Synthesis And Modification Of Cathode Material LiNi_1/3Co_1/3Mn_1/3O₂ For Lithium-ion Battery

Lithium-ion batteries has been widely used in the fast developed society, but it still can not meet the developed needs of today's technology, primarily because of the defects of the main stream materials LiCO₂. To find a new material which is more in line with current scientific and technological development has been to many researchers' main task.In our paper, the LiNi_1/3Co_1/3Mn_1/3O₂ was synthesized by a sol-gel and carbonate coprecipitation, and amorphous carbon was coated on it to improve its performance. We discussed the structure, morphology and electrochemical performance of the materials.We synthesized LiNi_1/3Co_1/3Mn_1/3O₂ with good morphology and excellent properities by sol-gel method with adding an appropriate amount of anhydrous ethanol. We can shorten the time of precursor forming and improve the reproducibility of synthesis. The effects of sythetic conditions on the crystal structure, morphology and electrochemical properties of products were investigated by XRD, SEM, electrochemical cell cycling, cyclic voltammetry and AC impedance spectroscopy test. The optimatal synthesis condition was that annealing at 900℃for 20h in flowed air atmosphere. The LiNi_1/3Co_1/3Mn_1/3O₂ had the well-crystallized structure and homogenous distribution, the particle size was between 0.3μm and 0.5μm. The electrochemical measurements revealed that this sample also had good lithium-ion de-embedding reversible and cycling performance, the initial discharge capacity of LiNi_1/3Co_1/3Mn_1/3O₂ reached 148.98mAh/g in the range of 2.8～4.4 V at 0.1C rate, and its discharge capacity remained 86.98% after 30 cycles, and the rate performance was good.In the carbonate co-precipitation methode, we introduced ultrasound technology and prepared LiNi_1/3Co_1/3Mn_1/3O₂ with excellent performance. Synthetic conditions, such as pH, preparing temperature and calcinate temperature and time, was investigated. The results showed that the optimized synthesis condition was at the 50℃, pH=8.5, and sintering 16h at 900℃. The initial discharge capacity of 174.3 mAh/g was obtained at 0.1C between 2.5～4.4 V and the discharge capacity retention ratio was 88.9% after 20 cycles, but the performance under high rate was poor. The effects of carbon-coating on the structure and electrochemical performance of LiNi_1/3Co_1/3Mn_1/3O₂ was studied. The results indicated that the appropriate amount of the carbon coating on the low temperature did not change the material structure, but can significantly reduce the reunion and improve the cycle performance.