Preparation and electrochemical properties of LLZO co-doping with Al and Ti for all solid-state battery

All solid-state lithium batteries have been widely used in mobile communications and electric vehicles due to their high energy density, wide operating voltage, and long cycle life. However, solid-state electrolytes have shortcomings such as insufficient stability and low conductivity. In this study, the sol–gel method prepared the solid electrolyte Li6.25Al0.25La3Zr2Ti0.25O12 co-doped with Al and Ti. The influence of Al and Ti on the structure and conductivity of Li7La3Zr2O12 was investigated by X-ray diffraction, impedance spectroscopy, scanning electron microscopy, and inductively coupled plasma spectrometer (ICP). With optimal additions of Al and optimal additions of Ti, Li6.25Al0.25La3Zr1.75Ti0.25O12 electrolyte calcined at 900 °C for only 6 h showed an ionic conductivity of 1.51 × 10−4 S/cm at room temperature. Li/Li6.25Al0.25La3Zr1.75Ti0.25O12/LiFePO4 all solid-state battery was assembled. The initial charge and discharge capacity of the lithium-ion phosphate positive electrode at 10 μA/cm2 was 165.1 mAh/g and 130.1 mAh/g at room temperature. The initial coulomb efficiency was 78.9%. After 100 cycles, the discharge capacity was 149.1 mAh/g, and the capacity retention rate was 99.8% at room temperature.