Ab initio calculations on Li-ion migration in Li2FeSiO4 cathode material with a P21 symmetry structure

Abstract

We have systematically investigated the diffusion mechanism of Li ions in Li2FeSiO4 and its delithiated product LiFeSiO4 based on the P21 symmetry using the first principle method. Calculations on the energy barriers for possible spatial hopping pathways predicted that the activation barriers along the [101] direction and Li ion layer in the ac plane are relatively low, which can ensure the facile lithium diffusion along those directions. The results indicate that Li2FeSiO4 with the P21 symmetry is an ionic conductor for Li ions with two-dimensional diffusion.