Study on preparation of nickel-iron-manganate sodium layered oxides and their properties
The O3-type NaNi0.4Fe0.2Mn0.4O2 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),con-stant current intermittent titration technique(GITT)and other electrochemical testing techniques,the morphology,lattice parameter,cycling performance,multiplicity performance,sodium-ion diffusion coefficient,and pseudocapacitance contri-bution of the NaNi0.4Fe0.2Mn0.4O2 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 electrochemi-cal test results of the NaNi0.4Fe0.2Mn0.4O2 material at the optimized pH showed that the discharge specific capacity of NaNi0.4Fe0.2Mn0.4O2 material at 30℃with a current density of 0.2C was 142.3 mA·h/g,which exhibited excellent electro-chemical performance.