Understanding size-dependent migration of a two-phase lithiation front coupled to stress

Abstract

Recent in-situ experiments show that stress-driven migration of the phase interface during two-phase lithiation in nanosized particles exhibits self-limiting and size-dependent behaviors wherein the mechanism remains unclear. In the reaction-limited regime, we develop a mechano-kinetic coupling model with a nonlinear kinetic law to study the size effect of such phase boundary movement accounting for possible sources of stresses by chemical lithiation, concurrent plasticity, surface/interface elasticity, and elastic softening of the lithiated phase. We show that both hydrostatic and non-hydrostatic stresses contribute to the driving force for the phase interface movement and result in the size-dependent slowing down behavior of the phase interface. The obtained results reveal why the interface movement slows down more dramatically in the smaller particle, and there are similar lithiation time scales in nanoparticles of different sizes observed in experiments.