Achieving High-Performance Spherical Natural Graphite Anode through a Modified Carbon Coating for Lithium-Ion Batteries

The electrochemical performance of modified natural graphite (MNG) and artificial graphite (AG) was investigated as a function of electrode density ranging from 1.55 to 1.7 g∙cm −3 . The best performance was obtained at 1.55 g∙cm −3 and 1.60 g∙cm −3 for the AG and MNG electrodes, respectively. Both AG, at a density of 1.55 g∙cm −3 , and MNG, at a density of 1.60 g∙cm −3 , showed quite similar performance with regard to cycling stability and coulombic efficiency during cycling at 30 and 45 °C, while the MNG electrodes at a density of 1.60 g∙cm −3 and 1.7 g∙cm −3 showed better rate performance than the AG electrodes at a density of 1.55 g∙cm −3 . The superior rate capability of MNG electrodes can be explained by the following effects: first, their spherical morphology and higher electrode density led to enhanced electrical conductivity. Second, for the MNG sample, favorable electrode tortuosity was retained and thus Li+ transport in the electrode pore was not significantly affected, even at high electrode densities of 1.60 g∙cm −3 and 1.7 g∙cm −3 . MNG electrodes also exhibited a similar electrochemical swelling behavior to the AG electrodes.