Computational Investigation of Site-Specific Doping Effects on Electronic Structure, Electrochemical Performance, Lithium-Ion Diffusion, and Transport in Li2GeO3 Anode.

Abstract

Li₂GeO₃ has gained attention as a potential anode material for lithium-ion batteries due to its high ion diffusion rate. This research uses advanced computational modeling to examine how different types of dopants and their substitution sites affect the defect properties, electronic structure, and lithium-ion diffusion in Li₂GeO₃. By analyzing isovalent and aliovalent dopants at various crystallographic positions, the study aims to uncover the mechanisms by which doping influences the material's performance as an anode. The findings indicate that halide dopants at the oxygen sites notably alter the electronic structure and ion diffusion rate. A decreasing trend in the band gap was observed with increasing concentrations of tetra- and trivalent dopants. Moreover, except for fluoride (F^-), other halide dopants at the 4a oxygen site exhibited the opposite effect on the electronic structure and ion diffusion rate. The 8b site was identified as the most favorable for F^- substitution, showing the lowest formation energy. Substitution of F^- at the 8b site significantly reduced the band gap (from 3.77 to 2.19 eV) by shifting the valence band maxima from the Z-point to the Y-point in high-symmetry representation and substantially increased the ion diffusion rate (1.70 × 10^-10 cm²/s) by broadening the diffusion pathway.