Method for manufacturing cylindrical battery

Abstract

This method for manufacturing a cylindrical battery comprises the steps for: accommodating an electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween in a bottomed cylindrical outer can (20); and electrically connecting the negative electrode to the outer can (20) so that the electrode body cannot be detached from the outer can (20), and then reducing the outer diameter of an opening end (20B) of the outer can (20) with the opening of the outer can (20) facing downward in the vertical direction. According to the method for manufacturing a cylindrical battery of the present disclosure, an increase in weight can be suppressed while increasing the capacity, and a cylindrical battery in which foreign matter is less likely to be mixed into the outer can can be manufactured.

Description

Cylindrical battery manufacturing method

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

[0002] In the case of a large, high-capacity cylindrical battery, the diameter of the outer can is large, which necessitates a larger diameter of the sealing body. Increasing the diameter of the sealing body also necessitates an increase in the crimping force when crimping the sealing body to the outer can and an increase in the sealing body's durability against external impacts, which in turn necessitates an increase in the thickness of the sealing body.

[0003] Increasing the thickness of the sealing body increases the weight of the sealing body, which leads to an increase in the weight of the cylindrical battery. Patent Document 1 discloses a cylindrical battery that achieves high capacity while suppressing weight increase by making the outer diameter of the open end of the outer can that houses the sealing body smaller than the outer diameter of the body part that houses the electrode assembly.

[0004] International Publication No. 2021 / 124813

[0005] When manufacturing the cylindrical battery, it is necessary to narrow the open end of the outer can to make the outer diameter of the open end smaller than the outer diameter of the body. However, there is a risk that foreign matter such as chips generated by narrowing the open end of the outer can may become mixed into the outer can, degrading battery performance. Therefore, an object of the present disclosure is to provide a method for manufacturing a cylindrical battery that can produce a cylindrical battery that can increase capacity while suppressing weight increase, and that is less likely to cause foreign matter to become mixed into the outer can.

[0006] In order to solve the above problems, the manufacturing method of a cylindrical battery according to the present disclosure includes the steps of: accommodating an electrode body in which a first electrode and a second electrode are wound with a separator interposed therebetween, in a cylindrical outer can with a bottom; electrically connecting the first electrode to the outer can so that the electrode body cannot be removed from the outer can; and then reducing the outer diameter of the open end of the outer can with the opening of the outer can facing vertically downward.

[0007] According to the manufacturing method of a cylindrical battery according to the present disclosure, it is possible to manufacture a cylindrical battery that has a high capacity while suppressing an increase in weight, and furthermore, foreign matter is less likely to become mixed into the outer can.

[0008] Fig. 1 is an axial cross-sectional view of a cylindrical battery that can be manufactured by a manufacturing method for a cylindrical battery according to an embodiment of the present disclosure; Fig. 2 is an axial cross-sectional view of the cylindrical battery, with illustration of the internal structure omitted; Fig. 3 is a flow diagram showing the steps of an example of a manufacturing method for the cylindrical battery; Fig. 4 is a diagram illustrating an example of a method for fixing an upper insulating plate to an electrode body; Fig. 5 is a diagram illustrating an example of a method for reducing the diameter of an outer can; Fig. 6 is a diagram illustrating a part of the manufacturing process for the cylindrical battery.

[0009] Embodiments of the present disclosure will be described below using the drawings. The shapes, materials, and quantities described below are illustrative examples and can be changed as appropriate depending on the specifications of the cylindrical battery. In the following, equivalent elements will be denoted by the same reference numerals in all drawings. In this specification, the sealing body 30 side in the axial direction (height direction) of the cylindrical battery 10 will be referred to as "upper," and the bottom side of the outer can 16 in the axial direction will be referred to as "lower." Of the components described below, those not recited in the independent claims representing the highest concept are optional components and are not essential components. First, a cylindrical battery 10 that can be manufactured using a cylindrical battery manufacturing method according to one embodiment of the present disclosure will be described using FIG. 1 . FIG. 1 is an axial cross-sectional view of the cylindrical battery 10.

[0010] 1 , cylindrical battery 10 includes an electrode assembly 14, an electrolyte (not shown), and an outer can 20 that houses the electrode assembly 14 and the electrolyte. Electrode assembly 14 includes a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which positive electrode 11 and negative electrode 12 are spirally wound with separator 13 interposed therebetween. Outer can 20 has a cylindrical shape with a bottom and an open top, and the opening of outer can 20 is closed by a sealing body 30.

[0011] The positive electrode 11 includes a positive electrode current collector and a positive electrode composite layer formed on at least one surface of the current collector. The positive electrode current collector can be a foil of a metal, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on the surface. The positive electrode composite layer preferably contains a positive electrode active material, a conductive material, such as acetylene black, and a binder, such as polyvinylidene fluoride, and is formed on both surfaces of the positive electrode current collector. For example, a lithium-containing transition metal composite oxide is used as the positive electrode active material. The positive electrode 11 can be manufactured by applying a positive electrode composite slurry containing a positive electrode active material, a conductive material, a binder, etc., onto the positive electrode current collector, drying the coating, and then compressing the coating to form a positive electrode composite layer on both surfaces of the positive electrode current collector.

[0012] The negative electrode 12 includes a negative electrode current collector and a negative electrode composite layer formed on at least one surface of the current collector. The negative electrode current collector can be a foil of a metal, such as copper or a copper alloy, that is stable within the potential range of the negative electrode 12, or a film with such a metal disposed on the surface. The negative electrode composite layer contains a negative electrode active material and a binder, such as styrene-butadiene rubber (SBR), and is preferably formed on both surfaces of the negative electrode current collector. Examples of the negative electrode active material include graphite and silicon-containing compounds. The negative electrode 12 can be manufactured by applying a negative electrode composite slurry containing a negative electrode active material and a binder, drying the coating, and then rolling the coating to form a negative electrode composite layer on both surfaces of the current collector.

[0013] The electrolyte may be, for example, a non-aqueous electrolyte. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous solvent may be, for example, an ester, an ether, a nitrile, an amide, or a mixed solvent of two or more of these. The non-aqueous solvent may contain a halogen-substituted compound in which at least a portion of the hydrogen atoms in these solvents are substituted with halogen atoms such as fluorine. The non-aqueous electrolyte is not limited to a liquid electrolyte, but may also be a solid electrolyte. The electrolyte salt may be, for example, LiPF ６ The type of electrolyte is not particularly limited, and may be an aqueous electrolyte.

[0014] The cylindrical battery 10 includes an upper insulating plate 18 disposed above the electrode body 14 (closer to the sealing body 30) and a lower insulating plate 19 disposed below the electrode body 14 (at the bottom). The upper insulating plate 18 and the lower insulating plate 19 are plate-shaped. The upper insulating plate 18 includes a base material 36 and an adhesive layer 38 fixed to the lower surface of the base material 36. The adhesive layer 38 is fixed to the upper end surface of the electrode body 14.

[0015] 1 , the positive electrode lead 15 attached to the positive electrode 11 passes through a through-hole in the upper insulating plate 18 and extends toward the sealing body 30, and the negative electrode lead 16 attached to the negative electrode 12 passes outside the lower insulating plate 19 and extends toward the bottom side of the outer can 20. The positive electrode lead 15 is connected by welding or the like to the underside of an internal terminal plate 31 which is the bottom plate of the sealing body 30, and a cap 35 which is the top plate of the sealing body 30 and is electrically connected to the internal terminal plate 31 serves as a positive electrode external terminal. The negative electrode lead 16 is connected by welding or the like to the inner bottom surface of the outer can 20, and the outer can 20 serves as a negative electrode external terminal.

[0016] The outer can 20 is a cylindrical metal container with a bottom. A gasket 39 is provided between the outer can 20 and the sealing body 30 to ensure airtightness inside the battery. The outer diameter of the open end 20B of the outer can 20, which houses the sealing body 30, is smaller than the outer diameter of the body portion 20A of the outer can 20, which houses the electrode assembly 14. A grooved portion 20C is formed near the open end 20B of the outer can 20, where a portion of the side surface protrudes inward and supports the sealing body 30. The grooved portion 20C is formed in an annular shape along the circumferential direction of the outer can 20 and supports the sealing body 30 on its upper surface. The upper insulating plate 18 is disposed below the grooved portion 20C. The outer diameter of the upper insulating plate 18 is larger than the inner diameter of the open end 20B. The sealing body 30 supported by the grooved portion 20C is disposed within the open end 20B and fixed to the outer can 20 by crimping the outer can 20 to the sealing body 30.

[0017] The sealing body 30 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 31, a lower valve body 32, an insulating member 33, an upper valve body 34, and a cap 35 are stacked. The components constituting the sealing body 30 are, for example, disk-shaped or ring-shaped, and all components except for the insulating member 33 are electrically connected to each other. The lower valve body 32 and the upper valve body 34 are connected to each other at their respective centers, and the insulating member 33 is interposed between their respective peripheral edges. When the internal pressure of the battery increases due to abnormal heat generation, the lower valve body 32 deforms and breaks, pushing the upper valve body 34 toward the cap 35, thereby interrupting the current path between the lower valve body 32 and the upper valve body 34. When the internal pressure further increases, the upper valve body 34 breaks, and gas is discharged through the vent hole 35A of the cap 35.

[0018] The outer can 20 and the sealing body 30 will be described in more detail using Figure 2. Figure 2 is an axial cross-sectional view of the cylindrical battery 10, with the internal structure not shown. As described above, the outer can 20 is a cylindrical metal container with a bottom that houses the electrode assembly 14 (see Figure 1) and electrolyte and is open at the top. As described above, the outer diameter of the open end 20B of the outer can 20 (φB in the figure) is smaller than the outer diameter of the body portion 20A (φA in the figure).

[0019] The body portion 20A is a portion of the exterior can 20 that is sandwiched between the bottom and the lower surface of the grooved portion 20C, and is a portion that houses the electrode assembly 14. The body portion 20A is formed in a cylindrical shape. The outer diameter of the body portion 20A is, for example, 20 mm or more and 35 mm or less.

[0020] The opening end 20B is a portion sandwiched between the shoulder portion of the outer can 20 and the upper surface of the grooved portion 20C, and is a portion that accommodates the sealing body 30. The opening end 20B is formed in a cylindrical shape. The outer diameter of the opening end 20B is, for example, 2% or more smaller than the outer diameter of the body portion 20A and 10% or less smaller than the outer diameter of the body portion 20A. In other words, the outer diameter of the opening end 20B is, for example, 90% or more and 98% or less of the outer diameter of the body portion 20A. The sealing body 30 is fixed to the opening end 20B of the outer can 20 by crimping. A gasket 39 is provided between the outer can 20 and the sealing body 30 to ensure the sealing of the interior of the outer can 20. The sealing body 30 has an outer diameter that corresponds to the inner diameter of the opening end 20B of the outer can 20.

[0021] In cylindrical batteries in which the body and open end have roughly the same outer diameter, increasing the battery size to increase capacity requires increasing the outer diameter of the open end as well as the body. However, if the outer diameter of the sealing body is also increased to match the open end, the sealing body will not have sufficient crimping force when crimping it to the outer can or will not be strong enough to withstand external impacts, so the sealing body must also be made thicker.

[0022] Increasing the thickness of the sealing body requires increasing the thickness of one or more components that make up the sealing body, such as the internal terminal plate, lower valve body, insulating member, upper valve body, or cap, which increases manufacturing costs. Furthermore, the increased weight of the sealing body increases the weight of the cylindrical battery. Furthermore, the increased thickness of the sealing body reduces the battery capacity by the amount of the increase in thickness.

[0023] In contrast, the cylindrical battery 10 described above can use a sealing body 30 with a diameter corresponding to the outer diameter of the open end 20B, which is smaller than the outer diameter of the body portion 20A. This not only allows an electrode body 14 with a larger outer diameter and filled with more active material to be accommodated in the body portion 20A with a larger outer diameter, but also prevents weight gain and capacity loss of the cylindrical battery due to an increase in sealing body thickness. This makes it possible to realize a cylindrical battery 10 that can increase capacity while preventing weight gain.

[0024] Furthermore, by adjusting the outer diameter of the open end 20B of the cylindrical battery 10, it is possible to use the sealing body and gasket of another cylindrical battery with a different outer diameter of the body portion 20A. Furthermore, the crimping die used to crimp the outer can to the sealing body can also be used for another cylindrical battery. In this way, common sealing bodies and gaskets can be used between cylindrical batteries with different outer diameters of the body portion, and it is possible to simplify the switching of manufacturing equipment when changing battery sizes during the manufacturing process. This reduces the manufacturing cost of the cylindrical battery 10.

[0025] Next, an example of a manufacturing method for the cylindrical battery 10 will be described using Figures 3 to 6. Figure 3 is a flow diagram showing the steps of an example of a manufacturing method for the cylindrical battery 10. Figures 4 to 6 are diagrams explaining part of the manufacturing process for the cylindrical battery 10. Note that Figures 5 and 6 omit illustration of the electrode body 14 and other components housed in the outer can 20.

[0026] 3 , in step S11, the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween to produce an electrode body 14. A positive electrode lead 15 is joined to the positive electrode 11 of the electrode body 14, and a negative electrode lead 16 is joined to the negative electrode 12 of the electrode body. The positive electrode lead 15 has an extension portion that extends upward from the electrode body 14, and the negative electrode lead 16 has an extension portion that extends downward from the electrode body 14.

[0027] In step S12, the upper insulating plate 18 is fixed to the upper end surface of the electrode assembly 14. Fig. 4 is a diagram illustrating an example of a method for fixing the upper insulating plate 18 to the electrode assembly 14. As shown in Fig. 4, in the electrode assembly 14, the separator 13 is set to be wider than the positive electrode 11 and the negative electrode 12 (see Fig. 1), and the separator 13 is overlapped and wound in a state in which a portion of the separator 13 protrudes from both ends of the positive electrode 11 and the negative electrode 12. In other words, the upper and lower ends of the electrode assembly 14 are constituted by protruding portions 13a, 13b in which a portion of the separator 13 protrudes from the positive electrode 11 and the negative electrode 12.

[0028] The upper insulating plate 18 has a base material 36 and an adhesive layer 38 provided on the lower surface of the base material 36. For example, a base material made of plastic such as polypropylene (PP) or a base material made of glass cloth impregnated with phenolic resin can be used as the base material 36. A base material made of glass cloth impregnated with phenolic resin has fine gaps and irregularities on the surface, which increases the contact area with the adhesive layer 38 and enables high adhesion with the adhesive layer 38.

[0029] The substrate 36 has, for example, a flat plate shape. The arithmetic mean roughness (Ra) of the surface of the substrate 36 is preferably 5 μm or more and 20 μm or less in order to improve adhesion to the adhesive layer 38. Furthermore, the maximum valley depth (Rv) of the surface of the substrate 36 is preferably 20 μm or more and 100 μm or less in order to improve adhesion to the adhesive layer 38.

[0030] The adhesive layer 38 comprises a cured product of a curable resin such as a thermosetting resin or a photocurable resin. A paste containing the curable resin applied to the lower surface of the flat substrate 36 is brought into contact with the protruding portion 13a of the separator 13, and then energy such as heat or light is applied to the paste containing the curable resin. The adhesive layer 38 is made of a curable resin that is cured by the application of this energy. In either case, an upper insulating plate 18 is formed on the lower surface of the substrate 36, with the adhesive layer 38 containing the cured product of the thermosetting resin disposed thereon, and the protruding portion 13a of the separator 13 that forms one end of the electrode body 14 is adhered to the adhesive layer 38.

[0031] The upper insulating plate 18 is fixed to the upper end surface of the electrode body 14 by adhering the protruding portion 13a of the separator 13 forming the upper end portion of the electrode body 14 to the adhesive layer 38 having a cured product of the curable resin. As the thermosetting resin used to cure the adhesive layer 38, for example, an epoxy resin, an acrylic resin, a polyurethane resin, a silicone resin, a melamine resin, a phenolic resin, or a polyester resin can be used. The paste containing the thermosetting resin may contain an additive such as a thermosetting catalyst.

[0032] The photocurable resin used to harden the adhesive layer 38 may be, for example, an ultraviolet-curable resin that hardens when irradiated with light (ultraviolet light) having a wavelength of 100 nm or more and 400 nm or less, a visible-light-curable resin that hardens when irradiated with light (visible light) having a wavelength of 400 nm or more and 800 nm or less, or an infrared-curable resin that hardens when irradiated with light (infrared light) having a wavelength of 1200 nm or more and 1500 nm or less. The paste containing the photocurable resin may contain an additive such as a photopolymerization initiator.

[0033] 3 , in step S13, the lower insulating plate 19 is placed in a cylindrical outer can 20 with a bottom that is made by drawing a steel plate, and then the electrode body 14 to which the upper insulating plate 18 is fixed is inserted into the outer can 20 so that the upper insulating plate 18 is positioned on the opening side of the outer can 20. In step S14, the inner bottom surface of the outer can 20 and the negative electrode lead 16 are welded by resistance welding or the like. By this welding, the negative electrode 12, which is an example of a first electrode, is electrically connected to the outer can 20 so that the electrode body 14 cannot be removed from inside the outer can 20.

[0034] In step S15, the diameter of the outer can 20 is reduced. Fig. 5 is a diagram illustrating an example of a method for reducing the diameter of the outer can 20. As shown in Fig. 5(a), in step S15, first, the outer can 20 is held stationary at a predetermined position by a holding device (not shown) formed of a chuck or the like, with the opening of the outer can 20 facing downward in the vertical direction. As shown in Fig. 5(a), it is preferable that the central axis of the outer can 20 is approximately parallel to the vertical direction when the outer can 20 is stationary.

[0035] Next, as shown in FIGS. 5( a) and 5(b), for example, a diameter-reducing die 51 having an inner diameter of φ18.2 mm or more and φ21 mm or less and a tapered portion (conical inner peripheral surface portion) with an inclination angle of 10° is placed so that its large diameter side faces the opening on the outer can 20 side and the central axis of the diameter-reducing die 51 is approximately aligned with the central axis of the outer can 20. From this state, the diameter-reducing die 51 is moved vertically toward the outer can 20 (vertically upward), and the open end 20B of the outer can 20 (for example, 10 mm from the opened upper end) is reduced in diameter from φ20 mm to φ18.2 mm.

[0036] 5(c), the reducing die 51 is moved vertically downward to separate it from the outer can 20. By using the tapered reducing die 51, it is possible to easily separate the reducing die 51 from the outer can 20 after processing. Although the case where the reducing die 51 is moved upward and then downward after the outer can 20 is fixed has been described, it is also possible to move the outer can downward and then upward after the reducing die 51 is fixed.

[0037] 3 , by performing step S15 after steps S13 and S14, an electrode body 14 having an outer diameter larger than the inner diameter of the opening end 20B can be inserted into the outer can 20, thereby increasing the battery capacity. Furthermore, by performing step S15 after steps S12 to S14, an upper insulating plate 18 having an outer diameter larger than the inner diameter of the opening end 20B can be inserted into the outer can 20, thereby effectively suppressing the occurrence of a short circuit due to contact between the positive electrode 11 or the positive electrode lead 15 and the outer can 20.

[0038] Furthermore, because the diameter is reduced with the opening of the outer can 20 facing vertically downward, even if foreign matter such as chips is generated during the diameter reduction, the foreign matter can be effectively prevented from entering the outer can 20. Therefore, a high-performance cylindrical battery 10 can be easily manufactured.

[0039] In order to accommodate an upper insulating plate with a large outer diameter inside an outer can, it is necessary to accommodate the upper insulating plate inside the outer can before shrinking the diameter of the outer can. However, when shrinking the diameter with the opening of the outer can facing downward, the shrinking must be performed while pressing the upper insulating plate from below, which makes shrinking the diameter of the outer can difficult.

[0040] In contrast, in this embodiment, step S12 is performed to integrate the upper insulating plate 18 with the electrode body 14, and then steps S13 and S14 are performed to make the upper insulating plate 18 unable to be detached from the outer can 20. Therefore, even if the opening of the outer can 20 is oriented vertically downward, the upper insulating plate 18 will not fall vertically downward from the outer can 20. Therefore, the diameter of the outer can 20 can be easily reduced without adding any additional equipment.

[0041] After step S15 is completed, the outer can 20 is turned over so that its opening faces vertically upward. In step S16, a spinning process is performed on the tapered outer peripheral surface of the outer can 20 after the diameter reduction process, thereby forming an annular grooved portion 20C in the outer can 20 (see FIG. 6A). In step S17, a sealing material is applied to the inner surface of the grooved portion 20C. In step S18, a gasket 39 is inserted into the grooved portion 20C. In step S19, the internal terminal plate 31 of the sealing body 30 and the positive electrode lead 15 are welded together. The outer diameters of the sealing body 30 and the gasket 39 are determined according to the inner diameter of the reduced opening end 20B. In step S20, an electrolyte is injected into the outer can 20. In step S21, the sealing body 30 is inserted into the opening end 20B of the outer can 20.

[0042] In step S22, the sealing body 30 is crimped using a crimping die (not shown) (see FIG. 6(b)). The crimping die has an upper die that moves up and down using, for example, a press device, and a lower die that receives the upper die at the grooved portion 20C. A split die divided into two is used for the lower die, and when the open end 20B is pressed, one part of the split die is inserted into the grooved portion 20C and receives pressure from the upper die. In step S23, the height of the cylindrical battery 10 is adjusted by pressing the cylindrical battery 10 in the axial direction.

[0043] The present disclosure is not limited to the above-described embodiment and its modifications, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents. Although the case where the first electrode electrically connected to the outer can 20 is the negative electrode 12 and the second electrode is the positive electrode 11 has been described, the first electrode may be the positive electrode and the second electrode may be the negative electrode.

[0044] In the above description, the upper insulating plate 18 is fixed to the upper end surface of the electrode body 14 using a curable resin. However, the upper insulating plate may also be fixed to the upper end surface of the electrode body 14 using an adhesive material, for example, an adhesive.

[0045] The case where the upper insulating plate 18 is disposed inside the outer can 20 before the diameter of the outer can 20 is reduced has been described. However, the upper insulating plate does not have to be fixed to the electrode body, and the upper insulating plate may be disposed inside the outer can after the diameter of the outer can is reduced.

[0046] REFERENCE SIGNS LIST 10 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 13a, 13b Protruding portion of separator, 14 Electrode body, 15 Positive electrode lead, 16 Negative electrode lead, 18 Upper insulating plate, 19 Lower insulating plate, 20 Outer can, 20A Body portion, 20B Opening end, 20C Grooved portion, 30 Sealing body, 31 Internal terminal plate, 32 Lower valve body, 33 Insulating member, 34 Upper valve body, 35 Cap, 35A Vent, 36 Substrate, 38 Adhesive layer, 39 Gasket, 51 Diameter-reducing mold.

Claims

1. A method for manufacturing a cylindrical battery, comprising the steps of: accommodating an electrode assembly, in which a first electrode and a second electrode are wound with a separator interposed therebetween, in a cylindrical outer can with a bottom; and electrically connecting the first electrode to the outer can so that the electrode assembly cannot be removed from the outer can, and then reducing the outer diameter of the open end of the outer can with the opening of the outer can facing vertically downward.

2. A method for manufacturing a cylindrical battery as described in claim 1, wherein an insulating plate having an outer diameter larger than the inner diameter of the opening end after reduction is fixed to the end face of the opening side of the electrode body, and then the reduction is carried out by directing the opening of the outer can vertically downward.

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