Internal connection system for high power electrochemical cell

Details Internal connection system for high power electrochemical cell Internal connection system for high power electrochemical cell

2002-05-13

2004-04-20

Cantelmo, Gregg (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Intracell assembly having cell electrode connector

C429S094000, C429S211000

Reexamination Certificate

active

06723468

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to high-power electrical storage cells, more particularly to high-power cylindrical cells, able to supply a discharge current representing 20 times the current needed to discharge the cell in one hour, for example. These cells generally have a diameter of 20 mm or more, in particular in formats usually called “KR14” (“R14” or “C”) and KR20 (“R20” or “D”). These formats are defined in the standard CRI/IRC 285§3.1. To be more precise, the invention relates to the electrical connection between the electrodes and the terminals of this kind of cell.
2. Description of the Related Art
Conventional cylindrical storage cells generally have an electrode assembly that is wound in a spiral to form a spool. The spiral winding then includes two electrodes, respectively of positive and negative polarity, and a separator between them. The cells have connections taking the form of rectangular tongues that emerge from the spool. One end of the connection is welded to the conductive support of one of the electrodes and the other end is connected to a current outlet terminal.
The document U.S. Pat. No. 4,009,053 describes an electrical storage cell including electrodes that are wound in a spiral to form a spool. The end of the spool is formed by the edge of the electrodes. The electrodes of the same polarity are connected to a current collector via their edges, which come into contact with projections formed in radial slots of the current collector. The connection between an electrode and a collector is therefore obtained by means of a pressed contact. However, this type of contact is not suitable for high discharge currents.
The document DE-A-301 91 86 discloses a gas-tight electrical storage cell having electrodes wound in a spiral electrically connected to a conductive disk. The conductive disk takes the form of a thin and flexible metal plate and is provided with a tongue which is attached to it and curved against it at an acute angle. The tongue is fixedly connected to the interior face of the lid of the storage cell. Oblique fins are formed on both sides of the tongue and are folded. The tongue can therefore be pressed onto the conductive disk in an elastic manner by means of the fins. The internal electrical resistance of the storage cell is high, however.
The document EP-B-0 545 906 discloses an alkaline electrolyte storage cell comprising a positive electrode, a negative electrode, a separator, a container providing a negative electrode and incorporating an opening, a lid covering the opening and providing a positive terminal, a current collector for the negative electrode, and a current collector for the positive electrode. The positive and negative electrodes are formed of plates wound in a spiral. The separator is disposed between the electrodes. The current collector of the negative electrode connects one end of the negative electrode to the container and the current collector of the positive electrode connects one end of the positive electrode to the lid. The current collector of the positive electrode has a collector portion connected to the end of the positive electrode and a conductive tongue connected to the lid. The conductive tongue has a thickness (0.5 mm) greater than that (0.15 mm) of the collector part to reduce the internal electrical resistance. The above document mentions the possibility of placing two collectors of standard thickness (0.15 mm) between the electrode and the lid. Each collector comprises a conductive half-disk with a conductive tongue on top. This halves the current in each connection, and the internal resistance is reduced by 20%. The above document also proposes increasing the thickness of the connection, but this solution gives rise to problems with welding the conductive disk and with bending when closing the lid.
The electrical storage cells described in DE-A-301 91 86 and EP-B-0 545 906 have further drawbacks. In these cells, the impedance is reduced only at the level of the conductive tongue. Accordingly, this kind of cell has a high electrical resistance at the connection of the electrodes to the terminals of the cells. This resistance causes large voltage drops when high currents are supplied and this makes the cell unsuitable for some applications, in particular when the diameter of the cell exceeds 20 mm. Also, this resistance causes internal heating of the cell, which reduces its service life.
During fabrication, assembling storage cells incorporating a collector with a tongue is also difficult. On the one hand, welding a tongue to the lid is difficult. On the other hand, closing the storage cell, after connecting the tongue to a terminal, is effected by bending the tongue. The increased cross section of the tongue makes it more rigid. Bending the tongue then damages it or damages the weld to the edge of the electrode.
BRIEF SUMMARY OF THE INVENTION
The invention proposes a solution to the above problems. Thus it proposes an electrical storage cell having reduced electrical resistance where the electrodes are connected to the terminals and a method of assembling the cell.
The invention also proposes an electrical storage cell and a method of assembling it that facilitates connecting a collector to an electrode. The connection is not damaged during assembly, but has a low electrical resistance.
To be more precise, the invention relates to an electrical storage cell including a positive terminal and a negative terminal, a positive electrode electrically connected to the positive terminal, a negative electrode electrically connected to the negative terminal, a collector of a first polarity having a plane part electrically connected to one of the electrodes, and flexible electrical connection means connecting said plane part to a terminal of said first polarity and having a minimum radius of curvature for bending on a support less than that of a part having the same thickness as the plane part of the collector.
In one embodiment of the invention the electrical connection means comprise a plurality of superposed flexible conductors electrically connecting the collector to the terminal of the first polarity.
In one embodiment the flexible conductors are in the form of laminations.
Each flexible conductor preferably has a thickness less than the average thickness of the plane part of the collector.
Each flexible conductor preferably has a thickness from 50 to 250 micrometers.
In one embodiment the flexible conductors are made of nickel or nickel-plated steel.
The flexible conductors can be bent to an S-shape.
In one embodiment the collector further includes a tongue projecting from its plane part.
In a further embodiment the tongue is more rigid than each flexible conductor.
In a still further embodiment the flexible conductors are welded on the one hand to the plane part of the collector and on the other hand to one end of the tongue.
In one embodiment electrical storage cell further comprises a collector of a second polarity electrically connected to the electrode of the second polarity and having a tongue electrically connecting it to the terminal of the second polarity.
In one embodiment the collector of the second polarity comprises two plates each having an area of connection with the electrode of the second polarity and the two plates are electrically isolated from each other in their connection areas.
In one embodiment the plates are electrically connected by a connection having an electrical resistance greater than the connection of the plates via the electrode of the second polarity.
In one embodiment the plates are connected by a tongue.
In one embodiment a bridge electrically connects the connection areas of the plates.
In one embodiment a bridge electrically connects one plate to a central cutout in the other plate.
In one embodiment the bridge is a projection on a plate that is bent and electrically connected to the other plate.
In one embodiment the first polarity is positive.
The invention also provides a method of fabricating an electrical storage cell, the

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