Influence of Al on the structure and ion transport in garnet-type Li7La3-xAlxZr2O12 solid electrolytes for Li-ion batteries

Abstract

This work reports on the preparation of garnet-type Al-doped Li7La3-xAlxZr2O12 (x = 0, 0.1, and 0.2) electrolytes for solid-state Li-ion batteries. The undoped and Al-doped cubic phase LLZO has been synthesized by conventional solid-state mixing and annealing at 1000 °C for 2 h. The prepared materials have been characterized by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy. The electrical properties were evaluated by impedance spectroscopy at varies temperatures. The ionic conductivities of Li7La3Zr2O12, Li7La2.9Al0.1Zr2O12, and Li7La2.8Al0.2Zr2O12 were determined to be 1.8x10−6, 4.1x10−6, and 6.5x10−6 S cm−1 at 100 °C respectively and their activation energy has been derived as 0.70, 0.69 and 0.73 eV from the Arrhenius plot. The DC conductivities were calculated as 1.6x10−4, 3.3x10−4, and 5.7x10−4 S cm−1 for Li7La3Zr2O12, Li7La2.9Al0.1Zr2O12, and Li7La2.8Al0.2Zr2O12 respectively. Furthermore, the hopping rates, charge carrier concentration, ionic mobility, and diffusion coefficient were also calculated and the results show an increasing trend with increasing temperature.