The invention claimed is:
1. A method for producing a composite conductive material, comprising:
(S1) supporting catalyst particles on surfaces of spherical carbon particles;
(S2) heat treating the catalyst particles in a helium or hydrogen atmosphere such that the catalyst particles penetrate the surfaces of the spherical carbon particles and are impregnated beneath the surfaces of the spherical carbon particles at a contact point between the spherical carbon particles and the impregnated catalyst particles;
(S3) heating the spherical carbon particles having the impregnated catalyst particles in the presence of a source gas to grow carbon nanofibers from the impregnated catalyst particles to form the composite conductive material, wherein the source gas contains a carbon source, and wherein the carbon nanofibers extend from the contact point to above the surfaces of the spherical carbon particles, and
oxidizing the spherical carbon particles prior to supporting the catalyst particles on the spherical carbon particles in step (S1).
2. The method according to claim 1 , further comprising:
heat treating the carbon nanofibers in an inert atmosphere.
3. The method according to claim 1 , wherein, in step (S3), the carbon nanofibers are grown in 15 minutes or less.
4. The method according to claim 1 , wherein the carbon source is one or a mixture of two or more selected from the group consisting of carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, and cyclopentadiene.
5. The method according to claim 1 , wherein the catalyst particles are not removed from the composite conductive material after formation of the carbon nanofibers.
6. The method according to claim 1 , wherein the carbon nanofibers have a shape selected from the group consisting of a platelet shape, a herringbone shape, and a tubular shape.