Tayhas Palmore, an associate professor of engineering at Brown University and his research associate used two strips of gold-coated plastic film with their tips coated by separate conduction altering chemicals and separated them by a papery membrane to create a hybrid plastic battery.
The research promised to herald a new era of high-performance batteries that did not use metals such as nickel and cadmium that are harmful to the environment. But the substrate materials have proven hard to mass-produce, and the battery has extremely poor cycling stability – that is, its performance tends to degrade rapidly after a small number of discharge cycles. But the concept of using conducting polymers with electroactive molecules for creating plastic batteries was established by this discovery.
Now, in an article published in Nanoletters, researchers at Uppsala University in Sweden have used cellulose-based coating substrates from Cladophora algae to fabricate a new polypyrrole battery. They claim it can store up to 600 mA per cm²p;, with only 6% loss through 100 charging cycles and can be fully charged in 11,3 seconds at 320 mA.
Cladophora is a branching, green filamentous alga, commonly known as a nuisance alga that has proliferated in shallow waters recently due to nutrient runoff from increased fertiliser use, sewage dumping into water bodies, and so on. There has been a lot of research focused on using cellulose-based coating substrates, but the charging performance of such cells has been unsatisfactory. Researchers at the Nanotechnology and Functional Materials Department of Engineering Sciences at the Ångström Laboratory have been investigating pharmaceutical applications of the cellulose from Cladophora algae, which have a unique nanostructure, for a number of years.
Cladophora cellulose has been proposed as an ideal thickening agent for pharmaceutical preparations and as a binder in foodstuffs. Because of its inordinately large surface area, the material is eminently suitable for use as coating substrates. The design proposes a nanostructure of algal cellulose coated with a 50 nm layer of polypyrrole. The extreme thinness of the polymer layer enables the higher charge capacity, but there is still a significant amount of ground to be covered in terms of cycling stability.
It is believed that the most significant advantage suggested by the prospect of using algae-based polymer batteries is that they would be extremely easy to mass-produce. But their charge capacity is still only about 25 Wh/kg, far behind the 100 to 160 Wh/kg achievable by current Lithium Ion batteries. But polymer batteries promise green, extremely thin and lightweight power sources that could be integrated into a variety of surfaces such as paper and clothing. In combination with flexible electronic devices, sensors and displays in various stages of development in labs around the world, such batteries would enable humans to turn virtually every aspect of their existence into active materials.
For more information contact Patrick Cairns, Frost & Sullivan, +27 (0)21 680 3274, [email protected], www.frost.com
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