Preparation And Peformance Studies Of Mesocarbon Microbeads

Mesocarbon microbead (MCMB) has become an excellent anode material of lithium-ion battery, because of its unique molecular layers parallel to the pile structure and micro-spherical features. However, research in this area is not very thorough, some basic conditions are not clear. Paper around the industrialization of MCMB has been discussed different conditions, different raw materials and other factors on the properties studied.The purpose of this research was to make MCMB using coal tar pitch by thermal polymerization, analyzing of the shape and size of MCMB by scanning electron microscopy (SEM), laser particle size analyzer. The results showed that, rising the thermal polymerization temperature and prolonging the time of thermal polymerization reaction within the system are conducive to the production of forming aromatic molecules, condensation into the ball more often, improving productivity, increasing the sphere diameter, sphericity better. Also, it is found the action of temperature was more apparent. Therefore, the key of preparation MCMB is optimization of thermal polymerization temperature and time. Stirring speed increased can promote the reaction and improve yield. System pressure increased can enhance the mobility of system, benefit the mutual association and mosaic of macromolecular components, form mesophase spherules. Pyridine, quinoline and toluene containing the ring structure, have better separation. The cake which was centrifugated by washing oil extracted using pyridine, can reduce the extraction time, drop consumption, get better separation.(2) Research the effects of raw material composition on the preparation of MCMB with different contents and softening point of quinoline insoluble (QI) materials and coal tar pitch doping different ratio of FCC slurry oil. The results showed that, QI can prevent the growth of small spheres and the aggregation between the financial spheres, also, preparing different size MCMB by controlling the content of QI. Raw materials with high softening point obtain mesophase pitch softening point too high and the viscosity too low, causing the reaction system coking, solubility of the reduced mesophase carbon microbeads separation and purification not easy. The reaction system with low softening point, for the raw material content of less aromatic molecules, is not conducive to formation of MCMB and reaction products undesirable. By Comparison, we can find soft asphalt (SP 30～40℃) is better than others. FCC slurry of single-core multi-ring with high molecular plane, while the coal tar pitch of multi-core multi-ring molecular with big plane degree, matching each other after the reaction process, can be complementary, thus be able to get a narrow particle size distribution of carbon Microspheres.(3) Study the carbonization and graphitization treatment of the MCMB, analysis by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrical performance testing and other research tools. The results showed that, after carbonization and graphitization of MCMB main contains C elements, while the N, H and other elements disappeared. Graphitization treated of MCMB is hexagonal crystal graphite body. Carbonization treated of MCMB, whose sphericity has no significant change, but its surface and uneven degree area increased, and its spacing has increased slightly, graphitization treated of MCMB, whose ball surface has a not complete depression, and its part of the sphere surface has shrinkage cracks and arranged layers has been more orderly, meanwhile, its surface area and spacing of layer decreased, also its density increased and its degree of graphitization is high, has been formed relatively completed crystal structure. Discharge capacity of MCMB treatmented with carbonization is higher than that of graphitized, because intercalation and deintercalation lithium ion is on the carbonizated MCMB's carbon layer and gap, and also on the graphited MCMB's carbon layer. Intercalation and deintercalation of lithium ion on the carbon layer, the reversibility of embedding and de-embedded is increased, and the charge-discharge capacity is stable, charge and discharge efficiency increased. The performance index of graphited MCMB we prepared has been reached the lithium-ion battery standard of graphite negative electrode material; its performance closes to similar products at home and abroad.