A functional gel polymer electrolyte based on PVDF-HFP/gelatin toward dendrite-free lithium metal batteries

The leakage of liquid electrolyte and the formation of lithium dendrites pose challenges to safety and stability of lithium metal batteries (LMBs). The appearance of gel polymer electrolyte (GPE) has obviously improved the safety of traditional LMBs. However, the limited inhibition of GPE on lithium dendrites is detrimental to the safety of LMBs. Herein, a kind of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/gelatin (GN) GPE with high ionic conductivity, high-temperature resistance, and flame-retardancy, was prepared by electrospinning and soaking method. Utilizing the electrospinning network of PVDF-HFP, its affinity to liquid electrolytes, makes this GPE more beneficial to ions transport and the formation of gel. And, the GN with sol-gel properties, enhances the mechanical property (13.5 MPa) of HFP-GN GPE. Meanwhile, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) suggest that the attraction of polar groups of GN to Li+ can regulate the distribution of Li+ and protect Li anodes. Consequently, the application of HFP-GN GPEs to LMBs with cathodes of LiFePO4 and LiCoO2 deliver excellent electrochemical performances: after 300 cycles, the LiFePO4/HFP-GN GPE/Li battery keeps a low capacity decay rate of 0.09% at 5 C; after 400 cycles at 2 C, the LiCoO2/HFP-GN GPE/Li cell retains a high capacity retention of 74%. This GPE is demonstrated for the application prospect of safe LMBs.