Coral-like Li7La3Zr2O12-Filled PVDF-HFP/LiODFB Composite Electrolytes for Solid-State Batteries with Excellent Cycle Performance

Development of an active filler with a large specific surface area, fast ion conductivity phase, special shape, and high electrochemical stability is a critical issue for prominent performance composite solid-state electrolytes (CSEs) in solid-state lithium-ion batteries. Here, we report large specific surface area and coral-like cubic Li7La3Zr2O12 (LLZO) that was synthesized via a metal–organic framework (MOF) at a low calcination temperature (1000 °C). As active fillers, the coral-like cubic LLZO and lithium oxalyldifluroborate (LiODFB) uniformly distributed in a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix provide an interconnected Li-ion transport channel in CSE, which manifests outstanding properties such as a favorable electrochemical stability window (of 4.85 V vs Li/Li+), high ionic conductivity (1.65 × 10–4 S cm–1, 20 °C), and superior interface compatibility with lithium metal. The assembled LiFePO4/CSE/Li and LiCoO2/CSE/Li cells convey predominate performance and initial specific capacities of 135.0 and 135.9 mA h g–1 at 0.5 C, with capacity retention values of 83.51% after 500 cycles and 93.90% after 200 cycles. The coral-like LLZO with a large specific area reduces polymer crystallinity and provides a large phase interface in CSE through interaction of LLZO with LiODFB and PVDF-HFP. The results suggest that coral-like LLZO prepared by MOFs is a promising filler in CSEs for solid-state lithium-ion batteries.