Avx Corporation

Jessica M Smith

Bharat Rawal

Dirk H Dreissig

Lee Shinaberger

Gang Ning

Jonathan Robert Knopsnyder

Bob Knopsnyder

A capacitor containing an electrochemical cell that includes ruthenium oxide electrodes and an aqueous electrolyte containing a polyprotic acid (e.g., sulfuric acid) is provided. More specifically, the electrodes each contain a substrate that is coated with a metal oxide film formed from a combination of ruthenium oxide and inorganic oxide particles (e.g., alumina, silica, etc.). Without intending to be limited by theory, it is believed that the inorganic oxide particles may enhance proton transfer (e.g., proton generation) in the aqueous electrolyte to form hydrated inorganic oxide complexes (e.g., [Al(HO)] to [Al(HO)(OH)]). The inorganic oxide thus acts as a catalyst to both absorb and reversibly cleave water into protons and molecular bonded hydroxyl bridges. Because the anions (e.g., sulfate and bisulfate ions) in the electrolyte are not bound in the coordination sphere of the formed aqua complexes, they do not impede the condensation of these complexes required to achieve the additional capacitance over the potential range. As a result, the ionic charges are kept separate and the chemical process may generate pseudo-capacitance. This, in turn, may result in an increase in the charge density and capacitance of the electrode.

Electrochemical capacitor containing ruthenium oxide electrodes

An electric double layer capacitor that contains at least one electrochemical cell is provided. The cell contains electrodes (e.g., two electrodes) that each contain a porous matrix of electrochemically-active particles (e.g., carbon). An aqueous-based electrolyte is disposed in contact with the porous matrix. In accordance with the present invention, the electrolyte is provided with an anionic polymer that serves as binding agent for the electrochemically active particles and thus reduces electrolyte loss, especially at higher temperatures. Because the polymer is anionic in nature, it is generally hydrophilic and thus can retain its binding properties in the presence of water. The anionic nature of the polymer also allows it to remain stable in the presence of a corrosive polyprotic acid, which is employed in the electrolyte to enhance charge density. Thus, as a result of the present invention, a capacitor may be formed that is capable of exhibiting good electrical performance (e.g., high capacitance and low ESR), even at high temperatures (e.g., 70&#xb0; C. and above).

Electric double layer capacitor

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Myrtle Beach, SC, United States of America

Jessica M Smith