Electrochemical Coinsertion of Magnesium and Lithium Ions with Silicon Anode: An Integrated Experiment and Finite Element Simulation Approach

Silicon is one of the most promising anode materials for high-capacity lithium-ion batteries. Introducing binary cations with a small amount of Mg2+ into the Li-ion electrolyte has shown promising outcomes in stabilizing Si. However, the mechanisms by which a binary cation matrix enhances the anode stability remain unclear. In this work, the insertion kinetics and quasi-equilibrium potential of Si in a binary cation electrolyte matrix containing Li+ and Mg2+ are thoroughly investigated, and results from finite-element simulations reveal that the Mg2+ coinsertion process is electrochemically favorable in a Li-rich environment of Si. Li-rich conditions with a total state of charge (SOC) >89.4% facilitate the Mg coinsertion process, whereas Li-poor environments are less favorable for Mg coinsertion. Findings from this work unveil the electrochemical coinsertion mechanisms of Mg and Li with Si, offering valuable guidance for the design of high-capacity batteries.