NEC Corp enabled an organic radical battery to be repeatedly charged/discharged 10,000 times or more with one second or shorter pulse discharge while enhancing its power density.
By utilizing a printing technology and a technique to evenly disperse electrode ink, the company increased the uniformities of the organic radical material and the carbon fiber, thereby reducing the internal resistance of the positive electrode of the organic radical battery. As a result, the power density of the battery was increased to 5,000W/L, which is three times as high as that of the company's existing organic radical battery.
In addition, by reviewing the structure of the battery and improving the compatibility between the organic radical material and the electrolytic solution, NEC confirmed that the battery can be repeatedly charged/discharged 10,000 times or more.
Specifically, when using a coin-sized organic radical battery with a thickness of 1mm or less, it is possible to discharge with a high current of 1A, achieve a high power output of 2W and repeatedly charge/discharge 10,000 times or more with a current of 100mA, according to the company.
An organic radical battery is a secondary battery that stores electricity utilizing the oxidation-reduction reaction of stable radical. The battery was first announced by NEC in 2001. It utilizes the oxidation-reduction reaction of a substance called "radical," which has unpaired electrons in the outermost shell of the electron orbit.
The battery allows high-speed charging/discharging because the reaction proceeds at a high speed. Also, a gel-type flexible electrode can be created by infiltrating an electrolytic solution into a composite positive electrode consisting of an organic radical compound and a carbon fiber.
Targeting the power sources for next-generation terminals such as highly-functional IC cards, electronic paper and wearable devices, NEC intends to improve the usability of the battery by combining it with contactless charging technology, etc.
Part of the research and development of the battery was conducted under the project called "Basic Technology Development for Fiber Materials with Advanced Functions and New Structures," which is promoted by Japan's Ministry of Economy, Trade and Industry (METI) and Japan's New Energy and Industrial Technology Development Organization (NEDO).
The printing technology and the technique to evenly disperse ink were developed by DIC Corp, while the improved radical material was co-developed by NEC and Sumitomo Seika Chemicals Co Ltd.
The new battery is scheduled for display at the International Nanotechnology Exhibition and Conference (nano tech 2009), which runs from Feb 18 to 20, 2009, at Tokyo Big Sight.