Ultraviolet‐Cured Semi‐Interpenetrating Network Polymer Electrolytes for High‐Performance Quasi‐Solid‐State Lithium Metal Batteries

Abstract

Solid polymer electrolytes with relatively low ionic conductivity at room temperature and poor mechanical strength greatly restrict their practical applications. Herein, we design semi-interpenetrating network polymer (SNP) electrolyte composed of an ultraviolet-crosslinked polymer network (ethoxylated trimethylolpropane triacrylate), linear polymer chains (polyvinylidene fluoride-co-hexafluoropropylene) and lithium salt solution to satisfy the demand of high ionic conductivity, good mechanical flexibility, and electrochemical stability for lithium metal batteries. The semi-interpenetrating network has a pivotal effect in improving chain relaxation, facilitating the local segmental motion of polymer chains and reducing the polymer crystallinity. Thanks to these advantages, the SNP electrolyte shows a high ionic conductivity (1.12 mS cm-1 at 30 °C), wide electrochemical stability window (4.6 V vs. Li+ /Li), good bendability and shape versatility. The promoted ion transport combined with suppressed impedance growth during cycling contribute to good cell performance. The assembled quasi-solid-state lithium metal batteries (LiFePO4 /SNP/Li) exhibit good cycling stability and rate capability at room temperature.