The synergistic effects of dual substitution of Bi and Ce on ionic conductivity of Li7La3Zr2O12 solid electrolyte

Li7La3Zr2O12 (LLZO) is a promising solid-state electrolytes (SSE) candidate with high ionic conductivity, wide electrochemical window, good chemical stability and thermal stability. However, LLZO is unstable at room temperature and is easily converted from a cubic structure to a tetragonal structure, resulting in a decrease in ionic conductivity. Stable cubic phase LLZO can be obtained by element doping and the ionic conductivity can be improved. We found that the doping of Bi and Ce can reduce the sintering temperature and increase the ionic conductivity, among which the Li7La2.5Ce0.5Zr1.625Bi0.3O12 (LLCZBO) solid electrolyte has the highest ionic conductivity of 5.12 × 10−4 S cm−1 and the electronic conductivity of 2.72 × 10−10 at room temperature. LLCZBO prepared by sol-gel method can reduce the sintering temperature and improve the degree of densification. These results indicate that double-doped Bi and Ce is a simple and effective strategy to develop oxide solid electrolytes with high ionic conductivity.