Synthesis And Electrochemical Performances Of LiNi_xCo_yMn_1-x-yO₂ For Lithium-Ion Battery Cathode Material

As a new generation cathode material, LiNi_xCo_yMn_1-x-yO₂ cathode material has great potential for being a new kind of cathode candidate for its excellent electrochemical performance and low cost, showing an attractive prospect at minitype-portable electric sources and large-scale power supplies. For these reasons, LiNi_xCo_yMn_1-x-yO₂ has been studied intensively as a cathode material to replace the presently used LiCoO2. However, the electrochemical performance of LiNi_xCo_yMn_1-x-yO₂ has been greatly affected by the oxidation of Ni2+ and Mn3+, and the layered structure of the material is hard to be synthesized. Recently, LiNi_xCo_yMn_1-x-yO₂ cathode material is made by being calcined at more than 900℃for more than 10 hours, and this technics is so complex that it makes this kind of material hard to be applying in industry. Furthermore, for this cathode material is studied for only a few years, there are not many reports on it and the discharge capacity of this kind of material, of which is made in our country, is about 160mAh/g, which makes the industrialized production of LiNi_xCo_yMn_1-x-yO₂ becoming impossible. For a solution to these problems, extensive studies have been carried out on the synthesizing of LiNi_xCo_yMn_1-x-yO₂ in this paper. The sample LiNi_xCo_yMn_1-x-yO₂, synthesized in air atmosphere and lower temperature, shows satisfactory performance. Its initial discharge capacity is 197.6mAh/g, its initial discharge efficiency is 73%, and the 50th discharge capacity only deceases 1.3%, showing good electrochemical stabilities.Differed from present cathode materials research thought and method, we have brought forward the idea of emphasizing on the study of the precursor. We studies on the influence of the precursor of the LiNi_xCo_yMn_1-x-yO₂ on the structure and electrochemical performance. In this paper, sol-gel method has been used to synthesized the precursor. The relations between the performance and crystal structure of the precursor and the chelated citric acid, pH, Li/Ni/Co/Mn ratio and different additives have been investigated. The results indicate that the process conditions including type of Ni-salts, the amount of citric acid, pH and Li/Ni/Co/Mn ratio, are important for the preparation of the precursor. At last, we synthesized the precursor of the LiNi_xCo_yMn_1-x-yO₂ in the process conditions that: using nitrate as stuff, the pH is 1.0, the amount of citric acid and the total metallic ions is equal(mol ratio), Li/Ni/Co/Mn ratio is 1.2:0.1:0.2:0.5(mol ratio), temperature is 75℃, respectively. The precursor we...