U.S. patent application number 13/673451 was filed with the patent office on 2013-12-12 for electrochemical device.
This patent application is currently assigned to TAIYO YUDEN CO., LTD.. The applicant listed for this patent is TAIYO YUDEN CO., LTD.. Invention is credited to Naoto HAGIWARA, Katsuei ISHIDA, Kyotaro MANO.
Application Number | 20130330596 13/673451 |
Document ID | / |
Family ID | 47435461 |
Filed Date | 2013-12-12 |
United States Patent
Application |
20130330596 |
Kind Code |
A1 |
MANO; Kyotaro ; et
al. |
December 12, 2013 |
ELECTROCHEMICAL DEVICE
Abstract
An electrochemical device includes a container, a storage
element, and a structure. The container includes a container main
body including a first inner surface, and a lid including a second
inner surface opposed to the first inner surface. The lid is bonded
to the container main body. The container contains an electrolyte.
The storage element includes first and second electrode layers
respectively adhered to the first and second inner surfaces and a
separator provided between the first and second electrode layers to
retain the electrolyte, and is sandwiched between the first and
second inner surfaces. The structure is provided in at least either
one of the first and second inner surfaces. The structure
compresses and deforms the storage element to form, in an area of
the separator sandwiched between the first and second electrode
layers, a thin wall portion thinner than in a peripheral area
around the area.
Inventors: |
MANO; Kyotaro; (Tokyo,
JP) ; HAGIWARA; Naoto; (Tokyo, JP) ; ISHIDA;
Katsuei; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TAIYO YUDEN CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
TAIYO YUDEN CO., LTD.
Tokyo
JP
|
Family ID: |
47435461 |
Appl. No.: |
13/673451 |
Filed: |
November 9, 2012 |
Current U.S.
Class: |
429/163 ;
361/502 |
Current CPC
Class: |
H01M 2/02 20130101; H01M
2/0207 20130101; Y02E 60/13 20130101; H01M 2/0469 20130101; H01G
11/74 20130101; H01M 10/0436 20130101; Y02E 60/10 20130101; H01G
11/52 20130101; H01M 2/04 20130101; H01G 11/82 20130101; H01M 2/16
20130101; H01M 2/18 20130101; H01G 9/155 20130101 |
Class at
Publication: |
429/163 ;
361/502 |
International
Class: |
H01M 2/16 20060101
H01M002/16; H01M 2/04 20060101 H01M002/04; H01G 9/00 20060101
H01G009/00; H01M 2/02 20060101 H01M002/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 8, 2012 |
JP |
2012-130400 |
Claims
1. An electrochemical device, comprising: a container including a
container main body including a first inner surface, wherein the
first inner surface is flat, and a lid including a second inner
surface that is opposed to the first inner surface and being joined
to the container main body, the container containing an electrolyte
sealed therein, wherein the second inner surface is flat; a storage
element including a first electrode layer that is bonded to the
first inner surface, a second electrode layer that is bonded to the
second inner surface, and a separator that is provided between the
first electrode layer and the second electrode layer to retain the
electrolyte, the storage element being sandwiched between the first
inner surface and the second inner surface; and a structure that is
provided in at least either one of the first inner surface and the
second inner surface, wherein the structure comprises at least one
protrusion, and wherein the structure compresses and deforms the
storage element to form, in an inner area of the separator that is
sandwiched between the first electrode layer and the second
electrode layer, a thin wall portion having a smaller thickness
than in a peripheral area around the inner area.
2. The electrochemical device according to claim 1, wherein the
separator includes a first surface that is held in contact with the
first electrode layer, and a second surface that is held in contact
with the second electrode layer, and the thin wall portion includes
at least one dimple that is formed in at least one of the first
surface and the second surface, the at least one dimple being
spaced from the peripheral area.
3. The electrochemical device according to claim 1, wherein the at
least one protrusion of the structure includes a first protrusion
that protrudes from the first inner surface to the first electrode
layer and is formed of a cured conductive adhesive.
4. The electrochemical device according to claim 3, wherein the
container main body further includes a first terminal that is
provided in the first inner surface to be electrically connected to
the first electrode layer, a second terminal that is provided in an
outer surface of the container main body, and a wiring portion that
electrically connects the first terminal and the second terminal to
each other, and the first protrusion is partially formed in the
first inner surface to cover the first terminal.
5. The electrochemical device according to claim 3, wherein the at
least one protrusion of the structure further includes a second
protrusion that protrudes from the second inner surface to the
second electrode layer and is formed of a cured conductive
adhesive.
6. The electrochemical device according to claim 5, wherein the
first protrusion and the second protrusion are provided to be
opposed to each other in a thickness direction of the
separator.
7. The electrochemical device according to claim 1, wherein the at
least one protrusion of the structure includes a protrusion that
protrudes from the second inner surface to the second electrode
layer and is formed of a cured conductive adhesive.
8. The electrochemical device according to claim 1, wherein the
thin wall portion is formed in a central portion of the
separator.
9. The electrochemical device according to claim 1, wherein the
structure is formed in a dome shape.
10. The electrochemical device according to claim 1, wherein the
separator is formed of a non-woven fabric containing a glass
fiber.
11. The electrochemical device according to claim 1, wherein the
container is formed in a cuboid shape.
12. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119 of Japanese Patent Application No. 2012-130400, filed
Jun. 8, 2012, which is hereby incorporated by reference in its
entirety.
BACKGROUND
[0002] The present disclosure relates to an electrochemical device
including a built-in chargeable/dischargeable storage element.
[0003] In an electrochemical device, an electrolyte serves as a
conduction path between positive and negative electrodes and as an
ion supply source for capacitance generation. Therefore, lack of
the electrolyte means malfunction of the electrochemical device.
Thus, the electrochemical device needs to be structured to retain
the electrolyte for a long time in order to enhance long-term
reliability.
[0004] In general, the electrochemical device including the
chargeable/dischargeable storage element is provided with a
hermetically sealed container. The container houses, together with
the electrolyte, the storage element including a positive
electrode, a negative electrode, and a separator provided between
the positive and negative electrodes.
[0005] For example, Japanese Patent Application Laid-open No.
2008-211056 (hereinafter, referred to as Patent Document 1)
describes an electrochemical element including a container and a
sealing plate having a projection that is to be fitted into an
opening of the container. In this electrochemical element, the
projection has a guide function, which facilitates positioning of
the sealing plate with respect to the container. Therefore, when
the sealing plate is seam-welded to the container, sealing
properties are improved.
[0006] Meanwhile, Japanese Patent Application Laid-open No.
2006-128080 (hereinafter, referred to as Patent Document 2)
describes an electric double-layer capacitor. The electric
double-layer capacitor includes a substrate made of ceramic, which
houses positive- and negative-electrode plates and an electrolyte,
and a plate-like cover joined to the substrate. The substrate has a
bottom surface warped so as to upward project and the cover is
warped so as to downward project. In this electric double-layer
capacitor, it is possible to securely fix inner components within
the container.
BRIEF SUMMARY
[0007] However, in the configuration described in Patent Document
1, there is a fear that, when the sealing plate is joined to the
opening of the container, the projection of the sealing plate may
cause the electrolyte within the container to flow out around the
container and the electrolyte may overflow to a surface joined to
the sealing plate. In this case, welding workability is
deteriorated, which leads to lower productivity. Also in the
configuration described in Patent Document 2, due to the substrate
and the cover warping, there is a fear that the electrolyte may
overflow upon joining of the cover, which makes it difficult to
ensure the productivity. However, if the amount of the electrolyte
within the container is reduced in order to avoid such a problem,
the duration of life of the element is shortened, which makes it
difficult to ensure the long-term reliability.
[0008] In view of the above-mentioned circumstances, it is
desirable to provide an electrochemical device capable of ensuring
productivity and enhancing long-term reliability.
[0009] According to an embodiment of the present disclosure, there
is provided an electrochemical device including a container, a
storage element, and a structure.
[0010] The container includes a container main body including a
first inner surface, and a lid that includes a second inner surface
that is opposed to the first inner surface and is joined to the
container main body, the container containing an electrolyte sealed
therein.
[0011] The storage element includes a first electrode layer that is
bonded to the first inner surface, a second electrode layer that is
bonded to the second inner surface, and a separator that is
provided between the first electrode layer and the second electrode
layer to retain the electrolyte. The storage element is sandwiched
between the first inner surface and the second inner surface.
[0012] The structure is provided in at least either one of the
first inner surface and the second inner surface. The structure
compresses and deforms the storage element to form, in an area of
the separator that is sandwiched between the first electrode layer
and the second electrode layer, a thin wall portion having a
smaller thickness than in a peripheral area around the area.
[0013] These and other objects, features and advantages of the
present disclosure will become more apparent in light of the
following detailed description of best mode embodiments thereof, as
illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a perspective view showing an entire configuration
of an electrochemical device according to a first embodiment of the
present disclosure;
[0015] FIG. 2 is a plan view of the electrochemical device;
[0016] FIG. 3 is a schematic cross-sectional view taken along the
line [A]-[A] of FIG. 2;
[0017] FIG. 4 is a plan view of a container main body of the
electrochemical device;
[0018] FIG. 5 is a schematic plan view of a separator forming a
part of the electrochemical device, which shows an example of a
thin wall portion formed in the separator;
[0019] FIG. 6 is a plan view showing another example of the thin
wall portion formed in the separator;
[0020] FIG. 7 is a schematic cross-sectional side view of an
electrochemical device according to a comparative example;
[0021] FIG. 8 is a schematic cross-sectional side view of an
electrochemical device according to a second embodiment of the
present disclosure;
[0022] FIG. 9 is a schematic cross-sectional side view of an
electrochemical device according to a third embodiment of the
present disclosure;
[0023] FIG. 10 is a schematic cross-sectional side view of an
electrochemical device according to a fourth embodiment of the
present disclosure; and
[0024] FIG. 11 is a schematic plan view of a separator forming a
part of the electrochemical device shown in FIG. 10.
DETAILED DESCRIPTION
[0025] According to an embodiment of the present disclosure, there
is provided an electrochemical device including a container, a
storage element, and a structure.
[0026] The container includes a container main body including a
first inner surface, and a lid that includes a second inner surface
that is opposed to the first inner surface and is joined to the
container main body, the container containing an electrolyte sealed
therein.
[0027] The storage element includes a first electrode layer that is
bonded to the first inner surface, a second electrode layer that is
bonded to the second inner surface, and a separator that is
provided between the first electrode layer and the second electrode
layer to retain the electrolyte. The storage element is sandwiched
between the first inner surface and the second inner surface.
[0028] The structure is provided in at least either one of the
first inner surface and the second inner surface. The structure
compresses and deforms the storage element to form, in an area of
the separator that is sandwiched between the first electrode layer
and the second electrode layer, a thin wall portion having a
smaller thickness than in a peripheral area around the area.
[0029] In the electrochemical device, the structure compresses and
deforms the storage element to form the thin wall portion in the
separator. The thin wall portion of the separator has higher
density than in other areas. Therefore, the electrolyte is
collected into the thin wall portion due to capillary action and a
larger amount of electrolyte is retained in the thin wall portion.
Accordingly, for example, even when the amount of electrolyte
within the container decreases due to decomposition of the
electrolyte with long-time use, it is possible to collect the
electrolyte into the thin wall portion of the separator, and hence
to ensure a long-term stable operation of the device.
[0030] Further, the thin wall portion is formed with smaller
thickness than in the peripheral area around the area of the
separator that is sandwiched between the first electrode layer and
the second electrode layer. Therefore, upon joining of the lid to
the container main body, it is possible to reduce the amount of
electrolyte flowing out of the area. Thus, it is possible to
suppress entering and mixing of the electrolyte into a joining
portion between the container main body and the lid. Therefore, it
is possible to ensure stable joining workability and enhance
production efficiency.
[0031] If the thin wall portion is formed in the peripheral area,
the electrolyte easily flows to an outer peripheral side of the
separator due to compression action upon assembling (sealing) of
the device. In order to inhibit this, in the electrochemical
device, the thin wall portion is formed at a position spaced from
the peripheral area around the area.
[0032] The thin wall portion may be formed of a dimple provided in
a surface of the separator. That is, the separator includes a first
surface that is held in contact with the first electrode layer, and
a second surface that is held in contact with the second electrode
layer. The thin wall portion includes at least one dimple that is
formed in at least one of the first surface and the second surface,
the at least one dimple being spaced from the peripheral area.
[0033] Thus, the thin wall portion can gradually decrease in
thickness toward a central portion thereof.
[0034] The structure is not particularly limited as long as the
thin wall portion can be formed at a predetermined position of the
separator. The structure may be provided in either one of the
container main body (first inner surface) and the lid (second inner
surface) or in the both.
[0035] The separator is not particularly limited as long as the
separator is made of an insulating material having durability
against the electrolyte and allowing ion migration between a
positive-electrode layer and a negative-electrode layer. The
separator may be formed of a porous material, a non-woven material,
or the like. Typically, the separator is formed of a non-woven
fabric containing a glass fiber. Thus, it is possible to easily
adjust the density of the thin wall portion depending on a degree
of compression.
[0036] Typically, island-shaped protrusions are provided in the
first and the second inner surfaces to protrude toward the storage
element. Due to the provision of the protrusions, the thin wall
portion including the dimple can be formed in the sandwiched area
of the separator.
[0037] The protrusion has a shape, width, height, hardness, and the
like capable of locally compressing and deforming the storage
element. Examples of the shape of the protrusion include a dome
shape and a circular truncated cone shape. The height of the
protrusion is set depending on, for example, the thickness of the
separator. The protrusion favorably has conductivity, so that
stable electrical connection is ensured between the inner surface
of the container and the storage element.
[0038] The position at which the protrusion is formed is not
particularly limited. Typically, the protrusion is provided so that
the thin wall portion is formed in the central portion of the
separator. Thus, the separator has, at a center thereof, a smaller
thickness than at a peripheral portion. Therefore, it is possible
to efficiently reduce the amount of electrolyte flowing around the
separator upon the assembling.
[0039] The single protrusion or a plurality of protrusions may be
formed in the first inner surface or the second inner surface.
Thus, it is possible to form a plurality of thin wall portions in
the separator and to stably retain the storage element within the
container.
[0040] For example, the structure may include a first protrusion
that protrudes from the first inner surface to the first electrode
layer and is formed of a cured conductive adhesive. Thus, a trace
of compression (dimple) by the first protrusion is formed in the
separator via the first electrode layer. Therefore, the trace of
compression can form the thin wall portion of the separator.
[0041] In this case, the container main body may further include a
first terminal that is provided in the first inner surface to be
electrically connected to the first electrode layer, a second
terminal that is provided in an outer surface of the container main
body, and a wiring portion that electrically connects the first
terminal and the second terminal to each other. The first
protrusion is partially formed in the first inner surface to cover
the first terminal. Thus, the first terminal can be protected from
the electrolyte.
[0042] Alternatively, the structure may further include a second
protrusion that protrudes from the second inner surface to the
second electrode layer and is formed of a cured conductive
adhesive. Thus, a trace of compression (dimple) by the second
protrusion is formed in the separator via the second electrode
layer. Therefore, the trace of compression can form the thin wall
portion of the separator.
[0043] Still alternatively, the structure may include a plurality
of protrusions including the first protrusion and the second
protrusion. Thus, a plurality of traces of compression are formed
in the separator. The plurality of traces of compression can form
the thin wall portion of the separator.
[0044] In this case, the first protrusion and the second protrusion
may be provided to be opposed to each other in a thickness
direction of the separator. Thus, it is possible to adjust the
thickness of the thin wall portion of the separator, and hence to
form the thin wall portion having a desired thickness.
[0045] Hereinafter, embodiments of the present disclosure will be
described with reference to the drawings.
First Embodiment
Entire Configuration
[0046] FIG. 1 is a perspective view showing an entire configuration
of an electrochemical device according to a first embodiment of the
present disclosure. FIG. 2 is a plan view of the electrochemical
device. FIG. 3 is a schematic cross-sectional view taken along the
line [A]-[A] of FIG. 2. In the figures, an X-axis, a Y-axis, a
Z-axis indicate three axis directions orthogonal to one
another.
[0047] An electrochemical device 100 according to the first
embodiment has a width direction in an X-axis direction, a length
direction in a Y-axis direction, and a height direction in a Z-axis
direction. For example, the electrochemical device 100 has a width
dimension of 2.5 mm along the X-axis direction, a length dimension
of 3.2 mm along the Y-axis direction, and a height dimension of 0.9
mm along the Z-axis direction.
[0048] The electrochemical device 100 according to the first
embodiment includes a container 10 and a storage element 20. The
storage element 20 is sealed together with an electrolyte 30 within
the container 10. The electrochemical device 100 is configured as a
chargeable/dischargeable electric double-layer capacitor or
secondary battery. The electrochemical device 100 is used as, for
example, a back-up power supply of an electronic apparatus. The
electrochemical device 100 is mounted on a circuit board of the
electronic apparatus (not shown) by, for example, a reflow
soldering method.
Container
[0049] The container 10 is formed in a cuboid shape and includes a
container main body 11, a lid 12, and a seal ring 13. The container
10 is formed by joining the container main body 11 and the lid 12
to each other with the seal ring 13 being sandwiched
therebetween.
[0050] FIG. 4 is a plan view of the container main body 11. The
container main body 11 is made of an insulating material such as a
ceramic and formed in an almost cuboid shape as a whole. As shown
in FIG. 3, the container main body 11 includes an upper surface 11a
in which a cuboid recess 14 is formed. The recess 14 includes a
flat bottom surface 14a (first inner surface) and four side
surfaces 14b. Covered with the lid 12, the recess 14 forms a liquid
chamber 40 that houses the storage element 20 and the electrolyte
30.
[0051] The lid 12 is made of an almost-rectangular plate material
that is joined to the upper surface 11a of the container main body
11 to cover the recess 14. The lid 12 is formed of a plate member
including a flat inner surface 12a (second inner surface) that is
opposed to the liquid chamber 40. For example, the lid 12 has a
width dimension of 2.2 mm along the X-axis direction, a length
dimension of 2.9 mm along the Y-axis direction, and a thickness
dimension of 0.14 mm along the Z-axis direction.
[0052] In the first embodiment, the lid 12 has such a shape that
four edge portions are lower than a central portion toward the
container main body 11. However, the lid 12 may have such a shape
that the central portion is lower than the edge portions toward the
container main body 11 in contrast. Alternatively, the lid 12 may
have such a flat shape that the edge portions are flush with the
central portion.
[0053] The lid 12 is made of a conductive material such as various
metals. For example, the lid 12 is made of kovar (Fe (iron)--Ni
(nickel)--Co (cobalt) alloy). Alternatively, the lid 12 may be made
of a clad material having a matrix of kovar or the like covered
with a film made of a metal having high corrosion resistance such
as Ni, Pt (platinum), Ag (silver), Au (gold), or Pd (palladium) in
order to inhibit galvanic corrosion.
[0054] The seal ring 13 is formed of a metal ring member. The seal
ring 13 is provided between the upper surface 11a of the container
main body 11 and the lid 12 to surround the recess 14. The seal
ring 13 is made of kovar similar to the lid 12. However, other
metal materials may be used for the seal ring 13. The seal ring 13
is made of the same kind of material as that of the lid 12 or a
material identical to that of the lid 12. Therefore, it is possible
to reduce generation of thermal stress due to differences in
coefficient of thermal expansion therebetween.
[0055] The lid 12 is joined to the container main body 11 via the
seal ring 13 after the storage element 20 is placed in the recess
14 and the electrolyte 30 is injected into the recess 14. In this
manner, the hermetically sealed liquid chamber 40 is formed within
the container 10. The lid 12 is joined to the container main body
11 by a laser welding method. However, the laser welding method may
be replaced by other welding techniques such as a seam welding
method or other joining techniques.
[0056] The container main body 11 is manufactured by burning a
plurality of laminated ceramic sheets. For example, the recess 14
is formed of a single ceramic sheet having an opening or formed by
laminating one or more ceramic sheets each having an opening. The
container main body 11 includes a positive-electrode wiring 15 and
a negative-electrode wiring 16. The positive-electrode wiring 15 is
electrically connected to a positive-electrode layer 21 of the
storage element 20 housed in the liquid chamber 40. The
negative-electrode wiring 16 is electrically connected to a
negative-electrode layer 22 of the storage element 20.
[0057] The positive-electrode wiring 15 includes via-holes 15a
(first terminal), an external positive-electrode terminal 15b
(second terminal), and interlayer wiring portions 15c. The
via-holes 15a are provided in the bottom surface 14a of the recess
14 to be electrically connected to the positive-electrode layer 21
of the storage element 20. The external positive-electrode terminal
15b is provided in an outer surface of the container main body 11.
In the first embodiment, the external positive-electrode terminal
15b is formed from one side surface 11c to a lower surface 11b of
the container main body 11.
[0058] The via-holes 15a are formed in the ceramic sheet
constituting the bottom surface 14a of the recess 14. The external
positive-electrode terminal 15b is formed in peripheral and bottom
surfaces of the ceramic sheet forming a bottom portion of the
container main body 11. The interlayer wiring portions 15c are
formed between layers of the plurality of ceramic sheets. The
via-holes 15a, the external positive-electrode terminal 15b, and
the interlayer wiring portions 15c are made of a conductive
material such as various metals. For example, the via-holes 15a,
the external positive-electrode terminal 15b, and the interlayer
wiring portions 15c are made of tungsten (W) or laminated films
having tungsten (W) on which Ni, Au, or the like is formed.
[0059] The via-holes 15a are arranged in an almost central portion
of the bottom surface 14a of the recess 14. One or more via-holes
15a may be provided. In the first embodiment, the via-holes 15a are
formed at three positions almost in the center of the bottom
surface 14a. The plurality of interlayer wiring portions 15c for
each connecting the via-holes 15a to the external
positive-electrode terminal 15b are provided. Note that, the
interlayer wiring portions 15c may be formed of a single wiring
portion common to the via-holes 15a.
[0060] The negative-electrode wiring 16 includes connection wiring
portions 16a, an external negative-electrode terminal 16b, and an
interlayer wiring portion 16c. The connection wiring portions 16a
are electrically connected to the negative-electrode layer 22 of
the storage element 20. The external negative-electrode terminal
16b is provided in the outer surface of the container main body 11.
In the first embodiment, the external negative-electrode terminal
16b is formed from the other side surface 11d to the lower surface
11b of the container main body 11.
[0061] The connection wiring portions 16a are formed inside side
walls of the container main body 11 to be electrically connected to
the seal ring 13 provided on the upper surface 11a of the container
main body 11. That is, the connection wiring portions 16a are
electrically connected to the negative-electrode layer 22 via the
seal ring 13, the lid 12, and a second protrusion 52, which will be
described later. Instead of the connection wiring portions 16a,
via-holes for connecting between the seal ring 13 and the external
negative-electrode terminal 16b or the interlayer wiring portion
16c through the inside of the side walls of the container main body
11 may be formed. The connection wiring portions 16a, the external
negative-electrode terminal 16b, and the interlayer wiring portion
16c are made of a conductive material such as various metals. For
example, the connection wiring portions 16a, the external
negative-electrode terminal 16b, and the interlayer wiring portion
16c are made of tungsten (W) or laminated films having tungsten (W)
on which Ni, Au, or the like is formed.
Storage Element
[0062] The storage element 20 includes a positive-electrode layer
21 (first electrode layer), a negative-electrode layer 22 (second
electrode layer), and a separator 23.
[0063] The positive-electrode layer 21 is formed of a sheet
containing an active material. Examples of the active material
include an active carbon and a polyacenic semiconductor (PAS).
Hereinafter, the active material contained in the
positive-electrode layer 21 is referred to as a positive-electrode
active material. Electric double layers form a capacitor between
the positive-electrode active material and the electrolyte and
predetermined capacitance [F] generates. The capacitance of the
positive-electrode layer 21 is defined by the product of the amount
[g] of the positive-electrode active material, the surface area
[m.sup.2/g] of the positive-electrode active material, and the
specific capacity [F/m.sup.2] of the positive-electrode active
material.
[0064] Specifically, the positive-electrode layer 21 is
manufactured by rolling a mixture of positive-electrode active
material particles (e.g., active carbon particles), a
conductivity-imparting agent (e.g., ketjen black), and a binder
(e.g., polytetrafluoroethylene (PTFE)) into a sheet and cutting the
sheet in a predetermined size. The thus manufactured
positive-electrode layer 21 can be suitably compressed and deformed
by being sandwiched between the bottom surface 14a of the recess 14
and the inner surface 12a of the lid 12. As an example, the
positive-electrode layer 21 is formed with a thickness of 0.2
mm.
[0065] The negative-electrode layer 22 is formed of a sheet
containing an active material similar to the positive-electrode
layer 21. Hereinafter, the active material contained in the
negative-electrode layer 22 is referred to as a negative-electrode
active material. The negative-electrode active material may be
identical to the positive-electrode active material. Thus, if the
positive-electrode active material is the active carbon, the
negative-electrode active material may also be the active carbon.
Also in the negative-electrode layer 22, electrolyte ions are
adsorbed onto a surface of the negative-electrode active material
and electric double layers are formed. The capacitance [F] of the
negative-electrode layer 22 is also defined by the product of the
amount [g] of the negative-electrode active material, the surface
area [m.sup.2/g] of the negative-electrode active material, and the
specific capacity [F/m.sup.2] of the negative-electrode active
material. The negative-electrode active material is identical to
the positive-electrode active material, and hence has the same
specific capacity as that of the positive-electrode active
material.
[0066] Similar to the positive-electrode layer 21, the
negative-electrode layer 22 is also manufactured by rolling a
mixture of negative-electrode active material particles (e.g.,
active carbon particles), a conductivity-imparting agent (e.g.,
ketjen black), and a binder (e.g., polytetrafluoroethylene (PTFE))
into a sheet and cutting the sheet in a predetermined size. The
thus manufactured negative-electrode layer 22 can be suitably
compressed and deformed by being sandwiched between the bottom
surface 14a of the recess 14 and the inner surface 12a of the lid
12. As an example, the negative-electrode layer 22 is formed with a
thickness of 0.2 mm.
[0067] The separator 23 is provided between the positive-electrode
layer 21 and the negative-electrode layer 22. The separator 23 is
made of an insulating material capable of retaining the electrolyte
30. The separator 23 is made of a porous material through which
ions can pass in a thickness direction thereof. For example, the
separator 23 is made of a polyolefin-based organic material or
non-woven fabric. In the first embodiment, the separator 23 is made
of a non-woven fabric containing glass fibers. However, the
non-woven fabric containing glass fibers may be replaced by a
non-woven fabric of another fiber material such as a cellulose
fiber and a plastic fiber. The thickness of the separator 23 is not
particularly limited. For example, the separator 23 has a thickness
from 0.05 to 0.2 mm.
[0068] The separator 23 is formed in an almost rectangular shape
larger than the positive-electrode layer 21 and the
negative-electrode layer 22. The separator 23 includes a first
surface 231 and a second surface 232. The first surface 231 is held
in contact with the positive-electrode layer 21. The second surface
232 is held in contact with the negative-electrode layer 22. The
separator 23 can be compressed and deformed in the thickness
direction, and hence is housed in the liquid chamber 40 while being
suitably compressed and deformed between the positive-electrode
layer 21 and the negative-electrode layer 22. Thus, internal
resistance between the positive-electrode layer 21 and the
negative-electrode layer 22 is reduced.
[0069] The electrolyte 30 is not particularly limited. Any
electrolyte material is applicable to the electrolyte 30. To the
electrolyte 30, for example, a quaternary ammonium salt solution
including BF.sub.4.sup.- (tetrafluoroborate ion), more
particularly, a 5-azoniaspiro[4.4]nonane-BF.sub.4 or
ethylmethylimidazoliumnonane-BF.sub.4 solution is applicable.
Structure
[0070] The electrochemical device 100 according to the first
embodiment includes a structure 50. The structure 50 compresses and
deforms the storage element 20 to form, in an area of the separator
23 that is sandwiched between the positive-electrode layer 21 and
the negative-electrode layer 22, a thin wall portion 23a having a
smaller thickness than in a peripheral area around the area.
[0071] In the first embodiment, the structure 50 includes a first
protrusion 51 and the second protrusion 52. The first protrusion 51
is provided in the bottom surface 14a of the recess 14. The second
protrusion 52 is provided in the inner surface 12a of the lid
12.
[0072] The first protrusion 51 is formed in an island shape on the
bottom surface 14a of the recess 14 to protrude from the bottom
surface 14a to the storage element 20 (positive-electrode layer
21). The second protrusion 52 is formed in an island shape on the
inner surface 12a of the lid 12 to protrude from the inner surface
12a to the storage element 20 (negative-electrode layer 22). The
first and second protrusions 51 and 52 are made of a harder
material than that of the positive-electrode layer 21 and the
negative-electrode layer 22.
[0073] The first and second protrusions 51 and 52 compress and
deform the storage element 20 in the thickness direction (Z-axis
direction) within the liquid chamber 40 to form the thin wall
portion 23a in the separator 23. In the first embodiment, the first
and second protrusions 51 and 52 are provided in the bottom surface
14a of the recess 14 and the inner surface 12a of the lid 12,
respectively, to be opposed to each other in the Z-axis direction.
Therefore, the storage element 20 is, at both surfaces thereof,
compressed and deformed by the first and second protrusions 51 and
52, so that the single thin wall portion 23a is formed in the
separator 23.
[0074] The thickness of the thin wall portion 23a is not
particularly limited. For example, the thin wall portion 23a has a
thickness from 5 .mu.m to 50 .mu.m inclusive. In this case, a
difference in thickness between the thin wall portion 23a and an
outermost peripheral portion of the separator 23 is in a range of
10 .mu.m to 150 .mu.m inclusive, for example.
[0075] The first and second protrusions 51 and 52 are formed of a
cured conductive adhesive. Accordingly, stable electrical
connections between the positive-electrode layer 21 and the
via-holes 15a and between the negative-electrode layer 22 and the
lid 12 can be ensured.
[0076] The first protrusion 51 constitutes a positive-electrode
adhesive layer that adheres and electrically connects the
positive-electrode layer 21 and the bottom surface 14a of the
recess 14 to each other. The first protrusion 51 is formed in a
partial area between the bottom surface 14a of the recess 14 and
the positive-electrode layer 21. In the first embodiment, as shown
in FIG. 4, the first protrusion 51 is formed in a size to cover the
three via-holes 15a. With this structure, the via-holes 15a are
protected from corrosion due to contact with the electrolyte
30.
[0077] For the conductive adhesive forming the first protrusion 51,
a synthetic resin material containing conductive particles is used.
Those having high conductivity and chemical stability are favorably
used as the conductive particles. For example, graphite particles
are used as the conductive particles. One having a low degree of
swelling in the electrolyte and high thermal resistance and
chemical stability is favorably used as the synthetic resin
material containing the conductive particles. For example, a phenol
resin is used as the synthetic resin material containing the
conductive particles.
[0078] The first protrusion 51 is formed in a circular dome shape.
With this structure, the thin wall portion 23a can be stably formed
in the separator 23 via the positive-electrode layer 21. The first
protrusion 51 locally compresses the first surface 231 of the
separator 23 via the positive-electrode layer 21 to form, in the
first surface 231, a dimple D1 having a predetermined depth as a
trace of compression. The dimple D1 is formed in the area of the
separator 23 that is sandwiched between the positive-electrode
layer 21 and the negative-electrode layer 22, the dimple D1 being
spaced from the peripheral area around the area. In this manner,
the dimple D1 forms a part of the thin wall portion 23a.
[0079] A method of forming the first protrusion 51 is not
particularly limited. For example, various application methods such
as a screen printing method and a potting method may be used. The
first protrusion 51 is formed in the dome shape, and hence the thin
wall portion 23a having a desired size can be formed without
applying too large stress to the positive-electrode layer 21.
[0080] The height of the first protrusion 51 is not particularly
limited and can be appropriately set depending on the height of the
liquid chamber 40, the thickness and elastic modulus of the
positive-electrode layer 21, the thickness of the thin wall portion
23a, and the like. For example, the first protrusion 51 has a
height of 10 .mu.m to 100 .mu.m inclusive. If the height of the
first protrusion 51 is smaller than 10 .mu.m, it is difficult to
form the thin wall portion 23a. If the height of the first
protrusion 51 is larger than 100 .mu.m, there is a fear that excess
stress may be applied to the positive-electrode layer 21, which may
damage the positive-electrode layer 21.
[0081] Meanwhile, the second protrusion 52 constitutes a
negative-electrode adhesive layer that adheres and electrically
connects the negative-electrode layer 22 and the inner surface 12a
of the lid 12 to each other. The second protrusion 52 is formed in
a partial area between the inner surface 12a of the lid 12 and the
negative-electrode layer 22. Similar to the first protrusion 51,
for the conductive adhesive forming the second protrusion 52, a
synthetic resin material containing conductive particles is used.
For the synthetic resin material, the same or a different kind of
conductive adhesive as/from the conductive adhesive forming the
first protrusion 51 can be used.
[0082] Similar to the first protrusion 51, the second protrusion 52
is also formed in a circular dome shape. With this structure, the
thin wall portion 23a can be stably formed in the separator 23 via
the negative-electrode layer 22. The second protrusion 52 locally
compresses the second surface 232 of the separator 23 via the
negative-electrode layer 22 to form, in the second surface 232, a
dimple D2 having a predetermined depth as a trace of compression.
The dimple D2 is formed in the area of the separator 23 that is
sandwiched between the positive-electrode layer 21 and the
negative-electrode layer 22, the dimple D2 being spaced from the
peripheral area around the area. In this manner, the dimple D2
forms a part of the thin wall portion 23a.
[0083] A method of forming the second protrusion 52 is not
particularly limited. For example, various application methods such
as a screen printing method and a potting method may be used. The
second protrusion 52 is formed in the dome shape, and hence the
thin wall portion 23a having a desired size can be formed without
applying too large stress to the negative-electrode layer 22.
[0084] The height of the second protrusion 52 is not particularly
limited and can be appropriately set depending on the height of the
liquid chamber 40, the thickness and elastic modulus of the
negative-electrode layer 22, the thickness of the thin wall portion
23a, and the like. For example, the second protrusion 52 has a
height of 10 .mu.m to 100 .mu.m inclusive. If the height of the
second protrusion 52 is smaller than 10 .mu.m, it is difficult to
form the thin wall portion 23a. If the height of the second
protrusion 52 is larger than 100 .mu.m, there is a fear that excess
stress may be applied to the negative-electrode layer 22, which may
damage the negative-electrode layer 22.
[0085] In the first embodiment, the shape, size, and height of the
second protrusion 52 are set to be the same as those of the first
protrusion 51. However, the shape, size, and height of the second
protrusion 52 are not limited thereto. For example, at least one of
the shape, size, and height of the second protrusion 52 may be set
to be different from that of the first protrusion 51.
[0086] FIG. 5 is a plan view of the separator 23 in which the thin
wall portion 23a is formed. In the figure, an area C indicated by
hatching represents the area of the separator 23 that is sandwiched
between the positive-electrode layer 21 and the negative-electrode
layer 22 and a dotted area shows the thin wall portion 23a. The
first and second protrusions 51 and 52 are formed in the dome shape
on the bottom surface 14a of the recess 14 and the inner surface
12a of the lid 12, respectively. As shown in FIG. 5, the first and
second protrusions 51 and 52 form the thin wall portion 23a at
positions spaced from a peripheral area Ca around the area C within
the area C.
[0087] As described above, the thin wall portion 23a includes the
dimple D1 and the dimple D2. The thin wall portion 23a is formed by
being compressed and deformed by the first and second protrusions
51 and 52. Therefore, the thin wall portion 23a has a thickness
smaller than that in the peripheral area Ca around the area C and
gradually decreases in thickness toward the central portion
corresponding to the shapes of the dimples D1 and D2.
[0088] FIG. 6 shows an example in which the thin wall portion is
formed also in the peripheral area around the area C. When a thin
wall portion 230a is formed also in the peripheral area around the
area C, the electrolyte soaking into the separator easily flows out
around the separator due to the compression action by the structure
upon assembling of the device.
[0089] As described above, the separator 23 is compressed by a
predetermined amount in the thickness direction upon assembling
(sealing). At this time, the thin wall portion 23a is compressed
and deformed due to the provision of the first and second
protrusions 51 and 52 more largely than other areas within the area
C. However, the first and second protrusions 51 and 52 are provided
at the positions spaced from the peripheral area Ca around the area
C toward the center of the separator 23, and hence the amount of
electrolyte flowing out of the area C when the thin wall portion
23a is formed can be suppressed.
[0090] Further, the separator 23 is formed of the non-woven fabric
containing the glass fibers. Thus, the thin wall portion 23a has
higher density than in the other areas of the separator 23.
Therefore, the electrolyte 30 is collected into the thin wall
portion 23a due to capillary action and a larger amount of
electrolyte is retained therein. Accordingly, for example, even
when the amount of electrolyte within the container 10 decreases
due to decomposition of the electrolyte with long-time use, it is
possible to collect the electrolyte into the thin wall portion 23a
of the separator 23, and hence to ensure a long-term stable
operation of the electrochemical device 100.
Actions of First Embodiment
[0091] FIG. 7 is a schematic cross-sectional side view of an
electrochemical device 200 shown as a comparative example. In FIG.
7, parts corresponding to those in FIG. 3 are denoted by the same
reference symbols and detailed description thereof will be
omitted.
[0092] The electrochemical device 200 according to the comparative
example has such a structure that a conductive adhesive layer 61
and a conductive adhesive layer 62 are in a flat shape. The
conductive adhesive layer 61 adheres a recess 14 of a container
main body 11 and a positive-electrode layer 21 to each other. The
conductive adhesive layer 62 adheres a lid 12 and a
negative-electrode layer 22 to each other. In the electrochemical
device 200 having such a structure, the separator 23 has a uniform
thickness in the liquid chamber 40, and hence, if the density or
gaps of the separator 23 is/are uniform, distribution of the
electrolyte retained by the separator 23 is also uniform.
Therefore, decomposition and lack of the electrolyte uniformly
occur in long-term use of the device. As a result, even when an
amount of the electrolyte that allows conduction between positive-
and negative-electrode layers 21 and 22 remains, if that
electrolyte is uniformly distributed in the separator 23, there is
a fear that the electrolyte may be insufficient.
[0093] In contrast, in the electrochemical device 100 according to
the first embodiment, the thin wall portion 23a having higher
density is formed in the central portion of the separator 23, and
hence it is possible to ensure conduction between the positive- and
negative-electrode layers 21 and 22 with a smaller amount of
electrolyte in the thin wall portion 23a. In addition, the
electrolyte 30 is supplied to the thin wall portion 23a due to
capillary action. Therefore, even when the electrolyte is
decomposed due to the long-term use of the device, the electrolyte
30 locally exists in the thin wall portion 23a. Thus, comparing the
first embodiment and the comparative example with each other in the
case of using a certain amount of electrolyte, according to the
first embodiment, it is possible to operate the device for a longer
term than with the electrochemical device 200 according to the
comparative example.
[0094] Further, in the electrochemical device 200 according to the
comparative example, when the container main body 11 and the lid 12
are joined to each other, the separator 23 is uniformly compressed
and deformed. Accordingly, the electrolyte 30 soaking into the
separator 23 isotropically flows out around the storage element 20.
Therefore, when the device is welded and sealed, it is more likely
that the electrolyte splashes outside and soaks into a welding
surface or is mixed into a welding portion. The mixing of the
electrolyte leads directly to welding failure and causes lower
yield.
[0095] In contrast, in the electrochemical device 100 according to
the first embodiment, an outer peripheral portion of the separator
23 retains a smaller amount of electrolyte 30 in comparison with
the thin wall portion 23a in the center. Therefore, the outer
peripheral portion of the separator 23 serves as a receiver for the
electrolyte that flows out of the storage element 20 upon sealing
with the lid 12. Accordingly, it is possible to suppress the
splashing of the electrolyte and the mixing of the electrolyte into
the welding portion, and hence to enhance the yield.
Second Embodiment
[0096] FIG. 8 is a schematic cross-sectional side view showing a
configuration of an electrochemical device according to a second
embodiment of the present disclosure. Hereinafter, components
different from those of the first embodiment will be mainly
described. Further, the same components as those of the
above-mentioned embodiment will be denoted by the same reference
symbols and description thereof will be omitted or simplified.
[0097] In an electrochemical device 300 according to the second
embodiment, a separator 23 includes, in a central portion thereof,
a thin wall portion 23b having higher density than in other areas.
In the second embodiment, a structure that forms the thin wall
portion 23b is constituted only by a protrusion 51. The protrusion
51 is provided between a recess 14 of a container main body 11 and
a positive-electrode layer 21 of a storage element 20. The
protrusion 51 forms a dimple D1 in a first surface 231 of the
separator 23. The dimple D1 forms the thin wall portion 23b.
[0098] Corresponding to the first protrusion 51 in the
above-mentioned first embodiment, the protrusion 51 has the same
configuration, and hence description thereof will be omitted.
Meanwhile, between the lid 12 and the negative-electrode layer 22,
a conductive adhesive layer 62 that adheres and electrically
connects the lid 12 and the negative-electrode layer 22 to each
other is provided. The conductive adhesive layer 62 is formed of a
flat layer formed over an entire surface in which the lid 12 and
the negative-electrode layer 22 are opposed to each other.
[0099] Also in the thus configured second embodiment, upon sealing
of a liquid chamber 40 with the lid 12, a trace of compression by
the protrusion 51 is formed in the separator 23 via the
positive-electrode layer 21, and hence that trace of compression
can form the thin wall portion 23b of the separator 23.
Accordingly, it is possible to provide the same action and effect
as those of the first embodiment described above.
Third Embodiment
[0100] FIG. 9 is a schematic cross-sectional side view showing a
configuration of an electrochemical device according to a third
embodiment of the present disclosure. Hereinafter, components
different from those of the first embodiment will be mainly
described. Further, the same components as those of the
above-mentioned embodiment will be denoted by the same reference
symbols and description thereof will be omitted or simplified.
[0101] In an electrochemical device 400 according to the third
embodiment, a separator 23 includes, in a central portion thereof,
a thin wall portion 23c having density higher than in other areas.
In the third embodiment, a structure that forms this thin wall
portion 23c is constituted only by a protrusion 52. The protrusion
52 is provided between an inner surface 12a of a lid 12 and a
negative-electrode layer 22 of a storage element 20. The protrusion
52 forms a dimple D2 in a second surface 232 of the separator 23.
The dimple D2 forms the thin wall portion 23c.
[0102] Corresponding to the second protrusion 52 in the first
embodiment described above, the protrusion 52 has the same
configuration, and hence description thereof will be omitted.
Meanwhile, between a positive-electrode layer 21 and via-holes 15a
provided in a bottom surface 14a of a recess 14, a conductive
adhesive layer 61 that adheres and electrically connects the
positive-electrode layer 21 and the via-holes 15a to each other.
The conductive adhesive layer 61 is formed of a flat layer formed
over an entire surface in which the bottom surface 14a and the
positive-electrode layer 21 are opposed to each other. Further, the
conductive adhesive layer 61 covers the via-holes 15a to protect
the via-holes 15a from corrosion due to contact with the
electrolyte 30.
[0103] Also in the thus configured third embodiment, upon sealing
of a liquid chamber 40 with the lid 12, a trace of compression by
the protrusion 52 is formed in the separator 23 via the
negative-electrode layer 22, and hence that trace of compression
can form the thin wall portion 23c of the separator 23.
Accordingly, it is possible to provide the same action and effect
as those of the first embodiment described above.
Fourth Embodiment
[0104] FIG. 10 is a schematic cross-sectional side view showing a
configuration of an electrochemical device according to a fourth
embodiment of the present disclosure. FIG. 11 is a schematic plan
view of a separator 23 of the electrochemical device. Hereinafter,
components different from those of the first embodiment will be
mainly described. Further, the same components as those of the
above-mentioned embodiment will be denoted by the same reference
symbols and description thereof will be omitted or simplified.
[0105] An electrochemical device 500 according to the fourth
embodiment is different from the above-mentioned embodiments in
that a plurality of thin wall portions are formed in the separator
23. That is, in the fourth embodiment, the separator 23 includes a
first thin wall portion 23d formed in a central portion thereof and
second and third thin wall portions 23e and 23f formed sandwiching
the first thin wall portion 23d therebetween. The first to third
thin wall portions 23d to 23f are formed with higher density than
in other areas of the separator 23.
[0106] The first thin wall portion 23d is formed by a first
protrusion 51 provided in a bottom surface of a recess 14 of a
container main body 11. The first thin wall portion 23d includes a
dimple D1 opposed to the first protrusion 51. Meanwhile, the second
and third thin wall portions 23e and 23f are formed by second and
third protrusions 52a and 52b formed on an inner surface 12a of a
lid 12, respectively. The second and third thin wall portions 23e
and 23f includes dimples D2a and D2b opposed to the second and
third protrusions 52a and 52b, respectively. The second and third
protrusions 52a and 52b are formed of a cured conductive adhesive.
The second and third protrusions 52a and 52b adhere and
electrically connect the lid 12 and a negative-electrode layer 22
to each other.
[0107] The second and third protrusions 52a and 52b are arranged at
such positions that the second and third protrusions 52a and 52b
are not opposed to the first protrusion 51 in the Z-axis direction,
the second and third protrusions 52a and 52b being separated from
each other. Further, the second and third protrusions 52a and 52b
are formed in a dome shape having smaller diameter than that of the
first protrusion 51. As a result, the first thin wall portion 23d
is different in position and size from the second and third thin
wall portions 23e and 23f as shown in FIG. 11. Also in this case,
the thin wall portions 23d, 23e, and 23f are formed at positions
insulated from a peripheral area around an area C.
[0108] The shape, size, position of the first to third protrusions
51, 52a, and 52b are not particularly limited. The shape, size,
position of the first to third protrusions 51, 52a, and 52b can be
appropriately set depending on the position, size, number, and the
like of thin wall portions to be formed.
[0109] Also in the fourth embodiment, it is possible to provide the
same action and effect as those of the first embodiment described
above. In particular, according to the fourth embodiment, the
separator 23 includes the plurality of thin wall portions (23d to
23f), and hence it is possible to further reduce internal
resistance and to distribute collection areas for the electrolyte
to a plurality of positions. In addition, it is possible to more
effectively suppress splashing of the electrolyte upon assembling
(sealing). Thus, it is possible to achieve an enhancement in
productivity.
[0110] Although the embodiments of the present disclosure has been
described above, it is needless to say that the present disclosure
is not limited to the above-mentioned embodiments and can be
variously changed without departing the gist of the present
disclosure.
[0111] For example, although, in the above-mentioned first
embodiment, the first protrusion 51 and the second protrusion 52
are provided to be opposed to each other in the Z-axis direction,
the first protrusion 51 and the second protrusion 52 may be
provided not to be opposed to each other. With this structure, for
example, it is possible to arbitrarily adjust the shape, size,
thickness, and the like of the thin wall portion. Alternatively,
either one of the first and second protrusions 51 and 52 may be
constituted of a plurality of protrusions.
[0112] Further, although, in the above-mentioned second and third
embodiments, the single protrusion 51 or the single protrusion 52
is provided, a plurality of protrusions 51 or a plurality of
protrusions 52 may be provided. Further, in the above-mentioned
fourth embodiment, a plurality of second protrusions 52a and a
plurality of third protrusions 52b may be provided or a single
annular protrusion may be provided as the second and third
protrusions 52a and 52b.
[0113] In addition, although, in the above-mentioned embodiments,
the positive-electrode layer 21 is provided to be opposed to the
container main body 11 and the negative-electrode layer 22 is
provided to be opposed to the lid 12, the positive-electrode layer
21 may be provided to be opposed to the lid 12 and the
negative-electrode layer 22 may be provided to be opposed to the
container main body 11 in contrast.
* * * * *