U.S. patent application number 09/975268 was filed with the patent office on 2002-02-21 for wound cell stack design for enhanced battery performance.
Invention is credited to Frustaci, Dominick J., Frysz, Christine A., Hallifax, Paul T., Moceri, Kenneth P., Paulot, William M..
Application Number | 20020022174 09/975268 |
Document ID | / |
Family ID | 22996774 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020022174 |
Kind Code |
A1 |
Hallifax, Paul T. ; et
al. |
February 21, 2002 |
Wound cell stack design for enhanced battery performance
Abstract
An electrochemical cell comprising an electrode assembly in
which overlayed electrodes are wound together in a bi-directional
fashion yielding a high energy density cell stack with low internal
impedance is described. The overlayed electrodes are such that
either a single cathode is paired with two anodes or a single anode
is paired with two cathodes prior to winding of the cell stack
assembly. For example, the electrode assembly is formed by
overlapping the two anode electrodes on opposite sides of the
cathode electrode across a midportion and then winding the
electrode strips bi-directionally about the midportion.
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.: |
09/975268 |
Filed: |
October 11, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09975268 |
Oct 11, 2001 |
|
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09262245 |
Mar 4, 1999 |
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Current U.S.
Class: |
429/94 ; 429/128;
429/211; 429/219; 429/231.2; 429/231.3; 429/231.5; 429/231.7;
429/231.8; 429/247 |
Current CPC
Class: |
Y02P 70/50 20151101;
Y10T 29/49112 20150115; Y10T 29/49108 20150115; H01G 9/04 20130101;
H01M 6/10 20130101; H01M 50/103 20210101; H01G 9/00 20130101 |
Class at
Publication: |
429/94 ; 429/211;
429/219; 429/231.2; 429/231.7; 429/231.3; 429/231.8; 429/128;
429/247; 429/231.5 |
International
Class: |
H01M 006/10; H01M
010/32; H01M 004/54; H01M 004/52; H01M 004/58; H01M 002/18 |
Claims
What is claimed is:
1. An electrode assembly, comprising: a) a first electrode strip
having a midportion and a predetermined first length; b) at least
two second electrode strips having a second length shorter than the
first length, wherein the at least two second electrode strips are
disposed on opposite sides of the first electrode strip and in an
overlapping fashion along the midportion of the first electrode
strip; and c) a separator material disposed between the first
electrode strip and the at least two second electrode strips,
wherein the first electrode strip and the at least two second
electrode strips bi-directionally foldable about the midportion of
the first electrode strip such that a wound cell stack is
formed.
2. The electrode assembly of claim 1 wherein the at least two
second electrode strips each have at least one tab for connection
to a battery case.
3. The electrode assembly of claim 1 wherein the first electrode
strip has a tab connectable to a terminal pin.
4. The electrode assembly of claim 1 wherein the first electrode
strip comprises an anode electrode and the at least two second
electrode strips comprise a cathode electrode.
5. The electrode assembly of claim 1 wherein the first electrode
strip comprises a cathode electrode and the at least two second
electrode strips comprise an anode electrode.
6. The electrode assembly of claim 1 wherein the first electrode
strip is a unitary member.
7. The electrode assembly of claim 1 wherein the at least two
second electrode strips are unitary members.
8. The electrode assembly of claim 1 of either a primary or a
secondary chemistry.
9. The electrode assembly of claim 1 wherein the first electrode
strip is of a first electrode active material selected from the
group consisting of SVO, CSVO and CF, and the at least two second
electrode strips are of a second electrode active material
comprising lithium.
10. The electrode assembly of claim 1 wherein the first electrode
strip is of a first electrode active material comprising lithium
cobalt oxide, and the at least two second electrode strips are of a
second electrode active material comprising a carbonaceous
material.
11. An electrochemical cell, comprising: (a) a cathode strip
comprising a cathode active material contacted to a cathode current
collector and having a midportion and a predetermined first length;
(b) at least two anode strips comprising lithium contacted to an
anode current collector and having a second length shorter than the
first length, wherein the at least two anode strips are disposed on
opposite sides of the cathode strip in an overlapping fashion along
the midportion of the cathode strip; (c) a separator material
disposed between the cathode strip and the at least two anode
strips; and (d) an electrolyte activating and operatively
associating the cathode strip and the anode strips, wherein the
cathode strip and the anode strips are bi-directionally foldable
about the midportion of the cathode strip to form a wound cell
stack.
12. The electrochemical cell of claim 11 wherein the at least two
anode strips each have at least one tab for connection to a battery
case.
13. The electrochemical cell of claim 11 wherein the cathode strip
has a tab connectable to a terminal pin.
14. The electrochemical cell of claim 11 of either a primary or a
secondary chemistry.
15. The electrochemical cell of claim 11 wherein the cathode active
material of the cathode strip is selected from the group consisting
of SVO, CSVO and CF.sub.x, and the anode active material of the at
least two anode strips comprises lithium.
16. The electrochemical cell of claim 11 wherein the cathode active
material of the cathode strip comprises lithium cobalt oxide, and
the anode active material of the at least two anode strips
comprises a carbonaceous material.
17. The electrochemical cell of claim 11 wherein the cathode strip
is a unitary member.
18. The electrochemical cell of claim 11 wherein the at least two
anode strips are unitary members.
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 its midportion. This assembly is
then wound from the center, resulting in a preferred cell stack
assembly. This configuration provides for 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. 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 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 anode strip 60 extends outwardly
a small distance past the opposed ends of the cathode strip 50 and
in a configuration such that the electrodes 50, 60 radiate
outwardly from the midportions 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.
[0028] 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.
[0029] 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.
[0030] 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 0.25 M to 1.5 M 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 1.0 M to 1.4 M 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 1 M LiPF.sub.6 or 1 M LiAsF.sub.6 in ethylene
carbonate/1,2-dimethoxyethane (3:7).
[0031] 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.
[0032] 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.
* * * * *