Secondary battery

Abstract

A secondary battery comprises: an outer packaging member; a battery element housed within the outer packaging member, comprising a positive electrode and a negative electrode, which are opposed and wound together; and an insulating member disposed on the positive electrode. The positive electrode comprises a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector; the negative electrode comprises a negative electrode current collector and a negative electrode active material layer disposed on the side of the negative electrode current collector opposite the positive electrode active material layer. The positive electrode comprises an exposed portion where the positive electrode current collector is exposed without the positive electrode active material layer; the exposed portion faces the negative electrode active material layer; and the insulating member covers at least the exposed portion. The positive electrode has a first direction in which the positive electrode active material layer is intermittently disposed on the positive electrode current collector via the exposed portion, and a second direction intersecting the first direction. In the second direction, the negative electrode protrudes further to both sides than the positive electrode. Furthermore, in the second direction, the insulating member protrudes further to both sides than the positive electrode. The size of the positive electrode in the second direction, the size of the negative electrode in the second direction, the size of the insulating part on one side of the two sides in the second direction protruding from the positive electrode, and the size of the insulating part on the other side of the two sides in the second direction protruding from the positive electrode satisfy the relationship expressed by the following formula (1): 0.50≤(W3+W4) / (W2-W1)≤3.00(1) (W1 is the size of the positive electrode in the second direction. W2 is the size of the negative electrode in the second direction. W3 is the size of the insulating part on one side of the two sides in the second direction protruding from the positive electrode. W4 is the size of the insulating part on the other side of the two sides in the second direction protruding from the positive electrode.).

Description

Technical Field

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

[0002] With the increasing prevalence of various electronic devices, such as mobile phones, the development of secondary batteries is underway as compact, lightweight, and high-energy-density power sources. These batteries consist of a positive electrode, a negative electrode, and an electrolyte housed within an outer casing, and various studies have been conducted on their structures.

[0003] Specifically, to prevent short circuits between the electrode plates and the housing, protective tape is provided on the positive electrode tab, the negative electrode tab, the positive electrode blank area, and the negative electrode blank area (see, for example, Patent Document 1). Furthermore, to prevent short circuits in the electrode assembly, protective tape is affixed to the cut edges of the electrode plates after they are cut during the manufacturing process of the wound electrode assembly (see, for example, Patent Document 2).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-168417

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2010-198770 Summary of the Invention

[0008] Various studies have been conducted to improve the performance of secondary batteries. However, the operational reliability and manufacturing stability of these secondary batteries are still insufficient, and thus there is room for improvement.

[0009] The present technology has been made in view of the above-mentioned problems, and an object of the present invention is to provide a secondary battery capable of achieving high operational reliability and excellent manufacturing stability.

[0010] A secondary battery according to one embodiment of the present technology comprises: an outer packaging member; a battery element housed within the outer packaging member, comprising a positive electrode and a negative electrode that are opposed and wound together; and an insulating member disposed on the positive electrode. The positive electrode comprises a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector; the negative electrode comprises a negative electrode current collector and a negative electrode active material layer disposed on the side of the negative electrode current collector that faces the positive electrode active material layer. The positive electrode comprises an exposed portion where the positive electrode current collector is exposed without the positive electrode active material layer; the exposed portion faces the negative electrode active material layer; and the insulating member covers at least the exposed portion. The positive electrode has a first direction in which the positive electrode active material layer is intermittently disposed on the positive electrode current collector via the exposed portion, and a second direction intersecting the first direction. In the second direction, the negative electrode protrudes further to both sides than the positive electrode. Furthermore, in the second direction, the insulating member protrudes further to both sides than the positive electrode. The size of the positive electrode in the second direction, the size of the negative electrode in the second direction, the size of the insulating part on one side of the two sides in the second direction protruding compared to the positive electrode, and the size of the insulating part on the other side of the two sides in the second direction protruding compared to the positive electrode satisfy the relationship expressed by the following formula (1).

[0011] 0.50≤(W3+W4) / (W2-W1)≤3.00…(1)

[0012] (W1 is the dimension of the positive electrode in the second direction. W2 is the dimension of the negative electrode in the second direction. W3 is the dimension of the insulating member protruding from the positive electrode on one side of the insulating member in the second direction. W4 is the dimension of the insulating member protruding from the positive electrode on the other side of the insulating member in the second direction.)

[0013] According to the secondary battery of one embodiment of the present technology, since the positive electrode, the negative electrode, and the insulating member satisfy the relationship represented by formula (1), high operational reliability and excellent manufacturing stability can be obtained.

[0014] It should be noted that the effects of the present technology are not limited to the effects described here, and may be any of a series of effects related to the present technology described later. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a perspective view showing the structure of a secondary battery in one embodiment of the present technology.

[0016] Figure 2 Yes Figure 1 A cross-sectional view of the structure of a secondary battery is shown.

[0017] Figure 3 Yes Figure 2 A cross-sectional view of the structure of a battery element is shown.

[0018] Figure 4 Yes Figure 3 A top view of the structures of the positive electrode and the negative electrode is shown.

[0019] Figure 5 Yes Figure 3 Cross-sectional views of the structures of the positive electrode and the negative electrode are shown.

[0020] Figure 6 Yes Figure 3 Another top view of the structure of the positive electrode is shown.

[0021] Figure 7 Yes Figure 2 A cross-sectional view showing the structure of the main parts of a secondary battery.

[0022] Figure 8 This is a perspective view showing the structure of an outer can used in the manufacturing process of a secondary battery.

[0023] Figure 9 It is a cross-sectional view for explaining the manufacturing process of a secondary battery.

[0024] Figure 10 It is a cross-sectional view showing the structure of the main part of the secondary battery of the first reference example.

[0025] Figure 11 It is a cross-sectional view showing the structure of the main part of a secondary battery according to a second reference example. DETAILED DESCRIPTION

[0026] Hereinafter, one embodiment of the present technology will be described in detail with reference to the accompanying drawings. Note that the order of description is as follows.

[0027] 1. Secondary batteries

[0028] 1-1. Structure

[0029] 1-2. Size requirements

[0030] 1-3. Action

[0031] 1-4. Manufacturing Method

[0032] 1-5. Actions and Effects

[0033] 2. Modification

[0034] <1. Secondary batteries>

[0035] First, a secondary battery according to an embodiment of the present technology will be described.

[0036] The secondary battery described herein has a flat and cylindrical three-dimensional shape, which is called a coin type or a button type. As described later, the secondary battery has a pair of bottoms facing each other and a side wall portion located between the pair of bottoms. In the secondary battery, the height is smaller than the outer diameter. The "outer diameter" refers to the diameter (maximum diameter) of each of the pair of bottoms, and the "height" refers to the distance (maximum distance) from the surface of one bottom to the surface of the other bottom.

[0037] The charging and discharging principle of a secondary battery is not particularly limited. Below, we will explain how the battery capacity is obtained by intercalation and deintercalation of electrode reaction substances. The secondary battery comprises a positive electrode, a negative electrode, and an electrolyte. In this secondary battery, to prevent the electrode reaction substances from precipitating on the surface of the negative electrode during charging, the charge capacity of the negative electrode is greater than the discharge capacity of the positive electrode. That is, the electrochemical capacity per unit area of the negative electrode is set to be greater than the electrochemical capacity per unit area of the positive electrode.

[0038] The type of electrode reaction material is not particularly limited, but specifically includes light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, while alkaline earth metals include beryllium, magnesium, and calcium.

[0039] The following uses lithium as an example. A secondary battery that achieves battery capacity through the intercalation and deintercalation of lithium is called a lithium-ion secondary battery. In this lithium-ion secondary battery, lithium is intercalated and deintercalated in an ionic state.

[0040] <1-1. Structure>

[0041] Figure 1 The three-dimensional structure of the secondary battery is shown. Figure 2 Shown Figure 1 The cross-sectional structure of the secondary battery shown. Figure 3 Shown Figure 2 The cross-sectional structure of the battery element 40 is shown. Figure 4 Shown Figure 3 The planar structures of the positive electrode 41 and the negative electrode 42 are shown. Figure 5 Shown Figure 3 The cross-sectional structures of the positive electrode 41 and the negative electrode 42 are shown in FIG. Figure 3 correspond. Figure 6 Shown Figure 3 Other planar structures of the positive electrode 41 shown are Figure 4 correspond. Figure 7 Shown Figure 2 The cross-sectional structure of the main parts of the secondary battery is shown.

[0042] In addition, Figure 2In order to simplify the illustration, the positive electrode 41, the negative electrode 42, the separator 43, the positive electrode lead 71 and the negative electrode lead 72 are respectively shown as lines, and the illustration of each of the insulating tapes 50 and 60 is omitted. Figure 3 In FIG, only a portion of the cross-sectional structure of the battery element 40 is magnified. Figure 4 as well as Figure 6 The positive electrode 41 and the negative electrode 42 are shown in the state before they are wound. Figure 7 , as main parts of the secondary battery, a battery element 40 , insulating tapes 50 , 60 , and a positive electrode lead 71 are shown.

[0043] For convenience, the following Figure 1 as well as Figure 2 The upper side of each of the above is described as the upper side of the secondary battery, and Figure 1 as well as Figure 2 The lower side of each of is described as the lower side of the secondary battery.

[0044] The secondary battery described here is as follows Figure 1 As shown, the secondary battery has a three-dimensional shape in which the height H is smaller than the outer diameter D, that is, a flat and cylindrical three-dimensional shape. Here, the three-dimensional shape of the secondary battery is a flat and cylindrical (columnar) shape.

[0045] The dimensions of the secondary battery are not particularly limited. For example, an outer diameter D is 3 mm to 30 mm, and a height H is 0.5 mm to 70 mm. Furthermore, the ratio of outer diameter D to height H (D / H) is greater than 1. The upper limit of this ratio (D / H) is not particularly limited, but is preferably 25 or less.

[0046] like Figures 1 to 7 As shown, the secondary battery includes an outer can 10, a battery element 40, and an insulating tape 50. The secondary battery also includes an external terminal 20, a gasket 30, an insulating tape 60, a positive electrode lead 71, and a negative electrode lead 72.

[0047] [Outer packaging can]

[0048] like Figure 1 as well as Figure 2 As shown, the outer can 10 is a hollow outer packaging member that houses the battery element 40 and the like.

[0049] Here, the outer can 10 has a flat, cylindrical three-dimensional shape based on the three-dimensional shape of a flat, cylindrical secondary battery. Therefore, the outer can 10 has a pair of bottoms M1 and M2 that are opposed to each other, and a side wall portion M3 located between the bottoms M1 and M2. The upper end of the side wall portion M3 is connected to the bottom M1, and the lower end of the side wall portion M3 is connected to the bottom M2. As described above, since the outer can 10 is cylindrical, the planar shape of each of the bottoms M1 and M2 is circular, and the surface of the side wall portion M3 is a convex curved surface.

[0050] The outer can 10 includes a housing portion 11 and a lid portion 12 that are joined to each other, and the housing portion 11 is sealed by the lid portion 12. The lid portion 12 is welded to the housing portion 11.

[0051] The housing portion 11 is a flat cylindrical housing member that houses the battery element 40 etc. The housing portion 11 has a hollow structure with an open upper end and a closed lower end, and thus has an opening 11K at its upper end.

[0052] The lid 12 is a substantially disk-shaped cover member that closes the opening 11K of the housing 11 and has a through-hole 12K. As described above, the lid 12 is welded to the housing 11 at the opening 11K. Since the external terminals 20 are mounted on the lid 12, the lid 12 supports the external terminals 20.

[0053] Here, because the cover 12 is bent so as to partially protrude toward the interior of the storage section 11, the cover 12 is partially recessed. In this case, a portion of the cover 12 is bent so as to form a step toward the center of the cover 12. As a result, the cover 12 has a recessed portion 12H formed by bending the cover 12 so as to partially protrude toward the interior of the storage section 11. It should be noted that the through-hole 12K is provided in the recessed portion 12H.

[0054] As described above, the outer can 10 is a welded can formed by welding two parts (the container 11 and the lid 12). Therefore, the outer can 10 after welding is physically a single part and cannot be separated into the two parts (the container 11 and the lid 12) afterwards.

[0055] The outer can 10 as the welded can has no mutually folded portions and no portions where two or more members overlap.

[0056] The phrase "no folded portions" means that the outer can 10 is not folded. Furthermore, the phrase "no overlapping portions of two or more components" means that after the secondary battery is completed, the outer can 10 is physically a single component and therefore cannot be separated into two or more components. In other words, the finished outer can 10 is not in a state where two or more components are combined and overlapped in a manner that allows for subsequent separation.

[0057] In particular, the welded outer can 10 is a so-called crimpless can, unlike crimped cans formed using riveting. This is because the component space volume within the outer can 10 increases, thereby increasing the energy density per unit volume of the secondary battery. This "component space volume" refers to the volume (effective volume) of the inner space of the outer can 10 that can accommodate the battery elements 40 involved in the charge and discharge reactions.

[0058] Here, the outer can 10 (the storage portion 11 and the lid 12) is conductive. As a result, the outer can 10 is connected to the battery element 40 (negative electrode 42) via the negative electrode lead 72, thereby functioning as an external connection terminal for the negative electrode 42. This is because the secondary battery does not need to have an external connection terminal for the negative electrode 42 that is separate from the outer can 10, thereby suppressing the reduction in the component space volume caused by the presence of the external connection terminal for the negative electrode 42. As a result, the component space volume increases, and thus the energy density per unit volume of the secondary battery increases.

[0059] Specifically, the outer can 10 (the container 11 and the lid 12) comprises one or more conductive materials such as metal materials and alloy materials. The conductive materials include iron, copper, nickel, stainless steel, iron alloys, copper alloys, and nickel alloys. The type of stainless steel is not particularly limited; specifically, it includes SUS304 and SUS316. Furthermore, the material forming the container 11 and the material forming the lid 12 may be the same or different.

[0060] It should be noted that, as described later, the outer can 10 (lid 12) is insulated from the external terminal 20, which functions as an external connection terminal for the positive electrode 41, via a gasket 30. This is to prevent contact (short circuit) between the outer can 10 (external connection terminal for the negative electrode 42) and the external terminal 20 (external connection terminal for the positive electrode 41).

[0061] [External terminal]

[0062] like Figure 1 as well as Figure 2As shown, the external terminal 20 is a terminal for connecting to an electronic device when the secondary battery is mounted on the electronic device. As described above, the external terminal 20 is attached to the outer can 10 (lid 12) and is therefore supported by the lid 12.

[0063] Here, since the external terminal 20 is connected to the battery element 40 (positive electrode 41) via the positive electrode lead 71, it functions as an external connection terminal for the positive electrode 41. Thus, when the secondary battery is used, the secondary battery is connected to an electronic device via the external terminal 20 (external connection terminal for the positive electrode 41) and the outer can 10 (external connection terminal for the negative electrode 42), allowing the electronic device to operate using the secondary battery as a power source.

[0064] The external terminal 20 is a flat, roughly plate-shaped member, positioned within the recess 12H via a gasket 30. Thus, the external terminal 20 is insulated from the lid 12 via the gasket 30. Here, the external terminal 20 is housed within the recess 12H so as not to protrude further upward from the lid 12. This is because the height H of the secondary battery is reduced compared to a case where the external terminal 20 protrudes further upward from the lid 12, thereby increasing the energy density per unit volume of the secondary battery.

[0065] It should be noted that, because the outer diameter of the external terminal 20 is smaller than the inner diameter of the recessed portion 12H, the external terminal 20 is isolated from the lid portion 12 on its periphery. Consequently, the gasket 30 is disposed only in a portion of the space between the external terminal 20 and the lid portion 12 (recessed portion 12H), more specifically, only in a portion where the external terminal 20 and the lid portion 12 would contact each other if the gasket 30 were not present.

[0066] Furthermore, the external terminal 20 comprises one or more conductive materials such as metal and alloy materials, and the conductive material is aluminum or an aluminum alloy. Alternatively, the external terminal 20 may be formed from a cladding material. The cladding material comprises, in order from the side closest to the gasket 30, an aluminum layer and a nickel layer, wherein the aluminum and nickel layers are roll-bonded to each other.

[0067] [washer]

[0068] like Figure 2 As shown, the gasket 30 is an insulating component disposed between the outer can 10 (lid 12) and the external terminal 20. The external terminal 20 is secured to the lid 12 via the gasket 30. The gasket 30 has a planar, annular shape with a through-hole at a location corresponding to the through-hole 12K. The gasket 30 is composed of one or more insulating materials such as an insulating polymer compound. Examples of the insulating material include polypropylene and polyethylene.

[0069] The installation range of the gasket 30 is not particularly limited and can be set arbitrarily. Here, the gasket 30 is arranged in the gap between the upper surface of the lid 12 and the lower surface of the external terminal 20 inside the recess 12H.

[0070] [Battery components]

[0071] like Figures 2 to 7 As shown, the battery element 40 is a power generation element that performs charge and discharge reactions and is housed inside the outer can 10. The battery element 40 includes a positive electrode 41, a negative electrode 42, a separator 43, and an electrolyte solution (not shown) as a liquid electrolyte.

[0072] The battery element 40 described here is a so-called wound electrode body. Specifically, in the battery element 40, a positive electrode 41 and a negative electrode 42 are stacked one on top of another with a separator 43 interposed therebetween, and the positive electrode 41, negative electrode 42, and separator 43 are wound together. Thus, since the positive electrode 41 and negative electrode 42 are wound while facing each other with the separator 43 interposed therebetween, a winding center space 40K is formed at the center of the battery element 40.

[0073] Here, the positive electrode 41, the negative electrode 42, and the separator 43 are wound so that the separator 43 is disposed at each of the outermost and innermost circumferences. The number of windings of each of the positive electrode 41, the negative electrode 42, and the separator 43 is not particularly limited and can be set arbitrarily.

[0074] The battery element 40 has the same three-dimensional shape as the outer can 10, and therefore has a flat, cylindrical three-dimensional shape. This is because, compared to a case where the battery element 40 has a different three-dimensional shape from the outer can 10, when the battery element 40 is housed within the outer can 10, the so-called dead space (the gap between the outer can 10 and the battery element 40) is less likely to form, allowing for efficient utilization of the internal space of the outer can 10. This increases the volume of the component space, and thus increases the energy density per unit volume of the secondary battery.

[0075] (positive electrode)

[0076] like Figures 3 to 6 As shown in FIG, the positive electrode 41 includes a positive electrode current collector 41A and a positive electrode active material layer 41B. Figure 4 as well as Figure 6 In each of the figures, the positive electrode active material layer 41B is indicated with light hatching.

[0077] The positive electrode current collector 41A has a pair of surfaces on which the positive electrode active material layer 41B is provided. The positive electrode current collector 41A contains a conductive material such as a metal material, and the metal material is aluminum.

[0078] The positive electrode active material layer 41B is provided on both surfaces of the positive electrode current collector 41A and contains one or more of a variety of positive electrode active materials capable of intercalating and deintercalating lithium. The positive electrode active material layer 41B may also contain a positive electrode binder and a positive electrode conductive agent. The method for forming the positive electrode active material layer 41B is not particularly limited; specifically, a coating method is used.

[0079] As described above, the positive electrode 41 is opposed to the negative electrode 42 via the separator 43, and the positive electrode active material layer 41B is provided on both sides of the positive electrode collector 41A. Therefore, the positive electrode 41 includes the positive electrode active material layer 41B provided on the side of the positive electrode collector 41A facing the negative electrode 42 (negative electrode active material layer 42B), and the positive electrode active material layer 41B provided on the side of the positive electrode collector 41A that does not face the negative electrode 42 (the side opposite to the side facing the negative electrode 42).

[0080] The positive electrode active material includes a lithium compound. The lithium compound is a general term for a compound containing lithium as a constituent element, more specifically, a compound containing lithium and one or more transition metal elements as constituent elements. This is because a high energy density can be obtained. In addition, the lithium compound may also contain any one or more of other elements (excluding lithium and transition metal elements). The type of lithium compound is not particularly limited, specifically, oxides, phosphate compounds, silicate compounds, borate compounds, etc. Specific examples of oxides are LiNiO2, LiCoO2, and LiMn2O4, etc., while specific examples of phosphate compounds are LiFePO4 and LiMnPO4, etc.

[0081] The positive electrode binder comprises one or more of a synthetic rubber and a polymer compound. The synthetic rubber may be styrene-butadiene rubber, for example, while the polymer compound may be polyvinylidene fluoride, for example. The positive electrode conductive agent comprises one or more of a conductive material such as a carbon material, such as graphite, carbon black, acetylene black, and Ketjen black. Alternatively, the conductive material may be a metal material or a polymer compound.

[0082] Here, if Figures 4 to 6 As shown, in the positive electrode 41, positive electrode active material layers 41B are provided on both surfaces of a positive electrode current collector 41A. Furthermore, the positive electrode 41 has an exposed portion 41R1 on the side facing the negative electrode 42. In this exposed portion 41R1, since the positive electrode active material layer 41B is not provided on the positive electrode current collector 41A, the positive electrode current collector 41A is exposed. The exposed positive electrode current collector 41A in this exposed portion 41R1 faces the negative electrode active material layer 42B. Furthermore, the exposed portion 41R1 is provided on the positive electrode 41 midway through the winding process.

[0083] Here, the positive electrode 41 further has an exposed portion 41R2 on the side not facing the negative electrode 42 (the side opposite to the side facing the negative electrode 42), at a position corresponding to the exposed portion 41R1. In this exposed portion 41R2, the positive electrode active material layer 41B is not provided, and the positive electrode current collector 41A is exposed. This "position corresponding to the exposed portion 41R1" refers to a position that overlaps with part or all of the exposed portion 41R1.

[0084] In this positive electrode 41, the positive electrode active material layer 41B is provided on the positive electrode current collector 41A so that the positive electrode active material layer 41B extends intermittently through the exposed portion 41R1. As a result, in areas without the exposed portion 41R1, the positive electrode active material layer 41B faces the negative electrode active material layer 42B, while in areas with the exposed portion 41R1, the positive electrode current collector 41A faces the negative electrode active material layer 42B. Furthermore, in the positive electrode 41, the positive electrode active material layer 41B is provided on the positive electrode current collector 41A so that the positive electrode active material layer 41B extends intermittently through the exposed portion 41R2.

[0085] Here, the positive electrode 41 has a “discontinuous direction U1” and a “cross direction U2”. The “discontinuous direction U1” is a direction in which the positive electrode active material layer 41B is discontinuously provided via the exposed portion 41R1 ( Figure 4 The left-right direction in the figure = the first direction), and the "cross direction U2" is a direction that crosses the intermittent direction U1 ( Figure 4 The up-down direction in the equation = the second direction).

[0086] In this case, the positive electrode active material layer 41B includes two portions (portions P1 and P2) separated from each other via the exposed portion 41R1. The portion P1 is located on one side of the exposed portion 41R1 in the intermittent direction U1 ( Figure 4 The first portion P2 is located on the right side of the exposed portion 41R1 in the intermittent direction U1. Figure 4 the second part of the left side of the ).

[0087] (negative electrode)

[0088] like Figures 3 to 5 As shown, the negative electrode 42 includes a negative electrode current collector 42A and a negative electrode active material layer 42B. Figure 4 In FIG, the negative electrode active material layer 42B is indicated with light shading.

[0089] The negative electrode current collector 42A has a pair of surfaces on which the negative electrode active material layer 42B is provided. The negative electrode current collector 42A contains a conductive material such as a metal material, and the metal material is copper or the like.

[0090] The negative electrode active material layer 42B is provided on both sides of the negative electrode current collector 42A and contains any one or more of the negative electrode active materials capable of intercalating and deintercalating lithium. In addition, the negative electrode active material layer 42B may further contain a negative electrode binder and a negative electrode conductive agent. The details of the negative electrode binder and the negative electrode conductive agent are the same as the details of the positive electrode binder and the positive electrode conductive agent. The method for forming the negative electrode active material layer 42B is not particularly limited. Specifically, it is any one or more of a coating method, a gas phase method, a liquid phase method, a spraying method, and a firing method (sintering method).

[0091] As described above, the negative electrode 42 is opposed to the positive electrode 41 via the separator 43, and the negative electrode active material layer 42B is provided on both sides of the negative electrode collector 42A. Therefore, the negative electrode 42 includes the negative electrode active material layer 42B provided on the negative electrode collector 42A on the side facing the positive electrode 41 (positive electrode active material layer 41B), and the negative electrode active material layer 42B provided on the negative electrode collector 42A on the side not facing the positive electrode 41 (the side opposite to the side facing the positive electrode 41).

[0092] The negative electrode active material contains one or both of a carbon material and a metal material. This is because a high energy density can be obtained. Carbon materials include easily graphitized carbon, difficultly graphitized carbon, and graphite (natural graphite and artificial graphite), etc. Metal materials are materials containing any one or two or more of metal elements and semi-metal elements that can form an alloy with lithium as constituent elements, and the metal elements and semi-metal elements are one or both of silicon and tin, etc. In addition, the metal material can be a monomer, an alloy, a compound, a mixture of two or more thereof, or a material containing two or more phases thereof. Specific examples of metal materials are TiSi2 and SiO x (0<x≤2, or 0.2<x<1.4) etc.

[0093] Here, if Figure 4 as well as Figure 5 As shown, in the negative electrode 42, the negative electrode active material layer 42B is provided on both surfaces of the negative electrode current collector 42A. Furthermore, the negative electrode 42 has an exposed portion 42R1 on the side facing the positive electrode 41, and an exposed portion 42R2 on the side not facing the positive electrode 41 (and the side opposite to the side facing the positive electrode 41). In each of the exposed portions 42R1 and 42R2, the negative electrode active material layer 42B is not provided on the negative electrode current collector 42A, so the negative electrode current collector 42A is exposed. The exposed portion 42R1 is provided on each of the outermost and innermost circumferences of the negative electrode 42, while the exposed portion 42R2 is provided on each of the outermost and innermost circumferences of the negative electrode 42.

[0094] In the negative electrode 42 , unlike the positive electrode 41 in which the positive electrode active material layer 41B is intermittently provided on the positive electrode collector 41A via the exposed portion 41R1 (or exposed portion 41R2 ), the negative electrode active material layer 42B is continuously provided on the negative electrode collector 42A.

[0095] In addition, the formation range of the negative electrode active material layer 42B is further expanded toward both sides in the discontinuous direction U1 than the formation range of the positive electrode active material layer 41B. That is, the formation range of the negative electrode active material layer 42B is expanded toward one side ( Figure 4 The right side in the discontinuity direction U1) is expanded compared to the formation range of the positive electrode active material layer 41B, and at the same time, the other side ( Figure 4 The left side in FIG. 1 is larger than the formation range of the positive electrode active material layer 41B. This is to prevent the deposition of lithium released from the positive electrode active material layer 41B.

[0096] The negative electrode 42 protrudes further toward both sides than the positive electrode 41 in the cross direction U2. That is, the negative electrode 42 protrudes toward one side ( Figure 4 The upper side in the middle) protrudes compared to the positive electrode 41, and the other side ( Figure 4 The lower side in the middle (in the figure) protrudes further than the positive electrode 41. This is to prevent the deposition of lithium released from the positive electrode active material layer 41B.

[0097] (diaphragm)

[0098] like Figure 2 、 Figure 3 as well as Figure 7 As shown, the separator 43 is an insulating porous film disposed between the positive electrode 41 and the negative electrode 42, and allows lithium ions to pass therethrough while preventing a short circuit between the positive electrode 41 and the negative electrode 42. The separator 43 is made of a polymer compound such as polyethylene.

[0099] Here, the separator 43 protrudes further toward both sides than the negative electrode 42 in the cross direction U2. That is, the separator 43 protrudes toward both sides ( Figure 7 The upper side in the middle) protrudes compared to the negative electrode 42, and the other side ( Figure 7 The lower side in the middle) protrudes compared to the negative electrode 42.

[0100] The diaphragm 43 includes an upper end portion 43M and a lower end portion 43N in the intersecting direction U2. The upper end portion 43M is the upper end portion of the diaphragm 43 in the intersecting direction U2, while the lower end portion 43N is the lower end portion of the diaphragm 43 in the intersecting direction U2.

[0101] The upper end portion 43M is further expanded in the lateral direction than the portion other than the upper end portion 43M (excluding the lower end portion 43N). That is, the upper end portion 43M is further expanded to one side ( Figure 7 The right side of the negative electrode 42 is expanded and the negative electrode 42 is expanded to the other side ( Figure 7 As a result, the upper end portion 43M is located above the positive electrode 41, and thus the upper end portion of the negative electrode 42 is shielded from the outer can 10 (lid 12).

[0102] In addition, the lower end portion 43N has the same structure as the upper end portion 43M. That is, the lower end portion 43N is expanded in the lateral direction compared to the portion other than the lower end portion 43N (excluding the upper end portion 43M), and is therefore more inclined to one side ( Figure 7 The right side of the positive electrode 41 is expanded and the positive electrode 41 is expanded to the other side ( Figure 7 As a result, the lower end portion 43N is located below the positive electrode 41, and thus the lower end portion of the positive electrode 41 is shielded from the outer can 10 (housing portion 11).

[0103] More specifically, as described later, during the secondary battery manufacturing process, after the wound body 40Z is produced, the upper end 43M and lower end 43N of the separator 43 wound in the wound body 40Z are each subjected to a heat treatment. The heating temperature during this heat treatment can be set arbitrarily, but is specifically set to 100°C or higher. This heat treatment causes the upper end 43M and lower end 43N to undergo thermal deformation or contraction, respectively, thereby expanding laterally to shield the upper and lower ends of the positive electrode 41.

[0104] In this case, since the positive electrode 41 and the separator 43 are wound separately, the positive electrode 41 is sealed by the separator 43 (the upper end 43M and the lower end 43N). That is, since the upper end portions 43M of the adjacent separators 43 expand laterally until they contact each other, the upper end portion of the positive electrode 41 is sealed by these upper end portions 43M. In addition, since the lower end portions 43N of the adjacent separators 43 expand laterally until they contact each other, the lower end portion of the positive electrode 41 is sealed by these lower end portions 43N. This is because, since each of the upper end portion and the lower end portion of the positive electrode 41 is difficult to be exposed, a short circuit between the positive electrode 41 and the outer can 10 (the storage portion 11 and the lid portion 12) can be suppressed.

[0105] It should be noted that the upper end portion 43M shields not only the upper end portion of the positive electrode 41 but also the upper end portion of the negative electrode 42. In addition, the lower end portion 43N shields not only the lower end portion of the positive electrode 41 but also the lower end portion of the negative electrode 42.

[0106] Here, both the upper end portion 43M and the lower end portion 43N are expanded laterally by heat treatment (thermal deformation or thermal contraction), but only one of the upper end portion 43M and the lower end portion 43N may be expanded laterally by heat treatment. In these cases, unlike the case where both the upper end portion 43M and the lower end portion 43N are not expanded laterally, a short circuit between the positive electrode 41 and the outer can 10 can be suppressed. Furthermore, the process for expanding each of the upper end portion 43M and the lower end portion 43N laterally is not limited to heat treatment and may also be another process such as stamping.

[0107] (Electrolyte)

[0108] The electrolyte solution, which impregnates each of the positive electrode 41, the negative electrode 42, and the separator 43, contains a solvent and an electrolyte salt. The solvent contains one or more non-aqueous solvents (organic solvents) such as carbonate compounds, carboxylate compounds, and lactone compounds. The electrolyte solution containing such a non-aqueous solvent is a so-called non-aqueous electrolyte solution. The electrolyte salt contains one or more light metal salts such as lithium salts.

[0109] [Insulating tape installed on the positive electrode]

[0110] like Figures 4 to 7 As shown, the insulating tape 50 is an insulating member that prevents the positive electrode 41 (positive electrode current collector 41A) and the negative electrode 42 from short-circuiting in the exposed portion 41R1 and is provided on the positive electrode 41. Figure 4 In FIG. 5 , the insulating tape 50 is shaded darker than the positive electrode active material layer 41B.

[0111] The insulating tape 50 exposes at least the exposed portion 41R1. Therefore, the insulating tape 50 may cover only the exposed portion of the positive electrode current collector 41A in the exposed portion 41R1, or may cover the positive electrode active material layer 41B along with the positive electrode current collector 41A. In the latter case, the insulating tape 50 may overlap only the portion P1, only the portion P2, or both.

[0112] The insulating tape 50 preferably overlaps both the portions P1 and P2 to prevent the positive electrode current collector 41A from being accidentally exposed in the exposed portion 41R1 due to dimensional tolerances and installation errors of the insulating tape 50 .

[0113] In addition, the insulating tape 50 protrudes further toward both sides than the positive electrode 41 in the cross direction U2. That is, the insulating tape 50 protrudes toward one side ( Figure 4 The upper side in the middle) protrudes compared to the positive electrode 41, and the other side ( Figure 4The lower side of the insulating tape 50 protrudes further than the positive electrode 41. This is to prevent the positive electrode current collector 41A from being accidentally exposed in the exposed portion 41R1 without being covered by the insulating tape 50 due to dimensional tolerance or installation error of the insulating tape 50.

[0114] Here, the insulating tape 50 also protrudes further toward both sides than the diaphragm 43 in the cross direction U2. That is, the insulating tape 50 protrudes toward one side ( Figure 7 The upper side in the middle) protrudes compared to the diaphragm 43, and the other side ( Figure 7 The lower side of the separator 43 protrudes further than the separator 43. This is to prevent the positive electrode 41 and the outer can 10 (the storage portion 11 and the lid 12) from short-circuiting due to dimensional tolerances and installation errors of the separator 43.

[0115] It should be noted that the structure of insulating tape 50 is not particularly limited. Here, insulating tape 50 has a structure in which a base layer and an adhesive layer are laminated. The base layer comprises a polymer compound such as polyethylene terephthalate (PET), while the adhesive layer comprises a rubber-based adhesive, etc. In this insulating tape 50, the base layer is adhered to the positive electrode 41 via the adhesive layer.

[0116] [Insulation tape installed on the positive lead]

[0117] like Figure 4 、 Figure 6 as well as Figure 7 As shown, the insulating tape 60 is another insulating component that prevents the positive lead 71 from short-circuiting with other conductive components, and is provided on the positive lead 71. The type of other conductive components is not particularly limited, and specifically, it is the outer can 10 (lid 12) and the like. Figure 4 as well as Figure 6 In each of the figures, the insulating tape 60 is shaded darker than the positive electrode active material layer 41B.

[0118] The insulating tape 60 is disposed on the side of the positive lead 71 facing the negative electrode 42, covering the portion of the positive lead 71 protruding from the positive electrode 41 and being sandwiched between the positive lead 71 and the insulating tape 50. In this case, the placement range of the insulating tape 60 is not particularly limited; therefore, the insulating tape 60 may or may not partially overlap with the insulating tape 50. In other words, the overlapping distance S of the insulating tape 60 relative to the insulating tape 50 can be arbitrarily set.

[0119] It is preferred that the insulating tape 60 partially overlaps the insulating tape 50. This is to prevent the positive electrode lead 71 from being accidentally exposed without being covered by the insulating tape 60 due to dimensional tolerances or installation errors of the insulating tape 60. In this case, the range of the overlap between the insulating tapes 50 and 60 is not particularly limited, and the insulating tape 60 may or may not overlap the positive electrode current collector 41A at the exposed portion 41R1.

[0120] It is preferred that the insulating tape 60 does not overlap the positive electrode current collector 41A. This is because the increase in the outer diameter of the battery element 40 due to the overlapping of the insulating tape 60 and the positive electrode current collector 41A can be suppressed, thereby ensuring the energy density per unit volume of the secondary battery.

[0121] It should be noted that the structure of the insulating tape 60 is the same as that of the insulating tape 50. In the insulating tape 60, a base layer is adhered to the positive electrode lead 71 via an adhesive layer.

[0122] [Positive lead]

[0123] The positive electrode lead 71 is a wiring member connected to the positive electrode current collector 41A at the exposed portion 41R2 and protrudes from the positive electrode current collector 41A in the cross direction U2. Figure 4 The upper side of the protrusion) is prominent.

[0124] The details of the material forming the positive electrode lead 71 are the same as those of the material forming the positive electrode current collector 41A. The material forming the positive electrode lead 71 and the material forming the positive electrode current collector 41A may be the same as or different from each other.

[0125] The connection position of the positive electrode lead 71 to the positive electrode 41 (positive electrode current collector 41A) is not particularly limited. That is, the positive electrode lead 71 may be connected to the positive electrode 41 at the outermost or innermost circumference, or may be connected to the positive electrode 41 midway through the winding process.

[0126] The positive electrode lead 71 is preferably connected to the positive electrode 41 at a position closer to the inner circumference than the outermost circumference of the positive electrode 41. This is because it can prevent corrosion of the outer can 10 caused by electrolyte creep. This "electrolyte creep" refers to the phenomenon that, when the positive electrode lead 71 is arranged close to the inner wall of the outer can 10, the electrolyte in the battery element 40 creeps up the positive electrode lead 71 and reaches the inner wall of the outer can 10. As a result, the outer can 10 dissolves or changes color due to contact with the electrolyte.

[0127] Here, since the positive electrode lead 71 is disposed midway in the winding of the positive electrode 41 and the through-hole 12K is provided in the recessed portion 12H of the lid 12, a portion of the positive electrode lead 71 (the portion protruding from the positive electrode 41) is bent along the upper end portion of the battery element 40. In this case, a portion of the positive electrode lead 71 bites into the portion of the separator 43 that shields the positive electrode 41 (the upper end portion 43M).

[0128] That is, as described above, the upper end 43M of the separator 43 shields the upper end of the positive electrode 41. In this case, as described later, during the secondary battery manufacturing process, after the wound body 40Z with the positive electrode lead 71 attached is produced, the positive electrode lead 71 is bent so that the positive electrode lead 71 is pressed against the upper end 43M. In this case, the separator 43 can be heated while the positive electrode lead 71 is pressed against it. As a result, the upper end 43M deforms in a concave shape in response to the pressure of the positive electrode lead 71, causing the positive electrode lead 71 to bite into the upper end 43M. More specifically, since a portion of the positive electrode lead 71 is disposed within the recessed portion 43H formed in the upper end 43M by the pressure of the positive electrode lead 71, the recessed portion 43H holds a portion of the positive electrode lead 71 through the upper end 43M. In this case, if the separator 43 is subjected to a heat treatment, the separator 43 is easily thermally deformed, and thus the positive electrode lead 71 is easily bitten into the upper end portion 43M.

[0129] This is because the positive electrode lead 71 is firmly fixed to the battery element 40 by the bite of the positive electrode lead 71 into the upper end portion 43M, and thus the positive electrode lead 71 is less likely to be damaged. Damage to the positive electrode lead 71 may include cracks in the positive electrode lead 71, cutting of the positive electrode lead 71, or detachment of the positive electrode lead 71 from the positive electrode 41.

[0130] Note that the positive electrode lead 71 is physically separated from the positive electrode collector 41A and is therefore separate from the positive electrode collector 41A. Alternatively, the positive electrode lead 71 may be integrated with the positive electrode collector 41A because the positive electrode lead 71 is physically continuous with the positive electrode collector 41A.

[0131] [Negative lead]

[0132] The negative electrode lead 72 is connected to the negative electrode current collector 42A at the exposed portion 42R2 and protrudes from the negative electrode current collector 42A in the cross direction U2. Figure 4 The lower side of the protrusion)

[0133] The details of the material forming the negative electrode lead 72 are the same as those of the negative electrode current collector 42A. Furthermore, the material forming the negative electrode lead 72 and the material forming the negative electrode current collector 42A may be the same or different. The connection position of the negative electrode lead 72 to the negative electrode 42 (negative electrode current collector 42A) is not particularly limited and can be set arbitrarily. Here, the negative electrode lead 72 is connected to the bottom surface (bottom portion M2) of the housing portion 11.

[0134] The negative electrode lead 72 is physically separated from the negative electrode current collector 42A, so the negative electrode lead 72 and the negative electrode current collector 42A are separate. Alternatively, the negative electrode lead 72 and the negative electrode current collector 42A may be physically continuous, so the negative electrode lead 72 and the negative electrode current collector 42A may be integrated.

[0135] [other]

[0136] It should be noted that the secondary battery may further include any one or two or more other components not shown.

[0137] Specifically, the secondary battery is equipped with a safety valve mechanism. When the internal pressure of the outer can 10 reaches a certain value or above, the safety valve mechanism cuts off the electrical connection between the outer can 10 and the battery element 40 (negative electrode 42). The reason why the internal pressure of the outer can 10 reaches a certain value or above is that a short circuit occurs inside the secondary battery, the secondary battery is heated from the outside, etc. The location of the safety valve mechanism is not particularly limited, wherein the safety valve mechanism is preferably provided at either the bottom M1 or M2, and more preferably provided at the bottom M2 where the external terminal 20 is not installed.

[0138] The secondary battery also includes an insulator between the outer can 10 and the battery element 40. This insulator, which includes one or more of an insulating film and an insulating sheet, prevents short circuits between the outer can 10 and the battery element 40 (positive electrode 41). The placement of the insulator is not particularly limited and can be arbitrarily set.

[0139] It should be noted that the outer can 10 is provided with a cleavage valve. This cleavage valve ruptures when the internal pressure of the outer can 10 reaches a certain value or above, thereby releasing the internal pressure. The location of the cleavage valve is not particularly limited; however, as with the location of the safety valve mechanism described above, either the bottom M1 or M2 is preferred, with the bottom M2 being more preferred.

[0140] <1-2. Size requirements>

[0141] In order to improve operational reliability and manufacturing stability, this secondary battery meets the following dimensional requirements. Hereinafter, the dimension in the intermittent direction U1 is referred to as "length," while the dimension in the intersecting direction U2 is referred to as "width." The dimensional requirements are explained with reference to the accompanying drawings.

[0142] Specifically, the positive electrode 41 has a length L1 and a width W1, while the negative electrode 42 has a length L2 and a width W2. As described above, the negative electrode 42 protrudes further to the sides than the positive electrode 41 in the cross direction U2, so the width W2 of the negative electrode 42 is greater than the width W1 of the positive electrode 41. It should be noted that the length L2 of the negative electrode 42 is greater than the length L1 of the positive electrode 41.

[0143] The insulating tape 50 has a width W5 . As described above, the insulating tape 50 protrudes further toward both sides than the positive electrode 41 in the intersecting direction U2 . Therefore, the width W5 of the insulating tape 50 is greater than the width W1 of the positive electrode 41 .

[0144] Furthermore, a portion of the insulating tape 50 that protrudes upward from the positive electrode 41 has a width W3 , and a portion of the insulating tape 50 that protrudes downward from the positive electrode 41 has a width W4 .

[0145] In this case, the width W1 of the positive electrode 41, the width W2 of the negative electrode 42, and the widths W3 and W4 of the protruding portion of the insulating tape 50 satisfy the relationship expressed by the following formula (1). Hereinafter, (W3+W4) / (W2-W1), which represents the relationship between widths W1 to W4, is referred to as the "width ratio."

[0146] 0.50≤(W3+W4) / (W2-W1)≤3.00…(1)

[0147] (W1 is the dimension of the positive electrode 41 in the cross direction U2. W2 is the dimension of the negative electrode 42 in the cross direction U2. W3 is the dimension of the insulating tape 50 protruding from the positive electrode 41 on one side (the upper side) of the two sides in the cross direction U2. W4 is the dimension of the insulating tape 50 protruding from the positive electrode 41 on the other side (the lower side) of the two sides in the cross direction U2.)

[0148] The dimensional condition related to the secondary battery (width ratio (W3 + W4) / (W2 - W1)) satisfies the relationship shown in equation (1) because widths W1 to W4 are mutually optimized. This allows for stable production of secondary batteries equipped with the outer can 10 (housing portion 11 and lid 12) while preventing short circuits between the battery element 40 (positive electrode 41) and the outer can 10 (housing portion 11 and lid 12). The reasons for this explanation will be described in detail later.

[0149] The width ratio (W3+W4) / (W2-W1) preferably satisfies the relationship represented by the following formula (2). This is because short circuits between the battery element 40 and the outer can 10 can be further prevented, and the secondary battery including the outer can 10 can be manufactured more stably.

[0150] 2.00≤(W3+W4) / (W2-W1)≤2.75…(2)

[0151] The separator 43 has a width W6 . As described above, the separator 43 protrudes further toward both sides than the positive electrode 41 in the intersecting direction U2 . Therefore, the width W6 of the separator 43 is greater than the width W1 of the positive electrode 41 .

[0152] In this case, as described above, the insulating tape 50 protrudes further to both sides than the diaphragm 43 in the intersecting direction U2 , and therefore the width W5 of the insulating tape 50 is larger than the width W6 of the diaphragm 43 .

[0153] <1-3. Action>

[0154] When the secondary battery is charged, lithium is extracted from the positive electrode 41 in the battery element 40, and the lithium is simultaneously absorbed into the negative electrode 42 via the electrolyte. On the other hand, when the secondary battery is discharged, lithium is extracted from the negative electrode 42 in the battery element 40, and the lithium is simultaneously absorbed into the positive electrode 41 via the electrolyte. During these charge and discharge operations, lithium is absorbed and extracted in an ionic state.

[0155] <1-4. Manufacturing method>

[0156] Figure 8 The three-dimensional structure of the outer can 10 used in the manufacturing process of the secondary battery is shown. Figure 1 correspond. Figure 9 Shown with Figure 7 The corresponding cross-sectional structure is shown to illustrate the manufacturing process of the secondary battery. Figure 8 In FIG, the cover 12 is shown before being welded to the housing portion 11, so the cover 12 is shown separated from the housing portion 11. Figure 9 In FIG, the positive electrode lead 71 is shown before being bent, and thus the positive electrode lead 71 is shown extending substantially in a straight line.

[0157] In the following description, refer to Figure 8 as well as Figure 9 At the same time, always refer to the Figures 1 to 7 .

[0158] Here, if Figure 8As shown, the outer can 10 is formed using a physically separate container 11 and lid 12. Container 11 is a component formed by integrating a bottom M2 and sidewall M3, and as described above, has an opening 11K. External terminals 20 are pre-installed in recessed portions 12H provided in lid 12 via gaskets 30.

[0159] Furthermore, since the bottom portion M2 and the side wall portion M3 are physically separated from each other, the housing portion 11 may be formed by welding the side wall portion M3 to the bottom portion M2 .

[0160] [Production of positive electrode]

[0161] First, a positive electrode mixture is prepared by mixing a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, etc., and then the positive electrode mixture is added to an organic solvent, etc., to prepare a paste-like positive electrode mixture slurry.

[0162] Next, the positive electrode mixture slurry is applied to both surfaces of the positive electrode current collector 41A to form the positive electrode active material layer 41B. In this case, the range of the positive electrode active material layer 41B is adjusted so that the exposed portions 41R1 and 41R2 are arranged midway during the winding process (when the positive electrode 41 is wound) of the wound body 40Z described later.

[0163] Finally, the positive electrode active material layer 41B is compression-molded using a roller press or the like. In this case, the positive electrode active material layer 41B can be heated while the compression molding process is repeated multiple times. This produces a positive electrode 41 (length L1 and width W1) having exposed portions 41R1 and 41R2.

[0164] [Production of negative electrode]

[0165] First, a negative electrode mixture is prepared by mixing a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent. The negative electrode mixture is then added to an organic solvent to prepare a paste-like negative electrode mixture slurry.

[0166] Next, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 42A to form the negative electrode active material layer 42B. In this case, the formation range of the negative electrode active material layer 42B is adjusted so that the exposed portions 42R1 and 42R2 are located at the outermost and innermost peripheries, respectively, during the later-described process of manufacturing the wound body 40Z (when winding the negative electrode 42).

[0167] Finally, the negative electrode active material layer 42B is compression-molded using a roller press or the like. The details of compression-molding the negative electrode active material layer 42B are the same as those of compression-molding the positive electrode active material layer 41B. This produces the negative electrode 42 (length L2 and width W2) having exposed portions 42R1 and 42R2.

[0168] [Preparation of electrolyte]

[0169] An electrolyte salt is added to a solvent, whereby the electrolyte salt is dispersed or dissolved in the solvent, thereby preparing an electrolytic solution.

[0170] [Assembly of Secondary Batteries]

[0171] First, using welding or the like, the positive electrode lead 71 is connected to the positive electrode 41 (positive electrode current collector 41A) at the exposed portion 41R2, while the negative electrode lead 72 is connected to the negative electrode 42 (negative electrode current collector 42A) at the exposed portion 42R2. The type of welding method is not particularly limited and may include any one, or two or more, of resistance welding, ultrasonic welding, and laser welding. Details of the welding method described here apply to the following description.

[0172] Next, insulating tape 60 is affixed to the positive electrode lead 71. Next, insulating tape 50 (width W5) is affixed to the positive electrode current collector 41A exposed in the exposed portion 41R1. In this case, the affixing position of insulating tape 50 is adjusted so that it protrudes further to both sides of the positive electrode 41 (widths W3 and W4) in the intersecting direction U2 and partially overlaps with insulating tape 60.

[0173] Next, the positive electrode 41 connected to the positive electrode lead 71 and attached with the insulating tapes 50 and 60 and the negative electrode 42 connected to the negative electrode lead 72 are stacked on each other via the separator 43 (width W6), and the positive electrode 41, the negative electrode 42 and the separator 43 are wound. Figure 8 As shown in FIG. 4 , a wound body 40Z is produced. This wound body 40Z has the same structure as the battery element 40 except that the positive electrode 41, the negative electrode 42, and the separator 43 are not impregnated with the electrolyte. Figure 9 As shown, the width W6 of the diaphragm 43 is greater than the width W5 of the insulating tape 50 .

[0174] Next, while heating each of the upper end portion 43M and the lower end portion 43N of the separator 43, the positive electrode lead 71 to which the insulating tape 60 is attached is bent. Figure 7As shown, since upper end portion 43M and lower end portion 43N expand laterally due to thermal deformation or thermal contraction, the upper and lower ends of positive electrode 41 are shielded by separator 43 (upper end portion 43M and lower end portion 43N). Furthermore, since positive electrode lead 71 is pressed against separator 43 (upper end portion 43M) while separator 43 (upper end portion 43M) is heated, positive electrode lead 71 bites into separator 43 (upper end portion 43M) via recess 43H.

[0175] Next, the wound body 40Z to which the positive electrode lead 71 and the negative electrode lead 72 are connected is housed through the opening 11K inside the housing portion 11. In this case, the negative electrode lead 72 is connected to the housing portion 11 by welding or the like.

[0176] Next, using the lid portion 12 to which the external terminal 20 is attached via the gasket 30 , the positive electrode lead 71 is connected to the external terminal 20 through the through-hole 12K by welding or the like.

[0177] Next, the electrolyte solution is injected from the opening 11K into the housing 11. This allows the electrolyte solution to permeate the wound body 40Z (positive electrode 41, negative electrode 42, and separator 43), thereby producing the battery element 40 as a wound electrode body.

[0178] Next, after covering the opening 11K with the lid 12, the lid 12 is welded to the housing 11 using welding or the like. Thus, the housing 11 and the lid 12 are joined to form the outer can 10. The battery element 40 and the insulating tape 50 are housed within the outer can 10, thereby assembling the secondary battery.

[0179] [Stabilization of Secondary Batteries]

[0180] The assembled secondary battery is then charged and discharged. Various conditions, such as the ambient temperature, number of charge and discharge cycles, and charge and discharge conditions, can be arbitrarily set. This forms a coating on the surface of the negative electrode 42, etc., thereby electrochemically stabilizing the state of the secondary battery. Thus, the secondary battery is completed.

[0181] <1-5. Functions and Effects>

[0182] According to this secondary battery, the width ratio (W3+W4) / (W2-W1), which represents the relationship between the width W1 of the positive electrode 41, the width W2 of the negative electrode 42, and the widths W3 and W4 of the insulating tape 50, satisfies the condition shown in formula (1) (0.50≤(W3+W4) / (W2-W1)≤3.00).

[0183] In this case, since the widths W4 and W5 are optimized in relation to the widths W1 and W2 , the widths W1 to W4 are optimized relative to each other.

[0184] As a result, the insulating tape 50 protrudes sufficiently to both sides relative to the positive electrode 41 in the cross direction U2, and thus the positive electrode 41 is sufficiently isolated from the outer can 10 (the housing 11 and the lid 12) via the insulating tape 50. Consequently, the positive electrode 41 is less likely to contact the outer can 10, which serves as an external connection terminal for the negative electrode 42. In other words, the positive electrode 41 is substantially less likely to contact the negative electrode 42, thereby suppressing short circuits between the battery element 40 (positive electrode 41) and the outer can 10.

[0185] Furthermore, because the insulating tape 50 does not protrude excessively toward either side of the positive electrode 41 in the cross direction U2, it does not hinder the joining process when the lid 12 is joined to the housing 11 to close the opening 11K. Consequently, the opening 11K of the housing 11 is fully sealed by the lid 12, and the housing 11 is hermetically sealed by the lid 12. Consequently, the housing 11 and lid 12 can be used to stably form the outer can 10, allowing for stable manufacturing of secondary batteries equipped with the outer can 10.

[0186] As described above, the use of the insulating tape 50 can suppress short circuits between the battery element 40 (positive electrode 41) and the outer can 10, and can also stably manufacture the secondary battery (the outer can 10 including the housing 11 and the lid 12). Therefore, high operational reliability and excellent manufacturing stability can be achieved.

[0187] In particular, if the width ratio (W3+W4) / (W2-W1) satisfies the condition shown in formula (2), short circuits can be further suppressed and the secondary battery can be manufactured more stably, thereby achieving a higher effect.

[0188] Furthermore, if the insulating tape 50 overlaps one or both of the positive electrode active material layers 41B (parts P1 and P2), it is possible to prevent the positive electrode current collector 41A from being accidentally exposed in the exposed portion 41R1 without being covered by the insulating tape 50. Therefore, short circuits can be further suppressed, resulting in a higher effect.

[0189] Furthermore, if the insulating tape 60 is provided on the positive electrode lead 71 and the insulating tape 60 partially overlaps the insulating tape 50 , short circuits caused by the positive electrode lead 71 can be suppressed for reasons described below, thereby achieving a higher effect.

[0190] Figure 10 The cross-sectional structure of the main part of the secondary battery of the first reference example is shown. Figure 7 The secondary battery of the first reference example has the same structure as the secondary battery of the present embodiment ( Figure 7 ) has the same structure.

[0191] In the secondary battery of the first reference example, Figure 10 As shown, the insulating tape 60 does not partially overlap the insulating tape 50. In this case, if there are dimensional tolerances or installation errors in the insulating tape 60, when the positive electrode lead 71 is bent, a portion of the positive electrode lead 71 may be exposed without being covered by the insulating tape 60, potentially causing a short circuit between the positive electrode lead 71 and the outer can 10 (lid 12).

[0192] In contrast, in the secondary battery of this embodiment, Figure 7 As shown, insulating tape 60 partially overlaps insulating tape 50. In this case, even if dimensional tolerances or placement errors occur in insulating tape 60, as long as the insulating tape 60 and insulating tape 50 maintain this partial overlap, a portion of positive lead 71 is less likely to be exposed when the positive lead 71 is bent. This reduces the likelihood of a short circuit between the positive lead 71 and the outer can 10 (lid 12). This prevents short circuits not only from the positive electrode 41 but also from the positive lead 71, achieving a higher level of effectiveness.

[0193] In this case, if the insulating tape 60 does not overlap the positive electrode 41, an increase in the outer diameter of the battery element 40 can be suppressed. Therefore, the energy density per unit volume of the secondary battery increases, and thus a higher effect can be obtained.

[0194] Furthermore, if the separator 43 protrudes further to both sides than the positive electrode 41 in the cross direction U2, and the insulating tape 50 protrudes further to both sides than the separator 43 in the cross direction U2, the positive electrode 41 is isolated from the outer can 10 (the housing 11 and the lid 12) via the separator 43 and the insulating tape 50. This prevents short circuits between the battery element 40 (positive electrode 41) and the outer can 10, resulting in a higher effect.

[0195] In this case, since one or both of the upper end 43M and the lower end 43N of the diaphragm 43 expand in the lateral direction, if one or both of the upper end and the lower end of the positive electrode 41 are shielded by the diaphragm 43, the short circuit between the battery element 40 (positive electrode 41) and the outer packaging can 10 can be further suppressed, thereby achieving a higher effect.

[0196] Moreover, if a portion of the positive lead 71 is bent along the battery element 40 and the portion of the positive lead 71 bites into the portion (upper end 43M) in the diaphragm 43 that shields the positive electrode 41, then due to the reasons described below, even when the secondary battery is subjected to external forces such as vibration and impact, the secondary battery is difficult to be damaged, and thus a higher effect can be obtained.

[0197] Figure 11 The cross-sectional structure of the main part of the secondary battery of the second reference example is shown. Figure 7 The secondary battery of the second reference example has the same structure as the secondary battery of the present embodiment ( Figure 7 ) has the same structure.

[0198] In the secondary battery of the second reference example, as Figure 11 As shown, since the positive electrode lead 71 does not bite into the upper end portion 43M, the positive electrode lead 71 is not held by the separator 43 via the recessed portion 43H. In this case, when the secondary battery is subjected to external forces such as vibration and impact, the positive electrode lead 71 is likely to move inside the outer can 10, and the positive electrode lead 71 may be damaged.

[0199] In contrast, in the secondary battery of this embodiment, Figure 7 As shown, since the positive electrode lead 71 bites into the upper end portion 43M, it is retained by the separator 43 via the recessed portion 43H. In this case, even if the secondary battery is subjected to external force, the positive electrode lead 71 is unlikely to move within the outer can 10, and thus is unlikely to be damaged. Thus, even if the secondary battery is subjected to external force, the secondary battery is unlikely to be damaged, thereby achieving a higher effect.

[0200] Furthermore, if the positive electrode lead 71 is connected to the positive electrode 41 at a position on the inner circumference side of the outermost circumference of the positive electrode 41 , corrosion of the outer can 10 due to the rise of the electrolyte can be suppressed, thereby achieving a higher effect.

[0201] In addition, if the secondary battery is flat and cylindrical, that is, the secondary battery is a coin-type or button-type secondary battery, even in a small secondary battery with large size restrictions, the secondary battery can be stably manufactured while suppressing short circuits, thereby achieving a higher effect.

[0202] Furthermore, if the secondary battery is a lithium ion secondary battery, sufficient battery capacity can be stably obtained by utilizing the insertion and extraction of lithium, and thus a higher effect can be obtained.

[0203] <2. Modifications>

[0204] As described below, the structure of the secondary battery described above can be modified as appropriate. In addition, any two or more of the series of modifications described below can be combined with each other.

[0205] [Variation 1]

[0206] exist Figure 4In the embodiment, since the positive electrode 41 has one exposed portion 41R1, one insulating tape 50 is provided on the positive electrode 41 (the positive electrode current collector 41A in the exposed portion 41R1). However, the number of insulating tapes 50 is not particularly limited and can be arbitrarily set.

[0207] Specifically, since the positive electrode 41 has multiple exposed portions 41R1, multiple insulating tapes 50 may be provided on the positive electrode 41 (positive electrode current collector 41A in the multiple exposed portions 41R1). Even in this case, if the width ratio (W3+W4) / (W2-W1) satisfies the above-mentioned conditions, the secondary battery can be stably manufactured while suppressing short circuits in each of the insulating tapes 50, thereby achieving the same effect.

[0208] [Variation 2]

[0209] exist Figure 4 In the embodiment, since the positive electrode 41 has a single exposed portion 41R2, a single positive electrode lead 71 is connected to the positive electrode 41 (the positive electrode current collector 41A in the exposed portion 41R2), and an insulating tape 60 is provided on the positive electrode lead 71. However, the number of positive electrode leads 71 and insulating tapes 60 is not particularly limited and can be arbitrarily set.

[0210] Specifically, since the positive electrode 41 has multiple exposed portions 41R2, multiple positive electrode leads 71 can be connected to the positive electrode 41 (positive electrode current collectors 41A in the multiple exposed portions 41R2), and multiple insulating tapes 60 can be provided on the multiple positive electrode leads 71. In this case, short circuits between the insulating tapes 60 can also be suppressed, thereby achieving the same effect.

[0211] [Variation 3]

[0212] exist Figure 7 In the embodiment, the positive electrode lead 71 is pressed against the separator 43 (upper end portion 43M), so the positive electrode lead 71 bites into the upper end portion 43M. However, the positive electrode lead 71 may not be pressed against the upper end portion 43M and may not bite into the upper end portion 43M. In this case, the same effect can be achieved.

[0213] Furthermore, as described above, in order to suppress damage to the secondary battery (positive electrode lead 71 ) due to external force, the positive electrode lead 71 preferably bites into the upper end portion 43M.

[0214] [Variation 4]

[0215] exist Figure 2 In the embodiment, the outer packaging can 10 as a welded can (no curling can) is used. However, although not specifically shown here, an outer packaging can as a curling can may be used instead of the outer packaging can 10 as a welded can.

[0216] The outer can of the curled can has the same structure as the outer can 10 of the welded can, except that it includes a housing portion and a lid portion that are physically separated from each other and the housing portion and the lid portion are riveted to each other via a gasket.

[0217] In this case, the battery element 40 and the like are housed inside the outer can, which is a rolled can, and therefore, the same effect can be obtained.

[0218] Example

[0219] An embodiment of the present technology will be described.

[0220] (Examples 1 to 10 and Comparative Examples 1 and 2)

[0221] After the secondary battery was manufactured, the performance of the secondary battery was evaluated.

[0222] [Production of Secondary Batteries]

[0223] By following the steps below, we can create Figures 1 to 6 The flat and cylindrical secondary battery (lithium-ion secondary battery) shown.

[0224] (Production of positive electrode)

[0225] First, a positive electrode mixture was prepared by mixing 91 parts by mass of a positive electrode active material (LiCoO 2 ), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride), and 6 parts by mass of a positive electrode conductor (graphite).

[0226] Next, the positive electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone) and stirred to prepare a paste-like positive electrode mixture slurry. Next, the positive electrode mixture slurry was applied to both sides of the positive electrode current collector 41A (a strip of aluminum foil with a thickness of 12 μm) using a coating device and then dried to form the positive electrode active material layer 41B. In this case, the formation range of the positive electrode active material layer 41B was adjusted to form exposed portions 41R1 and 41R2.

[0227] Finally, the positive electrode active material layer 41B was compression-molded using a roll press, thereby producing a positive electrode 41 (length L1 = 400 mm, width W1 = 3.8 mm) having exposed portions 41R1 and 41R2.

[0228] (Fabrication of negative electrode)

[0229] First, 95 parts by mass of a negative electrode active material (graphite) and 5 parts by mass of a negative electrode binder (polyvinylidene fluoride) were mixed to prepare a negative electrode mixture.

[0230] Next, the negative electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone) and stirred to prepare a paste-like negative electrode mixture slurry. This paste was then applied to both sides of the negative electrode current collector 42A (a 15 μm thick copper foil strip) using a coating device and dried to form the negative electrode active material layer 42B. In this case, the formation range of the negative electrode active material layer 42B was adjusted to form exposed portions 42R1 and 42R2.

[0231] Finally, the negative electrode active material layer 42B was compression-molded using a roll press, thereby producing a negative electrode 42 (length L2 = 420 mm, width W2 = 4.3 mm) having exposed portions 42R1 and 42R2.

[0232] (Preparation of Electrolyte)

[0233] After adding an electrolyte salt (LiPF6) to a solvent (ethylene carbonate and diethyl carbonate), the solvent was stirred. In this case, the solvent mixing ratio (weight ratio) was set to ethylene carbonate: diethyl carbonate = 30:70, and the electrolyte salt content was set to 1 mol / kg relative to the solvent. Thus, the electrolyte salt was dissolved or dispersed in the solvent, thereby preparing an electrolyte solution.

[0234] (Assembly of Secondary Batteries)

[0235] First, the aluminum positive electrode lead 71 is welded to the positive electrode 41 (positive electrode collector 41A) at the exposed portion 41R2 by resistance welding, while the nickel negative electrode lead 72 is welded to the negative electrode 42 (negative electrode collector 42A) at the exposed portion 42R2.

[0236] Next, insulating tape 60 (18 μm thick polyimide tape manufactured by Nitto Denko Corporation) was attached to positive electrode lead 71. The attachment range of insulating tape 60 was adjusted so that insulating tape 60 partially overlapped with insulating tape 50 and did not overlap with positive electrode 41.

[0237] Next, insulating tape 50 (a polyimide tape manufactured by Nitto Denko Corporation with a thickness of 18 μm) was attached to the positive electrode current collector 41A exposed at the exposed portion 41R1, so that the insulating tape 50 overlapped the positive electrode active material layer 41B (portions P1 and P2). In this case, the width W5 of the insulating tape 50 was adjusted to vary the widths W3 and W4, while maintaining the width W3 = width W4. This changed the width ratio (W3 + W4) / (W2 - W1), a dimensional condition for the secondary battery, as shown in Table 1.

[0238] Next, the positive electrode 41 and the negative electrode 42 were stacked with the separator 43 (polyethylene film with a width W6 of 5.8 mm and a thickness of 10 μm) interposed therebetween, and then the positive electrode 41 , the negative electrode 4 and the separator 43 were wound to produce a wound body 40Z.

[0239] Next, the wound body 40Z is housed in the housing portion 11 through the opening 11K. In this case, the negative electrode lead 72 is welded to the housing portion 11 using resistance welding.

[0240] Next, after the electrolyte is injected into the interior of the housing 11 from the opening 11K, the lid 12, to which the external terminal 20 is attached via the gasket 30, is welded to the housing 11 using a laser welding method. In this case, the positive electrode lead 71 is welded to the external terminal 20 using a resistance welding method. As a result, the electrolyte is impregnated into the wound body 40Z (positive electrode 41, negative electrode 42, and separator 43), thereby producing the battery element 40. At the same time, the lid 12 is joined to the housing 11, thereby forming the outer can 10. Thus, the battery element 40 and the insulating tape 50 are sealed inside the outer can 10, thereby assembling the secondary battery.

[0241] (Stabilization of Secondary Batteries)

[0242] The assembled secondary battery was charged and discharged for one cycle at room temperature (temperature = 23°C). When charging, constant current charging was performed at a current of 0.1C until the voltage reached 4.2V. Then, constant voltage charging was performed at this 4.2V voltage until the current reached 0.05C. When discharging, constant current discharge was performed at a current of 0.1C until the voltage reached 3.0V. 0.1C is the current value that completely discharges the battery capacity (theoretical capacity) within 10 hours, and 0.05C is the current value that completely discharges the battery capacity within 20 hours.

[0243] As a result, a coating is formed on the surface of the negative electrode 42 and the like, and thus the state of the secondary battery becomes electrochemically stable.

[0244] [Performance Evaluation]

[0245] When the performance (operation reliability and manufacturing stability) of the secondary battery was evaluated, the results shown in Table 1 were obtained.

[0246] In the case of evaluating the operational reliability, a drop test of the secondary battery is performed to investigate whether a short circuit occurs between the battery element 40 (positive electrode 41) and the outer can 10 (lid 12). In the drop test, the secondary battery is dropped from a height of 1.9 m onto a concrete floor in accordance with the drop test prescribed in the Electrical Appliance and Material Safety Act. In this case, the secondary battery is dropped three times in such a manner that the bottom M1, M2, and the side wall M3 collide with the floor, respectively, so that the secondary battery is dropped a total of nine times. In addition, by repeating the operation of investigating the presence or absence of a short circuit after the drop test (nine drops) 20 times (the number of secondary batteries tested in the drop test = 20), the number of secondary batteries that have experienced the short circuit (the number of short-circuit defects (units)) is investigated.

[0247] To evaluate manufacturing stability, the secondary battery manufacturing process investigated whether the lid 12 could be properly welded to the housing 11 after the wound body 40Z was housed within the housing 11. In this case, the operation of investigating whether a gap formed between the housing 11 and the lid 12 due to the insulating tape 50 after welding the lid 12 to the housing 11 was repeated 20 times (number of secondary batteries inspected during manufacturing = 20). The number of secondary batteries in which such a gap formed was investigated (number of sealing failures).

[0248] Table 1 (Number of drop tests = 20, number of inspections during manufacturing = 20)

[0249]

[0250] [Investigation]

[0251] As shown in Table 1, the operational reliability and manufacturing stability of the secondary battery vary depending on the dimensional conditions (width ratio (W3+W4) / (W2-W1)) of the secondary battery.

[0252] Specifically, when the width ratio (W3+W4) / (W2-W1) was less than 0.50 (Comparative Example 1), no sealing failure occurred, but a short circuit failure occurred. In this case, short circuit failure occurred in all secondary batteries.

[0253] When the width ratio (W3+W4) / (W2-W1) was greater than 3.00 (Comparative Example 2), no short circuit failure occurred, but sealing failure occurred. In this case, sealing failure occurred in about half of the secondary batteries.

[0254] In contrast, when the width ratio (W3+W4) / (W2-W1) was between 0.50 and 3.00 (Examples 1 to 10), either short circuits or sealing defects occurred, depending on the situation. However, the number of short circuits and sealing defects was significantly reduced to less than half. In this case, when the width ratio (W3+W4) / (W2-W1) was between 2.00 and 2.75 (Examples 5 to 8), neither short circuits nor sealing defects occurred.

[0255] (Example 11)

[0256] like Figure 7 As shown in Table 2, a secondary battery was manufactured by the same steps, except that the upper end 43M and the lower end 43N in the diaphragm 43 were expanded respectively by heat treatment, thereby using the upper end 43M and the lower end 43N to shield each of the upper end and the other end of the positive electrode 41. The performance (operation reliability) of the secondary battery was evaluated.

[0257] When manufacturing a secondary battery, after the wound body 40Z is formed, the upper end 43M and lower end 43N of the separator 43 are heated (heating temperature = 100°C). This heat treatment (thermal deformation or thermal contraction) causes the upper end 43M and lower end 43N to expand in the lateral direction. In this case, the heat treatment is continued until the width W6 of the separator 43 is smaller than the width W5 of the insulating tape 50.

[0258] When evaluating the operational reliability of secondary batteries, the same procedures were followed, except that a vibration test was performed instead of a drop test, and the number of secondary batteries tested was changed from 20 to 10. This vibration test is a test with stricter conditions than the drop test to investigate whether the secondary batteries have short circuits.

[0259] The vibration test method complies with the Electrical Appliance and Material Safety Act, with test conditions set at an amplitude of 0.8 mm, a frequency of 10 Hz to 55 Hz, a sweep rate of 1 Hz / minute, and vibration directions in three mutually orthogonal axes (X, Y, and Z). After the vibration test, the secondary battery was left for one hour to check for any rupture, fire, gas emission, or electrolyte leakage.

[0260] Table 2 (Number of vibration tests = 10)

[0261]

[0262] As shown in Table 2, when the separator 43 (upper end portion 43M) was not used to shield the positive electrode 41 (Example 5), a short circuit failure occurred. However, when the upper end portion 43M was used to shield the positive electrode 41 (Example 11), no short circuit failure occurred.

[0263] [Summarize]

[0264] The results shown in Tables 1 and 2 show that when the width ratio (W3+W4) / (W2-W1), which represents the relationship between the width W1 of the positive electrode 41, the width W2 of the negative electrode 42, and the widths W3 and W4 of the insulating tape 50, satisfies the condition shown in formula (1) (0.50≤(W3+W4) / (W2-W1)≤3.00), both short circuit failure and sealing failure are unlikely to occur. Therefore, high operational reliability and excellent manufacturing stability are achieved in the secondary battery.

[0265] Although the present technology has been described above by taking one embodiment and one example, the configuration of the present technology is not limited to the configuration described in one embodiment and one example, and various modifications are possible.

[0266] Specifically, although the case where the electrode reaction material is lithium has been described, the electrode reaction material is not particularly limited. Therefore, as described above, the electrode reaction material can be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reaction material can also be other light metals such as aluminum.

[0267] The effects described in this specification are merely examples, and the effects of this technology are not limited to those described in this specification. Therefore, this technology can also achieve other effects.

Claims

1. A secondary battery comprising: Outer packaging components; a battery element housed in the outer packaging member, comprising a positive electrode and a negative electrode facing each other and wound with an insulating separator interposed therebetween; and an insulating component, disposed on the positive electrode, The positive electrode comprises: a positive electrode current collector; and a positive electrode active material layer provided on the positive electrode current collector, The negative electrode includes: a negative electrode current collector; and a negative electrode active material layer, which is provided on the negative electrode current collector on a side opposite to the positive electrode active material layer. The positive electrode includes an exposed portion where the positive electrode active material layer is not provided and the positive electrode current collector is exposed. The exposed portion faces the negative electrode active material layer, The insulating member covers at least the exposed portion, The positive electrode has a first direction and a second direction. In the first direction, the positive electrode active material layer is intermittently provided on the positive electrode current collector via the exposed portion. The second direction intersects the first direction. In the second direction, the negative electrode protrudes further to both sides than the positive electrode. Furthermore, in the second direction, the insulating member protrudes further toward both sides than the positive electrode. The size of the positive electrode in the second direction, the size of the negative electrode in the second direction, the size of one side of the insulating member protruding from the positive electrode, and the size of the other side of the insulating member protruding from the positive electrode in the second direction satisfy the relationship expressed by the following formula (1): The separator protrudes further toward both sides than the negative electrode in the second direction. The insulating member protrudes further toward both sides than the diaphragm in the second direction. At least one of the one end and the other end of the separator in the second direction is shielded by the adjacent separators expanding until they contact each other. The secondary battery further comprises: a wiring member connected to the positive electrode, A portion of the wiring member is bent along the battery element and bites into a portion of the separator that shields the positive electrode. 0.50≤(W3+W4) / (W2-W1)≤3.00…(1), Among them, W1 is the size of the positive electrode in the second direction, W2 is the size of the negative electrode in the second direction, W3 is the size of the insulating part on one side of the two sides in the second direction protruding compared to the positive electrode, and W4 is the size of the insulating part on the other side of the two sides in the second direction protruding compared to the positive electrode.

2. The secondary battery according to claim 1, wherein The secondary battery satisfies the relationship represented by the following formula (2): 2.00≤(W3+W4) / (W2-W1)≤2.75…(2).

3. The secondary battery according to claim 1 or 2, wherein The positive electrode active material layer includes: a first portion arranged at a position closer to one side than the exposed portion in the first direction; and The second portion is arranged on the other side of the exposed portion in the first direction. The insulating member overlaps at least one of the first portion and the second portion.

4. The secondary battery according to claim 1 or 2, wherein The positive electrode includes: another positive electrode active material layer provided on the positive electrode current collector on the side opposite to the side facing the negative electrode; The positive electrode includes: another exposed portion, at a position corresponding to the exposed portion, the other positive electrode active material layer is not provided and the positive electrode current collector is exposed; The secondary battery further comprises: a wiring member connected to the positive electrode current collector at the other exposed portion and protruding further than the positive electrode current collector in the second direction; and Another insulating member covers the wiring member on the side facing the negative electrode, The other insulating member partially overlaps with the insulating member.

5. The secondary battery according to claim 4, wherein The other insulating member does not overlap with the positive electrode.

6. The secondary battery according to claim 1 or 2, wherein The diaphragm has a recessed portion, A bent portion of the wiring member is disposed inside the recessed portion and is held by the separator in the recessed portion.

7. The secondary battery according to claim 1 or 2, wherein At least one of the one end and the other end of the separator in the second direction is further shielded by the adjacent separators expanding until they contact each other.

8. The secondary battery according to claim 1 or 2, wherein The wiring member is connected to the positive electrode at a position closer to the inner circumference than the outermost circumference of the positive electrode.

9. The secondary battery according to claim 1 or 2, wherein The outer packaging component includes: a storage member having an opening portion for storing the battery element therein; and The cover member closes the opening and is welded to the housing member.

10. The secondary battery according to claim 1 or 2, wherein The secondary battery is a flat and cylindrical secondary battery.

11. The secondary battery according to claim 1 or 2, wherein The secondary battery is a lithium ion secondary battery.

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