Carbon nanotubes (also known as "bucky tubes") have shown promise for use as anode materials in rechargeable lithium-ion power cells. In comparison with graphite and other forms of carbon used under identical conditions, bucky tubes exhibit greater specific discharge capacity and greater specific energy; this increase has been attributed to the greater electronegativity of bucky tubes and the consequent ability of bucky tubes to accommodate more lithium ions per unit of carbon. The success achieved thus far in the development of bucky-tube anodes with high reversible (charge/discharge) lithium-ion capacities is a result of advances in (1) the production of single- and multi-walled bucky tubes by both arc and non-arc techniques, (2) techniques for purification, (3) techniques for opening the ends of the tubes to admit lithium ions for intercalation, and (4) techniques for fabricating electrodes from bucky tubes.
A recent experimental investigation undertaken as part of this development emphasized the electrochemical performances of open-ended single- and multi-wall bucky-tube anodes in half-cell tests. (In practical full cells, bucky tubes as anode materials would be used in conjunction with LiNiO2, LiMnO2, or LiCoO2 as cathode materials.) In the tests, anodes made from open-ended single-wall bucky tubes exhibited specific discharge capacities as high as 640 mAh/g, and anodes made from open-ended multi-wall bucky tubes exhibited discharge capacities of about 385 mAh/g. In contrast, the theoretical limit of capacity of graphite is only 372 mAh/g.
This work was done by R. O. Loutfy, S. Hossain, and M. Y. Saleh of Materials and Electrochemical Research Corp. for Glenn Research Center.
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