Very interesting! Ultra capacitors and Li-ion batteries are both used in Prius type hybrid vehicles. The ultracapacitors provide the burst of energy required for rapid acceleration and startup, while the batteries provide the energy density required for sustained driving. Ofcourse, a goal for ultra capacitors has been to increase the energy density so they could replace the Li-ion type batteries completely. The additional benefit would also include very rapid charging of such ultracapacitor based energy storage systems. (Source: Green Car Congress)
Researchers Develop Nanocomposite Paper Energy Storage Devices That Can Function as Batteries or SupercapacitorsResearchers at Rensselaer Polytechnic Institute (RPI) have developed a new nanocomposite paper energy storage technology which integrates the three basic components of an electrochemical storage device—electrode, separator and electrolyte—into single contiguous nanocomposite units that can serve as building blocks for a variety of thin, mechanically flexible energy storage devices.
These units can build various flexible battery, supercapacitor, hybrid, and dual-storage battery-in-supercapacitor devices. The nanoengineered battery is lightweight, ultra-thin and completely flexible, and can function in temperatures up to 300 degrees Fahrenheit and down to 100 below zero.
Details of the project are outlined in the paper “Flexible Energy Storage Devices Based on Nanocomposite Paper” to be published in the 21 August issue of the Proceedings of the National Academy of Sciences.
To build the devices, the researchers combined two essential materials—cellulose and carbon nanotubes (CNTs)—that fit the characteristics of spacer and electrode and provide inherent flexibility as well as porosity to the system.
More than 90% of the device is made up of cellulose. 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.
Two different fabrications of the device as a supercapacitor, one with an aqueous, the other with a non-aqueous electrolyte, yielded calculated specific capacitances of 36F/g and 22 F/g, respectively, with operating voltages of about 0.9 V and about 2.3V respectively.
A power density of 1.5 kW·kg-1 (energy density, ~ 13 Wh/kg) is obtained at room temperature for the nanocomposite (RTIL) [non-aqueous] supercapacitor, which are within reported ranges (0.01–10 kW·kg-1) of commercial supercapacitors and comparable to flexible devices reported.
Fabricated as a lithium-ion battery, the device used a of RTIL (room temperature ionic liquid)-free nanocomposite as cathode and a thin evaporated Li-metal layer as anode, with Al foil on both sides as current collectors. Aqueous LiPF6 in ethylene carbonate and dimethyl carbonate (1:1 vol/vol) is used as the electrolyte.
The charge-discharge cycles of the battery were measured between 3.6 and 0.1 V, at a constant current of 10 mA/g. A large irreversible-capacity (~430 mAh/g) is observed during the first charge-discharge cycle, and further charge–discharge cycles resulted in a reversible capacity of 110 mAh/g.
In recent years, supercapacitors coupled with batteries have been considered as promising hybrid devices to combine the best features of a battery and a supercapacitor. We show that our battery and supercapacitor devices could be integrated in parallel to build hybrids, as reported for conventional hybrids.
…In addition to this traditional hybrid, the nanocomposite units also allow for building new kinds of merged hybrid devices with three terminals… which would act as both battery and supercapacitor (a dual-storage device).
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.
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, authors of the paper include 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 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.
The paper energy storage device project was supported by the New York State Office of Science, Technology, and Academic Research (NYSTAR), as well as the National Science Foundation (NSF) through the Nanoscale Science and Engineering Center at Rensselaer.
- Victor L. Pushparaj, Shaijumon M. Manikoth, Ashavani Kumar, Saravanababu Murugesan, Lijie Ci, Robert Vajtai, Robert J. Linhardt, Omkaram Nalamasu, and Pulickel M. Ajayan; “Flexible energy storage devices based on nanocomposite paper”; PNAS 21 August 2007 Vol. 104 No. 34 13574–13577 http://www.pnas.org.cgi.doi.10.1073.pnas.0706508104