Mesoscale Complexations in Lithium Electrodeposition.

Mechanistic understanding of lithium electrodeposition and morphology evolution is critical for lithium metal anodes. In this study, we deduce that Li deposition morphology evolution is determined by the mesoscale complexations that underlie due to local electrochemical reaction, Li surface self-diffusion, and Li-ion transport in the electrolyte. Li-ion depletion at the reaction front for higher reaction rates primarily accounts for dendritic growth with needlelike or fractal morphology. Large Li self-diffusion barrier, on the other hand, may lead to the formation of porous Li film for lower reaction rates. Enhanced ion transport in the electrolyte contributes to homogeneous deposition, thereby avoiding nucleation for Li dendrite formation. This study also demonstrates that the substrate surface roughness strongly affects dendritic growth localization over the protrusive surface features. A nondimensional electrochemical Damkohler number is further proposed, which correlates surface diffusion rate and reaction rate and allows constructing a comprehensive phase map for lithium electrodeposition morphology evolution.