Secondary batteries

Abstract

The present invention provides a secondary battery which has higher reliability. A secondary battery according to one embodiment of the present disclosure is provided with: a battery element in which a first electrode and a second electrode are laminated via a separator and wound about a winding axis extending in a first direction; an external terminal; and a lead which includes a pair of end edge parts and connects the first electrode and the external terminal. The first electrode has: a first electrode current collector which includes a first end edge; and a first electrode active material layer which covers a part of the first electrode current collector. The lead is joined to the first electrode current collector in a state in which the pair of end edge parts are inclined with respect to the first end edge of the first electrode current collector.

Description

Technical Field

[0001] This disclosure relates to secondary batteries.

Background Art

[0002] Due to the widespread use of various electronic devices such as mobile phones, the development of secondary batteries is underway as a power source that is small and lightweight and can obtain a high energy density. This secondary battery includes a positive electrode, a negative electrode, and an electrolyte housed inside an exterior member, and various studies have been conducted on the configuration of the secondary battery (see, for example, Patent Document 1).

[0003] For example, Patent Document 1 describes a sealed power storage device including an electrode body in which a positive electrode body and a negative electrode body are laminated or wound via a separator, and an exterior case that houses the electrode body.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] Various studies have been conducted to improve the performance of secondary batteries. However, there is still room for improvement in the performance of secondary batteries.

[0006] Therefore, it is desirable to provide a secondary battery with higher reliability.

[0007] A secondary battery according to one embodiment of the present disclosure comprises a battery element in which a first electrode and a second electrode are stacked with a separator between them and wound around a winding axis extending in a first direction, an external connection terminal, and a lead that includes a pair of edges and connects the first electrode and the external connection terminal. The first electrode has a first electrode current collector including a first edge and a first electrode active material layer covering a part of the first electrode current collector. The lead is joined to the first electrode current collector with a pair of edges inclined with respect to the first edge of the first electrode current collector.

[0008] In one embodiment of the secondary battery of this disclosure, the leads joined to the first electrode current collector include a pair of edges that are inclined with respect to the first edge of the first electrode current collector. Therefore, the stress applied to the joint portion between the first electrode current collector and the leads is relieved. Consequently, a decrease in the strength of the first electrode current collector is suppressed, and cracks or fractures in the first electrode current collector can be avoided. Thus, the secondary battery of one embodiment of this disclosure can have high reliability.

[0009] Furthermore, the effects of this disclosure are not necessarily limited to those described herein, but may include any of the series of effects related to this technology described later. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a perspective view showing the configuration of a secondary battery as one embodiment of the present disclosure. [Figure 2] Figure 2 is a vertical cross-sectional view showing the configuration of the secondary battery shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing the configuration of the battery element shown in Figure 2. [Figure 4A] Figure 4A is a schematic unfolded diagram of the positive electrode of the battery element shown in Figure 3. [Figure 4B] Figure 4B is a schematic unfolded view of the negative electrode of the battery element shown in Figure 3. [Figure 5] Figure 5 is a horizontal cross-sectional view showing the configuration of the secondary battery shown in Figure 1. [Figure 6]FIG. 6 is an enlarged plan view of the negative electrode lead and its vicinity shown in FIG. 4B. [Figure 7] FIG. 7 is an exploded perspective view for explaining the manufacturing process of the secondary battery shown in FIG. 1. [Figure 8A] FIG. 8A is a partially enlarged cross-sectional view showing a part of the battery element shown in FIG. 5 enlarged. [Figure 8B] FIG. 8B is a partially enlarged cross-sectional view showing a part of the battery element shown in FIG. 2 enlarged. [Figure 9] FIG. 9 is an enlarged plan view of a part of the negative electrode of the first modification. [Figure 10] FIG. 10 is an enlarged plan view of a part of the negative electrode of the second modification. [Figure 11] FIG. 11 is an enlarged plan view of a part of the negative electrode of the third modification. [Figure 12] FIG. 12 is an enlarged plan view of a part of the negative electrode of the fourth modification. [Figure 13] FIG. 13 is an enlarged plan view of a part of the negative electrode of the fifth modification. [Figure 14] FIG. 14 is an enlarged plan view of a part of the negative electrode of the comparative example.

Mode for Carrying Out the Invention

[0011] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. The order of description is as follows. 1. One Embodiment 1-1. Configuration 1-2. Operation 1-3. Manufacturing Method 1-4. Action and Effect 2. Modifications of One Embodiment 2-1. The First Modification 2-2. The Second Modification 2-3. The Third Modification [[ID=]55] 2-4. The Fourth Modification 2-5. The Fifth Modification 3. Examples

[0012] <1. An Embodiment> First, a secondary battery according to an embodiment of the present disclosure will be described.

[0013] The secondary battery described here has an appearance with a flat and columnar three-dimensional shape and is called a so-called coin type and button type. As will be described later, this secondary battery has a pair of bottom portions facing each other and a side wall portion located between the pair of bottom portions. In this secondary battery, the height is smaller than the outer diameter. The "outer diameter" referred to here is the maximum diameter (maximum outer diameter) of the bottom portion. In this secondary battery, the maximum diameters of each of the pair of opposing bottom portions are substantially equal to each other. Also, the "height" referred to here is the maximum distance from the upper surface of one bottom portion to the lower surface of the other bottom portion. In the present embodiment, the direction in which the pair of bottom portions face each other is defined as the height direction Z.

[0014] [[ID=十一]] The charge-discharge principle of the secondary battery is not particularly limited. Hereinafter, the case where the battery capacity is obtained by utilizing the occlusion and release of electrode reaction substances will be described. This secondary battery includes an electrolyte together with a positive electrode and a negative electrode. In this secondary battery, in order to prevent the deposition of electrode reaction substances on the surface of the negative electrode during charging, the charging capacity of the negative electrode is larger than the discharging capacity of the positive electrode. That is, the electrochemical capacity per unit area of the negative electrode is set to be larger than the electrochemical capacity per unit area of the positive electrode. Note that the secondary battery of the present embodiment is a secondary battery with a high charging voltage specification that can exhibit good cycle characteristics without reducing the energy density even when charged at a high voltage of 4.38 V or more.

[0015] The type of the electrode reaction substance is not particularly limited. Specifically, it is a light metal such as an alkali metal and an alkaline earth metal. The alkali metals include lithium, sodium, potassium, etc., and the alkaline earth metals include beryllium, magnesium, calcium, etc.

[0016] In the following example, we will consider the case where lithium is the electrode reactant. A secondary battery that obtains battery capacity by utilizing the intercalation and deintercalation of lithium is a so-called lithium-ion secondary battery. In this lithium-ion secondary battery, lithium is intercalated and deintercalated in an ionic state.

[0017] (1-1. Structure) Figure 1 shows a perspective view of the secondary battery. Figure 2 shows a cross-sectional view of the secondary battery shown in Figure 1. Figure 3 shows a cross-sectional view of the battery element 40 shown in Figure 2 in an unfolded state. Furthermore, Figure 4A is an unfolded view of the positive electrode 41 (described later) of the battery element 40, schematically representing its state before winding. Figure 4B is an unfolded view of the negative electrode 42 (described later) of the battery element 40, schematically representing its state before winding.

[0018] For convenience, in the following explanation, the upper side of the paper in Figures 1 and 2 will be described as the upper side of the secondary battery, and the lower side of the paper in Figures 1 and 2 will be described as the lower side of the secondary battery.

[0019] The secondary battery described here has a three-dimensional shape in which the height H is smaller than the outer diameter D, as shown in Figure 1; that is, a flat and columnar three-dimensional shape. Here, the three-dimensional shape of the secondary battery is flat and cylindrical. In this embodiment, the vertical direction of the paper in Figures 1 and 2 is defined as the height direction Z. Therefore, the height H represents the dimension in the height direction Z of the secondary battery in this embodiment. The outer diameter D represents the dimension in the direction perpendicular to the height direction Z of the secondary battery in this embodiment.

[0020] The dimensions of a secondary battery are not particularly limited, but as an example, the outer diameter D is 3mm to 30mm and the height H is 0.5mm to 70mm. However, the ratio of the outer diameter D to the height H (D / H) is greater than 1. That is, the outer diameter D is greater than the height H. There is no particular upper limit to this ratio (D / H), but it is preferably 25 or less.

[0021] As shown in Figures 1 to 3, this secondary battery comprises an outer casing 10, external terminals 20, a battery element 40, and a positive electrode lead 51. In the configuration example shown in Figure 2, the secondary battery further comprises a gasket 30, a negative electrode lead 52, a sealant 61, and insulating films 62 and 63.

[0022] [Outer can] As shown in Figures 1 and 2, the outer casing 10 is a hollow outer component that houses the battery element 40 and the like. The outer casing 10 is made of a conductive material. The outer casing 10 is a specific example corresponding to the "external connection terminal" of this disclosure.

[0023] In the configuration example shown in Figure 1, the outer casing 10 has a flat and approximately cylindrical three-dimensional shape, corresponding to the flat and cylindrical three-dimensional shape of the secondary battery. Therefore, the outer casing 10 has a pair of opposing bottoms M1 and M2, and a side wall M3 located between bottoms M1 and M2. That is, the side wall M3 connects bottoms M1 and M2 and surrounds the battery element 40. The upper end of the side wall M3 is connected to bottom M1. The lower end of the side wall M3 is connected to bottom M2. As described above, the outer casing 10 is approximately cylindrical. The planar shapes of bottoms M1 and M2 are circular, and the surface of the side wall M3 is a convex curved surface.

[0024] Furthermore, the outer can 10 includes a storage section 11 and a lid section 12 that are welded to each other. That is, the internal space of the outer can 10 is sealed by welding the lid section 12 to the storage section 11. In this embodiment, the bottom section M1 constitutes the lid section 12, and the bottom section M2 and the side wall section M3 together constitute the storage section 11. Therefore, the outer edge of the lid section 12 is welded to the upper end of the side wall section M3.

[0025] The storage section 11 is a flat, cylindrical storage member that houses the battery element 40 and the like. The storage section 11 has a hollow structure with an open upper end and a closed lower end. That is, the storage section 11 has an opening 11K (Figure 2) at its upper end, which serves as a passage through which the battery element 40 can be inserted in the height direction Z.

[0026] The lid portion 12 is a substantially disc-shaped lid member that closes the opening 11K of the storage portion 11 and has a through-hole 12K. The through-hole 12K is used as a connection path for connecting the battery element 40 and the external terminal 20 to each other. As described above, the lid portion 12 is welded to the storage portion 11 at the opening 11K. The external terminal 20 is attached to the lid portion 12 via a gasket 30. That is, the lid portion 12 supports the external terminal 20 via the gasket 30. The external terminal 20 is attached to the lid portion 12 via the gasket 30 so as to close the through-hole 12K. The external terminal 20 is electrically insulated from the outer casing 10.

[0027] Furthermore, in the completed secondary battery, as described above, the lid 12 is welded to the storage section 11. As mentioned above, the opening 11K is closed by the lid 12. Therefore, it is possible that by looking at the exterior of the secondary battery, it is not possible to confirm whether the storage section 11 had an opening 11K.

[0028] However, if the lid 12 is welded to the storage section 11, welding marks will remain on the surface of the outer can 10, more specifically at the boundary between the storage section 11 and the lid 12. Based on the presence or absence of these welding marks, it is possible to retrospectively confirm whether the storage section 11 had an opening 11K.

[0029] In other words, if welding marks remain on the surface of the outer can 10, it means that the storage compartment 11 had an opening 11K. On the other hand, if no welding marks remain on the surface of the outer can 10, it means that the storage compartment 11 did not have an opening 11K.

[0030] The lid portion 12 is bent so as to partially protrude along the height direction Z toward the interior of the storage portion 11, forming a recessed portion 12H. That is, when viewed from the outside of the outer can 10, the lid portion 12 has a shape that is partially recessed in the height direction Z toward the battery element 40 housed inside the outer can 10. The recessed portion 12H includes a through-hole 12K that penetrates in the height direction Z, a bottom portion 12HB that surrounds the through-hole 12K along a horizontal plane perpendicular to the height direction Z, and a wall portion 12HW that is erected along the outer edge of the bottom portion 12HB.

[0031] Furthermore, the portion of the lid 12 other than the recessed portion 12H is the peripheral portion 12R. The peripheral portion 12R is an annular shape that surrounds the recessed portion 12H in a horizontal plane perpendicular to the height direction Z of the secondary battery. The peripheral portion 12R is a portion that surrounds the recessed portion 12H and protrudes away from the battery element 40 along the height direction Z. Therefore, in the height direction Z, the surface 12HS of the bottom 12HB of the recessed portion 12H is lower toward the interior of the storage portion 11 than the surface 12RS of the peripheral portion 12R. That is, in the height direction Z, the distance between the surface 12HS of the bottom 12HB of the recessed portion 12H and the battery element 40 is shorter than the distance between the surface 12RS of the peripheral portion 12R and the battery element 40.

[0032] The plan view shape of the recess 12H, that is, the shape defined by the outer edge of the recess 12H when the secondary battery is viewed from above, is not particularly limited. Here, the plan view shape of the recess 12H is approximately circular. The inner diameter and depth of the recess 12H are not particularly limited and can be set arbitrarily. However, when the external terminal 20 is attached to the recess 12H via the gasket 30, the depth of the recess 12H is set such that the height position of the surface 20S of the external terminal 20 is lower than the height position of the surface 12RS of the peripheral portion 12R.

[0033] As described above, the outer can 10 is a can in which the storage section 11 and the lid section 12, which were previously physically separated from each other, are welded together; in other words, it is a welded can. As a result, the outer can 10 after welding is a single, physically integrated component, and therefore cannot be separated into the storage section 11 and the lid section 12 afterward.

[0034] The outer can 10, which is a welded can, is a different type of can from a crimped can formed using a crimping process, and is a so-called crimp-pressed can. This is because the element space volume increases inside the outer can 10, thus increasing the energy density per unit volume. This "element space volume" refers to the volume (effective volume) of the internal space of the outer can 10 that can be used to house the battery elements 40.

[0035] Furthermore, the outer can 10, which is a welded can, does not have any overlapping parts, nor does it have any overlapping parts between two or more components.

[0036] "Having no overlapping parts" means that no part of the outer casing 10 is processed (bent) in a way that allows it to overlap with other parts. Furthermore, "Having no overlapping parts between two or more components" means that, after the secondary battery is completed, the outer casing 10 is physically a single component, and therefore cannot be subsequently separated into two or more components. In other words, the state of the outer casing 10 in the completed secondary battery is not one in which two or more components are combined while overlapping each other in a way that would allow for subsequent separation.

[0037] Here, the outer casing 10 is conductive. More specifically, the storage section 11 and the lid section 12 are both conductive. The outer casing 10 is electrically connected to the negative electrode 42 of the battery element 40 via the negative electrode lead 52. Therefore, the outer casing 10 also serves as an external connection terminal for the negative electrode 42. In this embodiment, the secondary battery does not need to have an external connection terminal for the negative electrode 42 separate from the outer casing 10, thus suppressing the reduction in element space volume caused by the presence of an external connection terminal for the negative electrode 42. As a result, the element space volume increases, and therefore the energy density per unit volume increases.

[0038] Specifically, the outer can 10 is a metal can containing one or more types of conductive materials, such as metal materials and alloy materials. The conductive materials that make up the metal can include iron, copper, nickel, stainless steel, iron alloys, copper alloys, and nickel alloys. The type of stainless steel is not particularly limited, but specifically, it includes SUS304 and SUS316. However, the forming material of the storage section 11 and the forming material of the lid section 12 may be the same or different from each other.

[0039] The lid portion 12 is insulated from the external terminal 20, which serves as the external connection terminal for the positive electrode 41, via a gasket 30. This is to prevent contact, i.e., short circuits, between the outer casing 10, which is the external connection terminal for the negative electrode 42, and the external terminal 20, which is the external connection terminal for the positive electrode 41.

[0040] [External terminals] As shown in Figures 1 and 2, the external terminal 20 is a connection terminal used to connect to electronic equipment when the secondary battery is mounted on that electronic equipment. As described above, the external terminal 20 is attached to and supported by the lid 12 of the outer casing 10. The external terminal 20 is located on the opposite side of the bottom M2 when viewed from the lid 12, and overlaps with the through-hole 12K in the height direction Z.

[0041] Here, the external terminal 20 is connected to the positive electrode 41 of the battery element 40 via the positive electrode lead 51. Therefore, the external terminal 20 functions as an external connection terminal for the positive electrode 41. As a result, when the secondary battery is used, the secondary battery is connected to the electronic device via the external terminal 20 (external connection terminal for the positive electrode 41) and the outer casing 10 (external connection terminal for the negative electrode 42). Thus, the electronic device can operate using the secondary battery as a power source.

[0042] The external terminal 20 is a flat, roughly plate-shaped member that extends along a horizontal plane perpendicular to the height direction Z of the secondary battery, and is located inside the recessed portion 12H via a gasket 30. The external terminal 20 is insulated from the lid portion 12 via the gasket 30. Here, as shown in Figure 2, in the height direction Z, the position of the surface 20S of the external terminal 20 is lower toward the battery element 40 than the position of the surface 12RS of the peripheral portion 12R of the outer casing 10. That is, the external terminal 20 is housed inside the recessed portion 12H such that its upper end surface 20S is recessed toward the battery element 40 than the surface 12RS. In the secondary battery of this embodiment, the height of the secondary battery is reduced compared to the case where the external terminal 20 protrudes above the lid portion 12. As a result, the energy density per unit volume of the secondary battery increases. In addition, it is possible to prevent short circuits between the outer casing 10 and the external terminal 20 via other conductive members. Furthermore, in this embodiment, the peripheral portion of the external terminal 20 overlaps with the bottom portion 12HB of the recessed portion 12H in the height direction Z. By having an overlapping portion between the external terminal 20 and the cover portion 12, the overall mechanical strength of the secondary battery can be improved. Here, the length of the overlapping portion between the external terminal 20 and the peripheral portion along the horizontal plane perpendicular to the height direction Z is preferably greater than the thickness of the external terminal 20 and greater than the thickness of the bottom portion 12HB.

[0043] The outer diameter of the external terminal 20 is smaller than the inner diameter of the recess 12H. Therefore, the outer edge 20T of the external terminal 20 is separated from the cover 12. The gasket 30 is placed only in a portion of the area between the external terminal 20 and the cover 12 (recess 12H). More specifically, it is placed only in the areas where the external terminal 20 and the cover 12 would come into contact with each other if the gasket 30 were not present. However, it is preferable that the gasket 30 also be provided between the inner wall surface of the wall portion 12HW of the recess 12H and the outer edge 20T of the external terminal 20. Furthermore, it is preferable that the cover 12 and the external terminal 20 are fixed together by the gasket 30.

[0044] Furthermore, the external terminal 20 contains one or more types of conductive materials, such as metal materials and alloy materials, and the conductive materials are aluminum and aluminum alloys. However, the external terminal 20 may be formed of a clad material. This clad material contains an aluminum layer and a nickel layer in order from the side closest to the gasket 30, and in this clad material, the aluminum layer and the nickel layer are roll-welded to each other. They are combined.

[0045] [gasket] As shown in Figure 2, the gasket 30 is an insulating member positioned between the outer can 10 (lid portion 12) and the external terminal 20. The external terminal 20 is fixed to the lid portion 12 via the gasket 30. The gasket 30 has a ring-shaped planar form with a through-hole at a location corresponding to the through-hole 12K. The gasket 30 also contains one or more types of insulating materials, such as insulating polymer compounds, and these insulating materials are resins such as polypropylene and polyethylene.

[0046] The installation range of the gasket 30 is not particularly limited and can be set arbitrarily. Here, the gasket 30 is positioned in the gap between the upper surface of the lid 12 and the lower surface of the external terminal 20 inside the recess 12H. However, as mentioned above, it is preferable that the gasket 30 also be provided between the inner wall surface of the wall 12HW of the recess 12H and the outer edge 20T of the external terminal 20. Furthermore, it is preferable that the lid 12 and the external terminal 20 are fixed together by the gasket 30.

[0047] [Battery element] The battery element 40 is a power generation element that carries out a charge-discharge reaction and is housed inside the outer casing 10 as shown in Figures 2 and 3. The battery element 40 includes a positive electrode 41 and a negative electrode 42. Here, the battery element 40 further includes a separator 43 and an electrolyte (not shown) which is a liquid electrolyte. Note that the battery element 40 is one specific example corresponding to the "battery element" in this disclosure.

[0048] The center line PC shown in Figure 2 is a line segment corresponding to the center of the battery element 40 in the direction along the outer diameter D of the secondary battery (casing 10). In other words, the position P0 of the center line PC corresponds to the position of the center of the battery element 40.

[0049] The battery element 40 is a so-called wound electrode body. That is, in the battery element 40, as shown in Figures 2 and 3, for example, the positive electrode 41 and the negative electrode 42 are stacked radially in the direction R via a separator 43. Radial direction R is the radial direction of the outer casing 10. Furthermore, as shown in Figure 5, the stacked positive electrode 41, negative electrode 42 and separator 43 are wound around the center line PC as the winding axis. The positive electrode 41 and the negative electrode 42 are wound while maintaining a state of facing each other via the separator 43. For this reason, a winding center space 40K is formed at the center of the battery element 40. Note that Figure 5 shows one example configuration along a horizontal cross section perpendicular to the height direction Z of the battery element 40. However, in Figure 5, the separator 43 is omitted from the illustration to ensure visibility.

[0050] Here, the positive electrode 41, negative electrode 42, and separator 43 are wound such that the separator 43 is positioned at the outermost circumference and innermost circumference of the wound electrode body, respectively. The number of turns for each of the positive electrode 41, negative electrode 42, and separator 43 is not particularly limited and can be set arbitrarily. Also, at the outermost circumference of the battery element 40, the negative electrode 42 is positioned outside the positive electrode 41. That is, as shown in Figure 5, the outermost positive electrode portion 41out, which is located at the outermost circumference of the positive electrode 41 included in the battery element 40, is located inside the outermost negative electrode portion 42out, which is located at the outermost circumference of the negative electrode 42 included in the battery element 40. Here, the outermost positive electrode portion 41out is the outermost one turn of the positive electrode 41 in the battery element 40. The outermost negative electrode portion 42out is the outermost one turn of the negative electrode 42 in the battery element 40. On the other hand, at the innermost circumference of the battery element 40, it is preferable that the negative electrode 42 is positioned inside the positive electrode 41. In other words, as shown in Figure 5, the innermost negative electrode portion 42in, located at the innermost circumference of the negative electrode 42 included in the battery element 40, is preferably located inside the innermost positive electrode portion 41in, located at the innermost circumference of the positive electrode 41 included in the battery element 40. Here, the innermost positive electrode portion 41in is the innermost one-turn portion of the positive electrode 41 in the battery element 40. The innermost negative electrode portion 42in is the innermost one-turn portion of the negative electrode 42 in the battery element 40.

[0051] The battery element 40 has a three-dimensional shape similar to the three-dimensional shape of the outer casing 10. Specifically, the battery element 40 has a flattened and substantially cylindrical three-dimensional shape. Compared to the case where the battery element 40 has a three-dimensional shape different from the three-dimensional shape of the outer casing 10, when the battery element 40 is housed inside the outer casing 10, so-called dead space, specifically the gap between the outer casing 10 and the battery element 40, is less likely to occur. As a result, the internal space of the outer casing 10 is effectively utilized. Consequently, the volume of the element space increases, and the energy density per unit volume of the secondary battery increases.

[0052] (positive electrode) The positive electrode 41 is the first electrode used to carry out the charge-discharge reaction, and as shown in Figures 3 to 5, it includes a positive electrode current collector 41A, a positive electrode active material layer 41B, and a protective tape 41C. Also, as shown in Figure 4A, the positive electrode 41 has a substantially rectangular planar shape with the height direction Z as the short side and the winding direction θ of the battery element 40 as the long side. That is, the positive electrode 41 is a strip-shaped member defined by an upper edge 41UT, an inner circumference edge 41S, a lower edge 41BT, and an outer circumference edge 41E. The upper edge 41UT is located above the height direction Z and extends along the long side (winding direction θ). The inner circumference edge 41S is located on the innermost circumference side of the winding direction θ and extends along the height direction Z. The lower edge 41BT is located below the height direction Z and extends along the long side (winding direction θ). The outer peripheral edge 41E is located on the outermost side in the winding direction θ and extends along the height direction Z.

[0053] The positive electrode current collector 41A has a pair of surfaces on which the positive electrode active material layer 41B is provided. More specifically, the positive electrode current collector 41A includes an inner surface facing the winding center side of the battery element 40, i.e., position P0, and an outer surface facing the opposite side of the winding center side of the battery element 40, i.e., the opposite side of the inner surface. The positive electrode current collector 41A contains a conductive material such as a metal material. The positive electrode current collector 41A is, for example, a metal foil made of aluminum or an aluminum alloy.

[0054] The positive electrode active material layer 41B is provided, for example, on both a portion of the inner surface and a portion of the outer surface of the positive electrode current collector 41A. However, the positive electrode active material layer 41B may be provided on only one side of the positive electrode current collector 41A. The positive electrode active material layer 41B contains one or more types of positive electrode active materials capable of intercalating and deintercalating lithium. The positive electrode active material layer 41B may also further 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, but specifically, it may be a coating method.

[0055] The positive electrode 41 has a positive electrode current collector covering region 411 and a positive electrode current collector exposed region 412. The positive electrode current collector covering region 411 is the region of the positive electrode 41 in which the positive electrode current collector 41A is covered by the positive electrode active material layer 41B. The positive electrode current collector exposed region 412 is the region of the positive electrode 41 other than the positive electrode current collector covering region 411. That is, the positive electrode current collector exposed region 412 is the region in which the positive electrode current collector 41A is exposed and not covered by the positive electrode active material layer 41B. As shown in Figure 4A, the positive electrode current collector covering region 411 and the positive electrode current collector exposed region 412 each extend along the height direction Z, which is the short side direction of the positive electrode 41, from the upper edge 41UT of the positive electrode 41 to the lower edge 41BT of the positive electrode 41. Furthermore, two positive electrode current collector exposed regions 412 are provided at both ends of the positive electrode 41 in the winding direction θ, which is the longitudinal direction of the positive electrode 41. One of the two positive electrode current collector exposed regions 412 includes the inner edge 41S of the innermost positive electrode portion 41in (Figure 5) of the positive electrode 41, and the other of the two positive electrode current collector exposed regions 412 includes the outer edge 41E of the outermost positive electrode portion 41out (Figure 5) of the positive electrode 41. The positive electrode current collector covering region 411 is positioned between the two positive electrode current collector exposed regions 412 in the winding direction θ. That is, the positive electrode active material layer 41B is not present at both ends of the positive electrode current collector 41A in the winding direction θ, which is the longitudinal direction of the positive electrode current collector 41A. The protective tape 41C is provided on a part of the positive electrode current collector covering region 411. More specifically, it covers the portion of the positive electrode current collector 41A in the positive electrode current collector exposed region 412 that faces the negative electrode active material layer 42B (described later). A positive electrode lead 51 is attached to the positive electrode current collector 41A in the positive electrode current collector exposed region 412 on the inner circumference side. A portion of the positive electrode lead 51 is provided to protrude upward from the upper end edge 41UT of the positive electrode 41.

[0056] The positive electrode active material contains a lithium compound. This lithium compound is a general term for compounds that contain lithium as a constituent element, and more specifically, it is a compound that contains lithium along with one or more transition metal elements as constituent elements. This is because a high energy density can be obtained. However, the lithium compound may further contain one or more other elements (excluding lithium and transition metal elements). The type of lithium compound is not particularly limited, but specifically, it includes oxides, phosphoric acid compounds, silicate compounds, and borate compounds. Specific examples of oxides include LiNiO2, LiCoO2, and LiMn2O4, and specific examples of phosphoric acid compounds include LiFePO4 and LiMnPO4.

[0057] The positive electrode binder contains one or more of the following: synthetic rubber and polymer compounds. Synthetic rubber is styrene-butadiene rubber, while polymer compounds are polyvinylidene fluoride. The positive electrode conductive agent contains one or more of the following: carbon materials, and carbon materials are graphite, carbon black, acetylene black, and Ketjen black. However, the conductive material may also be a metal material or a polymer compound.

[0058] (Negative electrode) The negative electrode 42 is a second electrode used to advance the charge-discharge reaction, and as shown in Figures 3 to 5, it includes a negative electrode current collector 42A and a negative electrode active material layer 42B. Also, as shown in Figure 4B, the negative electrode 42 has a substantially rectangular planar shape with the height direction Z as the short side and the winding direction θ of the battery element 40 as the long side. That is, the negative electrode 42 is a strip-shaped member defined by an upper edge 42UT, an inner circumference edge 42S, a lower edge 42BT, and an outer circumference edge 42E. The upper edge 42UT is located above the height direction Z and extends along the long side (winding direction θ). The inner circumference edge 42S is located on the inner side of the winding direction θ and extends along the height direction Z. The lower edge 42BT is located below the height direction Z and extends along the long side (winding direction θ). The outer peripheral edge 42E is located on the outer circumference side in the winding direction θ and extends along the height direction Z. The negative electrode 42 has a length H42 in the height direction Z.

[0059] The negative electrode current collector 42A has a pair of surfaces on which the negative electrode active material layer 42B is provided. More specifically, the negative electrode current collector 42A includes an inner surface 42A1 facing the winding center side of the battery element 40, i.e., position P0, and an outer surface 42A2 facing the opposite side of the winding center side of the battery element 40, i.e., the opposite side of the inner surface 42A1. The negative electrode current collector 42A is a metal foil made of, for example, nickel, a nickel alloy, copper, or a copper alloy.

[0060] The negative electrode active material layer 42B is provided, for example, on both a portion of the inner surface and a portion of the outer surface of the negative electrode current collector 42A. The negative electrode active material layer 42B contains one or more types of negative electrode active materials capable of intercalating and deintercalating lithium. However, the negative electrode active material layer 42B may further contain a negative electrode binder and a negative electrode conductive agent. Details regarding the negative electrode binder and negative electrode conductive agent are the same as the details regarding the positive electrode binder and positive electrode conductive agent. The method for forming the negative electrode active material layer 42B is not particularly limited, but specifically, it is one or more types from among coating, gas phase, liquid phase, thermal spraying, and firing (sintering).

[0061] As shown in Figure 4B, the negative electrode 42 has a negative electrode current collector covering region 421 and a negative electrode current collector exposed region 422. The negative electrode current collector covering region 421 is the region of the negative electrode 42 in which the negative electrode current collector 42A is covered by the negative electrode active material layer 42B. The negative electrode current collector exposed region 422 is the region of the negative electrode 42 other than the negative electrode current collector covering region 421. That is, the negative electrode current collector exposed region 422 is the region in which the negative electrode current collector 42A is exposed and not covered by the negative electrode active material layer 42B. The negative electrode current collector covering region 421 and the negative electrode current collector exposed region 422 each extend along the height direction Z, which is the short side direction of the negative electrode 42, from the upper edge 42UT of the negative electrode 42 to the lower edge 42BT of the negative electrode 42. Furthermore, two negative electrode current collector exposed regions 422 are provided at both ends of the negative electrode 42 in the winding direction θ, which is the longitudinal direction of the negative electrode 42. One of the two negative electrode current collector exposed regions 422 includes the inner edge 42S of the innermost negative electrode portion 42in (Figure 5) of the negative electrode 42, and the other of the two negative electrode current collector exposed regions 422 includes the outer edge 42E of the outermost negative electrode portion 42out (Figure 5) of the negative electrode 42. The negative electrode current collector covering region 421 is positioned between the two negative electrode current collector exposed regions 422 in the winding direction θ. That is, the negative electrode active material layer 42B is not present at both ends of the negative electrode current collector 42A in the winding direction θ, which is the longitudinal direction of the negative electrode current collector 42A.

[0062] As shown in Figures 3 to 5, the negative electrode lead 52 is attached to the negative electrode current collector 42A in the negative electrode current collector exposed region 422. More specifically, it is attached to the inner surface 42A1 of the negative electrode current collector 42A in the outermost negative electrode current collector exposed region 422 of the two negative electrode current collector exposed regions 422. As shown in Figure 4B, the negative electrode lead 52 is provided such that a portion of it protrudes downward from the lower end edge 42BT of the negative electrode 42. The negative electrode current collector 42A has a notch 42K in a portion of its lower end edge 42BT. The notch 42K has a curved contour, for example, that forms an arc.

[0063] Furthermore, as shown in Figure 4B, the length HWA in the height direction Z of the junction region WA of the negative electrode current collector 42A, which includes the junction portion WP to which the negative electrode lead 52 is joined, is shorter than the length H42 in the height direction Z of the negative electrode current collector 42A in the negative electrode current collector covering region 421. In other words, the distance between the upper edge 42UT and the lower edge 42BT of the negative electrode current collector 42A where the negative electrode lead 52 is attached is narrower than the distance between the upper edge 42UT and the lower edge 42BT of the negative electrode current collector 42A in the negative electrode current collector covering region 421.

[0064] As shown in Figures 4A, 4B and 5, the protective tape 41C of the positive electrode 41 covers the entire area of ​​the positive electrode current collector exposed region 412 of the positive electrode 41 that faces the negative electrode current collector covering region 421 of the negative electrode 42 via the separator 43. The protective tape 41C can effectively prevent internal short circuits in the secondary battery, for example, when foreign matter enters between the negative electrode current collector covering region 421 and the positive electrode current collector exposed region 412. In addition, the protective tape 41C can absorb shocks when the secondary battery is subjected to impact, effectively preventing bending of the positive electrode current collector exposed region 412 and short circuits between the positive electrode current collector exposed region 412 and the negative electrode 42. Furthermore, even if a localized potential increase occurs in the positive electrode current collector coating region 411 near the boundary between the positive electrode current collector coating region 411 and the positive electrode current collector exposed region 412, the outflow of metal ions from the positive electrode active material layer 41B can be suppressed, thereby preventing a short circuit between the positive electrode 41 and the negative electrode 42.

[0065] The negative electrode active material contains either or both carbon materials and metallic materials because they allow for high energy density. Carbon materials include easily graphitizable carbon, poorly graphitizable carbon, and graphite (natural graphite and artificial graphite). Metallic materials are materials that contain one or more metallic elements and metalloid elements capable of forming alloys with lithium, such as silicon and tin, either or both. However, metallic materials may be elements, alloys, compounds, mixtures of two or more of these, or materials containing two or more phases. Specific examples of metallic materials are TiSi2 and SiO2. x (0 <x≦2、または0.2<x<1.4)などである。

[0066] Here, the height of the negative electrode 42 is greater than the height of the positive electrode 41. That is, as shown in Figure 2, the upper edge 42UT of the negative electrode 42 protrudes above the upper edge 41UT of the positive electrode 41, and the lower edge 42BT of the negative electrode 42 protrudes below the lower edge 41BT of the positive electrode 41. This is to prevent lithium released from the positive electrode 41 from depositing. This "height" is the dimension corresponding to the height H of the secondary battery described above, that is, the vertical dimension (height direction Z) in Figures 1 and 2, respectively. The definition of height explained here will be the same hereafter.

[0067] (Separator) As shown in Figures 2 and 3, the separator 43 is an insulating porous membrane placed between the positive electrode 41 and the negative electrode 42. The separator 43 allows lithium ions to pass through while preventing a short circuit between the positive electrode 41 and the negative electrode 42. The separator 43 contains a polymer compound such as polyethylene.

[0068] Here, as shown in Figure 2, the height of the separator 43 is greater than the height of the negative electrode 42. That is, the separator 43 should protrude above the upper edge 42UT of the negative electrode 42 and below the lower edge 42BT of the negative electrode 42.

[0069] (electrolyte) The electrolyte is impregnated into the positive electrode 41, the negative electrode 42, and the separator 43, and contains a solvent and an electrolyte salt. The solvent contains one or more non-aqueous solvents (organic solvents) such as carbonate ester compounds, carboxylic acid ester compounds, and lactone compounds, and the electrolyte containing such a non-aqueous solvent is a so-called non-aqueous electrolyte. The electrolyte salt contains one or more light metal salts such as lithium salts.

[0070] [Positive lead] The positive electrode lead 51 is housed inside the outer casing 10, as shown in Figure 2. The positive electrode lead 51 is a connecting wire connected to the positive electrode 41 and the external terminal 20, respectively. The secondary battery shown in Figure 2 has one positive electrode lead 51. However, the secondary battery may have two or more positive electrode leads 51.

[0071] As previously mentioned, the positive lead 51 is connected to the positive current collector 41A in the positive current collector exposed region 412. The positive lead 51 is also connected to a portion of the surface 20S of the external terminal 20 via a through-hole 12K provided in the cover portion 12. The method of connecting the positive lead 51 is not particularly limited, but specifically, it is one or more welding methods, such as resistance welding and laser welding. Details regarding the welding methods described here will also be applied hereafter.

[0072] A portion of the positive electrode lead 51 is electrically insulated from the lid 12 of the outer casing 10 and the negative electrode 42 of the battery element 40, and is sandwiched between the lid 12 and the battery element 40 in the height direction of the secondary battery. As shown in Figure 2, the positive electrode lead 51 includes a first portion 511, a second portion 512, and a folded portion 513. The first portion 511 and the second portion 512 extend along a horizontal plane perpendicular to the height direction Z of the secondary battery. The first portion 511 and the second portion 512 also overlap each other in the height direction Z of the secondary battery via the sealant 61. The folded portion 513 is curved to connect the first portion 511 and the second portion 512. The first portion 511 and the second portion 512 are sandwiched between the battery element 40 and the recessed portion 12H of the lid 12 in the height direction Z of the secondary battery.

[0073] In this way, a portion of the positive electrode lead 51 extends along the lower surface of the lid 12 and the upper surface of the battery element 40, respectively, and is held in place by the lid 12 and the battery element 40. Therefore, the positive electrode lead 51 is fixed inside the outer casing 10. Even if the secondary battery is subjected to external forces such as vibration and shock, the positive electrode lead 51 is less likely to move, thus reducing the likelihood of damage to the positive electrode lead 51. Damage to the positive electrode lead 51 here refers to cracks occurring in the positive electrode lead 51, the positive electrode lead 51 being cut, or the positive electrode lead 51 being detached from the positive electrode 41.

[0074] In other words, "a portion of the positive electrode lead 51 is sandwiched between the outer casing 10 and the battery element 40" means that the positive electrode lead 51 is insulated from both the outer casing 10 and the battery element 40, and is held in place from above and below by the outer casing 10 and the battery element 40. Therefore, even if the secondary battery is subjected to external forces such as vibration and shock, the positive electrode lead 51 is unlikely to move inside the outer casing 10. The fact that the positive electrode lead 51 is unlikely to move inside the outer casing 10 means that the battery element 40 is also unlikely to move inside the outer casing 10. Consequently, when the secondary battery is subjected to vibration or shock, problems such as unwinding of the wound electrode body of the battery element 40 can be avoided.

[0075] As described above, the lid portion 12 includes a recessed portion 12H, and a portion of the positive electrode lead 51 is sandwiched between the recessed portion 12H and the battery element 40. That is, a portion of the positive electrode lead 51 extends along the lower surface of the recessed portion 12H and the upper surface of the battery element 40, respectively, so that it is held by the recessed portion 12H and the battery element 40. Since the positive electrode lead 51 is more easily held by utilizing the recessed portion 12H, the positive electrode lead 51 becomes less prone to damage.

[0076] Furthermore, a portion of the positive electrode lead 51 is insulated from the lid portion 12 and the negative electrode 42 via the separator 43, sealant 61, and insulating films 62 and 63, respectively.

[0077] Specifically, as described above, the height of the separator 43 is greater than the height of the negative electrode 42. As a result, a portion of the positive electrode lead 51 is separated from the negative electrode 42 via the separator 43, and is therefore insulated from the negative electrode 42 via the separator 43. This prevents a short circuit between the positive electrode lead 51 and the negative electrode 42.

[0078] Furthermore, the positive lead 51 is surrounded by an insulating sealant 61. This insulates a portion of the positive lead 51 from the cover 12 and the negative electrode 42 via the sealant 61. This prevents short circuits between the positive lead 51 and the cover 12, as well as between the positive lead 51 and the negative electrode 42.

[0079] Furthermore, an insulating film 62 is placed between the lid 12 and the positive lead 51. This insulates a portion of the positive lead 51 from the lid 12 via the insulating film 62, thereby preventing a short circuit between the positive lead 51 and the lid 12.

[0080] Furthermore, an insulating film 63 is placed between the battery element 40 and the positive electrode lead 51. This insulates a portion of the positive electrode lead 51 from the negative electrode 42 via the insulating film 63, thereby preventing a short circuit between the positive electrode lead 51 and the negative electrode 42.

[0081] Details regarding the forming material of the positive electrode lead 51 are the same as details regarding the forming material of the positive electrode current collector 41A. However, the forming material of the positive electrode lead 51 and the forming material of the positive electrode current collector 41A may be the same or different.

[0082] The connection position of the positive electrode lead 51 to the positive electrode 41 is not particularly limited and can be set arbitrarily. In particular, it is preferable that the positive electrode lead 51 is connected to the positive electrode 41 on the inner side of the positive electrode 41 rather than on the outermost side of the positive electrode 41. This is because, unlike when the positive electrode lead 51 is connected to the positive electrode 41 on the outermost side of the positive electrode 41, corrosion of the outer casing 10 caused by electrolyte creep is prevented. This "electrolyte creep" refers to the phenomenon where, when the positive electrode lead 51 is positioned close to the inner wall surface of the outer casing 10, the electrolyte in the battery element 40 creeps up the positive electrode lead 51 and reaches the inner wall surface of the outer casing 10. When the electrolyte comes into contact with the outer casing 10 due to this "electrolyte creep," the outer casing 10 may dissolve or discolor.

[0083] The positive electrode lead 51 is provided separately from the positive electrode current collector 41A. However, since the positive electrode lead 51 is physically continuous with the positive electrode current collector 41A, it may be integrated with the positive electrode current collector 41A.

[0084] [Negative lead] The negative electrode lead 52 is housed inside the outer casing 10, as shown in Figure 2. The negative electrode lead 52 electrically connects the negative electrode 42 to the outer casing 10 (storage section 11). Therefore, the storage section 11 (bottom M2) is electrically connected to the negative electrode 42 via the negative electrode lead 52. Here, the secondary battery has one negative electrode lead 52. However, the secondary battery may have two or more negative electrode leads 52. Note that the negative electrode lead 52 is just one specific example corresponding to the "lead" in this disclosure.

[0085] As previously mentioned, the negative electrode lead 52 is connected to the negative electrode current collector 42A so as to protrude from the lower end edge 42BT of the negative electrode 42. The negative electrode lead 52 is further connected to the bottom surface of the housing 11. The method of connecting the negative electrode lead 52 is not particularly limited, but specifically it is one or more of the welding methods such as resistance welding and laser welding.

[0086] Details regarding the material for forming the negative electrode lead 52 are the same as those regarding the material for forming the negative electrode current collector 42A. However, the material for forming the negative electrode lead 52 and the material for forming the negative electrode current collector 42A may be the same or different. Nickel is an example of a constituent material for the negative electrode lead 52.

[0087] The connection position of the negative electrode lead 52 to the negative electrode 42 is not particularly limited and can be set arbitrarily. Here, the negative electrode lead 52 is connected to the outermost part of the negative electrode 42 that constitutes the wound electrode body.

[0088] The negative electrode lead 52 is provided separately from the negative electrode current collector 42A. However, since the negative electrode lead 52 is physically continuous with the negative electrode current collector 42A, it may be integrated with the negative electrode current collector 42A.

[0089] Figure 6 is an enlarged plan view of the negative electrode lead 52 and its vicinity shown in Figure 4B. The negative electrode lead 52 includes a pair of end edges 52T1 and 52T2, which are the ends of the lead in the width direction (winding direction θ) perpendicular to the extending direction (height direction Z). As mentioned earlier, the negative electrode current collector 42A is provided with a notch 42K, and the negative electrode lead 52 is joined so as to overlap the notch 42K in the radial direction R. Therefore, the negative electrode lead 52 is joined to the negative electrode current collector 42A with the pair of end edges 52T1 and 52T2 inclined with respect to the lower end edge 42BT. The inclination of the pair of end edges 52T1 and 52T2 with respect to the lower end edge 42BT means that the angle at which the lower end edge 42BT and end edge 52T1 intersect, and the angle at which the lower end edge 42BT and end edge 52T2 intersect are not 90°. Furthermore, the length W42K of the notch 42K of the negative electrode current collector 42A in the winding direction θ is preferably longer than the length W52 of the negative electrode lead 52 in the winding direction θ. In the example configuration shown in Figure 6, the length W42K of the notch 42K in the winding direction θ is longer than the length H42K of the notch 42K in the height direction Z. The portion of the negative electrode lead 52 that connects to the negative electrode current collector 42A extends, for example, in the height direction Z. However, the portion of the negative electrode lead 52 that protrudes downward from the lower end edge 42BT is bent to follow a horizontal plane perpendicular to the height direction Z, as shown in Figure 2. Since the lower end edge 42BT of the negative electrode current collector 42A is provided with a notch 42K, the stress applied to the lower end edge 42BT by bending the negative electrode lead 52 is relieved.

[0090] [Sealant] As shown in Figure 2, the sealant 61 is a first insulating member that covers the periphery of the positive electrode lead 51. The sealant 61 is constructed by attaching two insulating tapes to the front and back surfaces of the positive electrode lead 51, respectively. Here, the sealant 61 covers the periphery of the middle portion of the positive electrode lead 51 in order to connect the positive electrode lead 51 to the positive electrode 41 and the external terminal 20, respectively. Note that the sealant 61 is not limited to having a tape-like structure, but may also have a tubular structure, for example.

[0091] The sealant 61 contains one or more insulating materials, such as insulating polymer compounds, and these insulating materials include polyimide.

[0092] [Insulating film] As shown in Figure 2, the insulating film 62 is an insulating member positioned between the lid 12 and the battery element 40 in the height direction Z. Here, the insulating film 62 has a ring-shaped planar form with an opening 62K at a location corresponding to the through-hole 12K in the height direction Z.

[0093] In this case, the insulating film 62 may be bonded to the lid portion 12 via an adhesive layer.

[0094] Furthermore, the insulating film 62 may contain one or more insulating materials, such as insulating polymer compounds. The insulating materials contained in the insulating film 62 are polyimide, etc.

[0095] As shown in Figure 2, the insulating film 63 is an insulating member placed between the battery element 40 and the positive electrode lead 51. Here, the insulating film 63 has a flat, planar shape. The insulating film 63 is positioned to shield the winding center space 40K and to cover the battery element 40 around the winding center space 40K.

[0096] Details regarding the material for forming the insulating film 63 are the same as those regarding the material for forming the insulating film 62. However, the material for forming the insulating film 63 and the material for forming the insulating film 62 may be the same or different from each other.

[0097] [others] Furthermore, the secondary battery may also comprise one or more other components. Specifically, the secondary battery is equipped with a safety valve mechanism. This safety valve mechanism disconnects the electrical connection between the outer casing 10 and the battery element 40 when the internal pressure of the outer casing 10 reaches a certain level. The causes of the internal pressure of the outer casing 10 reaching a certain level include a short circuit occurring inside the secondary battery and the secondary battery being heated from the outside. The location of the safety valve mechanism is not particularly limited, but it is preferable that the safety valve mechanism be provided on either the bottom M1 or M2, and more preferably on the bottom M2 where the external terminal 20 is not attached.

[0098] Furthermore, the secondary battery may have an insulator other than the insulating films 62 and 64 between the outer casing 10 and the battery element 40. This insulator includes one or more types of insulating films and insulating sheets, etc., and prevents short circuits between the outer casing 10 and the battery element 40. The installation range of the insulator is not particularly limited and can be set arbitrarily.

[0099] Furthermore, the outer can 10 contains: cleavage A valve is provided. cleavage The valve opens when the internal pressure of the outer can 10 reaches a certain level, thereby releasing that internal pressure. cleavage The location where the valve is installed is not particularly limited, but among them, the bottom M1 and M2 are preferred, and the bottom M2 is more preferred, similar to the installation location of the safety valve mechanism described above.

[0100] (1-2.Operation) During charging of the secondary battery, lithium is released from the positive electrode 41 in the battery element 40, and this lithium is absorbed into the negative electrode 42 via the electrolyte. Conversely, during discharging of the secondary battery, lithium is released from the negative electrode 42 in the battery element 40, and this lithium is absorbed into the positive electrode 41 via the electrolyte. During these charging and discharging processes, lithium is absorbed and released in an ionic state.

[0101] (1-3. Manufacturing method) Figure 7 shows a perspective view of the outer casing 10 used in the manufacturing process of secondary batteries, and corresponds to Figure 1.

[0102] Figure 7 shows the state in which the lid portion 12 is separated from the storage portion 11, before the lid portion 12 is welded to the storage portion 11.

[0103] In the following explanation, we will refer to Figures 1 through 6, which have already been explained, as well as Figure 7, from time to time.

[0104] Here, in order to form the outer container 10, a storage section 11 and a lid section 12, which are physically separated from each other, are prepared as shown in Figure 7. The storage section 11 is a roughly container-shaped member in which the bottom section M2 and the side wall section M3 are integrated with each other, and has an opening 11K. The lid section 12 is a roughly plate-shaped member corresponding to the bottom section M1, and the external terminals 20 are pre-attached to the recessed section 12H provided in the lid section 12 via a gasket 30.

[0105] However, the storage section 11 may be formed by preparing a bottom section M2 and a side wall section M3 that are physically separated from each other, and welding the side wall section M3 to the bottom section M2.

[0106] [Fabrication of the positive electrode] First, a positive electrode mixture is prepared by mixing positive electrode active material, positive electrode binder, and positive electrode conductive agent. Next, a paste-like positive electrode mixture slurry is prepared by adding the prepared positive electrode mixture to an organic solvent. Subsequently, the positive electrode mixture slurry is applied to both sides of the positive electrode current collector 41A to form a positive electrode active material layer 41B. Finally, the positive electrode active material layer 41B is compressed and molded using a roll press or the like. In this case, the positive electrode active material layer 41B may be heated, or the compression molding may be repeated multiple times. This produces the positive electrode 41.

[0107] [Fabrication of the negative electrode] The negative electrode 42 is manufactured using the same procedure as that used for manufacturing the positive electrode 41. Specifically, a negative electrode mixture, which consists of a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent, is added to an organic solvent to prepare a paste-like negative electrode mixture slurry. Then, the negative electrode mixture slurry is applied to both sides of the negative electrode current collector 42A to form a negative electrode active material layer 42B. After this, the negative electrode active material layer 42B is compressed and molded using a roll press or the like. This completes the manufacturing of the negative electrode 42.

[0108] [Preparation of electrolyte solution] The electrolyte salt is added to the solvent. This disperses or dissolves the electrolyte salt in the solvent, thus preparing the electrolyte solution.

[0109] [Assembly of rechargeable batteries] First, using a welding method such as resistance welding, the positive lead 51, which is covered with sealant 61, is connected to the positive electrode 41 (positive electrode current collector 41A), and the negative lead 52 is connected to the negative electrode 42 (negative electrode current collector 42A).

[0110] Next, the positive electrode 41 and the negative electrode 42 are stacked with a separator 43 in between, and then the stacked material including the positive electrode 41, the negative electrode 42, and the separator 43 is wound to produce a wound body 40Z, as shown in Figure 7. The wound body 40Z has the same configuration as the battery element 40, except that the positive electrode 41, the negative electrode 42, and the separator 43 are not impregnated with electrolyte. Note that the positive electrode lead 51 and the negative electrode lead 52 are not shown in Figure 7.

[0111] Next, the winding body 40Z, to which the positive lead 51 and the negative lead 52 are connected, is housed inside the storage section 11 through the opening 11K. In this case, the negative lead 52 is connected to the storage section 11 using a welding method such as resistance welding. Subsequently, an insulating film 63 is placed on top of the winding body 40Z.

[0112] Next, a cover portion 12 is prepared, which already has the external terminals 20 attached via a gasket 30 and an insulating film 62 provided. Then, the positive lead 51 is connected to the external terminals 20 via the through-hole 12K using a welding method such as resistance welding.

[0113] As a result, the wound body 40Z (positive electrode 41) housed inside the storage section 11 and the external terminal 20 attached to the lid section 12 are connected to each other via the positive electrode lead 51.

[0114] Next, electrolyte is injected into the storage section 11 through the opening 11K. In this case, as described above, even though the battery element 40 and the external terminal 20 are connected to each other via the positive electrode lead 51, the lid 12 does not block the opening 11K, so the electrolyte can be easily injected into the storage section 11 through the opening 11K. As a result, the electrolyte is impregnated into the wound body 40Z, which includes the positive electrode 41, the negative electrode 42, and the separator 43, and the battery element 40, which is a wound electrode body, is fabricated.

[0115] Next, the lid 12 is tilted down so as to approach the storage section 11, thereby closing the opening 11K with the lid 12, and then the lid 12 is welded to the storage section 11 using a welding method such as laser welding. In this case, as shown in Figure 2, a part of the positive electrode lead 51 is sandwiched between the lid 12 and the battery element 40, and a curved folded portion 513 is formed in front of the connection point to the external terminal 20 of the positive electrode lead 51. As a result, the outer casing 10 is formed, and the battery element 40 and other components are housed inside the outer casing 10, completing the assembly of the secondary battery.

[0116] [Stabilization of secondary batteries] The rechargeable battery is charged and discharged after assembly. Ambient temperature, number of charge / discharge cycles and charge Various conditions, such as discharge conditions, can be set arbitrarily. As a result, a coating is formed on the surface of the negative electrode 42, etc., which electrochemically stabilizes the state of the secondary battery. Thus, the secondary battery is completed.

[0117] (1-4. Action and Effects) Thus, in the secondary battery of this embodiment, the negative electrode lead 52 is joined to the negative electrode current collector 42A with the negative electrode 42 of the battery element 40 in a state where a pair of edge 52T1 and 52T2 are inclined with respect to the lower edge 42BT. Specifically, a notch 42K is provided in a part of the lower edge 42BT of the negative electrode current collector 42A, and the negative electrode lead 52 is joined to the portion of the negative electrode current collector 42A that overlaps with the notch 42K. Therefore, a decrease in the strength of the negative electrode current collector 42A is suppressed, Negative electrode current collector 42A This prevents cracks and fractures from occurring. This is because even when the negative electrode lead 52 is bent, the stress that the negative electrode lead 52 applies to the negative electrode current collector 42A is relieved.

[0118] The effects and advantages of the secondary battery of this embodiment will be explained in more detail with reference to Figures 8A and 8B. Figure 8A is a partially enlarged cross-sectional view showing a portion of the battery element 40 shown in Figure 5. Figure 8B is a partially enlarged cross-sectional view showing a portion of the battery element 40 shown in Figure 2. Figure 8B shows a cross-section in the direction of the arrow along the line VIII-VIII shown in Figure 8A. For example, as shown in Figure 8A, in a horizontal cross-section perpendicular to the height direction Z, the joint portion 52A of the negative electrode lead 52 that is joined to the negative electrode current collector 42A is curved in accordance with the shape of the negative electrode current collector 42A, which is wound around the center line PC as the winding axis. As shown in Figure 8B, near the lower end edge 42BT of the negative electrode current collector 42A to which the negative electrode lead 52 is attached, the lead-out portion 52B of the negative electrode lead 52 that protrudes from the lower end edge 42BT is bent at approximately a right angle to the joint portion 52A joined to the negative electrode current collector 42A. That is, the joint portion 52A extends in the height direction Z, while the lead-out portion 52B extends in the radial direction R. Therefore, the lead-out portion 52B, especially the portion near the lower end edge 42BT, tends to deform into a straight line. Therefore, the pair of end edges 52T1 and 52T2 of the lead portion 52B of the negative electrode lead 52 apply stress to the negative electrode current collector 42A in the directions indicated by arrows SS1 and SS2 in Figure 8A. As a result, localized compressive and tensile stresses are applied near the lower end edge 42BT of the negative electrode current collector 42A. In this embodiment of the secondary battery, a notch 42K is provided, and the negative electrode lead 52 is joined to the negative electrode current collector 42A with the pair of end edges 52T1 and 52T2 inclined relative to the lower end edge 42BT. This distributes the aforementioned compressive and tensile stresses applied to the lower end edge 42BT around the lower end edge 42BT, preventing stress concentration at the lower end edge 42BT. As a result, sufficient strength of the negative electrode current collector 42A is maintained, and the secondary battery of this embodiment can have high reliability.

[0119] In contrast, when the pair of edges 52T1 and 52T2 are perpendicular to the lower edge 42BT, unlike the secondary battery of this embodiment, the position where the lower edge 42BT and edge 52T1 come into contact, and the lower edge 42BT and edge 52 T2Stress tends to concentrate at each of the contact points. Therefore, the strength of the negative electrode current collector may be reduced compared to the secondary battery of this embodiment.

[0120] Furthermore, in the secondary battery of this embodiment, the negative electrode lead 52 is joined to the inner surface 42A1 of the negative electrode current collector 42A. Therefore, when the negative electrode lead 52 is located on the outermost part of the negative electrode current collector 42A, insertion into the storage section 11 of the outer casing 10 is improved compared to the case where the negative electrode lead 52 is joined to the outer surface 42A2 of the negative electrode current collector 42A.

[0121] Furthermore, if the secondary battery is a lithium-ion secondary battery, sufficient battery capacity can be stably obtained by utilizing the intercalation and deintercalation of lithium.

[0122] <2. Modified Examples of One Embodiment> (First variation) Next, a negative electrode 42-1 as a first modified example of one embodiment of the present disclosure will be described with reference to Figure 9. Figure 9 is an enlarged plan view of a part of the negative electrode 42-1 as a first modified example, and corresponds to Figure 6, which shows an enlarged view of a part of the negative electrode 42 of the above embodiment. The negative electrode current collector 42-1A of the negative electrode 42-1 has a notch 42-1K at the lower end edge 42BT of the negative electrode current collector exposed area 422. The notch 42-1K has a substantially triangular planar shape including two straight sections. Except for the above point, the configuration of the negative electrode 42-1 as a first modified example is substantially the same as the configuration of the negative electrode 42 of the above embodiment. The secondary battery equipped with the negative electrode 42-1 of this modified example can be expected to have the same effects as the secondary battery equipped with the negative electrode 42 of the above embodiment.

[0123] (Second variation) Next, a negative electrode 42-2 as a second modification of one embodiment of the present disclosure will be described with reference to Figure 10. Figure 10 is an enlarged plan view of a part of the negative electrode 42-2 as a second modification, and corresponds to Figure 6, which shows an enlarged view of a part of the negative electrode 42 of the first embodiment. The negative electrode current collector 42-2A of the negative electrode 42-2 has a notch 42-2K at the lower edge 42BT of the negative electrode current collector exposed area 422. The notch 42-2K has a substantially rectangular planar shape including three straight sections. The configuration of the negative electrode 42-2 as a second modification is substantially the same as the configuration of the negative electrode 42 of the first embodiment, except for the points mentioned above. The same effects as the secondary battery equipped with the negative electrode 42 of the first embodiment can be expected in a secondary battery equipped with the negative electrode 42 of this modification.

[0124] (Third variation) Next, a negative electrode 42-3 as a third modification of one embodiment of the present disclosure will be described with reference to Figure 11. Figure 11 is an enlarged plan view of a part of the negative electrode 42-3 as a third modification, and corresponds to Figure 6, which shows an enlarged view of a part of the negative electrode 42 of the above embodiment. The negative electrode current collector 42-3A of the negative electrode 42-3 has a notch 42-3K at the lower end edge 42BT of the negative electrode current collector exposed area 422. The notch 42-3K has a substantially trapezoidal planar shape including three straight sections. Except for the above point, the configuration of the negative electrode 42-3 as a third modification is substantially the same as the configuration of the negative electrode 42 of the above embodiment. The secondary battery equipped with the negative electrode 42-3 of this modification can be expected to have the same effects as the secondary battery equipped with the negative electrode 42 of the above embodiment.

[0125] (Fourth variation) Next, a negative electrode 42-4 as a fourth modification of one embodiment of the present disclosure will be described with reference to Figure 12. Figure 12 is an enlarged plan view of a part of the negative electrode 42-4 as the fourth modification, and corresponds to Figure 6, which shows an enlarged view of a part of the negative electrode 42 of the above embodiment. The negative electrode current collector 42-4A of the negative electrode 42-4 has a notch 42-4K at the lower end edge 42BT of the negative electrode current collector exposed area 422. The notch 42-4K has a semi-elliptical planar shape including a curved portion. The length H42K of the notch 42-4K is longer than half of the length W42K. Note that the length H42K may be equal to half of the length W42K. Except for the above point, the configuration of the negative electrode 42-4 as the fourth modification is substantially the same as the configuration of the negative electrode 42 of the above embodiment. The secondary battery equipped with the negative electrode 42-4 of this modification can be expected to have the same effects as the secondary battery equipped with the negative electrode 42 of the above embodiment.

[0126] (Fifth variation) Next, a negative electrode 42-5 as a fifth modification of one embodiment of the present disclosure will be described with reference to Figure 13. Figure 13 is an enlarged plan view of a part of the negative electrode 42-5 as the fifth modification, and corresponds to Figure 6, which shows an enlarged view of a part of the negative electrode 42 of the above embodiment. The negative electrode current collector 42-5A of the negative electrode 42-5 has a stepped notch 42-5K at the lower end edge 42BT of the negative electrode current collector exposed area 422. The notch 42-5K includes inclined portions 42-5K1 and 42-5K2 at the points where it intersects with the end edges 52T1 and 52T2 of the negative electrode lead 52, respectively. Except for the points mentioned above, the configuration of the negative electrode 42-5 as the fifth modification is substantially the same as the configuration of the negative electrode 42 of the above embodiment. The secondary battery equipped with the negative electrode 42-5 of this modification can be expected to have the same effects as the secondary battery equipped with the negative electrode 42 of the above embodiment.

[0127] <4. Examples> Examples of the present disclosure will be described below.

[0128] [Example 1] One hundred secondary batteries (lithium-ion secondary batteries) shown in Figures 1-6 were fabricated. Specifically, coin-type secondary batteries including a negative electrode 42 with a notch 42K formed therein were fabricated as follows.

[0129] (Fabrication of the positive electrode) First, a positive electrode mixture was prepared by mixing 91 parts by mass of positive electrode active material (LiCoO2), 3 parts by mass of positive electrode binder (polyvinylidene fluoride), and 6 parts by mass of positive electrode conductive agent (graphite). Next, the positive electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like positive electrode mixture slurry. Subsequently, 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 apparatus, and the positive electrode mixture slurry was dried to form a positive electrode active material layer 41B. Finally, the positive electrode active material layer 41B was compressed and molded using a roll press. This produced a positive electrode 41 (width = 3.3 mm). The thickness of the positive electrode inner active material layer 41B1 and the positive electrode outer active material layer 41B2 after compression molding were set to 0.037 mm, respectively.

[0130] (Fabrication of the negative electrode) First, a negative electrode mixture was prepared by mixing 95 parts by mass of negative electrode active material (graphite) and 5 parts by mass of negative electrode binder (polyvinylidene fluoride). Next, the negative electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like negative electrode mixture slurry. Subsequently, a strip of copper foil with a thickness of 15 μm was prepared, and a notch 42K was formed by punching out a part of its outer edge to create a negative electrode current collector 42A. Next, the positive electrode mixture slurry was applied to both sides of the negative electrode current collector 42A using a coating apparatus, and then the negative electrode mixture slurry was dried to form a negative electrode active material layer 42B. Finally, the negative electrode active material layer 42B was compressed and molded using a roll press. This produced a negative electrode 42 (width = 3.8 mm).

[0131] (Preparation of electrolyte solution) An electrolyte salt (LiPF6) was added to a solvent (ethylene carbonate and diethyl carbonate), and the solvent was then stirred. In this case, the solvent mixing ratio (by weight) was ethylene carbonate:diethyl carbonate = 30:70, and the electrolyte salt content was 1 mol / kg relative to the solvent. As a result, the electrolyte salt was dissolved or dispersed in the solvent, and an electrolyte solution was prepared.

[0132] (Assembly of secondary batteries) First, using resistance welding, an aluminum positive electrode lead 51 (thickness = 0.1 mm, width = 2.0 mm, protrusion length from positive electrode 41 = 11.7 mm), which was partially covered with a tubular sealant 61 (polypropylene film, outer diameter = 9.0 mm, inner diameter = 3.0 mm), was welded to the positive electrode 41 (positive electrode current collector 41A). Then, using resistance welding, a nickel negative electrode lead 52 (thickness = 0.1 mm, width = 2.0 mm, protrusion length from negative electrode 42 = 6.0 mm) was welded to the negative electrode 42 (negative electrode current collector 42A).

[0133] Next, the positive electrode 41 and the negative electrode 42 were stacked on top of each other via a separator 43 (a microporous polyethylene film with a thickness of 25 μm and a width of 4.0 mm). Then, the positive electrode 41, the negative electrode 42, and the separator 43 were wound together to produce a cylindrical wound body 40Z (outer diameter = 11.6 mm) having a winding center space 40K (inner diameter = 1.5 mm).

[0134] Next, a ring-shaped insulating film (polyimide film, outer diameter = 11.6 mm, inner diameter = 2.2 mm, thickness = 0.05 mm) for use as a base was placed inside a cylindrical storage section 11 (wall thickness = 0.15 mm, outer diameter = 12.0 mm, height = 5.0 mm) made of stainless steel (SUS316) through the opening 11K, and then the wound body 40Z was placed inside the storage section 11. The negative electrode lead 52 was welded to the storage section 11 using resistance welding. Next, using resistance welding, a positive lead 51 was welded to the external terminal 20 of a stainless steel (SUS316) disc-shaped lid portion 12 (wall thickness = 0.15 mm, outer diameter = 11.7 mm), which has a recessed portion 12H (inner diameter = 9.0 mm, step height = 0.3 mm) with a through-hole 12K (inner diameter = 3.0 mm) and an aluminum disc-shaped external terminal 20 (wall thickness = 0.3 mm, outer diameter = 7.2 mm) attached via a gasket 30 (polyimide film, outer diameter = 9.2 mm, inner diameter = 3.2 mm).

[0135] Next, with the lid 12 positioned upright relative to the storage section 11, electrolyte was injected into the storage section 11 through the opening 11K. This impregnated the wound body 40Z (positive electrode 41, negative electrode 42, and separator 43) with the electrolyte, and the battery element 40 was fabricated.

[0136] Finally, after closing the opening 11K with the lid 12, the lid 12 was welded to the storage section 11 using laser welding. When closing the opening 11K with the lid 12, a folded portion 513 was formed on a part of the positive electrode lead 51 to form a curved shape, and the folded portion 513 was positioned on the peripheral portion 12R. Specifically, the distance between the folded portion 513 and the inner surface of the side wall M3 was adjusted to 0.5 mm. In addition, a ring-shaped insulating film 62 (polyimide film, outer diameter = 9.2 mm, inner diameter = 3.2 mm) was placed between the lid 12 and the positive electrode lead 51, and a disc-shaped insulating film 63 (polyimide film, outer diameter = 3.2 mm) was placed between the battery element 40 and the positive electrode lead 51. As a result, the storage section 11 and the lid section 12 formed the outer can 10, and the battery element 40 was sealed inside the outer can 10, thus assembling a secondary battery (outer diameter = 12.0 mm, height = 5.0 mm).

[0137] (Stabilization of secondary batteries) The assembled secondary battery was subjected to one charge-discharge cycle in a normal temperature environment (temperature = 23°C). During charging, constant current charging was performed at a current of 0.1C until the voltage reached 4.2V, and then constant voltage charging was performed at that voltage of 4.2V until the current reached 0.05C. During discharging, constant current discharge was performed at a current of 0.1C until the voltage reached 3.0V. 0.1C is the current value required to completely discharge the battery capacity (theoretical capacity) in 10 hours, and 0.05C is the current value required to completely discharge the battery capacity in 20 hours.

[0138] As a result, a coating was formed on the surface of the negative electrode 42 and other components, which electrochemically stabilized the state of the secondary battery. Thus, the secondary battery was completed.

[0139] Next, the performance of the secondary batteries fabricated as described above was evaluated. Specifically, each of the 100 secondary batteries fabricated as described above and subjected to one charge-discharge cycle under the conditions described above was disassembled, and the presence or absence of damage (cracks or fractures) to the negative electrode current collector was visually inspected. The results are shown in Table 1.

[0140] [Table 1]

[0141] [Example 2] After fabricating 100 secondary batteries having the negative electrode 42-1 shown in Figure 9, these secondary batteries were evaluated in the same manner as the evaluation of the secondary battery in Example 1. The results are shown in Table 1.

[0142] [Example 3] After fabricating 100 secondary batteries having the negative electrode 42-2 shown in Figure 10, these secondary batteries were evaluated in the same manner as the evaluation of the secondary batteries in Example 1. The results are shown in Table 1.

[0143] [Example 4] After fabricating 100 secondary batteries having the negative electrode 42-3 shown in Figure 11, these secondary batteries were evaluated in the same manner as the evaluation of the secondary batteries in Example 1. The results are shown in Table 1.

[0144] [Example 5] After fabricating 100 secondary batteries having the negative electrode 42-4 shown in Figure 12, these secondary batteries were evaluated in the same manner as the evaluation of the secondary battery in Example 1. The results are shown in Table 1.

[0145] [Example 6] After fabricating 100 secondary batteries having the negative electrode 42-5 shown in Figure 13, these secondary batteries were evaluated in the same manner as the evaluation of the secondary battery in Example 1. The results are shown in Table 1. This is shown in conjunction with the above.

[0146] [Comparative Example 1] One hundred secondary batteries having the negative electrode 142 shown in Figure 14 were manufactured, and these secondary batteries were evaluated in the same manner as the evaluation of the secondary battery in Example 1. The results are shown in Table 1. The negative electrode 142 has a negative electrode current collector 142A that does not have a notch. The configuration of the negative electrode 142 of Comparative Example 1 is substantially the same as the configuration of the negative electrode 42 of the above embodiment, except for the points mentioned above.

[0147] As shown in Table 1, no cracks or fractures occurred in the negative electrode current collector in Examples 1 to 6. In contrast, in Comparative Example 1, cracks and fractures were observed in the negative electrode current collector in 20 out of 100 secondary batteries. From these results, it is presumed that in Comparative Example 1, the lower edge 42BT that intersects with the negative electrode lead 52 is perpendicular to the edges 52T1 and 52T2 of the negative electrode lead 52, so local stress was applied to the portion of the negative electrode current collector 42A where the negative electrode lead 52 is provided due to the expansion and contraction of the battery element 40 during charging and discharging, causing that portion to stretch. In contrast, in Examples 1 to 6, the lower edge 42BT that intersects with the negative electrode lead 52 intersects at an angle to the edges 52T1 and 52T2 of the negative electrode lead 52, so it is thought that the load on the negative electrode current collector 42A was reduced.

[0148] Although the present technology has been described above with reference to one embodiment and one example, the configuration of the present technology is not limited to the configuration described in the one embodiment and one example, and can be modified in various ways.

[0149] Specifically, the description has focused on the case where the outer casing is a welded can (crimped can), but the structure of the outer casing is not particularly limited, and a crimped can may also be used. In this crimped can, the storage section and lid section, which are separate from each other, are crimped together via a gasket. Furthermore, the configuration of the secondary battery described in the above embodiment is merely an example, and this disclosure is not limited to that configuration.

[0150] Furthermore, although the above embodiment illustrates a case where a notch is provided in a part of the negative electrode current collector, the present disclosure is not limited thereto. For example, a notch may be provided in the positive electrode current collector at the location where the positive electrode lead is joined.

[0151] Furthermore, while the above embodiment illustrates a case where the outer casing housing the battery element also serves as an external connection terminal connected to the leads, this disclosure is not limited to this. For example, the external connection terminal may be provided separately from the outer casing. Also, while the above embodiment illustrates a negative electrode lead as the lead, the lead in this disclosure may be a positive electrode lead 51 connecting the external terminal 20 and the positive electrode 41.

[0152] Furthermore, while we have described the case where the electrode reactant is lithium, the electrode reactant is not particularly limited. Therefore, as mentioned above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0153] The effects described herein are illustrative only, and the effects of this disclosure are not limited to those described herein. Therefore, other effects may be obtained with respect to this disclosure.

[0154] Furthermore, this disclosure may take the following forms: <1> A battery element in which a first electrode and a second electrode are stacked with a separator in between and wound around a winding axis extending in a first direction, External connection terminals, A lead including a pair of edges, connecting the first electrode and the external connection terminal Equipped with, The first electrode comprises a first electrode current collector including a first end edge, and a first electrode active material layer covering a portion of the first electrode current collector. The lead is joined to the first electrode current collector with the pair of ends inclined relative to the first end. Secondary battery. <2> The first electrode current collector has a notch at its first end edge. the above <1> The rechargeable battery described. <3> The first electrode includes a first electrode current collector covering region in which the first electrode current collector is covered by the first electrode active material layer, and a first electrode current collector exposed region in which the first electrode current collector is exposed without being covered by the first electrode active material layer. The lead is joined to a portion of the first electrode current collector in the exposed region of the first electrode current collector. the above <1> or <2> The rechargeable battery described. <4> In the first electrode current collector, the length in the first direction of the junction region including the junction portion to which the lead is joined is shorter than the length in the first direction of the first electrode current collector in the covering region of the first electrode current collector. the above <3> The rechargeable battery described. <5> The first electrode current collector includes an inner surface of the first electrode facing the winding shaft side and an outer surface of the first electrode opposite to the inner surface of the first electrode, The lead is bonded to the inner surface of the first electrode. the above <1> from <4> A rechargeable battery as described in one of the following. <6> The portion of the lead that connects to the first electrode current collector extends in the first direction. the above <1> from <5> A rechargeable battery as described in one of the following. <7> The aforementioned first edge is curved. the above <1> from <6> A rechargeable battery as described in one of the following. <8> The first electrode is the negative electrode, and the second electrode is the positive electrode. the above <1> from <7> A rechargeable battery as described in one of the following. <9> The battery further comprises an outer casing for housing the aforementioned battery element, The outer casing also serves as the external connection terminal. the above <1> from <8> A rechargeable battery as described in one of the following.

Claims

1. A battery element in which a first electrode and a second electrode are stacked with a separator in between and wound around a winding axis extending in a first direction, External connection terminals, A lead including a pair of edges, connecting the first electrode and the external connection terminal. Equipped with, The first electrode comprises a first electrode current collector including a first edge, and a first electrode active material layer covering a portion of the first electrode current collector. The lead is joined to the first electrode current collector with the pair of ends inclined relative to the first end, The portion of the lead that connects to the first electrode current collector extends in the first direction. Secondary battery.

2. The first electrode current collector has a notch at its first end edge. The secondary battery according to claim 1.

3. The first electrode includes a first electrode current collector covering region in which the first electrode current collector is covered by the first electrode active material layer, and a first electrode current collector exposed region in which the first electrode current collector is exposed without being covered by the first electrode active material layer. The lead is joined to a portion of the first electrode current collector in the exposed region of the first electrode current collector. The secondary battery according to claim 1.

4. In the first electrode current collector, the length in the first direction of the junction region including the junction portion to which the lead is joined is shorter than the length in the first direction of the first electrode current collector in the covering region of the first electrode current collector. The secondary battery according to claim 3.

5. The first electrode current collector includes an inner surface of the first electrode facing the winding shaft side and an outer surface of the first electrode opposite to the inner surface of the first electrode, The lead is bonded to the inner surface of the first electrode. The secondary battery according to claim 1.

6. The aforementioned first edge is curved. The secondary battery according to claim 1.

7. The first electrode is the negative electrode, and the second electrode is the positive electrode. The secondary battery according to claim 1.

8. The battery further comprises an outer casing for housing the aforementioned battery element, The outer casing also serves as the external connection terminal. A secondary battery according to any one of claims 1 to 7.

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