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

Abstract

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.

Keywords: Li−S batteries; interfacial stability; polyethylene oxide; solid polymer electrolyte; sulfide lithium ionic conductor.