Nano-Batteries Look Like Paper

Nano battery stores power on sheet of paper
A new energy storage device you could mistake for a sheet of black paper, may soon be able to power up almost any type of electronic device.
The nanoengineered battery is lightweight, ultra thin, completely flexible, and should be able to power devices not even created yet, like implantable medical equipment and transportation vehicles, said researchers at Rensselaer Polytechnic Institute (RPI) in Troy, N.Y.
Along with its ability to function in temperatures up to 300°F and down to 100 below zero, the device is completely integrated, and they can print it like paper. The device can function as a high-energy battery and a high-power supercapacitor, which are generally separate components in most electrical systems, the researchers said. Another key feature is the capability to use human blood or sweat to help power the battery.
More than 90% of the device consists of cellulose, the same plant cells used in newsprint, loose leaf, lunch bags, and nearly every type of paper.

RPI researchers infused this paper with aligned carbon nanotubes, which give the device its black color. The nanotubes act as electrodes and allow the storage devices to conduct electricity. The device, engineered to function as a lithium-ion battery and a supercapacitor, can provide the long, steady power output comparable to a conventional battery, as well as a supercapacitor’s quick burst of high energy.
The device can roll, twist, fold, or cut into any number of shapes with no loss of mechanical integrity or efficiency. The paper batteries can also be stacked, like a ream of printer paper, to boost the total power output.
“It’s essentially a regular piece of paper, but it’s made in a very intelligent way,” said Robert Linhardt, the Ann and John H. Broadbent Senior Constellation Professor of Biocatalysis and Metabolic Engineering at Rensselaer and a co-author of a paper on the subject.
“We’re not putting pieces together—it’s a single, integrated device,” he said. “The components are molecularly attached to each other: The carbon nanotube print is embedded in the paper, and the electrolyte is soaked into the paper. The end result is a device that looks, feels, and weighs the same as paper.”
The creation of this unique nanocomposite paper drew from a diverse pool of disciplines, requiring expertise in materials science, energy storage, and chemistry.
Researchers used ionic liquid, essentially a liquid salt, as the battery’s electrolyte. It is important to note ionic liquid contains no water, which means there is nothing in the batteries to freeze or evaporate. “This lack of water allows the paper energy storage devices to withstand extreme temperatures,” said Ashavani Kumar, a postdoctoral research associate.
Along with use in small handheld electronics, the paper batteries’ light weight could make them ideal for use in automobiles, aircraft, and boats. They could also mold the paper into different shapes, such as a car door, which would enable important new engineering innovations, the researchers said.
“Plus, because of the high paper content and lack of toxic chemicals, it’s environmentally safe,” said Shaijumon M. Manikoth, postdoctoral research associate.
Paper is also extremely biocompatible, and these new hybrid battery/supercapcitors have potential as power supplies for devices implanted in the body. The team printed paper batteries without adding any electrolytes and demonstrated naturally occurring electrolytes in human sweat, blood, and urine can activate the battery device.
“It’s a way to power a small device such as a pacemaker without introducing any harsh chemicals, such as the kind that are typically found in batteries, into the body,” said Victor Pushparaj, a senior research specialist.
The materials required to create the paper batteries are inexpensive, but the team has not yet developed a way to inexpensively mass produce the devices, said Saravanababu Murugesan, a postdoctoral research associate. The end goal is to print the paper using a roll-to-roll system similar to how a newspaper prints.
“When we get this technology down, we’ll basically have the ability to print batteries and print supercapacitors,” said Pulickel M. Ajayan, professor of materials science and engineering. “We see this as a technology that’s just right for the current energy market, as well as the electronics industry, which is always looking for smaller, lighter power sources. Our device could make its way into any number of different applications.”
The team of researchers has filed a patent protecting the invention.