Poly(ethylene oxide)–Li₁₀SnP₂S₁₂ Composite Polymer Electrolyte Enables High-Performance All-Solid-State Lithium Sulfur Battery

Composite polymer electrolyte membranes are fabricated by the incorporation of Li10SnP2S12 into the poly(ethylene oxide) (PEO) matrix using a solution-casting method. The incorporation of Li10SnP2S12 plays a positive role on Li-ionic conductivity, mechanical property, and interfacial stability of the composite electrolyte and thus significantly enhances the electrochemical performance of the solid-state Li-S battery. The optimal PEO-1%Li10SnP2S12 electrolyte presents a maximum ionic conductivity of 1.69 × 10-4 S cm-1 at 50 °C and the highest mechanical strength. The possible mechanism for the enhanced electrochemical performance and mechanical property is analyzed. The uniform distribution of Li10SnP2S12 in the PEO matrix inhibits crystallization and weakens the interactions among the PEO chains. The PEO-1%Li10SnP2S12 electrolyte exhibits lower interfacial resistance and higher interfacial stability with the lithium anode than the pure PEO/LiTFSI electrolyte. The Li-S cell comprising the PEO-1%Li10SnP2S12 electrolyte exhibits outstanding electrochemical performance with a high discharge capacity (ca. 1000 mA h g-1), high Coulombic efficiency, and good cycling stability at 60 °C. Most importantly, the PEO-1%Li10SnP2S12-based cell possesses attractive performance with a high specific capacity (ca. 800 mA h g-1) and good cycling stability even at 50 °C, whereas the PEO/LiTFSI-based cell cannot be successfully discharged because of the low ionic conductivity and high interfacial resistance of the PEO/LiTFSI electrolyte.