Electrode plate, electrode body, and battery

Abstract

Disclosed is an electrode plate 21 comprising a band-like first core body 22 having a first main surface 23 and a second main surface 24, and active material layers 29 formed on the first main surface 23 and the second main surface 24. The first core body 22 has a double-sided exposure part 25 in which the active material layers 29 are not formed on the first main surface 23 and the second main surface 24. The double-sided exposure part 25 includes a first bonding region 25a to which a first lead 32 is bonded. At least one of the first main surface 23 and the second main surface 24 in the double-sided exposure part 25 is provided with a first identification display part 31 so that at least a part thereof overlaps with the first bonding region 25a in the thickness direction of the first core body 22. This makes it possible to avoid a decrease in the battery capacity due to the identification display part.

Description

Electrode plate, electrode body, and battery

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

[0002] A technology for displaying information on an electrode plate included in a battery has been known (for example, see Patent Document 1). The electrode plate in Patent Document 1 includes a strip-shaped core body and active material layers formed on both sides of the core body, the core body having an exposed portion to which a current collecting lead is connected, and an identification marking that can identify the manufacturing process history is formed in a position of the exposed portion different from the current collecting lead.

[0003] International Publication No. 2019 / 193869

[0004] However, although the identification marking is necessary to identify the manufacturing process history, the active material layer cannot be disposed in the area where the identification marking is formed. In other words, the area where the identification marking is formed cannot effectively contribute to the development of battery capacity, and the presence of the identification marking can be seen as reducing the battery capacity. In this situation, one of the objectives of the present disclosure is to avoid the reduction in battery capacity due to the identification marking.

[0005] One aspect of the present disclosure relates to an electrode plate including a strip-shaped first substrate having a first main surface and a second main surface, and active material layers formed on the first and second main surfaces, the first substrate having a double-sided exposed portion where the active material layers are not formed on the first and second main surfaces, the double-sided exposed portion including a first bonding region to which a first lead is bonded, and a first identification mark formed on at least one of the first and second main surfaces of the double-sided exposed portion so as to at least partially overlap the first bonding region in a thickness direction of the first substrate.

[0006] Another aspect of the present disclosure relates to an electrode assembly including a first electrode plate and a second electrode plate wound with a separator interposed therebetween, the first electrode plate being the electrode plate described above.

[0007] Another aspect of the present disclosure relates to a battery including the above-described electrode assembly and a bottomed cylindrical outer can that houses the electrode assembly.

[0008] According to the present disclosure, it is possible to avoid a decrease in battery capacity due to an identification display portion.

[0009] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present application, will be better understood from the following detailed description taken in conjunction with the drawings.

[0010] 1A is a longitudinal cross-sectional view schematically illustrating an example of a battery according to the present disclosure; 2A is a perspective view schematically illustrating an example of an electrode body, with the first and second leads omitted; 3A is a plan view schematically illustrating an example of a first electrode plate (electrode plate), and 3B is a cross-sectional view taken along line III-III.

[0011] The following describes examples of embodiments of the electrode plate, electrode body, and battery according to the present disclosure. However, the present disclosure is not limited to the examples described below. While the following description may use specific numerical values ​​and materials, other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained.

[0012] (Electrode Plate) The electrode plate according to the present disclosure includes a strip-shaped first core and an active material layer. The following description will be given using an electrode plate used in a non-aqueous electrolyte secondary battery (e.g., a lithium-ion secondary battery) as an example, but the use of the electrode plate is not limited thereto. Note that the present disclosure also includes, in the category of secondary batteries, an electricity storage device (e.g., a lithium-ion capacitor) in which at least one of the positive electrode and the negative electrode is an electrode that generates capacity through a non-Faradic reaction.

[0013] The first core has a first main surface and a second main surface. When the electrode plate is used as a positive electrode plate, the first core may be a metal foil made of, for example, aluminum, an aluminum alloy, stainless steel, titanium, a titanium alloy, etc. When the electrode plate is used as a negative electrode plate, the first core may be a metal foil made of, for example, copper, a copper alloy, nickel, a nickel alloy, etc.

[0014] The active material layer is formed on the first main surface and the second main surface of the first substrate. When the electrode plate is used as a positive electrode plate, the active material layer is a positive electrode active material layer and may contain, in addition to the positive electrode active material, a conductive agent, a binder, a thickener, etc. When the electrode plate is used as a negative electrode plate, the active material layer is a negative electrode active material layer and may contain, in addition to the negative electrode active material, a conductive agent, a binder, a thickener, etc.

[0015] As the positive electrode active material, for example, a composite metal oxide of lithium and a transition metal such as cobalt, manganese, or nickel can be used. The positive electrode active material may be used alone or in combination of two or more. As the negative electrode active material, for example, natural graphite, spherical or fibrous artificial graphite, non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), and other carbon materials can be used.

[0016] Examples of the conductive agent include carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; and conductive fibers such as carbon fiber and metal fiber. Various graphites such as natural graphite and artificial graphite may also be used as the conductive agent for the positive electrode.

[0017] The binder is not particularly limited as long as it can be dissolved or dispersed in the dispersion medium by kneading. Examples of binders include fluororesins, rubbers, acrylic polymers, or vinyl polymers (e.g., homopolymers or copolymers of monomers such as acrylic monomers such as methyl acrylate and acrylonitrile, and vinyl monomers such as vinyl acetate). Examples of fluororesins include polyvinylidene fluoride, copolymers of vinylidene fluoride and propylene hexafluoride, and polytetrafluoroethylene. Examples of rubbers include acrylic rubber, modified acrylonitrile rubber, and styrene butadiene rubber (SBR). The binder may be used alone or in combination of two or more. Generally, fluororesins are preferred as binders for the positive electrode, and fluororesins and rubbers are preferred as binders for the negative electrode.

[0018] The first core has a double-sided exposed portion where no active material layer is formed on the first main surface and the second main surface. The double-sided exposed portion may be located midway along the length of the first core. The double-sided exposed portion includes a first bonding region to which the first lead is bonded. The first lead is a positive electrode lead when the electrode plate is used as a positive electrode plate, and is a negative electrode lead when the electrode plate is used as a negative electrode plate. The first bonding region is a region where the first core (double-sided exposed portion) and the first lead are bonded to each other (e.g., a region where they are fused together), and is typically contained within the outline of the first lead when viewed in the thickness direction of the first core.

[0019] Here, it is difficult to provide an active material layer in the first bonding region, and it is also difficult to provide an active material layer in the region where the identification mark is formed. Therefore, typically, the first bonding region and the region where the identification mark is formed each constitute dead space from the perspective of battery capacity development. In contrast, in the electrode plate disclosed herein, the first identification mark is formed on at least one of the first and second main surfaces of the both-side exposed portion so as to at least partially overlap with the first bonding region in the thickness direction of the first substrate. That is, as shown in FIG. 3( a), the first bonding region and the region where the first identification mark is formed at least partially overlap with each other when viewed from a direction perpendicular to the plane of the drawing. This reduces the dead space from the above perspective, and prevents a decrease in battery capacity.

[0020] The first identification marking may be an identification marking that can identify the history of the manufacturing process. The first identification marking may be, but is not limited to, a QR code (registered trademark), which is a two-dimensional code. For example, the first identification marking may be composed of numbers, letters, or a combination of numbers and letters, or may be composed of protrusions, holes, or a combination of protrusions and holes. The first identification marking may also be a one-dimensional code such as a barcode. The first identification marking may be formed, for example, by irradiating a laser onto the first main surface and / or the second main surface of the double-sided exposed portion.

[0021] The first core may further include a first double-coated portion extending continuously from one end of the double-sided exposed portion in the longitudinal direction of the first core, with active material layers formed on the first and second principal surfaces, and a second double-coated portion extending continuously from the other end of the double-sided exposed portion in the longitudinal direction of the first core, with active material layers formed on the first and second principal surfaces. In this configuration, the double-sided exposed portion is sandwiched between the first double-coated portion and the second double-coated portion in the longitudinal direction of the first core. The first and second double-coated portions are stronger than the double-sided exposed portion, and therefore deformation of the double-sided exposed portion is suppressed when forming the first identification mark on the double-sided exposed portion. This allows the first identification mark to be formed on the double-sided exposed portion with high precision. However, the first core does not necessarily have to include at least one of the first double-coated portion and the second double-coated portion.

[0022] The first core may further include a third double-coated section that is continuous with the double-sided exposed section in the width direction of the first core and has active material layers formed on the first and second main surfaces. With this configuration, the double-sided exposed section is reinforced in three directions by the first to third double-sided coated sections, making it even less susceptible to deformation. This allows the first identification mark to be formed on the double-sided exposed section with even greater precision. Furthermore, in the electrode plate according to the present disclosure, the area of ​​the third double-sided coated section can be increased because the formation space for the third double-sided coated section is not narrowed by the first identification mark.

[0023] The first double-sided coated portion, the second double-sided coated portion, and the third double-sided coated portion may be connected in the longitudinal direction of the first core. This configuration enhances the reinforcement effect of the double-sided exposed portion compared to when the first to third double-sided coated portions are not connected. This allows the first identification mark to be formed on the double-sided exposed portion with even greater precision.

[0024] The electrode plate may further include a first lead bonded to the first bonding region. An electrode plate having this configuration may also be referred to as an "electrode plate assembly" because it includes the first lead in addition to the above-described electrode plate. However, in this specification, there is no clear distinction between the electrode plate and the electrode plate assembly, and both will be referred to as the "electrode plate" unless otherwise specified.

[0025] (Electrode Assembly) The electrode assembly according to the present disclosure includes a first electrode plate and a second electrode plate wound with a separator interposed therebetween. In other words, the electrode assembly according to the present disclosure is a wound-type electrode assembly. The first electrode plate is the electrode plate described above. The first electrode plate may be either a negative electrode plate or a positive electrode plate. The separator may be formed in a strip shape. The separator may be made of a polyolefin-based material or a porous film combining a polyolefin-based material with a heat-resistant material. Examples of porous films made of polyolefin-based materials include porous films made of polyethylene, polypropylene, and ethylene-propylene copolymer. These resins may be used alone or in combination. If necessary, other thermoplastic polymers may be used in combination with the polyolefin. Examples of heat-resistant materials include heat-resistant resins and inorganic fillers. The porous film may be a single film or a multilayer film. The multilayer film may include a film made of a mixture of a heat-resistant resin and an inorganic filler.

[0026] The second electrode plate may include a strip-shaped second core having a second bonding region to which the conductive member is bonded. The second core may have a second identification mark formed thereon so as not to overlap the second bonding region in the thickness direction of the second core. The conductive member may be made of metal, and may be, for example, a second lead bonded to the main surface of the second electrode plate or a current collector plate bonded to the end of the second electrode plate. The conductive member may have a polarity opposite to that of the first lead. The second core may have a third main surface and a fourth main surface. The second bonding region is a region where the second core and the conductive member are bonded to each other (e.g., a region where the two are fused together), and is typically contained within the outline of the conductive member when viewed in the thickness direction of the second core.

[0027] The second identification marker may be an identification marker that can identify the history of the manufacturing process. The second identification marker may be, but is not limited to, a QR code (registered trademark), which is a two-dimensional code. For example, the second identification marker may be composed of numbers, letters, or a combination of numbers and letters, or may be composed of protrusions, holes, or a combination of protrusions and holes. The second identification marker may also be a one-dimensional code such as a barcode. The second identification marker may be formed, for example, by irradiating the third main surface and / or the fourth main surface of the second core with a laser. The second identification marker may or may not overlap the conductive member (e.g., the second lead) in the thickness direction of the second core, as long as it does not overlap the second bonding region.

[0028] The second identification marking may be linked to the first identification marking. In this configuration, information on not only the second electrode plate but also the first electrode plate can be checked via the second identification marking. This is particularly useful because the first identification marking may become unreadable after the first lead is joined to the first core. This linking may be achieved, for example, by registering information on the first and second identification marking marks in a predetermined terminal before winding the first electrode plate and the second electrode plate around the separator.

[0029] (Battery) A battery according to the present disclosure includes the electrode assembly described above and a bottomed, cylindrical outer can that houses the electrode assembly. The outer can may be, for example, a bottomed cylindrical shape or a bottomed, rectangular tubular shape. A first core or a second core may be in contact with the inner surface of the outer can. The outer can may house a nonaqueous electrolyte together with the electrode assembly. The nonaqueous electrolyte can be prepared by dissolving a lithium salt in a nonaqueous solvent. Examples of nonaqueous solvents include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; chain carbonates such as dimethyl carbonate and diethyl carbonate; and lactones such as γ-butyrolactone. The nonaqueous solvents can be used alone or in combination.

[0030] Examples of lithium salts include lithium salts with strong electron-withdrawing properties, such as LiPF, LiBF, LiClO, LiAsF, LiCFSO, LiN(SOCF), LiN(SOCF) and LiC(SOCF). These lithium salts can be used alone or in combination. The concentration of the lithium salt in the nonaqueous electrolyte is, for example, 0.5 to 1.5 M, preferably 0.7 to 1.2 M.

[0031] The non-aqueous electrolyte may contain additives as appropriate. For example, vinylene carbonate (VC), cyclohexylbenzene (CHB), and modified forms thereof may be used to form good films on the positive and negative electrodes. For example, terphenyl, cyclohexylbenzene, diphenyl ether, and the like may be used as additives that act when the non-aqueous electrolyte secondary battery is overcharged. The additives may be used alone or in combination of two or more. The proportion of these additives is not particularly limited, but is, for example, about 0.05 to 10 wt % of the non-aqueous electrolyte.

[0032] As described above, according to the present disclosure, by arranging the first identification indicator so that it at least partially overlaps with the first joint region, it is possible to avoid a decrease in battery capacity due to the first identification indicator. Furthermore, according to the present disclosure, by linking the first identification indicator and the second identification indicator to each other, it is possible to check information about the first electrode plate and the second electrode plate only using the latter.

[0033] Below, examples of an electrode plate, an electrode assembly, and a battery according to the present disclosure will be specifically described with reference to the drawings. The components described above can be applied to the components of the example electrode plate, electrode assembly, and battery described below. The components of the example electrode plate, electrode assembly, and battery described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiment. Among the components of the example electrode plate, electrode assembly, and battery described below, components that are not essential to the electrode plate, electrode assembly, and battery according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shape or number of actual components.

[0034] The battery 10 of this embodiment is configured as a lithium-ion secondary battery, but is not limited to this. As shown in Figures 1 to 3, the battery 10 includes a wound electrode assembly 20, a cylindrical outer can 40 with a bottom, and a sealing plate 50.

[0035] The electrode assembly 20 is formed by winding a strip-shaped first electrode plate 21 and a second electrode plate 33 with a strip-shaped separator 36 interposed therebetween. The electrode assembly 20 also includes a pair of tapes 37 arranged near both widthwise ends of the second electrode plate 33 (near the top and bottom ends in FIG. 2 ) and holding the electrode assembly 20 in a wound state. In this embodiment, the first electrode plate 21 is a positive electrode and the second electrode plate 33 is a negative electrode, but this is not limited thereto. The second electrode plate 33 is exposed along its entire periphery at the outermost periphery of the electrode assembly 20, but this is not limited thereto. At the outermost periphery of the electrode assembly 20, a second core 34 (see FIG. 2 ) of the second electrode plate 33 contacts the inner surface of the outer can 40.

[0036] 3 , the first electrode plate 21 includes a strip-shaped first core body 22 having a first main surface 23 and a second main surface 24, a first active material layer 29 formed on the first main surface 23 and the second main surface 24, and a conductive first lead 32. In this embodiment, the first active material layer 29 is a positive electrode active material layer. The first electrode plate 21 is an example of an electrode plate, and the first active material layer 29 is an example of an active material layer.

[0037] The first core 22 has a double-sided exposed portion 25, a first double-sided coated portion 26, a second double-sided coated portion 27, and a third double-sided coated portion 28. The double-sided exposed portion 25 does not have a first active material layer 29 formed on the first main surface 23 or the second main surface 24. The first double-sided coated portion 26 is provided continuously with one end (the left end in FIG. 3( a)) of the double-sided exposed portion 25 in the longitudinal direction (the left-right direction in FIG. 3( a)) of the first core 22, and the first active material layer 29 is formed on the first main surface 23 or the second main surface 24. The second double-sided coated portion 27 is provided continuously with the other end (the right end in FIG. 3( a)) of the double-sided exposed portion 25 in the longitudinal direction of the first core 22, and the first active material layer 29 is formed on the first main surface 23 or the second main surface 24. The third double-sided coated section 28 is provided continuously with the double-sided exposed section 25 in the width direction of the first core 22 (the vertical direction in FIG. 3( a)), and a first active material layer 29 is formed on the first main surface 23 and the second main surface 24. The first double-sided coated section 26, the second double-sided coated section 27, and the third double-sided coated section 28 are connected in the longitudinal direction of the first core 22. The first core 22 is made of, for example, aluminum foil or aluminum alloy foil.

[0038] The double-sided exposed portion 25 of the first core 22 includes a first bonding region 25a to which the first lead 32 is bonded. The width dimension (horizontal dimension in FIG. 3A ) of the first lead 32 may be, for example, 2 mm or more and 4 mm or less. The width dimension (horizontal dimension in FIG. 3A ) of the first bonding region 25a may be, for example, 1 mm or more and 3 mm or less. In this embodiment, the first lead 32 is ultrasonically bonded to the first core 22 in the first bonding region 25a, but this is not limited to this. The double-sided exposed portion 25 may be covered with insulating tape (not shown) provided to cover the first lead 32.

[0039] Both the first main surface 23 and the second main surface 24 of the double-sided exposed portion 25 are formed with a first identification mark 31, which allows identification of the manufacturing process history of the first electrode plate 21, so that the first identification mark 31 at least partially overlaps the first bonding region 25a in the thickness direction of the first core 22 (the vertical direction in FIG. 3B ). In this embodiment, the first identification mark 31 is a QR Code (registered trademark), which is a two-dimensional code, but is not limited thereto. While FIG. 3B illustrates the first identification mark 31 protruding from the first main surface 23 and the second main surface 24, this is for convenience of explanation, and the first identification mark 31 does not necessarily have to protrude from the first main surface 23 and the second main surface 24. For example, the first identification mark 31 may be composed of a number of depressions (not shown) formed on the first main surface 23 and the second main surface 24 by laser irradiation. The depth of the depressions may be, for example, 1 μm or more and 3 μm or less.

[0040] 3, the center of the first joint region 25a and the center of the first identification marking portion 31 coincide with each other in the longitudinal direction of the first core body 22, but this is not limiting. For example, the center of the first identification marking portion 31 may be shifted to one side (e.g., the left side in FIG. 3A ) from the center of the first joint region 25a in the longitudinal direction of the first core body 22. However, even when the centers of the first and second identification marking portions 31 and 31 are shifted in this manner, it is still necessary that at least a portion of the first identification marking portion 31 overlaps with the first joint region 25a in the thickness direction of the first core body 22.

[0041] Although not shown, the second electrode plate 33 includes a strip-shaped second core 34 having two main surfaces and a second active material layer formed on the two main surfaces. The second core 34 is made of, for example, copper foil or copper alloy foil. In this embodiment, the second active material layer is a negative electrode active material layer. In this embodiment, the length of the second electrode plate 33 is greater than the length of the first electrode plate 21, but this is not limited to this.

[0042] The second core 34 has a second bonding region (not shown) to which the second lead 61 is bonded. The second core 34 has a second identification mark 35 linked to the first identification mark 31 formed thereon so as not to overlap the second bonding region in the thickness direction. In other words, the second identification mark 35 is an identification mark that can identify the manufacturing history of the first electrode plate 21 and the second electrode plate 33. In this embodiment, the second identification mark 35 is a QR code (registered trademark), which is a two-dimensional code, but is not limited to this. In this embodiment, the second identification mark 35 is arranged on the outermost periphery of the electrode body 20, but is not limited to this. The second lead 61 is an example of a conductive member.

[0043] The exterior can 40 accommodates the electrode assembly 20 and a non-aqueous electrolyte (not shown). The exterior can 40 is made of metal and is formed into a cylindrical shape with a bottom and an opening at one end (the upper end in FIG. 1 ). A second lead 61, which is connected to the second electrode plate 33, is connected to the inner bottom surface of the exterior can 40. Thus, the exterior can 40 of this embodiment functions as an external negative electrode terminal. A ring-shaped second insulating plate 64 is provided between the inner bottom surface of the exterior can 40 and the electrode assembly 20.

[0044] The sealing plate 50 seals the opening of the outer can 40. A gasket 62 is disposed around the periphery of the sealing plate 50, and the inside of the outer can 40 is sealed by crimping the open edge of the outer can 40 together with the gasket 62. The sealing plate 50 is electrically connected to the first electrode plate 21 via the first lead 32. Therefore, the sealing plate 50 of this embodiment functions as an external positive electrode terminal. A ring-shaped first insulating plate 63 is provided between the sealing plate 50 and the electrode body 20.

[0045] <<Supplementary Note>> The above description of the embodiment discloses the following technology: (Technology 1) An electrode plate comprising: a strip-shaped first substrate having a first main surface and a second main surface; and active material layers formed on the first main surface and the second main surface, wherein the first substrate has double-sided exposed portions where the active material layers are not formed on the first main surface and the second main surface, the double-sided exposed portions include a first bonding region to which a first lead is bonded, and at least one of the first main surface and the second main surface of the double-sided exposed portion has a first identification mark formed thereon so as to overlap at least a portion of the first bonding region in the thickness direction of the first substrate. (Technology 2) The electrode plate according to Technology 1, wherein the first core further includes: a first double-sided coated portion provided contiguous to one end of the double-sided exposed portion in the longitudinal direction of the first core, the active material layer being formed on the first main surface and the second main surface; and a second double-sided coated portion provided contiguous to the other end of the double-sided exposed portion in the longitudinal direction of the first core, the active material layer being formed on the first main surface and the second main surface. (Technology 3) The electrode plate according to Technology 2, wherein the first core further includes a third double-sided coated portion provided contiguous to the double-sided exposed portion in the width direction of the first core, the active material layer being formed on the first main surface and the second main surface. (Technology 4) The electrode plate according to Technology 3, wherein the first double-sided coated portion, the second double-sided coated portion, and the third double-sided coated portion are connected in the longitudinal direction of the first core. (Technology 5) The electrode plate according to any one of Technology 1 to 4, further including the first lead joined to the first joining region. (Technology 6) An electrode body comprising a first electrode plate and a second electrode plate wound with a separator interposed therebetween, wherein the first electrode plate is the electrode plate described in Technology 5. (Technology 7) The electrode body described in Technology 6, wherein the second electrode plate comprises a strip-shaped second core body having a second bonding region to which a conductive member is bonded, and the second core body has a second identification marking portion formed on it so as not to overlap the second bonding region in the thickness direction of the second core body. (Technology 8) The electrode body described in Technology 7, wherein the second identification marking portion is linked to the first identification marking portion. (Technology 9) A battery comprising: the electrode body described in any one of Technology 6 to 8; and a bottomed cylindrical outer can that houses the electrode body.

[0046] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0047] The present disclosure can be used for electrode plates, electrode assemblies, and batteries.

[0048] 10: Battery 20: Electrode body 21: First electrode plate (electrode plate) 22: First core 23: First main surface 24: Second main surface 25: Double-sided exposed portion 25a: First bonding region 26: First double-sided coated portion 27: Second double-sided coated portion 28: Third double-sided coated portion 29: First active material layer (active material layer) 31: First identification marking portion 32: First lead 33: Second electrode plate 34: Second core 35: Second identification marking portion 36: Separator 37: Tape 40: Outer can 50: Sealing plate 61: Second lead (conductive member) 62: Gasket 63: First insulating plate 64: Second insulating plate

Claims

1. An electrode plate comprising: a band-shaped first core having a first main surface and a second main surface; and an active material layer formed on the first main surface and the second main surface, wherein the first core has a double-sided exposed portion where the active material layer is not formed on the first main surface and the second main surface, the double-sided exposed portion includes a first bonding region where a first lead is bonded, and at least one of the first main surface and the second main surface of the double-sided exposed portion has a first identification mark formed thereon so as to overlap at least a portion of the first bonding region in the thickness direction of the first core.

2. The electrode plate described in claim 1, wherein the first core further has: a first double-sided coated portion that is continuous with one end of the double-sided exposed portion in the longitudinal direction of the first core, and in which the active material layer is formed on the first main surface and the second main surface; and a second double-sided coated portion that is continuous with the other end of the double-sided exposed portion in the longitudinal direction of the first core, and in which the active material layer is formed on the first main surface and the second main surface.

3. An electrode plate as described in claim 2, wherein the first core body further has a third double-sided coated portion which is continuous with the double-sided exposed portion in the width direction of the first core body and in which the active material layer is formed on the first main surface and the second main surface.

4. An electrode plate as described in claim 3, wherein the first double-sided coated portion, the second double-sided coated portion, and the third double-sided coated portion are connected in the longitudinal direction of the first core body.

5. An electrode plate according to any one of claims 1 to 4, further comprising the first lead joined to the first joining region.

6. An electrode assembly comprising a first electrode plate and a second electrode plate wound with a separator interposed therebetween, the first electrode plate being the electrode plate according to claim 5.

7. An electrode body as described in claim 6, wherein the second plate comprises a band-shaped second core body having a second bonding region to which a conductive member is bonded, and the second core body has a second identification marking portion formed thereon so as not to overlap the second bonding region in the thickness direction of the second core body.

8. The electrode body according to claim 7, wherein the second identification display portion is associated with the first identification display portion.

9. A battery comprising: the electrode assembly according to claim 6; and a bottomed cylindrical exterior can housing the electrode assembly.