Poly(vinylidene fluoride-co-hexafluoropropylene)-Based Solid Polymer Electrolyte Incorporated with UiO-66 for Lithium Metal Batteries

All-solid-state lithium metal batteries (ASSLMBs) have garnered significant interest as a result of their enhanced safety features and higher energy density compared to traditional lithium-ion batteries with liquid electrolytes. Nonetheless, a substantial challenge within ASSLMBs lies in the constrained lithium-ion flux encountered in solid-state polymer electrolytes, resulting in subpar performance during high-current charging and discharging scenarios. This limitation detrimentally affects the electrochemical performance of ASSLMBs. In this present work, we introduce a novel composite solid polymer electrolyte (CSPE) comprising metal–organic frameworks, namely, UiO-66, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), and lithium bis(trifluoromethane)-sulfonimide (LiTFSI) (referred to as UPH-SPE). UPH-SPE containing 5 wt % UiO-66 demonstrates exceptional characteristics, including a high ionic conductivity of 4.7 × 10–4 S cm–1, an electrochemical stability window of 4.9 V, and a remarkable lithium-ion transference number of 0.58 at 25 °C. Full cell tests unequivocally showcase that these newly developed composite electrolytes exhibit significantly improved performance in terms of the rate capability and cycling stability at room temperature. Specifically, the discharge capacity of ASSLMBs with UPH-SPE remains at 140 mAh g–1 when operated at a current density of 0.5 C over 100 cycles. Even after 200 cycles, the capacity is sustained at 94 mAh g–1. This study underscores the potential of our CSPE film to advance the practical application of ASSLMBs, offering promising prospects for future developments in this field.