Researching for better electrode architectures for advanced hybrid supercapacitors and batteries using vertically aligned carbon nanotubes, conjugated polymers and/or transition metal oxides.
One of the most important energy storage systems is supercapacitors or electrochemical capacitors (ECs) due to their unmatched cycle life, and fast response time make them useful in applications such as unmanned aeronautical vehicles, submarines, cranes etc. and complementary in energy conversion systems used as range extender. However for the next generation applications, key improvements are needed in their overall performance to achieve energy densities on par with Li-ion batteries.
Exponential advancements in nanotechnology have brought forth a vast number of possibilities for new materials as nanoporous or subnanoporous carbon materials (e.g. carbon nanotubes) having high surface area that results in greater capacitance. Our objective will be to develop new types of hybrid supercapacitors using carbon nanomaterials, conducting polymers and metallic nanostructures.
Conventional capacitors offer very high specific power, but extremely low specific energy, making them impractical for applications requiring high energy. The major differences between a capacitor and a battery are their materials and the mechanism of charge storage. Briefly, a battery stores energy chemically and its energy limitation is the electrode mass. The mechanical stability and chemical reactions irreversibility determine the cycle life of batteries whereas ECs offer exceptional cycle life.
The implementation of conducting polymers or other redox active components into ECs can provide higher capacitance and higher power capacity in comparison to conventional carbon-based capacitors. A capacitor containing a redox active component is often called a pseudocapaciotor or hybrid capacitor. These types of capacitors can be designed in the form of redox active conducting polymer electrodes. Even higher capacitances can be obtained by metal oxides, the use of conducting polymers present innumerable advantages over metal oxides such as low cost, flexibility of design, the potential for lightweight devices, and environmental friendliness compared to heavy metal containing oxides.
The ECs store energy physically and its energy limitation is the electrode surface area. Implementing carbon nanotubes with extremely high surface area into hybrid ECs structure with a conducting polymer ensures to achieve enhanced capacitance behavior. Controlled morphology of carbon nanotubes with a preferential orientation in vertical direction offers fast ion transport and variability in packing density with improved mechanical strength assuring a great candidate as an electrode material with exceptional cycle life.
The main objective is to tailor and design hybrid supercapacitors with vertically aligned carbon nanotubes as an active electrode component and conducting polymer and/or transition metal oxides as a redox active component. For the active electrode, vertically aligned carbon nanotubes will be synthesized by a modified chemical vapor deposition technique.
The study was funded by TÜBİTAK under the 3501- Career Development Program.
Vertically aligned multi-walled carbon nanotube forests.
Image courtesy of the researchers.