Preparation And Properties Of Carbon Anode Materials Used For Lithium Ion Batteries

There is still rare research on carbon materials getting from pretreating mesophase pitch as anode materials of lithium ion battery. The preparation and properties of the mesophase pitch based carbon materials were discussed in this thesis. Carbon coating on graphite was an efficient method to develop its electrochemical performances.Mesophase pitch derived from petroleum residue was treated by different ways and these materials were investigated by X-ray diffraction and electrochemical methods. The electrochemical performances of the material treated by solvent-extraction, oxidation, carbonization and graphitization are better than the material treated by oxidation, carbonization and graphitization. Its first charging capacity is 422mAh·g^-1 and the initial efficiency is 91%, after 20 cycles the capacity is still 375mAh·g^-1.Natural flake-like graphite mixed with coal tar pitch at a proportion was treated by grinding, molding and shattering, after that the carbonization and graphitization were carried out. Carbonized sample, graphitized sample and natural graphite are investigated by X-ray diffraction and scanning electron microscopy. Li-ion batteries were assembled with them as the anode materials and then electrochemical properties were researched. The results show that the natural flake-like graphite is coated by a layer of pitch and the electrochemical properties are improved. The discharging capacity of graphitized sample is 383mAh·g^-1 which is higher than natural graphite by 16mAh·g^-1and its initial efficiency is 87.6% which is higher by 11%, its discharging capacity and efficiency are respectively 380mAh·g^-1 and 99.6%.The natural microcrystalline graphite was treated by resin-impnegnating, curing and carbonizing to prepare composite anode material. Resin carbon coated graphite was then investigated by X-ray diffraction and scanning electron microscopy. The discharging capacity and the initial efficiency of the resin carbon coated graphite are 313mAh·g^-1 and 74.5% respectively. Its initial efficiency is higher by 11% than graphite and its irreversible capacity is reduced by 65.5mAh·g^-1.