Green and Low-Carbon Synthesis of Lithium Sulfide (Li₂S): From Fundamental Mechanisms to Scalable Manufacturing for...

Lithium sulfide (Li₂S) is a critical cathode material for high-energy-density lithium sulfur batteries and an indispensable precursor for sulfide solid electrolytes. Traditional high-temperature carbothermal reduction remains energy-intensive and carbon-heavy, creating a significant mismatch with industrial sustainability targets. This review focuses on engineering-oriented green synthesis routes, systematically analyzing low-temperature solid-state reactions, magnesiothermal reduction, and solution-based metathesis pathways. It highlights process intensification, scale-up feasibility, techno-economic analysis, and by-product valorization. Current challenges in industrial amplification, including mass transfer limitations and cost competitiveness, are critically evaluated. Future directions emphasize continuous-flow manufacturing, closed-loop solvent recovery, and hybrid process integration, providing actionable technical pathways to enable cost-effective, low-carbon Li₂S production for industrial applications.