Will Nanotubes Lengthen Battery Life?

Originally Published MDDI February 2002

R & D DIGEST

Carbon nanotubes offer potential engineering advantages in a number of medical device applications, ranging from use as device actuators to incorporation in high-strength composites. Researchers now suggest that it may be possible to store more energy in batteries using carbon nanotubes rather than conventional graphite electrodes. Experiments conducted at the University of North Carolina (Chapel Hill) show that carbon nanotubes can contain roughly twice the energy density of graphite, which the researchers say could lead to longer-lasting batteries.

Although there had been speculation that nanotubes might be used to improve batteries, no research had been conducted to demonstrate that they might have advantages over conventional materials. According to Otto Z. Zhou, associate professor and director of the North Carolina Center for Nanoscale Materials, the UNC study revealed that "with graphite, we can store, reversibly, one charged lithium ion for every six carbon atoms, but we found that with nanotubes, we can store one charged lithium ion for every three carbons, also reversibly."

Single-wall carbon nanotubes were created by subjecting a carbon target to intense laser beams. Using chemical processing, the researchers were able to open the closed ends of the nanotubes and reduce their lengths. Says Zhou, "This allows the diffusion of lithium ions into the interior space of the nanotubes and reduces the diffusion time. We believe this is the reason for the enhanced storage capacity."

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