Effect of Ta-Doping on LLZO Garnet Solid Electrolytes for Solid State Batteries Applications

Abstract

Compared with conventional lithium-ion batteries, all-solid-state lithium batteries based on inorganic solid electrolytes have shown advantages over conventional lithium-ion batteries, such as explosion resulted from flammable liquid electrolyte, low energy density. Therefore, solid state batteries are considered a promising candidate with better safety features. Among oxide electrolytes, garnet-type LLZO electrolyte exhibits high ionic conductivity and electrochemical potential window. However, it is reported that there are difficulties to prepare Li7La3Zr2O12(LLZO) pellets with high relative density. In this study, LLZO containing Ta ion as a dopant is expected to show more Li vacant sites to enhance its conductivity and density. The LLZO powder calcined at 1200 °C with a cubic phase was confirmed by X-ray diffraction (XRD). The sintered Ta-LLZO pellets exhibit relative density of 88.45% and ionic conductivity of 1.04*10-4 S/cm at room temperature and good electrochemical stability with Li metal. After assembling LiCoO2/Ta-LLZO/Li battery, the discharge capacity reached 105.2 mAh/g for the first cycle.