Comparative Theoretical Investigation of Al- and Mg-Doped Li₂FeSiO₄ and its Pristine Form as Cathode Materials for...

Li₂FeSiO₄ exhibits intrinsically low electronic conductivity and sluggish lithium-ion diffusion kinetics, severely restricting its practical capacity. This paper systematically investigates two representative doping modification mechanisms with first-principles calculations, providing theoretical paradigms for potential research systems. DFT+U calculations demonstrate that Al-doped significantly enhances electronic conductivity by reducing the bandgap, whereas Mg-doped does not. Al as a shallow donor impurity decreases the bandgap via promoting the splitting of Fe-3d energy level. Climbing-image nudged elastic band (CI-NEB) calculations further reveal that both Al- and Mg- doped effectively lower the energy barrier for Li-ion migration, thereby facilitating enhanced Li-ion transport. Notably, Mg-doped demonstrates superior performance in reducing migration barriers compared to Al-doped. Ab initio molecular dynamics (AIMD) simulations confirm that doping improved Li-ion migration at ambient temperature (298 K). The above conclusions provide two different types of doping improvement for the optimization of LFS, which is conducive to promoting the commercial application of LFS.