[Exclusive] POSCO Builds Value Chain for All-Solid-State Batteries... Enters Lithium Sulfide Business

POSCO Holdings Mirae Yeon, Sample Manufacturing at Test Facility
Pilot Plant Construction Within the Year... Accelerating All-Solid-State Battery Development

POSCO Building, Yeoksam-dong, Gangnam-gu, Seoul. Photo by Younghan Heo younghan@

POSCO Group is advancing the production of lithium sulfide, a key material for all-solid-state batteries, often called the "battery of dreams." This move is expected to enhance the completeness of the all-solid-state battery value chain and reduce battery costs through mass production.

According to POSCO Holdings on the 13th, the company recently established a lithium sulfide production test facility within its Future Technology Research Institute and has begun sample production. They plan to build a pilot plant within the year.

The lithium sulfide produced by POSCO Holdings is manufactured through a process that heats lithium sulfate, derived from existing lithium production processes, with carbon to remove oxygen. This is similar to the reduction process in steelmaking, where carbon is heated with iron ore to remove oxygen, reflecting the company's accumulated technological expertise. Lithium sulfide produces hydrogen sulfide, which is harmful to humans, when it reacts with moisture or oxygen. Therefore, the oxygen content must be low, and the lithium sulfide produced by POSCO Holdings reportedly has an oxygen content as low as 0.4?0.5%.

Lithium sulfide is an essential material for manufacturing solid electrolytes. It is needed to increase the ionic conductivity of solid-state electrolytes. While lithium sulfide is used in solid electrolytes at the all-solid-state battery stage, it also replaces lithium hydroxide, which is used in the cathode materials of existing NCM (nickel-cobalt-manganese) batteries, in another next-generation battery called the lithium-sulfur battery. POSCO Holdings is expected to supply lithium sulfide to POSCO JK Solid Solution, a joint venture with Jungkwan, a battery and display materials company. This joint venture is developing solid electrolytes for all-solid-state batteries.

POSCO’s lithium sulfide production is attracting attention because large-scale mass production could significantly lower prices. Currently, the price of lithium sulfide is around $1,500 to $2,000 per kilogram, which is at least 160 times higher than the $9 per kilogram price of existing liquid electrolytes of the same weight. In South Korea, companies such as Lake Materials, Isu Specialty Chemical, and Jungseok Chemical are producing lithium sulfide. According to estimates by Hanwha Investment & Securities, the combined production capacity of these companies is currently about 200 tons. However, demand is expected to exceed 15,000 tons by 2030.

All-solid-state batteries are called the "battery of dreams" because they have high energy density and low fire risk. These batteries replace the electrolyte that transfers ions between the cathode and anode with a solid instead of a liquid. Solid electrolytes are more resistant to shocks and damage compared to liquids and also serve as a partition, allowing for the minimization or elimination of separators. This enables the battery to be lighter or to increase energy density by adding more active cathode material in the freed-up space.

Production by major domestic companies, including POSCO Holdings, is also expected to become visible soon. Samsung SDI announced plans to concretize mass production within the first half of this year, accelerating commercialization. Ko Ju-young, Vice President and Head of the Medium and Large Product Planning Team at Samsung SDI, who is leading the development and mass production of all-solid-state batteries, said at the NGBS seminar hosted by SNE Research last month, "Solid electrolyte materials are the most important supply chain component in all-solid-state batteries," adding, "Building the supply chain is crucial, and we are communicating with material companies."