Mesoscale Elucidation of Solid Electrolyte lnterphase Layer Formation in Li-Ion Battery Anode

Capacity fade in lithium-ion batteries largely originates from the undesired electrolyte decomposition, which results in the formation of solid electrolyte. interphase (SEI) and the anode surface passivation. In this work, a mesoscale interfacial modeling approach is developed to investigate the formation and growth of the SEI film on a typical graphite based anode over several cycles. It is found that lithium diffusion kinetics in the SEI film significantly affects the SEI growth rate. A lower lithium diffusion barrier leads to a higher growth rate. The present model demonstrates that the SEI thickness is a linear function of the square root of the charging time over long-time cycling. Growth of multicomponent SEI film is also elucidated. It is found that the heterogeneity of the SEI film may lead to instability in lithium ion concentration distribution.