Effects of surface stress on lithium-ion diffusion kinetics in nanosphere electrodes of lithium-ion batteries

The experimental evidence suggests that the lithium ions tend to aggregate on the near-surface of nanoscale electrode particles in lithium-ion batteries. However, the underlying mechanism has not been well understood. In this work, based on the established chemo-mechanical coupled model featuring surface stress, stress-dependent chemical potential, and stress-mediated diffusivity, the size-dependence of diffusion kinetics in nanosphere electrodes is investigated. The results show that additional compressive stresses caused by the surface stress retard the attainable lithiation due to the reduced surface stress-dependent diffusivity, and the high lithiation region has a growing tendency to move on the near-surface region with decreasing the dimensions of nanospheres. The work indicates that the effects of surface stress on lithium-ion diffusion kinetics may result in the capacitor-like behavior of battery materials consisting of electrode nanoparticles.