Study On The Effect Of Rubidium Doping On The Electrochemical Performance Of Li[Ni,Co,Mn]O₂ Cathode Materials

Lithium-ion battery is widely used in electric vehicles?EV?and hybrid electric vehicles?HEVs?for its high specific capacity,high power density and environment-friendly advantages.It has been regarded as one ofthemostattractiveenergystoragesystems.Typically,LiNi_xCo_yMn_1-x-yO₂ materials consist of the transition metal elements such as nickel,cobalt and manganese,which can be referred to as Li[Ni,Co,Mn]O₂ material or NCM material.It has been considered as one of the most promising lithium-ion battery cathode materials because of its low cost,high energy density and other characteristics.Although the Li[Ni,Co,Mn]O₂ cathode materials have many advantages,the problems such as poor rate capability,poor cycle performance and low coulombic efficiency are quite evident.Technically,the Li[Ni,Co,Mn]O₂ materials can be enhanced by doping with other transition metals or coating with metal oxides so as to improve its electrochemical performance.Especially,by selecting the appropriate doping ions and controlling the content of the dopants can effectively improve the rate capability and cycle performance of the Li[Ni,Co,Mn]O₂materials.In our work,we found that the cationic doping can increase the spacing of the crystal layer of the material and stable crystal structure,so that it will be easier for the lithium ion diffuse between the lattices,and thus greatly improving the electrochemical performance of the Li[Ni,Co,Mn]O₂ cathode material.In this study,we successfully prepared Li_1-xRb_xNi_0.4Co_0.2Mn_0.4O₂ and Li_1-xRb_xNi_1/3Co_1/3Mn_1/3O₂ by coprecipitation method and the dependence of the properties of the cathodic materials on the various contents of rubidium was also evaluated.The electrochemical performance of the composites was characterized by SEM,TEM,XRD and electrochemical performance,such as rate capability,cycle performance,cyclic voltammetry and EIS.It showed that the optimized formulas are Li_0.97Rb_0.03Ni_0.4Co_0.2Mn_0.4O₂ and Li_0.99Rb_0.01Ni_1/3Co_1/3Mn_1/3O₂ in this study which have improved electrochemical perfomance.Also the incorporation of rubidium can stabilize the crystal structure.Meanwhile,we presume that the developed doping strategy can also be used for the enhancement of the other types of Li[Ni,Co,Mn]O₂ materials,especially high-nickel content Li[Ni,Co,Mn]O₂ cathode material,which is expected to be able to effectively reduce the cation mixing effect to improve electrochemical performance.