KSEF R&D Excellence: Power Sources for MEMs using Modified Carbon Nanotube Arrays

Emerging commercial applications of power sources for microelectromechanical systems (MEMs) necessitate innovations in on-board design and device integration. Traditional power source design metrics, gravimetric and volumetric energy (and power) densities, are not sufficient for integrated portable power sources for small devices. For MEMs applications, constraints are placed on the areal "footprint" of the power source so the available energy and or power of the device must be normalized to this area. Therefore, scale-appropriate power sources with limited "real estate" must be configured to make effective use of their thickness. One approach to maximize energy and power density per unit area is through the three-dimensional configuration of active electrode materials and electrolyte, maximizing the number density of cathodes and anodes while preserving short ion transport distances between them. We propose investigating three-dimensional, nanoscale electrode architectures based on patterned arrays of carbon nanotubes. Using anodic aluminum oxide (AAO) membranes, multiwall carbon nanotubes having open ends will be prepared using a chemical vapor deposition (CYD) method. The proposed synthesis method has the ability to grow carbon nanotubes with open tube ends and controllable diameter, length, and number density. Carbon nanotube arrays will be filled with metals such as Co and Ni and their oxides using electrodeposition or thermal decomposition of organometallics. NiO, for example, shows promise as a cathode material for Li ion batteries. Additionally, B-doped (electron acceptor) and N-doped (electron donor) nanotube arrays will be grown to further enhance ion intercalation into the nanotube structure. Carbon nanotube arrays \vi11 be treated using chemical or electrochemical methods to enhance charge storage properties for electrochemical capacitor applications.