Permselective Metal–Organic Framework-Based Separators via In Situ Self-Assembly for High-Performance Lithium Metal Batteries

Lithium metal batteries (LMBs) have garnered considerable interest because of their substantial theoretical capacity. However, their development is hampered due to the grave issue of hazardous lithium dendrites arising from inhomogeneous lithium (Li) electrodeposition. An effective strategy for addressing dendritic growth is to regulate the migration behavior of target molecules and/or ions during cycling. Herein, we demonstrate an in situ self-assembly strategy where metal–organic frameworks (MOFs) grow on a polypropylene separator homogeneously along a certain orientation. By integration of abundant functional groups and secondary structural units, a continuous, uniform, and defect-free distribution of MOFs on the substrate membrane was achieved. The intrinsic subnanochannels of MOFs significantly benefit the transfer of Li+ ions and restrain the chaotic movement of target ions, resulting in a high Li+ migration number (0.86) and enhanced Li+ ionic conductivity. Consequently, a highly stable lithium plating/stripping behavior was observed, leading to efficacious lithium deposition and stable cycling over 1200 h at 2 mAh cm–2. Additionally, the permselective MOF-based separator with tunable channel sizes promises broad applicability in LMBs. Our approach paves a new pathway for in situ self-assembly strategies for permselective MOF-based separators, which is expected to help develop advanced LMBs with high energy density and long-life performance.