Study On Composition,Synthesis Techology And Nano-Cu Doping Of Cathode Materials For Lithium Ion Batteries

LiNixCoyMnzO₂ cathode materials for lithium ion batteries are widely attracted due to their high specific capacity and high temperature stability.The electrochemical properties of LiNixCoyMnzO₂ are depended on their composition,the LiNi1/3CO1/3Mn1/3O₂,LiNi0.4Co0.2Mn0.4O₂ and LiNi0.5Co0.2Mn0.3O₂ are the common and widely used composition.It has been found that the LiNixCoyMnzO₂ with high Ni content has high specific capacity,but its cycle property is poor.The LiNixCoyMnzO₂ with high Co and Mn content has rather good cycle property,however its specific capacity is low.The specific capacity of LiNixCoyMnzO₂ in industrial production is about 160mAh/g,and it is lower than its theoretical specific capacity of 275 mAh/g.The aim of this work was to enhance the electrochemical properties of the LiNixCoyMnzO₂ cathode materials by improving the chemical composition,synthesis technologies and doping with nano Cu.The main experimental results are as follows:?1?The Li_0.6Ni_0.2Co_0.2O₂,Li0.4Ni0.2Co0.4O₂ and Li0.4Ni0.4Co0.2O₂ cathode materials with different compositions were prepared by solid state reaction method sintered at 850? for 8 h.Their first discharge capacities at 0.2C were 152.1 mAh/g,138.7 mAh/g and 137.2 mAh/g,respectively,and their capacity retentions after 50 cycles of charge and discharge at 0.2C were 47.6%,86.9%and 78.1%,respectively.?2?The sintering temperatures played an important role on the electrochemical properties of the Li_0.6Ni_0.2Co_0.2O₂ cathode material.For Li_0.6Ni_0.2Co_0.2O₂ cathode material sintered at 800?,its specific capacity increased to 163.9 mAh/g.For Li_0.6Ni_0.2Co_0.2O₂ cathode material sintered at 750?,its capacity retention after 50 cycles of charge and discharge at 0.2C reached 71%.?3?The cycle property of the Li_0.6Ni_0.2Co_0.2O₂ cathode material could be improved by increasing the holding time during sintering.The capacity retention of the LiO.6Ni0.2Co0.2O₂ cathode material after 30 cycles of charge and discharge at 0.2C increased from 80.8%to 83.7%when its holding time increased from 8h to 16h during sintering at 800?.?4?The electrochemical property of the Li0.6Ni0.2CO0.2O₂ cathode material did not change significantly when the reaction atmosphere was changed from air to oxygen.?5?The addition of small amount of nano Cu into Li_0.6Ni_0.2Co_0.2O₂ cathode material would increase the specific capacity and the cycle property of the the cathode material.The specific capacity of Li[?Ni0.6Co0.2Mn0.2?0.99Cu0.01]O₂,sintered at 800? for 12h,reached a rather high value of 219.1 mAh/g,and its capacity retention was 59.1%after 50 cycles of charge and discharge at 0.5C.