered through a consortium arrangement, where Chiyoda will collaborate with selected partners to ensure timely delivery, it adds.

The lithium sulphide produced at the new facility will serve as a critical component for solid-state batteries, offering enhanced energy density, safety, and performance over conventional lithium-ion batteries. The move aligns with Japan’s national strategy to secure key battery materials domestically and reduce dependence on overseas supply chains.

With global EV adoption accelerating, the demand for advanced battery materials is expected to surge. Idemitsu’s investment reflects a proactive approach to establishing domestic manufacturing infrastructure that supports innovation in energy storage technologies.

As part of the EPC contract, Chiyoda will be responsible for detailed engineering design, equipment procurement, construction, and commissioning of the facility. The company’s proven track record in delivering complex chemical and high-purity manufacturing plants will be instrumental in meeting the stringent quality and safety requirements for lithium sulphide production.

The plant will incorporate advanced production technologies and is expected to operate with high environmental standards, contributing to sustainable manufacturing and reduced emissions.

Construction is undergoing with commercial operations slated for 2027.