Nano Has Flower Power

September 24, 2008

Cell phones, iPods and other electronic device need battery power. And if you own any of these, you know firsthand how quickly those batteries wear down. I got my cell phone plugged in right now and know that even if I leave it tethered to the socket for infinity plus one, I'll still see the battery bar depleted by the end of the day tomorrow.

Scientists own cell phones, too. And they get just as irked. Some of them, like Hao Zhang at the Research Institute of Chemical Defense and his colleagues at Peking University, are working on a solution:  nanoflower/carbon nanotube composite electrodes. They report their work in ACS' Nano Letters.

The researchers grew nano-sized flowers (right) made from manganese oxide, a metallic material already used in batteries. According to Zhang (I emailed him in China and asked), the flower shape has several powerful advantages.

First, each manganese oxide nanoflower is connected directly with the current collector (below) by two or more electron "stems" made from carbon nanotubes. Carbon nanotubes are strong, so they offer good mechanical support, and they are excellent for shuttling electrons. As a result, this shape "allows for efficient charge transport and enhances the electronic conductivity of composite significantly," said Zhang.

Second, the small nanometer size means the charged particles (ions) don't have to travel very far, which  ensure that their charge is fully utilized and very little goes to waste.

Third, micropores in the flower offer low resistance to the ions.

Fourth, because every manganese oxide flower is connected to the conducting framework, the need for binders or conducting additives, which add extra contact resistance or weight, is eliminated.

Images: Courtesy Hao Zhang