A Polymerized‐Ionic‐Liquid‐Based Polymer Electrolyte with High Oxidative Stability for 4 and 5 V Class Solid‐State Lithium Metal Batteries
Chengyin Fu, Gerrit Homann, Rabeb Grissa, Daniel Rentsch, Wengao Zhao, Tom Gouveia, Anaïs Falgayrat, Rongying Lin, Sébastien Fantini, Corsin Battaglia
Abstract
Abstract Polymer solid electrolytes for solid‐state batteries typically suffer from low ionic conductivity and low oxidative stability. Herein, a polymer electrolyte based on a polymerized ionic liquid and an ionic liquid plasticizer offering simultaneously a high room‐temperature ionic conductivity of 0.8 mS cm −1 and a high oxidative stability >5.0 V versus Li + /Li, is reported. The electrolyte is compatible with lithium metal and non‐flammable upon direct flame exposure. In symmetric lithium metal cells, the electrolyte enables stable lithium plating and stripping at 0.1 mA cm −2 with a capacity of 1 mAh cm −2 per half cycle for over 1700 h at 25 °C. Cells with a lithium metal anode cycled against a state‐of‐the‐art high‐energy uncoated layered LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode achieve an initial capacity of 162 mA h g −1 and a capacity retention of 72% after 600 cycles to an upper cut‐off voltage of 4.4 V at 25 °C. Cells with a high‐voltage spinel LiMn 1.5 Ni 0.5 O 4 cathode reach an initial capacity of 132 mAh g −1 and a capacity retention of 76% after 300 cycles to an upper cut‐off voltage of 5 V at 25 °C, confirming the high oxidative stability and technological potential of this electrolyte for high‐voltage solid‐state lithium metal batteries.