| Lithium ion batteries as an efficient and environmental friendly energy storage technology have received widespread concern.Nowadays,in lithium-ion battery system,the performance of the cathode material affects and restricts the development of lithium ion batteries,limiting the application of lithium-ion batteries in electric vehicles and large-scale energy storage.The layered lithium rich manganese based cathode materials xLi2MnO3·?1-x?LiMO2?0<x<1,M=Ni?Mn?Co?Fe and etc.?due to its high discharge specific capacity,environmental friendly,and low cost to meet the market for high capacity,high energy density lithium ion cathode materials requirements,it is expected to become one of the next generation of ideal lithium ion battery cathode material.In this article,the cerium doping method are adopted to carry on the lithium rich manganese based binary cathode materials for modified research.The detailed work is as follows:1.A series of cerium doped lithium rich manganese based cathode materials Li1.2Ni0.2Mn0.6-xCexO2?x=0,0.01,0.02,0.03?were successfully synthesized by a sol-gel method using citric acid as chelating agent,and the influence of the cerium doping on crystal structure,morphology and electrochemical performance of the material were investigated.The experimental results showed that the particle size of the prepared cathode material was between 200nm and 500nm in diameter,and all had a certain agglomeration.An appropriate amount of Ce element incorporation not only made the layered structure of the material more obvious,but also inhibited the cation mixed phenomenon.In particular,the cerium doped sample of x=0.01 exhibited a more excellent cycle performance and rate capability under high rate.This material achieved the discharge specific capacity of 234.4mAh·g-1at 1C rate and maintained189.3mAh·g-1 after 50 cycles with capacity retention of 80.8%.The material also yielded discharge specific capacity of 209.9m Ah·g-1,188.2mAh·g-1,175mAh·g-1,163.2mAh·g-1and 142.9mAh·g-1at 0.2C,0.5C,1C,2C and 5C rate,respectively,and it was better than the bulk material.In addition,cerium doped materials could inhibit voltage attenuation.This was mainly because cerium doped materials,which had a relatively stable structure and cycling performance,could inhibit the material's transition from layered structure to a like spinel structure during cycling process.2.Cerium doped lithium rich manganese based cathode materials were prepared by a co-precipitation method,and meanwhile compared with that of x=0.01 cerium doped sample prepared by a sol-gel method.The analysis results showed that the cerium doped materials prepared by co-precipitation method did not receive the anticipated results,which was related to the poor experimental synthesis conditions.The morphology of the prepared material was poor,and the particle size was not uniform as well.However,the cerium doped materials of x=0.01prepared by a sol-gel method not only had high discharge specific capacity,but also had better cycling stability and rate capability when compared with the material synthesis of CeO2 doped amount of 1wt%prepared by a co-precipitation method.For example,the activated material achieved discharge specific capacity of 190.4mAh·g-1 at 1C rate and maintained 136.3mAh·g-1after 60 cycles with capacity retention of 71.6%,which was higher than that 105.2mAh·g-1 prepared by a co-precipitation method. |
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