Role of Inter-Dopant Interactions on the Diffusion of Li and Na Atoms in Bulk Si Anodes

Abstract

ABSTRACTWe explore, via density functional theory (DFT) calculations, the effect on the barrier height for Li and Na diffusion in bulk Si of the presence of an extra Li/Na atom at the neighboring tetrahedral (T) or hexagonal (H) interstitial site. For both neighboring sites, the lowest diffusion barrier height is reduced, although the magnitude of the reduction depends on the inter-atomic distance between the 2 Li/Na atoms. We further calculate the effective interaction between the 2 atoms and show that it is a strong predictor of diffusion barrier heights for both Li-Si and Na-Si systems. Importantly, the correlation between inter-dopant interaction and barrier height may be used in future work to predict the diffusion barriers at higher concentration of inserted atoms.