“Lancet-Like” Mn-MOF Nanowires with Parallel Alignment for Separator Modification in Lithium Metal Batteries

Lithium metal has a status of a perfect anode material because of its very high theoretical specific capacity. However, lithium metal batteries (LMBs) often encounter obstacles related to uneven lithium-ion transport, bringing about the uncontrolled development of Li dendrites and significant safety risks. To address these issues, this study synthesizes “lancet-like” Mn-metal organic framework (Mn-MOF) nanowires (MMNWs) with parallel alignment through a one-step hydrothermal process to modify a commercial polypropylene separator (MMNWs/PP). MMNWs create the microelectric field via their negative sites, suppressing the transport and interference of anions in the battery system. By controlling the anion transference number (ta), the Li+ transference number (tLi+) is significantly improved. At the same time, the ionic conductivity (σ) is raised from 0.55 to 0.97 mS cm–1 for the PP separator. The MMNWs/PP separator-assembled Li//Li symmetric cell sustains up to 10 mA cm–2/1 mAh cm–2 in the rate performance test. At 1 C, the MMNWs/PP separator-assembled Li//LiFePO4 (Li//LFP) full cell conveys max discharge-specific capacity for 137 mAh g–1, with 94.8% for capacity retention after 500 cycles. Over and above that, the MMNWs/PP separator is also applicable to Li//LiNi0.5Co0.2Mn0.3 (Li//NCM523) full cells. Under 0.5 C, the MMNWs/PP separator-assembled Li//NCM523 full cell maintained 91.1% capacity retention after 100 cycles. These outstanding findings manifest that the proposed modification strategy provides valuable insights for advancing fast-charge technology in LMBs.