Nov 21, 2007
Nanotube boost for batteries
Researchers in the US have made the first batteries using a random network of carbon nanotubes. The devices have excellent energy-storage characteristics and can be made using "roll-to-roll" or inkjet processing. This means that they are compatible with "printed electronics".
"Our technique allows for simple solution-based printing of the batteries," team leader George Gruner told nanotechweb.org. "Eventually we will be able to print batteries just like we print newspapers. Maybe one day we could even print out our own batteries at home using an inkjet printer."
As their name suggests, printed, or plastic, electronics refers to devices that can be made using simple printing processes and which can be printed onto practically any surface, including fabrics. However, the problem is that conventional batteries are not compatible with such devices, which include smart cards, electronic paper, wearable medical devices and wearable electronics. "To put it simply, printed electronics need printed power," quipped Gruner.
His team, with Andreas Kiebele as the project leader, has now developed a battery architecture based on nanoscale components, such as carbon nanotubes or other nanowires, which are combined with active materials that provide the battery power. The nanowires form thin interpenetrating networks or films that serve as the electrode and charge collector for the device. "We capitalize on the three important properties of such networks: high electrical conductivity, high surface area and mechanical flexibility," explained Gruner.
In the new design, the charge collectors – which are typically made of metal sheets, meshes or films in conventional batteries – are replaced by random networks of nanotubes. These provide the required charge transport to the terminals of the device. "The batteries are similar to conventional batteries, with similar performance, but the high surface area and electrically conducting networks allow us to benefit from the unique properties of nanoscale materials," stated Gruner.
The team has already applied its concept to making supercapacitors, another class of storage devices. Here the electrodes (normally carbon black) are also replaced by nanotubes. These devices release their charges extremely fast but their storage capacity is somewhat smaller. "They were made from the same kind of nanomaterials and using the same fabrication methods and form a powerful pair, capable of supplying energy and power for a variety of electronic devices," explained Gruner.
Applications for the new batteries range from medical uses, such as single-use health monitoring and drug-delivery patches, to security – in smart RFID tags, for example. They could also be integrated with thin-film solar cells.
The team will now focus on optimizing its proof-of-concept device and industrial-scale production is the next step. "We are already meeting the price point requirements but further improvement is certainly possible," added Gruner.
The work was published in Appl. Phys. Lett.
• Show blog
To get the scoop on this year's MRS Fall Meeting from the convenience of your workstation, laptop or smartphone, don't forget to check out nanotechweb.org's show blog from Monday 26 November 2007.
About the author
Belle Dumé is contributing editor at nanotechweb.org