Electrodes Synthesized from Carbon Nanostructures Coated with a Smooth and Conformal Metal Adlayer

Abstract

High-surface-area carbon nanostructures coated with a smooth and conformal submonolayer-to-multilayer thin metal films and their method of manufacture are described. The preferred manufacturing process involves the initial oxidation of the carbon nanostructures followed by a surface preparation process involving immersion in a solution with the desired pH to create negative surface dipoles. The nanostructures are subsequently immersed in an alkaline solution containing a suitable quantity of non-noble metal ions which adsorb at surface reaction sites. The metal ions are then reduced via chemical or electrical means. The nanostructures are exposed to a solution containing a salt of one or more noble metals which replace adsorbed non-noble surface metal atoms by galvanic displacement. The process can be controlled and repeated to obtain a desired film coverage. The resulting coated nanostructures may be used, for example, as high-performance electrodes in supercapacitors, batteries, or other electric storage devices.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is a divisional application of copending U.S. patent application Ser. No. 12 / 603,216, filed Oct. 21. 2009, which claims the benefit of U.S. Provisional Application No. 61 / 107,048, filed Oct. 21, 2008; the contents of these applications are herein incorporated by reference in their entirety.STATEMENT OF GOVERNMENT LICENSE RIGHTS[0002]This invention was made with Government support under contract number DE-AC02-98CH10886, awarded by the U.S. Department of Energy. The Government has certain rights in the invention.BACKGROUND OF THE INVENTION[0003]I. FIELD OF THE INVENTION[0004]This invention relates generally to the field of energy storage devices. In particular, the present invention relates to the controlled deposition of smooth and conformal thin metal films on high-surface-area carbon nanostructures. This invention further relates to the use of these nanostructures for supercapacitor electrodes.[0005]II. BACKGROUND OF THE...

AI Technical Summary

Benefits of technology

This patent is about a new method for depositing thin metal films onto nanostructured surfaces. The method involves oxidizing the substrate, adsorbing a cation onto the oxidized surface, and then reducing the cation to a more stable, reactive state using a more noble metal. This results in a smooth, conformal layer of the metal with improved stability, reactivity, and reduced impurity levels. The method can be used to deposit metal films onto carbon nanostructures such as carbon nanohorns, which have conical, open structures that facilitate deposition on both inside and outside surfaces. The technique also allows for the formation of an atomic layer of the desired metal to a high degree of accuracy. Additionally, the patent describes the use of these metal-coated nanostructures as electrodes in a supercapacitor. The high surface area of the nanostructures increases the energy and power density of the supercapacitor.

Problems solved by technology

While batteries are capable of attaining high energy densities over a wide range of voltages, they cannot attain high power densities and can only undergo a limited number of recharge cycles.

Capacitors can provide high energy transfer rates with a nearly unlimited number of recharge cycles, but have limited charge storage capabilities.

However, its small pore size (typically a few nm in diameter) makes it difficult for ions in the electrolyte to access intrapore surfaces.

Furthermore, the use of insulating polymeric binders to fabricate the electrodes is detrimental to performance since it increases the resistance of the electrode.

However, access to inner wall surfaces of nanotubes is inhibited by the small diameter of the tube ends and its proportionally larger length.

The utilization of Ru is, however, inhibited by the high cost and scarcity of Ru as well as the toxicity of its oxides.

Controlled deposition of smooth, conformal thin films of Ru in the submonolayer to multilayer thickness range is also difficult to achieve.

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