WO2018162630A1

WO2018162630A1 - Energy storage device and energy storage apparatus

Info

Publication number: WO2018162630A1
Application number: PCT/EP2018/055732
Authority: WO
Inventors: Dominik Marcel WILKA
Original assignee: Lithium Energy and Power GmbH & Co. KG
Priority date: 2017-03-09
Filing date: 2018-03-08
Publication date: 2018-09-13
Also published as: JP2018147837A

Abstract

An energy storage device according to an aspect of the present invention includes: a case which is formed of a flexible sheet and in which the flexible sheet is joined in an overlapping manner at least at a portion of a peripheral portion of the flexible sheet; an energy storage element which has a positive electrode plate and a negative electrode plate accommodated in the case, and a pair of current collectors extending from the positive electrode plate and the negative electrode plate to the outside through a joined portion of the case; and a pair of connecting members which is connected to the current collectors outside the case, wherein the connecting members have a pair of contact surfaces disposed with a distance larger than a largest thickness of the case on both sides of the joined portion of the sheet in a sheet thickness direction.

Description

DESCRIPTION

TITLE OF THE INVENTION: ENERGY STORAGE DEVICE AND ENERGY STORAGE APPARATUS

TECHNICAL FIELD

[0001]

The present invention relates to an energy storage device and an energy storage apparatus.

BACKGROUND ART

[0002]

For example, in many cases, an energy storage apparatus having a relatively large capacitance which is used as a power source in an

automobile or the like is configured such that a plurality of energy storage devices (cells) are electrically connected to each other. In many cases, as the structure of the energy storage device in such an energy storage apparatus, the structure is adopted where an electrode assembly is sealed in a bag-shaped case formed by joining a peripheral portion of a flexible sheet, and a thin plate-like conductor extending from the electrode assembly is pulled out to the outside from a mating seam of the sheet.

[0003]

With respect to the electrical connection structure between these energy storage devices, a conductive connecting member is joined to the conductor extending from the mating seam of the sheet, and the connecting members of the energy storage devices disposed adjacently to each other are electrically connected to each other. For example, JP 2015-56341 A describes a technique where connecting members disposed adjacently to each other are connected to each other by cold rolling, ultrasonic welding, laser welding or the like.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0004]

Patent Document l: JP 2015-56341 A

SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0005]

In the configuration of the energy storage apparatus described in the above-mentioned publication, the connection between the connecting members requires time and efforts and hence, assembling of the energy storage apparatus becomes cumbersome. Further, in the configuration of the energy storage apparatus described in the above-mentioned publication, an operation of exchanging some energy storage devices is also cumbersome.

[0006]

The present invention has been made in view of the above- mentioned drawbacks, and it is an object of the present invention to provide an energy storage device and an energy storage apparatus where the energy storage apparatus can be easily assembled, and the energy storage device can be easily exchanged.

MEANS FOR SOLVING THE PROBLEMS

[0007]

According to an aspect of the present invention, there is provided an energy storage device which includes : a case which is formed of a flexible sheet and in which the flexible sheet is joined in an overlapping manner at least at a portion of a peripheral portion of the flexible sheet; an energy storage element which has a positive electrode plate and a negative electrode plate accommodated in the case, and a pair of current collectors extending from the positive electrode plate and the negative electrode plate to the outside through a joined portion of the case! and a pair of connecting members which is connected to the current collectors outside the case, wherein the connecting members have a pair of contact surfaces disposed with a distance larger than a largest thickness of the case on both sides of the joined portion of the sheet in a sheet thickness direction.

ADVANTAGES OF THE INVENTION

[0008]

In the energy storage device according to an aspect of the present invention, the connecting members have the pair of contact surfaces disposed with the distance larger than the largest thickness of the case on both sides of the joined portion of the sheet in the sheet thickness direction. Accordingly, by stacking the connecting members of the energy storage devices disposed adjacently to each other in such a manner that the contact surfaces of the connecting members are brought into contact with each other, and the plurality of stacked connecting members are sandwiched in a stacking direction and hence, the plurality of energy storage devices can be electrically connected to each other. Accordingly, in the energy storage device according to an aspect of the present invention, assembling and exchange of the energy storage devices can be performed relatively easily. BRIEF DESCRIPTION OF THE DRAWINGS

[0009]

Fig. 1 is a schematic cross- sectional view showing an energy storage apparatus according to an embodiment of the present invention.

Fig. 2 is a schematic plan view of an energy storage device shown in

Fig. 1.

Fig. 3 is a schematic plan view of an energy storage device according to an embodiment different from the embodiment of the present invention shown in Fig. 1.

Fig. 4 is a schematic plan view of an energy storage device according to an embodiment different from the embodiments of the present invention shown in Fig. 1 and Fig. 3.

Fig. 5 is a schematic cross- sectional view of an energy storage device according to an embodiment different from the embodiments of the present invention shown in Fig. 1, Fig. 3 and Fig. 4.

MODE FOR CARRYING OUT THE INVENTION

[0010]

Embodiments of the present invention are described in detail properly with reference to drawings hereinafter.

[0011]

[First embodiment]

An energy storage apparatus according to a first embodiment of the present invention shown in Fig. 1 includes^: a plurality of energy storage devices 1 which are respectively another embodiment of the present invention! and a holder 2 which holds the plurality of energy storage devices 1. The energy storage apparatus further includes a cooling member 3 which is brought into contact with the plurality of energy storage devices 1 and takes heat from the energy storage devices 1.

[0012]

[Energy storage device]

The energy storage device 1 includes^ a case 5 which is formed of a flexible sheet 4 and in which the flexible sheet 4 is joined in an overlapping manner at least at a portion of a peripheral portion of the flexible sheet 4; an energy storage element 11 which has a stacked body formed of positive electrode plates 6, negative electrode plates 7 and separators 8

accommodated in the case 5, and a pair of current collectors (a positive electrode current collector 9 and a negative electrode current collector 10) extending from the positive electrode plates 6 and the negative electrode plates 7 to the outside through a joined portion of the case 5; and a pair of connecting members (a positive electrode connecting member 12 and a negative electrode connecting member 13) connected to the current collectors 9, 10 outside the case 5.

[0013]

In the energy storage apparatus, the plurality of energy storage devices 1 are arranged such that the positive -negative directions of the energy storage elements 11 are alternately changed between each two neighboring energy storage elements 11, and the connecting members 12, 13 are brought into contact with each other. The energy storage apparatus also includes plate-like or sheet-like insulation members 14 each of which is arranged between the connecting members 12, 13 of the energy storage devices 1 disposed adjacently to each other and every other one of the connecting members 12, 13. With such a configuration, the plurality of energy storage devices 1 are electrically connected in series.

[0014]

<Case >

The case 5 is formed of two sheets 4, one two-folded sheet 4 or one cylindrically wound one sheet 4. By joining the opposedly facing sheets 4, a layered product formed of the positive electrode plates 6, the negative electrode plates 7 and the separators 8 and an electrolyte are sealed in the case 5. That is, the case 5 may be formed of a four- side sealed type bag where the sheets 4 are joined to each other at four peripheral portions, a three- side sealed type bag where the sheet 4 is folded back at one peripheral portion and other peripheral portions of the sheet 4 are joined to each other, or a pillow-type bag where the sheet 4 is joined in a cylindrical shape so as to form a cylindrical body and peripheral portions of both ends of the cylindrical body are joined to each other. In this embodiment, as shown in Fig. 2, the case 5 is formed of a four-side sealed bag where the case 5 is formed into a rectangular shape as viewed in a stacking direction of the positive electrode plates 6, the negative electrode plates 7 and the

separators 8, and the opposedly facing sheets 4 are welded to each other at four peripheral portions.

[0015]

As a method of welding the sheets 4 of the case 5, for example, thermo-compression bonding, ultrasonic welding or the like can be adopted.

[0016] It is sufficient that the sheet 4 for forming the case 5 be made of a material having a sufficient strength, a sufficient barrier property and a sufficient weldability, and a laminate film having a multi-layered structure can be used as the sheet 4.

[0017]

As the laminate film for forming the sheet 4 of the case 5, it is preferable to use a laminate film which includes^: a resin-made base material layer which is disposed on an outer surface side (a side opposite to the energy storage element 11) and possesses a sufficient strength; a resin-made sealant layer disposed on an inner surface side (a side opposedly facing the energy storage element 11) and possesses a sufficient weldability! and a metal-made barrier layer disposed between the base material layer and the sealant layer and possesses a barrier property.

[0018]

As a main component of the resin which forms the base material layer, for example, polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC) and the like are named.

[0019]

As a main component of the resin which forms the sealant layer, it is preferable to use a component which possesses not only mutual weldability with the sheet 4 but also adhesiveness with the current collectors 9, 10. As the main component of the resin which forms the sealant layer, for example, a thermoplastic resin such as polyethylene, polypropylene or the like can be named. An average thickness of the sealant layer may be set to 50 μηι to 500 μηι inclusive, for example. A resin having adhesiveness different from adhesiveness of the sheet 4 may be disposed between the sheet 4 and the current collector 9, 10.

[0020]

As metal for forming the barrier layer, for example, aluminum, stainless steel or the like can be named. Among these metals, aluminum is preferably used. The barrier layer may be formed of a metal foil or may be formed by depositing metal on the base material layer by a vapor deposition method.

[0021]

It is preferable that a sheet 4 joined portion of the case 5 be disposed parallel to the positive electrode plates 6 and the negative electrode plates 7 of the energy storage element 11.

[0022]

As described above, the energy storage element 11 has a stacked electrode assembly which is formed by stacking the positive electrode plates 6 and the negative electrode plates 7 with the separators 8 interposed therebetween respectively, and current collectors 9, 10 are extended from the positive electrode plates 6 and the negative electrode plates 7 of the stacked electrode assembly respectively.

[0023]

The electrode assembly of the energy storage element 11 may be formed by stacking one positive electrode plate 6, one negative electrode plate 7, and one separator 8 with each other, and may be formed by alternately stacking the plurality of positive electrode plates 6, the plurality of negative electrode plates 7, and the plurality of separators 8 such that the separator 8 is interposed between the positive electrode plate 6 and the negative electrode plate 7. The electrode assembly of the energy storage element 11 may be formed by winding, in a flat shape, an elongated strip^¬ like positive electrode plate 6 and an elongated strip-like negative electrode plate 7 with a separator 8 interposed between the positive electrode plate 6 and the negative electrode plate 7, or may be formed by folding a stacked body where an elongated strip- shaped positive electrode plate 6 and a negative electrode plate 7 are stacked with a separator 8 interposed between the positive electrode plate 6 and the negative electrode plate 7 in a zigzag manner (zig-zag-type electrode assembly). When the electrode assembly is a zig-zag-type electrode assembly, it is sufficient that at least one of the positive electrode 6, the negative electrode 7, and the separator 8 be formed in an elongated strip shape.

[0024]

As in the case of this embodiment, typically, the electrode assembly is formed into a rectangular shape as viewed in a stacking direction of the positive electrode plate 6, the negative electrode plate 7, and the separator 8.

[0025]

(Positive electrode plate)

The positive electrode plate 6 includes^ a foil-like or sheet-like positive electrode current collector base member having conductivity! and a porous positive electrode mixed material layer which is stacked on both surfaces of the positive electrode current collector base member. [0026]

As a material for forming the positive electrode current collector base member, a metal material such as aluminum, copper, iron or nickel, or an alloy of such metal materials is used. Among these metal materials, from a viewpoint of taking a balance between a level of conductivity and a cost, aluminum, an aluminum alloy, copper, and a copper alloy are

preferably used, and aluminum and an aluminum alloy are more preferably used. Further, as the configuration of the positive electrode current collector base member, a foil, a mesh, a vapor deposition film and the like can be named. From a viewpoint of a cost, the positive electrode current collector base member is preferably formed of a foil. That is, the positive electrode current collector base member is preferably made of an aluminum foil.

[0027]

An average thickness of the positive electrode current collector base member may be set to 5 μηι to 50 μηι inclusive, for example.

[0028]

The positive electrode mixed material layer is a porous layer made of a so-called mixed material containing a positive active material. The mixed material which forms the positive electrode mixed material layer contains arbitrary components such as a conductive agent, a binder, a thickening agent, a filler and the like when necessary.

[0029]

As the positive active material, for example, a composite oxide expressed by Li_xMO_y (M indicating at least one kind of transition metal) (Li_xCo02, Li_xNi02, Li_xMii204, Li_xMn03, Li_xNi_aCo(i-_a)02, Li_xNi_aMnpCoa-_a-p)02, Li_xNi_aMn(2-a)04 or the like), or a polyanion compound expressed by

Li_wMe_x(XOy)z (Me indicating at least one kind of transition metal, X being P, Si, B, V or the like, for example) (LiFeP0₄, LiMnP0₄, LiNiP0₄, L1C0PO4, Li3V2(P0₄)3, Li2MnSi0₄, Li2CoP0₄F or the like) can be named.

[0030]

The conductive agent is not particularly limited. As such a conductive agent, natural or artificial graphite, carbon black such as furnace black, acetylene black and Ketjen black, metal, conductive ceramics and the like can be named. As the shape of the conductive agent, a powdery form, a fibrous form and the like can be named.

[0031]

As the binder, for example, a thermoplastic resin such as a

fluororesin (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and the like), polyethylene, polypropylene and polyimide! elastomer such as ethylene-propylene- diene rubber (EPDM), sulfonated EPDM, styrene- butadiene rubber (SBR), and fluororubber! polysaccharide polymer and the like can be named.

[0032]

As the thickening agent, polysaccharide polymer such as

carboxymethyl cellulose (CMC), methyl cellulose and the like can be named. Further, when the thickening agent has a functional group reactable with lithium, it is preferable to preliminarily deactivate the functional group by methylation or the like.

[0033] (Negative electrode plate)

The negative electrode plate 7 includes^ a foil-like or sheet-like negative electrode current collector base member having conductivity! and a porous negative electrode mixed material layer which is stacked on both surfaces of the negative electrode current collector base member.

[0034]

Although the negative electrode current collector base member can be formed substantially in the same manner as the above-mentioned positive electrode current collector base member, copper or a copper alloy is preferably used as a material for forming the negative electrode current collector base member. That is, a copper foil is preferably used as the negative electrode current collector base member of the negative electrode plate 7. As a copper foil, for example, a rolled copper foil, an electrolytic copper foil and the like can be exemplified.

[0035]

The negative electrode mixed material layer is a porous layer made of a so-called mixed material containing a negative active material. The mixed material which forms the negative electrode mixed material layer may contain arbitrary components such as a conductive agent, a binder, a thickening agent, a filler and the like when necessary.

[0036]

As the negative active material, a material which can occlude and discharge lithium ions is preferably used. As a specific negative active material, metal such as lithium or a lithium alloy! a metal oxide! a polyphosphoric acid compound! a carbon material such as graphite! non- crystalline carbon (easily graphitizable carbon or hardly graphitizable carbon) or the like can be named, for example.

[0037]

(Separator)

The separator 8 is formed of a sheet-like or film-like porous resin, and is infiltrated with an electrolyte solution. The separator 8 separates the positive electrode plate 6 and the negative electrode plate 7 from each other and, at the same time, holds the electrolyte solution between the positive electrode plate 6 and the negative electrode plate 7.

[0038]

As a main component of the separator 8, for example, polyethylene (PE), polypropylene (PP), ethylene -vinyl acetate copolymer, ethylene- methylacrylate copolymer, ethylene-ethyl acrylate copolymer, a polyolefin derivative such as chlorinated polyethylene, polyolefin such as ethylene- propylene copolymer, or polyester such as polyethylene-terephthalate and copolyester can be adopted. Among these components, as the main component of the separator 8, polyethylene and polypropylene excellent in electrolyte solution resistance, durability and weldability are suitably used.

[0039]

(Current collector)

The current collectors 9, 10 may be made of any material provided that the material has conductivity and, typically, the current collectors 9, 10 are formed by projecting the above-mentioned positive electrode current collector base material of the positive electrode plate 6 and the above- mentioned negative electrode current collector base material of the negative electrode plate 7. Further, the current collector 9, 10 may be made of a conductor which is connected to the positive electrode current collector base material or the negative electrode current collector base material in the inside of the case 5.

[0040]

In this embodiment, the positive electrode current collector 9 and the negative electrode current collector 10 extend in the directions opposite to each other from joined portions (mating seams of the sheets 4) on two opposite sides of the case 5 having a rectangular shape. With such a configuration, the positive electrode current collector 9 and the negative electrode current collector 10 do not interfere with each other (short- circuited) and hence, widths of the current collectors 9, 10 can be relatively increased whereby heat of the electrode assembly in the inside of the case 5 can be relatively efficiently released to the connecting members 12, 13, and eventually to the cooling member 3 through the current collectors 9, 10.

[0041]

Each of the connecting members 12, 13 has a pair of contact surfaces 15 which is disposed with a distance larger than a largest thickness of the case 5 on both sides of a joined portion of the sheets 4 of the case 5 in the thickness direction. The pair of contact surfaces 15 has complementary surface shapes. That is, the connecting members 12, 13 have a fixed thickness in the thickness direction of the sheets 4 within the contact surfaces 15 as viewed in the thickness direction of the sheets 4. In this embodiment, the contact surfaces 15 are surfaces perpendicular to the thickness direction of the sheets 4 of the case 5.

[0042]

In the energy storage device 1 of this embodiment, portions of the pair of connecting members 12, 13 having the contact surfaces 15 are disposed on both sides of the case 5 as viewed in the thickness direction of the sheet 4. With such a configuration, by holding the connecting members 12, 13, the whole energy storage device 1 can be fixed and hence, the energy storage apparatus can be easily assembled. In the energy storage apparatus, the pair of connecting members 12, 13 form a gap between the cases 5 of the energy storage devices disposed adjacently to each other and hence, cooling of the energy storage devices 1 can be accelerated.

[0043]

It is preferable that the contact surface 15 overlap with the joined portion of the sheets 4 as viewed in the thickness direction of the sheet 4. With such a configuration, a dead space in the energy storage apparatus can be decreased thus enhancing energy density of the whole apparatus.

[0044]

It is preferable that a lower limit of a length of the contact surface 15 in a direction along a side edge of the overlapping sheet 4 as viewed in a thickness direction of the sheet 4 be set to 1/2 of the length of the side edge of the overlapping sheet 4, and more preferably set to 2/3 of the length of the side edge of the overlapping sheet 4. On the other hand, it is preferable that an upper limit of the length of the contact surface 15 be set to 1.2 times as long as a length of the side edge of the overlapping sheet 4, and more preferably set to 1.1 times as long as the length of the side edge of the sheet 4. By setting the length of the contact surface 15 to the above-mentioned lower limit or above, a sufficient heat radiation property can be acquired and, at the same time, the energy storage devices 1 can be fixed in a stable manner. Further, by setting the length of the above-mentioned contact surface 15 to the above-mentioned upper limit or below, it is possible to prevent a dead space from being unnecessarily increased thus increasing energy density of the energy storage apparatus.

[0045]

The connecting members 12, 13 have slits 16 which sandwich the current collectors 9, 10 therebetween. That is, the connecting members 12, 13 are compression-bonded to the current collectors 9, 10 by collapsing the slits 16 by pressing in a state where the current collectors 9, 10 are inserted into the slits 16 respectively. With such a configuration, the connecting members 12, 13 can be relatively easily electrically and mechanically connected to the current collectors 9, 10 respectively.

[0046]

Further, one of the connecting member 12, 13 of each energy storage device 1 has a cooling surface 17 which is brought into contact with the cooling member 3 on a side opposite to the case 5. The energy storage device 1 radiates heat from the cooling surfaces 17 to the cooling member 3.

[0047]

As a material for forming the connecting members 12, 13, a metal material excellent in conductivity and thermal conductivity is preferably used. As such a metal material, copper, iron, aluminum or the like can be named, for example. Among these metal materials, aluminum is preferably used. Further, the connecting members 12, 13 may be formed by applying plating of chromium or the like to a surface of a metal material, for example.

[0048]

The holder 2 holds the plurality of energy storage devices 1 in a state where the plurality of energy storage devices 1 are disposed parallel to each other in the thickness direction of the joined portion of the sheets 4. The holder 2 brings the contact surfaces 15 of the connecting portions 12, 13 of the energy storage devices 1 into pressure contact with each other. In such a configuration, an insulation member 14 is sandwiched between the connecting members 12, 13 disposed adjacently to each other in the thickness direction of the sheets 4 every one other of the connecting members 12, 13. That is, the holder 2 includes a first pressure contact mechanism which electrically connects the connecting members 12, 13 with each other by bringing the contact surfaces 15 of the connecting members 12, 13 into pressure contact with each other.

[0049]

As the configuration of the holder 2, it is possible to adopt

substantially the same configuration as a holder (a rack, a frame, a box or the like) of a conventional energy storage apparatus except for a point that the holder 2 includes the pressure contact mechanism.

[0050]

As the first pressure contact mechanism of the holder 2, for example, an arbitrary configuration such as screws or springs can be adopted, for example. In this embodiment, the holder 2 includes springs 18 which press the connecting members 12, 13 to each other as the pressure contact mechanism. In this manner, with the use of the springs 18, the connecting members 12, 13 can be relatively easily brought into contact with each other at a proper pressure with certainty thus electrically connecting the energy storage devices 1 with certainty.

[0051]

A pressure contact force generated by the first pressure contact mechanism can be set to 0.3 kN to 1.0 kN inclusive although the pressure contact force depends on a size of the energy storage device 1 and a size of the contact surface 15.

[0052]

The holder 2 includes a second pressure contact mechanism which presses the cooling member 3 to the cooling surfaces 17 of the connecting members 12, 13 on one side of the plurality of energy storage devices 1. As the second pressure contact mechanism, in the same manner as the first pressure contact mechanism, an arbitrary configuration such as screws or springs can be adopted. With such a configuration, the respective connecting members 12, 13 and the cooling member 3 can be thermally connected to each other with certainty. A resiliently compressible sheet having thermal conductivity or the like may be sandwiched between the cooling surfaces 17 of the connecting members 12, 13 and the cooling member 3 for accelerating heat transmission, for example.

[0053]

<Cooling member> The cooling member 3 may be made of any material provided that the material can take heat from the connecting members 12, 13. For example, a member which allows a coolant to pass therethrough, a member having a heat radiation fin, a heat pump or the like can be used. Among these members, from a viewpoint of increasing a heat radiation amount relatively easily, the member which allows a coolant to pass therethrough is preferably used.

[0054]

The insulation member 14 is sandwiched between the connecting members 12, 13 which are disposed adjacently to each other but should not to be connected with other in connecting the plurality of energy storage devices 1 in series. With such a configuration, it is possible to prevent the formation of a short-circuiting loop where an electric current circulates between the energy storage devices 1 disposed adjacently to each other.

[0055]

The insulation member 14 may be preliminarily adhered to the contact surface 15 of the energy storage device 1. That is, by forming the insulation member 14 integrally with the energy storage device 1, assembling of the energy storage apparatus and exchanging of the energy storage device 1 can be performed more easily.

[0056]

The insulation member 14 may be made of any material provided that the material has an insulation property, for example, polypropylene or the like can be used as such a material. [0057]

It is preferable to set a thickness of the insulation member 14 as small as possible within a range where the insulation member 14 can ensure an insulation property. As a specific average thickness of the insulation member 14, a thickness can be set to a value which falls within a range of from 50 μηι to 500 μηι inclusive. For example, the thickness of the insulation member 14 can be set to 100 μηι typically.

[0058]

As described above, the energy storage apparatus includes the plurality of energy storage devices having the connecting members 12, 13 each having the pair of contact surfaces 15 disposed with a distance therebetween larger than the largest thickness of the case 5 as described above. Accordingly, the connecting members 12, 13 of the energy storage devices 1 disposed adjacently to each other can be easily electrically connected to each other. In the energy storage apparatus, the energy storage devices 1 can be connected to each other by bringing the connecting members 12, 13 into pressure contact with each other and hence,

assembling of the energy storage apparatus and exchanging of the energy storage device 1 can be relatively easily performed.

[0059]

In the energy storage apparatus, since the distance between the pair of contact surfaces 15 is set larger than the largest thickness of the case 5, a gap is formed between the cases 5. Accordingly, even when a temperature of the case 5 is increased, the case 5 can expand so as to project into the gap. With such a configuration, there is no possibility that the expansion of the case 5 separates the connecting members 12, 13 from each other and hence, a pressure contact state between the connecting members 12, 13, that is, an electrical connection between the energy storage devices 1 can be

maintained.

[0060]

Further, the energy storage apparatus is configured such that the connecting members 12, 13 have the cooling surface 17 respectively, and the energy storage apparatus includes the cooling member 3 which is brought into contact with the cooling surfaces 17. Accordingly, the respective energy storage devices 1 can be efficiently cooled.

[0061]

[Second embodiment]

Fig. 3 shows an energy storage device la according to a second embodiment of the present invention. The energy storage device la includes^ a case 5a which is formed of a flexible sheet 4 and in which the flexible sheet 4 is joined in an overlapping manner at least at a portion of a peripheral portion of the flexible sheet 4; an energy storage element 11 which has a stacked body formed of positive electrode plates 6, negative electrode plates 7 and separators 8 accommodated in the case 5a, and a pair of current collectors (a positive electrode current collector 9a and a negative electrode current collector 10a) extending from the positive electrode plates 6 and the negative electrode plates 7 to the outside through the joined portion of the case 5a! and a pair of connecting members (a positive electrode connecting member 12a and a negative electrode connecting member 13a) connected to the current collectors 9a, 10a outside the case 5a.

[0062]

In the energy storage device la shown in Fig. 3, constitutional elements identical with the constitutional elements of the energy storage device 1 shown in Fig. 2 are given the same symbols and their repeated explanation is omitted.

[0063]

<Case>

In the energy storage device la of this embodiment, the case 5a is formed in a rectangular shape as viewed in a stacking direction of the positive electrode plates 6, the negative electrode plates 7 and the

separators 8, and is a four- side sealed type bag where the opposedly facing sheets 4 are welded to each other at four peripheral portions. The positive electrode current collectors 9a and the negative electrode current collectors 10a extend from one side of the bag parallel to each other.

[0064]

The connecting members 12a, 13a have a pair of contact surfaces 15a which is disposed with a distance larger than the largest thickness of the case 5a on both sides of a joined portion of the sheets 4 of the case 5a in the thickness direction. In this embodiment, the pair of contact surfaces 15 of the connecting member 12a, 13a has complementary concavo-convex shapes which engage with each other by fitting engagement. In this manner, by forming the contact surfaces 15 into the fitting engagement shape, in assembling the energy storage apparatus and in exchanging the energy storage device la, the energy storage device la can be relatively easily positioned. Accordingly, assembling of the energy storage apparatus and exchanging of the energy storage device la can be easily performed and, at the same time, cooling surfaces 17 of the plurality of energy storage devices la can be uniformly brought into contact with a cooling member 3.

[0065]

In the energy storage device la of this embodiment, portions of the pair of connecting members 12a, 13a having the contact surfaces 15 are disposed on one side of the case 5a as viewed in the thickness direction of the sheet 4. With such a configuration, all energy storage devices la can be electrically connected to each other only on one side of the energy storage apparatus. Accordingly, the energy storage device la can be preferably used for an energy storage apparatus to which a user can access from only one side in a state where the energy storage apparatus is assembled to an equipment.

[0066]

The energy storage device la may include a discharge device (not shown in the drawing) which can ensure the safety of the energy storage device by equalizing a potential of the positive electrode and a potential of the negative electrode when an abnormality such as internal short- circuiting occurs in the energy storage device la. To be more specific, the positive electrode connecting member 12a and the negative electrode connecting member 13a are connected to each other via the discharge device thus allowing the electrical connection between the positive electrode connecting member 12a and the negative electrode connecting member 13a when abnormality occurs. In the energy storage device la of this embodiment, the positive electrode connecting members 12a and the negative electrode connecting members 13a are disposed adjacently to each other and hence, a wiring between the discharge device and the positive electrode connecting member 12a and a wiring between the discharge device and the negative electrode connecting member 13a can be made small. By making the wiring small, a resistance caused by the discharge device can be made relatively small and hence, discharging at a relatively large electric current becomes possible. Further, the energy storage device and the energy storage apparatus can realize space saving.

[0067]

The connecting members 12a, 13a respectively have a cooling surface 17a which is brought into contact with a cooling member not shown in the drawing on a side opposite to the case 5a. The energy storage device la can radiate heat to the cooling member from the cooling surface 17a.

[0068]

[Third embodiment]

Fig. 4 shows an energy storage device lb according to a third embodiment of the present invention. The energy storage device lb includes^ a case 5a which is formed of a flexible sheet 4 and in which the sheet 4 is joined in an overlapping manner at least at a portion of a peripheral portion of the sheet 4; an energy storage element 11 which has a stacked body formed of positive electrode plates 6, negative electrode plates 7 and separators 8 accommodated in the case 5a, and a pair of current collectors (a positive electrode current collector 9a and a negative electrode current collector 10a) extending from the positive electrode plates 6 and the negative electrode plates 7 to the outside through the joined portion of the case 5a; and a pair of connecting members (a positive electrode connecting member 12b and a negative electrode connecting member 13b) connected to the current collectors 9a, 10a outside the case 5a.

[0069]

In the energy storage device lb in Fig. 4, constitutional elements identical with the constitutional elements of the energy storage device 1 in Fig. 2 or the constitutional elements of the energy storage device la in Fig. 3 are given the same symbols and their repeated explanation is omitted.

[0070]

The connecting members 12b, 13b respectively extend along the joined portion of the sheet 4 on a periphery of the case 5a in a bending manner from a side of the case 5a from which the current collectors 9a, 10a extend to sides disposed adjacently to the side, and on sides of the

adjacently disposed sides, a pair of contact surfaces 15b which is disposed with a distance larger than the largest thickness of the case 5a is formed on both sides of the joined portion of the sheet 4 of the case 5a in the thickness direction. That is, in the energy storage device lb of this embodiment, the portions of the pair of connecting members 12b, 13b having the contact surfaces 15a are disposed on both sides of the case 5a as viewed in a thickness direction of the sheet 4.

[0071]

The connecting members 12b, 13b can optimize a contact between the contact surfaces 15b at portions positioned on sides disposed adjacently to the side from which the current collectors 9a, 10a extend while optimizing the connection structure (for example, caulking structure) with the current collectors 9a, 10a at portions on sides where the current collectors 9a, 10a extend.

[0072]

Further, the connecting members 12b, 13b respectively have a cooling surface 17b which is brought into contact with a cooling member 3 on sides of the portions thereof being positioned on sides disposed adjacently to the side from which the current collectors 9a, 10a extend and opposite to the case 5. The energy storage device 1 can radiate heat from the cooling surfaces 17b to the cooling members 3.

[0073]

[Fourth embodiment]

Fig. 5 shows an energy storage device lc according to a fourth embodiment of the present invention. The energy storage device lc includes^ a case 5 which is formed of flexible sheets 4 and in which the flexible sheets 4 are joined to each other in an overlapping manner at least at a portion of a peripheral portion of the flexible sheet 4; an energy storage element 11 which has a stacked body formed of positive electrode plates 6, negative electrode plates 7 and separators 8 accommodated in the case 5, and a pair of current collectors (a positive electrode current collector 9 and a negative electrode current collector 10) extending from the positive electrode plates 6 and the negative electrode plates 7 to the outside through the joined portion of the case 5! and a pair of connecting members (a positive electrode connecting member 12c and a negative electrode connecting member 13c) connected to the current collectors 9, 10 outside the case 5.

[0074]

In the energy storage device lc in Fig. 5, constitutional elements identical with the constitutional elements of the energy storage device 1 in Fig. 1 are given the same symbols and their repeated explanation is omitted.

[0075]

The positive electrode connecting member 12c and the negative electrode connecting member 13c respectively have a pair of contact surfaces 15c, 15d which is disposed with a distance larger than the largest thickness of the case 5a on both sides in the thickness direction of a joined portion of the sheets 4 of the case 5. The positive electrode connecting member 12c and the negative electrode connecting member 13c extend along a front surface or a back surface of the case 5, and one contact surface 15c extends to a region where the contact surface 15c overlaps with the positive electrode plates 6 as viewed in a thickness direction.

[0076]

In an energy storage apparatus which uses the energy storage devices lc, one contact surface 15c of the positive electrode connecting member 12c of the energy storage device lc is brought into contact with one contact surface 15c of the negative electrode connecting member 13c of the adjacently disposed energy storage device lc and hence, the plurality of energy storage devices lc can be electrically connected to each other in series. [0077]

In the energy storage apparatus which uses the energy storage devices lc, an insulation member 14c is disposed between one contact surface 15c of the positive electrode connecting member 12c of the energy storage device lc and the other contact surface 15d of the positive electrode connecting member 12c of the adjacently disposed energy storage device lc and between one contact surface 15c of the negative electrode connecting member 13c of the energy storage device lc and the other contact surface 15d of the negative electrode connecting member 13c of the adjacently disposed energy storage device lc respectively and hence, the occurrence of short-circuiting can be prevented.

[0078]

The connecting member 12c, 13c respectively have a cooling surface 17c which is brought into contact with a cooling member 3 on a side opposite to the case 5. The energy storage device lc can radiate heat from the cooling surfaces 17c to the cooling members 3. The contact surface 15c extends along the front surface of the case 5 and is connected to the cooling surface 17c and hence, not only heat generated at areas in the vicinity of the positive electrode current collector 9a and the negative electrode current collector 10a but also heat generated at the center of the energy storage device lc can be efficiently radiated.

[0079]

[Other embodiments]

The above-mentioned embodiments are not intended to limit the configuration of the present invention. Accordingly, it should be construed that the above-mentioned embodiments can be modified by omission, replacement or addition of constitutional elements of respective parts of the embodiments based on the description of this specification and the common general technical knowledge, and all these modifications also fall within the scope of the present invention.

[0080]

The connection of the connecting member to the current collector may be performed by electric welding, ultrasonic welding or the like, for example.

[0081]

The energy storage device according to the present invention may not include the cooling surface. Accordingly, the energy storage apparatus according to the present invention may not include the cooling member. Further, the cooling surface of the energy storage device according to the present invention may be a surface of the connecting member other than a surface on a side opposite to the case. The cooling member 3 may be a temperature adjusting member, for example. The temperature adjusting member may perform not only cooling but also heating so as to make a temperature of the energy storage device constant.

INDUSTRIAL APPLICABILITY

[0082]

The energy storage device and the energy storage apparatus according to the present invention are preferably applicable to a storage battery for an automobile which requires relatively large capacity.

DESCRIPTION OF REFERENCE SIGNS 1, la, lb, lc: energy storage device

2^'· holder

3^: cooling member

4- sheet

5, 5a: case

6: positive electrode plate

T- negative electrode plate

8: separator

9, 9a: positive electrode current collector

10, 10a: negative electrode current collector

11: energy storage element

12, 12a, 12b, 12c: positive electrode connecting member

13, 13a, 13b, 13c: negative electrode connecting member

14, 14c^: insulation member

15, 15a, 15b, 15c, 15d: contact surface

16: slit

17, 17a, 17b, 17c: cooling surface

18: spring

Claims

1. An energy storage device comprising:

a case which is formed of a flexible sheet and in which the flexible sheet is joined in an overlapping manner at least at a portion of a peripheral portion of the flexible sheet;

an energy storage element which has a positive electrode plate and a negative electrode plate accommodated in the case, and a pair of current collectors extending from the positive electrode plate and the negative electrode plate to the outside through a joined portion of the case! and

a pair of connecting members which is connected to the current collectors outside the case,

wherein the connecting member has a pair of contact surfaces disposed with a distance larger than a largest thickness of the case on both sides of the joined portion of the sheet in a sheet thickness direction.

2. The energy storage device according to claim 1, wherein the contact surfaces overlap with the joined portion as viewed in the sheet thickness direction.

3. The energy storage device according to claim 2, wherein a length of the contact surface along a side edge of the overlapping sheet is 1/2 or more of the length of the side edge.

4. The energy storage device according to claim 1, 2, or 3, wherein portions of the pair of connecting members having the contact surfaces are disposed on both sides of the case as viewed in the sheet thickness direction.

5. The energy storage device according to any one of claims 1 to 4, wherein the pair of current collectors extends from the case in directions opposite to each other.

6. The energy storage device according to any one of claims 1 to 5, wherein the contact surface is a plane perpendicular to the sheet thickness direction.

7. The energy storage device according to any one of claims 1 to 5, wherein the pair of contact surfaces has shapes which engage with each other by fitting engagement.

8. The energy storage device according to any one of claims 1 to 7, wherein the connecting members have slits which sandwich the current collector therebetween.

9. An energy storage apparatus comprising:

a plurality of the energy storage devices described in any one of claims 1 to 8! and

a holder for holding the plurality of energy storage devices parallel to each other in the sheet thickness direction, wherein

the contact surfaces of the connecting members of the plurality of energy storage devices are brought into pressure contact with each other by the holder.

10. The energy storage apparatus according to claim 9, wherein the holder has a spring which presses the connecting members to each other.