Effects of doping on electronic structure and ion diffusion of Li2FeSiO4

First-principles calculations were performed to study the crystal structure, electronic structure, and ion diffusion of sulfur-doped Li2FeSiO4. The sulfur atoms preferred to substitute oxygen atoms around different iron atoms and the most stable configurations were chosen for each Li16Fe8Si8O32-xSx (x = 1, 2, 3, 4) system to study the influence of sulfur concentration. Moreover, the configuration of the Li16Fe8Si8O29S3 had the least band gap (2.456 eV), which indicated the best electronic conductivity. The results of mean square displacement confirmed that lithium ions could diffuse in a two-dimensional path in Li2FeSiO4 and S-doped Li2FeSiO4 along the a-axis and c-axis. Doping sulfur was able to reduce the energy barrier for diffusion to improve the diffusion of lithium ions. The diffusion coefficient of lithium-ion was 8 orders of magnitude larger and the diffusion rate was 7 orders of magnitude larger than that of the intrinsic system at most.

Automated summary

First-principles calculations were performed to investigate the crystal structure, electronic structure, and ion diffusion of sulfur-doped Li2FeSiO4. The results showed that sulfur doping can improve the electronic conductivity and reduce the energy barrier for ion diffusion.