Preparation of high safety self-assembled aramid-based nanofiber separator and its application in lithium metal batteries

Higher safety standards are essential for pursuing high-energy-density batteries within the rapidly advancing electric vehicle and large-scale energy storage industries. A novel, simple and successive process, which aims at coating the covalently crosslinked p-phenylene terephthamide (PPTA) onto commercial polypropylene (PP) separators, has been demonstrated. Without any additional binder, the PPTA nanofiber coating layer sticks to the porous PP separators by physical anchoring, endowing the composite separators with modified wettability toward electrolytes and heat resistance. Meanwhile, migration routes for lithium ions are guaranteed by the porous structure controlled by the self-assembly of the fibrillar units during the nonsolvent induced phase separation. The designed PPTA/TAB@PP separator shows a high lithium-ion transference number of 0.65. As a result, the symmetric Li//Li cell utilizing this separator demonstrates stable lithium plating and stripping. The associated Li//LiFePO4 and Li//NCM811 full cells exhibit high capacity, excellent rate performance, and remarkable cycling stability, significantly surpassing those that employ the commercial separator. This research presents an innovative method for designing functionalized separators to enhance the performance of lithium metal batteries.