Battery

Abstract

A battery according to an embodiment comprises: an electrode group in which a band-like positive electrode plate (11) and a band-like negative electrode plate are wound with a separator therebetween; an electrolyte; and an outer can. The positive electrode plate (11), in which a positive electrode mix layer (31) is formed on a band-like positive electrode core (30), comprises: a positive electrode tab (20) which is connected to an area on one end side of the positive electrode core (30) and not extending beyond the center in the width direction of the positive electrode plate (11); and a dummy tab (37) which is connected to an area on the other end side of the positive electrode core (30) and not extending beyond the center 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 to overlap at least a part of the positive electrode tab (20).

Description

battery

[0001] The present disclosure relates to a battery including an electrode group in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a separator interposed therebetween, an electrolyte, and an outer can.

[0002] In recent years, the popularity of electric vehicles, smartphones, and other smart devices has led to a growing demand for batteries with high energy density. However, increased energy density can also pose safety risks. For example, when a battery is subjected to external impact or stress, it can deform, causing the current collecting tabs or electrodes inside the battery to break through the separator, resulting in an internal short circuit. This poses a greater risk to batteries with high energy density than batteries with low energy density.

[0003] Patent Document 1 describes a battery designed to prevent shearing of the electrode assembly. In the battery described in Patent Document 1, a peeled-off portion of the material mixture is formed from the upper edge of the positive electrode plate toward the inside, the peeled-off portion having a width of 1 / 3 to 1 / 2 of the positive electrode width. A lead plate (current collecting tab) is connected to the peeled-off portion, and insulating tape is attached to the lead plate and the surface of the peeled-off portion. Furthermore, another insulating tape is attached to the surface of the electrode plate below the insulating tape, from the lower edge of the positive electrode plate toward the inside, and an exposed portion of the positive electrode material mixture exposed from the insulating tape is provided between the upper and lower insulating tapes. This ensures that the thicknesses of the upper and lower portions of the positive electrode plate are approximately equal, even when a lead plate is connected to the positive electrode plate, thereby preventing shearing of the electrode assembly.

[0004] Japanese Patent Application Publication No. 8-7877

[0005] As described above, in order to prevent the current collecting tabs from breaking through the separator or other components inside the battery even when an external impact or stress is applied to the battery, it is conceivable to improve safety by removing the current collecting tabs from the vertical center of the electrode assembly of the battery. For example, as shown in Figure 1 of Patent Document 1, it is conceivable to shorten the current collecting tab connected to one widthwise side of the positive electrode plate so that the current collecting tab does not extend beyond the widthwise center of the positive electrode plate. In this battery, it is easier to remove the current collecting tab from near the center of the winding axis direction of the electrode assembly, where deformation is likely to occur, and this may potentially improve safety.

[0006] On the other hand, while the configuration described in Patent Document 1 may be able to suppress thickness unevenness on both sides of the width of the positive electrode plate, there is still room for improvement in suppressing unevenness in rigidity on both sides of the width of the positive electrode plate. This leaves room for improvement in suppressing "winding misalignment," in which the winding direction of the positive electrode plate is tilted relative to the winding axis direction during electrode assembly formation. If winding misalignment occurs during battery manufacturing, the battery is treated as a defective product, which reduces the yield during battery manufacturing. While the above describes the inconvenience of connecting a short current collecting tab to a positive electrode plate, similar inconveniences may occur when connecting a short current collecting tab to a negative electrode plate. Therefore, there is still room for improvement in terms of efficiently producing batteries that can improve safety.

[0007] The battery according to the present disclosure is a battery comprising an electrode group in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a separator interposed therebetween, an electrolyte, and an outer can, wherein at least one of the positive electrode plate and the negative electrode plate has a mixture layer formed on a strip-shaped electrode core, and includes, in the width direction of the electrode plate corresponding to the winding axis direction of the electrode group, a current collecting tab connected to one end of the electrode core in an area not extending beyond the center of the electrode plate, and a dummy tab connected to the other end of the electrode core in an area not extending beyond the center of the electrode plate, and when the electrode plate is viewed in the width direction, the dummy tab is positioned so as to overlap at least a portion of the current collecting tab.

[0008] According to the battery of the present disclosure, the current collecting tab of at least one of the positive and negative electrode plates can be removed from the vicinity of the center of the winding axis direction of the electrode assembly, and both thickness and rigidity deviations at both ends of the electrode plate in the width direction can be suppressed. This suppresses winding misalignment during the formation of the electrode assembly. This suppresses deterioration of battery yield and allows for more efficient production of batteries with improved safety.

[0009] 2 is a cross-sectional view of a battery according to an embodiment; FIG. 3 is a perspective view of an electrode group constituting a battery according to an embodiment; FIG. 4 is a front view of a positive electrode plate constituting the electrode group shown in FIG. 2, showing a positive electrode tab and its vicinity; and FIG. 5 is an enlarged view of a longitudinal center portion of the positive electrode plate shown in FIG. 3, showing the tape omitted.

[0010] Hereinafter, an example of an embodiment of a battery according to the present disclosure will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present disclosure is not limited to the following embodiment. Furthermore, the present disclosure also includes embodiments obtained by selectively combining the components of the embodiments described below.

[0011] In the following, a cylindrical battery 10 in which a wound electrode group 14 is housed in a cylindrical outer can 16 with a bottom is exemplified as the battery, but the battery exterior 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, or a pouch-type battery with an outer can made of a laminate sheet including a metal layer and a resin layer. While the battery 10 of this embodiment is a secondary battery, the battery according to the present disclosure can also be applied to configurations other than secondary batteries, such as primary batteries.

[0012] FIG. 1 is a schematic diagram illustrating an axial cross section of a battery 10 according to an embodiment. FIG. 2 is a perspective view of an electrode group 14 constituting the battery 10. As shown in FIG. 1, the cylindrical battery 10 includes an electrode group 14, an electrolyte, and an outer can 16 that accommodates 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. 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 each correspond to an electrode plate. The outer can 16 is a cylindrical metal container with a bottom that is open 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.

[0013] 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

[0014] As shown in Fig. 2, the positive electrode plate 11, negative electrode plate 12, and separator 13 that make up the electrode group 14 are all long, strip-like bodies that are spirally wound and stacked in the radial direction of the electrode group 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.

[0015] The positive electrode plate 11 includes 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 includes the positive electrode mixture layer 31 formed on both sides of the positive electrode core 30. The positive electrode core 30 corresponds to an electrode core. The positive electrode core 30 may 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 having such a metal disposed on its 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 exposed portions 32 and 33 (see FIG. 3 ) described below. 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.

[0016] 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.

[0017] 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. Specifically, the negative electrode plate 12 has the negative electrode mixture layer 41 formed on both sides of the negative electrode core 40. The negative electrode core 40 corresponds to an electrode core. For the negative electrode core 40, a foil of a metal stable within the potential range of the negative electrode plate 12, such as copper or a copper alloy, or a film with such a metal disposed on the surface layer, can be used. 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 except for an exposed portion (not shown) for bonding the negative electrode tab 21 described below. As the binder, for example, styrene-butadiene rubber (SBR) can be used, and carboxymethyl cellulose or a salt thereof, or the like, may 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 substrate 40 and compressing the coating.

[0018] 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.

[0019] 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.

[0020] Insulating plates 18 and 19 are disposed above and below the electrode group 14, respectively. In the example shown in FIG. 1 , the positive electrode tab 20 passes through a through-hole in the insulating plate 18 and extends toward the sealing body 17, and the negative electrode tab 21 passes outside the insulating plate 19 and extends toward the bottom side of the outer casing 16. The positive electrode tab 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 a positive electrode terminal. The negative electrode tab 21 is connected to the inner bottom surface of the outer casing 16 by laser welding or the like, and the outer casing 16 serves as a negative electrode terminal. The positive electrode tab 20 and the negative electrode tab 21 each correspond to a current collecting tab.

[0021] The positive electrode tab 20 is joined to the positive electrode core 30 by ultrasonic welding, laser welding, or the like. The positive electrode tab 20 is joined, for example, to the longitudinal center of the positive electrode plate 11, away from both longitudinal ends. The positive electrode tab 20 may also be joined at a position substantially equidistant from both longitudinal ends of the positive electrode plate 11. The negative electrode tab 21 is joined to the negative electrode core 40 by ultrasonic welding, laser welding, or the like. In the example shown in FIG. 1 , the negative electrode tab 21 is joined to the longitudinal end of the negative electrode plate 12, which is the end on the winding end side, located on the outer periphery of the electrode group 14. 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 made of a metal primarily composed of aluminum. The negative electrode tab 21 is preferably made of a metal primarily composed of nickel or copper, or a metal containing both nickel and copper.

[0022] A separator 13 is disposed on the outer peripheral surface of the electrode group 14, but a negative electrode plate 12 may also be disposed thereon. 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 group 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 tab 21.

[0023] 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 groove 22 formed by a portion of the side surface protruding inward. The groove 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 groove 22 and the open end of the outer can 16, which is crimped to the sealing body 17.

[0024] 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 this order from the electrode group 14 side. 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.

[0025] The positive electrode plate 11 will be described in detail below with reference to FIGS. 3 and 4. FIG. 3 is a front view of the positive electrode plate 11, showing the positive electrode tab 20 and its vicinity. FIG. 4 is an enlarged view of the longitudinal center portion of the positive electrode plate 11 shown in FIG. 3, with tapes 34 and 35 (FIG. 3) omitted. In FIGS. 3 and 4, the mixture layer is indicated by diagonal 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.

[0026] As shown in FIG. 3 , on one side of the positive electrode plate 11, exposed portions 32, 33, in which the surface of the positive electrode core 30 is exposed, are formed at both ends of the positive electrode plate 11 in the width direction (vertical direction in FIG. 3 ) at the center of the positive electrode plate 11 in the length direction (horizontal direction in FIG. 3 ). In FIGS. 3 and 4 , the length direction of the positive electrode plate 11 is indicated by arrow α, and the width direction of the positive electrode plate 11 is indicated by 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. Each exposed portion 32, 33 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 portions 32, 33 may be formed by peeling off a portion of the positive electrode mixture layer 31. In this way, the two exposed portions 32, 33 are formed at both widthwise ends of the positive electrode plate 11, and therefore, on one side of the positive electrode plate 11, the positive electrode mixture layer 31 is present between the two exposed portions 32, 33 so as to include the widthwise center O1 ( FIG. 4 ) of the positive electrode plate 11. Note that the positions where the exposed portions 32, 33 are formed are not limited to the center portion in the lengthwise direction of the positive electrode plate 11, and they may be formed at multiple locations spaced apart in the lengthwise direction, for example.

[0027] The positive electrode plate 11 has a positive electrode tab 20 joined to one of the exposed portions 32, 33, i.e., the upper exposed portion 32. The upper exposed portion 32 is slightly larger than the overlapping portion of the positive electrode tab 20 and 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, in an area not exceeding the widthwise center O1. This shortens the overlap length of the positive electrode tab 20 with the positive electrode core 30, and therefore the positive electrode tab 20 can be excluded from near the center of the winding axis direction of the electrode group 14. This improves the safety of the battery 10.

[0028] On the other hand, the other of the exposed portions 32, 33, i.e., the lower exposed portion 33, is provided at approximately the same position as the upper exposed portion 32 in the longitudinal direction of the positive electrode plate 11, and has approximately the same shape and size as the upper exposed portion 32. The shapes and sizes of the exposed portions 32, 33 may be different from each other.

[0029] The exposed portion 32 preferably includes a first surface to which the positive electrode tab 20 is joined and a second surface opposite the first surface. That is, the positive electrode tab 20 is joined to only one surface of the positive electrode core 30, and an exposed portion 32 is also formed on the other surface on which the positive electrode tab 20 is not disposed. Similarly, the exposed portion 33 preferably includes a first surface on the side on which the positive electrode tab 20 is disposed and a second surface opposite the first surface. The second surfaces of each of the exposed portions 32, 33 are preferably formed to overlap the first surfaces in the thickness direction of the positive electrode plate 11 and have substantially the same size as the first surfaces.

[0030] The positive electrode plate 11 also has a dummy tab 37 joined to the lower exposed portion 33. The dummy tab 37 is connected to the other end side in the width direction of the positive electrode core 30, in an area not exceeding the center O1 in the width direction.

[0031] The lengths of the dummy tab 37 in the lengthwise and widthwise directions of the positive electrode plate 11 are preferably approximately the same as the lengths of the portion of the positive electrode tab 20 that overlaps with the positive electrode core 30 in the lengthwise and widthwise directions of the positive electrode plate 11. In addition, the thickness of the dummy tab 37 is preferably approximately the same as the thickness of the positive electrode tab 20.

[0032] The material of which the dummy tab 37 is made is not particularly limited, but it is preferable that the dummy tab 37 be made of the same metal material as the metal material that makes up the positive electrode tab 20 .

[0033] Furthermore, when the positive electrode plate 11 is viewed in the width direction, the dummy tab 37 is arranged so as to overlap substantially the entire positive electrode tab 20. This makes it possible to suppress both unevenness in thickness and unevenness in rigidity on both sides of the positive electrode plate 11 in the width direction. This makes it possible to suppress misalignment of the positive electrode plate 11 when winding the electrode group 14. This makes it possible to suppress deterioration in the yield of the battery 10, thereby enabling efficient production of batteries 10 with improved safety.

[0034] The configuration of the present disclosure is not limited to the present example, in which the dummy tab 37 is arranged to overlap substantially the entire positive electrode tab 20 when the positive electrode plate 11 is viewed in the width direction. For example, as shown by the two-dot chain line in FIG. 4 , if positions protruding outward from both ends of the positive electrode tab 20 in the width direction by a width length W1 of the positive electrode tab 20 are defined as ends E1 and E2, the dummy tab 37 can be arranged inward in the longitudinal direction of the positive electrode plate 11 from both ends E1 and E2, thereby allowing the dummy tab 37 to overlap at least a portion of the positive electrode tab 20. In this way, it is sufficient that the dummy tab 37 overlaps at least a portion of the positive electrode tab 20 when the positive electrode plate 11 is viewed in the width direction.

[0035] 4 , the positive electrode tab 20 and the dummy tab 37 are preferably arranged in a widthwise central portion of the positive electrode plate 11, centered on the widthwise center O1, excluding a range where the widthwise length A is 35% of the widthwise length La of the positive electrode plate 11. In this case, the electrode plate widthwise length A is A = La × 35 / 100. This more effectively prevents the positive electrode tab 20 and the dummy tab 37 from piercing the separator 13, etc., and therefore more effectively prevents internal short circuits and further improves the safety of the battery 10.

[0036] The corners of the exterior can 16 of the battery 10 are physically strong against external stress and impact. On the other hand, the side surfaces of the exterior can 16 have relatively low strength and are prone to deformation in the battery 10. In particular, the portion of the exterior can 16 below the grooved portion 22 houses the electrode group 14. The vertical center of this portion is physically prone to deformation. The vertical center of the portion of the battery 10 below the grooved portion 22 substantially coincides with the widthwise center of the positive plate 11. Therefore, by arranging the positive electrode tabs 20 and dummy tabs 37 in a portion of the battery 10 other than the widthwise center of the positive plate 11, internal short circuits in the battery 10 can be more effectively prevented, thereby further improving the safety of the battery 10. Furthermore, as described above, the above-mentioned effects are more pronounced when the positive electrode tabs 20 and dummy tabs 37 are arranged in the widthwise center of the positive plate 11, centered on the widthwise center O1, excluding the range where the widthwise length A is 35% of the widthwise length La of the positive plate 11.

[0037] 4, at least a portion of the dummy tabs 37 are preferably arranged inward from the lower end, which is the other end in the width direction of the positive electrode plate 11, within a range in which the widthwise length B is 20% of the widthwise length La of the positive electrode plate 11. In this case, B = La × 20 / 100. When the dummy tabs 37 are arranged in this manner, the balance of rigidity in the width direction of the positive electrode plate 11 can be improved so that winding misalignment of the positive electrode plate 11 can be significantly suppressed when forming the electrode group 14. This can suppress winding misalignment of the electrode group 14, thereby more effectively preventing a decrease in the yield of the battery 10.

[0038] In this example, the entire dummy tab 37 is arranged from the lower end, which is the other end in the electrode plate width direction of the positive electrode plate 11, toward the inside within a range in which the electrode plate width direction length B is 20% of the electrode plate width direction length La of the positive electrode plate 11. This allows for a better balance of rigidity in the width direction of the positive electrode plate 11.

[0039] As shown in FIG. 3 , the positive electrode plate 11 is provided with tapes 34 and 35 that 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 region 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 region of the positive electrode mixture layer 31 adjacent to the exposed portion 33. The tape 34 preferably covers the entire exposed portion 32, including the region where the positive electrode tab 20 is present. The tape 35 preferably covers the entire exposed portion 33, including the region where the dummy tab 37 is present. Each of the tapes 34 and 35 is formed in a rectangular shape that is slightly larger than the exposed portions 32 and 33, and is provided so as to extend beyond the exposed portions 32 and 33 in the length and width directions of the positive electrode plate 11. The tapes 34 and 35 are preferably provided on both sides of the positive electrode core 30.

[0040] The tapes 34 and 35 each have, 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 that is substantially non-conductive.

[0041] In the above embodiment, the two exposed portions 32, 33 are provided at both widthwise ends of the positive electrode plate 11, sandwiching a part of the positive electrode mixture layer 31 therebetween, but the exposed portions may be provided in the shape of strips over the entire widthwise length of the positive electrode plate 11. Even in this case, the positive electrode tab 20 and the dummy tab 37 are separated from each other at both widthwise end sides of the positive electrode plate 11, and are connected to each other in a range not exceeding the widthwise center of the positive electrode plate 11.

[0042] In this example, a configuration has been described in which the positive electrode tab 20 and the dummy tab 37 are connected to both widthwise ends of the positive electrode plate 11. However, in addition to or instead of this configuration, a configuration may be used in which a negative electrode tab and a dummy tab are connected to both widthwise ends of the negative electrode plate 12.

[0043] For example, two exposed portions are formed at both widthwise ends of the negative electrode plate 12, and a negative electrode tab is joined to one of the two exposed portions, the lower exposed portion, and a dummy tab is joined to the other exposed portion, the upper exposed portion.

[0044] The negative electrode tab is connected to the lower side, which is one end side in the width direction of the negative electrode substrate 40, in an area not extending beyond the width center of the negative electrode plate 12. The dummy tab is connected to the upper side, which is the other end side in the electrode plate width direction of the negative electrode substrate 40, in an area not extending beyond the width center of the negative electrode plate 12. When the negative electrode plate 12 is viewed in the width direction, the dummy tab is arranged to overlap at least a portion of the negative electrode tab. By excluding the negative electrode tab from near the center of the winding axis direction of the electrode group 14, the safety of the battery 10 can be improved. Furthermore, both thickness and rigidity variations at both ends in the width direction of the negative electrode plate 12 can be suppressed. This can suppress winding misalignment of the negative electrode plate 12 during the formation of the electrode group 14. Therefore, deterioration in the yield of the battery 10 can be suppressed, allowing for efficient production of batteries 10 with improved safety.

[0045] The negative electrode plate 12 may also be configured such that the negative electrode tab and dummy tab are arranged in a widthwise center portion of the negative electrode plate 12 excluding a range whose widthwise length is 35% of the widthwise length of the negative electrode plate 12. The negative electrode plate 12 may also be configured such that at least a portion of the dummy tab is arranged inward from the upper end, which is the other widthwise end of the negative electrode plate 12, within a range that is 20% of the widthwise length of the negative electrode plate 12. The other configuration of the negative electrode plate 12 is similar to that of the positive electrode plate in FIGS. 3 and 4 , in which the negative electrode tab and dummy tab of the negative electrode plate 12 are provided at the winding end of the negative electrode plate 12, and the positional relationship between the negative electrode tab and dummy tab is upside down compared to the positional relationship between the positive electrode tab 20 and dummy tab 37 of the positive electrode plate 11 in FIGS. 3 and 4 .

[0046] In addition, in the negative electrode plate 12, the negative electrode tab and dummy tab are not limited to being provided at the end of the winding of the negative electrode plate 12, but may be provided, for example, at the beginning of the winding of the negative electrode plate 12 or in the middle of the negative electrode plate 12 in the longitudinal direction.

[0047] REFERENCE SIGNS LIST 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 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, 33 exposed portion, 34, 35 tape, 37 dummy tab, 40 negative electrode core, 41 negative electrode mixture layer.

Claims

1. A battery including an electrode group in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a separator interposed therebetween, an electrolyte, and an outer casing, At least one of the positive electrode plate and the negative electrode plate is a mixture layer is formed on a strip-shaped electrode core, and in a width direction of the electrode plate corresponding to the winding axis direction of the electrode group, a current collecting tab is connected to one end side of the electrode core in an area not extending beyond the center of the electrode plate, and a dummy tab is connected to the other end side of the electrode core in an area not extending beyond 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 at least a part of the current collecting tab. battery.

2. the current collecting tabs and the dummy tabs are arranged in a central portion of the electrode plate in the width direction, excluding an area corresponding to 35% of the width direction length of the electrode plate; The battery of claim 1.

3. 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 that is 20% of the width direction length of the electrode plate. The battery of claim 1.