Highly porous zeolitic imidazolate framework-8@bacterial cellulose composite separator with enhanced electrolyte absorption capability for lithium-ion batteries

Currently, the commercial polyolefin-based separators suffer from inferior electrolyte absorption capability and poor thermal stability, leading to unsatisfactory electrochemical performance and severe safety hazards for lithium-ion batteries (LIBs). Herein, a high-performance zeolitic imidazolate framework-8@bacterial cellulose (ZIF-8@BC) composite separator was fabricated via in-situ synthesizing ZIF-8 on BC nanofibers followed by filtration process. The ZIF-8 particles served as micro-spacers to prevent the dense packing of BC nanofibers during drying and significantly improved the porosity from 54.6 (pure BC separator) to 73.2% (composite separator). Combining the exceptional electrolyte affinity and well-developed porous structure, the as-prepared ZIF-8@BC composite separator displayed high electrolyte uptake (340.5%) and good electrolyte wettability, which brought about superior ionic conductivity (1.12 mS cm−1) compared to commercial polypropylene separator (0.38 mS cm−1). These synergistic advantages eventually endowed the battery using ZIF-8@BC separator with excellent rate capability and cycling performance. Furthermore, the ZIF-8@BC separator showed suitable mechanical strength and outstanding thermal resistance, which ensured higher safety during battery operation. Accordingly, the ZIF-8@BC composite separator is a promising candidate for next-generation LIBs with both enhanced performance and high safety.Graphical abstract