Robust Polyimide Nanofibrous Membrane with Bonding Microstructures Fabricated via Dipping Process for Lithium‐Ion Battery Separators

Herein, an innovative polyimide (PI) nanofibrous membrane with unique bonding microstructures is fabricated for lithium‐ion battery (LIB) separator application via an elaborately designed dipping method using polyamic acid (PAA) glue as the joint binder. Furthermore, the bonding degree can be easily adjusted by simply varying the concentration of PAA glue. The introduction of bonding microstructures into the PI nanofibrous nonwoven membrane leads to the formation of tough 3D networks between PI nanofibers and turns the loose–weak nonwoven membrane to a compact–robust fabric membrane. The tensile strength of the PI nanofibrous membrane is consequently promoted from 5 to 36 MPa, which greatly improves the feasibility of the membrane for the LIB winding process and the safety of the LIB during long‐term running. The cells using the bonded PI nanofibrous separators exhibit an excellent cycling stability and rate capability, manifesting 80.3% capacity retention at 5 C (i.e., 128.5 mAh g −1 ) and can run stably at a high temperature of 120 °C. Herein, the prepared PI nanofibrous membranes with such bonding microstructures are demonstrated, which have the potential to be advanced separators for secure and high‐power LIBs.