ZnO@C Coated Cellulose-Based Separators Control Lithium Deposition Direction to Stable Lithium Metal Batteries

Li metal anodes have attracted attention due to their high specific capacity and low electrochemical potential. Nevertheless, the uncontrolled growth of Li dendrites hinders the practical application of Li metal batteries. Although the various approaches have made performance improvements, safety hazards still exist since Li dendrites are still growing along the anode to the separator during the continuous plating/stripping process. Herein, a straightforward method is proposed to achieve stable Li metal batteries with directional growth control by using a functional ZnO@C/cellulose membrane as a separator. The abundant pore structure and functional groups of biomass cellulose enhance the Li-ion transport and interface compatibility. The ZnO transforms in situ to form a Li-Zn alloy layer which is uniformly coated to the separator to direct uniform ion concentration polarization and charge distribution polarization, control the growth direction of Li, significantly improve the cycling stability, and promote the reversibility of the Li plating/exfoliation process. As a result, the symmetric cell exhibits an extreme lifetime of more than 4500 h and low polarization at 3 mA cm-2. The cycling performance of the Li||LiFePO4 full cell reaches a capacity retention of 98% after 270 cycles at a mass loading of 10 mg cm-2. The impacts of ZnO@C/cellulose on the electrode are investigated by eletrochemical evaluation, electron microscopy, X-ray photoelectron spectroscopy, and Comsol. The ZnO transforms in situ to form a Li-Zn alloy layer which is uniformly coated to the separator to direct uniform ion concentration polarization and charge distribution polarization and control the growth direction of Li. Furthermore, the solid electrolyte interphase with high LiOH and LiF content is achieved to enhance the interfacial stability. Hence, the dendritic Li growth is suppressed and the lifespan of Li metal batteries is significantly prolonged. image