U.S. patent number RE38,518 [Application Number 10/080,348] was granted by the patent office on 2004-05-18 for battery constructions having increased internal volume for active components.
This patent grant is currently assigned to Eveready Battery Company, Inc.. Invention is credited to Gary R. Tucholski.
United States Patent |
RE38,518 |
Tucholski |
May 18, 2004 |
**Please see images for:
( Certificate of Correction ) ** |
Battery constructions having increased internal volume for active
components
Abstract
An electrochemical cell constructed in accordance with the
present invention includes a can for containing electrochemical
materials including positive and negative electrodes and an
electrolyte, the can having an open end and a closed end; a
pressure relief mechanism formed in the closed end of the can for
releasing internal pressure from within the can when the internal
pressure becomes excessive; a first outer cover positioned on the
closed end of the can to be in electrical contact therewith and to
extend over the pressure relief mechanism; a second outer cover
positioned across the open end of the can; and an insulator
disposed between the can and the second outer cover for
electrically insulating the can from the second outer cover.
According to another embodiment, the second cover is dielectrically
isolated from a current collector. The battery comprises a
collector assembly and can defining a sealed internal volume within
the can and available for containing electrochemically active
materials.
Inventors: |
Tucholski; Gary R. (Parma
Heights, OH) |
Assignee: |
Eveready Battery Company, Inc.
(St. Louis, MO)
|
Family
ID: |
32303666 |
Appl.
No.: |
10/080,348 |
Filed: |
February 21, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
293376 |
Apr 16, 1999 |
06265101 |
Jul 24, 2001 |
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Current U.S.
Class: |
429/163; 429/164;
429/176; 429/177; 429/206 |
Current CPC
Class: |
H01M
50/154 (20210101); H01M 50/183 (20210101); H01M
10/283 (20130101); Y02E 60/10 (20130101) |
Current International
Class: |
H01M
2/00 (20060101); H01M 002/00 () |
Field of
Search: |
;429/163,164,176,177,206,224,229 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0217725 |
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Apr 1987 |
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EP |
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0415378 |
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Aug 1990 |
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EP |
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0741425 |
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Oct 1996 |
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EP |
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0837514 |
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Apr 1998 |
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EP |
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0841709 |
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May 1998 |
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EP |
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2627327 |
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Feb 1988 |
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FR |
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2241375 |
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Aug 1991 |
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GB |
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49051538 |
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May 1974 |
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JP |
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63004546 |
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Jan 1991 |
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JP |
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WO82002117 |
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Jun 1982 |
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WO |
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WO94024709 |
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Oct 1994 |
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WO |
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Other References
DI Can Battery Case Specification, Matsushita Battery Industrial
Co., Ltd., Material Division, 1998, 4 pages. .
Baylis C. Navel, "An Innovative Rupture Disk Vent for Lithium
Batteries," Electrochemical Society, 1046b Extended Abstracts, Fall
Meeting Oct. 18-23, 1987, 87-2 (1987), Abstract No. 31, pp. 45-46.
.
Alkaline Cell Constructions, Union Carbide Corp., 1970, 6
pages..
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Primary Examiner: Ryan; Patrick
Assistant Examiner: Martin; Angela J.
Attorney, Agent or Firm: Toye, Jr.; Russell H.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application
No. 60/102,951, filed Oct. 2, 1998, and U.S. Provisional
Application No. 60/097,445, filed Aug. 21, 1998.
Claims
What is claimed is:
1. A battery comprising: a can having an open end and a closed end;
and a collector assembly positioned across the open end of said
can, said collector assembly and can defining a sealed internal
volume within said can and available for containing
electrochemically active materials including at least positive and
negative electrodes and an electrolyte, the internal volume being
at least about 88.4% of the total volume of the battery.
2. The battery as defined in claim 1 and further including a
separator disposed within the internal volume.
3. The battery as defined in claim 1, wherein said collector
assembly comprises a cover and a collector for electrically
coupling said cover to said negative electrode, wherein the
internal volume available for said electrochemically active
materials is exclusive of the volume consumed by said
collector.
4. The battery as defined in claim 1, wherein the internal volume
available for said electrochemically active materials includes any
volume required for internal voids in which said electrochemically
active materials may migrate.
5. The battery as defined in claim 1, wherein said can is
cylindrical.
6. The battery as defined in claim 1, wherein said
electrochemically active materials define an alkaline battery
including a positive electrode made of MnO.sub.2, a negative
electrode made of Zn, and an electrolyte including KOH.
7. The battery as defined in claim 1, wherein said can is made of
chemically inert material.
8. A D sized battery comprising: a can having an open end and a
closed end; and a collector assembly positioned across the open end
of said can, said collector assembly and can defining a sealed
internal volume within said can and available for containing
electrochemically active materials including at least positive and
negative electrodes and an electrolyte, the internal volume being
at least about 89.2% of the total volume of the battery.
9. The D sized battery as defined in claim 8, wherein the internal
volume available for containing said electrochemically active
materials being at least about 90.9 percent of the total volume of
the battery.
10. The D sized battery as defined in claim 8, wherein the internal
volume available for containing said electrochemically active
materials being at least about 92.6 percent of the total volume of
the battery.
11. The D size battery as defined in claim 8, wherein the internal
volume available for containing said electrochemically active
materials being at least about 93.5 percent of the total volume of
the battery.
12. The D sized battery as defined in claim 8, wherein the internal
volume available for containing said electrochemically active
materials being at least about 94.9 percent of the total volume of
the battery.
13. The D sized battery as defined in claim 8, wherein the internal
volume available for containing said electrochemically active
materials being at least about 97.0 percent of the total volume of
the battery.
14. A C sized battery comprising: a can having an open end and a
closed end; and a collector assembly positioned across the open end
of said can, said collector assembly and can defining a sealed
internal volume within said can and available for containing
electrochemically active materials including at least positive and
negative electrodes and an electrolyte, the internal volume being
at least about .[.83.2%.]. .Iadd.85.1% .Iaddend.of the total volume
of the battery.
15. The C sized battery as defined in claim 14, wherein the
internal volume available for containing said electrochemically
active materials being at least about 86.4 percent of the total
volume of the battery.
16. The C sized battery as defined in claim 14, wherein the
internal volume available for containing said electrochemically
active materials being at least about 88.4 percent of the total
volume of the battery.
17. The C sized battery as defined in claim 14, wherein the
internal volume available for containing said electrochemically
active materials being at least about 90.6 percent of the total
volume of the battery.
18. An AA sized battery comprising: a can having an open end and a
closed end; and a collector assembly positioned across the open end
of said can, said collector assembly and can defining a sealed
internal volume within said can and available for containing
electrochemically active materials including at least positive and
negative electrodes and an electrolyte, the internal volume being
at least about 82.0% of the total volume of the battery.
19. The AA sized battery as defined in claim 18, wherein the
internal volume available for containing said electrochemically
active materials being at least about 83.5 percent of the total
volume of the battery.
20. The AA sized battery as defined in claim 18, wherein the
internal volume available for containing said electrochemically
chemically active materials being at least about 84.7 percent of
the total volume of the battery.
21. The AA sized battery as defined in claim 18, wherein the
internal volume available for containing said electrochemically
active materials being at least about 87.4 percent of the total
volume of the battery.
22. The AA sized battery as defined in claim 18, wherein the
internal volume available for containing said electrochemically
active materials being at least about 89.6 percent of the total
volume of the battery.
23. The AA sized battery as defined in claim 18, wherein the
internal volume available for containing said electrochemically
active materials being at least about 90.4 percent of the total
volume of the battery.
24. An AAA sized battery comprising: a can having an open end and a
closed end; and a collector assembly positioned across the open end
of said can, said collector assembly and can defining a sealed
internal volume within said can and available for containing
electrochemically active materials including at least positive and
negative electrodes and an electrolyte, the internal volume being
at least about 78.7% of the total volume of the battery.
25. The AAA sized battery as defined in claim 24, wherein the
internal volume available for containing said electrochemically
active materials being at least about 84.6 percent of the total
volume of the battery.
26. The AAA sized battery as defined in claim 24, wherein the
internal volume available for containing said electrochemically
active materials being at least about 88.0 percent of the total
volume of the battery.
27. The AAA sized battery as defined in claim 24, wherein the
internal volume available for containing said electrochemically
active materials being at least about 90.1 percent of the total
volume of the battery.
28. A D sized battery comprising: a can having an open end and a
closed end; and a collector assembly positioned across the open end
of said can, said collector assembly and can defining a sealed
internal volume within said can and available for containing
electrochemically active materials including at least positive and
negative electrodes and an electrolyte, the internal volume being
at least about 44.67 cc.
29. The D sized battery as defined in claim 28, wherein the
internal volume available for containing said electrochemically
active materials being at least about 45.53 cc.
30. The D sized battery as defined in claim 28, wherein the
internal volume available for containing said electrochemically
active materials being at least about 46.34 cc.
31. The D sized battery as defined in claim 28, wherein the
internal volume available for containing said electrochemically
active materials being at least about 46.82 cc.
32. The D sized battery as defined in claim 28, wherein the
internal volume available for containing said electrochemically
active materials being at least about 47.52 cc.
33. The D sized battery as defined in claim 28, wherein the
internal volume available for containing said electrochemically
active materials being .[.18.59.]. .Iadd.at least about 48.59
cc.
34. A C sized battery comprising: a can having an open end and a
closed end; and a collector assembly positioned across the open end
of said can, said collector assembly and can defining a sealed
internal volume within said can and available for containing
electrochemically active materials including at least positive and
negative electrodes and an electrolyte, the internal volume being
at least about 20.21 cc.
35. The C sized battery as defined in claim 34, wherein the
internal volume available for containing said electrochemically
active materials being at least about 20.92 cc.
36. The C sized battery as defined in claim 34, wherein the
internal volume available for containing said electrochemically
active materials being at least about 21.42 cc.
37. The C sized battery as defined in claim 34, wherein the
internal volume available for containing said electrochemically
active materials being at least about 21.73 cc.
38. The C sized battery as defined in claim 34, wherein the
internal volume available for containing said electrochemically
active materials being at least about 22.26 cc.
39. An AA sized battery comprising: a can having an open end and a
closed end; and a collector assembly positioned across the open end
of said can, said collector assembly and can defining a sealed
internal volume within said can and available for containing
electrochemically active materials including at least positive and
negative electrodes and an electrolyte, the internal volume being
at least about 64.7 cc.
40. The AA sized battery as defined in claim 39, wherein the
internal volume available for containing said electrochemically
active materials being at least about 6.56 cc.
41. The AA sized battery as defined in claim 39, wherein the
internal volume available for containing said electrochemically
active materials being at least about 6.68 cc.
42. The AA sized battery as defined in claim 39, wherein the
internal volume available for containing said electrochemically
active materials being at least about 6.77 cc.
43. The AA sized battery as defined in claim 39, wherein the
internal volume available for containing said electrochemically
active materials being at least about 6.95 cc.
44. The AA sized battery as defined in claim 39, wherein the
internal volume available for containing said electrochemically
active materials being at least about 7.0 cc.
45. An AAA sized battery comprising: a can having an open end and a
closed end; and a collector assembly positioned across the open end
of said can, said collector assembly and can defining a sealed
internal volume within said can and available for containing
electrochemically active materials including at least positive and
negative electrodes and an electrolyte, the internal volume being
at least about 2.811 cc.
46. The AAA sized battery as defined in claim 45, wherein the
internal volume available for containing said electrochemically
active materials being at least about 2.90 cc.
47. The AAA sized battery as defined in claim 45, wherein the
internal volume available for containing said electrochemically
active materials being at least about 3.02 cc.
48. The AAA sized battery as defined in claim 45, wherein the
internal volume available for containing said electrochemically
active materials being at least about 3.06 cc.
49. The AAA sized battery as defined in claim 45, wherein the
internal volume available for containing said electrochemically
active materials being at least about 3.14 cc.
50. The AAA sized battery as defined in claim 45, wherein the
internal volume available for containing said electrochemically
active materials being at least about 3.22 cc.
51. A battery comprising: a can having an open end and a closed
end; and a cover positioned across the open end of said can, said
cover and can defining a sealed internal volume within said can and
available for containing electrochemically active materials
including at least positive and negative electrodes and an
electrolyte, the internal volume being at least about 88.4% of the
total volume of the battery.
Description
BACKGROUND OF THE INVENTION
The present invention generally relates to the electrochemical cell
construction. More particularly, the present invention relates to
the containers and collector assemblies used for an electrochemical
cell, such as an alkaline cell.
FIG. 1 shows the construction of a conventional C sized alkaline
cell 10. As shown, cell 10 includes a cylindrically-shaped can 12
having an open end and a closed end. Can 12 is preferably formed of
an electrically conductive material, such that an outer cover 11
welded to a bottom surface 14 at the closed end of can 12 serves as
an electrical contact terminal for the cell.
Cell 10 further typically includes a first electrode material 15,
which may serve as the positive electrode (also known as a
cathode). The first electrode material 15 may be preformed and
inserted into can 12, or may be molded in place so as to contact
the inner surfaces of the can 12. For an alkaline cell, first
electrode material 15 will typically include MnO.sub.2. After the
first electrode 15 has been provided in can 12, a separator 17 is
inserted into the space defined by first electrode 15. Separator 17
is preferably a non-woven fabric. Separator 17 is provided to
maintain a physical separation of the first electrode material 15
and a mixture of electrolyte and a second electrode material 20
while allowing the transport of ions between the electrode
materials.
Once separator 17 is in place within the cavity defined by first
electrode 15, an electrolyte is dispensed into the space defined by
separator 17, along with the mixture 20 of electrolyte and a second
electrode material, which may be the negative electrode (also known
as the anode). The electrolyte/second electrode mixture 20
preferably includes a gelling agent. For a typical alkaline cell,
mixture 20 is formed of a mixture of an aqueous KOH electrolyte and
zinc, which serves as the second electrode material. Water and
additional additives may also be included in mixture 20.
Once the first electrode 15, separator 17, the electrolyte, and
mixture 20 have been formed inside can 12, a preassembled collector
assembly 25 is inserted into the open end of can 12. Can 12 is
typically slightly tapered at its open end. This taper serves to
support the collector assembly in a desired orientation prior to
securing it in place. After collector assembly 25 has been
inserted, an outer cover 45 is placed over collector assembly 25.
Collector assembly 25 is secured in place by radially squeezing the
can against collector assembly 25. The outer cover 45 is then
placed over and in contact with collector assembly 25. The end edge
13 of can 12 is then crimped over the peripheral lip of collector
assembly 25, thereby securing outer cover 45 and collector assembly
25 within the end of can 12. As described further below, one
function served by collector assembly 25 is to provide for a second
external electrical contact for the electrochemical cell.
Additionally, collector assembly 25 must seal the open end of can
12 to prevent the electrochemical materials therein from leaking
from this cell. Additionally, collector assembly 25 must exhibit
sufficient strength to withstand the physical abuse to which
batteries are typically exposed. Also, because electrochemical
cells may produce hydrogen gas, collector assembly 25 may allow
internally-generated hydrogen gas to permeate therethrough to
escape to the exterior of the electrochemical cell. Further,
collector assembly 25 should include some form of pressure relief
mechanism to relieve pressure produced internally within the cell
should this pressure become excessive. Such conditions may occur
when the electrochemical cell internally generates hydrogen gas at
a rate that exceeds that at which the internally-generated hydrogen
gas can permeate through the collector assembly to the exterior of
the cell.
The collector assembly 25 shown in FIG. 1 includes a seal 30, a
collector nail 40, an inner cover 44, a washer 50, and a plurality
of spurs 52. Seal 30 is shown as including a central hub 32 having
a hole through which collector nail 40 is inserted. Seal 30 further
includes a V-shaped portion 34 that may contact an upper surface 16
of first electrode 15.
Seal 30 also includes a peripheral upstanding wall 36 that extends
upward along the periphery of seal 30 in an annular fashion.
Peripheral upstanding wall 36 not only serves as a seal between the
interface of collector assembly 25 and can 12, but also serves as
an electrical insulator for preventing an electrical short from
occurring between the positive can and negative contact terminal of
the cell.
Inner cover 44, which is formed of a rigid metal, is provided to
increase the rigidity and supports the radial compression of
collector assembly 25 thereby improving the sealing effectiveness.
As shown in FIG. 1, inner cover 44 is configured to contact central
hub portion 32 and peripheral upstanding wall 36. By configuring
collector assembly 25 in this fashion, inner cover 44 serves to
enable compression of central hub portion 32 by collector nail 40
while also supporting compression of peripheral upstanding wall 36
by the inner surface of can 12.
Outer cover 45 is typically made of a nickel-plated steel and is
configured to extend from a region defined by the annular
peripheral upstanding wall 36 of seal 30 and to be in electrical
contact with a head portion 42 of collector nail 40. Outer cover 45
may be welded to head portion 42 of collector nail 40 to prevent
any loss of contact. As shown in FIG. 1, when collector assembly 25
is inserted into the open end of can 12, collector nail 40
penetrates deeply within the electrolyte/second electrode mixture
20 to establish sufficient electrical contact therewith. In the
example shown in FIG. 1, outer cover 45 includes a peripheral lip
47 that extends upwardly along the circumference of outer cover 45.
By forming peripheral upstanding wall 36 of seal 30 of a length
greater than that of peripheral lip 47, a portion of peripheral
upstanding wall 36 may be folded over peripheral lip 47 during the
crimping process so as to prevent any portion of the upper edge 13
of can 12 from coming into contact with outer cover 45.
Seal 30 is preferably formed of nylon. In the configuration shown
in FIG. 1, a pressure relief mechanism is provided for enabling the
relief of internal pressure when such pressure becomes excessive.
Further, inner cover 44 and outer cover 45 are typically provided
with apertures 43 that allow the hydrogen gas to escape to the
exterior of cell 10. The mechanism shown includes an annular metal
washer 50 and a plurality of spurs 52 that are provided between
seal 30 and inner cover 44. The plurality of spurs 52 each include
a pointed end 53 that is pressed against a thin intermediate
portion 38 of seal 30. Spurs 52 are biased against the lower inner
surface of inner cover 44 such that when the internal pressure of
cell 10 increases and seal 30 consequently becomes deformed by
pressing upward toward inner cover 44, the pointed ends 53 of spurs
52 penetrate through the thin intermediate portion 38 of seal 30
thereby rupturing seal 30 and allowing the escape of the
internally-generated gas through aperture 43.
Although the above-described collector assembly 25 performs all the
above-noted desirable functions satisfactorily, as apparent from
its cross-sectional profile, this particular collector assembly
occupies a significant amount of space within the interior of the
cell 10. Because the exterior dimensions of the electrochemical
cell are generally fixed by the American National Standards
Institute (ANSI), the greater the space occupied by the collector
assembly, the less space that there is available within the cell
for the electrochemical materials. Consequently, a reduction in the
amount of electrochemical materials that may be provided within the
cell results in a shorter service life for the cell. It is
therefore desirable to maximize the interior volume within an
electrochemical cell that is available for the electrochemically
active components.
It should be noted that the construction shown in FIG. 1 is but one
example of a cell construction. Other collector assemblies exist
that may have lower profiles and hence occupy less space within the
cell. However, such collector assemblies typically achieve this
reduction in occupied volume of the expense of the sealing
characteristics of the collector assembly or the performance and
reliability of the pressure relief mechanism. It is therefore
desirable to construct an electrochemical cell where the space
occupied by the collector assembly and the space occupied by the
container volume are minimized while still maintaining adequate
sealing characteristics and a reliable pressure relief
mechanism.
The measured external and internal volumes for several batteries
that were commercially available as of the filing date of this
application are listed in the tables shown in FIGS. 2A and 2B. The
tables list the volumes (cc) for D, C, AA, and AAA sized batteries.
Also provided in FIG. 2A is a percentage of the total cell volume
that constitutes the internal volume that is available for
containing the electrochemical active materials. The total cell
volume includes all of the volume, including any internal void
spaces, of the battery. For the battery shown in FIG. 1, the total
volume ideally includes all of the cross-hatched area as shown in
FIG. 3A. The "internal volume" of the battery is represented by the
cross-hatched area shown in FIG. 3B. The "internal volume," is used
herein, is that volume inside the cell or battery that contains the
electrochemically active materials as well as any voids and
chemically inert materials (other than the collector nail) that are
confined within the sealed volume of the cell. Such chemically
inert materials may include separators, conductors, and any inert
additives in the electrodes. As described herein, the term
"electrochemically active materials" include the positive and
negative electrodes and the electrolyte.
The collector assembly volume includes the collector nail, seal,
inner cover, and any void volume between the bottom surface of the
negative cover and the seal (indicated by the cross-hatched area in
FIG. 3C). It should be appreciated that the sum total of the
"internal volume,""collector assembly volume," and "container
volume" is equal to the total volume. Accordingly, the internal
volume available for electrochemically active materials can be
confirmed by measuring the collector assembly volume and container
volume and subtracting the collector assembly volume and the
container volume from the measured total volume of the battery. The
"container volume" includes the volume of the can, label, negative
cover, void volume between the label and negative cover, positive
cover, and void volume between the positive cover and can (shown by
the cross-hatched area in FIG. 3D). If the label extends onto and
into contact with the negative cover, the void volume present
between the label and negative cover is included in the container
volume, and therefore is also considered as part of the total
volume. Otherwise, that void volume is not included in either of
the container volume or the total volume. The collector assembly
volume and the percentage of the total cell volume that constitutes
the collector assembly volume is provided in FIG. 2B for those
commercially available batteries listed in FIG. 2A.
The total battery volume, collector assembly volume, and internal
volume available for electrochemically active material for each
battery are determined by viewing a Computer Aided Design (CAD)
drawing, a photograph, or an actual cross section of the battery
which has been encased in epoxy and longitudinally cross-sectioned.
The use of a CAD drawing, photograph, or actual longitudinal cross
section to view and measure battery dimensions allows for inclusion
of all void volumes that might be present in the battery. To
measure the total battery volume, the cross-sectional view of the
battery taken through its central longitudinal axis of symmetry is
viewed and the entire volume is measured by geometric computation.
To measure the internal volume available for electrochemically
active materials, the cross-sectional view of the battery taken
through its central longitudinal axis of symmetry is viewed, and
the components making up the internal volume, which includes the
electrochemically active materials, void volumes and chemically
inert materials (other than the collector nail) that are confined
within the sealed volume of the cell, are measured by geometric
computation. Likewise, to determine volume of the collector
assembly, the cross-sectional view of the battery taken through its
central longitudinal axis of symmetry thereof is viewed, and the
components making up the collector assembly volume, which include
the collector nail, seal, inner cover, and any void volume defined
between the bottom surface of the negative cover and the seal, are
measured by geometric computation. The container volume may
likewise be measured by viewing the central longitudinal cross
section of the battery and computing the volume consumed by the
can, label, negative cover, void volume between the label and
negative cover, positive cover, and void volume between the
positive cover and the can.
The volume measurements are made by viewing a cross section of the
battery taken through its longitudinal axis of symmetry. This
provides for an accurate volume measurement, since the battery and
its components are usually axial symmetric. To obtain a geometric
view of the cross section of a battery, the battery was first
potted in epoxy and, after the epoxy solidified, the potted battery
and its component were ground down to the central cross section
through the axis of symmetry. More particularly, the battery was
first potted in epoxy and then ground short of the central cross
section. Next, all internal components such as the anode, cathode,
and separator paper were removed in order to better enable
measurement of the finished cross section. The potted battery was
then cleaned of any remaining debris, was air dried, and the
remaining void volumes were filled with epoxy to give the battery
some integrity before completing the grinding and polishing to its
center. The battery was again ground and polished until finished to
its central cross section, was thereafter traced into a drawing,
and the volumes measured therefrom.
Prior to potting the battery in epoxy, battery measurements were
taken with calipers to measure the overall height, the crimp
height, and the outside diameter at the top, bottom, and center of
the battery. In addition, an identical battery was disassembled and
the components thereof were measured. These measurements of
components of the disassembled battery include the diameter of the
current collector nail, the length of the current collector nail,
the length of the current collector nail to the negative cover, and
the outside diameter of the top, bottom, and center of the battery
without the label present.
Once the battery was completely potted in epoxy and ground to
center through the longitudinal axis of symmetry, the
cross-sectional view of the battery was used to make a drawing. A
Mitutoyo optical comparator with QC-4000 software was used to trace
the contour of the battery and its individual components to
generate a drawing of the central cross section of the battery. In
doing so, the battery was securely fixed in place and the contour
of the battery parts were saved in a format that could later be
used in solid modeling software to calculate the battery volumes of
interest. However, before any volume measurements were taken, the
drawing may be adjusted to compensate for any battery components
that are not aligned exactly through the center of the battery.
This may be accomplished by using the measurements that were taken
from the battery before cross sectioning the battery and those
measurements taken from the disassembled identical battery. For
example, the diameter and length of the current collector nail, and
overall outside diameter of the battery can be modified to profile
the drawing more accurately by adjusting the drawing to include the
corresponding known cross-sectional dimensions to make the drawing
more accurate for volume measurements. The detail of the seal,
cover, and crimp areas were used as they were drawn on the optical
comparator.
To calculate the volume measurements, the drawing was imported into
solid modeling software. A solid three-dimensional volume
representation was generated by rotating the contour of the cross
section on both the left and right sides by one-hundred-eighty
degrees (180.degree.) about the longitudinal axis of symmetry.
Accordingly, the volume of each region of interest is calculated by
the software and, by rotating the left and right sides by
one-hundred-eighty degrees (180.degree.) and summing the left and
right volumes together an average volume value is determined, which
may be advantageous in those situations where the battery has
nonsymmetrical features. The volumes which include any
non-symmetrical features can be adjusted as necessary to obtain
more accurate volume measurements.
SUMMARY OF THE INVENTION
Accordingly, it is an aspect of the present invention to solve the
above problem by either eliminating the collector assembly from the
cell while retaining its functions, or by providing a collector
assembly having a significantly lower profile and thereby occupying
significantly less space within an electrochemical cell. Another
aspect of the present invention is to provide cell constructions
exhibiting lower water loss over time than prior assemblies,
thereby increasing the cell's shelf life. An additional aspect of
the invention is to provide a battery having a reliable pressure
relief mechanism that does not occupy a significant percentage of
the available cell volume. Still yet another aspect of the present
invention is to provide cell constructions that are simpler to
manufacture and that require less materials, thereby possibly
having lower manufacturing costs. Another aspect of the invention
is to provide cell constructions that require less radial
compressive force to be applied by the can to adequately seal the
cell, thereby allowing for the use of a can having thinner side
walls, and thus resulting in greater internal cell volume.
To achieve some of these and other aspects and advantages, a
battery of the present invention comprises a can for containing
electrochemical materials including positive and negative
electrodes and an electrolyte, the can having a first end, an open
second end, side walls extending between the first and second ends,
and an end wall extending across the first end; a pressure relief
mechanism formed in the end wall of the can for releasing internal
pressure from within the can when the internal pressure becomes
excessive, a first outer cover positioned on the end wall of the
can to be in electrical contact therewith and to extend over the
pressure relief mechanism; a second outer cover positioned across
the open second end of the can; and an insulator disposed between
the can and the second outer cover for electrically insulating the
can from the second outer cover.
Additionally, some of the above aspects and advantages may be
achieved by a battery of the present invention that comprises a can
for containing electrochemically active materials including at
least positive and negative electrodes and an electrolyte, the can
having a first end, an open second end, side walls extending
between the first and second ends, and an end wall extending across
the first end, the can further having a flange that extends outward
from the open second end of the can towards the first end; a cover
for sealing the open end of the can, the cover having a peripheral
edge that extends over and around the flange and is crimped between
the flange and an exterior surface of the side walls of the can;
and electrical insulation provided between the flange and the
peripheral edge of the cover and between the can and the peripheral
edge. The electrical insulating material is preferably provided in
the form of a coating deposited directly on at least one of the can
and the outer cover.
Further, some of the above aspects and advantages may also be
achieved by an electrochemical cell of the present invention that
comprises a can for containing electrochemically active materials
including at least positive and negative electrodes and an
electrolyte, the can having an open end and a closed end, and side
walls extending between the open end and closed end; a first outer
cover positioned across the open end of the can; a collector
electrically coupled to the first outer cover and extending
internally within the can to electrically contact one of the
positive and negative electrodes; and an annular seal having an
L-shaped cross section disposed between the can and the first outer
cover for electrically insulating the can from the first outer
cover and creating a seal between the first outer cover and the
can. The seal may further include an extended vertical member to
form a J-shaped cross section. According to this embodiment, a
pressure relief mechanism is preferably formed in a surface of the
can for releasing internal pressure from within the can when the
internal pressure becomes excessive.
Yet, some of the above aspects and advantages may be achieved by an
electrochemical cell of the present invention that comprises a can
for containing electrochemically active materials including at
least positive and negative electrodes and an electrolyte, the can
having an open end, a closed end, and side walls extending between
the open and closed ends; a cover positioned across the open end of
the can and connectable to the can, the cover having an aperture
extending therethrough; a current collector extending through the
aperture in the cover and extending internally within the can to
electrically contact one of the positive and negative electrodes;
and an insulating material disposed between the collector and the
cover for electrically insulating the collector from the cover and
creating a seal between the collector and the cover. In addition,
the electrochemical cell preferably includes a first contact
terminal electrically coupled to the collector and a dielectric
material disposed between the first contact terminal and the cover
for electrically insulating the cover from the first contact
terminal. Also provided is a method of manufacturing an
electrochemical cell which includes the steps of dispensing active
electrochemical materials in a can having a closed end and an open
end; disposing a collector through an aperture formed in a cover;
providing a dielectric insulating material between the cover and
the collector to provide electrical insulation therebetween; and
assembling the cover and collector to the open end of the can.
Further, some of the above aspects and advantages may also be
achieved by a battery of the present invention that comprises a can
for containing electrochemically active materials including
positive and negative electrodes and an electrolyte, and a label
printed directly on an exterior surface of the can. A method of
assembling a battery is also provided including the steps of
forming a can having an open end and a closed end, forming an outer
cover, dispensing electrochemically active materials in the can,
sealing the outer cover across the open end of the can with a layer
of electrical insulation provided therebetween, and printing a
label directly on the exterior surface of the can. According to
this embodiment, the diameter of the can may be correspondingly
increased to allow a significant increase in the internal volume of
the battery, while maintaining a predetermined total outside
diameter.
These and other features, advantages, and objects of the present
invention will be further understood and appreciated by those
skilled in the art by reference to the following specification,
claims, and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a cross section of a conventional C sized alkaline
electrochemical cell;
FIG. 2A is a table showing the relative total battery volumes and
internal cell volumes available for electrochemically active
materials, as measured for those batteries that were commercially
available at the time this application was filed;
FIG. 2B is a table showing the relative total battery volumes and
collector assembly volumes as measured for those batteries that
were commercially available as provided in FIG. 2A;
FIGS. 3A-3D are cross sections of a conventional C sized alkaline
electrochemical cell that illustrate the total battery and various
component volumes;
FIG. 4 is a cross section of a C sized alkaline electrochemical
cell having a low profile seal constructed in accordance with a
first embodiment of the present invention;
FIG. 5 is a partial cross section of an adaption of the first
embodiment for use in an AA sized battery shown in comparison with
a partial cross section of an adaptation of the conventional
construction as currently used in an AA sized battery;
FIG. 6 is a cross section of a C sized alkaline electrochemical
cell having an ultra low profile seal according to a second
embodiment of the present invention;
FIG. 7 is a cross section of a C sized alkaline electrochemical
cell having an ultra low profile seal and a formed positive cover
protrusion according to a third embodiment of the present
invention;
FIG. 8A is a cross section of a C sized alkaline electrochemical
cell constructed in accordance with a fourth embodiment of the
present invention having a rollback cover, an annular L-shaped or
J-shaped seal, and a pressure relief mechanism formed in the can
bottom surface;
FIG. 8B is a cross section of the top portion of a C sized alkaline
electrochemical cell constructed in accordance with the fourth
embodiment of the present invention having a rollback cover and
further including an L-shaped annular seal;
FIG. 8C is an exploded perspective view of the electrochemical cell
shown in FIG. 8A illustrating assembly of the collector seal and
cover assembly;
FIG. 9 is a bottom view of a battery can having a pressure relief
mechanism formed in the closed end of the can;
FIG. 10 is a cross sectional view taken along line X--X of the can
vent shown in FIG. 9;
FIG. 11 is a cross section of a C sized alkaline electrochemical
cell having a beverage can-type construction according to a fifth
embodiment of the present invention;
FIG. 12A is a partially exploded perspective view of the battery
shown in FIG. 11;
FIGS. 12B and 12C are cross-sectional views of a portion of the
battery shown in FIG. 11 illustrating the process for forming the
beverage can-type construction;
FIG. 12D is an enlarged cross-sectional view of a portion of the
battery shown in FIG. 11;
FIG. 13 is a cross section of a C sized alkaline electrochemical
cell having a beverage can-type construction according to a sixth
embodiment of the present invention;
FIG. 14A is a table showing the calculated total and internal cell
volume for various batteries constructed in accordance with the
present invention;
FIG. 14B is a table showing the calculated total volume and
collector assembly volume for various batteries constructed in
accordance with the present invention;
FIG. 15 is a cross section of a C sized alkaline electrochemical
cell having a collector feed through construction according to a
seventh embodiment of the present invention;
FIG. 16 is an exploded assembly view of the electrochemical cell
shown in FIG. 15; and
FIG. 17 is a flow diagram illustrating a method of assembly of the
electrochemical cell shown in FIGS. 15 and 16.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
As described above, a primary objective of the present invention is
to increase the internal volume available in a battery for
containing the electrochemically active materials to volumes
previously not obtained. To achieve this objective without
detrimentally decreasing the reliability of the pressure relief
mechanism provided in the battery and without increasing the
likelihood that the battery would otherwise leak, various novel
modifications are suggested below to the construction of batteries
of various sizes. The modifications described below may be
implemented separately or in combination in a battery to improve
its volume efficiency.
As described in further detail below, the various modifications of
the present invention that achieve greater internal volume for
containing the electrochemically active materials, include a low
profile seal (FIG. 4), an ultra low profile seal (FIG. 5), a
positive outer cover protrusion formed directly in the closed end
of the can used in combination with the ultra low profile seal
(FIG. 6) or the low profile seal, a can vent formed in the closed
end of the battery can (FIGS. 7-9) including an L-shaped and
J-shaped annular seal (FIGS. 8A-8C), a beverage can-type
construction used in combination with a can vent (FIG. 11), and a
beverage can-type construction with a collector feed through (FIGS.
15-17).
Additionally, through the use of the constructions noted above, the
battery can may be made with thinner walls, on the order of 4-8
mils, since the construction techniques outlined below do not
require the thicker walls that are required in conventional
batteries to ensure a sufficient crimp and seal. Further, in
accordance with the present invention, a label may be lithographed
directly onto the exterior surface of the battery can. By making
the can walls thinner and lithographing the label directly onto the
exterior of the can, the internal volume of the cell may be further
increased since one does not have to account for the thickness of
the label substrate to construct a cell that meets the ANSI
exterior size standards.
Low Profile Seal
FIG. 4 shows a battery constructed using a low profile seal in
accordance with a first embodiment of the present invention.
Similar to the battery shown in FIG. 1, battery 100 includes an
electrically conductive can 112 having a closed end 114 and an open
end in which a collector assembly 125 and negative cover 145 are
secured in place. Also, battery 100 includes a positive electrode
115 in contact with the interior walls of can 112 and in contact
with a separator layer 117 that lies between positive electrode 115
and a negative electrode 120. Further, battery 100 includes a
positive outer cover 111 attached to a bottom surface of the closed
end of can 112.
The difference between batteries 10 and 100 lies in the
construction of collector assembly 125 and cover 145. While seal
130 is similar to seal 30 in that it includes an upstanding wall
136 and a central hub 132, which has an aperture formed therein for
receiving the head portion 142 of a collector nail 140, seal 130
differs from seal 30 in that the V portion 34 of seal 30 is
inverted to extend upward toward inner cover 144, as indicated by
reference numeral 134. By inverting this V portion, collector
assembly 125 may rest more squarely upon an upper surface 116 of
positive electrode 115. Further, the volume occupied by the V
portion 34 of battery 10 may then be used for the chemically active
materials.
To also reduce the internal volume occupied by collector assembly
125, inner cover 144 is constructed to more closely conform to the
inner surface of outer cover 145 so as to eliminate the void space
between outer cover 45 and inner cover 44 in battery 10.
Additionally, by resting collector assembly 125 firmly on top
surface 116 of positive electrode 115, the peripheral edge 147 of
outer cover 145 may be flat rather than extend upward, as in the
case for battery 10. By laying peripheral edge 147 flat, collector
assembly 125 may be positioned even closer to the end of battery
100.
Collector assembly 125 of battery 100 further differs from
collector assembly 25 of battery 10 in that spurs 52 and washer 50
are eliminated. Collector assembly 125, nevertheless, has a
reliable pressure relief mechanism by the provision of a
thinned-out section 138 formed in seal 130 immediately adjacent hub
132. A thickened ring portion 139 of seal 130 is provided adjacent
thinned-out portion 138 such that thinned-out portion 138 lies
between thickened ring portion 139 and the relatively thick hub
132. Thus, when the internal pressure of cell 100 becomes
excessive, seal 130 rips open in the location of thinned-out
portion 138. As with the construction shown for battery 10, the
internally-generated gas then escapes through apertures 143 formed
in inner cover 144 and outer cover 145.
The internal volume available for containing electrochemically
active materials in a D sized battery having the conventional
construction shown in FIG. 1, is 44.16 cc, which is 87.7 percent of
the total volume of 50.38 cc (See the corresponding entry in the
table of FIG. 2A.) If the same cell were constructed using the low
profile seal construction shown in FIG. 4, the internal cell volume
may be increased to 44.67 cc, which represents 89.2 percent of the
total volume, which is 50.07 cc. The internal and external volumes
for the cell constructed with the low profile seal of the present
invention are for a cell having a 10 mil can thickness. Further, by
decreasing the can wall thickness, even greater internal cell
volumes may be achieved.
The low profile seal described above is disclosed in
commonly-assigned U.S. patent application Ser. No. 08/882,572
entitled "A V-SHAPED GASKET FOR GALVANIC CELLS," filed on Jun. 27,
1997, by Gary R. Tucholski, the disclosure of which is incorporated
by reference herein.
FIG. 5 shows a modified adaptation of the low profile seal as used
in an AA sized battery 100' in comparison with a commercial
adaptation of the construction shown in FIG. 1 as used for an AA
sized battery 10'. Like the collector assembly of battery 100 (FIG.
4), the collector assembly of battery 100' includes a seal 130
having an inverted-V portion 134, a hub portion 132, and a
thinned-out portion 138 provided between hub 132 and a thickened
portion 139.
The primary difference between the collector assemblies of
batteries 100 and 100' is the elimination of inner cover 144 of
battery 100. To ensure sufficient radial compressive force against
upstanding leg 136 of seal 130, battery 100' uses a rollback cover
145' in place of the flanged cover 145 used in battery 100 and also
utilizes a retainer 150. As will be apparent from a comparison of
FIGS. 4 and 5, a rollback cover differs from a flanged cover in
that the peripheral edge 147 of a flanged cover 145 is flat whereas
the peripheral edge 147' of a rollback cover 145' extends axially
downward and is folded to also extend axially upward. Rollback
cover 145' provides a sufficient spring force in the radial
direction to maintain compression of upstanding leg 136 of seal 130
against the inner wall of can 112 during normal use.
Retainer 150 is provided over and around the upper portion of hub
132 of seal 130 to compress hub 132 against collector nail 140.
Also, by configuring retainer 150 to have a J- or L-shaped cross
section, the lower radial extension of retainer 150 can ensure that
seal 130 will rupture in the vicinity of thinned-out portion 138
when the internal pressure reaches an excessive level.
Ultra Low Profile Seal
FIG. 6 shows a battery constructed in accordance with a second
embodiment of the present invention, which utilizes an ultra low
profile seal. Like the conventional cell 10 shown in FIG. 1, cell
200 also includes a cylindrical can 212 made of an electrically
conductive material. Also, a first electrode 215 is formed against
the inner walls of can 212 preferably by molding. A separator 217
is likewise inserted within the cavity defined by first electrode
material 215, and a mixture 220 of a second electrode and
electrolyte are provided within a cavity defined by the separator
217.
As shown in FIG. 6, collector assembly 225 includes an integral
seal/inner cover assembly 228 and a collector 240 that passes
through a central hole 236 provided in the integral seal/inner
cover assembly 228. Collector 240 is preferably a brass nail
including a bead 242 and a retainer flange 241 that is provided to
cooperate with a speed nut 250 to secure collector nail 240 within
central hole 236 of integrated seal/inner cover assembly 228.
Integrated seal/inner cover assembly 228 includes a rigid inner
core 210 and a seal 230 that is formed directly on rigid inner 210
by molding or lamination. Seal 230 is preferably made of neoprene,
butyl, or ethylene propylene rubber, and rigid inner cover 210 is
preferably formed of low-carbon steel 1008 or 1010. Because rubber
is more compressible than the nylon or polypropylene materials
often used in such collector assemblies, the radial compressive
strength of the rigid inner cover 210 need not be as great. Thus,
the inner cover could be made of thinner and/or softer metals.
Further, materials other than metal may be used. Also, seal 230 may
be formed of other materials provided such materials are chemically
inert, water impervious, compressible, and exhibit the ability to
bond to the material used to form rigid inner cover 210.
Additionally, by decreasing the radial force required to compress
the peripheral upstanding wall of the seal, the thickness of the
can walls may be decreased from 0.010 inch (10 mils) to
approximately 0.006 (6 mils) or possibly even 0.004 inch (4
mils).
By providing a structure that enables rubber materials such as
neoprene and butyl rubber to be used as the seal material, the
water permeability of the collector assembly is significantly
reduced. By reducing the water permeability of the cell, the
service maintenance of the battery should be increased.
Rigid inner cover 210 is generally disk shaped and has a central
aperture 218 formed at its center as well as a plurality of
additional apertures 217. Central aperture 218 and additional
apertures 217 extend through rigid inner cover 210 from its upper
surface to its bottom surface. If formed of metal, rigid inner
cover 210 is preferably produced by stamping it from a sheet of
metal. Inner cover 210 may, however, be formed using other known
manufacturing techniques. Subsequently, rigid inner cover 210 may
be subjected to a surface roughening process, such as sandblasting
or chemical etching, to enhance the strength of bond that is
subsequently formed between rigid inner cover 210 and seal 230. For
a C sized cell, rigid inner cover 210 is preferably 0.015 to 0.030
inch thick.
After rigid inner cover 210 has been stamped and surface treated,
it is preferably inserted into a transfer mold press into which the
rubber that forms seal 230 is subsequently supplied. The transfer
mold is preferably formed to allow the supplied rubber to form a
layer 232 across the bottom surface of rigid inner cover 210. The
thickness of layer 232 is between 0.010 and 0.020 inch thick, and
is preferably about 0.016 inch thick. The rubber also flows into
apertures 217 to form plugs 238. Also, the rubber flows within
central aperture 218 so as to line the surfaces of central aperture
218 but without completely filling the aperture so as to provide a
central hole 236 into which collector nail 240 may subsequently be
inserted. The diameter of central hole 236 is preferably
sufficiently smaller than the diameter of collector nail 240 such
that the rubber lining in central aperture 218 is significantly
compressed within aperture 218 when collector nail 240 is driven in
place through central hole 236. By providing a retainer 241 on
collector 240 that is pressed against bottom layer 232 of seal 230,
when collector nail 240 has been driven in place, its speed nut 250
and retainer 241 cooperate to also vertically compress the portion
of rubber layer 232 lying therebetween. By compressing the rubber
seal in the vicinity of collector nail 240 in this manner, the
possibility of a leak occurring in the interface between the
collector nail 240 and integrated seal/inner cover assembly 228 is
significantly reduced.
By filling apertures 217 with rubber seal plugs 238 in the manner
shown, a pressure relief mechanism is provided that not only works
reliably, but which may effectively reseal after internal pressure
has been released. When the internal pressure reaches levels
considered to be excessive, the excessive pressure ruptures at
least one of plugs 238 to allow the expedited release of
internally-generated gases. The pressure at which such rupturing
occurs is controllable based upon the materials selected for the
seal, the thickness of the seal material, and the diameter of
apertures 217. Further, because of the elasticity of the rubber
seal material, the rubber plug 238 substantially assumes to
original state once the pressure has been released. Thus, unlike
other venting mechanisms used in conventional collector assemblies,
the pressure relief mechanism of the present invention does not
create a permanent hole within the collector assembly through which
electromechanical materials may subsequently leak. Also, such
resaling minimizes deterioration of the cell's internal components,
thereby possibly extending the useful cell life.
Although only one aperture 217 in plug 238 need be provided to
serve as a pressure relief mechanism, added reliability is obtained
by providing a plurality of such plugged apertures. Unlike prior
art relief mechanism structures, the present invention allows for a
plurality of independently-operable pressure relief mechanisms.
Even the pressure relief mechanism illustrated in FIG. 1, which
includes a plurality of spurs, relies upon the inventions of washer
50 for any one of the spurs to penetrate the seal. Each of the
plugged apertures provided in the collector assembly of the present
invention, however, is not dependent upon one another, and
therefore provide for a more reliable pressure relief mechanism as
a whole.
As shown in FIG. 6, seal 230 has an upstanding wall 235 formed
directly on a peripheral edge of rigid inner cover 210. By
providing this upstanding wall 235, a sufficient seal may be
created when collector assembly 225 is inserted into can 212. This
seal is further enhanced by forming the outer diameter of seal 230
to be greater than the inside diameter of can 212 so that inner
cover 210 compresses upstanding wall 235 against the inner surface
of can 212.
Seal 230 may additionally be formed to include an extended portion
237 of upstanding wall 235 that extends vertically upward past the
upper surface of inner cover 210. By providing extension 237, seal
230 may be used as an electrical insulator between the crimped end
224 of can 212 and a peripheral edge of outer cover 245.
Although seal 230 is shown as including a continuous layer 232
across the entire bottom surface of inner cover 210, it will be
appreciated by those skilled in the art that seal 230 need not be
formed over the entire bottom surface of inner cover 210,
particularly if inner cover 210 is formed of an inert plastic
material. Depending upon the characteristics of the materials used
to form seal 230 and inner cover 210, a bonding agent may be
applied to the surfaces of inner cover 210 that will come into
contact and be bonded to seal material 230.
Once seal 230 has been molded to inner cover 210 and collector nail
240 is inserted through central hole 236 of integrated seal/inner
cover assembly 228 and through retainer 240, outer cover 245 is
placed on the upper surface of collector assembly 225 and is
preferably welded to head 242 of collector nail 240. Subsequently,
the collector assembly 225 with the outer cover 245 attached
thereto is inserted into the open end of cell can 212. To hold
collector assembly 225 in place prior to crimping, the bottom
surface of collector assembly 225 is rested upon an upper surface
216 of first electrode 215. Thus, collector assembly 225 may be
inserted with some degree of force to ensure that the bottom layer
232 of seal 230 rests evenly within the cell can opening on upper
surface 216 of electrode 215.
If first electrode 215 is formed by molding it in place within can
212, first electrode 215 is preferably constructed in the manner
disclosed in commonly-assigned U.S. patent application Ser. No.
09/036,115 entitled "ELECTROCHEMICAL CELL STRUCTURE EMPLOYING
ELECTRODE SUPPORT FOR THE SEAL," filed on Mar. 6, 1998, by Gary R.
Tucholski et al. to prevent any flashing resulting from the molding
of first electrode 215 from interfering with the proper alignment
and seal provided by the collector assembly. The disclosure of U.S.
patent application Ser. No. 09/036,115 is incorporated by reference
herein.
By resting collector assembly 225 on electrode 215, can 212 could
be crimped at its open end so as to provide a downward force that
is countered by electrode 215. Thus, the higher profile crimp used
in the conventional cell construction shown in FIG. 1 may be
replaced with a lower profile crimp, thereby creating about 0.060
inch more space inside the cell.
A collector assembly 225 having the construction shown in FIG. 6
has a much lower profile than the conventional collector assembly
as illustrated in FIG. 1. Thus, a cell 200 utilizing collector
assembly 225 may include greater amounts of electrochemical
materials 215 and 220, and the service life of the cell is
increased accordingly. Despite its lower profile, collector
assembly 225 nevertheless exhibits sufficient sealing and
electrical insulation. Additionally, the collector assembly of the
present invention provides a pressure relief mechanism that is not
only reliable, but which provides the advantage of multiple
independently-operable pressure relief mechanisms and partial
resealing after venting to prevent the subsequent leakage of
electrochemical materials from the cell. Further, the collector
assembly of the present invention offers improved water
permeability characteristics, thereby increasing the service
maintenance of the battery.
The calculated total volumes (cc) and internal volumes (cc)
available for containing electrochemically active materials for
batteries of various sizes constructed using the ultra low profile
seal shown in FIG. 6, are provided in the table shown in FIG. 14A.
As apparent from the table in FIG. 14A, the internal cell volumes
for such cells are generally greater than any of the prior
commercially-available cells. For example, a D sized battery
employing the ultra low profile seal has an internal volume
available for containing electrochemically active materials of
45.53 cc, which is 90.9 percent of the total volume of 50.07 cc.
This is greater than the internal volume measured on any of the
conventional cells listed in FIG. 2A. Further, for cells having a
can thickness of 8 mils or 6 mils, the internal cell volume may be
further significantly increased. The calculated total volumes (cc)
are further shown in the table presented in FIG. 14B, in comparison
with the collector assembly volumes for batteries of various sizes
constructed using the ultra low profile seal shown in FIG. 6. The
collector assembly volume as defined herein includes the collector
nail, seal, inner cover, and any void volume between the bottom
surface of the negative cover and the seal. The container volume as
defined herein includes the volume used by the can, label, negative
cover, void volume between the label and the negative cover,
positive cover, and the void volume between the positive cover and
can. It should be appreciated that the total volume of the battery
is equal to the summation of the internal volume available for
electrochemically active materials, the collector assembly volume,
and the container volume. The total volume of the battery,
collector assembly volume and container volume are determined by
viewing a CAD drawing of the central longitudinal cross-sectional
view of the battery. As is apparent from the table in FIG. 14B, the
collector assembly volume is generally less than any of the prior
commercially-available cells. It should be appreciated that the
collector assembly volume is decreased by using the ultra low
profile seal construction. For example, the collector assembly
volume consumed in the ultra low profile seal is 1.89 cc, which is
3.8 percent of the total volume of 50.07 cc as shown in FIG. 14B.
In contrast, this is less than any of the collector assembly
volumes measured from the conventional batteries as listed in FIG.
2B. The container volume may also be decreased. Similarly, for
cells having a reduced can thickness of 8 mils of 6 mils, the
internal cell volume may be further significantly increased, while
the container volume is decreased.
The ultra low profile seal described above, and several alternative
embodiments of the ultra low profile seal, are disclosed in
commonly-assigned U.S. patent application Ser. No. 09/036,208
entitled "COLLECTOR ASSEMBLY FOR AN ELECTROCHEMICAL CELL INCLUDING
AN INTEGRAL SEAL/INNER COVER," filed on Mar. 6, 1998, by Gary R.
Tucholski, the disclosure of which is incorporated by reference
herein.
Low Profile Seal and Ultra Low Profile Seal With Formed Positive
Protrusion
As shown in FIG. 7, the second embodiment shown in FIG. 6 may be
modified to have the protrusion 270 for the positive battery
terminal directly in the closed end 214' of can 212. In this
manner, the void space existing between the closed end 214 of can
212 and positive outer cover 211 (FIG. 6) may be used to contain
electrochemically active materials or otherwise provide space for
the collection of glasses, which otherwise must be provided within
the cell. It will further be appreciated by those skilled in the
art that the first embodiment shown in FIG. 4 may similarly be
modified, such that the positive outer cover protrusion is formed
directly in the bottom of can 112. Although the increase in cell
volume obtained by forming the protrusion directly in the bottom of
the can is not provided in the table in FIG. 14A, it will be
appreciated by those skilled in the art that the internal volume is
typically one percent greater than the volumes listed for the ultra
low profile seal or low profile seal listed in the table, which are
formed with a separate cover.
Pressure Relief Mechanism Formed in Can Bottom with L-Shaped
Seal
An electrochemical battery 300 constructed in accordance with a
fourth embodiment of the present invention is shown in FIGS. 8A
through 8C. Battery 300 differs from the prior battery
constructions in that a pressure relief mechanism 370 is formed in
the closed end 314 of can 312. As a result, complex collector/seal
assemblies may be replaced with collector assemblies that consume
less volume and have fewer parts. Thus, a significant improvement
in internal cell volume efficiency may be obtained. As shown in
FIG. 8A, 8B, 9, and 10, the pressure relief mechanism 370 is formed
by providing a groove 372 in the bottom surface of can 312. This
groove may be formed by coining a bottom surface of can 312,
cutting a groove in the bottom surface, or molding the groove in
the bottom surface of the can at the time the positive electrode is
molded. For an AA sized battery, the thickness of the metal at the
bottom of the coined groove is approximately 2 mils. For a D sized
battery, the thickness of the metal at the bottom of the coined
groove is approximately 3 mils. The groove may be formed as an arc
of approximately 300 degrees. By keeping the shape formed by the
groove slightly open, the pressure relief mechanism will have an
effective hinge.
The size of the area circumscribed by the groove 372 is preferably
selected such that upon rupture due to excessive internal pressure,
the area within the groove 372 may pivot at the hinge within the
positive protrusion of outer cover 311 without interference from
outer cover 311. In general, the size of the area defined by the
groove 372, as well as the selected depth of the groove, depends
upon the diameter of the can and the pressure at which the pressure
relief mechanism is to rupture and allow internally generated gases
to escape.
Unlike pressure relief mechanisms that have been described in the
prior art as being formed in the side or end of the can, the
pressure relief mechanism 370 of the present invention is
positioned beneath outer cover 311 so as to prevent the
electrochemical materials from dangerously spraying directly
outwardly from the battery upon rupture. Also, if the battery were
used in series with another batter such that the end of the
positive terminal of the battery is pressed against the negative
terminal of another battery, the provision of outer cover 311 over
pressure relief mechanism 370 allows mechanism 370 to bow outwardly
under the positive protrusion and ultimately rupture. If outer
cover 311 was not present in such circumstances, the contact
between the two batteries may otherwise prevent the pressure relief
mechanism from rupturing. Further, if outer cover 311 were not
provided over pressure relief mechanism 370, the pressure relief
mechanism at the positive end of the battery would be more
susceptible to damage. Outer cover 311 also shields pressure relief
mechanism 370 from the corrosive effects of the ambient environment
and therefore reduces the possibility of premature venting and/or
leaking. Thus, by forming the pressure relief mechanism under the
outer cover, the present invention overcomes the problems
associated with the prior art constructions, and thus represents a
commercially feasible pressure relief mechanism for a battery.
Because the formation of a pressure relief mechanism in the bottom
surface of a battery can eliminates the need for a complex
collector/seal assembly, the open end of the battery can may be
sealed using construction techniques that were not previously
feasible due to the need to allow gases to escape through the
pressure relief mechanism to the exterior of the battery. For
example, as shown in FIGS. 8A and 8B, the open end of can 312 may
be sealed by placing either a nylon seal 330 having a J-shaped
cross section or a nylon seal 330' having an L-shaped cross section
in the open end of can 312, inserting a negative outer cover 345
having a rolled back peripheral edge 347 within nylon seal 330 or
330', and subsequently crimping the outer edge 313 of can 312 to
hold seal 330 or 330' and cover 345 in place. To help hold seal 330
or 330' in place, a bead 316 may be formed around the circumference
of the open end of can 312. Nylon seal 330 or 330' may be coated
with asphalt to protect it from the electrochemically active
materials and to provide a better seal.
Referring particularly to FIGS. 8A and 8C, the annular nylon seal
330 is shown configured with a J-shaped cross section which
includes an extended vertical wall 332 at the outermost perimeter
thereof, a shorter vertical wall 336 at the radially inward side of
the seal and has a horizontal base member 334 formed between the
vertical walls 332 and 336. With the presence of the short vertical
section 336, the annular seal is referred to herein as having
either a J-shaped or L-shaped cross section. It should be
appreciated that the J-shaped nylon seal 330 could also be
configured absent the short vertical section 336 to form a plain
L-shaped cross section as shown in FIG. 8B.
With particular reference to FIG. 8C, the assembly of the
electrochemical cell shown in FIG. 8A is illustrated therein. The
cylindrical can 312 is formed with side walls defining the open end
and bead 316 for receiving internally disposed battery materials
prior to closure of the can. Disposed within can 312 are the active
electrochemical cell materials including the positive and negative
electrodes and the electrolyte, as well as the separator, and any
additives. Together, the outer cover 345, with the collector nail
340 welded or otherwise fastened to the bottom surface of cover
345, and annular nylon seal 330 are assembled and inserted into the
open end of can 312 to seal and close can 312. The collector nail
340 is preferably welded via spot weld 342 to the bottom side of
outer cover 345. Together, collector nail 340 and cover 345 are
engaged with seal 330 to form the collector assembly, and the
collector assembly is inserted in can 312 such that the rolled back
peripheral edge 347 of outer cover 345 is disposed against the
inside wall of annular seal 330 above bead 316 which supports seal
330. The collector assembly is forcibly disposed within the open
end of can 312 to snugly engage and close the can opening.
Thereafter, the outer edge 313 of can 12 is crimped inward to
axially force and hold seal 330 and outer cover 345 in place.
Referring back to FIG. 8B, the inside surface of outer cover 345
and at least a top portion of collector nail 340 are further shown
coated with an anti-corrosion coating 344. Anti-corrosion coating
344 includes materials that are electrochemically compatible with
the anode. Examples of such electrochemically compatible materials
include epoxy, Teflon.RTM., polyolefins, nylon, elastomeric
materials, or any other inert materials, either alone or in
combination with other materials. Coating 344 may be sprayed or
painted on and preferably covers the portion of the inside surface
of outer cover 345 and collector nail 340 which is exposed to the
active materials in the void region above the positive and negative
electrodes of the cell. It should also be appreciated that the
inside surface of cover 345 could be plated with tin, copper, or
other similarly electrochemically compatible materials. By
providing the anticorrosion coating 344, any corrosion of the outer
cover 345 and collector nail 340 is reduced and/or prevented, which
advantageously reduces the amount of gassing which may otherwise
occur within the electrochemical cell. Reduction in gassing within
the cell results in reduced internal pressure buildup.
As shown in FIG. 14A in the rows referred "Pressure Relief in Can
Bottom" and "Pressure Relief in Can Bottom With Thin Walls," a D
sized battery constructed using the construction shown in FIG. 8A,
has an internal volume that is 93.5 volume percent when the can
walls are 10 mils thick, and an internal volume that is 94.9 volume
percent when the can walls are 8 mls thick. As shown in FIG. 14B, a
D sized battery constructed using the construction shown in FIG.
8A, has a collector assembly volume that is 2 percent of the total
volume when the can walls are 10 mils thick and 8 mils thick. The
C, AA, and AAA sized batteries having similar construction also
exhibited significant improvements in internal volume efficiency,
as is apparent from the table in FIGS. 14A.
Beverage Can-Type Construction
The use of the pressure relief mechanism illustrated in FIGS.
8A-10, further allows the use of the beverage can-type construction
shown in FIG. 11. The beverage can-type construction shown differs
from other forms of battery seal constructions in that it does not
require any form of nylon seal to be inserted into the open end of
can 412. Instead, negative outer counter 445 is secured to the open
end of can 412 using a sealing technique commonly used to seal the
top of a food or beverage can to the cylindrical portion of the
can. Such sealing constructions had not previously been considered
for use in sealing batteries because they would not readily allow
for the negative outer cover to be electrically insulated from the
can.
The method of making a battery having the construction shown in
FIG. 11 is described below with reference, to FIGS. 12A-12D. Prior
to attaching negative outer cover 445 to the open end of can 412, a
collector nail 440 is welded to the inner surface of cover 445.
Next, as shown in FIG. 12A, the inner surface of cover 445, as well
as the peripheral portion of the upper surface of cover 445, is
coated with a layer 475 of electrical insulation material, such as
an epoxy, nylon, Teflon.RTM., or vinyl. The portion of collector
nail 440 that extends within the void area between the bottom of
cover 445 and the top surface of the negative electrode/electrolyte
mixture 120, is also coated with the electrical insulation.
Additionally, the inner and outer surfaces of can 412 are also
coated in the region of the open end of can 412. Such coatings 475
may be applied directly to the can and cover by spraying, dipping,
or electrostatic deposition. By providing such a coating, negative
outer cover 445 may be electrically insulated from can 412.
By applying the insulation coating to the areas of the can, cover,
and collector nail within the battery that are proximate the void
area within the battery's internal volume, those areas may be
protected from corrosion. While a coating consisting of a single
layer of the epoxy, nylon, Teflon.RTM., or vinyl materials noted
above will function to prevent such corrosion, it is conceivable
that the coating may be applied using layers of two different
materials of made of single layers of different materials applied
to different regions of the components. For example, the peripheral
region of the cover may be coated with a single layer of material
that functions both as an electrical insulator and an
anti-corrosion layer, while the central portion on the inner
surface of the cover may be coated with a single layer of a
material that functions as an anti-corrosion layer but does not
also function as an electrical insulator. Such materials may
include, for example, asphalt or polyamide. Alternatively, either
one of the can or cover may be coated with a material that
functions as both an electrical insulator and anti-corrosion layer,
while the other of these two components may be coated with a
material that functions only as an anti-corrosion layer. In this
manner, the electrical insulation would be provided where needed
(i.e., between the cover/can interface), while the surfaces
partially defining the void area in the internal volume of the cell
will still be protected from the corrosive effects of the
electrochemical materials within the cell. Further, by utilizing
different materials, materials may be selected that are lower in
cost or exhibit optimal characteristics of the intended
function.
To assist in the sealing of outer cover 445 to can 412, a a
conventional sealant 473 may be applied to the bottom surface of
peripheral edge 470 of cover 445. Once the sealing procedure is
complete, sealant 473 migrates to the positions shown in FIG.
12D.
Once collector nail 440 has been attached to outer cover 445 and
the electrical insulation coating has been applied, outer cover 445
is placed over the open end of can 412 as shown in FIG. 12B.
Preferably, can 412 has an outward extending flange 450 formed at
its open end. Further, outer cover 445 preferably has a slightly
curved peripheral edge 470 that conforms to the shape of flange
450. Once outer cover 445 has been placed over the open end of can
412, a seaming chuck 500 is placed on outer cover 445, such that an
annular downward extending portion 502 of seaming chuck 500 is
received by an annular recess 472 formed in outer cover 445. Next,
a first seaming roll 510 is moved in a radial direction toward the
peripheral edge 470 of outer cover 445. As first seaming roll 510
is moved toward peripheral edge 470 and flange 450, its curved
surface causes peripheral edge 470 to be folded around flange 450.
Also, a first seaming roll 510 moves radially inward, seaming chuck
500, can 412, and outer cover 445 are rotated about a central axis,
such that peripheral edge 470 is folded around flange 450 about the
entire circumference of can 412. Further, as first seaming roll 510
continues to move radially inward, flange 450 and peripheral edge
470 are folded downward to the position shown in FIG. 12C.
After peripheral edge 470 and flange 450 have been folded into the
position shown in FIG. 12C, first seaming roll 510 is moved away
from can 412, and a second seaming roll 520 is then moved radially
inward toward flange 450 and peripheral edge 470 Second seaming
roll 520 has a different profile than first seaming roll 510.
Second seaming roll 520 applies sufficient force against flange 450
and peripheral edge 470 to press and flatten the folded flange and
peripheral edge against the exterior surface of can 412, which is
supported by seaming chuck 500. As a result of this process, the
peripheral edge 470 of can 412 is folded around and under flange
450 and is crimped between flange 450 and the exterior surface of
the walls of can 412, as shown in FIGS. 11 and 12D. A hermetic seal
is this formed by this process.
To illustrate the hermetic nature of this type of seal, a D sized
can constructed in accordance with this embodiment of the present
invention was filled with water as was a D sized can constructed
with a conventional seal, such as that illustrated in FIG. 1. The
two cans were maintained at 71.degree. C. and weighted over time to
determine the amount of water lost from the cans. The conventional
construction lost 270 mg per week, and the construction in
accordance with the present invention did not lose any weight over
the same time period. These results were confirmed using KOH
electrolyte, with the conventional construction losing 50 mg per
week and the inventive construction again not losing any
weight.
As will be apparent to those skilled in the art, the beverage
can-type construction utilizes minimal space in the battery
interior, reduces the number of process steps required to
manufacture a battery, and significantly reduces the cost of
materials and the cost of the manufacturing process. Further, the
thickness of the can walls may be significantly reduced to 6 mils
or less. As a result, the internal volume available for containing
the electrochemically active materials may be increased. For
example, for a D size battery, the percentage of the total battery
volume that may be used to contain the electrochemically active
materials may be as high as 97 volume percent, while collector
assembly volume may be as low as 1.6 volume percent. The volumes of
batteries of other sizes are included in the table shown in FIGS.
14A and 14B.
By utilizing the inventive sealing constructions, not only can the
can wall thickness be decreased, but also the number of possible
materials used to form the can may be increased due to the lessened
strength requirements that must be exhibited by the can. For
example, the inventive constructions noted above may enable
aluminum or plastics to be used for the can rather than the
nickel-plated steel currently used.
A variation of the beverage can construction is shown in FIG. 13.
In the illustrated embodiment, the battery can is first formed as a
tube with two open ends. The tube may be extruded, seam welded,
soldered, cemented, etc., using conventional techniques. The tube
may be formed of steel, aluminum, or plastic. As shown in FIG. 13,
the tube defines the side walls 614 of can 612. A first open end of
the tube is then sealed by securing an inner cover 616 thereto
using the beverage can sealing technique outlined above, with the
exception that no electrical insulation is required between inner
cover 616 and side walls 614. A positive outer cover 618 may be
welded or otherwise secured to the outer surface of inner cover
616. The battery may then be filled and a negative outer cover 645
may be secured to the second open end of can 612 in the same manner
as described above.
Printed Label on Can
As noted above, the inventive battery constructions may be used in
combination with a printed label, rather than the label substrates
currently used. Current label substrates have thicknesses on the
order of 3 mils. Because such label substrates overlap to form a
seam running along the length of the battery, these conventional
labels effectively add about 10 mils to the diameter and 13 mils to
the crimp height of the battery. As a result, the battery can must
have a diameter that is selected to accommodate the thickness of
the label seam in order to meet the ANSI size standards. However,
by printing a lithographed label directly on the exterior surface
of the can in accordance with the present invention, the diameter
of the can may be correspondingly increased approximately 10 mils.
Such an increase in the diameter of the can significantly increases
the internal volume of the battery. All of the batteries listed in
the tables of FIGS. 14A and 14B, with the exception of the beverage
can constructions, include substrate labels. The internal volume of
the batteries with substrate labels can be further increased 2
percent (1.02 cc) for a D sized battery, 2.6 percent (0.65 cc) for
a C sized battery, 3.9 percent (0.202 cc) for an AA sized cell, and
5.5 percent (0.195 cc) for an AAA sized battery, if the labels were
printed directly on the exterior of the can. Labels may also be
printed on the can using transfer printing techniques in which the
label image is first printed on a transfer medium and then
transferred directly onto the can exterior. Distorted lithography
may also be used whereby intentionally distorted graphics are
printed on flat material so as to account for subsequent stress
distortions of the flat material as it is shaped into the tube or
cylinder of the cell can.
Prior to printing the lithographed label, the exterior surface of
the can is preferably cleaned. To enhance adherence of the print to
the can, a base coat a primer may be applied to the exterior
surface of the can. The print label is then applied directly on top
of the base coat on the can by known lithography printing
techniques. A varnish overcoat is preferably applied over the
printed label to cover and protect the printed label, and also to
serve as an electrical insulating layer. The printed label may be
cured with the use of high temperature heating or ultraviolet
radiation techniques.
With the use of the printed label, the thickness of a conventional
label substrate is significantly reduced to a maximum thickness of
approximately 0.5 mil. In particular, the base coat layer has a
thickness in the range of about 0.1 to 0.2 mil, the print layer has
a thickness of approximately 0.1 mil, and the varnish overcoat
layer has a thickness in the range of about 0.1 to 0.2 mil. By
reducing the label thickness, the can be increased in diameter,
thereby offering an increase in available volume for active cell
materials while maintaining a predetermined outside diameter of the
battery.
Beverage Can With Feed Through Collector
Referring to FIG. 15, an electrochemical cell 700 is shown
constructed with a feed through collector according to a seventh
embodiment of the present invention. Similar to the electrochemical
cell 400 with beverage can-type construction shown in FIG. 11,
electrochemical cell 700 includes an electrically conductive can
712 having a closed end 314 and an open end in which a low volume
collector assembly 725 and outer negative cover 750 are assembled.
Electrochemical cell 700 includes a positive electrode 115 in
contact with the interior walls of can 712 and in contact with a
separator 117 that lies between a positive electrode 115 and a
negative electrode 120. The positive electrode 115 is also referred
to herein as the cathode, while the negative electrode 120 is also
referred to herein as the anode. It should be appreciated that the
type of materials and their location internal to the
electrochemical cell may vary without departing from the teachings
of the present invention.
Electrochemical cell 700 also includes a pressure relief mechanism
370 formed in the closed end 314 of can 712. This allows for
employment of the low volume collector assembly 725 which consumes
less volume than conventional collector assemblies, and therefore
achieves enhanced internal cell volume efficiency. The pressure
relief mechanism 370 may be formed as a groove as described herein
in connection with FIGS. 8A, 8B, 9, and 10. In addition, a positive
outer cover 311 is connected to the closed end of can 712 and
overlies the pressure relief mechanism 370. The assembly and
location of positive outer cover 311 is provided as shown and
described herein in connection with FIG. 8A.
Electrochemical cell 700 includes a collector assembly 725 which
closes and seals the open end of can 712. Collector assembly 725
includes a collector nail 740 disposed in electrical contact with
the negative electrode 120. Also included in the collector assembly
725 is a first or inner cover 745 having a central aperture 751
formed therein. The collector nail 740 is disposed and extends
through the aperture 751 in inner cover 745. A dielectric
insulating material 744 is disposed between collector nail 740 and
first cover 745 to provide dielectric insulation therebetween.
Accordingly, the collector nail 740 is electrically isolated from
inner cover 745. Dielectric insulating material 744 is an organic
macromolecular material, such as an organic polymer, and may
include an epoxy, rubber, nylon, or other dielectric material that
is resistant to attack by KOH and is non-corrosive in the presence
of potassium hydroxide in the alkaline cell. The dielectric
insulating material is assembled as explained hereinafter.
Inner cover 745 in turn is connected and sealed to the open top end
of can 712. Inner cover 745 may be inserted into can 712 and sealed
to can 712 by forming a double seam closure at the peripheral edges
450 and 470 as explained herein in connection with FIGS. 11-13.
While a double seam can-to-cover closure is shown in connection
with the seventh embodiment of the present invention, it should be
appreciated that other can-to-cover closures may be employed,
without departing from the teachings of the present invention.
The electrochemical cell 700, according to the seventh embodiment
allows for a direct connection between can 712 and inner cover 745,
which preferably provides a pressure seal therebetween, but does
not require electrical isolation between inner cover 745 and the
side walls of can 712. Instead, the collector nail 740 is
dialectically insulated from inner cover 745 such that the negative
and positive terminals of the electrochemical cell are electrically
isolated from one another. While there is no requirement of
maintaining electrical isolation between the can 712 and inner
cover 745, it is preferred that a sealant be applied at the closure
joining the can to the cover to adequately seal the can. A suitable
sealant may be applied as explained in connection with the battery
shown and described herein in connection with FIGS. 11-12D. It
should be appreciated that the sealed closure along with the
insulating material should be capable of withstanding internal
pressure buildup greater than the venting pressure at which
pressure release mechanism 370 releases pressure.
To provide an acceptable outer battery terminal in accordance with
well accepted battery standards, the electrochemical cell 700
further includes an outer cover 750 in electrical contact with
collector nail 740. Outer cover 750 may be welded by spot weld 745
or otherwise electrically connected to collector nail 740. To
insure proper electrical insulation between outer cost cover 750
and inner cover 745, a dielectric material such as annular pad 748
is disposed between outer negative cover 750 and inner cover 745.
Suitable dielectric materials may include nylon, other elastomeric
materials, rubber, and epoxy applied on the top surface of inner
cover 745 or on the bottom surface of outer cover 750. Accordingly,
an acceptable standard battery terminal may be provided at the
negative end of electrochemical cell 700.
The assembly of electrochemical cell 700 according to the seventh
embodiment of the present invention is illustrated in the assembly
view of FIG. 16 and is further illustrated in the flow diagram of
FIG. 17. The method 770 of assembly of electrochemical cell 700
includes providing can 712 formed with a closed bottom end and open
top end. Step 774 includes disposing into can 712 the active
electrochemical materials including the negative electrode, the
positive electrode, and an electrolyte, as well as the separator
and other cell additives. Once the active electrochemical cell
materials are disposed within can 712, can 712 is ready for closure
and sealing with the collector assembly 725. Prior to closing the
can, the collector assembly is assembled by first disposing the
collector nail 740 within aperture 751 formed in inner cover 745
along with a ring of insulating material according to step 776.
Collector nail 740 is disposed in the opening 742 of insulating
ring 744 which may include a ring or disk of epoxy which provides
dielectric insulation and can be heated to reform and settle
between the inner cover 745 and collector nail 740. Alternately,
other organic macromolecular dielectric insulation materials may be
used in place of epoxy, such as a rubber grommet, an elastomeric
material, or other dielectric materials that may form adequate
insulation between collector nail 740 and inner cover 745. Also
shown formed in inner cover 745 is a recess 755 formed in the top
surface and centered about aperture 751.
According to the preferred embodiment, ring 744 of insulating
material is disposed in recess 755 on top of inner cover 745 and
the top head of collector nail 740 is disposed thereabove. In step
778, the insulating ring 744 is assembled to collector nail 740 and
cover 745 and the insulating ring 744 is heated to a temperature
sufficiently high enough to melt ring 744 such that ring 744
reforms and flows into the aperture 751 in cover 745 to provide
continuous dielectric insulation between collector nail 740 and
inner cover 745. For a ring 744 made of epoxy, a temperature of
20.degree. C. to 200.degree. C. for a time of a few seconds to
twenty-four hours may be adequate to reform and cure the insulating
material. Once dielectric material 744 forms adequate insulation
between collector nail 740 and inner cover 745, the insulated
material is preferably cooled in step 780. During the heating and
cooling steps 778 and 780, the collector nail 740 is centered in
aperture 751 such that nail 740 does not contact cover 745.
Thereafter, in step 782, an electrical dielectric insulating pad
748 such as an annular dielectric pad is disposed on top of inner
cover 745 and extends radially outward from the perimeter of nail
740. In step 784, disposed on top of collector nail 740 and pad 748
is a conductive negative cover 750 which is welded or otherwise
formed in electrical contact with collector nail 740. Once the
collector assembly is fully assembled, the collector assembly is
then connected to the can to sealingly close the open end as
provided in step 786. Can closure may employ a double seam closure
or other suitable can closure technique. In addition, the assembly
method 770 includes step 788 of connecting a second outer cover to
the closed end of the can, preferably overlying the pressure relief
mechanism 370.
While the present invention has been described above as having
primary applicability to alkaline batteries, it will be appreciated
by those skilled in the art that similar benefits may be obtained
be employing the inventive constructions in batteries utilizing
other electrochemical systems. For example, the inventive
constructions may be employed in primary systems such as
carbon-zinc and lithium based batteries and in rechargeable
batteries, such as NiCd, metal hydride, and Li based batteries.
Further, certain constructions of the present invention may be used
in raw cells (i.e., cells without a label as used in battery packs
or multi-cell batteries). Additionally, although the present
invention has been described above in connection with cylindrical
batteries, certain constructions of the present invention may be
employed in constructing prismatic cells.
The above description is considered that of the preferred
embodiments only. Modifications of the invention will occur to
those skilled in the art and to those who make or use the
invention. Therefore, it is understood that the embodiments shown
in the drawings and described above are merely for illustrative
purposes and not intended to limit the scope of the invention,
which is defined by the following claims as interpreted according
to the principles of patent law, including the Doctrine of
Equivalents.
* * * * *