Working Mechanisms for Enhanced Interface Stability and Electrochemical Properties in Dual‐Salt Polymer Electrolyte with In‐Situ Electrolyte‐Cathode Integration

Solid polymer electrolytes (SPEs) have attracted much attention due to their excellent flexibility, strong interfacial adhesion and good processibility. However, the incompatibility at the electrode/electrolyte interface often results in increased impedance and rapid capacity attenuation. In this work, dual-salt composite solid electrolytes (CSEs) with an integrated electrolyte/cathode structure are prepared by in-situ ultraviolet (UV) photopolymerization. With the addition of the lithium difluoro(oxalato)borate (LiDFOB), a robust, stable and low-resistance solid-electrolyte interface (SEI) layer is established during electrochemical reduction, eventually improving the overall performance of all solid-state lithium batteries (ASSLBs). The Li||Li symmetric cells with RTS-TH-2 % LiDFOB ASSLB exhibit stable cycling for over 2000 h at at 0.1 mA cm^-2@0.1 mAh cm^-2. LiFePO₄||Li cells deliver a high discharge capacity (155 mAh g^-1 at 0.5 C) and cycling stability (with the retention rate of more than 90 % at 0.5 C after 100 cycles) at 60 °C. This work provides a facile strategy to enhance electrodes compatibility with poly (ethylene glycol) acrylates (PEGAs)-based electrolytes.