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Abstract

Abstract In this work, we investigated the effect of Rb and Ta doping on the ionic conductivity and stability of the garnet Li 7+2x-y (La 3-x Rb x )(Zr 2-y Ta y )O 12 (0≤x≤0.375, 0≤y≤1) superionic conductor using first principles calculations. Our results indicate that doping does not greatly alter the topology of the migration pathway, but instead acts primarily to change the lithium concentration. The structure with the lowest activation energy and highest room temperature conductivity is Li 6.75 , has a lower activation energy than c-LLZO, but further Rb doping leads to a dramatic decrease in performance. We also examined the effect of changing the lattice parameter at fixed lithium concentration and found that a decrease in the lattice parameter leads to a rapid decline in Li + conductivity, whereas an expanded lattice offers only marginal improvement. This result suggests that doping with larger cations will not provide a significant enhancement in performance. Our result