A Tale of Conducting Polymers and Carbon Nanotubes

This blog recently relayed word that, in addition to investigators at Argonne National Laboratory testing combinations of batteries and ultra capacitors, there was active exploration of a combination of Nesscap Super Capacitors with Kokum Lithium-ion Batteries — two existing, advanced technologies are used together with integration determined by power electronics.

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PWM (Pulse Width Modulated) power electronics may mean that battery / ultracapacitor combinations could have broad applications. Developers have used a converter to 1) actively control the power flow from a battery, 2) couple the battery to an ultracapacitor for power enhancement, and 3) deliver the power to a load efficiently; and have demonstrated in experiments and simulations that such combinations could achieve much greater specific power while reducing battery current and its internal loss.Green Car Congress1 informs us that researchers at the University of Nottingham (UK) are developing new energy storage systems for use with renewable energy generation including a device that combines the properties of supercapacitors and batteries (“supercapattery”). (C’mon Mike, you can do better than “supercapattery”.)Supported by €1.4m (US$2.2 million) from E.ON, one of Europe’s leading power and gas companies, Dr. George Chen in the University’s School of Chemical and Environmental Engineering and Dr. Christian Klumpner in the School of Electrical and Electronic Engineering are developing a new electrical energy storage system.As previously noted, the basis for such development is experimental production of carbon nanotubes, which are characterized by fast, reversible surface redox. The U. Nottingham researchers specifically have designed manganese oxide-coated carbon nanotubes and conducting polymer-coated carbon nanotubes. In addition to these chemically modified core materials, the researchers are developing power electronics that will ensure current flow is of high-quality.

Photo: Riccardo Signorelli/MIT
At research and development centers around the world, the race is on to demonstrate commercial viability of the nanotube approach.Electricity generated from renewable sources can be transported instantly through cables over long distances but storage is a problem—if you don’t use it, you lose it. Our aim is to develop something which will bring together the best of both worlds—the high electrical energy storage capacity of a battery and the fast charge/discharge rates of a supercapacitor.The specific capacitance (Farads per gram) of the manganese oxide-carbon nanotubes composite is normal (140~150 F/g), but the electrode specific capacitance (Farads per square centimeter) is very high. The value reported, 4~5 Farads per square centimetre, is actually the world record amongst all published results. The charge/discharge chemistry of this composite is mainly that of manganese oxide with some contribution from carbon nanotubes. —George Chen

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