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.