U.S. patent application number 09/975349 was filed with the patent office on 2002-02-21 for cell stack design with bi-directionally wound slotted electrodes.
Invention is credited to Frustaci, Dominick J., Frysz, Christine A., Hallifax, Paul T., Moceri, Kenneth P., Paulot, William M..
Application Number | 20020022175 09/975349 |
Document ID | / |
Family ID | 22996774 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020022175 |
Kind Code |
A1 |
Hallifax, Paul T. ; et
al. |
February 21, 2002 |
Cell stack design with bi-directionally wound slotted
electrodes
Abstract
An electrochemical cell comprising an electrode assembly in
which opposite polarity electrodes are wound together in a
bi-directional fashion yielding a high energy density cell stack
with low internal impedance is described. Each electrodes is
constructed having a slot provided into its width at about a
midportion thereof. The slots are brought into registry with each
other to form a collapsible X-shaped electrode assembly, which is
then bi-directionally folded to provide a wound electrode
assembly.
Inventors: |
Hallifax, Paul T.; (Gasport,
NY) ; Frustaci, Dominick J.; (Williamsville, NY)
; Paulot, William M.; (Lancaster, NY) ; Moceri,
Kenneth P.; (North Tonawanda, NY) ; Frysz, Christine
A.; (New Milford, CT) |
Correspondence
Address: |
Michael F. Scalise
Hodgson Russ LLP
Suite 2000
One M&T Plaza
Buffalo
NY
14203-2391
US
|
Family ID: |
22996774 |
Appl. No.: |
09/975349 |
Filed: |
October 11, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09975349 |
Oct 11, 2001 |
|
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09262245 |
Mar 4, 1999 |
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Current U.S.
Class: |
429/94 ;
29/623.1; 429/219; 429/231.3; 429/231.7; 429/231.95; 429/232;
429/233 |
Current CPC
Class: |
Y10T 29/49108 20150115;
Y10T 29/49112 20150115; H01M 50/103 20210101; H01G 9/04 20130101;
H01M 6/10 20130101; Y02P 70/50 20151101; H01G 9/00 20130101 |
Class at
Publication: |
429/94 ; 429/233;
29/623.1; 429/231.3; 429/232; 429/231.95; 429/219; 429/231.7 |
International
Class: |
H01M 006/10; H01M
004/58; H01M 004/62; H01M 004/66; H01M 004/54 |
Claims
What is claimed is:
1. An electrode assembly, comprising: (a) a first electrode strip
having a midportion with a first slot defined therein; (b) a second
electrode strip having a midportion with a second slot defined
therein, wherein the first electrode strip and the second electrode
strip are registerable with each other through the first and the
second slots to form a collapsible X-shaped electrode assembly; and
(c) a layer of a separator material disposed between the first
electrode strip and the second electrode strip, wherein the
registered first and second electrode strips are bi-directionally
foldable to form a wound cell stack.
2. The electrode assembly of claim 1 wherein the first electrode
strip has at least one tab for connection to an electrode
terminal.
3. The electrode assembly of claim 1 wherein the second electrode
strip has at least one tab for connection to a battery case.
4. The electrode assembly of claim 1 of either a primary or a
secondary chemistry.
5. The electrode assembly of claim 1 wherein a first electrode
active material of the first electrode strip is selected from the
group consisting of SVO, CSVO and CFX, and a second electrode
active material of the second electrode strip comprises
lithium.
6. The electrode assembly of claim 1 wherein a first electrode
active material of the first electrode strip comprises lithium
cobalt oxide and a second electrode active material of the second
electrode strip comprises a carbonaceous material.
7. An electrochemical cell, which comprises: a) a cathode electrode
strip comprising a cathode active material contacted to a cathode
current collector and having a first midportion with a first slot
defined therein; b) an anode electrode strip comprising an anode
active material contacted to an anode current collector and having
a second midportion with a second slot defined therein, wherein the
cathode electrode and the anode electrode are registerable with
each other through the first and second slots to form a collapsible
X-shaped electrode assembly; and (c) a layer of a separator
material disposed between the first electrode strip and the second
electrode strip, wherein the registered first and second electrode
strips are bi-directionally foldable to form a wound cell
stack.
8. The electrochemical cell of claim 7 wherein the first electrode
strip has at least one tab connectable to an electrode
terminal.
9. The electrochemical cell of claim 7 wherein the second electrode
strip has at least one tab connectable to a battery case.
10. The electrochemical cell of claim 7 of either a primary or a
secondary chemistry.
11. The electrochemical cell of claim 7 wherein the first electrode
active material is selected from the group consisting of SVO, CSVO
and CF.sub.x, and the second electrode active material comprise
lithium.
12. The electrochemical cell of claim 7 wherein the first electrode
active material comprises lithium cobalt oxide, and the second
electrode active material comprises a carbonaceous material.
13. An electrode assembly, comprising: (a) a first electrode strip
having spaced apart first and second edges extending to and meeting
with opposed first and second ends to provide the first electrode
strip having a first length defined by the first and second edges
which is substantially greater than a first width defined by the
first and second ends, wherein the first electrode strip has a
first slot extending from one of the first and second edges toward
the other edge and partially through the first width; (b) a second
electrode strip having spaced apart third and fourth edges
extending to and meeting with opposed third and fourth ends to
provide the second electrode strip having a second length defined
by the third and fourth edges which is substantially greater than a
second width defined by the third and fourth ends, wherein the
second electrode strip has a second slot extending from one of the
third and fourth edges toward the other edge and partially through
the second width, wherein the first electrode strip and the second
electrode strip are registerable with each other through the first
and the second slots to form a collapsible electrode assembly; and
(c) a layer of a separator material disposed between the first
electrode strip and the second electrode strip, wherein the
registered first and second electrode strips are bi-directionally
foldable to form a wound cell stack.
14. The electrode assembly of claim 13 of either a primary or a
secondary chemistry.
15. A method for providing an electrode assembly, comprising the
steps of: a) providing a first electrode strip having a midportion
with a first slot defined therein; b) providing a second electrode
strip having a midportion with a second slot defined therein; c)
registering the first slot with the second slot, thereby forming
the first electrode and the second electrode into a collapsible
X-shaped electrode assembly with a layer of a separator material
disposed between the first and the second electrode strips; and d)
bi-directionally folding the X-shaped electrode assembly to form a
wound electrode assembly.
16. The method of claim 15 including providing the wound electrode
assembly of either a primary or a secondary chemistry.
17. The method of claim 15 including providing the first electrode
strip of a first electrode active material and selecting the first
electrode active material from the group consisting of SVO, CSVO
and CF.sub.x, and providing the second electrode strip of a second
electrode active material comprising lithium.
18. The method of claim 15 including providing the first electrode
strip of a first electrode active material comprising lithium
cobalt oxide, and providing the second electrode strip of a second
electrode active material comprising a carbonaceous material.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation-in-part
application of Ser. No. 09/262,245, filed Mar. 4, 1999.
FIELD OF INVENTION
[0002] The present invention generally relates to the art of
electrochemical energy, and more particularly, to an electrode
assembly, electrochemical cells in which the electrode assembly is
used, and a method for making the electrode assembly.
BACKGROUND OF THE INVENTION
[0003] Batteries or electrochemical cells are typically
volumetrically constrained systems that cannot exceed the available
volume of the battery case. The size and resulting volume of the
battery case are dictated by the space requirements available for
the particular application. The components that make up a battery,
namely, the cathode electrode, the anode electrode, the separator,
the current collectors, and the electrolyte all have to fit into
the limited space defined by the battery case. Therefore, the
arrangement of the components impacts on the amount of active
electrode material that can be fit into the case and the ease of
manufacturing the unit.
[0004] Some typical electrode assemblies include the "Z" folded
electrode assembly that is disclosed in U.S. Pat. No. 3,663,721 to
Blondel et al. In the "Z" folded electrode, a unitary and
continuous lithium anode is folded back and forth in a zigzag
fashion. The length of the individual folds determines the width of
the electrode assembly. Individual cathode plates are positioned
between pairs of the pleated anode electrode and electrically
connected to one another. The design has some drawbacks, including
the requirement that separate cathode plates be inserted between
each pair of adjacent layers of anode electrode and the requirement
that electrical connections be made between all of the inserted
cathode plates. This arrangement increases the time and costs
associated with manufacturing.
[0005] Another typical electrode assembly configuration is the
"jelly roll" design in which the anode electrode, the cathode
electrode, and the separator are overlaid with respect to each
other and coiled up. Such an electrode configuration is desirable
because the continuous anode and cathode electrodes require a
minimal number of mechanical connections to their respective
terminal leads, and the jelly roll assembly is generally recognized
as preferred for high discharge and current pulse applications.
However, in some applications, a cylindrically shaped electrode
assembly is not desired because of other factors, such as the shape
of the battery case.
[0006] U.S. Pat. No. 4,761,352 to Bakos et al. discloses yet
another electrode assembly design comprising an accordion folded
electrode assembly with unitary members for both the anode and
cathode strips. The cathode strip is approximately half the length
of the anode strip, and the anode strip is folded over the cathode
strip to "sandwich" the cathode between two layers of the anode.
The resulting form is then manually folded in an alternating series
of "V" folds (best shown in FIG. 4 of the patent). However, that
design provides some undesirable gaps which reduce the volumetric
density of the electrochemically active materials.
[0007] What is needed is an improved multi-layer, folded electrode
assembly design for high energy devices that includes many of the
desirable features of the jelly roll design, such as unitary anode
and cathode electrodes.
SUMMARY OF THE INVENTION
[0008] The present invention fills the above-described need by
providing an electrochemical cell comprising an electrode assembly
in which the electrodes are wound together in a bi-directional
fashion, yielding a high energy density cell with low internal
impedance. The anode and cathode electrodes are arranged in the
cell in such a fashion that provides efficient utilization of the
active components. The resultant wound assembly is configured such
that it can be conveniently packaged in either a cylindrical or
prismatic housing.
[0009] In one embodiment of the electrochemical cell, the
electrodes are provided as two anode assemblies and one cathode
assembly configured such that each anode is positioned on either
side of the cathode assembly, and extending in opposing directions.
At the center most portion of the assembly there is an overlap of
anodes. This assembly is then wound about the overlapping region in
a bi-directional fashion. The resultant assembly produces a wound
cell stack configuration with a uniform contact of anode and
cathode, such that the cell is balanced electrochemically and
provides for optimum volume utilization within the battery
enclosure. Each anode has one or more tabs that can be welded to
the case. Alternately, two cathode assemblies can be paired with
one anode assembly, with a resultant cathode tab welded to the
case. In both of the above configurations, the opposite electrode
may contain one or more tabs which are then electrically connected
to the battery feedthrough pin.
[0010] An alternate embodiment of this invention provides for an
anode electrode and a cathode electrode, wherein the electrodes are
slotted. The electrodes are inserted, one into the other,
essentially forming an "X". Upon collapsing the electrodes, a
variation of the above-described invention is obtained wherein the
anode is approximately equally disposed on opposite sides of the
cathode, radiating outwardly from the midportion thereof. This
assembly is then wound from the center, resulting in a preferred
cell stack assembly. This configuration provides the additional
advantage of having the anode registered to the cathode, and
mitigates the need for aligning two distinct anodes to the
cathode.
[0011] Other features and advantages of the present invention will
become apparent upon reading the following detailed description of
embodiments of the invention, when taken in conjunction with the
accompanying drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a side elevational view of the cathode strip and
separator of the present invention;
[0013] FIG. 2 is a side elevational view of the anode strip and
separator of the present invention;
[0014] FIG. 3 is a bottom plan view of the cell stack assembly of
the present invention;
[0015] FIG. 4 is a side elevational view of the cell stack assembly
of the present invention;
[0016] FIG. 5 is a partial plan view of the wound electrode
assembly of the present invention;
[0017] FIG. 6 is a perspective view of an alternate embodiment of
the electrode strips of the present invention;
[0018] FIG. 7 is a partial plan view of the wound electrode
assembly of the alternative embodiment; and
[0019] FIG. 8 is an exploded view of an electrochemical cell of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] The present invention is designed for high energy devices
such as batteries and capacitors and is adaptable in a wide variety
of electrode configurations and shapes for applications as
capacitors and batteries, including aqueous and nonaqueous primary
and secondary batteries.
[0021] Referring to FIG. 1, a first electrode 10 is preferably a
continuous structure comprising an active material 11 contacted to
a current collector 12 (shown in dashed lines). The active material
for a cathode electrode is preferably comprised of a metal, a metal
oxide, a metal sulfide, a mixed metal oxide, a carbonaceous
material, or the like and is combined with the current collector of
a conductive material such as a conductive screen. For an anode
electrode, the preferred active material is an alkali metal
selected from Group 1A of the Periodic Table of Elements and
contacted to an anode current collector. A preferred anode
electrode comprises lithium contacted to a nickel current
collector. In a preferred form of the present invention, the
electrode strip 10 is a cathode electrode having a set of cathode
tabs 15 provided for making an electrical connection to a positive
terminal.
[0022] Turning to FIGS. 2 and 3, a second electrode 16 includes a
pair of second electrode strips of a second electrode active
material 17 contacted to a current collector 18 (shown in dashed
lines) disposed on opposite sides of the first electrode 10. The
second electrode strips 16 overlap along a midportion 19 of the
first electrode 10 (FIG. 3). Preferably, the second electrode
strips 16 are part of the anode electrode. The anode electrode
strips 16 have anode tabs 22 that provide for electrical connection
to a negative terminal.
[0023] As shown in FIGS. 1, 2 and 4, a separator material 13 is
disposed behind each electrode to prevent contact between overlayed
layers of electrodes. Alternatively, the separator 13 is disposed
in front of each electrode strip. In a preferred embodiment, which
is not shown in the drawings, a separator 13 in the form of an
envelope encapsulates each of the first and second electrodes 10,
16. In that respect, whether the separator 13 is disposed between
immediately adjacent electrode strips or, the separator serves as
an envelope encapsulating at least one of the electrodes, the
separator must prevent direct physical contact between the
electrodes 10, 16.
[0024] Turning to FIG. 4, an electrode assembly according to the
present invention comprises a cathode electrode 10 and two anode
electrodes 16A, 16B, which are each preferably elongate, flat, and
rectangular. The anode electrodes 16A, 16B are disposed on opposite
sides of the cathode 10 and aligned such that they overlap across
the midportion 19 thereof. The anode electrodes 16A, 16B are a
little more than half the length of the cathode electrode 10, and
extend a short distance across the midportion 19 in order to
overlap. Alternately, two cathode electrode assemblies are paired
with one anode electrode in a similar overlapping
configuration.
[0025] From the alignment shown in FIGS. 3 and 4, the electrode
strips 10 and 16 are then folded about the overlapping region in a
bi-directional fashion to provide the electrode assembly 25. As
shown in FIG. 5, those portions of anode strips 16A and 16B on the
outside of the assembly 25 have the outside of the current
collector devoid of anode active material. This is because there is
no opposing cathode active material, and such anode active material
would provide very little, if any, additional volumetric
efficiency. Also, the ends of the anode strips 16A and 16B extend
somewhat beyond the end of the cathode electrode 10 to fully
utilize the discharge efficiency of the cathode electrode.
[0026] The term bi-directional refers to the fact that one side is
folded downwardly and the opposite side is folded upwardly, either
in succession or simultaneously, to generate the electrode assembly
25 shown in FIG. 5. The electrode assembly 25 produces a wound cell
stack configuration with uniform contact of anode and cathode
electrodes such that the cell is balanced electrochemically and
provides for optimum volume utilization within the battery
enclose.
[0027] An alternate embodiment of the present invention is shown in
FIGS. 6 and 7. In this embodiment, a cathode electrode strip 50
comprising a cathode active material 52 contacted to a cathode
current collector 54 has a downwardly facing slot 53 disposed in a
midportion 56 thereof. The slot 53 extends from a lower edge 58A
toward an upper edge 58B, but spaced therefrom. The lower and upper
edges 58A and 58B define the length of the strip 50. An anode
electrode strip 60 comprises an anode active material 62 contacted
to an anode current collector 64 and includes an upwardly facing
slot 63 disposed in a midportion 66. The slot 63 extends from an
upper edge 68A toward a lower edge 68B, but spaced therefrom. The
upper and lower edges 68A and 68B define the length of the strip
60.
[0028] As shown in FIG. 6, the anode strip 60 is provided with a
separation 13 to prevent direct physical contact with the cathode
strip 50. Preferably, the separator 13 envelopes the anode strip
60, and more preferably, each of the cathode strip 50 and the anode
step 60 are housed in their own separate envelopes.
[0029] To construct the electrode assembly, the strips 50 and 60
are moved together with the slots 53, 63 registering with each
other to form a collapsible X-shaped assembly. In this embodiment,
the opposed ends 68C and 68D of the anode strip 60 extends
outwardly a small distance past the opposed ends 58C and 58D of the
cathode strip 50 and in a configuration such that each electrode
50, 60 radiates outwardly from the midportion 56, 66 of the other
electrode. The electrode strips 50, 60 are then folded in a
bi-directional fashion from the center or midportions 56, 66 to
produce the wound electrode assembly 75 shown in FIG. 7. The
bi-directional folding is similar to that described with respect to
the electrode assembly 25 shown in FIGS. 1 to 5.
[0030] The completed electrode assembly 75 shown in FIG. 7 is
similar to the electrode assembly 25 in the respect that those
portions of anode strip 60 on the outside of the assembly have the
outside of the current collector devoid of anode active material.
As previously explained, this is because there is no opposing
cathode active material there, and such anode active material would
provide very little, if any, additional volumetric efficiency.
Also, the ends of the anode strip 60 extend somewhat beyond the
respective ends of the cathode strip 50 to fully utilize the
discharge efficiency of the cathode electrode. This alternate
embodiment provides the additional advantage of having the anode
registered to the cathode and mitigates the need for aligning two
distinct anodes to the cathode.
[0031] The present electrode assemblies 25, 75 provide several
advantages to cell design, including high energy density with low
internal impedance. Additionally, the anode and cathode electrodes
10, 16 for assembly 25 and the electrodes 50, 60 for assembly 75
are arranged in the cell in a way that provides efficient
utilization of the active components. The resultant wound cell
stacks are configured such that they can be conveniently packaged
in either a cylindrical or prismatic shaped casing. These casing
shapes are well known to those of ordinary skill in the art. The
electrode assemblies 25, 75 also provide a cell stack construction
in which the anode and cathode are uniformly utilized during cell
discharge. Finally, the assemblies 25, 75 provide a cell having a
relatively high inter electrode surface area which results in a
high current rate capability. This is advantageous for use in
applications such as powering an implantable defibrillator.
[0032] A preferred primary electrode chemistry for the electrode
assemblies 25, 75 according to the present invention has the first
electrode 10, 50 of a mixed metal oxide such as silver vanadium
oxide (SVO), copper silver vanadium oxide (CSVO) or a fluorinated
carbonaceous material (CF.sub.x), and the second electrode 16, 60
comprising lithium. A Li/SVO or Li/CSVO electrochemical couple is
activated with an electrolyte of 0.25M to 1.5M LiAsF.sub.6 or
LiPF.sub.6 in a 50:50, by volume, mixture of propylene carbonate
and 1,2-dimethoxyethane. For a Li/CF.sub.x cell, the preferred
electrolyte is 1.0M to 1.4M LiBF.sub.4 in .gamma.-butyrolactone. A
preferred secondary chemistry has a carbonaceous negative electrode
and a lithiated counter electrode. A preferred lithiated material
is lithium cobalt oxide. This couple is activated with an
electrolyte of 1M LiPF.sub.6 or 1M LiAsF.sub.6 in ethylene
carbonate/1,2-dimethoxyethane (3:7).
[0033] Referring to FIGS. 1, 2 and 8, the anode tabs 22 can be
welded to the case 80 (negative). Alternately, two cathode
assemblies can be paired with one anode assembly with the resultant
cathode tabs (not shown) welded to the case 80 (positive). In both
of the above configurations, the opposite electrode may contain one
or more tabs (cathode tabs 15) that are electrically connected to
the battery feedthrough or terminal pin 82. The terminal pin 82 is
electrically insulated from the lid 84 of the casing 80 by a
glass-to-metal seal 86. Similar electrical connections for the
cathode strip 50 and the anode strip 60 are made for the electrode
assembly 75 shown in FIGS. 6 and 7.
[0034] While the invention has been described in connection with
certain preferred embodiments, it is not intended to limit the
scope of the invention to the particular forms set forth, but, on
the contrary, it is intended to cover such alternatives,
modifications, and equivalents as may be included within the spirit
and scope of the invention, as defined by the appended claims.
* * * * *