Authors

Abstract

Uniform intercalation is desired to enable next-generation Li-ionbatteries. While we expect nonuniformity in materials undergoing a phase change,single-phase intercalation materials such as nickel manganese cobalt oxide arebelieved to lithiate uniformly at the particle/electrolyte interface. However, recentimaging reveals nonuniform lithiation. Motivated by this discrepancy, we examine ifaspherical particle shape can cause such nonuniformity since the conventional beliefis based on spherical particle theory. We obtain real particle geometries using rapidlab-based X-ray computed tomography and subsequently perform physics-basedcalculations accounting for electrochemical reactions at the particle/electrolyteinterface and lithium transport inside the particle bulk. The aspherical geometrybreaks the symmetry and causes nonuniform reaction distribution. Suchnonuniformity is exacerbated as the particle becomes more aspherical. The proposed mechanism represents a fundamentallimit on achievable lithiation uniformity in aspherical particles in the absence of other mechanisms causing inhomogeneity,such as grain structure, nonuniform carbon-binder coating, etc