Commercial lithium ion battery carbon negative electrode materials primarily include natural graphite and artificial graphite. The compatibility between natural graphite and electrolytes is poor, and co-intercalation of solvated lithium ions is likely to occur as charging, which makes the graphite layer peel off. Further, the electrolyte continues to react with the graphite layers, leading to a great disadvantage in cycle stability of the battery. At present, techniques to modify the materials mainly include surface-coating to construct a core-shell structure by multiphase coating technology, doping and surface oxidation, etc., thereby improving electrochemical properties. However there still exist many problems such as bad contact between one electrode material particle and another, and between one and a current collector, large surface resistance, poor peel strength, cycle swelling during charge-discharge process, etc. These problems above seriously affect the cycle life and stability of a lithium ion battery.
Chinese patent CN102299308A has reported a lithium ion battery negative electrode material and a method of preparing the same. The material is a composite material consisting of carbon nanotubes and/or carbon nanofibers directly grown in situ on the surface of graphite substrates, and carbon nanotubes and/or carbon nanofibers mixed between the graphite substrates by chemical vapor deposition method. Using the material as a lithium ion battery graphite negative electrode material enhances the discharge capacity, rate performance, liquid absorption and cycle performance. However, the specific surface area of the material obtained by this method is larger and the surface-coating layer formed merely by the vapor deposition method is looser, which leads to a poor stability of the SEI membrane formed during charge-discharge process, more consummation of electrolyte, and thus there still exists in deficiency in cycle stability of batteries at high temperature.