Zwitterion Modified Polyacrylonitrile Fiber Separator for Long-Life Zinc-Ion Batteries

The major challenges of aqueous zinc-ion batteries (ZIBs) are the dendrite formation and the passivation of zinc metal anode, which restrict their practical applications. Herein, polyacrylonitrile (PAN) and zwitterionic surfactant (Sulfobetaine methacrylate, SBMA) are combined as a precursor to design a modified PAN nanofiber separator by electrospinning. SBMA with sulfonate group [SO₃⁻] can alter the physical property of the precursor solution and electrostatic field during the electrospinning process. Besides, it can regulate the zinc ions crossing and homogenize the electric field by minimizing the zinc ion concentration polarization on the zinc foil surface due to the polar group. As a result, Zn symmetric cells with PAN@SBMA separators show long-term stability (up to 1700 h), which outdistances the cell with GF-D (only up to 50 h) under current density at 1 mA cm⁻². Meanwhile, the Zn//PAN@SBMA//NH4V4O10 full cells have high specific capacity (236 mAh g⁻¹) and excellent long-term durability with 84.2% capacity retention after 2000 cycles at 5 A g⁻¹. This work illustrates an easy and effective way to design a high ion transference number and functional PAN-based separator for regulating Zn²⁺ deposition for the development of high-performance ZIBs.