Silane-modified HMMM gel polymer electrolyte with wide electrochemical window and high flame retardance for lithium metal battery

•A Novel Silane-modified HMMM (PCSM-GPE) is synthesized firstly and used as gel polymer electrolyte (GPE) for lithium metal battery (LMB).•The GPE (abbr. PCSM-GPE) shows an outstanding flame-retardant property which is crucial for battery applications.•The GPE demonstrates high ionic conductivity by 1.76 × 10-3 S cm−1 at room temperature and a wide electrochemical window stable up to 5.3 V. The assembled Li/LiFePO4 cell exhibits high capacity retention of 93.1 % at 1C after 400 cycles and very good charging/discharging rate performances. Lithium metal batteries (LMBs) have been regarded as one of the most viable candidate as advanced energy storage devices due to their high theoretical capacity and ultra-low redox potential of Li metal anodes. However, the issues on the safety and cycling stability, caused by lithium dendrites and the liquid electrolyte leakage are seriously concerned. Here, a nonflammable silane-modified amino-resin gel polymer electrolyte (PCSM-GPE) is introduced in fabricating promising lithium metal batteries. The UV photo-polymerized PCSM-GPE exhibits high ionic conductivity of 1.76 × 10−3 S cm−1 at room temperature and a wide electrochemical window stable up to 5.3 V, especially, outstanding flame-retardant properties is achieved. Li/LiFePO4 cell with PCSM-GPE is assembled to verify the practical application. The initial capacity by 94.8 mAh/g at 1C under room temperature is obtained and 93.1 % is retained after 400 charge/discharge cycles. This work provides an effective strategy in the configuration of high-performance fireproof quasi-solid-state battery system.