Covalent Organic Framework-Coated Polyimide Ion-Track-Etched Separator with High Thermal Stability for Developing Lithium-Ion Batteries with Long Lifespans

Separators play a crucial role in inhibiting thermal runaway in lithium-ion batteries (LIBs). In this study, the doctor blade coating method and heavy-ion track etching technology were used to prepare a polyimide-based covalent organic framework (PICOF) separator with excellent thermal stability and a long cycle life. Specifically, COF300 was simply coated on the surface of a polyimide-based track-etched membrane (PITEM) with straight through holes, which provided a rigid framework and high-temperature stability at 300 °C. These features were conducive to inhibiting thermal runaway, while porous COF300 with large holes increased the wettability of the electrolyte, facilitating lithium-ion migration and suppression of lithium dendrite growth; consequently, LIBs with an excellent cycling performance and a high rate capacity were obtained. The cell with the PICOF separator delivered a high capacity of 90. 0 mA h g-1 after 1000 cycles. The PICOF separator with high thermal stability exhibited a long cycle life in LIBs. These features are beneficial for improving the safety characteristics of LIBs as well as for accelerating the practical application process of the PICOF separator.