Enhanced electrochemical performance of aluminum-ion batteries with novel polyimide nanofiber separators

For the first time, polyimide (PI) nanofiber membranes were fabricated using the electrospinning technique for aluminum-ion batteries. The microstructure, thermal stability, and mechanical properties of the PI membrane were thoroughly characterized, and Fourier-transform infrared spectroscopy was employed to confirm the complete imidization during the stepwise thermal process. The PI nanofiber membranes as separators were then tested in aluminum-ion batteries, where they were combined with graphite cathodes and aluminum foil anodes. The specific capacities for the PI and glass fiber separator systems were 77.2 and 74.7mAh g⁻¹, respectively. Aluminum cells with PI separators have higher specific capacity and coulombic efficiency compared to aluminum ion cells with GF separators under constant-current long-term cycling at current densities of 25 mA g⁻¹ and 100 mA g⁻¹.Furthermore, symmetric cells employing PI separators exhibited lower voltage polarization compared to that with glass fiber separator. Scanning electron microscopy (SEM) images of aluminum anodes after 50 stripping/deposition cycles revealed that the aluminum anodes in batteries with PI separators closely resembled the original aluminum foil, indicating a more efficient aluminum stripping/deposition process and more uniform aluminum deposition. These results demonstrate the feasibility of using PI nanofiber membranes in aluminum-ion batteries and offer new insights into the development of high performance separators for aluminum-ion batteries.