Stable solid electrolyte interphase induced by oxide coating on Anode: Insights from ReaxFF molecular dynamics simulations

Surface coating of anode materials is a promising way to inhibit the extreme volume expansion of high-capacity anodes and hence increases the stability of solid electrolyte interphase (SEI) layer, enhancing cycling performance and prolonging the lifespan of batteries. In this study, the effect of Si anode material coated with SiO₂ layer on SEI formation is studied by employing reactive force field molecular dynamics simulations. New insights into the variation, and the temperature and stress dependence of SEI layer thickness and lithium consumption are presented. It is found that the introduction of SiO₂ layer leads to stronger interactions between lithium ions and electrolyte and higher activation energy, and therefore the weaker lithium-ion diffusion, which contributes to the formation of a thinner SEI layer. The decrease in lithium consumption is attributed to mitigated interfacial side reactions, which is because that more unstable CO molecules are oxidized to stable CO₂ molecules. In addition, lowering temperature and applying pressure results in the thinner SEI. Different from the insignificant dependence of lithium consumption on stress, lithium consumption increases with the rising temperature. The findings offer a direction for developing anode materials with long cycle life and good cycling stability for high energy density lithium-ion batteries.