Storing Power in a Sheet of Paper
It resembles a sheet of black paper, like a piece of construction paper a child would draw on. But it’s really a battery — lightweight, ultrathin, completely flexible, and geared toward meeting the trickiest design and energy requirements of tomorrow’s gadgets, implantable medical equipment, and transportation vehicles.
Along with its ability to function in temperatures up to 300 degrees Fahrenheit and down to 100 below zero, the device, created by researchers at Rensselaer, is completely integrated and can be printed like paper. The device is also unique in that it can function as both a high-energy battery and a high-power supercapacitor, which are generally separate components in most electrical systems. Another key feature is the capability to use human blood or sweat to help power the battery.
How It’s Made
Rensselaer 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 both 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.
“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.
“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. Along with Linhardt, researchers include Pulickel Ajayan, professor of materials science and engineering, and Omkaram Nalamasu, former Rensselaer professor of chemistry with a joint appointment in materials science and engineering. Senior research specialist Victor Pushparaj, along with postdoctoral research associates Shaijumon Manikoth, Ashavani Kumar, and Saravanababu Murugesan, were also lead researchers of the project. Others include research associate Lijie Ci and Rensselaer Nanotechnology Center Laboratory Manager Robert Vajtai.
Plenty of Advantages
The device can be rolled, twisted, folded, 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.
Along with use in small handheld electronics, the paper batteries’ light weight could make them ideal for use in automobiles, aircraft, and even boats. The paper also could be molded into different shapes, such as a car door, which would enable important new engineering innovations.
“Plus, because of the high paper content and lack of toxic chemicals, it’s environmentally safe,” Shaijumon said.
Paper is also extremely biocompatible and these new hybrid battery/supercapacitors have potential as power supplies for devices implanted in the body. The team printed paper batteries without adding any electrolytes, and demonstrated that naturally occurring electrolytes in human sweat, blood, and urine can be used to 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,” Pushparaj said.
And because the battery’s electrolyte is ionic liquid, essentially a liquid salt that contains no water, there’s nothing in the batteries to freeze or evaporate. “This lack of water allows the paper energy storage devices to withstand extreme temperatures,” Kumar said.
The materials required to create the paper batteries are inexpensive, Murugesan said, but the team has not yet developed a way to inexpensively mass produce the devices. The end goal is to print the paper using a roll-to-roll system similar to how newspapers are printed.
“When we get this technology down, we’ll basically have the ability to print batteries and print supercapacitors,” Ajayan said. “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 already filed a patent protecting the invention. They are now working on ways to boost the efficiency of the batteries and supercapacitors, and investigating different manufacturing techniques."Energy storage is an area that can be addressed by nanomanufacturing technologies and our truly interdisciplinary collaborative activity that brings together advances and expertise in nanotechnology, room-temperature ionic liquids, and energy storage devices in a creative way to devise novel battery and supercapacitor devices," Nalamasu said.