Professor Pulickel Ajayan and his team from the Rice lab have built a complete lithium ion energy storage device in a single nanowire. The innovation is published in a paper in the American Chemical Society journal.
Scientists demonstrate two versions of their hybrid battery or supercapacitor. The first version is a package of polyaniline cathode, polyethylene oxide (PEO) electrolyte and nickel or tin anode layers. The lithium ions will effectively travel through the anode layer to the electrolyte and later to the cathode where the ions are stored in bulk. The stored ions provide the battery, an ability to charge and discharge rapidly. The second version is the single-nanowire device. Rice researches have constructed centimeter-scale arrays housing thousands of nanowire devices.
Researchers first developed three-dimensional nanobatteries in December 2010. Here, they have packed vertical arrays of nickel-tin nanowires in Plexiglas polymer (PMMA). Plexiglas serves both as an insulator and electrolyte. The nanowire was grown in an anodized alumina template over a copper substrate using an electrodeposition process. In this battery, nickel-tin acts as the anode and the cathode needs to be fixed externally.
However, in the new development, the cathode is attached inside the nanowires. PEO is used as an electrolyte and also as an electrical insulator connecting nanowires. After several testing, researchers have chosen polyaniline (PANI), a synthesized polymer as the cathode. Drop-coating the broadened alumina pores with PEO smears the interiors, encloses the anodes and places tubes at the top, into which PANI cathodes can be drop-coated. The circuit is completed by placing an aluminum current collector on top of the array.
The trial batteries are approximately 50 ì. tall and they are nearly invisible when seen edge-on. The nanowire energy storage devices provide excellent capacity. The team is enhancing the materials to improve their ability to constantly charge and discharge. Rice researchers still focus on the optimization of the devices for superior performance. The nanowire device could be a value-added innovation and such devices could be used as a rechargeable power source for the next-generations of nanoelectronics.
Source: http://www.media.rice.edu/