XLi 2 MnO 3 · (1-x)LiMn 1/3Preparation And Modification Of Co 1/3 Ni 1/3 O 2 Cathode Material

The Lithium-rich manganese based solid solution ternary cathode materials xLi₂MnO₃·?1-x?LiMO₂?M=Co,Mn,Ni,LNCM?have the advantages of high specific capacity,good thermal stability,low cost and no pollution.In recent years,it has been paid much attention and widely studied.In order to reveal the influence of material structure on its performance.In this paper,the LNCM materials with different stoichiometric ratios were prepared by changing the ratio of Li₂MnO₃ and LiMO₂,and then determine the optimal proportion.Then,the morphology of the corresponding Lithium-rich cathode materials was controlled,and the effect of metal ions doping was investigated.Firstly,the LNCM materials have been synthesized by using solid phase,sol-gel and coprecipitation method,respectively.The results show that when x=0.5,the Lithium-rich cathode materials have better electrochemical performance;under 0.5 C charge-discharge conditions,the capacity retention rate of the materials prepared by the above mentioned three methods are 84.1%,84.4%and 81%by cycling 100 cycles in 2.0?4.8 V;under 0.1 C charge conditions,the discharge capacity of these materials prepared by three methods are about 93 mAh·g-1,60.7 mAh·g-1 and 91.6 mAh·g-1 at 5 C discharge conditions.In order to further improve the electrochemical performance of the materials,a method for the preparation of hollow microspheres was prepared by molten salt method.The results show that the material is composed of particles with a particle size of about 50 nm,and the diameter of the hollow sphere is about 1 ?m,with a thickness of about 200 nm.Under 0.1 C charge-discharge conditions,the capacity retention rate of LNCM-HS and LNCM-bulk are 74%and 56%by cycling 35 cycles in 2.0?4.8V;under 0.1 C charge conditions,the discharge capacity of LNCM-HS and LNCM-bulk are about 101 mAh·g-1 and 60.2 mAh·g-1 at 5 C discharge conditions.The electrochemical properties of LNCM-HS samples is better than that of LNCM-bulk is due to the hollow hierarchical structure can signficantly shorten the diffusion distance of Li+,increase the contact area of the electrode and electrolyte,and effectively buffer the volume change caused by Li+ deintercalation process.In addition,the metal ions doping modification of lithium rich materials were also studied.Li_1.2-xMn_0.54Mg_xNi_0.13Co_0.13O₂?x=0,0.02,0.04,0.06?cathode materials doped with different Mg contents were synthesized by molten salt method.The results show that when the doping ratio of Mg2+ is 0.04,the electrochemical performance of the sample is the best:under 1 C charge-discharge conditions,the capacity retention rate is 93.5%by cycling 100 cycles in 2.0?4.8 V,Then,Li1.2Mn0.54-xRuxNi0.13Co0.13O₂?X=0,0.03,0.05,0.07?cathode materials doped with different Ru contents were also synthesized by molten salt method.The results show that when the doping ratio of Ru4+is 0.05,the electrochemical performance of the sample is the best:under 1 C charge-discharge conditions,the capacity retention rate is 97.2%by cycling 50 cycles in 2.0-4.8 V The results confirmed that the metal ion doping can better improve the electrochemical performance of lithium-ion battery cathode materials.