Battery packaging material having a valve device

A battery includes a battery element, a housing body, and a valve device. The housing body is constituted by at least one laminate including at least a base material layer, a barrier layer, and a heat-sealable resin layer layered in that order and houses the battery element. The valve device is in communication with the inside of the housing body. A joined edge portion in which the mutually facing heat-sealable resin layers are fused together is formed in a peripheral edge portion of the housing body. The valve device includes a first portion and a second portion. A valve mechanism configured to reduce the internal pressure of the housing body if the internal pressure is increased due to gas generated in the housing body is formed in the first portion. An air passage configured to guide gas generated in the housing body toward the valve mechanism is formed in the second portion. The first portion is located on an outer side of an edge of the joined edge portion. At least a portion of the second portion is sandwiched between the heat-sealable resin layers in the joined edge portion.

TECHNICAL FIELD

The present invention relates to a battery.

BACKGROUND ART

JP 2016-152231A (Patent Literature 1) discloses a lithium ion battery that includes a battery element and an enclosing bag that houses the battery element. In this lithium ion battery, a one-way exhaust valve is attached to the enclosing bag. When gas is generated in the enclosing bag as the lithium ion battery is charged or discharged, an excess of the gas is discharged from the one-way exhaust valve (see Patent Literature 1).

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Patent Literature 1 described above does not disclose a method for attaching the one-way exhaust valve to the enclosing bag. If the one-way exhaust valve is attached to the enclosing bag through heat sealing, a valve mechanism within the one-way exhaust valve may break due to heat and pressure that are applied thereto during the heat sealing process.

The present invention was made to solve this problem, and an object of the present invention is to provide a battery in which a valve mechanism is unlikely to break when a valve device is attached to the battery.

Solution to Problem

A battery according to the present invention includes a battery element, a housing body, and a valve device. The housing body is constituted by at least one laminate including at least a base material layer, a barrier layer, and a heat-sealable resin layer layered in that order and houses the battery element. The valve device is in communication with the inside of the housing body. The heat-sealable resin layers face each other in a peripheral edge portion of the housing body. A joined edge portion in which the mutually facing heat-sealable resin layers are fused together is formed in the peripheral edge portion of the housing body. The valve device includes a first portion and a second portion. A valve mechanism is formed in the first portion, the valve mechanism being configured to reduce an internal pressure of the housing body if the internal pressure is increased due to gas generated in the housing body. An air passage is formed in the second portion, the air passage being configured to guide gas generated in the housing body toward the valve mechanism. The first portion is located on an outer side of an outer edge of the joined edge portion. At least a portion of the second portion is sandwiched between the heat-sealable resin layers in the joined edge portion.

In this battery, the second portion of the valve device is sandwiched between the heat-sealable resin layers in the joined edge portion, but the first portion of the valve device is not sandwiched between the heat-sealable resin layers. Therefore, in this battery, a large pressure and a large amount of heat are not applied to the first portion, when compared to the second portion, when the mutually facing heat-sealable resin layers are fused. As a result, according to this battery, it is possible to keep the valve mechanism in the first portion from breaking due to pressure and heat applied when the mutually facing heat-sealable resin layers are fused.

Preferably, in a thickness direction of the battery, a length of the first portion may be longer than a length of the second portion, and a step may be formed at a boundary between the first portion and the second portion.

In this battery, the first portion is longer than the second portion at least in the thickness direction of the battery, and a step is formed at the boundary between the first portion and the second portion. Accordingly, in this battery, even if the valve device is excessively pressed toward the housing body to sandwich the second portion between the heat-sealable resin layers in a step of manufacturing the battery, the stepped portion is caught on end parts of the laminates. Therefore, according to this battery, it is possible to suppress a situation in which the first portion is sandwiched between the heat-sealable resin layers by mistake in the step of manufacturing the battery. Also, in the thickness direction of the battery described above, the difference between a length of a portion of the joined edge portion where the second portion is sandwiched and a length of a portion of the joined edge portion where the second portion is not sandwiched is small, when compared to a case where the step is not formed at the boundary between the first portion and the second portion. Accordingly, in the portion of the joined edge portion where the second portion is sandwiched, the heat-sealable resin layers are fused together without excessive heat and excessive pressure being applied to the heat-sealable resin layers. As a result, according to this battery, it is possible to suppress a reduction in sealing strength and a reduction in insulating performance, which would be caused if the heat-sealable resin layers become thin. Here, the reduction in the insulating performance refers to a phenomenon in which electricity passes between the barrier (metal) layer and an electrolytic solution as a result of a portion of the heat-sealable resin layers becoming thin or having cracks, for example.

Preferably, a length of the second portion in a width direction of the battery may be longer than a length of the second portion in a thickness direction of the battery.

In this battery, the length of the second portion in the thickness direction of the battery is short, when compared to a case where the cross-sectional shape of the second portion is a perfectly circular shape (the area is the same). That is, in the thickness direction of the battery described above, the difference between a length of a portion of the joined edge portion where the second portion is sandwiched and a length of a portion of the joined edge portion where the second portion is not sandwiched is small. Accordingly, in the portion of the joined edge portion where the second portion is sandwiched, the heat-sealable resin layers are fused together without excessive heat and excessive pressure being applied to the heat-sealable resin layers. As a result, according to this battery, it is possible to suppress a reduction in the sealing strength and a reduction in the insulating performance, which would be caused if the heat-sealable resin layers become thin.

Preferably, the second portion may include awing-shaped extended end part that is formed so as to be thinner toward an end part thereof in a width direction of the battery.

In this battery, the length in the thickness direction of the battery smoothly changes from a portion of the joined edge portion where the second portion is not sandwiched to a portion of the joined edge portion where the second portion is sandwiched, when compared to a case where the wing-shaped extended end part is not provided in the second portion. Accordingly, an excessive force is not applied to the laminates at the boundary between a position where the second portion is sandwiched between the heat-sealable resin layers and a position where the second portion is not sandwiched between the heat-sealable resin layers. As a result, according to this battery, the heat-sealable resin layers can be appropriately fused without excessive heat and excessive pressure being applied to the heat-sealable resin layers, and therefore it is possible to suppress a reduction in the sealing strength and a reduction in the insulating performance, which would be caused if the heat-sealable resin layers become thin.

Preferably, a cross-sectional shape of the air passage may be a circular shape.

Preferably, a length of a cross section of the air passage in a width direction of the battery may be longer than a length of the cross section of the air passage in a thickness direction of the battery

Preferably, the second portion may include a pillar that is formed in the air passage.

In this battery, the pillar is formed in the air passage in the second portion, and therefore the air passage is maintained even if pressure and heat are applied to the second portion sandwiched between the mutually facing heat-sealable resin layers. Therefore, according to this battery, the air passage in the second portion can be kept from breaking when the mutually facing heat-sealable resin layers are fused.

Preferably, an outer surface of the second portion may have a satin finish surface.

In this battery, the outer surface of the second portion has a satin finish surface, and accordingly, the heat-sealable resin easily melts at positions where the resin is in contact with the second portion. Therefore, according to this battery, the second portion of the valve device can be more firmly fixed to the housing body, when compared to a case where the outer surface of the second portion is smooth.

Preferably, at least one linear protrusion that extends in a circumferential direction may be formed on an outer surface of the second portion.

The linear protrusion securely comes into contact with the heat-sealable resin layers, and accordingly is easily fused with the laminates. In this battery, the linear protrusion extends in the circumferential direction on the outer surface of the second portion. Therefore, according to this battery, the heat-sealable resin layers and the second portion can be fused in the circumferential direction of the second portion. Also, in this battery, the area of contact between the outer surface of the second portion and the heat-sealable resin is large, when compared to a case where the linear protrusion is not formed on the second portion. Therefore, according to this battery, the second portion of the valve device can be relatively firmly fixed to the housing body. It is also possible to provide a plurality of linear protrusions to more firmly fix the second portion to the housing body.

Preferably, a corner of an end part of the second portion on a side opposite to the first portion is rounded in a plan view.

According to this battery, in a case where the end part on the side opposite to the first portion is located inside the housing body, for example, it is possible to reduce the possibility that the end part will damage the battery element within the housing body. According to this battery, it is also possible to reduce the possibility that the end part will damage the heat-sealable resin layer within the housing body and impair the insulating performance of the heat-sealable resin layer.

Preferably, an external shape of a cross section of the second portion with respect to which a center line of the air passage is the normal line may be a polygonal shape, and a corner of the polygonal shape may be rounded.

According to this battery, in a case where the end part of the second portion on the side opposite to the first portion is located inside the housing body, it is possible to reduce the possibility that the portion of the second portion located inside the housing body will damage the battery element within the housing body, and reduce the possibility that the portion of the second portion sandwiched between the heat-sealable resin layers will damage the heat-sealable resin layers and impair the insulating performance of the heat-sealable resin layers. Also, according to this battery, in a case where the end part of the second portion on the side opposite to the first portion is sandwiched between the heat-sealable resin layers, it is possible to reduce the possibility that the second portion will damage the heat-sealable resin layers and impair the insulating performance of the heat-sealable resin layers.

Preferably, the first portion and the second portion may be made of different materials, and the material of the first portion may have a higher melting point than the material of the second portion.

In this battery, the material of the first portion has a higher melting point than the material of the second portion, and therefore the first portion is unlikely to deform due to heat even if pressure and heat are applied to the second portion when the mutually facing heat-sealable resin layers are fused. Therefore, according to this battery, the valve mechanism in the first portion can be kept from breaking when the mutually facing heat-sealable resin layers are fused.

Preferably, a flat surface may be formed at least in a portion of an outer surface of at least one of the first portion and the second portion.

In this battery, the flat surface is formed in the outer surface of the valve device, and accordingly, the valve device is prevented from rolling over. According to this battery, the valve device does not roll over when the valve device is to be attached to the housing body, and therefore the valve device can be easily positioned.

Preferably, an adhesive member that is configured to adhere to both the second portion and the heat-sealable resin layers may be arranged between an outer peripheral surface of the second portion and the heat-sealable resin layers.

In this battery, the adhesive member that can adhere to the heat-sealable resin layers is bonded to the outer peripheral surface of the second portion. Therefore, according to this battery, a state where the housing body and the valve device are bonded can be easily maintained irrespective of the material of the second portion.

Preferably, a helium leakage amount from a secondary side to a primary side of the valve device measured in an environment at 25° C. in accordance with a method defined in “vacuum spraying method” of JIS Z2331:2006 “Method for helium leak testing” may be from 5.0×10−11Pa·m3/sec to 5.0×10−6Pa·m3/sec inclusive.

According to this battery, if gas is generated inside the housing body, the gas can be appropriately discharged to the outside of the housing body, and the intrusion of moisture from the external environment into the housing body can be effectively suppressed.

Preferably, a maximum distortion in a thickness direction of the housing body after gas generated in the housing body is discharged via the valve device to the outside of the housing body may be less than 30%.

According to this battery, gas is discharged via the valve device at appropriate timings, and therefore it is possible to reduce the possibility of the occurrence of a situation where large creases are formed in the housing body or the housing body largely deforms after gas is discharged via the valve device to the outside of the housing body.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a battery in which a valve mechanism is unlikely to break when a valve device is attached to the battery.

DESCRIPTION OF EMBODIMENTS

The following describes embodiments of the present invention in detail with reference to the drawings. Note that the same or corresponding portions are denoted with the same reference numerals in the drawings, and descriptions thereof will not be repeated.

1. First Embodiment

1-1. Overview of Battery

FIG.1is a plan view of a battery10according to a first embodiment.FIG.2is a cross-sectional view taken along line II-II inFIG.1. In the battery10, a positive electrode and a negative electrode of tabs300are arranged on opposite sides, and the battery10is configured to be used, for example, in an electrically driven vehicle such as an electric automobile or a hybrid automobile in which many batteries connected in series are used at a high voltage.

As shown inFIGS.1and2, the battery10includes a housing body100, a battery element400, the tabs300, tab films310, and a valve device200.

The housing body100includes packaging materials110and120. The packaging materials110and120are subjected to heat sealing in a peripheral edge portion of the housing body100to form a joined edge portion130. That is, the packaging materials110and120are fused together in the joined edge portion130. Details of the packaging materials110and120will be described later.

The battery element400is a power storage member such as a lithium ion battery or a capacitor. The battery element400is housed in the housing body100. If an abnormality occurs in the battery element400, gas may be generated in the housing body100. Also, if the battery element400is a capacitor, for example, gas may be generated in the housing body100due to a chemical reaction occurring in the capacitor.

The tabs300are metal terminals that are used to input and output power to and from the battery element400. One end part of each tab300is electrically connected to an electrode (a positive electrode or a negative electrode) of the battery element400, and the other end part protrudes from an edge of the housing body100to the outside.

Examples of metal materials that may constitute the tabs300include aluminum, nickel, and copper. If the battery element400is a lithium ion battery, for example, a tab300that is connected to the positive electrode is usually constituted by aluminum or the like, and a tab300that is connected to the negative electrode is usually constituted by copper, nickel, or the like.

The battery10includes two tabs300. One of the tabs300is sandwiched between the packaging materials110and120via a tab film310in an end part of the housing body100in the direction of the arrow L. The other tab300is sandwiched between the packaging materials110and120via a tab film310in an end part of the housing body100in the direction of the arrow R.

The tab films310are adhesive protective films and are configured to adhere to both the packaging materials110and120and the tabs300(metal). The tabs300made of metal can be fixed with the packaging materials110and120as a result of the tab films310being interposed therebetween.

Particularly, in a case where the battery is used at a high voltage, the tab films310preferably include a heat-resistant layer or a heat-resistant component and have a function of preventing short circuits.

The valve device200is in communication with the inside of the housing body100and is configured to discharge gas from the inside to the outside of the housing body100if the internal pressure of the housing body100has reached or exceeded a predetermined value due to gas generated in the housing body100. A housing of the valve device200is preferably made of a material that directly adheres to innermost layers of the packaging materials110and120, and is preferably made of a heat-sealable resin, such as polypropylene (PP), that is the same as the innermost layers of the packaging materials110and120. In a case where a material other than PP is used for reasons related to heat resistance or the like, it is effective to perform sealing via a film that can adhere to both the other material and PP, similarly to the tab films used for the tabs. An end part of the valve device200in the direction of the arrow B is sandwiched between the packaging materials110and120in an end part of the housing body100in the direction of the arrow F. Details of the valve device200will be described later.

The battery10according to the first embodiment employs various structural features that are devised to attach the valve device200to the housing body100. The following describes a configuration of the housing body100, a configuration of the valve device200, a state of the valve device200attached to the housing body100, and a method for manufacturing the battery10in that order.

Note that the directions indicated by arrows L, R, U, D, F, and B are common to the drawings. In the following description, the direction indicated by the arrows L and R will also be referred to as a “width direction of the battery10”, and the direction indicated by the arrows U and D will also be referred to as a “thickness direction of the battery10”.

1-2. Configuration of Housing Body

FIG.3is a diagram showing the housing body100. As shown inFIG.3, the housing body100includes the packaging materials110and120. The packaging materials110and120are each constituted by a laminated film and have substantially the same rectangular shape in a plan view.

The packaging material110includes a molded part112that is molded so as to form a space S1and a flange portion114that extends in the direction indicated by the arrows F and B and the direction indicated by the arrows L and R from the molded part112. The molded part112is open in a surface in the direction of the arrow U. The battery element400(FIG.1) is placed into the space S1via the opening in the surface.

FIG.4is a diagram showing an example of a cross-sectional structure of the packaging materials110and120. As shown inFIG.4, each of the packaging materials110and120is a laminate constituted by a base material layer31, an adhesive agent layer32, a barrier layer33, an adhesive layer34, and a heat-sealable resin layer35that are layered in that order. Note that each of the packaging materials110and120does not necessarily have to include the layers shown inFIG.4, and is only required to include at least the base material layer31, the barrier layer33, and the heat-sealable resin layer35layered in that order.

The base material layer31constitutes the outermost layer of the housing body100, and the heat-sealable resin layer35constitutes the innermost layer of the housing body100. When fabricating the battery10, portions of the heat-sealable resin layers35located in peripheral edge portions of the packaging materials110and120are thermally fused together in a state where the battery element400(FIG.2) is arranged in the space S1(FIG.3), whereby the joined edge portion130is formed, the battery element400is sealed in the housing body100, the valve device200is fixed to the joined edge portion130through fusion, and the tabs300are also fixed to the joined edge portion130through fusion via the tab films310. The following describes the layers included in the packaging materials110and120. Note that the packaging materials110and120each have a thickness of about 50 to 200 μm, for example, and preferably about 90 to 150 μm.

1-2-1. Base Material Layer

The base material layer31is a layer that functions as a base material of the packaging material110or120and constitutes the outermost layer of the housing body100.

Materials of the base material layer31are not specifically limited so long as the base material layer has an insulating property. Examples of materials of the base material layer31include polyesters, polyamides, epoxy resins, acrylic resins, fluorocarbon resins, polyurethanes, silicone resins, phenols, polyetherimides, polyimides, polycarbonates, and mixtures and copolymers thereof. The base material layer31may be a resin film made of any of these resins, or may be formed by applying any of these resins. The resin film may be an unstretched film or a stretched film. Examples of stretched films include a uniaxially stretched film and a biaxially stretched film, and the biaxially stretched film is preferable. Examples of stretching methods for forming the biaxially stretched film include a sequential biaxial stretching method, an inflation method, and a simultaneous biaxial stretching method. The base material layer31may be a single layer or may be constituted by two or more layers. In a case where the base material layer31is constituted by two or more layers, the base material layer31may be a laminate that is obtained by stacking resin films using an adhesive or the like, or a laminate that is constituted by two or more co-extruded resin films. A laminate constituted by two or more co-extruded resin films may be used as the base material layer31without being stretched, or may be used as the base material layer31after being subjected to uniaxial stretching or biaxial stretching. Specific examples of laminates that may be used as the base material layer31and are constituted by two or more resin films include a laminate of a polyester film and a nylon film, a laminate of two or more nylon films, and a laminate of two or more polyester films, and the base material layer31is preferably a laminate of a stretched nylon film and a stretched polyester film, a laminate of two or more stretched nylon films, or a laminate of two or more stretched polyester films. For example, in a case where the base material layer31is a laminate of two or more resin films, the base material layer31is preferably a laminate of a polyester resin film and a polyester resin film, a laminate of a polyamide resin film and a polyamide resin film, or a laminate of a polyester resin film and a polyamide resin film, and more preferably a laminate of a polyethylene terephthalate film and a polyethylene terephthalate film, a laminate of a nylon film and a nylon film, or a laminate of a polyethylene terephthalate film and a nylon film. Also, it is preferable that a polyester resin constitutes the outermost layer of the base material layer31.

The base material layer31has a thickness of about 3 to 50 μm, for example, and preferably about 10 to 35 μm.

1-2-2. Adhesive Agent Layer

The adhesive agent layer32is a layer that is arranged on the base material layer31as necessary to impart adhesiveness to the base material layer31. That is, the adhesive agent layer32is provided between the base material layer31and the barrier layer33as necessary.

The adhesive agent layer32is formed of an adhesive that can bond the base material layer31and the barrier layer33to each other. The adhesive used to form the adhesive agent layer32may be a two-liquid curable adhesive or a single-liquid curable adhesive. Also, the bonding mechanism of the adhesive used to form the adhesive agent layer32is not specifically limited, and may be any of a chemical reaction mechanism, a solvent volatilizing mechanism, a heat melting mechanism, and a thermocompression bonding mechanism.

The adhesive agent layer32has a thickness of about 1 to 10 μm, for example, and preferably about 2 to 5 μm.

The barrier layer33is a layer that improves the strength of the packaging material110or120and prevents water vapor, oxygen, light, and the like from entering the battery10. The barrier layer33may be constituted by a metal such as aluminum, stainless steel, or titanium, and is preferably constituted by aluminum. The barrier layer33can be formed from a metal foil, a vapor-deposited metal film, a vapor-deposited inorganic oxide film, a vapor-deposited carbon-containing inorganic oxide film, or a film provided with any of these vapor-deposited films, for example, and is preferably formed from a metal foil, and more preferably formed from an aluminum foil. In order to prevent the formation of creases or pinholes in the barrier layer33when manufacturing the packaging materials, the barrier layer is more preferably formed from a soft aluminum foil made of annealed aluminum (JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, JIS H4000:2014 A8079P-O, etc.), for example.

The thickness of the barrier layer33is not specifically limited so long as the barrier layer33functions as a barrier layer against water vapor or the like, and may be about 10 to 100 μm, for example, and preferably about 20 to 80 μm.

The adhesive layer34is a layer that is provided between the barrier layer33and the heat-sealable resin layer35as necessary to firmly bond the heat-sealable resin layer35.

The adhesive layer34is formed using an adhesive that can bond the barrier layer33and the heat-sealable resin layer35to each other. Although the composition of the adhesive used to form the adhesive layer34is not specifically limited, the composition is, for example, a resin composition that contains an acid-modified polyolefin. Although the acid-modified polyolefin is not specifically limited so long as it is a polyolefin modified with an acid, the acid-modified polyolefin is preferably a polyolefin grafted with an unsaturated carboxylic acid or an anhydride thereof.

The adhesive layer34has a thickness of about 1 to 50 μm, for example, and preferably about 2 to 40 μm.

The heat-sealable resin layer35constitutes the innermost layer of the housing body100. The battery element400is sealed in the housing body100by thermally fusing mutually facing heat-sealable resin layers35in the peripheral edge portion of the housing body100. Also, insulation quality can be maintained between an electrolytic solution and a metal constituting the barrier layer as a result of the barrier layer being covered with the heat-sealable resin layer that has at least a predetermined thickness.

Although a resin component that is used for the heat-sealable resin layer35is not specifically limited so long as the heat-sealable resin layer35can be thermally fused, the resin component is a polyolefin or an acid-modified polyolefin, for example.

Examples of polyolefins include: polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or noncrystalline polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymer of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymer of propylene and ethylene); and a terpolymer of ethylene, butene, and propylene. Among these polyolefins, polyethylenes and polypropylenes are preferable. Also, although the acid-modified polyolefin is not specifically limited so long as it is a polyolefin modified with an acid, the acid-modified polyolefin is preferably a polyolefin grafted with an unsaturated carboxylic acid or an anhydride thereof.

The thickness of the heat-sealable resin layer35is not specifically limited, but preferably 100 μm or less, more preferably about 15 to 90 μm, and further preferably about 30 to 80 μm.

1-3. Configuration of Valve Device

FIG.5is a plan view of the valve device200. As shown inFIG.5, the valve device200includes a valve function portion210and a seal attachment portion220. Although details will be described later, at least a portion of the seal attachment portion220is fixed in a state of being sandwiched between the packaging materials110and120(FIG.2), and an outer peripheral surface of the seal attachment portion220and the heat-sealable resin layers35, which are the innermost layers of the packaging materials110and120, are joined as a result of being fused through heat sealing.

Rs are formed at corners of an end part of the seal attachment portion220in the direction of the arrow B. That is, Rs (e.g., R=0.2 mm to 2.0 mm) are formed at corners of an end part of the seal attachment portion220on the side opposite to the valve function portion210in a plan view. Note that in the present specification, the expression “an R being formed” means that a corner is rounded. Here, in the description of a structure, the expression “an R being formed” means that a corner is rounded similarly to the case where the corner is chamfered, and where “R” is described alone, “R” represents the radius of curvature of the corner. Note that it is possible to chamfer sharp corners that are formed in a step of manufacturing the valve device200to make the corners round (form Rs), but if the housing of the valve device200is a resin molded article, Rs can also be formed by molding the housing so as to originally include rounded corners, without performing chamfering such as cutting.

FIG.6is a cross-sectional view taken along line VI-VI inFIG.5. As shown inFIG.6, cross sections of the valve function portion210and the seal attachment portion220of the valve device200have perfectly circular shapes, and an air passage A1is formed inside the seal attachment portion220. A cross section of the air passage A1has a perfectly circular shape.

In the valve device200, a length L2of the valve function portion210in the thickness direction (the direction indicated by the arrows U and D) of the battery10is longer than a length L1of the seal attachment portion220in the thickness direction of the battery10. A length L2of the valve function portion210in the width direction (the direction indicated by the arrows L and R) of the battery10is longer than a length L1of the seal attachment portion220in the width direction of the battery10. That is, the diameter of the cross section of the valve function portion210is longer than the diameter of the cross section of the seal attachment portion220. As a result, a step is formed at the boundary between the valve function portion210and the seal attachment portion220(FIG.5).

FIG.7is a cross-sectional view taken along line VII-VII inFIG.5. As shown inFIG.7, Rs (e.g., R=0.2 mm to 2.0 mm) are formed in the end part of the seal attachment portion220in the direction of the arrow B. Also, the air passage A1is formed inside the seal attachment portion220. The air passage A1guides gas generated in the housing body100toward the valve function portion210, for example.

A valve mechanism that is configured to discharge gas generated in the housing body100(FIG.1) is provided inside the valve function portion210. Specifically, the valve function portion210includes an O ring212, a ball214, a spring216, and a membrane218. That is, a ball spring valve mechanism is provided in the valve function portion210. Note that the valve mechanism provided in the valve function portion210is not specifically limited so long as the mechanism can reduce the internal pressure of the housing body100that has been increased by gas, and may also be a poppet valve mechanism, a duckbill valve mechanism, an umbrella valve mechanism, or a diaphragm valve mechanism, for example.

The O ring212is a hollow circular ring and is made of fluororubber, for example. The ball214and the spring216are made of stainless steel, for example. Note that the ball214may also be made of resin. The membrane218has a pore diameter of about 10−2to 100μm, for example, and is constituted by a PTFE membrane that keeps the electrolytic solution from leaking and allows only gas to permeate (selective permeation). Note that PTFE means polytetrafluoroethylene. Since the PTFE membrane is a soft material, if the strength of the membrane is insufficient, it is also possible to form the membrane and a mesh or a non-woven cloth of polypropylene, polyester, or the like into a single piece and use the thus reinforced membrane.

If the internal pressure of the housing body100reaches a predetermined pressure in a state where the valve device200is attached to the housing body100, gas guided through the air passage A1presses the ball214in the direction of the arrow F. As a result of the ball214being pressed and the spring216being compressed, the gas inside the housing body100passes through a gap that is formed between the ball214and the O ring212, permeates the membrane218, and is discharged from an exhaust port O1to the outside of the housing body100.

1-4. Attached State of Valve Device

FIG.8is a cross-sectional view taken along line VIII-VIII inFIG.1and shows an attached state of the valve device200. As shown inFIG.8, the valve function portion210of the valve device200is located on an outer side of an edge of the joined edge portion130. On the other hand, a portion of the seal attachment portion220of the valve device200is sandwiched between the heat-sealable resin layer35of the packaging material110and the heat-sealable resin layer35of the packaging material120in the joined edge portion130, and the outer peripheral surface of the seal attachment portion220and the heat-sealable resin layers35constituting the innermost layers of the packaging materials110and120are joined through fusion. Note that for the sake of convenience,FIG.8partially shows the heat-sealable resin layers35only in the vicinity of the joined edge portion130to show the state where the valve device200is joined through fusion with the heat-sealable resin layers35, which are the innermost layers of the packaging materials110and120, but the heat-sealable resin layers35are provided over all the surfaces of the packaging materials110and120.

The following describes reasons why the seal attachment portion220is sandwiched between the heat-sealable resin layers35in the joined edge portion130and the valve function portion210is not sandwiched between the heat-sealable resin layers35in the joined edge portion130in the battery10according to the first embodiment.

Assume that the valve function portion210is sandwiched between the heat-sealable resin layers35in the joined edge portion130. In this case, the valve mechanism in the valve function portion210may break due to heat and pressure that are applied when the heat-sealable resin layers35are fused together (subjected to heat sealing) in the peripheral edge portions of the packaging materials110and120.

In the battery10according to the first embodiment, the seal attachment portion220is sandwiched between the heat-sealable resin layers35in the joined edge portion130, but the valve function portion210is not sandwiched between the heat-sealable resin layers35. Therefore, in the battery10, a large pressure and a large amount of heat are not applied to the valve function portion210during the heat sealing process. That is, in the battery10, the valve function portion210is not sandwiched between the heat-sealable resin layers35to keep the valve mechanism from breaking due to pressure and heat applied during the heat sealing process.

Also, in the battery10according to the first embodiment, the cross section of the seal attachment portion220has a smaller diameter than the cross section of the valve function portion210as described above. Accordingly, in the thickness direction of the battery, the difference between a length L4of a portion of the joined edge portion130where the seal attachment portion220is sandwiched and a length L3of a portion of the joined edge portion130where the seal attachment portion220is not sandwiched is small, when compared to a case where the diameter of the cross section of the seal attachment portion220is larger than or equal to the diameter of the cross section of the valve function portion210. The larger the difference is, the more pressure applied during the heat sealing process needs to be increased to join the outer peripheral surface of the seal attachment portion220and the heat-sealable resin layers constituting the innermost layers of the packaging materials110and120without forming a gap therebetween. As a result, pressure applied to the peripheral edge portion of the housing body100during the heat sealing process is increased. If the pressure is increased, the heat-sealable resin layers35may become thin particularly at the position where the seal attachment portion220is sandwiched, and also at positions where the tab films310and the tabs300are sandwiched. If the heat-sealable resin layers35become thin, a dielectric breakdown may occur in the battery10.

In the battery10according to the first embodiment, the difference between the length L4and the length L3is small as described above. Accordingly, when the peripheral edge portion of the housing body100is sandwiched by a heat sealing apparatus, pressure and heat are appropriately applied to the heat-sealable resin layers over the entire periphery of the housing body100. As a result, according to the battery10, it is possible to appropriately fuse the mutually facing heat-sealable resin layers35and firmly fix the seal attachment portion220to the housing body100while reducing the possibility of a dielectric breakdown in the battery10.

Also, in the battery10according to the first embodiment, the end part of the seal attachment portion220in the direction of the arrow B protrudes into the space S1past the flange portion114. Therefore, depending on conditions in which the battery10is used, the end part of the seal attachment portion220in the direction of the arrow B may come into contact with the battery element400. In the battery10according to the first embodiment, Rs are formed in the end part of the seal attachment portion220in the direction of the arrow B as described above (FIG.5). Therefore, even if the end part of the seal attachment portion220comes into contact with the battery element400, the end part is unlikely to damage the battery element400. Also, depending on conditions in which the battery10is used, the end part of the seal attachment portion220in the direction of the arrow B may come into contact with the heat-sealable resin layer35of the packaging material120. In the battery10according to the first embodiment, Rs are formed in the end part of the seal attachment portion220in the direction of the arrow B as described above, and therefore, even if the end part of the seal attachment portion220comes into contact with the heat-sealable resin layer35of the packaging material120, the end part is unlikely to damage the heat-sealable resin layer35.

1-5. Manufacturing Method

FIG.9is a flowchart showing a procedure for manufacturing the battery10. The battery10is manufactured using a manufacturing apparatus, for example.

As shown inFIG.9, the manufacturing apparatus places components in the housing body100(step S100). For example, the manufacturing apparatus places the battery element400, to which the tabs300provided with the tab films310have been electrically connected through welding, into the space S1within the packaging material110such that the tabs provided with the tab films310are placed on the flange portion114of the packaging material110, and then places the valve device200on the flange portion114of the packaging material110. Note that it is also possible to place the battery element400into the space S1within the packaging material110, then electrically connect the tabs300provided with the tab films310to the battery element400through welding such that the tabs and the tab films310are placed on the flange portion114of the packaging material110, and then place the valve device200on the flange portion114of the packaging material110. Then, the manufacturing apparatus places the packaging material120on the packaging material110.

FIG.10is a diagram showing an operation of placing the valve device200between the flange portion114of the packaging material110and the packaging material120. As shown inFIG.10, a step is formed between the valve function portion210and the seal attachment portion220. Accordingly, even if the valve device200is excessively pressed toward the housing body100to sandwich the seal attachment portion220between the packaging materials110and120, the stepped portion is caught on end parts of the packaging materials110and120. Therefore, according to the battery10, it is possible to suppress a situation in which the valve function portion210is sandwiched between the packaging materials110and120(the heat-sealable resin layers35) by mistake in the step of manufacturing the battery10.

After the components are placed, the manufacturing apparatus performs heat sealing on the peripheral edge portion of the housing body100(step S110). That is, the manufacturing apparatus sandwiches the peripheral edge portion of the housing body100and applies pressure and heat to the peripheral edge portion of the housing body100. As a result, the mutually facing heat-sealable resin layers35are fused together in the peripheral edge portion of the housing body100, and the joined edge portion130is formed. Also, the battery element400is sealed in the housing body100, the valve device200is fixed to the joined edge portion130through fusion, and the tabs300are also fixed to the joined edge portion130through fusion via the tab films310, whereby the battery10is complete. Note that in the heat sealing step, gas is removed from the inside of the housing body100to achieve a state where unneeded gas is not contained inside the housing body100. Specifically, a portion of the periphery of the housing body100is left unjoined, without the entire periphery being joined, gas is removed via the unjoined portion of the periphery, and finally pressure and heat are applied to the unjoined portion of the periphery to complete the joined edge portion130over the entire periphery. In the case of a battery that requires an electrolytic solution, a portion of the periphery of the housing body100is left unjoined, without the entire periphery being joined, the electrolytic solution is introduced via the unjoined portion of the periphery, gas is removed, and finally pressure and heat are applied to the unjoined portion of the periphery to complete the joined edge portion130over the entire periphery.

Also, it is effective to make surfaces of seal bars of the manufacturing apparatus that sandwich the peripheral edge portion of the housing body100have a shape that conforms to the external shape of the seal attachment portion220. In this case, the heat-sealable resin layers35are more firmly joined together at the position where the seal attachment portion220is sandwiched. In this case as well, it is effective to make the seal attachment portion220have a flattened shape as in a second embodiment described below, in order to suppress deformation of the packaging materials110and120and a load applied thereto.

As described above, in the battery10according to the first embodiment, at least a portion of the seal attachment portion220of the valve device200is sandwiched between the heat-sealable resin layers35in the joined edge portion130, and the valve function portion210of the valve device200is not sandwiched between the heat-sealable resin layers35in the joined edge portion130. Therefore, in the battery10, a large pressure and a large amount of heat are not applied to the valve function portion210, when compared to the seal attachment portion220, when the mutually facing heat-sealable resin layers35are fused. As a result, according to the battery10, it is possible to keep the valve mechanism in the valve function portion210from breaking due to pressure and heat applied when the mutually facing heat-sealable resin layers35are fused.

Note that the battery element400is an example of a “battery element” in the present invention, the housing body100is an example of a “housing body” in the present invention, and the valve device200is an example of a “valve device” in the present invention. The base material layer31is an example of a “base material layer” in the present invention, the barrier layer33is an example of a “barrier layer” in the present invention, and the heat-sealable resin layer35is an example of a “heat-sealable resin layer” in the present invention. The joined edge portion130is an example of a “joined edge portion” in the present invention. The valve function portion210is an example of a “first portion” in the present invention, and the seal attachment portion220is an example of a “second portion” in the present invention. The air passage A1is an example of an “air passage” in the present invention.

For the sake of convenience, the size of the battery element400is shown as being small relative to the space S1within the housing body100in order to make it easy to understand that the battery element400is housed in the space S1within the housing body100. Although the space S1is slightly larger than the battery element400in order to place the battery element400into the space S1in a manufacturing step, gas is removed in a manufacturing step as described above, and accordingly, the space S1is slightly reduced as the gas is removed, and in a final state of the battery10, the space S1has substantially the same size as the battery element400, and the battery element400is housed in the space S1with almost no gap formed therebetween.

2. Second Embodiment

The second embodiment differs from the first embodiment described above in the configuration of the valve device. Other configurations are basically the same as those in the first embodiment. Here, differences from the first embodiment will be described.

FIG.11is a plan view of a valve device200A that is mounted in a battery according to the second embodiment. As shown inFIG.11, the valve device200A includes a valve function portion210A and a seal attachment portion220A. At least a portion of the seal attachment portion220A is sandwiched between the packaging materials110and120and is subjected to heat sealing. The cross-sectional shape of the seal attachment portion220A differs from that in the first embodiment. The valve function portion210A is basically the same as that in the first embodiment, but the shapes of the housing and the valve mechanism are partially changed since an air passage A6(FIG.12) formed in the seal attachment portion220A has a different shape.

FIG.12is a cross-sectional view taken along line XII-XII inFIG.11. As shown inFIG.12, in a cross section of the seal attachment portion220A, a length L5in the width direction (the direction indicated by the arrows L and R) of the battery is longer than a length L6in the thickness direction (the direction indicated by the arrows U and D) of the battery. More specifically, the cross-sectional shape of the seal attachment portion220A is an elliptical shape.

The air passage A6is formed inside the seal attachment portion220A. The length of the air passage A6in the width direction of the battery is longer than the length of the air passage A6in the thickness direction of the battery. More specifically, the cross-sectional shape of the air passage A6is an elliptical shape.

As described above, in the second embodiment, the length L5of the cross section of the seal attachment portion220A in the width direction of the battery is longer than the length L6of the cross section of the seal attachment portion220A in the thickness direction of the battery. That is, the length of the seal attachment portion220A in the thickness direction of the battery is short, when compared to a case where the cross-sectional shape of the seal attachment portion is a perfectly circular shape (the area is the same). In the thickness direction of the battery described above, the difference between a length of a portion of the joined edge portion130where the seal attachment portion220A is sandwiched and a length of a portion of the joined edge portion130where the seal attachment portion220A is not sandwiched is further reduced. Therefore, according to this battery, it is possible to appropriately apply pressure and heat to the heat-sealable resin layers35over the entire periphery of the housing body100and appropriately fuse the mutually facing heat-sealable resin layers35, and therefore the seal attachment portion220A of the valve device200A can be firmly fixed to the housing body100.

Note that the valve device200A is an example of the “valve device” in the present invention, the valve function portion210A is an example of the “first portion” in the present invention, and the seal attachment portion220A is an example of the “second portion” in the present invention. The air passage A6is an example of the “air passage” in the present invention.

A third embodiment differs from the first embodiment described above in the configuration of the valve device. Other configurations are basically the same as those in the first embodiment. Here, differences from the first embodiment will be described.

FIG.13is a plan view of a valve device200B that is mounted in a battery according to the third embodiment. As shown inFIG.13, the valve device200B includes a valve function portion210B and a seal attachment portion220B. At least a portion of the seal attachment portion220B is sandwiched between the packaging materials110and120and is subjected to heat sealing. The cross-sectional shape of the seal attachment portion220B differs from that in the first embodiment. The valve function portion210B is basically the same as that in the first embodiment, but the shapes of the housing and the valve mechanism are partially changed since an air passage A7(FIG.14) formed in the seal attachment portion220B has a different shape.

FIG.14is a cross-sectional view taken along line XIV-XIV inFIG.13. As shown inFIG.14, wing-shaped extended end parts40and41are formed on both end parts of the seal attachment portion220B in the width direction (the direction indicated by the arrows L and R) of the battery. The wing-shaped extended end parts40and41are formed so as to be thinner toward the ends thereof in the width direction of the battery. In other words, it could be said that the wing-shaped extended end parts40and41are portions in which the length thereof in the thickness direction of the battery gently changes in the direction indicated by the arrows L and R, when compared to the other portion (circular portion) of the seal attachment portion22.

In the battery according to the third embodiment, the length in the thickness direction of the battery smoothly changes from a portion of the joined edge portion130where the seal attachment portion220B is not sandwiched to a portion of the joined edge portion130where the seal attachment portion220B is sandwiched, when compared to the first embodiment (a case where the wing-shaped extended end parts40and41are not provided in the seal attachment portion220B). Accordingly, in this battery, an excessive force is not applied to the packaging materials110and120at the boundary between a position where the seal attachment portion220B is sandwiched between the heat-sealable resin layers35and a position where the seal attachment portion220B is not sandwiched between the heat-sealable resin layers35, and therefore the seal attachment portion220B of the valve device200B can be firmly fixed to the housing body100.

Note that the valve device200B is an example of the “valve device” in the present invention, the valve function portion210B is an example of the “first portion” in the present invention, and the seal attachment portion220B is an example of the “second portion” in the present invention. The wing-shaped extended end parts40and41are each an example of a “wing-shaped extended end part” in the present invention. The air passage A7is an example of the “air passage” in the present invention.

A fourth embodiment differs from the first embodiment described above in the configuration of the valve device. Other configurations are basically the same as those in the first embodiment. Here, differences from the first embodiment will be described.

FIG.15is a plan view of a valve device200C that is mounted in a battery according to the fourth embodiment. As shown inFIG.15, the valve device200C includes a valve function portion210C and a seal attachment portion220C. At least a portion of the seal attachment portion220C is sandwiched between the packaging materials110and120and is subjected to heat sealing. The cross-sectional shape of the seal attachment portion220C differs from that in the first embodiment. The valve function portion210C is basically the same as that in the first embodiment, but the shapes of the housing and the valve mechanism are partially changed since an air passage A2(FIG.16) formed in the seal attachment portion220C has a different shape.

FIG.16is a cross-sectional view taken along line XVI-XVI inFIG.15. As shown inFIG.16, pillars50and51are formed inside the seal attachment portion220C (in the air passage A2). The pillars50and51each extend in the thickness direction (the direction indicated by the arrows U and D) of the battery, and both ends of each pillar in the thickness direction of the battery are connected to an inner peripheral surface of the seal attachment portion220C. Also, the pillars50and51each extend in the direction indicated by the arrows F and B in the air passage A2(FIG.15). Note that the number of pillars does not necessarily have to be two, and it is sufficient that at least one pillar is provided.

In the battery according to the fourth embodiment, the pillars50and51are formed in the air passage A2, and therefore, the air passage A2is maintained even if pressure and heat are applied to the seal attachment portion220C sandwiched between the mutually facing heat-sealable resin layers35. Therefore, according to this battery, the air passage A2in the seal attachment portion220C can be kept from breaking when the mutually facing heat-sealable resin layers35are fused.

Note that the valve device200C is an example of the “valve device” in the present invention, the valve function portion210C is an example of the “first portion” in the present invention, and the seal attachment portion220C is an example of the “second portion” in the present invention. The pillars50and51are each an example of a “pillar” in the present invention. The air passage A2is an example of the “air passage” in the present invention.

A fifth embodiment differs from the first embodiment described above in the configuration of the valve device. Other configurations are basically the same as those in the first embodiment. Here, differences from the first embodiment will be described.

FIG.17is a plan view of a valve device200D that is mounted in a battery according to the fifth embodiment. As shown inFIG.17, the valve device200D includes a valve function portion210and a seal attachment portion220D. The configuration of the valve function portion210is the same as that in the first embodiment.

At least a portion of the seal attachment portion220D is sandwiched between the packaging materials110and120and is subjected to heat sealing. The outer surface of the seal attachment portion220D differs from that in the first embodiment. Specifically, the outer surface of the seal attachment portion220D has a satin finish surface. The satin finish surface has a surface roughness Ra of 1 μm to 20 μm, for example.

In the battery according to the fifth embodiment, the outer surface of the seal attachment portion220D has a satin finish surface, and accordingly, the heat-sealable resin easily melts at positions where the resin is in contact with the seal attachment portion220D. Therefore, according to this battery, the seal attachment portion220D of the valve device200D can be more firmly fixed to the housing body100, when compared to the first embodiment (a case where the outer surface of the seal attachment portion220D is smooth).

Note that the valve device200D is an example of the “valve device” in the present invention, and the seal attachment portion220D is an example of the “second portion” in the present invention.

A sixth embodiment differs from the first embodiment described above in the configuration of the valve device. Other configurations are basically the same as those in the first embodiment. Here, differences from the first embodiment will be described.

FIG.18is a plan view of a valve device200E that is mounted in a battery according to the sixth embodiment. As shown inFIG.18, the valve device200E includes a valve function portion210and a seal attachment portion220E. The configuration of the valve function portion210is the same as that in the first embodiment.

At least a portion of the seal attachment portion220E is sandwiched between the packaging materials110and120and is subjected to heat sealing. The outer surface of the seal attachment portion220E differs from that in the first embodiment. Specifically, linear protrusions60that continuously extend over the whole circumference of the seal attachment portion220E are formed on the outer surface. Three linear protrusions60are formed in the direction indicated by the arrows F and B in the seal attachment portion220E. Note that the number of linear protrusions60does not necessarily have to be three, and it is sufficient that at least one linear protrusion is provided.

FIG.19is a cross-sectional view taken along line XIX-XIX inFIG.18. As shown inFIG.19, a cross section of each linear protrusion60has a semicircular shape. R of the semicircular shape is 0.05 mm to 1.0 mm, for example. A diameter L12(the length in the thickness direction of the battery and the length in the width direction of the battery) of a portion of the seal attachment portion220E where the linear protrusion60is formed is larger than a diameter L11of a portion of the seal attachment portion220E where the linear protrusion60is not formed.

The linear protrusions60securely come into contact with the heat-sealable resin layers35during the heat sealing process, and accordingly, are easily fused with the packaging materials110and120. In the battery according to the sixth embodiment, the linear protrusions60continuously extend over the whole circumference of the seal attachment portion220E on its outer surface. Therefore, according to this battery, the heat-sealable resin layers35and the seal attachment portion220E can be fused over the whole circumference of the seal attachment portion220E. Also, in this battery, the area of contact between the outer surface of the seal attachment portion220E and the heat-sealable resin is large, when compared to the first embodiment (a case where the linear protrusions60are not formed in the seal attachment portion220E), and therefore the seal attachment portion220E of the valve device200E can be firmly fixed to the packaging material110.

Note that the valve device200E is an example of the “valve device” in the present invention, and the seal attachment portion220E is an example of the “second portion” in the present invention. The linear protrusions60are each an example of a “linear protrusion” in the present invention. The air passage A3is an example of the “air passage” in the present invention.

Although the linear protrusions60in the sixth embodiment continuously extend over the whole circumference, the linear protrusions60are only required to extend in the circumferential direction, and do not necessarily have to extend over the whole circumference or be continuous. For example, in a case where the wing-shaped extended end parts40and41are provided as in the third embodiment described above, the linear protrusions60need not extend over the whole circumference including the wing-shaped extended end parts40and41, and a configuration is also possible in which the linear protrusions60are not provided in leading end parts of the wing-shaped extended end parts40and41, the linear protrusions60are not provided in the wing-shaped extended end parts40and41, or the linear protrusions60are intermittently formed in the circumferential direction.

A seventh embodiment differs from the first embodiment described above in the configuration of the valve device. Other configurations are basically the same as those in the first embodiment. Here, differences from the first embodiment will be described.

FIG.20is a plan view of a valve device200F that is mounted in a battery according to the seventh embodiment. As shown inFIG.20, the valve device200F includes a valve function portion210F and a seal attachment portion220F. At least a portion of the seal attachment portion220F is sandwiched between the packaging materials110and120and is subjected to heat sealing. The cross-sectional shapes of the valve function portion210F and the seal attachment portion220F differ from those in the first embodiment.

FIG.21is a cross-sectional view taken along line XXI-XXI inFIG.20. As shown inFIG.21, a cross section of the valve function portion210F has a semicircular shape. That is, a surface of the valve function portion210F in the direction of the arrow U is a flat surface. Also, a cross section of the seal attachment portion220F includes wing-shaped extended end parts40F and41F on both end parts in the direction indicated by the arrows L and R. A surface of the seal attachment portion220F in the direction of the arrow U is a flat surface. The surface of the valve function portion210F in the direction of the arrow U and the surface of the seal attachment portion220F in the direction of the arrow U are flush with each other.

Accordingly, if the valve device200F is arranged such that the surface in the direction of the arrow U faces downward, the valve device200F does not roll over. According to the battery of the seventh embodiment, the valve device200F does not roll over when the valve device200F is to be attached to the housing body100, and therefore the valve device200F can be easily positioned.

FIG.22is a diagram showing a state where the valve device200F is to be attached to the housing body100. As shown inFIG.22, the flat surface of the valve device200F is placed on a surface of the innermost layer of the packaging material120when the valve device200F is to be attached to the housing body100. In this state, the valve device200F does not roll over. Therefore, according to the battery of the seventh embodiment, the valve device200F can be easily positioned when the valve device200F is to be attached to the housing body100. Also, in a state where the battery is complete, a bulge of the joined edge portion130that is formed by the valve device200F can be oriented in the direction in which the housing body100bulges, i.e., in the upward direction inFIG.22in which the molded part112protrudes.

Note that the valve device200F is an example of the “valve device” in the present invention, the valve function portion210F is an example of the “first portion” in the present invention, and the seal attachment portion220F is an example of the “second portion” in the present invention. The air passage A4is an example of the “air passage” in the present invention.

Although the first to seventh embodiments have been described, the present invention is not limited to the first to seventh embodiments described above, and various changes can be made without departing from the gist of the present invention. The following describes variations. Note that the following variations can be appropriately combined.

In the first to seventh embodiments described above, the cross-sectional shape of the seal attachment portion (e.g., the seal attachment portion220) is based on a circular shape.

However, the cross-sectional shape of the seal attachment portion is not limited to such a shape. For example, the cross-sectional shape of the seal attachment portion may also be based on a polygonal shape.

FIG.23is a diagram showing a cross section of a valve device200G according to a first variation. As shown inFIG.23, a cross section of a seal attachment portion220G of the valve device200G has a rhombic shape. A length L7of the seal attachment portion220G in the width direction of the battery is longer than a length L8of the seal attachment portion220G in the thickness direction of the battery. In the thickness direction of the battery described above, the difference between a length of a portion of the joined edge portion130where the seal attachment portion220G is sandwiched and a length of a portion of the joined edge portion130where the seal attachment portion220G is not sandwiched is further reduced. Therefore, according to this battery, it is possible to appropriately apply pressure and heat to the heat-sealable resin layers35over the entire periphery of the housing body100and appropriately fuse the mutually facing heat-sealable resin layers35, and accordingly, the seal attachment portion220G of the valve device200G can be firmly fixed to the housing body100.

FIG.24is a diagram showing a cross section of a valve device200H according to a second variation. As shown inFIG.24, a cross section of a seal attachment portion220H of the valve device200H has a rhombic shape of which both end parts in the thickness direction of the battery are chamfered, or a hexagonal shape. A length L9of the seal attachment portion220H in the width direction of the battery is longer than a length L10of the seal attachment portion220H in the thickness direction of the battery. In the thickness direction of the battery described above, the difference between a length of a portion of the joined edge portion130where the seal attachment portion220H is sandwiched and a length of a portion of the joined edge portion130where the seal attachment portion220H is not sandwiched is further reduced. Therefore, according to this battery, it is possible to appropriately apply pressure and heat to the heat-sealable resin layers35over the entire periphery of the housing body100and appropriately fuse the mutually facing heat-sealable resin layers35, and accordingly, the seal attachment portion220H of the valve device200H can be firmly fixed to the housing body100.

FIG.25is a diagram showing a cross section of a valve device200I according to a third variation. As shown inFIG.25, a cross section of a seal attachment portion220I of the valve device200I has a shape that is obtained by providing wing-shaped extended end parts40I and41I on both end parts of a rhombic shape (in the width direction of the battery). In this battery, the length in the thickness direction of the battery smoothly changes from a portion of the joined edge portion130where the seal attachment portion220I is not sandwiched to a portion of the joined edge portion130where the seal attachment portion220I is sandwiched, when compared to the first embodiment (a case where the wing-shaped extended end parts40I and41I are not provided in the seal attachment portion220I), for example. Accordingly, in this battery, an excessive force is not applied to the packaging materials110and120at the boundary between a position where the seal attachment portion220I is sandwiched between the heat-sealable resin layers35and a position where the seal attachment portion220I is not sandwiched between the heat-sealable resin layers35, and therefore the seal attachment portion220I of the valve device200I can be firmly fixed to the housing body100.

FIG.26is a plan view of a valve device200J according to a fourth variation. As shown inFIG.26, the valve device200J includes a valve function portion210J and a seal attachment portion220J. An air passage A5is formed inside the seal attachment portion220J.

FIG.27is a cross-sectional view taken along line XXVII-XXVII inFIG.26. This cross section can also be said as being a surface with respect to which a center line C1of the air passage A5is the normal line. As shown inFIG.27, the cross section of the seal attachment portion220J of the valve device200J has a hexagonal shape (polygonal shape). Rs (e.g., R=0.2 mm to 2.0 mm) are formed at corners of the hexagonal shape. According to this battery, for example, it is possible to reduce the possibility that a portion of the seal attachment portion220J located in the housing body100will damage the battery element400in the housing body100, and reduce the possibility that a portion of the seal attachment portion220J sandwiched between the heat-sealable resin layers35will damage the heat-sealable resin layers35and impair the insulating performance of the heat-sealable resin layers35.

In the first to seventh embodiments described above, the flange portion114of the packaging material110is flat. However, the shape of the flange portion114is not limited to such a shape. For example, a valve device arrangement portion for arranging the seal attachment portion220of the valve device200may also be formed in the flange portion114in advance.

FIG.28is a plan view of a packaging material110K according to a fifth variation. As shown inFIG.28, a valve device arrangement portion116K is formed in the flange portion114K.

FIG.29is a cross-sectional view taken along line XXIX-XXIX inFIG.28. As shown inFIG.29, the valve device arrangement portion116K formed in the flange portion114K has a semicircular shape. The diameter of this semicircle is slightly larger than the diameter of the seal attachment portion220, for example. Heat sealing is performed on the peripheral edge portion of the housing body in a state where the seal attachment portion220is arranged in the valve device arrangement portion116K, for example. As a result, deformation of the packaging material during the heat sealing process is suppressed, and it is possible to reduce the possibility that pinholes will be formed or the packaging material will break in the vicinity of the seal attachment portion220. Note that the valve device arrangement portion116K does not necessarily have to be provided in the packaging material110K, and may also be provided in the packaging material120. In this case as well, it is possible to achieve effects similar to those achieved in the case where the valve device arrangement portion116K is provided in the packaging material110K.

In the first to seventh embodiments described above, only a portion of the seal attachment portion (e.g., the seal attachment portion220) is sandwiched between the heat-sealable resin layers35in the joined edge portion130. However, the attached state of the seal attachment portion is not limited to such a state. For example, the entire seal attachment portion may also be sandwiched between the heat-sealable resin layers35in the joined edge portion130. In this case as well, Rs are formed at corners of the end part of the seal attachment portion (e.g., the seal attachment portion220) on the side opposite to the valve function portion (e.g., the valve function portion210) in a plan view, and therefore the end part is unlikely to damage the heat-sealable resin layers35and impair the insulating performance of the heat-sealable resin layers35.

In the first to seventh embodiments described above, a step is formed at the boundary between the valve function portion (e.g., the valve function portion210) and the seal attachment portion (e.g., the seal attachment portion220) of the valve device (e.g., the valve device200). However, the step does not necessarily have to be formed at the boundary between the valve function portion and the seal attachment portion. For example, a configuration is also possible in which the diameter of the cross section of the valve function portion is the same as the diameter of the cross section of the seal attachment portion, and the valve function portion and the seal attachment portion are continuous with each other forming a flat surface.

In the first to seventh embodiments described above, the cross-sectional shape of the air passage (e.g., the air passage A1) formed in the seal attachment portion (e.g., the seal attachment portion220) is based on a circular shape. However, the cross-sectional shape of the air passage is not limited to such a shape. For example, the cross-sectional shape of the air passage may also be based on a polygonal shape.

In the first to seventh embodiments described above, Rs are formed at corners of the end part of the seal attachment portion (e.g., the seal attachment portion220) on the side opposite to the valve function portion (e.g., the valve function portion210). However, Rs do not necessarily have to be formed at the corners.

In the first to seventh embodiments described above, the valve device (e.g., the valve device200) is a return valve. However, the valve device does not necessarily have to be a return valve. The valve device may also be a breaking valve or a selective permeation valve.

In the first to seventh embodiments described above, the tabs300are provided in both end parts of the housing body100in the direction indicated by the arrows L and R, and the valve device (e.g., the valve device200) is provided in the end part of the housing body100in the direction of the arrow F (seeFIG.1again). However, the positional relationship between the valve device200and the tabs300is not limited to such a relationship. For example, a configuration is also possible in which both of the tabs300are arranged on the same side of the peripheral edge portion of the housing body100and the valve device is arranged between the two tabs300, or both of the tabs300are arranged on the same side of the peripheral edge portion of the housing body100and the valve device is arranged on any of three sides other than the side on which the tabs300are arranged.

In the first to seventh embodiments described above, the housing body100includes the packaging material110that is formed through embossing or the like and the packaging material120that is separate from the packaging material110. However, the housing body100does not necessarily have to have such a configuration.

For example, the packaging material110and the packaging material120may also be formed as a single piece (i.e., connected) in advance so as to share a side. In this case, a configuration is also possible in which the packaging material110and the packaging material120are formed as a single piece (i.e., connected) in an end part of the flange portion114of the packaging material110, and the battery element400is sealed in the housing body100by sealing four sides in a state where the packaging materials110and120are overlaid on each other. Alternatively, a configuration is also possible in which the flange portion114is omitted along the side at which the packaging materials110and120are connected, and the battery element400is sealed in the housing body100by sealing three sides in a state where the packaging materials110and120are overlaid on each other.

Also, the packaging material120may also be formed so as to have a shape similar to that of the packaging material110, for example. The housing body100may also be a pouch-type housing body, for example. The pouch-type housing body may be any of a three-side sealing type, a four-side sealing type, a pillow type, a gusset type, and the like.

In the first to seventh embodiments described above, the housing of the valve function portion (e.g., the valve function portion210) and the housing of the seal attachment portion (e.g., the seal attachment portion220) are made of the same material (resin). However, the housing of the valve function portion and the housing of the seal attachment portion do not necessarily have to be made of the same material. For example, a configuration is also possible in which the housing of the valve function portion and the housing of the seal attachment portion are made of different materials, and the material of the valve function portion has a higher melting point than the material of the seal attachment portion. For example, the seal attachment portion may be made of polypropylene (PP) and the valve function portion may be made of a resin that has a higher melting point than PP (e.g., a fluorine-based resin, a polyester-based resin, a polyimide-based resin, a polycarbonate-based resin, or an acrylic resin) or metal. Fluorocarbon resins that have a good barrier property are preferably used for the seal attachment portion.

In this battery, the material of the valve function portion has a higher melting point than the material of the seal attachment portion, and therefore the valve function portion is unlikely to deform due to heat even if pressure and heat are applied to the seal attachment portion when the mutually facing heat-sealable resin layers35are fused. Therefore, according to this battery, the valve mechanism in the valve function portion can be kept from breaking when the mutually facing heat-sealable resin layers35are fused.

In the first to seventh embodiments described above, the housing of the valve device200is made of resin and the seal attachment portion220is directly sandwiched between the heat-sealable resin layers35. However, the housing of the valve device200does not necessarily have to be made of resin, and may also be made of metal (e.g., aluminum or stainless steel). In this case, an adhesive protective film may also be arranged between the seal attachment portion220and the heat-sealable resin layers35. The adhesive protective film is configured such that one surface adheres at least to resin and the other surface adheres at least to metal. Various known adhesive protective films can be employed as the adhesive protective film, and an adhesive protective film that is the same as the tab films310can be used, for example.

In the first to seventh embodiments described above, Rs are formed on the outer peripheral side of the seal attachment portion (e.g., the seal attachment portion220, i.e., at corners of the end part of the seal attachment portion on the side opposite to the valve function portion (e.g., the valve function portion210)), but Rs are not formed on the inner peripheral side of the seal attachment portion (i.e., in an end part of the air passage (e.g., the air passage A1)). However, Rs may also be formed on the inner peripheral side of the seal attachment portion. If Rs are formed on the inner peripheral side of the seal attachment portion, it is possible to reduce the possibility that corners on the inner peripheral side of the seal attachment portion will be chipped and chips (e.g., pieces of resin, metal, etc.) will fall into the housing body100.

In the seventh embodiment described above, flat surfaces are formed in outer surfaces of both the valve function portion210F and the seal attachment portion220F (seeFIG.21again). However, it is not always necessary to form flat surfaces in the outer surfaces of both the valve function portion210F and the seal attachment portion220F. It is sufficient to form a flat surface in the outer surface of at least one of the valve function portion210F and the seal attachment portion220F.

The battery10according to the first to seventh embodiments described above is a secondary battery, but is defined as being what outputs electricity, and accordingly encompasses power storage devices such as capacitors, electric double layer capacitors (EDLCs), and lithium ion capacitors. Also, the type of secondary battery is not specifically limited, and examples of the secondary battery include lithium ion batteries, lithium ion polymer batteries, lead storage batteries, nickel-hydrogen storage batteries, nickel-cadmium storage batteries, nickel-iron storage batteries, nickel-zinc storage batteries, silver oxide-zinc storage batteries, metal-air batteries, multivalent cation batteries, and solid-state batteries.

In the first to seventh embodiments described above, an adhesive film that is configured to adhere to both the seal attachment portion (e.g., the seal attachment portion220) and the packaging materials110and120may also be arranged between the seal attachment portions220and220A to220J and the packaging materials110and120. Such an example will be described below in detail.

FIG.30is a plan view of a valve device200K.FIG.31is a cross-sectional view taken along line XXXI-XXXI inFIG.30. As shown inFIGS.30and31, the valve device200K includes a valve function portion210K, a seal attachment portion220K, and an adhesive film600. That is, the adhesive film600that corresponds to an adhesive member is attached to the seal attachment portion220K of the valve device200K in advance.

The valve function portion210K and the seal attachment portion220K are made of metal. The valve function portion210K and the seal attachment portion220K are made of aluminum, brass, stainless steel, or the like. Note that the valve function portion210K and the seal attachment portion220K do not necessarily have to be made of metal, and may also be made of resin, for example.

The adhesive film600is configured to adhere to both the seal attachment portion220K and the heat-sealable resin layers35(FIG.4) of the packaging materials110and120through heat sealing. Various known adhesive films can be employed as the adhesive film600. For example, the adhesive film600may be a single-layer film of maleic anhydride-modified polypropylene (PPa) or a laminate film of PPa, polyethylene naphthalate (PEN), and PPa. Also, resins that can adhere to metal, such as an ionomer resin, modified polyethylene, and EVA, can also be employed instead of the PPa resin described above.

In the present embodiment, a laminate film that has a three-layer structure including a core material and is constituted by PPa/PEN (core material)/PPa is employed as the adhesive film600. Other than PEN, various known materials can also be employed as the core material. For example, the core material may also be polyester fibers, polyamide fibers, or carbon fibers.

The adhesive film600adheres to the seal attachment portion220K in a state of covering the outer peripheral surface of the seal attachment portion220K. As described above, the adhesive film600also adheres to the heat-sealable resin layers35of the packaging materials110and120, and accordingly, even if the seal attachment portion220K is made of metal, the valve device200K and the packaging materials110and120can be easily bonded through heat sealing. Also, even if the seal attachment portion220K is made of resin, the adhesive film600securely adheres to the heat-sealable resin layers35of the packaging materials110and120, and accordingly, the valve device200K and the packaging materials110and120can be securely bonded through heat sealing. The adhesive film600more effectively functions particularly in a case where the seal attachment portion220K is made of Teflon (registered trademark) among resins. Note that a cross section taken along line XXXI-XXXI inFIG.30has a teary eye shape (a shape that includes a circular portion613and wing-shaped extended end parts614and615). That is, the entire periphery of the shape of the cross section taken along line XXXI-XXXI inFIG.30is curved. More specifically, the outer periphery of the circular portion613is outwardly curved in the cross section, and both end sides of the circular portion613are smoothly connected to base end sides of the wing-shaped extended end parts614and615with the outer periphery inwardly curved in the cross section, and therefore the adhesive film600can be bonded to the outer periphery of the seal attachment portion220K with no gap formed therebetween.

Also, a length W1of the adhesive film600in the width direction is longer than a length W2of the seal attachment portion220K in the width direction. That is, in the valve device200K, the adhesive film600extends past the outer periphery of the seal attachment portion220K (FIG.31). Therefore, according to the valve device200K, the valve device200K and the packaging materials110and120can be more securely bonded since the adhesive film600is arranged over a wide range.

Also, the arrangement range of the adhesive film600reaches the lower end of the seal attachment portion220K. The reason for this will be described. As described above, a secondary battery is housed in the housing body100to which the valve device200K is attached. In this case, if the seal attachment portion220K (metal) is exposed in a wide range, an electrode of the secondary battery and the seal attachment portion220K are likely to come into contact with each other, and a short circuit is likely to occur. In the valve device200K, the arrangement range of the adhesive film600reaches the lower end of the seal attachment portion220K. Therefore, according to the valve device200K, it is possible to reduce the possibility that the valve device200K will cause a short circuit. Note that the adhesive film600may also be arranged so as to extend downward past the lower end of the seal attachment portion220K.

In the first to seventh embodiments described above, helium leakage amounts of the valve devices (the valve devices200and200A to200J) are not particularly described. The helium leakage amount of each valve device may be as described below, for example. The following describes the helium leakage amount of the valve device200as a representative example of the valve devices. Note that the helium leakage amount of the valve device200can also be applied as helium leakage amounts in the other embodiments (the second to seventh embodiments).

As described above, the valve device200is configured to discharge gas from the inside to the outside of the housing body100if the internal pressure of the housing body100has reached or exceeded a predetermined value due to gas generated in the housing body100. If sealing performance of the valve device200is excessively high, the valve device200may fail to function even if the internal pressure of the housing body100has reached or exceeded the predetermined value. On the other hand, if sealing performance of the valve device200is lower than required, it is highly likely that water vapor (moisture) will enter the housing body100from the external environment during a normal period (when the internal pressure of the housing body100is lower than the predetermined value).

In the valve device200according to the present embodiment, the helium leakage amount of the valve device200is adjusted to simultaneously realize high sealing performance of the valve device200and effective suppression of the intrusion of water vapor into the housing body100.

The inventor(s) of the present invention found that if the helium leakage amount from a secondary side to a primary side of the valve device200measured in an environment at 25° C. in accordance with a method defined in “vacuum spraying method” of JIS Z2331:2006 “Method for helium leak testing” is from 5.0×10−11Pa·m3/sec to 5.0×10−6Pa·m3/sec inclusive, it is possible to simultaneously realize high sealing performance of the valve device200and effective suppression of the intrusion of water vapor into the housing body100. Therefore, the helium leakage amount of the valve device200may be from 5.0×10−11Pa·m3/sec to 5.0×10−6Pa·m3/sec inclusive when measured in an environment at 25° C. using the method defined in the above-described standard. Note that the secondary side of the valve device200refers to the outside of the housing body100when the valve device200is attached to the housing body100. Also, the primary side of the valve device200refers to the inside of the housing body100when the valve device200is attached to the housing body100.

The upper limit of the helium leakage amount of the valve device200is preferably about 4.5×10−6Pa·m3/sec or less, more preferably about 1.0×10−6Pa·m3/sec or less, further preferably about 1.0×10−7Pa·m3/sec or less, and yet more preferably about 1.0×10−8Pa·m3/sec or less, for example, and the lower limit of the helium leakage amount of the valve device200is 5.0×10−11Pa·m3/sec or more. Preferable ranges of the helium leakage amount of the valve device200are from 5.0×10−11Pa·m3/sec to about 4.5×10−6Pa·m3/sec, from 5.0×10−11Pa·m3/sec to about 1.0×10−6Pa·m3/sec, from 5.0×10−11Pa·m3/sec to about 1.0×10−7Pa·m3/sec, and from 5.0×10−11Pa·m3/sec to about 1.0×10−8Pa·m3/sec, for example.

If the helium leakage amount satisfies the upper limit described above, the intrusion of water vapor (moisture) from the external environment into the housing body100can be effectively suppressed. Also, if the helium leakage amount satisfies the lower limit described above, gas generated in the housing body100can be discharged to the outside. Note that if the helium leakage amount is too small, it is difficult to stably discharge gas generated in the housing body100to the outside of the housing body100. Also, if a battery cell is continuously used with such a valve device being not opened for a long period, it is highly likely that the valve device will not appropriately open even if the internal pressure has increased to a design value.

Furthermore, if the helium leakage amount of the valve device200is set to a range from 5.0×10−11Pa·m3/sec to about 2.0×10−10Pa·m3/sec or from 5.0×10−11Pa·m3/sec to about 1.5×10−10Pa·m3/sec, the intrusion of water vapor (moisture) from the external environment into the housing body100can be particularly effectively suppressed. In order to set the helium leakage amount as described above, the shape of a portion in which a valve seat of the valve mechanism and the ball come into contact with each other needs to be designed and processed with very high precision that is not required in conventional check valves, as described later.

Note that the helium leak testing is carried out as follows. That is, in the helium leak testing, the helium leakage amount from the secondary side to the primary side of the valve device200is measured in accordance with the method defined in “vacuum spraying method” of JIS Z2331:2006 “Method for helium leak testing”. Specifically, a helium leak detector is used as a test apparatus. Also, a gas valve (the valve function portion210) of the valve device200is set in a leak test jig (a jig for which it was confirmed that helium does not leak when a dummy valve device including a closed gas valve was set), and the jig is set in the helium leak detector via a test port. It is confirmed that helium does not leak between the jig and the helium leak detector. Thereafter, the valve device200is evacuated to 13 Pa from the primary side, a 99.99% helium gas is sprayed from the secondary side of the valve device200, and measurement is started. Evaluation results are recorded with a spraying period set to 1 to 2 seconds and a waiting period set to 2 to 4 seconds. Note that it is also possible to cover the same valve device200with a hood having a capacity of 50 ml and wait for 20 seconds in accordance with the method defined in “vacuum covering method (vacuum hood method)” of JIS Z2331:2006 “Method for helium leak testing” to make it sure that similar measurement results can be obtained. In any case, measurement is performed in an environment at 25° C.

The lower limit of a pressure difference between the primary side and the secondary side of the valve device200(i.e., an opening pressure of the valve device200) is preferably about 0.05 MPa or more, and more preferably about 0.1 MPa or more, for example. The upper limit of the pressure difference is preferably about 1 MPa or less, and more preferably about 0.3 MPa or less, for example. Preferable ranges of the pressure difference are about 0.05 to 1 MPa, about 0.05 to 0.3 MPa, about 0.1 to 1 MPa, and about 0.1 to 0.3 MPa, for example. If the pressure difference is as described above, gas generated in the housing body100can be appropriately discharged to the outside, and the intrusion of water vapor (moisture) from the external environment can be effectively suppressed.

The internal pressure of the battery10(the housing body100) to which the valve device200has been attached is preferably set to be no higher than a predetermined pressure. Although the setting value of the internal pressure is appropriately determined according to the type of a package including the valve device, the setting value is preferably about 0.1 MPa or less, and more preferably about 1.0×10−2MPa or less. The lower limit of the setting value is about 1.0×10−10MPa or more, for example. Preferable ranges of the internal pressure are about 1.0×10−10to 0.1 MPa and about 1.0×10−10to 1.0×10−2MPa, for example.

The helium leakage amount of the valve device200can be set using a known method. For example, the helium leakage amount can be adjusted by designing materials, shapes, and sizes of members (e.g., the ball214, the o ring212, the spring216, and the exhaust port O1) constituting the valve function portion210of the valve device200and a force with which the ball214is pressed by the spring216.

For example, if an elastic body is used as one of the ball214and the O ring212of the valve mechanism and a member that has a high degree of hardness, such as metal, is used as the other, the helium leakage amount can be easily set to the range from 5.0×10−11Pa·m3/sec to 5.0×10−6Pa·m3/sec inclusive. In order to reduce the helium leakage amount, it is effective to use elastic bodies for both of the ball214and the O ring212of the valve mechanism, but if the helium leakage amount is too small, it is difficult to appropriately discharge gas generated in the housing body100to the outside as described above, and therefore, materials, shapes, sizes, and the like of the members constituting the valve mechanism are appropriately adjusted. For example, if a portion of the O ring212that comes into contact with the ball214in the valve mechanism has a shape that conforms to the shape of the surface of the ball214, the helium leakage amount can be easily designed to fall within the above-described ranges.

That is, in order to set the helium leakage amount of the valve device200to the range from 5.0×10−11Pa·m3/sec to about 2.0×10−1° Pa·m3/sec or from 5.0×10−11Pa·m3/sec to about 1.5×10−10Pa·m3/sec, the shape of the portion in which the O ring212and the ball214of the valve mechanism come into contact with each other needs to be designed and processed with very high precision that is not required in conventional check valves. For example, it is effective to make the ball214and a portion of the O ring212that comes into contact with the ball214have an average surface roughness of 20 μm or less, preferably 5 μm or less, and more preferably 1 μm or less. However, there is a problem in that the valve device200may fail to appropriately operate (the valve function portion210may fail to open) if members that are too precise are brought into contact with each other, and therefore the surface roughness needs to be adjusted such that the helium leakage amount falls within the above-described ranges.

In the first to seventh embodiments described above, a maximum distortion in the thickness direction of the housing body100after gas is discharged from the inside to the outside of the housing body100via the valve device (which hereinafter will also be simply referred to as the “maximum distortion”) is not particularly described. The maximum distortion in the thickness direction of the housing body100may be as described below, for example. The following describes, as a representative example, the maximum distortion of the housing body100in the first embodiment described above. Note that the maximum distortion of the housing body100in the first embodiment can also be applied as the maximum distortion of the housing body100in the other embodiments (the second to seventh embodiments).

The battery10includes the housing body100and the valve device200. The housing body100is constituted by at least one laminate including at least the base material layer, the barrier layer, and the heat-sealable resin layer that are layered in that order. The housing body100houses the battery element400. The valve device200is in communication with the inside of the housing body100. The valve device200is configured to reduce the internal pressure of the housing body100if the internal pressure is increased due to gas generated in the housing body100. The maximum distortion of the thickness of the housing body100(the packaging materials110and120) after gas is discharged from the inside to the outside of the housing body100via the valve device200may be less than 30%. That is, the opening pressure of the valve device200of the battery10may be set such that the maximum distortion of the thickness is less than 30%.

As a result of the battery10having such a feature, gas is discharged via the valve device200at appropriate timings, and therefore it is possible to suppress the occurrence of problems such as the formation of large creases in the housing body100after gas is discharged and large deformation of the housing body100after gas is discharged.

As described above, focusing on the relationship between the maximum distortion of the housing body100and the opening pressure of the valve device200, the maximum distortion of the housing body100of the battery10can be set to be less than 30%. As a result, in the battery10, gas can be discharged via the valve device200to the outside of the housing body100at appropriate timings before problems occur such as the formation of large creases in the housing body100after gas is discharged and large deformation of the housing body100after gas is discharged. That is, when the internal pressure of the housing body100is increased, if a change in the thickness of the housing body100is observed and the opening pressure of the valve device200is set such that the valve device200will open before the thickness is reduced by 30%, it is possible to effectively suppress problems such as the formation of large creases in the housing body100after the valve device200is open and large deformation of the housing body100after the valve device200is open.

The upper limit of the maximum distortion is preferably about 28% or less, and more preferably 27% or less, for example. Also, the lower limit of the maximum distortion is preferably about 2% or more, and more preferably about 4% or more, for example. If the maximum distortion is set as described above, gas can be discharged to the outside of the housing body100at more appropriate timings before problems occur such as the formation of large creases in the housing body100after gas is discharged and large deformation of the housing body100after gas is discharged. Preferable ranges of the maximum distortion are about 2% or more and less than 30%, and from about 4% to about 28%, for example.

The maximum distortion of the housing body100is measured as described below. First, the same two housing bodies100are prepared as targets of measurement of the maximum distortion. Next, lines are drawn in a lattice pattern at intervals of 1 mm on outer surfaces of the housing bodies100. At this time, the lines are drawn at the same positions on the respective outer surfaces of the two housing bodies100. Next, with respect to one of the housing bodies100, the valve device200is sealed and another air passage is provided in the housing body100, or the valve function is removed from the valve device200so that the valve device200functions as the air passage, and air is introduced via the air passage to the inside of the housing body100to increase the internal pressure up to 1 MPa and cause the housing body100to swell. Next, air is removed via the air passage to reduce the internal pressure to normal pressure, the housing body100is cut along a line of the above-described lattice pattern, and the thickness of the cross section is measured. The housing body100into which air has not been introduced is also cut along a line of the above-described lattice pattern, and the thickness of the cross section is measured. Next, a position at which the thickness decreased the most when compared to the thickness at the same position of the housing body100to which air has not been introduced is taken to be a position with the maximum distortion, and the ratio (%) of reduction in the thickness at the position with the maximum distortion is taken to be the maximum distortion (%). For example, if the housing body100of which the internal pressure has not been increased has a thickness of 100 μm at the position with the maximum distortion and the housing body100of which the internal pressure has been increased has a thickness of 70 μm at the same position, the maximum distortion is 30%.

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