层状锂离子正极材料Li_(1+x)(Co_(0.2)Ni_(0.4)Mn_(0.4))O_2的结构和电化学性能的研究

采用溶胶凝胶法,用柠檬酸作为鳌合剂,在不同的温度下合成制备均一的层状锂离子正极材料Li(Co0.2Ni0.4Mn0.4)O2。XRD、SEM实验数据表明,在较低温度700°C下便可制得层状Li1+x(Co0.2Ni0.4Mn0.4)O2,并具有均一的颗粒形貌,颗粒大小为300 nm左右。XPS显示其正极材料中的Co、Ni、Mn的化学价态分别为+3,+2,+4,均为它们的稳定价态。700°C下合成的材料在20mA/g,2.9~4.6 V电压范围内,首次放电比容量为210.2 mAh/g,50周后放电比容量仍高达185.3 mAh/g,容量损失为11.84%。

Study on Structural and Electrochemical Properties of Layered Cathode Li1+x (Co0.2Ni0.4Mn0.4) O2

Sol-gel process using citric acid as a chelating agent was applied.The oxide compounds were synthesized under different annealing temperatures.XRD and SEM experiments showed that the layered Li_(1+x)(Co_(0.2)Ni_(0.4)Mn_(0.4))O_2 materials could be synthesized at 700°C,and the oxidation state of Co,Ni,and Mn in the cathode confirmed by XPS were +3,+2 and +4,respectively.SEM observation illustrated that the fabricated materials had homogenous particle morphology and the particle size was about 300 nm.The cathode syntliesized at 700°C showed small irreversible capacity loss of(11.84%) and high discharge capacity of 210.2 mAh/g in the voltage range 2.9～4.6 V_(Li/Li~+).After 50 times cycling,a discharge capacity of 185.3 mAh/g remained.