JP7482189B2 - Treatment liquid and surface treatment method for valve structure - Google Patents

Description

This disclosure relates to a treatment liquid, a valve structure, a valve structure with a heat-sealable film, an electricity storage device, and a heat-sealable film.

In case some kind of abnormality occurs in the energy storage device and gas is generated inside, causing the internal pressure to rise excessively, there are methods to provide a gas vent valve, weak seal, hole, cut, etc. to release the gas.

For example, Patent Document 1 discloses a lithium secondary battery in which an electrode unit having a positive electrode and a negative electrode and a non-aqueous electrolyte are sealed in a battery container, the battery container having a flat shape with two opposing wide sides, and at least one of the wide sides of the battery container is provided with an internal pressure release mechanism that operates when the internal pressure of the container rises, the internal pressure release mechanism being designed to form a through hole that communicates between the inside and outside of the container with an opening area equivalent to 3% or more of the area of the wide side, and the internal pressure release mechanism is designed so that at least a part of the through hole opens in a position that is offset from the electrode unit in the planar direction when the battery is viewed through the thickness direction of the battery container.

However, when an internal pressure release mechanism is provided in the housing itself that seals the battery element, as in Patent Document 1, there is a concern that the strength of the housing made of a film-like exterior material will decrease, resulting in insufficient sealing. Furthermore, film-like exterior materials are more flexible and more easily deformed than metal cans and the like. For this reason, when an internal pressure release mechanism is provided in the exterior material itself, as in Patent Document 1, the pressure when the internal pressure is released is likely to vary, and there are cases in which the internal pressure release ability is lacking.

As such, in conventional electricity storage devices that have a gas release mechanism in the film-like exterior material itself, it is difficult to maintain a high level of sealing while properly releasing the gas generated inside to the outside.

In addition, for example, medium- and large-sized power storage devices for vehicle-mounted or stationary use have large electrical capacity and heavy battery elements, so they require particularly high sealing properties and appropriate gas release properties.

For example, Patent Document 2 discloses a bag shut-off valve (valve structure). This bag shut-off valve is attached to a sealed bag. Specifically, this bag shut-off valve is attached to the sealed bag by being heat-sealed while being sandwiched between the sealed bags.

Patent No. 4892842 Patent No. 6359731

For example, the bag shut-off valve (valve structure) described in Patent Document 2 is made of synthetic resin. Depending on the combination of the material of the bag shut-off valve and the inner layer material of the bag, and their shapes, it may not be possible to attach the bag shut-off valve to the sealed bag (container) by heat sealing.

In addition, electricity storage devices are used over long periods of time. Furthermore, the valve structure may be subjected to a large external force due to an increase in internal pressure inside the container. For this reason, when attaching the valve structure to the electricity storage device, high adhesion between the container of the electricity storage device and the valve structure is required.

To achieve high adhesion between the container and the valve structure of the electricity storage device, a method of bonding the container and the valve structure via a heat-sealing film is considered. In this case, high adhesion between the heat-sealing film and the valve structure is required.

The valve structure may also be made up of multiple components, and the components may be bonded together with an adhesive. In this case, high adhesion between the components that make up the valve structure and the adhesive is also required.

As such, the surface of the valve structure requires high adhesion to heat-sealable films and adhesives.

In this situation, the main objective of the present disclosure is to provide a treatment liquid for use in the surface treatment of a valve structure attached to a container, which can impart high adhesion to a heat-sealable film, adhesive, etc., to the valve structure. Furthermore, the present disclosure also aims to provide a valve structure, a valve structure with a heat-sealable film, and an electricity storage device that use the heat-sealable film.

The inventors of the present disclosure conducted intensive research to solve the above problems. As a result, they discovered that a treatment liquid for use in surface treatment of a valve structure to be attached to a container, the treatment liquid containing at least one of an acrylic resin and an aminated phenol polymer, chromium nitrate, and phosphoric acid, can impart high adhesiveness to a heat-sealable film, adhesive, etc., to the valve structure. The present disclosure was completed through further research based on this knowledge.

That is, the present disclosure provides the inventions of the following aspects.
A treatment liquid for use in surface treatment of a valve structure to be attached to a container, comprising:
The valve structure includes a casing having a passage formed therein for discharging gas generated inside the container to the outside of the container;
a valve mechanism held by the casing, which allows the gas to pass through the passage to the outside of the container when an internal pressure of the container increases due to the gas generated inside the container;
Equipped with
The treatment liquid is applied to at least a portion of a surface of the casing;
The treatment liquid contains at least one of an acrylic resin and an aminated phenol polymer, chromium nitrate, and phosphoric acid.

According to the present disclosure, it is possible to provide a treatment liquid for use in surface treatment of a valve structure attached to a container, which can impart high adhesion to a heat-sealing film, adhesive, etc. to the valve structure. Furthermore, according to the present disclosure, it is also possible to provide a valve structure surface-treated with the treatment liquid, a valve structure with a heat-sealing film, and an electricity storage device.

1 is a plan view of an electricity storage device including a valve structure for an electricity storage device according to an embodiment of the present disclosure. Cross-sectional view of FIG. FIG. FIG. FIG. VI-VI cross-sectional view of FIG. 4. Cross-sectional view taken along line VII-VII of FIG. 5A to 5C are diagrams illustrating a method for attaching the valve structure to a container. FIG. 11 is another diagram illustrating a method of attaching the valve structure to the container. 13 is yet another diagram illustrating a method of attaching the valve structure to the container. FIG. 13 is a cross-sectional view of a valve structure according to a modified example. FIG. 13 is a diagram showing a breakaway valve included in a valve structure according to a modified example. FIG. 13 is a rear view of a valve structure according to another modified example. FIG. 13 is a plan view of a valve structure according to still another modified example. FIG. 13 is a rear view of a valve structure according to still another modified example. FIG. 13 is a rear view of a valve structure according to still another modified example. FIG. 13 is a rear view of a valve structure according to still another modified example. FIG. 13 is a cross-sectional view of a valve structure according to still another modified example. FIG. 13 is a cross-sectional view of a valve structure according to still another modified example. FIG. 4 is an enlarged plan view of the periphery of a first portion of the valve structure. XV-XV cross-sectional view of Figure 14. FIG. 2 is a diagram showing a schematic diagram of the shape and size of the valve structure used in the examples. FIG. 17 is a view observed from the y1 side of FIG. 16.

The treatment liquid of the present disclosure is a treatment liquid for use in surface treatment of a valve structure attached to a container. The valve structure includes a casing having a passage formed therein for discharging gas generated inside the container to the outside of the container, and a valve mechanism held in the casing for passing gas through the passage to the outside of the container when the internal pressure of the container increases due to gas generated inside the container. The treatment liquid of the present disclosure is used on at least a portion of the surface of the casing of such a valve structure, and is characterized by containing at least one of an acrylic resin and an aminated phenol polymer, chromium nitrate, and phosphoric acid. By having this configuration, the treatment liquid of the present disclosure can impart high adhesiveness to a heat-sealable film, adhesive, etc. to the valve structure.

The treatment liquid, valve structure, valve structure with heat-sealable film, electricity storage device, and heat-sealable film disclosed herein are described in detail below. In this specification, the numerical ranges indicated with "-" mean "greater than or equal to" or "less than or equal to." For example, the expression 2-15 mm means 2 mm or greater and 15 mm or less.

The treatment liquid of the present disclosure is a treatment liquid for use in surface treatment of a casing of a valve structure to be attached to a container. Details of the valve structure to which the treatment liquid of the present disclosure is applied, the container to which the valve structure is attached, and the electricity storage device including the valve structure and the container will be described after the description of the treatment liquid of the present disclosure.

The treatment liquid of the present disclosure contains at least one of an acrylic resin and an aminated phenol polymer, chromium nitrate, and phosphoric acid. As described below, in the treatment liquid of the present disclosure, the phosphoric acid may be contained in the treatment liquid in the form of a salt (i.e., a phosphate) or in the form of polyphosphoric acid (condensed phosphoric acid). In addition, the chromium nitrate may be at least partially ionized (present as chromium ions and nitrate ions).

The acrylic resin is preferably polyacrylic acid, acrylic acid methacrylic acid ester copolymer, acrylic acid maleic acid copolymer, acrylic acid styrene copolymer, or a derivative thereof such as sodium salt, ammonium salt, or amine salt. In particular, a derivative of polyacrylic acid such as an ammonium salt, sodium salt, or amine salt of polyacrylic acid is preferable. In this disclosure, polyacrylic acid means a polymer of acrylic acid. The acrylic resin is also preferably a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic acid anhydride, and is also preferably an ammonium salt, sodium salt, or amine salt of a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic acid anhydride. Only one type of acrylic resin may be used, or two or more types may be mixed and used.

The weight average molecular weight of the acrylic resin is preferably about 1,000 to 1,000,000, more preferably about 3,000 to 800,000, and even more preferably about 10,000 to 800,000. The larger the molecular weight, the higher the durability, but the lower the water solubility of the acrylic resin, making the treatment solution unstable and lacking in manufacturing stability. Conversely, the smaller the molecular weight, the lower the durability. In this disclosure, when the weight average molecular weight of the acrylic resin is 1,000 or more, the durability is high, and when it is 1,000,000 or less, the manufacturing stability is good. In this disclosure, the weight average molecular weight of the acrylic resin is a value measured by gel permeation chromatography (GPC) under conditions using polystyrene as a standard sample.

In addition, the acid value of the acrylic resin is preferably high because it is believed that the more COOH groups there are, the greater the effect of contributing to adhesion.

In the treatment solution of the present disclosure, phosphoric acid may be present in the form of a salt (phosphate). Examples of phosphate include sodium phosphate, potassium phosphate, and ammonium phosphate. In the treatment solution of the present disclosure, phosphoric acid may be present as a polymer such as polyphosphoric acid (condensed phosphoric acid).

Examples of aminated phenol polymers include aminated phenol polymers having repeating units represented by the following general formulas (1) to (4). These aminated phenol polymers are used in chromate treatments and the like. Note that in the aminated phenol polymers, the repeating units represented by the following general formulas (1) to (4) may be contained alone or in any combination of two or more types.

In the general formulae (1) to (4), X represents a hydrogen atom, a hydroxy group, an alkyl group, a hydroxyalkyl group, an allyl group, or a benzyl group. R ¹ and R ² may be the same or different and represent a hydroxy group, an alkyl group, or a hydroxyalkyl group. In the general formulae (1) to (4), examples of the alkyl group represented by X, R ¹ , and R ² include linear or branched alkyl groups having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. Examples of the hydroxyalkyl group represented by X, R ¹ , and R ² include linear or branched alkyl groups having 1 to 4 carbon atoms and substituted with one hydroxy group, such as a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, a 1-hydroxybutyl group, a 2-hydroxybutyl group, a 3-hydroxybutyl group, and a 4-hydroxybutyl group. In the general formulae (1) to (4), the alkyl groups and hydroxyalkyl groups represented by X, R ¹ , and R ² may be the same or different. In the general formulae (1) to (4), X is preferably a hydrogen atom, a hydroxy group, or a hydroxyalkyl group. The number average molecular weight of the aminated phenol polymer having the repeating units represented by the general formulae (1) to (4) is preferably about 500 to 1,000,000, and more preferably about 1,000 to 20,000. The aminated phenol polymer is produced, for example, by polycondensing a phenol compound or a naphthol compound with formaldehyde to produce a polymer consisting of the repeating units represented by the general formula (1) or (3), and then introducing a functional group (-CH ₂ NR ¹ R ² ) into the polymer obtained above using formaldehyde and an amine (R ¹ R ² NH). The aminated phenol polymer may be used alone or in combination of two or more kinds.

Acrylic resins and aminated phenol polymers may be used in combination.

Particularly preferred compositions of the treatment liquid of the present disclosure include a composition containing polyacrylic acid, chromium (III) nitrate, and phosphoric acid, a composition containing an acrylic acid methacrylic acid ester copolymer, chromium (III) nitrate, and phosphoric acid, a composition containing a sodium salt of an acrylic acid maleic acid copolymer, chromium (III) nitrate, and phosphoric acid, a composition containing an acrylic acid styrene copolymer, chromium (III) nitrate, and phosphoric acid, a composition containing various salts of polyacrylic acid (such as sodium salts, ammonium salts, and amine salts), chromium (III) nitrate, and phosphoric acid, and a composition containing an aminated phenol polymer, chromium (III) nitrate, and phosphoric acid.

The ratio of chromium nitrate and phosphoric acid (which may be a salt) in the treatment liquid of the present disclosure is not particularly limited, but the ratio of phosphoric acid to 100 parts by mass of chromium nitrate is preferably about 30 to 120 parts by mass, more preferably about 40 to 110 parts by mass. The ratio of acrylic resin in the treatment liquid of the present disclosure is preferably about 30 to 300 parts by mass, more preferably about 40 to 250 parts by mass, and even more preferably about 50 to 200 parts by mass, to 100 parts by mass of chromium nitrate. The ratio of aminated phenol polymer in the treatment liquid of the present disclosure is preferably about 30 to 300 parts by mass, more preferably about 40 to 250 parts by mass, and even more preferably about 50 to 200 parts by mass, to 100 parts by mass of chromium nitrate. When an acrylic resin and an aminated phenol polymer are used in combination in the treatment liquid of the present disclosure, the total ratio of these is preferably about 30 to 300 parts by mass, more preferably about 40 to 250 parts by mass, and even more preferably about 50 to 200 parts by mass, to 100 parts by mass of chromium nitrate.

The treatment liquid of the present disclosure may contain a solvent for the purpose of improving the coatability of the treatment liquid. The solvent is not particularly limited, and is preferably an alcohol such as ethanol or isopropyl alcohol, so long as it evaporates when the treatment liquid is dried and baked (for example, at 120 to 190°C for 1 to 2 minutes) and does not impair the effects of the present disclosure. The content of the solvent in the treatment liquid may be, for example, about 10 to 50% by mass, more preferably about 10 to 30% by mass.

The solids concentration of the treatment liquid disclosed herein is not particularly limited, as long as a surface coating layer is formed by applying the treatment liquid to the casing and baking (e.g., at 120 to 190°C for 1 to 2 minutes), but may be, for example, about 1 to 10% by mass.

The thickness of the surface coating layer is not particularly limited, but from the viewpoint of optimally achieving the effects of the present disclosure, it is preferably about 1 nm to 10 μm, more preferably about 1 to 100 nm, and even more preferably about 1 to 50 nm. The thickness of the surface treatment layer can be measured by observation with a transmission electron microscope, or a combination of observation with a transmission electron microscope and energy dispersive X-ray spectroscopy or electron energy loss spectroscopy.

From the same viewpoint, the amount of Cr in the surface treatment layer per ^square meter of the casing surface is preferably about 0.5 to 30 mass %, more preferably about 1 to 20 mass %, and even more preferably about 3 to 10 mass %.

The treatment liquid of the present disclosure may contain other components in addition to at least one of an acrylic resin and an aminated phenol polymer, chromium nitrate, and phosphoric acid. Examples of other components include a solvent. As the solvent, various solvents such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents can be used, with water being preferred. Only one type of solvent may be used, or two or more types may be mixed together.

Other components include chromium compounds other than chromium nitrate (e.g., chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromate acetyl acetate, chromium chloride, potassium chromium sulfate, etc.). These other components may be used alone or in combination of two or more.

The method of forming a surface treatment layer using the treatment liquid of the present disclosure can be performed by applying the treatment liquid to at least a portion of the casing surface of the valve structure by a bar coating method, roll coating method, gravure coating method, immersion method, or the like, and then heating (drying) the casing surface to a temperature of about 70 to 200°C.

The treatment liquid is dried after it has been applied to the surface of the casing, without rinsing with water. There are no particular limitations on the drying method, and examples include drying methods using a batch-type drying oven, a continuous hot air circulation type drying oven, a conveyor-type hot air drying oven, and an electromagnetic induction heating oven using an IH heater. The air volume and air speed, etc., set in the drying method can be set as desired.

In addition, before applying the treatment liquid to the surface of the casing, the surface of the casing may be degreased in advance by alkaline immersion, electrolytic cleaning, acid cleaning, electrolytic acid cleaning, or the like. By carrying out the degreasing treatment in this manner, it becomes possible to carry out the chemical conversion treatment of the surface of the casing more efficiently. In addition, by using an acid degreaser in which a fluorine-containing compound is dissolved in an inorganic acid in the degreasing treatment, it is possible to not only degrease the surface of the casing but also form a fluoride of the metal that is in a passive state, and in such a case, only the degreasing treatment may be carried out.

The treatment liquid of the present disclosure may be used on at least a portion of the surface of the casing of the valve structure, and it is preferable to use the treatment liquid of the present disclosure at the position where the heat-sealing film is attached or where the adhesive is applied, for example. Furthermore, since the treatment liquid of the present disclosure can be easily applied to the surface of the casing, it is more preferable to use the treatment liquid of the present disclosure on the entire surface of the casing. When the treatment liquid of the present disclosure is used on the entire surface of the casing, for example, a surface treatment layer can be formed on the entire surface of the casing by immersing the casing in the treatment liquid of the present disclosure and drying it.

2. Valve Structure The valve structure of the present disclosure is a valve structure that is attached to a container. The valve structure of the present disclosure includes a casing having a passage formed therein for discharging gas generated inside the container to the outside of the container, and a valve mechanism that is held by the casing and passes the gas through the passage to the outside of the container when the internal pressure of the container increases due to the gas generated inside the container. Furthermore, the surface of the valve structure of the present disclosure is characterized by having a surface treatment layer formed with the treatment liquid of the present disclosure.

Details of the treatment liquid of the present disclosure used to form the surface treatment layer of the valve structure of the present disclosure are as described above. The valve structure of the present disclosure may have the configuration of a known valve structure, except that it has a surface treatment layer formed with the treatment liquid of the present disclosure. Below, a specific example of the configuration of the valve structure of the present disclosure will be described as one embodiment, but the configuration of the valve structure of the present disclosure is not limited to the configuration of the following embodiment.

3 is a plan view of the valve structure 200. As shown in the figure, the valve structure 200 has a casing 201, which includes a first portion 10, a second portion 20, and a third portion 30. As described above, a surface coating layer formed from the treatment liquid of the present disclosure is formed on at least a portion of the casing. In this embodiment, these portions 10 to 30 are consecutively arranged in the order of the first portion 10, the third portion 30, and the second portion 20 in the direction from the inside to the outside of the container 100 (from the rear side to the front side). FIG. 4 is a view of the valve structure 200 viewed from the first portion 10 side (from the rear side), and FIG. 5 is a view of the valve structure 200 viewed from the second portion 20 side (from the front side).

Figure 6 is a cross-sectional view taken along line VI-VI in Figure 4, and Figure 7 is a cross-sectional view taken along line VII-VII in Figure 3. As shown in Figures 6 and 7, the valve structure 200 of this embodiment is a check valve capable of repeated gas release, and in particular, a ball spring type check valve. The valve structure 200 is a relief valve that switches between an open state and a closed state depending on the pressure in the internal space S1. A passage L1 is formed inside the casing 201. The passage L1 has an inlet O1 facing the internal space S1 of the container 100 and an outlet O2 facing the external space. When the valve structure 200 is in an open state, the passage L1 connects the internal space S1 of the container 100 to the external space, and can discharge gas generated in the internal space S1 to the outside of the container 100. The valve structure 200 is in an open state when the pressure in the internal space S1 increases due to the gas generated in the internal space S1. On the other hand, when in the closed state, the valve structure 200 seals the internal space S1 from the external space.

The first part 10 is a portion for attaching the valve structure 200 to the container 100. The first part 10 is heat-sealed together with the packaging materials 110 and 120 when the container 100 is molded. This heat sealing fuses and bonds the outer peripheral surface of the first part 10 to the packaging materials 110 and 120, and the first part 10 is fixed to the peripheral seal portion 130 in a manner sandwiched between the packaging materials 110 and 120 (see FIG. 2). As described below, the surface of the first part 10 is preferably provided with a surface treatment layer formed with the treatment liquid of the present disclosure.

The third portion 30 is disposed outside the peripheral seal portion 130 and is not sandwiched between the packaging materials 110 and 120 (see Figures 1 and 2). The second portion 20, which is disposed further outboard than the third portion 30, is also disposed outside the peripheral seal portion 130 and is not sandwiched between the packaging materials 110 and 120. As a result, the risk of various components constituting the valve mechanism, which are held by the second portion 20 and will be described later, being deformed or destroyed by the heat generated when the first portion 10 is attached to the container 100 by heat sealing is reduced.

The first part 10, the second part 20, and the third part 30 extend coaxially and parallel to the front-rear direction (including the case where they are approximately parallel. The same applies below). Here, the central axis common to these parts 10 to 30 is represented by reference symbol C1. The first part 10 has a first air passage A1, the second part 20 has a second air passage A2, and the third part 30 has a third air passage A3. These air passages A1 to A3 also extend coaxially and parallel to the front-rear direction with the central axis C1 as the central axis. In this embodiment, the inlet O1 and the outlet O2 are arranged on the end surface in the front-rear direction rather than on the outer peripheral surface of the casing 201, and in particular, the central axis C1 extending linearly in the front-rear direction passes through the centers of the inlet O1 and the outlet O2. Although not limited thereto, the cross section perpendicular to the central axis C1 of the air passages A1 to A3 is circular. The air passages A1 to A3 are connected to each other and together form a passage L1. The third air vent passage A3 is disposed closer to the exterior of the container 100 than the first air vent passage A1, and the second air vent passage A2 is disposed even further outside the container 100 than the third air vent passage A3. In other words, the third air vent passage A3 is disposed closer to the interior of the container 100 than the second air vent passage A2, and the first air vent passage A1 is disposed even further inside the container 100 than the third air vent passage A3.

4 and 5, the outer shape of the second part 20 is generally a cylinder with the central axis C1 as the central axis. On the other hand, as shown in FIG. 4, the outer shape of the third part 30 is generally a shape of a cylinder with the central axis C1 as the central axis, with a part of the cylinder cut out. More specifically, the outer shape of the third part 30 is generally a shape of a cylinder with the central axis C1 as the central axis, with a plane cut out at a certain distance from the central axis C1, and further cut out at a plane symmetrical to the plane with respect to the central axis C1. Thus, the third part 30 has a pair of planes D1 and D2. Hereinafter, the plane indicated by D1 may be referred to as the first plane, and the plane indicated by D2 may be referred to as the second plane. The first plane D1 and the second plane D2 are parallel to each other (including the case where they are approximately parallel. The same applies below). The first plane D1 and the second plane D2 are parallel to the direction in which the central axis C1 extends (including the case where they are approximately parallel. The same applies below). In this embodiment, the first plane D1 and the second plane D2 are parallel (including substantially parallel) to the direction in which the peripheral seal portion 130 extends. The outer peripheral surface of the third portion 30 is composed of the first plane D1 and the second plane D2, and the curved surfaces D3 and D4 that connect these planes D1 and D2. When viewed along the direction in which the central axis C1 extends, the curved surfaces D3 and D4 are each an arc shape centered on the central axis C1, and overlap with the outer shape of the second portion 20. The third portion 30 as described above can be formed by cutting the outer peripheral surface of a cylindrical member so that a pair of planes D1 and D2 are formed.

As shown in FIG. 4, the first portion 10 has a non-circular outer shape when viewed along the direction of the central axis C1. More specifically, when viewed along the direction of the central axis C1, the first portion 10 has a first wing-shaped portion 41 that is thinner from the center in the left-right direction toward the left, and a second wing-shaped portion 42 that is thinner toward the right, when viewed along the direction of the central axis C1. Thus, in this embodiment, the first portion 10 becomes thicker as it approaches the center in the width direction (left-right direction) of the electricity storage device 1, and becomes thinner as it approaches the ends in the width direction (left-right direction) of the electricity storage device 1.

In this embodiment, the wings 41 and 42 allow the outer peripheral surface of the first portion 10 to form a smooth curved surface in both the lower half covered by the packaging material 110 and the upper half covered by the packaging material 120. In addition, the wings 41 and 42 allow the thickness of the power storage device 1 to change smoothly in the vertical direction at the transition from the portion of the peripheral seal portion 130 where the first portion 10 is not sandwiched to the portion of the peripheral seal portion 130 where the first portion 10 is sandwiched, compared to the case where the first portion 10 is formed into a cylindrical shape. As a result, no excessive force is applied to the packaging materials 110 and 120 in the peripheral portion of the peripheral seal portion 130 where the first portion 10 is attached, and the first portion 10 can be firmly fixed to the peripheral seal portion 130.

As described above, in this embodiment, the outer shapes of the first part 10, the second part 20, and the third part 30, when viewed along the direction in which the central axis C1 extends, are all different depending on the role assigned to each part.

The second part 20 holds a valve mechanism. When the pressure in the internal space S1 of the container 100 increases due to gas generated in the internal space S1, the valve mechanism passes the gas that has passed through the first air passage A1 and the third air passage A3 to the outside of the container 100 via the second air passage A2. That is, the second part 20 holds a part having a main structure for performing the function of the valve structure 200 as a gas vent valve. In this embodiment, the spring 212, the ball 213, and the valve seat 214 as the valve mechanism are housed in the second air passage A2 inside the second part 20. The second air passage A2 also houses an insertion part 215 that continues to the third part 30. These parts 212 to 215 are arranged in this order from the outlet O2 to the inlet O1 in the second air passage A2. In this embodiment, the second part 20, the valve seat 214, and the insertion part 215 are configured as separate parts, but at least a part of them may be configured integrally. In addition, in this embodiment, as shown in Figures 6 and 7, the insertion portion 215 is configured integrally with the third portion 30 and the first portion 10, but at least a portion of these may be configured as separate parts.

The valve seat 214 receives the ball 213 as a valve body biased from the outside by the spring 212, and at this time, the valve structure 200 is in a closed state. In the examples of Figs. 6 and 7, the spring 212 is a coil spring, but is not limited to this and can be, for example, a leaf spring. The valve seat 214 is bonded to the casing 201 via an adhesive, and the portion of the casing 201 to which the valve seat 214 is bonded is preferably surface-treated with the treatment liquid of the present disclosure and provided with a surface coating layer. A curing type adhesive is preferably used as the adhesive. Details of the adhesive will be described later.

The first part 10 is fixed to the peripheral seal portion 130 so that the gas generated in the internal space S1 of the container 100 flows into the first ventilation passage A1. That is, the first ventilation passage A1 inside the first part 10 is connected to the internal space S1 of the container 100. Therefore, when the pressure in the internal space S1, that is, the pressure in the first ventilation passage A1 and the third ventilation passage A3 communicating therewith, reaches a predetermined pressure, the gas that flows out of the internal space S1 and passes through the first ventilation passage A1 and the third ventilation passage A3 presses the ball 213 toward the outlet O2. When the ball 213 is pressed and separated from the valve seat 214, the spring 212 deforms, and the ball 213 moves toward the outlet O2, forming an open state of the valve structure 200. In this open state, the gas generated in the internal space S1 flows toward the outlet O2 through a gap formed between the ball 213 and the valve seat 214, and is discharged to the external space through the outlet O2. In this way, when the gas in the internal space S1 is discharged through the passage L1, the force pressing the ball 213 toward the outlet O2 weakens, and the force of the spring 212 urging the ball 213 toward the inlet O1 becomes greater. As a result, the shape of the spring 212 is restored, and the valve structure 200 is again in the closed state.

When the valve structure 200 is in the closed state, it is possible to prevent atmospheric air from entering the internal space S1 of the container 100. On the other hand, even when the container is in the open state, atmospheric air is unlikely to enter the internal space S1. This is because, in the open state, the pressure in the internal space S1 is maintained higher than or equal to the pressure in the external space. Therefore, the valve structure 200 can effectively prevent atmospheric air from entering the container 100, and prevent deterioration of the electricity storage device element 400 due to moisture and other factors contained therein.

The materials constituting each part of the valve structure 200 are not particularly limited. As a preferred example, the ball 213 can be made of fluororesin, and the valve seat 214 can be made of fluororubber. Furthermore, the spring 212 can be made of a metal such as stainless steel, and the first part 10, the second part 20, the third part 30, and the insertion part 215 can be made of a metal such as aluminum alloy, stainless steel, steel plate, or titanium. The first part 10 may also be made of a material that is directly bonded to the innermost layer of the packaging materials 110 and 120. For example, the first part 10 can be made of a material that has the same heat fusion properties as the innermost layer of the packaging materials 110 and 120, such as a resin such as polyolefin. If the first part 10 cannot be made of the above materials due to reasons such as heat resistance, for example, if the first part 10 is made of metal, they can be bonded via a film (heat fusion film) that can be bonded to both the first part 10 and the innermost layer of the packaging materials 110 and 120.

The method of fixing the valve sheet 214 and the casing 201 is not particularly limited, and for example, the rubber valve sheet 214 can be baked onto the casing 201. However, the valve sheet 214 and the insertion part 215 can also be bonded with an adhesive. The material of the adhesive is not particularly limited, but a hardening type adhesive can be preferably used. A preferred example of the valve sheet 214 made of fluororubber and the insertion part 215 made of metal such as aluminum can be made of acid-modified polyolefin and epoxy resin. Such an adhesive is superior in that it can suppress deterioration of adhesive performance due to the electrolyte, compared to, for example, a modified silicone resin adhesive. In addition, from the viewpoint of preventing the opening of the valve structure 200, adhesive can be applied appropriately to various other locations. For example, adhesive can be applied between the rear end face of the second part 20 and the front end face of the third part 30.

More generally, the curing type adhesive referred to here preferably contains a resin containing a polyolefin skeleton such as polyolefin or acid-modified polyolefin, and at least one selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and a compound having an epoxy group, and particularly preferably contains an acid-modified polyolefin and at least one selected from the group consisting of a compound having an isocyanate group and a compound having an epoxy group. The resin constituting the adhesive layer formed by the adhesive can be analyzed for polyolefin skeleton by, for example, infrared spectroscopy, gas chromatography mass spectrometry, etc. In addition, when the resin constituting the adhesive layer is analyzed by infrared spectroscopy, a peak derived from maleic anhydride is preferably detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak derived from maleic anhydride is detected at a wave number of about 1760 cm ^-1 and a wave number of about 1780 cm ^-1 . When the adhesive layer is a layer composed of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride is detected by infrared spectroscopy. However, if the degree of acid modification is low, the peak may be small and not detected. In that case, analysis can be performed by nuclear magnetic resonance spectroscopy.

Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. Among these, polypropylene is preferred. When the polyolefin resin is a copolymer, it may be a block copolymer or a random copolymer. These polyolefin resins may be used alone or in combination of two or more.

The polyolefin may be a cyclic polyolefin. A cyclic polyolefin is a copolymer of an olefin and a cyclic monomer. Examples of the olefin that is a constituent monomer of the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, and isoprene. Examples of the cyclic monomer that is a constituent monomer of the cyclic polyolefin include cyclic alkenes such as norbornene; and cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these, cyclic alkenes are preferred, and norbornene is more preferred.

An acid-modified polyolefin is a polymer modified by block polymerization or graft polymerization of a polyolefin with an acid component. The polyolefin to be acid-modified may be the above-mentioned polyolefin, a copolymer obtained by copolymerizing the above-mentioned polyolefin with a polar molecule such as acrylic acid or methacrylic acid, or a polymer such as a cross-linked polyolefin. In addition, examples of the acid component used for acid modification include carboxylic acids or anhydrides such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

The acid-modified polyolefin may be an acid-modified cyclic polyolefin. An acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin by replacing it with an acid component, or by block polymerizing or graft polymerizing an acid component to the cyclic polyolefin. The cyclic polyolefin to be acid-modified is the same as described above. The acid component used for the acid modification is the same as the acid component used for the modification of the polyolefin described above.

Preferred acid-modified polyolefins include polyolefins modified with carboxylic acids or their anhydrides, polypropylenes modified with carboxylic acids or their anhydrides, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

The compound having an isocyanate group is not particularly limited, but preferably includes a polyfunctional isocyanate compound. The polyfunctional isocyanate compound is not particularly limited as long as it has two or more isocyanate groups. Specific examples of polyfunctional isocyanate-based curing agents include pentane diisocyanate (PDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymerized or nurated versions of these, mixtures of these, and copolymers with other polymers. Other examples include adducts, biurets, and isocyanurates.

The compound having an oxazoline group is not particularly limited as long as it has an oxazoline skeleton. Specific examples of compounds having an oxazoline group include those having a polystyrene main chain and those having an acrylic main chain. In addition, examples of commercially available products include the Epocross series manufactured by Nippon Shokubai Co., Ltd.

An example of a compound having an epoxy group is an epoxy resin. The epoxy resin is not particularly limited as long as it is a resin capable of forming a crosslinked structure by the epoxy group present in the molecule, and any known epoxy resin can be used. The weight average molecular weight of the epoxy resin is preferably about 50 to 2000, more preferably about 100 to 1000, and even more preferably about 200 to 800. In this disclosure, the weight average molecular weight of the epoxy resin is a value measured by gel permeation chromatography (GPC) under conditions using polystyrene as a standard sample.

Specific examples of epoxy resins include glycidyl ether derivatives of trimethylolpropane, bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, bisphenol F glycidyl ether, novolac glycidyl ether, glycerin polyglycidyl ether, polyglycerin polyglycidyl ether, etc. Epoxy resins may be used alone or in combination of two or more types.

As described above, the surface of the first portion 10 is preferably provided with a surface treatment layer formed by the treatment liquid of the present disclosure. The treatment liquid of the present disclosure can be applied, for example, by immersing the first portion 10 in the treatment liquid and then drying, baking, or electrically attaching the treatment liquid attached to the surface of the first portion 10. This allows a surface treatment layer to be formed on the outer surface of the first portion 10 and the inner surface facing the first air passage A1. In addition, particularly from the viewpoint of electrolyte resistance, a similar treatment may be applied to the surfaces of not only the first portion 10 but also the third portion 30, the second portion 20, and the insertion portion 215 to form a surface treatment layer. Details of the treatment liquid of the present disclosure are as described above.

<Method of installing the valve structure>
Next, a method of attaching the valve structure 200 to the container 100 will be described. First, the packaging materials 110 and 120 are fixed in a state in which they face each other by a fixing tool (not shown). The valve structure 200 is gripped by a gripping tool 501 of a jig 500 (see FIG. 8A). At this time, the gripping tool 501 is firmly in contact with the first plane D1 and the second plane D2 of the third portion 30, and the valve structure 200 is gripped in such a manner that the gripping tool 501 firmly sandwiches the third portion 30. Note that in FIG. 8A to FIG. 8C, the molding parts 112 and 122 of the packaging materials 110 and 120 are not particularly shown in order to focus on the description of the attachment of the valve structure 200, but the molding parts 112 and 122 are appropriately formed before, during, or after the attachment of the valve structure 200.

In the above state, the jig 500 is driven, and the valve structure 200 grasped by the grasping tool 501 is moved, and the first portion 10 is inserted into the gap between the packaging materials 110 and 120 that face each other (see FIG. 8B). At this time, the valve structure 200 is moved so that the third portion 30 does not enter the gap. Thus, the first portion 10 is sandwiched between the outer periphery of the packaging materials 110 and 120. Also, at this time, the valve structure 200 is moved so that the portion of the packaging materials 110 and 120 that will become the peripheral seal portion 130 is parallel to the first plane D1 and the second plane D2 of the third portion 30.

In the above state, a pair of heated jigs 500 (seal bars) sandwich the outer peripheral portions of the packaging materials 110 and 120 from the outside (see FIG. 8C). As a result, the outer peripheral portions of the packaging materials 110 and 120 are fused by heat from the jigs 500 (seal bars), and the peripheral seal portion 130 is formed. As a result, only the first portion 10 of the valve structure 200 is sandwiched between the packaging materials 110 and 120, and the valve structure 200 is fixed to the peripheral seal portion 130. At this time, the wing-like portions 41 and 42 included in the first portion 10 are fixed without the line connecting their sharp ends being inclined with respect to the extension direction (left-right direction) of the peripheral seal portion 130. After that, the pair of jigs 500 (seal bars) retreat to a predetermined position, and the gripping tool 501 releases the valve structure 200 and retreats to a predetermined position.

In the above process, the gripping tool 501 can firmly grip the valve structure 200 with a pair of parallel first and second planes D1 and D2. Therefore, the valve structure 200 can be accurately transported to a desired position relative to the packaging materials 110 and 120. In addition, during the heat sealing process, the valve structure 200 can be firmly fixed at a desired position relative to the packaging materials 110 and 120. That is, the valve structure 200 can be accurately aligned with the container 100. Note that the alignment here includes adjusting the phase of the valve structure 200 around the central axis C1. That is, the angle of the first part 10 with respect to the peripheral seal portion 130 of the container 100 around the central axis C1 can be accurately adjusted. With the above configuration, the valve structure 200 can be easily attached to the container 100.

<Modifications of the valve structure>
Although one embodiment of the valve structure of the present disclosure has been described above, the valve structure of the present disclosure is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present disclosure. For example, the following modifications are possible. In addition, the gist of the following modifications can be combined as appropriate.

<Modification 1>
The valve structure 200 in the above embodiment is a ball spring type, but is not limited thereto, and may be, for example, a poppet type, a duckbill type, an umbrella type, a diaphragm type, or the like. The valve structure 200 in the above embodiment is a check valve capable of repeated gas release, but may be a break valve capable of one-time gas release. The valve structure 200 may also include both a check valve and a break valve. The valve body included in the valve structure 200 in the above embodiment is a spherical ball 213, but is not limited to such a shape, and various shapes can be adopted as long as it functions as a valve body. For example, the valve body may be hemispherical, oblong, or oblate. When the valve body is hemispherical, the spherical side may be received by the valve seat 214, and a columnar member may extend from the center of the flat surface opposite the spherical surface to the opposite side to the spherical surface. In this case, by configuring the columnar member to be received inside the spring 212, the position of the valve body in the casing 201 can be stabilized.

The break valve in this modified example can be configured in various ways. For example, as shown in FIG. 9A, the break valve can be configured by a thin plate or film 250 as a valve mechanism held by the casing 201 so as to block the passage L1 in the valve structure 200. This break valve (hereinafter, the break valve is given the reference symbol 250) can be configured, for example, by attaching a laminate film to the casing 201 by heat sealing so as to cover the outlet O2. In this example, when the pressure in the internal space S1 of the container 100 increases, the laminate film, which is the break valve 250, peels off to open the valve. In another example, the break valve 250 may be a thin metal plate such as aluminum, and as shown in FIG. 9B, the thin plate may have a notch 251 extending radially from the center. The notch 251 does not penetrate the break valve 250 in the thickness direction and is formed thinner than other parts. In this case, when the pressure in the internal space S1 of the container 100 increases, the breaker valve 250 can open by breaking the breaker valve 250, rather than by the breaker valve 250 falling off the casing 201.

<Modification 2>
The first plane D1 and the second plane D2 of the third portion 30 do not have to be parallel to the direction in which the peripheral seal portion 130 extends, and can be oriented in various directions. However, from the viewpoint of workability when attaching the valve structure 200 to the container 100, it is preferable that the first plane D1 and the second plane D2 are parallel to the direction in which the peripheral seal portion 130 extends (left-right direction) or perpendicular (including the case where they are approximately perpendicular, the same applies below) as shown in FIG. 10 .

<Modification 3>
In the above embodiment, the third portion 30 is disposed closer to the inside of the container 100 than the second portion 20. However, as shown in FIG. 11, the third portion 30 may be disposed closer to the outside of the container 100 than the second portion 20.

<Modification 4>
The shape of the first part 10 is not limited to the above. For example, the outer shape of the first part 10 may be non-circular as shown in FIG. 12A and FIG. 12B when viewed along the direction in which the first air passage A1 extends. In addition, the outer shape of the first part 10 may be circular as shown in FIG. 12C or elliptical when viewed along the direction in which the first air passage A1 extends. In the case of an elliptical shape, it is preferable that the major axis of the elliptical shape extends parallel (including substantially parallel) to the left-right direction. That is, the first part 10 may be a cylindrical shape or an elliptical cylindrical shape extending along the central axis C1.

<Modification 5>
The shape of the second part 20 is not limited to that described above, and the outer shape of the second part 20 may be non-circular when viewed along the direction in which the central axis C1 extends, for example, it may be elliptical, or it may be a polygon having a triangle, a rectangle, a pentagon or more sides.

<Modification 6>
The shape of the third portion 30 is not limited to the above. For example, as long as the third portion 30 has a pair of parallel planes D1 and D2, the shape of the other portions is not particularly limited. For example, the curved surfaces D3 and D4 may also be planar, and the external shape of the third portion 30 may be a rectangle when viewed along the extension direction of the central axis C1. Alternatively, the external shape of the third portion 30 may be a regular hexagon or a regular octagon when viewed along the extension direction of the central axis C1.

<Modification 7>
In the above embodiment, the first part 10 fixed to the peripheral seal portion 130, the second part 20 holding the valve mechanism, and the third part 30 including the pair of planes D1 and D2 are formed as separate parts independent of each other in the direction in which the passage L1 extends. However, the present invention is not limited to this embodiment, and for example, as shown in Fig. 13A, the second part 20 may be omitted and the valve mechanism may be moved to the first part 10. Alternatively, as shown in Fig. 13B, the pair of planes D1 and D2 may be formed on the outer surface of the second part 20 holding the valve mechanism, and the third part 30 may be omitted.

<Modification 8>
To facilitate and strengthen the fixation of the valve structure 200 to the container 100, an adhesive member may be interposed between the first portion 10 of the valve structure 200 and the peripheral seal portion 130 of the container 100. This aspect was briefly mentioned in the description of the above embodiment, but will be described in more detail below.

The adhesive member is a member that has adhesiveness to both the first part 10 of the valve structure 200 and the packaging materials 110 and 120 that constitute the peripheral seal portion 130, and can be configured as a heat-sealable film 600 as shown in FIG. 14 and FIG. 15. FIG. 14 is an enlarged plan view of the periphery of the first part 10 of the valve structure 200, and FIG. 15 is a cross-sectional view of line XV-XV thereof. The first part 10 is sandwiched between the packaging materials 110 and 120 via the heat-sealable film 600. By using the heat-sealable film 600 in this way, even if the outer surface of the first part 10 and the innermost layer (heat-sealable resin layer) of the packaging materials 110 and 120 are made of different materials, the two can be firmly fixed together. Note that, in FIG. 14, the part of the heat-sealable film 600 sandwiched between the packaging materials 110 and 120 cannot be seen, but the position of the part is shown by dotted lines for reference. In addition, the interior of the internal space S1 is partially shown by dotted lines in the figure.

When the container 100 is molded, the heat-sealable film 600, together with the first portion 10, is sandwiched between the packaging materials 110 and 120 that constitute the peripheral seal portion 130 and is bonded in a manner such as heat sealing. As a result, the outer surface of the first portion 10 and the innermost layer of the heat-sealable film 600 are fused and joined, and the innermost layers of the packaging materials 110 and 120 and the outermost layer of the heat-sealable film 600 are fused and joined.

The innermost layer of the heat-sealing film 600 is preferably made of a material that easily adheres to the first portion 10. Similarly, the outermost layer of the heat-sealing film 600 is preferably made of a material that easily adheres to the innermost layers of the packaging materials 110 and 120. As an example, the heat-sealing film 600 may be a monolayer film of maleic anhydride-modified polypropylene (PPa). However, the heat-sealing film 600 is preferably a laminated film of a three-layer structure or a three-layer or more structure having a core material between the innermost layer and the outermost layer. In this case, the heat-sealing film 600 may be, for example, a laminated film of PPa, polyethylene naphthalate (PEN) as a core material, and PPa, or a laminated film of PPa, polypropylene (PP) as a core material, and PPa. However, particularly preferred core materials include fibers such as polyamide fibers, polyester fibers, and carbon fibers, and among these, polyamide fibers can be preferably used. In this case, the adhesive resin is easily held between the fibers, the heat resistance (heat shrinkage resistance, etc.) of the heat-sealable film itself can be further improved, and deformation of the heat-sealable film in various processes can be effectively prevented. In addition, in the above example, instead of PPa, resins that can adhere to metals, such as ionomer resins, modified polyethylene, and EVA, can also be applied. In addition, from the viewpoint of improving the long-term adhesion between the heat-sealable film 600 and the surface treatment layer formed on the surface of the first part 10 by the treatment liquid of the present disclosure, an adhesive layer may be provided on at least one surface of the heat-sealable film 600. Examples of the resin composition that forms such an adhesive layer include a mixed resin of PPa and a hardener (e.g., an isocyanate compound, an epoxy resin, etc.). In addition, such an adhesive layer can be provided in advance on the surface treatment layer formed on the surface of the first part 10 to improve the long-term adhesion between the heat-sealable film 600 and the surface treatment layer formed on the surface of the first part 10.

A valve structure with a heat-sealable film is obtained by heat-sealing the heat-sealable film to the outer periphery of the valve structure. The outer periphery of the valve structure to which the heat-sealable film is attached is made of, for example, a metal having a surface treatment layer formed by surface treatment with the treatment liquid of the present disclosure.

3. Overall Configuration of the Electricity Storage Device FIG. 1 shows a plan view of an electricity storage device 1 according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. In these figures, for reference, parts that cannot be seen from the outside are partially shown with dotted lines. Hereinafter, for convenience of explanation, unless otherwise specified, the up-down direction in FIG. 1 will be referred to as "front-back", the left-right direction will be referred to as "left-right", and the up-down direction in FIG. 2 will be referred to as "up-down". However, the orientation of the electricity storage device 1 during use is not limited to this.

The energy storage device 1 includes a housing 101 and an energy storage device element 400 housed therein. The housing 101 includes a container 100 and a tab 300 and a tab film 310 attached to the container 100. The energy storage device element 400 is housed in the internal space S1 of the container 100.

The container 100 is composed of packaging materials 110 and 120. In a plan view, the packaging materials 110 and 120 are heat sealed and fused together at the outer periphery of the container 100, forming a peripheral seal portion 130. The peripheral seal portion 130 forms an internal space S1 of the container 100 that is isolated from the outside space. The peripheral seal portion 130 defines the periphery of the internal space S1 of the container 100. Note that the heat seal mode referred to here may be heat welding from a heat source, ultrasonic welding, or the like. In any case, the peripheral seal portion 130 refers to the portion where the packaging materials 110 and 120 are fused together to form a single unit.

The packaging materials 110 and 120 are composed of, for example, a resin molded product or a film. The resin molded product referred to here can be manufactured by a method such as injection molding, compressed air molding, vacuum molding, or blow molding, and in-mold molding may be performed to impart design and functionality. The type of resin may be polyolefin, polyester, nylon, ABS, or the like. The film referred to here is, for example, a plastic film that can be manufactured by a method such as an inflation method or a T-die method, or a film in which such a plastic film is laminated on a metal foil. The film referred to here may or may not be stretched, and may be a single-layer film or a laminated film. The laminated film referred to here may be manufactured by a coating method, may be a film in which multiple films are bonded together with an adhesive, or may be manufactured by a multi-layer extrusion method.

As described above, the packaging materials 110 and 120 can be configured in various ways, but in this embodiment, they are configured from a laminate film. The laminate film can be a laminate in which a base layer, a barrier layer, and a heat-sealable resin layer are laminated. The base layer functions as a base material for the packaging materials 110 and 120, and is typically an insulating resin layer that forms the outer layer side of the container 100. The barrier layer not only improves the strength of the packaging materials 110 and 120, but also has the function of preventing at least moisture and the like from penetrating into the electricity storage device 1, and is typically a metal layer made of an aluminum alloy or the like. The heat-sealable resin layer is typically made of a heat-sealable resin such as polyolefin, and forms the innermost layer of the container 100.

The shape of the container 100 is not particularly limited, and can be, for example, a bag-like (pouch-like) shape. The bag-like shape here can be a three-sided seal type, a four-sided seal type, a pillow type, a gusset type, or the like. However, the container 100 of this embodiment has a shape as shown in FIG. 2, and is manufactured by heat-sealing a packaging material 110 formed into a tray shape and a packaging material 120 similarly formed into a tray shape and superimposed on the packaging material 110 along the outer periphery in a plan view. The packaging material 110 includes a square ring-shaped flange portion 114 that corresponds to the outer periphery in a plan view, and a molded portion 112 that is continuous with the inner edge of the flange portion 114 and bulges downward from there. Similarly, the packaging material 120 includes a square ring-shaped flange portion 124 that corresponds to the outer periphery in a plan view, and a molded portion 122 that is continuous with the inner edge of the flange portion 124 and bulges upward from there. The packaging material 110 and the packaging material 120 are overlapped so that the respective molded portions 112 and 122 bulge in opposite directions. In this state, the flange portion 114 of the packaging material 110 and the flange portion 124 of the packaging material 120 are heat sealed to be integrated, forming the peripheral seal portion 130. The peripheral seal portion 130 extends around the entire outer periphery of the container 100 and is formed in a rectangular ring shape. Note that one of the packaging materials 110 and 120 may be in the form of a sheet.

The power storage device element 400 is, for example, a power storage member such as a lithium ion battery (secondary battery) or a capacitor, and contains an electrolyte. When an abnormality occurs in the power storage device element 400, gas may be generated in the internal space S1 of the container 100. Either a primary battery or a secondary battery may be housed in the container 100, but preferably a secondary battery is housed. The type of secondary battery housed in the container 100 is not particularly limited, and examples thereof include a lithium ion battery, a lithium ion polymer battery, an all-solid-state battery, a lead acid battery, a nickel-hydrogen battery, a nickel-cadmium battery, a nickel-iron battery, a nickel-zinc battery, a silver oxide-zinc battery, a metal-air battery, a polyvalent cation battery, a condenser, a capacitor, and the like. When the power storage device element 400 is a capacitor, gas may be generated in the internal space S1 of the container 100 due to a chemical reaction in the capacitor. When the power storage device 1 is an all-solid-state battery, the power storage device element 400 may contain a solid electrolyte that can generate gas. For example, if the solid electrolyte is a sulfide-based material, hydrogen sulfide gas may be generated.

The tabs 300 are metal terminals used for inputting and outputting power in the electric storage device element 400. The tabs 300 are arranged separately at the left and right ends of the peripheral seal portion 130 of the container 100, one of which constitutes a positive electrode terminal and the other of which constitutes a negative electrode terminal. One left and right end of each tab 300 is electrically connected to an electrode (positive electrode or negative electrode) of the electric storage device element 400 in the internal space S1 of the container 100, and the other end protrudes outward from the peripheral seal portion 130. The above-mentioned form of the electric storage device 1 is particularly preferable for use in electric vehicles such as electric vehicles and hybrid vehicles that use a large number of electric storage devices 1 connected in series at high voltage. The mounting positions of the two tabs 300 that constitute the positive and negative electrode terminals are not particularly limited, and may be arranged on the same side of the peripheral seal portion 130, for example.

The metal material constituting the tab 300 is, for example, aluminum, nickel, copper, etc. When the power storage device element 400 is a lithium ion battery, the tab 300 connected to the positive electrode is typically made of aluminum, etc., and the tab 300 connected to the negative electrode is typically made of copper, nickel, etc.

The left tab 300 is sandwiched between the packaging materials 110 and 120 at the left end of the peripheral seal portion 130 via the tab film 310. The right tab 300 is also sandwiched between the packaging materials 110 and 120 at the right end of the peripheral seal portion 130 via the tab film 310.

The tab film 310 is a so-called adhesive film (thermal adhesive film) and is configured to adhere to both the packaging materials 110 and 120 and the tab 300 (metal). By using the tab film 310, the tab 300 and the innermost layer (thermal adhesive resin layer) of the packaging materials 110 and 120 can be fixed together even if they are made of different materials.

When gas is generated in the internal space S1 of the container 100 as the power storage device 1 operates, the pressure in the internal space S1 gradually increases. If the pressure in the internal space S1 increases excessively, the container 100 may burst and the power storage device 1 may be destroyed. The container 101 is provided with a valve structure 200 as a mechanism for preventing such an event. The valve structure 200 is a gas vent valve for adjusting the pressure in the internal space S1, and is attached to the peripheral seal portion 130 of the container 100. Details of the configuration of the valve structure 200 are as described above.

The present disclosure will be described in detail below with reference to examples and comparative examples. However, the present disclosure is not limited to the examples.

In Examples 1 to 3 and Comparative Example 1, each evaluation was performed as follows. The results are shown in Table 1.

<Initial adhesion strength>
Assuming that the valve structure is made of an aluminum alloy, an aluminum plate (thickness 5 mm, width 6 mm, length 30 mm) was prepared. The surface of the aluminum plate was subjected to chemical conversion treatment using each of the treatment liquids A and B listed in Table 1. The chemical conversion treatment of the aluminum foil was performed by applying the treatment liquid to the aluminum surface so that the amount of chromium applied was 10 mg/m ² (dry mass) and baking at 190° C. for 2 minutes. Next, adhesives A, B, and C listed in Table 1 were bonded to one side of the aluminum plate by a dry lamination method. The compositions of the treatment liquids A and B and the adhesives A, B, and C are as follows. The treatment liquids A and B contain 30% by mass of isopropyl alcohol (IPA) as a solvent.
Treatment liquid A: Treatment liquid containing 2 parts by mass of acrylic resin (polyacrylic acid (molecular weight 10,000, acid value 778)), 2 parts by mass of chromium nitrate, and 2 parts by mass of phosphoric acid per 100 parts by mass of water. Treatment liquid B: Treatment liquid containing 43 parts by mass of aminated phenol polymer, 16 parts by mass of chromium fluoride, and 13 parts by mass of phosphoric acid per 100 parts by mass of water. Adhesive A: Resin composition containing maleic anhydride-modified polypropylene (molecular weight 70,000) and isocyanate-based curing agent (HDI) in a mass ratio of 100:3. Adhesive B: Resin composition containing maleic anhydride-modified polypropylene (molecular weight 110,000) and isocyanate-based curing agent (HDI) in a mass ratio of 100:3. Adhesive C: Resin composition containing 3 parts by mass of isocyanate-based curing agent (HDI) and 3 parts by mass of epoxy-based curing agent per 100 parts by mass of maleic anhydride-modified polypropylene (molecular weight 110,000).

The adhesive was applied to one side of the aluminum plate from the end in the length direction within a range of 20 mm in the length direction so that the thickness after curing was 3.5 μm. Next, the aluminum plate and a heat-sealing film (unstretched polypropylene film, thickness 40 μm, width 6 mm, length 50 mm) were bonded via the adhesive. At this time, the ends (sides where the adhesive was applied) of the aluminum plate and the heat-sealing film were aligned, arranged so that the width direction and length direction were the same, and left at 80 ° C for 40 hours to bond them. Next, two cuts were made in the length direction in the heat-sealing film bonded to the aluminum plate so that the width of the heat-sealing film was 5 mm (to measure the adhesion strength at a width of 5 mm), and this was used as a test sample. The two cuts were located 2.5 mm to the left and right from the center of the aluminum plate.

Next, the ends (non-bonded sides) of the aluminum plate and heat-sealing film of the test sample were each gripped with a chuck jig (at the 5 mm width position of the heat-sealing film), and the aluminum plate and heat-sealing film were peeled off in a 180° direction to measure the peel strength (N/5 mm) over a 5 mm width. The measurement temperature was 25°C. The chuck distance was 30 mm, the peel speed was 50 mm/min, and the average peel strength in the range of 5 mm to 10 mm from the start of peeling was taken as the initial adhesion strength (N/5 mm). The results are shown in Table 1.

<Adhesion strength in an 80°C environment>
A test sample was prepared in the same manner as in the above-mentioned <Initial adhesion strength>. Next, the end (non-bonded side) of the aluminum plate and the heat-sealing film of the test sample were each gripped with a chuck jig (the heat-sealing film was at a 5 mm width position) and placed in an 80°C environment for 5 minutes. Next, in an 80°C environment, the aluminum plate and the heat-sealing film were peeled off in a 180° direction to measure the peel strength (N/5 mm) at a width of 5 mm. The chuck distance was 30 mm, the peel speed was 50 mm/min, and the average value of the peel strength in the range of 5 mm to 10 mm from the start of peeling was taken as the adhesion strength (N/5 mm) in an 80°C environment. The results are shown in Table 1.

<Adhesion strength after immersion in electrolyte for 7 days>
A test sample was prepared in the same manner as in the above-mentioned <Initial adhesion strength>. Next, the test sample was placed in an electrolyte (a solution in which ethylene carbonate: diethyl carbonate: dimethyl carbonate = 1: 1: 1 volume ratio was mixed and lithium hexafluorophosphate (concentration in the solution: 1 x 10 ³ mol/m ³ ) was dissolved) so that the entire test sample was immersed in the electrolyte. In this state, the glass bottle was sealed with a lid and left to stand for 7 days in a 25 ° C. environment. Next, the test sample was taken out of the electrolyte, and the electrolyte was wiped off with a cloth. Next, in the same manner as in the above-mentioned <Initial adhesion strength>, the aluminum plate and the end (non-bonded side) of the heat-sealable film of the test sample were each held with a chuck jig (the heat-sealable film was at a position of 5 mm width), and the aluminum plate and the heat-sealable film were peeled off in a 180 ° direction, and the peel strength at a width of 5 mm was measured to obtain the adhesion strength (N/5 mm). The distance between the chucks was 30 mm, the peeling speed was 50 mm/min, and the average peel strength in the range of 5 mm to 10 mm from the start of peeling was taken as the adhesion strength (N/5 mm) after immersion in the electrolyte for 7 days in an environment of 25° C. The results are shown in Table 1.

<Adhesion strength after immersion in electrolyte for 30 days>
The peel strength was measured in the same manner as in the above <Adhesion strength after 7 days of immersion in electrolyte> except that the immersion time of the test sample in the electrolyte was 30 days, and the adhesion strength after 30 days of immersion in the electrolyte (N/5 mm) was recorded. The measurement environment was 25° C. The results are shown in Table 1.

<Adhesion strength after immersion in aqueous electrolyte for 24 hours>
A test sample was prepared in the same manner as in the above-mentioned <Initial adhesion strength>. Next, the test sample was placed in a glass bottle, and further, an electrolytic solution containing water (a solution of ethylene carbonate: diethyl carbonate: dimethyl carbonate = 1: 1: 1 mixed in a volume ratio, lithium hexafluorophosphate (concentration in the solution 1 x 10 ³ mol / m ³ ), water concentration 1000 ppm) was added so that the entire test sample was immersed in the electrolytic solution. In this state, the glass bottle was covered and sealed. The sealed glass bottle was placed in an oven set at 85 ° C and left to stand for 24 hours. Next, the glass bottle was removed from the oven, and the test sample was removed from the glass bottle and washed with water at 25 ° C., and then the test sample was immersed in a container containing water at 25 ° C.

Next, for the test sample taken out of the water, the aluminum plate and the end (non-bonded side) of the heat-sealing film of the test sample were gripped with a chuck jig (the heat-sealing film was at the 5 mm width position), and the aluminum plate and the heat-sealing film were peeled in a 180° direction, and the peel strength at the 5 mm width was measured and used as the adhesion strength (N/5 mm). The distance between the chucks was 30 mm, the peel speed was 50 mm/min, and the average value of the peel strength in the range of 5 mm to 10 mm from the start of peeling was used as the adhesion strength (N/5 mm) after immersion in the aqueous electrolyte for 24 hours and the electrolyte was thoroughly washed off. The peel strength of the test sample was measured 10 minutes after the test sample was taken out of the aqueous electrolyte, with the surface of the test sample still wet with water (i.e., the test sample was immersed in water for 10 minutes, and the electrolyte in the test piece was not thoroughly washed (removed).). The measurement environment was 25°C. The results are shown in Table 1.

<Adhesion strength after immersion in aqueous electrolyte for 24 hours, further immersion in water for 3 hours, and then thorough washing of electrolyte>
In the above-mentioned measurement method of <Adhesion strength after immersion in aqueous electrolyte for 24 hours and washing the electrolyte>, the test sample taken out of the aqueous electrolyte was washed with water, and then the test sample was further immersed in water at 25 ° C. in a container for 3 hours. The adhesion (referred to as "peel strength after immersion in water for 3 hours") measured after immersion is shown in Table 1. The measurement environment was 25 ° C. Note that, for the adhesion strength after 3 hours of water immersion, in the above-mentioned measurement method of <Adhesion strength after immersion in aqueous electrolyte for 24 hours and washing the electrolyte>, the test sample taken out of the aqueous electrolyte was further immersed in water for 3 hours, and the electrolyte that had permeated the test sample was dissolved in water, and the swelling of the heat-sealable resin layer (caused by the electrolyte permeating) was removed. The adhesion strength was measured in the same manner, and the adhesion was evaluated after the heat-sealable film was immersed in water to thoroughly remove the electrolyte.

The treatment solutions of Examples 1 to 3 contain acrylic resin, chromium nitrate, and phosphoric acid. As shown in Table 1, the treatment solutions of Examples 1 to 3 form a surface treatment layer with excellent resistance to hydrofluoric acid (adhesion strength when immersed in an aqueous electrolyte for 24 hours and then washed away from the electrolyte), and can impart high adhesion to heat-sealing films, adhesives, etc. to the valve structure.

(Surface treatment of valve structure)
In Examples 4 and 5, the treatment liquid A was prepared. In addition, a valve structure having the shape and size shown in Figs. 16 and 17 was prepared. The valve mechanism of the valve structure includes a spring (made of stainless steel), a ball (made of PTFE), and a valve seat (made of fluororubber (FKM)). The valve seat is bonded to the casing via an adhesive (Example 4 uses an adhesive containing acid-modified polypropylene and polyisocyanate, and Example 5 uses an adhesive containing acid-modified polypropylene and epoxy resin). The two casings are bonded to each other via an adhesive (Example 4 uses an adhesive containing acid-modified polypropylene and polyisocyanate, and Example 5 uses an adhesive containing acid-modified polypropylene and epoxy resin). The casing constituting the outer surface of the valve structure is made of aluminum. The casing was immersed in the treatment liquid A before assembling the valve structure to perform a surface treatment. The surface treatment of the casing was performed by applying the treatment liquid so that the amount of chromium applied was 10 mg/ ^m2 (dry mass) and baking at 190°C for 2 minutes.

(Attachment of heat-sealable film to valve structure)
The attachment portion (outer periphery) of the valve structure was sandwiched between two heat-sealing films (length 10 mm, width 15 mm), and in this state, the heat-sealing film was temporarily attached to the attachment portion of the valve structure using a heat seal bar at 190°C, 10 seconds, and 0.1 MPa, and then placed in an oven at 190°C for 2 minutes to perform heat fusion. As the heat-resistant resin film layer of the heat-sealing film, a polyarylate nonwoven fabric (outer thickness 45 μm, basis weight 14 g/ ^m2 , melting peak temperature over 300°C) was prepared. Next, block-based maleic anhydride-modified polypropylene (melting peak temperature 140°C) was laminated on both sides of the polyarylate nonwoven fabric by extrusion lamination to produce a heat-sealing film in which acid-modified polypropylene (42 μm)/polyarylate nonwoven fabric (basis weight 14 g/ ^m2 )/acid-modified polypropylene (42 μm) were laminated in this order.

(Evaluation of Adhesion of the Surface of the Valve Structure)
<Preparation of packaging materials>
A barrier layer made of aluminum foil (JIS H4160:1994 A8021H-O, thickness 40 μm) with acid-resistant coatings formed on both sides was laminated on a polyethylene terephthalate film (25 μm) as a base layer by a dry lamination method. Specifically, a two-liquid curing urethane adhesive (polyol compound and aliphatic isocyanate compound) was applied to one side of an aluminum foil with acid-resistant coatings (a coating formed by chromate treatment, chromium amount 10 mg/m ² ) formed on both sides, and an adhesive layer (thickness 3 μm after curing) was formed on the aluminum foil. Next, the adhesive layer on the aluminum foil and the polyethylene terephthalate film were laminated, and then aging treatment was performed to produce a laminate of a base layer/adhesive layer/barrier layer. Next, maleic anhydride-modified polypropylene (thickness 30 μm) as an adhesive layer and polypropylene (thickness 30 μm) as a heat-sealable resin layer were co-extruded on the barrier layer of the obtained laminate, thereby laminating an adhesive layer/heat-sealable resin layer on the barrier layer. Next, the obtained laminate was cooled once and then subjected to a heat treatment to obtain a packaging material in which a base layer (25 μm)/adhesive layer (3 μm)/barrier layer (30 μm)/adhesive layer (30 μm)/thermal adhesive resin layer (30 μm) were laminated in this order.

<Preparation of test samples>
The obtained packaging material was cut into strips of 130 mm long x 120 mm wide. One strip was cold molded so that the heat-sealing resin layer side was a recess, forming a molded part of 110 mm long x 100 mm wide x 5 mm deep. Next, the heat-sealing resin layer side of another strip was placed on top of the molded part, and the heat-sealing resin layers facing each other at the periphery were heat-sealed to seal the molded part. At this time, a valve structure with a heat-sealing film in which a heat-sealing film was heat-sealed to the valve structure in advance was interposed between the heat-sealing resin layers facing each other at the periphery, and the peripheral joint was formed by heat-sealing. The conditions for heat fusion were a temperature of 190°C, a sealing time of 30 seconds, and a seal width of 7 mm. In addition, 10 ml of electrolyte was injected into the molded part before sealing the packaging material. The electrolyte was a 1×10 ³ mol/m ³ LiPF ₆ solution (ethylene carbonate (EC)/dimethyl carbonate (DMC)/diethyl carbonate (DEC)=1/1/1 volume ratio). Next, the battery was left at 60° C. for 30 days to obtain a test sample.

For each of the obtained test samples, the packaging material and the valve structure were grasped with fingers and pulled apart to evaluate the adhesion of the surface of the valve structure. The evaluation criteria are as follows. The results are shown in Table 1.
A: No peeling occurs at the interface between the valve structure and the heat-sealable film.
C: Peeling occurs at the interface between the valve structure and the heat-sealable film.

Furthermore, as the casing material, two pipe-shaped AL5052 pieces with a wall thickness of 0.5 mm, a diameter of 6 mm, and a length of 30 mm were cut and immersed in the treatment liquid A to perform surface treatment. The surface treatment of the casing was performed by applying the treatment liquid so that the amount of chromium applied was 10 mg/m ² (dry mass) and baking at 190° C. for 2 minutes. Then, an adhesive was applied to the cross-section of one casing material so that the thickness after drying was about 3.5 μm, and the other casing was installed so that the cross-sections of the casings were in contact with each other. Then, each pipe was dropped five times from a height of 2 m onto a SUS plate to check whether peeling occurred due to impact. As a result, peeling did not occur even when the adhesives of Examples 4 and 5 were used. It is desirable to bond the casing in order to fix the valve mechanism by the casing, and if the bonded casing peels off due to the drop of the valve structure, the fixation of the valve mechanism may be insufficient.

<Initial adhesion strength 2>
Assuming that the valve structure is made of an aluminum alloy, an aluminum plate (thickness 5 mm, width 6 mm, length 30 mm) was prepared. The surface of the aluminum plate was subjected to chemical conversion treatment using each of the treatment liquids B and C shown in Table 3. The chemical conversion treatment of the aluminum foil was performed by applying the treatment liquid to the aluminum surface so that the amount of chromium applied was 10 mg/ ^m2 (dry mass) and baking at 190°C for 2 minutes. Note that the treatment liquids B and C contain 30 mass% isopropyl alcohol (IPA) as a solvent.
Treatment liquid B: A treatment liquid containing 43 parts by mass of aminated phenol polymer, 16 parts by mass of chromium fluoride, and 13 parts by mass of phosphoric acid per 100 parts by mass of water. Treatment liquid C: A treatment liquid containing 2 parts by mass of aminated phenol polymer, 1 part by mass of chromium nitrate, and 1 part by mass of phosphoric acid per 100 parts by mass of water.

Next, unlike the above-mentioned <Initial adhesion>, an aluminum plate and a heat-sealing film (unstretched polypropylene film, thickness 40 μm, width 6 mm, length 50 mm) were bonded together without the use of adhesive. At this time, the ends of the aluminum plate and the heat-sealing film were aligned and positioned so that their width and length directions matched, and then they were bonded together. Next, two slits were made in the length direction of the heat-sealing film bonded to the aluminum plate, so that the width of the heat-sealing film was 5 mm (to measure the adhesion strength at a width of 5 mm), and this was used as a test sample. The two slits were located 2.5 mm to the left and right of the center of the aluminum plate.

Next, the ends (non-bonded sides) of the aluminum plate and heat-sealing film of the test sample were each gripped with a chuck jig (at the 5 mm width position of the heat-sealing film), and the aluminum plate and heat-sealing film were peeled off in a 180° direction to measure the peel strength (N/5 mm) over a 5 mm width. The measurement temperature was 25°C. The chuck distance was 30 mm, the peel speed was 50 mm/min, and the average peel strength in the range of 5 mm to 10 mm from the start of peeling was taken as the initial adhesion strength (N/5 mm). The results are shown in Table 3.

<Adhesion strength 2 in an 80°C environment>
A test sample was prepared in the same manner as in the above-mentioned <Initial adhesion strength 2>. Next, the end (non-bonded side) of the aluminum plate and the heat-sealing film of the test sample were each gripped with a chuck jig (the heat-sealing film was at a 5 mm width position) and placed in an 80°C environment for 5 minutes. Next, in an 80°C environment, the aluminum plate and the heat-sealing film were peeled off in a 180° direction to measure the peel strength (N/5 mm) at a width of 5 mm. The chuck distance was 30 mm, the peel speed was 50 mm/min, and the average value of the peel strength in the range of 5 mm to 10 mm from the start of peeling was taken as the adhesion strength (N/5 mm) in an 80°C environment. The results are shown in Table 3.

<Adhesion strength 2 after 7 days of electrolyte immersion>
A test sample was prepared in the same manner as in the above-mentioned <Initial adhesion strength 2>. Next, the test sample was placed in an electrolyte (a solution in which ethylene carbonate: diethyl carbonate: dimethyl carbonate = 1: 1: 1 volume ratio was mixed and lithium hexafluorophosphate (concentration in the solution: 1 x 10 ³ mol/m ³ ) was dissolved) so that the entire test sample was immersed in the electrolyte. In this state, the glass bottle was sealed with a lid and left to stand for 7 days in a 25 ° C. environment. Next, the test sample was taken out of the electrolyte, and the electrolyte was wiped off with a cloth. Next, in the same manner as in the above-mentioned <Initial adhesion strength 2>, the aluminum plate and the end (non-bonded side) of the heat-sealable film of the test sample were each held with a chuck jig (the heat-sealable film was at a position of 5 mm width), and the aluminum plate and the heat-sealable film were peeled off in a 180 ° direction, and the peel strength at a width of 5 mm was measured to obtain the adhesion strength (N/5 mm). The distance between the chucks was 30 mm, the peeling speed was 50 mm/min, and the average peel strength in the range of 5 mm to 10 mm from the start of peeling was taken as the adhesion strength (N/5 mm) after immersion in the electrolyte for 7 days in an environment of 25° C. The results are shown in Table 3.

<Adhesion strength 2 after immersion in electrolyte for 30 days>
The peel strength was measured in the same manner as in <Adhesion strength 2 after 7 days of immersion in electrolyte> except that the test sample was immersed in the electrolyte for 30 days, and the adhesion strength after 30 days of immersion in the electrolyte (N/5 mm) was recorded. The measurement environment was 25° C. The results are shown in Table 3.

<Adhesion strength 2 after immersion in aqueous electrolyte for 24 hours>
A test sample was prepared in the same manner as in the above-mentioned <Initial adhesion strength 2>. Next, the test sample was placed in a glass bottle, and an electrolyte solution containing water (a solution of ethylene carbonate: diethyl carbonate: dimethyl carbonate = 1: 1: 1 mixed in a volume ratio, lithium hexafluorophosphate (concentration in solution 1 x 10 ³ mol / m ³ ), water concentration 1000 ppm) was added so that the entire test sample was immersed in the electrolyte solution. In this state, the glass bottle was covered and sealed. The sealed glass bottle was placed in an oven set at 85 ° C and left to stand for 24 hours. Next, the glass bottle was removed from the oven, and the test sample was removed from the glass bottle and washed with water at 25 ° C., and then the test sample was immersed in a container containing water at 25 ° C.

Next, for the test sample taken out of the water, the aluminum plate and the end (non-bonded side) of the heat-sealing film of the test sample were gripped with a chuck jig (the heat-sealing film was at the 5 mm width position), and the aluminum plate and the heat-sealing film were peeled in a 180° direction, and the peel strength at the 5 mm width was measured and used as the adhesion strength (N/5 mm). The distance between the chucks was 30 mm, the peel speed was 50 mm/min, and the average value of the peel strength in the range of 5 mm to 10 mm from the start of peeling was used as the adhesion strength (N/5 mm) after immersion in the aqueous electrolyte for 24 hours and the electrolyte was thoroughly washed off. The peel strength of the test sample was measured 10 minutes after the test sample was taken out of the aqueous electrolyte, with the surface of the test sample still wet with water (i.e., the test sample was immersed in water for 10 minutes, and the electrolyte in the test piece was not thoroughly washed (removed).). The measurement environment was 25°C. The results are shown in Table 3.

<Adhesion strength 2 after immersion in aqueous electrolyte for 24 hours, further immersion in water for 3 hours, and then thorough washing of electrolyte>
In the above-mentioned measurement method of <Adhesion strength after immersion in aqueous electrolyte for 24 hours and washing the electrolyte>, the test sample taken out of the aqueous electrolyte was washed with water, and then the test sample was further immersed in water at 25 ° C. in a container for 3 hours. The adhesion (referred to as "peel strength after 3 hours of water immersion") measured after immersion is shown in Table 3. The measurement environment was 25 ° C. Note that, for the adhesion strength after 3 hours of water immersion, in the above-mentioned measurement method of <Adhesion strength 2 after immersion in aqueous electrolyte for 24 hours and washing the electrolyte>, the test sample taken out of the aqueous electrolyte was further immersed in water for 3 hours, and the electrolyte that had permeated the test sample was dissolved in water, and the swelling of the heat-sealable resin layer (caused by the electrolyte permeating) was removed. The adhesion strength was measured in the same manner, and the adhesion was evaluated after the heat-sealable film was immersed in water to thoroughly remove the electrolyte.

In Example 6 and Comparative Example 2, unlike Examples 1 to 3 and Comparative Example 1, the aluminum plate and the heat-sealable film were directly bonded to each other without the use of an adhesive, and tests were conducted under more severe conditions. However, the adhesion of Example 6 was good.

As described above, the present disclosure provides the following aspects of the invention.
Item 1. A treatment liquid for use in surface treatment of a valve structure to be attached to a container, comprising:
The valve structure includes a casing having a passage formed therein for discharging gas generated inside the container to the outside of the container;
a valve mechanism held by the casing, which allows the gas to pass through the passage to the outside of the container when an internal pressure of the container increases due to the gas generated inside the container;
Equipped with
The treatment liquid is applied to at least a portion of a surface of the casing;
The treatment liquid contains at least one of an acrylic resin and an aminated phenol polymer, chromium nitrate, and phosphoric acid.
Item 2. The treatment liquid according to Item 1, which is applied to the entire surface of the casing.
Item 3. The treatment liquid according to item 1 or 2, wherein the valve structure and the container are attached via a heat-sealable film.
Item 4. The heat-sealable film is a laminated film in which an acid-modified polyolefin layer, a core material, and an acid-modified polyolefin layer are laminated in this order,
Item 4. The treatment liquid according to item 3, wherein the core material is made of polyester fibers.
Item 5. The valve mechanism includes a spring, a ball, and a valve seat,
The valve seat is bonded to the casing via an adhesive,
5. The treatment liquid according to any one of items 1 to 4, wherein a portion of the casing to which the valve seat is bonded is surface-treated with the treatment liquid.
Item 6. The treatment liquid according to item 5, wherein the adhesive contains a resin having a polyolefin skeleton and at least one compound selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and a compound having an epoxy group.
Item 7. A valve structure attached to a container,
The valve structure includes a casing having a passage formed therein for discharging gas generated inside the container to the outside of the container;
a valve mechanism that is held by the casing and that, when an internal pressure of the container increases due to the gas generated inside the container, allows the gas to pass through the passage to an outside of the container,
A valve structure, the surface of which is provided with a surface treatment layer formed from the treatment liquid according to any one of items 1 to 6.
Item 8. A valve structure with a heat-sealable film, comprising the valve structure according to item 7, and a heat-sealable film heat-sealed to the outer periphery of the valve structure.
Item 9. The valve structure with a heat-sealable film according to Item 8, wherein the outer periphery of the valve structure is made of metal.
Item 10. An electricity storage device element,
A container for accommodating the electricity storage device element;
a valve structure attached to the container;
Equipped with
Item 7. An electricity storage device, the surface of the valve structure being treated with the treatment liquid according to any one of items 1 to 6.
Item 11. A heat-sealable film used for heat-sealing to the outer periphery of the valve structure according to item 7.

1 Electricity storage device 100 Container 110 Packaging material 120 Packaging material 130 Peripheral seal portion 101 Container 200 Valve structure 201 Casing 10 First portion 20 Second portion 30 Third portion 400 Electricity storage device element 41 First wing portion 42 Second wing portion 600 Heat-sealable film L1 Passage A1 First ventilation passage A2 Second ventilation passage A3 Third ventilation passage D1 First plane D2 Second plane O1 Inlet O2 Outlet S1 Internal space

Claims (6)

A treatment liquid for use in surface treatment of a valve structure to be attached to a container, comprising:
the valve structure is made of an aluminum alloy;
The valve structure includes a casing having a passage formed therein for discharging gas generated inside the container to the outside of the container;
a valve mechanism held by the casing, which allows the gas to pass through the passage to the outside of the container when an internal pressure of the container increases due to the gas generated inside the container;
Equipped with
The treatment liquid is applied to at least a portion of a surface of the casing;
The treatment solution contains an aminated phenol polymer, chromium nitrate, and phosphoric acid,
The ratio of the phosphoric acid to 100 parts by mass of the chromium nitrate is 30 parts by mass or more and 120 parts by mass or less,
the valve structure and the container are attached via a heat-sealable film,
A processing solution in which the casing and the heat-sealable film are directly bonded to each other. The treatment liquid according to claim 1, wherein the treatment liquid is applied to the entire surface of the casing. The heat-sealable film is a laminated film in which an acid-modified polyolefin layer, a core material, and an acid-modified polyolefin layer are laminated in this order,
The treatment liquid according to claim 1 or 2, wherein the core material is made of polyester fibers. The valve mechanism includes a spring, a ball, and a valve seat.
The valve seat is bonded to the casing via an adhesive,
The treatment liquid according to any one of claims 1 to 3, wherein a portion of the casing to which the valve seat is bonded is surface-treated with the treatment liquid. The treatment liquid according to claim 4, wherein the adhesive contains a resin having a polyolefin skeleton and at least one compound selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and a compound having an epoxy group. A surface treatment method for a valve structure, comprising using the treatment liquid according to any one of claims 1 to 5 for surface treatment of a valve structure to be attached to a container, the method comprising the steps of:
the valve structure is made of an aluminum alloy;
The valve structure includes a casing having a passage formed therein for discharging gas generated inside the container to the outside of the container;
a valve mechanism held by the casing, which allows the gas to pass through the passage to the outside of the container when an internal pressure of the container increases due to the gas generated inside the container;
Equipped with
The method for treating a surface of a valve structure, wherein the treatment liquid is applied to at least a portion of the surface of the casing.