MOF-Ionic Liquid Structured Polymer Electrolytes with Multi-Channel Ion Transport Pathways for Wide-Temperature Solid-State Lithium Batteries.

Abstract

Composite polymer electrolytes (CPEs) enhanced with ionic liquids (ILs) are promising candidates for next-generation solid-state lithium metal batteries, offering advantages in interfacial compatibility and processability. However, their application across a broad temperature range has been hindered by a fundamental trade-off between mechanical robustness and ionic conductivity. To overcome this limitation, the study designs an innovative poly(ethylene oxide) (PEO)-based CPE architecture to decouple these properties. This architecture utilizes amino-functionalized metal-organic framework (MOF) nanoparticles to encapsulate and immobilize ILs within PEO-filled electrospun membranes, establishing stable multi-channel ion pathways across wide temperatures. Combined experimental and computational studies reveal that the functionalized MOF enables fast Li⁺ hopping at interfaces, and the MOF-confined IL boosts bulk ion transport. This multi-path mechanism ensures high Li⁺ conductivity and structural stability from -10 to 120 °C. Furthermore, the optimized CPE facilitates the formation of a LiF-enriched solid electrolyte interphase and an inorganic-dominated cathode electrolyte interphase, significantly enhancing interfacial stability. Consequently, LiFePO₄||Li cells exhibit excellent cyclability, retaining 96.8% capacity after 1000 cycles at 3 C, and demonstrate stable operation for over 400 cycles at both -10 and 120 °C. These results establish a novel strategy for decoupling the intrinsic compromise between mechanical and electrochemical performance in CPEs.