Novel Computational Approaches to Li Diffusion and Electron Transport for High Capacity Battery Materials

Abstract

ABSTRACTThe intrinsic channel structure and low volume work makes olivines phosphates (LiMPO4) versatile for Li uptake and release. The understanding of Li cation diffusion/transport mechanisms inside olivines are crucial aspects, which we address using advanced molecular dynamics simulations. Activation energies calculated from DFT concluded 1D diffusion within channels as also indicated by neutron diffraction direct imaging techniques. On explicitly including temperature we find that - besides main conduction paths along the easy channels - distinct, less frequent but relevant diffusion paths exist. We point out that capacity and diffusion/conduction issues must be understood in a much more detail-rich framework, under realistic simulation conditions within finite temperature simulations. For evaluating electrical conductivity, we use advanced DFT methods to correctly capture the insulating states of the charged and discharged olivine materials. Based on the Kubo formalism, reliable conductivity/resistivity curves can be calculated for comparison with experiments and for anticipating properties.