Structure and lithium-ion conductivity investigation of the Li7-xLa3Zr2-xTaxO12 solid electrolytes

Abstract

Abstract Currently solid electrolytes with high values of lithium-ion conductivity are required for creation high-energy lithium and lithium-ion power sources, including all-solid-state batteries. Compounds with a garnet structure based on Li7La3Zr2O12 are promising solid electrolytes for such power sources. In presented work solid electrolytes in the Li7-xLa3Zr2-xTaxO12 system were synthesised using the sol-gel method in a wide concentration range of tantalum from x=0 to x=2.0. According to X-ray diffraction analysis, compounds with x > 0 has a cubic modification with the space group Ia-3d. The electrical resistance of the obtained solid electrolytes was measured by the complex impedance method in the temperature range of 25-210 °C, and the values of total lithium-ion conductivity were calculated. It was found that Li6.4La3Zr1.4Ta0.6O12 has the maximum values of lithium-ion conductivity in studied system – 1.4•10−4 S/cm at 25 °C. The Density Functional Theory modeling confirms that moderate Ta-doping is most suitable for enhancing of Li diffusion.