Synthesis and electrochemical properties of LiNi_0.8Al_0.2-xTi_xO₂ cathode materials by an ultrasonic-assisted co-precipitation method

A new co-precipitation route was proposed to synthesize LiNi_0.8A1_0.2-xTi_xO₂ (x=0.0-0.20) cathode materials for lithium ion batteries, with Ni(NO₃)₂, Al(NO₃)₃, LiOH·H₂O, and TiO₂ as the starting materials. Ultrasonic vibration was used during preparing the precursors, and the precursors were protected by absolute ethanol before calcination in the air. The influences of doped-Ti content, calcination temperature and time, additional Li content, and ultrasonic vibration on the structure and properties of LiNi_0.8A1_0.2-xTi_xO₂ were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and charge-discharge tests, respectively. The results show that the optimal molar fraction of Ti, calcination temperature and time, and additional molar fraction of Li for LiNi_0.8A1_0.2-xTi_xO₂ cathode materials are 0.1,700℃, 20 h, and 0.05, respectively. Ti doping facilitates the formation of the α-NaFeO₂ layered structure, and ultrasonic vibration improves the electrochemical performance of LiNi_0.8A1_0.2-xTi_xO₂.