Method for manufacturing battery and battery

Abstract

To suppress generation of deformation or breakage when an electrolyte is injected from a liquid injection hole of a battery.SOLUTION: The battery includes: a liquid injection hole 32 for injecting an electrolyte into an electrode; and a through-hole 33 leading to the liquid injection hole 32. The through-hole 33 extends in a direction in which electrodes are stacked.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a battery and a battery.

Background Art

[0002] Patent Document 1 discloses that a liquid injection port is provided at the end of a bipolar battery by injection molding.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When injecting the electrolytic solution from the liquid injection port, applying a pressing force to the liquid injection frame formed to surround the liquid injection port to ensure sealing property may cause a load on the electrode and deformation or the like. To avoid this, further applying a force to restrain the liquid injection frame may cause excessive force on the liquid injection frame, resulting in damage or deformation of the liquid injection frame.

[0005] Therefore, an object of the present disclosure is to provide a method for manufacturing a battery that can suppress deformation and damage during injection of the electrolytic solution from the liquid injection hole of the battery. Also, a battery for that purpose is provided.

Means for Solving the Problems

[0006] Although details will be described later, as a result of intensive studies, the inventor has considered that in order to ensure the sealing property of the electrolytic solution during injection of the electrolytic solution, since there is a concern that deformation or the like may occur in the electrode because it is pressed from a direction intersecting the stacking direction of the battery during injection, it is conceived to ensure the sealing property by pressing from a direction different from that direction during injection, and means therefor have been embodied.

[0007] This application discloses a method for manufacturing a battery in which a plurality of electrodes are stacked, the method having a liquid injection step of supplying an electrolytic solution through an insertion hole that leads to a liquid injection hole for injecting the electrolytic solution into the electrodes, the insertion hole extending in a direction along the direction in which the plurality of electrodes are stacked, and inserting a device for injecting the electrolytic solution into the insertion hole to supply the electrolytic solution to the liquid injection hole.

[0008] This application also discloses a battery in which a plurality of electrodes are stacked, the battery having a liquid injection hole for injecting an electrolytic solution into the electrodes and an insertion hole that leads to the liquid injection hole, the insertion hole being a hole that extends in a direction along the direction in which the plurality of electrodes are stacked.

[0009] The insertion hole may be in the shape of a frustum of a cone whose diameter decreases toward the liquid injection hole.

Advantages of the Invention

[0010] According to the present disclosure, since it is not necessary to apply a force that presses the electrodes in order to ensure sealing performance when injecting the electrolytic solution, it is possible to suppress the occurrence of deformation and breakage of the electrodes. Further, since it is not necessary to apply another force (for example, a restraining force) to the liquid injection part in order to suppress deformation and breakage of the electrodes, it is possible to suppress the occurrence of deformation and breakage also in the liquid injection part.

Brief Description of the Drawings

[0011]

Figure 1

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DETAILED DESCRIPTION OF THE INVENTION

[0012] 1. Structure of the battery First, the structure of the secondary battery 10 according to one example of the present disclosure will be described with reference to the drawings. The drawings also show the directions of the three-dimensional orthogonal coordinate system. Here, the xy plane is the horizontal plane, the z-axis direction is the vertical direction, and the larger the z value, the higher.

[0013] FIG. 1 is a schematic external perspective view for explaining the structure of the 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 metal conductive plates 11 and power storage modules 12, respectively, and these are alternately stacked and electrically connected to form a series connection. The secondary battery 10 is typically used for batteries such as hybrid vehicles and electric vehicles. In addition, both ends in the stacking direction (the z-axis direction in FIG. 1) of the stacking are conductive plates 11. A positive electrode terminal (not shown) is connected to the conductive plate 11 at one end in the stacking direction, and a negative electrode terminal (not shown) is connected to the conductive plate 11 at the other end in the stacking direction.

[0014] The power storage module 12 is a flat single battery as a whole, having front and back surfaces and side surfaces 12a forming a thickness.

[0015] 1.1. Internal structure of the power storage module FIG. 2 shows a cross-sectional view schematically showing the internal structure of one power storage module 12 with attention focused thereon. In this embodiment, the power storage module 12 includes an electrode laminate L formed by laminating a plurality of bipolar electrodes 13, a plurality of sealing members 20 provided on each bipolar electrode 13, and a liquid injection portion 30 (see FIG. 1) which is a portion for injecting an electrolytic solution. The plurality of bipolar electrodes 13 are laminated along the thickness direction (z-axis direction, the thickness direction in the flat plate shape), and the sealing members 20 are arranged on each bipolar electrode 13.

[0016] 1.1.1. Electrode laminate [Bipolar electrode] Hereinafter, in the description of each member, there may be descriptions of "upper surface" and "lower surface". In FIG. 2, the "upper surface" means the larger side in the z-axis direction, and the "lower surface" means the smaller side in the z-axis direction. Although described in this way for convenience, the "upper surface" can be rephrased as "first surface" and the "lower surface" as "second surface". The bipolar electrode 13 includes a current collector foil 14, a positive electrode active material layer 15 (first active material layer) provided on the lower surface of the current collector foil 14, and a negative electrode active material layer 16 (second active material layer) provided on the upper surface of the current collector foil 14.

[0017] The current collector foil 14 is a foil-shaped conductive member, and for example, a metal foil is used. It does not need to be a single-layer metal foil, and a clad foil or a laminated foil in which different metal foils are laminated may be used. The type of metal is not particularly limited. 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. defined in JIS G 4305:2015), steel (for example, cold-rolled steel sheet (SPCC, etc.) defined 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, it is arranged 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 include a positive electrode active material, a conductive assistant, and a binder. The positive electrode active material includes, for example, composite oxides, lithium metal, sulfur, etc. The composition of the composite oxide includes, for example, at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Examples of the composite oxide include olivine-type lithium iron phosphate (LiFePO 4 ), LiCoO 2 , LiNiMnCoO 2 , etc. The binder serves to fasten the active material or the 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 fluororubber, 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 cross-linked products, starch-acrylic acid graft polymers, etc. These binders can be used alone or in combination. Examples of the conductive assistant include acetylene black, carbon black, graphite, etc.

[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 can contain a negative electrode active material, a conductive assistant, and a binder. The conductive assistant and the binder can be considered in the same way as 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 alloyable with lithium or compounds of the elements, boron-added carbon, etc. Examples of the elements alloyable with lithium include silicon and tin.

[0020] [Separator] A separator 17 is disposed between adjacent bipolar electrodes 13. The separator 17 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and holds a liquid electrolyte, and in this embodiment, is disposed between the positive electrode active material layer 15 and the negative electrode active material layer 16 of the electrodes adjacent in the z-axis direction. Examples of the material constituting the separator 17 include polypropylene, polyethylene, polyolefin, polyester, and the like. The separator 17 may have a single-layer structure or a multilayer structure. Examples of the electrolyte absorbed and held by the separator 17 include a liquid electrolyte (electrolyte 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, as the electrolyte salt, LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiCF3SO 3 , LiN(FSO 2 ) 2 , LiN(CF 3 SO 2 ) 2 and other known lithium salts can be used. Also, as the non-aqueous solvent, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers can be used.

[0021] [Sizes of each layer, etc.] 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 plan view. More specifically, the current collector foil 14 is the largest, followed by the separator 17, then the negative electrode active material layer 16, 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 plan view, and the difference in size appears in the degree of edge protrusion (overhang). 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 from the inside.

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

[0023] [Laminated Structure of Electrode Stack] In the electrode stack L, the bipolar electrodes 13 adjacent to each other in the stacking direction (z-axis direction) of the electrodes are stacked so as to overlap with a separator 17 interposed between the positive electrode active material layer 15 of one bipolar electrode 13 and the negative electrode active material layer 16 of the other bipolar electrode 13. Here, the size of the electrode stack L in plan view (size in the xy plane direction) is not particularly limited, but it may be a large electrode stack L such as 1 m × 1 m.

[0024] In addition, the electrode stack L has a positive terminal electrode 18 at the upper end and a negative terminal electrode 19 at the lower end at the stacking direction end of the stack formed by the bipolar electrodes 13. The positive terminal electrode 18 has the current collector foil 14 and the positive electrode active material layer 15 provided on the lower surface of the current collector foil 14. A separator 17 is interposed between the positive electrode active material layer 15 of the positive terminal electrode 18 and the negative electrode active material 16 of the adjacent bipolar electrode 13. The negative terminal electrode 19 has the current collector foil 14 and the negative electrode active material layer 16 provided on the upper surface of the current collector foil 14. A separator 17 is interposed between the negative electrode active material layer 16 of the negative terminal electrode 19 and the positive electrode active material layer 15 of the adjacent bipolar electrode 13. A conductive plate 11 is laminated on the current collector foil 14 of the positive terminal electrode 18 and the negative terminal electrode 19.

[0025] 1.1.2. Sealing Body The sealing body 20 is a member that seals the bipolar electrode 13 by being disposed at the outer peripheral end of the bipolar electrode 13. Accordingly, the sealing body 20 also seals between the bipolar electrodes 13 adjacent to each other in the stacking direction. In this embodiment, the sealing body 20 includes a first seal member 21, a second seal member 22, and a spacer 23.

[0026] [First Seal Member] The first seal member 21 is a frame-shaped member, and is disposed along the outer peripheral end (outer edge) of the bipolar electrode 13. Specifically, as can be seen from FIG. 2, the first seal member 21 is disposed and joined between the upper surface of the current collector foil 14 and the lower surface of the spacer 23 at the outer peripheral end of the bipolar electrode 13, so that the negative electrode active material layer 16 is disposed within its frame. In this embodiment, a predetermined interval is provided between the inner edge of the first seal member 21 and the negative electrode active material layer 16, and a space S is formed. On the other hand, the outer edge of the first seal member 21 is configured such that the first seal member 21 protrudes outside the current collector foil 14. In this embodiment, the peripheral edge of the separator 17 is welded and fixed to the first seal member 21.

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

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

[0029] [Spacer] The spacer 23 is a frame-shaped member, which is arranged along the outer peripheral end of the bipolar electrode 13. Specifically, as can be seen from FIG. 2, the spacer 23 is arranged between the first sealing member 21 and the second sealing member 22. By joining the adjacent first sealing member 21, spacer 23, and second sealing member, the space S of each cell is sealed. In this embodiment, the inner edge of the spacer 23 is arranged at a distance from the positive electrode active material layer 15 and the negative electrode active material layer 16. The outer edge of the spacer 23 protrudes outward from the edge of the current collector foil 14, and its outer edge is joined to the first sealing member 21 and the second sealing member 22 of the adjacent sealing body 20. The material of the spacer 23 can be considered in the same way as that of the first sealing member 21.

[0030] 1.1.3. Liquid injection part The liquid injection part 30 is formed on a part of the side surface 12a of the power storage module 12, and is a part for injecting (injecting liquid) the electrolytic solution into the power storage module 12. FIG. 3 shows an exploded perspective view (with the sealing material 34 separated and shown) of the part of the side surface 12a of one power storage module 12 in FIG. 1 where the liquid injection part 30 is arranged, enlarged. Also, to show the internal structure of the liquid injection part 30, FIG. 4 shows a cross-sectional view along the A-A line parallel to the x-axis in FIG. 3 (the resin film 34 is not separated), FIG. 5(a) shows a cross-sectional view along the B-B line in FIG. 4, and FIG. 5(b) shows a cross-sectional view along the C-C line in FIG. 4.

[0031] In this embodiment, the liquid injection part 30 has a main body 31, a liquid injection hole 32, an insertion hole 33, and a sealing material 34.

[0032] ["Main body"] The main body 31 is a member that forms the main body of the liquid injection part 30. A liquid injection hole 32 and an insertion hole 33 are formed here, and it is in a block shape. In this embodiment, the main body 31 is a rectangular parallelepiped, but it is not limited to this and can be set to an appropriate required shape as needed.

[0033] ["Liquid injection hole"] The liquid injection hole 32 is formed on the side surface 12a of the power storage module 12, and is a hole that penetrates the sealing body 20 and communicates the space S of the electrode laminate L with the outside. For example, one liquid injection hole 32 can be provided for one bipolar electrode 13. In that case, the number of liquid injection holes 32 corresponding to the number of bipolar electrodes 13 provided is formed. As described above, since the plurality of bipolar electrodes 13 are laminated and the positions in the z-axis direction in FIG. 4 are different, the position of the liquid injection hole 32 in the z-axis direction is also changed according to the position of the bipolar electrode 13 (in this embodiment, as an example, five liquid injection holes 32 arranged in the x-axis direction are provided).

[0034] In this embodiment, each liquid injection hole 32 is a horizontally long slit with a long side extending in the direction of going around the side surface 12a. This shape is not particularly limited, but since the shape of the space S communicated with the liquid injection hole 32 is small in the lamination direction of the bipolar electrode 13 (the z-axis direction in FIG. 3) and large in the plane direction (the xy plane direction in FIG. 3) due to its nature, by making the liquid injection hole 32 a slit, the injection of the electrolytic solution can be efficiently performed.

[0035] ["Insertion hole"] The insertion hole 33 is a hole into which the supply part 40 (see FIGS. 7 and 8) of the liquid supply device that supplies the electrolytic solution is inserted. The insertion hole 33 is a hole extending in the direction (z-axis direction) in which the electrodes of the electrode laminate L are laminated, and one end thereof is open at the end of the main body 31 in the z-axis direction. And the insertion hole 33 communicates with the liquid injection hole 32, and the electrolytic solution supplied to the insertion hole 33 flows into the liquid injection hole 32 and is finally injected into the electrode. As a result, as will be described later, when injecting the electrolytic solution, a force may be applied to insert the insertion portion 40 of the liquid supply device in the stacking direction of the electrode laminate L, and almost no pressing force is applied in a direction intersecting the stacking direction of the electrode laminate L (the direction of pressing the electrode laminate L in the y-axis direction). Therefore, deformation of the electrode laminate L can be suppressed, and since no other restraining member that applies a restraining force to the liquid injection portion 30 is required, no unnecessary force is applied, and the occurrence of deformation and damage to the liquid injection portion 30 can also be suppressed.

[0036] The shape of the insertion hole 33 is not particularly limited, but it is preferably columnar with an axis parallel to the stacking direction (z-axis direction) of the electrodes of the electrode laminate L. From the viewpoint of enhancing the sealing property, it is more preferably a part of a cone (truncated cone) whose diameter decreases toward the communication portion with the liquid injection hole 32 from the opening. Note that the depth of the insertion hole 33 can be appropriately adjusted according to the position of the liquid injection hole 32.

[0037] [Sealing material] The sealing material 34 is a sheet-like sealing material, which is placed on the main body 31 so as to close the opening of the insertion hole 33 formed on the surface of the main body 31 and is welded to the main body 31. Thereby, leakage of the injected electrolytic solution from the secondary battery 10 is prevented. The sealing material 34 may be formed of a known sheet. For example, an aluminum laminate sheet having a layer structure in which an aluminum foil is covered with a resin is typical.

[0038] 2. Manufacturing method of secondary battery The secondary battery 10 can be manufactured, for example, by a manufacturing method S10 as shown in the flow in FIG. 6. As can be seen from FIG. 6, the manufacturing method S10 of the secondary battery includes a liquid injection step S11, a first charging step S12, a high-temperature aging step S13, and a sealing step S14. Details will be described below.

[0039] 2.1. Liquid injection step In the electrolyte injection step S11, an electrolyte is injected into the bipolar electrode 13. FIGS. 7 and 8 show diagrams for explanation. FIG. 7 is a view from the same perspective as FIG. 4, FIG. 8(a) is a view from the same perspective as FIG. 5(a), and FIG. 8(b) is a view from the same perspective as FIG. 5(b).

[0040] In the electrolyte injection step S11, before injecting the electrolyte into the secondary battery 10 (the sealing material 34 is not welded), the supply part 40 of the liquid supply device is arranged so as to be inserted into the insertion hole 33 of the main body 31 of the liquid injection part 30. Here, a sealing material 41 such as an O-ring is arranged on the outer periphery of the supply part 40, and the sealing property is ensured by the sealing material 41 coming into contact with the inner surface of the insertion hole 33. Therefore, the sealing material 41 is preferably made of a material with a low elastic modulus, more preferably a viscoelastic material such as rubber.

[0041] In this way, the sealing property during the injection of the electrolyte can be ensured by the supply part 40. Conventionally, as schematically shown in FIG. 9, when pressing the jig of the liquid supply device having a supply hole for supplying the electrolyte against the liquid injection part, a force F1 is applied in the direction toward the electrode laminate L in order to ensure the sealing property. Therefore, it can also exert a pressing force on the electrode laminate L, and there is concern about the influence (such as deformation) on the electrode laminate L. In addition, in order to mitigate the influence of this force F1 on the electrode laminate L, when a force F2 is applied to restrain the liquid injection part, depending on the magnitude of the force F2, there is a risk of deforming or damaging the liquid injection part due to this force.

[0042] On the other hand, according to the present disclosure, since the insertion hole 33 faces the stacking direction (z-axis direction) of the electrodes of the electrode laminate L, even if the supply part 40 is inserted into the insertion hole 33 and the sealing property with the supply part 40 is ensured, almost no force is applied toward the electrode laminate L. Thereby, the influence exerted on the electrode laminate L can be reduced, and deformation and the like of the electrode laminate can be suppressed. Furthermore, according to this, since there is no need to apply a force (such as the force F2 in FIG. 9) to restrain the liquid injection part, there is no risk of deforming or damaging the liquid injection part 30.

[0043] With the supply unit 40 arranged in the insertion hole 33 as described above, a vacuum pump draws a vacuum through the vacuum suction pipe with the valve arranged in the liquid supply device via the supply unit, for example, as indicated by the arrow P in Fig. 8(a) within the bipolar electrode 13. Then the valve is closed to maintain a reduced pressure state. With the valve of the liquid supply pipe opened in that state, the electrolytic solution is discharged from the liquid supply unit 40 and fed into the bipolar electrode 13 from the liquid injection hole 32, for example, as indicated by the arrow Q in Fig. 8(b), and the electrolytic solution is injected into the bipolar electrode 13.

[0044] 2.2. Initial charging process In the initial charging process S12, the first charging is performed. The conditions of the initial charging process are as known and not particularly limited.

[0045] 2.3. High-temperature aging process Next, the high-temperature aging process S13 is performed. The process of high-temperature aging is as known. For example, the secondary battery 10 is conditioned by a procedure such as leaving it standing at 65°C for 15 hours.

[0046] 2.4. Sealing process In the sealing process S14, the sealing material 34 is placed over the main body 31 so as to cover the opening of the insertion hole 33, and the sealing material 34 is welded to the surface of the main body 31. The welding method is not particularly limited, and examples include pressing a heating body and irradiating with a laser.

Explanation of reference numerals

[0047] 10… Secondary battery, 11… Conductive plate, 12… Power storage module, 13… Bipolar electrode, 20… Sealing portion, 30… Liquid injection portion, 31… Main body, 32… Liquid injection hole, 33… Insertion hole, 34… Sealing material

Claims

1. A method for manufacturing a battery in which a plurality of electrodes are stacked, comprising: a liquid injection step of supplying an electrolytic solution through an insertion hole communicating with a liquid injection hole for injecting the electrolytic solution into the electrode; wherein the insertion hole extends in a direction along the direction in which the plurality of electrodes are stacked, and a device for injecting the electrolytic solution into the insertion hole is inserted to supply the electrolytic solution to the liquid injection hole; A method for manufacturing a battery.

2. A battery in which a plurality of electrodes are stacked, comprising: a liquid injection hole for injecting an electrolytic solution into the electrode; an insertion hole communicating with the liquid injection hole; wherein the insertion hole is a hole extending in a direction along the direction in which the plurality of electrodes are stacked; A battery.

3. The battery according to claim 2, wherein the insertion hole has a frustum shape with a diameter decreasing toward the liquid injection hole.

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