Battery

Abstract

A battery according to one embodiment of the present invention comprises: an electrode group in which a belt-shaped positive electrode plate (11) and a belt-shaped negative electrode plate are wound with a separator interposed therebetween; an electrolyte; and externally canning. A positive electrode plate (11) has a positive electrode mixture layer (31) formed on a belt-shaped positive electrode core (30), and has, in the width direction of the positive electrode plate (11), a positive electrode tab (20) connected to one end side of the positive electrode core (30) and within a range that does not exceed the center of the positive electrode plate (11), and a dummy tab (37) connected to the other end side of the positive electrode core (30) and within a range that does not exceed the center of the positive electrode plate (11) in the width direction of the positive electrode plate (11). When the positive electrode plate (11) is viewed in the width direction, the dummy tab (37) is disposed so as to overlap at least a part of the positive electrode tab (20).

Description

Technical Field

[0001] The present disclosure relates to a battery including an electrode group formed by winding a strip-shaped positive electrode plate and a strip-shaped negative electrode plate with a separator interposed therebetween, an electrolyte, and an outer can. Background Art

[0002] In recent years, with the popularity of smart devices such as electric vehicles and smartphones, the demand for batteries with high energy density has increased. On the other hand, there is a risk that the increase in energy density may compromise safety. For example, when an impact or stress is applied to the battery from the outside, the battery deforms, and there is a possibility that the collector lugs or plates inside the battery pierce the separator, causing an internal short circuit. Therefore, in high-energy-density batteries, the risk tends to be greater than that of low-energy-density batteries.

[0003] Patent Document 1 describes a battery designed to prevent winding deviation of an electrode group. In the battery described in Patent Document 1, a stripped portion of the positive electrode mixture is formed inward from the top edge of the positive electrode plate, with a width of 1 / 3 to 1 / 2 the width of the positive electrode. A lead plate (collector tab) is connected to the stripped portion, and insulating tape is applied between the lead plate and the stripped portion. Furthermore, another insulating tape is applied inward from the bottom edge of the positive electrode plate to the surface of the electrode plate below the insulating tape. An exposed portion of the positive electrode mixture is provided between the upper and lower insulating tapes. This ensures that, even when the lead plate is connected to the positive electrode plate, the thickness of the upper and lower portions of the positive electrode plate are approximately equal, thus preventing winding deviation of the electrode group.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 8-7877 Summary of the Invention

[0007] As mentioned above, in order to prevent the collector tabs inside the battery from puncturing the separators and the like even when external impact or stress is applied to the battery, it is considered to improve safety by excluding the collector tabs from the center of the battery electrode group in the vertical direction. For example, as described in Patent Document 1, Figure 1 As described in the aforementioned structure, the collector tab connected to one side of the positive electrode plate in the width direction is shortened so that the collector tab does not extend beyond the center of the positive electrode plate in the width direction. In this battery, since the collector tab can be easily removed from the center of the winding axis of the electrode group where deformation is likely to occur, there is a possibility of improving safety.

[0008] On the other hand, in the structure described in Patent Document 1, although there is a possibility of suppressing the bias in thickness on both sides of the width direction of the positive electrode plate, there is still room for improvement in suppressing the bias in rigidity on both sides of the width direction of the positive electrode plate. Therefore, there is still room for improvement in suppressing the "winding deviation" in which the winding direction of the positive electrode plate is tilted relative to the winding axis direction when the electrode group is formed. In the case of poor winding deviation during the manufacture of the battery, the battery is treated as a defective product, which becomes a cause of the deterioration of the yield during the manufacture of the battery. In the above, the adverse condition when the positive electrode plate is connected to a short collector ear is explained, but even in the case of a short collector ear connected to the negative electrode plate, there is the possibility of the same adverse condition. Therefore, there is still room for improvement in efficiently producing batteries with improved safety.

[0009] The battery involved in the present disclosure comprises: an electrode group formed by winding a strip-shaped positive electrode plate and a strip-shaped negative electrode plate with a separator; an electrolyte; and an outer can, at least one of the positive electrode plate and the negative electrode plate forms a composite layer on the strip-shaped electrode core, and in the width direction of the electrode plate corresponding to the winding axis direction of the electrode group, it includes a collector ear connected to one end side of the electrode core and not exceeding the center of the electrode plate, and a dummy ear connected to the other end side of the electrode core and not exceeding the center of the electrode plate. When the electrode plate is observed in the width direction, the dummy ear is configured to overlap with at least a portion of the collector ear.

[0010] The battery disclosed herein can exclude the collector tab of at least one of the positive and negative electrode plates from near the center of the winding axis of the electrode group, and can suppress both thickness and rigidity deviations at both ends of the electrode plate in the width direction. This can suppress winding deviation during electrode group formation. Consequently, since the battery yield can be suppressed, batteries with improved safety can be produced more efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a cross-sectional view of a battery according to an example of an embodiment.

[0012] Figure 2 It is a perspective view of an electrode group constituting a battery according to an example of the embodiment.

[0013] Figure 3 It is composed Figure 2 The front view of the positive electrode plate of the electrode group shown shows the positive electrode tab and its vicinity.

[0014] Figure 4 yes Figure 3 The enlarged view of the longitudinal center portion of the positive electrode plate shown is a view in which the tape is omitted. DETAILED DESCRIPTION

[0015] An example of an embodiment of a battery according to the present disclosure will be described in detail below with reference to the accompanying drawings. The embodiment described below is merely an example, and the present disclosure is not limited to the following embodiment. In addition, the present disclosure includes forms in which the components of the embodiments described below are selectively combined.

[0016] In the following, a cylindrical battery 10 is exemplified as a battery in which a wound electrode group 14 is housed in a bottomed cylindrical outer can 16. However, the outer casing of the battery is not limited to a cylindrical outer can. The battery involved in the present disclosure may be, for example, a prismatic battery having a prismatic outer can, or a pouch-type battery having an outer casing composed of a laminate sheet including a metal layer and a resin layer. In addition, the battery 10 of this embodiment is a secondary battery, but the battery involved in the present disclosure can also be applied to structures other than secondary batteries, such as primary batteries.

[0017] Figure 1 It is a diagram schematically showing an axial cross section of a battery 10 according to an example of an embodiment. Figure 2 1 is a perspective view of the electrode group 14 constituting the battery 10. Figure 1 As shown, the cylindrical battery 10 includes: an electrode group 14; an electrolyte; and an outer can 16 for housing the electrode group 14 and the electrolyte. The electrode group 14 includes a positive electrode plate 11, a negative electrode plate 12, and a separator 13, and has a structure in which the positive electrode plate 11 and the negative electrode plate 12 are spirally wound with the separator 13 interposed therebetween. The positive electrode plate 11 and the negative electrode plate 12 correspond to the electrode plates, respectively. The outer can 16 is a metal container with a bottom and a cylindrical shape that is open on one side in the axial direction. The opening of the outer can 16 is blocked by a sealing body 17. In the following, for the sake of convenience, the sealing body 17 side of the cylindrical battery 10 is set as the top, and the bottom side of the outer can 16 is set as the bottom.

[0018] 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 non-aqueous solvents include esters, ethers, nitriles, amides, and mixed solvents of two or more thereof. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents thereof. The non-aqueous solvent may also contain a halogen substituted product (e.g., fluoroethylene carbonate) in which at least a portion of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include lithium salts such as LiPF6.

[0019] like Figure 2As shown, the positive electrode plates 11, negative electrode plates 12, and separators 13 that comprise the electrode group 14 are all strips of tape, spirally wound and stacked in the radial direction of the electrode group 14. The negative electrode plates 12 are formed slightly larger than the positive electrode plates 11 to prevent lithium precipitation. Specifically, the negative electrode plates 12 are longer than the positive electrode plates 11 in both the longitudinal and width directions (the short-hand direction). The separators 13 are formed at least slightly larger than the positive electrode plates 11, with two separators positioned to sandwich the positive electrode plates 11.

[0020] 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. Specifically, the positive electrode plate 11 has a positive electrode mixture layer 31 formed on both sides of the positive electrode core 30. The positive electrode core 30 is equivalent to the electrode core. The positive electrode core 30 can be made of a foil of a metal such as aluminum or aluminum alloy that is stable in the potential range of the positive electrode plate 11, or a thin film of the metal configured on the surface. The positive electrode mixture layer 31 contains a positive electrode active material, a conductive agent such as carbon black and carbon nanotubes, and a binder such as polyvinylidene fluoride, and is preferably formed on the exposed portion 32, 33 (see FIG. 3 ) described later. Figure 3 ) on both sides of the positive electrode core 30. The positive electrode plate 11 can be manufactured 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.

[0021] An example of the positive electrode active material contained in the positive electrode mixture layer 31 is a lithium transition metal composite oxide. A lithium transition metal composite oxide is a composite oxide containing, in addition to Li, metal elements such as Co, Mn, Ni, and Al. The metal elements constituting this composite oxide are, 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 preferred that at least one selected from Ni, Mn, and Co be present.

[0022] The negative electrode plate 12 includes a negative electrode core 40 and a negative electrode mixture layer 41 formed on the negative electrode core 40. Specifically, the negative electrode plate 12 has the negative electrode mixture layers 41 formed on both surfaces of the negative electrode core 40. The negative electrode core 40 corresponds to the electrode core. The negative electrode core 40 can be made of a metal foil such as copper or a copper alloy that is stable within the potential range of the negative electrode plate 12, or a thin film of 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. It is preferably formed on both surfaces of the negative electrode core 40, excluding the exposed portion (not shown) for bonding the negative electrode tab 21, which will be described later. For example, styrene-butadiene rubber (SBR) can be used as the binder, and carboxymethyl cellulose or its salts can also be used in combination. The negative electrode plate 12 is fabricated by applying a negative electrode mixture slurry containing the negative electrode active material and the binder to both surfaces of the negative electrode core 40 and compressing the coating.

[0023] An example of a negative electrode active material contained in the negative electrode mixture layer 41 is a carbon material such as graphite that reversibly occludes and releases lithium ions. Graphite can be either natural graphite or artificial graphite. As the negative electrode active material, elements such as Si and Sn that alloy with Li, materials containing such elements, etc. can be used. Among these, composite materials containing Si are preferred. As a suitable example of a composite material containing Si, a material in which a fine Si phase is dispersed in a SiO2 phase, a silicate phase such as lithium silicate, a carbon phase, or a silicide phase can be cited.

[0024] The separator 13 uses a porous sheet with ion permeability and insulation. Specific examples of the porous sheet include microporous films, woven fabrics, non-woven fabrics, and the like. Suitable materials for the separator 13 include polyolefins such as polyethylene and polypropylene, and cellulose. The separator 13 may be a single-layer structure or a multi-layer structure. In addition, a resin layer with high heat resistance, such as aramid resin, may be formed on the surface of the separator 13. A filler layer containing an inorganic filler may also 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.

[0025] Insulating plates 18 and 19 are respectively arranged above and below the electrode group 14. Figure 1 In the example shown, the positive electrode tab 20 extends through the through-hole of the insulating plate 18 toward the sealing body 17, while the negative electrode tab 21 extends outside the insulating plate 19 toward the bottom of the outer can 16. The positive electrode tab 20 is connected to the lower surface of the internal terminal plate 23 of the sealing body 17 by laser welding or other means. The top plate of the sealing body 17, or cap 27, which is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal. The negative electrode tab 21 is connected to the inner bottom surface of the outer can 16 by laser welding or other means, with the outer can 16 serving as the negative electrode terminal. The positive electrode tab 20 and the negative electrode tab 21 each correspond to a collector tab.

[0026] The positive electrode tab 20 is joined to the positive electrode core 30 by ultrasonic welding or laser welding. The positive electrode tab 20 is joined to the longitudinal center away from the longitudinal ends of the positive electrode plate 11, for example. The positive electrode tab 20 can be joined to a position substantially equidistant from the longitudinal ends of the positive electrode plate 11. The negative electrode tab 21 is joined to the negative electrode core 40 by ultrasonic welding or laser welding. Figure 1In the example shown, the negative electrode tab 21 is joined to the longitudinal end of the negative electrode plate 12 located on the outer peripheral side of the electrode group 14, that is, the end on the winding end side. The positive electrode tab 20 and the negative electrode tab 21 are, for example, strip-shaped metal members having a thickness of 30 μm to 100 μm. The constituent materials of the positive electrode tab 20 and the negative electrode tab 21 are not particularly limited. The positive electrode tab 20 is preferably composed of a metal mainly composed of aluminum. The negative electrode tab 21 is preferably composed of a metal mainly composed of nickel or copper, or a metal containing both nickel and copper.

[0027] Separators 13 are disposed on the outer circumference of the electrode group 14, but negative electrode plates 12 may also be disposed thereon. Furthermore, an exposed portion may be formed on the outer circumference of the electrode group 14, where the surface of the negative electrode core 40 is exposed. This exposed portion may contact the inner surface of the outer can 16, thereby electrically connecting the negative electrode plates 12 and the outer can 16. In this case, the negative electrode plates 12 may not have negative electrode tabs 21.

[0028] As mentioned above, the outer can 16 is a metal container with a bottom and a cylindrical shape that is open on one side in the axial direction. A gasket 28 is provided between the outer can 16 and the sealing body 17 to ensure the airtightness of the battery interior and the insulation between the outer can 16 and the sealing body 17. The outer can 16 is formed with a groove portion 22 that extends inward from a portion of the side surface. The groove portion 22 is preferably formed in an annular shape along the circumference of the outer can 16, and supports the sealing body 17 on its upper surface. The sealing body 17 is fixed to the upper part of the outer can 16 by the groove portion 22 and the open end portion of the outer can 16 riveted to the sealing body 17.

[0029] The sealing body 17 has a structure in which an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26 and a cap 27 are stacked in sequence from the electrode group 14 side. The components constituting the sealing body 17 have, for example, a disc shape or a ring shape, and the components except the insulating member 25 are electrically connected to each other. The lower valve body 24 and the upper valve body 26 are connected at their respective central portions, and the insulating member 25 is located between their respective peripheral portions. If an abnormality occurs in the battery and the internal pressure rises, the lower valve body 24 is deformed to push the upper valve body 26 toward the cap 27 side and break, thereby cutting off the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further, the upper valve body 26 breaks and gas is discharged from the opening of the cap 27.

[0030] Below, reference Figure 3 、 Figure 4 The positive electrode plate 11 will be described in detail. Figure 3 It is a front view of the positive electrode plate 11 , showing the positive electrode tab 20 and its vicinity. Figure 4 yes Figure 3 The enlarged view of the longitudinal center of the positive electrode plate 11 shown is an image in which the tapes 34 and 35 are omitted ( Figure 3 ) and shown in the figure. Figure 3 、 Figure 4 As described above, the positive electrode plate 11 includes the positive electrode core 30 and the positive electrode core 30 and the positive electrode mixture layers 31 formed on both surfaces of the positive electrode core 30 .

[0031] like Figure 3 As shown, on one side of the positive electrode plate 11, in the longitudinal direction of the positive electrode plate 11 ( Figure 3 The width direction of the positive electrode plate 11 at the center of the positive electrode plate 11 ( Figure 3 The exposed portions 32 and 33 are formed at both ends (in the vertical direction) of the positive electrode core 30. Figure 3 、 Figure 4 In the figure, the length direction of the positive electrode plate 11 is indicated by the arrow α, and the width direction of the positive electrode plate 11 is indicated by the arrow β. The length direction of the positive electrode plate 11 corresponds to the winding direction of the electrode group 14, and the width direction of the positive electrode plate 11 corresponds to the winding axis direction of the electrode group 14. The positive electrode mixture slurry is not applied to the positive electrode core 30, and the positive electrode mixture layer 31 is not provided, thereby forming each exposed portion 32, 33. Alternatively, the exposed portions 32, 33 can also be formed by peeling off a part of the positive electrode mixture layer 31. Since two exposed portions 32, 33 are formed at both ends in the width direction of the positive electrode plate 11 in this way, on one side of the positive electrode plate 11, between the two exposed portions 32, 33, the center O1 in the width direction of the positive electrode plate 11 ( Figure 4 ) The positive electrode mixture layer 31 exists. In addition, the formation position of the exposed portions 32 and 33 is not limited to the longitudinal center of the positive electrode plate 11, and may be formed at a plurality of locations separated in the longitudinal direction, for example.

[0032] The positive electrode plate 11 includes a positive electrode tab 20 joined to one of the exposed portions 32 and 33, namely the upper exposed portion 32. The upper exposed portion 32 is slightly larger than the portion where the positive electrode tab 20 overlaps with the positive electrode core 30. The positive electrode tab 20 is connected to one end of the positive electrode core 30 in the width direction, but not exceeding the center O1 in the width direction. This shortens the overlapping length of the positive electrode tab 20 relative to the positive electrode core 30, allowing the positive electrode tab 20 to be removed from near the center of the winding axis of the electrode group 14. This improves the safety of the battery 10.

[0033] On the other hand, the other of the exposed portions 32 and 33, i.e., the lower exposed portion 33, is provided at approximately the same position as the upper exposed portion 32 with respect to the longitudinal direction of the positive electrode plate 11 and has approximately the same shape and size as the upper exposed portion 32. Furthermore, the exposed portions 32 and 33 may have different shapes and sizes.

[0034] The exposed portion 32 preferably includes a first surface that is bonded to the positive electrode tab 20 and a second surface opposite the first surface. That is, the positive electrode tab 20 is bonded to only one surface of the positive electrode core 30, with the exposed portion 32 also formed on the other surface where the positive electrode tab 20 is not located. Similarly, the exposed portion 33 preferably includes a first surface on the side where the positive electrode tab 20 is located and a second surface opposite the first surface. The second surface of each exposed portion 32 or 33 is preferably formed to overlap with the first surface in the thickness direction of the positive electrode plate 11, with substantially the same size.

[0035] The positive electrode plate 11 also includes a dummy tab 37 joined to the lower exposed portion 33. The dummy tab 37 is connected to the other widthwise end of the positive electrode core 30 and does not extend beyond the widthwise center O1.

[0036] The lengths of the dummy tab 37 in the longitudinal and width directions of the positive electrode plate 11 are preferably substantially the same as the lengths of the portion of the positive electrode tab 20 that overlaps with the positive electrode core 30. Furthermore, the thickness of the dummy tab 37 is preferably substantially the same as the thickness of the positive electrode tab 20.

[0037] The constituent material of the dummy tab 37 is not particularly limited, but is preferably made of the same metal material as that constituting the positive electrode tab 20 .

[0038] Furthermore, when viewing the positive electrode plate 11 in the width direction, the dummy tab 37 is arranged so as to overlap substantially the entirety of the positive electrode tab 20. This reduces both thickness and rigidity variations on both sides of the positive electrode plate 11 in the width direction. Consequently, deviation in the winding of the positive electrode plate 11 during formation of the electrode assembly 14 can be reduced. Consequently, since the yield of the battery 10 can be reduced, batteries 10 with improved safety can be efficiently produced.

[0039] In addition, the structure of the present disclosure is not limited to the structure in which the dummy tab 37 is arranged to overlap substantially all of the positive electrode tab 20 when the positive electrode plate 11 is viewed in the width direction as in this example. Figure 4 As shown in FIG. 1 , where the dummy tab 37 is indicated by a two-dot chain line, when the positions extending outward from the widthwise ends of the positive electrode tab 20 by a length W1 of the positive electrode tab 20 are defined as the ends E1 and E2, the dummy tab 37 can overlap at least a portion of the positive electrode tab 20 by arranging the dummy tab 37 within a range inward of the longitudinal direction of the positive electrode plate 11 relative to the ends E1 and E2. In this manner, when the positive electrode plate 11 is viewed in the widthwise direction, the dummy tab 37 can overlap at least a portion of the positive electrode tab 20.

[0040] like Figure 4As shown, the positive electrode tab 20 and dummy tab 37 are preferably placed in a portion excluding the widthwise center portion of the positive electrode plate 11, centered around the widthwise center O1, where the widthwise length A is 35% of the widthwise length La of the positive electrode plate 11. In this case, the plate widthwise length A is calculated as A = La × 35 / 100. This effectively prevents the separator 13 and other components from being punctured by the positive electrode tab 20 and dummy tab 37, thus more effectively preventing internal short circuits and further improving the safety of the battery 10.

[0041] The corners of the outer can 16 of the battery 10 are physically strong enough to withstand external stress and impact. Meanwhile, the side surfaces of the outer can 16 are relatively weak and easily deformed within the battery 10. In particular, the portion of the outer can 16 below the slot 22 houses the electrode group 14. The vertical center of this portion is susceptible to physical deformation. The vertical center of the portion below the slot 22 of the battery 10 is approximately aligned with the widthwise center of the positive electrode plate 11. Therefore, by arranging the positive electrode tab 20 and the dummy tab 37 in a portion excluding the widthwise center of the positive electrode plate 11, internal short circuits in the battery 10 can be more effectively prevented, thereby further enhancing the safety of the battery 10. Furthermore, as described above, by arranging the positive electrode tab 20 and the dummy tab 37 in a portion excluding the widthwise center of the positive electrode plate 11, where the widthwise center O1 is centered and the widthwise length A is 35% of the widthwise length La of the positive electrode plate 11, this effect is significantly enhanced.

[0042] In addition, if Figure 4 As shown, at least a portion of the dummy tab 37 is preferably positioned inward from the other widthwise end, i.e., the lower end, of the positive electrode plate 11, within a range where the widthwise length B is 20% of the widthwise length La of the positive electrode plate 11. In this case, B = La × 20 / 100. This arrangement of the dummy tab 37 improves the rigidity balance of the positive electrode plate 11 in the widthwise direction, significantly suppressing winding deviation of the positive electrode plate 11 during formation of the electrode assembly 14. This suppresses winding deviation defects of the electrode assembly 14, thereby more effectively preventing a decrease in the yield of the battery 10.

[0043] Furthermore, in this example, all of the dummy tabs 37 are arranged inward from the other end, i.e., the lower end, of the positive electrode plate 11 in the electrode plate width direction, within a range where the electrode plate width direction length B is 20% of the electrode plate width direction length La of the positive electrode plate 11. This further improves the balance of the rigidity in the width direction of the positive electrode plate 11.

[0044] In addition, if Figure 3As shown, tapes 34 and 35 are provided on the positive electrode plate 11 to cover the positive electrode tab 20 and the dummy tab 37. The tape 34 preferably covers the positive electrode tab 20, the exposed portion 32, and the area of ​​the positive electrode mixture layer 31 adjacent to the exposed portion 32. The tape 35 preferably covers the dummy tab 37, the exposed portion 33, and the area of ​​the positive electrode mixture layer 31 adjacent to the exposed portion 33. Furthermore, the tape 34 preferably covers the entire exposed portion 32, including the area where the positive electrode tab 20 is located. The tape 35 preferably covers the entire exposed portion 33, including the area where the dummy tab 37 is located. Each tape 34 and 35 is formed into a rectangular shape that is slightly larger than the exposed portion 32 and 33 and is provided to extend beyond the exposed portion 32 and 33 in the longitudinal and width directions of the positive electrode plate 11. The tapes 34 and 35 are preferably provided on both surfaces of the positive electrode core 30.

[0045] The tapes 34 and 35 each include, for example, a base material made of an insulating resin and an adhesive layer formed on one side of the base material. The tape 34 is preferably an insulating tape having substantially no electrical conductivity.

[0046] In the above embodiment, two exposed portions 32 and 33 are provided at the widthwise ends of the positive electrode plate 11, sandwiching a portion of the positive electrode mixture layer 31. However, a configuration may also be employed in which the exposed portions are provided in a strip shape along the entire widthwise length of the positive electrode plate 11. In this case, the positive electrode tab 20 and the dummy tab 37 are also separated and located at the widthwise ends of the positive electrode plate 11, and are connected to a region not exceeding the widthwise center of the positive electrode plate 11.

[0047] In this example, a structure is described in which the positive electrode tab 20 and the dummy tab 37 are connected at both ends in the width direction of the positive electrode plate 11. However, in addition to or in place of this structure, a structure in which the negative electrode tab and the dummy tab are connected at both ends in the width direction of the negative electrode plate 12 may be employed.

[0048] For example, two exposed portions are formed at both ends of the negative electrode plate 12 in the width direction. A negative electrode tab is bonded to one of the two exposed portions, the lower exposed portion, and a dummy tab is bonded to the other exposed portion, the upper exposed portion.

[0049] The negative electrode tab is connected to a range not exceeding the center of the width direction of the negative electrode plate 12 at one end side, i.e., the lower side, of the negative electrode core 40 in the width direction. The dummy tab is connected to a range not exceeding the center of the width direction of the negative electrode plate 12 at the other end side, i.e., the upper side, of the negative electrode core 40 in the width direction. When the negative electrode plate 12 is viewed in the width direction, the dummy tab is configured to overlap with at least a portion of the negative electrode tab. By excluding the negative electrode tab from near the center in the winding axis direction of the electrode group 14, the safety of the battery 10 can be improved. In addition, both the thickness deviation and the rigidity deviation at the two end sides in the width direction of the negative electrode plate 12 can be suppressed. For this reason, the winding deviation of the negative electrode plate 12 during the formation of the electrode group 14 can be suppressed. Therefore, since the deterioration of the yield of the battery 10 can be suppressed, the battery 10 with improved safety can be produced efficiently.

[0050] In addition, the negative electrode plate 12 may be configured such that the negative electrode tab and the dummy tab are arranged in a portion excluding the center portion of the negative electrode plate 12 in the width direction and a width length of 35% of the width length of the negative electrode plate 12. In addition, the negative electrode plate 12 may be configured such that at least a portion of the dummy tab is arranged inward from the other end, i.e., the upper end, in the width direction of the negative electrode plate 12 within a range of 20% of the width length of the negative electrode plate 12. In the negative electrode plate 12, another configuration is that Figure 3 、 Figure 4 In the positive electrode plate, the negative electrode tab and the dummy tab of the negative electrode plate 12 are set at the winding end of the negative electrode plate 12, and the positional relationship between the negative electrode tab and the dummy tab is the same as that of the positive electrode plate 12. Figure 3 、 Figure 4 The positive electrode tab 20 of the positive electrode plate 11 and the dummy tab 37 have the same structure in which the positional relationship is upside down.

[0051] Furthermore, the negative electrode tabs and dummy tabs are not limited to being located at the winding end of the negative electrode plate 12 . For example, they may be located at the winding start end of the negative electrode plate 12 or in the middle of the negative electrode plate 12 in the longitudinal direction.

[0052] Description of Reference Signs

[0053] 10: Battery, 11: Positive electrode plate, 12: Negative electrode plate, 13: Separator, 14: Electrode group, 16: Outer can, 17: Sealing body, 18, 19: Insulating plate, 20: Positive electrode tab, 21: Negative electrode tab, 22: Slotted 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, 33: Exposed portion, 34, 35: Tape, 37: Dummy tab, 40: Negative electrode core, 41: Negative electrode mixture layer.

Claims

1. A battery comprising: An electrode group formed by winding a strip-shaped positive electrode plate and a strip-shaped negative electrode plate with a separator between them; electrolytes; and Outer cans, At least one of the positive electrode plate and the negative electrode plate forms a composite layer on a strip-shaped electrode core body, and includes a collector tab connected to one end side of the electrode core body and not exceeding the center of the electrode plate in the width direction of the electrode plate corresponding to the winding axis direction of the electrode group, and a dummy tab connected to the other end side of the electrode core body and not exceeding the center of the electrode plate. When the electrode plate is viewed in the width direction, the dummy tab is arranged so as to overlap with at least a portion of the current collecting tab.

2. The battery according to claim 1, wherein The collecting tab and the dummy tab are arranged in a portion excluding a central portion in the width direction of the electrode plate and 35% of a length in the width direction of the electrode plate.

3. The battery according to claim 1, wherein At least a portion of the dummy tab is disposed inward from the other end in the width direction of the electrode plate within a range of 20% of a length in the width direction of the electrode plate.

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