Highly porous and thermally stable zeolitic imidazolate framework-8/aramid nanofibers composite separator for lithium-ion batteries

Currently, the inferior electrolyte wettability and poor thermal stability of conventional polyolefin separators have impeded the development of high-performance lithium-ion batteries (LIBs). Herein, a novel zeolitic imidazolate framework-8 (ZIF-8)/aramid nanofibers (ANFs) composite separator was fabricated via in-situ assembling ZIF-8 on ANFs followed by filtration process. The ZIF-8 particles prevented the dense packing of ANFs and significantly improved the porosity from 23.8% (in pure ANFs separator) to 61.6% (in composite separator). Combining the well-developed porous structure and exceptional electrolyte affinity, the as-prepared 30%ZIF-8/ ANFs composite separator (with 30 wt% of ZIF-8) exhibited high electrolyte uptake (224.0%) and good electrolyte wettability, which brought about superior ionic conductivity (1.37 mS cm(-1)), excellent rate performance and cycling stability. Furthermore, compared to commercial polypropylene separator, the 30%ZIF-8/ANFs separator showed suitable mechanical strength, outstanding thermal resistance and flame retardancy, which ensured higher safety during battery operation. Accordingly, the 30%ZIF-8/ANFs composite separator with both enhanced performance and high safety is a promising candidate for next-generation LIBs.

Automated summary

This study demonstrates the fabrication of a novel composite separator using zeolitic imidazolate framework-8 (ZIF-8) and aramid nanofibers (ANFs). The ZIF-8 particles improve the porosity of the ANFs, leading to enhanced electrolyte uptake and wettability. The composite separator shows high ionic conductivity, excellent rate performance, cycling stability, mechanical strength, thermal resistance, and flame retardancy, making it a promising candidate for next-generation lithium-ion batteries.