Anisotropic Phase Boundary Morphology in Nanoscale Olivine Electrode Particles

Abstract

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.

Nonlinear phase-field model for electrode-electrolyte interface evolution

“…The electrode reaction rate, which is assumed to be exponentially dependent on the variation of free energy with respect to lithium concentration, i.e. the nonlinear electrode reaction kinetics, is specified as boundary conditions at the fixed electrode/electrolyte interface [18][19][20][21][22][23].…”

Suppression of Phase Separation in LiFePO4 Nanoparticles During Battery Discharge

“…They predicted moving phase boundaries ("intercalation waves") sweeping across FePO 4 planes, consistent with experimental inferences of a "domino cascade" 27 as well as the suppression of equilibrium phase separation with decreasing particle size, 28 and Tang et al recently modeled the effect of coherency strain on intercalation wave structure. 29 No model, however, has yet addressed phase-separation dynamics under the experimentally relevant condition of constant applied current.…”

Morphological Instability of Grain Boundaries in Two-Phase Coherent Solids

“…• misorientation are shown in Fig 2 ) similar to the ones used to model phase-separation in Li-ion battery materials [27,38]. We focus on a geometry in which a planar grain boundary is initially centered inside a lamellar precipitate.…”