Idemitsu to Build Lithium Sulphide Plant in Chiba to Support Toyota’s All-Solid-State Battery Rollout

Idemitsu, Lithium Sulphide Plant

$142 Million Facility to Produce Key ASSB Material for 3GWh Annually, Backed by Japanese Government Subsidies

Idemitsu Advances Battery Strategy with New Lithium Sulphide Facility

Japanese energy firm Idemitsu Kosan has announced plans to construct a large-scale lithium sulphide production plant in Chiba, with completion targeted for June 2027. The project is part of Idemitsu’s broader strategy to establish an integrated supply chain for all-solid-state battery (ASSB) production—a technology expected to define the next generation of electric vehicle (EV) batteries.

The plant will produce lithium sulphide at volumes equivalent to powering 3GWh of ASSB output annually, reinforcing Japan’s position in the global battery supply chain. The ¥21.3 billion ($142 million) investment will be partially supported by ¥7.1 billion in government subsidies, according to Idemitsu.

ASSB Seen as Next-Generation EV Battery Solution

ASSBs offer significant advantages over traditional lithium-ion (Li-ion) batteries, including faster charging, higher energy density, better thermal stability, and reduced use of critical metals like nickel and cobalt. These benefits make them highly attractive for next-generation EV platforms.

In October 2023, Idemitsu and Toyota announced a partnership to commercialize ASSB for EVs by 2027–2028. Under this plan, Idemitsu will supply solid electrolytes, derived from its lithium sulphide, while Toyota integrates them into EV battery systems. Toyota’s goal is to produce vehicles capable of driving up to 1,200 km on a single charge—more than twice the range of its current EVs.

Integrated Upstream-Downstream Supply Secures Japan’s Battery Future

Idemitsu will manufacture lithium sulphide by processing lithium hydroxide sourced from its Australian mining assets with sulphur by-products from its oil refining operations. This vertically integrated model reflects Japan’s push to reduce battery supply chain dependencies on China while leveraging domestic expertise in refining and manufacturing.

As Japan’s second-largest oil refiner, Idemitsu is uniquely positioned to transform its fossil fuel legacy into a clean tech future. The company also plans to produce several thousand tonnes of solid electrolyte materials to support full-scale ASSB deployment across Toyota’s production lines.