Ultra-robust polyimide nanofiber separators with shutdown function for advanced lithium-ion batteries

Abstract

Safety issues have significantly impeded the development of modern lithium-ion batteries (LIBs), and fabricating advanced separators has been considered as a feasible solution to improve the security of LIBs. Here, we present an advanced polyimide (PI) nanofiber membrane (referred to as PIE) with ultrahigh strength and the shutdown function by optimizing precursor viscosity and nanofibers microstructure. Increasing chain length of the PI backbone and in -situ bonding technique can markedly promote mechanical properties of PI nanofiber separator (strength of pristine PI nonwoven >60 MPa, strength of modified PI nonwoven >90 MPa), which is a new record so far among current PI nanofiber membranes. The present PIE separator displayed superior wettability, heat-resistant, and ion conductivity compared to the commercial Celgard separator. Importantly, the excellent flame resistance and high-temperature shutdown function of PIE separators ensure the security of LIBs. Based on our rational separator design, the PIE separators possessed higher LIB capability (111.3 mAh g −1 at 10 C) than the Celgard separator (90.8 mAh g −1 at 10 C). Moreover, the PIE separator-based LIBs can run stably at 1 C and 5 C for 100 cycles. The present work demonstrated the likelihood of replacing the commercial polyolefin separator with the advanced PI nanofiber membranes. • Advanced PIE separators are prepared by increasing chain length of PI backbone and using in -situ bonding technique. • The strength of as-fabricated PI separators present a highest record so far (pristine PI nonwoven >60 MPa, modified PI nonwoven >90 MPa). • The excellent thermostability, flame resistance, and shutdown function can ensure the safety of LIBs. • PIE separators exhibit superior LIB capability and cycling stability.