Commercial carbonate based gel polymer electrolytes enable safe and stable high-voltage Li-metal batteries

The current lithium metal batteries (LMBs) are limited by their safety risks and poor cyclability owing to the lack of suitable electrolyte systems. Converting the conventional liquid electrolyte system to solid and quasi-solid states has thus become a critical concern for the advancement of LMBs. Herein, by using an in-situ polymerized poly(hexamethylene diisocyanate) (PHDI), we developed a non-flammable carbonate-based gel polymer electrolyte (GPE), which significantly inhibits the undesired reactivity of Li metal electrodes with the liquid electrolyte. The resulting GPE possesses high ionic conductivity (2 mS cm⁻¹ at 25 °C), a wide electrochemical stability window (4.8 V). Utilizing such an electrolyte, Li symmetric batteries cycled stably for 1000 h, Li/LiFePO₄ batteries exhibit a significantly improved Coulombic efficiency of 99.6 % within 600 cycles. Furthermore, the PHDI-GPE can remain unignited after being exposed to fire in 5 s. Therefore, the novel in-situ polymerized PHDI-GPE reveals tremendous potential for high-performance rechargeable LMBs.