Secondary battery

Abstract

The present invention provides a secondary battery that suppresses movement of an electrode body inside a battery case and prevents damage at a joint portion between an electrode tab group and a current collector. The secondary battery (100) disclosed herein includes an exterior body (12), a sealing plate (14), an electrode body (20), an electrode tab group, a terminal (30), and a current collector (50). The current collector (50) has a first region portion (51) joined to the electrode tab group, a second region portion (52) connected to the terminal (30), and a third region portion (53) closer to the electrode body (20) than the first region portion (51).

Description

Technical Field

[0001] The present invention relates to a secondary battery. Background Art

[0002] A secondary battery such as a lithium ion secondary battery generally has a structure in which an electrode body housed in a battery case and a terminal exposed to the outside of the battery case are electrically connected. For example, a secondary battery having such a structure includes: an electrode body having a first electrode plate and a second electrode plate having a polarity different from that of the first electrode plate; an outer package having an opening and housing the electrode body; a sealing plate for sealing the opening of the outer package; a terminal that is electrically connected to the electrode plate inside the outer package and extends from the sealing plate to the outside of the outer package; and a current collector that is electrically connected to the terminal and the electrode body. For example, in the electrode body of such a secondary battery, an electrode tab group (a positive electrode tab group and a negative electrode tab group) including a plurality of electrode tabs for current collection is provided, and the electrode body can be connected to the terminal via the electrode tab group and the current collector.

[0003] An example of the secondary battery having the above structure is shown in Japanese Patent Application Laid-Open No. 2015-141847. In the secondary battery disclosed in this patent document, a positive electrode tab is disposed at one end of the electrode body, and a negative electrode tab is disposed at the other end. Further, in this document, it is proposed to bend the positive electrode tab and the negative electrode tab and connect them to the current collector. Thereby, it is possible to simultaneously achieve a large capacity and a high output of the secondary battery. Summary of the Invention

[0004] In the secondary battery in which the electrode tab group is provided in the above electrode body, damage (such as foil breakage and peeling of the joint portion) may occur at the joint portion between the electrode tab group and the current collector. Specifically, the secondary battery may be externally applied with vibration, impact, etc. during use or manufacturing. If, under the action of such external forces as vibration, the electrode body moves inside the battery case and deviates from the specified arrangement position, a large stress will act on the joint portion between the electrode tab group and the current collector. Here, the electrode tabs constituting the electrode tab group are formed of a part of a current collecting foil or the like, and are very soft and have low strength. Therefore, if the stress generated due to the movement of the electrode body as described above acts repeatedly, it may be easily damaged.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a technique for suppressing the movement of the electrode body inside the battery case and preventing damage at the joint portion between the electrode tab group and the current collector.

[0006] The secondary battery disclosed herein includes: an outer package having a bottom wall, a pair of first side walls extending from the bottom wall and facing each other, a pair of second side walls extending from the bottom wall and facing each other, and an opening facing the bottom wall; a sealing plate for sealing the opening; an electrode body received inside the outer package and including a first electrode plate and a second electrode plate having a different polarity from the first electrode plate; a first electrode tab group provided on a first end surface of one side of the electrode body facing one of the pair of first side walls and electrically connected to the first electrode plate; a second electrode tab group provided on a second end surface of the electrode body facing the other of the pair of first side walls and electrically connected to the second electrode plate; a terminal fixed to the sealing plate; and a current collector electrically connected to the terminal and the electrode body. The current collector has a first current collector connected to the first electrode tab group and a second current collector connected to the second electrode tab group. At least one of the first current collector and the second current collector has: a first region portion joined to the first electrode tab group or the second electrode tab group; a second region portion connected to the terminal; and a third region portion closer to the electrode body than the first region portion.

[0007] The current collector of the secondary battery having the above structure has a third region portion closer to the electrode body than the first region portion. This third region portion restricts the movement of the electrode body, so that even when external forces such as vibration are applied to the secondary battery, a large stress can be prevented from acting on the joint portion between the electrode tab group and the current collector. As a result, damage at the joint portion between the electrode tab group and the current collector can be prevented.

[0008] In a preferred embodiment of the secondary battery disclosed herein, the third region portion is disposed at a position closer to the bottom wall of the outer package than the first region portion, and a step is provided between the first region portion and the third region portion. With this structure, the effects of the technology disclosed herein can be appropriately exerted.

[0009] In another preferred embodiment, the second region portion is disposed at a position closer to the sealing plate than the first region portion. A step is provided between the second region portion and the first region portion. The first region portion is closer to the first side wall of the outer package than the second region portion. With this structure, the effects of the technology disclosed herein can be appropriately exerted.

[0010] In another preferred embodiment, the third region portion is in contact with the first end surface or the second end surface. With this structure, the movement of the electrode body can be more appropriately suppressed.

[0011] In another preferred embodiment, the third region portion is closer to the electrode body than the second region portion. With this structure, the movement of the electrode body can be more appropriately suppressed.

[0012] In another preferred embodiment, the current collector has an insulating layer on the surface on the electrode body side of the third region portion. With this structure, in addition to preventing breakage at the joint portion, a short-circuit prevention effect can also be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a perspective view schematically showing a secondary battery according to an embodiment.

[0014] Figure 2 is a schematic cross-sectional view taken along Figure 1 line II-II.

[0015] Figure 3 is a schematic cross-sectional view taken along Figure 1 line III-III.

[0016] Figure 4 is a perspective view schematically showing an electrode body mounted on a sealing plate.

[0017] Figure 5 is a perspective view schematically showing an electrode body with a positive current collector and a negative current collector mounted thereon.

[0018] Figure 6 is a schematic view showing the structure of an electrode body according to an embodiment.

[0019] Figure 7 is a partially enlarged cross-sectional view schematically showing the vicinity of a positive terminal and a positive current collector in an embodiment.

[0020] Figure 8 is a perspective view schematically showing a positive current collector used in a secondary battery according to an embodiment.

[0021] Figure 9 is Figure 8 a perspective view of the positive current collector turned over.

[0022] Figure 10 is a partially enlarged cross-sectional view schematically showing the vicinity of a positive terminal and a positive current collector in a second embodiment.

[0023] Figure 11 is a partially enlarged cross-sectional view schematically showing the vicinity of a positive terminal and a positive current collector in a third embodiment.

[0024] Figure 12It is a partially enlarged cross-sectional view schematically showing the vicinity of the positive electrode terminal and the positive electrode current collector in the fourth embodiment. Detailed Embodiment

[0025] Hereinafter, several preferred embodiments of the technology disclosed herein will be described with reference to the drawings. In addition, matters required for the implementation of the present invention other than those specifically mentioned in this specification (for example, common structures and manufacturing processes of secondary batteries that do not characterize the technology disclosed herein) can be grasped as design matters made by those skilled in the art based on the prior art in this field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common general knowledge in this field.

[0026] In this specification, the term "secondary battery" refers to a general power storage device capable of being repeatedly charged and discharged, and is a concept including so-called storage batteries (chemical batteries) such as lithium-ion secondary batteries and nickel-metal hydride batteries, and capacitors (physical batteries) such as electric double layer capacitors.

[0027] 1. First Embodiment

[0028] <Secondary Battery 100>

[0029] Figure 1 It is a perspective view schematically showing a secondary battery according to an embodiment. Figure 2 It is along Figure 1 a schematic cross-sectional view taken along line II-II. Figure 3 It is along Figure 1 a schematic cross-sectional view taken along line III-III. In addition, in each of the drawings referred to in this specification, the reference numeral X in the drawing represents the "depth direction", the reference numeral Y represents the "width direction", and the reference numeral Z represents the "height direction". In addition, F in the depth direction X represents "front", and Rr represents "rear". L in the width direction Y represents "left", and R represents "right". Moreover, U in the height direction Z represents "up", and D represents "down". However, these directions are only for the convenience of explanation and do not limit the installation method of the secondary battery 100.

[0030] As Figure 2 shown, the secondary battery 100 includes a battery case 10, an electrode body 20, a positive electrode terminal 30, a negative electrode terminal 40, a positive electrode current collector 50, a negative electrode current collector 60, and an insulator 70. Although not shown in the figure, the secondary battery 100 further includes an electrolytic solution here. The secondary battery 100 is a lithium-ion secondary battery here. The positive electrode current collector 50 and the negative electrode current collector 60 are examples of the first current collector and the second current collector in the secondary battery disclosed herein.

[0031] The battery case 10 is a housing for the electrode body 20. Here, the battery case 10 has an outer shape of a flat-bottomed rectangular parallelepiped (square). The material of the battery case 10 can be the same as the materials used in the past, and there is no particular limitation. The battery case 10 is preferably made of metal, and more preferably composed of, for example, aluminum, aluminum alloy, iron, iron alloy, etc. In addition, inside the battery case 10, in addition to the electrode body 20, an electrolytic solution (not shown) is also housed. For this electrolytic solution, an electrolytic solution that can be used in such a secondary battery can be used without particular limitation, and since it does not characterize the technology disclosed herein, detailed description thereof is omitted.

[0032] As Figure 2 shown, the battery case 10 includes an outer package 12 having an opening 12h and a sealing plate (cover body) 14 that closes the opening 12h. As Figure 1 shown, the outer package 12 includes a bottom wall 12a having a rectangular shape in plan view, a pair of long side walls 12b extending from the long sides of the bottom wall 12a in the height direction Z and facing each other, and a pair of short side walls 12c extending from the short sides of the bottom wall 12a in the height direction and facing each other. The short side wall 12c is an example of the first side wall in the secondary battery disclosed herein. The long side wall 12b is an example of the second side wall in the secondary battery disclosed herein. The bottom wall 12a faces the opening 12h. The area of the short side wall 12c is smaller than the area of the long side wall 12b. The sealing plate 14 is attached to the outer package 12 so as to close the opening 12h of the outer package 12. The sealing plate 14 faces the bottom wall 12a of the outer package 12. The sealing plate 14 has a substantially rectangular shape in plan view. The battery case 10 is integrated by joining the sealing plate 14 to the periphery of the opening 12h of the outer package 12. The battery case 10 is hermetically sealed.

[0033] As Figure 2 shown, a liquid injection hole 15, a gas discharge valve 17, and two terminal lead-out holes 18 and 19 are provided in the sealing plate 14. The liquid injection hole 15 is used for injecting the electrolytic solution after the sealing plate 14 is assembled to the outer package 12. The liquid injection hole 15 is sealed by a sealing member 16. The gas discharge valve 17 is a thin-walled portion configured to break when the pressure inside the battery case 10 reaches a predetermined value or more and discharge the gas inside the battery case 10 to the outside. The terminal lead-out holes 18 and 19 are respectively formed at both ends in the width direction Y of the sealing plate 14. The terminal lead-out holes 18 and 19 penetrate the sealing plate 14 in the height direction Z. The terminal lead-out holes 18 and 19 respectively have an inner diameter capable of inserting the positive terminal 30 and the negative terminal 40 before being attached to the sealing plate 14 (before riveting).

[0034] The secondary battery disclosed herein includes terminals fixed to the sealing plate. Here, the positive terminal 30 and the negative terminal 40 are respectively fixed to the sealing plate 14. The positive terminal 30 is disposed on one side in the width direction Y of the sealing plate 14 (Figure 1 , Figure 2 on the other side in the width direction Y of the sealing plate 14). The negative terminal 40 is arranged on the other side ( Figure 1 , Figure 2 on the right side of). The positive terminal 30 is made of, for example, aluminum or the like.

[0035] The positive terminal 30 has a flat base portion 31 disposed on the outer surface of the sealing plate 14, a shaft portion 32 extending downward in the height direction Z (toward the bottom wall 12a side) from the base portion 31, and a current collector connection portion 33 connected to the positive current collector 50 and the shaft portion 32 (see Figure 7 ). As Figure 7 shown, the base portion 31 of the positive terminal 30 is exposed on the outer surface of the sealing plate 14. As Figure 7 shown, the shaft portion 32 of the positive terminal 30 passes through the terminal lead-out hole 18 and extends from the outside to the inside of the sealing plate 14. The positive terminal 30 is fixed to the peripheral portion of the sealing plate 14 surrounding the terminal lead-out hole 18 by riveting. In addition, the current collector connection portion 33 is a portion connected to the positive current collector 50 described later. The current collector connection portion 33 is formed in an L-shaped cross section and has an upper portion 33a arranged along the inner surface of the sealing plate 14 and a lower portion 33b extending downward (toward the bottom wall 12a side) from one end in the width direction Y of the upper portion 33a ( Figure 2 and Figure 7 left end of). A through hole 33h penetrating in the height direction Z is formed in the upper portion 33a of the current collector connection portion 33. The through hole 33h is arranged at a position corresponding to the terminal lead-out hole 18 of the sealing plate 14 for the shaft portion 32 to pass through. Thus, the positive terminal 30 is constructed. In addition, the current collector connection portion 33 can be formed by bending a single plate-like member by, for example, stamping, or can be formed by integrating a plurality of members by welding or the like. In addition, in the positive terminal 30 in the present embodiment, the base portion 31 and the shaft portion 32 are integral, and the current collector connection portion 33 is separate (see Figure 7 ). However, the detailed structure of the positive terminal 30 is not particularly limited, and it may also be formed such that the base portion 31, the shaft portion 32, and the current collector connection portion 33 are integral. In addition, although detailed description is omitted, in the secondary battery 100 of the present embodiment, the negative terminal 40 also has substantially the same structure as the positive terminal 30. In addition, the material of the negative terminal 40 is copper or the like.

[0036] As Figure 2 shown, the positive terminal 30 is electrically connected to the positive electrode plate 22 of the electrode body 20 (see Figure 6 ) via the positive current collector 50 inside the outer package 12. The negative terminal 40 is electrically connected to the negative electrode plate 24 of the electrode body 20 (see Figure 6)Electrically connected. In addition, both the positive terminal 30 and the negative terminal 40 are insulated from the sealing plate 14 through the insulator 70 and the gasket 90.

[0037] The insulator 70 is disposed between the inner surface of the positive terminal 30 (typically the current collector connection portion 33) and the sealing plate 14. The insulator 70 has a flat portion 71 disposed along the inner surface of the sealing plate 14 and a wall portion 72 formed so as to descend from the periphery of the flat portion 71 toward the electrode body 20 (see Figure 7 ). The positive terminal 30 is disposed in the recess surrounded by the wall portion 72. In addition, a through hole 71h is formed in the flat portion 71. The gasket 90 is disposed between the outer surface of the positive terminal 30 (typically the base portion 31) and the sealing plate 14. In addition, the gasket 90 has a cylindrical protrusion inserted into the terminal lead-out hole 18 of the sealing plate 14. The protrusion of the gasket 90 is disposed along the inner periphery of the through hole 71h of the insulator 70. By providing the insulator 70 and the gasket 90 having the above structure, contact between the positive terminal 30 and the sealing plate 14 can be prevented. In addition, for the insulation structure using an insulator and a gasket, the same structure is also provided on the negative terminal 40 side, and detailed description thereof is omitted. In addition, the constituent materials of the insulator 70 and the gasket 90 are not particularly limited, and may be resin materials such as polyolefin resins (e.g., polypropylene (PP), polyethylene (PE)), fluororesins (e.g., perfluoroalkoxy alkane (PFA), polytetrafluoroethylene (PTFE)).

[0038] Figure 4 is a perspective view schematically showing the electrode body mounted on the sealing plate. In addition, Figure 5 is a perspective view schematically showing the electrode body on which the positive current collector and the negative current collector are mounted. As Figure 3 and Figure 4 show, the secondary battery 100 of the present embodiment includes three electrode bodies 20. However, the number of electrode bodies disposed inside one outer package 12 is not particularly limited, and may be two or more (a plurality), or may be one. In addition, as Figure 4 and Figure 5 show, a positive current collector 50 and a negative current collector 60 described later are mounted on each electrode body 20. Moreover, the electrode body 20 is disposed inside the outer package 12 in a state of being covered by an electrode body holder 29 made of a resin sheet (see Figure 2 ).

[0039] Figure 6 is a schematic view showing the structure of the electrode body. As Figure 6As shown, the electrode body 20 has a positive electrode plate 22 and a negative electrode plate 24. Here, the electrode body 20 is a flat wound electrode body formed by laminating a strip-shaped positive electrode plate 22 and a strip-shaped negative electrode plate 24 with a strip-shaped separator 26 therebetween and winding them around a winding axis WL. The positive electrode plate 22 is an example of the first electrode plate in the secondary battery disclosed herein. Further, the negative electrode plate 24 is an example of the second electrode plate in the secondary battery disclosed herein. In addition, in the following description, the electrode body 20 will be appropriately referred to as the "wound electrode body 20". However, this description is not intended to limit the structure of the electrode body in the technology disclosed herein to a wound electrode body.

[0040] As Figure 2 shown, the wound electrode body 20 is disposed inside the exterior body 12 with the winding axis WL parallel to the width direction Y. In other words, the wound electrode body 20 is disposed inside the exterior body 12 with the winding axis WL parallel to the bottom wall 12a and orthogonal to the short side wall 12c. Further, both end faces of the wound electrode body 20 in the direction along the winding axis WL (in other words, Figure 6 the width direction Y therein) face the short side wall 12c of the exterior body 12. In the present specification, for ease of explanation, the end face of the wound electrode body 20 facing the short side wall 12c on the side closer to the positive electrode terminal 30 ( Figure 2 the left side in the width direction Y therein) is referred to as the "first end face 20a". Further, the end face of the wound electrode body 20 facing the short side wall 12c on the side closer to the negative electrode terminal 40 ( Figure 2 the right side in the width direction Y therein) is referred to as the "second end face 20b".

[0041] As Figure 6 shown, the positive electrode plate 22 is a long strip-shaped member. The positive electrode plate 22 has a positive electrode current collector foil 22c and a positive electrode active material layer 22a fixed on at least one surface of the positive electrode current collector foil 22c. Although not particularly limited, a positive electrode protective layer 22p may be provided on one side edge portion in the width direction Y of the positive electrode plate 22 as needed. In addition, the materials constituting the positive electrode active material layer 22a and the positive electrode protective layer 22p can be used without particular limitation as the materials used in such secondary batteries, and since they do not characterize the technology disclosed herein, detailed description thereof is omitted herein.

[0042] At one end portion ( Figure 6 the left end portion therein) in the width direction Y of the strip-shaped positive electrode current collector foil 22c, a plurality of positive electrode tabs 22t are provided. The plurality of positive electrode tabs 22t respectively face one side in the width direction Y ( Figure 6Protrude on the left side). A plurality of positive electrode tabs 22t protrude outward from the separator 26 in the width direction Y. The plurality of positive electrode tabs 22t are arranged at intervals (intermittently) along the length direction of the positive electrode plate 22. The plurality of positive electrode tabs 22t are each trapezoidal in shape. The positive electrode tab 22t is here a part of the positive electrode current collector foil 22c and is composed of a metal foil (such as an aluminum foil). The positive electrode tab 22t is the part (current collector foil exposed part) of the positive electrode current collector foil 22c where the positive electrode active material layer 22a and the positive electrode protective layer 22p are not formed. However, the positive electrode tab 22t may also be a member different from the positive electrode current collector foil 22c. In addition, the positive electrode tab 22t may be provided at the other end of the width direction Y ( Figure 6 the right end), or may be provided at both ends of the width direction Y respectively.

[0043] As Figure 2 , 3 shown, a plurality of positive electrode tabs 22t are stacked at one end of the width direction Y ( Figure 3 the left end) to form a positive electrode tab group 23. In other words, the positive electrode tab group 23 is provided on the first end face 20a of the wound electrode body 20 facing the short side wall 12c on one side (positive terminal 30 side) of the exterior body 12. The plurality of positive electrode tabs 22t are bent so that the outer ends are aligned. The positive electrode tab group 23 is electrically connected to the positive terminal 30 via the positive electrode current collector 50. The plurality of positive electrode tabs 22t are preferably bent. The dimensions of the plurality of positive electrode tabs 22t (the length in the width direction Y and the length orthogonal to the width direction Y, refer to Figure 6 ) can be appropriately adjusted according to, for example, its formation position, etc., considering the connection state with the positive electrode current collector 50. In addition, the positive electrode tab group 23 is an example of the first electrode tab group in the secondary battery disclosed herein.

[0044] Similar to the above positive electrode plate 22, the negative electrode plate 24 is also a long strip-shaped member. As Figure 6 shown, the negative electrode plate 24 has a negative electrode current collector foil 24c and a negative electrode active material layer 24a fixed on at least one surface of the negative electrode current collector foil 24c. In addition, the material constituting the negative electrode active material layer 24a can be used without particular limitation the materials used in such secondary batteries, and since it does not make the technology disclosed herein characteristic, the detailed description here is omitted.

[0045] On one end of the width direction Y of the strip-shaped negative electrode current collector foil 24c ( Figure 6 the right end), a plurality of negative electrode tabs 24t are provided. The plurality of negative electrode tabs 24t face one side of the width direction Y ( Figure 6protrudes on the right side). A plurality of negative electrode tabs 24t protrude outward in the width direction Y more than the separator 26. The plurality of negative electrode tabs 24t are arranged at intervals (intermittently) along the length direction of the negative electrode plate 24. The plurality of negative electrode tabs 24t are each trapezoidal in shape. The negative electrode tab 24t is here a part of the negative electrode current collector foil 24c and is made of a metal foil (e.g., copper foil). The negative electrode tab 24t is here a part of the negative electrode current collector foil 24c where the negative electrode active material layer 24a is not formed (current collector foil exposed portion). However, the negative electrode tab 24t may also be a member different from the negative electrode current collector foil 24c. In addition, the negative electrode tab 24t may be provided at the other end in the width direction Y ( Figure 6 the left end), or may be provided at both ends in the width direction Y, respectively.

[0046] As Figure 2 , 3 shown, a plurality of negative electrode tabs 24t are stacked at one end in the width direction Y ( Figure 6 the right end) to form a negative electrode tab group 25. In other words, the negative electrode tab group 25 is provided on the second end face 20b of the wound electrode body 20 facing the short side wall 12c on the other side (negative terminal 40 side) of the outer package 12. The plurality of negative electrode tabs 24t are bent so that the outer ends are aligned. The negative electrode tab group 25 is electrically connected to the negative terminal 40 via the negative electrode current collector 60. The plurality of negative electrode tabs 24t are preferably bent. The dimensions of the plurality of negative electrode tabs 24t (the length in the width direction Y and the length orthogonal to the width direction Y, refer to Figure 6 ) can be appropriately adjusted according to, for example, its formation position, etc., considering the connection state with the negative electrode current collector 60. In addition, the negative electrode tab group 25 is an example of the second electrode tab group in the secondary battery disclosed herein.

[0047] The separator 26 is an insulating member interposed between the positive electrode plate 22 and the negative electrode plate 24. As Figure 6 shown, the wound electrode body 20 in the present embodiment includes two long strip-shaped separators 26. In addition, the constituent material of the separator 26 may be the same as the separator used in such a secondary battery, and since it does not characterize the technology disclosed herein, the detailed description thereof is omitted here.

[0048] Here, the secondary battery 100 of the present embodiment is characterized by using a current collector having a structure capable of suppressing the movement of the wound electrode body 20 having the above structure. Hereinafter, with reference to Figures 7 - 9 the case where this current collector is used as the positive electrode current collector 50 will be described. In addition, Figure 7 is a partially enlarged cross-sectional view schematically showing the vicinity of the positive terminal and the positive electrode current collector in one embodiment. In addition, Figure 8 is a perspective view schematically showing the positive electrode current collector. Figure 9 is toFigure 8 A perspective view of the positive electrode current collector turned over.

[0049] The positive electrode current collector 50 is an example of the first current collector in the secondary battery disclosed herein. The positive electrode current collector 50 constructs a conduction path that electrically connects the positive electrode terminal 30 and the wound electrode body 20. Specifically, by connecting the current collector connection portion 33 of the positive electrode terminal 30 to the positive electrode current collector 50, a conduction path between the positive electrode terminal 30 and the positive electrode current collector 50 is constructed. In addition, by connecting the positive electrode tab group 23 of the wound electrode body 20 to the positive electrode current collector 50, a conduction path between the wound electrode body 20 and the positive electrode current collector 50 is constructed. Furthermore, the positive electrode current collector 50 may be made of the same metal type as the positive electrode current collector foil 22c. Moreover, as Figure 4 , 5 shown in FIGS. 7 to 9, the positive electrode current collector 50 in the present embodiment has a first region portion 51, a second region portion 52, and a third region portion 53.

[0050] The first region portion 51 is a portion that is joined to the positive electrode tab group 23 (i.e., a plurality of positive electrode tabs 22t). The first region portion 51 is a plate-like portion configured to face the short side wall 12c of the exterior body 12. In addition, the surface of the first region portion 51 joined to the positive electrode tab group 23 faces the first end face 20a of the wound electrode body 20. As Figure 3 shown, a joining portion J with the positive electrode tab group 23 is formed in the first region portion 51. The joining portion J is, for example, a welded joint portion that is welded to the surface of the first region portion 51 by a conventionally known welding method in a state where a plurality of positive electrode tabs 22t are overlapped. The joining portion J is arranged such that a plurality of positive electrode tabs 22t are closer to one side in the depth direction X of the wound electrode body 20 ( Figure 3 the front side in [FIG. X]).

[0051] The second region portion 52 is a portion that is connected to the positive electrode terminal 30. As Figure 4 , 5, as shown in FIGS. 7, the second region portion 52 is a plate-like portion disposed above the first region portion 51 (on the side of the sealing plate 14) and extending along the height direction Z. The upper end portion of the second region portion 52 is connected to the current collector connection portion 33 of the positive electrode terminal 30, thereby constructing a conduction path between the positive electrode terminal 30 and the positive electrode current collector 50. Specifically, a recess 52d having a thickness thinner than its surroundings is provided in the second region portion 52. A through hole 52e penetrating in the depth direction X is provided in the recess 52d. Further, the current collector connection portion 33 of the positive electrode terminal 30 is inserted through the through hole 52e of the second region portion 52 to form a joint portion. Thus, the positive electrode current collector 50 and the positive electrode terminal 30 are fixed. The joint portion at this time can be, for example, a welded joint portion formed by using a conventionally known welding method. Alternatively, a fuse portion may be provided in the second region portion 52. The fuse portion is a portion having a thickness smaller than other portions of the second region portion 52 and is configured to break due to heat applied during a short circuit or overcharge of the secondary battery 100.

[0052] In addition, a first stepped portion 54 is provided between the above-described first region portion 51 and the second region portion 52. The first stepped portion 54 connects the upper end of the first region portion 51 and the lower end of the second region portion 52. The first stepped portion 54 is disposed along the sealing plate 14 of the outer package 12. The first stepped portion 54 is formed such that the second region portion 52 is disposed at a position closer to the center side in the width direction Y (the side of the wound electrode body 20) than the first region portion 51. In other words, in the present embodiment, the second region portion 52 of the positive electrode current collector 50 is closer to the wound electrode body 20 than the first region portion 51, and the first region portion 51 is closer to the short side wall 12c of the outer package 12 than the second region portion 52. By disposing the first region portion 51 on the side of the short side wall 12c in this way, the size of the wound electrode body 20 in the width direction Y can be increased, which helps to increase the volume ratio of the wound electrode body 20 with respect to the internal volume of the outer package 12. In addition, by making the first region portion 51 below the second region portion 52 the joint position with the positive electrode tab group 23, the distance between the lower portion 33b of the current collector connection portion 33 and the wound electrode body 20 can be ensured, preventing their contact. In addition, Figure 7 , the first stepped portion 54 shown is formed substantially perpendicular to the first region portion 51 and the second region portion 52, respectively. However, the angle of the first stepped portion 54 with respect to the first region portion 51 is not particularly limited. In addition, in this specification, "A is substantially perpendicular to B" includes not only the case where the angle formed by A and B is 90 degrees, but also the case where it can be substantially regarded as perpendicular as long as the effects of the technology disclosed herein can be achieved. For example, it may include the case where the angle formed by A and B is 85 degrees or more and 95 degrees or less.

[0053] The third region portion 53 is a portion closer to the wound electrode body 20 than the first region portion 51. As Figure 7As shown, the third region portion 53 in the present embodiment is a plate-like portion connected to the first region portion 51. The third region portion 53 is disposed below the first region portion 51 (on the side of the bottom wall 12a) and extends along the height direction Z. Moreover, the third region portion 53 of the positive current collector 50 in the present embodiment contacts the first end face 20a of the wound electrode body 20. And, as described above, the positive current collector 50 is fixed to the positive terminal 30 at the second region portion 52. That is, in the secondary battery 100 of the present embodiment, the movement of the wound electrode body 20 can be restricted by the third region portion 53 of the positive current collector 50 fixed to the positive terminal 30. As a result, even when an external force such as vibration is applied to the secondary battery 100, a large stress can be prevented from acting on the joint portion J between the positive electrode tab group 23 and the positive current collector 50 (the first region portion 51). Therefore, damage can be prevented from occurring near the joint portion J. In addition, if the positive current collector 50 is given a function of restricting the movement of the wound electrode body 20 as in the above structure, the positive current collector 50 becomes an integral component that simultaneously realizes the connection to the positive terminal 30 and the restriction of the movement of the wound electrode body 20. Therefore, an additional component for restricting the movement of the wound electrode body 20 is no longer required, and the assembly operation can be simplified. For example, when mass-producing the secondary battery 100 using equipment, its equipment function can be reduced. In other words, by using the positive current collector 50 having the above structure, the number of components when assembling the secondary battery 100 can be reduced. Therefore, a secondary battery 100 with high assemblability can be provided.

[0054] In addition, a second stepped portion 55 is provided between the first region portion 51 and the third region portion 53 of the positive current collector 50 in the present embodiment. The second stepped portion 55 connects the lower end of the first region portion 51 and the upper end of the third region portion 53. The second stepped portion 55 is configured to be along the sealing plate 14. By providing this second stepped portion 55, it is possible to easily construct the positive current collector 50 in which the third region portion 53 is closer to the wound electrode body 20 than the first region portion 51. In addition, since the second stepped portion 55 can be formed only by bending the plate-like positive current collector 50, it can also contribute to the improvement of manufacturing efficiency.

[0055] Moreover, the positive current collector 50 in the present embodiment is formed such that the third region portion 53 is closer to the wound electrode body 20 than the second region portion 52. In other words, in this positive current collector 50, the length L1 in the width direction Y of the first stepped portion 54 is shorter than the length L2 of the second stepped portion 55 in the same direction, and the third region portion 53 is disposed at a position closer to the center than the second region portion 52. Thereby, the third region portion 53 can easily contact the first end face 20a of the wound electrode body 20, and thus, the movement of the wound electrode body 20 inside the battery case 10 can be more appropriately restricted.

[0056] In addition, as Figures 7 - 9As shown, an insulating layer 56 is provided on the surface of the winding electrode body 20 side of the third region portion 53. Thereby, the effect of preventing short circuit can be exerted. Although not particularly limited, when the secondary battery vibrates, if the end face of the electrode body comes into contact with the third region portion, deformation occurs at the contact portion, and it is possible for the first electrode plate (positive electrode plate) and the second electrode plate (negative electrode plate) to short-circuit through the current collector as a conduction path. As described above, due to the presence of the insulating layer, even in the case of excessive deformation, the above short circuit can be prevented. In addition, the insulating layer 56 can be formed by pasting a resin film on the third region portion 53 using an adhesive or the like. Alternatively, the insulating layer 56 can also be formed by coating the above surface with a resin material and curing it. The material constituting the insulating layer 56 is not particularly limited as long as it can insulate the positive current collector 50 from the winding electrode body 20, and resin materials such as polyethylene (PE) and polypropylene (PP) can be used. In addition, in the illustrated embodiment, the insulating layer 56 is formed on the entire above surface, but it is not limited thereto and can be formed on at least a part of the surface. Alternatively, the formation of the insulating layer 56 can be omitted.

[0057] In addition, the negative current collector 60 in the present embodiment is an example of the second current collector in the secondary battery disclosed herein. As Figure 2 shown, the negative current collector 60 also includes a first region portion 61, a second region portion 62, and a third region portion 63, similar to the above positive current collector 50. Thereby, the movement of the winding electrode body 20 inside the battery case 10 can be more appropriately restricted. In addition, as described above, since the negative current collector 60 has substantially the same structure as the positive current collector 50, repetitive descriptions will be formed, and therefore, detailed descriptions are omitted here. In addition, the current collector having the first region portion, the second region portion, and the third region portion can be used for either the positive current collector or the negative current collector.

[0058] In addition, the structure of the electrode body 20 in the secondary battery 100 of the present embodiment is not limited to the above winding electrode body. For example, the electrode body 20 can also be a stacked electrode body formed by stacking a plurality of square-shaped (typically rectangular-shaped) positive electrode plates and a plurality of square-shaped (typically rectangular-shaped) negative electrode plates in an insulated state.

[0059] As described above, the secondary battery 100 of one embodiment of the technology disclosed herein has been described. The secondary battery 100 having the above structure can be used for various purposes, and can preferably be used for applications where external forces such as vibration and impact are easily applied during use. For example, it can preferably be used as a power source (driving power source) for an electric motor mounted on a moving body (typically a vehicle such as a passenger car or a truck). The type of vehicle is not particularly limited, and examples include a Plug-in Hybrid Electric Vehicle (PHEV), a Hybrid Electric Vehicle (HEV), a Battery Electric Vehicle (BEV), and the like. The secondary battery 100 can also preferably be used as a battery pack formed by arranging a plurality of secondary batteries 100 in a specified arrangement direction and applying a load from the arrangement direction using a constraint mechanism.

[0060] 2. Other Embodiments

[0061] The above-described first embodiment is merely an example of the secondary battery disclosed herein. The technology disclosed herein can also be implemented in various other ways. Hereinafter, other embodiments of the technology disclosed herein will be described.

[0062] <Second Embodiment>

[0063] For example, in the above-described first embodiment, a second stepped portion 55 is provided between the first region portion 51 and the third region portion 53 of the positive electrode current collector 50. However, the shape of the positive electrode current collector 50 is not limited thereto. Figure 10 FIG. is a partially enlarged cross-sectional view schematically showing the vicinity of the positive electrode terminal and the positive electrode current collector in the second embodiment. The secondary battery 200 of this second embodiment includes a positive electrode current collector 250 that has an inclined portion 255 between a first region portion 251 and a third region portion 253. Specifically, as Figure 10 shown, the inclined portion 255 of the positive electrode current collector 250 is preferably configured to approach the end face 20a of the wound electrode body 20 (in other words, approach the center in the width direction Y) as it goes downward in the height direction Z (toward the bottom wall 12a side). When the positive electrode current collector 250 having this structure is used, the movement of the wound electrode body 20 can also be appropriately restricted, and breakage of the positive electrode tab group 23 due to external forces such as vibration can be prevented. In addition, the secondary battery 200 of the second embodiment can be the same as the secondary battery 100 of the first embodiment except for the above point. Further, in this second embodiment, a first stepped portion 254 is provided between the first region portion 251 and the second region portion 252. However, this first stepped portion 254 is not an essential structure and can be changed to an inclined portion or the like.

[0064] <Third Embodiment>

[0065] In addition, in the first embodiment, the third region portion 53 of the positive electrode current collector 50 is formed at a position closer to the bottom wall 12a side (below in the height direction Z) than the first region portion 51. However, the third region portion only needs to be closer to the wound electrode body than the first region portion, and the formation position in the height direction Z is not limited. Figure 11 FIG. is a partially enlarged cross-sectional view schematically showing the vicinity of the positive electrode terminal and the positive electrode current collector in the third embodiment. The secondary battery 300 of this third embodiment includes a positive electrode current collector 350, as Figure 11 shown, the positive electrode current collector 350 has a protruding third region portion 353 that protrudes from the second region portion 352 (typically near the first step portion 354) toward the wound electrode body 20. Moreover, the protruding third region portion 353 is closer to the wound electrode body 20 than the first region portion 351. In the case where the positive electrode current collector 350 having this structure is used, the movement of the wound electrode body 20 can be appropriately restricted, and breakage of the positive electrode tab group 23 due to external forces such as vibration can be prevented. In addition, although not particularly limited, the third region portion 353 may be in contact with the side surface of the wound electrode body 20. Further, the third region portion 353 may have an insulating layer (not shown) on the surface on the side of the wound electrode body 20. In addition, the secondary battery 300 of the third embodiment may be the same as the secondary battery 100 of the first embodiment except for the above point.

[0066] <Fourth Embodiment>

[0067] In addition, in the positive electrode current collector 50 in the first embodiment, the second region portion 52 and the third region portion 53 are formed of different members. However, a structure in which the second region portion is closer to the wound electrode body than the first region portion and also serves as the third region portion can also be adopted. Figure 12FIG. 0 is a partially enlarged cross-sectional view schematically showing the vicinity of the positive electrode terminal and the positive electrode current collector in the fourth embodiment. In the positive electrode current collector 450 of the secondary battery 400 of the fourth embodiment, the second region portion 452 is disposed between the lower portion 33b of the current collector connection portion 33 of the positive electrode terminal 30 and the first end face 20a of the wound electrode body 20 in the width direction Y. Specifically, in the present embodiment, the second region portion 452 of the positive electrode current collector 450 is inserted between the lower portion 33b of the current collector connection portion 33 and the first end face 20a of the wound electrode body 20. With this structure, the second region portion 452 is closer to the electrode body 20 than the first region portion 451 and functions as the third region portion 453, so that the movement of the wound electrode body 20 can be restricted. In addition, a first stepped portion 454 is provided between the second region portion 452 (third region portion 453) and the first region portion 451. Although not particularly limited, it is preferable to provide an insulating layer (not shown) on the surface of the second region portion 452 (third region portion 453) on the side of the wound electrode body 20. In addition, except for the above point, the secondary battery 400 of the fourth embodiment may be the same as the secondary battery 100 of the first embodiment.

[0068] As described above, several embodiments of the technology disclosed herein have been described, but it can also be implemented in various other ways. The technology disclosed herein can be implemented based on the content disclosed in this specification and common general knowledge in the art. For example, a part of the above-described embodiments can be replaced with other modified forms, and other modified forms can also be added to the above-described embodiments. In addition, if its technical features are not described as essential technical features, they can also be appropriately eliminated.

[0069] Description of Reference Numerals

[0070] 12 Outer package

[0071] 14 Sealing plate

[0072] 20 Electrode body

[0073] 23 Positive electrode tab group

[0074] 25 Negative electrode tab group

[0075] 30 Positive electrode terminal

[0076] 40 Negative electrode terminal

[0077] 50 Positive electrode current collector

[0078] 51 First region portion

[0079] 52 Second region portion

[0080] 53 Third region portion

[0081] 60 Negative electrode current collector

[0082] 70 Insulator

[0083] 90 Gasket

[0084] 100, 200, 300, 400 Secondary batteries.

Claims

1. A secondary battery, wherein, Comprising: An outer package having a bottom wall, a pair of first side walls extending from the bottom wall and facing each other, a pair of second side walls extending from the bottom wall and facing each other, and an opening facing the bottom wall; A sealing plate for sealing the opening; An electrode body received inside the outer package, including a first electrode plate and a second electrode plate having a polarity different from that of the first electrode plate; A first electrode tab group provided to partially protrude from a first end face of the electrode body facing one of the pair of first side walls and electrically connected to the first electrode plate; A second electrode tab group provided to partially protrude from a second end face of the electrode body facing the other of the pair of first side walls and electrically connected to the second electrode plate; A terminal fixed to the sealing plate; And A current collector electrically connected to the terminal and the electrode body, The current collector having a first current collector connected to the first electrode tab group and a second current collector connected to the second electrode tab group, At least one of the first current collector and the second current collector having: A first region portion joined to the first electrode tab group or the second electrode tab group; A second region portion connected to the terminal; And A third region portion closer to the electrode body than the first region portion.

2. The secondary battery according to claim 1, wherein The third region portion is disposed at a position closer to the bottom wall than the first region portion, and a step is provided between the first region portion and the third region portion.

3. The secondary battery according to claim 1 or 2, wherein The second region portion is disposed at a position closer to the sealing plate than the first region portion, a step is provided between the second region portion and the first region portion, and the first region portion is closer to the first side wall than the second region portion.

4. The secondary battery according to claim 1 or 2, wherein The third region portion contacts the first end face or the second end face.

5. The secondary battery according to claim 1 or 2, wherein The third region portion is closer to the electrode body than the second region portion.

6. The secondary battery according to claim 1 or 2, wherein The current collector has an insulating layer on a surface on the electrode body side of the third region portion.

Images