Core–Shell Structured Nanofibers for Lithium Ion Battery Separator with Wide Shutdown Temperature Window and Stable Electrochemical Performance

Endowing separators in lithium ion batteries with highly sensitive shutdown function and good thermal stability is critical for the large-scale energy storage application of lithium ion batteries. In this work, a thermally induced shutdown separator with high thermal sensitivity and stability has been successfully fabricated via coaxial electrospinning of polyacrylonitrile (core) and poly(butylene succinate) (shell) (PAN@PBS). The separator is composed of core–shell structured and intersected nanofibers, which brings about the high porosity, excellent electrolyte wettability, and desirable electrolyte uptake. Meanwhile, the coaxial nanofibrous separator exhibits prompt shutdown response at 110 °C and remains structural integrity at 250 °C, indicating the coexisting characteristics of high thermal sensitivity and high thermal stability. Moreover, compared with the Celgard separator, the coaxial nanofibrous separator displays stable electrochemical properties in terms of higher ionic conductivity (2.1 mS cm–1) and superior cycling stability with capacity retention of 93.2% after 100 cycles at a 1 C rate and higher rate capability. Considering the high safety and good electrochemical performance, the as-prepared PAN@PBS nanofibrous membrane is a promising separator candidate for lithium ion batteries with enhanced safety.