Battery employing an electrode pellet having an inner electrode embedded therein

Abstract

An electrochemical battery cell comprising a cell housing defining an inner space, a first terminal and a second terminal; and at least one pre-formed pellet disposed within the inner space of the cell housing. The pellet includes an outer electrode portion formed from a material to geometrically define the pellet in a solid form. The outer electrode portion is in electrical communication with the first terminal of the cell housing. The pellet also includes an inner electrode encapsulated by a separator and embedded within the material of the outer electrode portion. The inner electrode is in electrical communication with the second terminal of the cell housing and electrically insulated from the outer electrode material. In a preferred embodiment, the inner electrode comprises an anode and the outer electrode portion comprises a cathode portion. The integrated anode / cathode pellet configuration facilitates lowers costs, a more robust design and ease of manufacturability while maintaining and allowing increased performance characteristics of the battery cell.

Description

[0001] This application claims priority to U.S. Provisional Application No. 60 / 464,698, filed Apr. 23, 2003, which is incorporated herein by reference.BACKGROUND OF INVENTION[0002] The present invention generally relates to electrochemical battery cells, and more particularly to electrochemical pellet-type battery cells that employ electrode assemblies in the form of pellets.[0003] There are many types and configurations of electrochemical battery cells employed in a variety of applications and in both rechargeable and disposable platforms. The most popular battery cells for consumer applications, particularly high current drain applications, include alkaline cells, nickel metal hydride cells, nickel cadmium cells, and lithium ion cells. As an example, alkaline batteries based on manganese oxide cathodes are widely used for consumer applications. As device power requirements of consumer applications have increased in recent years, alkaline battery producers have sought methods for i...

AI Technical Summary

Benefits of technology

[0009] The present invention facilitates integration of an anode and a cathode in a single pellet configuration for use with an electrochemical battery cell of any type or format utilizing one or more pellets. In accordance with the principles of the present invention as embodied and described herein, one particular characterization of the present invention comprises an electrochemical battery cell comprising a cell housing defining an inner space, a first terminal and a second terminal; and at least one pre-formed pellet disposed within the inner space of the cell housing. The pellet includes an outer electrode portion formed from a material to geometrically define the pellet in a solid form. The outer electrode portion is in electrical communication with the first terminal of the cell housing. The pellet also includes an inner electrode encapsulated by a separator and embedded within the material of the outer electrode portion. The inner electrode is in electrical communication with the second terminal of the cell housing and electrically insulated from the outer electrode portion.

[0023] The present invention facilitates integration of an inner electrode, preferably an anode, and an outer electrode, preferably a cathode, into a single pellet configuration for use with an electrochemical battery cell in any type of format utilizing one or more electrode pellets. The pellet configuration can be utilized in any number of battery cell electrochemistry formats, such as, for example, nickel metal hydride (NiMH), lithium ion (Li-ion), nickel cadmium (NiCd), and alkaline cells. Further, the pellet configuration is applicable to any type of battery cell format utilizing one or more pellets, such as, for example, bobbin type cylindrical cells, coin cells or flat plate cells. The integration of the inner and outer electrodes into a single pellet structure that can be inserted into a cell housing or casing, rather than being separately assembled as discrete component materials, facilitates lowers costs, a more robust design and ease of manufacturability, as well as other benefits. Multiple pellets may be used in a single battery cell to achieve a desired cell capacity. The integration of the electrodes in accordance with the principles of the present invention does not adversely affect the performance characteristics of the battery cell.

[0027] In addition to the embedded anode 64, a coiled current collector 70 may be embedded into the cathode portion of the pellet, as shown in FIG. 3. The current collector 70 facilitates additional current collection for the cathode portion 62. Preferably, the current collector 70 is a nickel mesh-like material and is incorporated into the cathode portion 62 of the pellet 60.

[0038] In this example, an alkaline manganese dioxide cell incorporating a relatively high surface area anode structure is embedded within the cathode material of the cathode portion when it is formed to geometrically define the pellet. The anode structure is flexible so that it may be coiled within the pellet mold prior to pressing and may be deformed during pressing without breaking. In this embodiment, the anode structure consists of a composite mixture of zinc powder and or fiber, polymer binders, absorbers and other additives overlaying a thin metal foil or mesh current collector, which may be copper or brass. The anode structure is coated with a separator layer that is also flexible so that it does not crack or tear away from the anode surface in the pellet molding process. The separator coating is suitably microporous to allow good ion transport between the anode and cathode while not permitting short circuit contact between the two electrodes either before or subsequent to the pressing operation. A parallel cathode current collector may also be embedded in the pellet to improve electron transfer to the cathode. A wire, lead, or tab connection can be bonded to the anode structure prior to pellet formation and brought outside the pellet during or after formation. The wire, lead or tab connection facilitates connection to the negative contact of the can or cell housing. By thus increasing the anode to cathode interfacial area and thinning the anode structure relative to a conventional bobbin cell design, better material utilization is realized and the cell can deliver more runtime at higher drain rates.

Problems solved by technology

This remains a significant challenge given the current trend of designing consumer electronics with ever increasing power requirements while constantly seeking to reduce product and manufacturing costs to increase profit margins.

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