Synthesis And Application Of Co₃O₄for Lithium-ion Batteries By Spray Method

Co3O4is the most important precursor of the cathode material LiCoO2. Synthesising the Co3O4with good performances by exploring new methods is one of the effective measures to improve the performance of LiCoO2. Meanwhile, Co3O4is considered to be one of the more promising metal oxides anode material for lithium-ion batteries. Based on the review for the previous research, we synthesis Co3O4by spray method, and research its application in lithium-ion battery materials in this thesis.Pure Co3O4is synthesised with spray drying method. After a series of exploratory experiments, we fail to synthesize the spherical Co3O4. We use this pure Co3O4to synthesis LiCoO2, but this LiCoO2exhibits poor cycling performance.Spherical Co3O4is synthesized by ultrasonic spray pyrolysis method. The optimized synthetic conditions were found as-follow:pyrolysis temperature850℃, CoCl2solution concentration0.5mol L-1, the solution feed rate2mL min-1, carrier gas flow rate0.5m h-1. The LiCoO2synthesized by this Co3O4exhibits excellent charge-discharge performance in the3.0-4.3V:its discharge capacity is151.6mAh g-1at1C, the capacity retention after100cycles is90.9%at1C. When the voltage rises to4.5V, the cycle performance deteriorates, the capacity retention rate after100cycles decreased to65.4%at1C.To improve cycling performance at4.5V, LiCo1-xMgxO2(0≤x≤0.1) are synthesized by ultrasonic spray pyrolysis method. Our research shows that Mg-doping can make the lattice parameters increased, improve the cycle performance of the material at4.5V. The LiCo1-xMgxO2exhibits the better cycle performance:its discharge capacity is177.3mAh g-1at1C, the capacity retention after100cycles increases to84.9%at1C. As shown in electrochemical impedance spectroscopy(EIS), it indicate that Mg-doping can lower the charge transfer resistance. A facile ultrasonic spray pyrolysis method without any template and organic additive assistance, was demonstrated to synthesize porous Co3O4microspheres. As anode material, the Co3O4exhibits good electrochemical performance:its initial charge capacity is950mAh g-1, its initial coulombic efficiency is76.2%. it exhibits remarkable cyclic performance at a current density of50mA g-1. Moreover, it retains superior rate performance.