A Polymerized‐Ionic‐Liquid‐Based Polymer Electrolyte with High Oxidative Stability for 4 and 5 V Class Solid‐State Lithium Metal Batteries

Polymer solid electrolytes for solid-state batteries typically suffer from low ionic conductivity and oxidative stability. Herein, a polymer electrolyte based on polymerized liquid an plasticizer offering simultaneously high room-temperature of 0.8 mS cm−1 stability >5.0 V versus Li+/Li, is reported. The compatible with lithium metal non-flammable upon direct flame exposure. In symmetric cells, the enables stable plating stripping at 0.1 mA cm−2 capacity 1 mAh per half cycle over 1700 h 25 °C. Cells anode cycled against state-of-the-art high-energy uncoated layered LiNi0.8Mn0.1Co0.1O2 cathode achieve initial 162 g−1 retention 72% after 600 cycles to upper cut-off voltage 4.4 high-voltage spinel LiMn1.5Ni0.5O4 reach 132 76% 300 5 °C, confirming technological potential this batteries.