A novel high-performance electrospun of polyimide/lignin nanofibers with unique electrochemical properties and its application as lithium-ion batteries separators

Polypropylene is currently one of the most widely used separators in lithium batteries because of its low cost and chemical stability. However, it also has some intrinsic flaws that hamper the battery performance, such as poor wettability, low ionic conductivity, and some safety issues. This work introduces a novel electrospun nanofibrous consisting of polyimide (PI) blended with lignin (L) to serve as a new class of bio-based separators for lithium-ion batteries. The morphology and properties of the prepared membranes were studied in detail and compared with those of a commercial polypropylene separator. Interestingly, the polar groups in lignin promoted the affinity to the electrolytes and improved the liquid absorption properties of the PI-L membrane. Besides, the PI-L separator showed a higher ionic conductivity (1.78 x 10-3 S/cm) and Li+ transference number (0.787). Furthermore, the battery's cycle and rate performance improved due to adding of lignin. The capacity retention of the assembled LiFePO4 | PI-L | Li Battery was 95.1 % after 100 cycles at 1C current density, which was higher than that of the PP (90 %). Based on the results, PI-L, a bio-based battery separator, can potentially replace the current PP separators in lithium metal batteries.