Coiled electrode assembly cell construction with telescopic terminal tab

The invention relates to a cell employing a coiled electrode assembly having the edge of at least one electrode strip protruding above the coiled electrode assembly and wherein said electrode edge is electronically connected to a tab having a telescopic center portion that can flex below and then above the plane of the tab so that any bulge in the cell's housing will flex the tab without disturbing the electronic contact between the cell's housing and the edge of the electrode strip protruding above the coiled electrode assembly.

FIELD OF THE INVENTION 
The invention relates to a coiled electrode assembly cell construction 
having the edge of at least one coiled electrode strip extending beyond 
the coiled electrode assembly and electronically connected to the 
peripheral portion of a conductive tab that can be flexed at its center so 
that a conductive terminal cover electronically secured to the tab may 
bulge without disturbing the electronic contact to the electrode strip via 
the tab. 
BACKGROUND OF THE INVENTION 
The galvanic cell has become a primary power source for many portable 
electronic devices such as tape recorders, portable telephones, lanterns, 
radios and the like. In order to maintain the overall electronic devices 
as compact as possible, the electronic devices are usually designed with 
cavities to accommodate batteries as their power source. The cavities are 
usually made so that a battery can be snugly positioned therein, thus 
making electronic contact with appropriate terminals within the device. To 
accommodate the electronic component manufacturers, the battery industry 
has adapted several conventional size cells which the manufacturers can 
rely upon in designing their devices which require portable power sources. 
Due to the large number of battery-powered devices on the market, there 
has been a demand for increased power output capacities of standard size 
cells. Accordingly, various cell constructions have been employed so as to 
provide a sufficient output capacity. For example, cells with coiled 
electrode assemblies (jellyroll construction) have been used to increase 
the interfacial area contact between the active cell components. Use of 
coiled electrodes serves to decrease the cell's internal resistance and 
thereby increase the maximum possible drain rates. Cells that incorporate 
a jellyroll construction are widely known in the battery art and usually 
involve placement of the coiled electrode in a composite housing which 
serves as the current conductive terminals for the cell. In such 
structures, the electrode of one polarity can be electrically connected to 
a conductive housing portion, and the electrode of the opposite polarity 
can be generally electrically connected to another conductive housing 
portion which is insulated relative to the electrically conductive 
first-mentioned housing portion. The electrical contact between each 
electrode and its respective housing portion is generally formed by an 
elongated flexible electrically conductive connecting tab (current 
collector tab) or element which is secured at one end to the electrode and 
at the other end is secured to the respective housing portion. The current 
collector tabs are generally attached to the electrodes or electrode 
carriers, by welding pressure contact or other conventional means. This 
technique requires time-consuming manual operations in the cell assembly 
process which serve to reduce line productivity and add to the 
manufacturing costs. For example, some of the problems associated with 
using this method of tabbing are: (1) the obvious difficulty of handling 
and welding narrow strips of metal within the configured space of the 
cell; (2) dedicating a disproportionate percentage of the volume within 
the cell to accommodate the tab and assembly process; and (3) the tab is 
connected to the electrode in only one spot and therefore it is possible 
that any bulging of the cell could break the weld causing an open circuit; 
and (4) coil insertion is difficult due to the ease with which the 
electrodes and/or separator may by damaged. 
U.S. Pat. No. 4,332,867 discloses a cell utilizing a coil assembly formed 
by winding negative and positive plates together with at least one 
separator therebetween. Each of the positive and negative plates is 
constituted by a main portion containing battery active materials and an 
edge portion free of the active material. In the coil assembly, the edge 
portions of the respective plates protrude outwardly beyond the opposite 
edges of the separator and are positioned on respective sides of the coil 
assembly. Positive and negative current collectors are made of a holeless 
nickel-plated steel sheet and welded to the edge portions of the 
respective plates by means of a plurality of welds. Although this type of 
cell construction provides a plurality of weld connectors to the 
electrode, it is possible that internal pressure buildup would cause the 
container to bulge thereby stressing the welds and eventually breaking the 
contact. 
It is an object of the present invention to provide a coiled electrode 
assembly cell construction that can accommodate internal pressure buildup 
and bulging of the terminal cover without disrupting the electronic 
continuity between the terminal and one of the cell's electrodes. 
Another object of the present invention is to provide a coiled electrode 
assembly cell construction with a telescopic tab secured to a terminal 
cover and one of the cell's electrodes and adapted to flex upon bulging of 
the cell without disturbing the electronic continuity of the cell. 
Another object of the invention is to provide a coiled electrode cell 
construction that employs a telescopic type tab which can follow the edge 
of an unevenly wound electrode protruding from the coiled assembly and 
which is electronically secured to the edge of the electrode so that it 
can accommodate a degree of bulge without disrupting the electronic 
circuit of the cell. 
The foregoing and additional objects will become fully apparent from the 
following description and the accompanying drawings. 
SUMMARY OF THE INVENTION 
The invention relates to a galvanic cell comprising a coiled electrode 
assembly contained in a housing comprising a container sealed with a 
cover, said coiled electrode assembly comprising a first electrode strip 
superimposed on and overlapping a second electrode strip and a separator 
disposed between said first electrode strip and said second electrode 
strip; said first electrode strip, said second electrode strip and said 
separator are wound into a coiled electrode assembly such that said first 
electrode strip is electronically insulated from said second electrode 
strip by said separator and the edge of at least one electrode strip 
protrudes from the coiled electrode assembly at one end and electronically 
contacts a conductive terminal at one end of the housing, and the second 
electrode strip electronically contacts a conductive terminal at the 
opposite end of the housing; the improvement wherein a conductive tab has 
at least one slit disposed substantially about the central area of the tab 
to enable the central area to flex above or below the plane of the tab 
without effectively distorting the peripheral area of the tab, said tab 
being in electronic contact with the protruding edge of the electrode 
strip, and a conductive portion of the housing is electronically connected 
to said tab whereby adapting said conductive portion as the conductive 
terminal for said electrode strip having its edge protruding from the 
coiled electrode assembly. 
A second conductive tab could be employed in the cell of this invention and 
electronically connected to a protruding edge of the other electrode strip 
in a similar manner. In the preferred embodiment of this invention at 
least one opening, preferably two or more equally spaced openings, would 
be disposed in the area between the peripheral edge of the tab and the 
central area of the tab. The opening would be defined by an inward flange 
that would contact the protruding edge of the electrode and thus provide 
numerous contact points between the tab and the edge of the electrode. 
Preferring three or more circular openings disposed concentrically about 
the center of the tab with each opening defined by an inwardly disposed 
flange would provide a substantial number of contact points between the 
edge of the electrode and the tab. If one of the electronic connections 
between the flange and electrode breaks, there still would be several 
contact points remaining for adequate electronic continuity. The slit 
disposed substantially about the central area of the tab could be in the 
form of one arcuate shaped slit or two or more arcuate or straight line 
shaped slits or combinations thereof as long as the central area of the 
tab can flex about the plane of the tab without effectively distorting the 
peripheral area of the tab. Thus, in the preferred embodiment of the 
invention, the tab, through the inward disposed flanges, would provide 
numerous contact points to the electrode edge which could easily be welded 
together while the center area of the tab would flex through the use of 
the slits and thereby accommodate any bulging of the cell without breaking 
the welds. The tab of this invention is relatively inexpensive to make and 
can be easily handled on automatic assembly machines. 
The coiled electrode assembly of this invention typically comprises two 
electrode strips and a separator. One electrode strip acts as an anode or 
anode current collector and the other serves as a cathode or cathode 
current collector. The anode or anode current collector, cathode or 
cathode current collector and separator are made of flexible materials and 
are typically formed into strips and superimposed upon each other with one 
electrode overlapping the other. This is accomplished by superimposing and 
overlapping the first electrode strip over the second electrode strip with 
the separator interposed between the two electrode strips. This assembly 
is then wound to form the coiled electrode assembly which is preferably 
cylindrical in outer contour with a central opening and which has at least 
the edge of one electrode strip protruding from the top or bottom of the 
electrode assembly. The central opening in the coiled electrode assembly 
is typically cylindrical, however, it could be elliptical or of any other 
configuration. 
One electrode strip could be electronically connected to the housing in a 
conventional manner such as through the use of a tab that has been welded 
or pressure secured to the electrode and the housing or a peripheral 
exposed portion of the electrode strip could provide direct electrical 
contact with the housing. However, the protruding edge of the other 
electrode strip, according to this invention, has to be electronically 
connected to the above described tab and in turn said tab is secured to a 
terminal on the cell's housing. 
The tab for use in this invention can be made of any conductive material 
such as nickel plated steel, nickel foil, aluminum and stainless steel or 
a non-conductive material coated with a conductive layer, such as plastic 
films (polyester) coated with a metallic layer or a layer of conductive 
paint. Generally, this tab should be circular in shape to be compatible 
with the coiled electrode assembly and relatively thin so that it can flex 
easily. For most applications the circular tab could be between about 
0.001 inch and about 0.01 inch thick and more preferably between about 
0.002 and 0.005 inch thick. The tab is relatively thin and therefore 
occupies only a small volume within the cell. 
Preferably at least one peripheral opening should be defined in the tab and 
spaced from the central area of the tab and more preferably four 
peripheral openings spaced 90.degree. apart should be disposed 
concentrically about the central area of the tab. Each opening should be 
defined by an inwardly disposed flange which is adapted to make pressure 
contact with the protruding edge of the electrode. The openings are placed 
between the central area of the tab and the peripheral edge to insure 
proper contact with the protruding edge of the electrode. Once the 
circular tab is placed over the coiled electrode assembly, the depending 
flanges can be welded to the edge of the protruding electrode using known 
welding means. With the coiled electrode assembly in a container and the 
tab welded to the edge of the protruding electrode strip, a terminal cover 
can be placed over and secured to the tab using conventional welding means 
or the like. This arrangement adapts the cover as the terminal for the 
electrode strip. If desired, the second electrode strip could project from 
the opposite side of the coiled electrode assembly and be secured to a 
similar type tab and cover terminal in accordance with this invention. 
Bulging of the cell could be accommodated by the telescoping of the 
central area of the tab without disrupting the electronic contact between 
the tab and the electrode strip. 
In an alternate embodiment of the invention, the openings disposed in the 
area between the peripheral edge of the tab and the central area of the 
tab could be replaced by inward protrusions such as dimples. These inward 
protrusions would contact the edge of the electrode strip and provide 
numerous contact points between the tab and the electrode strip. 
The terminal cover could be a circular disc which would be insulated from 
the container and used as one terminal for the cell. The cover could also 
employ a conventional glass-to-metal seal in which a conductive terminal 
within the glass seal could be electronically connected to the conductive 
tab thereby adapting the terminal as the electrode terminal for the cell. 
Other embodiments of the cover can be used with this invention. 
As used herein, an electrode strip shall mean an active electrode such as a 
solid anode or cathode of the cell or an electrochemically inactive strip 
such as an anode collector or a cathode collector employed along with an 
active liquid, solid or gas anode or cathode, respectively. 
Because of the accepted battery polarity of the commercially available 
power sources it is preferred that for consumer cells of conventional 
power, the outer exposed electrode strip which is in electrical contact 
with the container of the cell be the cathode and the inner wound 
electrode which is in electrical contact with the cover be the anode. 
However, in customized cell constructions, the polarity could be reversed 
to minimize corrosion since the container will be anodically protected. 
The coiled electrode assembly of this invention can be used in many 
different types of cell systems such as aqueous (i.e., alkaline) or 
nonaqueous cell systems employing solid or liquid cathodes. When the 
coiled electrode assembly is employed in lithium nonaqueous cells, it 
would sometimes be preferable to make the lithium the outer wound 
electrode. The lithium electrode could be superimposed and overlayed on a 
cathode strip such as MnO.sub.2, CuO, CF.sub.x, FeS.sub.2 or the like with 
a separator interposed between them, and then wound with the edge of 
either or both electrodes protruding from the coiled electrode assembly. 
The separator for use in this invention could be selected from a number of 
ionically permeable materials such as polypropylene, felted glass fibers 
and coated papers. 
Cathode current collectors suitable for use in the invention would be 
sintered nickel or carbonaceous materials such as Teflon-bonded carbon or 
the like. Anode current collectors suitable for use in the invention would 
be nickel foil, stainless steel foil, expanded metal, perforated metal or 
the like. 
The cylindrical container and cover for use in an embodiment of this 
invention can be stainless steel, nickel-plated steel or some other 
conductive material that will not corrode or otherwise deteriorate when in 
contact with the active cell components. Preferably for nonaqueous systems 
the container and cover could be made of 304L type stainless steel. 
Any insulating gasket member disposed between the cover and the container 
has to be stable in the presence of the active components and discharge 
products and can be selected from such materials as nylon, polypropylene, 
polyethylene, polytetrafluoroethylene, fluorinated ethylene-propylene 
polymer, ethylene copolymer with fluorinated ethylenepropylene, polyester, 
polychlorotrifluoroethylene, perfluoroalkoxy polymer and the like. 
Anodes suitable for use in this invention could be lithium, calcium, 
magnesium, sodium, zinc and the like. Cathodes suitable for use in this 
invention could be MnO.sub.2, HgO, Ag.sub.2 O, CuO, FeS.sub.2, TiS.sub.2, 
(CF.sub.x).sub.n with x greater than 0 and less than 1.1, SOCl.sub.2, 
(C.sub.2 F).sub.n, SO.sub.2 Cl.sub.2 and SO.sub.2. Some preferred cell 
system for use in this invention would be as shown in the table below. 
TABLE 
______________________________________ 
Anode Cathode Electrolyte 
______________________________________ 
lithium MnO.sub.2 organic 
lithium SOCl.sub.2 LiAlCl.sub.4 in SOCl.sub.2 
lithium (CF.sub.x).sub.n 
organic 
zinc MnO.sub.2 aqueous alkaline 
cadmium nickel hydroxide 
aqueous alkaline 
______________________________________ 
When the anode for use in this invention is lithium, then a lithium foil 
could be secured onto a metallic conductive foil or carrier (anode 
collector) such as nickel. 
The foregoing and additional objects will become more fully apparent from 
the description hereinafter and the accompanying drawings.

Referring to the drawing FIG. 1 shows a circular conductive tab 2 having a 
first arcuate slit 4 and an opposite disposed arcuate slit 6. Each slit 
comprises about a 220.degree. concentric arc cut through the tab material 
and each slit overlaps such that the central area 7 can be projected above 
and also below the plane of the tab thereby forming a telescopic center. 
Disposed concentric about the center of tab 2 at 90.degree. intervals are 
openings 8, 10, 12 and 14, with each opening being defined by a depending 
flange 9, 11, 13 and 15, respectively. FIG. 2 shows a cross-section of a 
cell employing a coiled electrode assembly 16 comprising a first electrode 
strip 18, a second electrode strip 20 and a separator 22 therebetween 
housed in container 21. The first electrode strip 18 and second electrode 
strip 20 are superimposed and overlapping such that upon being coiled the 
edge of electrode strip 20 projects above the coiled electrode assembly 
16. Tab 2 of FIG. 1 is shown disposed over the projected edge of electrode 
strip 20 such that flanges 9, 11, 13 and 15 physically contact the edge of 
electrode strip 20. The flanges 9, 11, 13 and 15 are welded using 
conventional welding means to electronically and physically connect and 
secure tab 2 to electrode strip 20. A cover 24 is shown disposed over 
container 21 and secured to container 21 at its edge 23 using welding or 
similar conventional means. The cover 24 is also secured to tab 2 using 
spot welds or other securing means. The center of the cover 24 defines an 
opening 26 which can be used as the electrolyte solution filling hole. 
After the electrolyte solution is fed into the container, a closure 28 can 
be secured to cover opening 26. If desired, the cover 24 could be a solid 
disc without any openings. As can be appreciated from FIGS. 1 and 2, if 
the cover 26 was to bulge from internal pressure buildup then the central 
area would flex or telescope outward from slits 4 and 6 without disturbing 
the numerous welded contacts between flanges 9, 11, 13 and 15 and the edge 
of electrode strip 20. Thus building of the cell during storage or 
discharge would not break the electrical continuity of the cell. As is 
also apparent from FIG. 2, the height of tab 2 is extremely small and 
therefore move volume for a given cell size is available for the active 
cell components. 
FIG. 3 shows another circular tab 30 having a plurality of straight line 
slits 32 disposed concentric about the center area of tab 30. As is 
apparent from FIG. 3, the central area of tab 30 can flex or telescope 
above and also below the plane of the tab through the use of the slits 32. 
Disposed concentric about the center of each tab 30 at 90.degree. 
intervals are openings 34, 36, 38 and 40, with each opening being defined 
by a depending flange 33, 35, 37 and 39, respectively. The tab 30 would 
operate in the same manner as tab 2 shown in FIG. 1. 
FIG. 4 shows another circular tab 42 having a plurality of straight line 
slits 44 disposed about the center area of tab 42. As is apparent from 
FIG. 4, the central area of tab 42 can flex or telescope above and also 
below the plane of the tab through the use of the slits 44. Disposed 
concentric about the center of each tab 42 at 90.degree. intervals are 
openings 46, 48, 50 and 52, with each opening being defined by a depending 
flange 45, 47, 49 and 51, respectively. The tab 42 would operate in the 
same manner as tab 2 shown in FIG. 1. 
FIG. 5 shows another circular tab 54 having a plurality of straight line 
slits 56 and curve slits 55 disposed about the center area of tab 54. As 
is apparent from FIG. 5, the central area of tab 54 can flex or telescope 
above and then below the plane of the tab through the use of the slits 56. 
Disposed concentric about the center of each tab 54 at 90.degree. 
intervals art openings 58, 60, 62 and 64, with each opening being defined 
by a depending flange 57, 59, 61 and 63, respectively. The tab 54 would 
operate in the same manner as tab 2 shown in FIG. 1. 
FIG. 6 shows another circular tab 66 having a coiled slit 68 disposed 
concentric about the center area of tab 66. As is apparent from FIG. 6, 
the central area of tab 66 can flex or telescope above and then below the 
plane of the tab through the use of the slit 68. Disposed concentric about 
the center of each tab 66 at 90.degree. intervals are openings 70, 72, 74 
and 76, with each opening being defined by a depending flange 69, 71, 73 
and 75, respectively. The tab 66 would operate in the same manner as tab 2 
shown in FIG. 1. 
Although preferred embodiments of this invention have been described in 
detail, it is contemplated that modifications and changes to the preferred 
embodiments of the invention herein shown and described can be made 
without departing from the spirit and scope of the invention.