U.S. patent application number 12/355242 was filed with the patent office on 2009-05-14 for batteries including a flat plate design.
Invention is credited to A. Gordon Barr, Reilly M. Dillon, Benjamin J. Haasl, Richard J. Kavanagh, Michael J. O'Phelan, Lawrence D. Swanson, Tom G. Victor.
Application Number | 20090123825 12/355242 |
Document ID | / |
Family ID | 32658861 |
Filed Date | 2009-05-14 |
United States Patent
Application |
20090123825 |
Kind Code |
A1 |
O'Phelan; Michael J. ; et
al. |
May 14, 2009 |
BATTERIES INCLUDING A FLAT PLATE DESIGN
Abstract
A battery having flat, stacked, anode and cathode layers. The
battery can be adapted to fit within an implantable medical
device.
Inventors: |
O'Phelan; Michael J.;
(Lutsen, MN) ; Victor; Tom G.; (Minneapolis,
MN) ; Haasl; Benjamin J.; (Forest Lake, MN) ;
Swanson; Lawrence D.; (White Bear Lake, MN) ;
Kavanagh; Richard J.; (Brooklyn Park, MN) ; Barr; A.
Gordon; (Burnsville, MN) ; Dillon; Reilly M.;
(Chanhassen, MN) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG & WOESSNER/BSC-CRM
PO BOX 2938
MINNEAPOLIS
MN
55402
US
|
Family ID: |
32658861 |
Appl. No.: |
12/355242 |
Filed: |
January 16, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10360551 |
Feb 7, 2003 |
7479349 |
|
|
12355242 |
|
|
|
|
60437537 |
Dec 31, 2002 |
|
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Current U.S.
Class: |
429/136 ;
429/139; 429/211 |
Current CPC
Class: |
H01M 10/0404 20130101;
H01M 2220/00 20130101; H01M 6/005 20130101; H01M 50/10
20210101 |
Class at
Publication: |
429/136 ;
429/211; 429/139 |
International
Class: |
H01M 2/18 20060101
H01M002/18; H01M 6/02 20060101 H01M006/02 |
Claims
1. A battery stack comprising: a plurality of alternating anode and
cathode layers, each of the anode layers having a base layer, the
anode layer including an anode tab extending from a first position,
the anode tab having a thickness greater than a thickness of the
anode base layer; and wherein each cathode layer includes a cathode
tab extending from a second position.
2. The battery stack of claim 1, wherein each of the anode and
cathode layers includes a substantially non-rectangular shape.
3. The battery stack of claim 1, wherein the cathode material layer
includes MnO2.
4. The battery stack of claim 3, wherein the MnO2 layer does not
cover the cathode tab.
5. The battery stack of claim 1, wherein the base layer includes a
metal sheet.
6. The battery stack of claim 1, further including a separator
layer between each anode layer and each cathode layers.
7. The battery stack of claim 6, wherein an outer perimeter edge
surface of each cathode layer is offset from an outer perimeter
edge surface of each anode layer that is adjacent to the cathode
layer.
8. The battery stack of claim 7, wherein the outer perimeter of
each cathode layer is completely offset from the outer perimeter of
each anode layer.
9. The battery stack of claim 6, wherein each separator is
connected to an adjacent separator to form a substantially sealed
pocket around each cathode layer.
10. The battery stack of claim 9, wherein the tab of each cathode
layer is exposed beyond the substantially sealed pocket.
11. The battery stack of claim 1, wherein each cathode layer has a
first separator on one side and a second separator on a second
side, wherein the first separator and the second separator are
connected to each other around at least a portion of their
edges.
12. The battery stack of claim 11, wherein the first separator and
the second separator define a flange at the connection of the first
separator and the second separator, wherein the flange extends
beyond an edge of the cathode layer and encloses the edge of the
cathode layer.
13. The battery stack of claim 12, wherein the connection between
the first separator and the second separator includes a heat
seal.
14. The battery stack of claim 1, wherein each of the plurality of
cathode layers is stacked such that the cathode tabs of each
cathode layer overlay one another and wherein each of the plurality
of anode layers is stacked such that the anode tabs of each anode
layer overlay one another.
15. The battery stack of claim 1, wherein the anode tabs are
approximately as thick as a combined thickness of the anode base
layer and the anode material layer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 10/360,551, filed Feb. 7, 2003, which claims the benefit under
35 U.S.C. 119(e) of U.S. Provisional Application Ser. No.
60/437,537 filed Dec. 31, 2002, the specification of which is
hereby incorporated by reference.
TECHNICAL FIELD
[0002] The present invention concerns implantable medical devices,
such as defibrillators and cardioverters, and more specifically to
a battery for such devices.
BACKGROUND
[0003] Patients prone to irregular heart rhythms sometimes have
miniature heart devices, such as defibrillators and cardioverters,
implanted in their bodies. These devices detect onset of abnormal
heart rhythms and apply corrective electrical therapy to the heart.
The defibrillator or cardioverter includes a set of electrical
leads, which extend from a device housing into the heart. Within
the device housing are a battery for supplying power, circuitry for
detecting abnormal heart rhythms, and a capacitor for delivering
bursts of electric current through the leads to the heart. Since
defibrillators and cardioverters are typically implanted in the
left region of the chest or in the abdomen, a smaller size device,
which is still capable of delivering the required level of
electrical energy, is desirable.
[0004] The basic components that make up a battery are an anode, a
cathode, a separator between the anode and the cathode,
electrolyte, and packaging hardware such as the case. Batteries can
be of a wound, jellyroll, style of design that may be cylindrical
or flattened cylindrical in shape. Some designs fold the battery
components on top of one another.
[0005] The anodes and cathodes of the battery are opposed to each
other throughout the battery. This continuous opposition
requirement creates packaging inefficiencies, such as wasted volume
at bend lines or, in the wound configuration, the mandrel volume
itself. Moreover, these folded or wound design approaches are
limited to simple cross-sectional areas due to the manufacturing
constraints of producing such a battery cell. It is desirable to
improve the packaging efficiency of the battery particularly for
medical implantable devices, since this will provide a smaller
battery. Also, consistency from one battery to the next is a
desirable feature for implantable medical devices. A heightened
consistency allows the battery's life-cycle to be predictable and
allows the battery to be replaced at an opportune time without
emergency.
BRIEF DESCRIPTION OF DRAWINGS
[0006] FIG. 1 is an exploded perspective view of a flat battery
according to one embodiment.
[0007] FIG. 2 is an exploded perspective view of the battery stack
of FIG. 1.
[0008] FIG. 3 is a perspective view of an anode according to one
embodiment.
[0009] FIG. 4A is a front view of an anode collector manifold
according to one embodiment.
[0010] FIG. 4B shows a detailed portion of the anode collector
manifold of FIG. 4A.
[0011] FIG. 5 shows a front view of an anode collector according to
one embodiment.
[0012] FIG. 6 shows a front view of an anode collector according to
one embodiment.
[0013] FIG. 7 shows a front view of an anode collector according to
one embodiment.
[0014] FIG. 8 shows a front view of an anode collector according to
one embodiment.
[0015] FIG. 9 shows an exploded view of a cathode assembly
according to one embodiment.
[0016] FIG. 10 is a front view of a cathode collector manifold
according to one embodiment.
[0017] FIG. 11A shows a front view of a cathode collector according
to one embodiment.
[0018] FIG. 11B shows a detailed portion of the cathode collector
of FIG. 11A.
[0019] FIG. 12 shows a front view of a cathode collector according
to one embodiment.
[0020] FIG. 13 shows a front view of a cathode collector according
to one embodiment.
[0021] FIG. 14 shows a front view of a cathode collector according
to one embodiment.
[0022] FIG. 15 shows a perspective view of an alignment fixture for
constructing a battery stack according to one embodiment.
[0023] FIG. 16 is a perspective view of a battery stack within the
fixture of FIG. 15.
[0024] FIG. 17 is a top view of FIG. 16.
[0025] FIG. 18A shows a sectional front view of a stacking fixture
for constructing a battery stack according to one embodiment.
[0026] FIG. 18B shows a perspective view of a stacking fixture for
constructing a battery stack according to one embodiment.
[0027] FIG. 18C shows a detail of the upper members of the stacking
fixture of FIG. 18B.
[0028] FIG. 18D shows an upper member of the stacking fixture of
FIG. 18B, according to one embodiment.
[0029] FIG. 18E shows an upper member of the stacking fixture of
FIG. 18B, according to one embodiment.
[0030] FIG. 18F shows a schematic front view of the stacking
fixture of FIG. 18B.
[0031] FIG. 18G shows a front view of portion of a battery stack
and an upper member of a stacking fixture according to one
embodiment.
[0032] FIG. 19 is a top view of a battery stack according to one
embodiment.
[0033] FIG. 20 is a side schematic view of the battery stack of
FIG. 19.
[0034] FIG. 21 is a perspective view of the battery stack of FIG.
1.
[0035] FIG. 22A is a side view of the battery stack of FIG. 1.
[0036] FIG. 22B is a perspective view of an insulating member
according to one embodiment.
[0037] FIG. 22C is a side view of the insulating member of FIG.
22B.
[0038] FIG. 23A shows a side view of the battery stack and battery
case lid of FIG. 1.
[0039] FIG. 23B shows a cross-section of the battery stack of FIG.
23A.
[0040] FIG. 23C shows a cross-section of the feedthrough assembly
of the battery of FIG. 23A.
[0041] FIG. 24A shows a side view of a battery according to one
embodiment.
[0042] FIG. 24B shows a cross-section of the battery of FIG.
24A.
[0043] FIG. 24C shows a close-up detail of the cross-section of
FIG. 24B.
[0044] FIG. 25 shows a perspective view of a battery according to
one embodiment.
[0045] FIG. 26A shows an exploded view of the battery of FIG.
25.
[0046] FIG. 26B shows a battery stack according to one
embodiment.
[0047] FIG. 27 shows an exploded view of a battery stack according
to one embodiment.
[0048] FIG. 28 shows a top view of a cathode within a sealed
separator, according to one embodiment.
[0049] FIG. 29 is a side view of a cathode sealed within a
separator according to one embodiment.
[0050] FIG. 30 shows a side view of a detail of the upper portion
of the cathode of FIG. 29.
[0051] FIG. 31 shows a side view of a detail of the lower portion
of the cathode of FIG. 29.
[0052] FIG. 32 shows a top view of a cathode for a battery stack
according to one embodiment.
[0053] FIG. 33 shows a top view of an anode for a battery stack
according to one embodiment.
[0054] FIG. 34 shows a top view of a separator for a battery stack
according to one embodiment.
[0055] FIG. 35 shows a top view of a battery stack having the
cathode, anode, and separator of FIGS. 32-34.
[0056] FIG. 36A shows a top view of the extension members of the
battery stack of FIG. 35.
[0057] FIG. 36B shows a top view of a cathode according to one
embodiment.
[0058] FIG. 36C shows a side view of the cathode of FIG. 36B.
[0059] FIG. 36D shows a detail view of FIG. 36C.
[0060] FIG. 36E shows a partial perspective view of a battery
according to one embodiment.
[0061] FIG. 37 shows a top view of a cathode layer according to one
embodiment.
[0062] FIG. 38 shows a top view of an anode layer according to one
embodiment.
[0063] FIG. 39 shows a perspective view of a battery stack
constructed according to one embodiment.
[0064] FIG. 40 shows a perspective view of the battery stack of
FIG. 39.
[0065] FIG. 41 shows a perspective view of a taping fixture
according to one embodiment.
[0066] FIG. 42 shows a top view of the taping fixture of FIG.
41.
[0067] FIGS. 43A and 43B show top views of an example battery stack
being taped according to one embodiment.
[0068] FIGS. 44A and 44B show top views of an example battery stack
being taped according to one embodiment.
[0069] FIG. 45 shows a partial cut-away view of the terminal
connections of a battery according to one embodiment.
[0070] FIG. 46 shows a partial top view of a battery according to
one embodiment.
[0071] FIG. 47A shows a section view of FIG. 46.
[0072] FIG. 47B shows another section view of FIG. 46.
[0073] FIG. 48A shows a terminal according to one embodiment.
[0074] FIG. 48B shows a side view of the terminal of FIG. 48A being
attached to a case in accordance with one embodiment.
[0075] FIG. 48C shows a view of the terminal of FIG. 48A after
being attached to the case.
[0076] FIG. 48D shows a detail side view of a terminal according to
one embodiment.
[0077] FIGS. 49A, 49B, and 49C shows a backfill plug welding
technique according to one embodiment.
[0078] FIG. 50A shows a backfill plug for a battery according to
one embodiment.
[0079] FIGS. 50B and 50C shows a backfill plug welding technique
according to one embodiment.
[0080] FIG. 50D shows a backfill plug terminal for a battery
according to one embodiment.
[0081] FIG. 50E shows a backfill plug terminal for a battery
according to one embodiment.
[0082] FIG. 51 is a flowchart of a method of constructing a
battery, in accordance with one embodiment.
[0083] FIG. 52 shows a schematic view of a system for manufacturing
anodes, in accordance with one embodiment.
[0084] FIG. 53 shows a system for constructing cathodes, in
accordance with one embodiment.
[0085] FIG. 54 shows a schematic view of a fixture for constructing
cathodes, in accordance with one embodiment.
[0086] FIG. 55 shows a side view of the fixture of FIG. 54.
[0087] FIG. 56 shows a schematic view of a system for constructing
cathodes, in accordance with one embodiment.
[0088] FIG. 57 shows a side view of the system of FIG. 56.
[0089] FIG. 58 shows a top view of a cathode forming fixture
according to one embodiment.
[0090] FIG. 59 shows a side view of the fixture of FIG. 58.
[0091] FIG. 60 shows a front view of the fixture of FIG. 58.
[0092] FIG. 61 is a block diagram of a implantable medical device
system according to one embodiment.
[0093] FIG. 62 is a chart of a battery constructed according tone
embodiment.
DESCRIPTION OF EMBODIMENTS
[0094] In the following detailed description, reference is made to
the accompanying drawings which form a part hereof, and in which is
shown by way of illustration specific embodiments in which the
invention may be practiced. These embodiments are described in
sufficient detail to enable those skilled in the art to practice
the invention, and it is to be understood that other embodiments
may be utilized and that structural changes may be made without
departing from the scope of the present invention. Therefore, the
following detailed description is not to be taken in a limiting
sense, and the scope of the present invention is defined by the
appended claims and their equivalents.
[0095] FIG. 1 shows an exploded view of a battery 18 according to
one embodiment. The present embodiment shows a D-shaped battery. In
other embodiments, battery 18 can be designed in a variety of flat
shapes to conform to various housing shapes. The discussion herein
provides techniques to manufacture a battery having virtually any
arbitrary shape, such as rectangular or non-rectangular. Moreover,
the edges of the battery can be curved to allow the battery to fit
in a shape-friendly curved case, as will be detailed below. The
battery includes a metallic case 20 defining a chamber 22 which
holds a battery stack 24. In one embodiment, case 20 is
manufactured from a conductive material, such as stainless steel.
In another option, the case 20 is manufactured using a
nonconductive material, such as a ceramic or a plastic.
[0096] Case 20 includes a base 26 and a lid 28 positionable on an
upper rim 27 of base 26. Battery stack 24 has a cutout region 34 at
its periphery, with cutout region 34 being positioned when the
stack 24 is installed in case 20 to provide space for electrical
connections. A feedthrough post 36 passes through lid 28 to stack
24 and is electrically insulated from case 20 and lid 28.
Feedthrough post 36 is connected to a cathode tab 35, while an
anode tab 37 is directly attached between lid 28 and base 26 such
that the case itself acts as the anode terminal. In some
embodiments, these roles are reversed and the cathode tab is
connected to the case and the anode tab connects to a feedthrough.
In some embodiments, two feedthroughs are provided, one for the
anode and one for the cathode. Battery stack 24 is covered with
insulating member 38 when mounted within case 20. Other embodiments
of insulating members, such as member 38, will be discussed below.
In one embodiment, a backfill port 43 is located in the battery
case. A backfill plug 41 and an optional cover 45 seal the backfill
port after the battery case is filled with electrolyte.
[0097] Battery stack 24 is constructed to provide optimal power
storage in a small space and allows for a battery having almost any
arbitrary shape or form factor. This allows battery 18 to be
designed and dimensioned to fit within an implantable medical
device, for example, and take up as little volume within the device
as possible. In one embodiment, stack 24 includes a plurality of
alternating anode and cathode layers separated by separators. As
will be detailed below, these alternating electrode layers are
stacked, aligned, and interconnected to allow for maximal electrode
area in a minimal volume with minimal wasted space. For example, in
one embodiment, battery 18 includes a layered stack of electrodes
where the interconnections between layers are spread out so as to
minimize the interconnection volume.
[0098] FIG. 2 illustrates an exploded view of battery stack 24
according to one embodiment. Battery stack 24 includes an anode
assembly including a plurality of anode sub-assemblies 100-100D and
a cathode assembly including a plurality of cathode sub-assemblies
300-300D, with separator layers 200 interposed between each of the
sub-assembly layers. This flat, stacked, layered structure omits
the wasted mandrel volume of wound batteries and the wasted edge
fold volume of folded batteries. Moreover, the flat, discrete
layers allow the battery designer to make the stack almost any
shape desirable. This allows a medical device designer to choose a
battery which can accommodate a given space within the medical
device.
[0099] One anode sub-assembly is a base, manifold anode collector
layer 100 which includes one or more tabs (A-E) extending from an
edge of the anode layer body. Other anode sub-assembly layers in
stack 24 include secondary anode collectors 100A-100D, which each
include an extension tab, designated A-D, respectively. In this
example, secondary anode sub-assembly collectors 100A each have a
tab A which overlays and is aligned with base anode layer 100's tab
A. In a likewise manner, secondary anode sub-assembly collectors
100B-100D each include an extension tab (B-D, respectively) which
vertically matches or overlays and aligns upon base layer 100 tabs
B-D respectively. In this embodiment, base layer 100 tab E includes
tab 37 which connects the anode assembly to the battery case (FIG.
1). By spreading the anode interconnections to base layer 100 out
over four separate areas, the overall thickness required by the
interconnections is lessened and less space is needed between stack
24 and case 20 (FIG. 1).
[0100] The cathode assembly of battery 24 includes a base, manifold
cathode collector layer 300 which includes one or more tabs (A-D)
extending from an edge of the cathode layer body. Other cathode
sub-assembly layers in stack 24 include secondary cathode
collectors 300A-300D, which each include an extension tab,
designated A-D, respectively. In this example, secondary cathode
sub-assembly collectors 300A each have a tab A which overlays and
is aligned with base cathode layer 300's tab A. In a likewise
manner, secondary cathode sub-assembly collectors 300B-300D each
include an extension tab (B-D, respectively) which overlies and
aligns upon base layer 300 tabs B-D respectively. In this
embodiment, base layer 300 includes tab 35 which connects the
cathode assembly to feedthrough 36 (FIG. 1). Again, by spreading
the cathode interconnections to base layer 300 out over four
separate areas, the overall thickness required by the
interconnections is lessened and less space is needed between stack
24 and case 20 (FIG. 1).
[0101] Each separator 200 separates an anode sub-assembly 100-100D
from a cathode sub-assembly 300-300D. Each separator 200 includes a
first edge 251, a clearance area defined by a second edge 252, and
a flat edge 253. The clearance area of separator 200 allows for
interconnections to the feedthrough. Separator 200 is, in one
option, made from a roll or sheet of separator material. Suitable
materials for the separator material include, but are not limited
to, a polyethylene, such as Tonen.TM., or a trilayer
(polypropylene, polyethylene, polypropylene) separator material
such as Celgard.TM. 2325, for example. Other chemically inert
materials are suitable as well, such as porous polymeric materials.
In one embodiment, each separator layer 200 is cut slightly larger
than the anode layers (or cathode layers) to accommodate
misalignment during the stacking of layers, to prevent subsequent
shorting between electrodes of opposite polarity, and to act as an
outermost edge for alignment.
[0102] FIGS. 3-8 show further details of an anode assembly of stack
24 according to one embodiment. FIG. 3 shows an anode material 110.
In this example anode 110 is a lithium (Li) anode. Each anode
sub-assembly 100-100D includes either one or two anodes 110 on the
major surfaces of the sub-assembly. In various embodiments, the
anode material 110 can be pressed into a mesh or etched base layer,
or onto the surface of a base layer, or be of pure Lithium and have
no base layer. In one example, a sheet of Lithium is attached to a
base layer and then die cut to the desired shape.
[0103] FIG. 4A shows base manifold anode collector layer 100.
Collector layer 100 includes an outer edge 130, a cut-out 132, an
upper flat edge 134, and an edge 136. The base layer 100 also
includes extension tabs A-E. In one embodiment, each extension tab
A-E is integral to layer 100. Some embodiments attach separate tabs
A-E to layer 100. FIG. 4B shows a detail of base layer 100. In one
embodiment, layer 100 is formed of a main body 120 including a
stainless steel material, such as 316L SST, or a nickel material. A
plurality of holes 125 are optionally incorporated into the
stainless steel material. One or two anodes 110 (FIG. 3) are
attached to the major surfaces of body 120. Tabs A-E (FIG. 4A) are
not covered with anode material. In one embodiment, the anodes can
be formed by attaching strips of Lithium to one or both sides of
strips of stainless steel, leaving an edge open along a portion of
the stainless steel strip for the tabs. One or more anode parts of
desired shape are then excised from the strip.
[0104] FIGS. 5-8 show anode sub-assemblies 100A-100D. Each of these
secondary anode layers includes an outer edge 130, a cut-out 132,
an upper flat edge 134, and an edge 136 designated by the
corresponding letters A-D in the respective Figures. Each layer
also includes a tab 140A-140D, respectively, with the tab of each
separate layer being offset from the previous and subsequent
layers.
[0105] FIGS. 9-14 show further details of a cathode assembly
according to one embodiment. FIG. 9 shows an exploded view of a
cathode sub-assembly having a metal collector sheet 301 and a
cathode material 310 on one major surface and a cathode material
312 on a second major surface. In one embodiment, cathodes 310 and
312 are MnO.sub.2 (manganese dioxide). One mix ratio is about 90%
MnO.sub.2, 5% PTFE, and 5% carbon. Another embodiment provides a
mix ratio of 90% MnO.sub.2, 5% binder, and 5% carbon or graphite.
In one example, the cathode material can be a powder which is
pressed into a mesh base layer. In one embodiment, a cathode paste
can be provided which can be laminated, pressed, rolled, or
otherwise mounted onto the surface of a base layer, as will be
detailed below. In various examples, the cathode material can be a
powder, paste, or adhered slurry.
[0106] FIG. 10 shows base manifold cathode collector 300. Collector
300 includes an outer edge 330, cut-out 332 having tab 35 therein,
and upper flat edge 334. Collector layer 300 also includes four
extension tabs A-D.
[0107] FIG. 11A shows cathode sub-assembly secondary layer 300A
having outer edge 330A, cut-out 332A, and flat edge 334A. A tab
340A extends from edge 334A. FIG. 11B shows a detail of collector
300A. In this embodiment, collector 300A is formed of a main body
320 including a stainless steel sheet. A plurality of diamond
structures 305 are incorporated into the main body by etching, an
expanded metal process, by a mechanical process, or by laser, for
example. One or two cathodes 310 and 312 (FIG. 9) are attached to
the major surfaces of body 320. Tab 340A is not covered with
cathode material. In one embodiment of forming the cathodes, a
layer of a paste or slurry is applied to one or both sides of a
stainless steel base layer, the strip is rolled or pressed to meter
and attach the cathode material to the base layer, and then one or
more cathodes are excised from the strip. In one example, the
cathode layer is applied leaving the cathode tabs bare.
[0108] FIGS. 12-14 show secondary cathode sub-assembly layers
300B-300D, respectively. Each secondary cathode layer includes an
outer edge 330, cut-out 332 and upper flat edge 334 shown by the
corresponding letters B-D in the respective Figures. Each layer
also includes a tab 340B-340D, respectively, with the tab of each
separate layer being offset from the previous and subsequent
layers.
[0109] Again, each anode tab 140A-140D and each cathode tab
340A-340D corresponds to a tab A-D on either the base anode layer
100 or the base cathode layer 300.
[0110] Also, these spread out interconnections of the anodes and
cathodes decrease the overall thickness of the space between the
stack and the case, allowing for a smaller battery size. To ensure
that a battery stack takes up as little volume as possible and to
optimize the consistency between each battery being manufactured,
it is important to carefully align each layer of the battery stack
when constructing the stack. In one embodiment, battery stack 24
described above is aligned using an alignment fixture to provide
for optimal surface area of the battery.
[0111] FIG. 15 illustrates an alignment mechanism or fixture 400
used to assemble battery stack 24, in accordance with one
embodiment. Alignment mechanism 400 includes a plurality of
precisely placed alignment elements 501-504. Alignment elements
501-504 are vertically oriented alignment elements which extend
from a base 402. Base 402 supports battery components thereon,
while the alignment elements 501-504 align the battery layers while
the layers are being stacked therein.
[0112] FIGS. 16-17 shows one example use of alignment fixture 400.
FIG. 16 shows a perspective view of stack 24 within the fixture and
FIG. 17 illustrates a top view of battery stack 24 within fixture
400. Battery stack 24 includes a plurality of discrete electrode
layers with each layer aligned relative to the position of the
alignment elements 501-504. A channel can be provided in base 402
to hold a fastener for wrapping around a portion of the battery
stack 24 once it has been stacked and aligned. In one example, a
tool can be inserted into the channel to clamp the stack and remove
it for taping. Precise alignment of battery stack 24 is maintained
by the alignment elements 501-504 when wrapping the battery stack
24.
[0113] In one example, to align the layers of battery stack 24, a
separator layer 200 is attached to each respective electrode layer
of the stack. The separators 200 can dimensioned such that they
slightly overhang the edges of each electrode layer. Each layer is
then placed between alignment elements 501-504. One or more points
on the outer perimeter edges (251-253, etc.) of each separator
layer abut against each of the elements 501-504, precisely aligning
that layer. This technique helps to reduce variances in alignment
which may result from varying tolerance stack ups between layers of
the assembly and the alignment fixture used. Moreover, by using the
outer edges, no area within the body of each layer is wasted by
using alignment holes, for example.
[0114] In one embodiment, each separator layer 200 is aligned
relative to the plurality of alignment elements 501-504 by placing
the separator so that outer edge 251 and edge 253 extend to contact
the alignment elements 501, 502, 503, and 504. In one example, the
separator layer 200 is then attached to an anode assembly 100-100D
or a cathode assembly 300-300D while the separator is positioned
within the fixture. These sub-assembly layers are then put one by
one into fixture 400 between elements 501-504. The edges of the
separators 200 contact the elements 501-504 and align the electrode
layers.
[0115] In one embodiment, each sub-layer or series of sub-layers
are pressed to help reduce warpage and thus to reduce the overall
height of the battery stack 24. A fastener 351 (FIG. 21) can be
wrapped around a portion of the stack 24 to retain the alignment of
the layers relative to one another. In one embodiment, the fastener
includes a tape that is wrapped around a central portion of the
battery stack 24. The battery stack 24 can then be clamped and
annealed.
[0116] In some embodiments, the anode sub-assembly layers 100-100D
and the cathode sub-assembly layers 300-300D are aligned relative
to one another within case 20, instead of using the external
alignment mechanism 400, and then are coupled to one another in the
aligned position. For instance, an outer edge of a separator of the
anode sub-assembly and an outer edge of a separator of a cathode
sub-assembly can contact an interior surface of the case 20, and
would be aligned therein.
[0117] Among other advantages, use of the alignment fixture
described above provides for a battery making efficient use of
space within the case, permits increased anodic and cathodic
surface area, and increased capacity for a battery of a given set
of dimensions. Variation in the outer dimensions of one battery
stack 24 to another battery stack 24 is reduced because each is
formed within alignment elements positioned the same manner.
Moreover, dimensional variations in the battery stack resulting
from variation in the reference points from case to case or
alignment apparatus to alignment apparatus are eliminated. This
provides improved dimensional consistency in production and allows
for reduced tolerances between the battery stack and the battery
case. This allows for more efficient use of space internal to the
battery case.
[0118] Furthermore, multiple points can be used to make the
alignment, reducing the effect of the tolerance stack up between
the conductive layer or separator being aligned and the alignment
element at any one position. This also facilitates for alignment of
components which during certain steps in the manufacturing process
have portions which extend beyond the dimensions defined by the
case and are later formed to fit within the case.
[0119] The battery stack structure described above provides for
greater cathodic/anodic surface area since, by aligning to the
separator, the cathode/anode surface area is optimized by not
having to provide extraneous alignment notches or other alignment
features within or on the electrodes themselves which decrease the
electrode surface area. However, in some embodiments, one or more
features, such as holes or notches can be provided in the surface
of each of cathode assembly 300-300D, anode assemblies 100-100D,
and separators 200 allowing for internal alignment of the stack.
For example, fixture 400 can include a central post and each layer
is mounted over the central post such that each layer is
registered.
[0120] FIG. 18A shows a sectional side view of an alignment
mechanism 600 for forming a battery stack according to one
embodiment. Alignment mechanism 600 generally includes a base 610,
a base pad 620, and first and second upper members 634 and 636. In
use, fixture 600 helps to continually keep all the layers of a
battery stack 624 in compression as the battery stack is being
formed. In one embodiment, as will be detailed below, as each
separate layer of the battery stack is placed upon base pad 620,
the base pad urges the stack upward while upper members 634 and 636
provide a holding, downward force on the stack such that the stack
is squeezed between base pad 620 and upper members 634 and 636.
This squeezing or compression holds each layer of the battery stack
in the position in which it was placed on the stack, thus keeping
the alignment of the battery stack.
[0121] Base 610 includes an interior cavity 640. In one embodiment,
interior cavity 640 is shaped to accommodate base pad 620 therein
to allow the base pad to translate up and down. Base pad 620 and
cavity 640 are shaped to accommodate example battery stack 624 As
noted above, flat batteries can be formed into almost any shape.
Accordingly, base pad 620 can have almost any shape.
[0122] Base pad 620 includes a flat top surface for supporting a
bottom surface of battery stack 624. In one embodiment, the surface
area of the base pad surface is slightly larger than the surface
area of the battery stack. In one embodiment, a straight,
longitudinal groove 627 is provided in the top surface of base pad
620. Along with a corresponding groove in base pad 610, groove 627
provides a space for a binder such as a tape to be laid into while
a battery stack is being formed in fixture 600. After the stack is
formed, the tape can be wrapped around the battery stack to bind
the stack and to hold the stack's alignment. Groove 627 can also be
used as a stack picking feature. For example, a tool can be
inserted into the channel of groove 627 to clamp the stack and
remove it for taping. Some embodiments omit groove 627.
[0123] Fixture 600 includes one or more forcing or biasing members
such as springs 626 which are located beneath base pad 620 to urge
base pad 620 upward. In use, the spring force grows as the stack is
formed until the force is approximately 2 lbs. when the base pad is
fully depressed. In other examples, the high end force can range
from 1/4 lb. to approximately 3 lbs., approximately 4 lbs., or
more, depending on the material being stacked. Also, the low-end
force (i.e., when the stack is empty) can be varied. For example, a
pre-load can be applied on the springs to urge the base pad against
the bottom of members 634 and 636 before any battery layers have
been placed therein. This pre-load force can range from zero, less
than approximately 1/4 lb to approximately 1/4 lb., approximately
1/2 lb., or more, depending on the application. In one embodiment,
the spring is omitted and a pressurized air dashpot mechanism is
located under base pad 620 to urge the base pad upward. The
pressurized air mechanism can have adjustable air pressure
settings, and allow for a constant upward force on the base
pad.
[0124] In one embodiment, each upper member 634 and 636 is a thin,
flat member, such as a metal strip or a plastic strip. In this
example, the upper members 634 and 636 are located so as to contact
the top side edges of the battery stack when the stack is being
formed. This helps keep the edges of a given layer from curling up.
This helps prevent misalignment of the stack since any deviation
from flatness can be a cause of misalignment.
[0125] In one example use, a robotically controlled vacuum
placement arm 660 places each new layer 624X on top of the previous
layer. Some embodiments provide manual placement of each layer. A
vision alignment system can be used to align the layers. Upper
members 634 and 636 are movably attached to the fixture so that
they can rotate off and on the stack. For example, uppers members
634 and 636 are moved out of the way when a new layer is being
place on the stack and arm 660 holds the stack in compression.
After the new layer is placed correctly the members 634 and 636
move back over the edges of the top of the stack and the arm 660 is
removed and the arms then hold the stack in compression. This
process is then repeated until the stack is formed.
[0126] Fixture 600 allows for precise alignment of a battery stack
which has a curved or non-uniform profile (See FIGS. 21 and 22 for
example, where the upper and lower portions of stack 24 are smaller
in area than the middle portion, resulting in a curved profile
battery stack). In such a curved profile battery stack, the edges
are not uniform so as to provide precise alignment when stacking in
a fixture such as fixture 400. However, by squeezing the stack,
fixture 600 allows for precise alignment regardless of the edge
profile of the stack.
[0127] Further details of some embodiments of alignment mechanism
600 are discussed in co-pending and co-assigned U.S. application
Ser. No. 10/050,598 (filed Jan. 15, 2002) entitled METHOD OF
CONSTRUCTING A CAPACITOR STACK FOR A FLAT CAPACITOR, which is
incorporated herein by reference in its entirety.
[0128] FIGS. 18B-18F show a stacking fixture 670 according to one
embodiment. Stacking fixture 670 includes some similar features as
discussed above for fixture 600 and certain details will be omitted
for sake of brevity. Fixture 670 includes a base 672 to hold a
stack as the stack is being built layer by layer. One embodiment
includes springs or other forcing members (such as an air pressure
dashpot mechanism, as discussed above) under base 672 to urge the
base and the battery stack upwards (as discussed above for fixture
600). Fixture 670 includes a placement member 671B to deliver each
anode, cathode, or separator layer to the stack. In some
embodiments, placement member 671B can include manual placement
members, vacuum placement members, robotically controlled placement
members, vision alignment systems and so on as discussed above. In
one embodiment, an upper clamping member 671A is rotatably coupled
to fixture 670 to apply top pressure on the stack when upper
members 673 and 674 are moved away and placement member 671B is
moved away. Other embodiments omit member 671A and utilize the
technique described below. A groove or channel can be provided in
the upper portion of the base 672 to allow for a tape strip or a
tool to be inserted to remove the stack from the fixture.
[0129] Fixture 670 includes upper members 673 and 674 which are
situated on opposite sides of the stack. Each upper member 673 and
674 includes a contacting member 675 and 676, respectively. Each of
the contacting members 675 and 676 is held in tension and supported
by being mounted to arms 680 and 681 at each of the contacting
members ends. Contacting members 675 and 676 contact the top
surface of the top layer of the battery stack as it is being built.
The compression or holding force between the contact members 675
and 676 and the base pad 672 keeps the battery stack in alignment
as the stack is being built layer by layer.
[0130] FIG. 18C shows a view of contacting members extending across
a top surface of a top layer 677 of a battery stack 678. It is
noted that the battery stack can be oriented in any manner
desirable (e.g. the stack can be turned 90 degrees relative to FIG.
18C). FIG. 18D shows one embodiment of a contacting member 675B.
Contacting member 675B includes a thin strip of plastic, such as a
mylar, polyethelyne, or polypropylene film web, for example.
Various embodiments have contacting members having a thickness of
approximately 0.001 inches or less, to approximately 0.005 inches.
This end-supported thin web of material is stronger and better
supported than a cantilevered member and the thinness of the
material allows for a minimal deflection of each new layer as it is
put on top of the stack.
[0131] FIG. 18E show a contacting member 675C which includes a roll
of thin plastic material. In this example, the web of member 675C
can be indexed and drawn through arms 680 and 681 every one or more
times it is used. This can provide clean material for contacting
the battery stack and allow the web to maintain its strength.
[0132] FIG. 18F shows an example use of fixture 670 in placing top
layer 677 onto a battery stack 678. In this example each layer of
the battery stack is aligned and placed upon the stack which rests
on base pad 672. Only contacting member 675 is shown in FIG. 18F
for sake of clarity. In one embodiment, second contacting member
676 is used on the opposite side of the stack as shown in FIG.
18B.
[0133] In use, placement member 671B places layer 677 on top of the
stack and holds the layer as originally aligned in place on top of
the stack. In such a position the edge of layer 677 is then on top
of contacting member 675. Contacting member 675 is then moved
outward to position 1, upward to position 2 then back to positions
3 and 4 where the bottom of contacting member 675 then contacts and
holds layer 677 down upon stack 678. Placement member 671B then
moves away to get the next layer with contacting member 675 (and
676) holding the stack in alignment. This process is then continued
until the battery stack is formed, with member 671B and members 675
and 676 alternatingly keeping the stack in compression.
[0134] As with fixture 600, fixture 670 allows for precise
alignment of a battery stack which has a curved or non-uniform
profile (See FIGS. 21 and 22). In such a stack, the edges are not
uniform so as to provide precise alignment when stacking in a
fixture such as fixture 400. However, by squeezing or at least
holding the stack still, fixture 670 allows for precise alignment
regardless of the edge profile of the stack since the stack never
has the opportunity to shift once a layer is aligned and placed
onto the stack. Moreover, thin contacting members 675 and 676
provide for the minimal deflection of the layer when they move away
from the stack. For example, FIG. 18G shows how each top layer 677
is deflected by contacting member 675 as it is being placed on
stack 678 by the placement member. By providing a thin contacting
member, this deflection can be minimized.
[0135] In some embodiments, the edges of the cathode layers and
anode layers of the battery stack 24 described above are generally
co-extensive or aligned with each other within stack 24. In other
embodiments, a battery stack can include anode and cathode layers
having at least partially offset edges.
[0136] For example, FIGS. 19 and 20 show top and side views of a
battery stack 724 according to one embodiment. Battery stack 724
includes an anode layer 701, a separator 702, and a cathode layer
703 that are configured in a layered structure analogous to battery
stack 24 described above. The bottom surface in FIG. 19 is the
cathode layer, and the top surface is the anode layer with the
separator interposed there between. In one embodiment, separator
702 can extend beyond both anode layer 701 and cathode layer
703.
[0137] Some cutting and punch-die processes used to make anode and
cathode battery layers can produce burrs on the layers that can
result in a short circuit if a burr on an anode layer edge portion
makes contact with an adjacent cathode layer or vice-versa. When
the dimensions of the cathode and anode layers are the same so that
the edges of each layer are aligned, a burr on a cathode layer edge
portion can then contact a burr on an anode layer edge portion.
Burrs on overlapping edge portions of the anode and cathode layers
may then make contact and cause a short circuit by traversing only
half of the thickness of the separator between the two layers.
[0138] Accordingly, in one embodiment, the battery stack is
constructed with layers having edge portions that are offset from
one another. In one embodiment, this is done by having a cathode
layer with a different dimension than the anode layer so that
portions of their edges are offset in the layered structure (i.e.,
either the anode layer or the cathode layer is smaller than the
other). The anode and cathode layers may be of the same general
shape, for example, but of different surface areas so that the
perimeter of one layer is circumscribed by the perimeter of the
other layer.
[0139] The capacity of a lithium-based battery is determined by the
amount of cathode material (such as MnO.sub.2) that can safely be
packaged in the device. Also, it can be desirable to have the anode
fully opposed by the cathode. Accordingly, altering the surface
area of the anode layer does not appreciably affect the capacity of
the device. Such an arrangement is shown in FIGS. 19 and 20 where
the anode layer 701 is of the same general shape as the cathode
layer 703 but with a smaller surface area such that the edge
portions of the anode layer are inwardly offset from the cathode
layer edges. In this structure, only an edge burr on the anode
layer that traverses the entire thickness of the separator can
produce a short circuit. This is in contrast to the case where the
edge portions of the two layers are aligned rather than being
offset. Offsetting the edge portions results in a greater tolerance
for edge burrs and allows a less constrained manufacturing process
and a thinner separator to be used.
[0140] Battery stack 724 can include a plurality of electrode
elements that are stacked on one another with each electrode
element being a layered structure such as shown in FIG. 19. The
anode layers 701 are stacked on cathode layers 703 in alternate
fashion with separator 702 interposed between each anode layer and
each cathode layer.
[0141] In one embodiment, the offset structure described above can
be incorporated into a cylindrical battery. For instance, the anode
and cathode layers are cut from a sheet in a desired width and
length. The anode layer is made narrower than the cathode layer so
that the edges of the anode layer are inwardly offset from the
cathode layer edges. The cylinder configuration is then produced by
rolling the layers into concentric anode and cathode layers that
are separated by separators.
[0142] Offsetting of anode layer and cathode layer edge portions
may be accomplished by using a variety of differently shaped and/or
dimensioned cathode or anode layers.
[0143] In one embodiment, for example, a battery used in
implantable defibrillators and designed to operate at a rated
voltage of approximately 2.75 volts to 3.4 volts, includes a ratio
of the anode layer surface area to the cathode layer surface area
of approximately 1.2 or greater. In some embodiments, the ratio is
approximately 1.3 to approximately 1.4. In various embodiments of
the present system, a ratio of Li/MnO.sub.2 capacity can vary
between approximately 0.85 to 1.7.
[0144] Referring again to FIG. 16, once stack 24 is stacked as
shown, the anode sub-assembly layers are interconnected via anode
tabs A-D and the cathode sub-assembly layers are interconnected via
cathode tabs A-D. The interconnections can be made by welding,
staking, or other techniques. Each tab of the various electrode
layers is electrically coupled to the other tabs through base
manifold layer 100 or 300. Each secondary electrode layer has at
least one extension tab positioned to overlay, be co-extensive
with, or match with one of the plurality of tab positions A-D.
[0145] In this embodiment, the cathode layers are positioned to
include four tab groups 350A-350D. Similarly, anode layers are
positioned to include four anode tab groups 150A-150D. The tab
groups are in electrical contact with each other through the base
layer 100 or 300. Thus, each cathode layer is electrically
connected to tab 35 and finally through the feedthrough 36, and
each anode layer is connected to tab 37 and then to the case.
[0146] In other words, from a top view perspective, anode tabs A-D
and cathode tabs A-D are commonly positioned or co-extensive with
anode and cathode base tabs A-D respectively.
[0147] The base tabs and matching secondary tabs may be separate
members attached or welded to the metal sheets or the tabs may be
integral with the foil layer. The base anodes and cathodes are
shown with four tabs and the secondary electrodes are shown with
one tab, however, any number of tabs can be provided as needed. In
some embodiments, the secondary layers include two or more tabs to
create redundancy.
[0148] Again, since the extension tabs are spread out, the size
needed to fit the stack within the battery case is reduced.
Moreover, the integral interconnects provide for a reduced
resistance of the interconnections. This results in an optimized
maximal battery surface area per unit volume of the battery.
Moreover, the battery then has reduced impedance due to the
integral interconnects. For example, because the battery has an
interconnect at each layer, it is in effect a multi-parallel
interconnection scheme that has lower impedance than that of a
rolled or folded battery with only one or two tabs.
[0149] In one embodiment, battery stack 24 includes the matching
tabs of each secondary layer group welded to the corresponding tab
of the base layer. These groups are folded against the battery
stack, forming the anode tab groups 150A-150D and cathode tab
groups 350A-350D. Again, tab groups 350A-350D electrically connect
to an external cathode connection via tab 35 which provides an
external electrical connection. Tab groups 150A-150D electrically
connect to tab 37.
[0150] In this embodiment, tab groups 150A-150D and 350A-350D are
folded into position on a top surface 32 of battery stack 24. The
tab groups are folded onto the top of the stack and taped.
Alternatively, the tab groups are cut just beyond the weld and
taped against a face 30 of the stack (See FIG. 21). Each tab group
150A-150D and 350A-350D has a thickness that is less than the sum
of the base layer and all the secondary layers.
[0151] In one example, the thickness of the tab groups are
approximately equal to or less than the space between the main body
of stack 24 and lid 28 of case 20 (FIG. 1). In some embodiments,
the space is merely a line-to-line interference fit. The present
cathode and anode structure provides that the cathode
interconnections and anode interconnections fit within the limited
room available.
[0152] For example, in one or more of the embodiments described
above the electrode interconnects are spread out or distributed
over multiple locations. For example, the cathode or anode layers
can be spread out over four locations with four tab groups, with
the thickness of each tab group at each location being about 0.006
inch after welding (assuming that four layers at 0.001 inch per
layer are at each location). This thinness of the tab group allows
the stacked unit to be placed into the housing with the tab groups
occupying the space between the housing and the edge of the stack
or the clearance space between the lid and the top of the stack.
These clearance spaces are allowed for inserting the stack into the
housing. As a comparison, if the cathode tabs were all brought out
at one location, the thickness would be greater than 0.015 inch and
make it difficult, if not practically impossible, to fold the tabs
collectively over the stack as in FIG. 21. Thus, this thickness
would require that part of the stack be removed or the case
enlarged to allow space for routing and connecting the cathode
layer connections, thereby reducing the packing efficiency of the
battery.
[0153] The embodiment described above show the base layer and
secondary layer as cathode and anode layers. However, in some
examples only the anode or the cathode layer is arranged in the
present fashion and the other is arranged in a different
manner.
[0154] FIG. 22A shows front view of stack 24 of FIG. 21. Here it
can be seen that in one embodiment, the present system allows for
the use of non-uniform layers of a battery. In this example,
generally designated are a top stack portion 24A, a middle stack
portion 24B and a bottom stack portion 24C. Each of the stack
portions 24A-24C includes one or more cathode layers, separator
layers, and anode layers. The layers of top portion 24A have at
least one dimension which is smaller than the similar layers in
middle stack portion 24B. Likewise, bottom stack portion 24C
includes at least one dimension smaller than similar layers in
middle stack portion 24B. This dimensional difference results in
the curved profile of stack 24.
[0155] Portions 24A-24C are staggered so that their perimeter edges
generally (or at least a portion of a side of the stack) define a
profile that generally conforms or is substantially congruent to an
adjacent curved interior portion of battery case 20 (FIG. 1)
without wasting any space within the case. FIG. 21 shows that
portions 24A-24C can be staggered in two dimensions. As discussed
above, fixture 600 (FIG. 18) can be used to form the curved or
staggered profile stack 24.
[0156] In various embodiments, stack 24 can have a variety of
profiles and can be curved along zero, 1, 2, 3, or more sides of
the battery. The stack can be curved along a top portion, a bottom
portion, or both.
[0157] Thus, the curved profile stack allows for a curved profile
battery case (FIG. 1). This advantageously takes advantage of an
implantable medical device housing, which can include a curved
outer surface and a curved inner surface. Thus, the present shape
provides an optimal amount of battery power packaged in a way that
takes advantage of the preferred shape of an implantable medical
device. This allows the battery stack 24 to fit tightly within a
curved case with as little wasted space as possible. A curved case
is usually a better fit within an implantable medical device. Thus,
this structure allows for a smaller medical device without lowering
the available energy of the battery by increasing the volumetric
and gravimetric energy density of the battery.
[0158] FIG. 22B is a perspective view of an insulating sheath or
insulating member 50 according to one embodiment and FIG. 22C is a
side view of insulating member 50. In this example, insulating
member 50 is shaped and dimensioned to hold a battery stack shaped
as battery stack 24 (FIGS. 1 and 21), for example. Other
embodiments can shape insulating member 50 as needed to conform to
and cover the outer surfaces of a battery stack. In one embodiment,
insulating member 50 is used in place of insulating member 38 (FIG.
1) to insulate the battery stack from case 20.
[0159] In one embodiment, insulating member 50 includes a main
insulating body 52 which defines a cup shape and includes a top
surface 61 and an opposing bottom surface 62 and having an opening
54 along a side of the body. One or more flaps 55 and 56 extend
from an edge of opening 54. Flaps 55 and 56 are dimensioned to fold
over and cover opening 54 after a battery stack has been inserted
into main body 52. In one embodiment, a first flap portion 57
covers the exposed surface of the battery stack and a second flap
portion 58 can be attached to the top surface of main body 52.
Thus, a battery stack, such as stack 24, can be inserted through
opening 54 into the hollow area within main body 52. Flaps 55 and
56 are folded over the exposed portion of the stack and the battery
stack is separated from and insulated from the battery case. One or
more gaps or spaces 59 and 60 can be provided between or adjacent
to flaps 55 and 56 to provide room for extension tabs 37 and 35
(FIG. 1) to extend from the stack.
[0160] In one embodiment, flaps 55 and 56 are integrally formed
with body 52. This integral structure allows for more efficient use
of insulating member 50 during manufacturing than a two or more
part construction. Integral flaps provide for cost savings in both
piece part and manufacturing assembly. Moreover, the integral
structure of insulating member 50 reduces the volumetric
inefficiencies of two part insulators since the present structure
reduces or eliminates any overlap region of the insulating
structure when it is mounted around the battery stack. For example,
only a single, top seam results when the edge of flaps 55 and 56
meet top surface 61.
[0161] FIG. 23A shows a side view of battery stack 24 and battery
case lid 28. Feedthrough 36 extends through a feedthrough hole 45
in lid 28 and is connected to tab 35. FIG. 23B shows a
cross-section of the connection. Tab 35 wraps around feedthrough 36
and is attached at section 35x. This allows for a stress-relief
area of the tab attachment.
[0162] FIG. 23C shows a cross-section of the feedthrough assembly
40 of battery 18. Feedthrough assembly 40 includes a ferrule
portion 42 integrally fashioned from a wall 43 of lid 28. In other
embodiments, the ferrule member can be fashioned from the base 26
of case 20. Ferrule portion 42 includes an integrally formed
annular structure defining feedthrough hole 45 which has an inward
facing cylindrical surface 45S. An annular insulating member 44 is
located within ferrule portion 42. In one embodiment, annular
insulating member 44 can be a glass member, an epoxy member, a
ceramic member, or a composite member, for example. In one
embodiment, annular member 44 includes a TA23 glass or equivalent
glass. Feedthrough post 36 extends through annular member 44.
Feedthrough post 36 can include a molybdenum material. Annular
member 44 electrically insulates feedthrough 36 from lid 28 and
provides a hermetic seal of battery 18.
[0163] Annular member 44 has an outer surface abutting inward
facing cylindrical surface 45S. Annular member 44 includes an inner
hole 48. Feedthrough post 36 extends through inner hole 48 and is
glassed into the battery case. This allows the feedthrough post to
have one end connected to a portion of the electrode assembly, such
as cathode tab 35, and a second end expose externally to the
housing to provide a cathode terminal for the battery. The integral
ferrule structure provides ease of manufacturing a battery since
the ferrule does not need to be welded onto the case. Moreover, it
can be a cost-effective and size advantageous approach for a
hermetically sealed battery. By installing the feedthrough directly
into the feedthrough hole in the case, a difficult welding step is
eliminated since the case and the feedthrough ferrule are a
combined assembly rather that two separate subassemblies that need
to be joined together.
[0164] FIG. 24A shows a side view of battery 18 after the battery
has been assembled. FIG. 24B shows a cross-section of battery 18,
and FIG. 24C shows a close-up detail of the cross-section of FIG.
24B. Here it can be seen that by staggering the tab connections of
the present embodiment. A space 60 between stack 24 and lid 28 can
be small to allow for an optimal use of space within the battery
case.
[0165] FIG. 25 shows a battery assembly 800 according to one
embodiment and FIG. 26A shows an exploded view of battery 800.
Battery 800 can be constructed using some features and techniques
discussed above and the above discussion is incorporated herein by
reference. Battery 800 is a flat, stacked battery having a
non-rectangular shape. Again, the techniques described above and
below allow the manufacture of almost any arbitrarily shaped
battery to allow a designer to fit the battery in a given space
within an implantable medical device, for example. A battery stack
814 is mounted within a battery case 802. In one embodiment, case
802 is a two-part clamshell case having a first part 803 and a
second part 804. Case 802 can be a metallic case manufactured from
a conductive material, such as stainless steel. In another option,
case 802 is manufactured using a nonconductive material, such as a
ceramic or a plastic.
[0166] Battery stack 814 has a region 815 at its periphery which is
indented relative to the shape of case 802. This indented region
815 is positioned when the stack 814 is installed in case 802 to
provide space for electrical connections. A feedthrough post 808
passes through case 802 to stack 814 and is electrically insulated
from case 802. Feedthrough post 808 is connected to a cathode tab
824, while an anode tab 822 is directly attached to case 802. An
anode terminal 810 is connected to the outer surface of case 802.
In some embodiments, these roles are reversed and the cathode tab
is connected to the case and the anode tab connects to a
feedthrough. In some embodiments, two feedthroughs are provided,
one for the anode and one for the cathode. Battery stack 814 is
wrapped by a strip of tape 828 to help hold the stack together and
in alignment. Stack 814 is covered with one or more insulating
members 811 and 812 when mounted within case 802. In other
embodiments, other insulating members, such as the one-piece
integral insulating member discussed above can also be used. A
backfill port 806 is provided in the case. In one embodiment, an
annular insulating member 827 is positioned beneath and around a
feedthrough ferrule (see also FIG. 47A) to prevent any short
circuits between interconnect 824 and the case. Insulating member
827 also helps minimize galvanic corrosion potential. One example
material for member 827 is a polyethylene material.
[0167] First part 803 of clamshell case 802 includes a lip 825
which is indented to allow edge 826 of second part 804 to matingly
mount around lip 825.
[0168] Battery stack 814 is constructed to provide optimal power
storage in a small space. This allows battery 800 to be dimensioned
to fit within an implantable medical device, for example, and take
up as little volume within the device as possible. In one
embodiment, stack 814 includes a plurality of alternating anode and
cathode layers separated by separators. As will be detailed below,
these alternating electrode layers are stacked, aligned, and
interconnected to allow for maximal electrode area in a minimal
volume with no wasted space.
[0169] In one embodiment, stack 814 can include one or more
staggered portions or profiles. For example, stack 814 can include
non-uniform anode or cathode layers. Stack 814 includes a top
portion 820, a middle portion 818 and a bottom portion 816. Each of
the stack portions 816-820 includes one or more cathode layers,
separator layers, and anode layers. In one embodiment, the layers
of top portion 820 have at least one dimension which is smaller
than the similar layers in middle stack portion 818. Likewise,
bottom stack portion 816 includes at least one dimension smaller
than similar layers in middle stack portion 818. This dimensional
difference results in the curved profile of stack 814.
[0170] Portions 816-820 are staggered so that their perimeter edges
generally (or at least a portion of side of the stack) define a
profile that generally conforms or is substantially congruent to an
adjacent curved interior portion of battery case 802. In various
embodiments, stack 814 can have a variety of profiles and can be
curved along zero, 1, 2, 3, or more sides of the battery. The stack
can be curved along a top portion, a bottom portion, or both.
[0171] Thus, the curved profile stack 814 allows for a curved
profile battery case 802. This takes advantage of an implantable
medical device housing, which can include a curved outer surface
and a curved inner surface. Thus, the present shape provides an
optimal amount of battery power packaged in a way which takes
advantage of the preferred shape of an implantable medical device.
This allows the battery stack 814 to fit tightly within a curved
case with as little wasted space as possible. A curved case is
usually a better fit within an implantable medical device. Thus,
this structure allows for a smaller medical device with out
lowering the power of the battery. (See FIG. 22A and accompanying
discussion for other details).
[0172] FIG. 26B shows battery stack 814 according to one
embodiment. In this example, insulating members 811 and 812 (FIG.
26A) are omitted and stack 814 is insulated by wrapping the
peripheral edge of the stack with an insulating member such as an
insulating strip 811B. In one embodiment, strip 811B includes a
strip of polyimide tape wrapped twice around the edge of the stack.
Two wraps provides for increased heat resistance along the weld
line of the battery case 803, 804 (FIG. 26A) and the ability to
manage variations in the height of the battery stack. In this
example, the top and bottom surfaces of stack 814 do not need to be
insulated from the battery case because they are the same
electrical potential as the case. This design also improves the
packaging density of battery 802.
[0173] FIG. 27 shows an exploded view of battery stack 814
according to one embodiment. Battery stack 814 includes an anode
assembly including a plurality of anode sub-assemblies 840, 842,
and 844 and a cathode assembly including a plurality of cathode
sub-assemblies 841 and 843. Anode sub-assemblies 840 and 844,
located near the top and bottom of stack 814, are smaller than the
other anode assemblies, and cathode sub-assemblies 841 are smaller
than the other cathode sub-assemblies to accommodate a curved
battery case edge. In this example, anodes 840 and 844 have lithium
attached to a single side of the anode. Each anode sub-assembly
includes a tab extending from the body of the anode at a location
A. Each cathode sub-assembly includes a tab extending from the body
of the cathode at a location B. To form stack 814, a stacking
fixture such as those discussed above can be used, such as fixtures
600 or 670, for example. After stacking, the anode tabs are brought
together and welded to connect each of the anode layers into an
anode assembly. Likewise all of the cathode tabs are brought
together and welded to form a cathode assembly.
[0174] In some embodiments, the anode and cathode layers of stack
814 are separated by separator as discussed above. In other
embodiments, each of the cathode sub-assemblies 841 and 843
includes a heat-sealed separator 846 which is formed to
substantially surround, encapsulate, or envelop the cathode member
of the sub-assembly while allowing the extension tab of the cathode
to be open.
[0175] FIGS. 28, 29, 30, and 31 show one embodiment of an
encapsulated cathode assembly 843. (The present encapsulation
technique is also applicable to the anodes discussed herein.) FIG.
28 shows a top view of cathode sub-assembly 843 which includes a
cathode 853 sandwiched between two layers of separator material 847
with one layer of separator material on either side of the cathode.
In one embodiment the separator material is polyethylene, such as
Tonen.TM., or a trilayer (polypropylene, polyethylene,
polypropylene) separator material such as Celgard.TM. 2325.
[0176] To form the encapsulated cathode assembly 843, the region
periphery 848, just outside the outer edge of the cathode is sealed
to attach the two layers of the separator 847 together and thus
encapsulate the cathode 853 between the separators 847. One
technique of sealing the layers includes heat sealing. This can
include a thin line heat sealed around the entire periphery as
shown as region 848 in FIG. 28. In this example, the entire
periphery of the cathode is encapsulated within the separator
envelope except for the lead 849. In one example, the heat sealing
process also cuts the sealed cathode sub-assembly 843 from the web.
In some embodiments, the encapsulation process includes ultrasonic
welding, ultrasonic sealing, hot die sealing, or inductive sealing
the separators together along the periphery of the cathode to form
the encapsulated cathode sub-assembly.
[0177] When encapsulated, cathode 853 is constrained within the
separator envelope-like structure such that cathode 853 does not
shift when sub-assembly 843 is grabbed by the separator material
847. This saves time in manufacturing. For example, instead of
stacking and carefully aligning an anode, a separator, and a
cathode, the stacking operation includes stacking and aligning an
anode and an encapsulated cathode assembly 843. This saves
manufacturing time and makes alignment simpler since each separator
does not have to be aligned with each anode and each cathode since
the separator is automatically aligned during the encapsulation
process. In other words, it cuts the number of individual pieces to
be stacked in half.
[0178] FIG. 30 shows a detail of the tab portion of the
encapsulated cathode sub-assembly 843. The cathode 853 include a
base layer 851 having cathode material 852 pressed or otherwise
mounted onto one or both sides of the base layer. The two separator
layers 847 are sealed at region 850 with tab 849 extending from the
sealed region.
[0179] FIG. 31 shows a detail of a bottom portion of the
encapsulated cathode sub-assembly 843. The sealed region 848 of
separator layers 847 forms a flange 851 around the periphery of the
encapsulated assembly 843. Flange 847, which extends around the
periphery of the cathode sub-assembly (See FIG. 28), offers
shorting protection around the entire periphery of the cathode
rather then just the main surfaces of the cathode as when a single
separator layer is placed between each cathode and each anode
layer. Moreover, the encapsulated structure prevents any flaking
cathode material from floating around the cell once
constructed.
[0180] In one embodiment, stack 814 is formed using the anodes and
cathodes shown in FIGS. 32-33. FIGS. 32-36 show a cathode and anode
interconnection technique according to one embodiment. FIG. 32
shows a cathode 860 having a cathode material 861 mounted upon a
base layer and an uncoated connection portion or tab portion 862
having a proximal portion 863 connected to the main body of cathode
860 and a distal portion 864 extending therefrom. FIG. 33 shows an
anode 865 having an anode material 866 mounted upon a base layer
and an uncoated connection portion or tab portion 867 having a
proximal portion 868 connected to the main body of anode 865 and a
distal portion 869 extending therefrom. In one embodiment,
connection members 862 and 867 include one or more separate members
attached to the anode or cathode by welding, staking, or other
connection method. In other embodiments, connection members 862 and
867 can be integral portions of the anode or the cathode, and can
be punched, laser-cut, or otherwise shaped from the base
layers.
[0181] In one embodiment, an additional layer of material is
provided on either or both of connection members 862 and 867 to
give them a thickness approximately equal to or slightly larger
than the thickness of either cathode 860 or anode 865. This extra
material minimizes the movement of the connection members when they
are squeezed together. A similar structure is discussed below for
FIG. 36B, the discussion of which is incorporated herein by
reference.
[0182] FIG. 34 shows a separator according to one embodiment.
Separator 870 includes a cut-out region 873 which allows the
connection members 862 and 867 to extend beyond the separator. In
some embodiments, a discrete separator is omitted and cathode 860
can be encapsulated within a separator envelop or bag, such as
discussed above.
[0183] FIG. 35 shows a top view of a battery stack 871 including
alternating layers of anodes 865, separators 870 and cathodes 860.
In stack 871, connection members 862 and 867 are overlaying and
underlying each other. As used herein, overlay and underlay refer
to the position or location of portions of the cathodes and anodes
which are commonly positioned from a top view. In the embodiment of
FIG. 35, it is seen that connection members 862 and 867 have some
commonly positioned portions relative to each other and some
portions which are exclusively positioned relative to each
other.
[0184] For instance, proximal sections 868 and 863 are exclusively
positioned or located. This means that at least a portion of
proximal sections 868 and 863 do not overlay or underlay a portion
of the proximal sections of the other proximal section. Conversely,
distal sections 864 and 869 are commonly positioned and each
include at least a portion overlaying or underlaying each
another.
[0185] When stacked as shown in FIG. 35, the edges of distal
sections 864 and 869 form a surface 874. This surface 874 provides
for ease of edge-welding or otherwise connecting connection members
862 and 867 together, as will be described below. Other embodiments
leave one or more gaps in surface 874 when the anodes and cathodes
are stacked.
[0186] After being stacked as discussed above, at least portions of
connection members 862 and 867 are connected to each other. In one
embodiment, distal sections 864 and 867 are edge-welded all along
surface 874. In one embodiment, distal sections 864 and 867 are
soldered along surface 874. In some embodiments, portions of distal
sections 864 and 867 are staked, swaged, laser-welded, or connected
by an electrically conductive adhesive. In one embodiment, they are
spot-welded.
[0187] After being connected, portions of connection members 867
and 864 are removed or separated so that proximal sections 863 and
868 are electrically isolated from each other.
[0188] FIG. 36A shows a portion of stack 871 after portions of
distal sections 864 and 869 have been removed from the stack,
forming a separation 872 between anode connection members 867 and
cathode connection members 862. Separation 872 in the present
embodiment electrically isolates section 862 from section 867.
Proximal sections 863 of each cathode in the stack are still
coupled to each other as are proximal sections 868 of each anode in
the stack. In various embodiments, separation 872 is formed by
laser cutting, punching, and/or tool or machine cutting. In some
embodiments, an electrically insulative material is inserted in
separation 872.
[0189] The battery interconnection example of FIGS. 32-36A can help
prevent errors during the manufacturing steps which may cause
defects in the battery or decrease the reliability of the battery
after it is constructed. It can also help decrease the space of the
interconnections within the battery, which can be important if the
battery is used in an application such as an implantable medical
device. This simple interconnection technique allows
interconnections to be made with as few steps as possible.
[0190] FIGS. 36B, 36C, and 36D show a cathode 843B according to one
embodiment. In this example, cathode 843B includes a connection tab
844B extending from the main body of the cathode. FIG. 36C shows a
side view of cathode 843B. FIG. 36D shows a detail of connection
tab 844B. Connection tab 844B includes one or more additional
layers of a conductive material 845B on each side of a base layer
848B. Material 845B is thick enough to make connection tab 844B
approximately as thick as the cathode itself including base layer
848B and a cathode material 847B. Thus, a stack of cathodes such as
cathode 843B results in the cathode tabs of adjacent cathodes being
generally flush with each other. A neck area 846B is provided to
allow room for the heat sealed separator, as discussed above.
Moreover, neck area 846B also allows for flexibility in the joint
to take up manufacturing tolerance variations.
[0191] FIG. 36E shows a portion of a battery 849B having a battery
stack 850B constructed using cathodes 843B and similarly configured
anodes 851B having thicker connection tabs 860B, which can be
constructed by using additional material on one or both sides of
the anode base layer. In one embodiment, cathodes 843B are
constructed of a paste cathode material as described above. In some
respects, stack 850B is similar to stack 814 discussed above and
the above discussion is incorporated herein by reference. Stack
850B allows for the cathode connection members 843B to be connected
by edge welding, a spot weld, staking, laser welding, etc.
Likewise, the anode connection members 851B are connected together.
Again, the thicker tab structure of the connections members 843B
and 851B allows for the interconnections to be made without having
to squeeze the tabs together, which may damage the structure.
[0192] FIGS. 37-40 show a battery stack 884 constructed according
to one embodiment. Battery stack 884 includes some features as
discussed above for battery stack 24 shown and discussed in FIGS.
2-14, and the above discussion is incorporated herein by
reference.
[0193] FIG. 37 shows a base cathode layer 880 having a terminal tab
881 and one or more legs or extensions A, B, and C. FIG. 38 shows a
base cathode layer 882 having a terminal tab 883. And one or more
legs or extensions D, E, and F.
[0194] FIG. 39 shows battery stack 884 having a sequential stack of
alternating cathode layers and anode layers separated by a
separator. Stack 884 includes base cathode layer 880 and a
plurality of cathode layers which include a tab located in either
the A, B, or C position. Likewise, stack 884 includes base anode
layer 882 and a plurality of anode layers which each include a tab
located in either the D, E, or F position.
[0195] FIG. 40 shows stack 884 after the respective tabs have been
connected together and wrapped around the stack. As noted above, by
spreading the cathode and anode interconnections out over separate
areas, the overall thickness required by the interconnections is
lessened and less space is needed between stack 884 and the battery
case. Terminal tabs 883 and 884 are then attachable to a
feedthrough or the case, as discussed above.
[0196] After being stacked, any of the battery stacks described
above can be taped around the outer surface of the stack to hold
the stack in strict alignment. For example, stack 814 includes a
tape 828.
[0197] FIG. 41 shows a taping fixture 890 according to one
embodiment. Taping fixture 890 includes a tape dispenser 891 that
holds a roll of tape 892. Taping fixture 890 includes a stack
holding fixture 893 which includes a stack holding member 894. A
rotating member 895 is operatively coupled to stack holding member
894 and rotates the stack around a first axis 896. In one example,
the first axis is along the long axis of the battery stack.
Rotating member 895 can include a manual or motor-operated crank.
An indexing member 898 can be used to index and measure the amount
of rotation of the rotating member 895.
[0198] Either one or both of dispenser 891 and fixture 893 are
rotatable around a second, vertical axis 899 so that the two
members 891 and 893 are rotatable relative to each other around the
second axis 899. Second axis 899 is approximately perpendicular to
first axis 896, and generally vertical relative to the work
surface. In one example, second axis 899 approximately intersects
first axis 896.
[0199] FIG. 42 shows a top view of fixture 890. As tape 892 comes
off of tape dispenser 891, the tape forms an angle relative to
stack 897. By rotating the stack or dispenser about second axis
899, the angle of the tape relative to the stack can be varied.
[0200] FIGS. 43A and 43B show one example of a taping process. In
use, tape 892 is applied to a first surface 897A of stack 897. The
stack is then rotated along axis 896. When the tape strip 892 comes
to the edge of the stack 897, the tape dispensing location swings
on an arc about axis 899 to match the angle of the first strip
relative to the tangent line of the edge profile and the stack
continues to rotate around axis 896.
[0201] For example, strip 892 starts out as section 1 across
surface 897A of stack 897. In this example, section 1 has an
approximately 10 degree angle relative to a perpendicular line of
the edge of the stack, which in this example is the tangent line of
the edge. When the tape strip reaches the edge of the stack, the
dispenser is rotated relative to the stack such that the strip is
positioned along side 897B oriented as section 2 (FIG. 43B) which
is approximately 10 degrees on the other side of the perpendicular
from strip 1. Thus there is a 20 degree angle between the two
strips with approximately 10 degrees on each side of a
perpendicular line to the tangent line. When the stack is then
rotated enough along axis 896 such that the tape reaches the edge
of the stack, the dispenser is rotated relative to the stack such
that the strip then is oriented along section 3 (FIG. 43A). This
process can be continued through 2, 3, 4, or more rotations.
[0202] As can be seen by the dotted lines showing strip 2 in FIG.
43A, the tape's orientation is changed as it rounds each edge so
that each side is the matching angle of the other side relative to
the perpendicular of the tangent line of the edge. For example, a
tangent line 893 is shown at the edge between strips 2 and 3. The
angles of strips 2 and 3 are approximately equal relative to this
tangent line. This technique helps eliminate bunching of the tape
at the edges. Moreover, this simple and elegant solution provides
for ease of taping and manufacturing battery stack having
non-standard, non-rectangular shapes.
[0203] FIGS. 44A and 44B show another example wrapping in
accordance with one embodiment. In this example, the tape strip is
started at approximately 10 degrees off the perpendicular. Strip 2
is applied approximately 10 degrees on the other side of the
perpendicular. (FIG. 44B). Strips 3 and 4 are likewise oriented as
described above.
[0204] In general, the degree of rotation of the dispenser relative
to the stack is dependent on the shape of the stack. This system is
general in that it can wrap almost any shape stack. Again, this is
helpful for use on complex, or oddly shaped stacks. Moreover,
fixture 890 allows a stack 897 to be taped in a fixture having only
two rotational axes. This simple fixture allows taping of a stack
having an arbitrarily complex geometry in a single piece,
multi-pass, taping operation.
[0205] Due to the complex geometry on the outer profile of the
stack, a simple tape operation can be difficult. This system
simplifies the equipment needed to dispense and apply a single
continuous piece of tape around the stack and to make multiple
wraps without requiring many axes of motion.
[0206] Referring again to the general configuration of battery 800
shown in FIGS. 25 and 26, FIG. 45 shows further details of battery
800 according to one embodiment. Stack 814 is shown inserted in
case 802 with a portion of case half 804 shown in broken form. The
anode layer subassemblies of stack 814 have their tabs or extension
members 817 brought together and interconnected. A tab 822 is then
attached to the anodes by welding, for example, and attached
directly to case 802, by welding, for example. The extension
members or tabs 819 of the cathode sub-assemblies are brought
together and interconnected and a connection member 824 is
connected to the cathode tabs. Feedthrough post 808 is connected to
tab 824 and extends through a feedthrough hole 809 in the battery
case. The top stack portion 820 is indented relative to middle
stack portion 818 to allow for maximum stack size with the curved
edge case 802.
[0207] FIG. 46 shows a top view of a portion of battery 800.
Feedthrough post 808 communicates outside the battery by being
connected to the cathodes via connection 824. FIG. 47A shows a
cross-section of FIG. 46. In one embodiment, feedthrough hole 809
is a cylindrical structure integral with case 804. Hole 809
includes an inwardly facing surface defining a ferrule portion
809A. Feedthrough post 808 is electrically insulated from case 804
by annular insulating member 813. In one embodiment, annular
insulating member 813 can be a glass member, a ceramic member, an
epoxy member, or a composite member, for example. In one
embodiment, annular member 813 includes TA23 glass, or equivalent.
Feedthrough post 808 extends through a hole in annular member 813.
Feedthrough post 808 can include a molybdenum material. Annular
member 813 electrically insulates feedthrough 808 from case 802 and
provides a hermetic seal of battery 800.
[0208] Annular insulating member 813 has an outer surface abutting
the inward facing cylindrical surface of ferrule portion 809A.
Annular member 813 includes an inner hole that feedthrough post 808
extends through. In one embodiment, annular member 813 is glassed
into the battery case. The integral ferrule structure of this
embodiment provides ease of manufacturing a battery since the
ferrule does not need to be welded onto the case. Moreover, it can
be a cost-effective and size advantageous approach for a
hermetically sealed battery. By installing the feedthrough directly
into the case, a difficult welding step is eliminated since the
case and the feedthrough ferrule are a combined assembly rather
that two separate subassemblies that need to be joined
together.
[0209] FIG. 47B shows a cross-section of FIG. 46. Anode terminal
810 is directly attached to case 802 to complete the connection
from the anodes through tab 822 and via case 802 to terminal
810.
[0210] FIG. 48A shows a terminal 810B according to one embodiment.
Terminal 810B includes a base 64 having a surface 66. A main
terminal extension 63 extends from one surface of base 64 and a
nipple or protrusion 65 extends from opposing surface 66. Terminal
810B can be formed of a metal such as gold-plated nickel.
[0211] FIG. 48B shows a side view of terminal 810B being attached
to a case 802 in accordance with one embodiment. Case 802 is a
metal, such as 304L or 316l SST. A fixture 68 is used to hold
terminal 810B. Fixture 68 and case 802 are oppositely charged. For
example, fixture 68 can negatively charged, while case 802 is
positively charged by an electrode 67, or vice versa. Terminal 810B
is positioned such that protrusion 65 is facing case 802 and is the
closest portion of terminal 810B to the case. As the terminal is
brought closer to the case, protrusion 65 concentrates or focuses
the electrical field developed between the oppositely charged case
and terminal. When the terminal is close enough, a spark or arc is
sent between the protrusion and the case. This spark vaporizes the
nipple and welds the terminal to the case. One example uses a
HCD125 MicroJoin.TM. welding machine set at 30-40 watt-sec power
level at 5 lb. force with a pulse width at the #4 setting on the
machine.
[0212] FIG. 48C shows a view of terminal 810B after being attached
to case 802. The protrusion has vaporized and surface 66 of base 64
is tightly attached to case 802.
[0213] In some embodiments, resistance welding can also be used to
attach terminal 810B to the case. For example, terminal 810B and
the case can be brought in contact and a current is delivered.
Protrusion 65 then melts down and collapses and surface 66 and case
802 are tightly attached.
[0214] FIG. 48D shows further details of terminal 810B according to
one embodiment. In one embodiment, base 64 includes a chamfered
rear surface 64S, for example of approximately 45 degrees. Front
surface 66 can have an angle of approximately 3 degrees. In this
example, base 64 has a diameter of approximately 0.022 to 0.030
inches and protrusion 65 has a diameter of approximately 0.005 to
0.008 inches.
[0215] After the stack is mounted within the battery case, the case
can be welded shut. An electrolyte is filled into the case through
a backfill port, for example. The backfill port is then sealed.
[0216] FIGS. 49A-49B shows a technique for mounting a backfill ball
plug 41 to a backfill port 901, in accordance with one embodiment.
Backfill plug 41 is shown being mounted to a battery case 803.
Backfill port 901 in the battery case has been used to fill the
battery case with electrolyte. One problem during the mounting of
backfill plugs is that the electrolyte can leach out around the
plug before the plug is welded to the case. When this fluid leaches
out, it makes welding difficult. The present technique minimizes
leaching and allows for a hermetically sealed battery.
[0217] In one embodiment, a first welding electrode 902 is adapted
to be used as an applicator to force ball 41 into port 901. For
example, electrode 902 can be given a rounded tip to match the
shape of the backfill plug. In one embodiment, plug 41 can be a
spherical-shaped ball having a diameter slightly larger than port
901 such that there is an interference fit between plug 41 and the
walls 901A defining port 901. For example, in one embodiment, plug
41 has a diameter of approximately 0.026 inches and port 901 has a
diameter of approximately 0.025 inches. As applicator/electrode 902
forces plug 41 into port 901, a second welding electrode 903 is
applied against case 803. A current develops between electrode 902
and 903 traveling through plug 41 and case 803. This welds the
periphery of plug 41 to the case at weld location 905. This welding
technique seals the ball within the port without allowing any
leaching of electrolyte through the gap between the ball and the
port walls.
[0218] In one embodiment, after weld 905 is formed, electrodes 903
and 902 are removed and the battery is sealed. In other
embodiments, as shown in FIG. 49C an optional laser welding step is
provided by a laser welder 907 to further seal the upper periphery
of the ball-shaped plug 41 to the case.
[0219] FIG. 50A shows a backfill plug 910 according to one
embodiment. Plug 910 is a cap-shaped plug having a top portion 911.
In one embodiment, top portion 911 expands outward to cap portion
912 defining a chamfered region 916 between top portion 911 and cap
portion 912. Plug 910 includes a waist section 913 which expands
into a widened section 914 and then a narrowed section 915. In one
embodiment widened section 914 is slightly wider than the diameter
of backfill port 901. For example, widened section 914 can be
approximately 0.026 inches and backfill port 901 can be
approximately 0.025 inches in diameter.
[0220] FIGS. 50B and 50C shows an example of plug 910 being mounted
to backfill port 901. An applicator electrode 917 is adapted to
insert and force plug 910 into backfill port 901 in an interference
fit. During or after applicator/electrode 917 forces plug 910 into
port 901, a second welding electrode 903 is applied against case
803. A current develops between electrodes 910 and 903 traveling
through plug 910 and case 803. This welds the widened portion 914
of plug 910 to a wall 901A of the case at weld location 919. Again,
this technique of welding while forcing seals the plug within the
port without allowing any leaching of electrolyte through the gap
between the plug and the port walls.
[0221] In one embodiment, as shown in FIG. 50C an optional laser
welding step is provided by a laser welder 907 to laser weld the
periphery of the cap 912 of plug 910 to the outer surface of case
803. By providing a chamfered region 916, the laser welding step is
improved. FIG. 50C shows how plug 910 fits within port 901. Cap
portion 912 rests against the outer surface of case 803. Waist
portion 913 is located inside of and not touching the walls of port
901. In one embodiment, plug 910 is formed from stainless
steel.
[0222] FIG. 50D shows a terminal 810C according to one embodiment.
Terminal 810C is a combination backfill plug/terminal. Terminal
810C includes an elongated terminal portion 63C and a spherical
plug portion 41C. Plug portion 41C is dimensioned to interference
fit within backfill hole 901. In one embodiment, terminal 810C can
be attached within the backfill hole 901 and be coupled to the case
803 using the techniques discussed above. For example, a welding
fixture 902 can be used to bring terminal 810C within the backfill
hole 901 and in contact with case 803 as a second welding electrode
903 is brought against the case to weld the spherical ball portion
41C within the hole, as in FIGS. 49A-49C. The combination terminal
810C allows for the elimination of separate terminals and fill
plugs (such as terminal 810 and plug 41 discussed above). By
combining the two members, manufacturing is eased.
[0223] FIG. 50E shows a terminal 810D according to one embodiment.
Terminal 810D is a combination backfill plug/terminal. Terminal
810D includes an elongated terminal portion 63D and a plug portion
910D. Plug portion 910D is similar to plug 910 discussed above and
the above discussion is incorporated herein by reference. As with
terminal 810C, terminal 810D can be attached within the backfill
hole of a battery case.
[0224] In various embodiments of the techniques and structures of
FIGS. 49A-49C and 50A-50E, a parallel gap welder can be used to
perform the weld. Various embodiments utilize a current of
approximately 10 to approximately 45 watt-sec or higher. One
embodiment uses a HCD125 MicroJoin.TM. welder with settings of 30
watt-seconds and 2 lb. force and pulse width at the #4 setting.
[0225] FIG. 51 shows a method for manufacturing a battery in
accordance with one embodiment. The method of FIG. 51 is an example
of one embodiment and it is understood that different steps may be
omitted, combined, and/or the order changed within the scope of one
or more embodiments. Among other steps, method 51 includes
assembling an anode subassembly (930A), assembling a cathode
subassembly (930B), stacking a plurality of anode and cathode
subassemblies into a battery stack (930C), welding the tabs of each
of the anode subassemblies together and welding each of the tabs of
each of the cathode subassemblies together and taping the stack
(930D), providing a battery case for holding the stack (930E),
insulating the outer surface of the stack and inserting the stack
into the case (930F), welding the anodes to the case (930G),
welding the cathodes to a feedthrough (930H), assembling the
feedthrough assembly including glassing the feedthrough through a
feedthrough insulator (930I), welding the case shut and filling the
case with electrolyte (930J), and inserting and welding a backfill
plug to the case (930K).
[0226] In one embodiment, assembling the anode sub-assembly (930A)
can include forming a plurality of discrete anode layers such as
the various anodes discussed above. FIG. 52 shows a schematic
representation of an anode assembly system 940 according to one
embodiment. System 940 includes a first spool 941 holding a roll of
metal base anode material, such as an expanded metal, a solid
metal, or an etched metal. A pair of spools 942A and 942B provide a
layer of lithium on either side or both of the base material. One
or more brushes 946A and 946B clean the lithium layers. The lithium
is laminated onto the base layer at a stage 943. A die-cut
mechanism 944 cuts the individual anodes, and a robotic system 945
removes them.
[0227] FIG. 53 shows a schematic system 950 for forming cathode
layers according to one embodiment. A first spool 951 holds a base
cathode material. A die cut system 952 cuts the layer to a desired
shape. A heat seal system 954 can be provided to seal the
separators around the cathode. The cathode assembly can then
transferred by a robotic system 953.
[0228] FIG. 54 shows a schematic representation of a fixture 1960
for forming a cathode in accordance with one embodiment. Fixture
1960 provides a technique to load a predetermined, precise amount
of a cathode powder onto a cathode carrier strip for use in the
manufacture of cathode layers of a battery. Fixture 1960 generally
includes a pair of dies or clamp members 1961A and 1961B. One or
more guide posts 1964 extend from the inner surface of one of the
clamp members 1961A and 1961B. The opposing clamp member includes
corresponding holes which mate with the guide posts to keep the
pair of members 1961A and 1961B in alignment when they are brought
together. Each of the clamp members 1961A and 1961B include a cut
out or cavity portion 1969.
[0229] A cathode carrier strip 1966 includes a cathode base section
1967 and one or more guide holes 1968. Guide holes 1968 mate with
guide posts 1964 to keep the cathode carrier strip 1966 tightly
aligned in fixture 1960.
[0230] Fixture 1960 includes a pair of punch members or press heads
1962A and 1962B. Each punch member 1962A and 1962B is associated
with one of clamp members 1961A or 1961B such that each punch
member moves back and forth through cut-out portion 1969.
[0231] In use, a preset amount of MnO.sub.2 matrix material is
poured into the cavity in the bottom clamp member 1961B. In one
example, the MnO.sub.2 powder includes a mixture of 90% pure
MnO.sub.2, 5% powder carbon, and 5% PTFE slurry binder. A flat edge
tool is used to spread the MnO.sub.2 powder evenly in the cavity.
The collector strip 1966 is placed in position over the cavity. A
shim 1980 is placed onto the collector strip and fastened down to
hold in position. A preset amount of MnO.sub.2 matrix material is
poured into the cavity 1981 of the shim. The flat edge tool is used
to spread the powder evenly in the shim cavity. Top clamp member
1961A is then positioned over and fastened to the bottom clamp
member.
[0232] FIG. 55 shows a press 1963 applying force to punch members
1962A and 1962B. The fixture 1960 is placed into press 1963 and the
press is cycled with several pressures in steps from low pressure
to high pressure until the powder is compacted to the desired
density. In one embodiment, a pressure of approximately 48,000 psi
is used. In one embodiment, a pressure of approximately 16-21 tons
per square inch is used.
[0233] In one embodiment, fixture 1960 is mounted to a vibrating
system which is actuated to vibrate the fixture either after the
powder is placed within the cavities. The vibration settles the
powder to fill any gaps and makes the powder have a generally
uniform density within the fixture.
[0234] Since the size of the cavities of the fixture and the
density of the cathode powder is known, a precise amount of powder
is compacted onto the carrier strip. Battery cathodes that are
later punched or removed from the strip then contain precise
amounts of the cathode powder and the cathode powder is evenly
distributed across the surfaces of the cathode carrier in a uniform
density. This improves the consistency and reliability of the
batteries. In one example, the powder has a pressed density of
approximately 2.7 g/cm.sup.3 and the cathode has an overall
thickness (including base metal) of approximately 0.0182 inches.
Other embodiments an range form approximately 2.5 to 3.2
g/cm.sup.3.
[0235] FIG. 56 shows a schematic representation of a fixture 960
for forming a cathode in accordance with one embodiment. Fixture
960 provides a technique to load a predetermined, precise amount of
a cathode powder onto a cathode carrier strip for use in the
manufacture of cathode layers of a battery. Fixture 960 generally
includes a pair of clamp members 961A and 961B. One or more guide
posts 964 extend from the inner surface of one of the clamp members
961A and 961B. The opposing clamp member includes corresponding
holes which mate with the guide posts to keep the pair of members
961A and 961B in alignment when they are brought together. Each of
the clamp members 961A and 961B include a cut out portion 969. When
clamp members 961A and 961B are brought together, cut out portions
969 define a cavity 970.
[0236] A cathode carrier strip 966 includes a cathode base section
967 and one or more guide holes 968. Guide holes 968 mate with
guide posts 964 to keep the cathode carrier strip 966 tightly
aligned in fixture 960 such that cathode base section 967 is
located within cavity 970.
[0237] Fixture 960 includes a pair of punch members or press heads
962A and 962B. Each punch member 962A and 962B is associated with
one of clamp members 961A or 961B such that each punch member moves
back and forth through cut-out portion 969. A press 963 applies
force to punch members 962A and 962B. A punch surface 971A and 971B
of each respective member 962A and 962B is brought close together
within cavity 970.
[0238] FIG. 57 shows an example of carrier strip 966 mounted in a
substantially vertical orientation within fixture 960. Members 961A
and 961B are clamped together to hold the carrier strip 966 in
place. A cathode powder 972, such as an MnO.sub.2 mixture, is
placed or deposited within cavity 970. In one embodiment cavity 970
has a width of approximately 0.030 to 0.040 inches. In one example,
powder 972 includes a mixture of 90% pure MnO.sub.2, 5% powder
carbon, and 5% PTFE slurry binder.
[0239] In one embodiment, fixture 960 is mounted to a vibrating
system 974 which is actuated to vibrate the fixture either during
or after the powder is placed within cavity 970. The vibration
settles the powder to fill any gaps and makes the powder have a
generally uniform density within cavity 970. In one embodiment, a
precise amount of powder 972 is placed within cavity 970. The
amount of cathode powder can be varied depending on application of
the cathode.
[0240] After cavity 970 is activated, press 963 is activated and
punch members 962A and 962B press the powder into and onto the base
carrier 966. In one embodiment, a 50 ton press 963 is utilized. In
one embodiment, a pressure of approximately 48,000 psi is used to
press the powder. Another example uses a pressure of approximately
16-21 tons per square inch.
[0241] In one embodiment, cathode powder 972 is sieved before it is
deposited into the cavity to prevent any larger pieces of the
powder to clog up the cavity.
[0242] Since the size of cavity 970 and the tap density of the
cathode powder is known, a precise amount of powder is compacted
onto the carrier strip. Battery cathodes that are later punched or
removed from the strip then contain precise amounts of the cathode
powder and the cathode powder is evenly distributed across the
surfaces of the cathode carrier in a uniform density. This improves
the consistency and reliability of the batteries. In one example,
the powder has a pressed density of approximately 2.7 g/cm.sup.3
and the cathode has an overall thickness (including base metal) of
approximately 0.0182 inches. Other embodiments an range from
approximately 2.5 to 3.2 g/cm.sup.3.
[0243] FIGS. 58, 59, and 60 show a top, side and front view of a
cathode forming fixture 974 according to one embodiment. Fixture
974 includes base tabs 975 to mount the fixture to a surface.
Clamps 976A and 976B hold a carrier strip within the fixture with a
guide member 984 to hold the carrier strip and to keep the two
halves of fixture 974 in alignment.
[0244] A pair of punch heads 977A and 977B each have a punch member
983A and 983B associated therewith. The area between the punch
members 983A and 983B defines the cavity of the fixture. A spring
980 is positioned between each punch head 977A and 977B and its
associated punch member 983A and 983B. A pair of plug members 978A
and 978B are located on top of the fixture, and each plug member
has a thumbscrew or other retaining member 979 engaged through the
plug and into a block member 981 or 982 located below the plug. A
guide post 982 provides further alignment between the two halves of
the fixture. A bushing 982 can be used around guide post 982.
[0245] As noted above, some embodiments use a cathode paste (such
as an MnO.sub.2 paste) which is coated and then rolled or pressed
onto one or more sides of a cathode base layer, such as stainless
steel strip or a mesh strip. Individual cathodes can be then
excised out of the strip. In some examples, the base layer is at
least partially pre-cut or pre-scored into the desired cathode
shape.
[0246] Referring again to FIG. 51, forming a cathode sub-assembly
(930B) can include encapsulating each cathode in a separator
envelop, as discussed above.
[0247] In one embodiment, the present system provides a battery
electrode stack having 12 anode sub-assemblies and 11 cathode
sub-assemblies (having sealed separators). The two anode
sub-assemblies located on the stack ends are smaller to accommodate
a radius case edge. These two end anode sub-assemblies have lithium
attached to one side of their base collector plate only. The two
outside cathode sub-assembly layers are also smaller in order to
accommodate the radius of the case. Each anode and cathode
sub-assembly layer includes an extension tab that extends out of
the stack. The extension tabs are welded together when the stack is
completed in order to connect the layers to one another. In one
example, the extension tabs are welded with three spot welds and
the ends of the tabs are clipped. A ribbon tab is welded to the
cathode extensions for connecting them to the feedthrough. The cell
is insulated and inserted into the case. The ribbon extension is
welded to the feedthrough and the anode extension is welded
directly to the case. The case portions are put together and welded
around their interface.
[0248] FIG. 61 illustrates one of the many applications for the
battery. For example, one application includes an implantable
medical device 990 which provides therapeutic stimulus to a heart
muscle, for instance, a defibrillator or a cardiac
resynchronization therapy device (CRTD). The medical device 990 is
coupled with a lead system 991. The lead system 991 is implantable
in a patient and electrically contacts strategic portions of a
patient's heart. The medical device 990 includes circuitry 992
which can include monitoring circuitry, therapy circuitry, and a
capacitor coupled to a battery 993. Circuitry 992 is designed to
monitor heart activity through one or more of the leads of the lead
system 991. The therapy circuitry can deliver a pulse of energy
through one or more of the leads of lead system 991 to the heart,
where the medical device 990 operates according to well known and
understood principles. The energy of the device are developed by
charging up the capacitor by using battery 993.
[0249] In addition to implantable defibrillators, the battery can
be incorporated into other cardiac rhythm management systems, such
as heart pacers, combination pacer-defibrillators, congestive heart
failure devices, and drug-delivery devices for diagnosing or
treating cardiac arrhythmias. Moreover, the battery can be
incorporated also into non-medical applications. One or more
teachings of the present discussion can be incorporated into
cylindrical batteries.
[0250] FIG. 62 shows a performance chart of an example battery
constructed according to one embodiment. The battery of FIG. 62 was
constructed having anodes and cathodes having the values shown in
Chart A, below, and was formed in the manner of battery stack of
FIG. 27.
TABLE-US-00001 CHART A Active Estimated Area Total Area Volume
Material Capacity Type Quantity (cm2) (cm2) (cc) Mass (g) (A-h)
Anode- 2 surfaces 7.526 15.05 0.1147 0.0612 0.236 small (2 anode
layers) Anode- 20 surfaces 8.013 160.26 1.2211 0.652 2.517 large
(10 anode layers) Total 15.539 175.31 1.3358 0.7132 2.753 Cathode-
4 surfaces 7.796 31.184 0.6812 1.6552 0.3724 small (2 cathode
layers) Cathode - 18 surfaces 8.29 149.22 3.2596 7.9207 1.7821
large (9 cathode layers) Total 16.086 180.404 3.9407 9.576 2.1546
Ratio 1.278 Li/Mn02 Cathode 0.017 a/cm.sup.2 current density
[0251] A total of 12 lithium anodes were used, with the anodes on
each end of the stack only having one surface with lithium and
having a smaller area than the other anodes. The chart indicates
that the two end anodes each provide one anode surface with the
remainder of the anodes providing two anode surfaces each. A total
of 11 MnO.sub.2 cathodes were used, with the end two cathodes being
of smaller surface area. All the cathodes had both surfaces having
MnO.sub.2, so the chart indicates four small cathode surfaces and
18 large cathode surfaces. The cathodes were prepared using a
precisely measured amount of cathode powder pressed into the base
layer, as discussed above.
[0252] After being pressed, the cathodes were heat-sealed between
two separators, as discusses above. The anodes and cathodes were
then alternatingly stacked using the fixture of FIG. 18B. The stack
was then taped using the fixture of FIG. 41. The outer periphery of
the stack was then taped by a double wrapping of an insulative tape
as in FIG. 26B. The anode and cathode extension tabs were brought
together and welded. The cathode tabs were connected to the
feedthrough and the anode tabs were connected to the case. The case
portions were put together and welded around their interface. The
battery was filled with electrolyte and sealed using techniques
discussed above.
[0253] The battery of chart A and FIG. 62 was designed for an
implantable medical device, such as a defibrillator. The battery
was designed to have a capacity of approximately 2.0 amp-hours with
a life span of 6 to 7 years and a peak current level of
approximately 3 amps. Using the methods and structures discussed
herein, the battery was constructed to such specifications while
having a shape friendly design suitable for fitting into a design
space within the defibrillator case and while only having a total
volume of 8.64 cm.sup.3.
[0254] In various embodiments, batteries for different applications
can be constructed using various design parameters. For example,
some embodiments have a total battery volume of less than
approximately 9.0 cm.sup.3. Some embodiments have a total battery
volume of between approximately 8.0 cm.sup.3 and 9.0 cm.sup.3. Some
embodiments have a total battery volume of between approximately
8.5 cm.sup.3 and 9.0 cm.sup.3. Some batteries have a power of
approximately 2 to 5 amps and a capacity of approximately 2.0
amp-hours or greater. Other batteries can be manufactured using the
techniques herein for different applications. Various embodiments
include batteries having sizes ranging from about 3.0 cm.sup.3 to
about 12 cm.sup.3. In general, the capacity in amp-hours/cm.sup.3
of these different size batteries scales up linearly
[0255] Referring again to FIG. 62, the charge time A of the battery
is seen to be substantially constant over the useful life of the
battery. For example, with a 2-4 amp current drain, in one
embodiment, the charge time is generally about 6 to 7 seconds. Some
embodiments have a substantially constant charge time between
approximately 5 to 10 seconds. The line C in FIG. 62 denotes the
open circuit voltage (OCV) of the battery. The line B denotes the
Pulse One Average (PlA) of the battery. In one example, the P1A can
be used to trigger ERI (elective replacement indicator). This
triggers a 3 month clock until EOL (end of life). In the present
example, EOL is approximately when OCV reaches 2.75 volts or when
P1A reaches 1.75 volts.
[0256] The battery of FIG. 62 can also be constructed using a paste
cathode construction, as discussed above. Moreover, the other anode
and cathode interconnection techniques discussed above can also be
used to construct a battery of the desired characteristics.
[0257] In one or more embodiments, the above described methods and
structures provide for a battery making efficient use of space
within the case, increased electrode surface area and increased
capacity for a battery of a given set of dimensions. In one
example, variation in the outer dimensions of one battery stack to
another battery stack is reduced because each is formed of a
precisely aligned series of electrode layers. Dimensional
variations in the battery stack resulting from variation in the
reference points from case to case or alignment apparatus to
alignment apparatus can be reduced or eliminated. This provides
improved dimensional consistency in production and allows for
reduced tolerances between the battery stack and the battery case.
This allows for more efficient use of space internal to the battery
case.
[0258] In one or more embodiments, different battery chemistries
can be used for the cathode structures discussed above. For
example, silver vanadium oxide (SVO), carbon monoflouride (Cfx),
and carbon vanadium (CVO) can be utilized in accordance with some
embodiments. In addition to primary batteries, batteries according
to some embodiments can be formed as secondary type batteries or
rechargeable batteries such as Lithium ion.
[0259] It is to be understood that the above description is
intended to be illustrative, and not restrictive. Many other
embodiments will be apparent to those of skill in the art upon
reading and understanding the above description. It should be noted
that embodiments discussed in different portions of the description
or referred to in different drawings can be combined to form
additional embodiments of the present invention. The scope of the
invention should, therefore, be determined with reference to the
appended claims, along with the full scope of equivalents to which
such claims are entitled.
* * * * *