Abstract:

The O3-type NaNi_0.4Fe_0.2Mn_0.4O₂ cathode material has the characteristics of high specific capacity and excellent high/low-temperature performance，which is a kind of sodium-ion cathode material with practical application value.A series of cathode materials were prepared by co-precipitation method，and the effects of pH on the characteristics and performance of the materials were investigated.With the help of scanning electron microscope（SEM），X-ray diffractometer（XRD），constant current intermittent titration technique（GITT） and other electrochemical testing techniques，the morphology，lattice parameter，cycling performance，multiplicity performance，sodium-ion diffusion coefficient，and pseudocapacitance contribution of the NaNi_0.4Fe_0.2Mn_0.4O₂ materials were analyzed，and the samples were found to have a decreasing particle size with the increase of pH.It was found that the particle size of the samples decreased with the increase of pH，and excessive high pH would cause a sharp decrease in the particle size of the samples，and the optimal synthesis pH was 11.The electrochemical test results of the NaNi_0.4Fe_0.2Mn_0.4O₂ material at the optimized pH showed that the discharge specific capacity of NaNi_0.4Fe_0.2Mn_0.4O₂ material at 30 ℃ with a current density of 0.2C was 142.3 mA·h/g，which exhibited excellent electrochemical performance.

Key words: sodium-ion battery, coprecipitation, sodium-ion diffusion coefficient, pseudocapacitance