Modeling for homogeneous Mg electrodeposition on Mg metal negative electrode in rechargeable Mg batteries

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Rechargeable Mg batteries have received intense attention as affordable rechargeable batteries with high electromotive force, energy density, and safety. Achieving uniform dissolution and electrodeposition of Mg metal negative electrode is vital for the development of rechargeable Mg batteries. This study investigates the behavior of Mg electrodeposition on non-uniform Mg metal surfaces formed through several discharge/charge cycles using simulations based on the Newman model followed by experimental validation. The simulations revealed that the surface morphology of the Mg metal negative electrode affected the distribution of the Mg 2+ ion concentration, flux, and current density in the electrolyte. Uniform electrodeposition can be achieved by maintaining a higher concentration of Mg 2+ ions in the pits formed on the surface, for example by ensuring a higher Mg 2+ ion diffusion coefficient, a smaller current density, and larger but shallower pits. The experimental results support these findings, providing a strategy to achieve uniform Mg electrodeposition and optimal design of the electrolyte. • Mg deposition on pit-structured surfaces was studied via simulation and experiment • Newman's model was successfully applied to rechargeable Mg battery simulations • Mg Surface morphology affects Mg²⁺ concentration, flux, and current density profiles • High Mg²⁺ diffusivity and low current density yielded uniform electrodeposition • Simulation results were validated by experimental Mg deposition observations