Doping implications of Li solid state electrolyte Li7La3Zr2O12

Abstract

Solid-state electrolytes, like Li₇La₃Zr₂O₁₂ (LLZO), can enable safer, more energy dense and longer lasting batteries. We investigate the effect of doping in LLZO with Al, Ga, Nb, Ta, and Y by hybrid density functional theory calculations and a full defect model. The site preferences of Al, Ga, Nb, and Ta result in donor defects that favour more Li vacancies and thus a more disordered Li substructure. This also implies stabilisation of the more ionic conducting cubic phase at the expense of the tetragonal, as seen experimentally. Furthermore, our calculations indicate that the effect of the dopants on the sintering process is even more important than the ability to induce more ionic charge carriers. Finally, differences in Li vacancy formation energies suggest a new possible explanation for the two orders of magnitude increase in ionic conductivity upon stabilising the cubic phase.