Anisotropic Phase Boundary Morphology in Nanoscale Olivine Electrode Particles

Li-insertion-induced phase transformation in nanoscale olivine particles is studied by phase-field simulations in this paper. We show that the anisotropic growth morphology observed in experiments is thermodynamically controlled by the elastic energy arising from the misfit strain between the Li-rich and Li-poor olivine phases and kinetically influenced by the Li surface-reaction kinetics. The one-dimensional Li diffusivity inherent to the olivine structure is found to kinetically stabilize the phase boundary morphology after Li insertion termintates and facilitate ex-situ observation. Our calculations suggest that examination of the phase boundary morphology provides an effective approach to determine the limiting process of the Li intercalation kinetics in olivine nanoparticles.