ZnO-gCN Coated Separator for Modulating the Solid-Electrolyte Interphase 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 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. Herein, the modification of the polypropylene (PP) separator with lithiophilic zinc oxide (ZnO) and graphitic carbon nitride (gCN) is reported as an indirect yet effective strategy to tackle the interfacial instability of lithium. 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, leading to much lower nucleation overpotential, reduced polarization, and remarkable cycling stability of more than 500 cycles at 1 mA cm⁻². The GITT studies further manifested the improved mass and charge-transfer kinetics of Li⁺ in the presence of ZnO.gCN PP. The postcycling high-resolution scanning electron microscopy and X-ray photoelectron spectroscopy analysis confirmed that the enhanced electrochemical performance resulted from uniform Li plating/stripping and suppressed electrolyte degradation. Furthermore, the practicality of ZnO.gCN PP is demonstrated through the significantly improved electrochemical performance of NCM811.