Carbon Nanotube Anodes for Lithium Ion Batteries

Highly purified single-wall carbon nanotubes (SWCNT) were investigated for use as an anode material for thin film lithium ion batteries. The high purity nanotubes were obtained through chemical refinement of soot generated by pulsed laser ablation. The purity of the nanotubes was determined via thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. The specific surface area and lithium capacity of the SWCNT's was compared to that of other conventional anode materials (i.e., carbon black, graphite, and multi-walled carbon nanotubes). The Brunauer, Emmett, and Teller (BET) technique based on nitrogen adsorption was used to measure the specific surface area of the various anode materials. The SWCNT's exhibited a specific surface area on the order of 915 m2/g, much higher than the other carbonaceous materials. Cyclic voltammetric behavior and the lithium-ion capacity of the materials were measured using a standard 3-electrode electrochemical cell. The cyclic voltammetry showed evidence of “staging” that was similar to other carbonaceous materials. The electrochemical discharge capacity of the purified single walled carbon nanotubes was in excess of 1300 mAh/g after 30 charge/discharge cycles when tested using a current density of 20μA/cm2.