Battery assembly

A battery cell including a cylindrical container having a cap assembly positioned in the open end thereof. The cap assembly includes a terminal extending into the container, a rigid plate, a thermal disconnect assembly and a contact cap. A seal fits about the cap assembly to electrically isolate the cap from the container and provide a sealing function and vent for the battery. A sleeve is associated with the seal to tightly seal the terminal. The terminal is associated with a spiral wrapped cell by means of a tab welded thereto. The cell is assembled in a flat layered arrangement and then wrapped about the terminal prior to placement in the container.

BACKGROUND OF THE INVENTION 
The field of the present invention is dry cell batteries and their 
structure. 
Dry cell batteries typically employ a container with a closure element in 
one end thereof. The container acts as one terminal while the closure 
element is electrically isolated from the container to act as the second 
terminal. Such operation of the closure element dictates its electrical 
isolation from the container, requires its coupling with either the anode 
or cathode of the cell structure itself, provides a closure of the 
container against leakage and internal overpressure and, particularly in 
the case of lithium cells, can include a thermal disconnect assembly to 
shut down the battery in the event of excessive internal heat. The battery 
container must also cooperate to provide appropriate containment and 
reliable contact with the other of the anode or cathode material of the 
cell itself. Finally, the cell must be constructed in such a way that 
internal shorts between the anode material and cathode material cannot 
occur. The employment of structures to eliminate the possibility of 
internal shorts during manufacture is additionally advantageous for safety 
and to reduce production costs. 
SUMMARY OF THE INVENTION 
The present invention is directed to a structure for a dry cell battery 
arranged to isolate reliably the closure element from the container. To 
this end a first aspect of the present invention provides a seal 
operatively enclosing the closure assembly on all portions thereof facing 
toward or associated with the container. Compression of the seal may 
assist at appropriate locations. Compression of the seal may be achieved 
through advantageous forming techniques such as magnetic forming 
processes. In another aspect of the present invention a terminal 
associated with the closure assembly is coupled with the cell through a 
tab. The terminal then acts as a mandrel with the cell spiral wrapped 
thereabout so as to avoid internal shorting. A terminal of opposite 
polarity may be defined by interference contact between the cell and one 
end of the container. Assembly of the cell elements and introduction of 
the electrolyte to the cell while outside of the container may be 
advantageously practiced. 
Batteries adhering to the principles of the present invention can provide a 
minimal possibility of internal shorting both during manufacture and in 
use, an integral seal for assuring closure of the cell container and safe 
response to thermal overloads. Other objects and advantages will appear 
hereinafter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning in detail to the drawings, FIGS. 1, 2 and 3 illustrate a first 
embodiment of the present invention. A container 10 defines the body of 
the dry cell battery. The container is generally cylindrical in shape and 
closed at one end with a formed, upraised contact 12. The container 10 may 
conveniently be formed of aluminum or plated low carbon steel. One end of 
the container 10 is open. A cap assembly, generally designated 14, is 
positioned in the opening in the container 10 with the container 10 then 
swaged to be compressed against the cap assembly 14 for permanent closure 
of the cell. Magnetic forming may be conveniently employed for this 
swaging operation. 
The cap assembly 14 may be constructed prior to association with the 
container 10. The assembly 14 includes a plate 16 which is relatively 
rigid and substantially closes the opening in the container 10. With the 
container 10 being cylindrical, the plate 16 is formed into a circular 
disk. Welded to the plate 16 is a terminal 18 which extends concentrically 
into the container 10. The terminal 18 does not extend the full length of 
the container 10 in order that it avoids contact with the closed end of 
the container. 
Assembled with the plate 16 is a thermal disconnect assembly 20. In this 
embodiment, the thermal disconnect assembly 20 is a positive temperature 
coefficient device. Such devices are designed to change state at a 
preselected temperature such that they are conductors below the 
preselected temperature and insulators above that temperature. In effect, 
this device operates as a safety switch against continued use of the 
battery under elevated internal battery temperatures. 
A contact cap 22 is positioned on the thermal disconnect assembly 20. The 
contact cap 22 includes an upstanding contact area and an annular mounting 
flange. The mounting flange is designed to rest upon the thermal 
disconnect assembly 20 to insure electrical contact therewith. An annular 
insulator 24 is positioned on the mounting flange of the contact cap 22. 
The insulator extends over the outer edge of the flange fully about its 
periphery and upwardly on the cylindrical side of the contact portion of 
the contact cap 22 to insure complete electrical isolation from the 
remainder of the assembly. Thus, the sole electrical path between the 
contact cap 22 and the plate 16 is through the thermal disconnect assembly 
20. An annular compression ring 26 is then positioned around the cap 
assembly 14 and swaged in place to interlock with the plate 16. The 
annular compression ring 26 includes a flange which interlocks with the 
thermal disconnect assembly 20, the mounting flange of the contact cap 22 
and the insulator 24 to hold these elements onto the plate 16. As can be 
seen in FIG. 1, the insulator 24 is arranged to insure that there will be 
no contact between the annular compression ring 26 and the contact cap 22. 
A nonconductive seal 28 is positioned about the cap assembly 14. The seal 
28 may be of polypropylene. The seal 28 includes a central cylindrical 
portion 30 positioned at the plate 16 about the terminal 18. The seal 28 
also includes a radially extending portion 32 which extends outwardly on 
the inner side of the plate 16 to its periphery. A peripheral cylindrical 
portion 34 extends upwardly about the periphery of the plate 16, outwardly 
of the annular compression ring 26. The peripheral cylindrical portion 34 
extends up far enough such that it prevents the possibility of contact 
between the annular compression ring 26 and the container 10. Thus, the 
cap assembly 14 is electrically isolated from the container 10. The 
peripheral cylindrical portion 34 also provides a resilient barrier 
between the cap assembly 14 and the container 10. Thus, the nonconductive 
seal 28 provides electrical isolation as well as a mechanical sealing of 
the cell. The central cylindrical portion 30 includes a concentric 
cylindrical cavity into which is positioned a sleeve 36. The sleeve 36 is 
preferably metallic such that it may be compressed about the terminal 18. 
In the concentric cylindrical cavity of the nonconductive seal 28, the 
sleeve 36 is positioned such that a portion of the seal is located between 
the sleeve 36 and the terminal 18 and a portion of the seal encloses the 
sleeve. Thus, the sleeve 36 is isolated from the cell and may be of any 
convenient material such as aluminum, copper or low carbon steel and also 
is positioned to compress the seal 28 against the terminal 18 for 
additional sealing. To cause the compression of the sleeve 36, magnetic 
swaging techniques are preferred. 
With the foregoing cap assembly 14, the seal 28 and the container 10, a 
battery cell enclosure is provided which insures electrical isolation of 
the end cap assembly from the main cavity of the cell with the exception 
of the terminal 18. By providing a rigid end cap in a sealed relationship 
with the container using a resilient material therebetween, a safer 
battery results. Under extreme thermal conditions, the end cap can be 
forced outwardly from the end of the container such that the wide mouth of 
the container 10 is open. Under conditions of fire, for example, this 
broad opening prevents disadvantageous accidental creation of a nozzle 
which would either propel the battery like a rocket or release a jet of 
combusting material. The seal 28 would melt if made of polypropylene. The 
container 10 is configured such that, without the seal, the cap assembly 
14 is not in interlocking engagement therewith. Such a configuration 
assures proper operation of the battery under such adverse thermal 
conditions. In addition, the thermal disconnect assembly 20 is to be 
designed with a transition temperature well below the severe heat required 
to disassociate the cap assembly 14 from the container 10. 
Two additional embodiments of the cap assembly 14 are disclosed as 
illustrated in FIG. 4 and in FIGS. 5 and 6. An inspection of these 
additional embodiments illustrates that they employ the same general cap 
assembly 14 but for the thermal disconnect assembly mechanism employed. In 
the first embodiment, the thermal disconnect assembly 20 is contemplated 
to be a commercially available positive temperature coefficient device. In 
the embodiment of FIG. 4, the thermal disconnect assembly includes an 
annular insulating washer 38. This washer is positioned between the plate 
16 and the contact cap 22. Located inwardly of the annular insulating 
washer 38 is a bimetal disc 40. The bimetal disc 40 is configured and has 
sufficient strength below a preselected temperature to contact the plate 
16 at the center thereof and extend upwardly about the periphery to the 
contact cap 22 as illustrated in FIG. 4. Positioned between the contact 
cap 22 and the bimetal disc 40 is a resilient and nonconductive washer 42. 
This washer 42 is in compression. When the bimetal disc 40 is heated to a 
preselected temperature, the disc distorts to move away from the 
peripheral contact with the contact cap 22. The nonconductive washer 42 
keeps the bimetal disc 40 from distorting asymmetrically. As the sole 
electrical path between the plate 16 and the contact cap 22 is through the 
bimetal disc 40, the battery is shut off above the preselected 
temperature. 
The thermal disconnect assembly 20 of the third embodiment illustrated in 
FIGS. 5 and 6 employs a fusible washer designed to loose strength at a 
preselected elevated temperature. The thermal disconnect assembly includes 
an annular insulating washer 38 as in the second embodiment. A contact 
element 44 is arranged with dished contacts 46. The center of the contact 
element 44 is in contact with the plate 16. The contacts 46 extend to the 
contact cap 22 at the ends of each contact 46. The location of each 
contact 46 is determined by a compressed resilient washer 48 and a fusible 
washer 50. With the fusible washer below a preselected temperature, the 
resilient washer 48 is unable to move the contacts 46 away from the 
contact cap 22. Above a preselected temperature, the fusible washer 50 
looses strength and the resilient washer 48 disconnects the contacts 46 
from the contact cap 22. 
Following the swaging operation to close the container 10 about the cap 
assembly 14, an insulator 52 is placed above the annular compression ring 
26. A shrink fit label is positioned over the entire battery and heated to 
shrink it tightly against the assembly. The label is long enough to 
overhang the ends of the container 10. This allows retention of both the 
label 54 itself and the insulator 52. The use of such an insulating label 
and the insulator defines the electrical contacts only at either end of 
the battery. 
Looking to the structure of the cell itself, reference is made to FIGS. 2 
and 3. The terminal 18 is employed as a mandrel in the fabrication of the 
cell. In both FIGS. 2 and 3, the cell material is shown to be laid out in 
sheet form. This is the manner in which the assembly is constructed prior 
to being spiral wrapped around the mandrel defined by the terminal 18. 
Associated with the terminal 18 by means of spot welding is a tab 60. The 
tab 60 runs substantially the length of the terminal 18 and extends in one 
direction from a tangential attachment. The tab 60 is preferably of 
formable metallic material. The tab 60 is prepunched with three corner 
rosettes along its extended portion for association with the anode. 
Prior to welding of the tab 60 to the terminal 18, the cell is assembled in 
flat form. To fabricate the cell assembly, a first tape 62 is placed with 
the adhesive side up. Next a separator sheet 64 is positioned on the tape 
62. The positioning is such that the separator sheet 64 overlaps only a 
portion of the tape 62. A lithium anode sheet 66 is then placed on the 
tape 62 and separator sheet 64 such that the anode sheet 66 extends just 
beyond the edge of the tape 62 as seen in FIG. 3. The separator sheet 64 
is conveniently of polypropylene or other suitable material and is 
sufficiently porus to allow conventional battery operation. The anode 
sheet 66 has a first end adjacent the mandrel 18 and a second end at the 
opposite end of the sheet. Parallel side edges are appropriately spaced 
such that the anode sheet 66 does not extend to the edge of the separator 
sheet 64 or to the end thereof. In this way, the separator sheet prevents 
direct contact between the anode and the associated cathode. 
With the anode sheet 66 in position, the tab 60 is positioned on the anode 
and the rosettes forced into the lithium. The tab 60 extends for only a 
short distance onto the anode sheet 66 to insure positive interlocking 
through the rosettes. The tab 60 extends beyond the anode sheet 66 at its 
first end for later welding to the terminal 18. The tab 60 is preferably 
arranged and proportioned with the diameter of the terminal 18 such that 
the rosettes do not overlay the cathode when spiral wrapped about the 
terminal 18. This prevents accidental contact by a rosette poking through 
the separator sheet 64 and contacting the cathode rather than either the 
terminal 18 or the prior pitch of the anode sheet 66. 
Positioned on top of the anode sheet 66 is a second separator sheet 68. 
This second separator sheet 68 abuts against the tab 60 and extends 
coextensively with the first separator sheet 64. An insulating strip of 
tape 70 is then positioned over a portion of the tab 60 and a portion of 
the second separator sheet 68. The tape 70 is taped adhesive side down 
such that it will adhere to the tab 60 and to the second separator sheet 
68 to retain it in position for assembly. 
A cathode sheet 72 of magnesium dioxide or other suitable cathode material 
is positioned on top of the tape 70 and second separator sheet 68. As the 
second separator sheet 68 extends beyond the anode sheet 66, there is no 
direct contact between the cathode sheet 72 and the anode sheet 66. The 
cathode sheet 72 is also positioned such that it does not overlap the tab 
60, thereby insuring against accidental contact through some flaw in the 
strip of tape 70. The cathode sheet 72 is made up of a substrate screen 74 
and the cathode material. The substrate screen 74 extends beyond the 
separator sheets 64 and 68 on one side thereof as best seen in FIG. 2. 
Lastly, an upper strip of insulating tape 76 retains the cathode sheet 72 
in place for assembly. 
Once the foregoing sheets and tape is arranged, the tab 60 is spot welded 
to the terminal 18 and the terminal 18 acts as a mandrel to spiral wrap 
the cell assembly thereabout. The second separator 68 is preferably of 
additional length such that it will wrap about the cell bundle two extra 
wraps then heat sealed to form a closed package. 
The cap assembly 14 with the attached terminal 18 and spiral wrapped cell 
is then subjected to a vacuum. The cell material is emersed in electrolyte 
and the vacuum is released. This causes the electrolyte to be drawn into 
the cell body. The wet cell body is then positioned in the container 10 
which may have additional electrolyte if required. The fit is such that 
the substrate screen 74 associated with the cathode sheet 72 is placed 
into interference fit in a slightly crushed arrangement against the bottom 
of the container 10. This insures contact of the cathode with the contact 
12. The insulator 52 is then placed and the shrink fit label 54 is 
positioned and contracted about the battery. The device is then complete. 
Thus, a battery structure is defined which provides a complete seal of the 
cap assembly 14 from the container 10 and the interior of the battery with 
the exception of the protruding terminal 18. This seal provides an 
appropriate physical closure between the cap assembly 14 and the container 
10 as well as electrical isolation. The extension of the terminal 18 
provides a convenient mechanism for the fabrication of the cell material 
in such a way that internal shorting is again eliminated. The plate 16 in 
association with the container 10 provides a closure which, under extreme 
temperature, properly may be ejected such that a nozzle is not created 
through which combusting materials may be improperly directed. While 
embodiments and applications of this invention have been shown and 
described, it would be apparent to those skilled in the art that many more 
modifications are possible without departing from the inventive concepts 
herein. The invention, therefore is not to be restricted except in the 
spirit of the appended claims.