Advancing sulfide solid electrolytes via green Li₂S synthesis.

Area of Science:

• Materials Science
• Electrochemistry
• Green Chemistry

Background:

• Sulfide-based solid electrolytes offer superior safety and performance over organic electrolytes.
• Widespread adoption of these advanced electrolytes is limited by the high cost of lithium sulfide (Li₂S).

Purpose of the Study:

• To develop a cost-efficient and scalable synthesis for high-purity Li₂S.
• To reduce the production costs of sulfide-based solid electrolytes for all-solid-state batteries.

Main Methods:

• A solvent-free metathesis reaction using thiourea as an S²⁻ donor to sulfurize LiOH.
• Scalable production of Li₂S (∼100 g per batch) with in-situ removal of gaseous byproducts (CO₂, NH₃).

Main Results:

• Achieved significant cost reductions in producing Li₁₀GeP₂S₁₂ (27.5%) and Li₅.₅PS₄.₅Cl₁.₅ (92.9%) at laboratory scale (1 kg).
• Demonstrated that all-solid-state batteries using the synthesized Li₂S exhibit performance comparable to those using commercial Li₂S.
• Successfully synthesized high-purity Li₂S via a scalable, eco-friendly route.

Conclusions:

• The developed solvent-free metathesis route offers a promising pathway for low-cost Li₂S synthesis.
• This method facilitates the practical application of sulfide-based solid electrolytes, potentially accelerating the commercialization of high-performance all-solid-state batteries.