Coral-like Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub>-Filled PVDF-HFP/LiODFB Composite Electrolytes for Solid-State Batteries with Excellent Cycle Performance
Shengdong Tao, Jian Li, Lihua Wang, Weiguo Huang, Minchao Zhang, Zhexi Chi, Shuohan Wang, Yongzhi Chen, Lei Shang
Abstract
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.