Effects of doped copper on electrochemical performance of the raw carbon nanotubes anode

Abstract

The raw carbon nanotubes pre-doped with copper are used as anode materials for lithium ion batteries. Constant current discharge and charge tests using the raw carbon nanotubes pre-doped with copper as Li + storage compounds show lower specific capacities than that of the acid-oxidized carbon nanotubes. The acids play an important role; H 2SO 4 and HNO 3 can easily permeate through the graphene sheets, then they will make the defects or pores in the graphene sheets, and this reaction can make the expansion of the graphite. Meanwhile, Cu 2+ will diffuse into the pores and onto the outer surfaces of the carbon nanotubes. Cu 2+ can be easily turned into Cu at high temperature in the presence of the carbon nanomaterial. So parts of the pores and the surfaces of the carbon nanotubes will be filled with the Cu atom. Once the space positions of the nanotubes were occupied, lithium cannot intercalate into the pores and onto the outer surface of the carbon nanotubes, thus the doped carbon nanotubes will have a low specific capacity.