Solid Polymer Electrolytes Based on Phosphonate and Cyclocarbonate Units for Safer Full Solid State Lithium Metal Batteries

Abstract

AbstractSolid‐state polymer electrolytes are key components for future batteries with higher energy density as well as increased safety and processability. In this context, a solid polymer electrolyte is developed from statistical copolymers containing flame‐retardant phosphonate units and ion‐conductive cyclocarbonate moieties mixed with lithium salts. Ionic conductivity measured at room temperature for those copolymers (≈10−5 S cm−1) are in the same range as typical solid polymeric electrolytes not based on poly(ethylene oxide). Moreover, those copolymers electrolytes are stable in a wide electrochemical window (0.5 – 4.5 V vs Li+/Li) and at high temperature (>120 °C) and they lead to a better ionic conductivity than the corresponding homopolymer blends of a similar composition, which is explained by a better lithium salt solubility and better‐defined ion‐conduction pathways in case of the copolymer. Finally, it has demonstrated the possibility to have fire‐retardant properties afforded by phosphonate groups in copolymers without impacting the ionic conductivity.