ZnO‐gCN Coated Separator for Modulating the SEI on Lithium Metal Anodes

Lithium metal batteries are recognized as potential candidates for the next‐generation energy storage system. Nevertheless, their chemical reactivity, volumetric changes and dendritic deposition profoundly influence their overall performance. Introducing an artificial solid‐electrolyte interphase (ASEI) is one of the most effective ways to tackle this interfacial instability. However, due to unparalleled reactivity, the direct interfacial engineering of lithium is challenging. Here, we report the modification of the polypropylene (PP) separator with lithiophilic zinc oxide (ZnO) and graphitic carbon nitride (gCN) as an indirect yet effective strategy to tackle the interfacial instability of lithium metal. This work substantiates that ZnO.gCN PP modulates the electrolyte uptake, ionic conductivity, and Li+ transportation and reacts with the lithium metal to form an ASEI having rigid inorganic materials like ZnF2, gCN, and Li3N leading to much lower nucleation overpotential, reduced polarization, and remarkable cycling stability of more than 500 cycles at 1mA/cm2. The GITT studies further manifested the improved mass and charge transfer kinetics of Li+ over the interphase. The post‐cycling HR‐SEM and XPS analysis confirmed that the improved electrochemical performance resulted from uniform Li plating/stripping and mitigated electrolyte degradation. Furthermore, the practicality of ZnO.gCN PP is demonstrated through the significantly enhanced electrochemical performance of NCM811.