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Farjand • Jul 30, 2011

Rice University Fabricate Lithium Ion Battery Into Single Nanowire

Lithium ion battery is possibly the world’s most efficient and commercial battery available today. It is a prime force behind many of today's electrical gadgets. Scientists at Rice lab Pulickel Ajayan have now designed this battery on a nano scale such that the whole battery can be fitted in a single nanowire. This is perhaps the world’s smallest battery that a Lithium ion battery can be reduced to.


The research work presented in American Chemical Society journal Nano Letters reports this unusual achievement. Ajayan has researched about battery pack consisting of a Nickel/tin anode and polyaniline cathode. In this he used Polyethylene oxide (PEO) as an electrolyte. The battery unit proves the feasibility of lithium ion can move efficiently between the anode and cathode through the electrolyte. The cathode stores these ions in bulk so that the device can charge and discharge rapidly.

As this appears to be a macro system, Ajayan has developed a second type of battery with similar working but on a device scaled down to centimeters. Each unit with dimensions 150 nanometers wide has closely packed thousands of nanowire devices. This time the researchers used cathode made up of an easily synthesized polymer called Polyaniline (PANI), the electrolyte used is LiPF6.The electromechanical system thus obtained works on a hybrid mechanism which is based on a Li intercalation at the anode and PF6 doping at the cathode.

The initial idea of the researchers was fabrication of ultrathin nanowire energy storage system with an negligible separation between two adjacent electrodes. The researchers feel that this would be a useful tool in probing any nanoscale phenomenon, given the ultrathin spacing between electrodes. The use of PANI was after a much negotiation between various substances and chemicals. Last December, Ajayan and his team had reported fabrication of a 3D nanobattery. In which they had encased vertical arrays of Nickel-Tin nanowires in Plexiglas as electrolyte. In this process, the scientists tried to grow nanowires with the help of anodized alumina template on a copper substrate. However the template's pores were still narrow. The team employed simple etching techniques to widen them chemically and then drop coated the Plexiglas thereby encasing wires in a smooth and consistent sheath.

The parallel array of nanowires so developed by the team shows a capacity of almost 3?Ah/cmat a current rate of 0.03 mA/cm2. However there is a lot to be done in these battery in case right from optimization to exploring different electrode material. The research is about to make Lithium ion battery even more compact. Who knows, if it may also increase battery's energy density? The other researchers in Ajayan's team were Sanketh R. Gowda, Arava Leela Mohana Reddy and Xiaobo Zhan.

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