Ultra thin, flexible 'paper' battery by Rensselaer boffins
The nanoengineered device is capable of functioning in temperatures up to 300 degrees Fahrenheit and down to 100 below zero, and furthermore, it is completely integrated and can be printed like paper.
"We used ionic liquid, essentially a liquid salt, as the battery's electrolyte. It's important to note that ionic liquid contains no water, which means there's nothing in the batteries to freeze or evaporate. This lack of water allows the paper energy storage devices to withstand extreme temperatures," said postdoctoral research associate Ashavani Kumar.
According to its inventors, the device is also unique in the sense 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 capability to use human blood or sweat to help power the battery, they said.
For creating this battery, the scientists infused paper with aligned carbon nanotubes, which gave the device its black colour. The nanotubes act as electrodes and allow the storage devices to conduct electricity.
According to co-author Robert Linhardt, the Ann and John H. Broadbent Senior Constellation Professor of Biocatalysis and Metabolic Engineering at Rensselaer, the device is engineered to function as both a lithium-ion battery and a supercapacitor, and 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 also be rolled, twisted, folded, or cut into any number of shapes with no loss of mechanical integrity or efficiency. The paper batteries can be stacked, like a ream of printer paper, to boost the total power output, he said.
"It's essentially a regular piece of paper, but it's made in a very intelligent way. We're not putting pieces together - it's a single, integrated device. 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," said Prof. Linhardt.
Prof. Linhardt said the paper batteries' light weight could make them ideal for use in small handheld electronic gadgets, implantable medical equipment, automobiles, aircraft, and even boats.
The paper could also be moulded into different shapes, such as a car door, which would enable important new engineering innovations, he said.
These apart, the battery, is also extremely biocompatible and the high paper content and lack of toxic chemicals makes it environmentally safe, said postdoctoral research associate Shaijumon M. Manikoth.
Though the materials required to create the paper batteries are inexpensive, 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," said postdoctoral research associate Saravanababu Murugesan.
"When we get this technology down, we'll basically have the ability to print batteries and print supercapacitors. 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," said Pulickel M. Ajayan, professor of materials science and engineering at Rensselaer.
Details of the project are outlined in the paper "Flexible Energy Storage Devices Based on Nanocomposite Paper" published Aug. 13 in the Proceedings of the National Academy of Sciences (PNAS).