Sandwich structured PVDF-HFP-based composite solid electrolytes for solid-state lithium metal batteries

It is crucial to develop solid electrolyte with good mechanical and electrochemical stability for the application of lithium metal battery. In this work, a sandwich-structured composite solid electrolyte is designed and prepared based on the blend of polyvinylidene fluoride-hexafluoropropylene/polyacrylonitrile (PVDF-HFP/PAN) polymer, Li6.46La3Zr1.46Ta0.54O12 as filler, and a layer of PE film is introduced in the middle to act as a skeleton. The sandwich-structured PVDF-HFP/PAN-10%LLZTO-PE composite solid electrolyte displays a tensile strength of 66.58 MPa, high ionic conductivity of 2.28 × 10-4 S/m at 25 °C, wide electrochemical stable window of 4.8 V, and high lithium ion transfer number of 0.44. The LiFePO4 | PVDF-HFP/PAN-10%LLZTO-PE | Li coin battery shows a high specific capacity of 161.9 mAh/g and retains 150.2 mAh/g after 300 cycles at 1 C. Furthermore, the LiFePO4 | PVDF-HFP/PAN-10%LLZTO-PE | Li pouch battery shows excellent safety and functionality.