A paper battery is a battery engineered to use a paper-thin sheet of cellulose (which is the major constituent of regular paper, among other things) infused with aligned carbon nanotubes. The nanotubes act as electrodes; allowing the storage devices to conduct electricity. The battery, which functions as both a lithium-ion battery and a supercapacitor, can provide a long, steady power output comparable to a conventional battery, as well as a supercapacitor?s quick burst of high energy -- and while a conventional battery contains a number of separate components, the paper battery integrates all of the battery components in a single structure, making it more energy efficient.
The creation of this unique nanocomposite paper drew from a diverse pool of disciplines, requiring expertise in materials science, energy storage, and chemistry. In August 2007, a research team at Rensselaer Polytechnic Institute (led by Drs. Robert Linhardt, the Ann and John H. Broadbent Senior Constellation Professor of Biocatalysis and Metabolic Engineering at Rensselaer; Pulickel M. Ajayan, professor of materials science and engineering; and Omkaram Nalamasu, professor of chemistry with a joint appointment in materials science and engineering) developed the paper battery. Senior research specialist Victor Pushparaj, along with postdoctoral research associates Shaijumon M. Manikoth, Ashavani Kumar, and Saravanababu Murugesan, were co-authors and lead researchers of the project. Other co-authors include research associate Lijie Ci and Rensselaer Nanotechnology Center Laboratory Manager Robert Vajtai.
The researchers used ionic liquid, essentially a liquid salt, as the battery?s electrolyte. The use of ionic liquid, which contains no water, 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,? Kumar said. It gives the battery the ability to function in temperatures up to 300 degrees Fahrenheit and down to 100 below zero. The use of ionic liquid also makes the battery extremely biocompatible; 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. According to Pushparaj ?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.?
A paper battery is a flexible, ultra-thin energy storage and production device formed by combining carbon nanotube s with a conventional sheet of cellulose-based paper. A paper battery acts as both a high-energy battery and supercapacitor , combining two components that are separate in traditional electronics . This combination allows the battery to provide both long-term, steady power production and bursts of energy. Non-toxic, flexible paper batteries have the potential to power the next generation of electronics, medical devices and hybrid vehicles, allowing for radical new designs and medical technologies.
Paper batteries may be folded, cut or otherwise shaped for different applications without any loss of integrity or efficiency . Cutting one in half halves its energy production. Stacking them multiplies power output. Early prototypes of the device are able to produce 2.5 volt s of electricity from a sample the size of a postage stamp.
The devices are formed by combining cellulose with an infusion of aligned carbon nanotubes that are each approximately one millionth of a centimeter thick. The carbon is what gives the batteries their black color. These tiny filaments act like the electrode s found in a traditional battery, conducting electricity when the paper comes into contact with an ionic liquid solution. Ionic liquids contain no water, which means that there is nothing to freeze or evaporate in extreme environmental conditions. As a result, paper batteries can function between -75 and 150 degrees Celsius.
One method of manufacture, developed by scientists at Rensselaer Polytechnic Institute and MIT, begins with growing the nanotubes on a silicon substrate and then impregnating the gaps in the matrix with cellulose. Once the matrix has dried, the material can be peeled off of the substrate, exposing one end of the carbon nanotubes to act as an electrode . When two sheets are combined, with the cellulose sides facing inwards, a supercapacitor is formed that can be activated by the addition of the ionic liquid. This liquid acts as an electrolyte and may include salt-laden solutions like human blood, sweat or urine. The high cellulose content (over 90%) and lack of toxic chemicals in paper batteries makes the device both biocompatible and environmentally friendly, especially when compared to the traditional lithium ion battery used in many present-day electronic devices and laptops.
Widespread commercial deployment of paper batteries will rely on the development of more inexpensive manufacturing techniques for carbon nanotubes. As a result of the potentially transformative applications in electronics, aerospace, hybrid vehicles and medical science, however, numerous companies and organizations are pursuing the development of paper batteries. In addition to the developments announced in 2007 at RPI and MIT, researchers in Singapore announced that they had developed a paper battery powered by ionic solutions in 2005. NEC has also invested in R & D into paper batteries for potential applications in its electronic devices.
Specialized paper batteries could act as power sources for any number of devices implanted in humans and animals, including RFID tags, cosmetics, drug-delivery systems and pacemakers. A capacitor introduced into an organism could be implanted fully dry and then be gradudally exposed to bodily fluids over time to generate voltage. Paper batteries are also biodegradable, a need only partially addressed by current e-cycling and other electronics disposal methods increasingly advocated for by the green computing movement.
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