Strain effects on Li₃OX (X = Cl, Br) anti-perovskite solid lithium-ion electrolytes: DFT study

We have systematically explored the impact of strain on various properties of Li3OX(X=Cl,Br) anti-perovskite solid lithium-ion electrolytes based on the density functional theory. The responses of bandgap, defect formation energy, Li-ion migration barrier energy and diffusivity were discussed under different strain conditions, encompassing isotropic and biaxial compressive/tensile strains ranging from -4% to 4%. Our results reveal intriguing insights: Tensile strain leads to a substantial reduction in the bandgap by up to 0.5 eV, whereas for Li3OCl/Br under compressive strain, the reduction is only similar to 0.1 eV. Additionally, tensile strain facilitates the formation of Li+ vacancies and Li interstitials, thereby promoting the Li-ion diffusivity. Furthermore, the Li-ion migration barrier energy decreases when tensile strain is applied along the O-Li-O distribution direction. Analysis of AIMD results shows that tensile strain effectively enhances the diffusivity of Li ions. These findings suggest that isotropic strain strongly affects Li-ion conductivities in Li3OCl/Br anti-perovskite electrolytes, and applying tensile strain can be a potential method to enhance lithium transport.