Interpenetrating Network-Based Hybrid Solid and Gel Electrolytes for High Voltage Lithium Metal Batteries

Solid-state lithium metal batteries (SSLMBs) are a desired future energy supply choice because of their improved safety and higher energy density compared with traditional liquid electrolyte-based lithium ion batteries. Poly(ethylene oxide) (PEO)-based network solid polymer electrolytes (SPEs) have recently attracted increasing attention in the research field due to their low cost, chemical versatility, excellent lithium dendrite resistance, and good device cyclability. However, the low anodic stability renders this system incompatible with high voltage cathodes, such as lithium nickel manganese cobalt oxides. In this work, we tackled this problem by introducing an interpenetrating network (IPN), which consisted of a primary PEO-contained network SPE and a linear poly(acrylonitrile) (PAN) secondary network. The chemical and architectural nature of these IPN-SPEs allowed us to significantly increase the oxidative stability of the SPEs from 4.1 V to over 5.1 V by incorporating only 2 wt % of PAN. The IPN network can be used as both the SPE as well as the host to form gel electrolytes. In SSLMBs based on the IPN-SPEs, lithium metal anodes, and LiNi0.6Mn0.2Co0.2O2 cathodes, a capacity of over 150 mAh g–1 was achieved at 90 °C with excellent cyclability. By infiltrating diglyme-based liquid electrolytes into the IPN-SPEs, a gel electrolyte was formed with excellent electrochemical properties and high conductivity at room temperature. LMBs using such electrolytes delivered a capacity of over 170 mAh g–1 with excellent Coulombic efficiency and cycling stability. Our study demonstrated that the IPN-based SPEs are promising to address the challenges of high voltage secondary batteries.