Green and Low‐Carbon Synthesis of Lithium Sulfide (Li ₂ S): From Fundamental Mechanisms to Scalable Manufacturing for Next‐Generation Energy Storage

Lithium sulfide (Li 2 S) 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 Li 2 S production for industrial applications.