Friday, August 27, 2010

Nokia and Cambridge University Build Better Battery with Carbon Nanotubes

Nokia Corporation (Finland) and University of Cambridge (United Kingdom)  in U.S. Patent Application 20100216023 detail improved batteries and supercapacitors made with carbon nanotubes.

According to inventors Di Wei, Alan Colli, Markku Antti Kyosti Rouvala, Husnu Emrah Unalan, Pritesh Hiralal, Gahan Amaratunga, and Nalin Rupesinghe, an energy storage device structure comprises a first electrode layer, an electrolyte layer and a second electrode layer. At least one of the electrode layers comprise a metallic foil base layer and a layer of carbon nanotubes grown on the base layer, the carbon nanotube layer being arranged to face the electrolyte layer.

The structure may be made in such a way that its width and length are much larger than its thickness, so that it can rolled up or folded and then hermetically sealed to form an energy storage unit. The layer of carbon nanotubes is grown on the metallic foil base layer by a chemical vapor deposition process at a temperature no higher than 550.degree. C. The carbon nanotubes in the carbon nanotube layer are at least partially aligned in a direction that is perpendicular to the surface of the metallic base layer.

The invention was made under a joint research agreement between Nokia Corporation, Finland, and University of Cambridge, United Kingdom.

This disclosure details a process for producing carbon nanostructures, especially carbon nanotubes, on a flexible metallic substrate. Also the disclosure describes energy conversion and storage devices, such as batteries and supercapacitors, having charge collectors made with the carbon nanotubes grown on the flexible substrate. In the process, the carbon nanotubes may be grown to a length of 10 to 100 microns. The carbon nanotubes grown on the metal foil may be at least partially aligned in a direction, the direction being at least nearly perpendicular to the surface of the metal foil. The process is carried out in a chemical vapor deposition system.

The ever-increasing demand for portable electronic devices motivates technological improvements in energy conversion and storage units used in these devices. In developing the energy conversion and storage units, lightweight construction, long lifetime, high power density and flexibility to meet various design and power needs are important factors to consider. Examples of the energy conversion and storage units suitable for portable electronic devices include lithium ion batteries, lithium metal batteries and supercapacitors.

Lithium ion batteries are currently one of the most popular types of solid-state batteries for portable electronic devices, with one of the best energy-to-weight ratios, no memory effect, and a slow loss of charge when not in use. The three primary functional components of a lithium ion battery are anode, cathode and electrolyte, for which a variety of materials may be used. Commercially, the most popular material for the anode is graphite. The cathode may be made with an intercalation lithium compound such as lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, etc. An electrolyte is any substance containing free ions that behaves as an electrically conductive medium. Because they generally consist of ions in solution, electrolytes are also known as ionic solutions, but molten electrolytes and solid electrolytes are also possible

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