As the technical route of solid-state batteries converges rapidly, the sulfide route has emerged as the industry's mainstream choice due to its excellent performance. Lithium sulfide (Li₂S), as a core raw material, is becoming the "decisive factor" determining the industrial mass production process. Automakers and battery enterprises worldwide are actively deploying layouts, promoting lithium sulfide from laboratory research to kiloton-level mass production, yet its high cost and stringent production requirements remain to be addressed.
     The core value of lithium sulfide stems from its unique chemical properties and industrial adaptability. As the basic raw material for sulfide solid electrolytes, both the mainstream Li₆PS₅Cl (LPSCl) and high-performance Li₁₀GeP₂S₁₂ (LGPS) are highly dependent on lithium sulfide to provide critical Li⁺ and S²⁻. Its large and soft anion structure can construct efficient lithium ion migration channels, simplifying the electrolyte synthesis process and avoiding complex reduction and rearrangement of sulfur elements. Data shows that lithium sulfide accounts for 82% of the manufacturing cost of LPSCl electrolytes, and 70%-80% of the cost of most sulfide electrolytes, directly determining the cost reduction process of solid-state batteries.
     The current lithium sulfide industry faces three core challenges. Chemically, it is not a naturally stable state and requires synthesis in high-temperature, oxygen-free and water-free environments; technically, the oxygen and water content must be controlled at the ppm level throughout the production process, and the semiconductor-like environmental requirements push up equipment and energy costs; in terms of scale, the global effective capacity of battery-grade lithium sulfide is still at the kiloton level, far lower than the megaton-level scale of lithium carbonate, leading to persistently high unit costs. Currently, the tax-included price of battery-grade lithium sulfide is about 2 million yuan per ton, making the cost of solid-state battery cells more than twice that of traditional electrolyte batteries.
     The industrial sector has launched initiatives to break through these bottlenecks. Chinese enterprises have performed prominently: Ganfeng LiEnergy has an existing annual capacity of 5,000 tons, GRINM can quickly expand production to 3,000 tons, and companies such as Enjie Co., Ltd. and Tianqi Lithium are accelerating the construction of pilot and mass production lines; Japan's Idemitsu Kosan and Sumitomo Chemical also plan to put kiloton-level production lines into operation in 2027. At the policy level, China has allocated 6 billion yuan in special R&D funds to support solid-state battery research, and enterprises including CATL will complete the acceptance of pilot lines in 2027, with international automakers such as Toyota also targeting mass production in the same period. The industrial chain is collaborating to drive down the cost of lithium sulfide and improve yield.

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