Preparation and Electrochemical Performance of Carbon nanotubes/Micro-expanded?Graphite Composite Anodes for Lithium-ion Batteries

Micro-expanded?flake?graphite (MEFG) and micro-expanded?spherical?graphite (MESG) were prepared from two kinds of natural graphite by intercalation reaction and rapid heating processes. Then carbon nanotubes/ micro-expanded?graphite (CNTs/MEG) composites were prepared by chemical vapor deposition (CVD) process, for which CNTs were grown in the pores of micro-expanded?graphite. Electrochemical test results?show that first discharge/ charge capacities of CNTs/MEFG and CNTs/MESG could respectively accommodate up to 443 and 477 mAh/g. Both of the prepared CNTs/MEG composites keep more than 95% capacities after 30 cycles at the rate of 0.2C and their capacities are stable at?259 and 195 mAh/g after 50 cycles at 1C rate, respectively. The nanoporous structure and the CNTs network can improve the discharge capacities and effectively?buffer the volumetric change of the composite electrode materials in the charge/discharge process. The diffusion path of Li+ can be reduced because of the electrolyte solution that filled in the nanopores, which significantly improves the rate capability of the electrodes. In addition, the growing ivy-like CNTs could improve the electric conductive property of the composites in the charge/discharge process.