Enhancing ionic conductivity of garnet-type Nb-doped Li7La3Zr2O12 by cerium doping

Abstract

We investigated the effect of additional doping with Ce on the ionic conductivity of the Nb-doped Li7La3Zr2O12 (LLZO) garnet ceramics using a combination of experimental and modeling approaches. Our results indicate that Ce doping can alter lattice parameters of the LLZNO, leading to the enhanced lithium ionic conductivity. The (Ce, Nb)-co-doped LLZO (LLZNCO) structure with composition Li6.5La3Zr1.5‒xNb0.5CexO12 (x = 0.125) exhibits a lower activation energy (Ea = 0.39 eV) than Li6.5La3Zr1.5 Nb0.5O12 (LLZNO) (Ea = 0.41 eV). Furthermore, Ce doping leads to an increase in Li+ conductivity from 6.4 × 10−4 to 7 × 10−4 S/cm at room temperature. In addition, we discuss the diffusivity and conductivity of our samples using ab initio molecular dynamics simulations and propose possible mechanisms to explain the enhanced Li-ion conductivity caused by co-doping with Ce and Nb. Our results demonstrate that the LLZNCO ceramics are promising candidates for potential solid-state electrolytes for Li-ion batteries.