Case Western Reserve University

Other

Donald L McGervey

Gerhard E Welsch

Paul T Szozdowski

A method of forming battery electrodes with high specific surface and thin layers of active material is disclosed. The method enables low series resistance and high battery power.

High-power battery

A capacitor anode () includes a substrate () which is formed from an alloy, metal, or metal compound which has a high tensile yield strength and high elastic modulus. The material has a composition which can be anodized, yielding an adherent and compressively stressed dielectric film () of pure, mixed, alloyed, or doped oxide that has a high usable dielectric strength (e.g., over 50 V/&#x3bc;m) and high dielectric constant (e.g., 20 to over 10,000). A capacitor formed from the anode has a high energy density.

Strong substrate alloy and compressively stressed dielectric film for capacitor with high energy density

An anode () and/or cathode () of a capacitor has a large surface area. The high surface area of the anode is provided by forming the anode from a thin, electrically conductive layer () formed from metal particles () or an electrically conductive metallic sponge (). These materials provide a porous structure with a large surface area of high accessibility. The particles are preferably directional or non-directional sponge particles of a metal, such as titanium. The conductive layer has a dielectric film () on its surface, formed by anodizing the particle surfaces. The dielectric film has a combination of high dielectric constant and high dielectric strength. The cathode () of the capacitor is either a conventional solid material or, more preferably, has a large surface provided by forming the surface from a sponge or particles analogously to the anode. The high dielectric strengths obtainable from the capacitor allow for extreme miniaturization, making the capacitor particularly suited for integrated circuit applications.

High power capacitors from thin layers of metal powder or metal sponge particles

A dendritic sponge which is directionally-grown on a substrate material has a high surface to volume ratio and is suitable for forming anodes for highly efficient capacitors. A dielectric film is formed on the sponge surface by oxidizing the surface. In a preferred embodiment, the dielectric is grown on titanium sponge and is doped with oxides of Ca, Mg, Sr, Be, or Ba to improve the film's dielectric constant or with higher valent cations, such as Cr , V , Ta , Mo , Nb , W , and P , to reduce the oxygen vacancy concentration and leakage current of the dielectric film. A capacitor formed from the sponge includes a cathode electrolyte which serves as an electrical conductor and to repair the dielectric film by re-oxidizing the anode surface at areas of local breakdown. Sponges of titanium, tantalum, and aluminum form efficient dielectric films. In another embodiment, sponges of elements which do not form efficient dielectric films are coated with a dielectric material. Capacitors formed with titanium sponges have energy densities of 10 to 50 Watt hours and power densities of 100,000 to 10,000,000 Watts per kilogram of titanium.

Method for forming capacitor anodes

A dendritic sponge which is directionally-grown on a substrate material has a high surface to volume ratio and is suitable for forming anodes for highly efficient capacitors. A dielectric film is formed on the sponge surface by oxidizing the surface. In a preferred embodiment, the dielectric is grown on titanium sponge and is doped with oxides of Ca, Mg, Sr, Be, or Ba to improve the film's dielectric constant or with higher valent cations, such as Cr,, V,, Ta,, Mo,, Nb,, W,, and P,, to reduce the oxygen vacancy concentration and leakage current of the dielectric film. A capacitor formed from the sponge includes a cathode electrolyte which serves as an electrical conductor and to repair the dielectric film by re-oxidizing the anode surface at areas of local breakdown. Sponges of titanium, tantalum, and aluminum form efficient dielectric films. In another embodiment, sponges of elements which do not form efficient dielectric films are coated with a dielectric material. Capacitors formed with titanium sponges have energy densities of 10,to 50 Watt hours and power densities of 100,000 to 10,000,000 Watts per kilogram of titanium.

Growing community of inventors

Cleveland Heights, OH, United States of America

Donald L McGervey