Cylindrical battery

Abstract

This battery comprises: an electrode body; a bottomed cylindrical exterior can that accommodates the electrode body; and a lower collector plate (60) that is provided with a lower surface joined to a bottom part of the exterior can and an upper surface to which a negative electrode core body exposed portion from which a negative electrode core body is exposed is joined, while being provided at a lower end of the electrode body. The bottom part has a thin, easily breakable part (37a). The tip side of a protruding part (78) that appears on the lower collector plate (60) on the basis of deformation of the lower collector plate (60) accompanying an increase in internal pressure comes into contact with the bottom part. According to the battery of the present disclosure, the occurrence of multi-point ignition in the electrode body can be suppressed even in a severe environment, and safety can be increased.

Description

Cylindrical battery

[0001] The present disclosure relates to a cylindrical battery.

[0002] Conventionally, as a cylindrical battery, there is one described in Patent Document 1. This cylindrical battery includes an electrode body, a bottomed cylindrical outer can that houses the electrode body, and a sealing body that closes the opening of the outer can. A thin and easily breakable portion is provided at the bottom of the outer can. When the battery abnormally generates heat due to an internal short circuit or the like, this easily breakable portion preferentially breaks, and the high-pressure gas inside the battery is discharged to the outside through the opening generated by the break. Therefore, it is possible to prevent the internal pressure of the battery from becoming excessively high and improve the safety of the cylindrical battery.

[0003] Japanese Patent Application Laid-Open No. 10-308206

[0004] The inventor of the present invention has confirmed that in a malicious test in which a cylindrical battery is intentionally ignited in an extremely harsh environment, due to the rapid increase in internal pressure up to the sealing pressure resistance or the outer can rupture pressure resistance, exhaust other than the exhaust after the breakage of the easily breakable portion occurs, that is, exhaust caused by the cracking of the outer can occurs, and due to this exhaust, a phenomenon in which a flame is ejected to the outside can occur. Here, as one of the causes of such a rapid increase in internal pressure, it can be cited that the battery temperature has rapidly increased due to the occurrence of ignition over a wide range in the electrode body (multi-point ignition in the electrode body). Therefore, an object of the present disclosure is to provide a cylindrical battery with high safety that can suppress multi-point ignition from occurring in the electrode body even in a harsh environment.

[0005] To solve the above problems, the cylindrical battery according to the present disclosure includes a long first electrode having a first electrode core and a first electrode binder layer and a long second electrode having a second electrode core and a second electrode binder layer wound via a long separator to form an electrode body, a bottomed cylindrical outer can that houses the electrode body, a first end face in the axial direction provided at an end of the electrode body on the bottom side of the outer can in the axial direction and having a first electrode core exposed portion to which the exposed first electrode core is joined, and a current collector plate having a second end face in the axial direction joined to the bottom, the bottom having a thin and easily breakable portion, and the tip side of the protruding portion that appears on the current collector plate based on the deformation of the current collector plate accompanying the increase in internal pressure being adapted to contact the bottom.

[0006] The cylindrical battery described herein offers high safety because it can suppress the occurrence of multiple point ignitions in the electrode body even under harsh conditions.

[0007] This is an axial cross-sectional view of a cylindrical battery according to one embodiment of the present disclosure. This is a perspective view showing a part of the electrode body and the positive electrode lead. This is a plan view showing the inner surface of the winding of the positive electrode, and is a plan view illustrating the formation position and structure of the exposed portion of the positive electrode core to which the positive electrode lead is joined in the positive electrode. This is a bottom view (plan view) of the lower current collector plate when viewed from below. This is an enlarged bottom view of the area around the connecting portion in Figure 4. This is a cross-sectional view taken along line A-A in Figure 5, and is a cross-sectional view taken with plane P2, which passes through a part of the connecting portion other than the slit and is perpendicular to plane P1, as the cutting plane. (a) is a schematic perspective view of the cylindrical battery in a normal state when viewed from diagonally below, and (b) is a schematic perspective view of the cylindrical battery when the internal pressure has risen due to an internal short circuit or the like, when viewed from diagonally below. This is a perspective view of the lower current collector plate of the cylindrical battery with increased internal pressure when viewed from diagonally below. This is an enlarged perspective view of the area around the connecting portion in Figure 8. This is a bottom view of the lower current collector plate of a modified example, corresponding to Figure 4.

[0008] Hereinafter, embodiments of the cylindrical battery according to this disclosure will be described in detail with reference to the drawings. The cylindrical battery of this disclosure may be a primary battery or a secondary battery. Furthermore, the cylindrical battery of this disclosure may be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. In the following, a cylindrical lithium-ion secondary battery using a non-aqueous electrolyte will be given as an example of one embodiment of the cylindrical battery 10, but the cylindrical battery of this disclosure is not limited to this.

[0009] Where multiple embodiments and modifications are included below, it is anticipated from the outset that new embodiments may be constructed by appropriately combining their characteristic features. In the following embodiments, the same reference numerals are used for the same components in the drawings, and redundant explanations are omitted. Multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. In this specification, the axial (height) side of the sealing body 17 of the cylindrical battery 10 is referred to as "upper," and the axial side of the bottom 37 of the outer casing 16 is referred to as "lower." Among the components described below, components not described in the independent claim indicating the highest-level concept are optional components and are not essential components.

[0010] Figure 1 is an axial cross-sectional view of a cylindrical battery 10 according to one embodiment of the present disclosure. As shown in Figure 1, the cylindrical battery (hereinafter simply referred to as "battery") 10 comprises a wound electrode body 14, a non-aqueous electrolyte (not shown), a bottomed cylindrical metal outer casing 16 that houses the electrode body 14 and the non-aqueous electrolyte, and a sealing body 17 for closing the opening of the outer casing 16.

[0011] Non-aqueous electrolytes are ionic conductive (e.g., lithium ion conductive). Non-aqueous electrolytes may be liquid electrolytes (electrolytes) or solid electrolytes. Liquid electrolytes (electrolytes) contain 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 mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. Non-aqueous solvents may contain halogen-substituted compounds (e.g., fluoroethylene carbonate) in which at least some of the hydrogen atoms in these solvents are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include LiPF4. ６ Lithium salts such as these are used.

[0012] As solid electrolytes, for example, solid or gel-like polymer electrolytes, inorganic solid electrolytes, etc., are used. Polymer electrolytes include, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As matrix polymers, for example, polymer materials that absorb non-aqueous solvents and gel are used. As polymer materials, for example, fluororesins, acrylic resins, polyether resins, etc., are used. As inorganic solid electrolytes, for example, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) are used.

[0013] Figure 2 is a perspective view showing a portion of the electrode body 14 and the positive electrode lead 20. In Figure 2, the positive electrode mixture layer 32 and the negative electrode mixture layer 42 are shown with diagonal hatching. As shown in Figure 2, the electrode body 14 has a long positive electrode 11, a long negative electrode 12, and two long separators 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound around the separators 13. The negative electrode 12 constitutes the first electrode, and the positive electrode 11 constitutes the second electrode. One or more positive electrode leads 20 are joined to the positive electrode 11, and in this embodiment, four positive electrode leads 20 are joined to the positive electrode 11 with spacing between them in the longitudinal direction of the positive electrode. It is preferable that six or more positive electrode leads 20 are joined to the positive electrode 11 at intervals from each other in the longitudinal direction of the positive electrode, and it is even more preferable that eight or more positive electrode leads 20 are joined to the positive electrode 11 at intervals from each other in the longitudinal direction of the positive electrode.

[0014] The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. The negative electrode 12 is formed to be longer than the positive electrode 11 in the winding direction and axial direction. The two separators 13 are formed to be slightly larger than the positive electrode 11 and are arranged to sandwich the positive electrode 11. The separators 13 protrude above the positive electrode 11 and the negative electrode 12, and the negative electrode 12 protrudes below the positive electrode 11 and the separators 13.

[0015] The negative electrode 12 has a negative electrode core body exposed portion 41 at its lower axial end, extending from the inner end to the outer end in the longitudinal direction of the negative electrode, where the negative electrode mixture layer 42 is not provided in the negative electrode core body 40. The lower axial end of the electrode body 14 is composed of at least a part of the negative electrode core body exposed portion 41. The negative electrode 12 may constitute the inner end of the electrode body 14. However, generally, the separator 13 extends beyond the inner end of the negative electrode 12, and the inner end of the separator 13 becomes the inner end of the electrode body 14.

[0016] The positive electrode 11 has a positive electrode core 30 and a positive electrode mixture layer 32 formed on both sides of the positive electrode core 30. In this embodiment, the positive electrode core 30 constitutes the second electrode core, and the positive electrode mixture layer 32 constitutes the second electrode mixture layer. The positive electrode core 30 can be made of a metal foil that is stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. The positive electrode mixture layer 32 contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core 30, drying the coating, and then compressing it to form the positive electrode mixture layer 32 on both sides of the positive electrode core 30.

[0017] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Examples of metal elements contained in the lithium-containing metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. A preferred example of a lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0018] Examples of conductive agents included in the positive electrode mixture layer 32 include carbon black such as acetylene black and Ketjen black, and carbon materials such as graphite. Examples of binders included in the positive electrode mixture layer 32 include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resin, acrylic resin, and polyolefin resin. These resins may be used in combination with cellulose derivatives such as carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc. To increase capacity, it is preferable that the longitudinal length of the positive electrode 11 is 3000 mm or more.

[0019] Figure 3 is a plan view showing the inner surface 5 of the winding of the positive electrode 11, and is a plan view illustrating the formation position and structure of the positive electrode core exposed portion 35 to which the positive electrode lead 20 is joined in the positive electrode 11. The area hatched with diagonal lines in Figure 3 is the arrangement area of ​​the positive electrode mixture layer 32. In this embodiment, the case in which the positive electrode lead 20 is joined to the inner surface 5 of the winding of the positive electrode 11 is described, but the positive electrode lead may also be joined to the outer surface of the winding of the positive electrode.

[0020] As shown in Figure 3, the positive electrode 11 has one or more positive electrode core exposed portions 35 in which the positive electrode core 30 is exposed. In this embodiment, there are four positive electrode core exposed portions 35 that are spaced apart in the positive electrode width direction. One positive electrode lead 20 is joined to each positive electrode core exposed portion 35 by ultrasonic welding or the like. The positive electrode mixture layer 32 has core adjacent portions 32a that are positioned adjacent to the positive electrode core exposed portions 35 in the positive electrode width direction. Because the positive electrode mixture layer 32 has core adjacent portions 32a, the arrangement area of ​​the positive electrode mixture layer 32 is increased, and the capacity is increased. Since the reduction in electrical resistance is increased by effectively shortening the positive electrode side current path, when there are three or more positive electrode leads 20, it is preferable that the center positions of the three or more positive electrode leads 20 in the positive electrode longitudinal direction are arranged at approximately equal intervals in the positive electrode longitudinal direction. Furthermore, the exposed positive electrode core portion 35 may extend from one end to the other in the positive electrode width direction of the positive electrode 11, and the battery does not necessarily have a core adjacent portion 32a.

[0021] To suppress short circuits between the positive electrode 11 and the negative electrode 12, it is preferable that at least a portion of the overlapping portion of the positive electrode lead 20 that overlaps the positive electrode core exposed portion 35 in the positive electrode thickness direction is covered with a first insulating tape (not shown), and it is preferable that the first insulating tape covers the entire positive electrode core exposed portion 35. Furthermore, to suppress short circuits between the positive electrode 11 and the negative electrode 12, it is preferable that a second insulating tape (a headband-shaped insulating tape: not shown) is applied around the entire circumference of the base portion of the extension portion that extends from the positive electrode 11 in the positive electrode lead 20. The first insulating tape and the second insulating tape are made of insulating materials, for example, a polyimide film may be used as the base material and silicone as the adhesive.

[0022] As shown in Figure 2, the negative electrode 12 has a negative electrode core 40 and a negative electrode mixture layer 42 formed on both sides of the negative electrode core 40. The negative electrode core 40 constitutes the first electrode core, and the negative electrode mixture layer 42 constitutes the first electrode mixture layer. For the negative electrode core 40, a metal foil that is stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with the metal arranged on its surface, can be used. The negative electrode mixture layer 42 contains a negative electrode active material and a binder. The negative electrode 12 can be manufactured, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder onto the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode mixture layer 42 on both sides of the negative electrode core 40.

[0023] Generally, carbon materials that reversibly intercept and release lithium ions are used as the negative electrode active material. Preferred carbon materials are graphites such as natural graphite such as flake graphite, lump graphite, and clay graphite, and artificial graphite such as lump graphite and graphitized mesophase carbon microbeads. Since it is easy to increase the capacity, it is preferable that the negative electrode active material of the negative electrode mixture layer 42 contains a Si material containing silicon (Si) particles, and it is preferable that the mass ratio of Si elements in the negative electrode mixture layer 42 is 5% by mass or more. It is also preferable that 3.0% by mass or more of the negative electrode mixture layer is composed of silicon oxide. Other metals that alloy with lithium besides Si, alloys containing such metals, compounds containing such metals, etc., may also be used as the negative electrode active material.

[0024] The binder contained in the negative electrode mixture layer 42 may be fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, etc., as in the case of the positive electrode 11, but preferably styrene-butadiene rubber (SBR) or a modified version thereof is used. In addition to SBR, the negative electrode mixture layer 42 may also contain CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, etc.

[0025] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material of the separator 13 is preferably polyethylene, polyolefin resins such as polypropylene, or cellulose. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer or the like may be formed on the surface of the separator 13.

[0026] As shown in Figure 1, the battery 10 is equipped with an annular insulating plate 18 on the upper side of the electrode body 14. The positive electrode lead 20 attached to the positive electrode 11 extends towards the sealing body 17 through a through hole in the insulating plate 18. The sealing body 17 has an upper current collector plate 50 and a terminal cap 27. The upper current collector plate 50 is a metal annular plate member and has a through hole 50a in the radial center. The terminal cap 27 is a metal plate-like member without a through hole and is located on the axial upper side of the sealing body 17. The axial upper end face of the terminal cap 27 is exposed to the outside except for the outer edge, and this exposed portion constitutes the positive electrode terminal. The sealing body 17 further has a metal plate 51. The metal plate 51 is a metal annular member and has a through hole.

[0027] Each positive electrode lead 20 is bent from the positive electrode 11 through the through hole 50a of the upper current collector plate 50 so as to follow the upper surface of the upper current collector plate 50. The tip of each positive electrode lead 20 is sandwiched between the upper surface of the upper current collector plate 50 and the lower surface of the metal plate 51. Each positive electrode lead 20 is joined to the upper surface of the upper current collector plate 50. The upper current collector plate 50 and the metal plate 51 are also joined, and each positive electrode lead 20 is also joined to the metal plate 51. These joining can be achieved, for example, by laser welding by irradiating the metal plate 51 from above with laser light in the axial direction while the tip of each positive electrode lead 20 is sandwiched between the upper current collector plate 50 and the metal plate 51. By laser welding the tip of the positive electrode lead 20 while it is sandwiched between the upper current collector plate 50 and the metal plate 51, the positive electrode lead 20 can be reliably and easily welded and joined to the upper current collector plate 50.

[0028] The sealing body 17 has a laminated portion 55 on its outer edge in which the terminal cap 27 and the upper current collector plate 50 are stacked. By irradiating the laminated portion 55 from above with laser light, the terminal cap 27 and the upper current collector plate 50 are laser-welded and electrically connected. The annular upper surface of the upper current collector plate 50 has an annular recess 53 that is radially inward from the laminated portion 55. Because the upper surface of the upper current collector plate 50 has a recess 53 that is recessed downward, a space is provided between the terminal cap 27 and the recess 53 of the upper current collector plate 50. Each positive electrode lead 20 is joined to the upper current collector plate 50 within the recess 53.

[0029] The upper current collector plate 50 does not need to be joined to the metal plate 51, and the positive electrode lead 20 does not need to be joined to the metal plate 51. Also, the battery does not need to have the metal plate 51. Also, the positive electrode lead 20 may be joined to the lower surface of the upper current collector plate 50. The current collection structure that electrically connects the positive electrode 11 to the sealing body 17 has been described in the case where it includes one or more positive electrode leads 20. However, the current collection structure that electrically connects the positive electrode to the sealing body may include a structure in which a strip-shaped positive electrode core exposed portion that constitutes the upper end of the electrode body is joined to the current collector plate by welding or the like.

[0030] The battery 10 is equipped with a metal, integrated lower current collector plate 60 on the axially lower side of the electrode body 14. Figure 4 is a bottom view (plan view) of the lower current collector plate 60 as seen from below. As shown in Figure 4, the lower current collector plate 60 has a central part 61, a plurality of arm parts 62 extending from the central part 61, and a connecting part 63 that connects two adjacent arm parts 62 in the circumferential direction without including the central part 61 (without going through the central part 61). The plurality of arm parts 62 are arranged at approximately equal intervals in the circumferential direction, and in this embodiment, four arm parts 62 are arranged at approximately equal intervals in the circumferential direction. The central part 61 is located in the radial center and has a substantially square shape in a plan view when viewed from the axial direction (thickness direction). The central part 61 may have a substantially circular shape or the like in a plan view when viewed from the axial direction (thickness direction).

[0031] The central part 61 is connected to the arm part 62 via a stepped part 64, and the lower surface 61a of the central part 61 is located one step lower than the arm part 62. The arm part 62 has a groove 62b in the widthwise center of its lower surface 62a that extends in the direction of extension of the arm part 62 (a direction substantially coinciding with the radial direction), and a protruding part 62c (see Figure 1) on the upper surface where it is opposite the groove 62b in the thickness direction (where they overlap in the thickness direction). The groove 62b and the protruding part 62c are created simultaneously, for example, by press molding, which causes the part that overlaps the groove 62b in the thickness direction to be plastically deformed upwards.

[0032] Referring to Figures 1 and 2, the electrode body 14 is pressed against the protruding portion 62c of the lower current collector plate 60 so that the elongated negative electrode core exposed portion 41 is tilted radially inward, and a laser beam is irradiated onto the groove portion 62b from below, thereby joining the negative electrode core exposed portion 41 to the upper surface of the arm portion 62 over a wide area by laser welding. In addition, by irradiating the bottom portion 37 of the outer casing 16 from below, the bottom portion 37 of the outer casing 16 is joined to the lower surface 61a of the central portion 61 by laser welding.

[0033] As a result, the negative electrode 12 of the electrode body 14 is electrically connected to the outer casing 16 via the lower current collector plate 60. By joining the exposed portion 41 of the negative electrode core to the upper surface of the lower current collector plate 60 over a wide area, it is possible to suppress the flow of current along the longitudinal direction of the long negative electrode 12, thereby reducing the electrical resistance of the battery 10. Since the lower surface 61a of the central part 61 is located one level lower than the arm portion 62, the lower surface 61a of the central part 61 can be placed in close contact with the upper surface of the bottom portion 37, and the central part 61 can be reliably and easily joined to the bottom portion 37.

[0034] The outer can 16 has a cylindrical portion 39 and a bottom portion 37. The cylindrical portion 39 includes an annular grooved portion 22 and an annular shoulder portion 29. The grooved portion 22 is formed by spinning a part of the cylindrical portion 39 to create a recess radially inward along its entire circumference. The shoulder portion 29 is formed when the upper end of the cylindrical portion 39 is bent radially inward and crimped to the outer edge of the sealing body 17, and extends radially inward from the upper end of the cylindrical portion 39. The sealing body 17 is placed on the grooved portion 22 and is fixed to the opening of the outer can 16 by being sandwiched between the grooved portion 22 and the shoulder portion 29 via a resin gasket 28 through the crimping.

[0035] The internal space of the battery 10 is sealed by an annular gasket 28 sealing the space between the outer casing 16 and the sealing body 17. The gasket 28 is sandwiched between the outer casing 16 and the sealing body 17, insulating the sealing body 17 from the outer casing 16. The gasket 28 serves as a sealing material to maintain airtightness inside the battery and as an insulating material to insulate the outer casing 16 and the sealing body 17. The gasket 28 is preferably made of an insulating material with excellent compressibility and resistance, for example, polyolefin, and more specifically, preferably PP (polypropylene), PPS (polyphenylene sulfide), PFA (perfluoroalkoxyalkane), or PPT (polypropylene terephthalate). The terminal cap 27 electrically connected to the positive electrode lead 20 becomes the positive electrode terminal, and the outer casing 16 electrically connected to the negative electrode core body exposed portion 41 via the lower current collector plate 60 becomes the negative electrode terminal.

[0036] The battery 10 has a thin, easily breakable portion 37a at the bottom 37 of the outer casing 16. The easily breakable portion 37a is formed, for example, by marking the lower surface of the bottom 37 with a circular or C-shaped mark. In this embodiment, it is formed by providing a circular annular groove 38 on the lower surface of the bottom 37. The center of the annular groove 38 is approximately located on the central axis of the outer casing 16. The center of this circular annular groove 38 approximately coincides with the center of the approximately circular bottom 37. By providing an easily breakable portion 37a at the bottom 37, the easily breakable portion 37a can break when the internal pressure rises due to abnormal heat generation in the battery 10, allowing the high-pressure gas inside the battery 10 to be released to the outside, thereby increasing the safety of the battery 10.

[0037] The case in which the sealing body 17 is composed of an upper current collector plate 50, a terminal cap 27, and a metal plate 51 has been described. However, the cylindrical battery of this disclosure only needs to have a configuration in which the electrode core (negative electrode core or positive electrode core) constituting the lower end of the electrode body is joined to the bottom of the outer casing via a current collector plate, and furthermore, a thin, easily breakable portion is provided at the bottom, and the sealing body may have any structure. For example, the sealing body may consist of only one rupture plate. Alternatively, the sealing body may have a laminated structure including two rupture plates (lower valve body and upper valve body) joined at their radial centers, an annular insulating plate sandwiched between the two rupture plates, and a convex terminal cap covering the rupture plate. Alternatively, the sealing body may have a structure in which an internal terminal plate, an annular insulating plate, and a rupture plate are laminated in order from the electrode body side.

[0038] As shown in Figure 4, the connecting portion 63 has a webbed structure and connects the upper sides of two adjacent arm portions 62 in the circumferential direction. The thickness of the connecting portion 63 is smaller than the thickness of the central portion 61 and also smaller than the thickness of the arm portions 62. As a result, the rigidity of the connecting portion 63 is smaller than that of the central portion 61 and the arm portions 62, making the connecting portion 63 more prone to bending. Figure 5 is an enlarged bottom view of the area around the connecting portion 63 in Figure 4. In the bottom view (plan view) shown in Figure 5, the connecting portion 63 is recessed radially inward and has a recess 67 on the outer circumference. As shown in Figure 5, in the plan view when viewed from the axial direction, the recess 67 has the shape of a roughly isosceles triangle and is roughly bisected symmetrically by a plane P1 that is roughly symmetrical to the two adjacent arm portions 62.

[0039] The connecting portion 63 has a slit 70, and the edge 71 of the slit 70 includes a concave edge portion 71a. In this embodiment, the slit 70 has a shape that is substantially symmetrical with respect to the plane P1, and in the plan view of Figure 5, it has a substantially V-shape. In this embodiment, the concave edge portion 71a has a substantially V-shape and is recessed radially inward. Figure 6 is a cross-sectional view taken along line A-A in Figure 5, and is a cross-sectional view taken with plane P2, which passes through the part of the connecting portion 63 other than the slit 70 and is perpendicular to plane P1, as the cutting plane. As shown in Figure 6, the connecting portion 63 has a linear groove 73 on its upper surface that extends along a line that intersects with plane P1. In the cross-section shown in Figure 6, the linear groove 73 has a shape that is substantially symmetrical with respect to plane P1, and in this embodiment, it has a V-shape.

[0040] Next, the effects of the battery 10 of this disclosure will be described. Figure 7(a) is a schematic perspective view of the battery 10 in a normal state, viewed from diagonally below, and Figure 7(b) is a schematic perspective view of the battery 10, whose internal pressure has increased due to an internal short circuit or the like, viewed from diagonally below. As shown in Figure 7(b), when the internal pressure increases due to an internal short circuit or the like, the bottom portion 37 protrudes in a tapered shape downward in the axial direction. In this embodiment, since the easily breakable portion 37a has a circular shape, the central portion 37b of the bottom portion 37 protrudes downward in the axial direction in an axisymmetric tapered shape that is close to a cone shape.

[0041] In this case, the outer peripheral portion 37c of the bottom portion 37, which is located radially outward from the annular groove 38, is deformed, and the radially outward end 62d of the arm portion 62 catches on the outer peripheral portion 37c. Therefore, as the bottom portion 37 deforms in this way, the central portion 61 joined to the central portion 37b protrudes axially downward along the central axis of the outer can 16 together with the central portion 37b, causing each arm portion 62 to deform so as to tilt axially upward toward the radially outward side, as shown in Figures 8 and 9. In Figure 8, the three-dimensional position of the easily breakable portion 37a is also shown.

[0042] As the arm portion 62 is deformed, the scraping-like connecting portion 63 that connects the upper sides of two adjacent arm portions 62 in the circumferential direction is also deformed so as to incline upward in the axial direction toward the radially outer side, and bends at the groove 73 forming portion (see FIG. 6) having a low rigidity linear shape within the connecting portion 63. At this time, since the inner portion 77 surrounded by the concave edge portion 71a within the connecting portion 63 is separated by the slit 70 (see FIG. 5), it is difficult to receive the stress on the upper side in the axial direction from the adjacent portion, and stands up on the lower side in the axial direction.

[0043] Due to the standing up of this inner portion 77, a protruding portion 78 having a V-shaped edge appears, and the tip of the appeared protruding portion 78 makes point contact with the inside in the radial direction rather than the annular groove 38 at the bottom portion 37. As a result, as shown in FIG. 7(b), the current generated by the surface short circuit of the electrode body 14 flows to the bottom portion 37 through the sharp tip of the protruding portion 78 having an extremely small cross-section and an excessive resistance, and a large amount of Joule heat is generated on the tip side of the protruding portion 78. Thereby, due to this large amount of Joule heat, the electrode body portion near the point contact portion ignites preferentially, preventing multi-point ignition of the electrode body 14 and effectively suppressing the power at the time of ignition.

[0044] Therefore, it is possible to realize a safe battery 10 that can effectively suppress the rupture of the outer can even when exposed to severe conditions. Furthermore, in the present embodiment, since the tip of the protruding portion 78 makes point contact with the inside in the radial direction rather than the annular groove 38 at the bottom portion 37, the ignition starting point can be controlled to a position away from the side surface of the battery 10. Therefore, even when exposed to severe conditions, side surface cracking due to the flame can be more effectively suppressed, and an extremely safe battery 10 can be realized.

[0045] The present disclosure is not limited to the above-described embodiments and their modifications, and various improvements and changes can be made within the scope of the matters described in the claims of the present application and their equivalent scope. For example, in the above-described embodiment, a circular annular groove 38 is provided in the bottom portion 37, whereby a circular breakable portion 37a is formed in the bottom portion 37. However, a breakable portion may be formed in the bottom portion of the outer can by providing a groove that is not circular in plan view. For example, as described above, a C-shaped groove may be provided in plan view. Alternatively, a groove including an annular first groove that is polygonal (e.g., square or rectangular) or substantially polygonal in plan view and a second groove that extends outward from each of a plurality of vertices of the first groove may be provided in the bottom portion of the outer can.

[0046] The inventor of the present case has confirmed that even in these cases, as the internal pressure increases, the bottom portion of the outer can is deformed such that the central portion thereof protrudes downward in the axial direction. When providing those grooves in the bottom portion of the outer can, in order to more effectively suppress side cracking due to the flame, when the maximum outer diameter of the outer can is R, it is preferable that the tip side of the protruding portion that appears on the current collector plate based on the deformation of the lower current collector plate accompanying the increase in the internal pressure contacts a location where the radial distance from the central axis at the bottom is 2R / 3 or less.

[0047] The tip side of the protruding portion that appears on the lower current collector plate based on the deformation of the lower current collector plate accompanying the increase in the internal pressure may contact a bottom portion location that is radially outside the circular groove provided in the breakable portion, and may contact a location where the radial distance from the central axis at the inner bottom is greater than 2R / 3 when the maximum outer diameter of the outer can is R. Even in these cases, the location of the electrode body that ignites preferentially can be restricted, and multi-point ignition of the electrode body can be suppressed.

[0048] Since the connecting portion 63 can be easily and neatly bent along the center of the width direction of the linear groove 73, it is preferable that the linear groove 73 has a V-shape that is substantially symmetrical with respect to plane P1 in a cross-sectional view with plane P2 as the cutting plane, as shown in Figure 5. However, the linear groove may have a shape other than a V-shape that is substantially symmetrical with respect to plane P1 in a cross-sectional view with plane P2 as the cutting plane, for example, a U-shaped groove that is substantially symmetrical with respect to plane P1, a semicircular groove that is substantially symmetrical with respect to plane P1, or a rectangular groove that is substantially symmetrical with respect to plane P1. Alternatively, the connecting portion may have a linear groove extending in an inclined direction that is inclined with respect to the line of intersection with plane P1, which is substantially symmetrical with respect to adjacent arms in the circumferential direction, or it may not have a linear groove.

[0049] As a result of the deformation of the lower current collector plate 60 due to the increase in internal pressure, the protrusion 78 that appears on the lower current collector plate 60 will have a pointed tip, and a large amount of Joule heat will be generated when the tip and the bottom come into contact. Therefore, it is preferable that the concave edge portion 71a provided in the slit 70 be V-shaped. However, the concave edge portion provided in the slit may be any concave shape other than V-shaped, for example, U-shaped, semicircular, isosceles trapezoidal, or rectangular.

[0050] Providing a recess 67 on the outer circumference of the connecting portion 63 that is recessed radially inward allows the connecting portion to bend smoothly and cleanly when the internal pressure rises. However, as shown in Figure 10, the connecting portion 163 of the lower current collector plate 160 does not need to have a recess on the outer circumference that is recessed radially inward. Furthermore, the case described above has a connecting portion 63 that connects adjacent arm portions 62 in the circumferential direction without going through the center portion 61, and a slit 70 is provided in the arm portions 62. However, the lower current collector plate does not need to have a connecting portion, and a slit for raising a protruding portion may be provided in the arm portion. Also, the positive electrode may constitute the first electrode and the negative electrode may constitute the second electrode. That is, the exposed portion of the positive electrode core that constitutes the lower end of the electrode body may be joined to the upper surface of the lower current collector plate, and the lower surface of the lower current collector plate may be joined to the bottom of the outer can, and the negative electrode may be electrically connected to the sealing body.

[0051] Furthermore, the cylindrical battery of this disclosure may have the following configurations: Configuration 1: A cylindrical battery comprising an electrode body in which a long first electrode having a first electrode core and a first electrode mixture layer and a long second electrode having a second electrode core and a second electrode mixture layer are wound around a long separator; a bottomed cylindrical outer casing that houses the electrode body; and a current collector plate having an axial first end face to which the exposed portion of the first electrode core, which is exposed and is provided at the bottom end of the electrode body in the axial direction of the outer casing, is joined, and an axial second end face joined to the bottom, wherein the bottom has a thin, easily breakable portion, and the tip of a protrusion that appears on the current collector plate due to deformation of the current collector plate as the internal pressure rises contacts the bottom. Configuration 2: The cylindrical battery according to Configuration 1, wherein an annular groove is provided in the easily breakable portion, and when the internal pressure rises, the tip of the protrusion contacts the bottom radially inward from the annular groove. Configuration 3: A cylindrical battery according to Configuration 1 or 2, wherein, when the maximum outer diameter of the outer casing is R, the tip of the protrusion contacts a location at the bottom where the radial distance from the central axis is 2R / 3 or less when the internal pressure rises. Configuration 4: A cylindrical battery according to any one of Configurations 1 to 3, wherein the current collector plate is provided with a slit, the edge of the slit includes a concave edge, and the protrusion appears when the portion of the current collector plate surrounded by the edge rises when the internal pressure rises. Configuration 5: A cylindrical battery according to Configuration 4, wherein the edge has a V-shape. Configuration 6: A cylindrical battery according to Configuration 4 or 5, wherein the current collector plate has a central part, a plurality of arms extending from the central part, and a connecting part that connects two of the arms without including the central part, and the slit is provided in the connecting part. Configuration 7: A cylindrical battery according to Configuration 6, wherein the connecting part is recessed radially inward. Configuration 8: A cylindrical battery according to Configuration 6 or 7, wherein a linear groove is provided in the connecting part.

[0052] 5. Inner surface of winding, 10. Battery, 11. Positive electrode, 12. Negative electrode, 13. Separator, 14. Electrode body, 16. Outer can, 17. Sealing body, 18. Insulating plate, 20. Positive electrode lead, 22. Grooved section, 27. Terminal cap, 28. Gasket, 29. Shoulder section, 30. Positive electrode core, 32. Positive electrode mixture layer, 32a. Core adjacent section, 35. Positive electrode core exposed section, 37. Bottom section, 37a. Easily breakable section, 37b. Center section, 37c. Outer circumference section, 38. Annular groove, 39. Cylindrical section, 40. Negative electrode core, 41. Negative electrode core exposed section, 42. Negative electrode mixture layer, 50. Upper current collector plate, 50a. Through hole, 51. Metal plate, 53. Recessed portion, 55 Laminated portion, 60, 160 Lower current collector plate, 61 Center portion, 61a Lower surface of the center portion, 62 Arm portion, 62a Lower surface of the arm portion, 62b Groove portion, 62c Protruding portion, 62d End of the arm portion on the radially outward side, 63, 163 Connecting portion, 64 Step portion, 67 Recess of the arm portion, 70 Slit, 71 Edge of the slit, 71a Recessed edge of the slit, 73 Straight groove, 77 Inner portion of the recessed edge, 78 Protruding portion, P1, P2 Plane.

Claims

1. A cylindrical battery comprising: an electrode body in which a long first electrode having a first electrode core and a first electrode mixture layer and a long second electrode having a second electrode core and a second electrode mixture layer are wound around a long separator; a bottomed cylindrical outer can housing the electrode body; and a current collector plate having an axial first end face to which the exposed portion of the first electrode core, which is attached to the bottom end of the electrode body on the bottom side of the outer can in the axial direction, is joined, and an axial second end face joined to the bottom, wherein the bottom has a thin, easily breakable portion, and the tip of a protrusion that appears on the current collector plate due to deformation of the current collector plate due to an increase in internal pressure contacts the bottom.

2. The cylindrical battery according to claim 1, wherein an annular groove is provided in the easily breakable portion, and when the internal pressure rises, the tip of the protruding portion contacts the radially inward portion of the annular groove at the bottom.

3. The cylindrical battery according to claim 1, wherein, when the maximum outer diameter of the outer casing is R, the tip of the protruding portion contacts a location at the bottom where the radial distance from the central axis is 2R / 3 or less when the internal pressure rises.

4. The cylindrical battery according to any one of claims 1 to 3, wherein the current collector plate is provided with a slit, the edge of the slit includes a concave edge, and the protruding portion appears when the internal pressure rises and the portion of the current collector plate surrounded by the edge rises up.

5. The cylindrical battery according to claim 4, wherein the edge portion has a V-shape.

6. The cylindrical battery according to claim 4, wherein the current collector plate has a central part, a plurality of arms extending from the central part, and a connecting part that connects two of the arms without including the central part, and the slit is provided in the connecting part.

7. The cylindrical battery according to claim 6, wherein the connecting portion is recessed radially inward.

8. The cylindrical battery according to claim 6, wherein a straight groove is provided in the connecting portion.

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