Method for manufacturing secondary battery

Abstract

To provide a method for manufacturing a secondary battery capable of suppressing adhesion of an electrolyte to a joint portion between a liquid injection port and a sealing material.SOLUTION: A method for manufacturing a secondary battery containing an electrolytic solution therein includes: a liquid injection step of injecting an electrolytic solution from a through hole 31 into the secondary battery; a first sealing step of sealing at least part of the through hole with a first sealing material 34 made of resin having a vent hole after the liquid injection step; an initial charging step of performing initial charging of the secondary battery after the first sealing step; and a second sealing step of bonding and sealing a second sealing material on the first sealing material after the initial charging step.SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] In the manufacturing of lithium-ion batteries, there is a process in which an electrolyte is injected through a filling port and then the filling port is sealed with a sealant. If the electrolyte adheres to the part of the filling port where the sealant is bonded for some reason during filling, the initial charging after filling, or aging, this will result in poor bonding of the sealant.

[0003] Patent Document 1 discloses that in order to prevent the electrolyte from adhering to the portion where the sealing material is bonded, a frame that forms the bonding portion is provided with an inclination. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-150991 A Summary of the Invention [Problem to be solved by the invention]

[0005] Even when the frame is inclined as in the past, it cannot be said that the adhesion of the electrolyte is sufficiently suppressed. In addition, a frame with an inclination has limitations in its manufacture (for example, it is difficult to remove from the mold), and there are problems with productivity.

[0006] In view of the above, an object of the present disclosure is to provide a method for manufacturing a secondary battery that can prevent the electrolyte from adhering to the joint between the liquid injection hole and the sealant. [Means for solving the problem]

[0007] The present application discloses a method for manufacturing a secondary battery containing an electrolyte solution therein, the method including: a liquid injection step of injecting an electrolyte solution into the interior of the secondary battery through a through hole; a first sealing step of sealing at least a portion of the through hole with a first sealing material made of resin having an air hole after the liquid injection step; an initial charging step of charging the secondary battery for the first time after the first sealing step; and a second sealing step of adhering a second sealing material to be placed on top of the first sealing material to seal the battery after the initial charging step.

[0008] The ventilation hole of the first sealing material may be formed at a position not overlapping with the through hole in the normal direction of the surface on which the through hole is provided.

[0009] During the initial charging process, the vent hole may be configured to be located upward from the center. Effect of the Invention

[0010] According to the present disclosure, by performing the first sealing with a first sealing material having an air hole, it is possible to prevent adhesion of the electrolyte to the joint of the sealing material while allowing gas generated during the subsequent initial charging to escape, thereby preventing poor bonding when bonding the sealing members. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is an external view illustrating an outline of a secondary battery 10. As shown in FIG. [Diagram 2] FIG. 2 is a diagram illustrating the internal structure of the electricity storage module 12. As shown in FIG. [Diagram 3] FIG. 3 is a diagram illustrating the liquid injection section 30. As shown in FIG. [Figure 4] FIG. 4 is a diagram illustrating the flow of a method S10 for producing a secondary battery. [Diagram 5] FIG. 5 is a diagram illustrating the first sealing material 34. As shown in FIG. [Figure 6] FIG. 6 is a diagram illustrating a state where the first sealing material 34 is adhered. [Figure 7] FIG. 7 is a diagram illustrating a state where the first sealing material 34 is adhered. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 1. Structure of secondary batteries First, the structure of a secondary battery 10 according to one embodiment produced by the method for producing a secondary battery of the present disclosure will be described with reference to the drawings. The directions of a three-dimensional orthogonal coordinate system are also shown in the drawings. Here, the xy plane is the horizontal plane, the z direction is the vertical direction, and the side with larger z is the upper side.

[0013] 1 is a schematic external perspective view illustrating the structure of a secondary battery 10. In this embodiment, the secondary battery 10 is a bipolar lithium ion secondary battery. Thus, the secondary battery 10 has a plurality of metallic conductive plates 11 and power storage modules 12, which are alternately stacked and electrically connected to form a series connection. The secondary battery 10 is typically used as a battery for hybrid vehicles, electric vehicles, etc. In addition, in this stack, both ends in the stacking direction (z direction in Figure 1) are conductive plates 11, and a positive terminal (not shown) is connected to the conductive plate 11 at one end in the stacking direction, and a negative terminal (not shown) is connected to the conductive plate 11 at the other end in the stacking direction.

[0014] The electricity storage module 12 is a flat plate-shaped cell as a whole, and has a front and back surface and a side surface 12a that defines a thickness.

[0015] 1.1. Internal structure of energy storage module FIG. 2 is a cross-sectional view showing a schematic internal structure of one electricity storage module 12. The electricity storage module 12 includes an electrode stack formed by stacking a plurality of bipolar electrodes 13, a plurality of sealing bodies 20 provided in each bipolar electrode 13, and a liquid injection section 30 (see FIG. 1) in which an electrolyte is injected. The plurality of bipolar electrodes 13 are stacked in the thickness direction (z direction, thickness direction in a flat plate), and a sealing body 20 is disposed in each bipolar electrode 13.

[0016] 1.1.1. Electrode stack [Bipolar electrode] In the following explanation of each component, the terms "upper surface" and "lower surface" may be used, but in Fig. 2, the "upper surface" refers to the larger side in the z direction, and the "lower surface" refers to the smaller side in the z direction. Although these terms are used for convenience, the "upper surface" can also be referred to as the "first surface" and the "lower surface" as the "second surface." The bipolar electrode 13 includes a current collecting foil 14, a positive electrode active material layer 15 (first active material layer) provided on the lower surface of the current collecting foil 14, a negative electrode active material layer 16 (second active material layer) provided on the upper surface of the current collecting foil 14, and a separator 17.

[0017] The current collector foil 14 is a foil-shaped conductive member, and for example, a metal foil is used. It does not have to be a single-layer metal foil, and may be a clad foil or a laminated foil in which different types of metal foils are laminated. The type of metal is not particularly limited, and for example, a foil in which an aluminum foil and a copper foil are laminated so that the upper surface is an aluminum layer and the lower surface is a copper layer can be mentioned. Other metals include titanium, nickel, stainless steel (for example, SUS304, SUS316, SUS301, etc. specified in JIS G 4305:2015), steel (for example, cold-rolled steel plate (SPCC, etc.) specified in JIS G 3141:2005), etc.

[0018] The positive electrode active material layer 15 constitutes the positive electrode of the bipolar electrode 13, and in this embodiment is disposed on the lower surface of the current collector foil 14 via an adhesive layer such as acetylene black. The positive electrode active material layer 15 can contain a positive electrode active material, a conductive assistant, and a binder. Examples of the positive electrode active material include a composite oxide, metallic lithium, and sulfur. The composition of the composite oxide includes at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Examples of the composite oxide include olivine-type lithium iron phosphate (LiFePO4), LiCoO2, and LiNiMnCoO2. The binder serves to bind the active material or conductive assistant to the surface of the current collector foil 14 and maintain the conductive network in the electrode. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluorine rubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, acrylic resins containing monomer units such as acrylic acid and methacrylic acid, styrene-butadiene rubber (SBR), carboxymethyl cellulose, alginates such as sodium alginate and ammonium alginate, water-soluble cellulose ester crosslinked bodies, and starch-acrylic acid graft polymers. These binders can be used alone or in combination. Examples of the conductive assistant include acetylene black, carbon black, and graphite.

[0019] The negative electrode active material layer 16 constitutes the negative electrode of the bipolar electrode 13, and is disposed on the upper surface of the current collector foil 14 in this embodiment. The negative electrode active material layer 16 may contain a negative electrode active material, a conductive additive, and a binder. The conductive additive and the binder may be considered to be similar to those of the positive electrode active material layer 15. Examples of the negative electrode active material include carbon such as graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, metal compounds, elements capable of being alloyed with lithium or compounds of such elements, boron-doped carbon, etc. Examples of elements capable of being alloyed with lithium include silicon and tin.

[0020] The separator 17 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains the liquid electrolyte, and in this embodiment, is placed on the upper surface of the negative electrode active material layer 16 . Examples of materials constituting the separator 17 include polypropylene, polyethylene, polyolefin, polyester, etc. The separator 17 may have a single-layer structure or a multi-layer structure. The electrolyte absorbed and held in the separator 17 may be, for example, a liquid electrolyte (electrolytic solution) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. When the separator 17 is impregnated with an electrolyte, the electrolyte salt may be a known lithium salt such as LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, or LiN(CF3SO2)2. The non-aqueous solvent may be a known solvent such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, or ethers.

[0021] The current collector foil 14, the positive electrode active material layer 15, the negative electrode active material layer 16, and the separator 17 are configured to have different sizes in a plan view. More specifically, the current collector foil 14 is the largest, the separator 17 is the next largest, the negative electrode active material layer 16 is the next largest, and the positive electrode active material layer 17 is the smallest. As can be seen from FIG. 2, the current collector foil 14, the positive electrode active material layer 15, the negative electrode active material layer 16, and the separator 17 are arranged with their centers aligned in a plan view, and the difference in size is expressed by the degree of protrusion (overhang) of the edges. Therefore, the edge of the current collector foil 14 protrudes the most, and the edges of the separator 14, the negative electrode active material layer 16, and the positive electrode active material layer 15 protrude in this order so as to be inside the current collector foil 14.

[0022] To form the positive electrode active material layer 15 and the negative electrode active material layer 16 on the current collector foil 14, a conventionally known method such as roll coating, die coating, dip coating, doctor blade coating, spray coating, curtain coating, etc. Specifically, an active material, a solvent, and, if necessary, a binder and a conductive assistant are mixed to produce a slurry-like active material layer forming composition, which is then applied to the upper and lower surfaces of the current collector foil 14 and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water.

[0023] [Layer structure of electrode laminate] In the electrode laminate, bipolar electrodes 13 adjacent to each other in the lamination direction (z direction) are laminated such that the positive electrode active material layer 15 of one bipolar electrode 13 and the separator 17 of the other bipolar electrode 13 overlap each other.

[0024] In addition, the electrode laminate has a positive terminal electrode 18 at the upper end and a negative terminal electrode 19 at the lower end of the laminate made of bipolar electrodes 13 in the lamination direction. The positive terminal electrode 18 has a current collecting foil 14 and a positive active material layer 15 provided on the lower surface of the current collecting foil 14, with the positive active material layer 15 laminated to the adjacent bipolar electrode 13 and the current collecting foil 14 laminated on its upper surface. The negative terminal electrode 19 has a current collector 14, a negative electrode active material layer 16 provided on the upper surface of the current collector foil 14, and a separator 17 laminated on the upper surface thereof. The separator 17 is laminated on the adjacent bipolar electrode 13, and the negative electrode active material layer 16 is laminated on its lower surface, and the current collector foil 14 is further laminated on its lower surface. The positive terminal electrode 18 and the negative terminal electrode 19 are each laminated on the conductive plate 11 adjacent to the current collecting foil 14 .

[0025] 1.1.2. Sealed body The sealing body 20 is a member that is disposed on the outer peripheral end of the bipolar electrode 13 to seal the bipolar electrode 13. This also serves to seal the space between adjacent bipolar electrodes 13 in the stacking direction. In this embodiment, the sealing body 20 has a first sealing member 21, a second sealing member 22, and a spacer 23.

[0026] [First sealing member] The first sealing member 21 is a frame-shaped member that is disposed along the outer peripheral end (outer edge) of the bipolar electrode 13. Specifically, as can be seen from Fig. 2, the first sealing member 21 is disposed and joined between the upper surface of the current collecting foil 14 and the lower surface of the separator 17 at the outer peripheral end of the bipolar electrode 13, so that the negative electrode active material layer 16 is disposed within the frame. In this embodiment, a predetermined gap is provided between the inner edge of the first seal member 21 and the negative electrode active material layer 16 to form a space S. On the other hand, the outer edge of the first seal member 21 is configured so that the first seal member 21 protrudes outward beyond the current collector foil 14.

[0027] The first sealing member 21 has electrical insulation properties and can be made of a known material, for example, an electrolyte-resistant resin material such as acid-modified polyethylene (acid-modified PE), acid-modified polypropylene (acid-modified PP), polyethylene, or polypropylene.

[0028] [Second sealing material] The second sealing member 22 is a frame-shaped member that is disposed along the outer peripheral end (outer edge) of the bipolar electrode 13. Specifically, as can be seen from Fig. 2, the second sealing member 22 is disposed and joined between the lower surface of the current collecting foil 14 and the upper surface of the spacer 23 at the outer peripheral end of the bipolar electrode 13, and the positive electrode active material layer 15 is disposed within the frame in combination with the spacer 23. In this embodiment, a predetermined gap is provided between the inner edge of the second seal member 22 and the positive electrode active material layer 15 to form a space S. On the other hand, the outer edge of the second seal member 22 is configured so that the second seal member 22 protrudes outward from the current collector foil 14, and the upper surface of the second seal member 22 and the lower surface of the first seal member 21 are joined together. The material of the second seal member 22 can be considered to be similar to that of the first seal member 21 .

[0029] [Spacer] The spacer 23 is a frame-shaped member that is disposed along the outer peripheral edge of the bipolar electrode 13. Specifically, as can be seen from Fig. 2, the spacer 23 is combined with the second seal member 22 so that the spacer 23 is disposed and joined between the lower surface of the second seal member 22 and the upper surface of the separator 17 of the adjacent bipolar electrode 13 at the outer peripheral edge of the bipolar electrode 13, and the positive electrode active material layer 15 is disposed within the frame. In this embodiment, the inner edge of the spacer member 23 is disposed so as to be spaced apart from the positive electrode active material layer 15. On the other hand, the outer edge of the spacer 23 protrudes outward from the separator 17, and the lower surface of the spacer 23 is joined to the upper surface of the first seal member 21 of the adjacent sealing body 20. The material of the spacer 23 can be considered to be similar to that of the first seal member 21 .

[0030] 1.1.3. Liquid injection section The liquid injection section 30 is formed in a part of the side surface 12a of the electricity storage module 12, and is a section for injecting (pouring) the electrolyte into the interior of the electricity storage module 12. Fig. 3 focuses on one electricity storage module 12 in Fig. 1 and shows an enlarged exploded perspective view (with the sealing material 33 separated) of a section of the side surface 12a where the liquid injection section 30 is arranged.

[0031] In this embodiment, the liquid injection section 30 has a through hole 31 , a liquid injection port forming frame 32 , and a sealant 33 .

[0032] [Through hole] The through hole 31 is a hole formed in the side surface 12a of the power storage module 12, and penetrates the sealing body 30 to communicate the space S with the outside. For example, one through hole 31 can be provided for each bipolar electrode 13, in which case the number of through holes 13 formed corresponds to the number of bipolar electrodes 13 provided. As described above, the multiple bipolar electrodes 13 are stacked and therefore have different positions in the z direction in FIG. 3, and therefore the positions of the through holes 31 in the z direction can also be changed according to the positions of the bipolar electrodes 13.

[0033] In this embodiment, each through hole 31 is a horizontally long slit whose long side extends in a direction surrounding the side surface 12a. This shape is not particularly limited, but the shape of the space S communicated by the through holes 31 is small in the stacking direction of the bipolar electrodes 13 (z direction in FIG. 3) and large in the planar direction (xy plane direction in FIG. 3) by nature, so that the injection of the electrolyte can be efficiently performed by forming the through holes 31 as slits.

[0034] [Pouring hole formation frame] The liquid filling port forming frame 32 is a frame-shaped member and is disposed on the side surface 12a. The liquid filling port forming frame 32 is disposed so as to surround the external opening of the through-hole 31. As a result, a recess 32a is formed as a liquid filling port, the recess 32a being surrounded by the liquid filling port forming frame 32 and having the side surface 12a having the through-hole 31 as a bottom due to the thickness of the liquid filling port forming frame 32 (the size in the y direction in FIG. 3). In addition, a surface 32b of the liquid filling port forming frame 32 opposite to the side in contact with the side surface 12a becomes an adhesive surface with the sealant 33.

[0035] In this embodiment, one pouring port forming frame 32 is provided for each through hole 31, and these are arranged side by side on side surface 12a. However, this is not limited to this, and they may be integrated (an outer frame and a shape in which the inside of the outer frame is partitioned by a plurality of rods).

[0036] [Sealing material] The sealing material 33 is a sheet-like member that is placed over the liquid filling port forming frame 32 so as to cover the recess 32a (liquid filling port) formed by the liquid filling port forming frame 32, and is adhered to the surface 32b. This prevents the injected electrolyte from leaking from the secondary battery 10. The sealing material 33 has certain characteristics from the viewpoint of the manufacturing method described later, and the specific characteristics will be explained when explaining the manufacturing method.

[0037] 2. Manufacturing method of secondary batteries 4 shows a flow of steps in a method S10 for producing a secondary battery according to one embodiment. Each step will be described below.

[0038] 2.1.Liquid injection In the liquid injection step S11, an electrolyte is injected into the bipolar electrode 13. In the liquid injection step S11, for example, the secondary battery 10 before injection (with the sealing material 33 not yet attached) is placed in the chamber, and a liquid supply device is connected to the injection port forming frame 32 that functions as an injection port. The inside of the bipolar electrode 13 is evacuated by a vacuum pump through a vacuum drawing tube with an open valve arranged in the liquid supply device, and the valve is closed to maintain the inside of the chamber in a reduced pressure state. In this state, the valve of the liquid supply tube is opened, and the electrolyte is sent into the bipolar electrode 13 through the recess 32a and the through hole 31, and the electrolyte is injected into the bipolar electrode 13. At this time, the secondary battery 10 can be placed upright (vertically). That is, the secondary battery 10 is injected with the liquid injection section 30 of the secondary battery 10 in the uppermost position (largest side in the z direction) in the xy plane. This allows the liquid injection to be carried out smoothly by the action of gravity, and makes it difficult for the electrolyte to flow back during and after injection.

[0039] 2.2. First Seal In the first sealing step S12, a first sealing material is placed over the liquid pouring port forming frame 32 so as to cover the recess 32a formed by the liquid pouring port forming frame 32, and the first sealing material is bonded to the surface 32b. The bonding method is not particularly limited, but may be, for example, thermal bonding.

[0040] Here, the first sealing material is a resin sheet and has ventilation holes, as described in more detail below. The first sealing material is a sheet made of resin such as polypropylene resin, polyethylene resin, etc. This can improve the thermal adhesiveness.

[0041] Furthermore, the first sealing material has air vents penetrating the front and back of the sheet at positions corresponding to each recess 32a of the liquid injection port forming frame 32. The shape of the air vents is not particularly limited, but it is preferable that the opening area is small, and they can be slits or small holes. Fig. 5 shows perspective views of several examples of the first sealing material 34. Fig. 5(a) shows an example in which the first sealing material 34 is provided with a cross-shaped vent hole 34a, Fig. 5(b) shows an example in which the first sealing material 34 is provided with a straight slit vent hole 34a, Fig. 5(c) shows an example in which the straight slit vent hole 34a is provided in a different direction from that in Fig. 5(b), and Fig. 5(d) shows an example in which the small circular vent hole 34a is provided.

[0042] Fig. 6 shows a diagram for explaining a scene in which the first sealing material 34 having the vent hole 34a shown in Fig. 5(b) is placed on the liquid injection port forming frame 32. Fig. 6(a) is a perspective view, and Fig. 6(b) is a view of the side surface 12a as seen from the front. In Figs. 6(a) and 6(b), the parts hidden by the first sealing material 34 are shown by dotted lines. As can be seen from FIGS. 6(a) and 6(b), the vent holes 34a are provided for each of the recesses 32a of the liquid injection hole forming frame 32.

[0043] In this embodiment, the ventilation hole 34a is arranged so that the through hole 31 and the ventilation hole 34a do not overlap when the side surface 12a, which is the surface on which the through hole 31 is provided, is viewed from the front. That is, the ventilation hole 34a of the first sealing material 34 is formed at a position that does not overlap the through hole 31 in the normal direction of the side surface 12a, which is the surface on which the through hole 31 is provided. According to this, even if the electrolyte flows back and out of the through hole 31 during the subsequent initial charging step S13, the electrolyte can be prevented from directly reaching the air hole 34a, and spillage of the electrolyte can be more reliably prevented.

[0044] Furthermore, when the subsequent initial charging step S13 is performed in a horizontal position (the position shown in FIG. 1), the air vent 34a may be positioned above the through hole 31 when viewed facing forward with the side surface 12a, on which the through hole 31 is provided, as shown in FIG. 7. According to this, even if the electrolyte flows back and out of the through hole 31 during subsequent initial charging step S13, the electrolyte will flow downward due to gravity and will be prevented from reaching the air vent 34a located above, making it possible to more reliably prevent the electrolyte from spilling.

[0045] 2.3. First charge After the first sealing step S12 is performed, the initial charging step S13 is performed. The conditions for the initial charging (first charging) are not particularly limited and are as known in the art. In the initial charging step S13, gas may be generated by charging, and a part of the electrolyte may flow back and out. Even if this occurs, according to the present disclosure, the first sealing material 34 can release the gas through the ventilation hole 34a while preventing the electrolyte from leaking to the outside. That is, by performing the first sealing with the first sealing material 34 having the ventilation hole 34a, it is possible to prevent adhesion of the electrolyte to the outer surface of the first sealing material 34 (the joint with the subsequent second sealing material) while allowing gas generated during the initial charging to escape, and to prevent poor bonding with the second sealing material in the subsequent second sealing step S15.

[0046] The initial charging may be performed in either a vertical position (the position explained in the liquid injection step S11) or a horizontal position (the position shown in FIG. 1). In addition, if the vent hole 34a is not provided, degassing is required to reduce the pressure inside the bipolar electrode 13 that has risen after the initial charge, but in this embodiment, degassing is already performed by the vent hole 34a, so degassing is not necessarily required again. However, this is not the only option, and degassing can be further promoted by, for example, reducing the pressure.

[0047] 2.4. High-temperature aging Next, a high-temperature aging step S14 is performed. The high-temperature aging step S14 is a known procedure, for example, the secondary battery 10 is allowed to stand at 65° C. for 15 hours for acclimatization. Note that, in the high-temperature aging step S14, gas generation and outflow due to backflow of the electrolyte may occur as in the initial charging step S13, so the first sealing material 34 acts in the same manner as above.

[0048] 2.5. Secondary Seal Next, the final sealing is performed in the second sealing step S15. In the second sealing step S15, the second sealing material is laminated on the first sealing material and bonded. The bonding method is not particularly limited, but may be, for example, thermal bonding. That is, the above-mentioned sealing material 33 is formed by a laminate of the first sealing material and the second sealing material.

[0049] Here, the second sealing material is not particularly limited, but may be an aluminum resin laminate foil sheet. That is, an aluminum foil is coated with a polypropylene resin or a polyethylene resin. From the viewpoint of adhesion to the first sealing material, it is preferable that the resin of the second sealing material is the same material as the resin of the first sealing material. The second sealing material does not have any ventilation holes.

[0050] 2.6. Cooling In the cooling step S16, the temperature increased in the high temperature aging step S14 is lowered to cool the product. The cooling method is not particularly limited, and may be natural cooling or forced cooling. [Explanation of symbols]

[0051] REFERENCE SIGNS LIST 10: secondary battery, 11: conductive plate, 12: power storage module, 13: bipolar electrode, 20: sealing portion, 30: liquid injection portion, 31: through hole, 32: liquid injection port forming frame, 33: sealing material, 34: first sealing material

Claims

1. A method for manufacturing a secondary battery containing an electrolyte solution therein, comprising the steps of: a liquid injection step of injecting an electrolyte solution into the secondary battery through a through hole; a first sealing step of sealing at least a part of the through hole with a first sealing material made of a resin having an air hole, after the liquid injection step; an initial charging step of initially charging the secondary battery after the first sealing step; and a second sealing step of bonding a second sealing material to the first sealing material after the initial charging step. A method for manufacturing a secondary battery.

2. The method for manufacturing a secondary battery according to claim 1 , wherein the vent hole of the first sealing material is formed at a position not overlapping with the through hole in a normal direction of a surface on which the through hole is provided.

3. The method for manufacturing a secondary battery according to claim 1 , wherein in the initial charging step, the vent hole is positioned upward from the center.

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