Jessica MacNeil

Student research leads to energy storage innovation
May 21, 2008

Researchers at Rensselaer Polytechnic Institute in Troy, NY hope to revolutionize energy storage with the introduction of a nanocomposite paper battery. The product of student research, the device is only a few inches square, ultra thin, light and flexible.

Two groups of students at RPI were working on methods to dissolve paper and cast it into membranes for use in dialysis machines, and making carbon nanotube composites, using polymers. What one of the groups came up with, a thin sheet black on one side and white on the other, sparked an investigation into using paper rather than polymers. This research led to the creation of an integrated paper device that functioned as a battery.

The battery is more than 90 percent cellulose, which is the same plant cell used in newsprint and many other kinds of paper. The paper is infused with electrolytes and carbon nanotubes, which give the device its black color. The carbon nanotubes form electrodes, and allow the storage devices to conduct electricity, while the electrolyte allows the current to flow. (See a BBC diagram)

The device, engineered to function as both a lithium-ion battery and a supercapacitor, can provide the steady power output of a conventional battery, and a supercapacitor’s burst of high energy.

The battery can also be activated by natural electrolytes, like those found in human blood, sweat or urine. This feature makes it ideal for powering devices like pacemakers, so dangerous chemicals normally found in batteries don’t have to be put into the body.

Because the device uses an ionic liquid that contains no water to freeze or evaporate, it can function in temperatures up to 300 degrees Fahrenheit and down to 100 below zero.

The device is particularly unique because it can be rolled, folded, or cut into different shapes with no loss of mechanical integrity or efficiency. The paper batteries can also be stacked to boost the total power output. These features should allow for many new engineering innovations.

Details of the project are outlined in the paper “Flexible Energy Storage Devices Based on Nanocomposite Paper” published August 13, 2007 in the Proceedings of the National Academy of Sciences.

The paper discusses how the basic components, the electrode, separator, and electrolyte, can form contiguous nanocomposite units to create thin mechanically-flexible energy storage devices. “Nanoporous cellulose paper embedded with aligned carbon nanotube electrode and electrolyte constitutes the basic unit,” the introduction explains.

Involved in the research were professors of different disciplines, including materials science, energy storage, and chemistry. Authors of the paper include Robert J. 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. 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 materials used are inexpensive and environmentally safe, but a method to mass produce the device cost-effectively hasn’t been developed yet. The team hopes to print the paper using a roll-to-roll system similar to how newspapers are printed.

The researchers have already filed a patent and are working on ways to boost the efficiency of the batteries and supercapacitors.

The National Science Foundation and New York State's Office of Science and Technology have been funding this project.

Posted by Jessica MacNeil on May 21, 2008 | Comments (0)