As a promising raw material for solid-state battery electrolyte, Chinese market players have been actively expanding their businesses to lithium sulfide (Li2S) production, with a few already achieving solid progress.
1. Current Industry Landscape
Guanghua Technology employs a "wet purification + vapor deposition" dry process, achieving Li2S purity of 99.9999% at a cost of Yuan 200,000/tonne. With scale-up, costs are expected to drop below Yuan 100,000/tonne. Currently the company holds a capacity of 300 tonnes/year, expandable to 3,000 tonnes/year. The company has supplied samples (ranging from tens to hundreds of tonnes) to leading firms like Qingtao Energy and WELION New Energy, making it the only enterprise with mass-production capabilities.
Grinm Advanced Materials has mastered high-purity Li2S preparation technology, achieving small-scale stable production. Samples have been sent to industry leaders such as CATL and Huawei for validation, and the company has entered CATL's supply chain through collaboration with National Innovation Institute of Light Industry.
SEM Corp. is expanding into Li2S, sulfide-based solid-state electrolyte powders and electrolyte membranes through its Hunan subsidiary, with stable purity of 99.9%. Its innovative molecular-level homogenization technology reduces sintering temperatures by 35% and improves interface compatibility. A pilot line with hundreds of tonnes of capacity has been built, with plans to launch a 10-tonne production line by end-2025, eventually scaling to 1,000 tonnes/year.
Tianqi Lithium has completed R&D on battery-grade micro-powder Li2S, compiled full industrial-scale data packages, and provided samples to over a dozen downstream customers while continuously optimizing quality and cost.
Ruitai New Materials, in a joint venture with CATL, has secured a patent for high-purity Li2S through their company Tairui Lianteng. The production process boasts wide raw material availability and an eco-friendly approach, enabling the manufacturing of high-purity lithium sulfide. The company is also China's sole mass producer of LiTFSI, a key material compatible with sulfide-based, oxide-based, and other solid-state battery systems. The product has already achieved large-scale commercial sales.
2. Properties and Synthesis Methods
Lithium sulfide is a white-to-yellow crystalline solid with an anti-fluorite structure and a high melting point (938°C). It is highly reactive, prone to hydrolysis in air, and releases toxic hydrogen sulfide (H2S), necessitating complex production and storage processes.
And the currently available synthesis methods include:
Ball Milling: Mechanically mixing lithium/sulfur compounds in a sealed, high-temperature environment. Drawback: Low purity, requiring solvent purification.
High-Temperature/High-Pressure (HTHP): Reacting lithium/sulfur compounds under inert/reducing atmospheres. Advantage: High purity; Drawback: Low yield per batch.
Solvent Method: Reacting lithium/sulfur compounds in a solvent medium. Advantage: High purity; Drawback: Requires secondary extraction.
Carbothermal Reduction: Reducing lithium sulfate with carbon at high temperatures (400°C dehydration, 800°C decomposition, 1,100°C reduction). Advantage: 35% lower raw material costs; Drawback: Requires SO2 tail gas treatment, unstable product quality, and poor morphology control.
3. Industrialization Challenges
Despite the promising future, the Li2S still faces multiple challenges on the way to industrialization. First of all, Li2S is highly sensitive to moisture and oxygen, requiring airtight conditions during production, storage, and transport, introducing uncertainty and high risks.
On the raw material end, lithium metal and lithium hydride are expensive and reactive. The hydrogen sulfide is extremely toxic, posing hazards in handling and storage. In addition, the organic solvents are often flammable and explosive.
There are also equipment constraints as industrial-scale production demands stringent sealing and material specifications for equipment, complicating scale-up from lab to mass production.
Written by Aggie Hu, huchenying@mysteel.com
