Interfacial engineering of Poly(Ionic Liquid)-based composite electrolyte via ionic liquid modification for high-performance solid-state lithium batteries

This study addresses the critical challenges of low ionic conductivity in polymer-based composite electrolytes for solid-state lithium batteries (SSLBs) arising from high interfacial impedance. A poly(ionic liquid) (PIL)-based composite electrolyte was engineered by modifying Li 7 La 3 Zr 2 O 12 (LLZO) nanowire surfaces with pyridine-functionalized ionic liquid via electrostatic adsorption. This interfacial strategy constructs efficient Li + transport pathways at the PIL/LLZO interface, significantly enhancing PIL chain segmental motion. The optimized electrolyte membrane achieves a high ionic conductivity of 2.79×10 -4 S cm -1 at 25 °C. Symmetrical Li||Li cells demonstrate stable plating/stripping for 600 hours, while the assembled LiFePO 4 ||Li half cell delivers 169.81 mAh g -1 at 55 °C (0.5 C rate) with 77.35% capacity retention after 400 cycles, outperforming the unmodified system. This interfacial engineering approach provides a scalable strategy for developing high-performance SSLB electrolytes. By functionalizing the surface of LLZO nanowires with pyridine ionic liquid (LLZO@Bpy), a poly(ionic liquid)(PIL)-based composite electrolyte was developed. This interfacial modification strategy facilitated the formation of efficient Li + transport pathways at the PIL/LLZO interface, thereby significantly enhancing the composite electrolyte’s electrochemical performance at room temperature. The solid-state battery incorporating the LLZO@Bpy composite electrolyte demonstrated exceptional long-term cycling stability, retaining 77.35% of its initial capacity after 400 cycles at 55 °C under a 0.5 C rate, outperforming pure PIL-based and unmodified LLZO CPEs.