Power storage device and method for manufacturing power storage device

Abstract

An electricity storage device includes an electrode body (14) in which a first electrode plate and a second electrode plate are wound with a separator interposed therebetween, and an exterior body (15) that accommodates the electrode body. The first electrode plate has a first core body and a first mixture layer formed on a surface of the first core body. A first exposed portion in which the first core body is exposed is provided at a side end portion in a winding axis direction of the electrode body. The first exposed portion has a folded portion that is folded in such a manner that it is folded back one or more times and overlaps. The folded portion is inclined in a first direction, and the folded portions at adjacent winding portions of the first electrode plate overlap, thereby forming a current collecting portion at the side end portion in the winding axis direction.

Description

Technical Field

[0001] This disclosure relates to an energy storage device and a method for manufacturing the energy storage device. Background Technology

[0002] Previously, a cylindrical secondary battery and other energy storage devices were known, which included an electrode body formed by winding a positive electrode plate and a negative electrode plate separated by a separator, and an outer casing housing the electrode body.

[0003] Patent Document 1 describes the following: In a cylindrical battery, the upper end of the internal current collector on the positive electrode side forms a side end without active material. This side end is bent inward at the upper end, and the bent portion is welded to the disc-shaped current collector in one step. The current collector is then welded to the disc portion of the positive terminal, thereby welding the positive terminal to the internal current collector.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 11-185725 Summary of the Invention

[0007] In the structure described in Patent Document 1, there is room for improvement in terms of enhancing the reliability of the energy storage device.

[0008] The purpose of this disclosure is to improve reliability in energy storage devices.

[0009] The energy storage device disclosed herein includes: an electrode body formed by stacking a first electrode plate and a second electrode plate in a first direction with a separator; and an outer casing housing the electrode body, wherein the first electrode plate includes a first core and a first adhesive layer formed on the surface of the first core, a first exposed portion of the first core is disposed at one end in the winding axis direction of the electrode body, the first exposed portion has a folded portion formed by folding back and overlapping once or more, the folded portion tilting in the first direction, and the folded portions of the first electrode plate at adjacent winding portions in the first direction overlap, thereby forming a current collecting portion at one end in the winding axis direction.

[0010] The energy storage device disclosed herein can achieve improved reliability. Attached Figure Description

[0011] Figure 1 This is a cross-sectional view along the axial direction of an energy storage device, namely a cylindrical secondary battery, as an example of an implementation method.

[0012] Figure 2 It is Figure 1The diagram shown is a partial unfolded view of the electrode body of the cylindrical secondary battery, illustrating the state before the formation of the positive and negative current collectors.

[0013] Figure 3 It is shown by omitting a portion. Figure 1 Enlarged view of part A.

[0014] Figure 4 From Figure 1 The electrode body and the upper insulating plate are removed, and the image is viewed from above.

[0015] Figure 5 From Figure 4 The diagram shows the result after removing the upper insulating plate.

[0016] Figure 6 This is an unfolded diagram of the positive electrode plate before the positive electrode fold is formed.

[0017] Figure 7 (a) is Figure 6 (b) is an enlarged view of section C of (a) showing the state in which a positive electrode fold is formed in the positive electrode exposed part during the folding step.

[0018] Figure 8 This is a cross-sectional view showing the case where adjacent rotating portions of the positive electrode plate overlap during the winding process.

[0019] Figure 9 The diagram shows a cross-sectional view of the following situation: During the tilting step, at one end of the electrode body in the winding axis direction, the positive electrode folds at multiple rotating portions of the positive electrode plate tilt inwards, and the positive electrode folds at adjacent rotating portions of the positive electrode plate overlap.

[0020] Figure 10 It is a cross-sectional view showing the state in which the positive electrode folds at multiple rotating parts of the positive electrode plate are welded together in the welding process.

[0021] Figure 11 This illustrates how, during the tilting step, the positive electrode folds at multiple rotating portions of the positive electrode plate are tilted relative to... Figure 9 A schematic diagram showing the tilted position closer to the inner circumference of the electrode. Detailed Implementation

[0022] Conventionally, a known structure exists in an energy storage device with a wound electrode body, in which the exposed portion of the electrode plate protrudes from one end in the winding axis direction and is joined to a current collector. With this structure, unlike the case where a connecting lead is led out and joined to a portion of the electrode plate in the winding direction and then joined to the current collector, it is possible to achieve low resistance. However, since the various winding portions of the exposed portion of the electrode plate are connected only in the winding direction, the rigidity of the portion formed by the exposed portion at the end of the electrode plate in the winding axis direction may be low. Therefore, the shape and position of the portion formed by the exposed portion become unstable, and there is room for improvement in terms of reliability.

[0023] Through repeated and in-depth research, the inventors discovered that reliability can be improved by the following operation: a first exposed portion of the first core is arranged at one end of the electrode body in the winding axis direction. The first exposed portion has a folded portion formed by folding back and forth at least once and overlapping. The folded portion is tilted towards the stacking direction of the electrode body, i.e., the first direction. The folded portions at adjacent winding portions of the electrode body overlap, thereby forming a current collector at one end of the electrode body in the winding axis direction. Specifically, by increasing the rigidity of the current collector formed by the exposed portion, the shape and position of the current collector can be stabilized, thus achieving the aforementioned effect.

[0024] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description, specific shapes, materials, values, directions, etc., are examples used to facilitate understanding of the present invention and can be appropriately varied depending on the specifications of the energy storage device. Furthermore, the term "approximately" is used hereafter to mean, for example, that cases considered substantially the same, in addition to cases that are completely identical. Moreover, in the following cases, when multiple embodiments and modifications are included, it is initially envisioned that their characteristic parts be appropriately combined. Additionally, the energy storage device described below as an embodiment is a cylindrical secondary battery, but the energy storage device disclosed herein is not limited to cylindrical secondary batteries; various structures can be adopted as long as the energy storage device has a wound electrode body and an outer casing housing the electrode body. For example, the energy storage device can also be an alkaline battery or a capacitor.

[0025] Figure 1 This is a cross-sectional view along the axial direction of the battery 10 of the energy storage device as an embodiment. Figure 2 This is a view showing a portion of the electrode body 14 of the battery 10 unfolded, and a perspective view showing the state before the formation of the positive electrode current collector and the negative electrode current collector. Figure 3 It is shown by omitting a portion. Figure 1 Enlarged view of part A. Figure 4 From Figure 1Figure showing the removal of electrode body 14 and upper insulating plate 19, viewed from above. Figure 5 From Figure 4 The diagram shows the result after removing the upper insulating plate 19.

[0026] like Figure 1 , Figure 2 As shown, battery 10 is a non-aqueous electrolyte secondary battery, comprising a wound electrode body 14, a non-aqueous electrolyte (not shown), a metal can-shaped outer casing 15, and a sealing body 16 fixed to the open end of the outer casing 15. The wound electrode body 14 has a positive electrode plate 11, a negative electrode plate 12, and two separators 13a and 13b, with the positive electrode plate 11 and the negative electrode plate 12 wound into a spiral shape with the separators 13a and 13b in between. Hereinafter, the sealing body 16 side will be referred to as "upper" and the bottom side of the outer casing 15 as "lower". The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.

[0027] like Figure 2 As shown, the electrode body 14 has a wound structure formed by stacking and winding elongated positive electrode plates 11 and 12 in a first direction, separated by two elongated spacers 13a and 13b. Alternatively, the electrode body of this disclosure can also be constructed by alternately stacking multiple single-piece positive electrode plates and multiple negative electrode plates separated by multiple spacers. In this case, the folded portions formed at the exposed portions of each electrode plate (described later) are tilted in the stacking direction. Furthermore, the exposed positive electrode portion of the positive electrode plate 11 protrudes upward relative to the negative electrode plate 12 and the spacers 13a and 13b, while the exposed negative electrode portion of the negative electrode plate 12 protrudes downward relative to the positive electrode plate 11 and the spacers 13a and 13b. One of the two spacers 13a and 13b has its spacer 13a protruding upward relative to the other spacer 13b, and the other spacer 13b protruding downward relative to the first spacer 13a. Hereinafter, the two separators 13a and 13b will sometimes be referred to as separator 13.

[0028] The positive electrode plate 11, from the end of the winding start side in the long side direction of the electrode plate to the end of the winding end side, has a positive electrode exposed portion 34 at one end in the winding axis direction (hereinafter, sometimes referred to as the axial direction), i.e., the upper end, where the positive electrode compound layer 32 is not provided, thus exposing the positive electrode core 30. Furthermore, at the upper end of the positive electrode plate 11, a positive electrode protection layer 36 is provided between the positive electrode compound layer 32 and the positive electrode exposed portion 34 to achieve short-circuit suppression of the positive electrode core 30. However, the positive electrode protection layer 36 may be omitted in the energy storage device of this disclosure. In addition, in this embodiment, the case where one side in the winding axis direction is the upper side is described, but the case where one side in the winding axis direction is the lower side may also be described.

[0029] The negative electrode plate 12, from the end of the long side of the plate in the winding start direction to the end of the winding end direction, has a negative electrode exposure portion 44 at the lower end on the other side in the axial direction, where the negative electrode compound layer 42 is not provided, thus exposing the negative electrode core 40. Therefore, the upper end of the electrode body 14 in the axial direction (width direction of the positive electrode plate) is formed by the positive electrode exposure portion 34, and the lower end of the electrode body 14 in the axial direction is formed by the negative electrode exposure portion 44. In addition, at the lower end of the negative electrode plate 12, a negative electrode protection layer 46 is provided between the negative electrode compound layer 42 and the negative electrode exposure portion 44 to achieve short-circuit suppression of the negative electrode core 40. However, the negative electrode protection layer 46 may be omitted in the energy storage device of this disclosure.

[0030] In this embodiment, the positive electrode plate 11 corresponds to the first electrode plate, and the negative electrode plate 12 corresponds to the second electrode plate. The positive electrode core 30 corresponds to the first core, and the positive electrode flux layer 32 corresponds to the first flux layer. The negative electrode core 40 corresponds to the second core, and the negative electrode flux layer 42 corresponds to the second flux layer. Alternatively, the first electrode plate may be the negative electrode plate 12, and the second electrode plate may be the positive electrode plate 11.

[0031] The positive electrode exposed portion 34, as described later, has a positive electrode folded portion formed by folding back and forth more than once and overlapping. The positive electrode folded portion tilts towards the inner periphery of the electrode body 14, and the positive electrode folded portions at adjacent rotating portions of the positive electrode plate 11 overlap, thereby forming a positive electrode current collector 37 at the upper end in the axial direction. The negative electrode exposed portion 44, as described later, has a negative electrode folded portion formed by folding back and forth more than once and overlapping. The negative electrode folded portion tilts towards the inner periphery of the electrode body 14, and the negative electrode folded portions at adjacent rotating portions of the negative electrode plate 12 overlap, thereby forming a negative electrode current collector 47 at the lower end in the axial direction.

[0032] The non-aqueous electrolyte has ionic conductivity (e.g., lithium-ion conductivity). The non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte (non-aqueous electrolyte solution) and can also be a solid electrolyte using a gel polymer, etc. Battery 10 is preferably a lithium-ion battery. The electrolyte salt may be, for example, lithium salts such as LiBF4 and LiPF6. The non-aqueous solvent may be, for example, esters, ethers, nitriles, amides, and mixtures of two or more of these solvents, such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP). The non-aqueous solvent may also contain a halogen-substituted form, in which at least a portion of the hydrogen atoms of the aforementioned solvents are replaced by halogen atoms such as fluorine.

[0033] Examples of halogen substitutes include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylic acid esters such as methyl fluoropropionate (FMP). Considering factors such as suppressing the decrease in charge-discharge cycle characteristics of the non-aqueous electrolyte secondary battery or improving its input characteristics, the non-aqueous electrolyte preferably contains 5% by mass or more of FEC relative to the mass of the non-aqueous electrolyte, and more preferably contains 5% to 15% by mass of FEC relative to the mass of the non-aqueous electrolyte.

[0034] As solid electrolytes, examples include solid or gel-like polymer electrolytes and inorganic solid electrolytes. Polymer electrolytes, for example, contain lithium salts and a matrix polymer, or contain non-aqueous solvents, lithium salts, and a matrix polymer. As a matrix polymer, for example, a polymer material that gels by absorbing non-aqueous solvents is used. As a polymer material, for example, fluoropolymers, acrylic resins, polyether resins, etc., are used. As inorganic solid electrolytes, for example, materials known in all-solid-state lithium-ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) are used.

[0035] The positive electrode plate 11 has a strip-shaped positive electrode core 30 and positive electrode additive layers 32 formed on both sides of the positive electrode core 30. For the positive electrode core 30, a foil of a metal stable within the potential range of the positive electrode plate 11, such as aluminum or an aluminum alloy, or a thin film of the metal disposed on its surface can be used. The thickness of the positive electrode core 30 is, for example, 10 μm or more and 30 μm or less. The positive electrode additive layer 32 contains a positive electrode active material, a conductive agent, and a binder. For example, the positive electrode plate 11 can be manufactured by coating the positive electrode core 30 with a positive electrode additive slurry containing a positive electrode active material, a conductive agent, and a binder, and after the coating is dried, compression is performed to form the positive electrode additive layer 32 on both sides of the positive electrode core 30. Alternatively, the positive electrode additive layer 32 may be formed only on one side of the positive electrode core 30. The thickness of the positive electrode compound layer 32 is, for example, more than 10 μm and less than 150 μm on one side of the positive electrode core 30.

[0036] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Examples of metal elements contained in the lithium-containing metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. A preferred example of a lithium-containing metal composite oxide is one containing at least one of Ni, Co, Mn, and Al.

[0037] Examples of conductive agents included in the positive electrode binder layer 32 include carbon materials such as carbon black, acetylene black, Ketjen black, and graphite. Examples of binders included in the positive electrode binder layer 32 include fluoropolymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These resins may also be used simultaneously with cellulose derivatives such as carboxymethyl cellulose (CMC) or its salts, and polyethylene oxide (PEO).

[0038] On both sides of the upper end of the positive electrode core 30, a positive electrode protective layer 36 is provided between the positive electrode additive layer 32 and the exposed positive electrode portion 34. The positive electrode protective layer 36 is configured to contain, for example, inorganic materials such as alumina, resins such as polyvinylidene fluoride (PVdF), and conductive additives such as acetylene black (AB) and carbon black (CB) in a predetermined ratio. For example, the positive electrode protective layer 36 can be configured such that the mass ratio of the contained inorganic materials to the conductive additives is 100:0.5. Furthermore, the conductive additives may be omitted from the positive electrode protective layer 36. The positive electrode protective layer 36 can be provided on the surface of the positive electrode core 30, and various positive electrode protective layers can be used as long as they have the function of short-circuit suppression of the positive electrode core 30.

[0039] The negative electrode plate 12 has a strip-shaped negative electrode core 40 and negative electrode binder layers 42 formed on both sides of the negative electrode core 40. The negative electrode core 40 can be made of a foil of a metal stable within the potential range of the negative electrode plate 12, such as copper or a copper alloy, or a thin film of the metal disposed on its surface. The thickness of the negative electrode core 40 is, for example, 5 μm or more and 30 μm or less. The negative electrode binder layer 42 contains a negative electrode active material and a binder. For example, the negative electrode plate 12 can be manufactured by coating a negative electrode binder slurry containing a negative electrode active material and a binder onto the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode binder layer 42 on both sides of the negative electrode core 40. Alternatively, the negative electrode binder layer 42 may be formed only on one side of the negative electrode core 40. The thickness of the negative electrode binder layer 42 is, for example, 10 μm or more and 150 μm or less on one side of the negative electrode core 40.

[0040] For the negative electrode active material, carbon materials that reversibly absorb and release lithium ions are typically used. Preferred carbon materials include natural graphite such as flake graphite, block graphite, and amorphous graphite, as well as artificial graphite such as block graphite and graphitized mesophase carbon microspheres. The negative electrode additive layer 42 may also contain silicon (Si) materials as the negative electrode active material. Alternatively, metals other than Si alloyed with lithium, alloys containing such metals, and compounds containing such metals may also be used as the negative electrode active material.

[0041] As the binder included in the negative electrode binder layer 42, similar to the case of the positive electrode plate 11, fluoropolymers, PAN, polyimide resins, acrylic resins, polyolefin resins, etc., can also be used, with styrene-butadiene rubber (SBR) or its modifiers being preferred. The negative electrode binder layer 42 may also include, for example, CMC or its salts, polyacrylic acid (PAA) or its salts, polyvinyl alcohol, etc., in addition to SBR.

[0042] On both sides of the lower end of the negative electrode core 40 (in the width direction), a negative electrode protective layer 46 is provided between the negative electrode mixture layer 42 and the exposed negative electrode portion 44. The negative electrode protective layer 46 can have the same structure as the positive electrode protective layer 36. The negative electrode protective layer 46 can be provided on the surface of the negative electrode core 40; any negative electrode protective layer can be used as long as it has the function of short-circuit suppression of the negative electrode core 40.

[0043] As the separator 13, a porous sheet with ion permeability and insulation is used. Specific examples of porous sheets include microporous films, woven fabrics, and nonwoven fabrics. As the material of the separator 13, polyolefin resins such as polyethylene and polypropylene, and cellulose are preferred. The separator 13 can be either a single-layer structure or a multilayer structure. A heat-resistant layer may also be formed on the surface of the separator 13.

[0044] like Figure 1 As shown, a positive electrode current collector 37 and a negative electrode current collector 47 are respectively provided at the upper and lower ends of the electrode body 14 along its axial direction. As described later, the positive electrode folding portion formed in the positive electrode exposed portion 34 tilts inward to the inner circumference, and the positive electrode folding portions at adjacent rotating portions of the positive electrode plate 11 overlap from the outermost circumference to the innermost circumference of the positive electrode plate 11 and are integrated by welding, thereby forming the positive electrode current collector 37. Alternatively, the positive electrode folding portion may tilt outward to the outer circumference. Alternatively, some of the positive electrode folding portions arranged radially in the electrode body may tilt inward to the inner circumference, and some may tilt outward to the outer circumference.

[0045] As will be described later, the negative electrode folding portion formed in the negative electrode exposed portion 44 tilts inward to the inner periphery, and the negative electrode folding portions at the adjacent rotating portions of the negative electrode plate 12 overlap from the outermost periphery to the innermost periphery and are integrated by welding, thereby forming the negative electrode current collector portion 47.

[0046] Additionally, the battery 10 has an upper insulating plate 19 on the axial upper side of the positive electrode current collector 37. This insulating plate 19 is circular and has a cross-shaped through hole 19a. Alternatively, the insulating plate 19 may be omitted. One end of the positive electrode lead 20 is joined to the upper surface of the positive electrode current collector 37 by welding or the like. The positive electrode lead 20 extends towards the sealing body 16 through the through hole 19a of the insulating plate 19, and the other end of the positive electrode lead 20 is connected to the lower surface of the filter 22 of the sealing body 16 by welding or the like. The cover 26, which constitutes the top plate of the sealing body 16, is electrically connected to the filter 22. Thus, the positive electrode current collector 37 is electrically connected to the cover 26, and the cover 26 becomes the positive terminal. The positive electrode lead 20 is a conductive member made of a metal, such as aluminum. Alternatively, the positive electrode current collector in this disclosure may be joined to a positive electrode current collector plate, which is a metal plate, and the positive electrode current collector plate may be connected to the positive electrode lead. At this point, the insulating plate is positioned on top of the positive current collector. Alternatively, the positive current collector can be connected to the filter without using a positive lead.

[0047] Furthermore, the battery 10 has an insulating plate 17 on the axial lower side of the negative electrode current collector 47. This insulating plate 17 is circular and has a cross-shaped through hole 17a. Alternatively, the insulating plate 17 may be omitted. One end of the negative electrode lead 28 is joined to the lower surface of the negative electrode current collector 47 by welding or the like. The negative electrode lead 28 is folded back in a U-shape inside the through hole 17a of the insulating plate 17. The other end of the negative electrode lead 28 is connected to the inner surface of the bottom of the outer casing 15 by welding or the like. Thus, the negative electrode current collector 47 is electrically connected to the outer casing 15, and the outer casing 15 becomes the negative terminal. The negative electrode lead 28 is a conductive member made of a metal such as copper. Alternatively, the negative electrode current collector in this disclosure may be joined to a negative electrode current collector plate, which is a metal plate, and the negative electrode current collector plate is connected to the positive electrode lead. In this case, the insulating plate is disposed on the positive electrode current collector plate. Alternatively, the negative current collector can be connected to the outer casing without using a negative lead.

[0048] The battery 10 also includes a resin gasket 27 disposed between the outer casing 15 and the sealing body 16. The gasket 27 is held between the outer casing 15 and the sealing body 16, thus insulating the sealing body 16 relative to the outer casing 15. The gasket 27 functions as a sealing material for maintaining the airtightness of the battery interior and as an insulating material for insulating the outer casing 15 from the sealing body 16. The outer casing 15 has an annular groove 21 in a portion along its axial direction.

[0049] For example, a portion of the side surface is spun radially inward to create a recessed radially inward groove 21. The outer casing 15 has a bottomed cylindrical portion including the groove 21 and an annular shoulder. The bottomed cylindrical portion houses the electrode body 14 and a non-aqueous electrolyte, and the shoulder bends radially inward from the open end of the bottomed cylindrical portion and extends inward. The shoulder is formed when the upper end of the outer casing 15 is bent inward and riveted to the periphery of the sealing body 16. The sealing body 16 is riveted to the outer casing 15 with a gasket 27 spaced between the shoulder and the groove 21. In this way, the internal space of the battery 10 is sealed.

[0050] The sealing body 16 has a structure in which a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cover 26 are stacked sequentially from the electrode body 14 side. Each component constituting the sealing body 16 has, for example, a circular or annular shape, and all components except the insulating member 24 are electrically connected to each other. The filter 22 has at least one through hole. Furthermore, the lower valve body 23 and the upper valve body 25 are connected at their respective central portions, and the insulating member 24 is sandwiched between their respective peripheral portions.

[0051] When the battery 10 overheats abnormally and its internal pressure rises, the lower valve body 23 deforms and breaks by pushing the upper valve body 25 towards the cover 26, thus cutting off the current path between the lower valve body 23 and the upper valve body 25. When the internal pressure rises further, the upper valve body 25 breaks, allowing gas to escape from the through-hole 26a of the cover 26. This gas release prevents the battery 10 from rupturing due to excessive internal pressure, thereby improving the safety of the battery 10.

[0052] use Figures 3-10 The structure and manufacturing method of the positive current collector 37 are explained in detail. Figure 3 It is shown by omitting a portion. Figure 1 Enlarged view of part A. Figure 4 From Figure 1 Figure showing the removal of electrode body 14 and upper insulating plate 19, viewed from above. Figure 5 From Figure 4 The diagram shows the result after removing the upper insulating plate 19. Figure 6 This is an unfolded view of the positive electrode plate 11 before the positive electrode fold is formed.

[0053] like Figures 3-5As shown, a positive electrode current collector 37 with a generally annular upper end is formed at the upper end of the positive electrode exposed portion 34. The positive electrode current collector 37 is formed from the positive electrode exposed portion 34 and is disposed at the upper end of the electrode body 14. Specifically, the positive electrode exposed portion 34 has a positive electrode folded portion 38 formed by folding back and overlapping twice, as described later, and the positive electrode folded portion 38 tilts towards the inner periphery of the electrode body 14. By providing the positive electrode folded portion in this way, the density of the positive electrode exposed portion in the positive electrode current collector of the electrode body can be increased, thus improving the welding reliability of the positive electrode current collector. The bent portion of the tilted positive electrode folded portion 38 can also be disposed in the positive electrode exposed portion at a position closer to the adhesive layer side than the positive electrode folded portion before tilting. By arranging the bent portion in this way, the positive electrode folded portion can be easily tilted. Furthermore, the positive electrode folded portions 38 at each rotating portion of the positive electrode plate 11 overlap in a state where adjacent rotating portions in the radial direction (first direction) abut against each other, and the upper ends are integrated by welding, thereby forming the aforementioned positive electrode current collector 37. In addition, at least one slit arranged in the winding direction of the electrode body may be formed in the positive electrode folded portion. This slit facilitates the tilting of the positive electrode folded portion. Furthermore, when the exposed portion is folded more than twice, the folded portion can be folded into a spiral shape or a serrated shape.

[0054] At this time, on both sides of the upper end of the positive electrode plate 11, the aforementioned positive electrode protective layer 36 is provided between the positive electrode mixture layer 32 and the exposed positive electrode portion 34. Figure 6 The image shows one side of the positive electrode plate 11 in the thickness direction. Figure 6 In the diagram, the positive electrode compound layer 32 is shown using dotted portions, and the positive electrode protective layer 36 is shown using oblique grid portions. For example... Figure 6 As shown, the positive electrode protective layer 36 is provided along the long side direction of the positive electrode plate 11 from one end to the other end.

[0055] By providing the positive electrode protection layer 36 as described above, a rigidity difference can be formed at the upper end of the positive electrode plate 11, making it easy for the exposed positive electrode portion 34 to bend stably toward the inner periphery of the electrode body 14 near the root of the portion that protrudes compared to the upper end of the positive electrode protection layer 36.

[0056] Additionally, an upper insulating plate 19 is disposed on the upper side of the positive electrode current collector 37. For example... Figure 4 As shown, a cross-shaped through hole 19a is formed in the insulating plate 19. The two straight portions forming the through hole 19a intersect at the center of the insulating plate 19. When the insulating plate 19 is viewed from above, the positive electrode current collector 37 is exposed in a cross shape through the through hole 19a of the insulating plate 19.

[0057] Welding, such as laser welding, is performed by irradiating, for example, a position extending radially from the upper side of the insulating plate 19 through the through hole 19a onto the upper surface of the positive electrode current collector 37. Then, using… Figure 4 The multiple dots inside the dashed box represent points that appear as dots. Figure 4 The positive electrode current collector 37 is integrated by welding four welding parts 39 to the overlapping positive electrode folded parts 38 of the positive electrode current collector 37. Figure 5 The diagram of the welded section is omitted.

[0058] One end of the positive electrode lead 20 is connected by welding or the like to one or more of the four straight sections on the upper surface of the positive electrode current collector 37, which is exposed to the upper side of the insulating plate 19 through the through hole 19a. The other end of the positive electrode lead 20 is connected by welding or the like to the filter 22 that constitutes the sealing body 16. Thus, the positive electrode current collector 37 is connected to the sealing body 16 via the strip-shaped positive electrode lead 20 without passing through a positive electrode current collector different from the positive electrode plate 11. Therefore, the placement space of the positive electrode current collector within the outer casing 15 can be reduced, thereby achieving high capacity of the battery 10, and the component resistance of the positive electrode current collector disappears, thereby achieving low resistance.

[0059] use Figure 6 and Figures 7-10 The manufacturing method of battery 10 is described. The manufacturing method of battery 10 includes a positive electrode substrate forming step, a folding part forming step, a winding step, a tilting step, and a welding step.

[0060] Figure 7 (a) is Figure 6 BB cross-sectional view. Figure 7 (b) shows the state in which a positive electrode folded portion 38 is formed in the positive electrode exposed portion 34 during the folding step. Figure 7 The enlarged corresponding diagram of part C in (a). For example... Figure 6 , Figure 7 As shown in (a), in the positive electrode substrate formation step, a positive electrode binder layer 32 and a positive electrode protective layer 36 are formed on both sides of the positive electrode core 30, and a positive electrode exposed portion 34 is formed on both sides of the upper end of the positive electrode core 30, forming a positive electrode plate 11 before the formation of the positive electrode fold portion 38. At this time, at the upper end of the positive electrode plate 11, it is possible to pre-form a positive electrode binder layer 32 and a positive electrode protective layer 36. Figure 6 The dotted line B1 indicates the predetermined position along the short side of the electrode plate, which is the pre-defined bending position when the positive electrode folded portion 38 is tilted during the tilting step described later. This causes the exposed positive electrode portion 34 to bend and then bend back. Thus, it is possible to perform a bending shaping at the predetermined position of the exposed positive electrode portion 34. In this case, during the tilting step described later, starting from the predetermined shaped position, it is easy to bend the exposed positive electrode portion 34 towards the inward periphery.

[0061] Furthermore, in the folding step described later, Figure 6 The dashed lines B2 and B3 are designated as folding sections. Therefore, to facilitate this folding, at the positions of dashed lines B2 and B3, the lines are also folded back after bending, thus enabling the bending shape.

[0062] like Figure 7 As shown in (b), in the folding step, Figure 6 The positions of the dashed lines B2 and B3 are set as bending positions, so that the exposed positive electrode portion 34 is folded back and overlapped twice in the direction of the electrode end, thereby forming the positive electrode folded portion 38. At this time, as Figure 7 As shown in (b), the exposed positive electrode portion 34 is less likely to be bent back when folded in a coiled manner, which is therefore preferable. The exposed positive electrode portion 34 is folded in a way that minimizes gaps on the inner side. Furthermore, in this example, the positive electrode folded portion 38 is formed by folding back twice, but it can also be formed by folding back only once or more than three times. The more times the positive electrode folded portion is folded, the more its rigidity can be improved.

[0063] Figure 8 This is a cross-sectional view showing the case where the positive electrode fold 38 overlaps with adjacent winding portions of the positive electrode plate 11 during the winding step. (See diagram below.) Figure 8 As shown, in the winding step, the positive electrode plate 11 is wound together with the negative electrode plate 12 and the separator 13. Figure 8 and the following Figures 9-11 In the illustration, the negative electrode plate 12 and the separator 13 are omitted, and the spacing between adjacent rotating portions of the positive electrode plate 11 is shown in a manner that is much smaller than the actual spacing.

[0064] like Figure 8 As shown, by winding the positive electrode plate 11 in the winding step, the positive electrode folds 38 at adjacent winding portions of the positive electrode plate 11 are brought into contact or close to each other.

[0065] Figure 9 The diagram shows a cross-sectional view illustrating the following situation: During the tilting step, at the upper end of the positive electrode plate 11, the positive electrode folds 38 at multiple rotating portions of the positive electrode plate 11 tilt inwards, and the positive electrode folds 38 at adjacent rotating portions of the positive electrode plate 11 overlap. Figure 9 As shown, in the pouring step, the electrode body 14, which is in a wound state obtained in the winding step, is inserted into the outer casing 15. Figure 1 Inside the positive electrode 34, an insulating plate 19 is then placed on the upper side of the positive electrode exposed portion 34. Figure 1The positive electrode exposed portion 34 is pressed downward from the top using the insulating plate 19. Then, the positive electrode exposed portion 34 is bent near the root of the portion protruding upward from the positive electrode protective layer 36, causing the positive electrode folded portion 38 to tilt towards the inner periphery of the electrode body 14. Then, the positive electrode folded portions 38 at adjacent rotating portions of the positive electrode plate 11 are overlapped, thereby forming a positive electrode current collector portion 37 at the upper end of the electrode body 14. At this time, the positive electrode folded portions 38 at adjacent rotating portions overlap in a manner that does not create gaps between the positive electrode folded portions 38.

[0066] In addition, before winding the positive electrode plate 11, a predetermined position is set in the short side direction of the electrode plate ( Figure 6 When the positive electrode plate 11 is bent at the specified position (as indicated by the dotted line B1), the positive electrode fold 38 is easily tilted toward the inner periphery of the electrode body 14.

[0067] In the above-described tilting process, in reality, between each rotating portion of the positive electrode plate 11, as... Figure 3 The configuration includes two separators 13a and 13b and one negative electrode plate 12, as shown. At this time, as... Figure 2 , Figure 3 As shown, since the upper end of one of the two separators 13a and 13b protrudes upwards compared to the other separator 13b, the upper end of one separator 13a also tilts towards the inner periphery of the electrode body 14 along with the positive electrode exposed portion 34, thus covering the upper side of the negative electrode plate 12. Therefore, even when the positive electrode exposed portion 34 is tilted towards the upper side of the negative electrode plate 12, short circuits can be prevented more reliably.

[0068] Figure 10 This is a cross-sectional view showing the state in which the positive electrode folds 38 at multiple rotating portions of the positive electrode plate 11 are welded together during the welding process. Figure 10 In the diagram, the welded portion 39 is schematically shown by the area painted with black quadrilaterals. For example... Figure 10 As shown, during the welding step, as described above, when viewed from above the insulating plate 19, the portion of the upper surface of the positive electrode current collector 37 exposed through the through hole 19a of the insulating plate 19 is welded using methods such as laser welding. This welding joins the adjacent rotating portions 38 of the positive electrode plate 11 in the exposed positive electrode portion 34 to each other, thereby integrating the positive electrode current collector 37 with the positive electrode folds 38 tightly overlapping.

[0069] Figure 11 This illustrates how, during the tilting step, the positive electrode fold 38 at the multiple rotating portions of the positive electrode plate 11 is tilted relative to... Figure 9 A schematic diagram showing the tilted position closer to the inner circumference of the electrode. (See diagram below.) Figure 11As shown, in the above-mentioned pouring steps, with Figure 9 Compared to the situation shown, which further tilts towards the inner periphery of the electrode body 14, this makes the positive electrode folds 38 at the multiple rotating portions of the positive electrode plate 11 closer to a radially extending state. Welding is then performed in this state to integrate the positive electrode current collector 37 with the positive electrode folds 38 tightly overlapping. Figure 11 The image shows the positive electrode fold 38 being welded in the portion surrounded by the single-dotted line D.

[0070] Furthermore, in the above embodiment, a structure was described in which the positive electrode current collector 37 is welded with the insulating plate 19 disposed on the upper side of the electrode body 14 after the tilting step. However, it is also possible to remove the insulating plate 19 from the electrode body 14 after the tilting step using the insulating plate 19, and then perform welding such as laser welding from the upper side of the positive electrode current collector 37. After welding, the insulating plate 19 is disposed on the upper side of the electrode body 14 again.

[0071] On the other hand, such as Figure 1 As shown, a negative electrode current collector 47 with a circular lower end is formed at the lower end of the negative electrode exposed portion 44. The negative electrode current collector 47 is formed from the negative electrode exposed portion 44 and is disposed at the lower end of the electrode body 14. Specifically, similar to the positive electrode exposed portion 34, the negative electrode exposed portion 44 has a negative electrode folded portion formed by folding back and forth twice and overlapping, and the negative electrode folded portion tilts towards the inner periphery of the electrode body 14. Then, the negative electrode folded portions at each of the rotating portions of the negative electrode plate 12 overlap each other at adjacent rotating portions, and then the lower ends are fused and integrated by welding. Thus, the aforementioned negative electrode current collector 47 is formed.

[0072] At this time, on both sides of the lower end of the negative electrode plate 12, on the negative electrode compound layer 42 ( Figure 2 The aforementioned negative electrode protective layer 46 is provided between the negative electrode and the exposed negative electrode portion 44. Figure 2 By providing the negative electrode protective layer 46, a rigidity difference can be formed at the lower end of the negative electrode plate 12, making it easier for the exposed negative electrode portion 44 to bend stably towards the inner periphery of the electrode body 14 near the root of the portion protruding compared to the lower end of the negative electrode protective layer 46. Alternatively, the negative electrode protective layer 46 of the negative electrode plate 12 can be omitted.

[0073] Furthermore, when the negative electrode fold is tilted towards the inner periphery of the electrode body 14, two separators 13a and 13b and one positive electrode plate 11 are actually arranged between each rotating portion of the negative electrode plate 12. At this time, as... Figure 2As shown, since the other separator 13b of the two separators 13a and 13b protrudes downwards compared to the other separator 13a, the other separator 13b also tilts towards the inner periphery of the electrode body 14 together with the negative electrode exposed portion 44, thereby covering the lower side of the positive electrode plate 11. Therefore, even when the negative electrode exposed portion 44 is tilted towards the lower side of the positive electrode plate 11, short circuits can be prevented more reliably.

[0074] Furthermore, a lower insulating plate 17 is disposed above the negative electrode current collector 47. Similar to the upper insulating plate 19, a cross-shaped through hole 17a is formed in the lower insulating plate 17. The negative electrode current collector 47 protrudes from the through hole 17a of the insulating plate 17 in a cross shape to the lower side of the insulating plate 17.

[0075] Laser welding or similar welding is performed by irradiating, for example, a laser, onto the radially extending lower surface of the negative electrode current collector 47 through the through-hole 17a from the lower side of the insulating plate 17. Then, multiple welding points are used to weld the overlapping negative electrode folds of the negative electrode current collector 47, integrating the negative electrode current collector 47 into a state of close overlap with the negative electrode folds. Furthermore, when the insulating plate 17 is viewed from below, one end of the negative electrode lead 28 is connected by welding or similar means to one or more of the four straight sections exposed on the lower surface of the negative electrode current collector 47 through the through-hole 17a. The negative electrode lead 28 is folded back into a roughly U-shape within the through-hole 17a. The other end of the negative electrode lead 28 is welded to the bottom of the outer casing 15 by laser welding or similar means. Thus, the negative electrode current collector 47 is connected to the outer casing 15 via the negative electrode lead 28 without passing through a negative electrode current collector different from the negative electrode plate 12. Therefore, the space for the negative current collector can be reduced within the outer casing 15, thus enabling high capacity of the battery 10, and the component resistance of the negative current collector disappears, thus enabling low resistance.

[0076] For example, by inverting the electrode body 14 before inserting it into the outer casing 15, welding of the negative electrode current collector 47 can be performed from the upper side of the insulating plate 17 by means of laser welding or the like, while the insulating plate 17 is positioned on the upper side of the negative electrode current collector 47.

[0077] Furthermore, the lower insulating plate 17 and negative electrode lead 28 can be omitted. After inserting the electrode body 14 into the outer casing 15, the exposed negative electrode portion 44 is pushed towards the bottom of the outer casing 15, thereby causing the folded portion of the exposed negative electrode portion 44 to tilt inward to form the negative electrode current collector 47. Then, by irradiating a laser from the outside of the bottom of the outer casing 15, laser welding is performed on the bottom of the negative electrode current collector 47 and the outer casing 15, while welding the lower ends of the overlapping negative electrode folds of the negative electrode current collector, thereby making the negative electrode current collector 47 integrated with the negative electrode folds tightly overlapping. According to this structure, the space for the insulating plate 17 and negative electrode lead 28 can also be reduced within the outer casing 15, thus enabling further high-capacity increases in the battery 10.

[0078] According to the battery 10 described above, a positive electrode exposed portion 34, exposing the positive electrode core 30, is disposed at one axial end of the electrode body 14. The positive electrode exposed portion 34 has a positive electrode folded portion 38 formed by folding back and overlapping at least once. Furthermore, the positive electrode folded portion 38 tilts towards the inner periphery of the electrode body 14, and the positive electrode folded portions 38 at adjacent rotating portions of the electrode body 14 overlap, thereby forming a positive electrode current collector 37 at one axial end. As a result, the rigidity of the positive electrode current collector 37 formed by the positive electrode exposed portion 34 can be improved, thus stabilizing the shape and position of the positive electrode current collector 37. Therefore, the connection state between the positive electrode current collector 37 and the positive electrode connection lead can be maintained well and stably, thereby improving the reliability of the battery 10.

[0079] Similarly, the rigidity of the negative electrode current collector 47 formed by the exposed negative electrode portion 44 can be improved, thus stabilizing the shape and position of the negative electrode current collector 47. Therefore, the reliability of the battery 10 can be further improved.

[0080] Furthermore, unlike the structure where the positive electrode lead is connected to the sealing body only in a portion of the winding direction of the positive electrode plate, in the positive electrode current collector 37, current can flow not only in the winding direction of the positive electrode plate 11, but also in directions other than the winding direction, such as the radial direction of the wound positive electrode plate, through the overlapping positive electrode folds 38, thus achieving low resistance. Similarly, low resistance can also be achieved in the negative electrode current collector 47. Moreover, by welding, the positive electrode current collector 37 and the negative electrode current collector 47 are integrated with their respective folds tightly overlapping, thus achieving further low resistance. As a result, the high performance of the battery 10 can be achieved. Alternatively, the positive electrode current collector 37 and the negative electrode current collector 47 can be integrated without welding.

[0081] Furthermore, while the above embodiments describe the case where both the positive and negative current collectors are provided on the electrode body, it is also possible to configure it so that only one of the positive and negative current collectors is provided on the electrode body. Additionally, while the above embodiments omit the structure of the positive current collector for contacting the exposed positive electrode and the negative current collector for contacting the exposed negative electrode, it is also possible to configure it so that one or both of the positive and negative current collectors are provided. In this case, by configuring it to include one or both of the positive and negative current collectors, its rigidity can be improved, thus improving the reliability of the cylindrical secondary battery.

[0082] Furthermore, in the above embodiments, the case of forming a cross-shaped through hole in the insulating plate has been described, but the through hole formed in the insulating plate is not limited to this. For example, it may also be a straight through hole extending radially, or a through hole in the shape of three or more straight sections extending radially and intersecting at the center.

[0083] Furthermore, in the above-described embodiment, the following situation was described: in each of the positive and negative current collectors, the exposed folded portion tilts towards the inner periphery of the electrode body, and the folded portions at adjacent winding portions of the positive or negative electrode plate overlap, thereby forming a current collector at the end in the winding axis direction. On the other hand, it may also be configured such that in one or both of the positive and negative current collectors, the exposed folded portion tilts towards the outer periphery of the electrode body, and the folded portions at adjacent winding portions of the positive or negative electrode plate overlap, thereby forming a current collector at the end in the winding axis direction.

[0084] This disclosure is further illustrated by the following embodiments.

[0085] Structure 1: An energy storage device, comprising:

[0086] An electrode body, which is formed by stacking a first electrode plate and a second electrode plate in a first direction with a separator between them; and

[0087] An outer casing that houses the electrode body.

[0088] The first electrode plate includes a first core and a first adhesive layer formed on the surface of the first core.

[0089] A first exposed portion of the first core is provided at one end in the winding axis direction of the electrode body.

[0090] The first exposed portion has a folded portion formed by folding back and overlapping more than once, the folded portion tilting in the first direction, the folded portions of the first electrode plate overlapping at adjacent winding portions in the first direction, thereby forming a current collector portion at one end in the winding axis direction.

[0091] Structure 2: The energy storage device according to Structure 1, wherein,

[0092] In the electrode body, the first electrode plate and the second electrode plate are stacked and wound together with the separator in between.

[0093] The first direction is perpendicular to the winding axis of the electrode body.

[0094] Structure 3: The energy storage device according to Structure 1, wherein,

[0095] The current collector is connected to the sealing body fixed to the outer casing via a long strip-shaped connecting lead, without passing through a current collector different from the first electrode plate.

[0096] Structure 4: The energy storage device according to any one of structures 1 to 3, wherein,

[0097] The current collector is connected to the current collector body.

[0098] Structure 5: An energy storage device according to any one of structures 1 to 4, wherein,

[0099] A protective layer for short-circuit suppression is provided between the first compound layer and the first exposed portion.

[0100] Structure 6: An energy storage device according to any one of structures 1 to 5, wherein,

[0101] The adjacent rotating portions of the current collector in the first exposed portion are joined together by welding.

[0102] Structure 7: An energy storage device according to any one of structures 1 to 6, wherein,

[0103] The folded portion is folded in a manner that involves folding back and forth more than twice and overlapping.

[0104] Structure 8: An energy storage device according to any one of structures 1 to 7, wherein,

[0105] The bending point of the folded portion is located in the first exposed portion in an area that does not overlap with the folded portion before bending.

[0106] Structure 9: A manufacturing method, which is the manufacturing method of the energy storage device according to Structure 1, wherein,

[0107] The first exposed portion is formed on one end of the first electrode plate in the direction of the short side of the electrode plate corresponding to the winding axis direction.

[0108] After the folded portion is formed by folding the first exposed portion in the short side direction of the electrode plate in a manner that involves folding back and forth more than once and overlapping,

[0109] The folded portion is tilted toward the inner or outer circumference of the electrode body, and the folded portions at adjacent winding portions of the first electrode plate are overlapped, thereby forming the current collector at one end in the winding axis direction.

[0110] Structure 10: A method for manufacturing an energy storage device according to Structure 9, wherein,

[0111] After tilting the folded portion toward the inner or outer periphery of the electrode body and overlapping the folded portions at adjacent rotating portions of the first electrode plate, adjacent rotating portions in the first exposed portion are joined together by welding to form an integrated current collector.

[0112] Structure 11: A method for manufacturing an energy storage device according to Structure 9 or 10, wherein,

[0113] Before the first electrode plate is wound, it is bent at a predetermined position in the short side direction of the electrode plate, which is the predetermined bending position when the folded part is tilted, and then bent back, thereby shaping the bending at the predetermined position.

[0114] Explanation of reference numerals in the attached figures

[0115] 10 Battery; 11 Positive plate; 12 Negative plate; 13a, 13b Separators; 14 Electrode body; 15 Outer can; 16 Sealing body; 17 Insulating plate; 19 Insulating plate; 20 Positive lead; 21 Groove section; 22 Filter; 23 Lower valve body; 24 Insulating component; 25 Upper valve body; 26 Cover; 26a Through hole; 27 Gasket; 28 Negative lead; 30 Positive core; 32 Positive flux layer; 34 Positive exposed part; 36 Positive protective layer; 37 Positive current collector; 38 Positive folded part; 39 Welding part; 40 Negative core; 42 Negative flux layer; 44 Negative exposed part; 46 Negative protective layer.

Claims

1. An energy storage device, comprising: An electrode body, which is formed by stacking a first electrode plate and a second electrode plate in a first direction with a separator between them; and An outer casing that houses the electrode body. in, The first electrode plate includes a first core and a first adhesive layer formed on the surface of the first core. A first exposed portion of the first core is provided at one end in the winding axis direction of the electrode body. The first exposed portion has a folded portion formed by folding back and overlapping more than once, the folded portion tilting in the first direction, the folded portions of the first electrode plate overlapping at adjacent winding portions in the first direction, thereby forming a current collector portion at one end in the winding axis direction.

2. The energy storage device according to claim 1, wherein, In the electrode body, the first electrode plate and the second electrode plate are stacked and wound together with the separator in between. The first direction is perpendicular to the winding axis of the electrode body.

3. The energy storage device according to claim 1, wherein, The current collector is connected to the sealing body fixed to the outer casing via a long strip-shaped connecting lead, without passing through a current collector different from the first electrode plate.

4. The energy storage device according to claim 1, wherein, The current collector is connected to the current collector body.

5. The energy storage device according to claim 1, wherein, A protective layer for short-circuit suppression is provided between the first compound layer and the first exposed portion.

6. The energy storage device according to claim 1, wherein, The adjacent rotating portions of the current collector in the first exposed portion are joined together by welding.

7. The energy storage device according to claim 1, wherein, The folded portion is folded in a manner that involves folding back and forth more than twice and overlapping.

8. The energy storage device according to claim 1, wherein, The bending point of the folded portion is located in the first exposed portion in an area that does not overlap with the folded portion before bending.

9. A method for manufacturing an energy storage device, comprising the method for manufacturing an energy storage device according to claim 1, wherein, The first exposed portion is formed on one end of the first electrode plate in the direction of the short side of the electrode plate corresponding to the winding axis direction. After the folded portion is formed by folding the first exposed portion in a manner that overlaps and folds it back and forth more than once in the short side direction of the electrode plate, the folded portion is formed. The folded portion is tilted toward the inner or outer circumference of the electrode body, and the folded portions at adjacent winding portions of the first electrode plate are overlapped, thereby forming the current collector at one end in the winding axis direction.

10. The method for manufacturing an energy storage device according to claim 9, wherein, After tilting the folded portion toward the inner or outer periphery of the electrode body and overlapping the folded portions at adjacent rotating portions of the first electrode plate, adjacent rotating portions in the first exposed portion are joined together by welding to form an integrated current collector.

11. The method for manufacturing an energy storage device according to claim 9, wherein, Before the first electrode plate is wound, it is bent at a predetermined position in the short side direction of the electrode plate, which is the predetermined bending position when the folded part is tilted, and then bent back, thereby shaping the bending at the predetermined position.

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