Gradient distribution construction of ZIF particles in nanofibrous battery separator for high strength and ionic transport capacity

Nanofibrous separators with their inherent high porosity exhibit the outstanding advantages of low resistance and high liquid retention, which can significantly enhance the charging-discharging performance of lithium-ion batteries (LIBs). However, the weak mechanical strength of nanofiber separators poses an obstacle to the safe operation of the batteries. Herein, we develop a robust nanofibrous composite separator (CGPM) with a gradient distribution along the thickness direction by in-situ generating different contents of zeolitic imidazolate framework (ZIF-8) particles on polyacrylonitrile (PAN) nanofibers. Such a structural design endows the CGPM separator with high porosity (88.3 %) and a strength that is greatly improved by 148 % compared with that of the pure PAN. The mechanical enhancement mechanism can be attributed to the ideal interface elimination caused by the “continuous electrospinning and in-situ generation” method and the stress relaxation provided by the gradient distribution of particles. Meanwhile, the CGPM presents excellent ionic transport capacity with high ionic conductivity (2.06 mS cm −1 ) and lithium-ion transference number (0.59), rendering the battery with an initial specific discharge capacity of 151 mAh g −1 at 0.5C and a capacity retention of 93 % after 100 cycles. The designed CGPM holds great promise as a potential material for high-performance LIBs separators, providing valuable insights for the development of advanced battery materials.