Cylindrical battery

Abstract

According to the present invention, a first plane surface, a second plane surface, and a third plane surface are provided on the bottom face of an exterior can of a cylindrical battery. The first plane surface is provided in a portion including at least part of the outer circumferential edge of the bottom face. The second plane surface is provided in a portion including the center of the bottom face. In the third plane surface, at least part of the bottom face is located radially closer to the outer circumference than the outermost circumferential position of the second plane surface. The circumferential length of the third plane surface at the radial inner end is 1 / 10 or less the circumferential length of a circle passing through the radial outer end of the second plane surface. A connecting portion and / or a hole to be sealed by a sealing portion is provided on the inner face of the third plane surface on the opposite side in the thickness direction. The height positions T1, T2, and T3 of the first, second, and third plane surfaces are related such that T1 < T3 ≤ T2.

Description

Cylindrical battery

[0001] The present disclosure relates to cylindrical batteries.

[0002] Conventionally, cylindrical batteries have been known that include an electrode assembly in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween, and an outer can which is a metal case that houses the electrode assembly, with the opening of the outer can being sealed with a sealing body.

[0003] In recent years, improvements in energy density and capacity in cylindrical batteries have increased the possibility of internal pressure increasing in the event of an abnormality.

[0004] Patent Document 1 describes that in a cylindrical battery, a structure that is a rigid reinforcing member having a large area, such as a disk, is attached to the inner surface of the bottom of the outer can by welding or adhesive, thereby preventing the bottom from expanding due to an increase in the internal pressure of the battery.

[0005] JP 2013-134861 A

[0006] Incidentally, it is conceivable to provide a connection portion with the electrode assembly, such as by welding a connection lead connected to the electrode assembly, on the inner surface of the bottom of the exterior can, or a hole sealed with a sealing portion for injecting an electrolyte into the interior of the exterior can. In this case, if the bottom is deformed overall due to an increase in internal pressure, this will cause a decrease in the reliability of the connection portion and the sealing portion.

[0007] On the other hand, the configuration described in Patent Document 1 may be able to suppress deformation of the bottom of the exterior can, but it requires the placement of a special reinforcing member near the bottom of the exterior can, which increases the number of parts. It is also conceivable to increase the thickness of only the portions of the bottom of the exterior can where the connection portions and holes are provided, but this makes it difficult to manufacture the exterior can and causes an increase in costs.

[0008] An object of the present disclosure is to provide a cylindrical battery that can increase the reliability of the connection or sealing portion with the electrode body at the bottom of the outer can without placing a special reinforcing member near the bottom of the outer can or changing the plate thickness of part of the bottom.

[0009] The cylindrical battery according to the present disclosure includes an electrode assembly having a positive electrode plate and a negative electrode plate, a cylindrical outer can with a bottom that houses the electrode assembly, and a sealing body that closes the opening of the outer can, and the bottom surface of the outer can is provided with a first plane that is the bottommost surface, and second and third planes that are at different height positions relative to the first plane, the first plane being provided in a portion that includes at least a part of the outer periphery of the bottom surface, the second plane being provided in a portion that includes the center of the bottom surface, and the third plane being provided with at least a part that is not flush with the second plane in the radial direction of the bottom surface. the third plane has a circumferential length at its radial inner end that is 1 / 10 or less of the circumferential length of a circle passing through the radial outer end of the second plane on the bottom surface; and at least one of a connection portion with the electrode body and a hole sealed with a sealing portion is provided on the inner surface on the opposite side of the third plane in the plate thickness direction; and when the height position of the first plane when the bottom surface is facing down is T1, the height position of the second plane is T2, and the height position of the third plane is T3, T1 < T3 ≦ T2.

[0010] According to the cylindrical battery of the present disclosure, the reliability of the connection or sealing portion with the electrode body at the bottom of the outer can can be increased without placing a special reinforcing member near the bottom of the outer can or changing the plate thickness of part of the bottom.

[0011] FIG. 2 is a cross-sectional view taken along the axial direction of a cylindrical battery according to an example of an embodiment. FIG. 3 is an enlarged view of the lower end of the cylindrical battery shown in FIG. 1, with a portion omitted. FIG. 4 is a perspective view of the bottom of the cylindrical battery shown in FIG. 1, viewed from below. FIG. 5 is a perspective view of the bottom of the cylindrical battery shown in FIG. 1, viewed from below. FIG. 6 is a perspective view of the bottom of a cylindrical battery according to another example of an embodiment, viewed from below, in a state before a sealing portion is attached. FIG. 7 is a view corresponding to FIG. 2, showing the state after a sealing portion is attached in the cylindrical battery shown in FIG. 5. FIG. 8 is a view of the bottom of a cylindrical battery according to another example of an embodiment, viewed from below.

[0012] It has been considered to provide a connection portion with the electrode assembly or a hole to be sealed with a sealing portion on the inner surface of the bottom of an outer can. In this case, if the bottom is deformed overall due to an increase in internal pressure, the reliability of the connection portion and the sealing portion will be reduced. On the other hand, if a special reinforcing member is provided near the bottom of the outer can, the number of parts will increase, and if the thickness of only a portion of the bottom of the outer can is increased, the cost will be increased. As a result of extensive research, the inventors have found that by providing a first plane, which is the bottommost plane, and second and third planes, which are located at different heights relative to the first plane, on the bottom surface of the outer can, appropriately controlling the positional relationship between these planes and the circumferential length of the third plane, and providing at least one of a connection portion with the electrode assembly and a hole to be sealed with a sealing portion on the inner surface on the opposite side of the third plane in the thickness direction, the reliability of the connection portion or the sealing portion at the bottom of the outer can can be improved without providing a special reinforcing member near the bottom of the outer can or changing the thickness of a portion of the bottom.

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, specific shapes, materials, numerical values, directions, etc. are merely examples for facilitating understanding of the present invention and can be appropriately changed to suit the specifications of the cylindrical battery. In addition, the term "substantially" is used below to mean, for example, not only completely the same, but also substantially the same. Furthermore, when multiple embodiments and variations are included below, it is assumed from the outset that their characteristic features will be used in appropriate combination. In the following, a cylindrical battery will be described as a nonaqueous electrolyte secondary battery, but the configuration of the cylindrical battery is not limited to this and can be various primary or secondary batteries.

[0014] FIG. 1 is a cross-sectional view of a cylindrical battery 10 according to an embodiment, taken along its axial direction. FIG. 2 is an enlarged view of the lower end of the cylindrical battery 10, with a portion omitted. As illustrated in FIGS. 1 and 2 , the cylindrical battery 10 includes a wound electrode assembly 14, a nonaqueous electrolyte (not shown) serving as an electrolytic solution, an outer can 15, and a sealing member 16. The electrode assembly 14 includes a positive electrode plate 11, a negative electrode plate 12, and a separator 13, with the positive electrode plate 11 and the negative electrode plate 12 being spirally wound with the separator 13 interposed therebetween. Hereinafter, one side of the electrode assembly 14 in the direction of the winding axis may be referred to as the "upper" and the other side of the winding axis may be referred to as the "lower." The nonaqueous electrolyte includes a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent.

[0015] The positive electrode plate 11 has a positive electrode core made of a strip-shaped metal foil and positive electrode mixture layers formed on the inner winding surface (inner radial surface) and the outer winding surface (outer radial surface) of the positive electrode core. The positive electrode plate 11 has a positive electrode connection lead 19 joined to the positive electrode core. The positive electrode core may be made of a metal foil such as aluminum, or a film with such a metal disposed on its surface. A suitable positive electrode core is a metal foil primarily composed of aluminum or an aluminum alloy. The thickness of the positive electrode core is, for example, 10 μm to 30 μm. In this example, the positive electrode mixture layers are formed on both surfaces of the positive electrode core, but may also be formed on only one surface in the thickness direction of the positive electrode core.

[0016] The positive electrode mixture layer preferably contains a positive electrode active material, a conductive agent, and a binder. The positive electrode plate 11 is produced by applying a positive electrode mixture slurry containing the positive electrode active material, the conductive agent, the binder, and a solvent such as N-methyl-2-pyrrolidone (NMP) to both sides of a positive electrode core, followed by drying and rolling.

[0017] Examples of the positive electrode active material include lithium-containing transition metal oxides containing transition metal elements such as Co, Mn, and Ni. ｘ CoO ２ , Li ｘ NiO ２ , Li ｘ MnO ２ , Li ｘ Co ｙ Ni １－ｙ O ２ , Liｘ Co ｙ M １－ｙ O ｚ , Li ｘ Ni １－ｙ M ｙ O ｚ , Li ｘ Mn ２ O ４ , Li ｘ Mn ２－ｙ M ｙ O ４ , LiMPO ４ , Li ２ MPO ４ F (M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B, and 0<x≦1.2, 0<y≦0.9, and 2.0≦z≦2.3). These may be used alone or in combination.

[0018] Examples of the conductive agent include carbon black (CB) such as acetylene black (AB) and Ketjen black, and carbon materials such as graphite. Examples of the binder include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resins, and polyolefin resins. These resins may also be used in combination with carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), or the like. These may be used alone or in combination of two or more.

[0019] The positive electrode connection lead 19 is a conductive member for electrically connecting the positive electrode core and the positive electrode terminal, and extends from the upper end of the positive electrode core of the electrode body 14 to one side (upward) in the winding axis direction. The positive electrode connection lead 19 is provided, for example, at approximately the center in the radial direction of the electrode body 14. The positive electrode connection lead 19 is a strip-shaped conductive member. The constituent material of the positive electrode connection lead 19 is not particularly limited. The positive electrode connection lead 19 is preferably made of a metal containing aluminum as a main component. Furthermore, in the positive electrode plate 11, a positive electrode mixture layer is formed on each of the inner winding surface (inner radial surface) and the outer winding surface (outer radial surface) of the positive electrode core.

[0020] The negative electrode plate 12 has a negative electrode core made of a strip-shaped metal foil, and negative electrode mixture layers formed on the inner winding surface (inner surface in the radial direction) and the outer winding surface (outer surface in the radial direction) of the negative electrode core. The negative electrode plate 12 has a negative electrode connection lead 31 joined to the outermost peripheral surface of the negative electrode core. For the negative electrode core, for example, a foil of a metal such as copper, or a film with such a metal disposed on the surface layer, is used. The thickness of the negative electrode core is, for example, 5 μm to 30 μm.

[0021] The negative electrode mixture layer preferably contains a negative electrode active material and a binder. The negative electrode plate 12 is produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, water, etc. to both surfaces of a negative electrode core, followed by drying and rolling. The negative electrode mixture layer is formed on both surfaces of the negative electrode core, but may also be formed on only one surface in the thickness direction of the negative electrode core.

[0022] The negative electrode active material is not particularly limited as long as it can reversibly absorb and release lithium ions. For example, carbon materials such as natural graphite and artificial graphite, metals that alloy with lithium such as Si and Sn, or alloys or composite oxides containing these, can be used. The binder contained in the negative electrode active material layer is, for example, the same resin as that used in the positive electrode plate 11. When preparing the negative electrode mixture slurry using an aqueous solvent, styrene-butadiene rubber (SBR), CMC or a salt thereof, polyacrylic acid or a salt thereof, polyvinyl alcohol, etc. can be used. These materials may be used alone or in combination of two or more.

[0023] The negative electrode connecting lead 31 is a conductive member for electrically connecting the negative electrode core and the negative electrode terminal, and extends from the lower end of the negative electrode core of the electrode body 14 to the other side (downward) in the winding axis direction. The negative electrode connecting lead 31 is a strip-shaped conductive member. There are no particular restrictions on the material of the negative electrode connecting lead 31. The negative electrode connecting lead 31 is preferably made of a metal such as nickel.

[0024] The non-aqueous electrolyte has ion conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte (nonaqueous electrolytic solution), but may be a solid electrolyte using a gel polymer or the like. The cylindrical battery 10 is preferably a lithium ion battery. The electrolyte salt may be, for example, LiBF ４ , LiPF ６ Examples of the non-aqueous solvent include esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain a halogen-substituted product in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine.

[0025] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylic acid esters such as methyl fluoropropionate (FMP). From the viewpoint of suppressing a decrease in the charge-discharge cycle characteristics of a nonaqueous electrolyte secondary battery or improving input characteristics, the nonaqueous electrolyte preferably contains 5% by mass or more of FEC, and more preferably 5% by mass to 15% by mass of FEC, relative to the mass of the nonaqueous electrolyte.

[0026] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. The separator 13 is preferably made of an olefin resin such as polyethylene or polypropylene. The thickness of the separator 13 is, for example, 10 μm to 50 μm. Separators 13 tend to be thinner as batteries become higher in capacity and power output. The separator 13 has a melting point of, for example, about 130°C to 180°C.

[0027] Then, tape (not shown) is attached to the outermost surface of the separator 13 , which is the outermost surface of the electrode body 14 , so as to fix the winding end of the separator 13 to the outermost surface of the separator 13 .

[0028] The outer can 15, together with the sealing body 16, constitutes a metal battery case that houses the electrode assembly 14 and non-aqueous electrolyte. Insulating plates 17, 18 are provided above and below the electrode assembly 14. A positive electrode connection lead 19 passes through a through-hole in the upper insulating plate 17, extends toward the sealing body 16, and is welded to the underside of a filter 22, which is the bottom plate of the sealing body 16. In the cylindrical battery 10, a cap 26, which is the top plate of the sealing body 16 and is electrically connected to the filter 22, serves as the positive electrode terminal.

[0029] The outer can 15 is a cylindrical metal container with a bottom. A sealing body 16 is crimped to the opening at the top end of the outer can 15 via a gasket 27, thereby closing the opening. The outer can 15 has a flange 20 formed by crimping the entire inner periphery of the open end of the outer can 15, and a groove 21. The groove 21 is formed, for example, by pressing the side surface of the outer can 15 from the outside, and serves to support the sealing body 16. Furthermore, as shown in FIG. 2 , the outer can 15 has three flat surfaces on its bottom surface 40: a first flat surface 41, a second flat surface 42, and a third flat surface 43. The positional relationships, including the height relationships, of these flat surfaces 41, 42, and 43 are regulated. This will be described in detail later.

[0030] The sealing body 16 has a structure in which a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26 are stacked in this order from the electrode body 14 side. Each member constituting the sealing body 16 has, for example, a disk or ring shape, and each member except for the insulating member 24 is electrically connected to one another. The filter 22 has at least one through-hole. The lower valve body 23 and the upper valve body 25 are connected at their respective centers, with the insulating member 24 interposed between their respective peripheral edges.

[0031] When the cylindrical battery 10 generates abnormal heat and its internal pressure rises, the lower valve body 23 deforms and breaks, pushing the upper valve body 25 toward the cap 26, interrupting the current path between the lower valve body 23 and the upper valve body 25. If the internal pressure rises further, the upper valve body 25 breaks, and gas is released through the through-hole 26a in the cap 26. This gas release prevents the cylindrical battery 10 from exploding due to an excessive increase in internal pressure, thereby improving the safety of the cylindrical battery 10. The upper valve body 25 may be provided with an easily breakable portion formed by a thin, annular or C-shaped portion. This causes the easily breakable portion to break when the internal pressure of the cylindrical battery 10 rises, easily creating a gas release path.

[0032] The negative electrode connection lead 31 passes around the outside of the outer peripheral surface of the lower insulating plate 18, then is bent at a substantially right angle toward the central axis of the cylindrical battery 10, and joined by welding or the like to the inner surface of a third plane 43 (described below) on the opposite side in the plate thickness direction, thereby providing a connection portion 32 with the electrode body 14. In this way, the negative electrode connection lead 31 is electrically connected to the outer can 15, which serves as the negative electrode terminal. The lower insulating plate 18 is disc-shaped with a through-hole 70 formed in its center.

[0033] Furthermore, the positional relationship, including the height positional relationship, of the first flat surface 41, the second flat surface 42, and the third flat surface 43 provided on the bottom surface 40 of the outer can 15 is regulated. As a result, when the internal pressure increases, the connection portion 32 is provided on the inner surface of the bottom 15a of the outer can 15 opposite in the thickness direction to the third flat surface 43 that is deviated from the second flat surface that is easily deformed. Therefore, the connection strength of the connection portion 32 can be increased regardless of the increase in internal pressure, and the reliability of the connection portion 32 can be improved.

[0034] 1 and 2, the positional relationship of the bottom surface 40 of the exterior can 15 will be explained using Figures 3 and 4. Figure 3 is a perspective view of the bottom of the cylindrical battery 10 as seen from below. Figure 4 is a view of the bottom 15a of the cylindrical battery 10 as seen from below.

[0035] 1 to 4 , the bottom surface 40 of the outer can 15 is provided with a first plane 41, which is the bottommost surface, and a second plane 42 and a third plane 43, which are located at different heights relative to the first plane 41. A curved chamfered portion 71 having an arc-shaped cross section is formed at the joint between the outer peripheral edge of the bottom surface 40 of the outer can 15 and the outer peripheral surface of the cylindrical portion 15b of the outer can 15. A tapered chamfered portion, whose cross section is a straight line inclined with respect to the central axis of the outer can 15, may also be formed at the joint between the outer peripheral edge of the bottom surface 40 and the outer peripheral surface of the cylindrical portion 15b.

[0036] The first plane 41 is a generally C-shaped plane in bottom view, with a constant radial width, located on the entire outer periphery of the bottom surface 40 except for the outer periphery formed by the third plane 43 described below. Because the first plane 41 is located on the bottommost surface, it serves as the reference surface when the cylindrical battery 10 is stood with the bottom surface 40 facing downwards, and is the surface most susceptible to external forces. However, because it is located on the portion of the bottom surface 40 that includes the outer periphery, it is less likely to deform in response to an increase in internal pressure than the plane including the center of the bottom surface.

[0037] The second plane 42 is located in a portion of the bottom surface 40 that includes the center O, and is a plane inside a circle centered at the center O. Therefore, the second plane 42 is the portion farthest from the tubular portion 15b, and is the surface that is most susceptible to deformation due to an increase in the internal pressure of the cylindrical battery 10.

[0038] The entire third plane 43 is located radially outward of the outermost position of the second plane 42 in the radial direction of the bottom surface 40. In this example, the third plane 43 is an inner plane of a substantially rectangular shape that is arranged at a position that overlaps with the first plane 41 in the circumferential direction of the bottom surface 40.

[0039] When the bottom surface 40 is placed downward, the height position of the first plane 41 is T1, the height position of the second plane 42 is T2, and the height position of the third plane 43 is T3, so that T1 < T3 < T2 holds. As a result, the third plane 43 is located between the first plane 41 and the second plane 42 in the height direction, and is sandwiched between both circumferential ends of the first plane 41 in bottom view.

[0040] The radially inner ends of the third flat surface 43 and the first flat surface 41 and the radially outer end of the second flat surface 42 are connected by a tapered surface 72 ( FIG. 2 ), the diameter of which decreases toward the inside in the axial direction of the outer can 15. As described above, the third flat surface 43 is located between the first flat surface 41 and the second flat surface 42 in the height direction. Therefore, compared to when the third flat surface 43 and the second flat surface 42 are located at the same height, the third flat surface 43 is less susceptible to deformation of the second flat surface 42 due to an increase in internal pressure. Furthermore, since the third flat surface 43 is located higher than the first flat surface 41, it is less susceptible to external forces. Note that the radially inner ends of the third flat surface 43 and the first flat surface 41 and the radially outer end of the second flat surface 42 may be connected by a cylindrical surface parallel to the central axis of the outer can 15 instead of the tapered surface 72.

[0041] Furthermore, the circumferential length d1 ( FIG. 4 ) at the radially inner end of the third flat surface 43 is 1 / 10 or less of the circumferential length of a circle E that passes through the radially outer end of the second flat surface 42 on the bottom surface 40. This allows the third flat surface 43 to be sufficiently small relative to the circumferential lengths and areas of the first flat surface 41 and the second flat surface 42, making it less susceptible to the effects of internal pressure and external forces. On the other hand, if the circumferential length d1 at the radially inner end of the third flat surface 43 exceeds 1 / 10 of the circumferential length of the circle E, the effect of suppressing deformation due to an increase in internal pressure may be reduced depending on the height positional relationship, such as when the third flat surface 43 is close to the second flat surface 42 in height position.

[0042] In this example, the thickness of the bottom 15a of the outer can 15 is constant and may be any thickness that ensures strength sufficient for normal use, but is preferably 0.25 mm or more. The circumferential length of a circle E passing through the radial outer edge of the second flat surface 42 of the bottom surface 40 is preferably at least two-thirds of the length of a circle passing through the outer periphery of the bottom surface 40.

[0043] As described above, the connection portion 32 for connecting to the electrode body 14 is provided on the inner surface opposite to the third plane 43 in the plate thickness direction.

[0044] Furthermore, it is preferable that the difference C1 (FIG. 2) between the height position T3 of the third plane 43 and the height position T1 of the first plane 41 is 1 / 10 or more of the plate thickness of the first plane 41.

[0045] In the cylindrical battery 10 described above, the third flat surface 43 is located between the first flat surface 41 and the second flat surface 42 in the height direction, and the entire bottom surface 40 is located radially outward of the outermost periphery of the second flat surface 42. The circumferential length d1 at the radial inner end of the third flat surface 43 is 1 / 10 or less of the circumferential length of a circle E passing through the radial outer end of the second flat surface 42 on the bottom surface 40. The connection portion 32 is provided on the inner surface opposite the third flat surface 43 in the thickness direction. This allows the connection portion 32 to be provided on the inner surface of the bottom 15a of the outer can 15 opposite the third flat surface 43 in the thickness direction, away from the second flat surface 42, which is prone to deformation due to an increase in internal pressure. This allows the connection strength of the connection portion 32 to be increased regardless of an increase in internal pressure, thereby improving the reliability of the connection portion 32. Furthermore, there is no need to provide a special reinforcing member near the bottom 15a of the exterior can 15 or to change the thickness of part of the bottom 15a.

[0046] Furthermore, if the difference C1 between the height position T3 of the third plane 43 and the height position T1 of the first plane 41 is set to 1 / 10 or more of the plate thickness of the first plane 41, deformation of the third plane 43 due to external forces can be further suppressed.

[0047] Fig. 5 is a perspective view of the bottom 15a of a cylindrical battery 10a according to another embodiment before the sealing portion is attached, Fig. 6 is a view of the bottom 15a of the cylindrical battery 10a from below, and Fig. 7 is a view corresponding to Fig. 2 showing the cylindrical battery 10a after the sealing portion 51 is attached.

[0048] In the configuration of this example, a connection portion 32 (see FIG. 2 ) for the electrode assembly 14 (see FIG. 1 ) is not provided on the inner surface opposite the third plane 43 in the plate thickness direction. Instead, a hole 50 penetrating in the plate thickness direction is formed in the plate portion 73 including the third plane 43. The hole 50 is closed by a sealing portion 51 ( FIG. 7 ). The hole 50 is provided for injecting the electrolyte solution into the interior. The sealing portion 51 closes the hole 50 after the electrolyte solution is injected. The sealing portion 51 is formed of a resin or the like and may have a columnar shape, or a shape in which a circular plate with an outer diameter larger than that of the columnar portion is connected to a portion protruding from the bottom surface 40 of the columnar portion. In a configuration in which the connection portion 32 is not provided as described above, for example, the winding end side end of the negative electrode plate of the electrode assembly 14 is made longer in the winding end direction than the winding end side end of the separator, and the negative electrode plate is disposed on the outermost peripheral surface of the electrode assembly 14, and the negative electrode core is exposed on the outermost peripheral surface of the electrode assembly 14. Then, the negative electrode plate is electrically connected to the outer can 15 by bringing the exposed portion of the negative electrode substrate on the outermost peripheral surface of the electrode body 14 into contact with the inner peripheral surface of the cylindrical portion 15 b of the outer can 15 .

[0049] Furthermore, as shown in Figure 6, a notch 18a extending radially inward may be formed on the outer peripheral surface of the lower insulating plate 18 at a position that coincides with the sealing portion 51 in the circumferential direction, so that the electrolyte injected through the hole 50 can be quickly supplied to the electrode body 14 side.

[0050] Furthermore, an easy-to-break portion 60 is provided on the second flat surface 42. The easy-to-break portion 60 is provided so as to break when the internal pressure of the outer can 15 rises to or exceeds a predetermined value. The easy-to-break portion 60 is formed by a groove 62 made up of a plurality of straight portions 61 extending radially from the center of the bottom surface 40a at equal intervals in the circumferential direction. While Figures 5 and 6 show a case in which the groove 62 is formed from three straight portions 61, the number of straight portions 61 may be various, such as one, two, four or more.

[0051] In addition, it is preferable to have three or more straight line portions so that the easily breakable portion breaks when the internal pressure increases, making it easier to form a gas discharge path. In such a configuration, the sealing body provided at the open end of the outer can can be configured to have no easily breakable portion that will break when the internal pressure of the outer can increases to a predetermined value or higher. For example, the sealing body may simply be configured to be a metal terminal cap with a positive electrode connection lead 19 (see FIG. 1 ) extending from the electrode body 14 connected to its underside, and the terminal cap may be configured to be crimped and fixed to the opening of the outer can 15 via a gasket.

[0052] According to the configuration of this example, the easily breakable portion 60 is provided in a portion of the bottom surface 40 that includes the second plane 42, which is most susceptible to deformation due to an increase in internal pressure. This allows the effect of the easily breakable portion 60 to be more pronounced. Even in this case, a hole sealed with a sealing portion is provided on the inner surface on the opposite side in the plate thickness direction to the third plane 43, which is less likely to deform regardless of an increase in internal pressure. This allows the reliability of the sealing portion 51 to be increased regardless of an increase in internal pressure.

[0053] The fragile portions are not limited to grooves having radially extending straight portions, but may be formed as circular or C-shaped grooves in a bottom view. In the configuration of this example, other configurations and functions are the same as those of the configurations of Figures 1 to 4.

[0054] In the configuration of this example, similar to the configurations of Figures 1 to 4, a connection portion 32 for the electrode body 14 may be provided on the inner surface opposite the plate thickness direction of the third plane 43, together with or in place of the hole 50 sealed with the sealing portion 51.

[0055] Figure 8 is a bottom view of a cylindrical battery 10b according to another embodiment. In this configuration, the third planes 44 and 45 are located at multiple positions on the bottom surface 40b and are positioned at the same height as the second plane 42. Specifically, in this configuration, the third planes 44 and 45 are positioned higher than the third plane 43 in Figure 2 and are aligned with the second plane 42 in the configurations shown in Figures 1 to 4. For ease of understanding, the third planes 44 and 45 are shown as sandy areas in Figure 8.

[0056] Furthermore, two third flat surfaces 44, 45 are provided on the bottom surface 40b at positions symmetrical with respect to the center O when viewed from the bottom. Each of the third flat surfaces 44, 45 is located radially outward of the outermost position of the second flat surface 42. As a result, each of the third flat surfaces 44, 45 is provided at the same height position in a plurality of positions in the circumferential direction of the bottom surface 40. Furthermore, the first flat surface 41a is divided into two by the two third flat surfaces 44, 45.

[0057] Furthermore, the sum (d1 + d2) of the circumferential lengths d1, d2 at the radial inner ends of the two third flat surfaces 44, 45 is 1 / 10 or less of the circumferential length of a circle E that passes through the radial outer end of the second flat surface 42 on the bottom surface 40. The circumferential lengths d1, d2 at the radial inner ends of the third flat surfaces 44, 45 may be the same as or different from each other.

[0058] A connection portion 32 (see FIG. 2) for the electrode body 14 (see FIG. 1) is provided on the inner surface opposite in the plate thickness direction of each of the third flat surfaces 44, 45. Note that the connection portion 32 (see FIG. 2) may be provided on the inner surface opposite in the plate thickness direction of one of the two third flat surfaces 44, 45, and a hole 50 (see FIG. 7) sealed with a sealing portion 51 may be provided on the other.

[0059] 1 to 4 in terms of suppressing deformation of the third flat surfaces 44, 45 due to an increase in internal pressure. However, even in this case, the circumferential length 44, 45 at the radial inner end of the third flat surface 43 is 1 / 10 or less of the circumferential length of a circle E passing through the radial outer end of the second flat surface 42 on the bottom surface 40, so that a practically necessary deformation suppression effect can be obtained. Furthermore, even when two third flat surfaces 44, 45 are provided, the sum (d1 + d2) of the circumferential lengths of the two third flat surfaces 44, 45 at the radial inner ends is 1 / 10 or less of the circumferential length of a circle E passing through the radial outer end of the second flat surface 42 on the bottom surface 40, so that a practically necessary deformation suppression effect can be obtained for each third flat surface 44, 45.

[0060] In this example, there are two third flat surfaces 44, 45, but three or more third flat surfaces may be provided. Even in this case, the sum of the circumferential lengths of the radially inner ends of the plurality of third flat surfaces is preferably 1 / 10 or less of the circumferential length of a circle E passing through the radially outer end of the second flat surface 42 on the bottom surface 40. In this example, the other configurations and functions are the same as those of Figures 1 to 4. Furthermore, in the configuration of this example, an easily breakable portion 60 may be provided on the second flat surface 42, as in the configurations of Figures 5 to 7.

[0061] Although not shown, in another example of the embodiment, in a configuration in which the height position of the third plane is midway between the height positions of the first plane 41 and the second plane 42, the third plane may be provided so as to straddle the same radial position as the outer circumferential edge of the second plane 42 in a plan view of the bottom surface. In this case, only a portion of the third plane 43 in the radial direction of the bottom surface 40 is located on the outer circumferential side of the outermost position of the second plane 42.

[0062] The present disclosure is further described by the following configurations. Configuration 1: An electrode assembly including a positive electrode plate and a negative electrode plate, a cylindrical outer can with a bottom that houses the electrode assembly, and a sealing body that closes an opening of the outer can, wherein a first plane that is the bottommost surface, and a second plane and a third plane that are located at different heights relative to the first plane are provided on the bottom surface of the outer can, the first plane is provided in a portion that includes at least a part of the outer periphery of the bottom surface, the second plane is provided in a portion that includes the center of the bottom surface, at least a part of the third plane in the radial direction of the bottom surface is located outer than the outermost periphery position of the second plane, the circumferential length of the radial inner end of the third plane is 1 / 10 or less of the circumferential length of a circle that passes through the radial outer end of the second plane on the bottom surface, and at least one of a connection portion with the electrode assembly and a hole that is sealed with a sealing portion is provided on an inner surface on the opposite side of the third plane in the plate thickness direction, A cylindrical battery in which, when the bottom surface is placed downward, the height position of the first plane is T1, the height position of the second plane is T2, and the height position of the third plane is T3, T1 < T3 ≦ T2. Configuration 2: The cylindrical battery according to Configuration 1, in which T1 < T3 < T2. Configuration 3: The cylindrical battery according to Configuration 1 or 2, in which the difference between the height position T3 of the third plane and the height position T1 of the first plane is 1 / 10 or more of the plate thickness of the first plane. Configuration 4: The cylindrical battery according to any one of Configurations 1 to 3, in which the third planes are provided at the same height position in a plurality of positions around the circumferential direction of the bottom surface, and the sum of the circumferential lengths of the plurality of third planes at the radially inner ends is 1 / 10 or less of the circumferential length of a circle passing through the radially outer ends of the second planes on the bottom surface. Configuration 5: The cylindrical battery according to any one of Configurations 1 to 4, wherein the second flat surface is provided with an easy-to-break portion that breaks when the internal pressure of the outer can rises to or exceeds a predetermined value.

[0063] 10, 10a, 10b Cylindrical battery, 11 Positive electrode plate, 12 Negative electrode plate, 13 Separator, 14 Electrode body, 15 Outer can, 15a Bottom, 15b Cylindrical portion, 16 Sealing body, 17, 18 Insulating plate, 19 Positive electrode connection lead, 20 Flange portion, 21 Grooved portion, 22 Filter, 23 Lower valve body, 24 Insulating member, 25 Upper valve body, 26 Cap, 26a Through hole, 27 Gasket, 31 Negative electrode connection lead, 32 Connection portion, 40, 40a, 40b Bottom surface, 41, 41a First plane, 42 Second plane, 43, 43a, 44, 45 Third plane, 50 Hole, 51 Sealing portion, 60 Easy-to-break portion, 61 Straight portion, 62 Groove, 70 Through hole, 71 Chamfered portion, 72 Tapered surface, 73 plate section.

Claims

1. A cylindrical battery comprising: an electrode body having a positive electrode plate and a negative electrode plate; a bottomed cylindrical exterior can housing the electrode body; and a sealing body closing an opening of the exterior can, wherein a first plane which is the bottommost surface, a second plane and a third plane having different height positions with respect to the first plane are provided on a bottom surface of the exterior can, the first plane is provided at a portion including at least a part of an outer peripheral edge of the bottom surface, the second plane is provided at a portion including a center of the bottom surface, at least a part of the third plane is located on an outer peripheral side with respect to an outermost peripheral position of the second plane in a radial direction of the bottom surface, a circumferential length at an inner end in the radial direction of the third plane is 1 / 10 or less of a circumferential length of a circle passing through an outer end in the radial direction of the second plane on the bottom surface, at least one of a connection portion with the electrode body and a hole sealed by a sealing portion is provided on an inner surface on a side opposite to a plate thickness direction of the third plane, and when a height position of the first plane is T1, a height position of the second plane is T2, and a height position of the third plane is T3 with the bottom surface facing downwards, T1 < T3 ≦ T2.

2. The cylindrical battery according to claim 1, wherein T1 < T3 < T2.

3. The cylindrical battery according to claim 1, wherein a difference between the height position T3 of the third plane and the height position T1 of the first plane is 1 / 10 or more of a plate thickness of the first plane.

4. The cylindrical battery according to claim 1, wherein the third plane is provided at a plurality of positions in a circumferential direction of the bottom surface at the same height position, and a total circumferential length at inner ends in the radial direction of the plurality of third planes is 1 / 10 or less of a circumferential length of a circle passing through an outer end in the radial direction of the second plane on the bottom surface.

5. The cylindrical battery according to claim 1, wherein an easily breakable portion that breaks when an internal pressure of the exterior can rises to a predetermined value or more is provided on the second plane.

Images