A polyethylene oxide/metal-organic framework composite solid electrolyte with uniform Li deposition and stability for lithium anode by immobilizing anions

All solid-state batteries (ASSBs) are regarded as promising energy storage batteries with high energy density and high safety. The polyethylene oxide (PEO)-based electrolyte with succinonitrile (SN) has attracted critical attention for its high ionic conductivity at room temperature. However, SN can react with Li metal to result in an unstable interface between electrolyte and electrode, which deteriorates the electrochemical performance. In this work, zeolitic imidazolate framework-67 (ZIF-67) is used as a filler to construct composite electrolytes and solve the aforementioned instability issue. The composite electrolyte shows nonflammability, high processability, and a competitive ionic conductivity of 2.78 * 10-5 S/cm at room temperature. Due to the regular dodecahedron structure and abundant Lewis acid sites, the composite electrolyte film exhibits a high Li-ion transference number of 0.654 and a wide electrochemical window of more than 5 V. Moreover, the ZIF-67 helps to construct a uniform and fast ion transport channel and can promote the generation of LiF to prevent SN from contacting Li anode, which contributes to the excellent stability of the Li symmetric batteries cycling for over 1000 h at a current density of 1 mA cm-2. And the assembled LiFePO4||Li batteries based on the composite electrolyte display high discharge specific capacities of 158.6 and 70 mAh g-1 at 60 °C and room temperature, respectively.