Interplay of Lithium Intercalation and Plating on a Single Graphite Particle

Improving safety while increasing the charging rates and extending the lifetime is the grand challenge for lithium-ion batteries. The key challenge is to control lithium plating, a parasitic reaction on graphite anodes that competes with lithium intercalation. Here, we determine the fundamental mechanism for the onset of lithium plating on graphite particles. We perform in situ optical microscopy coupled with electrochemical measurements to resolve the spatial dynamics of lithiation and plating on the surface of a single graphite particle. We observe that the onset of plating is strongly coupled with phase separation in graphite and occurs only on the fully lithiated edges of the particles. The competition between Li insertion and plating is further elucidated by examining the energetics and kinetics of both reactions. Based on the physical insights drawn from the experiments, we propose a phase-field model that predicts the onset of Li plating.