Carbon nanotube synthesis, characteristics, and microbattery applications

The stabilities and efficiencies of cathodes of microbatteries are important for their superior performance. The performance of cathode of microbattery systems can be improved by applying new materials or combining components with unique properties into cathode materials. Individual carbon nanotubes exhibit extraordinary mechanical, thermal and electrical properties. Composite materials, using carbon nanotubes as fillers are, expected to show similar superior properties. This study reports synthesis of carbon nanotubes by microwave chemical vapor deposition (MACVD) and applying them in the cathode of microbatteries to improve battery performance. Carbon nanotubes were grown on Ni deposited porous alumina substrates in a flowing gas mixture of methane and hydrogen. Characterization of the carbon nanotubes was carried out using scanning electronic microscopy, transmission electron microscopy, and Raman spectroscopy. It was found that the carbon nanotubes were randomly oriented, spaghetti-like, and with a high aspect ratio. The diameters of CNTs, as determined by transmission electron microscopy (TEM) were between 10 and 100 nm. TEM also showed that the nanotubes had a central hollow with amorphous carbons covering outside wall. The CNTs were nanocoated with a V2O5 sol-gel, which upon curing formed a xeorgel about the carbon nanotubes. This formed a molecular composite cathode. Microbatteries/microcapacitors were made and subjected to charge/discharge cycles with a consistent maximum charge of 4.60 V.