Synergistic Effect of Graphene Oxide for Impeding the Dendritic Plating of Li

Dendritic growth of lithium (Li) has severely impeded the practical application of Li-metal batteries. Herein, a 3D conformal graphene oxide nanosheet (GOn) coating, confined into the woven structure of a glass fiber separator, is reported, which permits facile transport of Li-ions thought its structure, meanwhile regulating the Li deposition. Electrochemical measurements illustrate a remarkably enhanced cycle life and stability of the Li-metal anode, which is explained by various microscopy and modeling results. Utilizing scanning electron microscopy, focused ion beam, and optical imaging, the formation of an uniform Li film on the electrode surface in the case of GO-modified samples is revealed. Ab initio molecular dynamics (AIMD) simulations suggest that Li-ions initially get adsorbed to the lithiophilic GOn and then diffuse through defect sites. This delayed Li transfer eliminates the "tip effect" leading to a more homogeneous Li nucleation. Meanwhile, CC bonds rupture observed in the GO during AIMD simulations creates more pathways for faster Li-ions transport. In addition, phase-field modeling demonstrates that mechanically rigid GOn coating with proper defect size (smaller than 25 nm) can physically block the anisotropic growth of Li. This new understanding is a significant step toward the employment of 2D materials for regulating the Li deposition.