Combined Experimental and Computational Study of Ce-Doped La3Zr2Li7O12 Garnet Solid-State Electrolyte

Li-containing garnet materials have been attracting considerable interest as potential solid-state electrolytes for Li ion batteries. In such Ln(3)M(2)Li(x)O(12) (Ln = lanthanide, alkaline earth; M = Zr, Hf, Sn, Nb, Ta, Sb, Bi, Te), the best Li ion conductivity is observed for Li contents, x, just below the maximum 7.0. The decrease in conductivity for x = 7.0 systems is related to Li ordering (cell changes from cubic to tetragonal) to prevent too short Li-Li interactions. In this work, we report a combined experimental and modeling study of Ce4+ doping in La3Zr2Li7O12. We show for the first time that Ce4+ can be doped onto the Zr4+ site in this material. This doping strategy results in a reduction in the tetragonal distortion as well as a lowering of the temperature of the tetragonal-cubic phase transition, attributed to the increase in cell size reducing Li-Li interaction strain. Coupled with these changes, the conductivity shows a significant (1.5 orders of magnitude) improvement. Furthermore, the Ce doping also reduces the interfacial resistance (388 Omega cm(2) Li(7)La(3)Z(1.75)Ce(0.25)O(12)) in contact with Li metal, giving additional potential benefits to this doping strategy. The long-term cycling stability of a Li//garnet//Li symmetric cell over 190 h has been demonstrated.