Kinetic Monte Carlo Study of Ambipolar Lithium Ion and Electron–Polaron Diffusion into Nanostructured TiO₂

Nanostructured titania (TiO 2 ) polymorphs have proved to be promising electrode materials for next-generation lithium ion batteries. However, there is still a lack of understanding of the fundamental microscopic processes that control charge transport in these materials. Here, we present microscopic simulations of the collective dynamics of lithium ion (Li + ) and charge-compensating electron–polarons (e – ) in rutile TiO 2 nanoparticles in contact with an idealized conductive matrix and electrolyte. Kinetic Monte Carlo simulations are used, parametrized by molecular-dynamics-based predictions of activation energy barriers for Li + and e – diffusion. Simulations reveal the central role of electrostatic coupling between Li + and e – on their collective drift diffusion at the nanoscale. They also demonstrate that a high contact area between the conductive matrix and rutile nanoparticles leads to undesirable coupling-induced surface saturation effects during Li + insertion, which limits the overall capacity and conductivity of the material. These results help provide guidelines for design of nanostructured electrode materials with improved electrochemical performance.