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

Abstract

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.

Polyimide separators for rechargeable batteries

“…To date, various PI nanofiber mats have been fabricated by the electrospinning technique [73]. Because PI nonwovens are usually prepared with rather low mechanical properties because of the weak interaction between PI fibers, polymers with low melting temperatures are incorporated to fuse nanofibers and therefore enhance the separator's tensile strength [74]. Liang et al developed a polyethylene oxide (PEO)-coated electrospun PI fibrous separator by an electrospinning method followed by a dip-coating and drying process [75].…”

Synthetic polymer-based membranes for lithium-ion batteries

“…Polyimide (PI) nanofibrous membrane separators with bonding microstructures have been prepared via a dipping method by employing PAA (polyamic acid) as shown in Figure 5.5, which turned the loose-weak nonwoven structure to a compact robust fabric structure. This separator exhibits excellent high-rate capability and cycling stability at high temperature [119].…”

Core–Shell Structured Polyimide@γ-Al2O3 Nanofiber Separators for Lithium-Ion Batteries

“…22 Like polyolefin materials, the wettability of PI nanofiber membranes is also poor, which means that they cannot meet the application requirements of LIBs at present. 29,30 In many studies, the electrolyte affinity of PI membranes can be further improved by combining inorganic materials. For example, a SiO 2 nanoparticle-coated PI nanofiber was fabricated by Shayapat et al 31 The PI/SiO 2 separator improves the electrolyte affinity and performs better than commercial PE and PI nonwoven separators.…”