Lid member and method for producing same

Abstract

The present invention provides: a lid member of a sealed battery, the lid member having a relatively simple structure with a small number of components and being yet capable of reliably preventing leakage of the electrolyte solution and intrusion of moisture or the like from the outside; and a method for producing the same.　Provided is a lid member for closing a battery container that has an opening, the lid member comprising: a terminal member; a sealing plate that has an attachment hole to which the terminal member is to be attached; and a resin sealing material for sealing the terminal member by attaching the terminal member to the attachment hole of the sealing plate. With respect to a terminal sealing structure which is obtained by attaching the terminal member to the attachment hole of the sealing plate by the intermediary of the sealing material, a helium leak amount in a helium leak test for evaluating sealability by the sealing material is less than 1.0 × 10- 7 PA∙m3 / sec. Also provided is a method for producing a lid member, wherein when the lid member is obtained by injection molding, a terminal sealing structure is formed by two-stage injection in which a molten resin is injected into the cavity.

Description

Lid and manufacturing method thereof

[0001] The present invention relates to a lid body and a manufacturing method thereof, and more particularly to a lid body and a manufacturing method thereof that can provide a sealed battery having a simple structure and excellent sealing properties.

[0002] Secondary batteries such as lithium-ion batteries, which can be repeatedly charged and discharged, are widely used in a variety of applications, including small mobile devices such as mobile phones and laptops, transportation vehicles such as automobiles, aircraft, and ships, and facility power sources for factories, buildings, schools, hospitals, and other facilities.

[0003] These secondary batteries generally have an electrode assembly with a positive electrode and a negative electrode housed in a battery container with an opening and sealed with a lid. The lid has mounting holes corresponding to the positive electrode and the negative electrode, and terminal members are inserted into these mounting holes to connect to lead wires drawn from the electrode assembly, thereby establishing electrical continuity between the inside and outside of the battery.

[0004] However, since the electrolyte used in secondary batteries is flammable, the battery lid is required to have a lid structure with high sealing properties (airtightness) that can prevent leakage of the electrolyte.

[0005] For example, Patent Document 1 discloses a lid body (top lid assembly) for a sealed battery in which an electrode terminal is placed in an electrode extraction hole in a top lid plate via a sealing ring, and this electrode terminal is covered with a ring-shaped fixing member (metal holder) and welded to the top lid plate.

[0006] Furthermore, Patent Document 2 discloses a lid structure in which a hole is formed in a metal lid, a seal gasket having a cylindrical portion and made of thermoplastic resin is inserted from the back surface of the lid, a metal external terminal is inserted into the cylindrical portion of the seal gasket, the inner surface of the hole (aperture) in the lid and the outer surface of the cylindrical portion of the seal gasket are joined by laser irradiation, and the inner surface of the cylindrical portion of the seal gasket and the outer surface of the external terminal are joined by laser irradiation, thereby providing a tight seal.

[0007] Furthermore, Patent Document 3 discloses a lid for a sealed battery in which a terminal member is attached to a sealing plate having an attachment hole (hole) for attaching the terminal member.

[0008] The lid disclosed in Patent Document 3 uses a sealing material that contains a polyarylene sulfide resin as a thermoplastic resin and further contains an inorganic filler that has a reduced volume expansion coefficient in response to an electrolyte, and the terminal member is inserted into the sealing plate with the sealing material bonded to the peripheral edge of the mounting hole. The contact surface of the terminal member with the sealing material and the contact surface of the sealing plate with the sealing material each have fine irregularities formed by laser processing, sandblasting, or the like, allowing these contact surfaces to bond by an anchor effect. The sealing material is formed by melting a polyarylene sulfide resin and an inorganic filler and injection molding the lid.

[0009] JP 2021-526707 A JP 2012-33339 A JP 2022-103899 A

[0010] As described above, in sealed batteries such as lithium ion secondary batteries, it is necessary to reliably prevent leakage of electrolyte, and various lid structures have been investigated to date.

[0011] However, the lid structures described in Patent Documents 1 and 2 require a large number of parts and a large number of manufacturing steps, which reduces production efficiency.

[0012] On the other hand, although the lid body disclosed in Patent Document 3 has a relatively simple structure without using a gasket such as a sealing ring or a seal gasket, the presence of an inorganic filler contained in the seal material can cause air layers (voids) to form at the contact surface between the terminal member and the seal material or at the contact surface between the sealing plate and the seal material. If moisture (moisture from the air, etc.) exists in such air layers, the moisture can cause the electrolyte (for example, LiPF ６ There is a risk of hydrogen fluoride, a poison, being generated from fluorine-containing compounds such as fluorine-containing compounds.

[0013] Therefore, the inventors conducted extensive research to solve the above problems, and as a result, they discovered that by forming a sealing material by injection molding in which molten resin is injected into a mold, and then using this sealing material to obtain a terminal sealing structure in which a terminal member is attached to an attachment hole in a sealing plate, the terminal sealing structure is formed by a two-stage injection process in which the molten resin is intentionally allowed to flow into an air vent provided in the mold, causing burrs to form, and then molten resin is further injected to form the sealing material, thereby making it possible to obtain a lid for a sealed battery with excellent sealing properties while still having a simpler structure than conventional ones, and thus completed the present invention.

[0014] Therefore, an object of the present invention is to provide a lid for a sealed battery that has a small number of parts and a relatively simple structure, while being able to reliably prevent leakage of electrolyte and intrusion of moisture from the outside, etc. Another object of the present invention is to provide a method for manufacturing the lid.

[0015] That is, the present invention provides a lid for closing a battery container having an opening, the lid comprising: a terminal member; a sealing plate having an attachment hole for attaching the terminal member; and a resin sealant for attaching and sealing the terminal member in the attachment hole of the sealing plate, wherein the terminal member is attached to the attachment hole of the sealing plate via the sealant, and the amount of helium leakage in a helium leak test for evaluating the sealing performance of the sealant is 1.0×10 －７ PA・m ３ The lid body is characterized by a thermal expansion coefficient of less than 1 / sec.

[0016] The present invention also provides a method for manufacturing the above-mentioned lid body for closing a battery container having an opening, comprising: arranging the sealing plate and the terminal member in a mold, providing a gap between the mounting hole in the sealing plate and the terminal member, and injecting molten resin that forms the sealing material to form a terminal sealing structure in which the terminal member is attached to the mounting hole in the sealing plate via the sealing material; the mold having a cavity that forms the sealing material, a gate for injecting molten resin into the cavity, and an air vent for venting air at the leading end of the flow direction of the molten resin that is injected from the gate and flows within the cavity; and the molten resin injected into the cavity is caused to flow into the air vent so that it occupies a portion of the height of the air vent, forming a burr while venting the air to the outside of the mold, and then further injecting molten resin into the cavity to form the sealing material, thereby forming a terminal sealing structure. This is a method for manufacturing a lid body, characterized in that the terminal sealing structure is formed by a two-stage injection.

[0017] The lid body in the present invention includes a terminal member, a sealing plate having an attachment hole for attaching the terminal member, and a resin sealing material for attaching and sealing the terminal member in the attachment hole of the sealing plate. In a terminal sealing structure in which the terminal member is attached to the attachment hole of the sealing plate via the sealing material, as shown in the examples described later, a helium leak test for evaluating the sealing performance of the sealing material shows a helium leak amount of 1.0 x 10 －７ PA・m ３ / sec, preferably less than 1.0 × 10 －８ PA・m ３ / sec or less.

[0018] Although not particularly limited in the present invention, the terminal member can be attached to the mounting hole of the sealing plate via a resin sealing material so that the outer diameter of the terminal member is smaller than the inner diameter of the mounting hole of the sealing plate, thereby forming a terminal sealing structure.

[0019] Preferably, the terminal member has a flange on its outer circumferential surface, and the sealing plate has a flange on the inner wall surface of the mounting hole. Meanwhile, the sealing material has a flange gripping portion that grips the flange of the terminal member and a flange gripping portion that grips the flange of the sealing plate. This allows for a stronger terminal sealing structure.

[0020] The terminal member may also have a hydroxyl-containing coating on its outer peripheral surface. Similarly, the sealing plate may have a hydroxyl-containing coating on the inner wall surface of the mounting hole. Such a hydroxyl-containing coating can be formed, for example, by laser treatment using laser light. The hydroxyl-containing coating formed by laser treatment has a surface irregularity, which is advantageous in terms of exhibiting an anchoring effect for the resin sealing material. In the case of laser treatment, preferably, the resulting hydroxyl-containing coating has oxygen elements localized in the surface layer so that the oxygen content measured by EPMA in the surface layer from the outermost surface to a depth of 3 μm is 0.1 mass% or more and 50 mass% or less.

[0021] In addition to the laser treatment described above, the hydroxyl-containing coating can also be formed using known methods such as hydrated oxide treatment using warm or hot water, zincate treatment, chemical conversion treatment containing an organic compound component having hydroxyl groups, etc. The hydroxyl-containing coating varies depending on the type of metal forming the terminal member or sealing plate, and examples include metal hydroxides (metal hydroxides) such as aluminum hydroxide (Al(OH)), aluminum oxide hydroxide (AlO(OH)), copper hydroxide (Cu(OH)), iron (II) hydroxide (Fe(OH)), iron (III) oxide hydroxide (FeO(OH)), and metal oxide hydroxides (metal hydroxide oxides). Furthermore, depending on the metal forming the terminal member or sealing plate, the hydroxyl group-containing coating may contain a metal oxide (metal oxide) such as aluminum oxide (AlO), copper (I) oxide (CuO), copper (II) oxide (CuO), iron (II) oxide (FeO), iron (II, III) oxide (FeO), iron (III) oxide (FeO), etc.

[0022] The sealing material in the present invention is not particularly limited as long as it is made of resin, but it is preferable to select one that is suitable for forming the sealing material by injection molding as described below. Among these, it is preferable to use a material containing a polyarylene sulfide resin as a thermoplastic resin. Polyarylene sulfide resin is an insulating resin that is resistant to fluorine-containing compounds and hydrogen fluoride contained in the electrolyte in the electrolytic solution, and can be used as a sealing material that has excellent adhesion to metals, chemical resistance, cold and heat resistance, good moldability, etc. The content of polyarylene sulfide resin in the sealing material is preferably 50% by mass or more and 100% by mass or less, and more preferably 70% by mass or more and 99.9% by mass or less.

[0023] The polyarylene sulfide resin has a structure in which, like polyphenylene sulfide, for example, benzene rings (p-phenylene groups) and sulfur atoms (sulfide bonds) are alternately bonded. Specific examples include homopolymers or copolymers composed of p-phenylene sulfide units, m-phenylene sulfide units, o-phenylene sulfide units, phenylene sulfide sulfone units, phenylene sulfide ketone units, phenylene sulfide ether units, and biphenylene sulfide units. More specific examples include poly(p-phenylene sulfide), polyphenylene sulfide sulfone, polyphenylene sulfide ketone, and polyphenylene sulfide ether. Of these, poly(p-phenylene sulfide) is preferred because of its particularly excellent heat resistance and strength properties.

[0024] In the present invention, the sealing material may contain an acrylic ester. In particular, when a hydroxyl-containing coating is provided on the outer peripheral surface of the terminal member or the inner wall surface of the mounting hole in the sealing plate, the carbonyl groups contained in the acrylic ester interact with the hydroxyl groups of the hydroxyl-containing coating to form close contact, thereby suppressing the formation of an air layer at the interface between the sealing material and the hydroxyl-containing coating, resulting in a lid with excellent sealing properties.

[0025] Here, the acrylic acid ester contained in the sealing material is preferably one or more selected from the group consisting of methyl acrylate, ethyl acrylate, butyl acrylate, 2-dimethylaminoethyl acrylate, and 2-hydroxyethyl acrylate, from the viewpoints of facilitating injection molding and obtaining higher adhesion.

[0026] When the sealing material contains an acrylic acid ester to exert the above-mentioned effect, the content of the acrylic acid ester in the sealing material is preferably 0.1% by mass or more and 10% by mass or less. If the content of the acrylic acid ester is too low, the effect is not observed, and conversely, if the content is too high, the effect is saturated and no further effect can be expected. Therefore, it is preferable to keep the content within the above range.

[0027] In the present invention, the sealing material may contain one or more polyolefins selected from the group consisting of polyethylene and polypropylene. When the sealing material contains a polyolefin in addition to a polyarylene sulfide resin, the sealing material can ensure resistance to external impacts (impact resistance) as a lid constituting a sealed battery.

[0028] The polyolefin content in the sealing material is preferably 0.1% by mass or more and 20% by mass or less. If the polyolefin content is too low, the effect may not be sufficient, and if the content is too high, the effect will saturate and no further effect can be expected. If the content is within the above range, a lid with excellent impact resistance can be reliably obtained.

[0029] Furthermore, in the present invention, the encapsulant may contain polydimethylsiloxane (PMDS) as an additive. When the encapsulant is formed by injection molding, the inclusion of polydimethylsiloxane (PMDS) in the encapsulant can improve the fluidity and mold releasability of the resin composition (which may optionally contain a polyolefin and the polydimethylsiloxane) that is injected and contains at least a polyarylene sulfide resin and an acrylic acid ester, thereby improving processability.

[0030] To achieve this effect, the encapsulant preferably contains 0.2% by mass or more and 9.5% by mass or less of polydimethylsiloxane (PMDS). If the content of polydimethylsiloxane (PMDS) is too low, the effect may not be fully achieved, while if the content is too high, the effect will saturate and no further effect can be expected. If the content is within the above range, processability during injection molding can be improved.

[0031] In the present invention, the method for obtaining such a lid is not particularly limited, but the following method can be preferably mentioned.

[0032] That is, in the present invention, a sealing plate and a terminal member are placed in a mold, a gap is provided between the mounting hole in the sealing plate and the terminal member, and molten resin that forms the sealing material is injected to obtain a lid body having a terminal sealing structure in which the terminal member is attached to the mounting hole in the sealing plate via the sealing material.A mold is used that is equipped with a cavity that forms the sealing material, a gate for injecting molten resin into the cavity, and an air vent for exhausting air at the tip of the flow direction of the molten resin that is injected from the gate and flows within the cavity.

[0033] The terminal sealing structure is then formed by a two-stage injection process in which the molten resin injected into the cavity of the mold is allowed to flow into the air vent so that it occupies a portion of the height of the air vent, forming burrs while venting the air to the outside of the mold, and then the molten resin is further injected into the cavity to form a sealing material.

[0034] Generally, molds used for injection molding are formed with air vents (gas vent holes) that connect the cavity to the outside of the injection mold. When molten resin is injected (sometimes simply referred to as "injection") into the cavity, the air originally present in the cavity and the gas generated by the molten resin (collectively referred to as "air") are exhausted to the outside of the mold through the air vents. If the air vents are clogged with molten resin, the molten resin will not flow efficiently through the cavity. Therefore, measures have been taken to prevent the molten resin from entering the air vents, such as reducing the pressure inside the cavity using a pressure reducing device and blocking the air vents with a pin or the like before the molten resin reaches the air vents (see JP 2005-178184 A) or forming a groove between the cavity and the air vents that is wide enough to prevent the molten resin from flowing in (see JP 2014-104660 A).

[0035] In the present invention, in the first stage of the two-stage injection described above, the molten resin injected into the cavity occupies a portion of the height of the air vent, and the molten resin flows into the air vent, forming flash and venting air to the outside of the mold. At this time, the air present in the cavity is pushed out by the molten resin flowing through the cavity, but air that is entrained in the molten resin by fountain flow or the like as the molten resin flows, along with gas contained in the molten resin, is collected at the leading edge of the flow direction (the flow front). In this way, the molten resin at the leading edge of the flow direction (i.e., the molten resin at the flow front), which contains a relatively large amount of air, is intentionally allowed to flow into the air vent.

[0036] Next, in the second injection of the two-stage injection described above, molten resin is further injected into the cavity to form the sealing material. The molten resin fills the area where the skin layer hardened in the first injection, resulting in a so-called sink mark. This increases the density of the molten resin that forms the sealing material in the cavity. By forming the sealing material using this two-stage injection, a terminal sealing structure with excellent sealing properties can be obtained.

[0037] In addition, the two-stage injection of the present invention includes not only the injection of resin in two stages as described above, but also an embodiment in which the injection is divided into a first stage that mainly controls the flow rate of the resin being injected in injection molding, and a second stage that subsequently controls the pressure of the injected resin.

[0038] In the present invention, the molten resin injected into the cavity is allowed to flow into the air vent so that it occupies a portion of the air vent in the height direction, and the portion of the molten resin that flows out forms a flash. If the entire height of the air vent were blocked by the molten resin, air would not be able to be exhausted to the outside of the mold through the air vent. Therefore, the molten resin is allowed to flow out so that it occupies a portion of the air vent in the height direction. The height of the air vent is difficult to specify in general because it varies depending on the type of molten resin. However, for example, when the resin forming the encapsulant contains a polyarylene sulfide resin, the height of the air vent should be greater than 0.06 mm.

[0039] Furthermore, the shape of the burr made of the molten resin that has flowed into the air vent is not particularly limited. For example, it may be an annular burr that extends concentrically from the outer periphery of the sealing material, or a partial burr that extends to a portion of the outer periphery of the sealing material. The burr made of the molten resin that has flowed into the air vent does not perform any particular function after the terminal sealing structure is obtained, so it may be left as is, but it is preferable to cut it off because it is an unnecessary part.

[0040] According to the present invention, the thus obtained lid is used to close the opening of a battery container housing an electrode assembly having a positive electrode and a negative electrode, thereby obtaining a sealed battery with excellent impact resistance that can reliably prevent leakage of the electrolyte and intrusion of moisture from the outside. In particular, according to the present invention, a sealed battery with a small number of parts and a relatively simple structure can be obtained that has excellent sealing properties (airtightness), and is suitable for obtaining sealed batteries such as lithium ion secondary batteries, for example.

[0041] According to the present invention, it is possible to obtain a lid having a small number of parts and a relatively simple structure, while having excellent sealing properties (airtightness) that can reliably prevent leakage of the electrolyte and the intrusion of moisture from the outside. Furthermore, the sealed battery obtained by the present invention has excellent sealing properties and can minimize the formation of an air layer in the sealing material of the lid structure, thereby reliably eliminating the risk of moisture remaining in the air layer infiltrating the battery interior and contaminating the electrolyte.

[0042] FIG. 1 is a schematic plan view illustrating a lid having a sealing material with burrs, where FIG. 1(a) shows the surface of the lid, and FIG. 1(b) shows the back surface of the lid. FIG. 2 is a schematic cross-sectional view showing the II-II cross section of FIG. 1(a). FIG. 3 is a schematic plan view illustrating the surface of the lid having the sealing material after burrs have been removed. FIG. 4 is a schematic cross-sectional view showing the II-II cross section of FIG. 3. FIG. 5 is a schematic view illustrating the manufacturing process of a lid using a mold device (with a sealing plate and terminal member inserted into a movable mold). FIG. 6 is a schematic view illustrating the manufacturing process of a lid using a mold device (with the mold clamped and molten resin injected). FIG. 7 is a schematic view illustrating the manufacturing process of a lid using a mold device (with the mold opened after cooling and the lid removed). FIG. 8 is a partial schematic cross-sectional view illustrating the state of a mold used to form a test sealing body in the examples. FIG. 9 is an explanatory view illustrating the adjustment conditions for the air vents formed in the mold (Vented_Modified 1-2) in the examples. FIG. 10 is an explanatory diagram illustrating the adjustment conditions for air vents formed in a mold in the examples (Vented_Modified 3 to 4). FIG. 11 is a schematic diagram illustrating a test sealed body obtained in the examples (for "Vented_Modified 1" and "Vented_Modified 2"). FIG. 11(a) is a plan view of the test sealed body, and FIG. 11(b) is a cross-sectional view taken along III-III in FIG. 11(a). FIG. 12 is a schematic diagram illustrating a test sealed body obtained in the examples (for "Vented_Modified 3" and "Vented_Modified 4"). FIG. 12(a) is a plan view of the test sealed body, and FIG. 12(b) is a cross-sectional view taken along III-III in FIG. 12(a).

[0043] The present invention will be described in more detail below with reference to the drawings. Fig. 1 shows an example of a lid obtained by the method of the present invention, with Fig. 1(a) being a plan view schematic of the front surface and Fig. 1(b) being a plan view schematic of the back surface. The lid of the present invention includes a terminal member 1 made of an aluminum electrode corresponding to the positive electrode, a terminal member 2 made of a copper electrode corresponding to the negative electrode, a sealing plate 3 made of an aluminum base material and having mounting holes 3b for mounting the terminal members 1 and 2, and a resin sealant 4 that mounts and seals the terminal members 1 and 2 in the mounting holes 3b of the sealing plate 3.

[0044] 1(a) and 2, the resin sealing material 4 has an annular burr 5 formed concentrically extending from its outer periphery. This annular burr 5 was formed when the sealing material 4 was formed by injection molding, which will be described later, and is unnecessary when the sealing material 4 is used as a lid that closes the opening of a battery container, so the annular burr 5 is finally removed. Fig. 3 is a schematic plan view illustrating the state of the lid after the annular burr 5 has been removed.

[0045] 4, the terminal member 1 (terminal member 2) has a flange portion 1a (flange portion 2a) on its outer circumferential surface, and the sealing plate 3 has a flange portion 3a on the inner wall surface of each mounting hole 3b. Note that while Fig. 4 shows the state of the terminal member 1 corresponding to the positive electrode, the same applies to the terminal member 2 corresponding to the negative electrode.

[0046] Furthermore, the outer peripheral surfaces of the terminal members 1 and 2, including the surfaces of the flange portions 1a and 2a, are provided with a hydroxyl-containing coating formed by laser treatment. Similarly, the inner wall surfaces of each mounting hole 3b of the sealing plate 3, including the surfaces of the respective flange portions 3a, are provided with a hydroxyl-containing coating formed by laser treatment.

[0047] On the other hand, the sealing material 4 contains a polyarylene sulfide resin as a thermoplastic resin and also contains an acrylic ester, and has flange gripping portions 4a that grip the flange portions 1a, 2a of the terminal members 1, 2 as described above, and also has a flange gripping portion 4b that grips the flange portion 3a of the sealing plate 3. At this time, the hydroxyl groups of the hydroxyl-containing film on the outer peripheral surfaces of the terminal members 1, 2 interact with the carbonyl groups of the acrylic ester to form a strong bond, and the hydroxyl groups of the hydroxyl-containing film on the inner wall surface of the mounting hole 3b of the sealing plate 3 interact with the carbonyl groups of the acrylic ester to form a strong bond.

[0048] In this way, to obtain a terminal sealing structure in which the terminal members 1 and 2 are attached to the mounting holes 3b of the sealing plate 3 via the sealing material 4, the sealing plate 3 and the terminal members 1 and 2 are placed in a mold, and a gap is provided between the mounting holes 3b of the sealing plate 3 and the terminal members 1 and 2, and then the resin that forms the sealing material 4 is injected.

[0049] Here, the resin forming the sealing material 4 may be a resin composition containing polyolefins such as polyethylene and polypropylene, in addition to polyarylene sulfide resin and acrylic ester, or containing polydimethylsiloxane or the like as an additive.

[0050] When the encapsulating material contains an acrylic acid ester and a polyolefin in addition to a polyarylene sulfide resin, these may form an olefin copolymer, specifically an olefin copolymer in which one or more selected from the group consisting of methyl acrylate, ethyl acrylate, butyl acrylate, 2-dimethylaminoethyl acrylate, and 2-hydroxyethyl acrylate are copolymerized with one or more polyolefins selected from the group consisting of polyethylene and polypropylene, and this copolymer is contained as an elastomer in the polyarylene sulfide resin.

[0051] 5, a mold apparatus equipped with movable molds 6a and 6b and a fixed mold 7 can be used. That is, this mold apparatus is equipped with a cavity 8 formed by arranging (inserting) the sealing plate 3 and terminal members 1 and 2 on the movable mold 6a side, a gate 9 for injecting molten resin into the cavity, and an air vent 10 for exhausting air at the leading end of the flow direction of the molten resin injected from the gate and flowing inside the cavity.

[0052] First, the mold device is heated to about 140 to 160°C, and then the movable molds 6a and 6b and the fixed mold 7 are clamped together as shown in Figure 6. After that, a resin composition containing, for example, a polyarylene sulfide resin and an acrylic ester is melted to 300°C or higher and injected.

[0053] In this case, the molten resin is injected by two-stage injection. In the first stage of injection, the molten resin 11 injected into the cavity 8 occupies a portion of the air vent 10 in the height direction, and the molten resin 11 is allowed to flow into the air vent 10, forming flash 5 while air is exhausted to the outside of the mold apparatus. At this time, as described above, the air present in the cavity 8 is pushed out by the molten resin 11 flowing within the cavity 8. However, since the air entrapped as the molten resin 11 flows, together with the gas contained in the molten resin 11, is collected at the leading edge of the flow direction (i.e., the molten resin at the flow front), which contains a relatively large amount of air, is allowed to flow out to the air vent 11.

[0054] Next, as the second stage of the two-stage injection, molten resin 11 is further injected into cavity 8 to form sealing material 4. This allows molten resin 11 to fill areas where sink marks occurred in the previous first stage of injection, and increases the density of molten resin 11 that forms sealing material 4 in cavity 8.

[0055] In the present invention, in addition to the case where the resin is injected in two stages as described above, it is also possible to divide the injection molding process into a first stage which mainly controls the flow rate of the resin to be injected and a second stage which controls the pressure of the injected resin, thereby causing molten resin 11 to flow into air vent 10, forming flash 5 while venting air to the outside of the mold device, and then further filling with molten resin 11 to increase the density of molten resin 11 that forms sealing material 4 in cavity 8.

[0056] After the mold device is cooled, the mold consisting of the movable molds 6a and 6b and the fixed mold 7 is opened as shown in Figure 7. As a result, a lid body is formed in the movable mold 6a, in which the terminal members 1 and 2 are attached to the respective mounting holes 3b of the sealing plate 3 with the sealing material 4. However, since the sealing material 4 at this time has burrs 5 as shown in Figure 1, these are removed as necessary. By doing this, in a terminal sealing structure in which the terminal members are attached to the mounting holes of the sealing plate via the sealing material, the helium leak amount in a helium leak test to evaluate the sealing performance of the sealing material is 1.0 x 10 －７ PA・m ３ You can get something like less than / sec.

[0057] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0058] (Test Nos. 1 to 11) An aluminum substrate made of A5052 aluminum alloy, measuring 55 mm in outer diameter, 20 mm in inner diameter, and 2 mm in thickness, with an opening in the center, was prepared. This aluminum substrate was irradiated with a laser in a 2 mm wide donut-shaped area on one surface, framing the central opening. The laser treatment conditions are as follows. <Laser Treatment Conditions> - Equipment: Keyence Corporation, 3Axis Fiber Laser Marker (Model: MDF-5200) - Laser light wavelength: 1090 nm - Transmission method: Pulse - Output: 42.5 W - Frequency: 60 kHz - Beam diameter: 60 μm - Irradiation interval: 90 μm - Scanning speed: 340 mm / s - Number of scans (number of irradiations): 1 - Energy density: 1.45 J / mm ２

[0059] A hydroxyl-containing coating was formed by laser treatment under the above conditions. Measurements of the laser-treated area by GD-OES showed that the detected amount of aluminum was 41.8 and the detected amount of hydroxyl groups was 3.6 in the range from the time when the luminescence intensity derived from aluminum and hydroxyl groups was detected until the 3.33 seconds required for 200 nm sputtering had elapsed. The hydroxyl group abundance ratio was calculated to be 7.93.

[0060] Next, as schematically shown in Figure 8, this aluminum substrate 21 was placed in a mold consisting of a first mold 24 and a second mold 25. At this time, the aluminum substrate 21 was set in the second mold 25 so that the laser-treated portion 21a faced the first mold 24. Here, the first mold 24 was provided with a gate 26 for injecting molten resin into a cavity formed when these molds were clamped together, and also with an air vent 27 for venting air at the leading edge of the flow direction of the molten resin injected from the gate 26 and flowing through the cavity. In this test, the width and depth of the grooves provided in the first mold 24 and the second mold 25 were changed to adjust the air vent 27 formed when these molds were clamped together.

[0061] Specifically, as shown in FIG. 9, the air vents formed under the following conditions were adjusted: i) when a groove 5 mm wide x 0.03 mm deep was provided on the outside of the cavity-equivalent portion of the first mold 24 (the air vent formed in this case is referred to as "Vented_Modified 1"); ii) when a groove 5 mm wide x 0.03 mm deep was provided on the cavity-equivalent portion of the second mold 25 ("Vented_Modified 2"); and as shown in FIG. 10, iii) when a groove 0.03 mm deep was provided on the outer circumference of the cavity-equivalent portion of the first mold 24 and a groove 0.03 mm deep was provided along the circumference of the cavity-equivalent portion of the second mold 25 ("Vented_Modified 3"); iv) when a groove 0.06 mm deep was provided on the outer circumference of the cavity-equivalent portion of the first mold 24 ("Vented_Modified 4"); and v) when these grooves were not provided in the first mold 24 or the second mold 25 ("No Vent").

[0062]

[0063] Then, using polyarylene sulfide resin (Z-200-E2 manufactured by DIC Corporation) as the resin to be injection molded, the molten resin was injected by two-stage injection into a mold consisting of a first mold 24 and a second mold 25 as follows. For injection molding, a micro injection molding machine (Moldlock X-801U manufactured by Century Innovation Co., Ltd.) was used, and the molten resin was injected from the gate 26 of the first mold 24. At that time, the mold temperature and resin temperature were as shown in Table 1, and the maximum filling pressure was 6 MPa, and the molten resin was injected under the air vent adjustment conditions described above until air exhaust from the air vent 27 ceased. The injection of the molten resin was terminated when air exhaust from the air vent 27 could no longer be confirmed.

[0064] Next, the test sealed body was either removed after sufficient natural cooling with the mold closed (Test Nos. 2, 5 to 11, 13), or the mold was opened immediately after the completion of injection molding without such natural cooling and the test sealed body was removed (Test Nos. 1, 3, 4, 12).

[0065] The test seals obtained above were formed by sealing an aluminum substrate 21 with a central opening, with the sealant 22 covering the opening. The sealant 22 was disk-shaped with a height H of 0.06 mm and an outer diameter W of 20 mm, and was firmly bonded to the laser-processed portion 21a of the aluminum substrate 21. In particular, the test seals Nos. 2 to 4 obtained in the "Vented_Modified 1" and "Vented_Modified 2" cases had a burr 23 extending from a portion of the outer periphery of the sealant 22, as shown in FIG. 11 . Furthermore, the test seals Nos. 5 to 11 and 13 obtained in the "Vented_Modified 3" and "Vented_Modified 4" cases had a ring-shaped burr 23 extending concentrically from the outer periphery of the sealant 22. The height t of each of these burrs was approximately 0.06 mm, and the length d of each burr was approximately 0.1 to 0.5 mm. Therefore, the length of the burr (the length protruding horizontally from the outer peripheral side surface of the sealing material) d was measured for each test sealing body, and the burr was evaluated on a four-point scale: if d = 0.5 mm or so, sufficient burr was formed (evaluation A), if d = 0.1 to 0.2 mm, somewhat insufficient burr was formed (evaluation B), if d = 0.1 mm or so, insufficient burr was formed (evaluation C), and if d = 0, no burr was formed (evaluation D). The results are shown in Table 2.

[0066] The test sealed body obtained above was subjected to a helium leak test to evaluate the sealing property as follows: All burrs formed on the outer periphery of the sealing material were removed before the test.

[0067] [Helium Leak Test] That is, in order to evaluate the sealing property (airtightness) of the sealing material 22 of the test sealed body, a helium leak test was performed using a helium leak detector (HELIOT 901W1 manufactured by ULVAC, Inc.) The test sealed body was set on a lower jig made of SUS304 attached to the helium leak detector via an O-ring, and the helium leak value was 1×10 －１２ P.A.M. ３A vacuum was drawn using a roughing pump and a turbomolecular pump until the pressure reached the order of 1 / s. Next, an upper jig made of SUS304 stainless steel was set on the test sealed body via an O-ring, helium (He) gas was injected into the upper jig, and a resin lid was placed over the opening of the upper jig. The amount of He gas leaking from the opening of the aluminum substrate 21 sealed with the sealant 22 was detected, and the helium leak amount (helium leak rate) was calculated. Note that when the He gas leak amount was measured multiple times, the average value was used as the He gas leak amount (helium leak amount). The results are shown in Table 2.

[0068]

[0069] (Test Nos. 12 to 13) A copper substrate made of oxygen-free copper C1020, measuring 55 mm in outer diameter, 20 mm in inner diameter, and 2 mm in thickness, with an opening in the center, was prepared. This copper substrate was irradiated with a laser in a 2 mm-wide donut-shaped area on one surface, framing the central opening. The laser treatment conditions are as follows. <Laser Treatment Conditions> - Equipment: Keyence Corporation, 3Axis Fiber Laser Marker (Model: MDF-5200) - Laser light wavelength: 1090 nm - Oscillation method: Pulse - Output: 42.5 W - Frequency: 60 kHz - Beam diameter: 60 μm - Irradiation interval: 90 μm - Scanning speed: 400 mm / s - Number of scans (number of irradiations): 5 - Energy density: 5.9 J / mm ２

[0070] A hydroxyl-containing coating was formed by laser treatment under the above conditions. Measurements of the laser-treated area by GD-OES showed that the detected amount of copper was 38.2 and the detected amount of hydroxyl groups was 2.6 in the range from the time when the emission intensity derived from copper and hydroxyl groups was detected until the time when the 1.25 seconds required for 200 nm sputtering had elapsed. The hydroxyl group abundance ratio was calculated to be 6.37.

[0071] Test seals according to Test Nos. 12 and 13 were obtained in the same manner as in Test Nos. 1 to 11, except that the above copper substrate was used. Furthermore, the obtained test seals were evaluated for the appearance of burrs and the amount of helium leakage was measured in the same manner as in the previous cases. The results are shown in Table 2.

[0072] The results shown in Table 2 show that there is a correlation between the degree of burr formation appearing on the periphery of the sealing material and the amount of He gas leakage (helium leakage amount). That is, the test sealing bodies of Test Nos. 1 and 12, in which no burr formation was confirmed, and the test sealing bodies in which the burr formation was insufficient all had large helium leakage amounts, whereas the test sealing bodies of Test Nos. 9 to 11 and 13, in which the burr formation appearing on the periphery of the sealing material was sufficient, all had helium leakage amounts of 1.0 x 10 －７ PA・m ３ / sec.

[0073] That is, according to the present invention, a lid having excellent sealing properties (airtightness) can be obtained. In particular, according to the method of the present invention, the density of the resin forming the encapsulant can be increased by forming the encapsulant by two-stage injection, and a terminal sealing structure having excellent sealing properties can be obtained. Therefore, a lid having a small number of parts and a relatively simple structure can be realized that can reliably prevent leakage of electrolyte and intrusion of moisture from the outside.

[0074] 1, 2: terminal members, 1a, 2a: flange portion, 3: sealing plate, 3a: flange portion, 3b: mounting hole, 4: resin sealing material, 5: burr, 6 (6a, 6b): movable mold, 7: fixed mold, 8: cavity, 9: gate, 10: air vent, 11: molten resin, 21: aluminum substrate, 21a: laser processing portion, 22: sealing material, 23: burr, 24: first mold, 25: second mold, 26: gate, 27: air vent

Claims

1. A lid for closing a battery container having an opening, comprising: a terminal member; a sealing plate having an attachment hole for attaching the terminal member; and a resin sealant for attaching and sealing the terminal member in the attachment hole of the sealing plate, wherein the terminal member is attached to the attachment hole of the sealing plate via the sealant, and the amount of helium leakage in a helium leak test for evaluating the sealing performance of the sealant is 1.0 x 10 －７ PA・m ３ A lid body characterized by a viscosity of less than 1 / sec.

2. The lid according to claim 1, wherein the outer diameter of the terminal member is smaller than the inner diameter of the mounting hole in the sealing plate.

3. A method for manufacturing a lid as claimed in claim 1, comprising arranging the sealing plate and the terminal member in a mold with a gap between the mounting hole in the sealing plate and the terminal member, and injecting molten resin that forms the sealing material to form a terminal sealing structure in which the terminal member is attached to the mounting hole in the sealing plate via the sealing material, wherein the mold is provided with a cavity that forms the sealing material, a gate that injects molten resin into the cavity, and an air vent that exhausts air at the tip of the flow direction of the molten resin that is injected from the gate and flows through the cavity, and the molten resin is caused to flow into the air vent so that the molten resin injected into the cavity occupies a part of the height direction of the air vent, forming a burr while exhausting the air to the outside of the mold, and then further injecting molten resin into the cavity to form the sealing material, thereby forming a terminal sealing structure by a two-stage injection.

4. The method for manufacturing a lid according to claim 3, further comprising cutting off burrs made of molten resin that has flowed into the air vent.

5. The method for manufacturing a lid according to claim 3, wherein the height of the air vent provided in the mold is greater than 0.06 mm.

6. A method for manufacturing a lid as described in claim 3, wherein the burr made of molten resin that has flowed into the air vent is an annular burr formed by extending concentrically from the outer periphery of the sealing material, or a partial burr formed by extending to a portion of the outer periphery of the sealing material.

7. The method for manufacturing a lid according to claim 3, wherein the sealing material contains a polyarylene sulfide resin as a thermoplastic resin and contains 0.1% by mass or more and 10% by mass or less of an acrylic ester.

8. The method for producing a lid according to claim 3, wherein the acrylic ester is one or more selected from the group consisting of methyl acrylate, ethyl acrylate, butyl acrylate, 2-dimethylaminoethyl acrylate, and 2-hydroxyethyl acrylate.

9. The method for producing a lid according to claim 3, wherein the sealing material further contains one or more polyolefins selected from the group consisting of polyethylene and polypropylene.

10. The method for manufacturing a lid according to claim 9, wherein the sealing material contains 0.1% by mass or more and 20% by mass or less of polyolefin.

11. The method for manufacturing a lid according to claim 3, wherein the sealing material further contains polydimethylsiloxane as an additive.

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