Secondary battery

Abstract

The present application provides a secondary battery capable of further increasing the capacity of the secondary battery. According to the technology disclosed herein, a secondary battery is provided, which has a flat-shaped wound electrode body in which a first electrode and a second electrode different from the first electrode are stacked with a separator interposed therebetween and wound. The secondary battery has a first current collecting member connected to the first electrode. The first end portion of the wound electrode body in the winding axis direction has a plurality of first electrode tabs connected to the first electrode. The first electrode tabs are provided in 10 or more. The plurality of first electrode tabs are stacked. In the thickness direction of the wound electrode body, the ratio (N 1A / N 1B ) of the number N 1B of the first electrode tabs to the number N 1A of the first electrode layers satisfies 0.3 to 0.7. The plurality of first electrode tabs are connected to the first electrode current collecting member in a state of being bent.

Description

Technical Field

[0001] This disclosure relates to secondary batteries. Background Technology

[0002] Secondary batteries, such as lithium-ion batteries, are used as high-output power sources for vehicle propulsion. These secondary batteries, for example, have a so-called wound electrode body, formed by stacking and winding a first electrode and a second electrode separated by a separator, as a power generation element. Patent Document 1 discloses a wound electrode body with multiple electrode tabs at one end in the winding axis direction. These multiple electrode tabs overlap in the thickness direction of the wound electrode body and are connected to a current collector (electrode terminal) in a bent state. Patent Document 1 proposes a scheme in which electrode tabs are formed on one side along the radial direction with the winding axis of the wound electrode body as a reference.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 5174840 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In addition, with the increasing popularity of rechargeable batteries in recent years, the demand for further improving the capacity of rechargeable batteries is getting higher and higher.

[0008] Methods for solving problems

[0009] According to the technology disclosed herein, a secondary battery is provided, which has a flat, wound electrode body formed by stacking and winding a first electrode and a second electrode different from the first electrode through a separator. The secondary battery has a first current collector connected to the first electrode. The wound electrode body has a plurality of first electrode tabs connected to the first electrode at a first end in the winding axis direction. Ten or more first electrode tabs are provided. The plurality of first electrode tabs are stacked. In the thickness direction of the wound electrode body, the number of stacked first electrode tabs is N. 1A The number of layers N with the first electrode 1B The ratio (N) 1A / N 1B The value is between 0.3 and 0.7. Multiple first electrode tabs are connected to the first electrode current collector in a bent state.

[0010] In this secondary battery structure, the number of layers of the first electrode tab in the wound electrode body and the ratio of the number of layers of the first electrode tab to the number of layers of the first electrode are set within the aforementioned range. This allows for sufficient output from the secondary battery and reduces the size of the current collector near the first electrode tab. Consequently, the size of the main body of the electrode body can be increased, thereby increasing the capacity of the secondary battery.

[0011] In a preferred embodiment of the secondary battery disclosed herein, when the surface passing through the winding shaft of the wound electrode body and perpendicular to the thickness direction of the wound electrode body is designated as the first surface, this first surface intersects with the first electrode current collector. According to this structure, the effects of the technology disclosed herein can be better achieved.

[0012] In another preferred embodiment of the secondary battery disclosed herein, the secondary battery comprises a battery housing that internally accommodates the wound electrode body. The battery housing has: an outer body having a bottom, an opening, a pair of first sidewalls, and a pair of second sidewalls; and a sealing plate that seals the opening. The effects of the technology disclosed herein can be more preferably achieved in so-called prismatic secondary batteries.

[0013] In another preferred embodiment of the secondary battery disclosed herein, the wound electrode body has a first flat outer surface and a second flat outer surface at both ends in the thickness direction of the wound electrode body. The wound electrode body has a plurality of second electrode tabs connected to the second electrode at a second end different from the first end in the winding axis direction, and these plurality of second electrode tabs are stacked. A surface passing through the winding axis of the wound electrode body and perpendicular to the thickness direction of the wound electrode body is designated as a first surface. In the wound electrode body, when a region closer to the first flat outer surface than the first surface is designated as a first region and a region closer to the second flat outer surface than the first surface is designated as a second region, in the first region, the ratio A of the number of stacked first electrode tabs to the number of stacked first electrodes is 0.8 or more, and the ratio B of the number of stacked second electrode tabs to the number of stacked second electrodes is 0.2 or less. In the second region, the ratio C of the number of stacked first electrode tabs to the number of stacked first electrodes is 0.2 or less, and the ratio D of the number of stacked second electrode tabs to the number of stacked second electrodes is 0.8 or more. According to this structure, in addition to the effects described above, deviations in the current density distribution within the wound electrode body can also be suppressed. Furthermore, the following structure is preferred: a plurality of first electrode tabs are bundled together on the first flat outer surface side, and a plurality of second electrode tabs are bundled together on the first flat outer surface side. Additionally, the plurality of first electrode tabs are bent such that the portion of the bundled portion closer to its tip faces the second flat outer surface, and the plurality of second electrode tabs are bent such that the portion of the bundled portion closer to its tip faces the second flat outer surface.

[0014] In another preferred embodiment of the secondary battery disclosed herein, the wound electrode body has a first flat outer surface and a second flat outer surface at both ends in the thickness direction of the wound electrode body. The wound electrode body has a plurality of second electrode tabs connected to the second electrode at a second end different from the first end in the winding axis direction, and these plurality of second electrode tabs are stacked. A surface passing through the winding axis of the wound electrode body and perpendicular to the thickness direction of the wound electrode body is designated as a first surface. In the wound electrode body, when a region closer to the first flat outer surface than the first surface is designated as a first region and a region closer to the second flat outer surface than the first surface is designated as a second region, in the first region, the ratio A of the number of stacked first electrode tabs to the number of stacked first electrodes is 0.8 or more, and the ratio B of the number of stacked second electrode tabs to the number of stacked second electrodes is 0.8 or more. In the second region, the ratio C of the number of stacked first electrode tabs to the number of stacked first electrodes is 0.2 or less, and the ratio D of the number of stacked second electrode tabs to the number of stacked second electrodes is 0.8 or more. According to this structure, in addition to increasing the capacity of the secondary battery, it is also possible to suppress deviations in the current density distribution within the wound electrode body. Furthermore, the following structure is preferred: a plurality of first electrode tabs are bundled together on the first flat outer surface side, and a plurality of second electrode tabs are bundled together on the first flat outer surface side. Additionally, the plurality of first electrode tabs are bent such that the portion of the bundled portion closer to its tip faces the second flat outer surface, and the plurality of second electrode tabs are bent such that the portion of the bundled portion closer to its tip faces the second flat outer surface. Attached Figure Description

[0015] Figure 1 This is a perspective view schematically showing the secondary battery of the first embodiment.

[0016] Figure 2 yes Figure 1 Sectional view II-II.

[0017] Figure 3 This is a perspective view showing a wound electrode body mounted on a sealing plate.

[0018] Figure 4 This is a perspective view showing a wound electrode body with a second current collector installed.

[0019] Figure 5 This is a schematic diagram illustrating the structure of the wound electrode.

[0020] Figure 6 This is a cross-sectional view of the wound electrode body in the first embodiment.

[0021] Figure 7 This is a top view illustrating the configuration of the electrode tabs in the first embodiment.

[0022] Figure 8 This is a schematic diagram illustrating the connection between the electrode tab and the electrode current collector.

[0023] Figure 9 This is a cross-sectional view of the wound electrode body in the second embodiment.

[0024] Figure 10 This is a top view illustrating the configuration of the electrode tabs in the second embodiment.

[0025] Figure 11 This is a perspective view of the wound electrode body in the third embodiment.

[0026] Explanation of reference numerals in the attached figures

[0027] 1. Secondary battery

[0028] 2a First flat outer surface

[0029] 2b Second flat outer surface

[0030] 10 Battery casing

[0031] 20, 220, 320 wound electrode bodies

[0032] 22 Positive electrode

[0033] 22a Positive electrode active material layer

[0034] 22c positive current collector foil

[0035] 22p Positive electrode protective layer

[0036] 22t positive electrode tab

[0037] 23 Positive electrode tab group

[0038] 24 Negative electrode

[0039] 24a Negative electrode active material layer

[0040] 24C negative electrode current collector foil

[0041] 24t negative electrode tab

[0042] 25 Negative electrode tabs

[0043] 26. Diaphragm

[0044] 30 Positive extremes

[0045] 35, 45 External conductive components

[0046] 40 Negative extremes

[0047] 50 Positive current collector component

[0048] 60 Negative current collector component

[0049] 70 Insulator

[0050] 90 sealing gasket

[0051] F1 First Side

[0052] R First Region

[0053] S Second Region Detailed Implementation

[0054] Hereinafter, several preferred embodiments of the technology disclosed herein will be described with reference to the accompanying drawings. The embodiments described herein are not intended to specifically limit the invention. The drawings are schematic depictions and do not necessarily reflect actual objects. Furthermore, components and parts that perform the same function are appropriately labeled with the same reference numerals, and repeated descriptions are omitted. In addition, matters necessary for implementing the technology disclosed herein, other than those specifically mentioned in this specification (e.g., the general structure and manufacturing process of secondary batteries that do not represent the technology disclosed herein), can be understood as design matters by those skilled in the art based on prior art. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the field. Furthermore, in this specification, the expression "A to B" indicating a numerical range means "A or more and B or less," and also includes cases exceeding A but below B.

[0055] In this specification, "secondary battery" refers to all energy storage devices that can be repeatedly charged and discharged, including lithium-ion secondary batteries, nickel-metal hydride batteries and other so-called storage batteries (chemical batteries), and capacitors such as double-layer capacitors.

[0056] In the accompanying drawings referenced in this specification, reference numeral X indicates "depth direction," reference numeral Y indicates "width direction," and reference numeral Z indicates "height direction." Furthermore, in the depth direction X, F indicates "front," and Rr indicates "rear." In the width direction Y, L indicates "left," and R indicates "right." And in the height direction Z, U indicates "up," and D indicates "down." However, these directions are merely for ease of explanation and do not impose any limitations on the arrangement of the secondary battery or the battery pack.

[0057] First Implementation Method

[0058] Figure 1 This is a perspective view schematically showing the secondary battery of the first embodiment. Figure 2 yes Figure 1 Sectional view II-II. (See example) Figure 1 , 2 As shown, the secondary battery 1 includes a battery casing 10, a wound electrode body 20, a positive terminal 30, a negative terminal 40, external conductive members 35 and 45, a positive current collector 50, a negative current collector 60, an insulator 70, a sealing gasket 90, and an external insulating member 92. The positive current collector 50 is an example of a "first electrode current collector." The negative current collector 60 is an example of a "second electrode current collector." In this embodiment, the secondary battery 1 is a lithium-ion secondary battery. Although the figures are omitted, the secondary battery 1 includes, for example, an electrolyte. As the electrolyte, any electrolyte used in this type of lithium-ion secondary battery can be used without particular limitation. The composition of this electrolyte does not characterize the technology disclosed herein, and therefore a detailed description is omitted here.

[0059] In this embodiment, the battery casing 10 is a frame that internally houses the wound electrode body 20 and the electrolyte. Here, the battery casing 10 has a flat, bottomed cuboid shape (square). The material of the battery casing 10 can be the same as conventionally used materials, and there are no particular limitations. The battery casing 10 is preferably made of metal, and more preferably of materials such as aluminum, aluminum alloy, iron, or iron alloy.

[0060] In this embodiment, the battery casing 10 includes an outer body 12 and a sealing plate (cover) 14. For example... Figure 1 As shown, the outer casing 12 includes: a planar rectangular bottom 12a; a pair of first sidewalls 12b, which extend along the height direction Z from a pair of opposing sides of the bottom 12a and face each other; and a pair of second sidewalls 12c, which extend along the height direction Z from a pair of opposing sides of the bottom 12a and face each other. In this embodiment, the first sidewalls 12b are long sidewalls extending from a pair of opposing long sides of the bottom 12a. The second sidewalls 12c are short sidewalls extending from a pair of opposing short sides of the bottom 12a. In this embodiment, the area of ​​the second sidewalls 12c is smaller than the area of ​​the first sidewalls 12b. The portion facing the bottom 12a and surrounded by the pair of first sidewalls 12b and the pair of second sidewalls 12c forms an opening 12h. A sealing plate 14 is a component that seals the opening 12h of the outer casing 12. The sealing plate 14 faces the bottom 12a of the outer casing 12. The sealing plate 14 is generally rectangular in shape when viewed from above. The battery casing 10 is integrally formed by joining the sealing plate 14 to the periphery of the opening of the outer casing 12. The joining method is, for example, welding such as laser welding. The battery casing 10 is hermetically sealed (airtight).

[0061] The sealing plate 14 is provided with an injection hole 15 and a gas discharge valve 17. The injection hole 15 is used to inject electrolyte after the sealing plate 14 is assembled to the outer casing 12. The injection hole 15 is sealed by a sealing member 16. The gas discharge valve 17 is configured to break when the pressure inside the battery casing 10 reaches a predetermined value, thereby venting the gas inside the battery casing 10 to the outer thin-walled portion.

[0062] In this embodiment, the positive terminal 30 and the negative terminal 40 are mounted on the sealing plate 14. In this embodiment, the positive terminal 30 is disposed at one end of the sealing plate 14 along the long side direction Y. Figure 1 , 2 (The left end). In this embodiment, the negative end 40 is disposed at the end of the sealing plate 14 on the other side in the long side direction Y. Figure 1 , 2 (the right end).

[0063] like Figure 2 As shown, the positive terminal 30 is located inside the outer casing 12 via the positive current collector 50 and the positive terminal 22 of the wound electrode body 20 (see reference). Figure 5 Electrical connection. The positive terminal 30 is led out from the inside of the sealing plate 14 to the outside, for example, by inserting through the terminal lead-out hole 18. The positive terminal 30 is insulated from the sealing plate 14 by an insulator 70 and a sealing gasket 90. The positive terminal 30 is preferably made of metal, more preferably of, for example, aluminum or an aluminum alloy. An external conductive member 35 is fixed on the positive terminal 30. The positive terminal 30 is engaged with the external conductive member 35.

[0064] like Figure 2 As shown, the negative terminal 40 is located inside the outer casing 12 via the negative current collector 60 and the negative terminal 24 of the wound electrode body 20 (see reference). Figure 5 Electrical connection. The negative terminal 40 is led out from the inside of the sealing plate 14 to the outside, for example, by inserting through the terminal lead hole 19. The negative terminal 40 is insulated from the sealing plate 14 by the insulator 70 and the sealing gasket 90. The negative terminal 40 is preferably made of metal, more preferably, for example, copper or a copper alloy. An external conductive member 45 is fixed on the negative terminal 40. The negative terminal 40 is engaged with the external conductive member 45.

[0065] The positive current collector 50 is, for example, a component that electrically connects the positive electrode 22 and the positive terminal 30 inside the outer casing 12. Figure 2 As shown, the positive current collector 50 includes a first current collector 51 and a second current collector 52. The first current collector 51 is, for example, formed in an L-shaped cross-section. The first current collector 51 includes, for example, a base 51a and a lead 51b. Figure 2As shown, the base 51a is arranged along the inner surface of the sealing plate 14. A lead 51b extends, for example, from one end of the base 51a in the width direction Y towards the bottom 12a. A second current collector 52 is connected to the lead 51b, for example.

[0066] Figure 3 This is a perspective view showing a wound electrode body mounted on a sealing plate. Figure 4 This is a perspective view showing a wound electrode body with a second current collector installed. (See diagram below.) Figures 2-4 As shown, the second current collector 52 extends toward the bottom 12a of the outer casing 12. In this embodiment, the second current collector 52 has a first connecting piece 52a and a second connecting piece 52b. The first connecting piece 52a is, for example, a portion electrically connected to the first current collector 51. In this embodiment, the first connecting piece 52a is connected to the first current collector 51 via a connecting portion 521. The connecting portion 521 is, for example, a thin-walled portion. The first connecting piece 52a extends, for example, along the vertical direction Z. In this embodiment, the first connecting piece 52a is arranged substantially perpendicularly to the winding axis WL of each wound electrode body 20. Although not particularly limited, a fuse portion 52f may also be formed in the first connecting piece 52a. The fuse portion 52f is configured to melt when a current of 1000A or more (e.g., a short-circuit current) flows through the secondary battery 1.

[0067] The second connecting piece 52b is, for example, the part that engages with the positive electrode tab assembly 23. In this embodiment, the second connecting piece 52b extends along the vertical direction Z. The second connecting piece 52b is arranged substantially perpendicular to the winding axis WL of each electrode body 20. The surface of the second connecting piece 52b that connects to the plurality of positive electrode tabs 22t is arranged substantially parallel to the second sidewall 12c of the outer casing 12. From the viewpoint of reducing the battery resistance of the secondary battery 1 by sufficiently ensuring the width of the second connecting piece 52b, the surface of the second connecting piece 52b that connects to the plurality of positive electrode tabs 22t is arranged facing the first end 201 of the wound electrode body 20.

[0068] The negative current collector 60 is a component inside the outer casing 12 that electrically connects the negative electrode 24 to the negative terminal 40. For example... Figures 2-4 As shown, the negative current collector 60 includes a first current collector 61 and a second current collector 62. The first current collector 61 has a base 61a and a lead 61b. The second current collector 62 has a first connecting piece 62a and a second connecting piece 62b. The structure of the negative current collector 60 is the same as that of the positive current collector 50 described above, therefore a detailed description is omitted here. Furthermore, regarding the negative current collector 60, Figure 4 In the attached drawing, reference numeral "621" indicates the connecting part, and reference numeral "62f" indicates the fuse part.

[0069] like Figure 3As shown, the secondary battery 1 has three wound electrode bodies 20. Figure 3 , 4 As shown, the second current collector 52 of the positive current collector 50 is disposed on one side in the long side direction Y. Figure 3 , 4 (on the left side), the second collector part 62 of the negative electrode collector 60 is disposed on the other side in the long side direction Y ( Figure 3 , 4 (to the right of), connected side by side. For example... Figure 2 As shown, one or more wound electrode bodies 20 are disposed inside the outer casing 12, covered by an electrode body retainer 29 made of a resin sheet such as polypropylene (PP). Furthermore, the number of wound electrode bodies 20 housed in the secondary battery 1 is not particularly limited; for example, it can be one, two, or more than four.

[0070] Another example of increasing the capacity of a secondary battery is increasing the size of the electrode body. Here, the inventors focus on the volume required to house components other than the electrode body (e.g., other than the main body) within the battery casing. According to the inventors' research, by setting the balance between the number of electrode layers in the thickness direction of the wound electrode body and the number of electrode tabs of the same polarity within an appropriate range, it is possible to reduce the volume occupied by conventional electrode tabs, increase the size of the wound electrode body, and thereby increase the capacity of the secondary battery. Hereinafter, the case where the "first electrode" is used as the positive electrode 22 and the "second electrode" is used as the negative electrode 24 will be described in more detail regarding the technology disclosed herein.

[0071] Figure 5 This is a schematic diagram illustrating the structure of the wound electrode body. For example... Figure 5 As shown, the wound electrode body 20 includes a positive electrode 22, a negative electrode 24, and a separator 26 disposed between the positive electrode 22 and the negative electrode 24. Figure 5 As shown, the wound electrode body 20 is an electrode body formed by stacking and winding the positive electrode 22 and the negative electrode 24 with a diaphragm 26 in between.

[0072] like Figures 2-4 As shown, the wound electrode body 20 includes a main body 20a, a positive electrode tab group 23, and a negative electrode tab group 25. The main body 20a is a portion in which a positive electrode 22, a negative electrode 24, and a diaphragm 26 are stacked, and is, for example, flat in shape.

[0073] The width of the main body 20a is, for example, 20 cm or more. The width of the main body 20a can be, for example, 25 cm or more, or 30 cm or more. The width of the main body 20a can be, for example, 50 cm or less, or 40 cm or less. In this specification, "width of the main body 20a" refers to, for example, the short side direction of the positive electrode 22 and the negative electrode 24 (in...). Figure 5 The length of the main body 20a in the width direction (Y) is shown in the middle.

[0074] like Figure 1 , 2 As shown in Figure 5, the wound electrode body 20 is disposed inside the outer casing 12 with its winding axis WL parallel to the width direction Y. In this embodiment, the wound electrode body 20 is disposed inside the outer casing 12 with its winding axis WL parallel to the bottom 12a and orthogonal to the second sidewall 12c. Furthermore, both ends of the wound electrode body 20 along the direction of the winding axis WL (hereinafter also referred to as the "winding axis direction") face the second sidewall 12c of the outer casing 12. In this specification, the side closest to the positive electrode current collector 50 ( Figure 2 , 4 The end of the wound electrode body 20 (e.g., the main body 20a) facing the second sidewall 12c (on the left side of the width direction Y) is referred to as the "first end 201". The side closest to the negative electrode current collector 60 ( Figure 2 , 4 The end of the electrode body 20 (e.g., the main body 20a) facing the second sidewall 12c (to the right of the width direction Y) is called the "second end 202".

[0075] The separator 26 is a component that insulates the positive electrode active material layer 22a of the positive electrode 22 from the negative electrode active material layer 24a of the negative electrode 24. The separator 26 forms the outer surface of the wound electrode body 20. As the separator 26, for example, a porous sheet made of resin composed of polyolefin resins such as polyethylene (PE) and polypropylene (PP) is used. As the separator 26, for example, a separator having a substrate (the porous sheet made of the resin) and an adhesive layer disposed on the substrate can be used.

[0076] The positive electrode 22 is, for example, a positive electrode plate having a long strip-shaped positive electrode current collector foil 22c (e.g., aluminum foil) 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 also be provided on one side edge in the width direction Y of the positive electrode 22 as needed. Furthermore, the materials constituting the positive electrode active material layer 22a and the positive electrode protective layer 22p can be materials used in such secondary batteries (in this embodiment, lithium-ion secondary batteries) without particular limitation, and do not represent the technology disclosed herein, so detailed descriptions are omitted here.

[0077] At one end of the positive electrode current collector foil 22c in the width direction Y ( Figure 5 Multiple positive electrode tabs 22t are provided at the left end. The multiple positive electrode tabs 22t are respectively oriented towards one side of the width direction Y ( Figure 5The positive electrode tabs 22t protrude from the left side of the positive electrode 22. Multiple positive electrode tabs 22t are spaced apart (intermittently) along the long side of the positive electrode 22. The positive electrode tabs 22t are part of the positive electrode current collector foil 22c, specifically the portion 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 (exposed portion of the current collector foil). In this embodiment, the multiple positive electrode tabs 22t protrude beyond the separator 26 in the width direction Y. For example, at one end of the multiple positive electrode tabs 22t in the width direction Y... Figure 5 The left end) is stacked to form the positive electrode tab group 23 (refer to Figures 2-4 ).like Figure 2 As shown, a positive current collector 50 is connected to the positive electrode tab group 23. (As indicated...) Figures 1-3 As shown, the positive electrode tab group 23, which is coupled to the positive electrode current collector 50, is bent such that the top ends of the plurality of positive electrode tabs 22t constituting the positive electrode tab group 23 are arranged along the second sidewall 12c. Furthermore, in Figure 5 The diagram shows positive electrode tabs 22t that are roughly the same length and shape, but the length and shape of each positive electrode tab 22t can also be different from each other.

[0078] The negative electrode 24 is, for example, a negative electrode plate having a strip-shaped negative electrode current collector foil 24c (e.g., copper foil) and a negative electrode active material layer 24a fixed on at least one surface of the negative electrode current collector foil 24c. Furthermore, the material constituting the negative electrode active material layer 24a can be any material used in such a secondary battery (in this embodiment, a lithium-ion secondary battery) without particular limitation, and does not represent the technology disclosed herein; therefore, detailed description is omitted here.

[0079] At one end of the negative electrode current collector foil 24c in the width direction Y ( Figure 5 Multiple negative electrode tabs 24t are provided at the right end. The multiple negative electrode tabs 24t face one side of the width direction Y. Figure 5 The right side of the negative electrode 24 protrudes. Multiple negative electrode tabs 24t are spaced apart (intermittently) along the long side of the negative electrode 24. The negative electrode tabs 24t are part of the negative electrode current collector foil 24c, specifically the portion of the negative electrode current collector foil 24c where the negative electrode active material layer 24a is not formed (exposed portion of the current collector foil). In this embodiment, the negative electrode tabs 24t protrude beyond the separator 26 in the width direction Y. For example, the multiple negative electrode tabs 24t protrude at one end in the width direction Y (…). Figure 5 The right end of the electrode is stacked to form the negative electrode tab group 25 (refer to the right end of the electrode). Figures 2-4 ).like Figure 2 As shown, a negative electrode current collector 60 is joined to the negative electrode tab assembly 25. The negative electrode tab assembly 25, which is joined to the negative electrode current collector 60, is bent such that the tips of the plurality of negative electrode tabs 24t constituting the negative electrode tab assembly 25 are arranged along the second sidewall 12c. Furthermore, in Figure 5The diagram shows negative electrode tabs 24t that are roughly the same length and shape, but the length and shape of each negative electrode tab 24t can also be different from each other.

[0080] The positive electrode tab 22t and the negative electrode tab 24t can be arranged in a manner that achieves the structure described later, for example, in a wound electrode body 20 made by overlapping and winding the positive electrode 22, the negative electrode 24 and the diaphragm 26. Figure 6 This is a cross-sectional view of the wound electrode body in the first embodiment. Figure 7 This is a top view illustrating the configuration of the electrode tabs in the first embodiment.

[0081] During the above winding process, in this embodiment, the number N of the positive electrode tab 22t stacked in the thickness direction of the winding electrode body 20 is... 1A The number of layers N with the positive electrode 22 1B The ratio (N) 1A / N 1B The ratio (N) satisfies 0.3 to 0.7. 1A / N 1B The preferred thickness is 0.4 to 0.6. In this specification, "the thickness direction of the wound electrode body 20" refers to, for example, in... Figure 6 The direction T in which the electrode and the diaphragm are stacked between the first flat outer surface 2a and the second flat outer surface 2b of the wound electrode body 20 shown is also referred to as the "thickness direction T". The number of layers N of the positive electrode tab 22t is also shown. 1A For example, it can be defined based on the number of overlapping positive electrode tabs 22t when viewed along the thickness direction T. The number of layers N of the positive electrode 22... 1B For example, it can be specified based on the number of layers of the positive electrode body 22m existing between the first flat outer surface 2a and the second flat outer surface 2b of the wound electrode body 20 in the thickness direction T (refer to...). Figure 7 The positive electrode body 22m refers, for example, to the long strip-shaped portion of the positive electrode 22 other than the positive electrode tab 22t.

[0082] Unless otherwise specified, the number N of the positive electrode 22 in the wound electrode body 20 is... 1B For example, the number of pieces can be appropriately set to 20 to 50 (preferably 30 to 40 pieces). In contrast, the positive electrode tab 22t is located at the first end 201 (refer to...). Figure 2 For example, there are more than 10 pieces at this location. The number of layers N of the positive electrode tab 22t is... 1A The upper limit can be compared to (N) 1A / N 1B The method is set to meet the above range. For example, a positive electrode tab of 22t with fewer than 20 tabs is set.

[0083] In order to use the ratio (N) 1A / N 1BThe method of setting in a way that satisfies the above range, for example, regarding the positive electrode 22 with n positive electrode tabs 22t (n is an integer satisfying 10≤n≤20), the length L relative to the long side of the positive electrode 22 can also be appropriately changed. A The length L in this direction of multiple positive electrode tabs 22t n The total ΣL n (That is, L1 + L2 + ... + L) n The proportion of ). Here, the length L is... n This refers to the root width of the positive electrode tab 22t along the long side of the positive electrode 22. "Root of the positive electrode tab 22t" refers, for example, to the boundary between the positive electrode tab 22t and the positive electrode body 22m. "Root width of the positive electrode tab 22t" refers, for example, to the width of the positive electrode tab 22t along the long side of the positive electrode 22 at the boundary. Figure 7 As shown, the k-th (k is an integer satisfying 1≤k≤n) positive electrode tab 22t is located along the long side of the positive electrode 22, from the first end edge 221 towards the second end edge 222. k Root width L k For example, based on the positive electrode tab 22t k The endpoint P of the root k With the other end Q k The shortest distance is used to define it.

[0084] In this embodiment, the length L A Total ΣL n The ratio (ΣL) n / L A The value is set to 0.1 or higher. To more effectively suppress the degradation of the input / output performance of secondary battery 1 and further increase its capacity, the value is set to (ΣL) n / L A More preferably, it is 0.2 or more, and even more preferably 0.3 or more. If improving the bendability of the positive electrode tab 22t is considered, then compared to (ΣL) n / L A For example, it is preferably 0.8 or less, more preferably 0.7 or less, and even more preferably 0.6 or less.

[0085] like Figure 6 As shown, the wound electrode body 20 has a first flat outer surface 2a and a second flat outer surface 2b at both ends in the thickness direction T. The wound electrode body 20, for example, has a first region R on the side of the first flat outer surface 2a and a second region S on the side of the second flat outer surface 2b. Figure 6As shown, the first region R refers to the region in the wound electrode body 20 that is closer to the first flat outer surface 2a than the first surface F1. The second region S refers to the region in the wound electrode body 20 that is closer to the second flat outer surface 2b than the first surface F1. In this specification, "first surface F1" refers to the surface that passes through the winding axis WL of the wound electrode body 20 and is perpendicular to the thickness direction T of the wound electrode body 20 (see reference). Figure 5 , Figure 6 ).

[0086] In this embodiment, in the first region R, the number of layers N of the positive electrode tab 22t is... R1A The number of layers N relative to the positive electrode 22 R1B The proportion A(N) R1A / N R1B The ratio A(N) is 0.8 or higher. R1A / N R1B The value is preferably 0.9 or higher, and the closer it is to 1.0, the more preferred. Furthermore, in this embodiment, in the second region S, the number of layers N of the positive electrode tab 22t is... S1A The number of layers N relative to the positive electrode 22 S1B The proportion C(N) S1A / N S1B The ratio C(N) is below 0.2. S1A / N S1B The preferred value is below 0.1, and the closer it is to 0, the better.

[0087] Regarding the negative electrode 24, in this embodiment, the ratio of the number of stacked negative electrode tabs 24t in each region to the number of stacked negative electrodes 24 is set as follows. Furthermore, for example, from the viewpoint of connection with the negative electrode current collector 60 described later, it is preferable that the length of the negative electrode tab 24t in the short side direction of the negative electrode 24 is greater than the length of the positive electrode tab 22t in that direction. Apart from this, the same structure as the positive electrode side is adopted on the negative electrode side, therefore, repeated descriptions are omitted.

[0088] In this embodiment, in the first region R, the number of layers N of the negative electrode tab 24t is... R2A The number of layers N relative to the negative electrode 24 R2B The proportion B(N) R2A / N R2B The ratio B(N) is below 0.2. R2A / N R2B The value is preferably 0.1 or less, and the closer it is to 0, the more preferred. Furthermore, in this embodiment, in the second region S, the number of layers N of the negative electrode tab 24t is... S2A The number of layers N relative to the negative electrode 24 S2B The proportion D(N) S2A / N S2BThe ratio D(N) is 0.8 or higher. S2A / N S2B The preferred value is 0.9 or higher, and the closer it is to 1.0, the better.

[0089] like Figure 7 As shown, when the positive electrode 22 and the negative electrode 24 overlap with the separator 26, in the short side direction of the electrodes, the multiple negative electrode tabs 24t do not overlap with the positive electrode tabs 22t. When the positive electrode 22, the negative electrode 24, and the separator 26 are overlapped and wound in this configuration of electrode tabs, it is possible to achieve... Figure 6 The structure of the wound electrode body 20 shown.

[0090] In this embodiment, the positional relationship between the negative electrode tab 24t and the two adjacent positive electrode tabs 22t is preferably set as follows: For example... Figure 7 As shown, when the distance from one negative electrode tab 24t to the closer positive electrode tab 22t among the two adjacent positive electrode tabs 22t is defined as W1, and the distance to the other positive electrode tab 22t is defined as W2, the ratio of distance W1 to distance W2 (W2 / W1) is, for example, greater than 1.0 and less than 1.5. From the viewpoint of better achieving the effect of the technology disclosed herein, the ratio (W2 / W1) is preferably less than 1.2, more preferably less than 1.1. Furthermore, distance W1 is, for example, the distance from the center point M of the root of the negative electrode tab 24t to the center point N1 of the root of the closer positive electrode tab 22t. Distance W2 is, for example, the distance from the center point M to the center point N2 of the root of the other positive electrode tab 22t. The center point M is, for example, the center point between the endpoint I of one of the roots of the negative electrode tab 24t and the endpoint J of the other. "The root of the negative electrode tab 24t" refers, for example, to the boundary between the negative electrode tab 24t and the negative electrode body (not shown).

[0091] like Figure 6 As shown, multiple positive electrode tabs 22t are bundled at a position closer to the first flat outer surface 2a than the first surface F1, and bent such that the portion closer to the top of the bundled portion faces the second flat outer surface 2b. In this embodiment, the multiple positive electrode tabs 22t engage with the second current collector portion 52 of the positive current collector member 50 at a position closer to the top of the bundled portion. Furthermore, as... Figure 6 As shown, a plurality of negative electrode tabs 24t are bundled at a position closer to the first flat outer surface 2a than the first surface F1, and bent such that the portion closer to the top of the bundled portion faces the second flat outer surface 2b. In this embodiment, the plurality of negative electrode tabs 24t engage with the second current collector portion 62 of the negative electrode current collector member 60 at a position closer to the top of the bundled portion.

[0092] That is, in Figure 6, 7 In the illustrated embodiment, a plurality of positive electrode tabs 22t are mainly disposed in the first region R, and a plurality of negative electrode tabs 24t are mainly disposed in the second region S. In the wound electrode body 20, by separating the region (first region R) where the plurality of positive electrode tabs 22t are disposed and the region (second region S) where the plurality of negative electrode tabs 24t are disposed, for example, deviations in the distance between the closest positive electrode tabs 22t and negative electrode tabs 24t can be suppressed. Therefore, in this embodiment, the capacity of the secondary battery 1 can be increased, and deviations in the current density distribution within the wound electrode body 20 can be suppressed.

[0093] Although not specifically limited, the top of the positive electrode tab 22t can be positioned closer to the second flat outer surface 2b than the first surface F1. This ensures sufficient contact allowance in the positive electrode tab 22t, enabling a more stable connection. Furthermore, as... Figure 6 As shown, preferably, at least a portion of the area where the negative electrode tab 24t is bound is positioned closer to the first flat outer surface 2a than the first surface F1, and the top end of the negative electrode tab 24t is positioned closer to the second flat outer surface 2b than the first surface F1. This ensures sufficient engagement allowance in the negative electrode tab 24t, enabling a more stable connection.

[0094] like Figure 5 , Figure 6 As shown, the shortest distance H1 between the first end 201 of the main body 20a and the positive electrode current collector 50 in the winding axis direction is shorter than the shortest distance H2 between the second end 202 and the negative electrode current collector 60. For example, when the length of the positive electrode tab 22t in the protruding direction is shorter than the length of the negative electrode tab 24t in that direction, by setting the foil collection space of the positive electrode tab 22t to be smaller, the size of the wound electrode body 20 can be increased, thereby increasing the capacity of the secondary battery 1.

[0095] Figure 8 This is a schematic diagram illustrating the connection between the electrode tab and the electrode current collector. For example... Figure 8 As shown, after fabricating the wound electrode body 20, the wound electrode body 20 is connected to the positive current collector 50 and the negative current collector 60. In this connection, for example, firstly, using a foil clamp (not shown), multiple positive electrode tabs 22t are bundled together on the first flat outer surface 2a side. Next, the bundled positive electrode tabs 22t are overlapped with the second current collector portion 52 of the positive current collector 50. Then, from the overlap direction, the overlapping positive electrode tabs 22t and the second current collector portion 52 are clamped together using bonding probes 3a and 3b, and energy is applied to perform bonding (connection). Bonding (connection) is also performed on the negative side in the same way. This bonding can be achieved using conventionally known methods such as ultrasonic bonding, laser welding, or resistance welding.

[0096] When considering the bending of the electrode tabs as described later, the joining is preferably performed with the contact surfaces of the bundled positive electrode tabs 22t with the second current collector 52 and the contact surfaces of the bundled negative electrode tabs 24t with the second current collector 62 arranged on approximately the same plane. Furthermore, it is even more preferable that the joining is performed with these two contact surfaces arranged on approximately the same plane as the first flat outer surface 2a of the wound electrode body 20. By taking this into account, it is possible to pre-design the length of the electrode tabs to prevent them from becoming excessive or insufficient while maintaining good productivity.

[0097] After the multiple positive electrode tabs 22t, which are bundled as described above, are joined together, the multiple positive electrode tabs 22t are bent, and the surface of the second current collector portion 52 of the positive current collector member 50 with the positive electrode tabs 22t is aligned with the first end portion 201 of the wound electrode body 20. Similarly, after the multiple negative electrode tabs 24t, which are bundled as described above, are joined together, the multiple negative electrode tabs 24t are bent, and the surface of the second current collector portion 62 of the negative current collector member 60 with the negative electrode tabs 24t is aligned with the second end portion 202 of the wound electrode body 20.

[0098] The secondary battery 1 can be used for various purposes, such as serving as a power source (drive power source) for motors in passenger cars, trucks, and other vehicles. There are no particular limitations on the type of vehicle; examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs).

[0099] As described above, according to the technology disclosed herein, a secondary battery 1 is provided, which has a flat wound electrode body 20 formed by stacking and winding a positive electrode 22 and a negative electrode 24 separated by a separator 26. The secondary battery 1 has a positive electrode current collector 50 connected to the positive electrode 22. The wound electrode body 20 has a plurality of positive electrode tabs 22t connected to the positive electrode 22 at a first end 201 in the winding axis direction. More than 10 positive electrode tabs 22t are provided. The plurality of positive electrode tabs 22t are stacked. The number N of the stacked positive electrode tabs 22t in the thickness direction T of the wound electrode body 20 is... 1A The number of layers N with the positive electrode 22 1B The ratio (N) 1A / N 1B The value is between 0.3 and 0.7. Multiple positive electrode tabs 22t are connected to the positive current collector 50 in a bent state.

[0100] In other words, in the secondary battery 1, by setting the number of positive electrode tabs 22t stacked in the wound electrode body 20 to 10 or more, and setting the ratio of the number of positive electrode tabs 22t stacked to the number of positive electrode stacked to 0.3 to 0.7, sufficient output can be maintained, and the size of the current collector near the positive electrode tabs 22t can be reduced. This allows for space saving near the connection between the positive electrode tab group 23 and the positive current collector member 50. Therefore, the size of the wound electrode body 20 can be increased, thereby increasing the capacity of the secondary battery 1.

[0101] Furthermore, when the surface passing through the winding axis WL of the winding electrode body 20 and perpendicular to the thickness direction T of the winding electrode body 20 is designated as the first surface F1, the first surface F1 intersects with the positive electrode current collector 50. By bending the multiple positive electrode tabs 22t, the first surface F1 intersects with the positive electrode current collector 50. Therefore, it is possible to achieve better space saving near the connection between the positive electrode tab group 23 and the positive electrode current collector 50, thereby enabling the secondary battery 1 to achieve a higher capacity.

[0102] In this embodiment, the first electrode is a positive electrode 22, and the second electrode is a negative electrode 24. That is, the first electrode tab is a positive electrode tab 22t, and the second electrode tab is a negative electrode tab 24t. For example, the metal constituting the positive electrode tab 22t (aluminum, aluminum alloy, or stainless steel, etc.) has a higher resistance than the metal constituting the negative electrode tab 24t (copper or copper alloy, etc.). Therefore, for example, by making the positive electrode tab 22t shorter than the negative electrode tab 24t, the internal resistance of the secondary battery 1 can be reduced.

[0103] However, it is also possible that the first electrode is the negative electrode 24 and the second electrode is the positive electrode 22. That is, it is also possible that the first electrode tab is the negative electrode tab 24t and the second electrode tab is the positive electrode tab 22t. For example, the positive electrode tab 22t can be made of a metal with a yield strength lower than that of the negative electrode tab 24t. Therefore, it can be considered that when the wound electrode body 20 moves within the battery casing 10 due to vibration, impact, etc., it is repeatedly subjected to bending and stretching, and the risk of breakage of the positive electrode tab 22t is higher. Therefore, for example, by making the positive electrode tab 22t shorter than the negative electrode tab 24t, the risk of electrode tab breakage can be reduced.

[0104] The above provides a detailed description of specific examples of the technology disclosed herein, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes technologies obtained by various modifications and alterations to the specific examples described above. Other embodiments of the technology disclosed herein will be described below. Furthermore, in the following embodiments, the content other than that described above is the same as that described in the first embodiment above, and therefore, repeated descriptions are omitted here.

[0105] Second Implementation Method

[0106] In the first embodiment described above, a plurality of positive electrode tabs 22t are mainly disposed in the first region R of the wound electrode body 20, and a plurality of negative electrode tabs 24t are mainly disposed in the second region S. However, this is not a limitation. Figure 9 This is a cross-sectional view of the wound electrode body in the second embodiment. Figure 9 The following situation is shown: In the wound electrode body 220, with the first surface F1 as a reference, the first flat outer surface 2a side in the thickness direction T is designated as the first region R, and the second flat outer surface 2b side is designated as the second region S.

[0107] like Figure 9 As shown, in the first region R, the number of layers N of the positive electrode tab 22t is... R1A The number of layers N relative to the positive electrode 22 R1B The proportion A(N) R1A / N R1B The ratio A(N) is 0.8 or higher. R1A / N R1B The preferred value is 0.9 or higher, and the closer to 1.0, the better. Additionally, in this region, the number of layers N of the negative electrode tab 24t is... R2A The number of layers N relative to the negative electrode 24 R2B The proportion B(N) R2A / N R2B The ratio B(N) is 0.8 or higher. R2A / N R2B The preferred value is 0.9 or higher, and the closer it is to 1.0, the better.

[0108] In addition, such as Figure 9 As shown, in the second region S, the number of layers N of the positive electrode tab 22t is... S1A The number of layers N relative to the positive electrode 22 S1B The proportion C(N) S1A / N S1B The ratio C(N) is below 0.2. S1A / N S1B The preferred value is below 0.1, and the closer to 0, the more preferred. Additionally, in this region, the number of layers N of the negative electrode tab 24t is... S2A The number of layers N relative to the negative electrode 24 S2B The proportion D(N) S2A / N S2B The ratio D(N) is 0.8 or higher. S2A / N S2B The preferred value is 0.9 or higher, and the closer it is to 1.0, the better.

[0109] Figure 10 This is a top view illustrating the configuration of the electrode tabs in the second embodiment. (Example) Figure 10As shown, when the positive electrode 22 and the negative electrode 24 overlap with the separator 26, in the short side direction of the electrodes, a portion of the multiple negative electrode tabs 24t overlap with the positive electrode tab 22t, while the other negative electrode tabs 24t do not overlap with the positive electrode tab 22t. When the positive electrode 22, the negative electrode 24, and the separator 26 are overlapped and wound in this configuration of electrode tabs, it is possible to achieve... Figure 9 The structure of the wound electrode body 220 shown.

[0110] In this embodiment, a plurality of positive electrode tabs 22t are mainly disposed in the first region R of the wound electrode body 220, and a plurality of negative electrode tabs 24t are disposed in either the first region R or the second region S. In this embodiment, the number of positive electrode tabs 22t is less than the number of negative electrode tabs 24t. By using the wound electrode body 220 with this structure, the size of the structure near the junction of the positive electrode tab group 23 and the positive current collector 50 can be reduced, thereby increasing the capacity of the secondary battery 1. In addition to this effect, deviations in the distribution of current density in the wound electrode body 220 can also be suppressed.

[0111] Third Implementation Method

[0112] In the first and second embodiments described above, a plurality of positive electrode tabs 22t are provided at the first end 201 of the wound electrode bodies 20 and 220, and a plurality of negative electrode tabs 24t are provided at the second end 202. However, this is not a limitation. Figure 11 This is a perspective view of the wound electrode body in the third embodiment. (See image below.) Figure 11 As shown, in the wound electrode body 320, a plurality of positive electrode tabs 22t and a plurality of negative electrode tabs 24t are provided at the first end 201. In this embodiment, the plurality of positive electrode tabs 22t are provided in a first region R on the side of the first flat outer surface 2a, and the plurality of negative electrode tabs 24t are provided in a second region S on the side of the second flat outer surface 2b. When the wound electrode body 320 of this embodiment is used as the wound electrode body, the positive electrode current collector 50 and the negative electrode current collector 60 can be provided on the inner surface of the sealing plate 14. Even when using the wound electrode body 320, the effects of the technology disclosed herein can be achieved. Furthermore, in this embodiment, similar to the second embodiment described above, the following structure can be adopted: the plurality of positive electrode tabs 22t are mainly provided in the first region R of the wound electrode body 320, and the plurality of negative electrode tabs 24t are provided in either the first region R or the second region S.

[0113] Other Implementation Methods

[0114] In the above embodiment, for both poles, the tips of the electrode tabs that are engaged with the electrode current collectors all face the same direction (e.g., the side of the second flat outer surface 2b). However, this is not a limitation. For example, the tip of the positive electrode tab 22t may be arranged to be the side of the second flat outer surface 2b, and the tip of the negative electrode tab 24t may be arranged to be the side of the first flat outer surface 2a.

Claims

1. A secondary battery, the secondary battery having a flat, wound electrode body formed by stacking and winding a first electrode and a second electrode different from the first electrode, separated by a separator, wherein, The secondary battery has a first current collector connected to the first electrode. The wound electrode body has a plurality of first electrode tabs at its first end in the winding axis direction, which are connected to the first electrode. The first electrode tab has more than 10 pieces. Multiple first electrode tabs are stacked. The number of layers N of the first electrode tab in the thickness direction of the wound electrode body 1A The number of layers N with the first electrode 1B The ratio (N) 1A / N 1B It satisfies 0.3~0.

7. Multiple first electrode tabs are connected to the first electrode current collector in a bent state. The wound electrode body has a first flat outer surface and a second flat outer surface at both ends in the thickness direction of the wound electrode body. The wound electrode body has a plurality of second electrode tabs connected to the second electrode at a second end that is different from the first end or in the direction of the winding shaft, and the plurality of second electrode tabs are stacked. When the surface passing through the winding shaft of the winding electrode body and perpendicular to the thickness direction of the winding electrode body is designated as the first surface... In the wound electrode body, when the region closer to the first flat outer surface than the first surface is designated as the first region, and the region closer to the second flat outer surface than the first surface is designated as the second region,... In the first region, the ratio A of the number of layers of the first electrode tab to the number of layers of the first electrode is 0.8 or more, and the ratio B of the number of layers of the second electrode tab to the number of layers of the second electrode is 0.8 or more. In the second region, the ratio C of the number of layers of the first electrode tab to the number of layers of the first electrode is 0.2 or less, and the ratio D of the number of layers of the second electrode tab to the number of layers of the second electrode is 0.8 or more. Multiple first electrode tabs are bundled together on the first flat outer surface side. Multiple second electrode tabs are bundled together on the first flat outer surface side.

2. The secondary battery according to claim 1, wherein, When the surface that passes through the winding shaft of the wound electrode body and is perpendicular to the thickness direction of the wound electrode body is designated as the first surface, the first surface intersects with the first electrode current collector.

3. The secondary battery according to claim 1 or 2, wherein, The secondary battery has a battery casing that internally houses the wound electrode body. The battery casing has: An outer casing having a bottom, an opening, a pair of first sidewalls, and a pair of second sidewalls; and A sealing plate that seals the opening.

4. The secondary battery according to claim 1, wherein, Multiple first electrode tabs are bent such that the portion of the first electrode tab closest to the top of the bound portion faces the second flat outer surface. Multiple second electrode tabs are bent toward the second flat outer surface in a manner that the portion closer to the top side of the bound portion is oriented toward the second flat outer surface.

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