Strain effects on Li3OXX=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 ∼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.