Secondary battery

Abstract

This secondary battery comprises an exterior member, a battery element, an external terminal, and connection wiring. The battery element is housed in the exterior member, and includes a first electrode and a second electrode. The external terminal is attached to the exterior member, and is electrically insulated from the exterior member. The connection wiring is electrically insulated from the exterior member, and is electrically connected to each of the first electrode and the external terminal. The connection wiring includes a first part, a second part that overlaps the first part, and a folded part that is curved to connect the first part and the second part.

Description

[Technical field]

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

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as power sources that are small and lightweight and can provide high energy density. These secondary batteries include a positive electrode, a negative electrode, and an electrolyte housed inside an exterior member, and various studies have been conducted on the structure of the secondary battery (see, for example, Patent Documents 1 to 3).

[0003] For example, Patent Document 1 discloses a sealed type electricity storage device in which an electrode body is housed in an exterior case. In this sealed type electricity storage device, the exterior case has, for example, a case body and a cover plate member. The cover plate member is joined by welding to an opening formed on the opposite side of the bottom of the case body. Patent Document 2 discloses a secondary battery in which a battery cover is placed on and crimped onto a battery can housing a wound electrode body. Furthermore, Patent Document 3 discloses a cylindrical battery having two positive electrode leads. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-046639 A [Patent Document 2] JP 2003-178805 A [Patent Document 3] International Publication No. 2018 / 180828 Summary of the Invention

[0005] Various studies have been conducted to improve the performance of secondary batteries, but the physical durability of the secondary batteries is still insufficient and there is room for improvement.

[0006] Therefore, a secondary battery capable of achieving excellent physical durability is desired.

[0007] A secondary battery according to an embodiment of the present technology includes an exterior member, a battery element, an external terminal, and a connection wiring. The battery element is housed in the exterior member and includes a first electrode and a second electrode. The external terminal is attached to the exterior member and is electrically insulated from the exterior member. The connection wiring is electrically insulated from the exterior member and is electrically connected to each of the first electrode and the external terminal. The connection wiring includes a first portion, a second portion overlapping the first portion, and a folded portion curved to connect the first portion and the second portion.

[0008] According to the secondary battery of one embodiment of the present technology, the connection wiring includes a curved folded-back portion so as to connect the first portion and the second portion, and therefore excellent physical durability can be obtained.

[0009] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below. [Brief description of the drawings]

[0010] [Figure 1] 1 is a perspective view illustrating a configuration of a secondary battery according to an embodiment of the present technology. [Diagram 2] 2 is a cross-sectional view illustrating a configuration of the secondary battery illustrated in FIG. [Diagram 3] 3 is a cross-sectional view illustrating the configuration of the battery element shown in FIG. 2. [Figure 4] 3 is a partially enlarged cross-sectional view showing the positive electrode lead and its vicinity shown in FIG. 2 in an enlarged scale. [Diagram 5] FIG. 2 is a perspective view illustrating a configuration of an exterior can used in a manufacturing process of a secondary battery. [Figure 6] 4A to 4C are cross-sectional views showing the structure of an exterior can for explaining a manufacturing process of a secondary battery. [Figure 7] 11 is a cross-sectional view illustrating a configuration of a secondary battery according to a third modified example. [Figure 8]FIG. 11 is a cross-sectional view illustrating a configuration of a secondary battery according to a fourth modified example. [Figure 9] 13 is a cross-sectional view illustrating a configuration of a secondary battery according to a fifth modified example. [Figure 10] 13 is a cross-sectional view illustrating a configuration of a secondary battery according to a sixth modified example. [Figure 11] FIG. 13 is a cross-sectional view illustrating a configuration of a secondary battery according to a seventh modified example. [Figure 12] 1 is a cross-sectional view illustrating a configuration of a secondary battery of Experimental Example 2. FIG. [Figure 13] 11 is a cross-sectional view illustrating the configuration of a secondary battery of Experimental Example 3. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be given in the following order. 1. Secondary battery 1-1.Configuration 1-2.Operation 1-3. Manufacturing method 1-4. Actions and Effects 2. Variations

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

[0013] The secondary battery described here has a flat, columnar, three-dimensional shape, and is called a coin type or button type. As described below, this secondary battery has a pair of bottoms facing each other and a side wall portion located between the pair of bottoms, and the height of this secondary battery is smaller than the outer diameter. The "outer diameter" here refers to the diameter (maximum diameter) of each of the pair of bottoms, and the "height" refers to the distance (maximum distance) from the surface of one bottom to the surface of the other bottom.

[0014] The charge / discharge principle of the secondary battery is not particularly limited, but the following describes a case where the battery capacity is obtained by utilizing the absorption and release of the electrode reactant. This secondary battery includes a positive electrode and a negative electrode as well as an electrolyte. In this secondary battery, the charge capacity of the negative electrode is larger than the discharge capacity of the positive electrode in order to prevent the electrode reactant from being deposited on the surface of the negative electrode during charging. 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.

[0015] The type of the electrode reactant is not particularly limited, but specifically, it is a light metal such as an alkali metal or an alkaline earth metal, etc. The alkali metal is lithium, sodium, potassium, etc., and the alkaline earth metal is beryllium, magnesium, calcium, etc.

[0016] In the following, an example will be given in which the electrode reactant is lithium. A secondary battery that obtains battery capacity by utilizing the absorption and release of lithium is a so-called lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and released in an ionic state.

[0017] <1-1. Configuration> Fig. 1 shows a perspective configuration of a secondary battery. Fig. 2 shows a cross-sectional configuration of the secondary battery shown in Fig. 1. Fig. 3 shows a cross-sectional configuration of a battery element 40 shown in Fig. 2. However, in Fig. 2, the positive electrode lead 51 is shaded, and in Fig. 3, only a portion of the cross-sectional configuration of the battery element 40 is enlarged.

[0018] In the following, for convenience, the upper side in each of FIGS. 1 and 2 will be described as the upper side of the secondary battery, and the lower side in each of FIGS. 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 with a height H smaller than an outer diameter D, that is, a flat and columnar three-dimensional shape, as shown in Fig. 1. Here, the three-dimensional shape of the secondary battery is flat and cylindrical (columnar).

[0020] The dimensions of the secondary battery are not particularly limited, but as an example, the outer diameter D is 3 mm to 30 mm and the height H is 0.5 mm to 70 mm. However, the ratio (D / H) of the outer diameter D to the height H is greater than 1. The upper limit of this ratio (D / H) is not particularly limited, but is preferably 25 or less.

[0021] 1 to 3, this secondary battery includes an outer can 10, an external terminal 20, a battery element 40, and a positive electrode lead 51. Here, the secondary battery further includes a gasket 30, a negative electrode lead 52, a sealant 61, and insulating films 62, 63.

[0022] [Outer can] As shown in FIGS. 1 and 2, the exterior can 10 is a hollow exterior member that houses the battery element 40 and other components.

[0023] Here, the exterior can 10 has a flat, cylindrical three-dimensional shape in accordance with the three-dimensional shape of the secondary battery, which is flat and cylindrical. Therefore, the exterior can 10 has a pair of bottoms M1, M2 facing each other, and a side wall M3 located between the bottoms M1, M2. The upper end of the side wall M3 is connected to the bottom M1, and the lower end of the side wall M3 is connected to the bottom M2. As described above, since the exterior can 10 is cylindrical, the planar shape of each of the bottoms M1, M2 is circular, and the surface of the side wall M3 is a convex curved surface.

[0024] Moreover, the exterior can 10 includes a storage portion 11 and a lid portion 12 which are welded to each other, and the storage portion 11 is sealed by the lid portion 12. That is, the lid portion 12 is welded to the storage portion 11.

[0025] The storage section 11 is a flat, cylindrical storage member that stores therein the battery element 40, etc. The storage section 11 has a hollow structure with an open upper end and a closed lower end, and therefore has an opening 11K at the upper end.

[0026] The lid portion 12 is a substantially disk-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. Since the external terminal 20 is attached to the lid portion 12, the lid portion 12 supports the external terminal 20.

[0027] As described above, in the completed secondary battery, the lid 12 is already welded to the storage section 11, and therefore the opening 11K is closed by the lid 12. This means that it is considered that even if one looks at the exterior of the secondary battery, it is not possible to confirm whether the storage section 11 had the opening 11K or not.

[0028] However, when the lid portion 12 is welded to the storage portion 11, welding marks remain on the surface of the outer can 10, more specifically, at the boundary between the storage portion 11 and the lid portion 12, so that it is possible to confirm after the fact whether or not the storage portion 11 had an opening 11K based on the presence or absence of the welding marks.

[0029] That is, if there are weld marks remaining on the surface of the outer can 10, this means that the storage section 11 had an opening 11K. On the other hand, if there are no weld marks remaining on the surface of the outer can 10, this means that the storage section 11 did not have an opening 11K.

[0030] Here, the lid 12 is bent so as to partially protrude toward the inside of the storage section 11, forming a protruding section 12P. That is, when viewed from the outside of the outer can 10, the lid 12 has a partially recessed shape. Therefore, the protruding section 12P becomes a recessed section 12H when viewed from the outside of the outer can 10. The through hole 12K is provided in the protruding section 12P or the recessed section 12H. The portion of the lid 12 other than the protruding section 12P becomes a peripheral section 12R. The peripheral section 12R is annular and provided to surround the protruding section 12P in a horizontal plane perpendicular to the height direction Z of the secondary battery.

[0031] The planar shape of the recessed portion 12H, i.e., the shape defined by the outer edge of the recessed portion 12H when the secondary battery is viewed from above, is not particularly limited. Here, the planar shape of the recessed portion 12H is substantially circular. The inner diameter and depth of the recessed portion 12H are not particularly limited and can be set arbitrarily.

[0032] As described above, the exterior can 10 is a so-called welded can in which the storage section 11 and the lid section 12, which were previously physically separate, are welded together. As a result, the exterior can 10 after welding is a single physically integrated member as a whole, and therefore cannot be separated into the storage section 11 and the lid section 12 later.

[0033] The exterior can 10, which is a welded can, is different from a crimp can formed by crimping, and is a so-called crimpless can. This is because the element space volume increases inside the exterior can 10, and the energy density per unit volume increases. This "element space volume" refers to the volume (effective volume) of the internal space of the exterior can 10 that can be used to store the battery element 40.

[0034] Furthermore, the exterior can 10, which is a welded can, does not have any parts that are folded over each other, and does not have any parts where two or more members overlap each other.

[0035] "Having no overlapping parts" means that parts of the exterior can 10 are not folded (folded) so that they overlap each other. Also, "having no parts where two or more components overlap each other" means that after the secondary battery is completed, the exterior can 10 is physically one component, and therefore the exterior can 10 cannot be separated into two or more components later. In other words, the state of the exterior can 10 in the completed secondary battery is not in a state where two or more components are combined while overlapping each other so that they can be separated later.

[0036] Here, since the exterior can 10 is conductive, the storage section 11 and the lid section 12 are both conductive. As a result, the exterior can 10 is electrically connected to the battery element 40 (negative electrode 42) via the negative electrode lead 52, and functions as an external connection terminal for the negative electrode 42. This is because the secondary battery does not need to have an external connection terminal for the negative electrode 42 separate from the exterior can 10, and therefore a reduction in the element space volume due to the presence of the external connection terminal for the negative electrode 42 is suppressed. As a result, the element space volume increases, and the energy density per unit volume increases.

[0037] Specifically, the exterior can 10 is a metal can containing one or more types of conductive materials such as metal materials and alloy materials. The conductive materials constituting 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 specific examples include SUS304 and SUS316. However, the material forming the storage section 11 and the material forming the lid section 12 may be the same as or different from each other.

[0038] As described later, the lid portion 12 is insulated via a gasket 30 from the external terminal 20 that functions as an external connection terminal for the positive electrode 41. This is because contact (short circuit) between the exterior can 10 (external connection terminal for the negative electrode 42) and the external terminal 20 (external connection terminal for the positive electrode 41) is prevented.

[0039] [External terminal] 1 and 2, the external terminal 20 is a connection terminal that is connected to an electronic device when the secondary battery is mounted in the electronic device. As described above, the external terminal 20 is attached to the exterior can 10 (lid portion 12) and is therefore supported by the lid portion 12.

[0040] 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 an electronic device via the external terminal 20 (external connection terminal for the positive electrode 41) and the exterior can 10 (external connection terminal for the negative electrode 42). Therefore, the electronic device can operate using the secondary battery as a power source.

[0041] The external terminal 20 is a flat, generally plate-shaped member, and is disposed inside the recessed portion 12H via the gasket 30. This insulates the external terminal 20 from the lid portion 12 via the gasket 30. Here, the external terminal 20 is housed inside the recessed portion 12H so as not to protrude above the lid portion 12. This is because, compared to the case where the external terminal 20 protrudes above the lid portion 12, the height H of the secondary battery is smaller, and the energy density per unit volume of the secondary battery is increased.

[0042] Since the outer diameter of the external terminal 20 is smaller than the inner diameter of the recessed portion 12H, the external terminal 20 is separated from the lid portion 12 at its periphery. As a result, the gasket 30 is disposed only in a part of the region between the external terminal 20 and the lid portion 12 (recessed portion 12H), more specifically, it is disposed only in a place where the external terminal 20 and the lid portion 12 would come into contact with each other if the gasket 30 was not present.

[0043] The external terminal 20 includes one or more 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 includes an aluminum layer and a nickel layer in this order from the side closer to the gasket 30, and the aluminum layer and the nickel layer are roll-bonded to each other in the clad material.

[0044] [gasket] 2, the gasket 30 is an insulating member disposed between the exterior can 10 (lid portion 12) and the external terminal 20, and the external terminal 20 is fixed to the lid portion 12 via the gasket 30. The gasket 30 has a ring-like planar shape with a through hole at a position corresponding to the through hole 12K. The gasket 30 contains one or more types of insulating materials such as insulating polymer compounds, and the insulating materials are polypropylene, polyethylene, etc.

[0045] The installation range of the gasket 30 is not particularly limited and can be set arbitrarily. Here, the gasket 30 is disposed in the gap between the upper surface of the lid portion 12 and the lower surface of the external terminal 20 inside the recessed portion 12H.

[0046] [Battery element] 2 and 3, the battery element 40 is a power generating element that causes charge / discharge reactions to proceed, and is housed inside the exterior can 10. 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 electrolytic solution (not shown) that is a liquid electrolyte.

[0047] 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 (outer can 10). In other words, position P of the center line PC corresponds to the position of the center of the battery element 40.

[0048] The battery element 40 is a so-called wound electrode body. That is, in the battery element 40, the positive electrode 41 and the negative electrode 42 are stacked on top of each other with a separator 43 interposed therebetween. Furthermore, the stacked positive electrode 41, the negative electrode 42, and the separator 43 are wound. The positive electrode 41 and the negative electrode 42 are wound while maintaining a state in which they face each other with the separator 43 interposed therebetween. Therefore, a winding central space 40K is formed at the center of the battery element 40.

[0049] Here, the positive electrode 41, the negative electrode 42, and the separator 43 are wound so that the separator 43 is disposed on the outermost circumference and the innermost circumference of the wound electrode body. The number of turns of the positive electrode 41, the negative electrode 42, and the separator 43 is not particularly limited and can be set arbitrarily.

[0050] The battery element 40 has a three-dimensional shape similar to that of the exterior can 10, and therefore has a flat and cylindrical three-dimensional shape. When the battery element 40 is housed inside the exterior can 10, so-called dead space, specifically, a gap between the exterior can 10 and the battery element 40, is less likely to occur, as compared with a case in which the battery element 40 has a three-dimensional shape different from that of the exterior can 10. Therefore, the internal space of the exterior can 10 is effectively utilized. As a result, the element space volume increases, and the energy density per unit volume of the secondary battery increases.

[0051] (positive electrode) The positive electrode 41 is a first electrode used for promoting charge / discharge reactions, and includes a positive electrode current collector 41A and a positive electrode active material layer 41B, as shown in FIG.

[0052] Positive electrode current collector 41A has a pair of surfaces on which positive electrode active material layer 41B is provided. Positive electrode current collector 41A contains a conductive material such as a metal material, and the metal material is aluminum or the like.

[0053] The positive electrode active material layer 41B is provided on both sides of the positive electrode current collector 41A, and contains one or more types of positive electrode active materials capable of absorbing and releasing lithium. 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 may 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 includes a coating method.

[0054] The positive electrode active material contains a lithium compound. This lithium compound is a general term for compounds containing lithium as a constituent element, and more specifically, a compound containing lithium and one or more transition metal elements as constituent elements. This is because a high energy density can be obtained. However, the lithium compound may further contain one or more of other elements (excluding lithium and transition metal elements). The type of lithium compound is not particularly limited, and specific examples include oxides, phosphate compounds, silicate compounds, and borate compounds. Specific examples of oxides include LiNiO2, LiCoO2, and LiMn2O4, and specific examples of phosphate compounds include LiFePO4 and LiMnPO4.

[0055] The positive electrode binder contains one or more of synthetic rubber and polymer compounds. The synthetic rubber is styrene butadiene rubber and the polymer compounds are polyvinylidene fluoride. The positive electrode conductive agent contains one or more of conductive materials such as carbon materials, and the carbon materials are graphite, carbon black, acetylene black, ketjen black, and the like. However, the conductive materials may be metal materials and polymer compounds.

[0056] (Negative electrode) The negative electrode 42 is a second electrode used for promoting charge / discharge reactions, and includes a negative electrode current collector 42A and a negative electrode active material layer 42B, as shown in FIG.

[0057] The negative electrode current collector 42A has a pair of surfaces on which the negative electrode active material layer 42B is provided. The negative electrode current collector 42A contains a conductive material such as a metal material, and the metal material is, for example, copper.

[0058] The negative electrode active material layer 42B is provided on both sides of the negative electrode current collector 42A, and contains one or more types of negative electrode active materials capable of absorbing and releasing lithium. However, the negative electrode active material layer 42B may be provided on only one side of the negative electrode current collector 42A. The negative electrode active material layer 42B may further contain a negative electrode binder and a negative electrode conductor. Details regarding the negative electrode binder and the negative electrode conductor are the same as those regarding the positive electrode binder and the positive electrode conductor. The method of forming the negative electrode active material layer 42B is not particularly limited, and specifically, it is one or more types of a coating method, a gas phase method, a liquid phase method, a thermal spraying method, a baking method (sintering method), and the like.

[0059] The negative electrode active material contains one or both of a carbon material and a metal-based material. This is because a high energy density can be obtained. Carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite). The metal-based material is a material that contains, as a constituent element, one or more of metal elements and metalloid elements that can form an alloy with lithium, and the metal elements and metalloid elements are one or both of silicon and tin. However, the metal-based material may be a single element, an alloy, a compound, a mixture of two or more of them, or a material containing two or more of them. Specific examples of metal-based materials are TiSi2 and SiO x (0 <x≦2、または0.2<x<1.4)などである。

[0060] Here, the height of the negative electrode 42 is greater than the height of the positive electrode 41. That is, the negative electrode 42 protrudes upward from the positive electrode 41 and also protrudes downward from the positive electrode 41. This is to prevent lithium released from the positive electrode 41 from being deposited. This "height" is a dimension corresponding to the height H of the secondary battery described above, that is, the dimension in the vertical direction in each of Figs. 1 and 2. The definition of height described here will be the same hereinafter.

[0061] (Separator) 2 and 3, the separator 43 is an insulating porous film disposed 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.

[0062] Here, the height of the separator 43 is greater than the height of the negative electrode 42. In other words, the separator 43 may protrude upward from the negative electrode 42 and also protrude downward from the negative electrode 42. This is because the separator 43 is used to insulate the positive electrode lead 51 from the negative electrode 42, as described later.

[0063] (electrolyte) The electrolyte is impregnated into each of 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 of non-aqueous solvents (organic solvents) such as carbonate ester compounds, carboxylate ester compounds, and lactone compounds, and the electrolyte containing the non-aqueous solvent is a so-called non-aqueous electrolyte. The electrolyte salt contains one or more of light metal salts such as lithium salt.

[0064] [Positive lead] As shown in Fig. 2, the positive electrode lead 51 is housed inside the exterior can 10. The positive electrode lead 51 is a connection wire connected to each of the positive electrode 41 and the external terminal 20. The secondary battery shown in Fig. 2 includes one positive electrode lead 51. However, the secondary battery may include two or more positive electrode leads 51.

[0065] The positive electrode lead 51 is connected to the upper end of the positive electrode 41. Specifically, the positive electrode lead 51 is connected to the upper end of the positive electrode current collector 41A. The positive electrode lead 51 is also connected to the lower surface of the external terminal 20 via a through hole 12K provided in the lid portion 12. The method of connecting the positive electrode lead 51 is not particularly limited, but specifically, it is any one or more of welding methods such as resistance welding and laser welding. The details of the welding method described here are the same hereinafter.

[0066] A part of the positive electrode lead 51 is sandwiched between the lid part 12 of the outer can 10 and the negative electrode 42 of the battery element 40 in the height direction of the secondary battery while being electrically insulated from each of them. FIG. 4 is a partially enlarged cross-sectional view showing the positive electrode lead 51 and its vicinity in the cross-sectional configuration of the secondary battery shown in FIG. 2. As shown in FIG. 4, 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. In addition, the first portion 511 and the second portion 512 overlap each other in the height direction Z of the secondary battery via the sealant 61. The folded portion 513 is curved so as to connect the first portion 511 and the second portion 512. Here, the folded portion 513 is curved so as to form a space V on the inside. Here, thickness 51H2 of folded portion 513 is thicker than thickness 51H1 of an overlapping portion of first portion 511 and second portion 512. Note that thickness 51H1 includes the thickness of sealant 61 covering first portion 511 and second portion 512. Similarly, thickness 51H2 includes the thickness of sealant 61 covering folded portion 513. Both thicknesses 51H1 and 51H2 are dimensions along the height direction Z of the secondary battery.

[0067] The first portion 511 and the second portion 512 are sandwiched between the battery element 40 and the protruding portion 12P of the lid portion 12 in the height direction Z of the secondary battery. However, the folded portion 513 is sandwiched between the battery element 40 and a portion of the lid portion 12 other than the protruding portion 12P in the height direction Z of the secondary battery. The portion of the lid portion 12 other than the protruding portion 12P here is the peripheral portion 12R surrounding the protruding portion 12P of the lid portion 12. As shown in FIG. 4, in the height direction Z of the secondary battery, the distance between the peripheral portion 12R and the battery element 40 is larger than the distance between the protruding portion 12P and the battery element 40. Therefore, the overlapping portions of the first portion 511 and the second portion 512 are arranged so as to be sandwiched between the battery element 40 and the protruding portion 12P, while the folded portion 513 having a thickness 51H2 larger than the thickness 51H1 of the overlapping portion can be arranged in the gap between the battery element 40 and the peripheral portion 12R. Therefore, even if the dimension of the secondary battery in the height direction is reduced, positive electrode lead 51 can be accommodated inside exterior can 10 without applying a mechanical load to folded-back portion 513 .

[0068] In this way, a part of the positive electrode lead 51 extends along the lower surface of the lid portion 12 and the upper surface of the battery element 40, and is thereby held by the lid portion 12 and the battery element 40. Therefore, the positive electrode lead 51 is fixed inside the exterior can 10. Even if the secondary battery is subjected to external forces such as vibration and impact, the positive electrode lead 51 is less likely to move, and the positive electrode lead 51 is less likely to be damaged. The damage to the positive electrode lead 51 here refers to the occurrence of cracks in the positive electrode lead 51, the positive electrode lead 51 being cut, the positive electrode lead 51 falling off from the positive electrode 41, and the like. In addition, since the positive electrode lead 51 includes the curved folded-back portion 513, the occurrence of damage to the positive electrode lead 51 can be sufficiently reduced compared to, for example, the case in which the positive electrode lead 51 includes a bent portion.

[0069] That is, "a part of the positive electrode lead 51 is sandwiched between the outer can 10 and the battery element 40" means that the positive electrode lead 51 is insulated from the outer can 10 and the battery element 40, while being held from above and below by the outer can 10 and the battery element 40, so that the positive electrode lead 51 is in a state in which it is difficult to move inside the outer can 10 even if the secondary battery is subjected to external forces such as vibration and impact. The state in which the positive electrode lead 51 is in a state in which it is difficult to move inside the outer can 10 means that the battery element 40 is also in a state in which it is difficult to move inside the outer can 10. Therefore, when the secondary battery is subjected to vibration or impact, it is possible to avoid problems such as collapse of the winding of the battery element 40, which is a wound electrode body.

[0070] It is preferable that the positive electrode lead 51 is pressed against the battery element 40 and thus bites into the battery element 40. More specifically, since the height of the separator 43 is greater than the heights of the positive electrode 41 and the negative electrode 42 as described above, it is preferable that the positive electrode lead 51 bites into the upper end of the separator 43. In this case, a recess is formed at the upper end of the separator 43 due to the pressing of the positive electrode lead 51. Since a part or the whole of the positive electrode lead 51 is accommodated inside the recess, the positive electrode lead 51 is held by the separator 43. This is because the positive electrode lead 51 becomes less likely to move inside the exterior can 10, and therefore the positive electrode lead 51 becomes less likely to be damaged.

[0071] Here, as described above, the lid portion 12 includes the protruding portion 12P, and a portion of the positive electrode lead 51 is sandwiched between the protruding portion 12P and the battery element 40. That is, a portion of the positive electrode lead 51 extends along the lower surface of the protruding portion 12P and the upper surface of the battery element 40, and is thereby held by the protruding portion 12P and the battery element 40. Since the positive electrode lead 51 is more easily held by utilizing the protruding portion 12P, the positive electrode lead 51 becomes less likely to be damaged.

[0072] 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, the sealant 61, and the insulating films 62, 63, respectively.

[0073] Specifically, as described above, the height of the separator 43 is greater than the height of the negative electrode 42. As a result, a part 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 is because a short circuit between the positive electrode lead 51 and the negative electrode 42 is prevented.

[0074] In addition, the periphery of the positive electrode lead 51 is covered with an insulating sealant 61. As a result, a part of the positive electrode lead 51 is insulated from each of the lid portion 12 and the negative electrode 42 via the sealant 61. This is because a short circuit between the positive electrode lead 51 and the lid portion 12 is prevented, and a short circuit between the positive electrode lead 51 and the negative electrode 42 is also prevented.

[0075] Further, an insulating film 62 is disposed between the lid portion 12 and the positive electrode lead 51. As a result, a part of the positive electrode lead 51 is insulated from the lid portion 12 via the insulating film 62. This is because a short circuit between the positive electrode lead 51 and the lid portion 12 is prevented.

[0076] Furthermore, an insulating film 63 is disposed between the battery element 40 and the positive electrode lead 51. As a result, a part of the positive electrode lead 51 is insulated from the negative electrode 42 via the insulating film 63. This is because a short circuit between the positive electrode lead 51 and the negative electrode 42 is prevented.

[0077] The details regarding the material for forming the positive electrode lead 51 are similar to the details regarding the material for forming the positive electrode current collector 41A. However, the materials for forming the positive electrode lead 51 and the positive electrode current collector 41A may be the same as or different from each other.

[0078] Here, the positive electrode lead 51 is connected to the positive electrode 41 in a region in front of the center line PC, that is, in a region to the right of the center line PC in FIG. 2. As shown in FIG. 4, the positive electrode lead 51 has a folded portion 513 on the way to the external terminal 20 in order to be connected to the external terminal 20. The folded portion 513 exists in a region behind the center line PC, that is, in a region to the left of the center line PC in FIG. 2. The positive electrode lead 51 has a first portion 511 as a portion from a portion connected to the positive electrode 41 through the center position P to the folded portion 513. The first portion 511 extends in a direction perpendicular to the height direction Z along the upper surface of the battery element 40. Furthermore, the positive electrode lead 51 has a second portion 512 as a portion on the way from the folded portion 513 to a portion connected to the external terminal 20. The second portion 512 extends in a direction perpendicular to the height direction Z along the upper surface of the battery element 40 so as to cover the first portion 511. In this manner, a portion of the positive electrode lead 51 extends toward the external terminal 20 while being sandwiched between the lid portion 12 and the battery element 40 in both the region in front of the center line PC and the region behind the center line PC.

[0079] Here, as is clear from FIG. 2, the "region in front of the center line PC" refers to one of the regions in which the connection portion of the positive electrode lead 51 to the positive electrode 41 exists when the battery element 40 is divided into two regions in the direction along the outer diameter D with the center line PC as a reference. In FIG. 2, the "region in front of the center line PC" refers to the region on the right side of the center line PC. In contrast, as is clear from FIG. 2, the "region behind the center line PC" refers to the other of the two regions described above, which is the region on the left side of the center line PC in FIG. 2. In other words, the "region behind the center line PC" refers to the other region in which the connection portion of the positive electrode lead 51 to the positive electrode 41 does not exist when the battery element 40 is divided into two regions in the direction along the outer diameter D with the center line PC as a reference.

[0080] 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 outermost periphery of the positive electrode 41. This is because, unlike the case where the positive electrode lead 51 is connected to the positive electrode 41 at the outermost periphery of the positive electrode 41, corrosion of the outer can 10 caused by the electrolyte creeping up is prevented. This "electrolyte creeping up" refers to the electrolyte in the battery element 40 creeping up the positive electrode lead 51 and reaching the inner wall surface of the outer can 10 when the positive electrode lead 51 is disposed close to the inner wall surface of the outer can 10. When the electrolyte comes into contact with the outer can 10 due to the "electrolyte creeping up", a phenomenon occurs in which the outer can 10 dissolves or discolors.

[0081] Here, the positive electrode lead 51 is folded back at least once between the positive electrode 41 and the external terminal 20, and is therefore folded over at least once. The number of times the positive electrode lead 51 is folded back is not particularly limited as long as it is folded back at least once. This "positive electrode lead 51 is folded back" means that the extending direction of the positive electrode lead 51 changes so as to form an angle greater than 90° in the middle. The folded back portion of the positive electrode lead 51 may have a curved shape without bending, as in the folded back portion 513 illustrated in an enlarged view in FIG. 4. In addition, although the positive electrode lead 51 includes one folded back portion 513 in FIG. 2 and FIG. 4, the positive electrode lead 51 may include multiple folded back portions 513.

[0082] The positive electrode lead 51 is folded back at a folded back portion 513 on the way from the positive electrode 41 to the external terminal 20. Specifically, as shown in FIG. 2, the first portion 511 extends from a first position P1 other than the center position P of the outer can 10 to a second position P2 on the opposite side of the first position P1 as viewed from the center position in a horizontal plane perpendicular to the height direction of the secondary battery. The second portion 512 extends from the second position P2 toward the center position P. In the positive electrode lead 51, the overlapping portion of the first portion 511 and the second portion 512 is a surplus portion. That is, it can be said that the positive electrode lead 51 has a length margin in its longitudinal direction.

[0083] As a result, when forming the exterior can 10 using the storage section 11 and the lid section 12 in the manufacturing process of the secondary battery, as described below, there is a margin for changing the attitude of the lid section 12 relative to the storage section 11. Specifically, as shown in FIG. 6, it becomes possible to stand the lid section 12 upright relative to the storage section 11. Furthermore, when the secondary battery is subjected to an external force such as vibration or impact, the external force is mitigated by utilizing the length margin of the positive electrode lead 51, so that the positive electrode lead 51 is less likely to be damaged. Furthermore, by utilizing the length margin of the positive electrode lead 51, it becomes possible to arbitrarily change the connection position of the positive electrode lead 51 relative to the positive electrode 41 without changing the length of the positive electrode lead 51.

[0084] In this case, the length of the positive electrode lead 51 (total length including a length margin) is not particularly limited and can be set arbitrarily. In particular, the length of the positive electrode lead 51 is preferably equal to or greater than half the outer diameter D of the outer can 10. This is because the length of the positive electrode lead 51 ensures a length margin for standing the lid part 12 against the storage part 11, making it easier to stand the lid part 12 against the storage part 11.

[0085] The connection range of the positive electrode lead 51 to the external terminal 20 is not particularly limited. In particular, the connection range of the positive electrode lead 51 to the external terminal 20 is preferably sufficiently wide so that the positive electrode lead 51 is unlikely to fall off the external terminal 20, and is also preferably sufficiently narrow so that a length margin of the positive electrode lead 51 can be obtained. The reason why the connection range of the positive electrode lead 51 to the external terminal 20 is preferably sufficiently narrow is that the portion of the positive electrode lead 51 that is not connected to the external terminal 20 becomes the length margin, and therefore the length margin of the positive electrode lead 51 becomes sufficiently large.

[0086] The positive electrode lead 51 is provided as a separate body from the positive electrode current collector 41A. However, since the positive electrode lead 51 is physically continuous with the positive electrode current collector 41A, the positive electrode lead 51 may be integrated with the positive electrode current collector 41A.

[0087] [Negative lead] 2, the negative electrode lead 52 is stored inside the outer can 10. The negative electrode lead 52 is connected to both the negative electrode 42 and the outer can 10 (storage section 11). Here, the secondary battery includes one negative electrode lead 52. However, the secondary battery may include two or more negative electrode leads 52.

[0088] The negative electrode lead 52 is connected to the lower end of the negative electrode 42, more specifically, to the lower end of the negative electrode current collector 42A. The negative electrode lead 52 is also connected to the bottom surface of the storage section 11. Details of the method of connecting the negative electrode lead 52 are the same as the details of the method of connecting the positive electrode lead 51.

[0089] The details regarding the material for forming the negative electrode lead 52 are similar to the details regarding the material for forming the negative electrode current collector 42A. However, the materials for forming the negative electrode lead 52 and the negative electrode current collector 42A may be the same as or different from each other.

[0090] 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 peripheral portion of the negative electrode 42 that constitutes the wound electrode body.

[0091] The negative electrode lead 52 is provided as a separate body from the negative electrode current collector 42A. However, since the negative electrode lead 52 is physically continuous with the negative electrode current collector 42A, the negative electrode lead 52 may be integrated with the negative electrode current collector 42A.

[0092] [Sealant] 2, the sealant 61 is a first insulating member that covers the periphery of the positive electrode lead 51, and is formed by attaching two pieces of insulating tape to the front and back surfaces of the positive electrode lead 51, respectively. Here, the sealant 61 covers the periphery of the middle part 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, and may have, for example, a tube-like structure.

[0093] The sealant 61 contains one or more kinds of insulating materials such as insulating polymer compounds, and the insulating material is, for example, polyimide.

[0094] [Insulating film] 2, the insulating film 62 is a second insulating member disposed between the lid portion 12 and the positive electrode lead 51. Here, the insulating film 62 has a ring-like planar shape having a through hole at a position corresponding to the through hole 12K.

[0095] Here, the insulating film 62 may have an adhesive layer (not shown) on one surface and be adhered to either the lid portion 12 or the positive electrode lead 51 via the adhesive layer. Alternatively, the insulating film 62 may have adhesive layers on both surfaces and be adhered to both the lid portion 12 and the positive electrode lead 51 via the adhesive layers.

[0096] Furthermore, the insulating film 62 may contain one or more types of insulating materials such as insulating polymer compounds, etc. The insulating material contained in the insulating film 62 is polyimide, etc.

[0097] 2, the insulating film 63 is a third insulating member disposed between the battery element 40 and the positive electrode lead 51. Here, the insulating film 63 has a flat plate-like shape. The insulating film 63 is disposed so as to shield the winding center space 40K and to cover the battery element 40 around the winding center space 40K.

[0098] The details regarding the material for forming the insulating film 63 are similar to the details 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 as or different from each other.

[0099] [others] The secondary battery may further include one or more other components.

[0100] Specifically, the secondary battery is provided with a safety valve mechanism. This safety valve mechanism is configured to cut off the electrical connection between the outer can 10 and the battery element 40 when the internal pressure of the outer can 10 reaches a certain level or higher. The internal pressure of the outer can 10 reaches a certain level or higher due to a short circuit occurring inside the secondary battery, the secondary battery being heated from the outside, etc. 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 portion M1 or M2, and more preferably on the bottom portion M2 to which the external terminal 20 is not attached.

[0101] The secondary battery may also include an insulator between the exterior can 10 and the battery element 40. This insulator includes one or more types of insulating film and insulating sheet, and prevents short-circuiting between the exterior can 10 and the battery element 40. The installation range of the insulator is not particularly limited and can be set arbitrarily.

[0102] The outer can 10 is provided with a series opening valve. This series opening valve breaks when the internal pressure of the outer can 10 reaches a certain level or higher, thereby releasing the internal pressure. There are no particular limitations on the location of the series opening valve, but in particular, like the location of the safety valve mechanism described above, either of the bottoms M1 and M2 is preferable, and the bottom M2 is more preferable.

[0103] <1-2. Operation> When the secondary battery is charged, in the battery element 40, lithium is released from the positive electrode 41 and the lithium is absorbed in the negative electrode 42 via the electrolyte. On the other hand, when the secondary battery is discharged, in the battery element 40, lithium is released from the negative electrode 42 and the lithium is absorbed in the positive electrode 41 via the electrolyte. During these charge and discharge operations, lithium is absorbed and released in an ionic state.

[0104] <1-3. Manufacturing method> Fig. 5 shows a perspective configuration of an exterior can 10 used in the manufacturing process of a secondary battery, and corresponds to Fig. 1. Fig. 6 shows a cross-sectional configuration of the exterior can 10 to explain the manufacturing process of a secondary battery, and corresponds to Fig. 2.

[0105] Fig. 5 shows a 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. Fig. 5 shows a state in which the lid portion 12 is upright with respect to the storage portion 11 before the lid portion 12 is welded to the storage portion 11.

[0106] In the following description, reference will be made from time to time to FIGS. 1 to 4, which have already been described, in addition to FIGS.

[0107] Here, in order to form the exterior can 10, a storage section 11 and a lid section 12 that are physically separated from each other are prepared as shown in Fig. 5. The storage section 11 is a roughly container-shaped member in which a bottom section M2 and a side wall section M3 are integrated with each other, and has an opening section 11K. The lid section 12 is a roughly plate-shaped member that corresponds to the bottom section M1, and an external terminal 20 is attached in advance to a recessed section 12H provided in the lid section 12 via a gasket 30.

[0108] However, the storage section 11 may be formed by preparing the bottom section M2 and the side wall section M3 which are physically separated from each other, and welding the side wall section M3 to the bottom section M2.

[0109] [Preparation of positive electrode] First, a positive electrode mixture is prepared by mixing a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, and the like. Next, the prepared positive electrode mixture is poured into an organic solvent or the like to prepare a paste-like positive electrode mixture slurry. Next, the positive electrode mixture slurry is applied to both sides of a positive electrode current collector 41A to form a positive electrode active material layer 41B. Finally, the positive electrode active material layer 41B is compression 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. In this way, the positive electrode 41 is prepared.

[0110] [Preparation of negative electrode] The negative electrode 42 is produced by the same procedure as that for producing the positive electrode 41. Specifically, a negative electrode mixture obtained by mixing a negative electrode active material, a negative electrode binder, a negative electrode conductive agent, and the like is poured into an organic solvent to prepare a paste-like negative electrode mixture slurry, and then the negative electrode mixture slurry is applied to both sides of a negative electrode current collector 42A to form a negative electrode active material layer 42B. Thereafter, the negative electrode active material layer 42B is compression molded using a roll press or the like. In this way, the negative electrode 42 is produced.

[0111] [Preparation of electrolyte] An electrolyte salt is added to a solvent, whereby the electrolyte salt is dispersed or dissolved in the solvent, and an electrolyte solution is prepared.

[0112] [Secondary battery assembly] First, using a welding method such as resistance welding, the positive electrode lead 51, whose periphery is covered with a sealant 61, is connected to the positive electrode 41 (positive electrode current collector 41A), and the negative electrode lead 52 is connected to the negative electrode 42 (negative electrode current collector 42A).

[0113] Next, the positive electrode 41 and the negative electrode 42 are laminated with the separator 43 interposed therebetween, and then the laminate including the positive electrode 41, the negative electrode 42, and the separator 43 is wound to produce the wound body 40Z as shown in Fig. 5. The wound body 40Z has a similar configuration to that of the battery element 40, except that the positive electrode 41, the negative electrode 42, and the separator 43 are not impregnated with an electrolyte. Note that in Fig. 5, the positive electrode lead 51 and the negative electrode lead 52 are not shown.

[0114] Next, the wound body 40Z to which the positive electrode lead 51 and the negative electrode lead 52 are respectively connected is accommodated inside the accommodation section 11 through the opening 11K. In this case, the negative electrode lead 52 is connected to the accommodation section 11 by using a welding method such as resistance welding. Next, an insulating film 63 is placed on the wound body 40Z.

[0115] Next, after preparing the lid portion 12 to which the external terminal 20 is attached via the gasket 30 and to which the insulating film 62 is already provided, the positive electrode lead 51 is connected to the external terminal 20 via the through hole 12K using a welding method such as resistance welding.

[0116] As a result, the wound body 40Z (positive electrode 41) stored inside the storage unit 11 and the external terminal 20 attached to the lid portion 12 are connected to each other via the positive electrode lead 51. Therefore, as shown in FIG. 5, in a state in which the wound body 40Z and the external terminal 20 are connected to each other via the positive electrode lead 51, it becomes possible to stand the lid portion 12 on the storage unit 11. The reason for standing the lid portion 12 on the storage unit 11 is to prevent the lid portion 12 from blocking the opening 11K. When standing the lid portion 12, it is possible to hold the lid portion 12 using a holding jig.

[0117] As is clear from FIG. 6, "standing the lid 12 against the storage section 11" means arranging the lid 12 so as to be substantially perpendicular to the bottom surface of the storage section 11 while maintaining the state in which the battery element 40 and the external terminal 20 are connected to each other via the positive electrode lead 51. In this case, by making the length of the positive electrode lead 51 sufficiently large, even if the lid 12 is stood against the storage section 11, the positive electrode lead 51 is prevented from being excessively pulled or twisted. By standing the lid 12 against the storage section 11, the lid 12 is arranged on the inside, i.e., on the inside side of the storage section 11, and the positive electrode lead 51 is arranged on the outside, i.e., on the opposite side to the inside side of the storage section 11. As a result, when welding the positive electrode lead 51 to the external terminal 20 using a laser welding method or the like, foreign matter generated during welding is less likely to enter the inside of the storage section 11.

[0118] Next, the electrolyte is injected into the storage section 11 through the opening 11K. In this case, as described above, even if the battery element 40 and the external terminal 20 are connected to each other via the positive electrode lead 51, the lid section 12 does not close the opening 11K, so that the electrolyte can be easily injected into the storage section 11 through the opening 11K. As a result, the wound body 40Z including the positive electrode 41, the negative electrode 42, and the separator 43 is impregnated with the electrolyte, and the battery element 40, which is a wound electrode body, is produced.

[0119] 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 Fig. 2, a part of the positive electrode lead 51 is sandwiched between the lid 12 and the battery element 40, and a curved folded-back portion 513 is formed in the positive electrode lead 51 before the connection location to the external terminal 20. In this way, the outer can 10 is formed, and the battery element 40 and the like are housed inside the outer can 10, completing the assembly of the secondary battery.

[0120] [Stabilization of secondary batteries] The assembled secondary battery is charged and discharged. Various conditions such as the environmental temperature, the number of charge / discharge cycles (number of cycles), and the charge / discharge conditions can be set arbitrarily. As a result, a coating is formed on the surface of the negative electrode 42, etc., and the state of the secondary battery is electrochemically stabilized. Thus, the secondary battery is completed.

[0121] <1-4. Actions and Effects> Thus, according to the secondary battery of the present embodiment, the positive electrode lead 51 includes the folded-back portion 513 that is curved so as to connect the first portion 511 and the second portion 512. This improves the durability of the positive electrode lead 51. This is because local stress concentration is also unlikely to occur in the folded-back portion 513, and therefore the positive electrode lead 51 is unlikely to crack or break. Therefore, the secondary battery of the present embodiment can obtain excellent physical durability.

[0122] In particular, since the folded-back portion 513 of the positive electrode lead 51 is curved so as to form a space V on the inside, local stress is less likely to occur in the folded-back portion 513 .

[0123] In the secondary battery of this embodiment, the lid 12 is provided with a recess 12H, and the external terminal 20 is disposed in the recess 12H. This allows the height dimension of the secondary battery to be reduced while ensuring the battery capacity. Furthermore, in the secondary battery of this embodiment, the first portion 511 and the second portion 512 are sandwiched between the protruding portion 12P of the lid 12 and the battery element 40 in the height direction of the secondary battery, while the folded portion 513 is sandwiched between the peripheral portion 12R of the lid 12 and the battery element 40 in the height direction of the secondary battery. That is, the overlapping portion of the relatively thin first portion 511 and the second portion 512 of the positive electrode lead 51 is disposed in a relatively narrow space, while the relatively thick folded portion 513 is disposed in a relatively narrow wide space. This allows the internal space of the outer can 10 to be used more efficiently, and the secondary battery to be made thinner. Thus, the secondary battery of this embodiment is suitable for achieving both an improvement in energy density per unit volume and an improvement in physical durability.

[0124] In the secondary battery of this embodiment, the folded portion 513 is located at the peripheral portion 12R of the lid portion 12, and the first portion 511 and the second portion 512 extend in the radial direction of the secondary battery from the center position of the secondary battery toward the peripheral portion 12R. Specifically, the first portion 511 extends from a first position P1 other than the center position P of the outer can 10 to a second position P2 on the opposite side of the first position P1 as viewed from the center position P in a horizontal plane perpendicular to the height direction Z of the secondary battery. The second portion 512 extends from the second position P2 toward the center position. In addition, the overlapping portion of the first portion 511 and the second portion 512 is sandwiched between the protruding portion 12P and the battery element 40. This makes it possible to secure a larger area where the first portion 511 contacts the battery element 40 via the sealant 61, and a larger area where the second portion 512 contacts the protruding portion 12P directly or via the sealant 61. This sufficiently limits the movement of the positive electrode lead 51 and the battery element 40 inside the exterior can 10. Therefore, even if the secondary battery is subjected to impact or vibration, problems such as damage to the positive electrode lead 51 and collapse of the battery element 40 are unlikely to occur. Therefore, the secondary battery of this embodiment can obtain excellent physical durability.

[0125] In particular, in the secondary battery of this embodiment, the above-mentioned functions and effects can be obtained for the reasons explained below.

[0126] The secondary battery of this embodiment, which is called a coin type or a button type, i.e., a secondary battery having a flat and columnar three-dimensional shape, is provided with a small external terminal 20 that functions as an external connection terminal for the positive electrode 41, as is clear from Fig. 1 and Fig. 2. In this case, since the size of the external terminal 20 is small, the connection area of ​​the positive electrode lead 51 to the external terminal 20 is small. Therefore, in order to maintain the electrical connection state between the external terminal 20 and the positive electrode lead 51, it is necessary to sufficiently fix the positive electrode lead 51 inside the outer can 10.

[0127] In this regard, in the secondary battery of this embodiment, the movement of the positive electrode lead 51 inside the exterior can 10 is sufficiently suppressed, so that even if the connection area of ​​the positive electrode lead 51 to the external terminal 20 is small, the possibility that the positive electrode lead 51 will come off from the external terminal 20 or break is extremely low. Therefore, according to the secondary battery of this embodiment, even if it is subjected to an external force such as vibration or impact, it is possible to maintain a good electrical connection state between the external terminal 20 and the positive electrode lead 51. Therefore, according to the secondary battery of this embodiment, it is possible to achieve high physical durability even when it is miniaturized.

[0128] In the secondary battery of this embodiment, which includes a small external terminal 20 that is an external connection terminal for the positive electrode 41, the lid 12 of the exterior can 10 that functions as an external connection terminal for the negative electrode 42 is disposed close to the external terminal 20, as is clear from FIG. 2. That is, the lid 12 and the external terminal 20 that are two external connection terminals having different polarities are close to each other. Therefore, in order to prevent a short circuit between the lid 12 and the external terminal 20, it is desirable to make the connection area of ​​the positive electrode lead 51 to the external terminal 20 sufficiently small and to place the positive electrode lead 51 sufficiently far from the lid 12.

[0129] In this regard, in the secondary battery of this embodiment, the movement of the positive electrode lead 51 inside the exterior can 10 is sufficiently suppressed, so that even if the connection area of ​​the positive electrode lead 51 to the external terminal 20 is small, the possibility that the positive electrode lead 51 will come off from the external terminal 20 or break is extremely low. Therefore, according to the secondary battery of this embodiment, even if it is subjected to an external force such as vibration or impact, it is possible to maintain a good electrical connection state between the external terminal 20 and the positive electrode lead 51. Therefore, according to the secondary battery of this embodiment, even if it is miniaturized, it is possible to realize high physical durability while preventing a short circuit between the lid portion 12 and the external terminal 20.

[0130] Furthermore, if the height of the insulating separator 43 is greater than the height of the negative electrode 42 and a portion of the positive electrode lead 51 is insulated from the negative electrode 42 via the separator 43, a short circuit between the positive electrode lead 51 and the negative electrode 42 is prevented, thereby achieving higher reliability.

[0131] In this case, if the positive electrode 41 and the negative electrode 42 are wound facing each other with the separator 43 interposed therebetween and the positive electrode lead 51 is connected to the positive electrode 41 on the inner side of the outermost periphery of the positive electrode 41, corrosion of the outer can 10 caused by creeping up of the electrolyte can be prevented, thereby achieving even higher reliability.

[0132] Furthermore, if the sealant 61 covers the periphery of the positive electrode lead 51 and a portion of the positive electrode lead 51 is insulated from both the outer casing 10 and the negative electrode 42 via the sealant 61, a short circuit between the positive electrode lead 51 and the outer casing 10 is prevented, and a short circuit between the positive electrode lead 51 and the negative electrode 42 is also prevented, thereby achieving higher reliability.

[0133] In this case, particularly when the periphery of the positive electrode lead 51 is covered with the sealant 61, the following action and effect can be obtained. That is, when the positive electrode lead 51 is sandwiched between the outer can 10 and the battery element 40 via the sealant 61, a gripping force is generated between the outer can 10 and the sealant 61, and a gripping force is also generated between the battery element 40 and the sealant 61. As a result, the positive electrode lead 51 is easily held by the outer can 10 and the battery element 40 by utilizing the gripping force supplied to the positive electrode lead 51 via the sealant 61. Therefore, the positive electrode lead 51 is insulated from the outer can 10 and the negative electrode 42 via the sealant 61. In addition, the sealant 61 is used to more easily fix the positive electrode lead 51 inside the outer can 10, thereby obtaining even higher physical durability.

[0134] Furthermore, if the insulating film 62 is disposed between the exterior can 10 and the positive electrode lead 51, and a portion of the positive electrode lead 51 is insulated from the exterior can 10 via the insulating film 62, a short circuit between the positive electrode lead 51 and the exterior can 10 is prevented, thereby achieving higher reliability.

[0135] Furthermore, if the insulating film 63 is disposed between the battery element 40 and the positive electrode lead 51, and a part of the positive electrode lead 51 is insulated from the negative electrode 42 via the insulating film 63, a short circuit between the positive electrode lead 51 and the negative electrode 42 is prevented, thereby achieving higher reliability.

[0136] In addition, since the exterior can 10 includes the storage section 11 and the lid section 12 which are welded together, and the positive electrode lead 51 is folded back at least once, a length margin for the positive electrode lead 51 is obtained. Therefore, it becomes possible to stand the lid section 12 upright relative to the storage section 11 during the manufacturing process of the secondary battery, particularly during the process of forming the exterior can 10. This makes it easier to inject the electrolyte, and also makes it possible to arbitrarily change the connection position of the positive electrode lead 51 relative to the positive electrode 41, thereby making it easier to manufacture.

[0137] In this case, if the length of the positive electrode lead 51 is equal to or greater than half the outer diameter D of the exterior can 10, the lid portion 12 can be easily stood upright on the housing portion 11 in the manufacturing process of the secondary battery, thereby achieving even greater ease of manufacturing.

[0138] Furthermore, if the secondary battery is flat and columnar, that is, the secondary battery is called a coin type or button type secondary battery, the positive electrode lead 51 is less likely to be damaged even in small secondary batteries that are subject to significant size restrictions, and therefore greater effects can be obtained in terms of physical durability.

[0139] Furthermore, if the secondary battery is a lithium ion secondary battery, sufficient battery capacity can be stably obtained by utilizing the absorption and release of lithium.

[0140] <2. Modifications> The configuration of the secondary battery described above can be modified as appropriate, as described below, although any two or more of the series of modifications described below may be combined with each other.

[0141] [Variation 1] 2, the secondary battery includes a sealant 61 and insulating films 62 and 63. However, the secondary battery of the present technology is not limited to the case where it includes all of the sealant 61 and the insulating films 62 and 63, as long as the positive electrode lead 51 is insulated from the outer can 10 and the negative electrode 42, respectively.

[0142] Specifically, first, when the positive electrode lead 51 is insulated from the negative electrode 42 via the separator 43, the secondary battery may not include the insulating film 63. Second, when the positive electrode lead 51 is insulated from each of the outer can 10 and the negative electrode 42 via the sealant 61, the secondary battery may not include one or both of the insulating films 62, 63. Third, when the positive electrode lead 51 is insulated from each of the outer can 10 and the negative electrode 42 via the separator 43 and the insulating film 62, the secondary battery may not include one or both of the sealant 61 and the insulating film 63.

[0143] In these cases as well, since the positive electrode lead 51 is insulated from both the outer casing 10 and the negative electrode 42, the same effects as those of the secondary battery of the above embodiment can be obtained.

[0144] [Variation 2] 2, since the height of the separator 43 is greater than the height of the negative electrode 42, the positive electrode lead 51 is insulated from the negative electrode 42 via the separator 43. However, when the installation range of the insulating film 63 is expanded so that the positive electrode lead 51 is insulated from the negative electrode 42 via the insulating film 63, the positive electrode lead 51 does not need to be insulated from the negative electrode 42 via the separator 43.

[0145] Even in this case, the positive electrode lead 51 is insulated from the negative electrode 42 via the insulating film 63, so that the same effect as in the secondary battery of the above embodiment can be obtained. However, in order to prevent the lithium released from the positive electrode 41 from being precipitated, it is preferable that the height of the separator 43 is greater than the height of the negative electrode 42.

[0146] [Variation 3] 2, the insulating film 62 covers only the lower surface of the lid portion 12 (the protruding portion 12P). However, the installation range of the insulating film 62 is not particularly limited as long as a part of the positive electrode lead 51 is insulated from the exterior can 10 via the insulating film 62.

[0147] Specifically, as shown in Fig. 7 corresponding to Fig. 2, the insulating film 62 may cover not only the lower surface of the lid portion 12 but also the side surface of the lid portion 12, i.e., the inner wall surface of the through hole 12K. In this case, the exposed portion of the positive electrode lead 51 that is not covered by the sealant 61 and the lid portion 12 are less likely to come into contact with each other. This further prevents a short circuit between the positive electrode lead 51 and the outer casing 10, thereby achieving higher reliability.

[0148] [Variation 4] In the present disclosure, the coverage of the positive electrode lead 51 with the sealant 61 is not particularly limited and can be set arbitrarily. Specifically, as shown in FIG. 8 corresponding to FIG. 2, the folded portion 513, the second portion 512, and a part of the first portion 511 of the positive electrode lead 51 may not be covered with the sealant 61. In addition, in the fourth modification shown in FIG. 8, the portion of the first portion 511 that overlaps with the second portion 512 is not covered with the sealant 61. The positive electrode lead 51 and the battery element 40 are electrically insulated from each other by the insulating film 63.

[0149] In the fourth modification shown in FIG. 8, the overlapping portion between the first portion 511 and the second portion 512 is not covered with the sealant 61, so that the thickness of the overlapping portion between the first portion 511 and the second portion 512 can be made thinner. In the fourth modification shown in FIG. 8, the folded-back portion 513 is also not covered with the sealant 61, so that the thickness of the folded-back portion 513 can also be made thinner. This makes it possible to further improve the volume occupancy rate of the battery element 40 inside the outer can 10. Therefore, the secondary battery as the fourth modification shown in FIG. 8 is more suitable for improving the energy density per unit volume.

[0150] In addition, compared to the fourth modified example shown in FIG. 8, in the secondary battery of FIG. 2 described in the above embodiment, the positive electrode lead 51 is more easily insulated from the outer casing 10 and the negative electrode 42 via the sealant 61, and therefore higher reliability can be obtained.

[0151] [Variation 5] The present disclosure is not limited to the case where the folded portion 513 of the positive electrode lead 51 is disposed at a position corresponding to the peripheral portion 12R of the lid portion 12. Specifically, as shown in FIG. 9 corresponding to FIG. 8, the folded portion 513 may be provided in the gap between the protruding portion 12P of the lid portion 12 and the battery element 40. In the modified example 5 shown in FIG. 9, the folded portion 513 of the positive electrode lead 51 has a curved shape, so that the possibility of damage to the positive electrode lead 51 occurring can be reduced. However, in the modified example 5 shown in FIG. 9, the gap between the protruding portion 12P and the battery element 40 is made larger than the thickness of the folded portion 513 in the height direction Z of the secondary battery. Therefore, from the viewpoint of improving the energy density per unit volume, it is more desirable that the folded portion 513 is disposed in the gap between the peripheral portion 12R of the lid portion 12 and the battery element 40 as in the configuration examples shown in FIG. 2, FIG. 7, FIG. 8, etc. than in the modified example 5 shown in FIG. 9.

[0152] [Variations 6-7] In Fig. 2, an outer can 10 is used in which a flat external terminal 20 is attached to the outside of a lid portion 12 having a protruding portion 12P (or a recessed portion 12H). However, the configuration of the outer can 10 is not particularly limited and may be changed as desired. Note that the configuration of a series of secondary batteries described below has the same configuration as the secondary battery shown in Fig. 2, except that the configurations of the lid portion 12 and the external terminal 20 are different.

[0153] Specifically, as shown in Fig. 10 corresponding to Fig. 2, an exterior can 10 may be used in which a flat external terminal 20 is attached to the inside of a flat lid portion 12 that does not have a protruding portion 12P. In this exterior can 10, the flat external terminal 20 is attached via a gasket 30 to the inside of the lid portion 12 having a through hole 12K. The external terminal 20 is partially exposed at the through hole 12K. In this case, the location of the insulating film 63 may be adjusted to prevent a short circuit between the negative electrode 42 and the portion of the positive electrode lead 51 that is not covered with the sealant 61 (variation 6).

[0154] 11 corresponding to Fig. 2, an outer can 10 may be used in which a flat external terminal 20 is attached to the outside of a flat lid portion 12 that does not have a protrusion 12P. In the outer can 10, the external terminal 20 is attached via a gasket 30 to the outside of the lid portion 12 that has a through hole 12K (variation 7). EXAMPLES

[0155] An embodiment of the present technology will be described.

[0156] As described below, a secondary battery (lithium ion secondary battery) was produced, and then the performance of the secondary battery was evaluated.

[0157] [Preparation of secondary battery] Here, the secondary battery shown in Fig. 1 to Fig. 4 was fabricated as the secondary battery of Experimental Example 1. Furthermore, secondary batteries of Experimental Examples 2 to 4 were also fabricated. The following will explain each in turn.

[0158] (Experimental Example 1) A coin-type secondary battery provided with a positive electrode lead 51 including a curved folded-back portion 513 was fabricated by the procedure described below.

[0159] (Preparation of positive electrode) First, 91 parts by mass of a positive electrode active material (LiCoO2), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride), and 6 parts by mass of a positive electrode conductive agent (graphite) were mixed to prepare a positive electrode mixture. 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. Next, the positive electrode mixture slurry was applied to both sides of a positive electrode current collector 41A (a strip-shaped aluminum foil having a thickness of 12 μm) using a coating device, and then 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 compression molded using a roll press machine. As a result, a positive electrode 41 (width = 3.3 mm) was produced.

[0160] (Preparation of negative electrode) First, 95 parts by mass of the negative electrode active material (graphite) and 5 parts by mass of the negative electrode binder (polyvinylidene fluoride) were mixed to prepare a negative electrode mixture. 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. Next, the positive electrode mixture slurry was applied to both sides of the negative electrode current collector 42A (a strip-shaped copper foil having a thickness of 15 μm) using a coating device, and the negative electrode mixture slurry was dried to form the negative electrode active material layer 42B. Finally, the negative electrode active material layer 42B was compression-molded using a roll press machine. This produced the negative electrode 42 (width = 3.8 mm).

[0161] (Preparation of electrolyte) After adding the electrolyte salt (LiPF6) to the solvent (ethylene carbonate and diethyl carbonate), the solvent was stirred. In this case, the mixing ratio (weight ratio) of the solvent was ethylene carbonate:diethyl carbonate=30:70, and the content of the electrolyte salt 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.

[0162] (Secondary battery assembly) First, an aluminum positive electrode lead 51 (thickness = 0.1 mm, width = 2.0 mm, protruding length from the positive electrode 41 = 11.7 mm) 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) by using a resistance welding method. In addition, a nickel negative electrode lead 52 (thickness = 0.1 mm, width = 2.0 mm, protruding length from the negative electrode 42 = 6.0 mm) was welded to the negative electrode 42 (negative electrode current collector 42A) by using a resistance welding method. In this case, the welding position of the positive electrode lead 51 was adjusted so that the welding position of the positive electrode lead 51 was in the middle of winding the positive electrode 41.

[0163] Next, the positive electrode 41 and the negative electrode 42 were laminated together via a separator 43 (a microporous polyethylene film having a thickness of 25 μm and a width of 4.0 mm), and then the positive electrode 41, the negative electrode 42, and the separator 43 were wound to produce a cylindrical wound body 40Z (outer diameter = 11.6 mm) having a winding central space 40K (inner diameter = 2.0 mm).

[0164] Next, a ring-shaped insulating film (polyimide film, outer diameter = 11.6 mm, inner diameter = 2.2 mm, thickness = 0.05 mm) for underlay 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. In this case, the negative electrode lead 52 was welded to the storage section 11 by using a resistance welding method. Next, using a resistance welding method, the positive electrode lead 51 was welded to the external terminal 20 of the disk-shaped cover portion 12 (wall thickness = 0.15 mm, outer diameter = 11.7 mm) made of stainless steel (SUS316) having 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 disk-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).

[0165] Next, with the lid 12 standing on the storage section 11, the electrolyte was injected into the storage section 11 through the opening 11K. As a result, the wound body 40Z (the positive electrode 41, the negative electrode 42, and the separator 43) was impregnated with the electrolyte, and the battery element 40 was produced.

[0166] Finally, the opening 11K was closed using the lid 12, and then the lid 12 was welded to the storage section 11 using a laser welding method. When the opening 11K was closed with the lid 12, a folded portion 513 was formed in a part of the positive electrode lead 51 so as to have a curved shape, and the folded portion 513 was positioned in the peripheral portion 12R. Specifically, the distance between the folded portion 513 and the inner surface of the side wall portion M3 was adjusted to be 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 disk-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 housing portion 11 and the lid portion 12 formed the outer can 10, and the battery element 40 was sealed inside the outer can 10, thereby assembling a secondary battery (outer diameter=12.0 mm, height=5.0 mm).

[0167] (Stabilization of secondary batteries) The assembled secondary battery was charged and discharged for one cycle in a room temperature environment (temperature = 23°C). During charging, the battery was charged at a constant current of 0.1C until the voltage reached 4.2V, and then charged at a constant voltage of 4.2V until the current reached 0.05C. During discharging, the battery was discharged at a constant current of 0.1C until the voltage reached 3.0V. 0.1C is the current value at which the battery capacity (theoretical capacity) is fully discharged in 10 hours, and 0.05C is the current value at which the battery capacity is fully discharged in 20 hours.

[0168] As a result, a coating was formed on the surface of the negative electrode 42 etc., so that the state of the secondary battery was electrochemically stabilized, and the secondary battery was thus completed.

[0169] (Experimental Example 2) After the electrolyte was injected into the storage section 11 from the opening 11K, the opening 11K was closed by using the lid section 12 so that the positive electrode lead 51 had a bent shape at the folded-back portion 513 (see FIG. 12). FIG. 12 is a cross-sectional view showing a cross-sectional configuration of a secondary battery as Experimental Example 2. The folded-back portion 513 was also sandwiched in the gap between the protruding portion 12P and the battery element 40. Specifically, the distance between the folded-back portion 513 and the inner surface of the side wall section M3 was adjusted to be 3.0 mm. Except for these points, a secondary battery having the same configuration as that of Experimental Example 1 was obtained.

[0170] (Experimental Example 3) After the electrolyte was injected into the storage section 11 from the opening 11K, the opening 11K was closed with the lid section 12 so that the positive electrode lead 51 was bent at the folded-back portion 513 (see FIG. 13). FIG. 13 is a cross-sectional view showing the cross-sectional configuration of a secondary battery as Experimental Example 3. A secondary battery having the same configuration as that of Experimental Example 1 was obtained except for this point.

[0171] (Experimental Example 4) 9, the folded portion 513 was sandwiched in the gap between the protruding portion 12P and the battery element 40. Specifically, the distance between the folded portion 513 and the inner surface of the side wall portion M3 was adjusted to 3.0 mm. Except for this point, a secondary battery having the same configuration as in the above-mentioned Experimental Example 1 was obtained.

[0172] [Performance evaluation] When the physical durability of each of the secondary batteries of Experimental Examples 1 to 4 was evaluated, the results shown in Table 1 were obtained. To evaluate the physical durability, a vibration test of the secondary batteries conforming to the UN test was performed to check whether the positive electrode lead of the secondary battery was damaged or not. Here, 30 batteries were tested, and the number of secondary batteries whose positive electrode lead was cut is recorded in the "Number of cut defects (units)" column of Table 1, and the number of secondary batteries whose positive electrode lead fell off from the positive electrode terminal is recorded in the "Number of detachment defects (units)" column of Table 1.

[0173] Furthermore, a vibration test was conducted on each secondary battery to check whether a short circuit had occurred inside the secondary battery. Ten batteries were tested. The results are also shown in Table 1. The vibration test conditions were an amplitude of 0.8 mm, a frequency of 10 to 55 Hz, a sweep rate of 1 Hz / min, and a test time of 90 to 100 min. In addition, the open circuit voltage (OCV) was measured before and after the vibration test, and an open circuit voltage of 4 V or less after the vibration test was determined to be an internal short circuit defect.

[0174] [Table 1]

[0175] [Consideration] As shown in Table 1, in Experimental Examples 2 and 3, in which the folded back portion of the positive electrode lead was bent, one positive electrode lead in each of the 30 leads had a cutting failure. This is thought to be because in Experimental Examples 2 and 3, the folded back portion of the positive electrode lead was bent, which made it easier for cracks to occur when subjected to vibration, and the cracks were easier to propagate.

[0176] In addition, in Experimental Example 2, the positive electrode lead fell off from the positive electrode terminal in one out of 30 batteries. This is believed to be due to the fact that in Experimental Example 2, the folded portion of the positive electrode lead is located closer to the center position than in Experimental Examples 1 and 3. That is, in Experimental Example 2, the contact area between the positive electrode lead and the lid and the contact area between the positive electrode lead and the battery element are smaller than in Experimental Examples 1 and 3, and the movement of the positive electrode lead and the battery element inside the exterior can due to vibration could not be sufficiently suppressed. In Experimental Examples 2 to 4, internal short circuit defects occurred in one or two out of 10 batteries.

[0177] In contrast, in Experimental Example 1, the positive electrode lead was not broken in any of the 30 pieces, and neither the number of cutting defects nor the number of falling-off defects occurred. In Experimental Example 1, no internal short circuit defects occurred. In Experimental Example 1, since the folded portion of the positive electrode lead has a curved shape, even if it is subjected to vibration, cracks or the like do not occur in the positive electrode lead, and cutting defects of the positive electrode lead can be avoided. Furthermore, in Experimental Example 1, the folded portion is arranged at a position corresponding to the peripheral portion, so that the movement of the positive electrode lead and the battery element inside the outer can due to vibration can be sufficiently suppressed. This is thought to be because the contact area between the positive electrode lead and the lid portion and the contact area between the positive electrode lead and the battery element can be sufficiently secured.

[0178] [summary] From the results shown in Table 1, it was confirmed that the durability of the positive electrode lead is improved by including a curved folded-back portion in the secondary battery of the present disclosure. This is because the folded-back portion has a curved shape, which makes it less likely for local stress concentration to occur than when the folded-back portion has a bent shape, and therefore makes it less likely for cracks or breaks to occur in the positive electrode lead. Therefore, it was found that the secondary battery of the present disclosure can obtain excellent physical durability.

[0179] Although the present technology has been described above with reference to an embodiment and examples, the configuration of the present technology is not limited to the configuration described in the embodiment and examples and can be modified in various ways.

[0180] Specifically, the case where the outer can is a welded can (crimpless can) has been described, but the configuration of the outer can is not particularly limited, and it may be a crimp can that has been crimped. In this crimp can, a storage section and a lid section that are separated from each other are crimped together via a gasket.

[0181] In addition, although the battery element has a wound structure, the element structure of the battery element is not particularly limited, and may be other element structures such as a stacked type in which the electrodes (positive and negative electrodes) are stacked, or a zigzag-folded type in which the electrodes (positive and negative electrodes) are folded.

[0182] Furthermore, although the electrode reactant is lithium, the electrode reactant is not particularly limited. Therefore, as described 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.

[0183] The effects described in this specification are merely examples, and the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

Claims

1. An exterior member; a battery element housed in the exterior member and including a first electrode and a second electrode; an external terminal attached to the exterior member and electrically insulated from the exterior member; a connection wiring electrically insulated from the exterior member and electrically connected to each of the first electrodes and the external terminals; Equipped with the connection wiring includes a first portion, a second portion overlapping the first portion, and a folded-back portion curved to connect the first portion and the second portion; the exterior member has a container including an opening through which the battery element can be inserted and capable of housing the battery element through the opening, and a lid portion that closes the opening, the connecting wire is located between the lid portion and the battery element, the lid portion includes a protrusion protruding toward the battery element, at least a part of the first portion and at least a part of the second portion are sandwiched between the protrusion and the battery element in a first direction; The folded portion is sandwiched between a portion of the lid other than the protruding portion and the battery element in the first direction. Secondary battery.

2. The folded portion is curved to form a space inside. The secondary battery according to claim 1 .

3. In the first direction, the thickness of the folded portion is greater than the thickness of an overlapping portion between the first portion and the second portion. The secondary battery according to claim 1 or 2.

4. the first portion extends, in a plane perpendicular to the first direction, from a first position other than a center position of the exterior member to a second position on an opposite side to the first position as seen from the center position, The second portion extends from the second location toward the central location. The secondary battery according to claim 1 .

5. the lid portion includes a recess portion formed by the protrusion, The external terminal is housed in the recess. The secondary battery according to claim 1 .

6. a first end portion of the first portion opposite to the folded portion is connected to the first electrode of the battery element; A second end of the second portion opposite to the folded portion is connected to a first electrode terminal located on the opposite side of the battery element as viewed from the lid portion. The secondary battery according to any one of claims 1 to 5.

7. Further, an insulating member is provided to cover the periphery of the connection wiring, A portion of the connection wiring is electrically insulated from each of the exterior member and the second electrode by the insulating member. The secondary battery according to any one of claims 1 to 6.

8. The exterior member is a metal can. The secondary battery according to claim 1 .

9. The metal can is formed of a conductive material including at least one of iron, copper, nickel, stainless steel, an iron alloy, a copper alloy, and a nickel alloy. The secondary battery according to claim 8.

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