Sealed battery

Abstract

A sealed battery according to one embodiment of the present invention comprises: an electrode body (14) in which a positive electrode plate (11) and a negative electrode plate (12) are stacked with a separator (13) therebetween; an exterior body which houses the electrode body and has an opening at one end; and a sealing body (19) which closes the opening of the exterior body. The sealing body has an identification label (30) formed on a movable portion so as to be separated from the exterior body when the internal pressure of the battery has increased.

Description

sealed battery

[0001] The present disclosure relates to sealed batteries.

[0002] Sealed batteries equipped with identification marks are known (see, for example, Patent Documents 1 and 2). The identification marks enable the battery's production line, production date, etc. For example, if a defect occurs during the battery production process or after the battery is shipped, the identification marks can be used to analyze the cause of the defect.

[0003] Patent Document 1 describes providing an identification barcode (identification mark) on the outer circumferential surface or end surface of a battery can. Patent Document 2 describes providing an identification code (identification mark) on a sealing body that closes an opening of a prismatic exterior body of a prismatic secondary battery, at a position different from the gas release valve.

[0004] JP 2015-524142 A JP 2019-29189 A

[0005] When an identification mark is provided on the outer periphery of a battery can, as in the configuration described in Patent Document 1, there is a possibility that the identification mark may be damaged if other components, such as a battery holder, come into contact with the outer periphery of the battery during the manufacturing process of a battery module comprising multiple batteries and a battery holder. This may make the identification mark difficult to read. Furthermore, if the identification mark is provided in a position other than the outer periphery, end face, or gas release valve of the battery seal when the battery abnormally heats up, the battery may become so hot that the identification mark may discolor or deform, making it difficult to read.

[0006] The sealed battery according to the present disclosure is a sealed battery comprising an electrode assembly in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween, an outer casing that houses the electrode assembly and has an opening at one end, and a sealing body that closes the opening of the outer casing, wherein the sealing body has an identification mark formed in a portion that can move away from the outer casing when the internal pressure of the battery increases.

[0007] The sealed battery according to the present disclosure can provide an identification mark on a portion of the sealing body that is unlikely to come into contact with other components during the manufacturing process of a battery module containing the battery, and that moves away from the battery before being exposed to high temperatures in the event of abnormal battery heat generation. This makes it easy to read the identification mark both after the battery is assembled into the battery module and after abnormal heat generation.

[0008] 3A is a diagram showing a schematic axial cross section of a cylindrical battery as a sealed battery according to an embodiment. FIG. 3A is a schematic side view of the cylindrical battery of FIG. 1, and FIG. 3B is a diagram showing part A of FIG. 1A from above. FIG. 3A is a schematic view showing a state in which the valve portion of the sealing body is blown off due to an increase in the internal pressure of the battery when the cylindrical battery of FIG. 1 is abnormally heated, and FIG. 3B is a diagram showing the outer surface of the valve portion shown in part B of FIG. 3A. FIG. 3B is a schematic view showing a state in which the temperature rise of the cylindrical battery has progressed further after the state of FIG. 3A. FIG. 3C is a diagram corresponding to FIG. 2B in a cylindrical battery as a sealed battery according to another embodiment. FIG. 3D is a schematic view showing a state in which the rupture plate of the sealing body is broken and the valve portion is deformed so as to move outward when abnormal heat is generated in another embodiment.

[0009] Hereinafter, an example of an embodiment of a sealed battery according to the present disclosure will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present disclosure is not limited to the following embodiment. Furthermore, the present disclosure also includes configurations obtained by selectively combining the components of the embodiments described below.

[0010] In the following, a cylindrical battery 10 in which a wound electrode assembly 14 is housed in a cylindrical outer can 20 with a bottom is exemplified as a sealed battery, but the outer can of the battery is not limited to a cylindrical outer can. The sealed battery according to the present disclosure may also be, for example, a prismatic battery equipped with a prismatic outer can.

[0011] FIG. 1 is a schematic diagram illustrating an axial cross section of a cylindrical battery 10 as a sealed battery according to an embodiment. As shown in FIG. 1 , the cylindrical battery 10 includes an electrode assembly 14, an electrolyte, and an outer can 20 that accommodates the electrode assembly 14 and the electrolyte. The electrode assembly 14 includes a positive electrode plate 11, a negative electrode plate 12, and a separator 13. The positive electrode plate 11 and the negative electrode plate 12 are stacked with the separator 13 interposed therebetween and wound in a spiral shape. The outer can 20 is a cylindrical metal container with a bottom and an opening at one axial end. The opening of the outer can 20 is closed by a sealing member 19. Hereinafter, for convenience of explanation, the sealing member 19 side of the cylindrical battery 10 is referred to as the top, and the bottom side of the outer can 20 is referred to as the bottom.

[0012] The electrolyte may be an aqueous electrolyte, but in this embodiment, a non-aqueous electrolyte is used. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixed solvents of two or more of these. Examples of the non-aqueous solvent include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents of these. The non-aqueous solvent may contain a halogen-substituted compound (e.g., fluoroethylene carbonate) in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine. The electrolyte salt may include, for example, LiPF ６ Lithium salts such as

[0013] The positive electrode plate 11, negative electrode plate 12, and separator 13 that make up the electrode assembly 14 are all long, strip-shaped bodies that are spirally wound and stacked in the radial direction of the electrode assembly 14. The negative electrode plate 12 is formed to be slightly larger than the positive electrode plate 11 in order to prevent lithium deposition. That is, the negative electrode plate 12 is formed to be longer in the length direction and width direction (short direction) than the positive electrode plate 11. The separator 13 is formed to be at least slightly larger than the positive electrode plate 11, and two separators 13 are arranged to sandwich the positive electrode plate 11.

[0014] The positive electrode plate 11 has a positive electrode core and a positive electrode mixture layer formed on the positive electrode core. The positive electrode core 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 plate 11, or a film with such a metal disposed on the surface layer. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, such as carbon black or carbon nanotubes, and a binder, such as polyvinylidene fluoride, and is preferably formed on both sides of the positive electrode core. The positive electrode plate 11 can be produced by applying a positive electrode mixture slurry containing the positive electrode active material, the conductive agent, and the binder to both sides of the positive electrode core and compressing the coating.

[0015] An example of the positive electrode active material contained in the positive electrode mixture layer is a lithium transition metal composite oxide. The lithium transition metal composite oxide is a composite oxide containing metal elements such as Co, Mn, Ni, and Al in addition to Li. The metal element constituting the composite oxide is, for example, at least one selected from Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, and Bi. Among these, it is preferable to contain at least one selected from Ni, Mn, and Co.

[0016] The negative electrode plate 12 has a negative electrode core and a negative electrode mixture layer formed on the negative electrode core. The negative electrode core 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 plate 12, or a film with such a metal disposed on the surface layer. The negative electrode mixture layer contains a negative electrode active material, a binder, and, if necessary, a conductive agent such as carbon black or carbon nanotubes, and is preferably formed on both sides of the negative electrode core. For example, styrene-butadiene rubber (SBR) can be used as the binder, and carboxymethyl cellulose or a salt thereof may also be used in combination. The negative electrode plate 12 can be produced by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to both sides of the negative electrode core and compressing the coating.

[0017] An example of the negative electrode active material contained in the negative electrode mixture layer is a carbon material such as graphite that reversibly absorbs and releases lithium ions. The graphite may be either natural graphite or artificial graphite. As the negative electrode active material, an element that alloys with Li, such as Si or Sn, or a material containing such an element may be used. Among these, a composite material containing Si is preferred. A suitable example of a composite material containing Si is SiO ２ Examples of such a material include a material in which a fine Si phase is dispersed in a silicon phase, a silicate phase such as lithium silicate, a carbon phase, or a silicide phase.

[0018] The separator 13 is made of a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator 13 include polyolefins such as polyethylene and polypropylene, and cellulose. The separator 13 may have a single-layer structure or a multi-layer structure. A highly heat-resistant resin layer such as an aramid resin may be formed on the surface of the separator 13. A filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode plate 11 and the negative electrode plate 12.

[0019] Insulating plates 15 and 16 are disposed above and below the electrode body 14. In the example shown in Fig. 1 , the positive electrode lead 17 passes through a through hole in the insulating plate 15 and extends toward the sealing body 19, and the negative electrode lead 18 passes outside the insulating plate 16 and extends toward the bottom 20a of the outer can 20. The positive electrode lead 17 is connected to the underside of an internal terminal plate 21 of the sealing body 19 by laser welding or the like, and a rupture plate 22 (described below), which is the top plate of the sealing body 19 and is electrically connected to the internal terminal plate 21, serves as the positive electrode terminal. The negative electrode lead 18 is connected to the inner surface of the bottom 20a of the outer can 20 by laser welding or the like, and the outer can 20 serves as the negative electrode terminal.

[0020] The positive electrode lead 17 is joined to the positive electrode core by ultrasonic welding or the like. The positive electrode lead 17 is joined, for example, to a longitudinal center portion of the positive electrode plate 11, spaced from both longitudinal ends. The positive electrode lead 17 may be joined to a position substantially equidistant from both longitudinal ends of the positive electrode plate 11. The negative electrode lead 18 is joined to the negative electrode core by ultrasonic welding or the like. In the example shown in FIG. 1 , the negative electrode lead 18 is joined to the winding end side, which is the longitudinal end of the negative electrode plate 12 located on the outer periphery of the electrode body 14. The positive electrode lead 17 and the negative electrode lead 18 are, for example, strip-shaped metal members, and have a thickness of 30 μm to 100 μm.

[0021] The negative electrode plate 12 may be disposed on the outer peripheral surface of the electrode body 14. Furthermore, an exposed portion where the surface of the negative electrode core is exposed may be formed on the outer peripheral surface of the electrode body 14, and this exposed portion may be in contact with the inner surface of the outer can 20 to electrically connect the negative electrode plate 12 and the outer can 20. In this case, the negative electrode plate 12 may not have a negative electrode lead 18.

[0022] As described above, the outer can 20 is a cylindrical metal container with a bottom and an opening at one axial end. A resin gasket 24 is provided between the outer can 20 and the sealing body 19 to ensure sealing of the battery interior and insulation between the outer can 20 and the sealing body 19. The outer can 20 has a grooved portion 20b formed on its side surface that protrudes inward and supports the sealing body 19. The grooved portion 20b is preferably formed in an annular shape along the circumferential direction of the outer can 20, and supports the sealing body 19 on its top surface. The sealing body 19 is fixed to the top of the outer can 20 by the grooved portion 20b and the open end of the outer can 20 that is crimped to the sealing body 19.

[0023] The sealing body 19 is a disk-shaped member equipped with a current interruption mechanism. The sealing body 19 has a structure in which an internal terminal plate 21, an insulating plate 23, and a rupture plate 22 are stacked in this order from the electrode body 14 side. The internal terminal plate 21 has a thin-walled portion in the center that is thinner than the outer annular portion to which the positive electrode lead 17 is connected.

[0024] The insulating plate 23 is a disk-shaped member made of an insulating material and has an opening 23a in the center. The rupture plate 22 is disposed opposite the internal terminal plate 21, with the insulating plate 23 sandwiched therebetween. The center of the rupture plate 22 is connected to the thin-walled portion in the center of the internal terminal plate 21 through the opening 23a of the insulating plate 23 by welding or the like.

[0025] Furthermore, the rupture plate 22 has an easily breakable portion 22a in the radially intermediate portion. The easily breakable portion 22a is formed by a ring-shaped thin portion 22b formed in a radial portion of the rupture plate 22. The easily breakable portion 22a is formed by forming an annular groove 22c in a radial portion of the inner surface (lower surface in FIG. 1 ) of the rupture plate 22. The groove for forming the easily breakable portion 22a may be formed in the outer surface (upper surface in FIG. 1 ) of the rupture plate 22. A valve portion 22d is formed by a portion of the rupture plate 22 radially inward from the easily breakable portion 22a.

[0026] The sealing body 19 is fixed by crimping to the outer can 20 via a gasket 24, radially outward from the easily breakable portion 22a. The pressure inside the battery acts on the groove 22c of the rupture plate 22 through the vent holes formed in the internal terminal plate 21 and the insulating plate 23.

[0027] When the internal pressure of the battery rises and exceeds a predetermined threshold, the easily breakable portion 22a of the rupture plate 22 breaks, and the valve portion 22d radially inward of the easily breakable portion 22a moves away from the outer can 20.

[0028] In the cylindrical battery 10, the internal terminal plate 21, to which the positive electrode lead 17 is connected, is electrically connected to the rupture plate 22, forming a current path from the electrode assembly 14 to the rupture plate 22. When an abnormality occurs in the battery and the internal pressure increases, the internal terminal plate 21 breaks, the thin-walled portion of the internal terminal plate 21 is separated from its outer annular portion, and the valve portion 22d deforms to become convex toward the outside of the battery. This interrupts the current path. When the internal pressure of the battery further increases, the fragile portion 22a breaks as described above, forming a gas outlet. If the fragile portion 22a breaks along its entire circumference, the valve portion 22d is blown out of the battery. If only a portion of the fragile portion 22a breaks circumferentially and a portion of the valve portion 22d remains connected to the remaining portion of the rupture plate 22, the valve portion 22d deforms and moves outward. In either case, the valve portion 22d is a portion that can move away from the outer can 20 when the internal pressure of the battery increases.

[0029] An identification mark 30 is formed on the outer surface of the rupture plate 22 in the area indicated by the arrow α in Figure 1. Figure 2(a) is a schematic diagram of the cylindrical battery 10 as seen from the side, and Figure 2(b) is a diagram of part A in Figure 2(a) as seen from above.

[0030] 2(b), sealing body 19 has an identification mark 30 formed on the outer surface of valve portion 22d, radially inward of frangible portion 22a. Identification mark 30 is preferably formed at a position away from the center of valve portion 22d so as to avoid the connection position of an external lead provided on a positive electrode terminal plate (not shown) to rupture plate 22.

[0031] The identification mark 30 is an individual mark affixed to each cylindrical battery 10, providing identification information for distinguishing it from other cylindrical batteries 10. A different identification mark 30 is provided for each cylindrical battery 10, or for each group of a predetermined number of cylindrical batteries 10. The identification mark 30 may be a lot number affixed to a group of products manufactured at the same time, or a product number affixed to each individual product.

[0032] The identification mark 30 makes it possible to distinguish between individual cylindrical batteries 10 or individual production lots, and is used to obtain information related to the manufacture of the cylindrical batteries 10. For example, the manufacturer of the cylindrical batteries 10 may have a database that contains information related to the manufacture of the cylindrical batteries 10, linked to the identification mark 30 of the cylindrical batteries 10. Therefore, by reading the identification mark 30 with a reading device such as a reader and identifying the cylindrical battery 10, information related to the manufacture of the cylindrical battery 10 can be obtained. An example of information related to the manufacture of the cylindrical battery 10 is the history of the manufacturing process, including information on the production line, production date and time, etc.

[0033] The identification mark 30 is composed of at least one selected from, for example, numbers, letters, and an identification code. The identification mark 30 may be a display consisting of a combination of numbers and letters. The identification code constituting the identification mark 30 may be any of a one-dimensional code, a two-dimensional code, and a three-dimensional code, but is preferably a two-dimensional code. In the example shown in FIG. 2 , a square-shaped two-dimensional code (QR Code (registered trademark)) is formed as the identification mark 30.

[0034] The identification mark 30 may be readable by a reading device such as a reader, and may be composed of at least one selected from a protrusion and a depression. Alternatively, the identification mark 30 may have a color different from its surroundings. The numbers, letters, or identification code constituting the identification mark 30 may not have a protrusion or depression, and may only have a color different from its surroundings.

[0035] The identification mark 30 may be formed by printing, such as inkjet printing, or by press processing, but is preferably formed by laser marking. Laser marking is a method of forming a mark by irradiating the valve portion 22d with laser light. When the identification mark 30 is a laser marking mark, the mark is formed, for example, by discoloring the area irradiated with the laser light. Alternatively, a depression may be formed in the area irradiated with the laser light. Laser marking marks are highly durable, making them less likely to be readable even after the cylindrical battery 10 has been used.

[0036] In the cylindrical battery 10 described above, the sealing body 19 has an identification mark 30 formed in a portion that can move away from the outer can 20 if the battery's internal pressure increases. This makes it less likely to come into contact with other components during the manufacturing process of the battery module containing the battery, and allows the identification mark 30 to be provided in a portion of the sealing body 19 that moves away from the battery before being exposed to high temperatures in the event of abnormal battery heat generation. This makes it easy to read the identification mark both after the battery is assembled into the battery module and after abnormal heat generation.

[0037] Figure 3(a) is a schematic diagram showing the state in which the valve portion 22d of the sealing body 19 is blown off due to an increase in the internal pressure of the battery when abnormal heat generation occurs in the cylindrical battery 10, and Figure 3(b) is a diagram showing the outer surface of the valve portion 22d shown in part B of Figure 3(a).

[0038] 3 shows a state in which the easily breakable portion 22a (FIGS. 1 and 2) breaks along the entire circumference of the easy-to-break portion 22a when the internal pressure of the battery rises due to abnormal heat generation in the cylindrical battery 10, causing the valve portion 22d to be blown outward. As shown in FIG. 3(b), the identification mark 30 remains formed on the blown-out valve portion 22d.

[0039] Figure 4 is a schematic diagram showing the state of the cylindrical battery 10 after the temperature rise has progressed further. In Figure 4, the dashed line indicates the localized generation of a large amount of heat at the top of the cylindrical battery 10. For example, if the cylindrical battery 10 is used under extremely harsh conditions or is subjected to excessively large external forces, there is a non-zero possibility of a fire resulting in a localized generation of a large amount of heat. Even in this case, the valve portion 22d on which the identification mark is formed will have separated from the cylindrical battery 10 and fallen to the periphery of the cylindrical battery 10 before such a large amount of heat is generated. This prevents the identification mark 30 from being affected by the heat of the cylindrical battery 10, causing discoloration or deformation that makes the mark difficult to read.

[0040] In the above embodiment, the identification mark 30 is formed on the outer surface of the valve portion 22d, but the identification mark may be formed on the inner surface of the valve portion 22d. However, from the viewpoint of ease of forming the identification mark 30, it is preferable to form the identification mark 30 on the outer surface of the valve portion 22d as in the embodiment shown in Figures 1 to 4.

[0041] Fig. 5 is a view corresponding to Fig. 2(b) of a cylindrical battery 10a according to another embodiment. Fig. 6 is a schematic view showing a state in which the rupture plate 32 of the sealing body 19a is broken and the valve portion 32d is deformed so as to move outward during abnormal heat generation in the cylindrical battery 10a according to another embodiment.

[0042] In the configuration of this example, the thin-walled portion 32b that forms the easily breakable portion 32a of the rupture plate 32 is provided in a C-shape on the inner surface of the rupture plate 32, and is not provided around the entire circumference. The valve portion 32d is formed by a portion of the rupture plate 32 that is radially inward from the easily breakable portion 32a. The identification mark 30 is formed on the outer surface of the valve portion 22d, radially inward from the easily breakable portion 32a.

[0043] In this configuration, when abnormal heat buildup occurs in the cylindrical battery 10a, the internal battery pressure rises, causing the frangible portion 32a to rupture, forming a gas outlet, as shown in Figure 6. This rupture causes the valve portion 22d to move outward from the battery, away from the outer can 20, while remaining connected to the remaining outer periphery of the rupture plate 32 at the circumferentially discontinuous portion of the frangible portion 32a. This prevents the temperature of the outwardly deformed valve portion 22d from rising even if the temperature of the cylindrical battery 10 subsequently rises. This prevents the thermal effects of the cylindrical battery 10 from affecting the identification marking 30, resulting in discoloration or deformation that makes the marking difficult to read. Other configurations and functions of this configuration are similar to those of Figures 1 to 4.

[0044] 10, 10a Cylindrical battery, 11 Positive electrode plate, 12 Negative electrode plate, 13 Separator, 14 Electrode body, 15, 16 Insulating plate, 17 Positive electrode lead, 18 Negative electrode lead, 19 Sealing body, 20 Outer can, 20a Bottom, 20b Grooved portion, 21 Internal terminal plate, 22 Rupture plate, 22a Easy-to-break portion, 22b Thin-walled portion, 22c Groove, 22d Valve portion, 23 Insulating plate, 23a Opening, 24 Gasket, 30 Identification mark, 32 Rupture plate, 32a Easy-to-break portion, 32b Thin-walled portion, 32d Valve portion.

Claims

1. A sealed battery comprising: an electrode assembly in which positive and negative electrode plates are stacked with a separator between them; an exterior body that houses the electrode assembly and has an opening at one end; and a sealing body that closes the opening of the exterior body, wherein the sealing body has an identification mark formed in a portion that can move away from the exterior body when the internal pressure of the battery increases.

2. The sealed battery according to claim 1, wherein the sealing body has a ring-shaped or C-shaped easily breakable part and is fixed by crimping to the exterior body via a resin gasket radially outward from the easily breakable part, and the identification mark is formed radially inward from the easily breakable part.

3. The sealed battery according to claim 2, wherein the easily breakable portion is formed by a thin-walled portion.

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