Carbon nanotubes (CNTs) and carbon nanofilaments (CNFs) have attracted considerable interest in industry and many other fields such as for their use in electronic devices. In this study, CNFs were synthesized by decomposition of ethylene over Pd-and Ni-loaded oxidized diamond catalysts using a fluidized-bed reactor. We examined the effects of various internal structures on Li-ion battery anode properties. Electrochemical measurements indicated that CNF anodes displayed near the theoretical discharge capacity of graphite intercalation compounds (372 mAh/g) as well as high cycle retention. CNF anodes were thus found to be appropriate materials for the use in Li-ion batteries.