Enhancement of Li doping/undoping reaction rate of carbonaceous materials by coating with an evaporated metal film

A novel method for enhancing the charge/discharge rate of the graphite anode of Li-ion batteries has been developed. The method involves covering the surface of the carbon material with a film of an appropriate metal. Simple vacuum evaporation was found to be effective in covering the entire surface of a carbon fiber sample. The metals examined were Ag, Au, Bi, In, Pb, Pd, Sn and Zn. All the metals exhibited a more or less rate-enhancing effect, but Ag, Sn and Zn were the most effective. The effect was dependent on the film thickness. The effects of heat-treatment were also studied with an eye toward obtaining a stable cycleability.