Freestanding and Ultra-flexible PAN/ZIF-67 Hybrid Membrane with Controlled Porosity for High-Performance and High-Safety Lithium Batteries Separator

Herein, a flexible ZIF-67/PAN hybrid membrane was successfully prepared by the incorporation of ZIF-67 nanoparticles and PAN nanofibers through electrospinning method. The hybrid membrane presented tomatoes on sticks structures with one single PAN fiber stringing series of ZIF-67 nanoparticles. The morphology, electrolyte wettability, heat resistance, flexibility, and electrochemical properties of the electrospun ZIF-67/PAN membranes were discussed. Among the membranes prepared with different percentage of ZIF-67, the 30% ZIF-67/PAN membrane exhibited outstanding heat shrinkage resistance (remained intact at 200 ℃ for 1 h), excellent electrolyte uptake (556.39%), wide electrochemical window (~ 5.25 V) and high ionic conductivity (2.98 mS cm−1). When used as lithium-ion batteries (LIBs) separators, the cells assembled by 30% ZIF-67/PAN membrane presented excellent rate capacity and high capacity retention of 86.9% after 300 cycles at 1C. More importantly, the cells assembled with ZIF-67/PAN membranes repeated bent for 1000 times also exhibited high rate performance and maintained capacity retention of 92% after 100 cycles at 1 C. The characterization and the electrochemical testing suggest the electrospinning prepared ZIF-67/PAN flexible membranes can be expected to be used as potential separator for advanced batteries with high safety and high performance.