U.S. patent application number 14/198875 was filed with the patent office on 2014-07-03 for film-clad battery and method of producing a film-clad battery.
This patent application is currently assigned to NEC CORPORATION. The applicant listed for this patent is Makihiro OTOHATA, Hiroshi YAGETA. Invention is credited to Makihiro OTOHATA, Hiroshi YAGETA.
Application Number | 20140182119 14/198875 |
Document ID | / |
Family ID | 34430954 |
Filed Date | 2014-07-03 |
United States Patent
Application |
20140182119 |
Kind Code |
A1 |
OTOHATA; Makihiro ; et
al. |
July 3, 2014 |
FILM-CLAD BATTERY AND METHOD OF PRODUCING A FILM-CLAD BATTERY
Abstract
A joint section where covering films 2a, 2b of film-covered
battery 1 are heat-sealed together is formed with flat surface 6'
having thickness t.sub.1 and groove 6 having thickness t.sub.2.
Groove 6 serves to reduce the projection area of film-covered
battery 1 by folding side 2c toward receiving section 2a1 with
groove 6 serving as an edge, and groove 6 is made thinner than flat
surface 6' by .DELTA.t=t.sub.1-t.sub.2. Therefore, the length of
covering films 2a, 2b produced on outer side 6a is shortened as
compared with the case of folding the portion that has thickness
t.sub.1.
Inventors: |
OTOHATA; Makihiro;
(Sagamihara-shi, JP) ; YAGETA; Hiroshi;
(Sagamihara-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OTOHATA; Makihiro
YAGETA; Hiroshi |
Sagamihara-shi
Sagamihara-shi |
|
JP
JP |
|
|
Assignee: |
NEC CORPORATION
Tokyo
JP
|
Family ID: |
34430954 |
Appl. No.: |
14/198875 |
Filed: |
March 6, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10574562 |
Apr 4, 2006 |
8697277 |
|
|
PCT/JP2004/014364 |
Sep 30, 2004 |
|
|
|
14198875 |
|
|
|
|
Current U.S.
Class: |
29/623.2 ;
29/623.1 |
Current CPC
Class: |
B29C 53/063 20130101;
B29C 66/72321 20130101; B29C 66/4332 20130101; B29C 66/83221
20130101; B29L 2009/00 20130101; B29C 65/02 20130101; H01M 2/021
20130101; B29C 66/433 20130101; H01M 2/0212 20130101; B29C 59/007
20130101; H01G 13/003 20130101; B29C 65/08 20130101; B29C 66/7234
20130101; H01M 2/08 20130101; H01M 2/0275 20130101; B29C 66/1122
20130101; H01G 9/08 20130101; B29C 66/131 20130101; H01M 2/0267
20130101; Y10T 29/4911 20150115; B29C 66/80 20130101; B29C 66/53461
20130101; Y10T 29/49108 20150115; B29C 66/0324 20130101; B29L
2031/7146 20130101; B29L 2031/3468 20130101; Y02E 60/10 20130101;
H01M 2/0287 20130101; B29C 66/112 20130101 |
Class at
Publication: |
29/623.2 ;
29/623.1 |
International
Class: |
H01M 2/02 20060101
H01M002/02; H01M 2/08 20060101 H01M002/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 7, 2003 |
JP |
2003-348126 |
Claims
1. A fabrication method of a film-covered battery which has a
battery element encapsulated within a covering film having at least
one folded joint section formed around said battery element, said
method characterized by comprising the steps of: forming at least
one fold thinner than the thickness of said joint section
therearound in said joint section; and folding said joint section
along said fold.
2. The fabrication method of a film-covered battery according to
claim 1, comprising the step of forming said fold by pressing at
least one side of said joint section with a member having a
protrusion.
3. The fabrication method of a film-covered battery according to
claim 2, comprising the step of heat-sealing and joining said joint
section of said covering film having a heat-sealing property by
heating and pressing said joint section with said member.
4. The fabrication method of a film-covered battery according to
claim 1, comprising the step of preparing one of a chemical battery
and a capacitor as said battery element.
Description
[0001] This is a divisional application based upon U.S. patent
application Ser. No. 10/574,562 filed Apr. 4, 2006, which is a
National Stage of International Application No. PCT/JP2004/014364
filed Sep. 30, 2004, claiming priority based on Japanese Patent
Application No. 2003-348126 filed Oct. 7, 2003, the contents of all
of which are incorporated herein by reference in their
entirety.
TECHNICAL FIELD
[0002] The present invention relates to a film-covered battery
which has a battery element encapsulated in a flexible materials
used to cover the battery, and a method of producing the
film-covered battery.
BACKGROUND ART
[0003] In recent years, a reduction in weight and thickness has
been strictly required for batteries as a power supply for portable
devices and the like. Thus, in regard to materials used to cover
the batteries, laminate films capable of a further reduction in
weight and thickness have been used more and more instead of
conventional metal cans in which there is a limit to weight and
thickness reductions. This laminate film which can be freely formed
into different shapes, compared with a metal can, comprises a thin
metal film or a laminate of a thin metal film and a heat-seal resin
film.
[0004] As a representative example of a laminate film used for
materials used to cover the batteries, there is a three-layer
laminate film that has a heat-seal resin film, which is a heat seal
layer, laminated on one side of an aluminum thin film, which is a
thin metal film, and a protection film laminated on the other
side.
[0005] Generally, in a film-covered battery which uses a laminate
film for a covering material, a battery element comprising a
positive electrode, a negative electrode, an electrolyte and the
like is hermetically sealed (hereinafter simply called "sealed") by
covering the battery elements with the covering material in such a
manner that heat-seal resin film is positioned inside, and by
heat-sealing the covering material around the battery element.
Polyethylene or polypropylene, for example, is used for the
heat-seal resin film, while a nylon film or a polyethylene
terephthalate film, for example, is used for the protection
film.
[0006] For reference, as a battery element, other than chemical
batteries such as a lithium battery, a nickel hydrogen battery and
the like, those having a charge accumulating function such as a
capacitor also use laminate film as a covering material.
[0007] In a film-covered battery, lead terminals are connected to a
positive electrode and a negative electrode of a battery element,
respectively, for leading the positive electrode and negative
electrode to the outside of the covering material to extend these
lead terminals from the covering material. The lead terminals are
connected to the battery element by ultrasonic welding or the like
before the battery element is sealed. Also, the battery element is
sealed by sandwiching the battery element with two sheets of
covering material, and by heat-sealing the covering materials along
the peripheral edge. The covering materials are heat-sealed by
first heat-sealing three sides of the covering materials for
formation into a bag. Subsequently, air is exhausted from the
interior of the covering materials to produce a vacuum inside the
covering materials, the covering materials are brought into close
contact with the battery element by atmospheric pressure, and the
one side that remains is heat-sealed in this state.
[0008] When the battery element has a certain degree of thickness,
the general approach is to form one of the covering materials into
the shape of a collared container shape by deep-draw molding, such
that the battery element is readily received therein, cover the
covering material formed into the container shape from above the
battery element, and join the collar by thermal fusing.
[0009] For preventing external moisture and the like from being
introduced into the film-covered battery and to prevent the
electrolytic solution and the like within the film-covered battery
from escaping to the outside, a thin metal film of aluminum or the
like is used in the covering film as a barrier layer, but the
heat-seal resin film layer is exposed along the edge of the joint
section around the battery element, causing a leak path based on
the molecular transport phenomenon of the resin itself. Therefore,
to improve the reliability of sealing for the film-covered battery,
the leak can be reduced by increasing the width of the joint
section to extend the transmission path and to increase the
resistance, however this causes the problem that a larger
projection area of the film-covered battery. Thus, JP-A-2002-25514
proposes a reduction in projection area by folding a joint section
toward a battery element receiving section.
DISCLOSURE OF THE INVENTION
[0010] However, the foregoing folded joint section of the
conventional film-covered battery causes a problem of possible
damage such as cracks that open in the folded portion because of
the inability of the outside layer to follow elongation of the
film. This is because of the thickness of the laminate film causes
a difference in elongation between the inside and outside of the
fold of the film. This phenomenon will be described below with
reference to FIGS. 1, 2, and 3.
[0011] For example, as illustrated in FIG. 1, film-covered battery
101 has a shape such that joint sections of two opposite sides are
folded substantially at right angles toward a battery element
receiving section in order to reduce the projection area a
projection area. As can be seen in a cross-sectional view near a
joint section before folding illustrated in FIG. 2, hardly any of
protection film 102c, thin metal film 102d, and heat-seal resin
film 102e hardly vary in thickness in the joint section.
[0012] However, as illustrated in FIG. 3, when this joint section
is folded from the bottom substantially at right angles toward the
battery element receiving section, a layer on outer side 106a of
the fold is elongated to become thinner, possibly causing a crack
to appear. If a crack opens in thin metal film 102d layer, a leak
path is created through the crack, and a short transmission path is
formed from the crack to the interior of the battery, resulting in
possible damage to the performance and to the reliability of
film-covered battery 101.
[0013] To solve the foregoing problems, it is an object of the
present invention to provide a film-covered battery which has a
battery element encapsulated in a flexible covering material, which
is capable of preventing the covering material from damage that
occurs when a joint section is folded, and a method of producing
the film-covered battery.
[0014] To achieve the above object, a film-covered battery of the
present invention comprises battery elements having a configuration
in which a positive electrode faces a negative electrode, and in
which a covering film having at least a heat-seal resin layer and a
thin metal film layer are laminated, for encapsulating the battery
element with the heat-seal resin layer being positioned inside, and
for sealing the battery element by heat-sealing a joint section
having at least one folded side along a peripheral edge, and is
characterized in that the joint section is formed with at least one
fold, and the fold has a thickness smaller than a thickness of the
joint section around the fold.
[0015] The film-covered battery of the present invention configured
as described above is formed with the fold having a smaller
thickness in the joint section. Specifically, since the fold has a
smaller thickness, the outer side of the fold is not excessively
elongated when the joint section is folded along the fold. It is
therefore possible to prevent a crack from appearing due to
elongation of the covering films. Also, since the existence of the
fold defines the folded position, the joint section will not be
folded at an inconvenient position. In this way, the film-covered
battery after folding is readily made in uniform dimensions.
[0016] Also, in the film-covered battery, the fold may be a groove,
or the groove may be formed in at least one side of the joint
section.
[0017] Also, in the film-covered battery, a plurality of the folds
may be formed in the joint section, such that the joint section is
folded along each of the folds.
[0018] A film-covered battery of the present invention comprises a
battery element having a configuration in which a positive
electrode faces a negative electrode, and in which a covering film
having at least a heat-seal resin layer and a thin metal film layer
are laminated, for encapsulating the battery element with the
heat-seal resin layer being positioned inside, and for sealing the
battery element by heat-sealing a joint section having at least one
folded side along a peripheral edge, and is characterized in that
the joint section is formed with a plurality of folds, the folds
have a thickness smaller than a thickness of the joint section
around the folds, the folds are grooves formed in at least one side
of the joint section, and the joint section is folded along each of
the folds.
[0019] Also, in the film-covered battery, the battery element may
be one of a chemical battery and a capacitor.
[0020] A fabrication method of a film covered battery of the
present invention is characterized in having a battery element
encapsulated within a covering film that has at least one folder
joint section formed around the battery element, by comprising the
steps forming at least one folder thinner than a thickness of the
joint section therearound in the joint section, and folding the
joint section along the fold.
[0021] The film-covered battery of the present invention configured
as described above is formed with the fold having a smaller
thickness in the joint section. For this reason, the force required
for folding is reduced. Also, since the existence of the fold
defines the folded position, the joint section will not be folded
at an inconvenient position. In this way, the film-covered battery
after folding is readily made in uniform dimensions. Further, since
the outer side of the fold is not excessively elongated when the
joint section is folded along the fold, a crack is unlikely to
appear due to the elongation of the covering films, thus making it
possible to produce a reliable film-covered battery.
[0022] Also, the fabrication method of a film-covered battery may
include the step of forming the fold by pressing at least one side
of the joint section with a member having a protrusion, or may
include the step of heat-sealing and joining the joint section of
the covering film having a heat-sealing property by heating and
pressing the joint section with the member.
[0023] Also, the fabrication method of a film-covered battery may
include the step of preparing one of a chemical battery and a
capacitor as the battery element.
[0024] As described above, since the present invention forms a
folded portion of the joint section of the covering films so that
it is thinner, the folding operation is facilitated. Also, since
the elongation on the outer side is reduced when the joint section
is folded, the covering material can be prevented from incurring
damage. From the foregoing, the present invention can prevent a
crack from opening in the middle of the joint section to form a
short transmission path into the interior of the battery, and can
also prevent the introduction of moisture and the escape of an
electrolytic solution from accelerating, thus making it possible to
improve the performance and reliability of the battery.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 A perspective view of a conventional film-covered
battery.
[0026] FIG. 2 A cross-sectional view of a joint section along the
length a long side of the film-covered battery illustrated in FIG.
1 before it is folded.
[0027] FIG. 3 A cross-sectional view of the joint section of the
length long side of the film-covered battery illustrated in FIG.
1.
[0028] FIG. 4 A perspective view of a film-covered battery
according to a first embodiment of the present invention.
[0029] FIG. 5 An exploded perspective view of the film-covered
battery illustrated in FIG. 4.
[0030] FIG. 6 A perspective view illustrating the state of the
film-covered battery illustrated in FIG. 4 before a joint section
is folded.
[0031] FIG. 7 A cross-sectional view illustrating the state of the
film-covered battery illustrated in FIG. 4 when the length a long
side is connected.
[0032] FIG. 8 A cross-sectional view of the joint section along the
length long side of the film-covered battery illustrated in FIG. 4
before it is folded.
[0033] FIG. 9 A perspective view of the joint section along the
length long sides of the film-covered battery illustrated in FIG.
4.
[0034] FIG. 10 A perspective view of a film-covered battery
according to a second embodiment of the present invention.
[0035] FIG. 11 A perspective view illustrating the state of the
film-covered battery illustrated in FIG. 10 before a joint section
is folded.
[0036] FIG. 12 An exploded perspective view of the film-covered
battery illustrated in FIG. 10.
[0037] FIG. 13 A perspective view of another film-covered battery
according to the second embodiment of the present invention.
[0038] FIG. 14 A perspective view illustrating the state of the
film-covered battery illustrated in FIG. 13 before a joint section
is folded.
[0039] FIG. 15 An exploded perspective view of the film-covered
battery illustrated in FIG. 13.
[0040] FIG. 16 A perspective view of a film-covered battery
according to a third embodiment of the present invention.
[0041] FIG. 17 A perspective view illustrating the state of the
film-covered battery illustrated in FIG. 16 before a joint section
is folded.
[0042] FIG. 18 A perspective view of another film-covered battery
according to the third embodiment of the present invention.
[0043] FIG. 19 A perspective view illustrating the state of the
film-covered battery illustrated in FIG. 18 before a joint section
is folded.
[0044] FIG. 20 An exploded perspective view illustrating the
configuration of a battery element in an example of the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0045] Next, embodiments of the present invention will be described
with reference to the drawings.
First Embodiment
[0046] FIG. 4 is a perspective view illustrating the appearance of
a film-covered battery according to a first embodiment of the
present invention, FIG. 5 is an exploded perspective view
illustrating the configuration of the film-covered battery
illustrated in FIG. 4, and FIG. 6 is a perspective view
illustrating the state of the film-covered battery illustrated in
FIG. 4 before a joint section is folded. In this regard, FIG. 5
illustrates a film-covered battery which is not formed with a
groove that is a feature of the present invention.
[0047] As illustrated in FIG. 5, film-covered battery 1 of this
embodiment comprises laminate type battery element 5 (see FIG. 20)
having positive electrode plates 8 and negative electrode plates 9
laminated through separators 10; rectangular covering films 2a, 2b
for receiving battery element 5 together with an electrolytic
solution; and positive electrode's lead terminal 3 and negative
electrode's lead terminal 4 connected to a positive electrode and a
negative electrode of battery element 5, respectively.
[0048] As covering films 2a, 2b, known covering materials generally
used for film-covered batteries can be used, such as laminate film
which is made of lamination of thin metal film and heat-seal resin.
Covering films 2a, 2b of this embodiment are made by laminating
protection film 2f, thin metal film 2d, and heat-seal film 2e (see
FIG. 8).
[0049] Covering film 2a is formed with receiving section 2a1 for
receiving battery element 5. Receiving section 2a1 may be formed,
for example, by deep-draw molding. Battery element 5 is received in
receiving section 2a1 of covering material 2a, and sealed by
surrounding battery element 5 by sandwiching the same from above
and from below together with covering film 2b, and by heat-sealing
the peripheral edges of these covering films 2a, 2b. In this event,
three sides of covering film 2a, 2b are first heat-sealed for
formation into a bag shape. After pouring electrolytic solution
into bag-shaped covering films 2a, 2b, air remaining therein is
exhausted from the remaining open sides. Then, covering films 2a,
2b are hermetically sealed by heat-sealing the remaining sides.
[0050] Covering films 2a, 2b are heat-sealed using thermal fusing
head 7 having protrusions 7a and flat areas 7b, shown in a
cross-sectional view in FIG. 7 when the joint section is
heat-sealed. As illustrated in FIG. 7, thermal fusing head 7
sandwiches covering films 2a, 2b from both sides to heat seal them.
FIG. 8 illustrates a partial cross-sectional view of the joint
section after thermal fusing. A portion heat-sealed by flat area 7b
is formed as flat surface 6' having thickness t.sub.1, while a
portion heat-sealed by protrusion 7a is formed as groove 6 having
thickness t.sub.2. In other words, the portion of groove 6 in
covering film 2a, 2b is thinner than flat surface 6' by
.DELTA.t=t.sub.1-t.sub.2. Grooves 6 are formed in sides 2c which
are two opposing long sides from which neither positive electrode
lead terminal 3 nor negative electrode lead terminal 4 extend.
These grooves 6 are folds along sides 2c which are folded toward
receiving section 2a1 for reducing a projection area of
film-covered battery 1.
[0051] In the case of film-covered battery 1 of this embodiment,
the force required for folding is reduced by folding along groove 6
which is thinner than flat surface 6' by .DELTA.t. Also, since the
existence of groove 6 defines the folded position, the joint
section will not be folded at an inconvenient position. In this
way, film-covered battery 1, after the folding, is readily made in
uniform dimensions.
[0052] Also, according to this embodiment, in addition to the
effect of improving the workability in the foregoing manner, groove
6 has thickness t.sub.2 smaller than flat surface 6' by .DELTA.t,
so that elongation of covering films 2a, 2b on outer side 6a can be
reduced as compared with the covering films folded in the area
having a thickness of t.sub.1. Thus, this embodiment can prevent a
crack from appearing due to excessive elongation of outer side 6a
of the folded portion to improve the reliability.
[0053] As described above, film covered battery 1 formed with
grooves 6 along sides 2c of this embodiment can have improved
folding workability, be in uniform dimensions, and have improved
reliability as a film covered battery.
[0054] In this regard, while this embodiment has shown the
configuration in which grooves 6 are formed along two opposing
sides 2c for folding the same, groove 6 may be formed along one or
more arbitrary sides. Also, groove 6 need not be formed over the
entire length of the side, and may not be formed, for example, in
end regions of the side. Also, positive electrode lead terminal 3
and negative electrode's lead terminal 4 may be extended from two
or more different sides. Also, the joint section may be folded in
an arbitrary direction and at an arbitrary angle, such as folded
substantially at 180.degree. on the side opposite to battery
element 5 receiving section. Also, while this embodiment has shown
an example in which grooves 6 are formed by thermal fusing head 7
having protrusions 7a on both sides of side 2c, groove 6 may be
formed only on one side.
Second Embodiment
[0055] Next, a film-covered battery according to a second
embodiment of the present invention will be described with
reference to FIGS. 10 to 15. In this regard, since the film-covered
battery of this embodiment is similar in basic structure, groove
forming method, and structure to the film-covered battery of the
first embodiment, a detailed description is omitted.
[0056] While the first embodiment has shown a configuration in
which the battery element is encapsulated by two covering films,
and sealed by heat-sealing the four sides therearound, film-covered
batteries 11, 21 of this embodiment have battery elements 15, 25
encapsulated in folded single covering films 12, 22, and sealed by
heat-sealing the three surrounding sides.
[0057] In an example of FIGS. 10-12, groove 16 is formed along one
side opposing a side created by folding covering film 12, and a
joint section thereof is folded toward receiving section 12a1 which
receives battery element 15. FIG. 10 is a perspective view
illustrating the appearance of the film-covered battery, FIG. 11 is
a perspective view illustrating the state of the film-covered
battery illustrated in FIG. 10 before the joint section is folded,
and FIG. 12 is an exploded perspective view illustrating the
configuration of the film-covered battery illustrated in FIG.
10.
[0058] Film-covered battery 11 illustrated in FIGS. 10-12 has
covering film 12 folded along fold-over section 12' of side 12c'
adjacent to a side from which positive lead terminal 13 and
negative electrode lead terminal 14 extend. This film-covered
battery 11 has three sides other than fold-over section 12'
connected by thermal fusing as illustrated in FIG. 11, and groove
16 is formed only along side 12c opposing fold-over section 12'.
The method for forming the groove and configuration of groove 16
are basically similar to the method shown in the first embodiment.
Film-covered battery 11 is also formed into film-covered battery 11
having only one side folded, illustrated in FIG. 10, by folding
side 12c along groove 16 toward receiving section 12a1.
[0059] On the other hand, in the example of FIGS. 13-15,
protrusions for positive electrode lead terminal 23 and negative
electrode lead terminal 24 are provided on a side created by
folding covering film 22 and on an opposing side, and grooves 26
are formed along the two other sides, and these two other sides are
folded. The remaining configuration is similar to the first
embodiment, so that a description thereon is omitted. FIG. 13 is a
perspective view illustrating the appearance of the film-covered
battery, FIG. 14 is a perspective view illustrating the state of
the film-covered battery illustrated in FIG. 13 before the joint
section is folded, and FIG. 15 is an exploded perspective view
illustrating the configuration of the film-covered battery
illustrated in FIG. 13.
[0060] As illustrated in the exploded perspective view of FIG. 15,
film-covered battery 21 illustrated in FIGS. 13-15 has covering
film 22 folded along fold-over section 22' on side 22c' which
opposes a side from which positive electrode's lead terminal 23 and
negative electrode's lead terminal 24 extend. As illustrated in
FIG. 14, film-covered battery 21 has three sides connected by
thermal fusing except for fold-over section 22'. Then, grooves 26
are formed along this side 22c' and two sides 22c except for the
side from which positive electrode's lead terminal 23 and negative
electrode's lead terminal 24 extend. The method for forming the
groove and configuration of grooves 26 are also basically similar
to the method shown in the first embodiment. A The Film-covered
battery is also formed into film-covered battery 21 which has two
sides folded in a manner similar to film-covered battery 1 in the
first embodiment, as illustrated in FIG. 13, by folding each side
22c along groove 26 toward receiving section 22a1.
[0061] Thus, like film-covered battery 1 in the first embodiment,
film-covered batteries 11, 21 of this embodiment formed with
grooves 16, 26 along sides 12c, 22c can have improved folding
workability and be made in uniform dimensions.
[0062] Also, film-covered batteries 11, 21 of this embodiment can
reduce exposed sides of heat-seal resin film 22e, which can be a
leak path, by receiving the battery element in single folded
covering films 12, 22, as compared with the battery element
received using two covering films, thus making it possible to
better prevent a degradation in performance and reliability of
film-covered batteries 11, 22 due to the introduction of external
moisture and the escape of electrolytic solution.
[0063] Likewise, in this embodiment, the groove need not be formed
over the entire length of the side, and may not be formed, for
example, in end regions of the side. Also, the positive electrode's
lead terminal and negative electrode's lead terminal may be
extended from two or more different sides. Also, the joint section
may be folded in an arbitrary direction and at an arbitrary angle,
such as folded substantially at 180.degree. on the side opposite to
the battery element receiving section. Also, grooves 16, 26 may be
formed on both sides or formed only on one side.
Third Embodiment
[0064] Next, a film-covered battery according to a third embodiment
of the present invention will be described with reference to FIGS.
16-19. In this regard, since the film-covered battery of this
embodiment is similar in basic structure, groove forming method,
and structure to the film-covered battery of the first embodiment,
a detailed description is omitted.
[0065] The film-covered battery according to the third embodiment
of the present invention has a heat-sealed section of covering
films folded a plurality of times to further reduce the projection
area of the film-covered battery. FIGS. 16 and 17 illustrate an
example in which two grooves are formed along one side, while FIGS.
18 and 19 illustrate an example in which three grooves are formed
along one side.
[0066] FIG. 16 is a perspective view illustrating the appearance of
the film-covered battery having two grooves formed along one side
according to the third embodiment of the present invention, and
FIG. 17 is a perspective view illustrating the state of the
film-covered battery illustrated in FIG. 16 before the joint
section is folded.
[0067] As illustrated in FIG. 17, two grooves 36a, 36b are formed
substantially in parallel along two sides 32c from which neither
positive electrode's lead terminal 33 nor negative electrode's lead
terminal 34 is extended. Groove 36a is provided for folding side
32c toward receiving section 32a1 in a manner similar to the
respective embodiments described above. Groove 36b formed outside
of groove 36a is provided for again folding over side 32c which has
been folded up along groove 36a which results in an edge. In other
words, groove 36b is located at the peak of side 32c folded in a
mountain shape. Since side 32c is folded along grooves 36a, 36b,
film-covered battery 31 has a further reduced projection area.
[0068] On the other hand, FIG. 18 is a perspective view
illustrating the appearance of a film-covered battery formed with
three grooves along one side, and FIG. 19 is a perspective view
illustrating the state of the film-covered battery illustrated in
FIG. 18 before the joint section is folded.
[0069] As illustrated in FIG. 18, three grooves 46a, 46b, 46c are
formed substantially in parallel, respectively, along two sides 42c
from which neither positive electrode's lead terminal 44 nor
negative electrode's lead terminal 44 extend. Groove 46a is
provided for folding side 42c toward receiving section 42a1 in a
manner similar to the respective embodiments described above.
Grooves 46b, 46c formed outside of grooves 46a, which are formed in
close proximity to each other, are provided for again folding over
side 42c which has been folded up along groove 46a which results in
an edge. Specifically, although side 42c is folded in a mountain
shape in this embodiment as well, side 43c is folded by nearly
90.degree. at each of two locations along grooves 46b, 46c, instead
of folding by nearly 180.degree. at one location as in the example
illustrated in FIGS. 16 and 17, thereby further reducing damage to
the covering films due to folding at an acute angle. Film-covered
battery 41 also has a further reduced projection area because side
42c is folded along grooves 46a, 46b, 46c.
[0070] Thus, film-covered batteries 31, 41 of this embodiment
formed with grooves 36a, 36b along side 32c and grooves 46a, 46b,
46c along side 42c can have improved the folding workability, be
made in uniform dimensions, and have improved reliability as a
film-covered battery, like film-covered battery 1 of the first
embodiment.
[0071] Also, the film-covered batteries of this embodiment have
further reduced projection areas because the battery element is
placed in covering films 32, 42 which are folded in a mountain
shape.
[0072] Likewise, in this embodiment, the groove need not be formed
over the entire length of the side, but may not be formed, for
example, in end regions of the side. Also, the positive electrode's
lead terminal and negative electrode's lead terminal may be
extended from two or more different sides. Also, the joint section
may be folded on the side opposite to the battery element receiving
section, and the number of formed grooves may be three or more.
[0073] Also, in the respective embodiments described above, the
fold has been made in a so-called groove shape, but the fold may be
in any shape as long as the thickness of the fold is smaller than
the thickness of the joint section other than the fold. For
example, the fold may be in the shape of smooth concave.
[0074] Also, in the respective embodiments described above, the
grooves on the outer side and inner side of the fold, shown as an
example, have substantially the same groove shape, but the grooves
are not so limited, and the groove on the outer side may have a
different cross-sectional shape from the groove on the inner side.
For example, the groove on the outer side may have the bottom wider
than that of the groove on the inner side, or vice versa. Also,
while the respective embodiments have shown the grooves in a
concave shape on both sides as an example, the grooves are not so
limited, but only one of those on the outer side and inner side of
the fold may be in a concave shape.
EXAMPLE
[0075] Next, a specific example of the present invention will be
described with reference to the drawings used for describing the
first embodiment, giving film-covered battery 1 in the
aforementioned first embodiment as an example.
<Fabrication of Positive Electrodes>
[0076] In this example, lithium manganate powder having a spinel
structure, a material which is carbonaceous and imparts electrical
conductivity, and polyvinylidene fluoride were mixed and dispersed
in N-methyl-pyrolidone (represented by NMP in some cases) in a mass
ratio of 90:5:5, and stirred into slurry. The amount of NMP was
adjusted such that the slurry would have a proper viscosity. This
slurry was uniformly coated on one side of an aluminum foil having
a thickness of 20 .mu.m, which would serve as positive electrode
plate 8, using a doctor blade. The coating was made such that
striped parts of a small region(in which the aluminum foil exposed)
were left uncoated. Next, the aluminum foil coated with this slurry
was dried in vacuum at 100.degree. C. for two hours. Subsequently,
the other side of the aluminum foil was also coated with the slurry
in a similar manner, and dried in a vacuum. In this event, the
slurry was coated such that the uncoated regions matched on the
front and back sides.
[0077] The aluminum foil thus coated with an active material on
both sides was roll pressed. This was cut into rectangles,
including the region not coated with the active material, which
were used as positive electrode plates 8. The region which was not
coated with active material was cut away except for a portion
thereof on one side which was left in a rectangular shape, and the
left portion was used as a tab.
<Fabrication of Negative Electrodes>
[0078] Amorphous carbon powder and polyvinylidene fluoride were
mixed and dispersed in NMP in a mass ratio of 91:9, and stirred
into slurry. The amount of NMP was adjusted such that the slurry
would have a proper viscosity. This slurry was uniformly coated on
one side of a copper foil having a thickness of 10 .mu.m, which
would serve as negative electrode plate 6, using a doctor blade.
The coating was made such that striped parts of a small region(in
which the acopper foil exposed) were left uncoated. Next, the
copper foil coated with this slurry was dried in a vacuum at
100.degree. C. for two hours. In this event, the thickness in which
the active material had been coated was adjusted such that the
logical capacity of negative electrode plate 9 per unit area and
the logical capacity of positive electrode plate 8 per unit area
was 1:1. Subsequently, the other side of the copper foil was also
coated with the slurry in a similar manner, and dried in a
vacuum.
[0079] The copper foil thus coated with an active material on both
sides was roll pressed. This was cut into rectangles whose vertical
and horizontal dimensions were each 2 mm larger than those of
positive electrode plates 8, including the region not coated with
the active material, which was used as negative electrode plates 9.
The region which was not coated with active material was cut away
except for a portion thereof on one side which was left in a
rectangular shape, and the left portion was used as a tab.
<Fabrication of Battery Element>
[0080] Positive electrode plates 8 and negative electrode plates 9
fabricated in the foregoing manner, and separators 10 made of a
micro-porous sheet having a three-layered structure of
polypropylene layer/polyethylene layer/polypropylene layer were
laminated one on another as illustrated in FIG. 20. In this event,
negative electrode plate 9 was chosen for the outermost electrode
plate, and separator 10 was placed further outside this negative
electrode plate 9 (in other words, they were laminated in the order
of separator/negative electrode plate/separator/positive electrode
plate/separator/ . . . /negative electrode plate/separator).
[0081] Next, the tabs of positive electrode plates 8 and positive
electrode's lead terminal 3 made of an aluminum plate with a
thickness of 0.1 mm were collectively ultrasonic-welded to make a
charge collector with a positive electrode. Likewise, the tabs of
negative electrode plates 9 and negative electrode's lead terminal
4 made of a nickel plate with a thickness of 0.1 mm were
collectively ultrasonic-welded to make a charge collector with a
negative electrode.
<Sealing of Battery Element>
[0082] Two covering films 2a, 2b which are aluminum laminate films
having a four-layered structure of nylon layer/aluminum layer/acid
modified polypropylene layer/polypropylene layer were used as
covering materials. Covering film 2a was formed with a recess whose
size was slightly larger than battery element 5 by deep-draw
molding, such that covering film 2a is concave on polypropylene
layer side, to create receiving section 2a1.
[0083] Battery element 5 mentioned above was received by two
covering films 2a, 2b, laid one on top of the other, such that only
positive electrode's lead terminal 3 and negative lead terminal 4
extended from covering films 2a, 2b, and three surrounding sides of
covering films 2a, 2b were connected by thermal fusing. The length
of the two the two opposing long sides adjacent to the side from
which the lead terminals extended were heat-sealed using a thermal
fusing apparatus having protrusions on the surfaces of the fusing
part of thermal fusing head 7, as illustrated in FIG. 7 to create a
joint section having grooves 6 illustrated in the perspective view
of FIG. 6 and in the cross-sectional view of FIG. 8.
[0084] Next, an electrolytic solution was poured into the interior
of covering films 2a, 2b, in which battery element 5 had been
received, from the remaining sides which were not connected.
[0085] The electrolytic solution that was used was made up of 1
mol/liter of LiPF.sub.6 serving as a supporting electrolyte, and a
mixed solvent of propylene carbonate and ethylene carbonate (mass
ratio is 50:50). After the electrolytic solution was poured, air
remaining inside was exhausted from the remaining open sides of
covering films 2a, 2b, and battery element 5 was sealed by
heat-sealing the remaining side.
[0086] Finally, the joint section was folded substantially at right
angles toward receiving section 2a1 such that groove 6 formed an
edge, as illustrated in the cross-sectional view of FIG. 9, thereby
fabricating film-covered battery 1 which was a lithium secondary
battery having covering materials made of a laminate film.
[0087] While the present invention has been described in connection
with several representative embodiments and specific examples, it
is apparent that the present invention is not limited to them, and
can be modified as appropriate within the scoop of the technical
philosophy of the present invention.
[0088] For example, while a laminate film of a thin metal film and
a heat-seal resin have been used as a flexible covering material,
other materials can also be used so long as they have a property
that will adequately seal the battery element
[0089] Also, while the battery element that is used as an example
is a laminate type which has been used to alternatively laminate
the positive electrode plates and the negative electrode plates,
the present invention can also be applied to winding type element.
Also while the battery elements of a lithium secondary battery has
been given as an example to describe the battery elements, the
present invention can be applied to battery elements for other
types of chemical batteries such as a nickel hydrogen battery, a
nickel cadmium battery, a lithium metal primary battery or
secondary battery, a lithium polymer battery and the like, as well
as a capacitor element and the like.
* * * * *