Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Reexamination Certificate
1998-07-01
2001-07-17
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
C429S053000, C429S165000
Reexamination Certificate
active
06261709
ABSTRACT:
BACKGROUND
This invention relates to elongate, closed-shell air depolarized electrochemical cells. This invention is related specifically to metal-air air depolarized electrochemical cells illustrated herein as elongate cylindrical cells, and is described herein in relation to cells having the size generally known as “AA.”
The advantages of air depolarized cells have been known as far back as the 19th century. Generally, an air depolarized cell draws oxygen from air of the ambient environment, for use as the cathode active material. Because the cathode active material need not be carried in the cell, the space in the cell that would have otherwise been required for carrying cathode active material can, in general, be utilized for containing anode active material.
Accordingly, the amount of anode active material which can be contained in an air depolarized cell is generally significantly greater than the amount of anode active material which can be contained in a 2-electrode cell of the same overall size. By “2-electrode” cell, we mean an electrochemical cell wherein the entire charge of both anode active material and cathode active material are contained inside the cell structure when the cell is received by the consumer.
Generally, for a given cell size, and similar mass, an air depolarized cell can provide a significantly greater number of watt-hours of electromotive force than can a similarly sized, and similar mass, 2-electrode cell using the same, or a similar, material as the anode electroactive material.
Several attempts have been made to develop and market commercial applications of metal-air cells. However, until about the 1970's, such cells were prone to leakage, and other types of failure.
In the 1970's, metal-air button cells were successfully introduced for use in hearing aids, as replacement for 2-electrode cells. The cells so introduced were generally reliable, and the incidence of leakage had generally been controlled sufficient to make such cells commercially acceptable.
By the mid 1980's, zinc-air cells became the standard for hearing aid use. Since that time, significant effort has been made toward improving metal-air hearing aid cells. Such effort has been directed toward a number of issues common to all manufacturers of such cells. For example, efforts have been directed toward increasing electrochemical capacity of the cell, toward consistency of performance from cell to cell, toward control of electrolyte leakage, toward providing higher voltages desired for newer hearing aid technology, toward higher limiting current, and toward controlling movement of moisture into and out of the cell, and the like.
While metal-air button cells have found wide-spread use in hearing appliances, air depolarized cells have not had wide-spread commercial application for any other end uses, or in other than small button cell sizes.
The air depolarized button cells readily available as items of commerce are generally limited to sizes of no more than 0.6 cm
3
overall volume. In view of the superior ratio of “watt-hour capacity/mass” of air depolarized cells, it would be desirable to provide air depolarized electrochemical cells for other applications. It would especially be desirable to provide air depolarized electrochemical cells which are relatively much larger than button cells. For example, it would be desirable to provide such cells in “AA” size.
It is an object of the invention to provide an air depolarized cell which is relatively larger than a hearing aid button cell and which has a greater overall discharge cycle capacity than a similarly-sized alkaline manganese dioxide cell.
It is another object to provide an air depolarized cell which is relatively larger than a hearing aid button cell, which has an overall discharge capacity at least as great as a similarly-sized alkaline manganese dioxide cell, and wherein the energy/mass ratio of such cell is significantly greater than the energy/mass ratio of a similarly-sized alkaline manganese dioxide cell.
SUMMARY OF THE DISCLOSURE
In a first family of embodiments, the invention comprehends an air depolarized electrochemical cell, comprising a cathode, an anode, and a separator, the cathode including a cathode assembly defining a closed structure, open on opposing ends thereof. The separator is disposed inwardly of, and against or proximate, the air cathode assembly. A bottom member defines a bottom of the cell. An anode cavity is defined inwardly of the separator and the bottom member. A mass of electroactive anode material is disposed in the anode cavity. An anode current collector is in electroactive contact with the mass of electroactive anode material. Electrolyte is dispersed in the electroactive anode material, the cathode, and the separator. The cell further comprises a mass-control chamber in the anode cavity, closed to entry of anode material and electrolyte thereinto. Density of any material contained in the mass-control chamber is no more than 80% of the density of the mass of electroactive anode material. The lesser mass of material in the mass-control chamber is effective to increase the energy/mass ratio of the cell at 1 Amp/hr constant discharge, over a cell wherein the space defined by the mass-control chamber is occupied by additional electroactive anode material or by additional mass of metal in the anode current collector.
The mass-control chamber is preferably an elongate chamber inside said anode current collector. The size of the mass control chamber is preferably greater than any space required for expansion of the anode material during discharge of the electrochemical cell.
In some embodiments, the combination of the air cathode assembly, the separator, and the bottom member defines a circular cross-section of the anode cavity. In other embodiments, the anode cavity is ovoid, or polygonal in cross-section.
In some embodiments, the mass-control chamber is embodied in a hollow tube anode current collector comprising a metal tube having a relatively thick wall, sufficiently strong to withstand, and to substantially hold a uniform cross-sectional shape under, force generated inside the cell.
In other embodiments, the mass-control chamber is embodied in a tube having a relatively thin wall, for example a collapsible thin metal wall, such that force extant inside the cell as the cell is discharged tends to collapse the relatively thin wall of the tube, thereby to create additional space inside the cell for accommodating the force.
In yet other embodiments, the mass-control chamber is embodied in a hollow tube current collector comprising a polymeric substrate composition, coated on an outer surface with at least one layer of a conductive current collecting material suitable to collect electrical energy from the anode mass and to conduct such electrical energy between the anode mass and an anode terminal.
In those embodiments wherein the wall of the mass-control chamber is designed to collapse, a collar can be used to reinforce the wall of the chamber especially adjacent top and/or bottom structural elements of the cell.
In any of the embodiments, the material comprising the current collecting surface, whether a coating material or otherwise, can comprise compositions such as brass, copper, tin, gold, platinum, palladium, or any other material, or combination of materials, known for current collecting and current conducting properties, including combinations of such materials, for example alloys, mixtures, or multiple-layer combinations thereof suitable for collecting electrical energy from the anode mass and conducting such electrical energy between the anode mass and an anode terminal.
In preferred embodiments, the mass-control chamber is defined in a hollow elongate anode current collector extending into a mass of electroactive anode material, and the separator defines an average width across a cross-section of the cell, the average distance between the anode current collector and the separator comprising no more than 40 percent, in some embodiments no more than 35 percent, in other em
Moy Gregory Scott
Passaniti Joseph Lynn
Ward Michael Andrew
Chaney Carol
Rayovac Corporation
Seurer Jerad G.
Tsang Susy
Wilhelm Thomas D.
LandOfFree
Air depolarized electrochemical cell having mass-control... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Air depolarized electrochemical cell having mass-control..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Air depolarized electrochemical cell having mass-control... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2495936