Pressure bag for secondary battery

Abstract

To prevent deformation of a bag body of a pressure bag for a secondary battery when pressurized, and prevent leakage of the contents of the pressure bag.SOLUTION: Provided is a pressure bag for secondary battery (1) in which at the time of pressurizing a secondary battery (5), sheet materials (11, 12) are stacked, and in order to suppress deformation of a bag body, which has a penetrating member (2) built into one side as a content inlet / outlet port, a cover member (3) is further placed outside the sheet material to sandwich a built-in portion and one side of the bag body, thereby suppressing deformation of the bag body when pressurized and preventing leakage of the contents and a decrease in the power generation capacity of the secondary battery due to a decrease in the pressure.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a pressure bag that applies pressure to a thin, flat secondary battery in the thickness direction. [Background technology]

[0002] In recent years, there has been a demand for small, lightweight, and highly safe secondary batteries for battery packs used in electric vehicles and hybrid vehicles. Conventional secondary batteries using liquid electrolytes require the use of aqueous solutions or organic solvents as solvents, which pose problems such as electrolyte evaporation, decomposition, leakage, and fire. Therefore, so-called all-solid-state batteries, which use non-flammable solid electrolytes, have become increasingly popular.

[0003] On the other hand, in the case of secondary batteries with liquid electrolytes, the secondary battery is sometimes pressurized in a pressure bag to remove air from the secondary battery package and fill it with electrolyte without any gaps. Also, in all-solid-state batteries, secondary batteries are used in a pressurized environment using a pressure bag, due to the need to increase the adhesion between the solid electrolyte and the electrodes to operate the battery and to prevent the formation of crystalline precipitates.

[0004] For example, Patent Documents 1 and 2 disclose a technology in which multiple secondary batteries are stacked at equal intervals, a spacer (pressurized bag) that can be expanded by air (gas) pressure is placed, and the spacer pressurizes the secondary batteries in the thickness direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. WO2015-141631 [Patent Document 2] Japanese Patent Application Publication No. 2019-128980 Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology for pressurizing secondary batteries, a pressure bag may be used, which is a flat bag made by overlapping flexible sheet materials and joining their peripheries. For example, a pressure bag such as a pouch bag made by overlapping laminate films is used. Such pressure bags can be made thin, which can contribute to making assembled batteries more compact.

[0007] However, if the peripheral edges of the pressure bag are not securely fixed, when contents such as air (which inflates the pressure bag) are introduced into the pressure bag, even if the pressure bag has a generally rectangular shape when viewed from the front before the contents are introduced, the four peripheral edges of the pressure bag will deform into a concave arc as the contents are introduced, which may apply undue force to the content introduction path (tubes or piping connected to an introduction pump, etc.) connected to the content introduction port provided on the bag body of the pressure bag, or may impair the reliability of the connection and pressurization. Furthermore, insecure pressurization may result in a decrease in power generation, failure of the secondary battery, or accelerated deterioration.

[0008] An object of the present invention is to provide a pressure bag for a secondary battery that can suppress excessive deformation of the pressure bag for a secondary battery and can apply appropriate pressure to the secondary battery. [Means for solving the problem]

[0009] After extensive research, the inventor discovered that when constructing a thin-plate pressurized bag for a secondary battery, it is possible to suppress deformation of the bag main body and thereby suppress leakage of the contents introduced into the pressurized bag by providing a penetrating member within the bag main body, which is formed by overlapping airtight and flexible sheet materials and joining the peripheral edges of both sheet materials, to expand the bag main body, and by using a cover member that sandwiches at least the internal portion and one side of the bag main body, including at least a part of the peripheral edge of the bag main body other than the internal portion, from the outside of the bag main body, and thus completing the present invention.

[0010] The present invention is a thin-plate pressurization bag for a secondary battery, the pressurization bag for a secondary battery including a bag main body, a penetrating member, and a cover member, the bag main body having a generally rectangular shape in front view formed by overlapping airtight and flexible sheet materials with their peripheral edges joined together, the penetrating member being disposed within the bag main body at at least one location along the peripheral edge of the bag main body so as to penetrate the bag main body from the inside to the outside, the cover member sandwiching an internal portion disposed between the penetrating member and the bag main body from the outside and being bonded to the bag main body, and the cover member including a laminated portion covering the internal portion and an expanding portion covering at least a portion of the peripheral edge of the bag main body that is not the internal portion (first invention).

[0011] In the pressurization bag for a secondary battery according to the first invention, it is preferable that the penetrating member includes a penetration portion for introducing and escaping contents into and from the bag main body portion, and a joining portion joined to the inside of the sheet material of the bag main body portion (a second invention).

[0012] In addition, in the second invention, it is preferable that the extension direction of the penetrating portion of the penetrating member is inclined with respect to the vertical direction of the penetrating member (third invention), and in the second invention, it is preferable that the cover member is arranged along the side of the bag main body portion and has an approximately C-shaped cross-section that connects from the front side to the back side of the bag main body portion (fourth invention). [Effects of the Invention]

[0013] According to the pressure bag for secondary batteries of the present invention (first to fourth inventions), when a secondary battery is pressurized using the pressure bag, deformation of the bag main body portion can be suppressed, displacement of the penetrating member and change in the extension direction of the penetrating portion can be suppressed, and further, leakage of the contents introduced into the bag main body portion when pressurizing the secondary battery can be suppressed, thereby allowing appropriate pressure to be applied to the secondary battery. [Brief explanation of the drawings]

[0014] [Figure 1]1 is a schematic diagram showing the structure of a battery pack incorporating a pressurizing bag for a secondary battery according to a first embodiment. [Figure 2] 1 is a schematic view of a pressurizing bag for a secondary battery according to a first embodiment. [Figure 3] 1A and 1B are a perspective view and a cross-sectional view showing an example of a penetrating member used in the practice of the present invention. [Figure 4] 10 is a schematic diagram showing another embodiment of a penetrating member used in the practice of the present invention. FIG. [Figure 5] 1 is a schematic diagram showing an example of a flow of a manufacturing process of a pressure bag for a secondary battery used in carrying out the present invention. [Figure 6] 3 is a cross-sectional view of the XX end in FIG. 2. [Figure 7] FIG. 3 is a YY end view of FIG. 2. [Figure 8] FIG. 3 is a ZZ end view of FIG. 2. [Figure 9] FIG. 6 is a schematic view of a pressurizing bag for a secondary battery according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, with reference to the drawings, an embodiment of the invention will be described using as an example a pressurized bag 1 for a secondary battery that is stacked together with secondary batteries stacked one on top of another in a battery pack, particularly a battery pack used in an electric vehicle or hybrid vehicle. The invention is not limited to the individual embodiments shown below, and can be implemented by modifying the form. Note that the invention can be implemented in both secondary batteries that use a liquid electrolyte and all-solid-state batteries that use a solid electrolyte. An example of a secondary battery is a lithium-ion battery.

[0016] FIG. 1 schematically shows the structure of a battery pack 9 incorporating a pressurized bag 1 for a secondary battery according to a first embodiment of the present invention. The secondary batteries 5, 5 are flat, and a plurality of flat secondary batteries 5, 5 are stacked to form the battery pack 9. The secondary batteries 5, 5 are electrically connected to each other by bus bars (not shown) or the like, and function as the battery pack 9. The secondary battery is not particularly limited, but is typically a lithium-ion battery or an all-solid-state battery.

[0017] The pressurized bag 1 for a secondary battery according to this embodiment is disposed in the gaps between stacked secondary batteries 5, 5, and is provided in an assembled battery 9 in which the secondary batteries are disposed. In addition, a tube, a pipe, or the like is connected to the bag main body 10 as an introduction path from a pump or the like (not shown) for introducing contents.

[0018] Furthermore, in the battery pack 9, the secondary batteries 5,5 may be sandwiched between the secondary battery pressure bags 1,1 and pressurized on both sides by the secondary battery pressure bag 1, or the secondary batteries 5,5 may be arranged at both ends such that only one end face is in contact with and pressurized by the secondary battery pressure bag 1, and the other end face is in contact with the end plate 6, so that the secondary batteries 5,5 are pressurized from both sides.

[0019] 2 shows an outline of a pressurizing bag 1 for a secondary battery according to the present invention, which can be broadly divided into a bag main body 10, a penetrating member 2, and a cover member 3. Although not essential, a pressure measurement terminal may be provided on the surface of the bag main body 10. This allows the pressure applied from the pressurizing bag 1 for a secondary battery to the secondary batteries 5, 5 to be measured in real time, making it possible to instantly identify the condition when a malfunction occurs.

[0020] The bag body 10 may be designed so that its short and long sides are at least the same size as the secondary batteries to be pressurized, for example, with short sides of approximately 100 mm, long sides of approximately 600 mm, and a thickness of approximately 1 mm (before contents are introduced), and the thickness of the bag body increases depending on the introduction and removal of contents. The bag body 10 may be shorter than the secondary batteries. As a result, it is possible to apply the necessary pressure in the thickness direction of the secondary batteries 5,5 while minimizing uneven pressure applied to the secondary batteries 5,5.

[0021] The bag body 10 has a generally rectangular shape when viewed from the front, and is configured as a bag formed by overlapping sheet materials 11 and 12 and joining their peripheral edges at sheet material joining portions AA1 and AA2. A penetrating member 2 is disposed within the bag body 10 at at least one location of the peripheral edge of the bag body 10. That is, the penetrating member 2 is disposed so as to be sandwiched between the sheet materials 11 and 12, and the penetrating member 2 and the sheet materials 11 and 12 are joined and sealed. Furthermore, the penetrating member 2 is more firmly fixed to the bag body 10 by a cover member 3 that is joined from the outside of the bag body 10 so as to sandwich the internal portion in which the bag body 10 is disposed and at least a portion of the peripheral edge of the bag body 10 that is not the internal portion, thereby constituting the pressurizable bag 1 for a secondary battery according to the present invention.

[0022] As shown in the schematic diagram of the manufacturing method of the pressurized bag 1 for a secondary battery shown in FIG. 5 , the sheet materials 11 and 12 constituting the bag main body 10 are not particularly limited as long as they are airtight and flexible enough to be used for the pressurized bag 1 for a secondary battery. Sheet materials that can withstand the pressure of the bag itself, are airtight or liquid-tight enough to prevent gas or liquid from passing through even when filled with gas or liquid contents, and have appropriate stretchability and flexibility can be used. For example, the sheet materials may be single-layer or multi-layer. Single-layer sheets include metal sheets such as aluminum foil, resin sheets such as polypropylene (PP) and polyethylene terephthalate (PET), and even rubber or thermoplastic elastomer sheets. Multi-layer sheets include sheets obtained by laminating and integrating the same single-layer sheets. Furthermore, composite sheets with vapor-deposited metals, silica, or the like can also be used. Reinforcing fibers may be mixed into the sheet materials to improve their physical properties. In this embodiment, a multi-layer sheet in which aluminum foil is sandwiched between PET resin sheets can be used.

[0023] Depending on the environment in which the secondary batteries 5,5 are used, the temperature change range of the secondary batteries 5,5 can reach approximately 100°C, so it is preferable that the sheet materials 11,12 constituting the bag main body 10 are resistant to deformation, alteration, and deterioration due to that temperature, and it is preferable that they use metal foil or have metal vapor deposition.

[0024] The front sheet material 11 and the back sheet material 12 of the bag body 10 are joined together so that the bag is closed all around. Various methods can be used for this joining depending on the materials of the two sheet materials. The joining may be by adhesion using an adhesive or by cross-linking adhesion using the cross-linking effect of rubber or the like. Furthermore, if the sheet materials are made by laminating a thermoplastic resin on one side of both sheet materials, the joining may be by welding. Examples of welding methods include so-called hot plate welding, ultrasonic welding, high-frequency welding, laser welding, and infrared welding.

[0025] When joining the front sheet material 11 and the back sheet material 12, for example, a process of installing the penetrating member 2 later may be performed. Therefore, as shown in Fig. 5(b), the sheet materials may first be joined at a joint except for the edge where the penetrating member 2 will be installed (the joint is designated as AA1 and is shown hatched in Fig. 5(b)), and a bag shape may be formed. Thereafter, as shown in Fig. 5(c), the penetrating member 2 is placed between the sheet materials 11 and 12, and the penetrating member 2 and the sheet materials 11 and 12, as well as the sheet materials 11 and 12 themselves, are joined in the portion where the penetrating member is not installed (the joint that is joined in the process of Fig. 5(d) is designated as AA2 and is shown hatched in Fig. 5(d)). Although Fig. 5 shows an example in which one penetrating member 2 is installed, multiple penetrating members 2 may be used per bag body.

[0026] 3 shows an embodiment of the penetrating member 2, which has a penetrating portion 21 (for example, a through hole) through which the contents can be introduced into and extracted from the bag main body 10. The penetrating portion 21 may be connected to a pump or the like (not shown) for transporting the contents to be introduced into the bag main body 20, and may serve as a path for introducing the contents into the bag main body 10. The penetrating member 2 also has a joining portion 22 that is joined to the sheet material of the bag main body when joining it to the inside of the bag main body 10.

[0027] Various methods can be used to join the bag body 10 and the penetrating member 2 depending on the materials of both members. The joining may be by adhesion using an adhesive, heat welding using a thermoplastic resin, or cross-linking adhesion using the cross-linking effect of rubber or the like.

[0028] Furthermore, the through-hole 21 is a through-hole that penetrates the top and bottom surfaces of the penetrating member 2, and may penetrate the penetrating member 2 vertically or at an angle as shown in FIG. 3(b). The tip of a tube from a pump or the like is connected to the through-hole on the top surface of the penetrating member 2, allowing the contents discharged from the pump or the like to be introduced into the bag body. To strengthen the adhesion and bond between the through-hole and the tube from the pump, it is preferable that the diameter of the tube be larger than the diameter of the through-hole. Furthermore, adhesion can be improved by bonding the tube to the inside of the through-hole or the outside of the tube from the pump or the like using an adhesive, cross-linking agent, or the like.

[0029] As shown in Fig. 4, the penetrating member 2 may be provided with an introduction convex portion (e.g., a nipple) 23 that is joined to a tube from a pump or the like. The introduction convex portion 23 is hollow and tubular, and may be formed airtight on the penetrating member 2. It is provided on the upper surface of the penetrating member 2, but may also be provided on both the upper and lower surfaces. Even in this case, it is possible to introduce the contents discharged from the pressure-regulating pump into the bag main body 10. The length of the introduction convex portion 23 is sufficient to at least provide an airtight connection with the pump and tube piping, and is preferably shorter than the bag main body 10.

[0030] In the pressurized bag 1 for a secondary battery according to this embodiment, the penetrating member 2 is preferably made of a hard resin such as polypropylene (PP) or acrylonitrile-butadiene-styrene copolymer resin (ABS resin), and more preferably, a fiber-based reinforcing material such as glass fiber is mixed in to suppress dimensional changes due to temperature changes in the secondary battery.

[0031] The joint 22 of the penetrating member 2 need only have a length and width sufficient to secure and seal the penetrating member 2 to the periphery of the bag body 10. As shown in FIG. 4 , the penetrating member 2 may have a joint wing 24 extending from the joint wing 22. The joint wing 24 extends across one side of the bag body 10. Preferably, the joint wing 24 is joined to the bag body 10 at one side of the periphery of the bag body 10, excluding the area where the joint wing 22 and the bag body 10 are joined. Furthermore, from the viewpoint of airtightness of the pressurizable bag 1 for secondary batteries and preventing sheet peeling of the bag body 10, if the joint wing 24 is provided, it is preferable that the joint wing 24 be thinner than the joint wing 22. By providing the joint wing 24, one side of the bag body 10 is fixed to the joint wing wing 24, which facilitates molding when the cover member 3 described below is provided.

[0032] The cover member 3 sandwiches the bag body 10 from the outside so as to cover the portion where the penetrating member 2 is provided inside the bag body 10 and at least a portion of the peripheral edge of the bag body 10 where the penetrating member 2 is provided, where the penetrating member 2 and the bag body 10 are not joined. The cover member 3 includes a laminated portion 31 that covers, from the outside of the bag body 10, the joint portion (internal contact portion) where the penetrating member 2 is provided inside the bag body 10, and an expanded portion 32 that covers, from the outside of the bag body 10, at least a portion of the peripheral edge of the bag body 10 where the penetrating member 2 is provided, where the penetrating member 2 and the bag body 10 are not joined. The cover member 3 is joined to the bag body 10, and various methods can be used for this joining depending on the materials of the sheet materials 11 and 12 that make up the cover member 3 and the bag body 10. The joining may be by adhesion using an adhesive, heat fusion using a thermoplastic resin, or cross-linking adhesion using the cross-linking effect of rubber or the like.

[0033] FIG. 5 shows an example of a manufacturing process for the pressurized bag 1 for a secondary battery according to the first aspect of the present invention, with the steps proceeding in the order of (a) to (e). Each step can be achieved by applying known techniques. Specifically, (a) flexible sheet materials 11 and 12 are prepared, (b) the sheet materials are stacked together and the peripheral edges of the sheet materials 11 and 12 are joined at the sheet material joint (AA1), (d) the penetrating member 2 is appropriately positioned between the edges of the sheets 11 and 12, and the peripheral edges of the sheets 11 and 12 are joined (AA2) to prepare a bag body 10 integrated with the penetrating member 2, and then (e) one edge of the bag body 10 integrated with the penetrating member 2 is placed inside an injection mold for molding the cover member 3, the mold is closed, and a resin for the cover member 3 is injected into the mold to form the cover member 3, thereby forming the cover member 3 integral with the bag body 10 and the penetrating member 2 by insert injection molding. This process is also known as the overmolding process.

[0034] For manufacturing efficiency, it is preferable to provide the cover member 3 by an overmolding process, and by using a mold that corresponds to the installation location of the penetrating member 2, it is possible to efficiently mold and produce the pressurized bag 1 for the secondary battery.

[0035] In the pressurized bag 1 for a secondary battery in this embodiment, the cover member 3 is preferably made of the same material as the penetrating member 2, and is provided by overmolding the penetrating member 2 into the bag main body 10, and then molding the cover member 3 to cover at least a part of one side of the bag main body 10 with the penetrating member 2 provided therein. The cover member 3 is also provided with a substantially semi-cylindrical laminated portion 31 provided to cover the internal portions of the penetrating member 2 and the bag main body 10, and a flat-plate-shaped unfolded portion 32 provided from the laminated portion 31 along the periphery of the bag main body 10.

[0036] The laminated portion 31 of the cover member 3 covers the penetrating member 2 and the internal portion of the bag main body 10 from the outside. The contact between the tops of the approximately cylindrical laminated portions can also serve as a support portion when ensuring clearance (equal to or greater than the thickness of the battery cell) between the bag main bodies 10. Furthermore, by joining the cover member 3 having the laminated portion 31 and the expanding portion 32 to the main body, deformation of one side of the bag main body 10 into a concave arc due to expansion of the bag main body 10 as the internal pressure of the bag main body 10 increases, although the expanding portion 32 does not necessarily have to be provided over the entire length of the side. Furthermore, when the cover member 3 integrally joins the front and back sides of the bag main body 10, deformation of one side of the bag main body 10 (particularly the side including the penetrating member and the internal portion of the bag main body 10) into a concave arc in front view due to an increase in internal pressure of the bag main body 10 is particularly effectively prevented. This suppresses displacement of the penetrating member 2 and changes in its extension direction, thereby preventing leakage of the contents.

[0037] Furthermore, although not essential, a second cover member 4 may be provided on an edge of the bag main body 10 that does not have the penetrating member 2. By providing the second cover member 4, it is possible to reduce the number of edges of the bag main body 10 that undergo a concave arc-like deformation when pressurized, thereby enabling the secondary battery pressurization bag 1 to function more efficiently. In this case, the second cover member 4 may be composed of only the flat expansion portion 32.

[0038] Furthermore, in the present invention, the cover member 3 may be formed with a U-shaped cross section so as to connect the front side to the back side of the bag body 10, as in the first embodiment. In this case, the inner top surface of the U-shaped laminated portion 31 is tightly joined to the top surface of the penetrating member 2, preventing peeling of the sealed portion between the sheet material of the bag body 10 and the interior of the penetrating member 2 as the pressure applied to the pressurized bag 1 for a secondary battery increases. Even if the sealed portion does peel, the tightly-fitting portion prevents leakage of the contents. The U-shaped portion of the unfolding portion 32 serves as a sheet material pressing member to prevent peeling of the sealed portion between the sheets of the bag body, thereby ensuring a more reliable seal and preventing leakage of the contents.

[0039] In the present invention, the contents introduced into the bag body 10 may be liquid or gas. However, since it is expected that the temperature change range of the secondary battery will be within a range of approximately 100°C depending on the state of use, it is preferable that the contents be liquid, and more preferably, an antifreeze solution whose main components are glycerin, ethylene glycol, propylene glycol, or the like.

[0040] When the penetrating member 2 is installed in only one location on the bag main body portion 10, a receiving member (not shown) may be provided on the side of the bag main body portion 10 opposite to the side of the bag main body portion 10 on which the penetrating member 2 is installed, to facilitate installation on the battery pack 9. [Industrial Applicability]

[0041] The pressurizing bag 1 for a secondary battery of the above embodiment can be used as a pressurizing bag for a secondary battery, and has high industrial applicability. [Explanation of symbols]

[0042] 1. Pressure bag for secondary batteries 10 Bag body 11 Front sheet material 12 Back sheet material 2 Penetrating member 21 Penetration 22 Joint 23 Introduction convex part 24 Joint blade section 3 Cover material 31 Lamination section 32 Development Section 4 Second cover member 5 Secondary battery 6 End Plate AA1, AA2 sheet material joint 9 Battery pack

Claims

1. A thin-plate pressurized bag for a secondary battery, The pressurized bag for a secondary battery includes a bag main body, a penetrating member, and a cover member, The bag body has a generally rectangular shape in front view, and is formed by overlapping airtight and flexible sheet materials and joining the peripheral edges of both sheet materials together. the penetrating member is provided inside the bag body portion at at least one location on the periphery of the bag body portion so as to penetrate the bag body portion from the inside to the outside, The cover member sandwiches the penetrating member and the internal portion provided inside the bag main body portion from the outside, and the cover member is joined to the bag main body portion, and the cover member includes a laminated portion that covers the internal portion and an expanded portion that covers at least a part of the peripheral portion of the bag main body portion that is not the internal portion. Pressure bag for secondary batteries.

2. The penetrating member includes a penetrating portion for introducing and urging contents into and out of the bag body portion, The bag body includes a joining portion joined to the inner side of the sheet material constituting the bag body. The pressure bag for a secondary battery according to claim 1 .

3. The penetrating portion of the penetrating member is The extending direction of the bag is inclined with respect to the periphery of the bag body. The pressure bag for a secondary battery according to claim 2 .

4. The cover member is provided along a side of the bag body portion, The bag body has a cross section that is approximately U-shaped so as to connect the front side to the back side. The pressure bag for a secondary battery according to claim 2 .

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