Battery pack manufacturing method

Abstract

To provide a manufacturing method for a battery pack, in which an adhesive can be efficiently cured while the heating of a unit cell is suppressed.SOLUTION: A manufacturing method for a battery pack includes the steps of: accommodating a multilayer battery 100 including a plurality of unit cells 10 stacked in a thickness direction and an intermediate member 20 disposed between the adjacent unit cells in a battery case 200; injecting an adhesive F in the battery case; and heating the injected adhesive by introducing hot air into the intermediate member. The intermediate member includes a tube that makes a first opening and a second opening communicate and passes through the intermediate member. The tube includes an external tube part passing an outer edge part of the intermediate member, and an internal tube part passing inside the external tube part. The heating step includes a first hot air process in which the hot air is introduced from the first opening and passes at least the external tube part and the internal tube part in this order and then is discharged from the second opening.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a battery pack. [Background technology]

[0002] BACKGROUND ART Battery packs in which a plurality of unit cells are housed in a battery case and fixed to the battery case with an adhesive (filler) and methods for manufacturing battery packs are known.

[0003] For example, Patent Document 1 discloses a battery pack in which the inner surface of a case and the outer surface of the battery cells are bonded with a reactive hot melt to secure the battery cells. Patent Document 2 discloses a battery pack including a battery stack in which a plurality of batteries are arranged, a case for accommodating the battery stack, and a thermally conductive layer made of a thermally conductive adhesive that fills the gaps between the battery stack and the case. Furthermore, although not directly related to battery pack manufacturing methods, Patent Document 3 discloses a resin filling method for molding and integrally sealing the coils that make up a motor with resin, in which resin is filled while applying a current to the coils to heat them. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-243364 [Patent Document 2] Japanese Patent Publication No. 2021-140914 [Patent Document 3] Japanese Patent Publication No. 2020-092521 Summary of the Invention [Problem to be solved by the invention]

[0005] In the manufacture of a battery pack, a battery case containing cells is filled with an adhesive (filler), and the cells are fixed to the battery case with the hardened adhesive. When the adhesive is a two-component curing adhesive containing a base agent and a curing agent, the adhesive is heated to promote curing. However, heating the adhesive to heat the electrode layer of the cells can result in a deterioration in battery performance.

[0006] The present disclosure has been made in consideration of the above-described circumstances, and has as its main object to provide a method for manufacturing a battery pack that can efficiently harden an adhesive while suppressing heating of the unit cells. [Means for solving the problem]

[0007] [1] a first hot air treatment in the heating step of introducing the hot air from the first opening, passing through at least a path that passes through the outer edge of the intermediate member and a path that passes inside the outer pipe portion; and

[0008] [2] The manufacturing method of a battery pack described in [1], wherein the heating step includes a second hot air treatment in which the hot air is introduced from the second opening, passes through at least a path that passes the outer pipe portion and the inner pipe portion in this order, and is then discharged from the first opening, and the first hot air treatment and the second hot air treatment are alternately performed in the heating step.

[0009] [3] [1] or [2], wherein, when the intermediate member is viewed in a plane from the thickness direction, the intermediate member has a first side, a second side, a third side, and a fourth side, and the outer pipe portion has a first outer pipe portion extending along the first side, a second outer pipe portion extending along the second side, a third outer pipe portion extending along the third side, and a fourth outer pipe portion extending along the fourth side, and in the first hot air treatment, the hot air passes through the first outer pipe portion, the second outer pipe portion, the third outer pipe portion, the fourth outer pipe portion, and the inner pipe portion in that order, and is then discharged from the second opening.

[0010] [4] [1] or [2], wherein, when the intermediate member is viewed in a plane from the thickness direction, the intermediate member has a first side, a second side, a third side, and a fourth side, and the outer pipe portion has a first outer pipe portion extending along the first side, a second outer pipe portion extending along the second side, a third outer pipe portion extending along the third side, and a fourth outer pipe portion extending along the fourth side, and in the first hot air treatment, the hot air passes through the first outer pipe portion, the second outer pipe portion, the inner pipe portion, the fourth outer pipe portion, and the third outer pipe portion in that order, and is then discharged from the second opening.

[0011] [5] The method for manufacturing a battery pack according to any one of [1] to [4], wherein the single battery has an electrode having a current collector and an electrode layer arranged on at least one surface of the current collector in the thickness direction, and the electrode layer overlaps with the inner tube portion in the thickness direction. [Effects of the Invention]

[0012] The present disclosure provides the effect of suppressing heating of the unit cells while efficiently curing the adhesive. [Brief explanation of the drawings]

[0013] [Figure 1] 1A to 1C are schematic diagrams illustrating a method for manufacturing a battery pack according to the present disclosure. [Figure 2] FIG. 2 is a schematic perspective view illustrating an intermediate member according to the present disclosure. [Figure 3] FIG. 2 is a schematic plan view illustrating an intermediate member according to the present disclosure. [Figure 4] FIG. 1 is a schematic cross-sectional view illustrating a unit cell according to the present disclosure. [Figure 5] FIG. 2 is a schematic cross-sectional view illustrating an example of a battery case according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] The manufacturing method of a battery pack according to the present disclosure will be described in detail below. The figures shown below are schematic illustrations, and the size and shape of each part are appropriately exaggerated for ease of understanding. Hatching of each part may be omitted where appropriate. Furthermore, in this specification, when describing the arrangement of another member relative to a certain member, the term "above" or "below" refers to both the case where another member is arranged directly above or below the certain member, so as to be in contact with the certain member, and the case where another member is arranged above or below the certain member via another member, unless otherwise specified.

[0015] FIG. 1 is a schematic diagram illustrating a manufacturing method of a battery pack according to the present disclosure. FIG. 1(a) is a schematic side view of a stacked battery prepared in a preparation step. FIG. 1(b) is a schematic plan view of the accommodation step as viewed from the thickness direction, and FIG. 1(c) is a cross-sectional view taken along line AA in FIG. 1(b). FIG. 1(d) is a schematic plan view of the injection step and the heating step as viewed from the thickness direction, and FIG. 1(e) is a cross-sectional view taken along line AA in FIG. 1(d). Note that in the cross-sectional views shown in FIGS. 1(c) and 1(e), the cross sections of the tubes in the intermediate member (described later) are usually also observed, but the tubes are not shown for ease of understanding. FIG. 2 is a schematic perspective view illustrating an intermediate member according to the present disclosure, and FIG. 3 is a schematic plan view illustrating an intermediate member according to the present disclosure.

[0016] As shown in FIG. 1(a), in the method for manufacturing a battery pack according to the present disclosure, first, T A stacked battery 100 is prepared (preparation step) having a plurality of unit cells 10 stacked in a straight line and an intermediate member 20 arranged between adjacent unit cells 10. As shown in Figs. 2 and 3, the intermediate member 20 has a first opening 21, a second opening 22, and a pipe 23 that communicates with the first opening 21 and the second opening 22 and passes through the interior of the intermediate member 20. The intermediate member 20 is also arranged in a thickness direction D. T When viewed from above, the tube 23 has outer pipe portions 23A (23A1-23A4) that pass through the outer edge of the intermediate member 20 and inner pipe portions 23B that pass more inward than the outer pipe portions 23A. Next, as shown in FIGS. 1(b) and 1(c), the stacked battery 100 is housed in the battery case 200 (housing step). Then, as shown in FIGS. 1(d) and 1(e), an adhesive F containing a base agent and a curing agent is injected into the battery case 200 housing the stacked battery 100 (injection step), and hot air is introduced into the interior of the intermediate member 20 to heat the injected adhesive F (heating step). The heating step also includes a first hot air treatment in which the hot air is introduced through the first opening 21, passes through at least a path that passes through the outer pipe portions 23A and the inner pipe portions 23B in this order, and is then discharged from the second opening 22.

[0017] According to the present disclosure, in the heating process, hot air is introduced through the first opening and discharged through the second opening after passing through at least the outer pipe portion and the inner pipe portion in that order. Therefore, the hot air passes through the outer pipe portion along the outer edge, heating the adhesive in contact with the outer periphery of the intermediate member and effectively hardening the adhesive. Furthermore, the inner pipe portion, which is located more inward than the outer pipe portion, is passed by the cooled hot air that has passed through the outer pipe portion, preventing the inside of the cell from being overheated.

[0018] 1. Preparation process The preparation step in the present disclosure is a step of preparing a stacked battery having a plurality of unit cells stacked in the thickness direction and intermediate members disposed between adjacent unit cells.

[0019] (1) Battery 4 is a schematic cross-sectional view illustrating a unit cell according to the present disclosure. As shown in FIG. 4, a unit cell 10 generally has an electrode E. The electrode E has a current collector 1 and a T and an electrode layer (positive electrode active material layer 2 or negative electrode active material layer 3) disposed on at least one surface of the current collector 1. As shown in FIG. 4, the unit cell 10 may have, as an electrode E, a bipolar electrode BP having a positive electrode active material layer 2 disposed on one surface of the current collector 1 and a negative electrode active material layer 3 disposed on the other surface of the current collector 1 in the thickness direction. Note that the unit cell in the present disclosure does not necessarily have a bipolar electrode.

[0020] The cell 10 shown in FIG. 4 has bipolar electrodes BP1, BP2, a positive electrode end electrode CA, and a negative electrode end electrode AN as electrodes E. Bipolar electrodes BP1 and BP2 are as described above. The positive electrode end electrode CA has a current collector 1 and a positive electrode active material layer 2 disposed on one surface of the current collector 1. The negative electrode end electrode AN has a current collector 1 and a negative electrode active material layer 3 disposed on one surface of the current collector 1. Although not specifically shown, the cell is typically sealed in an exterior package such as a laminate film.

[0021] As shown in FIG. 4, a cell 10 typically includes power generating units U (U1 to U3). Each power generating unit U includes a positive electrode active material layer 2, a negative electrode active material layer 3, and a separator (electrolyte layer) 4 disposed between the positive electrode active material layer 2 and the negative electrode active material layer 3. The power generating unit U shown in FIG. 4 is sealed with a seal member 5 and a cover member 6, and the power generating unit U is filled with an electrolyte 7. As a result, the positive electrode active material layer 2, the negative electrode active material layer 3, and the separator 4 are each impregnated with the electrolyte. A cell according to the present disclosure may include one power generating unit or two or more power generating units. In the cell, the separator may be a solid electrolyte layer, and the cell may not include an electrolyte.

[0022] The current collectors (positive electrode current collector and negative electrode current collector), electrode layers (positive electrode active material layer and negative electrode active material layer), and separator may be conventionally known materials.

[0023] The unit cell may be an all-solid-state battery containing a solid electrolyte as the electrolyte, or a liquid-based battery containing a liquid electrolyte (electrolytic solution) as the electrolyte. The unit cell is typically a lithium-ion battery.

[0024] The planar shape of the unit cell (shape viewed from the thickness direction) can be, for example, a quadrangle such as a square or a rectangle. The length of each side constituting the planar shape of the unit cell is, for example, 30 cm or more, or may be 60 cm or more, or may be 100 cm or more. On the other hand, the length of each side is, for example, 200 cm or less.

[0025] (2) Intermediate parts The intermediate member is disposed between the plurality of unit cells stacked in the thickness direction, and has a first opening, a second opening, and a pipe that communicates with the first opening and the second opening and passes through the interior of the intermediate member.

[0026] 2 is a schematic perspective view illustrating an intermediate member in the present disclosure, and FIG. 3 is a schematic plan view of the intermediate member as viewed from the thickness direction. Note that tubes are not shown in FIG. 2. As shown in FIG. 2, the intermediate member usually has a top surface 20a and a thickness direction D T The substrate 20 has a bottom surface 20b facing the top surface 20a, and four side surfaces (a first side surface 20c, a second side surface 20d, a third side surface 20e, and a fourth side surface 20f) connecting the top surface 20a and the bottom surface 20b.

[0027] 2 and 3, the intermediate member 20 is T When viewed from above, the intermediate member 20 is L and the transverse direction D S 3, when the intermediate member is viewed in plan from the thickness direction, the intermediate member preferably has a first side S1, a second side S2, a third side S3, and a fourth side S4. The first side S1 and the third side S3 are opposite sides, and the second side S2 and the fourth side S4 are opposite sides.

[0028] The planar shape of the intermediate member (the shape seen from the thickness direction) may be, for example, a quadrilateral such as a square or a rectangle.

[0029] The first opening and the second opening connect the inside and outside of the intermediate member. Typically, the first opening and the second opening are arranged on the side surfaces of the intermediate member. The first opening and the second opening may be arranged on the same surface (the same side surface) or on different surfaces (different side surfaces). Furthermore, the first opening and the second opening may each have a connection portion for connection to a device that blows hot air.

[0030] As shown in Figures 3(a) to 3(c), the pipe 23 connects the first opening 21 and the second opening 22 and passes through the inside of the intermediate member 20. The pipe 23 also functions as a flow path for hot air, which will be described later. As shown in Figures 3(a) to 3(c), the intermediate member 20 is formed in the thickness direction D TWhen viewed from above, the pipe 23 has an outer pipe portion 23A that passes through the outer edge of the intermediate member 20, and an inner pipe portion 23B that passes inside the outer pipe portion 23A.

[0031] Here, the outer edge of the intermediate part refers to a portion that includes at least the outer edge of the planar shape of the intermediate part. The outer edge is, for example, an area within 3 cm, or may be an area within 1 cm, from a side that constitutes the planar shape of the intermediate part.

[0032] The outer pipe portion is a portion of the pipe that passes through the outer edge of the intermediate member. As shown in FIGS. 3(a) to 3(c), when the intermediate member has the first side S1 to fourth side S4 described above, the outer pipe portion preferably includes a first outer pipe portion 23A1 extending along the first side S1, a second outer pipe portion 23A2 extending along the second side S2, a third outer pipe portion 23A3 extending along the third side S3, and a fourth outer pipe portion 23A4 extending along the fourth side S4. The intermediate members shown in FIGS. 3(a) and 3(b) each include one of the first outer pipe portion 23A1 to fourth outer pipe portion 23A4. The intermediate member shown in FIG. 3(c) includes one of the first outer pipe portion 23A1, third outer pipe portion 23A3, and fourth outer pipe portion 23A4, and two of the second outer pipe portions 23A2. In this way, the first outer pipe portion to the fourth outer pipe portion may each have one intermediate member or may each have a plurality of intermediate members.

[0033] As shown in Figure 3(a), the outer pipe portion may be a single continuous portion from the first outer pipe portion 23A1 to the fourth outer pipe portion 23A4. Alternatively, as shown in Figures 3(b) and 3(c), the outer pipe portion may be multiple portions separated by inner pipe portions (described below). Furthermore, the outer pipe portion may be connected to only either the first opening or the second opening, as shown in Figure 3(a), or may be connected to both the first opening and the second opening, as shown in Figures 3(b) and 3(c).

[0034] The inner pipe portion passes inside the outer pipe portion. As long as the inner pipe portion passes inside the outer pipe portion, it may or may not pass through the outer edge of the intermediate member. Also, as shown in Figures 3(a) and 3(b), the inner pipe portion may be a single continuous part. On the other hand, as shown in Figure 3(c), the inner pipe portion may be multiple parts separated by the outer pipe portion.

[0035] The area of ​​the intermediate member as viewed in the thickness direction may be equal to or smaller than the area of ​​the cell, and in the latter case, it is preferable that the outer edge of the intermediate member as viewed in the thickness direction is located outside the outer edges of the electrode layers of the cell.

[0036] The intermediate member may be a single member or a member composed of multiple members. In the latter case, the intermediate member may be composed of, for example, three members stacked in the thickness direction. The material of the intermediate member is not particularly limited, but examples thereof include metals such as aluminum, copper, iron, and SUS.

[0037] In a battery pack, the intermediate member can also function as a cooling member for cooling the unit cells. For example, by introducing a refrigerant such as air into the tube, the unit cells that generate heat due to charging and discharging can be cooled.

[0038] (3) Stacked battery In the stacked battery, the number of the unit cells is 2 or more, and may be 3 or more, 5 or more, or 10 or more. On the other hand, the number of the unit cells is, for example, 50 or less. In addition, in the stacked battery, the number of the intermediate members may be 1, or may be 2 or more. Note that when the number of unit cells is N (N≧2), the number of intermediate members is N−1.

[0039] 2. Storage process The housing step in the present disclosure is a step of housing the stacked battery in a battery case.

[0040] As shown in Fig. 1(b), in the accommodation step, the stacked battery 100 is typically accommodated with a gap between it and the inner surface of the battery case 200 (the wall of the battery case, described below). Also, as shown in Fig. 1(b), in the accommodation step, a control device 300 that performs various controls on the battery may be accommodated in the battery case 200 together with the stacked battery 100. The control device may have, for example, a function of electrically connecting the stacked battery to an external device and a function of blowing (introducing) hot air to an intermediate member, described below.

[0041] 5 is a schematic cross-sectional view illustrating a battery case. As shown in FIG. 5, the cross-sectional shape of a battery case 200 is generally a concave shape having a bottom 201, a wall 202, and a flange 203. The inside of the battery case is defined as the area in the thickness direction D T In this case, it can be considered as the space on the bottom 201 side of the flange 203. The material of the battery case is not particularly limited, and may be any conventionally known material.

[0042] 3. Injection process The injection step in the present disclosure is a step of injecting an adhesive into the battery case containing the laminated battery. The injection step may be performed in parallel with the heating step described below, or may be performed independently before the heating step, but the former is preferred.

[0043] The injection process is continued until a predetermined amount of adhesive is injected into the battery case. The amount of adhesive injected in the injection process is preferably an amount that allows all of the cells in the stacked battery to come into contact with the adhesive. Furthermore, as shown in Figure 1(d), the adhesive is preferably injected so as to surround the outer periphery of the stacked battery.

[0044] The adhesive in the present disclosure is a so-called two-component curing adhesive containing a base agent and a curing agent. The type of adhesive is not particularly limited, but examples include epoxy adhesives and urethane adhesives. Note that the adhesive is preferably ejected from a nozzle in a mixed state of two components (base agent and curing agent).

[0045] As shown in Fig. 1(e), the adhesive is discharged from a nozzle 400 that is connected to an adhesive container (not shown) and that is positioned above the battery case 200 (above the flange portion) toward the gap between the battery case 200 and the stacked battery 100. As shown in Fig. 1(d), it is preferable to inject the adhesive while scanning the nozzle 400 along the gap.

[0046] The temperature of the adhesive to be injected (adhesive to be discharged from the nozzle) is, for example, 15° C. or higher and 25° C. or lower. The injection speed of the adhesive is, for example, 5 cc / sec. or higher and 20 cc / sec. or lower.

[0047] 4.Heating process The heating step in the present disclosure is a step of heating the injected adhesive by introducing hot air into the intermediate member, and includes a predetermined first hot air treatment.

[0048] (1) First hot air treatment The first hot air treatment is a treatment in which hot air is introduced from the first opening, passes through at least the outer pipe portion and the inner pipe portion in this order, and is then discharged from the second opening.

[0049] In the first hot air treatment, hot air passes through the outer pipe portion that passes through the outer edge of the intermediate member, thereby heating the adhesive in contact with the outer edge of the intermediate member. Furthermore, the hot air that has been cooled by passing through the outer pipe portion passes through the inner pipe portion, thereby preventing the central portion of the intermediate member from being heated. Therefore, the electrode layer disposed in the central portion of the cell can be prevented from being heated.

[0050] The hot air introduced through the first opening passes through at least a path that passes through the outer pipe portion and the inner pipe portion in this order, and is then discharged from the second opening. For example, if the intermediate member 20 has the first side S1 to the fourth side S4 and the first outer pipe portion 23A1 to the fourth outer pipe portion 23A4, as shown in FIG. 3(a), the hot air may pass through the first outer pipe portion 23A1, the second outer pipe portion 23A2, the third outer pipe portion 23A3, the fourth outer pipe portion 23A4, and the inner pipe portion 23B in this order, and then be discharged from the second opening 22. Alternatively, as shown in FIG. 3(b), the hot air may pass through the first outer pipe portion 23A1, the second outer pipe portion 23A2, the inner pipe portion 23B, the fourth outer pipe portion 23A4, and the third outer pipe portion 23A3 in this order, and then be discharged from the second opening 22. Also, as shown in Figure 3(c), the hot air may pass through the first outer pipe portion 23A1, the second outer pipe portion 23A2, the inner pipe portion 23B, the fourth outer pipe portion 23A4, the inner pipe portion 23B, the second outer pipe portion 23A2 and the third outer pipe portion 23A3 in that order, and then be discharged from the second opening 22.

[0051] The temperature of the hot air is not particularly limited and is, for example, 80° C. or higher and 150° C. or lower. The speed at which the hot air is introduced can be adjusted appropriately depending on the size of the intermediate member, but is, for example, 1 m / sec. or higher and 3 m / sec. or lower.

[0052] (2) Second hot air treatment The heating step may also include a second hot air treatment in which hot air is introduced from the second opening, passes through at least the outer pipe portion and the inner pipe portion in this order, and is then discharged from the first opening. When the heating step includes the second hot air treatment, the first hot air treatment and the second hot air treatment are performed alternately.

[0053] For example, as shown in Figures 3(b) and 3(c), if the first opening and the second opening are each connected to an outer pipe portion, cooled hot air passes through the third outer pipe portion 23A3 connected to the second opening during the first hot air treatment. Therefore, if only the first hot air treatment is performed, uneven heating may occur around the outer periphery of the intermediate part. However, by performing the second hot air treatment, uneven heating can be suppressed.

[0054] The second hot air treatment can be performed in the same manner as the first hot air treatment, except that hot air is introduced through the second opening. In other words, the path of the hot air in the second hot air treatment is opposite to the path of the hot air in the first hot air treatment.

[0055] 5. Battery pack The battery pack may have a lid that seals the battery case filled with the adhesive. That is, the battery pack according to the present disclosure may have a sealing step of sealing the battery case with a lid after the filling step and the heating step.

[0056] The use of the battery pack in the present disclosure is not particularly limited, but examples include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. It is particularly preferred that the battery pack be used as a driving power source for hybrid electric vehicles, plug-in hybrid electric vehicles, or electric vehicles. The battery pack in the present disclosure may also be used as a power source for mobile objects other than vehicles (e.g., trains, ships, and aircraft), or as a power source for electrical appliances such as information processing devices.

[0057] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Explanation of symbols]

[0058] 1...Current collector 2...Cathode active material layer 3...Negative electrode active material layer 4...Separator E...Electrode 10...Double cell 20...Intermediate parts 100...Stacked battery 200... Battery case

Claims

1. A method for manufacturing a battery pack, comprising: a preparation step of preparing a stacked battery including a plurality of unit cells stacked in a thickness direction and an intermediate member disposed between adjacent unit cells; a housing step of housing the stacked battery in a battery case; an injection step of injecting an adhesive containing a base agent and a curing agent into the battery case housing the laminated battery; a heating step of heating the injected adhesive by introducing hot air into the intermediate member, the intermediate member has a first opening and a second opening, and a tube that communicates between the first opening and the second opening and passes through the interior of the intermediate member; When the intermediate member is viewed in a plan view from the thickness direction, the pipe has an outer pipe portion passing through an outer edge portion of the intermediate member and an inner pipe portion passing inside the outer pipe portion, The method for manufacturing a battery pack includes a first hot air treatment, in which the heating process introduces the hot air from the first opening, passes it through at least the outer pipe portion and the inner pipe portion in this order, and then discharges it from the second opening.

2. the heating step includes a second hot air treatment in which the hot air is introduced from the second opening, passes through at least the outer pipe portion and the inner pipe portion in this order, and is then discharged from the first opening; The method for manufacturing a battery pack according to claim 1 , wherein the first hot air treatment and the second hot air treatment are alternately performed in the heating step.

3. When the intermediate member is viewed in plan view from the thickness direction, the intermediate member has a first side, a second side, a third side, and a fourth side; the outer pipe portion includes a first outer pipe portion extending along the first side, a second outer pipe portion extending along the second side, a third outer pipe portion extending along the third side, and a fourth outer pipe portion extending along the fourth side, 2. The method for manufacturing a battery pack according to claim 1, wherein in the first hot air treatment, the hot air passes through the first outer pipe portion, the second outer pipe portion, the third outer pipe portion, the fourth outer pipe portion, and the inner pipe portion in that order, and is then discharged from the second opening.

4. When the intermediate member is viewed in plan view from the thickness direction, the intermediate member has a first side, a second side, a third side, and a fourth side; the outer pipe portion includes a first outer pipe portion extending along the first side, a second outer pipe portion extending along the second side, a third outer pipe portion extending along the third side, and a fourth outer pipe portion extending along the fourth side, 2. The method for manufacturing a battery pack according to claim 1, wherein in the first hot air treatment, the hot air passes through the first outer pipe portion, the second outer pipe portion, the inner pipe portion, the fourth outer pipe portion, and the third outer pipe portion in that order, and is then discharged from the second opening.

5. The unit cell has an electrode including a current collector and an electrode layer disposed on at least one surface of the current collector in the thickness direction, The method for manufacturing a battery pack according to claim 1 , wherein the electrode layer overlaps the inner tubular portion in the thickness direction.

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