Effect of quenching method on Li ion conductivity of Li5La3Bi2O12 solid state electrolyte

Effect of the quenching method on conductivity of Li5La3Bi2O12 ceramics prepared by sol-gel process was studied. In a synthesis process, lithium hydroxide, acetic bismuth, and acetic lanthanum were used as starting materials, while water was used as solvent. The temperature to synthesize the high density Li5La3Bi2O12 with cubic garnet type structure is 750 °C for 8 h in air with 10% excess lithium salt. The samples were prepared by the same synthesis route with the only difference from cooling methods. The samples were characterized by XRD, SEM, 6Li MAS NMR and ionic conductivity measurement. The XRD patterns of Li5La3Bi2O12 ceramics showed that there was a single phase oxides with garnet-like structure by the furnace cooling and the quenching method. The Li5La3Bi2O12 electrolyte by the furnace cooling exhibits the highest total ionic conductivity of 2.0 × 10− 5 S cm− 1 at 22 °C, and that by the quenching method exhibits the highest conductivity of 2.0 × 10− 4 S cm− 1 with a motional activation energy of 0.36 eV, which is an order of magnitude higher than that by the furnace cooling. The reason is that the relative density of Li5La3Bi2O12 by the quenching method is higher than that by the furnace cooling. The SEM images are also shown that the density of Li5La3Bi2O12 is very high by the quenching method and there exists lots of pores by the furnace cooling. And the 6Li-MAS-NMR results indicate the Li5La3Bi2O12 samples by the quenching method possess high Li ion mobility.