Rayovac Corporation

Randall L Collien

Robert B Dopp

John Edward Oltman

Michael J Root

Joseph Lynn Passaniti

John David Burns

Patrick J Spellman

Janna L Rose

Ronald J Ekern

Kenneth H Kenyon

Patricia S Bennett

Alane M Boutelle

This invention pertains to novel alkaline electrochemical cells having high drain capacities, especially cells having high drain rate capabilities at voltages of at least 1.1 volts for use in small appliances such as hearing aids. The anode includes anode material in the cells including potassium hydroxide, zinc powder, 0.02% to 0.5% of a reaction rate enabling compound selected from a compound of indium, cadmium, gallium, thallium, germanium, tin, or lead, with indium compounds being preferred. The anode material optionally further includes a low level of mercury, and preferably a surfactant comprising hydroxyethylcellulose. The cathode provides sufficient oxidative capability to oxidize the zinc at a sufficient rate to support the electrical drain demands on the cell. A cathode, in a preferred zinc air cell for a hearing aid, includes at least 5 air ports, evenly distributed over the surface of the bottom of the cathode can. Cells of the invention exhibit prolonged operation at relatively constant voltage over 1.1 volts, and relatively constant power output at a power density of at least about 210 milliwatts per square inch of the reaction surface area of the cathode assembly, for periods significantly longer than conventional cells of the same type.

Electrochemical cell anode and high discharge rate electrochemical cell

This invention pertains to novel electrochemical metal air cells having improved closed circuit voltage characteristics. The improved voltage characteristics are illustrated at a constant load of 51 ohms. The closed circuit voltage during an initial placement into use of the cell of the invention has a decreased voltage drop relative to prior art cells, and recovers to a higher voltage. For example, the closed circuit voltage of the metal air cell drops to a minimum voltage during the first 20 seconds of initial placement into use. The minimum voltage is no more than 22% less than the initial open circuit voltage. This voltage drop is less than the voltage drop of other known metal air cells at 51 ohms. Metal air cells of the invention recover, during the first minute of use, to a closed circuit voltage of at least 79% of the initial open circuit voltage. The value of the open circuit voltage of the metal air cell of the invention is preferably about 1.43 volt.

Low mercury, high discharge rate electrochemical cell

This invention pertains to novel alkaline electrochemical cells having high drain capacities, especially cells having high drain rate capabilities at voltages of at least 1.1 volts for use in small appliances such as hearing aids. The anode includes anode material in the cells including potassium hydroxide, zinc powder, 0.02% to 0.5% indium as indium compound separate from the zinc powder, optionally a low level of mercury, and preferably a surfactant comprising hydroxyethylcellulose. The cathode provides sufficient oxidative capability to oxidize the zinc at a sufficient rate to support the electrical drain demands on the cell. A cathode, in a preferred zinc air cell for a hearing aid, includes at least 5 air ports, evenly distributed over the surface of the bottom of the cathode can. Cells of the invention exhibit prolonged operation at relatively constant voltage over 1.1 volts, and relatively constant power output at a power density of at least about 210 milliwatts per square inch of the reaction surface area of the cathode assembly, for periods significantly longer than conventional cells.

A potassium polyacrylate superabsorbent polymer made by modified bulk polymerization and characterized as described herein is a superior gelling agent when provided at a suitable concentration in a gelled anode for an alkaline electrochemical cell. Suitable gelled anodes, alkaline electrochemical cells containing such gelled anodes, and methods for making and using same are also described.

Gelling agent for alkaline electrochemical cells

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Madison, WI, United States of America

Randall L Collien