Electrode plate, electrode body, battery, and method for manufacturing electrode plate

Abstract

A cylindrical battery (10), which is an example of an embodiment of the present invention, comprises an electrode body (14) including a positive electrode plate (11) and a negative electrode plate (12) as electrode plates. Each electrode plate comprises a core body and a mixture layer formed on the core body. An identification marking is formed on a surface of the mixture layer. The identification marking is covered with, for example, tape.

Description

Electrode plate, electrode body, battery, and method for manufacturing electrode plate

[0001] The present disclosure relates to an electrode plate, an electrode assembly, a battery, and a method for manufacturing an electrode plate.

[0002] Conventionally, electrode plates provided with identification marks have been known (see, for example, Patent Documents 1 and 2). From this identification mark, it is possible to identify the manufacturing line and manufacturing date of the electrode plate. For example, if a defect occurs for some reason during the battery manufacturing process or after the battery is shipped, the identification mark on the electrode plate is used to analyze the cause of the defect.

[0003] Patent Document 1 describes providing an identification mark on at least one of the positive electrode lead, the negative electrode lead, the exposed portion of the positive electrode core, and the exposed portion of the negative electrode core. Patent Document 2 describes providing an identification mark on the exposed portion of the core, and providing a mixture layer on the surface of the core opposite the identification mark in the thickness direction of the core.

[0004] JP 2006-040875 A International Publication No. 2019 / 193869

[0005] As described above, it is possible to provide an identification mark on a lead, but since the lead generally has a small width, it is not easy to provide an identification mark on the lead surface. Furthermore, since the area of ​​the exposed core portion of the electrode body is required to be small from the viewpoints of increasing capacity and improving safety, it is becoming more difficult to provide an identification mark on the exposed core portion. Furthermore, since the exposed core portion has low rigidity, there is also the issue that if an identification mark is provided on the exposed core portion, the identification mark is easily deformed by the tensile force acting on the exposed portion during charging and discharging of the battery. Deformation of the identification mark may make it difficult to read the mark.

[0006] The electrode plate according to the present disclosure is an electrode plate having a core and a mixture layer formed on the core, and an identification mark is formed on the surface of the mixture layer.

[0007] The electrode body according to the present disclosure is a wound electrode body provided with the above-mentioned electrode plate, wherein the electrode plate is at least a negative electrode plate, and the above-mentioned mixture layer in the negative electrode plate has a non-facing region that does not face the positive electrode mixture layer, and the identification mark is formed in the non-facing region.

[0008] A battery according to the present disclosure includes an electrode assembly including the above-described electrode assembly, and an exterior body that houses the electrode assembly.

[0009] The method for manufacturing an electrode plate according to the present disclosure is a method for manufacturing an electrode plate including a core body and a mixture layer formed on the core body, and an identification mark is formed by irradiating the surface of the mixture layer with laser light.

[0010] According to the electrode plate of the present disclosure, the identification marking is easy to form, and there is no need to widen the exposed portion of the core body to provide the identification marking. Furthermore, the identification marking of the electrode plate of the present disclosure is less likely to deform with use of the electrode plate. Therefore, misreading of the identification marking is less likely to occur.

[0011] Fig. 1 is a cross-sectional view of a cylindrical battery according to an embodiment; Fig. 2 is a front view of a positive electrode plate according to an embodiment, showing a positive electrode lead and its vicinity; Fig. 3 is a front view of a negative electrode plate according to an embodiment, showing a negative electrode lead and its vicinity; Fig. 4 is a view showing a manufacturing process of an electrode plate according to an embodiment.

[0012] Hereinafter, with reference to the drawings, an example of an embodiment of an electrode plate according to the present disclosure, an electrode assembly using the electrode plate, and a battery will be described in detail. 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 embodiments obtained by selectively combining the components of the embodiments described below.

[0013] In the following, a cylindrical battery 10 in which a wound electrode assembly 14 is housed in a cylindrical outer can 16 with a bottom is exemplified as the battery, but the outer can of the battery is not limited to a cylindrical outer can. The battery according to the present disclosure may be, for example, a prismatic battery with a prismatic outer can, a coin battery with a coin-shaped outer can, or a pouch-type battery with an outer can composed of a laminate sheet including a metal layer and a resin layer. Note that while the cylindrical battery 10 of this embodiment is a secondary battery, the electrode plate according to the present disclosure can also be applied to power storage devices other than secondary batteries, such as primary batteries and capacitors.

[0014] FIG. 1 is a schematic diagram showing an axial cross section of a cylindrical battery 10 according to an embodiment. As shown in FIG. 1 , the cylindrical battery 10 includes an electrode assembly 14, an electrolyte, and an outer can 16 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, and is configured such that the positive electrode plate 11 and the negative electrode plate 12 are spirally wound with the separator 13 interposed therebetween. The outer can 16 is a cylindrical metal container with a bottom and an opening on one axial side, and the opening of the outer can 16 is closed by a sealing member 17. Hereinafter, for convenience of explanation, the sealing member 17 side of the cylindrical battery 10 is referred to as the top, and the bottom side of the outer can 16 is referred to as the bottom.

[0015] 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

[0016] The positive electrode plate 11, negative electrode plate 12, and separator 13 that make up the electrode assembly 14 are all long, strip-like bodies that are spirally wound and alternately 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.

[0017] The positive electrode plate 11 has a positive electrode core 30 and a positive electrode mixture layer 31 formed on the positive electrode core 30. The positive electrode core 30 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. The positive electrode mixture layer 31 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 30 except for an exposed portion 32 (see FIG. 2 ), which will be described later. The positive electrode plate 11 can be produced by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder to both sides of the positive electrode core 30 and compressing the coating.

[0018] An example of the positive electrode active material contained in the positive electrode mixture layer 31 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 that the composite oxide contains at least one selected from Ni, Mn, and Co.

[0019] The negative electrode plate 12 has a negative electrode core 40 and a negative electrode mixture layer 41 formed on the negative electrode core 40. The negative electrode core 40 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. The negative electrode mixture layer 41 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 40, excluding the exposed portion 42 (see FIG. 3), which will be described later. 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 40 and compressing the coating.

[0020] An example of the negative electrode active material contained in the negative electrode mixture layer 41 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 materials 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.

[0021] 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.

[0022] Insulating plates 18 and 19 are disposed above and below the electrode body 14. In the example shown in Fig. 1 , the positive electrode lead 20 passes through a through hole in the insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes outside the insulating plate 19 and extends toward the bottom side of the outer can 16. The positive electrode lead 20 is connected to the underside of an internal terminal plate 23 of the sealing body 17 by laser welding or the like, and a cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal. The negative electrode lead 21 is connected to the inner bottom surface of the outer can 16 by laser welding or the like, and the outer can 16 serves as the negative electrode terminal.

[0023] The positive electrode lead 20 is connected to the positive electrode core 30 by ultrasonic welding or the like. The positive electrode lead 20 is joined, for example, to a longitudinal center portion of the positive electrode plate 11, away from both longitudinal ends. The positive electrode lead 20 may be joined to a position substantially equidistant from both longitudinal ends of the positive electrode plate 11. The negative electrode lead 21 is connected to the negative electrode core 40 by ultrasonic welding or the like. In the example shown in FIG. 1 , the negative electrode lead 21 is joined to the longitudinal end of the negative electrode plate 12, which is located on the outer periphery of the electrode body 14. The positive electrode lead 20 and the negative electrode lead 21 are, for example, strip-shaped metal members, and have a thickness of 30 μm to 100 μm.

[0024] 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 40 is exposed may be formed on the outer peripheral surface of the electrode body 14, and the exposed portion may be in contact with the inner surface of the outer can 16, thereby electrically connecting the negative electrode plate 12 and the outer can 16. In this case, the negative electrode plate 12 may not have a negative electrode lead 21.

[0025] As described above, the outer can 16 is a cylindrical metal container with a bottom and an opening on one axial side. A gasket 28 is provided between the outer can 16 and the sealing body 17 to ensure sealing of the battery interior and insulation between the outer can 16 and the sealing body 17. The outer can 16 has a grooved portion 22 that protrudes inward from a portion of its side surface and supports the sealing body 17. The grooved 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 top surface. The sealing body 17 is fixed to the top of the outer can 16 by the grooved portion 22 and the open end of the outer can 16 that is crimped to the sealing body 17.

[0026] The sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked. Each member constituting the sealing body 17 has, for example, a disk or ring shape, and each member except for the insulating member 25 is electrically connected to one another. The lower valve body 24 and the upper valve body 26 are connected at their respective centers, and the insulating member 25 is interposed between their respective peripheral edges. If an abnormality occurs in the battery and the internal pressure increases, the lower valve body 24 deforms and breaks, pushing the upper valve body 26 toward the cap 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure further increases, the upper valve body 26 breaks, and gas is discharged from the opening of the cap 27.

[0027] The positive electrode plate 11 and the negative electrode plate 12 will be described in detail below with reference to Figures 2 and 3. In Figures 2 and 3, the mixture layers are indicated by diagonal hatching, and the tapes 33 and 43 are indicated by dot hatching. As described above, the positive electrode plate 11 has a positive electrode core 30 and a positive electrode mixture layer 31 formed on both sides of the positive electrode core 30. Similarly, the negative electrode plate 12 has a negative electrode core 40 and a negative electrode mixture layer 41 formed on both sides of the negative electrode core 40.

[0028] As shown in Fig. 2, the positive electrode plate 11 has an exposed portion 32 where the surface of the positive electrode core 30 is exposed. The exposed portion 32 is formed by not applying a positive electrode mixture slurry to the positive electrode core 30 and not providing a positive electrode mixture layer 31. Alternatively, the exposed portion 32 may be formed by peeling off a portion of the positive electrode mixture layer 31. In this embodiment, the exposed portion 32 is formed in one location in the center of the positive electrode plate 11 in the longitudinal direction. Note that the position where the exposed portion 32 is formed is not limited to the center of the positive electrode plate 11 in the longitudinal direction, and the exposed portion 32 may be formed in multiple locations spaced apart in the longitudinal direction, for example.

[0029] As will be described in detail later, the positive electrode plate 11 has an identification mark 36 formed on the surface of the positive electrode mixture layer 31. In this embodiment, the positive electrode mixture layer 31 is formed on both sides of the positive electrode core 30, but the identification mark 36 may be formed only on the positive electrode mixture layer 31 on one side (hereinafter, may be referred to as the "first positive electrode mixture layer 31"), or may be formed on both the first positive electrode mixture layer 31 and the positive electrode mixture layer 31 formed on the opposite side (hereinafter, may be referred to as the "second positive electrode mixture layer 31").

[0030] The exposed portion 32 is a portion to which the positive electrode lead 20 is joined, and a joint portion 35 with the positive electrode lead 20 is formed in at least a portion of the exposed portion 32 that contacts the positive electrode lead 20. The joint portion 35 is formed, for example, by ultrasonic welding. The exposed portion 32 preferably includes a first surface to which the positive electrode lead 20 is joined and a second surface opposite the first surface. That is, the positive electrode lead 20 is joined only to one surface of the positive electrode core 30, and the exposed portion 32 is also formed on the other surface where the positive electrode lead 20 is not disposed. The second surface of the exposed portion 32 is preferably formed to be substantially the same size as the first surface and overlap the first surface in the thickness direction of the positive electrode plate 11.

[0031] The exposed portion 32 may be formed so as not to extend from one end of the positive electrode plate 11 to the other end in the width direction, but in the example shown in FIG. 2 , it is formed over the entire width direction. The exposed portion 32 is formed wider than the positive electrode lead 20. The positive electrode lead 20 has a width of 2.5 mm to 4.0 mm, for example, from the viewpoint of achieving both high capacity and low resistance of the battery. The width of the exposed portion 32 is made small as long as it does not interfere with the connection of the positive electrode lead 20. In the positive electrode plate 11, the identification mark 36 is formed on the positive electrode mixture layer 31, so it is not necessary to make the exposed portion 32 large in consideration of the area where the identification mark is formed.

[0032] The positive electrode plate 11 is provided with tape 33 that covers the positive electrode lead 20 joined to the exposed portion 32. The tape 33 preferably covers the positive electrode lead 20, the exposed portion 32, and an adjacent region X adjacent to the exposed portion 32 on the surface of the positive electrode mixture layer 31. At least a portion of the exposed portion 32 is covered with the tape 33. In this embodiment, the tape 33 is formed in a strip shape that is slightly larger than the exposed portion 32, covers the entire exposed portion 32, and also covers the adjacent region X of the positive electrode mixture layer 31. The width of the adjacent region X covered with the tape 33 is smaller than the width of the exposed portion 32, and is, for example, 2.0 mm to 3.5 mm.

[0033] The tape 33 is preferably provided on both sides of the positive electrode core 30. The tape 33 covers the entire first and second surfaces of the exposed portion 32, and further covers an adjacent region X of the first positive electrode mixture layer 31 that is adjacent to the first surface, and an adjacent region X of the second positive electrode mixture layer 31 that is adjacent to the second surface. In addition, the tape 34 is preferably provided on the portion of the positive electrode lead 20 that extends from the exposed portion 32, at least in a range that faces the negative electrode plate 12 with the separator 13 interposed therebetween.

[0034] The tape 33 has, for example, a substrate made of an insulating resin and an adhesive layer formed on one side of the substrate. The same material as the tape 33 can be used for the tape 34. The tape 33 is preferably an insulating tape that is substantially non-conductive. The tape 33 may have a layer structure of three or more layers, and the substrate may be composed of two or more layers of the same or different laminated films. The tape 33 may contain an inorganic filler such as titania, alumina, silica, or zirconia, but preferably has sufficient translucency to allow the identification mark 36 to be read through the tape 33. The tape 33 may be either colored and transparent or colorless and transparent.

[0035] Examples of resins constituting the base material of the tape 33 include polyesters such as polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), polyphenylene sulfide (PPS), polyetherimide (PEI), and polyamide. The adhesive layer is formed, for example, by coating one side of the base material with an adhesive. The adhesive constituting the adhesive layer may be a hot-melt type that develops adhesiveness when heated or a thermosetting type that hardens when heated, but from the standpoint of productivity and the like, adhesives that are adhesive at room temperature are preferred. Examples of adhesives constituting the adhesive layer include acrylic adhesives and synthetic rubber adhesives.

[0036] As described above, the identification mark 36 is formed on the surface of the positive electrode mixture layer 31. The positive electrode plate 11 includes a tape, such as the tape 33, that covers a portion of the positive electrode mixture layer 31, and the identification mark 36 is preferably formed in the area of ​​the surface of 31 that is covered by the tape. The identification mark 36 is an individual mark attached to the positive electrode plate 11 and provides identification information for distinguishing the positive electrode plate 11 from other positive electrode plates 11. A different identification mark 36 is provided for each positive electrode plate 11 or for each group of a predetermined number of positive electrode plates 11. The identification mark 36 may be a lot number attached to a group of products manufactured at the same time using the same material, or may be a product number attached to each individual product.

[0037] The identification mark 36 enables individual positive electrode plates 11 or individual production lots to be distinguished from one another, and is used to obtain information relating to the manufacture of the positive electrode plates 11. For example, the manufacturer of the positive electrode plates 11 has a database that contains information relating to the manufacture of the positive electrode plates 11, linked to the identification mark 36 of the positive electrode plates 11. Therefore, by reading the identification mark 36 with a reading device such as a reader and identifying the positive electrode plate 11, information relating to the manufacture of the positive electrode plate 11 can be obtained. An example of information relating to the manufacture of the positive electrode plates 11 is a history of the manufacturing process, including information such as the manufacturing line and the date and time of manufacture.

[0038] The identification mark 36 is composed of at least one selected from, for example, numbers, letters, and an identification code. The identification mark 36 may be a display consisting of a combination of numbers and letters. The identification code constituting the identification mark 36 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 rectangular two-dimensional code (QR Code (registered trademark)) is formed as the identification mark 36.

[0039] The identification mark 36 may be readable by a reading device such as a reader, and may be composed of at least one selected from a protrusion, a recess, and a through-hole. Alternatively, the identification mark 36 may have a color different from its surroundings. The numbers, letters, or identification code constituting the identification mark 36 may not have a protrusion, recess, or through-hole, and may only have a color different from its surroundings.

[0040] The identification mark 36 may be formed by printing such as inkjet printing or press processing, but is preferably formed by laser marking. Laser marking is a method of forming a mark by irradiating the positive electrode mixture layer 31 with laser light. When the identification mark 36 is a laser marking mark, the mark is formed, for example, by discoloring the portion irradiated with the laser light. Furthermore, a depression or a through-hole may be formed in the portion irradiated with the laser light. Laser marking marks are highly durable, and are therefore less likely to cause reading problems even after the positive electrode plate 11 has been used.

[0041] In the positive electrode plate 11, the identification mark 36 is formed on the surface of the positive electrode mixture layer 31. However, because the positive electrode mixture layer 31 expands and contracts with the charging and discharging of the battery, it was thought that the identification mark 36 formed on the positive electrode mixture layer 31 would be significantly deformed, making it prone to misreading. However, in reality, it has been found that the identification mark 36 does not significantly deform even after repeated charging and discharging of the battery, and the mark can be read without problem by a reading device such as a reader. When the identification mark 36 is formed on the positive electrode mixture layer 31, there is a wide range of options for the position where it is formed, making it easy to form the identification mark 36.

[0042] The identification mark 36 can be formed at any position on the surface of the positive electrode mixture layer 31. The identification mark 36 is preferably covered with tape such as tape 33. The area of ​​the positive electrode mixture layer 31 covered with tape does not substantially contribute to charge / discharge and undergoes only a small volume change during charge / discharge. Therefore, by covering the identification mark 36 with tape, deformation of the identification mark 36 can be more effectively suppressed. It is sufficient that at least a portion of the identification mark 36 is covered with tape, but it is preferable that the entire identification mark 36 is covered with tape.

[0043] In this embodiment, the identification mark 36 is formed in an adjacent region X adjacent to the exposed portion 32 on the surface of the positive electrode mixture layer 31. This makes it easy to cover the identification mark 36 with the tape 33 covering the exposed portion 32. The adjacent region X covered by the tape 33 has a shape that is elongated in the width direction of the positive electrode plate 11 when viewed from the front. Therefore, the identification mark 36 is also formed in a rectangular shape that is elongated in the width direction of the positive electrode plate 11 so that the identification mark 36 is entirely covered by the tape 33. Note that when other tape, such as tape that protects the peripheral portion of the positive electrode mixture layer 31, is provided, the identification mark 36 may be formed on the peripheral portion of the positive electrode mixture layer 31 so as to be covered by the other tape.

[0044] Furthermore, as a result of investigations by the present inventors, it was found that when the identification mark 36 is formed by laser marking, the constituent materials of the positive electrode mixture layer 31, particularly the binder, are altered in the area irradiated with the laser light. Normally, the binder is present on the surface of the active material in the form of an agglomeration of fine particles, but in the area of ​​the positive electrode mixture layer 31 irradiated with the laser light, the binder melts and becomes a film that covers the surface of the active material. This change in state may suppress volumetric change of the positive electrode mixture layer 31 during charge and discharge in the area where the identification mark 36 is formed, making it less likely that deformation of the identification mark 36 will occur.

[0045] As described above, the identification mark 36 may be formed on only one or both of the surfaces of the first and second positive electrode mixture layers 31. The identification mark 36 is formed, for example, in adjacent regions X on both surfaces of the positive electrode plate 11, overlapping in the thickness direction of the positive electrode plate 11. The identification mark 36 is formed, for example, in one location on the surface of the first positive electrode mixture layer 31, but may also be formed in multiple locations. That is, multiple identification marks 36 may be formed on the first positive electrode mixture layer 31. In this case, the identification mark 36 in the best condition can be selected and read. The multiple identification marks 36 do not need to be identical and may be different from each other. One identification mark 36 may be formed on each of the surfaces of the first and second positive electrode mixture layers 31, or multiple identification marks 36 may be formed on each surface.

[0046] As shown in Fig. 3, the negative electrode plate 12 has an exposed portion 42 where the surface of the negative electrode core 40 is exposed. The exposed portion 42 is formed by not applying a negative electrode mixture slurry to the negative electrode core 40 and not providing a negative electrode mixture layer 41. Alternatively, the exposed portion 42 may be formed by peeling off a portion of the negative electrode mixture layer 41. In this embodiment, the exposed portion 42 is formed in one location at the longitudinal end of the negative electrode plate 12 located on the outer periphery of the electrode body 14. Note that the location where the exposed portion 42 is formed is not limited to the longitudinal end of the negative electrode plate 12, and the exposed portion 42 may be formed in multiple locations spaced apart in the longitudinal direction, for example.

[0047] Similar to the case of the positive electrode plate 11, the negative electrode plate 12 has an identification mark 46 formed on the surface of the negative electrode mixture layer 41. The negative electrode plate 12 has a tape 43 covering the exposed portion 42 and an adjacent region Y of the surface of the negative electrode mixture layer 41 that is adjacent to the exposed portion 42. The tape 43 may be the same as the tape 33 of the positive electrode plate 11. Similar to the exposed portion 32 of the positive electrode plate 11, the exposed portion 42 preferably includes a first surface to which the negative electrode lead 21 is joined and a second surface opposite to the first surface. A joint portion 45 with the negative electrode lead 21 is formed on the first surface of the exposed portion 42. The tape 43 is attached to both sides of the negative electrode plate 12.

[0048] The identification mark 46 can have the same configuration as the identification mark 36 of the positive electrode plate 11, and therefore the description of the identification mark 36 can be used. The identification mark 46 is preferably formed entirely in the adjacent region Y of the negative electrode mixture layer 41 that is covered by the tape 43. The identification mark 46 may be formed on only one or both of the surfaces of the first and second negative electrode mixture layers 41. Furthermore, one identification mark 46 may be formed on each of the surfaces of the first and second negative electrode mixture layers 41, or multiple identification marks 46 may be formed on each surface.

[0049] The negative electrode mixture layer 41 is formed to have a larger area than the positive electrode mixture layer 31 in order to prevent lithium precipitation. Therefore, the negative electrode mixture layer 41 has a non-facing region that does not face the positive electrode mixture layer 31. The identification mark 46 may be formed in this non-facing region. Since the non-facing region does not substantially contribute to charge / discharge and experiences small volume changes during charge / discharge, forming the identification mark 46 in this region can more effectively suppress deformation of the mark. Note that the adjacent region Y shown in FIG. 3 may be a non-facing region that does not face the positive electrode mixture layer 31.

[0050] FIG. 4 shows an example of a process for forming an identification mark 36 on the positive electrode mixture layer 31 of the positive electrode plate 11. As shown in FIG. 4 , the identification mark 36 can be formed by laser marking, in which a laser beam α is irradiated onto the surface of the positive electrode mixture layer 31. Laser marking is a non-contact marking method using a laser beam, and allows for high-speed marking. The laser beam α is scanned, for example, on the positive electrode mixture layer 31 in the lengthwise and widthwise directions of the positive electrode plate 11. The portion irradiated with the laser beam α changes color or becomes a minute depression, thereby forming the identification mark 36 (two-dimensional code). The identification mark 36 is formed in an area adjacent to the exposed portion 32, in an area that will be covered by tape 33 when it is applied in a later process.

[0051] 4, a long positive electrode core 30 is intermittently coated with a positive electrode mixture slurry to form a positive electrode mixture layer 31 and an exposed portion 32, and then a region of the surface of the positive electrode mixture layer 31 adjacent to the exposed portion 32 is irradiated with laser light α to form an identification mark 36. It is preferable that the long positive electrode core 30 on which the positive electrode mixture layer 31 and the exposed portion 32 have been formed is transported to an irradiation spot of the laser light α to continuously form the identification mark 36. In the example shown in FIG. 4, the laser light α is irradiated onto the positive electrode core 30 in a state in which a predetermined tension is applied between transport rollers 100 and 101.

[0052] As described above, with the cylindrical battery 10 having the above configuration, the identification marks 36, 46 are easy to form, and deformation of the identification marks 36, 46 due to charge / discharge is unlikely to occur, making it less likely that the marks will be misread. When forming the identification marks 36, 46 on the positive electrode mixture layers 31, 41, respectively, there is a wide range of options for the formation position, making it easy to form the identification marks 36, 46. Furthermore, forming the identification marks 36, 46 in areas of the surfaces of the positive electrode mixture layers 31, 41 that will be covered with tape improves the effect of suppressing deformation of the marks and effectively suppresses wear of the identification marks 36, 46 and deterioration of the marks due to exposure to the electrolyte, etc.

[0053] In the above embodiment, the identification markings are provided on both the positive electrode plate and the negative electrode plate, but the identification markings may be provided only on the positive electrode plate or only on the negative electrode plate.

[0054] The present disclosure will be further described by the following embodiments. Configuration 1: An electrode plate having a core and a mixture layer formed on the core, wherein an identification mark is formed on the surface of the mixture layer. Configuration 2: The electrode plate according to Configuration 1, wherein the identification mark is covered with tape. Configuration 3: The electrode plate according to Configuration 2, wherein the surface of the core has an exposed portion, and the identification mark is formed in an area of ​​the surface of the mixture layer adjacent to the exposed portion, and at least a portion of the exposed portion is covered with the tape. Configuration 4: The electrode plate according to any one of Configurations 1 to 3, wherein the identification mark is a laser-marked mark. Configuration 5: A wound electrode body including the electrode plate according to any one of Configurations 1 to 4, wherein the electrode plate is at least a negative electrode plate, the mixture layer of the negative electrode plate has a non-facing area that does not face a positive electrode mixture layer, and the identification mark is formed in the non-facing area. Configuration 6: A battery comprising an electrode assembly including the electrode plate according to any one of configurations 1 to 4, and an exterior body that houses the electrode assembly. Configuration 7: A method for manufacturing an electrode plate having a core and a mixture layer formed on the core, the method comprising irradiating a surface of the mixture layer with laser light to form an identification mark.

[0055] REFERENCE SIGNS LIST 10 Cylindrical battery, 11 Positive electrode plate, 12 Negative electrode plate, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18, 19 Insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved portion, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive electrode core, 31 Positive electrode mixture layer, 32, 42 Exposed portion, 33, 34, 43 Tape, 35, 45 Joint portion, 36, 46 Identification mark, 40 Negative electrode core, 41 Negative electrode mixture layer, 100, 101 Conveyor roller

Claims

1. An electrode plate having a core body and a mixture layer formed on the core body, wherein an identification mark is formed on the surface of the mixture layer.

2. The electrode plate of claim 1, wherein the identification marking is covered with tape.

3. The electrode plate according to claim 2, wherein the surface of the core body has an exposed portion, the identification mark is formed in an area of ​​the surface of the mixture layer adjacent to the exposed portion, and at least a portion of the exposed portion is covered by the tape.

4. The electrode plate according to claim 1, wherein the identification marking is a laser marking marking.

5. A wound electrode body comprising the electrode plate according to claim 1, wherein the electrode plate is at least a negative electrode plate, the mixture layer of the negative electrode plate has a non-facing region that does not face the positive electrode mixture layer, and the identification mark is formed in the non-facing region.

6. A battery comprising: an electrode assembly including an electrode plate according to any one of claims 1 to 4; and an exterior housing that houses the electrode assembly.

7. A method for manufacturing an electrode plate having a core body and a mixture layer formed on the core body, comprising irradiating a surface of the mixture layer with laser light to form an identification mark.