H<sub>3</sub>PO<sub>4</sub>‑Impregnated Covalent\nOrganic Framework Membrane on Separators to Prevent Lithium Metal\nAnode Dendrite Growth

Inhibiting the growth of lithium dendrites is crucial\nfor battery\nsafety. For separators, their favorable electrolyte wettability, uniform\ncurrent density, and high ionic conductivity are beneficial for avoiding\nLi dendrite growth. In this work, we propose a separator (PA@COF/PP)\nby modifying a polypropylene separator with H<sub>3</sub>PO<sub>4</sub>-functionalized covalent organic frameworks. The uniform channels\nof the covalent organic frameworks and H<sub>3</sub>PO<sub>4</sub> can homogenize the current and act as ionic conductors for efficient\nLi<sup>+</sup> migration. The synthesized separator effectively suppresses\nthe growth of lithium dendrites and improves the stability of the\nbatteries. A symmetric cell with the PA@COF/PP separator exhibits\na stable life span over 4000 hours at a high current density of 5\nmA cm<sup>–2</sup>, compared to the commercial PP separator,\nwhich lasts only 159 hours. This work provides an efficient method\nand novel inspiration for the construction of dendrite-free lithium\nmetal batteries.