Battery and current collector plate

Abstract

According to the present invention, a cylindrical battery (10) comprises: an electrode assembly (14) in which a long negative electrode (12), having a core body exposed section (12c) in which a negative electrode core body is exposed on one side in the width direction thereof, and a long positive electrode (11) are wound with a separator (13) therebetween; and a lower current collector (19) which has a flat part (51) that axially overlaps a central portion of a hollow section (14a) of the electrode assembly (14) and does not have a through-hole, a protruding bead part (56) to which the core body exposed section (12c) is joined, and one or more through-holes (52a) positioned on a further outer circumferential side in the radial direction than the flat part (51) and further inside in the radial direction than the protruding bead part (56).

Description

[Technical Field]

[0001] This disclosure relates to batteries and current collector plates. [Background technology]

[0002] Conventionally, cylindrical batteries include those described in Patent Document 1. This cylindrical battery comprises an electrode body in which a positive electrode and a negative electrode are wound with a separator in between, a bottomed cylindrical outer casing that houses the electrode body, and current collector plates arranged on both sides of the electrode body in the axial direction. The current collector plates have a disc shape and a through hole in the radial center. The current collector plates also have a plurality of through holes located at circumferential intervals on the outer circumference. The through hole in the center and the plurality of through holes on the outer circumference are provided for injecting electrolyte into the electrode body. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2007-335156 [Overview of the Initiative]

[0004] The central part of the current collector plate is often joined to a conductive part such as the bottom plate of the outer casing, but if the current collector plate has a through hole in the center, it becomes difficult to ensure a secure connection. On the other hand, when the battery overheats and the battery's safety valve is activated, it is desirable that the high-temperature gas be smoothly guided to the safety valve, and from this viewpoint, it is desirable that the current collector plate has a gas passage. Therefore, the object of this disclosure is to provide a battery in which the current collector plate can be easily and securely joined to a conductive part such as the bottom plate of the outer casing, and in which gas can easily flow to the safety valve when the safety valve is activated. Another object of this disclosure is to provide a current collector plate that can realize such a battery.

[0005] To solve the above problems, the battery according to the present disclosure comprises an electrode body in which a long first electrode and a long second electrode are wound around a separator, with the first electrode core exposed on one side in the width direction and the first electrode core exposed on one side, and a current collector plate having a flat plate portion that overlaps the hollow portion of the electrode body in the axial direction and does not have through holes, a joint portion to which the core exposed portion is joined, and one or more through holes located radially outward from the flat plate portion and radially inward from the joint portion.

[0006] Furthermore, the current collector plate according to this disclosure is a current collector plate to which an electrode core located on one side in the axial direction of a wound electrode body is joined, and comprises a flat plate portion located in the center and having no through holes, a joining portion extending in the radial direction to which the electrode core is joined, and one or more through holes located radially outward from the flat plate portion and radially inward from the joining portion.

[0007] The axial direction mentioned above is the axial direction of the electrode body, and if the battery is a cylindrical battery, it coincides with the axial direction of the battery. The radial direction mentioned above is the radial direction of the electrode body, and if the battery is a cylindrical battery, it coincides with the radial direction of the battery.

[0008] The battery according to this disclosure allows for reliable bonding of the current collector plate to conductive parts such as the bottom plate of the outer casing, and facilitates smooth gas flow to the safety valve when the safety valve is activated. Furthermore, the current collector plate according to this disclosure facilitates good bonding to conductive parts such as the bottom plate of the outer casing, and enables the realization of a battery in which gas flows smoothly to the safety valve when the safety valve is activated. [Brief explanation of the drawing]

[0009] [Figure 1] This is an axial cross-sectional view of a cylindrical battery according to one embodiment of the present disclosure. [Figure 2] This is a perspective view of the electrode body. [Figure 3] This is a schematic plan view of the negative electrode unfolded into a long, rectangular shape. [Figure 4] This is a schematic plan view of a positive electrode unfolded into a long, rectangular shape. [Figure 5] This is a perspective view of the lower current collector plate. [Figure 6] It is a plan view of the lower current collector plate when viewed from the side opposite to the negative electrode core body joining side in the thickness direction. [Figure 7] It is an axial cross-sectional view of the lower current collector plate. [Figure 8] It is a perspective view of the lower current collector plate of the comparative example. [Figure 9] It is a plan view of the lower current collector plate of the comparative example when viewed from the side opposite to the negative electrode core body joining side in the thickness direction. [Figure 10] It is an axial cross-sectional view of the lower current collector plate of the comparative example. [Figure 11] It is a schematic plan view of the lower current collector plate of the comparative example. [Figure 12] It is a schematic cross-sectional view of the axially lower side of the cylindrical battery of the comparative example provided with the lower current collector plate of the comparative example. [Figure 13] It is a diagram for explaining a joining method of the lower current collector plate of the comparative example to the bottom plate portion of the outer can. [Figure 14] It is a schematic plan view of the lower current collector plate of the above embodiment. [Figure 15] It is a schematic cross-sectional view of the axially lower side of the cylindrical battery of the above embodiment. [Figure 16] It is a diagram for explaining a joining method of the lower current collector plate of the above embodiment to the bottom plate portion of the outer can. [Figure 17] It is a perspective view of the lower current collector plate of the modified example. [Figure 18] It is a plan view of the lower current collector plate of the modified example when viewed from the side opposite to the negative electrode core body joining side in the thickness direction. [Figure 19] It is an axial cross-sectional view of the lower current collector plate of the modified example. [Figure 20] It is a schematic cross-sectional view of the axially lower end portion of the cylindrical battery of the above embodiment. [Figure 21] It is a plan view of the cylindrical battery of the above embodiment in a state where the easily breakable portion is broken and the safety valve has flown off, when viewed from the axially lower side. [Figure 22] It is a schematic cross-sectional view of the axially lower end portion of the cylindrical battery of the modified example. [Figure 23]This is a plan view of the cylindrical battery of the above modified example, as seen from the axial lower side, in a state where the easily breakable part has broken and the safety valve has flown off. [Figure 24] This is a schematic cross-sectional view of the axial lower end of the cylindrical battery of the comparative example described above. [Figure 25] This is a plan view of the cylindrical battery of the above comparative example, as seen from the axial lower side, in a state where the easily breakable part has broken and the safety valve has flown off. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the battery according to this disclosure will be described in detail with reference to the drawings. In the following, a cylindrical battery 10, which is a non-aqueous electrolyte secondary battery (lithium-ion battery), will be given as an example of one embodiment of the battery, but the battery of this disclosure is not limited to this. The battery of this disclosure may be a primary battery or a secondary battery. It may also be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. Furthermore, the battery of this disclosure may be a prismatic battery. The battery of this disclosure only needs to have a wound electrode body.

[0011] Where multiple embodiments and modifications are included below, it is intended 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. In addition, 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 side of the battery case 15 with the sealing body 17 in the axial direction (height direction) is referred to as "upper," and the side of the outer casing 16 with the bottom plate portion 68 in the axial direction is referred to as "lower." In the following description, the radial direction refers to the radial direction of the electrode body 14, which coincides with the radial direction of the cylindrical battery 10. In addition, the circumferential direction refers to the circumferential direction of the electrode body 14, which coincides with the circumferential direction of the cylindrical battery 10. Furthermore, 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.

[0012] Figure 1 is an axial cross-sectional view of a cylindrical battery 10 according to one embodiment of the present disclosure. In this embodiment, the case in which the first electrode is a negative electrode 12 and the second electrode is a positive electrode 11 will be described. As shown in Figure 1, the cylindrical battery 10 comprises a wound electrode body 14, a non-aqueous electrolyte (not shown), an outer casing 16 that houses the electrode body 14 and the non-aqueous electrolyte, and a sealing body 17. The electrode body 14 includes a positive electrode 11, a negative electrode 12, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound around each other via the separator 13. The battery case 15 consists of a bottomed cylindrical outer casing 16 and a sealing body 17 that closes the opening of the outer casing 16.

[0013] A non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous solvent may include, for example, esters, ethers, nitriles, amides, and mixtures of two or more of these. The non-aqueous solvent may also contain halogen-substituted solvents in which at least some of the hydrogen atoms of the solvent are replaced with halogen atoms such as fluorine. The non-aqueous electrolyte is not limited to a liquid electrolyte, but may also be a solid electrolyte using a gel-like polymer. Lithium salts such as LiPF6 are used as the electrolyte salt.

[0014] Figure 2 is a perspective view of the electrode body 14. 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. Multiple positive electrode leads 20 are joined to the positive electrode 11 at intervals along its longitudinal direction. In the example shown in Figures 1 and 2, three positive electrode leads 20 are joined to the positive electrode 11 and electrically connected. Figure 3 is a schematic plan view of the negative electrode 12 unfolded in a long shape. As shown in Figure 3, the negative electrode 12 has a negative electrode core exposed portion 12c at the lower end in the width direction indicated by arrow β, where the negative electrode compound layer 12b is not provided in the negative electrode core 12a. The negative electrode core exposed portion 12c has a strip shape and is continuously provided from one end to the other in the longitudinal direction of the negative electrode 12 indicated by arrow α. The negative electrode core 12a is an example of a first electrode core. As shown in Figure 2, the lower axial end of the electrode body 14 is composed of a negative electrode core exposed portion 12c. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to suppress lithium deposition, and is longer than the positive electrode 11 in both the longitudinal and widthwise (short-side) directions. The two separators 13 are also formed to be at least slightly larger than the positive electrode 11 and are arranged to sandwich the positive electrode 11.

[0015] Figure 4 is a schematic plan view of the positive electrode 11 unfolded into a long shape. As shown in Figure 4, the positive electrode 11 has a positive electrode core 11a and a positive electrode mixture layer 11b formed on both sides of the positive electrode core 11a. The positive electrode core 11a 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 11b 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 11a, drying the coating, and then compressing it to form the positive electrode mixture layer 11b on both sides of the positive electrode core 11a.

[0016] 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.

[0017] Examples of conductive agents included in the positive electrode mixture layer 11b include carbon materials such as carbon black, acetylene black, Ketjen black, and graphite. Examples of binders included in the positive electrode mixture layer 11b include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resin, acrylic resin, and polyolefin resin. These resins may also be used in combination with cellulose derivatives such as carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0018] As shown in Figure 4, the positive electrode 11 has, for example, three positive electrode core exposed portions 11c arranged at approximately equal intervals in the longitudinal direction indicated by arrow γ. The positive electrode core exposed portions 11c are provided, for example, over the entire width direction indicated by arrow δ on the positive electrode core 11a. The positive electrode core exposed portions 11c are predetermined longitudinal regions where the positive electrode mixture layer 11b is not applied. The three positive electrode leads 20 are joined to the three positive electrode core exposed portions 11c. By joining the three positive electrode leads 20 at approximately equal intervals in the longitudinal direction of the elongated positive electrode core 11a, the current path in the longitudinal direction of the positive electrode 11 can be shortened, thereby reducing the internal resistance of the cylindrical battery 10. The positive electrode leads 20 are covered with insulating tape 24, and as a result, short circuits between the positive electrode 11 and the negative electrode 12 are suppressed. It is preferable that the insulating tape 24 covers all of the positive electrode core exposed portions 11c.

[0019] As shown in Figure 3, the negative electrode 12 has a negative electrode core 12a and a negative electrode mixture layer 12b formed on both sides of the negative electrode core 12a. The negative electrode core 12a can be made of 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. The negative electrode mixture layer 12b 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 12a, drying the coating, and then compressing it to form the negative electrode mixture layer on both sides of the core.

[0020] Generally, carbon materials that reversibly intercalate 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. The negative electrode mixture layer 12b may contain a silicon (Si) material as the negative electrode active material. In addition, metals that alloy with lithium other than Si, alloys containing such metals, compounds containing such metals, etc., may be used as the negative electrode active material.

[0021] The binder contained in the negative electrode mixture layer 12b 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 may also contain CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, etc.

[0022] The separator 13 is made of a porous sheet having ion permeability and insulating properties. 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 may be formed on the surface of the separator 13. The negative electrode 12 may constitute the winding start end of the electrode body 14, but generally the separator 13 extends beyond the winding start end of the negative electrode 12, and the winding start end of the separator 13 becomes the winding start end of the electrode body 14.

[0023] As shown in Figure 1, the cylindrical battery 10 includes an insulating plate 18 positioned above 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 40 and a sealing plate 27. The upper current collector plate 40 is an annular metal plate member with a through hole 40a in the radial center. The sealing plate 27 is a metal plate member without a through hole and closes the opening of the outer casing 16.

[0024] Each positive electrode lead 20 is bent from the positive electrode 11 through the through hole 40a of the upper current collector plate 40 so as to follow the upper surface 45 of the upper current collector plate 40. The tip of each positive electrode lead 20 is joined to the upper surface 45 of the upper current collector plate 40. This joining can be achieved, for example, by laser welding. Outer periphery of the upper current collector plate 40 47 It is in contact with the sealing plate 27. Upper current collector plate 40 The outer periphery 47 is preferably joined to the sealing plate 27 by laser welding or the like. The annular upper surface 45 of the upper current collector plate 40 is the outer periphery 47 It has an annular recess 45a on its radially inward side. The bottom surface 45b of the recess 45a extends in a direction substantially perpendicular to the axial direction. Because the upper surface 45 of the upper current collector plate 40 has a recess 45a that is recessed downward, a space is provided between the sealing plate 27 and the recess 45a of the upper current collector plate 40. Each positive electrode lead 20 is housed in the recess 45a.

[0025] The cylindrical battery 10 has a lower current collector plate 19 made of metal, such as nickel or a nickel alloy, located axially outward (downward) from the electrode body 14. The exposed negative electrode core portion 12c of the electrode body 14 is joined to the lower current collector plate 19. The lower current collector plate 19 is also joined to the inner surface 68a of the bottom plate portion 68 of the outer casing 16. Next, the structure of the lower current collector plate 19, the joining of the exposed negative electrode core portion 12c to the lower current collector plate 19, and the joining of the lower current collector plate 19 to the bottom plate portion 68 of the outer casing 16 will be described in detail.

[0026] Figure 5 is a perspective view of the lower current collector plate 19, and Figure 6 is a plan view of the lower current collector plate 19 as seen from the opposite side of the negative electrode core body connection side in the thickness direction. Figure 7 is an axial cross-sectional view of the lower current collector plate 19. As shown in Figures 5 and 6, the lower current collector plate 19 has a flat plate portion 51 in the radial center that is approximately circular in plan view. The flat plate portion 51 does not have through holes, and gas cannot pass through the flat plate portion 51. In the examples shown in Figures 5 to 7, the flat plate portion 51 has a disc shape. However, the flat plate portion can have any shape as long as it is a flat plate shape without through holes. The shape of the flat plate portion in plan view can be any shape other than circular, for example, a rectangular shape. The lower current collector plate 19 also has a plurality of radially extending portions 53 connected to the flat plate portion 51 via connecting portions 52, and in this embodiment, there are four radially extending portions 53. The radially extending portion 53 has a columnar shape and extends in the radial direction. Preferably, the multiple radially extending portions 53 are arranged at equal intervals in the circumferential direction. The connecting portion 52 is provided with multiple through holes 52a spaced apart in the circumferential direction, and in this embodiment, four through holes 52a are provided. Preferably, the multiple through holes 52a are arranged at equal intervals in the circumferential direction. However, the connecting portion may also have a configuration with only one through hole.

[0027] As shown in Figure 7, the connecting portion 52 is connected to the radially extending portion 53 via the stepped portion 54, and the bottom surface of the flat plate portion 51 is located axially lower than the bottom surface of the radially extending portion 53. This arrangement allows the bottom surface of the flat plate portion 51 to be tightly pressed against the inner surface 68a of the bottom plate portion 68 without any gaps when joining the flat plate portion 51, as described later, making it easier to achieve a good joint of the flat plate portion 51. As shown in Figure 5, the radially extending portion 53 has a protruding portion 56 on the negative electrode core joining side. The protruding portion 56 is provided in the center of the width direction of the radially extending portion 53 and protrudes in the thickness direction. The protruding portion 56 extends radially. On the surface of the radially extending portion 53 opposite to the negative electrode core joining side, a groove 57 extending radially is provided where it overlaps with the protruding portion 56 in the thickness direction. The central part in the width direction of the radially extending portion 53 on the side opposite to the negative electrode core body joining side is press-formed by a predetermined distance in the radial direction and toward the negative electrode core body joining side in the thickness direction. This press-forming creates the protrusions 56 and grooves 57.

[0028] The protruding portion 56 constitutes a joint to which the exposed negative electrode core portion 12c is joined. Specifically, with the exposed negative electrode core portion 12c, which constitutes the axial lower side of the electrode body 14, pressed against the protruding portion 56, laser light is shone from the side of the radially extending portion 53 opposite to the negative electrode core joining side toward the bottom of the groove 57. This laser light irradiation joins the exposed negative electrode core portion 12c of the electrode body 14 to the protruding portion 56 by laser welding.

[0029] As shown in Figure 5, all through holes 52a are located radially outward from the flat plate portion 51 and radially inward from the ridge portion (joint portion) 56. The lower current collector plate 19 further has one or more protrusions 58. The protrusions 58 are located radially outward from the flat plate portion 51 and radially inward from the ridge portion 56. The protrusions 58 extend to a position higher than the tip surface 56a of the ridge portion 56. The number of protrusions 58 corresponds to the number of radially extending portions 53. The protrusions 58 include portions located on the radially inward extension of the corresponding radially extending portion 53 in the ridge portion 56, and include opposing portions 58a radially facing the upper region of the tip surface 56a of the ridge portion 56.

[0030] When the exposed negative electrode core portion 12c is pressed against the protruding portion 56 for joining, the exposed negative electrode core portion 12c may tilt inward toward the flat plate portion 51. The protruding portion 58 is provided to prevent the radially inward tip of the tilted portion from reaching a position where it overlaps with the flat plate portion 51 in the thickness direction, even if the exposed negative electrode core portion 12c tilts inward toward the flat plate portion 51. The reason why it is undesirable for the radially inward tip of the tilted portion to reach a position where it overlaps with the flat plate portion 51 in the thickness direction will be explained later.

[0031] The number of protrusions 58 corresponds to the number of through holes 52a. Each protrusion 58 includes a bent portion 69 that bends from the edge of the opening on the electrode body 14 side of the through hole 52a. In this embodiment, the protrusions 58 are formed on the lower current collector plate 19 as follows. Specifically, an incision is made in the through hole forming portion of the lower current collector plate 19. Then, the portion of the lower current collector plate 19 with the incision is bent toward the electrode body joining side in the thickness direction and folded back toward the electrode body 14. This bending process (folding back process) forms the protrusions 58 and the through holes 52a. The protrusions may also be formed by joining a metal piece to the lower current collector plate having the through holes. In this embodiment, multiple protrusions 58 are arranged at approximately the same radial position on the lower current collector plate 19 with circumferential spacing, but the lower current collector plate may also have a configuration with a single annular protrusion.

[0032] As shown in Figure 1, the disc-shaped flat portion 51 and all the through holes 52a are located in a position that axially overlaps with the hollow portion 14a of the electrode body 14. In addition, a circular thin-walled portion 71 is provided on the bottom surface 68b of the bottom plate portion 68 of the outer casing 16, centered on the radial center of the bottom plate portion 68. The thin-walled portion 71 constitutes an easily breakable portion. The portion of the bottom plate portion 68 surrounded by the circular thin-walled portion 71 constitutes a safety valve 72. All the through holes 52a of the lower current collector plate 19 axially overlap with the safety valve 72. When the cylindrical battery 10 overheats abnormally, the thin-walled portion 71 is designed to break. In this way, an opening is formed at the location of the safety valve 72, allowing the high-temperature gas inside the battery to be discharged to the outside. In this embodiment, the case in which the easily breakable portion is made of a circular thin-walled portion 71 has been described, but the easily breakable portion may also be made by, for example, providing a C-shaped thin-walled portion on the bottom side of the bottom plate portion, and as long as an opening can be formed at the location of the safety valve 72, it is not limited to a circular or C-shaped form.

[0033] The outer casing 16 has an annular groove 35 on a portion of its cylindrical outer surface in the axial direction. The groove 35 can be formed, for example, by spinning a portion of the cylindrical outer surface radially inward to create a recess on the radially inward side. The sealing body 17 is placed on the groove 35 and is crimped and fixed to the opening of the outer casing 16 via a gasket 28. The annular gasket 28 seals the space between the outer casing 16 and the sealing body 17, thereby sealing the internal space of the battery case 15. 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.

[0034] In the cylindrical battery 10, the sealing plate 27 electrically connected to the positive electrode lead 20 serves as the positive electrode terminal, and the outer casing 16 electrically connected to the negative electrode core exposed portion 12c via the lower current collector plate 19 serves as the negative electrode terminal. In this embodiment, the case in which multiple positive electrode leads 20 are electrically connected to the sealing plate 27 has been described, but a configuration in which only one positive electrode lead is electrically connected to the sealing plate is also possible. Alternatively, an upper current collector plate having a similar configuration to the lower current collector plate may be placed on the axial upper side of the electrode body. Furthermore, a strip-shaped positive electrode core exposed portion, extending from one end in the width direction of the positive electrode to the other, may be joined to the upper current collector plate. Finally, the upper current collector plate may be electrically connected to the sealing body.

[0035] Next, the effects of the cylindrical battery 10 of this disclosure will be explained by comparing it with a cylindrical battery using a lower current collector plate in a comparative example. Figure 8 is a perspective view of the lower current collector plate 219 of the comparative example, and Figure 9 is a plan view of the lower current collector plate 219 as seen from the opposite side of the negative electrode core body joining side in the thickness direction. Figure 10 is an axial cross-sectional view of the lower current collector plate 219. As shown in Figures 8 to 10, the lower current collector plate 219 differs from the lower current collector plate 19 shown in Figures 5 to 7 in that it does not have a through hole 52a and does not have a protruding portion 58, while the other configurations of the lower current collector plate 219 are the same as those of the lower current collector plate 19 shown in Figures 5 to 7.

[0036] Figure 11 is a schematic plan view of the lower current collector plate 219 of the comparative example, and Figure 12 is a schematic cross-sectional view of the axial lower side of the cylindrical battery 210 of the comparative example equipped with the lower current collector plate 219. Figure 13 is a diagram illustrating the method of joining the lower current collector plate 219 to the bottom plate portion 68. Figure 14 is a schematic plan view of the lower current collector plate 19, and Figure 15 is a schematic cross-sectional view of the axial lower side of the cylindrical battery 10. Figure 16 is a diagram illustrating the method of joining the lower current collector plate 19 to the bottom plate portion 68.

[0037] As shown in Figure 12, in the comparative example cylindrical battery 210, the lower current collector plate 219 does not have a through hole 52a, so electrolyte and gas cannot pass through the lower current collector plate 219. Therefore, there is no electrolyte penetration path through the lower current collector plate 219 indicated by arrow A, making it difficult to smoothly permeate the electrolyte into the cylindrical battery 210. Also, since there is no gas passage through the lower current collector plate 219 indicated by arrow B, even if the cylindrical battery 210 overheats and the safety valve at the bottom of the can opens, it is difficult to smoothly flow the high-temperature gas to the safety valve.

[0038] Furthermore, the lower current collector plate 219 does not have a protruding portion 58. Therefore, as shown in Figure 13, when the negative electrode core exposed portion 12c of the electrode body 14 is pressed against the protruding portion of the lower current collector plate 219, the negative electrode core exposed portion 12c tilts inward, and the radially inward tip portion 12d of the tilted negative electrode core exposed portion 12c tends to overlap the radially centered flat plate portion 51 in the thickness direction. As a result, the tip portion 12d of the negative electrode core exposed portion 12c gets caught between the welding rod 90 and the flat plate portion 51, making it difficult to reliably press the flat plate portion 51 with the welding rod 90, and making it difficult to perform good welding of the lower current collector plate 219 to the bottom plate portion 68.

[0039] In contrast, according to the cylindrical battery 10 of this embodiment, as shown in Figure 14, there is one or more through holes 52a on the radially outer side of the flat plate portion 51 located in the center of the lower current collector plate 19. Therefore, as shown in Figure 15, the lower current collector indicated by arrow A Board 1 The electrolyte easily penetrates smoothly into the cylindrical battery 10 through the electrolyte penetration pathway that passes through 9. Also, if the cylindrical battery 10 overheats abnormally, the safety valve at the bottom of the can will be activated. 72 When it opens, the high-temperature gas is released through the gas path that passes through the lower current collector plate 19 indicated by arrow B, into the safety valve 72 This allows the gas to reach the safety valve smoothly. Therefore, the high-temperature gas can be smoothly discharged to the outside, achieving a high level of safety. Also, as shown in Figure 1, if all the through holes 52a are located in a position that axially overlaps with the safety valve 72, the high-temperature gas can be discharged to the safety valve 72 It can be discharged to the outside even more efficiently through this method.

[0040] Furthermore, in the cylindrical battery 10 of this embodiment, a disc-shaped flat plate portion 51 without a through hole is located in a position that axially overlaps with the hollow portion 14a of the electrode body 14, and the lower current collector plate 19 has a protruding portion 58 that protrudes radially outward from the flat plate portion 51 and axially upward from the protruding portion 56. Therefore, as shown in Figure 16, even if the exposed negative electrode core portion 12c of the electrode body 14 tilts inward when pressed against the protruding portion 56 of the lower current collector plate 19, the protruding portion 58 can prevent the tilted portion from reaching a position that axially overlaps with the flat plate portion 51. Therefore, the synergistic effect of the configuration in which the flat plate portion 51 does not have a through hole and the configuration in which the inward tilt of the negative electrode core body exposed portion 12c does not reach a position where it overlaps the flat plate portion 51 in the axial direction, allows the tip surface of the welding rod 90 to be in close contact with the flat plate portion 51, and the tip surface of the welding rod 90 to reliably press the flat plate portion 51 against the bottom plate portion 68. Therefore, since the flat plate portion 51 can be laser-welded to the bottom plate portion 68 by irradiating laser light from the bottom side of the can while the flat plate portion 51 is in close contact with the inner surface 68a of the bottom plate portion 68, a good joining of the lower current collector plate 19 to the bottom plate portion 68 can be achieved. The protruding portion 58 is a safety valve 72 During operation, the inward tilting of the exposed negative electrode core portion 12c prevents the hollow portion 14a and the through hole 52a from being blocked, and the safety valve is activated by passing through the through hole 52a from the hollow portion 14a. 72 It plays a role in ensuring a reliable gas exhaust path to reach the safety valve. The protruding portion 58 also plays a role in radially positioning the lower current collector plate 19 relative to the hollow portion 14a. This prevents the position of the through hole 52a from shifting relative to the hollow portion 14a, and prevents gas from passing through the through hole 52a from the hollow portion 14a to the safety valve. 72 It also has the effect of ensuring a reliable gas exhaust path that reaches the target area.

[0041] In the above embodiment, the case in which the lower current collector plate 19 has one or more protrusions 58 was described. However, as will be explained below, the lower current collector plate does not have to have protrusions 58. Figure 17 is a perspective view of a modified lower current collector plate 119, and Figure 18 is a plan view of the lower current collector plate 119 as seen from the opposite side of the negative electrode core joint in the thickness direction. Also, Figure 19 is the lower current collector plate 1This is a cross-sectional view of the 19 in the axial direction. As shown in Figures 17 to 19, the lower current collector plate 119 has a flat plate portion 51 located in the radial center and one or more through holes 152a located radially outward from the flat plate portion 51. The lower current collector plate 119 does not have a protrusion 58. The shape of the through holes 152a of the lower current collector plate 119 is slightly different from the shape of the through holes 52a of the lower current collector plate 19. The other configurations of the lower current collector plate 119 are the same as those of the lower current collector plate 19.

[0042] [Gas emission test] Gas emission tests were conducted on the cylindrical battery of Example 1, the cylindrical battery of Example 2, and the cylindrical battery of the comparative example to evaluate their gas emission performance.

[0043] <Cylindrical battery of Example 1> A cylindrical battery 10 (see Figure 1) equipped with a lower current collector plate 19 (see Figures 5-7) was used as the cylindrical battery of Example 1. The inner diameter of the cylindrical portion 16a (see Figure 1) of the outer casing 16 of the cylindrical battery 10 was set to 44.86 [mm], and the diameter (stamped diameter) of the circular thin-walled portion 71 was set to 32 [mm]. The outer diameter of the electrode body 14 was set to 43.4 [mm], and the diameter (hollow portion diameter) of the hollow portion 14a of the electrode body 14 was set to 5 [mm]. The outer diameter of the lower current collector plate 19 was set to 43 [mm], and the width of the radially extending portion 53 of the lower current collector plate 19 was set to 7 [mm]. The diameter of the central protruding portion that abuts the bottom plate portion 68 on the lower current collector plate 19 was set to 6 [mm], and the diameter of the welded portion welded to the bottom plate portion 68 on the lower current collector plate 19 was set to 4 [mm]. Furthermore, the width of the groove 57 in the radially extending portion 53 was set to 1.5 mm. These dimensions are the same for the cylindrical battery 110 of Example 2 and the cylindrical battery 210 of the Comparative Example, which are described below.

[0044] Figure 20 is a schematic cross-sectional view of the axial lower end of the cylindrical battery 10, and Figure 21 is a plan view of the cylindrical battery 10 as seen from the axial lower side, in a state where the easily breakable section has broken and the safety valve 72 has flown off. In Figure 21, the shaded area is the area of ​​the opening 93 created when the safety valve 72 is blown off that is blocked by the lower current collector plate 19. Regarding the cylindrical battery 10 in the state shown in Figure 21, where the easily breakable section has broken and the safety valve 72 has flown off, the area that can contribute to gas exhaust was measured. The gas can pass through the electrode body 14. The area of ​​the electrode body 14 that is exposed to the opening 93 of the bottom plate portion 68 of the cylindrical battery 10 without being obstructed by the lower current collector plate 19 is 408.8 [mm²] 2 ]. In addition, in the cylindrical battery 10 of Example 1, four through holes 52a are exposed in the opening 93, and this area is 1.5 [mm²] 2 ] × 4 = 6 [mm 2 ] was.

[0045] <Cylindrical battery of Example 2> The cylindrical battery of Example 2 differs from the cylindrical battery 10 of Example 1 only in that the lower current collector plate 19 is replaced with a modified lower current collector plate 119 (see Figures 17 to 19). Figure 22 is a schematic cross-sectional view of the axial lower end of the cylindrical battery 110, and Figure 23 is a plan view of the cylindrical battery 110 as seen from the axial lower side when the easily breakable part has broken and the safety valve 72 has flown off. In Figure 23, the area shown in shaded areas is the area of ​​the opening 93 created when the safety valve 72 is blown off that is blocked by the lower current collector plate 119. With respect to the cylindrical battery 110 shown in Figure 23 when the easily breakable part has broken and the safety valve 72 has flown off, the area that can contribute to gas exhaust was measured. The area of ​​the electrode body 14 that is exposed to the opening 93 of the bottom plate portion 68 of the cylindrical battery 110 without being obstructed by the lower current collector plate 119 is 408.8 [mm²] 2 ]. In addition, in the cylindrical battery 110 of Example 2, four through holes 152a are exposed in the opening 93, and the area of ​​this is 0.75 [mm²]. 2 ] × 4 = 3 [mm 2 ] was.

[0046] <Cylindrical battery in the comparative example> The cylindrical battery of Example 2 differs from the cylindrical battery 10 of Example 1 only in that the lower current collector plate 19 is replaced with the lower current collector plate 219 of the comparative example (see Figures 8 to 10). Figure 24 is a schematic cross-sectional view of the axial lower end of the cylindrical battery 210, and Figure 25 is a plan view of the cylindrical battery 210 as seen from the axial lower side when the easily breakable part has broken and the safety valve 72 has flown off. In Figure 25, the area shown by the shaded area is the area of ​​the opening 93 created when the safety valve 72 is blown off that is blocked by the lower current collector plate 219. With respect to the cylindrical battery 210 shown in Figure 25, when the easily breakable part has broken and the safety valve 72 has flown off, the area that can contribute to gas exhaust was measured. The area is only the area of ​​the electrode body 14 that is not obstructed by the lower current collector plate 219 and is exposed to the opening 93 of the bottom plate portion 68 of the cylindrical battery 210, which is 408.8 [mm²] 2 ] was.

[0047] (Exam content) When each of the cylindrical batteries 10, 110, and 210 was subjected to a heating test while fully charged, the safety valve opened at 140°C in all cases, and gas exhaust began from inside the cylindrical batteries 10, 110, and 210. The gas flow velocity during gas exhaust was measured for each of the cylindrical batteries 10, 110, and 210.

[0048] (Test results) [Table 1]

[0049] In all three cylindrical batteries 10, 110, and 210, a gas flow velocity of 20 [m / s] was generated in the path from the electrode body (the part containing the electrode plates and separators) to the safety valve. On the other hand, in Examples 1 and 2, in addition to the gas flow velocity of 20 [m / s] in the path from the electrode body to the safety valve, a gas flow velocity of 160 [m / s] was generated in the path from the hollow section 14a and through holes (exhaust holes) 52a and 152a to the safety valve. Therefore, the exhaust capacity was calculated as "flow velocity [m / s] × exhaust area [mm²]". 2 A comparison using "[ ]" yielded the results shown in Table 1. For example, the values ​​in the Total column in Example 1 were calculated using the following formula (1). 9.14×10 6 [mm 3 / s]=408.8[mm 2 ×20[m / s]+6[mm 2 ×160[m / s]···(1) Through tests, it was confirmed that, compared with the comparative example, the exhaust capacity was improved by 10.5% in Example 1, and the exhaust capacity was improved by 5.5% in Example 2.

[0050] (Modification) The present disclosure is not limited to the above embodiments and modifications thereof, 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 ranges. For example, in the above embodiment, the through hole 52a is provided at a position overlapping the hollow portion 14a of the electrode body 14 in the axial direction, but the through hole of the current collector plate may be provided at a position not overlapping the hollow portion 14a of the electrode body 14 in the axial direction. In addition, although the through hole 52a is provided at a position overlapping the safety valve 72 in the axial direction, the through hole of the current collector plate may be provided at a position not overlapping the safety valve in the axial direction.

[0051] Further, although the current collector plate (lower current collector plate 19) of the present disclosure is disposed on the axially lower side of the electrode body 14 and the safety valve is provided on the can bottom, the current collector plate of the present disclosure may be disposed on the axially lower side of the electrode body 14, and the safety valve may be provided on the sealing body on the axially upper side. Even in this case, if the current collector plate of the present disclosure is used, the electrolyte can penetrate smoothly. Further, the current collector plate of the present disclosure may be disposed on the axially upper side of the electrode body, or the current collector plate of the present disclosure may be disposed on the axially lower side of the electrode body and also on the axially upper side of the electrode body.

[0052] When the current collector plate of the present disclosure is disposed on the side where the safety valve is provided with respect to the electrode body in the axial direction, high-temperature gas can be smoothly guided to the safety valve through the through hole of the current collector plate during operation of the safety valve, and exhaust can be efficiently performed, which is preferable. It goes without saying that when the current collector plate of the present disclosure is disposed on the axially upper side of the electrode body, the axially upper end portion of the electrode body is constituted by the core exposed portion of one electrode, and this core exposed portion is joined to the current collector plate. [Description of Reference Signs]

[0053] 10,110 Cylindrical battery, 11 Positive electrode, 11a Positive electrode core, 11b Positive electrode mixture layer, 11c Positive electrode core exposed part, 12 Negative electrode, 12a Negative electrode core, 12b Negative electrode mixture layer, 12c Negative electrode core exposed part, 12d Tip part, 13 Separator, 14 Electrode body, 14a Hollow part, 15 Battery case, 16 Outer can, 16a Cylindrical part, 17 Sealing body, 18 Insulating plate, 19,119 Lower current collector plate, 20 Positive electrode lead, 24 Insulating tape, 27 Sealing plate, 28 Gasket, 35 Grooved part, 40 Upper current collector plate, 40a Through hole, 45 Top surface, 45a Recess, 45b Bottom surface, 47 Outer circumference, 51 Flat plate section, 52 Connecting section, 52a, 152a Through hole, 53 Radially extending section, 54 Step section, 56 Protruding section, 56a Tip surface, 57 Groove, 58 Projection section, 58a Opposing section, 68 Bottom plate section, 68a Inner surface, 68b Bottom surface, 69 Bent section, 71 Thin-walled section, 72 Safety valve, 90 Welding rod, 93 Opening formed after the safety valve is blown off.

Claims

1. An electrode body in which a long first electrode and a long second electrode are wound around each other via a separator, with the first electrode core exposed on one side in the width direction, A current collector plate having a flat plate portion that overlaps the central part of the hollow portion of the electrode body in the axial direction and does not have a through hole, a joint portion to which the exposed core portion is joined, and one or more through holes located radially on the outer circumference side of the flat plate portion and radially inward from the joint portion, Equipped with, The current collector plate has one or more protrusions that are located radially outward from the flat plate portion and radially inward from the joint portion, and that protrude axially toward the second electrode portion toward the joint portion. The number of the protrusions matches the number of the through holes. A battery in which the protruding portion includes a bent portion that bends from the edge of the opening on the second electrode side of the through hole.

2. The outer container is a cylindrical container with a bottom, including a bottom plate portion to which the aforementioned flat plate portion is joined. The bottom plate portion has a safety valve defined by a thin, easily breakable portion. The battery according to claim 1, wherein the one or more through holes overlap the safety valve in the axial direction.

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