Molecular Self-Assembled Ether-Based Polyrotaxane Solid Electrolyte for Lithium Metal Batteries
Peipei Ding, Lingqiao Wu, Zhiyuan Lin, Chenjie Lou, Mingxue Tang, Xianwei Guo, Hongxia Guo, Yongtao Wang, Haijun Yu
Abstract
Poly(ethylene oxide) has been widely investigated as a potential separator for solid-state lithium metal batteries. However, its applications were significantly restricted by low ionic conductivity and a narrow electrochemical stability window (<4.0 V vs Li/Li + ) at room temperature. Herein, a novel molecular self-assembled ether-based polyrotaxane electrolyte was designed using different functional units and prepared by threading cyclic 18-crown ether-6 (18C6) to linear poly(ethylene glycol) (PEG) via intermolecular hydrogen bond and terminating with hexamethylene diisocyanate trimer (HDIt), which was strongly confirmed by local structure-sensitive solid/liquid-state nuclear magnetic resonance (NMR) techniques. The designed electrolyte has shown an obviously increased room-temperature ionic conductivity of 3.48 × 10 –4 S cm –1 compared to 1.12 × 10 –5 S cm –1 without assembling polyrotaxane functional units, contributing to the enhanced cycling stability of batteries with both LiFePO 4 and LiNi 0.8 Co 0.15 Al 0.05 O 2 cathode materials. This advanced molecular self-assembled strategy provides a new paradigm in designing solid polymer electrolytes with demanded performance for lithium metal batteries.