Preparation And Electrochemistry Performance Modification Of Ternary Cathode Material For Li-ion Battery

The synergism of the three transition metallic elements in LiNi1-x-yCoxMnyO2 makes it a outstanding and promising cathode material for Li-ion battery which has high energy, high working voltage, better cyclic performance and environmental protection. In this article, LiNi0.5Co0.2Mn0.3O2 is the study object, and the most studies is on the technological conditions and the modification of electrochemistry performance.LiNi0.5Co0.2Mn0.3O2 is prepared through the hydroxide co-precipitation and high temperature calcination mixed method, We discuss the influence of synthesis condition, such as the calcination temperature, the calcination time and the effect of Li/M to the final structure and the electrochemistry performance of material. The results demonstrate that material has best electrochemistry performance when it is calcined at 900 ℃ for 10 h and Li/M=1.1:1. We achieve the discharge capacity of 189.97 mAh/g at 0.2 C and the capacity retention of 90.90% after 30 cycles at 1 C (3.0-4.5 V). LiNi0.5Co0.2Mn0.3O2 material is synthesized and characterized via CR2032 coin-type cell at different working voltages of 3-4.25 V,3-4.4 V,3-4.5 V, 3-4.6 V as well as 3-4.7 V. The results indicate that better comprehensive electrochemistry performance is achieved at 4.5 V.Studying the dopings to the LiNi0.5Co0.2Mn0.3O2 material of four different elements (Ce, Pr, Sr, Ti) through XRD and electrochemistry test methods, moderate doping doesn’t change the basic layered structure. If the doping mass is low, it has lower capacity than non-doping material, but it has better electrochemistry performance. Among them, Ti and Sr elements both improve the cyclic performance and rate performance of material, Ti-doped material has capacity retention of 96.22% after 30 cycles; Pr element doping slightly enhances the cyclic performance, but reduces the rate capacity. Ce-doped material has best electrochemistry performance, EIS and CV results indicate Ce element doesn’t change the structure, may resist the Li+/Ni2+ cation mixing, promote primary particles coarsening, enhance the tap density, reduce the charge transfer impedance and increase the Li+ diffusion coefficient. Thus Ce element can improve the cyclic performance and rate performance, after 30 cycles the capacity retention is 97.35%, discharge capacity at 5 C is 134.87 mAh/g, which is 72.93% of 0.2 C capacity.We study the effect of superficial modification to the material. When the MWCNTs compound quantity is lwt%, the electrochemistry performance of material is best, after 30 cycles the capacity retention is up to97.46% from 90.90%, retention of 5 C capacity is up to 55.00% from 19.62%. When the TiO2 coating quantity is 3wt%, it achieved best electrochemistry performance, after 30 cycles the capacity retention is up to 94.42%, retention of 5 C capacity is up to 36.35%.