Impact of strain and doping on Li-ion transport in Li3OBr0.5Cl0.5 anti-perovskite solid lithium-ion electrolytes: Insights from DFT and AIMD calculations

Abstract

The impact of applying strain on the Li-ion transport characteristics of Li₃OBr_0.5Cl_0.5 anti-perovskite solid lithium-ion electrolytes with different doping positions have been systematically studied within the framework of density functional theory. We have examined the changes in bandgap, defect formation energy, and Li-ion migration barrier under triaxial compressive and tensile strains, spanning from −4% to 4 %. Following, by calculating of the diffusion and conductivity of different structures of Li₃OBr_0.5Cl_0.5, we have screened out one structure (Br-ions and Cl-ions are diagonally distributed at each vertex of the lattice) with the highest conductivity at room temperature from six structures of Li₃OBr_0.5Cl_0.5. Afterward, the changes of diffusion, conductivity and MSD of the structure with the highest conductivity at room temperature under applying −4% and 4 % triaxial strains have been studied. The results reveal intriguing implications: Tensile strains increase the defect formation energy for both Li-ion vacancies and Li interstitials, while simultaneously lowering the migration barrier of Li-ion. The influences of the formation energy and migration barrier significantly enhance the conductivity of Li-ion. This consequence is confirmed by AIMD simulation that both diffusivity and conductivity are enhanced under applying tensile strains, while an opposing effect observed under applying compressive strains. These findings unequivocally demonstrate that strains exert a profound influence on Li-ion conductivities in Li₃OBr_0.5Cl_0.5 anti-perovskite electrolytes. Specifically, the application of tensile strain emerges as a promising strategy to augment lithium-ion transport.