Notched electrode and method of making same

Details Notched electrode and method of making same Notched electrode and method of making same

1999-08-16

2001-10-09

Chaney, Carol (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Plural concentric or single coiled electrode

Reexamination Certificate

active

06300002

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to an electrode for an electrochemical cell, and more specifically, to an electrode wound into a jellyroll configuration prior to insertion into a cell container.
Typically, jellyroll cells are made by forming an electrode assembly of two electrode strips having opposing polarities with a separator interposed in between and winding the assembly into a jellyroll. Typically, the electrodes are offset from each other at each end of the assembly, so at one end the positive electrode extends beyond the edge of the negative electrode, while the negative electrode extends beyond the edge of the positive electrode at the opposing end of the assembly. The purpose of the offset is to enable the collection of current from the electrodes to the appropriate terminal. For nickel metal hydride cells, the can typically functions as the negative terminal while the cover assembly includes the positive terminal for the cell. Therefore, the positive electrode is typically extended at the cover end of the cell while the negative electrode is extended at the opposing end of the cell.
Part of the closing process of the typical jellyroll cell involves the creation of a groove around the circumference of the cell after the assembly has been inserted into the cell. The groove results from a radially exerted force. Typically, the electrode assembly and a current collector are contained below the groove. Internal shorting can be caused by unintentional contact between the extended positive electrode edge at the top of the electrode assembly and the groove. One solution to this problem has been to introduce an insulator ring around the outer circumference of the top of the electrode assembly to prevent contact between the extended edge of the positive electrode and the groove. However, the insulator ring tends to push the positive electrode into contact with the sidewall of the can, producing another unintentional and undesirable opportunity for internal shorting.
There is therefore a need for an electrode that avoids unintended contact with the cell container.
SUMMARY OF THE INVENTION
The electrode of the within invention has a length extending between two ends and a width extending between two edges, and a notch along one edge of the electrode terminating at one end of the electrode. Preferably, the notch is positioned such that when the electrode is wound about an axis parallel to the electrode width, the notch is at least as long as the circumference of the outermost wrap of the electrode. The notch prevents the protruding edge of the electrode from inadvertent contact with the can.
A method of manufacturing the electrode of the present invention includes the creation of a chamfered surface at the electrode end opposing the end where the notch occurs. The chamfer surface extends between a point on the opposing electrode end and one of the electrode edges. The chamfer aids the introduction of the electrode into a winder and avoids jamming that can be caused when an edge or a corner of the electrode is caught along the manufacturing path to and within a winder.


REFERENCES:
patent: 62-123652 (1987-06-01), None
patent: 4-28175 (1992-01-01), None
patent: 5-234598 (1993-09-01), None
patent: 6-260172 (1994-09-01), None
patent: 10-74522 (1998-03-01), None
patent: 10-270014 (1998-10-01), None

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