Idemitsu to build lithium sulphide plant for solid-state batteries
Idemitsu Kosan Co., Ltd. has announced plans to build a large-scale production facility for lithium sulphide (Li₂S), a key intermediate material for all-solid-state lithium-ion rechargeable batteries. The facility, to be constructed at the company’s Chiba Complex in Ichihara City, Chiba Prefecture, is expected to be completed by June 2027.
This investment will enable Idemitsu to scale up lithium sulphide production to a world-class level, equivalent to 3 gigawatt-hour (GWh) per year of storage batteries. By doing so, the company aims to establish a fully integrated value chain from raw materials to battery components, reinforcing its position as a key supplier to automakers and battery manufacturers.
The Japanese Ministry of Economy, Trade and Industry has approved this initiative as part of its efforts to ensure a stable supply of storage batteries. Of the total project cost of approximately JPY21.3 billion (USD141.07 million), a maximum grant of JPY7.1 billion (USD47.04 million) has been allocated.
Founded in 1911, Idemitsu Kosan is one of Japan’s leading energy companies, with a diverse portfolio spanning petroleum refining, petrochemicals, renewable energy, and high-performance materials. The company has played a pivotal role in Japan’s industrial growth and continues to innovate in sustainable energy solutions, including next-generation battery technologies. With a strong focus on technological advancement and environmental responsibility, Idemitsu is committed to contributing to a decarbonised society through its expertise in energy storage and material science.
Pioneering solid-state battery technology
All-solid-state batteries offer several advantages over conventional lithium-ion batteries. By replacing the liquid electrolyte with a solid counterpart, these next-generation batteries promise faster ion movement, reduced charging times, and improved power output—key attributes for advancing electric vehicle (EV) technology. Additionally, their resistance to high voltage and high temperatures enhances energy density and battery lifespan, making them a highly anticipated breakthrough in energy storage.
Idemitsu has been at the forefront of lithium sulphide technology since 1994, leveraging its expertise in handling sulphur-based materials, a byproduct of petroleum refining. The company has been operating two small-scale verification facilities and launched the basic design of a large pilot facility in October 2024. The decision to proceed with a large-scale Li₂S production facility marks a critical milestone in the commercialisation of solid electrolytes and all-solid-state batteries, which the company aims to bring to market between 2027 and 2028.
Advancing Japan’s battery supply chain
By enhancing mass production capabilities for lithium sulphide, Idemitsu seeks to accelerate the commercialisation of high-performance solid electrolytes, which will be supplied to various battery manufacturers. This initiative aligns with Japan’s national strategy to fortify its storage battery supply chain and improve the country’s competitiveness in battery production.
As Idemitsu continues to refine its proprietary high-purity lithium sulphide technology, it aims to contribute to the global adoption of all-solid-state batteries, supporting the transition towards next-generation, sustainable energy solutions.
