In-situ polymerization of a free-standing and tough gel polymer electrolyte for lithium metal batteries

In-situ polymerization of gel polymer electrolyte (GPE) is expected to be promising approach to solve the safety and interfacial problems of lithium ion battery, but it is still challenging ways to tradeoff the high electrochemical properties and mechanical toughness. Here, 30 μm thickness of free-standing GPEs with extremely high monomer conversion were obtained by in-situ UV approach on lithium metal anode within only few seconds. The coordination of amide and aliphatic carbonyl groups with lithium ion endows the tough mechanical properties, which tensile strength and elongation at break reach up to ∼1.0 MPa and ∼920 %. Furthermore, the good degree of graphitization on the surface of burned polymer gel contribute to its flame resistance. The ionic conductivity and lithium ion transferance number are up to 1.03 mS/cm and 0.44 at room temperature, respectively. Finally, Li/LiFePO4 half cells assembled with the optimized GPEs exhibit stable cycle performance at 0.5C rate, delivering 77.44 % of capacity retention after 1000 cycles.