Carbon Nanotubes Enhance Battery Power

The pores between the nanotubes shown in this image can store lithium ions in a high-power battery. Image courtesy of Nature Nanotechnology.

Batteries might gain a boost in power capacity as a result of recent research at MIT. Scientists at the university  found that using carbon nanotubes for one of the battery’s electrodes produced a significant increase — up to tenfold — in the amount of power it could deliver from a given weight of material, compared to a conventional lithium-ion battery. Such electrodes might find applications in small electrical devices, and with further research might also lead to improved batteries for larger, more power-hungry applications.

To produce the new electrode material, the team used a layer-by-layer fabrication method, in which a base material is alternately dipped in solutions containing carbon nanotubes that have been treated with simple organic compounds that give them either a positive or negative net charge. When these layers are alternated on a surface, they bond tightly together because of the complementary charges, making a stable and durable film.

Professors Yang Shao-Horn and Paula Hammond reported the findings in a paper published June 20 in the journal Nature Nanotechnology. 

Batteries, such as the lithium-ion batteries widely used in portable electronics, are made up of three basic components: two electrodes (called the anode and the cathode) separated by an electrolyte, an electrically conductive material through which charged particles, or ions, can move easily. When these batteries are in use, positively charged lithium ions travel across the electrolyte to the cathode, producing an electric current; when they are recharged, an external current causes these ions to move the opposite way, so they become embedded in the spaces in the porous material of the anode.

In the new battery electrode, carbon nanotubes — a form of pure carbon in which sheets of carbon atoms are rolled up into tiny tubes — “self-assemble” into a tightly bound structure that is porous at the nanometer scale. In addition, the carbon nanotubes have many oxygen groups on their surfaces, which can store a large number of lithium ions; this enables carbon nanotubes to serve as the positive electrode in lithium batteries, instead of just the negative electrode.

More information on the research is available from MIT.

Tags: batteries, carbon nanotubes, MIT, Paula Hammond, Yang Shao-Horn