Surface Modification of Natural Graphite by Phenolic Resin Carbon Coating for Improvement of Cyclic Performances in Lithium Ion Batteries

Natural graphite was coated with different concentrations of phenolic resin and methane solution. To obtain modified graphite, the coated natural graphite was further carbonized at a temperature of 1000°C for 1 h under a N2 stream after removing the solvent of methane. The surface morphology and microstructure of modified graphite were investigated with scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The computer-controlled constant-current cycler investigated charge and discharge performances. Results showed that the phenolic resin carbon with disordered structure formed on the surface of graphite could protect the graphite from exfoliation and improve its cyclic performances successfully. The reversible capacity and coulombic efficiencies of modified graphite were higher than that of natural graphite during charge and discharge cycling tests at a rate of 50 mA ˙ g-1. It is confirmed that modified graphite has an advantage for an application of high power density lithium ion battery.