Stanford Report, December 7, 2009

At Stanford, nanotubes + ink + paper = instant battery

Dip an ordinary piece of paper into ink infused with carbon nanotubes and silver nanowires, and it turns into a battery or supercapacitor. Crumple the piece of paper, and it still works. Stanford researcher Yi Cui sees many uses for this new way of storing electricity.

Jack Hubbard

Post doctoral students in the lab of Prof. Yi Cui, Materials Science and Engineering, light up a diode from a battery made from treated paper, similar to what you would find in a copy machine. The paper batteries are treated with a nanotube ink, baked and folded into electrical generating sources like the one wrapped in foil seen here.

BY JANELLE WEAVER

Stanford scientists are harnessing nanotechnology to quickly produce ultra-lightweight, bendable batteries and supercapacitors in the form of everyday paper.

Simply coating a sheet of paper with ink made of carbon nanotubes and silver nanowires makes a highly conductive storage device, said Yi Cui, assistant professor of materials science and engineering.

"Society really needs a low-cost, high-performance energy storage device, such as batteries and simple supercapacitors," he said.

Like batteries, capacitors hold an electric charge, but for a shorter period of time. However, capacitors can store and discharge electricity much more rapidly than a battery.

Cui's work is reported in the paper "Highly Conductive Paper for Energy Storage Devices," published online this week in the Proceedings of the National Academy of Sciences.

"These nanomaterials are special," Cui said. "They're a one-dimensional structure with very small diameters." The small diameter helps the nanomaterial ink stick strongly to the fibrous paper, making the battery and supercapacitor very durable. The paper supercapacitor may last through 40,000 charge-discharge cycles – at least an order of magnitude more than lithium batteries. The nanomaterials also make ideal conductors because they move electricity along much more efficiently than ordinary conductors, Cui said.

L.A. Cicero

Bing Hu, a post-doctoral fellow, prepares a small square of ordinary paper to with an ink that will deposit nanotubes on the surface that can then be charged with energy to create a battery.

Cui had previously created nanomaterial energy storage devices using plastics. His new research shows that a paper battery is more durable because the ink adheres more strongly to paper (answering the question, "Paper or plastic?"). What's more, you can crumple or fold the paper battery, or even soak it in acidic or basic solutions, and the performance does not degrade. "We just haven't tested what happens when you burn it," he said.

The flexibility of paper allows for many clever applications. "If I want to paint my wall with a conducting energy storage device," Cui said, "I can use a brush." In his lab, he demonstrated the battery to a visitor by connecting it to an LED (light-emitting diode), which glowed brightly.

A paper supercapacitor may be especially useful for applications like electric or hybrid cars, which depend on the quick transfer of electricity. The paper supercapacitor's high surface-to-volume ratio gives it an advantage.

"This technology has potential to be commercialized within a short time," said Peidong Yang, professor of chemistry at the University of California-Berkeley. "I don't think it will be limited to just energy storage devices," he said. "This is potentially a very nice, low-cost, flexible electrode for any electrical device."

Cui predicts the biggest impact may be in large-scale storage of electricity on the distribution grid. Excess electricity generated at night, for example, could be saved for peak-use periods during the day. Wind farms and solar energy systems also may require storage.

"The most important part of this paper is how a simple thing in daily life – paper – can be used as a substrate to make functional conductive electrodes by a simple process," Yang said. "It's nanotechnology related to daily life, essentially."

Cui's research team includes postdoctoral scholars Liangbing Hu and JangWook Choi, and graduate student Yuan Yang.

Janelle Weaver is a science-writing intern at the Stanford News Service.

the golden motor is spinning again, just as I suspected it was going to take alot of trial and error getting it back together so that the axle was oriented correctly. Much thanks to the forum members at endless sphere and golden motor, not so much to the golden motor staff but...whatever. Even without the help of the manufacturer I believe that this is another step towards understanding the full capabilities of this motor.

Now the next step will finnaly be mounting this motor to the frame of the bike using a 8 inch diameter steel tube cut to about six or seven inches and placed right behind the seat tube.I do believe after taking the motor apart that the claims of the motor being waterproof are possible with a bit of modification and precaution in the placement of this motor on the bike. The weak points seem to be at the axle berrings and where the motor cover and the rear housing meet. I think that if the berrings on the drive shaft are kept inclosed and the rear housing/cover joining is treated to some sort of sealant this baby should be able to ride in the rain no prob. This comes as a relief to me as I really wanted to be able to have a good portion of the motor exposed not only to show off the motor but to alow the motor case to sink that heat away with air flow.

Now if I can just get my hands on a bunch of A123 cells I might actually be able to get this project rolling. But the light at the end of the tunnel is still quite a ways down cosidering I haven't even begun to think about a BMS.