Sealed battery

Abstract

The purpose of the present disclosure is to provide a sealed battery that can expand a joint area of an electrode lead with respect to a sealing body or the like without using a large-width electrode lead. A sealed battery, which is an example of an embodiment, comprises: an electrode body (14) having an electrode lead (20); a bottomed tubular exterior can (16) that accommodates the electrode body; and a sealing body (17) that plugs an opening section of the exterior can. The electrode lead is welded, with energy beams, to the inner surface of the sealing body. In addition, the electrode lead includes: a first main surface (30) making contact with the inner surface of the sealing body; and a second main surface (31) on the opposite side of the first main surface, wherein the first main surface and the second main surface are formed in non-parallel with each other.

Description

Technical Field

[0001] The present disclosure relates to a sealed battery, and more particularly to a sealed battery in which an electrode lead is welded to at least one of an inner surface of a sealing body and an outer can.

Background Art

[0002] Conventionally, a sealed battery including an electrode body having an electrode lead, a bottomed cylindrical outer can that houses the electrode body, and a sealing body that closes an opening of the outer can has been widely known. The electrode lead includes a positive electrode lead connected to the positive electrode and a negative electrode lead connected to the negative electrode. For example, in a cylindrical battery, the positive electrode lead is joined to the inner surface of the sealing body, and the negative electrode lead is joined to the inner surface of the outer can, respectively. Patent Document 1 discloses a sealed battery in which an electrode lead is laser-welded to the inner surface of a sealing body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, it is preferable that the joint portion of the electrode lead to the sealing body or the like is strongly joined so that the electrode lead does not come off due to vibration or impact. In addition, in order to suppress not only the bonding force but also the resistance heat generation, it is necessary to secure a certain degree of bonding area.

[0005] In order to secure the bonding area of the electrode lead to the sealing body or the like, the width of the lead may be increased. However, in this case, there is a problem that the energy density of the battery decreases. In addition, since the electrode lead has high rigidity and is difficult to deform, when the lead is widened, particularly in a cylindrical battery having a wound electrode body, the electrode body is likely to be distorted or displaced, and the battery performance may deteriorate.

Means for Solving the Problems

[0006] A sealed battery according to one aspect of the present disclosure includes an electrode body having an electrode lead, a bottomed cylindrical outer can that houses the electrode body, and a sealing body that closes an opening of the outer can, and the electrode lead is energy beam welded to an inner surface of at least one of the sealing body and the outer can. The electrode lead includes a first main surface that contacts the inner surface of the sealing body or the outer can, and a second main surface on the side opposite to the first main surface, and the first main surface and the second main surface are formed non-parallel to each other.

Advantages of the Invention

[0007] According to one aspect of the present disclosure, it is possible to provide a sealed battery capable of expanding the bonding area of the electrode lead to a sealing body or the like without using a wide electrode lead.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0009] Hereinafter, an example of an embodiment of the present disclosure will be described in detail. Hereinafter, as an example of an embodiment of the sealed battery according to the present disclosure, a cylindrical battery in which a wound electrode body 14 is housed in a bottomed cylindrical outer can 16 will be exemplified, but the battery may be a rectangular battery having a rectangular outer can. Further, the electrode body may be of a stacked type in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with a separator interposed therebetween. In this specification, for convenience of explanation, the side of the sealing body 17 will be described as "upper" and the bottom side of the outer can 16 will be described as "lower".

[0010] FIG. 1 is a cross-sectional view of a sealed battery 10 which is an example of an embodiment. As shown in FIG. 1, the sealed battery 10 includes an electrode body 14, a bottomed cylindrical outer can 16 that houses the electrode body 14, and a sealing body 17 that closes the opening of the outer can 16. Further, an electrolyte is housed in the outer can 16. The electrode body 14 includes a positive electrode 11, a negative electrode 12, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12, and has a positive electrode lead 20 and a negative electrode lead 21 as electrode leads. The electrode leads are generally formed of strip-shaped metal plates that are thicker than the core of the electrode. Further, the electrode body 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween.

[0011] The electrolyte may be either an aqueous electrolyte or a non-aqueous electrolyte. An example of a preferred sealed battery 10 is a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte such as a lithium-ion battery. The non-aqueous electrolyte includes, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. As the non-aqueous solvent, esters, ethers, nitriles, amides, and mixed solvents of two or more of these are used. The non-aqueous solvent may contain a halogen-substituted product in which at least a part of the hydrogen of these solvents is substituted with a halogen atom such as fluorine. Note that the non-aqueous electrolyte is not limited to a liquid electrolyte and may be a solid electrolyte. As the electrolyte salt, for example, a lithium salt such as LiPF6 is used.

[0012] The electrode body 14 includes a long positive electrode 11, a long negative electrode 12, two long separators 13, a positive electrode lead 20 connected to the positive electrode 11, and a negative electrode lead 21 connected to the negative electrode 12. The negative electrode 12 is formed with dimensions slightly larger than those of the positive electrode 11 in order to suppress the precipitation of lithium. That is, the negative electrode 12 is formed longer than the positive electrode 11 in the longitudinal direction and the short-side direction (vertical direction). The two separators 13 are formed with dimensions at least slightly larger than those of the positive electrode 11 and are arranged, for example, to sandwich the positive electrode 11.

[0013] The positive electrode 11 includes a positive electrode core and positive electrode mixture layers provided on both sides of the positive electrode core. For the positive electrode core, a foil of a metal stable within the potential range of the positive electrode 11 such as aluminum or an aluminum alloy, a film having the metal disposed on the surface layer, or the like can be used. The positive electrode mixture layer contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF). The positive electrode 11 can be manufactured by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc. onto the positive electrode core, drying the coating film, and then compressing it to form the positive electrode mixture layer on both sides of the positive electrode core.

[0014] For the positive electrode active material, for example, a lithium transition metal composite oxide is used. Examples of the metal elements contained in the lithium transition metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, etc. An example of a suitable lithium transition metal composite oxide is a lithium metal composite oxide containing at least one of Ni, Co, and Mn. Specific examples include a composite oxide containing Ni, Co, and Mn, and a composite oxide containing Ni, Co, and Al.

[0015] The negative electrode 12 has a negative electrode core body and negative electrode binder layers provided on both surfaces of the negative electrode core body. For the negative electrode core body, foils of metals stable within the potential range of the negative electrode 12 such as copper and copper alloys, films with such metals disposed on the surface layer, etc. can be used. The negative electrode binder layer contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR). The negative electrode 12 can be manufactured by applying a negative electrode binder slurry containing a negative electrode active material, a binder, etc. onto the negative electrode core body, drying the coating film, and then compressing it to form negative electrode binder layers on both surfaces of the negative electrode core body.

[0016] For the negative electrode active material, carbon-based active materials such as natural graphite like flaky graphite, massive graphite, and earthy graphite, artificial graphite like massive artificial graphite, and graphitized mesophase carbon microbeads are used, for example. As the negative electrode active material, metals that alloy with lithium such as Si and Sn, alloys containing such metals, compounds containing such metals, etc. may be used, and these may be used in combination with the carbon-based active materials.

[0017] Insulating plates 18 and 19 are respectively disposed above and below the electrode body 14. In the example shown in FIG. 1, the positive electrode lead 20 attached to the positive electrode 11 extends toward the sealing body 17 side through the through-hole of the insulating plate 18, and the negative electrode lead 21 attached to the negative electrode 12 extends toward the bottom side of the exterior can 16 through the outside of the insulating plate 19. The positive electrode lead 20 is welded to the inner surface of the sealing body 17 facing the inside of the battery, and the sealing body 17 serves as the positive electrode external terminal. The negative electrode lead 21 is welded to the inner surface of the bottom of the exterior can 16, and the exterior can 16 serves as the negative electrode external terminal. Note that the negative electrode lead 21 may be connected to the inner surface of the sealing body 17, and in this case, the sealing body 17 serves as the negative electrode external terminal.

[0018] The outer can 16 is, for example, a metal container having a bottomed cylindrical shape. A resin gasket 28 is provided between the outer can 16 and the sealing body 17. The gasket 28 closes the gap between the outer can 16 and the sealing body 17, and the inside of the battery is sealed. Further, the outer can 16 has, for example, a groove portion 22 formed on the side surface by spinning from the outside of the side surface and supporting the sealing body 17. The groove portion 22 is preferably formed in an annular shape along the circumferential direction of the outer can 16, and supports the sealing body 17 on its upper surface. The upper end portion of the outer can 16 is bent inward of the can and clamped to the peripheral edge portion of the sealing body 17.

[0019] The sealing body 17 has a structure in which an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are laminated in this order from the side of the electrode body 14. Each member constituting the sealing body 17 has, for example, a disc shape or a ring shape, and each member except the insulating member 25 is electrically connected to each other. The lower valve body 24 and the upper valve body 26 are connected at their central portions, and the insulating member 25 is interposed between the peripheral edge portions of each. When the internal pressure of the battery rises due to abnormal heat generation, the lower valve body 24 deforms and breaks so as to push up the upper valve body 26 toward the cap 27 side, thereby cutting off the current path between the lower valve body 24 and the upper valve body 26. When the internal pressure further rises, the upper valve body 26 breaks, and gas is discharged from the opening 27a of the cap 27.

[0020] In the present embodiment, the positive electrode lead 20 is welded to the core body exposed portion of the positive electrode 11 formed at the portion corresponding to the negative electrode 12, and the positive electrode lead 20 is inserted into the electrode body 14. However, a part of the positive electrode core body may be projected upward to form a positive electrode tab, and the positive electrode lead 20 may be welded to this positive electrode tab.

[0021] Hereinafter, with reference to FIGS. 2 and 3, the configuration of the positive electrode lead 20 and the joining form of the positive electrode lead 20 to the sealing body 17 will be described in detail. FIG. 2 is a perspective view of the sealing body 17 and the positive electrode lead 20, and FIG. 3 is a view showing a part of the cross section taken along line AA in FIG. 2. Further, in FIG. 3, the welded portion 40 in the bottom view of the lower surface 23b of the sealing body 17 is shown.

[0022] As shown in FIGS. 2 and 3, the positive electrode lead 20 is welded to the lower surface 23b of the internal terminal plate 23, which is the component of the sealing body 17 and is located closest to the inside of the battery. The positive electrode lead 20 includes a first main surface 30 in contact with the lower surface 23b of the internal terminal plate 23, a second main surface 31 on the side opposite to the first main surface 30, and side surfaces 32 and 33 along the thickness direction of the lead. And a welding portion 40 for joining the first main surface 30 and the lower surface 23b is formed at least in part of the portion where the first main surface 30 and the lower surface 23b are in contact. Note that a plurality of openings 23a are formed in the internal terminal plate 23. Therefore, the welding portion 40 is formed so as not to cover the openings 23a.

[0023] The positive electrode lead 20 is composed of a strip-shaped metal member. The metal constituting the positive electrode lead 20 is not particularly limited, and for example, aluminum can be mentioned. The positive electrode lead 20 has a constant width over the entire length, and the tip portion extending from the upper end of the positive electrode 11 is bent along the lower surface 23b of the internal terminal plate 23 (see FIG. 1). Further, the internal terminal plate 23 is composed of a disk-shaped metal plate in which the openings 23a are formed. The metal constituting the internal terminal plate 23 is not particularly limited, and for example, aluminum can be mentioned. The portion of the lower surface 23b where the positive electrode lead 20 is welded is flat.

[0024] The positive electrode lead 20 is welded to the lower surface 23b of the internal terminal plate 23 by energy beam welding. Here, energy beam welding is a welding method in which, with the positive electrode lead 20 disposed on the lower surface 23b of the internal terminal plate 23, an energy beam is irradiated from the second main surface 31 side of the positive electrode lead 20 to melt and join the positive electrode lead 20 and the internal terminal plate 23. Therefore, there are melting marks 41 where the metal has melted and then solidified again on the positive electrode lead 20 and the internal terminal plate 23. Note that the welding portion 40 is the portion where the first main surface 30 and the lower surface 23b are joined and is part of the melting mark 41.

[0025] Examples of the energy beam for forming the welded portion 40 include a laser, an electron beam, etc. Among these, it is preferable to use a laser. The type of laser is not particularly limited as long as it can weld the positive electrode lead 20. For example, a YAG laser, a CO2 laser, a YVO4 laser, a semiconductor (LD) laser, etc. can be mentioned. The laser beam needs to be irradiated substantially perpendicular to the second main surface 31 of the positive electrode lead 20. When the laser beam is incident obliquely on the second main surface 31, the laser beam reflected by the second main surface 31 increases and the energy loss increases, making it difficult to form the welded portion 40. Hereinafter, the laser will be taken as an example of the energy beam for explanation.

[0026] In the positive electrode lead 20, the first main surface 30 and the second main surface 31 are formed non-parallel. The shape of the cross-section in the width direction of the positive electrode lead 20 shown in FIG. 3 is a rectangular shape close to a triangular shape, and the length of the side surface 33 is significantly shorter than the length of the side surface 32. The side surfaces 32 and 33 are formed parallel to each other, orthogonal to the first main surface 30, and are arranged perpendicular to the lower surface 23b of the internal terminal plate 23.

[0027] In the cross-section in the width direction of the positive electrode lead 20, assuming the virtual line along the first main surface 30 is α and the virtual line along the second main surface 31 is β, the virtual lines α and β are non-parallel and intersect at the tip of the shorter side surface 33. In the example shown in FIG. 3, the entire second main surface 31 is non-parallel to the first main surface 30. And the entire second main surface 31 is inclined with respect to the lower surface 23b of the internal terminal plate 23 where the first main surface 30 contacts.

[0028] As described above, the positive electrode lead 20 is laser-welded to the lower surface 23b of the internal terminal plate 23. At this time, it is necessary to irradiate the laser beam substantially perpendicular to the second main surface 31 to suppress the reflection of the laser beam. According to the positive electrode lead 20, since the first main surface 30 and the second main surface 31 are non-parallel, when the laser beam is irradiated perpendicular to the second main surface 31, the laser beam will be incident obliquely on the portion where the first main surface 30 and the lower surface 23b contact. This obliquely incident laser beam makes it possible to expand the area of the welded portion 40 compared with the case of using a conventional electrode lead where the first main surface and the second main surface are parallel.

[0029] In this embodiment, the length L1 along the virtual line α of the fusion mark 41 (i.e., the welded portion 40) formed on the lower surface 23b of the internal terminal plate 23 is longer than the length L2 along the virtual line β of the fusion mark 41 formed on the second main surface 31 of the positive electrode lead 20. Note that when a conventional electrode lead is used, the lengths L1 and L2 are substantially equal. That is, in this embodiment, the welded portion 40 expands as compared with the case of using a conventional electrode lead due to the laser light obliquely incident on the portion where the first main surface 30 and the lower surface 23b are in contact.

[0030] The shape of the irradiation spot of the laser light on the second main surface 31 of the positive electrode lead 20 (the shape of the fusion mark 41) is not particularly limited, and may be substantially circular (see FIG. 2), or may be linear and long in the width direction of the positive electrode lead 20. For example, by scanning the laser light along the width direction of the positive electrode lead 20, a welded portion 40 that is long in the width direction can be formed. Generally, the larger the irradiation area of the laser light, the larger the area of the welded portion 40. When the irradiation area of the laser light on the second main surface 31 is the same, by using the positive electrode lead 20, the welded portion 40 can be made larger than the case of using a conventional electrode lead.

[0031] In the cross section in the width direction of the positive electrode lead 20, the angle θ1 formed by the virtual line α along the first main surface 30 and the virtual line β along the second main surface 31, that is, the inclination angle of the second main surface 31 with respect to the lower surface 23b of the internal terminal plate 23 is not particularly limited, but is preferably 5° or more, and more preferably 10° or more. The larger the angle θ1, the larger the magnification of the length L1 with respect to the length L2.

[0032] The upper limit value of the angle θ1 is, for example, 45°. In the case of the wound electrode body 14, if the angle θ1 is made too large, the electrode body 14 may be deformed or displaced. Note that the portion of the positive electrode lead 20 connected to the positive electrode 11 may be formed such that the first main surface 30 and the second main surface 31 are parallel, and the tip portion welded to the internal terminal plate 23 may be formed such that the first main surface 30 and the second main surface 31 are non-parallel. In this case, even if the angle θ1 is increased, the above problems do not occur. Another metal member may be provided only at the tip portion of the positive electrode lead 20 to make the first main surface 30 and the second main surface 31 non-parallel.

[0033] An example of a preferred range of the angle θ1 is 1 to 45°, more preferably 5 to 45°, or 5 to 30°, or 10 to 30°. In the example shown in FIG. 3, the angle θ2 formed by the first main surface 30 (virtual line α) and the side surface 32 is about 90°, and the shape of the cross section in the width direction of the positive electrode lead 20 is substantially a right triangle. When the angle θ2 is a right angle, the angle θ3 formed by the second main surface 31 (virtual line β) and the side surface 32 is, for example, 45 to 89°, preferably 45 to 75°, or 50 to 75°, or 50 to 70°.

[0034] The ratio (T2 / T1) of the maximum thickness T2 to the minimum thickness T1 of the positive electrode lead 20 is preferably 0 < T2 / T1 ≤ 100. In the example shown in FIG. 3, the ratio of the length of the side surface 33 to the length of the side surface 32 is equal to T2 / T1. The maximum thickness T2 of the positive electrode lead 20 is, for example, 1 mm, and from the viewpoint of improving the energy density of the battery, etc., it is preferably 0.7 mm, more preferably 0.5 mm. Also, the minimum thickness T1 of the positive electrode lead 20 is, for example, 0.01 mm, and from the viewpoints of suppressing resistance heat generation and ensuring strength, etc., it is preferably 0.05 mm or more, more preferably 0.1 mm or more.

[0035] Figs. 4 and 5 are cross-sectional views of the positive electrode leads 20x and 20y in the width direction, which are another example of the embodiment. Hereinafter, the same components as those in the above embodiment are denoted by the same reference numerals, and redundant descriptions are omitted. In the positive electrode lead 20 shown in Fig. 3, the first main surface 30 and the side surface 32 are orthogonal, and the angles θ2 and θ3 are different. However, in the positive electrode lead 20x shown in Fig. 4, the first main surface 30 and the side surface 32x are not orthogonal, and the angles θ2 and θ3 are substantially the same. The positive electrode lead 20x is formed such that the first main surface 30 and the second main surface 31x substantially intersect, and the shape of its cross-section in the width direction is substantially an isosceles triangle. Also in this case, the angle θ1 formed by the virtual line α along the first main surface 30 and the virtual line β along the second main surface 31x is, for example, 1 to 45°, more preferably 5 to 45°, or 5 to 30°, or 10 to 30°.

[0036] Further, as shown in Fig. 5, the second main surface 31y may include an inclined surface non-parallel to the first main surface 30 and a plane parallel to the first main surface 30. Note that the inclined surface portion is preferably formed to have a larger area than the plane portion. In the positive electrode lead 20y shown in Fig. 5, the angles θ2 and θ3 are substantially the same, and the shape of the cross-section of the positive electrode lead 20y in the width direction is a pentagon. Also in this case, the angle θ1 formed by the virtual line α along the first main surface 30 and the virtual line β along the inclined surface portion of the second main surface 31y is, for example, 1 to 45°, more preferably 5 to 45°, or 5 to 30°, or 10 to 30°.

[0037] As described above, by using the positive electrode leads 20, 20x, and 20y having the above-described configuration, it is possible to increase the bonding area of the positive electrode lead 20 with respect to the internal terminal plate 23 as compared with the case of using a conventional electrode lead in which the first main surface and the second main surface are parallel.

[0038] In addition to or instead of the positive electrode lead 20, the first main surface and the second main surface of the negative electrode lead 21 may be formed non-parallel, and the configuration of the positive electrode lead 20 described above may be applied to the negative electrode lead 21.

Description of Reference Numerals

[0039] 10 Sealed battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Exterior can, 17 Sealing body, 18, 19 Insulating plates, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved portion, 23 Internal terminal board, 23a, 27a Openings, 23b Bottom surface, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 First main surface, 31 Second main surface, 32, 33 Side surfaces, 40 Weld portion, 41 Melting mark, α, β Virtual lines, θ1, θ2, θ3 Angles

Claims

1. A sealed battery comprising an electrode body having an electrode lead, a bottomed cylindrical outer can housing the electrode body, and a sealing body closing an opening of the outer can, wherein the electrode lead is energy beam welded to an inner surface of at least one of the sealing body and the outer can, the electrode lead includes a first main surface in contact with the inner surface of the sealing body or the outer can and a second main surface on the side opposite to the first main surface, and in a cross section in the width direction, the first main surface and the second main surface are formed non-parallel to each other, a fusion mark including a welding portion joining the first main surface and the inner surface is formed so as to be inclined with respect to a direction perpendicular to the first main surface. A sealed battery.

2. The sealed battery according to claim 1, wherein an angle θ formed by a virtual line α along the first main surface and a virtual line β along the second main surface is 1 to 45° in a cross section in the width direction of the electrode lead.

3. The sealed battery according to claim 1 or 2, wherein a ratio (T2 / T1) of a maximum thickness T2 to a minimum thickness T1 of the electrode lead satisfies 0 < T2 / T1 ≤ 100.

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