Dual‐Modified Electrospun Fiber Membrane as Separator with Excellent Safety Performance and High Operating Temperature for Lithium‐Ion Batteries

Abstract Polyacrylonitrile/Boric acid/Melamine/the delaminated BN nanosheets electrospun fiber membrane (PB₃N₁BN) with excellent mechanical property, high thermal stability, superior flame‐retardant performance, and good wettability are fabricated by electrospinning PAN/DMF/H₃BO₃/C₃H₆N₆/ the delaminated BN nanosheets (BNNSs) homogeneous viscous suspension and followed by a heating treatment. BNNSs are obtained by delaminating the bulk h‐BN in isopropyl alcohol (IPA) with an assistance of Polyvinylpyrrolidone (PVP). Benefiting from the cross‐linked pore structure and high‐temperature stability of BNNSs, PB₃N₁BN electrospun fiber membrane delivers high thermal dimensional stability (almost no size contraction at 200 °C), excellent mechanical property (19.1 MPa), good electrolyte wettability (contact angle about 0°), and excellent flame retardancy (minimum total heat release of 3.2 MJ m⁻²). Moreover, the assembled LiFePO₄/PB₃N₁BN/Li asymmetrical battery using LiFePO₄ as the cathode and Li as the anode has a high capacity (169 mAh g⁻¹ at 0.5 C), exceptional rate capability (129 mAh g⁻¹ at 5 C), the prominent cycling stability without obvious decay after 400 cycles, and a good discharge capacity of 152 mAh g⁻¹ at a high temperature of 80 °C. This work offers a new structural design strategy toward separators with excellent mechanical performance, good wettability, and high thermal stability for lithium‐ion batteries.