ENERGY

Carbon nanotubes have the intrinsic characteristics desired for material used as electrodes in batteries, capacitors, and fuel cells. These characteristics include tremendously high surface area (~1000 m2/g), good electrical conductivity, excellent chemical stability in acidic environments, and very importantly, their linear geometry makes their surface highly accessible to the electrolyte. Conceptually, batteries, capacitors, and fuel cells all have the structure shown below.


Carbon nanotubes serve as material for the electrodes (anode, cathode or both) in batteries, capacitors and fuel cells. Research has shown that carbon nanotubes have the highest reversible capacity of any carbon material for use in lithium-ion batteries [B. Gao, Chem. Phys. Lett. 327, 69 (2000); Frackowiak et al, carbon 40, 1775 (2002)]. Addition of carbon nanotubes to the carbon black traditionally used as lithium ion battery electrode material increases the conductivity of the electrode, improves the electrolyte penetration into the electrodes and enables the electrodes to maintain their mechanical integrity during the charge-discharge cycles as they absorb and desorb lithium ions. All these, taken together, provide for more efficient, longer lasting Li-ion batteries [Endo et al. Phil. Trans. Roy. Soc. Lond. A 362 2223 (2004). In addition, carbon nanotubes are outstanding materials for supercapacitor electrodes [Baughman et al Science 297, 787 (2002)] and capacitors with carbon nanotube electrodes can provide capacitances exceeding 100 Farads/gram.