Innovative Separator Engineering: Hydrogen Bond-Driven Layer-By-Layer Assembly for Enhanced Stability and Efficiency in Lithium Metal Batteries

Lithium metal batteries (LMBs) face critical challenges due to uncontrolled lithium dendrite growth and inhomogeneous Li⁺ flux, largely attributed to conventional separators' poor interfacial compatibility. To address this, we propose a hydrogen bond-driven layer-by-layer (LbL) assembly strategy for engineering functional separators using poly(vinyl alcohol) (PVA) and tannic acid (TA). The optimized PP/(TA/PVA)₁₅ separator leverages the synergistic interplay between PVA's hydroxyl groups and TA's carbonyl moieties, forming a robust hydrogen-bonded network that simultaneously enhances lithiophilicity, regulates Li⁺ flux uniformity, and immobilizes anions. The interfacial design achieves exceptional electrochemical performance: Li//Li symmetric cells maintain stable operation for 800 h at 0.5 mA cm^-2/0.5 mAh cm^-2, while Li//LiFePO₄ half cells retain 73.8% capacity after 1000 cycles at 5C (decay rate: 0.026% per cycle). The separator further exhibits high ionic conductivity (0.94 mS cm^-1) and Li⁺ transference number (0.63), outperforming conventional polyolefin counterparts. By integrating simplicity, scalability, and eco-friendliness, this work pioneers a universal interface chemistry paradigm for next-generation LMBs, offering transformative insights into separator engineering through molecular-level hydrogen-bonding control.