Synthesis And Pilot-Production Technique Development Of Cathode Materials For Rechargeable Lithium Ion Batteries

The conditions by means of mechanical fluid activation have been systematically investigated for systhesizing cathode materials of secondary lithium ion batteries. The results showed that the source of raw materials and the recipe of the raw materials and the heat treatment were key factors affecting the electrochemical characteristics of the cathode materials. The results also showed that pretreated electro-deposited mangnese dioxide (EMD) and Li2CO3 were the optimal raw materials to synthesize LiMn2O4; the LiMn2O4 was of standard spinel structure and preferable charge -discharge performance when the Li/Mn mole ratio was 0.5-0.55; and the cathode materials were of relatively integrated crystal structure and high specific capacity and excellent charge-discharge cycle performance while being synthesized with three sequential steps heat treatment . The optimal raw materials for synthesizingLiCoO2 were CoCO3 and C0364 and Li2CO3; the LiCoO2 was of the normal alayered structure and preferable charge-discharge performance when the Li/Co mole ratio was 0.98-1.05; and the cathode materials were of relatively integrated crystal structure and high specific capacity and excellent charge-discharge cycle performance while being synthesized with two sequential steps heat treatment.The effect of doped rare-earth elements has been investigated as well on electrochemical performance and spinel structure of LiMn2O4. The research results showed that the cathode materials modified by doped rare earth elements were of standard spinel structure, more excellent electrochemical reversibility, the specific capacity, and cycle performance. At another hand , such cathode materials performed better at higher operating temperature. Further improved capacity and cycle performance of the cathode materials were indicated a multiple components compound Li,Mn2-r-zCozRE7y 604 (0.95<=x<=1.1, O<=y<=O. 3, O<=z<=O. 3) . The multiple components compound was synthesized with the application of doping rare earth elements, and coating cobalt on the surface of the cathode materials. Crystal field theory was applied to explain the function and mechanism of doped rare earth element and cobalt coating on cathode materialsABSTRACTproperties .Based on laboratory research, a pilot-production technique was especially developed to synthesize LiCo02 and LiMnA . Two production lines were established with a capacity to synthesize 15 ton LiCo02 annually, and to synthesize 50 ton LiMnA annually, respectively . The pilot-production technique synthesizing LiMn2O4 was of the characteristics of simple synthesis route, low facility investment , short operation process and low production cost . The produced LixMn2-y-zCozRE7y B04 (0. 95x1. 1, OyO.3, 0 zO. 5) modified by rare earth elements and coated with cobalt was of the standard spinel structure, and its capacity was deteriorated less than 15% after 300 cycles. At another hand, the pilot-produced cathode materials performed well at elevated temperature. The tests by battery manufacturers indicated that the pilot-produced cathode materials LiCoC2 was of high specific capacity and good charge-discharge cycle performance and cycle efficiency as compared with the similar products imported from outside China.