High-rate charge/discharge properties of Li-ion battery using carbon-coated composites of graphites, vapor grown carbon fibers, and carbon nanohorns

• We succeeded in preparing the carbon-coated composites of graphites, VGCF, and CNHs.
• The quantity of coated carbon films was estimated as 4 wt% from the weight change of TGA.
• The carbon-coated composites achieved the excellent high-rate properties for half-cell.

The mixture of graphite, vapor grown carbon fibers (VGCFs), and carbon nanohorns (CNHs) was heat-treated in Ar atmosphere and carbon-coated by using a chemical vapor deposition (CVD) method (C-graphite/VGCF/CNH). Scanning electron microscopy observation showed that graphite, VGCF, and CNHs were covered by carbon film. Thermogravimetric analysis also indicated that carbon film formed by the CVD method combusted at 550 °C and the quantity of carbon film was about 4 wt%. The C-rate properties of half-cell for C-graphite/VGCF/CNH were superior to those for the mixture of graphite, VGCF, and CNHs (C-graphite/VGCF/CNH (discharge) : 3C/0.1C, 85%, graphite/VGCF/CNH (discharge) : 3C/0.1C, 50%), accelerating a promising application for quick charge–discharge of Li-ion batteries.