Visualization of Stochastic Nucleation and Confined Propagation in Graphite Lithiation.

Fast charging in lithium-ion batteries demands a fundamental understanding of lithiation kinetics in graphite anodes, particularly their phase transformations. Using operando optical imaging with high spatiotemporal resolution, we directly visualized phase transitions in individual graphite microparticles under realistic conditions. We uncovered a previously unrecognized "stochastic nucleation and confined propagation" regime during the stage 1L-3L and 3L-2 transitions, marked by asynchronous domain evolution. Kinetic analysis further revealed distinct rate-limiting mechanisms: interfacial ion transport governs early transitions, whereas solid-state diffusion controls the final 2-1 transition. These insights establish a unified mechanistic framework for graphite phase transformations and offer guidance for designing materials and charging strategies to enable fast-charging lithium-ion batteries.