Lithium Nickel Cobalt Oxide Cathode Materials For The Preparation Of New Technology Research

With the development of science and technology and the electronic equipments are miniaturized increasingly, the performances of batteries are required to be enhanced. Lithium-ion batteries are widely used in portable electronics due to its the advantages of high specific capacity, low self-discharge, high voltage and non-pollution. Lithium-ion battery is one of the high energy batteries, which have a good prospect in development and application.The key technologies of lithium-ion batteries are the development of cathode materials. At present, research work is mainly focused on LiCoO₂, LiMn₂O₄ and LiNiO₂. As cathode material, LiNiO₂ with layered structure has the characteristics of high specific capacity, low cost and non-pollution, which is regarded as one of the most promising material to replace LiCoO₂. LiNiO₂ doped with Co can improve its thermal stability and electrochemical properties. Cobalt doped LiNiO₂ is regarded as the most prospect cathode material.In order to decrease cost, enhance specific capacity and cycle stability of cathode material, LiNi_0.8Co_0.2O₂ was prepared by the chemical co-precipitation, mechanical activation and high temperature synthesis method. Co-precipitation. The precursor of Ni_0.8 Co_0.2(OH)₂ powders were prepared by the chemical co-precipitation method, which was mingled with LiOH·H₂O in proportion by mechanical activation. The some factors, such as the temperature and time of the second synthesis step, ball-milling activation time and method on the physical characteristics and electrochemical performances of Ni_0.8 Co_0.2O₂ were investigated in oxygen atmosphere. The test button cell were fabricated by using the prepared LiNi_0.8 Co_0.2O₂ as cathode activate material and charge/discharge experiment was carried out with 0.25mA and in the voltage range from 3.0 to 4.3V.It was shown that the layered structure was more explicit, the crystal lattice's integrity and order are higher with the increasing intemperature and time of the second synthesis step and ball-milling times. The integrity of the layered structure increases with the extension of the activation time. It was also concluded that the initial charge/discharge specific capacity was enhanced, the specific capacity retention was increased and the electrochemical performance was improved. LiNio.8Coo.2O2 synthesized under the optimum conditions displays good electrochemical property as cathode material of the test cell. It was shown a initial charge/discharge specific capacity of 183.0mAh/g and 169.8mAh/g, respectively, the discharge specific capacity retention was 97.87% in the first 5 cycles.The cathode material LiNio.sCoo.2O2 doped with Al3+ was studied in this paper by the same method. It was found that the cathode material LiNio.8Coo.2-xAl.rO2 (x=0.01,0.03,0.05) has a stable layered crystal structure and show better charge-discharge cycling properties than LiNio.8Coo.2O2. The initial charge/discharge specific capacity of LiNio.8Coo.17Alo.03O2 was 199.4mAh/g and 163mAh/g, respectively. The specific capacity was remained 156.1mAh/g after 20 cycles, and the specific capacity retention was 95.77%. The result showed LiNio.sCoo.2O2 doped with Al3+ of 3% had favorable electrochemical properties.