Kinetic Monte Carlo simulation of surface heterogeneity in graphite anodes for lithium-ion batteries: Passive layer formation

The properties and chemical composition of the solid-electrolyte-interface (SEI) layer have been a subject of intense research due to their importance in the safety, capacity fade, and cycle life of Li-ion secondary batteries. Kinetic Monte Carlo (KMC) simulation is applied to explore the formation of the passive SEI layer in the tangential direction of the lithium- ion intercalation in a graphite anode. The simulations are found to consistent with observations in the literature that the active surface coverage decreases with time slowly in the initial stages of the battery operation, and then decreases rapidly. The effects of operating parameters such as the exchange current density and temperature on the formation of the passive SEI layer are investigated. The active surface coverage at the end of each charging cycle was initially lower at higher temperature, but remained constant for more cycles. The temperature that optimizes the active surface in a lithium-ion battery at Cycle 1 can result in less active surface area for most of the battery life.