镍铁锰酸钠层状氧化物的制备及性能研究

Study on preparation of nickel⁃iron⁃manganate sodium layered oxides and their properties

O3型NaNi_(0.4)Fe_(0.2)Mn_(0.4)O_(2)正极材料具有比容量高、高低温性能优良等特性,是一种具有实际应用价值的钠离子正极材料。通过共沉淀法制备了一系列正极材料,重点研究了pH对材料特征和性能的影响。借助扫描电子显微镜(SEM)、X射线衍射仪(XRD)、恒电流间歇滴定技术(GITT)及其他电化学测试技术对NaNi_(0.4)Fe_(0.2)Mn_(0.4)O_(2)材料的形貌、晶格参数、循环性能、倍率性能、钠离子扩散系数及赝电容贡献率等进行分析,发现随着pH的增大,样品粒径呈减小趋势,且过高的pH会造成样品粒径锐减,最佳合成pH为11。最佳pH条件下NaNi_(0.4)Fe_(0.2)Mn_(0.4)O_(2)材料的电化学测试结果表明,在30℃下电流密度为0.2C时,其放电比容量为142.3mA·h/g,展现出优异的电化学性能。

The O3-type NaNi_(0.4)Fe_(0.2)Mn_(0.4)O_(2) cathode material has the characteristics of high specific capacity and excellent high/low-temperature performance,which is a kind of sodiumion cathode material with practical application value.A series of cathode materials were prepared by coprecipitation 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 contribution of the NaNi_(0.4)Fe_(0.2)Mn_(0.4)O_(2) 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_(0.4)Fe_(0.2)Mn_(0.4)O_(2) material at the optimized pH showed that the discharge specific capacity of NaNi_(0.4)Fe_(0.2)Mn_(0.4)O_(2) material at 30℃with a current density of 0.2C was 142.3 mA·h/g,which exhibited excellent electro-chemical performance.