U.S. patent application number 13/740572 was filed with the patent office on 2013-05-30 for thin film battery.
This patent application is currently assigned to RENATA AG. The applicant listed for this patent is RENATA AG. Invention is credited to Stefan PFROMMER, Han WU.
Application Number | 20130133185 13/740572 |
Document ID | / |
Family ID | 40596401 |
Filed Date | 2013-05-30 |
United States Patent
Application |
20130133185 |
Kind Code |
A1 |
WU; Han ; et al. |
May 30, 2013 |
THIN FILM BATTERY
Abstract
The present invention concerns a flat battery comprising a
package formed by a cathode, an anode, and a separator layer
sandwiched between the cathode and the anode, a sealing frame
extending circumferentially around said package, a first current
collector contacting the anode, and a second current collector
contacting the cathode. The first and second current collectors
each partly cover the sealing frame in a zone being adjacent to the
package. According to the invention, the battery further comprises
a first polymeric jacket layer being arranged on the first current
collector and a second polymeric jacket layer being arranged on the
second current collector, said first and second polymeric jacket
layers extending circumferentially beyond the current collectors
and beyond the sealing frame and being sealed together to form an
outer jacket for the battery. Furthermore, the present invention
also concerns a method to produce such a battery.
Inventors: |
WU; Han; (Barrington,
IL) ; PFROMMER; Stefan; (Eiken, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RENATA AG; |
Itingen |
|
CH |
|
|
Assignee: |
RENATA AG
Itingen
CH
|
Family ID: |
40596401 |
Appl. No.: |
13/740572 |
Filed: |
January 14, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13061844 |
Apr 18, 2011 |
|
|
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13740572 |
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Current U.S.
Class: |
29/623.2 ;
29/623.4; 29/623.5 |
Current CPC
Class: |
H01M 2/08 20130101; H01M
2/0267 20130101; H01M 2/0212 20130101; H01M 2/0277 20130101; H01M
2/0275 20130101; Y10T 29/49114 20150115; H01M 2/0207 20130101; Y10T
29/49115 20150115; H01M 2/0215 20130101; Y10T 29/4911 20150115;
H01M 6/40 20130101; H01M 2/027 20130101; H01M 6/005 20130101 |
Class at
Publication: |
29/623.2 ;
29/623.5; 29/623.4 |
International
Class: |
H01M 6/00 20060101
H01M006/00; H01M 6/40 20060101 H01M006/40 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2008 |
EP |
PCT/EP2008/061816 |
Claims
1. A method for making a flat battery comprising the following
steps: (a) providing a first polymeric jacket layer, (b) providing
a first current collector and arranging same on said first
polymeric sheet, (c) applying an anode material on said first
current collector, (d) providing a second polymeric sheet, (e)
providing a second current collector made of a metal foil and
arranging same on said second polymeric sheet, (f) providing a
sealing frame having an inner contour corresponding substantially
to an outer contour of the anode material and the separator on the
first current collector, (g) arranging said frame on one of the
current collectors, the frame covering the outer circumference of
the current collector, (h) providing a cathode material and
applying same on the second current collector, (i) providing a
separator layer and arranging same on the cathode material, (j)
assembling the flat battery by returning one of the two polymeric
jacket layers and arranging it and on the other polymeric jacket
layer such that the separator layer is sandwiched between the
cathode material and the anode material, the sealing frame then
extending circumferentially around the anode material, the cathode
material and the separator, and (k) sealing together said first and
second polymeric jacket layer in a zone extending circumferentially
beyond the current collectors to form an outer jacket for the
battery package, wherein said polymeric jacket layers are also
sealed to the frame in a region which lies circumferentially
outwards of the current collectors.
2. The method according to claim 1, wherein the sealing frame is
arranged on the second current collector before step h is
executed.
3. The method according to claim 2, wherein the sealing frame
consists of two sealing frame elements, and wherein a first frame
element is applied on the first current collector before execution
of step (c), and a second frame element is applied on the second
current collector before execution of step (h), and the two frame
elements are bonded together to form a frame upon execution of step
(k).
4. The method according to claim 3, wherein each sealing frame
element, the current collector on which it is arranged and the
polymeric jacket layer on which said current collector is arranged)
are bonded to each other before the execution of steps (c) and (h),
respectively.
5. The method according to 4, wherein the sealing frame is coated
with a heat-sealable material and is bonded to the current
collector on which it is arranged before step (j) is executed.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of U.S. patent
application Ser. No. 13/061,844, filed Apr. 18, 2011, which is a
National Stage of International Application No. PCT/EP2008/061816
filed on Sep. 5, 2008, the contents of all of which are
incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates in general to thin film
primary batteries.
[0003] Electrochemical elements, i.e. batteries, are known in many
different physical forms. In most cases, they have a mechanically
robust housing and are in the form of round, button or prismatic
cells. A positive and a negative electrode, a separator and an
electrolyte are arranged in such a cell. The housing of this type
of cells is in general composed of steel, a stainless steel alloy
or aluminum.
[0004] However, for certain applications very thin batteries having
a flexible housing are needed. These applications include active
radio frequency identification (RFID) tags, PCMCIA cards, smart
cards, etc. A battery which shall be used in such applications must
be flexible and compact, deliver high energy density and specific
energy with a low rate of self discharge, and should be provided
with a reliable sealing. The sealing is extremely important, as
moisture should be prevented from entering into the battery to
avoid drain and self discharge, as well as to prevent drying out
resulting from loosing the organic solvents in the electrolyte,
even when the battery is distorted or under mechanical stress.
Furthermore, the battery should be manufacturable in a
cost-efficient and reliable way.
[0005] Different thin film batteries are known from prior art, most
of them using lithium as the anode material.
[0006] U.S. Pat. No. 5,989,751 for example, discloses a primary
lithium battery having a flexible and compact design. The cell is
provided with an electrolyte-containing composite cathode. A
packaging using a spacer and polymeric sheets is provided.
[0007] U.S. 2003/0228517 A1 shows a thin cell with a packaging
being formed by two plastic sheets sealed to each other. The thin
cells described in this document are stacked to form a larger
electrochemical element. The plastic sheets are metallized in
certain areas to form the electrical contacts with the electrodes
of the cell.
[0008] U.S. 2005/0239917 also discloses a thin film lithium
battery, wherein the anode is printed on a copper current collector
using lithium metal powder based ink. The anode and cathode current
collectors are sealed around the perimeter of the battery by a
polyester sealant frame.
[0009] U.S. Pat. No. 6,752,842 B2 discloses a thin film cell which
is manufactured by printing different layers on top of each
other.
[0010] In terms of quality of the sealing and cost-efficiency upon
production, the above described batteries are not yet completely
satisfying.
SUMMARY OF THE INVENTION
[0011] The present invention relates to a flat battery comprising a
package formed by a cathode, an anode, and a separator layer
sandwiched between the cathode and the anode. A sealing frame
extends circumferentially around said package. The battery further
comprises a first current collector contacting the anode and a
second current collector made of a metal foil and contacting the
cathode, wherein the first and second current collectors each
partly cover the sealing frame in an area being adjacent to the
package.
[0012] Said battery further comprises a first polymeric jacket
layer being arranged on the first current collector and a second
polymeric sheet being arranged on the second current collector,
said first and second polymeric sheets extending circumferentially
beyond the current collectors and beyond the sealing frame and
being sealed together to form an outer jacket for the battery.
[0013] The present invention also relates to a method for making a
flat battery comprising the following steps: [0014] (a) providing a
first polymeric jacket layer, [0015] (b) providing a first current
collector and arranging same on said first polymeric sheet, [0016]
(c) applying an anode material on said first current collector,
[0017] (d) providing a second polymeric jacket layer, [0018] (e)
providing a second current collector and arranging same on said
second polymeric jacket layer, [0019] (f) providing a sealing frame
having an inner contour corresponding substantially to an outer
contour of the anode material and the separator on the first
current collector, [0020] (g) arranging said frame on one of the
current collectors, the frame covering the outer circumference of
the current collector, [0021] (h) providing a cathode material and
applying same on the second current collector, [0022] (i) providing
a separator layer and arranging same on the cathode material,
[0023] (j) assembling the flat battery by returning one of the two
polymeric jacket layer and arranging it and on the other polymeric
jacket layer such that the separator layer is sandwiched between
the cathode material and the anode material, the sealing frame then
extending circumferentially around the anode material, the cathode
material and the separator, and [0024] (k) sealing together said
first and second polymeric jacket layer in a zone extending
circumferentially beyond the current collectors to form an outer
jacket for the battery package.
[0025] The first and second polymeric jacket layers which are
sealed together to form an outer jacket for the battery help to
avoid that water or other liquids enter the cell and establish a
conductive path which may result in high self-discharge rates.
Furthermore, electrolyte is prevented from escaping the battery,
and a dry-out of the battery is thereby avoided. The sealing frame
extending circumferentially around the package formed by the anode,
the cathode, the separator and the electrolyte, further contributes
to the high quality of the sealing. Due to the fact that the
sealing frame extends circumferentially around said package, while
the first and second polymeric sheets extend circumferentially
beyond the frame, a double sealing is provided. The current
collectors partly covering the sealing frame form a first sealing
zone and the polymeric sheets extending circumferentially beyond
said sealing area form a second additional sealing zone.
[0026] According to a preferred embodiment of the invention, the
sealing frame is coated with a heat-sealable material. The sealing
frame itself can be made of a polymer such as nylon, polyester
(PET), polypropylene or any suitable polymer, in particular of PET
(poly(ethylene terephthalate), a resin in the polyester family).
The coating may consist of hot-melt adhesive EVA (ethylene vinyl
acetate) or EMA (ethyl methyl acrylate), or another suitable
heat-sealable material. Due to the coating, the frame can easily be
sealed to the current collectors and the polymeric sheets. The
sealing frame can also consist of two frame elements, each of these
elements forming a frame itself. Typically, one such frame element
will be arranged on the cathode side, and another one on the anode
side during assembly of the battery, and the two frame elements
will be bonded together during a final assembly step to form one
frame. In case of the use of two frame elements, the separator can
arranged with its circumferential edges lying between the two frame
elements. It will thus be held in place by the two frame elements
when they are bonded together, and any contact between the anode
material and the cathode can be avoided in a very reliable and
simple way.
[0027] The first and second polymeric jacket layer may also be
coated with a hot-melt adhesive on the side lying on the first and
second current collectors, respectively. The two polymeric jacket
layer can thus be sealed together to form the outer jacket just by
applying heat in a laminating operation.
[0028] The polymeric jacket layers can be simple polymeric sheets
having a surface which is larger than the surface of the current
collector on which it is arranged. The complete current collector
will then covered by the polymeric sheets, and the jacket formed by
the two polymeric sheets will thus not leave any parts of the
battery accessible, except for two contact tabs.
[0029] Alternatively, the polymeric jacket layers can also be
formed by a polymeric frame which will typically be cut out from a
polymeric sheet, and which covers the outer contour of the current
collector on which it is arranged. The use of such a frame has the
advantage that the whole battery will be thinner than when complete
sheets are used, and the additional sealing is limited to those
areas where such a sealing is really critical, namely to the outer
contour of the current collector. On the other hand, it is easier
to obtain certain desired surface properties for the battery when
using a whole sheet than when using merely a frame. A complete
sheet might thus be the preferred solution when a certain adhesion
or a certain appearance is needed.
[0030] The current collectors are preferably metal foils, in
particular copper foils. Contact tabs for contacting the battery
from the outside can be formed integrally with such a copper foil,
and there is thus no need for additional contacts. However, the use
of a metallized polymeric film or sheet instead of a metal foil is
also possible. According to a preferred embodiment of the
invention, at least one of the current collectors is a preformed
metal foil having a depression formed in a central area thereof.
Such a depression can form a receptacle for a cathode mixture when
same is applied to the current collector, and will thus facilitate
the assembly of the battery.
[0031] Preferably, the anode material is lithium. However, it is
also possible to use another material such as zinc (Zn), cadmium
(Cd), lead (Pb), hydrogen absorbing alloys or any other suitable
material for the anode without departing from the scope of the
present invention.
[0032] According to a preferred embodiment of the invention, the
cathode comprises manganese-dioxide (MnO.sub.2) as the active
material. Typically, electrolytic manganese dioxide, or EMD, will
be used for this purpose. However, it is also possible to use
another material such as nickel hydroxide, silver oxide, carbon
monofluoride or any other suitable material for the cathode without
departing from the scope of the present invention.
[0033] It should further be noted that the first and the second
polymeric jacket layers can be made of one single sheet which is
folded in the middle to form the outer jacket and thereby seal the
battery. The advantage of such a solution is that the folding line
already provides one side which will be perfectly sealed.
[0034] The present invention also concerns a method to make a
battery according to claim 12. Preferred embodiments of this method
arise from the dependent claims and from the description of two
preferred embodiments given below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The subject matter of the invention will be explained more
in detail in the following description with reference to the
drawings, wherein
[0036] FIG. 1 is a sectional view of a flat battery according to a
first embodiment of the invention;
[0037] FIG. 2 is a sectional view of a flat battery according to a
second embodiment of the invention;
[0038] FIG. 3(a) is a top view of a first preassembled part of the
flat battery of FIG. 1;
[0039] FIG. 3(b) is a top view of a second preassembled part of the
flat battery of FIG. 1
DETAILED DESCRIPTION
[0040] It will be appreciated that the following description is
intended to refer to two specific embodiments of the invention
which have been selected for illustration in the drawings but which
are not intended to define or limit the invention, other than in
the appended claims.
[0041] FIG. 1 shows a cross-section through a flat battery
according to the invention, whereas FIGS. 3(a) and 3(b) each show a
top view of a preassembled part of the flat battery shown in FIG.
1. More precisely, FIG. 3(a) shows the upper layers of the battery
shown in FIG. 1, while FIG. 3(b) shows the lower layers of the
same.
[0042] Referring to FIGS. 3(a) and 3(b), a method according to the
invention to produce the battery as shown in FIG. 1 will now be
described.
[0043] Firstly, the preassembly of the lower layers as shown in
FIG. 3(b) will be described.
[0044] In a first step, a first rectangular polymeric sheet 24
being coated with a heat-sealable material on one side is provided.
It should be noted that, although rectangular components have been
chosen for the embodiments described herein, the individual
components and the assembled battery can have any desired shape,
e.g. rectangular with rounded edges, oval, circular etc. A first
current collector 18 is arranged on the side being coated with a
heat-sealable material of said polymeric sheet 24. Said current
collector 18 is made of a rectangular copper foil or another
appropriate metal foil and has a perimeter which is smaller than
the perimeter of the polymeric sheet 24, for example by some
millimeters on all sides. On one side, it is provided with a
contact tab 17 extending beyond the outer contour of the polymeric
sheet 24. The current collector 18 will be arranged in the centre
of the first polymeric sheet 24 such that a frame-like outer zone
of the polymeric sheet 24 remains uncovered, as it can be seen in
FIG. 3(a).
[0045] In the next step, a first frame element 22a will be arranged
on the first polymeric sheet 24 and the first current collector 18.
This frame element is a rectangular polyester frame 22 having a
thickness lying In the order of about 100 .mu.m and being coated
with hot-melt adhesive EVA (ethylene vinyl acetate) on its upper
and its lower surface. The outer perimeter of this frame element
22a is smaller than the perimeter of the polymeric sheet 24, but
larger than the perimeter of the current collector 18, whereas the
inner perimeter of the frame element 22a is smaller than the
perimeter of the current collector 18. The frame element 22a will
be arranged on the polymeric sheet 24 and the current collector 18
symmetrically with respect to the center of all components, such
that an inner region of the frame element 22a lies on the current
collector 18, while an outer region of the frame element 22a lies
directly on the polymeric sheet 24.
[0046] These three elements, i.e. the first polymeric sheet 24, the
first current collector 18, and the first frame element 22a will be
bonded to each other. To do so, it is sufficient to apply heat and
pressure, e.g. by applying a heated block, and the hot-melt coating
on the polymeric sheet and on the frame element 22a will melt and
adhere to the metal foil lying in the middle. Alternatively, one
can also bond these three elements together only temporarily by
applying heated pins to some selected points.
[0047] In the next step, a lithium foil which will form an anode 12
is arranged on the current collector copper foil 18. This is
normally done under a low moisture environment to protect the
lithium. The anode lithium foil 12 is also rectangular with its
surface being slightly smaller than the surface of the current
collector 18. It will preferably be arranged symmetrically in the
middle of the current collector 18, thereby leaving a frame-like
outer region of the current collector 18 uncovered.
[0048] Now referring to FIG. 3(a), in the same manner, a second
polymeric sheet 26 identical to the first polymeric sheet 24 and
thus also coated with a heat-sealable material will be provided. A
second current collector 20 with a second contact tab 19 will be
arranged on said second polymeric sheet 26 in the same way as
described above for the first polymeric sheet 24 being arranged on
the first current collector 18. In a next step, a second frame
element 22b identical to the first frame element 22a described
above will be arranged on the on the second polymeric sheet 26 and
the second current collector 20 just as described above. The second
polymeric sheet 26, the second current collector 20, and the second
frame element 22b will then also be bonded to each other just as
described above referring to FIG. 3(a).
[0049] Once the frame element 22b lies on the copper foil forming
the current collector 20 and has been bonded thereto and to the
polymeric sheet 26 as described above, instead of the lithium foil
forming the anode 12, a mixture which will form the cathode 16 is
applied to the central zone of the current collector 20. This
central zone is bordered by the frame element 22b which forms a
wall to hold the mixture in place. Said mixture contains preferably
manganese dioxide as the active cathode material, but other
suitable cathode materials can also be chosen without departing
from the scope of the present invention. In addition to the active
cathode material, the mixture further comprises an electrolyte,
typically a lithium salt, such as lithium perchlorate
(LiClO.sub.4), lithium hexafluorophosphate (LiPF.sub.6), or lithium
triflate (LiCF.sub.3SO.sub.3), in a mixture of aprotic organic
solvents, such as PC:EC (propylene carbonate:ethylene carbonate),
EC:DME (ethylene carbonate:dimethoxyethane), or EC:DMC (ethylene
carbonate:dimethyl carbonate). Any other suitable electrolyte can
also be used. Furthermore, the cathode mixture comprises a
conductive phase to promote electrical conductance and to enhance
utilization of the active material, such as conductive carbon,
graphite, or another suitable material. The mixture further
comprises a substance acting as binder to hold the different
components together, such as PTFE (Polytetrafluoroethylene) or
PVDF.
[0050] After the application of the cathode mixture forming a
composite cathode 16, a porous film serving as a separator 14, e.g.
a PE or PP film, as it is well known in the art, is arranged on
this cathode 16. For the example shown here, the outer contour of
the separator 14 corresponds to the inner contour of the two frame
elements 22a, 22b. The separator can also have a bigger surface
than the cathode and extend circumferentially beyond the cathode.
Such a solution will in general be preferred, because it allows to
avoid that the cathode and the anode contact each other. To be kept
in place, the separator might be arranged between the two frame
elements described above on its outer circumference.
[0051] The preassembled unit shown in FIG. 3(b) comprising the
first polymeric sheet 24, the first current collector 18, frame
element 22a and the anode 12 can now be assembled to the
preassembled unit shown in FIG. 3(a). To do so, one of the two
preassembled units will be flipped over, and the two halves will be
arranged on each other such that the two frame elements 22a, 22b
are aligned with each other and form one frame 22. The anode 12 is
thereby brought into contact with the separator 14, the outer
contours of the two polymeric sheets 24, 26 now lying on top of
each other. It should be noted that it is also possible to use a
frame made in one piece instead of a frame comprising two frame
elements as described herein. This frame will then preferably
arranged on the cathode side before the two units shown in FIGS.
3(a) and 3(b) are assembled to each other, just as it is described
below for the second embodiments shown in FIG. 2.
[0052] As shown in FIG. 1, the anode 12, separator 14 and cathode
16 then form a substantially block-shaped package 10 in the heart
of the battery with the frame 22 formed by the frame elements 22a,
22b circumscribing said package 10. The inner contour of the frame
22 corresponds to the outer contour of the package 10, and the
height h of the frame 22 corresponds to the height h of the package
10 formed by the anode 12, the cathode 16 and the separator 14. The
circumferentially outer area of the current collector 18 extending
beyond the anode 12 lies on the sealing frame 22 in an area being
adjacent to the package 10, i.e. in an circumferentially inner area
of the frame 22, thereby partly covering said frame. As one can see
in FIGS. 1 and 2, approximately half of the surface of the frame 22
is covered by the current collectors 18, 20, whereas a
circumferentially outer area of the frame 22 is not covered by the
current collector 18, 20 and is in direct contact with the
polymeric sheets 24, 26 when the battery is assembled.
[0053] In a laminating operation the heat-melt adhesive coatings on
the contact surface of the frame elements 22a, 22b are melted, such
that the two frame elements 22a, 22b are now definitively bonded to
form one frame 22. If this has not happened beforehand, the frame
elements 22a, 22b will also be bonded to the current collectors 18,
20. At the same time, the two polymeric sheets 24, 26 being coated
with a heat-sealable material on their inner sides contacting each
other are sealed together on their outer circumference in an outer
sealing area having a width W. The polymeric sheet 24, 26 serving
as a polymeric jacket layer to form the outer jacket will typically
have a thickness of 50-75 .mu.m. This laminating operation can be
limited to three sides of the battery in a first step, a fourth
side being left unsealed temporarily. In this case, a vacuum will
be applied in a next step to remove any air, vapor, moisture etc.
from the battery. While this vacuum is applied, the fourth side
will be laminated to seal the battery completely. It is also
possible to seal all for sides in one step while evacuating the
battery at the same time, but this is slightly more difficult to
handle. As this evacuation step may take longer than the assembly
steps previously described, the batteries may be grouped during
evacuation and during sealing of the fourth side, even if the
previous assembly steps have been carried out individually, e.g. on
a rotating assembly diode or on a conveyer belt.
[0054] It should be noted that it is also possible to use only one
polymeric sheet instead of two separate sheets 24, 26. In this
case, the first current collector 18, the first frame element 22a,
and the anode 12 will be applied on one half of this sheet as
described above, while the second current collector 20, the cathode
16, the second frame element 22b and the separator 14 will be
arranged on the second half just as previously described for two
separate sheets 24, 26. The polymeric sheet will then be folded in
the middle to assemble the battery, and one proceeds with the
laminating operation as described above. One advantage of this
method is that one side, namely the one which is folded, does not
need to be sealed, and that it can be easier to align the two
halves forming the battery with each other.
[0055] FIG. 2 shows a second embodiment of a battery according to
the invention. The same parts are denoted using the same reference
numerals, and in the following only the differences with respect to
the first embodiment will be described.
[0056] As one can see in FIG. 2, instead of the polymeric sheets
24, 26 shown in FIG. 1, polymeric frames 24', 26' are used. These
have the same function as the polymeric sheets 24, 26 in the first
embodiment. Said polymeric frames 24', 26' can be cut out in a
polymeric sheet as it is used for the polymeric sheets 24, 26 of
the first embodiment, and will thus also typically have a thickness
of 50-75 .mu.m. The outer contour of the polymeric frames 24', 26'
shown in FIG. 2 corresponds to the outer contour of the sheets 24,
26 used for the first embodiment and shown in FIG. 1. The inner
contour of the frames 24', 26' is slightly smaller than the outer
contour of current collectors 18', 20', such that the outer contour
of the current collectors 18', 20' is covered by the frames 24, 26'
after assembly of the battery. The outer jacket formed by the two
polymeric frames 24', 26' is thus not completely closed, and the
current collectors 18', 20' are not covered in their center. The
uncovered centre can also serve as a contact, and contact tabs as
shown in FIGS. 3(a), 3(b) are thus not absolutely necessary, when a
frame instead of complete sheets is used to form the jacket.
[0057] The current collectors 18', 20' are copper foils just as for
the first embodiments, but the second current collector 20' has
been preformed and is provided with a depression in its center.
This depression forms a receptacle for the cathode mixture 16', as
it can be seen in FIG. 2. The first current collector 18' can also
be provided with a depression to receive the lithium foil forming
the anode 12', but as the thickness of the anode is rather small
compared to the thickness of the cathode, the advantages of such a
depression on the lithium side are less obvious than for the
depression on the cathode side forming a receptacle for the cathode
mixture.
[0058] The frame 22' is not formed by two frame elements 22a, 22b
as described for the first embodiment above, but is merely formed
by one single frame. This frame will be arranged on the cathode
side, i.e. on the second current collector 20' and polymeric frame
26' just as described above for the first embodiment, and these
three parts will be bonded together before application of the
cathode mixture 16'. The total thickness of the frame 22' is
smaller than the thickness of the package 10' formed by the active
materials and can lie somewhere between the thickness of the
separator layer 14 and the thickness of the package 10. In the
final laminating step, the frame 22', which is coated with a
hot-meld adhesive on both sides, will be bonded to the first
current collector 18' and to the polymeric frames 24', 26' forming
the outer jacket.
[0059] With the embodiment as shown in FIG. 2, one can obtain a
battery having a total thickness lying under the thickness one can
achieve with the embodiment of FIG. 1.
[0060] One of the main advantages of the battery described herein
is the multiple sealing zones. As it can be seen in FIGS. 1 and 2,
a circumferentially inner part of the frame 22, 22' is sandwiched
between the two current collectors 18,18', 20, 20' and is bonded to
them via the melted hot-melt-adhesive coating of the frame 22, 22'.
The current collectors 18, 18', 20, 20' and the frame 22 lying
between them thus form a hermetically sealed "housing" protecting
the package 10, 10' and thus the battery's anode and cathode from
the entry of moisture.
[0061] In addition to this inner sealing provided by the frame 22,
22' sealed to the current collectors 18, 18', 20, 20', an outer
sealing jacket is formed by the two polymeric jacket layers, i.e.
by polymeric sheets 24, 26 in the first embodiment, or by polymeric
frames 24', 26' in the second embodiment, which are sealed to each
other on their outer circumference. This jacket forms an additional
protection for the complete battery, including the current
collectors 18, 18', 20, 20'. Furthermore, the polymeric jacket
layers 24, 24', 26, 26' are also sealed to the frame 22, 22' in a
region which lies circumferentially outwards of the current
collectors 18, 18', 20, 20'. Finally, the polymeric jacket layers
24, 24', 26, 26' are sealed to the current collectors 18, 18', 20,
20' on the complete surface of these current collectors. Due to the
low thickness of the single layers, i.e. of the polymeric jacket
layers, the current collectors, the active materials as well as the
frame, the whole battery will remain flexible while being perfectly
sealed.
[0062] The combination of the frame sandwiched between the current
collectors in a circumferentially inner region and sandwiched
between the two polymeric jacket layers in an outer region with the
jacket formed by these jacket layers thus provides an excellent
sealing for the battery according to the invention.
* * * * *