Cocross-Linked Nanofibrous Separator with High Ion Transport Capacity for Lithium-Ion Batteries

The safety and performance of lithium-ion batteries (LIBs) are strongly dependent on the structure and properties of the separator. In this work, a cocross-linked nanofibrous separator (PVA/CA-CD) was prepared by electrospinning poly(vinyl alcohol) (PVA), citric acid (CA), and β-cyclodextrin (β-CD), followed by heat-induced cross-linking. The effects of β-CD content on the composite separator's structure and performance were examined. As a result of the multiple interactions including chemical cross-linking and hydrogen bonding between PVA, CA, and β-CD, the mechanical strength and thermal dimensional stability of the PVA/CA-CD composite separator were greatly enhanced. In the meantime, the numerous reactive hydroxyl groups in β-CD significantly enhanced the separator's electrolyte wettability, which enhanced its ionic conductivity (1.78 mS/cm) and lithium-ion transference number (0.65), thus making the cell with PVA/CA-CD separator exhibit a capacity retention of 93.1% after 200 cycles at 1 C. Furthermore, the elevated ion transport capacity of the PVA/CA-CD composite separator, synergized with its uniform pore size and high porosity, which facilitated the uniform deposition of lithium-ion with a result of inhibiting the growth of lithium dendrites. Therefore, these excellent properties of the PVA/CA-CD composite separator demonstrate its promise to achieve superior performance and safety in LIBs.