Solid-state lithium batteries (SSBs) promise high energy and power densities, as well as enhanced safety, owing to the use of Li metal and nonflammable solid-state electrolytes.

Poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) based gel polymer electrolyte is regarded as a promising candidate to settle the safety issues of liquid electrolytes. However, the currently reported gel polymer electrolytes are still not safe enough owing to high amount of flammable liquid solvents contained in them. Herein, a fireproof PVDF‐HFP based gel polymer electrolyte is designed and synthesized through an in situ crosslinking method, with Li6.4Ga0.2La3Zr2O12 as initiator and ion‐conductive filler. The obtained gel polymer electrolyte demonstrates superior fire resisting properties. The optimized gel polymer electrolyte exhibits an ionic conductivity as high as 1.84 × 10−3 S cm−1 at 20 °C with an electrochemical window up to 4.75 V at room temperature. Moreover, the obtained gel polymer electrolyte shows excellent compatibility with lithium anodes. Therefore, the lithium anode is well protected. Lithium batteries assembled with the gel polymer electrolyte possess superb safety properties in cutting and burning tests. Furthermore, the batteries also show a discharge retention rate as high as 94.08% (in comparison with the initial discharge capacity) after cycling at 0.5 C for 360 cycles with an average columbic efficiency higher than 98%. The purpose of this report is to show the great potential of applying fire‐retardant gel polymer electrolyte to achieve high safety lithium batteries.

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