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

This work reports on the preparation of garnet-type Al-doped Li 7 La 3-x Al x Zr 2 O 12 (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 Li 7 La 3 Zr 2 O 12 , Li 7 La 2.9 Al 0.1 Zr 2 O 12 , and Li 7 La 2.8 Al 0.2 Zr 2 O 12 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 Li 7 La 3 Zr 2 O 12 , Li 7 La 2.9 Al 0.1 Zr 2 O 12 , and Li 7 La 2.8 Al 0.2 Zr 2 O 12 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.