A porous, mechanically strong and thermally stable zeolitic imidazolate framework-8@bacterial cellulose/aramid nanofibers composite separator for advanced lithium-ion batteries

Currently, the commercial polyolefin-based separators suffer from inferior electrolyte wettability and poor thermal resistance, leading to unsatisfied electrochemical performance and severe safety hazards for lithium-ion batteries (LIBs). Herein, a high-performance composite membrane composed of zeolitic imidazolate framework-8@bacterial cellulose (ZIF-8@BC) matrix and aramid nanofibers (ANFs) filler was developed as the LIB separator via the facile in-situ synthesis and subsequent filtration process. The as-prepared ZIF-8@BC/30%ANFs composite separator (with 30 wt% of ANFs) showed high tensile strength (70.7 MPa), outstanding thermal resistance and flame retardancy, which significantly enhanced the safety of LIBs during operation. Moreover, due to the well-developed porous structure and exceptional electrolyte affinity, the ZIF-8@BC/30%ANFs composite separator exhibited good electrolyte wettability and high electrolyte uptake (267.8%), which brought about superior ionic conductivity (1.60 mS cm−1) compared to commercial polypropylene separator. These synergistic advantages eventually endowed the battery with excellent rate capability and cycling performance. Accordingly, the ZIF-8@BC/30%ANFs composite separator is a promising candidate for next-generation LIBs with both high safety and enhanced performance. [Display omitted] •A novel composite separator composed of ZIF-8@BC matrix and ANFs filler was developed for advanced LIBs.•The highly porous ZIF-8@BC separator matrix was constructed via in-situ synthesis of ZIF-8 on BC nanofibers.•The insufficient thermomechanical properties of ZIF-8@BC separator matrix were improved with the incorporation of ANFs.•The ZIF-8@BC/ANFs composite separator achieved the combination of both high safety and excellent electrochemical performance.