A Multiscale, Dynamic Elucidation of Li Solubility in the Alloy and Metallic Plating Process

Li‐containing alloys and metallic deposits offer substantial Li+ storage capacities as alternative anodes to commercial graphite. However, the thermodynamically in sequence, yet kinetically competitive mechanism between Li solubility in the solid solution and intermediate alloy‐induced Li deposition remains debated, particularly across the multiple scales. The elucidation of the mechanism is rather challenging due to the dynamic alloy evolution upon the non‐equilibrium, transient lithiation processes under coupled physical fields. Here, influential factors governing Li solubility in the Li‐Zn alloy are comprehensively investigated as a demonstrative model, spanning from the bulk electrolyte solution to the ion diffusion within the electrode. Through real‐time phase tracking and spatial distribution analysis of intermediate alloy/Li metallic species at varied temperatures, current densities and particle sizes, the driving force of Li solubility and metallic plating along the Li migration pathway are probed in‐depth. This study investigates the correlation between kinetics (pronounced concentration polarization, miscibility gap in lattice grains) and rate‐limiting interfacial charge transfer thermodynamics in dedicating the Li diffusion into the solid solution. Additionally, the lithiophilic alloy sites with the balanced diffusion barrier and Li adsorption energy are explored to favor the homogeneous metal plating, which provides new insights for the rational innovation of high‐capacity alloy/metallic anodes. The underlying rationales that govern the rate‐determining Li+ mass‐transfer kinetics are comprehensively investigated across multiple scales, from the bulk solution, the faradic reaction at the interface to the solid‐state diffusion. This study provides insights of thermodynamically in sequence, yet kinetics competitive processes, which facilitates innovation of the high‐capacity alloy/metallic anodes.