Charge-discharge characteristics of raw acid-oxidized carbon nanotubes

Lithium intercalation with raw acid-oxidized carbon nanotubes was studied. The results show that the total capacity of 660 mA h g(-1) was obtained after the first discharge. The reversible part is 200 mA h g(-1). The solid electrolyte interface (SEI) is formed by reaction of surface groups on the carbon nanotubes with lithium upon discharge. The nature of this interface to a large extent determines the reversible and irreversible capacities of the carbon nanotubes. During oxidation in the mixture of acid, the residual acids will play an important role in this work. The residual acids will react with Li ion and cause irreversible capacity. The H2SO4 and HNO3 can easily permeate through the graphene sheets, then they will make defects or pores in graphene sheets and cause the reversible capacity. The surface groups formed upon oxidation have been characterized using Fourier transform infrared spectroscopy. (C) 2002 Elsevier Science B.V. All rights reserved.