Electrochemical insertion of lithium in catalytic multiwall carbon nanotubes

Catalytic multiwall carbon nanotubes (MWNT) have been prepared by decomposition of acetylene on supported cobalt at 900 degrees C. The purified nanotubes were used as a host material for studying the electrode processes during insertion and extraction of lithium in aprotic medium. The degree of irreversible (500 mAh/g) and reversible (450 mAh/g) insertion of lithium has been estimated from the galvanostatic reduction-oxidation characteristics. A large hysteresis was remarked during the extraction of lithium, that confirms the interaction of surface functional groups with lithium ions, e.g. C-O- Li+. The voltammetry experiments on as received MWNT showed a strong capacitance effect (35F/g), mainly played by the central canal. High temperature treatment of MWNT up to 2800 degrees C allowed to improve their structural and microtextural organization as well as to eliminate heteroatoms introduced at the surface during the purification process. A good correlation was found between the electrochemical and physical properties of annealed MWNT.