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November 23, 2009

Purposely Adding Defects in Carbon Nanotubes increases Energy Stored in Supercapacitors by up to 200%


University of California San Diego researchers have developed a method to enhance the capacitance (up to three times) of carbon nanotube (CNT) electrode-based electrochemical capacitors by controllably incorporating extrinsic defects into the CNTs.

“While batteries have large storage capacity, they take a long time to charge; while electrostatic capacitors can charge quickly but typically have limited capacity. However, supercapacitors/electrochemical capacitors incorporate the advantages of both,” Bandaru said.

Defects on nanotubes create additional charge sites enhancing the stored charge. The researchers have also discovered methods which could increase or decrease the charge associated with the defects by bombarding the CNTs with argon or hydrogen.

Carbon nanotubes could serve as supercapacitor electrodes with enhanced charge and energy storage capacity.

“It is important to control this process carefully as too many defects can deteriorate the electrical conductivity, which is the reason for the use of CNTs in the first place. Good conductivity helps in efficient charge transport and increases the power density of these devices,” Bandaru added.

The researchers think that the energy density and power density obtained through their work could be practically higher than existing capacitor configurations which suffer from problems associated with poor reliability, cost, and poor electrical characteristics.




We characterize the methodology of, and a possible way to enhance, the capacitance of carbon nanotube (CNT) electrode based electrochemical capacitors. Argon irradiation was used to controllably incorporate extrinsic defects into CNTs and increase the magnitude of both the pseudocapacitance and double-layer capacitance by as much as 50% and 200%, respectively, compared to untreated electrodes. Our work has implications in analyzing the prospects of CNT based electrochemical capacitors, through investigating ways and means of improving their charge storage capacity and energy density

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