U.S. patent application number 10/665687 was filed with the patent office on 2004-03-18 for electric storage battery construction and method of manufacture.
This patent application is currently assigned to Quallion LLC. Invention is credited to Skinlo, David M..
Application Number | 20040053116 10/665687 |
Document ID | / |
Family ID | 26863390 |
Filed Date | 2004-03-18 |
United States Patent
Application |
20040053116 |
Kind Code |
A1 |
Skinlo, David M. |
March 18, 2004 |
Electric storage battery construction and method of manufacture
Abstract
An electric storage battery and method of manufacture thereof
characterized by a feedthrough pin which is internally directly
physically and electrically connected to an inner end of a positive
electrode substrate. A C-shaped mandrel extends around the pin and
substrate end enabling the pin/mandrel to be used during the
manufacturing process as an arbor to facilitate winding layers of a
spiral jellyroll electrode assembly. The pin additionally extends
from the battery case and in the final product constitutes one of
the battery terminals with the battery case comprising the other
terminal. Active material is removed from both sides of the outer
end of the negative electrode in the jellyroll to allow room for
adhesive tape to secure the jellyroll. The electrolyte is injected
through the open end of the case after the endcap is welded to the
negative electrode but before sealing the endcap to the case. The
electrolyte is preferably injected through the C-shaped mandrel to
facilitate and speed filling.
Inventors: |
Skinlo, David M.; (Valencia,
CA) |
Correspondence
Address: |
M. Elizabeth Bush
Quallion LLC
P.O. Box 923127
Sylmar
CA
91392-3127
US
|
Assignee: |
Quallion LLC
Sylmar
CA
|
Family ID: |
26863390 |
Appl. No.: |
10/665687 |
Filed: |
September 17, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10665687 |
Sep 17, 2003 |
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10167688 |
Jun 12, 2002 |
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6670071 |
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60348665 |
Jan 15, 2002 |
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Current U.S.
Class: |
429/94 ;
29/623.1; 429/186 |
Current CPC
Class: |
H01M 50/119 20210101;
H01M 50/545 20210101; Y10T 29/49112 20150115; Y10T 29/49115
20150115; H01M 6/10 20130101; H01M 50/543 20210101; Y02P 70/50
20151101; H01M 50/538 20210101; H01M 50/548 20210101; Y10T 29/49108
20150115; H01M 50/154 20210101; H01M 50/107 20210101; H01M 10/0431
20130101; H01M 50/116 20210101; H01M 50/559 20210101; Y10T 29/4911
20150115; Y02E 60/10 20130101 |
Class at
Publication: |
429/094 ;
429/186; 029/623.1 |
International
Class: |
H01M 006/10; H01M
010/04 |
Claims
We claim:
1. An electric storage battery including: a case comprising a
peripheral wall defining an interior volume; and an electrode
assembly mounted in said interior volume, said electrode assembly
including: an electrically conductive elongate pin; and first and
second opposite polarity electrode strips wound together to form a
spiral roll, each electrode strip having inner and outer ends,
wherein said first electrode strip is electrically coupled to said
pin at said inner end; and a hollow elongate mandrel closely fitted
around said pin for mechanically reinforcing said pin.
2. The battery of claim 1 wherein said pin extends exteriorly of
said case peripheral wall to function as a first battery
terminal.
3. The battery of claim 1 wherein said mandrel is electrically
coupled to said pin.
4. The battery of claim 1 wherein said first electrode strip inner
end is directly connected to said pin by at least one weld.
5. The battery of claim 1 wherein said pin consists of a PtIr
alloy.
6. The battery of claim 1 further comprising a first end cap
mounted on said pin, said first end cap including an electrical
insulator; and wherein said pin extends through and is hermetically
sealed to said end cap electrical insulator.
7. The battery of claim 1 wherein said mandrel defines an elongate
slot; and wherein said first electrode strip extends through said
mandrel slot.
8. The battery of claim A1 wherein said mandrel is welded to said
pin.
9. The battery of claim A1 wherein said mandrel comprises titanium
or an alloy thereof.
10. An electric storage battery made by the steps of: providing an
electrically conductive elongate pin having inner and outer ends;
providing a first polarity electrode strip; providing a second
polarity electrode strip; electrically connecting a first end of
the first polarity electrode strip to the pin proximate to the pin
inner end; mounting a reinforcing mandrel on the pin; and winding
together the first polarity electrode strip and the second polarity
electrode strip to form a spiral roll having at least a portion of
the pin within the spiral roll.
11. The battery of claim 10 wherein said steps further include the
step of mounting the spiral roll in a case with the pin outer end
extending exteriorly of the case to form a first battery
terminal.
13. The battery of claim 10 wherein said steps further includ the
step of electrically coupling the reinforcing mandrel to the
pin.
14. The battery of claim 10 wherein said step of winding together
the first polarity electrode strip and the second polarity
electrode strip comprises rotating the pin.
15. The battery of claim 10 wherein said step of providing an
electrically conductive elongate pin includes a step of: forming an
end cap including an insulating member on the pin hermetically
sealed thereto and positioned proximate to but spaced from the pin
outer end.
16. The battery of claim 3 wherein said steps further include a
step of mounting a conductive member around the insulating member;
and electrically connecting the conductive member to the case.
17. The battery of claim 1 wherein said steps further include a
step of welding the reinforcing mandrel to the pin.
18. The battery of claim 1 wherein the mandrel comprises a tube
having a slot therein and wherein said winding step further
includes the steps of: inserting a drive key into the slot; and
orbiting the drive key to rotate the mandrel and pin.
19. The battery of claim 1 wherein the mounted mandrel comprises a
channel and wherein said steps further include a step of injecting
electrolyte through the channel.
20. A method of constructing an electric storage battery including:
providing an electrically conductive elongate pin having inner and
outer ends; providing a first polarity electrode strip; providing a
second polarity electrode strip; electrically connecting a first
end of said first polarity electrode strip to said pin proximate to
said pin inner end; mounting a reinforcing mandrel on the pin;
winding together said first polarity electrode strip and said
second polarity electrode strip to form a spiral roll having at
least a portion of the pin within the spiral roll.
21. The method of claim 20 and further including the step of:
mounting said spiral roll in a case with said pin outer end
extending exteriorly of said case to form a first battery
terminal.
22. The method of claim 20 and further including the step of:
electrically coupling the reinforcing mandrel to the pin.
23. The method of claim 20 wherein said step of winding together
the first polarity electrode strip and the second polarity
electrode strip comprises rotating the pin.
24. The method of claim 20 wherein said step of providing said
electrically conductive elongate pin includes a step of: forming an
end cap including an insulating member on said pin hermetically
sealed thereto and positioned proximate to but spaced from said pin
outer end.
25. The method of claim 24 including the further step of mounting a
conductive member around said insulating member; and electrically
connecting said conductive member to said case.
26. The method of claim 20 including a further step of welding the
reinforcing mandrel to the pin.
27. The method of claim 20 said step of mounting a reinforcing
mandrel comprises mounting a mandrel comprising a tube having a
slot therein; and wherein said winding step further includes the
steps of: inserting a drive key into the slot; and orbiting the
drive key to rotate the mandrel and pin.
28. The method of claim 20 wherein the said step of mounting a
reinforcing mandrel comprises providing a channel and wherein said
steps further include a step of injecting electrolyte through the
channel.
29. An electrode assembly including: an electrically conductive,
elongate pin; an elongate reinforcing mandrel mounted on at least a
portion of said pin; and a spiral roll comprising first and second
opposite polarity electrode strips and at least one separator strip
separating said electrode strips mounted on said pin, wherein one
of said electrode strips is electrically coupled to said pin.
30. The electrode assembly of claim 29 wherein said mandrel is
C-shaped and defines a longitudinal slot; and wherein an inner nd
of said first electrode strip extends through said mandrel slotand
is electrically connected to said pin.
31. The electrode assembly of claim 29 wherein said pin comprises a
portion extending beyond said spiral roll to form a battery
terminal.
32. The electrode assembly of claim 29 wherein said mandrel is
crimped onto said pin.
33. The electrode assembly of claim 29 wherein the mounted mandrel
has a channel through which electrolyte can be injected.
34. An electrode assembly made by the steps of: providing an
electrically conductive, elongate pin; providing a first polarity
electrode strip; providing a second polarity electrode strip;
electrically connecting a first end of the first polarity electrode
strip to the pin; mounting a reinforcing mandrel on the pin; and
winding together the first polarity electrode strip and the second
polarity electrode strip to form a spiral roll having at least a
portion of the pin and the mandrel interior to the spiral roll.
35. The assembly of claim 34 wherein said steps further include a
step of crimping the reinforcing mandrel to the pin.
36. The assembly of claim 34 wherein said steps further include a
step of welding the reinforcing mandrel to the pin.
37. The assembly of claim 34 wherein said step of winding together
the first polarity electrode strip and the second polarity
electrode strip comprises rotating the pin and the mandrel.
38. The assembly of claim 34 wherein said step of winding together
the first polarity electrode strip and the second polarity
electrode strip to form a spiral roll comprises leaving a portion
of the pin extending beyond the spiral roll to form a battery
terminal.
39. A method of constructing an electric storage battery including:
providing an electrically conductive, elongate pin; providing a
first polarity electrode strip; providing a second polarity
electrode strip; electrically connecting a first end of said first
polarity electrode strip to said pin; mounting a reinforcing
mandrel on said pin; and winding together the first polarity
electrode strip and the second polarity electrode strip to form a
spiral roll.
40. The method of claim 39 including the further step of crimping
the reinforcing mandrel to the pin.
41. The method of claim 39 including the further step of welding
the reinforcing mandrel to the pin.
42. The method of claim 39 wherein said step of winding together
the first polarity electrode strip and the second polarity
electrode strip comprises rotating the pin and the mandrel.
42. The method of claim 39 wherein said step of winding together
the first polarity electrode strip and the second polarity
electrode strip to form a spiral roll comprises leaving a portion
of the pin extending beyond the spiral roll to form a battery
terminal.
43. An electric storage battery comprising: an electrically
conductive case sealed by first and second end caps; an
electrically conductive terminal pin extending through said first
end cap and electrically insulated from said case; an electrode
assembly disposed within said case and comprising first and second
opposite polarity electrodes separated by separators wherein said
first electrode is electrically coupled to said pin; a flexible
conductive tab electrically coupled to said second electrode
proximate a first location at the seal formed between said second
end cap and said case; wherein said second end cap has a center and
wherein said second end cap has a width from said first location to
a second location at the seal formed between said second end cap
and said case measured along a line through said center; and said
tab electrically connected to said second end cap at a third
location between said second location and said center of said
second end cap.
44. The battery of claim 43 wherein said case has no separate fill
hole.
45. The battery of claim 43 wherein said second end cap is welded
to said tab flat against an inner face of said second end cap.
46. The battery of claim 43 wherein said second end cap is circular
and wherein said width is a diameter.
47. An electric storage battery made by the steps of: providing a
case comprising a peripheral wall of electrically conductive
material defining an interior volume and having first and second
wall openings communicating with the interior volume; providing an
electrically conductive terminal pin extending through a first end
cap and electrically insulated from the case providing an electrode
assembly comprising first and second opposite polarity electrodes
electrically connecting the first electrode to the pin; forming a
flexible conductive tab extending beyond a second edge of the
electrode assembly and electrically connected to the second
electrode; mounting the electrode assembly in the interior volume
with the pin extending out through the first wall opening and the
tab extending out through the second wall opening; mounting the
first end cap to seal the first wall opening; providing a second
end cap of electrically conductive material; and fastening the
second end cap to the tab in a manner to provide an electrical
connection therebetween.
48. The electric storage battery of claim 47 wherein said steps
further include a further step of depositing electrolyte into the
case through the second wall opening following said step of
fastening the second end cap to the tab.
49. The electric storage battery of claim 47 wherein said step of
fastening the second end cap to the tab includes welding the tab
flat against an inner face of the second end cap.
50. The electric storage battery of claim 49 including the further
step of mounting the end cap in the second wall opening to seal the
second wall opening.
51. A method of constructing an electric storage battery including:
providing a case comprising a peripheral wall of electrically
conductive material defining an interior volume and having first
and second wall openings communicating with the interior volume;
providing an electrically conductive terminal pin extending through
a first end cap and electrically insulated from the case providing
an electrode assembly comprising first and second opposite polarity
electrodes wherein the first electrode is electrically connected to
the pin; forming a flexible conductive tab extending beyond a
second edge of the electrode assembly and electrically connected to
the second electrode; mounting the electrode assembly in the
interior volume with the pin extending out through the first wall
opening and the tab extending out through the second wall opening;
mounting the first end cap to seal the first wall opening;
providing a second end cap of electrically conductive material; and
fastening the second end cap to the tab in a manner to provide a
mechanical and electrical connection therebetween.
52. The method of claim 51 including a further step of depositing
electrolyte into the case through the second wall opening after
said step of fastening the second end cap to the tab.
53. The method of claim 51 wherein said step of fastening the
second end cap to the tab includes welding the tab flat against an
inner face of the second end cap.
54. The method of claim 53 including the further step of mounting
the end cap in the second wall opening to seal the second wall
opening.
55. An electric storage battery comprising: an electrically
conductive case hermetically sealed by first and second end caps,
wherein said case has no separate fill holes and wherein said first
and second end caps have no separate fill holes; an electrically
conductive terminal pin extending through said first end cap and
electrically insulated from said case; an electrode assembly
disposed within said case and comprising first and second opposite
polarity electrodes separated by separators wherein said first
electrode is electrically coupled to said pin; and a flexible
conductive tab electrically coupled to said second electrode and to
said second end cap.
56. An electric storage battery made by the steps of: providing a
case comprising a peripheral wall of electrically conductive
material defining an interior volume and having first and second
wall openings communicating with the interior volume; providing an
electrically conductive terminal pin extending through the first
end cap and electrically insulated from the case; providing an
electrode assembly comprising first and second opposite polarity
electrodes electrically coupling the first electrode to the pin;
mounting the electrode assembly in the interior volume with the pin
extending out through the first wall opening; mounting the first
end cap to seal the first wall opening; providing a second end cap
of electrically conductive material; and electrically coupling the
second electrode to the second end cap; depositing electrolyte into
the case through the second wall opening; and mounting the end cap
in the second wall opening to seal the second wall opening.
57. The electric storage battery of claim 56 wherein the step of
electrically coupling the second electrode to the second end cap
precedes the step of depositing electrolyte into the case through
the second wall opening.
58. A method of constructing an electric storage battery including:
providing a case comprising a peripheral wall of electrically
conductive material defining an interior volume and having first
and second wall openings communicating with the interior volume;
providing an electrically conductive terminal pin extending through
the first end cap and electrically insulated from the case;
providing an electrode assembly comprising first and second
opposite polarity electrodes electrically coupling the first
electrode to the pin; mounting the electrode assembly in the
interior volume with the pin extending out through the first wall
opening; mounting the first end cap to seal the first wall opening;
providing a second end cap of electrically conductive material; and
electrically coupling the second electrode to the second end cap;
depositing electrolyte into the case through the second wall
opening; and mounting the end cap in the second wall opening to
seal the second wall opening.
59. The method of claim 58 wherein the step of electrically
coupling the second electrode to the second end cap precedes the
step of depositing electrolyte into the case through the-second
wall opening.
60. A hermetically sealable electric storage battery comprising: a
case having an open end; a first electrically conductive terminal
electrically insulated from said case; an electrode assembly
disposed within said case and comprising first and second opposite
polarity electrodes separated by separators wherein said first
electrode is electrically coupled to said first terminal; a
flexible conductive tab electrically coupled to said second
electrode proximate a first location at said case open end; said
tab electrically connected to said end cap at a second location
whereby said end cap has a first bias position tending to keep said
case open end open and a second bias position tending to close said
case open end.
61. The battery of claim 60 wherein said first bias position
orients said end cap approximately perpendicular to said open
end.
62. The battery of claim 60 wherein said second end cap is welded
to said tab flat against an inner face of said second end cap.
63. The battery of claim 60 wherein: said end cap is circular and
has a radius R; the distance from said second location to said case
open end is a length L; and L.ltoreq.2R.
64. The battery of claim 63 wherein said second location is above
the center of said end cap in said first bias position.
65. The battery of claim 63 wherein said end cap overlaps the case
by approximately R/2 in said second bias position.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/348,665, filed Jan. 15, 2002.
FIELD OF THE INVENTION
[0002] This invention relates generally to electric storage
batteries and more particularly to a battery construction, and
method of manufacture thereof, suitable for use in implantable
medical devices.
BACKGROUND OF THE INVENTION
[0003] Rechargeable electric storage batteries are commercially
available in a wide range of sizes for use in a variety of
applications. As battery technology continues to improve, batteries
find new applications which impose increasingly stringent
specifications relating to physical size and performance. Thus, new
technologies have yielded smaller and lighter weight batteries
having longer storage lives and higher energy output capabilities
enabling them to be used in an increasing range of applications,
including medical applications, where, for example, the battery can
be used in a medical device which is implanted in a patient's body.
Such medical devices can be used to monitor and/or treat various
medical conditions.
[0004] Batteries for implantable medical devices are subject to
very demanding requirements, including long useful life, high power
output, low self-discharge rates, compact size, high reliability
over a long time period, compatibility with the patient's internal
body chemistry, etc. Although various battery chemistries have been
tried, lithium ion technology is generally accepted as the
preferred chemistry for medical implant applications.
[0005] Such electric storage batteries are generally comprised of a
tubular metal case enveloping an interior cavity which contains an
electrode assembly surrounded by a suitable electrolyte. The
electrode assembly generally comprises a plurality of positive
electrode, negative electrode, and separator layers which are
typically stacked and/or spirally wound to form a jellyroll. The
positive electrode is generally formed of a metal substrate having
positive active material coated on both faces of the substrate.
Similarly, the negative electrode is formed of a metal substrate
having negative active material coated on both faces of the
substrate. In forming an electrode assembly, separator layers are
interleaved between the positive and negative electrode layers to
provide electrical isolation.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to an electric storage
battery incorporating one or more aspects described herein for
enhancing battery reliability while minimizing battery size. In
addition, the invention is directed to a method for efficiently
manufacturing the battery at a relatively low cost.
[0007] In accordance with a first significant aspect of the
invention, a feedthrough pin is provided which is directly
physically and electrically connected to the inner end of an
electrode substrate (e.g., positive), as by welding. The pin is
used during the manufacturing process as an arbor to facilitate
winding the layers to form an electrode assembly jellyroll.
Additionally, in the fully manufactured battery, the pin extends
through a battery case endcap and functions as one of the battery
terminals. The battery case itself generally functions as the other
battery terminal.
[0008] More particularly, in accordance with an exemplary preferred
embodiment, the inner end of the positive electrode substrate is
spot welded to the feedthrough pin to form an electrical
connection. The substrate, e.g., aluminum, can be very thin, e.g.,
0.02 mm, making it difficult to form a strong mechanical connection
to the pin, which is preferably constructed of a low electrical
resistance, highly corrosion resistant material, e.g., platinum
iridium, and can have a diameter on the order of 0.40 mm. In order
to mechanically reinforce the pin and secure the pin/substrate
connection, a slotted C-shaped mandrel is provided. The mandrel is
formed of electrically conductive material, e.g., titanium-6AI-4V,
and is fitted around the pin, overlaying the pin/substrate
connection. The mandrel is then preferably welded to both the pin
and substrate. The mandrel slot defines a keyway for accommodating
a drive key which can be driven to rotate the mandrel and pin to
wind the electrode assembly layers to form the spiral
jellyroll.
[0009] In accordance with a further significant aspect of the
invention, the outer layer of the jellyroll is particularly
configured to minimize the size, i.e., outer radius dimension, of
the jellyroll. More particularly, in the exemplary preferred
embodiment, the active material is removed from both faces of the
negative electrode substrate adjacent its outer end. The thickness
of each active material coat can be about 0.04 mm and the thickness
of the negative substrate can be about 0.005 mm. By baring the
outer end of the negative electrode substrate, it can be adhered
directly, e.g., by an appropriate adhesive tape, to the next inner
layer to close the jellyroll to while minimizing the roll outer
radius dimension.
[0010] A battery case in accordance with the invention is comprised
of a tubular case body having open first and second ends. The
feedthrough pin preferably carries a first endcap physically
secured to, but electrically insulated from, the pin. This first
endcap is preferably secured to the case body, as by laser welding,
to close the open first end and form a leak free seal. With the
jellyroll mounted in the case and the first endcap sealed, the
interior cavity can thereafter be filled with electrolyte from the
open second end.
[0011] In accordance with a still further aspect of the invention,
the jellyroll assembly is formed with a flexible electrically
conductive tab extending from the negative electrode substrate for
electrical connection to the battery case. In accordance with a
preferred embodiment, the tab is welded to a second endcap which is
in turn welded to the case. The tab is sufficiently flexible to
enable the second endcap to close the case body second end after
the interior cavity is filled with electrolyte via the open second
end. In accordance with an exemplary preferred embodiment, the tab
is welded to the inner face of the second endcap such that when the
jellyroll is placed in the body, the tab locates the second endcap
proximate to the body without obstructing the open second end.
After electrolyte filling, the case body is sealed by bending the
tab to position the second endcap across the body second end and
then laser welding the endcap to the case body.
BRIEF DESCRIPTION OF THE FIGURES
[0012] FIG. 1 is a side view of a feedthrough pin subassembly in
accordance with the invention;
[0013] FIG. 2 is a longitudinal sectional view through the
subassembly of FIG. 1;
[0014] FIG. 3 is a plan view of a positive electrode strip utilized
in the exemplary preferred electrode assembly in accordance with
the invention;
[0015] FIG. 4 is a side view of the positive electrode strip of
FIG. 3;
[0016] FIG. 5 is an enlarged sectional view of the area A of FIG. 4
showing the inner end of the positive electrode strip of FIGS. 3
and 4;
[0017] FIG. 6 is an isometric view showing the bared inner end of
the positive electrode substrate spot welded to the feedthrough pin
and configured to receive a C-shaped mandrel thereon;
[0018] FIG. 7 is an end view showing the C-shaped mandrel being
crimped to the pin and electrode;
[0019] FIG. 8 is an end view showing the C-shaped mandrel mounted
on the pin and capturing the positive electrode substrate
therebetween;
[0020] FIG. 9 is an isometric view depicting a drive key
accommodated in the slot of the C-shaped mandrel;
[0021] FIG. 10 is a plan view showing the drive key coupled to a
drive motor for rotating the C-shaped mandrel;
[0022] FIG. 11 is a schematic end view depicting how rotation of
the C-shaped mandrel and pin can wind positive electrode, negative
electrode, and separator strips to form a spiral jellyroll
electrode assembly;
[0023] FIG. 12 is a plan view of a negative electrode strip
utilized in the exemplary preferred electrode assembly in
accordance with the invention;
[0024] FIG. 13 is a side view of the negative electrode strip of
FIG. 12;
[0025] FIG. 14 is an enlarged sectional view of the area A of FIG.
13 showing the inner end of the negative electrode strip of FIGS.
12 and 13;
[0026] FIG. 15 is an enlarged sectional view of the area B of FIG.
13 showing the outer end of the negative electrode strip of FIGS.
11 and 12;
[0027] FIG. 16 is an isometric view showing that the layers of a
spirally wound electrode assembly, i.e., jellyroll;
[0028] FIG. 17 is a plan view of the negative electrode strip
showing the attachment of a flexible electrically conductive tab to
the bared outer end of the negative electrode substrate;
[0029] FIG. 18 is an enlarged sectional view showing how the outer
turn of the negative electrode strip is taped to the next inner
layer to close the jellyroll to minimize its outer radius
dimension;
[0030] FIG. 19 is an isometric view depicting the jellyroll
electrode assembly being inserted into a cylindrical battery case
body;
[0031] FIG. 20 is an isometric view showing a battery case body
with the negative electrode tab extending from the open case
body;
[0032] FIG. 21 is an isometric view showing how the negative
electrode tab is mechanically and electrically connected to an
endcap for sealing the case body second end;
[0033] FIG. 22 is a side view showing how the negative electrode
tab holds the second endcap proximate to the case body second end
without obstructing the open second end;
[0034] FIG. 23 is a front view showing the weld position and the
relationship between the various components; and
[0035] FIG. 24 is an enlarged sectional view of the second end of
the battery case showing the endcap in sealed position.
DETAILED DESCRIPTION
[0036] Attention is initially directed to FIGS. 1 and 2 which
illustrate a preferred feedthrough pin subassembly 10 utilized in
accordance with the present invention. The subassembly 10 is
comprised of an elongate pin 12, preferably formed of a solid
electrically conductive material, having low electrical resistance
and high corrosion resistance such as platinum iridium, preferably
90Pt/10lr. The pin 12 extends through, and is hermetically sealed
to a header 14. The header 14 is comprised of dielectric disks,
e.g., ceramic, 16 and 18 which sandwich a glass hollow cylinder 20
therebetween. The glass hollow cylinder is hermetically sealed to
the pin 12. The outer surface of the glass hollow cylinder 20 is
sealed to the inner surface of an electrically conductive hollow
member 22, e.g., titanium-6AI-4V. As will be seen hereinafter, the
conductive hollow material 22 functions as a battery case endcap in
the final product to be described hereinafter.
[0037] Attention is now directed to FIGS. 3, 4, and 5 which
illustrate a preferred positive electrode strip 30 which is
utilized in the fabrication of a preferred spirally wound jellyroll
electrode assembly in accordance with the present invention. The
positive electrode strip 30 is comprised of a metal substrate 32
formed, for example, of aluminum. Positive electrode active
material 34, 36 is deposited, respectively on the upper and lower
faces 38 and 40 of the substrate 32. Note in FIGS. 3, 4, and 5 that
the right end of the substrate 32 is bare, i.e. devoid of positive
active material on both the upper and lower faces 38, 40.
[0038] It is to be pointed out that exemplary dimensions are
depicted in FIGS. 1-5 and other figures herein. These exemplary
dimensions are provided primarily to convey an order of magnitude
to the reader to facilitate an understanding of the text and
drawings. Although the indicated dimensions accurately reflect one
exemplary embodiment of the invention, it should be appreciated
that the invention can be practiced utilizing components having
significantly different dimensions.
[0039] FIG. 6 depicts an early process step for manufacturing a
battery in accordance with the invention utilizing the pin
subassembly 10 (FIGS. 1, 2) and the positive electrode strip 30
(FIGS. 3-5). A topside electrode insulator (not shown), which may
comprise a thin disk of DuPont Kapton.RTM. polyimide film, is
slipped onto the pin 12 adjacent the header 14. In accordance with
the present invention, the bare end of the electrode strip
substrate 32 is electrically connected to the pin 12 preferably by
resistance spot welding, shown at 44. Alternatively, substrate 32
may be ultrasonically welded to the pin 12. The thinness, e.g.
point 0.02 mm of the substrate 32, makes it very difficult to form
a strong mechanical connection between the substrate and the pin
12. Accordingly, in accordance with a significant aspect of the
present invention, an elongate C-shaped mandrel 48 is provided to
mechanically reinforce the pin 12 and secure the substrate 32
thereto.
[0040] The mandrel 48 preferably comprises an elongate titanium or
titanium alloy such as Ti-6AI-4V tube 50 having a longitudinal slot
52 extending along the length thereof. The arrow 54 in FIG. 6
depicts how the mandrel 48 is slid over the pin 12 and substrate
32, preferably overlaying the line of spot welds 44. The mandrel
48, pin 12, and substrate 32 are then preferably welded together,
such as by resistance spot welding or by ultrasonic welding.
Alternatively, the mandrel 48 may be crimped onto the pin 12 at
least partially closing the "C" to create a strong mechanical
connection. In the case of forming only a mechanical connection and
not necessarily a gas-tight electrical connection between the
mandrel 48 and the pin and substrate, the mandrel material is
preferably made of a material that will not lead to electrolysis.
When used with electrolytes that tend to contain hydrofluoric acid,
the mandrel is preferably made of 304, 314, or 316 stainless steels
or aluminum or an alloy thereof chosen for its compatibility with
the other materials. FIG. 7 is an end view showing the step of
crimping the mandrel 48 to the pin 12 and substrate 32. Supporting
die 126 is used to support the mandrel 48 and crimping dies 124 and
125 are used to deform the edges of the mandrel 48 to bring them
closer together and mechanically connect the mandrel 48 to the pin
12 and substrate 32. By crimping in the direction of arrows 127 and
128, a strong connection is formed without damaging the thin
electrode or disturbing the electrical connection between the pin
and the electrode.
[0041] FIG. 8 is an end view showing the slotted mandrel 48 on the
pin 12 with the substrate 32 extending tangentially to the pin 12
and terminating adjacent the interior surface of the mandrel tube
50. The tube 50 is preferably sufficiently long so as to extend
beyond the free end of the pin 12. As depicted in FIG. 9, this
enables a drive key 56 to extend into the mandrel slot 52.
[0042] FIG. 10 schematically depicts a drive motor 60 for driving
the drive key 56 extending into mandrel slot 52. With the pin
subassembly header 14 supported for rotation (not shown),
energization of the motor 60 will orbit the key drive 56 to rotate
the mandrel 48 and subassembly 10 around their common longitudinal
axes. The rotation of the mandrel 48 and subassembly 10 is employed
to form a jellyroll electrode assembly in accordance with the
present invention.
[0043] More particularly, FIG. 11 depicts how a jellyroll electrode
assembly is formed in accordance with the present invention. The
bare end of the substrate 32 of the positive electrode strip 30 is
electrically connected to the pin 12 as previously described. The
conductive mandrel 48 contains the pin 12 and bare substrate end,
being welded to both as previously described. A strip of insulating
separator material 64 extending from opposite directions is
introduced between the mandrel 48 and positive electrode substrate
32, as shown. A negative electrode strip 70 is then introduced
between the portions of the separator material extending outwardly
from mandrel 48.
[0044] The preferred exemplary negative electrode strip 70 is
depicted in FIGS. 12-15. The negative electrode strip 70 is
comprised of a substrate 72, e.g. titanium, having negative active
material formed on respective faces of the substrate. More
particularly, note in FIG. 14 that negative active material 74 is
deposited on the substrate upper surface 76 and negative active
material 78 is deposited on the substrate lower surface 80. FIG. 14
depicts the preferred configuration of the inner end 82 of the
negative electrode strip 70 shown at the left of FIGS. 12 and 13.
FIG. 15 depicts the configuration of the outer end 83 of the
negative electrode strip 70 shown at the right side of FIGS. 12 and
13.
[0045] Note in FIG. 14 that one face of the substrate inner end 82
is bared. This configuration can also be noted in FIG. 11 which
shows how the negative substrate inner end 82 is inserted between
turns of the separator strip 64. After the strip 70 has been
inserted as depicted in FIG. 11, the aforementioned drive motor 60
is energized to rotate pin 12 and mandrel 48, via drive key 56, in
a counterclockwise direction, as viewed in FIG. 11. Rotation of pin
12 and mandrel 48 functions to wind positive electrode strip 30,
separator strip 64, and negative electrode strip 70, into the
spiral jellyroll assembly 84, depicted in FIG. 16. The assembly 84
is comprised of multiple layers of strip material so that a cross
section through the assembly 84 would reveal a sequence of layers
in the form pos/sep/neg/sep/pos/sep/neg/ . . . , etc.
[0046] FIG. 15 depicts a preferred configuration of the outer end
83 of the negative electrode strip 70. Note that the outer end 88
of the substrate 72 is bared on both its top and bottom faces.
Additionally, as shown in FIG. 17, a flexible metal tab 90 is
welded crosswise to the substrate 72 so as to extend beyond edge
92. More particularly, note that portion 94 of tab 90 is
cantilevered beyond edge 92 of negative electrode strip 70. This
tab portion, as will be described hereinafter, is utilized to
mechanically and electrically connect to an endcap for closing a
battery case.
[0047] Attention is now called to FIG. 18, which illustrates a
preferred technique for closing the jellyroll assembly 84. That is,
the bared end 88 of the negative electrode substrate 72 extending
beyond the negative active material coat 78 is draped over the next
inner layer of the jellyroll assembly 84. The nd 88 can then be
secured to the next inner layer, e.g., by appropriate adhesive tape
96. One such suitable adhesive tape is DuPont Kapton.RTM. polyimide
tape. It is important to note that the outer end configuration 88
of the negative electrode strip 70 enables the outer radius
dimension of the jellyroll assembly 84 to be minimized as shown in
FIG. 18. More particularly, by baring the substrate 72 beyond the
active material 78, the tape 96 is able to secure the substrate end
without adding any radial dimension to the jellyroll assembly. In
other words, if the outer end of the substrate were not
sufficiently bared, then the tape 96 would need to extend over the
active material and thus add to the outer radius dimension of the
jellyroll 84. Furthermore, the bare substrate 72 is more flexible
than the substrate coated with active material 78 and conforms more
readily to the jellyroll assembly 84, making it easier to adhere it
to the surface of the jellyroll. These space savings, although
seemingly small, can be clinically important in certain medical
applications. It should be noted that the electrode need only be
bared at an end portion long enough to accommodate the tape 96, as
shown in FIG. 18. Because the uncoated substrate does not function
as an electrode, it would waste space in the battery to bare any
more than necessary to accommodate the tape. In a preferred
embodiment, the length of uncoated substrate is between 1 and 8 mm,
and more preferably about 2 mm.
[0048] FIG. 19 depicts the completed jellyroll assembly 84 and
shows the cantilevered tab portion 94 prior to insertion into a
battery case body 100. The case body 100 is depicted as comprising
a cylindrical metal tube 101 having an open first end 104 and open
second end 106. Arrow 107 represents how the jellyroll assembly 84
is inserted into the cylindrical tube 101. FIG. 20 depicts the
jellyroll assembly 84 within the tube 101 with the cantilevered
negative electrode tab 94 extending from the case open second end
106. The case open first end 104 is closed by the aforementioned
header 14 of the pin subassembly 10 shown in FIGS. 1 and 2. More
particularly, note that the metal hollow member 22 is configured to
define a reduced diameter portion 108 and shoulder 110. The reduced
diameter portion 108 is dimensioned to fit into the open end 104 of
the cylindrical tube 101 essentially contiguous with the tube's
inner wall surface. The shoulder 110 of the hollow member 22
engages the end of the case tube 101. This enables the surfaces of
the reduced diameter portion 108 and shoulder 110 to be laser
welded to the end of the case 100 to achieve a hermetic seal.
[0049] Attention is now directed to FIGS. 21-24, which depict the
tab 94 extending from the second open end 106 of the case tube 101.
Note that the tab 94 extends longitudinally from the body close to
the case tube adjacent to tube's inner wall surface. In accordance
with a preferred embodiment of the invention, the tab 94 is welded
at 110 to the inner face 112 of a circular second endcap 114. In
accordance with a preferred embodiment, the tab 94 is sufficiently
long to locate the weld 110 beyond the center point of the circular
endcap 114. More particularly, note in FIGS. 21-24 that by locating
the weld 110 displaced from the center of the cap 114, the tab 94
can conveniently support the endcap 114 in a vertical orientation
as depicted in FIG. 22 misaligned with respect to the open end 106.
This end cap position approximately perpendicular to the end 122 of
the case 100 is a first bias position wherein the end cap
advantageously tends to remain in that orientation with the case
end open prior to filling. To further describe the relationship
between the weld location and the various components, FIG. 23 shows
a front view with various dimensions. L represents the length from
the weld 110 to the top of the case 100 as measured parallel to the
edge of the case. R is the radius of the end cap 114. For the
preferred geometry, L.ltoreq.2R. Weld 110 is preferably made above
the center point 111 of the end cap 114. Preferably, the end cap
114 overlaps the case 100 by approximately R/2. By configuring the
tab 94 and weld 110 as indicated, the endcap 114 can be supported
so that it does not obstruct the open end 106, thereby facilitating
electrolyte filling of the case interior cavity via open end 106. A
filling needle or nozzle can be placed through open end 106 to fill
the case. This obviates the need for a separate electrolyte fill
port, thereby reducing the number of components and number of seals
to be made, thus reducing cost and improving reliability.
Furthermore, for small medical batteries, the end caps would be
very small to have fill ports therein. In a preferred embodiment in
which the case wall is very thin, for example, 0.002 inches,
providing a fill port in the side wall of the case would be
impractical. Even in the case of larger devices where space is less
critical and the wall is more substantial, providing a fill port in
the side of the case would mean the electrolyte would have a very
long path length to wet the jellyroll. Note that while the case
could be filled with electrolyte prior to welding tab 94 to endcap
114, it would be difficult and messy to do so. Therefore, it is
advantageous to configure the tab 94 and weld 110 as described to
allow the weld to be made prior to filling.
[0050] Preferably before filling, a bottomside electrode insulator
(not shown), which may comprise a thin disk of DuPont Kapton.RTM.
polyimide film, is installed into the case between the rolled
electrode assembly and the still open end of the battery case.
[0051] In a preferred filing method, there is a channel of air
between the pin and the crimped or welded C-shaped mandrel, which
is used as a conduit for quickly delivering the electrolyte to the
far end of the battery and to the inside edges of the electrodes
within the jellyroll. Filling from the far end of the battery
prevents pockets of air from being trapped, which could form a
barrier to further filling. This facilitates and speeds the filling
process, ensuring that electrolyte wets the entire battery.
[0052] Thereafter, the flexible tab 94 can be bent to the
configuration depicted in FIG. 24. Note that the endcap 114 is
configured similarly to header hollow member 22 and includes a
reduced diameter portion 118 and a shoulder 120. The reduced
diameter portion snugly fits against the inner surface of the wall
of tube 101 with the endcap shoulder 120 bearing against the end
122 of the cylindrical case 100. The relatively long length of the
tab 94 extending beyond the center point of the endcap surface 112
minimizes any axial force which might be exerted by the tab portion
94 tending to longitudinally displace the endcap 114. The end cap
position covering the end 122 of the case 100 is a second bias
position wherein the end cap advantageously tends to remain in that
orientation prior to welding. With the endcap in place, it can then
be readily welded to the case wall 101 to hermetically seal the
battery. With tab 90 welded to negative substrate 72 and with the
negative electrode strip 70 as the outermost layer of the
jellyroll, the endcap 114 becomes negative. In turn, welding the
endcap 114 to the case 100 renders the case negative.
[0053] From the foregoing, it should now be appreciated that an
electric storage battery construction and method of manufacture
have been described herein particularly suited for
manufacturing-very small, highly reliable batteries suitable for
use in implantable medical devices. Although a particular preferred
embodiment has been described herein and exemplary dimensions have
been mentioned, it should be understood that many variations and
modifications may occur to those skilled in the art falling within
the spirit of the invention and the intended scope of the appended
claims.
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