Abstract:In the spent LIBs after multiple charge-discharge cycles, the cathode material LiCoO2 will undergo phase transition to produce Co3O4, resulting in a decrease in the conduction rate of Li+ and a decrease in the electrochemical performance. In order to study the mechanism of hydrothermal regeneration of Co3O4 to LiCoO2, pure Co3O4 was used as the test object, and the hydrothermal reaction test was carried out in LiOH solution. The effects of four operational factors, i.e., H2O2 dosage, hydrothermal temperature, reaction time and initial Li+ concentration, on the yield of LiCoO2 were explored by orthogonal test and single factor test, and the microstructures, phase composition and cobalt valence of the material before and after hydrothermal reaction were comprehensively analyzed by SEM, XRD, and XPS. The results show that Co3O4 can undergo hydrothermal synthesis reaction in LiOH solution and can be transformed into LiCoO2 by adding H2O2 solution as oxidant. The orthogonal test results show that the influence sequence of each operating factor on reaction of hydrothermal LiCoO2 is as follows: H2O2 dosage > hydrothermal temperature > reaction time > Li+ concentration. The yield of LiCoO2 is 80.72% under the conditions including hydrothermal temperature of 220 ℃, reaction time of 6 h, dosage of H2O2 of 0.3 mL/g and initial concentration of Li+ 3 mol/L.