Polymer/ceramic gel electrolyte with in-situ interface forming enhances the performance of lithium metal batteries

With the introduction of solid-state electrolytes, solid-state lithium-metal batteries face enormous challenges of low electrolyte ion conductivity and high electrode electrolyte interface impedance. Here, we adopt a strategy of combining rigidity and flexibility to design a polymer/ceramic composite gel electrolyte films (CSEs) with a fiber like structure and local defect channels for rechargeable lithium metal batteries. The CSEs synthesized in situ on LiFePO4 electrode by ultraviolet (UV) curing method, which combines the high ionic conductivity of Li6.5La3Zr1.5Ta0.5O12 (LLZTO) ceramic particles and the flexibility of poly(vinylidene fluoride-co -hexafluoropropylene) (PVDF-HFP) polymer electrolyte. In order to investigate the effect of crosslinker on the performance of electrolytes, 1,6-hexanediol diacrylate (HDDA) and ethoxylated trimethylolpropane triacrylate (ETPTA) were used in the preparation process of ultraviolet (UV) curing method. A comparison was made between gel electrolytes using HDDA and ETPTA crosslinkers, electrolytes containing ETPTA exhibited good overall performance in terms of ion conductivity (7.89 × 10−4 S cm−1), Li+ transference number (0.63), glass transition temperature (−26.2 °C), good flexibility, thermal stability. As a result, the assembled LiFePO4||electrolytes containing ETPTA||Li batteries exhibit excellent the first discharge capacity (151.9 mAh g−1 with 0.1C), good rate performance and its capacity retention rate is 93.1 % after 300 cycles. This study provides a new strategy for the rational design and process method of high-performance CSEs for rechargeable solid lithium metal batteries.