Structural,electronic,and Li-ion mobility properties of garnet-type Li₇La₃Zr₂O₁₂ surface:An insight from first-principles calculations

【摘要】 Garnet-type Li₇La₃Zr₂O₁₂（LLZO） is a promising solid-state electrolyte for Li-ion batteries,but Li-dendrite’s formation greatly limits the applications.In this paper,we systematically investigate the stability,electronic properties,and Li-ion mobility of the LLZO surface by the ifrst-principles calculations.We consider the（110） and（001） slab structures with different terminations in the t-and c-LLZO.Our results indicate that both（110） and（001） surfaces prefer to form Li-rich termination due to their low surface energies for either t-or c-LLZO.Moreover,with the decrease of Li contents the stability of Li-rich surfaces is improved initially and degrades later.Unfortunately,the localized surface states at the Fermi level can induce the formation of metallic Li on the Li-rich surfaces.In comparison,Li/La-termination has a relatively low metallic Li formation tendency due to its rather low diffusion barrier.In fact,Li-ion can spontaneously migrate along path II（Li3→Li2） on the Li/La-T（001） surface.In contrast,it is more difficult for Li-ion diffusion on the Li-T（001） surface,which has a minimum diffusion barrier of 0.50 eV.Interestingly,the minimum diffusion barrier decreases to 0.34 eV when removing four Li-ions from the Li-T（001） surface.Thus,our study suggests that by varying Li contents,the stability and Li-ion diffusion barrier of LLZO surfaces can be altered favorably.These advantages can inhibit the formation of metallic Li on the LLZO surfaces.更多还原

【Abstract】 Garnet-type Li₇La₃Zr₂O₁₂（LLZO） is a promising solid-state electrolyte for Li-ion batteries,but Li-dendrite’s formation greatly limits the applications.In this paper,we systematically investigate the stability,electronic properties,and Li-ion mobility of the LLZO surface by the ifrst-principles calculations.We consider the（110） and（001） slab structures with different terminations in the t-and c-LLZO.Our results indicate that both（110） and（001） surfaces prefer to form Li-rich termination due to their low surface energies for either t-or c-LLZO.Moreover,with the decrease of Li contents the stability of Li-rich surfaces is improved initially and degrades later.Unfortunately,the localized surface states at the Fermi level can induce the formation of metallic Li on the Li-rich surfaces.In comparison,Li/La-termination has a relatively low metallic Li formation tendency due to its rather low diffusion barrier.In fact,Li-ion can spontaneously migrate along path II（Li3→Li2） on the Li/La-T（001） surface.In contrast,it is more difficult for Li-ion diffusion on the Li-T（001） surface,which has a minimum diffusion barrier of 0.50 eV.Interestingly,the minimum diffusion barrier decreases to 0.34 eV when removing four Li-ions from the Li-T（001） surface.Thus,our study suggests that by varying Li contents,the stability and Li-ion diffusion barrier of LLZO surfaces can be altered favorably.These advantages can inhibit the formation of metallic Li on the LLZO surfaces.更多还原