U.S. patent application number 10/709253 was filed with the patent office on 2004-12-23 for battery employing an electrode pellet having an inner electrode embedded therein.
This patent application is currently assigned to RECHARGEABLE BATTERY CORPORATION. Invention is credited to Coffey, Brendan, Sesock, Charles.
Application Number | 20040258982 10/709253 |
Document ID | / |
Family ID | 33310937 |
Filed Date | 2004-12-23 |
United States Patent
Application |
20040258982 |
Kind Code |
A1 |
Coffey, Brendan ; et
al. |
December 23, 2004 |
BATTERY EMPLOYING AN ELECTRODE PELLET HAVING AN INNER ELECTRODE
EMBEDDED THEREIN
Abstract
An electrochemical battery cell comprising a cell housing
defining an inner space, a first terminal and a second terminal;
and at least one pre-formed pellet disposed within the inner space
of the cell housing. The pellet includes an outer electrode portion
formed from a material to geometrically define the pellet in a
solid form. The outer electrode portion is in electrical
communication with the first terminal of the cell housing. The
pellet also includes an inner electrode encapsulated by a separator
and embedded within the material of the outer electrode portion.
The inner electrode is in electrical communication with the second
terminal of the cell housing and electrically insulated from the
outer electrode material. In a preferred embodiment, the inner
electrode comprises an anode and the outer electrode portion
comprises a cathode portion. The integrated anode/cathode pellet
configuration facilitates lowers costs, a more robust design and
ease of manufacturability while maintaining and allowing increased
performance characteristics of the battery cell.
Inventors: |
Coffey, Brendan; (Austin,
TX) ; Sesock, Charles; (College Station, TX) |
Correspondence
Address: |
FACTOR & LAKE, LTD
1327 W. WASHINGTON BLVD.
SUITE 5G/H
CHICAGO
IL
60607
US
|
Assignee: |
RECHARGEABLE BATTERY
CORPORATION
809 University Drive East, Suite 100-E
College Station
TX
|
Family ID: |
33310937 |
Appl. No.: |
10/709253 |
Filed: |
April 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60464698 |
Apr 23, 2003 |
|
|
|
Current U.S.
Class: |
429/94 ;
29/623.1; 429/224; 429/229; 429/232; 429/59 |
Current CPC
Class: |
H01M 10/0422 20130101;
Y02E 60/10 20130101; H01M 2004/025 20130101; H01M 4/24 20130101;
H01M 6/08 20130101; Y10T 29/49115 20150115; Y10T 29/49108 20150115;
H01M 4/50 20130101; H01M 4/06 20130101; H01M 4/42 20130101; H01M
50/107 20210101; H01M 4/0433 20130101; H01M 4/244 20130101; H01M
10/24 20130101; H01M 10/283 20130101; H01M 4/30 20130101; H01M 6/42
20130101; H01M 50/174 20210101 |
Class at
Publication: |
429/094 ;
429/229; 429/224; 429/232; 429/059; 029/623.1 |
International
Class: |
H01M 004/42; H01M
004/50; H01M 004/62; H01M 010/04 |
Claims
1. An electrochemical battery cell comprising: a cell housing
defining an inner space, a first terminal and a second terminal;
and at least one pre-formed pellet disposed within the inner space
of the cell housing, the pellet comprising: an outer electrode
portion formed from a material to geometrically define the pellet
in a solid form, the outer electrode portion in electrical
communication with the first terminal of the cell housing; and an
inner electrode encapsulated by a separator and embedded within the
material of the outer electrode portion, the inner electrode in
electrical communication with the second terminal of the cell
housing and electrically insulated from the outer electrode
portion.
2. The battery cell of claim 1, wherein the inner electrode
comprises a thin and substantially flat structure in a coiled
configuration.
3. The battery cell of claim 1, wherein the inner electrode
includes an electrical lead to facilitate electrical communication
with the negative terminal of the cell housing.
4. The battery cell of claim 1, wherein the inner electrode
comprises an anode and the outer electrode portion comprises a
cathode portion, and wherein the first terminal has a positive
polarity and the second terminal has a negative polarity.
5. The battery cell of claim 4, wherein the anode comprises a thin
and substantially flat structure in a coiled configuration.
6. The battery cell of claim 4, wherein the anode includes an
electrical lead to facilitate electrical communication with the
negative terminal of the cell housing.
7. The battery cell of claim 4, wherein the anode comprises a
material selected from the group consisting of zinc, metallic zinc,
zinc alloy, zinc oxide and combinations thereof; and wherein the
cathode portion comprises MnO.sub.2.
8. The battery cell of claim 4, the material of the cathode portion
consisting essentially of: MnO.sub.2; a conductive powder; and an
additive selected from the group consisting of a binder, an
electrolyte, a recombination catalyst, and combinations
thereof.
9. The battery cell of claim 4, the material of the cathode portion
consisting essentially of: about 88 percent by weight of MnO2;
about 7.5 percent by weight of a conductive powder; and about 4.5
percent by weight of an additive selected from the group consisting
of a binder, an electrolyte, a recombination catalyst, and
combinations thereof.
10. The battery cell of claim 4, further comprising a current
collector embedded within the within the material of the cathode
portion.
11. An electrochemical battery cell comprising: a cell housing
defining an inner space, a positive terminal and a negative
terminal; and a plurality of pre-formed pellets disposed within the
inner space of the cell housing, each of the pellets comprising: a
cathode portion formed from a material to geometrically define the
pellet in a solid form, the cathode portion in electrical
communication with the positive terminal of the cell housing; and
an anode encapsulated by a separator and embedded within the
material of the cathode portion, the anode in electrical
communication with the negative terminal of the cell housing and
electrically insulated from the cathode material.
12. The battery cell of claim 11, wherein the cathode portion of
each of the plurality of pellets is in direct electrical contact
with the cathode portion of at least one of the other pellets.
13. The battery cell of claim 11, wherein the anode of each of the
plurality of pellets includes an electrical lead, the electrical
lead of the anode of each of the plurality of pellets being in
direct electrical contact with one of either the electrical lead of
the anode of one of the other pellets or the negative terminal of
the cell housing.
14. The battery cell of claim 11, wherein the anode comprises a
thin and substantially flat structure in a coiled
configuration.
15. The battery cell of claim 11, wherein the anode comprises a
material selected from the group consisting of metallic zinc, zinc
alloy, zinc oxide and combinations thereof.
16. The battery cell of claim 11, the material of the cathode
portion consisting essentially of: MnO2; a conductive powder; and
an additive selected from the group consisting of a binder, an
electrolyte, a recombination catalyst, and combinations
thereof.
17. The battery cell of claim 11, the material of the cathode
portion consisting essentially of: about 88 percent by weight of
MnO2; about 7.5 percent by weight of a conductive powder; and about
4.5 percent by weight of an additive selected from the group
consisting essentially of a binder, an electrolyte, a recombination
catalyst, and combinations thereof.
18. The battery cell of claim 11, further comprising a current
collector embedded within the within the material of the cathode
portion.
19. A pellet for use in an electrochemical battery cell, the pellet
comprising: an outer electrode portion formed from a material to
geometrically define the pellet in a solid form, the outer
electrode portion in electrical communication with a first terminal
of the cell housing; and an inner electrode encapsulated by a
separator and embedded within the material of the outer electrode
portion, the inner electrode having an electrical lead in
electrical communication with a second terminal of the cell housing
and electrically insulated from the outer electrode material.
20. The pellet of claim 19, wherein the inner electrode comprises a
thin and substantially flat structure in a coiled
configuration.
21. The pellet of claim 19, wherein the inner electrode comprises
an anode and the outer electrode portion comprises a cathode
portion.
22. The pellet of claim 21, further comprising a current collector
embedded within the within the material of the cathode portion.
23. An electrochemical battery cell comprising: a cell housing
defining an interior space; a positive terminal and a negative
terminal connected to the cell housing and having a portion
disposed exteriorly the cell housing; and at least one pre-formed
pellet disposed within the interior space of the cell housing, the
pellet comprising a cathode portion and an anode encapsulated by a
separator, the pellet being formed by embedding the anode into a
material used to form the cathode portion and forming the cathode
portion to geometrically define the pellet the cathode portion in
electrical communication with the positive terminal of the cell and
the anode in electrical communication with the negative terminal of
the cell.
24. The battery cell of claim 23, wherein the pellet further
comprises a current collector embedded the within the material used
to form the cathode portion.
25. A method of manufacturing a pellet for use in an
electrochemical battery cell, the method comprising the steps of:
forming an inner electrode; applying a separator to the inner
electrode; embedding the inner electrode into an outer electrode
material formulation; and forming the outer electrode material
formulation to geometrically define the pellet.
26. A method of manufacturing a pellet for use in an
electrochemical battery cell, the method comprising the steps of:
forming an anode; applying a separator to the anode; embedding the
anode into a cathode material formulation; and forming the cathode
material formulation to geometrically define the pellet.
27. The method of claim 26, wherein the step of forming the anode
comprises coiling the anode into a spiral-like configuration.
28. The method of claim 26, wherein the step of forming the cathode
material formulation comprises molding the material formulation to
geometrically define the pellet.
29. The method of claim 26, wherein the step of forming the cathode
material formulation comprises compression-forming the material
formulation to geometrically define the pellet.
30. The method of claim 26, further comprising the step of
attaching an insulated electrical lead to the anode before it is
embedded into the cathode material formulation.
31. The method of claim 26, wherein the step of applying the
separator to the anode comprises coating the anode with an adherent
and flexible microporous separator material.
32. The method of claim 26, further comprising the steps of
blending electrolytic MnO2; conductive powder; and an additive
selected from the group consisting of a binder, an electrolyte, a
recombination catalyst, and combinations thereof; to create the
cathode material formulation.
33. The method of claim 26, further comprising the step of
embedding a current collector into the cathode material
formulation.
34. A method of manufacturing an electrochemical battery cell, the
method comprising the steps of: forming a battery cell casing
including a first terminal and a second terminal; forming an inner
electrode; applying a separator to the inner electrode; embedding
the inner electrode into an outer electrode material formulation;
forming the outer electrode material formulation to geometrically
define a pellet; connecting the inner electrode to the second
terminal; and disposing the pellet into the battery cell casing
such that the outer electrode material formulation is in
communication with the first terminal.
35. A method of manufacturing an electrochemical battery cell, the
method comprising the steps of: forming a battery cell casing
including a positive terminal and a negative terminal; forming an
anode; applying a separator to the anode; embedding the anode into
a cathode material formulation; forming the cathode material
formulation to geometrically define a pellet; connecting the anode
to the negative terminal; and disposing the pellet into the battery
cell casing such that the cathode material formulation is in
communication with the positive terminal.
36. The method of claim 35, wherein the step of forming the anode
comprises coiling the anode into a spiral-like configuration.
37. The method of claim 35, wherein the step of forming the cathode
material formulation comprises molding the material formulation to
geometrically define the pellet.
38. The method of claim 35, wherein the step of forming the cathode
material formulation comprises compression-forming the material
formulation to geometrically define the pellet.
39. The method of claim 35, further comprising the step of
attaching an insulated electrical lead to the anode before it is
embedded into the cathode material formulation to facilitate
connection to the negative terminal.
40. The method of claim 35, wherein the step of applying the
separator to the anode comprises coating the anode with an adherent
and flexible microporous separator material.
41. The method of claim 35, further comprising the steps of
blending electrolytic MnO2; conductive powder; and an additive
selected from the group consisting of a binder, an electrolyte, a
recombination catalyst, and combinations thereof; to create the
cathode material formulation.
42. The method of claim 35, further comprising the step of
embedding a current collector into the cathode material
formulation.
43. A method of manufacturing an electrochemical battery cell, the
method comprising the steps of: (A) forming a battery cell casing
including a positive terminal and a negative terminal; (B) forming
a plurality of pellets, each pellet formed by: forming an anode in
a configuration having a large surface area; applying a separator
to the anode; embedding the anode into a cathode material
formulation; forming the cathode material formulation to
geometrically define the pellet; (C) connecting each of the anodes
to one of either the negative terminal or another anode; and (D)
disposing the pellets into the battery cell casing such that the
cathode material formulation of each of the pellets is in
communication with the positive terminal.
44. A method of manufacturing a pellet for use in an
electrochemical battery cell, the method comprising the steps of:
providing an anode having a separator applied thereto; embedding
the anode into a cathode material formulation; and forming the
cathode material formulation to geometrically define the
pellet.
45. The method of claim 44, further comprising the step of
embedding a current collector into the cathode material
formulation.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 60/464,698, filed Apr. 23, 2003, which is
incorporated herein by reference.
BACKGROUND OF INVENTION
[0002] The present invention generally relates to electrochemical
battery cells, and more particularly to electrochemical pellet-type
battery cells that employ electrode assemblies in the form of
pellets.
[0003] There are many types and configurations of electrochemical
battery cells employed in a variety of applications and in both
rechargeable and disposable platforms. The most popular battery
cells for consumer applications, particularly high current drain
applications, include alkaline cells, nickel metal hydride cells,
nickel cadmium cells, and lithium ion cells. As an example,
alkaline batteries based on manganese oxide cathodes are widely
used for consumer applications. As device power requirements of
consumer applications have increased in recent years, alkaline
battery producers have sought methods for improving the high drain
output of their cells while retaining a simple low cost design and
method of assembly. Numerous design strategies have been proposed
and implemented to address the requirement of higher capacity
utilization at high drain rates.
[0004] By way of background and referring to FIG. 1, a typical
primary disposable or rechargeable alkaline battery cell
configuration is shown in the form of a bobbin cell 10. The cell 10
includes: a cell housing in the form of a steel can 12 defining a
cylindrical inner space and interior surface, which can optionally
be coated with a conductive coating; a manganese dioxide cathode 14
formed by a plurality of hollow or tubular cylindrical pellets 16
pressed in the can 12; a zinc anode 18 made of an anode gel and
arranged within the hollow portion of the cylindrical pellets 16
forming the cathode 14; and a cylindrical separator 20 separating
the anode 18 from the cathode 14. The ionic conductivity between
the anode and the cathode is facilitated by the presence of an
electrolyte, such as potassium hydroxide (KOH), which is added into
the cell in a predetermined quantity.
[0005] The can 12 is closed at its bottom, and has a central
circular pip 22 serving as a positive terminal for the cell. A cell
closure assembly hermetically seals a top end of the can 12. The
cell closure assembly comprises a negative cap 24 formed by a thin
metal sheet, a current collector nail 26 attached to the negative
cap 24 and disposed within the anode 18 to provide electrical
contact with the anode 18, and a plastic top 28 that electrically
insulates the negative cap 24 from the can 12 and separates gas
spaces formed beyond the cathode and anode structures,
respectively.
[0006] As illustrated in FIG. 1, the bottom of the separator 20 is
typically sealed by means of a hot-melt bead 34, which is used to
seal the separator 20 to a washer 33 in the cell. In another
variation, the washer is omitted and only a hotmelt adhesive is
used. In yet another variation, a bottom seal cup may be employed
without the use of a hot-melt adhesive.
[0007] While FIG. 1 illustrates a viable alkaline battery cell
configuration, there is a growing need for battery cell
configurations having lower costs, more robust design
characteristics, and ease of manufacturability while maintaining
and continually improving current outputs and other performance
parameters. This remains a significant challenge given the current
trend of designing consumer electronics with ever increasing power
requirements while constantly seeking to reduce product and
manufacturing costs to increase profit margins.
[0008] The present invention provides an improved battery cell
that, among other things, addresses these growing needs.
SUMMARY OF INVENTION
[0009] The present invention facilitates integration of an anode
and a cathode in a single pellet configuration for use with an
electrochemical battery cell of any type or format utilizing one or
more pellets. In accordance with the principles of the present
invention as embodied and described herein, one particular
characterization of the present invention comprises an
electrochemical battery cell comprising a cell housing defining an
inner space, a first terminal and a second terminal; and at least
one pre-formed pellet disposed within the inner space of the cell
housing. The pellet includes an outer electrode portion formed from
a material to geometrically define the pellet in a solid form. The
outer electrode portion is in electrical communication with the
first terminal of the cell housing. The pellet also includes an
inner electrode encapsulated by a separator and embedded within the
material of the outer electrode portion. The inner electrode is in
electrical communication with the second terminal of the cell
housing and electrically insulated from the outer electrode
portion.
[0010] Among other things, the integrated inner/outer electrode
pellet configuration of the present invention facilitates lowers
costs, a more robust design and ease of manufacturability while
maintaining and allowing increased performance characteristics of
the battery cell. In contrast to prior art cells, such as typical
spirally-wound cells, the present invention provides the advantages
of a high surface area electrochemical cell wherein the formation
of an integrated inner/outer electrode pellet configuration allows
for greater tolerances in positioning and alignment of the
electrodes with respect to each other while preserving efficient
usage of space within the cell housing or container.
[0011] According to another aspect of the present invention, the
inner electrode comprises a thin and substantially flat structure
in a coiled configuration.
[0012] According to yet another aspect, the inner electrode
includes an electrical lead to facilitate electrical communication
with the second terminal of the cell housing.
[0013] According to another aspect, in a specific embodiment
wherein the battery cell is an alkaline cell, the outer electrode
is a cathode of positive polarity and the inner electrode is an
anode of negative polarity. In the alkaline battery cell
embodiment, the cathode is preferably formed largely from manganese
dioxide and the anode is preferably formed largely of zinc.
[0014] According to yet another aspect, the anode comprises a
material selected from the group consisting of metallic zinc, zinc
alloy, zinc oxide and combinations thereof. The material of the
cathode portion consists essentially of MnO.sub.2; a conductive
powder; and an additive selected from the group consisting of a
binder, an electrolyte, a recombination catalyst, and combinations
thereof.
[0015] According to yet another aspect of the present invention,
methods of manufacturing a pellet for use with a battery cell and
methods of manufacturing a battery cell that utilize one or more
pellets are also contemplated. One particular embodiment of a
method of manufacturing a pellet for use in an electrochemical
battery cell comprises the steps of forming an inner electrode;
applying a separator to the inner electrode; embedding the inner
electrode into an outer electrode material formulation; and forming
the outer electrode material formulation to geometrically define
the pellet. One particular embodiment of a method of manufacturing
an electrochemical battery cell comprises the steps of forming a
battery cell casing including a first terminal and a second
terminal; forming an inner electrode; applying a separator to the
inner electrode; embedding the inner electrode into an outer
electrode material formulation; forming the outer electrode
material formulation to geometrically define a pellet; connecting
the inner electrode to the second terminal; and disposing the
pellet into the battery cell casing such that the outer electrode
material formulation is in communication with the first terminal.
Yet another embodiment of a method of manufacturing an
electrochemical battery cell comprises the steps of: (A) forming a
battery cell casing including a first terminal and a second
terminal; (B) forming a plurality of pellets, each pellet formed by
forming an inner electrode; applying a separator to the inner
electrode; embedding the inner electrode into an outer electrode
material formulation; and forming the outer electrode material
formulation to geometrically define the pellet; (C) connecting each
of the inner electrodes to one of either the second terminal or
another inner electrode; and (D) disposing the pellets into the
battery cell casing such that the outer electrode material
formulation of each of the pellets is in communication with the
first terminal.
[0016] These and other aspects of the present invention will be
apparent after consideration of the written description, drawings
and claims herein.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a cross-sectional view of a typical cylindrical
battery bobbin cell as known in the prior art.
[0018] FIG. 2A is a cross-sectional view of a cylindrical battery
cell incorporating a first embodiment of a pellet in accordance
with the principles of the present invention.
[0019] FIG. 2B is a schematic cross-sectional plan view of the
first embodiment of the pellet utilized in the battery cell of FIG.
2A in accordance with the principles of the present invention.
[0020] FIG. 2C is a cross-sectional elevational view of the pellet
of FIG. 2B.
[0021] FIG. 3 is a schematic cross-sectional plan view of a second
embodiment of a pellet for use with a battery cell in accordance
with the principles of the present invention, wherein a current
collector has been added.
DETAILED DESCRIPTION
[0022] While the present invention is capable of embodiment in many
different forms, there is shown in the drawings, and will herein be
described in detail, one or more specific embodiments with the
understanding that the present disclosure is to be considered an
exemplification of the principles of the invention and is not
intended to limit the invention to these specific embodiments.
[0023] The present invention facilitates integration of an inner
electrode, preferably an anode, and an outer electrode, preferably
a cathode, into a single pellet configuration for use with an
electrochemical battery cell in any type of format utilizing one or
more electrode pellets. The pellet configuration can be utilized in
any number of battery cell electrochemistry formats, such as, for
example, nickel metal hydride (NiMH), lithium ion (Li-ion), nickel
cadmium (NiCd), and alkaline cells. Further, the pellet
configuration is applicable to any type of battery cell format
utilizing one or more pellets, such as, for example, bobbin type
cylindrical cells, coin cells or flat plate cells. The integration
of the inner and outer electrodes into a single pellet structure
that can be inserted into a cell housing or casing, rather than
being separately assembled as discrete component materials,
facilitates lowers costs, a more robust design and ease of
manufacturability, as well as other benefits. Multiple pellets may
be used in a single battery cell to achieve a desired cell
capacity. The integration of the electrodes in accordance with the
principles of the present invention does not adversely affect the
performance characteristics of the battery cell.
[0024] Referring generally now to FIGS. 2A-2C, and particularly to
FIG. 2A, one particular characterization of the present invention
comprises an electrochemical battery cell 50 having a cell housing
52 defining an inner space 54, a first terminal in the form of a
positive terminal 56 and a second terminal in the form of a
negative terminal 58. The terminals 56 and 58 can be integrally
formed with the housing 52 or connected thereto as a separate
component as part of the housing, such as a cap. Further, depending
on the particular embodiment, the polarity of each of the terminals
56 and 58 is not limited to one of either a positive or negative
polarity. The battery cell 50 includes at least one pre-formed
pellet 60 disposed within the inner space 54 of the cell housing
52. As best shown in FIGS. 2B and 2C, the pellet 60 includes an
outer electrode in the form of a cathode portion 62, which is
formed from a cathode material formulation that, when formed,
geometrically defines the pellet. The material formulation can be
of any type typically utilized to form cathode pellets and known in
the art. In a preferred embodiment, the material formulation of the
cathode portion consists essentially of electrolytic MnO.sub.2
(EMD), a conductive powder, and one or more additives, such as, for
example, a binder, an electrolyte, a recombination catalyst, or one
or more combinations thereof. The pellet 60 also includes an inner
electrode in the form of an anode 64 embedded within the cathode
portion 62. It should be understood that in all of the embodiments
described herein, both the inner electrode and the outer electrode
may be configured as either an anode or a cathode, depending on the
particular application. The cathode portion 62 is in electrical
communication with the positive terminal 56 of the cell housing. In
the embodiment shown in FIG. 2A, the electrical communication is
established by contact between the cathode portion 62 and an inner
surface of the cell housing 52, which is ultimately in electrical
communication with the positive terminal 56. The anode 64 is in
electrical communication with the negative terminal 58 of the
battery cell 50 and electrically insulated from the cathode
material. In configurations utilizing a plurality of pellets, such
as that shown in FIG. 2A, each of the anodes 64 is either in direct
electrical contact with another anode 64 or the negative terminal
58 of the battery cell 50. Electrical connection of the anodes 64
is facilitated by an electrical lead 64a, such as a wire, tab,
terminal, extension of the anode, or the like. In the embodiment
shown in the figures, the pellets 60 include a thru-hole 65 to
facilitate electrical connections between the anodes 64 of the
pellets 60. Other electrical connection schemes known in the art
are contemplated as well.
[0025] Prior to formation of the cathode portion 62 from the
cathode material, the anode 64 is embedded within the material.
Formation of the cathode portion 62 may be facilitated by a number
of formation techniques and means, such as, for example,
compression formation, molding, casting, extruding, or the like. As
shown in the embodiment depicted in FIG. 2B, the anode 64 is a thin
and substantially flat or plate-like structure in a coiled
configuration. However, other types of configurations or shapes may
be utilized, particularly configurations that maximize surface area
of the anode 64.
[0026] The anode 64 is encapsulated by a separator 66. The
separator 66 comprises a laminated or composite material typically
used as a separator material. In a preferred embodiment, the
separator 66 comprises a combination of an absorbent fibrous sheet
material wettable by an electrolyte and an insulating material that
is impermeable to small particles while being permeable to ions.
The absorbent material is preferably a macro-porous structure, such
as a non-woven polyamide. Shorting is prevented by the insulating
material, which may comprise one or more layers of a micro-porous
or non-porous material laminated to or coated onto the absorbent
fibrous sheet material. As an example, the insulating material may
comprise one or more cellophane membranes laminated onto a
non-woven polyamide sheet. Another example of an insulating
material is one or more coatings of regenerated cellulose or
viscose coated onto and partially impregnating the non-woven
polyamide sheet, resulting in a composite material. Another
suitable coating comprises a polymeric material such as sulfonated
polyphenylene oxide and its derivatives. One or more layers of the
laminated or composite material are preferably wound or coiled to
form a spiral-like or coiled structure as shown in the figures.
[0027] In addition to the embedded anode 64, a coiled current
collector 70 may be embedded into the cathode portion of the
pellet, as shown in FIG. 3. The current collector 70 facilitates
additional current collection for the cathode portion 62.
Preferably, the current collector 70 is a nickel mesh-like material
and is incorporated into the cathode portion 62 of the pellet
60.
[0028] With the understanding provided by the above description,
methods of manufacturing a pellet and methods of manufacturing a
battery cell that utilize one or more pellets in accordance with
the principles of the present invention will now be described.
[0029] In a particular embodiment, a method of manufacturing a
pellet for use in an electrochemical battery cell is provided in
accordance with the principles of the present invention. The method
comprises the steps of: (A) forming an inner electrode, such as an
anode, preferably in a configuration having a large surface area;
(B) applying a separator to the inner electrode; (C) embedding the
inner electrode into an outer electrode material formulation, such
as a cathode material formulation; and (D) forming the outer
electrode material formulation to geometrically define the
pellet.
[0030] In another embodiment, a method of manufacturing an
electrochemical battery cell utilizing at least one pellet is
provided in accordance with the principles of the present
invention. The method comprises the steps of: (A) forming a battery
cell casing including a first terminal, preferably of positive
polarity, and a second terminal, preferably of negative polarity;
(B) forming an inner electrode, preferably an anode and in a
configuration having a large surface area; (C) applying a separator
to the inner electrode; (D) embedding the inner electrode into an
outer electrode material formulation, preferably a cathode material
formulation; (E) forming the outer electrode material formulation
to geometrically define a pellet; (F) connecting the inner
electrode to the second terminal; and (G) disposing the pellet into
the battery cell casing such that the outer electrode material
formulation is in communication with the first terminal.
[0031] Yet another embodiment of a method of manufacturing an
electrochemical battery cell in accordance with the principles of
the present invention comprises the steps of: (A) forming a battery
cell casing including a first terminal, preferably a positive
terminal, and a second terminal, preferably a negative terminal;
(B) forming a plurality of pellets, each pellet formed by: forming
an inner electrode, preferably an anode in a configuration having a
large surface area; applying a separator to the inner electrode;
embedding the inner electrode into an outer electrode material
formulation, preferably a cathode material formulation; and forming
the outer electrode material formulation to geometrically define
the pellet; (C) connecting each of the inner electrodes to one of
either the second terminal or another inner electrode; and (D)
disposing the pellets into the battery cell casing such that the
outer electrode material formulation of each of the pellets is in
communication with the first terminal.
[0032] Other aspects may be included in these methods consistent
with the description herein. For example, the step of forming the
inner electrode may comprise coiling the inner electrode into a
spiral-like configuration; the step of forming the outer electrode
material formulation may comprise molding the material formulation
to geometrically define the pellet; the step of applying the
separator to the inner electrode may comprise coating the inner
electrode with an adherent and flexible microporous separator
material; or the step of forming the outer electrode material
formulation may comprise compression-forming the material
formulation to geometrically define the pellet.
[0033] Further steps may be included in the above-described methods
in accordance with the description herein, such as including a step
of attaching an insulated electrical lead to the inner electrode
before it is embedded into the outer electrode material
formulation; a step of blending electrolytic MnO.sub.2, conductive
powder, and an additive to create the outer electrode material
formulation; or a step of embedding a current collector into the
outer electrode material formulation.
[0034] To help illustrate the principles of the present invention
and to assist those skilled in the art to better understand the
invention and its principles and advantages, the following example
is provided, which provides more detail regarding some of the
preferred embodiments of the present invention. It is to be
understood, however, that this example is intended to be
illustrative of the invention and not limiting to the scope
thereof.
EXAMPLE
[0035] This example specifies some details concerning an embodiment
of the present invention in the form of an alkaline manganese
dioxide cell. In this particular example, each alkaline cell
contains three cathode/anode pellets, such as the three pellets 60
shown in the cell 50 in FIG. 2A. The outer electrode material
portion of each pellet, which in this example is a cathode material
portion, is approximately 3.4 g. The cathode material formulation
is a Type I formulation typical of primary alkaline cells and
consists of 88 wt % EMD (MnO.sub.2), 7.5 wt % conductive powder,
and the remainder being other additives such as binders,
electrolyte, and recombination catalyst. The components of the
cathode material formulation are blended and an inner electrode in
the form of an anode is embedded therein. The material formulation
is then pressed into a pellet geometry. Sufficient zinc weight
(approx. 1 g) should be present in the anode to match the cathode
capacity per pellet. The anode is pre-formed, preferably with a
solid density of 4-5 g/cm3 of dry thin flexible charge zinc
structures coated onto an absorber and/or a thin flexible metal
mesh current collector. Suitable formulation ingredients for the
anode include Zn powder in a range of particle sizes, a composite
including Zn fibers to give good electrical conductivity throughout
the composite, polymers such as ground KC32 or other absorber
material, nylon, PP, or Kraton.RTM.. Suitable processing methods
for the anode formulation include pasting, melt processing, roll
milling, pasting impregnated absorber or expanded metal such as
Exmet.RTM., pressing the formulation onto the absorber or expanded
metal. Pressing dry Pgel-Size should be about 80% of pellet height,
length 1.5 2 inches and thickness 30-60 mils. Anodes should be
semi-solid, rigid to hold their shape once formed, but not so
brittle that they crack on bending or compressing. Dimensions
should be reasonably controlled but anodes should absorb
electrolyte with moderate swelling. An insulated wire can be
attached to the metal substrate in the anode to facilitate
electrical connections. Other means of making electrical
connections to the embedded anode may also be devised, such as, for
example, an electrical lead integrally formed with the anode and
allowed to extend outwardly during formation of the pellet. The
formed anode is encapsulated by a separator coating before being
embedded in the pellet. The separator coating in this example is
"starch," which could further include suspended TiO2 powder. The
anode is preferably dried after coating. Alternatively, the anode
may be wrapped with a flexible separator material made from
polytetrafluoroethylene (PTFE), such as that manufactured by W.L.
Gore and Associates, Inc. under the trade name Excellerator.RTM.,
or other suitable separator materials, such as separators
manufactured by Advanced Membrane Systems, Inc under the trade name
FAS.TM., or the like.
[0036] Either before or after applying the separator the anode is
preferably loosely coiled in a spiral-like configuration and
embedded in the cathode material formulation in such a way as to
ensure that there is not excessive deformation of the anode coil
and shorting during forming of the cathode material into the pellet
form. A cathode current collector may optionally be embedded
alongside the coiled anode or integrated therewith so as to be
embedded by virtue of the anode being embedded.
[0037] Cells of each of the various types may be subjected to a
cyclic electrical test regimen consisting of discharge at 1 Amp to
1 volt, and in the case of rechargeable forms of cells, followed by
taper charging at 1.75 Volts for 12 hours with a 500 mA current
limit.
[0038] In this example, an alkaline manganese dioxide cell
incorporating a relatively high surface area anode structure is
embedded within the cathode material of the cathode portion when it
is formed to geometrically define the pellet. The anode structure
is flexible so that it may be coiled within the pellet mold prior
to pressing and may be deformed during pressing without breaking.
In this embodiment, the anode structure consists of a composite
mixture of zinc powder and or fiber, polymer binders, absorbers and
other additives overlaying a thin metal foil or mesh current
collector, which may be copper or brass. The anode structure is
coated with a separator layer that is also flexible so that it does
not crack or tear away from the anode surface in the pellet molding
process. The separator coating is suitably microporous to allow
good ion transport between the anode and cathode while not
permitting short circuit contact between the two electrodes either
before or subsequent to the pressing operation. A parallel cathode
current collector may also be embedded in the pellet to improve
electron transfer to the cathode. A wire, lead, or tab connection
can be bonded to the anode structure prior to pellet formation and
brought outside the pellet during or after formation. The wire,
lead or tab connection facilitates connection to the negative
contact of the can or cell housing. By thus increasing the anode to
cathode interfacial area and thinning the anode structure relative
to a conventional bobbin cell design, better material utilization
is realized and the cell can deliver more runtime at higher drain
rates.
[0039] In a preferred embodiment, an alkaline manganese
dioxide-zinc cell is provided comprising a manganese dioxide
cathode, a zinc anode, a separator between the anode and cathode,
and an aqueous alkaline potassium hydroxide electrolyte. The anode
comprises a zinc component, an absorber, a polymer and other
additives formed into a high surface area form and coated with a
well adherent and flexible microporous separator. The anode is
coiled and placed into a pellet mold wherein the cathode material
formulation is added as a powder and the entire mass pressed into a
pellet. The pellet can then be disposed in a cell housing or
casing, such as a can of the typical bobbin type cylindrical cell.
If necessary, leads or wires are brought out from the anode
structure and connected to the negative can terminal. Additional
electrolyte may be added and the anode may undergo some volume
changes. However throughout these processing steps the separator
coating retains a suitable microporous characteristic to prevent
zinc dendrites and shorting between the anode and the cathode.
[0040] While specific embodiments have been illustrated and
described herein, numerous modifications may come to mind without
significantly departing from the spirit of the invention, and the
scope of protection is only limited by the scope of the
accompanying claims.
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