Chemistry: electrical current producing apparatus – product – and – Plural concentric or single coiled electrode
Reexamination Certificate
1998-06-15
2001-09-11
Brouillette, Gabrielle (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Plural concentric or single coiled electrode
C429S099000, C429S164000, C429S159000
Reexamination Certificate
active
06287719
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to batteries having one or more electrochemical cells. The present invention further generally relates to batteries including an electrochemical cell having a spiral-wound electrode assembly in which the positive and negative electrodes of the electrochemical cell are wound about a mandrel in a spiral manner.
Batteries are known that include an electrochemical cell in which the positive and negative electrodes are wound into a spiral-wound electrode assembly (also known as a jelly roll assembly). The positive and negative electrodes in these types of batteries are typically constructed of elongated conductive foil strips made of aluminum or copper that have a mixture of materials including active electrochemical materials coated on both sides. The positive and negative electrodes are wound by a mandrel with layers of a separator material disposed between the electrode layers so as to prevent any physical contact between the positive and negative electrodes. After the spiral-wound electrode assembly has been wound about the mandrel, the spiral-wound electrode assembly is removed and inserted into an open end of a cylindrical or prismatic metal cell housing. Subsequently, an electrolyte is dispensed into the open end of the cell housing. The liquid electrolyte flows around and within the spiral-wound electrode assembly and is absorbed into the separator layers between the positive and negative electrodes so as to enable the transport of ions between the positive and negative electrodes.
After the electrolyte has been dispensed within the cell housing, the cell housing is sealed by inserting a cover assembly into the open end such that the cover assembly is electrically connected to one of the electrodes, and crimping the cell housing to hold the cover assembly in place. The cover assembly is also preferably electrically insulated from the cell housing so that the cover assembly and the cell housing each serve as electrical contact terminals having opposite polarities.
Such spiral-wound electrode-type cells are typically used in combination in rechargeable battery packs for video cameras, cellular telephones, and portable computers. Because battery packs of these types require high output voltages, the cells used typically have cell voltages at or in excess of 3 volts. The components used to construct these electrochemical cells are typically more expensive and require more stable electrolytes and binders, which bind the active electrochemical materials to the conductive electrode strips.
A further problem with the construction of spiral-wound electrode-type electrochemical cells constructed as described above, results from the use of the microporous separators. Such microporous separators are one of the more expensive components of the electrochemical cell. Further, these separators typically increase the internal resistance of the cell and, as a consequence, may decrease the high-rate performance of the cell. Moreover, the separators themselves are not electrochemically active components and consume space within the cell housing that could otherwise be filled with electrochemically active components.
It is known in the art of alkaline batteries to construct a high-voltage battery using a plurality of lower voltage electrochemical cells coupled in series. For example, conventional 9-volt batteries are constructed by coupling six 1.5-volt cells in series. Such multi-cell batteries are typically constructed using electrochemical cells that have separate sealed housings so as to keep the liquid electrolyte contained therein separate from each of the other cells. If the liquid electrolyte were allowed to flow freely between the cells, inter-cell leakage current would result. Because of the space that would be required within the battery housing for including separate sealed cells, such batteries make poor use of the total battery volume. As a result, low-voltage cells are poor candidates for high-voltage battery construction.
SUMMARY OF THE INVENTION
Accordingly, it is an aspect of the present invention to solve the above problems by providing a battery having a multi-cell, spiral-wound electrode-type construction that does not require separate sealed containers for each of the cells. An additional aspect of the present invention is to provide a battery having a spiral-wound electrode-type construction that does not require the use of expensive separators. It is yet another aspect of the present invention to provide a battery that is capable of generating cell voltages of 3 or more volts while enabling the use of less-expensive lower voltage components. A further aspect of the present invention is to provide a multi-cell construction that is relatively easy to manufacture using conventional electrode winding equipment.
To achieve these and other aspects and advantages, a battery constructed in accordance with the present invention comprises a housing and a spiral-wound electrode assembly disposed in the housing and defining at least two concentric electrochemical cells that are electrically connected in series. Each of the cells includes wound layers of a positive electrode, a negative electrode, and a polymer electrolyte provided between the positive and negative electrode layers. Preferably, the cells are electrically insulated from one another by providing an insulating layer that is wound between electrode layers of the cells that are otherwise adjacent to one another.
By utilizing a polymer electrolyte, the electrolyte cannot flow between the cells and thereby create an inter-cell leakage current. Thus, the need for separate sealed containers is eliminated. By eliminating the need for sealed containers within the battery housing, the electrochemical cells may be disposed in the battery housing in the most space-efficient manner. Also, by utilizing a polymer electrolyte, the need for microporous separator layers is eliminated since the polymer electrolyte prevents physical contact between the positive and negative electrode layers. The term “polymer electrolyte” as used herein means a material which has ionic conductivity but is substantially physically immobile and hence remains positioned between the anode and cathode. The composition of such polymer electrolytes can range from a salt dissolved in a high molecular weight polymer with no low molecular weight plasticizer to compositions containing electrolyte salt, a large amount of one or more low molecular weight solvents, and only sufficient polymer to immobilize (gel) the low molecular weight solvent.
In addition, by enabling the creation of a multi-cell, spiral-wound electrode assembly, higher voltage batteries may be constructed that utilize lower voltage cells that in turn may utilize less-expensive lower voltage components.
These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.
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Vinal, George Wood, “Dry Cells—Material Production,”Primary Batteries, John Wiley & Sons, Inc., pp. 53-56.
Vin
Brouillette Gabrielle
Eveready Battery Company Inc.
Toye, Jr. Russell H.
Welsh Robert W.
Wills M.
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