U.S. patent application number 10/820788 was filed with the patent office on 2005-01-13 for electric coupling of a connection to an electrochemical bundle.
This patent application is currently assigned to SAFT, SA. Invention is credited to Fargeas, Franck, Lacoste, Philippe, Ligeois, Dominique.
Application Number | 20050008933 10/820788 |
Document ID | / |
Family ID | 33041795 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050008933 |
Kind Code |
A1 |
Ligeois, Dominique ; et
al. |
January 13, 2005 |
Electric coupling of a connection to an electrochemical bundle
Abstract
The subject of the present invention is a system for electric
coupling of a plane connection (64, 67) to the electrodes of the
same polarity of an electrochemical bundle (63) comprising an
alternating sequence of at least one positive electrode and at
least one negative electrode framing a separator, each electrode
comprising a metal strip less than 50 .mu.m thick, serving as
current collector, at least one surface of which is coated with a
paste containing the electrochemically active material, the strips
of the electrodes of each polarity comprising a non-coated lateral
band emerging respectively from the opposite ends of said bundle,
characterized in that the lateral bands of the strips of the same
polarity are folded in a direction approximately perpendicular to
their initial direction at a height at least equal to the distance
separating them from the adjacent strips of the same polarity in
order to form an approximately plane and continuous base (65, 68)
to which said plane connection is welded.
Inventors: |
Ligeois, Dominique; (St.
Loubes, FR) ; Lacoste, Philippe; (US) ;
Fargeas, Franck; (US) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
SAFT, SA
|
Family ID: |
33041795 |
Appl. No.: |
10/820788 |
Filed: |
April 9, 2004 |
Current U.S.
Class: |
429/161 ;
29/623.4; 429/160 |
Current CPC
Class: |
Y02E 60/10 20130101;
Y10T 29/49114 20150115; Y10T 29/49108 20150115; H01M 50/54
20210101; H01M 50/538 20210101 |
Class at
Publication: |
429/161 ;
429/160; 029/623.4 |
International
Class: |
H01M 002/26 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 11, 2003 |
FR |
0304528 |
Claims
1. System for electric coupling of a plane connection to the
electrodes of the same polarity of an electrochemical bundle
comprising an alternating sequence of at least one positive
electrode and at least one negative electrode framing a separator,
each electrode comprising a metal strip less than 50 .mu.m thick,
serving as current collector, at least one surface of which is
coated with a paste containing the electrochemically active
material, the strips of the electrodes of each polarity comprising
a non-coated lateral band emerging respectively from the opposite
ends of said bundle, characterized in that the lateral bands of the
strips of the same polarity are folded in a direction approximately
perpendicular to their initial direction at a height at least equal
to the distance separating them from the adjacent strips of the
same polarity in order to form an approximately plane and
continuous base to which said plane connection is welded.
2. System according to claim 1, in which said lateral bands are
folded at a height comprised between 3 and 4 mm.
3. System according to claim 1, in which said strips have a minimum
thickness comprised between 10 .mu.m and 15 .mu.m.
4. System according to claim 1, in which said plane connection is
laser-welded with addition of material to said folded strips.
5. System according to claim 1, in which said plane connection is
transparency laser-welded to said folded strips.
6. System according to claim 1, in which said connection is
electrically connected to a current output.
7. System according to claim 1, in which said connection
constitutes a current output.
8. System according to claim 1, in which said bundle comprises a
positive electrode and a negative electrode, framing a separator,
which are spirally wound in order to form a coil.
9. System according to claim 1, in which said lateral band of the
positive electrode has a height comprised between 13 mm and 17
mm.
10. System according to claim 1, in which said lateral band of the
negative electrode has a height comprised between 8 mm and 12
mm.
11. System according to claim 1, in which said plane connection is
welded at a distance of at least 3 mm from one end of the separator
of the electrochemical bundle.
12. System according to claim 1, in which said lateral bands are
folded in a concertina manner.
13. System according to claim 1, in which said plane connection is
a blade not covering all of the surface of the plane base formed by
said folded lateral bands.
14. Electrochemical generator comprising a system for electric
coupling of a plane connection to the electrodes of the same
polarity of an electrochemical bundle comprising an alternating
sequence of at least one positive electrode and at least one
negative electrode framing a separator, each electrode comprising a
metal strip less than 50 .mu.m thick, serving as current collector,
at least one surface of which is coated with a paste containing the
electrochemically active material, the strips of the electrodes of
each polarity comprising a non-coated lateral band emerging
respectively from the opposite ends of said bundle, characterized
in that the lateral bands of the strips of the same polarity are
folded in a direction approximately perpendicular to their initial
direction at a height at least equal to the distance separating
them from the adjacent strips of the same polarity in order to form
an approximately plane and continuous base to which said plane
connection is welded.
15. Generator according to claim 14, comprising electrode
plates.
16. Generator according to claim 15, in which said plane connection
is welded according to at least one weld line perpendicular to the
plane of the electrodes.
17. Generator according to claim 14, comprising spirally wound
electrodes.
18. Generator according to claim 17, in which said plane connection
is welded according to at least one weld line tangent to the
winding axis of the electrodes.
19. Generator according to claim 14, chosen from lithium generators
and supercapacitors.
20. Method of electric coupling of a plane connection to the
electrodes of the same polarity of an electrochemical bundle
comprising an alternating sequence of at least one positive
electrode and at least one negative electrode framing a separator,
each electrode comprising a metal strip less than 50 .mu.m thick,
serving as current collector, at least one surface of which is
coated with a paste containing the electrochemically active
material, the method comprising the following steps: at least one
positive electrode, at least one negative electrode and at least
one separator are put together to form an electrochemical bundle in
order to let a lateral band of said electrodes of opposite polarity
respectively protrude from the opposite ends of said bundle. a
pressure is exerted on the section of said lateral bands of the
electrodes of the same polarity in order to fold them, a plane
connection is welded to the base constituted by said folded lateral
bands.
21. Method according to claim 20, in which said plane connection is
laser-welded with addition of material to said folded bands.
22. Method according to claim 20, in which said plane connection is
transparency laser-welded to said folded bands.
23. Method according to claim 20, in which the folding of the
lateral bands is carried out by repeated flattening of said bands
by small successive passes of a hammer over the same surface.
24. Method according to claim 23, in which the surface flattened by
one pass is comprised between 20 and 50 mm.sup.2.
Description
[0001] The present invention relates to a system of electric
coupling between a connection electrically connected to a current
output terminal, and an electrochemical bundle. It moreover extends
to the method for producing this coupling.
[0002] An electrochemical generator comprises an electrochemical
bundle comprising an alternating sequence of positive and negative
electrodes framing a separator impregnated with electrolyte. Each
electrode most often comprises a metal current collector supporting
on at least one of its surfaces the electrochemically active
material. The electrode is connected electrically to a current
output which ensures electrical continuity between the electrode
and the external application with which the generator is
associated. This current output can be the container of the
generator or a current output terminal.
[0003] There are several ways of electrically coupling an electrode
to a current output terminal. One of these ways is the use of a
plane connection which is applied to the juxtaposed collectors of
the electrodes of the same polarity.
[0004] According to the document EP-0 029 925, the electric
coupling is carried out by means of a full disk arranged then
welded on the winding section of the spirally wound electrodes.
[0005] For example the document USA 009 053 describes a generator
with alkaline electrolyte and spirally wound electrodes. It shows a
plane circular connection carrying radial slots having the form of
lances, the turned-down edges of which serve to establish the
electric contact with the collector of the spirally wound
electrode.
[0006] In electrochemical generators with aqueous electrolyte such
as the Ni--Cd generators, the electrode support is a nickel-coated
steel strip approximately 0.2 mm thick. There are no particular
difficulties with welding directly to the strip section a piece
electrically connected to the terminal. On the other hand, in
electrochemical generators with organic electrolyte with which the
invention is concerned, such as lithium generators or
supercapacitors, the support of the positive electrode is generally
a thin aluminium strip less than 50 .mu.m thick and that of the
negative electrode is a thin copper strip less than 50 .mu.m thick.
Such thinnesses do not offer the mechanic resistance necessary for
producing reliable welds on the electrode section.
[0007] From the document EP 1 102 337 an electrochemical generator
is known comprising an alternating sequence of spirally wound
positive and negative electrodes constituting an electrochemical
bundle. Each electrode comprises a metal strip serving as a current
collector. The strips of the same polarity respectively jut out
towards the outside of the bundle in order to form a plane base on
which a plane connection is attached.
[0008] The portions of the strips jutting out on either side of the
electrochemical bundle do not however form a continuous plane base.
The strips are folded at 90.degree. by a pressing tool. Such a
method does not make it possible to produce a metal barrier with
folded strips forming a continuous plane base.
[0009] As regards techniques developed within the context of
electrode plates (not spirally wound), the document FR-2 748 606
proposes for example a method of connection by expansion. The edges
of the electrodes are put together in two semi-bundles coupled
horizontally to the current output terminal.
[0010] The present invention aims to eliminate the drawbacks of the
prior art and, in particular, to propose a solution which can
easily be produced industrially.
[0011] More precisely, the invention aims to propose a system of
electric coupling by the welding of a plane connection to the
electrode section of the same polarity in a manner simpler than the
systems described in the prior art.
[0012] The subject of the present invention is a system of electric
coupling of a plane connection to the electrodes of the same
polarity of an electrochemical bundle comprising an alternating
sequence of at least one positive electrode and at least one
negative electrode framing a separator, each electrode comprising a
metal strip less than 50 .mu.m thick, serving as current collector,
at least one surface of which is coated with electrochemically
active material, the strips of the electrodes of each polarity
comprising a non-coated lateral band emerging respectively from the
opposite ends of said bundle, characterized in that the lateral
bands of the strips of the same polarity are folded in a direction
approximately perpendicular to their initial direction at a height
at least equal to the distance separating them from the adjacent
strips of the same polarity in order to form an approximately plane
and continuous base to which said plane connection is welded.
[0013] According to a preferred embodiment, the lateral bands are
folded at a height comprised between 3 and 4 mm. Thus the space
found between two successive strips is re-covered and closed by the
folded part, preventing any intrusion of material inside the
electrochemical bundle. The invention therefore has the advantage
of considerably reducing the risks of short-circuits between the
electrodes of the opposite polarity.
[0014] In order to allow them to fold in the desired manner, the
strips must not exceed 50 .mu.m in thickness. However for reasons
of mechanical strength and resistance to manipulation, the strips
preferably have a minimum thickness comprised between 10 .mu.m and
15 .mu.m; a minimum of 10 .mu.m for a copper strip and a minimum of
15 .mu.m for an aluminium strip.
[0015] According to a first variant, the connection is electrically
connected to a current output.
[0016] According to a second variant, the connection constitutes a
current output.
[0017] According to a particular embodiment, the electrochemical
bundle comprises a positive electrode and a negative electrode,
framing a separator, which are spirally wound in order to form a
coil. In this case the non-coated part of the positive strip will
project out of one of the circular sections and that of the
negative strip symmetrically out of the other section.
[0018] Preferably, the lateral band of the positive electrode has a
height comprised between 13 mm and 17 mm.
[0019] Preferably, the lateral band of the negative electrode has a
height comprised between 8 mm and 12 mm.
[0020] Preferably, the plane connection is welded at a distance of
at least 3 mm from one end of the separator of the electrochemical
bundle.
[0021] Preferably, the lateral bands are folded in a concertina
manner.
[0022] Preferably, the plane connection is a blade not covering all
of the surface of the plane base formed by said folded lateral
bands.
[0023] A subject of the present invention is also an
electrochemical generator comprising an electric coupling system as
described previously. The electrochemical generator according to
the invention can comprise electrode plates or spirally wound
electrodes. This generator can also be a lithium generator, in
particular a rechargeable generator, for example of the
"lithium-ion" type, or a supercapacitor.
[0024] In the case where the electrochemical generator is of the
lithium-ion type, it comprises a negative electrode in which the
active material is a carbonated material capable of inserting
lithium into its structure, chosen in particular from graphite,
coke, carbon black, and glassy carbon. It also comprises a positive
electrode in which the active material is chosen from a transition
metal oxide, a sulphide, a sulphate and their mixtures.
[0025] In the case where the generator in question is a
supercapacitor, the electrodes have activated carbon as active
material.
[0026] According to a first variant, in which the generator
comprises electrode plates, the plane connection is welded
according to at least one weld line perpendicular to the plane of
the electrodes.
[0027] According to a second variant, in which the generator
comprises spirally wound electrodes, the plane connection is welded
according to at least one weld line tangent to the winding axis of
the electrodes.
[0028] A subject of the present invention is also a method of
electric coupling of a plane connection to the electrodes of the
same polarity of an electrochemical bundle with a view to obtaining
the system described previously, comprising the following
steps:
[0029] at least one positive electrode, at least one negative
electrode and at least one separator are put together to form an
electrochemical bundle in order to let a lateral band of the
electrodes of opposite polarity respectively protrude from the
opposite ends of the bundle.
[0030] a pressure is exerted on the section of the lateral bands of
the electrodes of the same polarity in order to fold them,
[0031] a plane connection is welded to the base constituted by the
folded lateral bands.
[0032] According to a first variant embodiment, the plane
connection is laser-welded with addition of material to the folded
bands.
[0033] According to a second variant embodiment, said connection is
transparency laser-welded onto the folded bands.
[0034] According to one embodiment, the folding of the lateral
bands is carried out by repeated flattening of said bands by small
successive passes of a hammer over the same surface.
[0035] Preferably, the surface flattened by one pass is comprised
between 20 and 50 mm.sup.2.
[0036] A subject of the present invention is also a method for
manufacturing an electrochemical generator comprising the system of
electric coupling of a plane connection to the electrodes of the
same polarity of an electrochemical bundle described
previously.
[0037] An advantage of the present invention is a considerable
reduction in the duration of the stage of coupling of the
connection.
[0038] The invention will be understood better and other advantages
and features will become apparent on reading the description which
follows, provided by way of illustration, but by no means
limitatively, accompanied by the attached drawings in which:
[0039] FIG. 1 shows an electrode,
[0040] FIG. 2 represents diagrammatically in section part of the
electrochemical bundle,
[0041] FIG. 3 shows a cross-section of a generator during the
operation of folding the non-coated lateral bands,
[0042] FIG. 4 shows in cross-section an electrochemical bundle
after folding of the non-coated bands
[0043] FIG. 5 is a top view of the bundle equipped with its
connection,
[0044] FIG. 6 diagrammatically represents a cross-section of an
electrochemical generator according to the invention.
[0045] FIG. 1 represents the end of an electrode 1 of total width L
on which is distinguished the layer 2 of active material occupying
the greater part of the surface of the electrode and a lateral band
3 of height H constituted by the one strip which has not been
covered with active material.
[0046] Electrodes of the type represented in FIG. 1 and carrying
respectively positive and negative active materials are assembled
in a bundle. Part of an electrochemical bundle, comprising a
positive electrode 10 and a negative electrode 11 between which are
interposed separators 12 is represented in FIG. 2. The positive
electrode 10 comprises a strip 13 covered with a layer 14
containing the positive active material. At one of the ends of the
strip 13 a lateral band 15 has been reserved which does not carry
any active material. This band 15 protrudes from the bundle and has
a height H.sup.+ comprised between 13 mm and 17 mm. The negative
electrode 11 comprises a strip 16 covered by a layer 17 containing
the negative active material. At one of the ends of the strip 16 a
lateral band 18 has been reserved which does not carry any active
material. This band 18 protrudes from the end of the bundle
opposite that where the band 15 is situated. It has a height
H.sup.- comprised between 8 mm and 12 mm. The separators 12 project
slightly from the part of the electrodes coated with active
material in order to avoid short-circuits.
[0047] The electrochemical bundle 30 once constituted is held in a
centring tool 31, as shown in FIG. 3, and the non-coated protruding
lateral bands 32 are curved using a tool 33, such as for example a
hammer with a diameter of 15 to 20 mm. The hammer 33 can be
advantageously constituted by a plurality of small hammers, from 5
to 8 mm in diameter, arranged in series.
[0048] The hammer 33 is moved from top to bottom with a travel of 3
mm, then is moved towards the centre of the bundle in the direction
indicated by the arrow 34 after each rotation of the latter. A set
of folded strips 35 is obtained at a height H' of approximately 3
to 4 mm.
[0049] The abovementioned heights H.sup.+ and H.sup.- of the
lateral bands 15, 18 are such that the non-folded strips protrude 6
to 7 mm from the ends of the separators 12. Thus, during the
subsequent stage of folding of the lateral bands at a height H',
the ends of the separators are still remoted at least 3 mm away
from the base of the folded strips 35. Such a distance between the
folded strips and the ends of the separators makes it possible to
avoid any risk of burning the separators during the subsequent
stage of welding a plane connection to the folded strips.
[0050] According to a preferred embodiment, the folding of the
non-coated lateral bands 32 of the strips 15 is obtained by
repeated flattening of said bands by small successive passes of the
hammer 33 over the same surface of approximately 20 to 50 mm.sup.2,
the hammer 33 carrying out a movement from top to bottom until a
plane surface is obtained. The lateral bands of the strips of the
same polarity are thus folded in a sort of "concertina" in order to
form a continuous plane base approximately perpendicular to the
initial direction of the strips.
[0051] FIG. 4 shows the appearance of the bundle of electrodes 30
after this operation in which the folded lateral bands 35 are seen,
forming a plane and continuous base.
[0052] The base 35 thus formed constitutes a metal barrier allowing
laser-welding of a plane connection.
[0053] This base 35 receives a connection 36 which is laser-welded,
with addition of material or by transparency, in order to form two
parallel beads 37 visible in FIG. 5.
[0054] This laser-welding is carried out without piercing the
connection plate 36. During transparency welding, material from the
base 35 is melted by the laser beam which heats the lateral bands
of the folded strips. This molten material spreads over the base 35
in order to constitute the weld. Such a welding method makes it
possible to avoid any risk of the weld projecting inside the
bundle.
[0055] The plane connection 36 can be a blade not covering all of
the surface of the plane base 35 formed by the lateral bands of the
folded strips. Thus, the gases released from the electrochemical
bundle can be directly evacuated via the ends of the bundle. In
fact, the continuous plane base formed by the folded strips is not
gas-tight.
[0056] Moreover, the plane connection 36 can also be pierced with a
hole 38 in the axis of the bundle of electrodes 30 in order to
allow a good release of gases via this opening.
[0057] FIG. 6 represents an electrochemical generator 60,
cylindrical in shape, with a hollow axis 61 comprising a container
62 made of aluminium into which a bundle 63 has been introduced,
comprising a spirally wound positive electrode and negative
electrode. The plane positive connection 64 made of aluminium is
welded on the one hand by laser-welding to the non-coated bands 65
of the aluminium strip of the negative electrode, previously folded
down in the manner described previously. The positive connection 64
is on the other hand welded to the base 66 of the container 62 by
laser-welding or by electric welding, the two types of welding
being tight. The plane negative connection 67, made of copper or
nickel-coated copper, is welded in the same manner to the
non-coated bands 68 of the copper strip of the positive electrode
previously folded down in the manner described previously. The
negative connection 67 is on the other hand welded to a current
output terminal 69 by laser-welding or ultrasound welding. The
terminal 69 of negative polarity is fixed to a cover 70 which is
welded or crimped onto the container 62. The terminal 69 is
electrically insulated from the cover 70 by an isolating seal
71.
[0058] In the case of an electrochemical generator comprising
spirally wound electrodes, the plane connection is welded according
to at least one welding line tangent to the winding axis of the
electrodes, as close as possible to this winding axis, in order to
cover a maximum of the metal strips.
[0059] Moreover, in the case of an electrochemical generator
comprising electrode plates, the plane connection is welded
according to at least one weld line perpendicular to the plane of
the electrodes.
* * * * *