Synthesis and Application of a Conjugated Polydianion-Based Single-Ion Conducting Polymer for High-Performance Solid Lithium-Ion Batteries

Graphical Ask the conductor :A polyanionic perfluoroimide-based conducting Li salt (LiPFSDI) is synthesized and blended with polyethylene oxide (PEO) to fabricate the polymer electrolyte membrane. The PEO-LiPFSDI composite electrolyte exhibits high ionic conductivity, a wide electrochemical window (up to 6 V versus Li + /Li), high t Li + (0.89), and excellent cycling performance. Fluorosulfonimide lithium salts have been widely used as conductors in solid polymer electrolytes for solid Li-ion batteries (LIBs). However, low conductivity and poor compatibility with the polymer host (usually polyethylene oxide, PEO) remain challenges in the design of these salts. In this paper, we synthesized a highly Li + -conductive salt containing the poly(perfluoroalkylsulfonyl)diimide (PFSDI − ) dianion for the first time. LiPFSDI represents the first example of a single Li-ion-conducting polymer (SLICP) with a conjugated sulfonimide moiety (−SO 2 −N (−) −SO 2 −N (−) −SO 2 −). The PEO−LiPFSDI blend electrolyte exhibits significant enhancements in ionic conductivity (2.24×10 −4 S cm −1 at 80 °C)and electrochemical stability (up to 6 V vs. Li + /Li). A prototype LiFePO 4 /Li battery with the PEO−LiPFSDI composite electrolyte shows excellent cycling performance with a high reversible capacity of 148 mAh g −1 at a rate of 0.1 C and 135 mAh g −1 at 0.2 C (70 °C), and maintains 100 stable cycles for over 1500 hours.