Secondary batteries

Abstract

To provide a secondary battery with higher reliability.SOLUTION: A secondary battery includes a core material, a battery element, an exterior member, and an external terminal. The core material extends in a first direction. The battery element is formed by winding a laminate including a first electrode and a second electrode around the core material. The exterior member includes a lid portion provided with a through hole penetrating in the first direction, a bottom portion facing the lid portion across the battery element in the first direction, and a side wall portion that connects the lid portion and the bottom portion and surrounds the battery element, and accommodates the battery element. The external terminal is provided at a position opposite to the bottom portion when viewed from the lid portion and overlaps the through hole in the first direction. Here, the core material is fixed to the external terminal, and the outer edge of the lid portion is welded to the end of the side wall portion on the opposite side of the bottom portion.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This technology relates to secondary batteries.

Background Art

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

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

[0006] This disclosure has been made in view of such problems, and an object thereof is to provide a secondary battery having higher reliability.

Means for Solving the Problems

[0007] A first secondary battery according to one embodiment of the present disclosure comprises a core material, a battery element, an outer casing member, and an external terminal. The core material extends in a first direction. The battery element is formed by winding a laminate including a first electrode and a second electrode around the core material. The outer casing member has a lid portion with a through-hole extending in the first direction, a bottom portion facing the lid portion with the battery element in the first direction, and a side wall portion connecting the lid portion and the bottom portion and surrounding the battery element, and houses the battery element. The external terminal is provided at a position opposite the bottom portion when viewed from the lid portion and overlapping with the through-hole in the first direction. Here, the core material is fixed to the external terminal, and the outer edge of the lid portion is welded to the end of the side wall portion opposite the bottom portion.

[0008] A second secondary battery according to one embodiment of the present disclosure comprises a core material, a battery element, an outer casing member, and an external terminal. The core material extends in a first direction. The battery element is formed by winding a laminate including a first electrode and a second electrode around the core material. The outer casing member has a lid portion with a through-hole extending in the first direction, a bottom portion facing the lid portion with the battery element in the first direction, and a side wall portion connecting the lid portion and the bottom portion and surrounding the battery element, and houses the battery element. The external terminal is provided on the opposite side of the bottom portion as viewed from the lid portion and in a position that overlaps with the through-hole in the first direction. The core material is fixed to the bottom portion, and the outer edge of the bottom portion is welded to the end of the side wall portion opposite to the lid portion. [Effects of the Invention]

[0009] According to the first secondary battery of one embodiment of the present disclosure, since the core material is fixed to the external terminals, the winding of the battery elements wound around the core material is less likely to collapse. Therefore, it has high reliability. Furthermore, since this secondary battery has a structure in which the outer edge of the lid is welded to the end of the side wall opposite the bottom, it can be easily manufactured.

[0010] According to the second secondary battery of one embodiment of the present disclosure, since the core material is fixed to the bottom of the outer casing member, the winding of the battery elements wound around the core material is less likely to collapse. Therefore, it has high reliability. Furthermore, since this secondary battery has a structure in which the outer edge of the lid is welded to the end of the side wall opposite to the lid, it can be easily manufactured.

[0011] Furthermore, the effects of this disclosure are not necessarily limited to those described herein, but may include any of the series of effects related to this technology described later. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view showing the configuration of a secondary battery as a first embodiment of the present disclosure. [Figure 2] Figure 1 is a cross-sectional view showing the configuration of a secondary battery. [Figure 3] Figure 2 is a cross-sectional view showing the configuration of the battery element. [Figure 4] Figure 1 is a perspective view showing the structure of the outer casing used in the manufacturing process of the secondary battery. [Figure 5] Figure 1 is an explanatory diagram illustrating one step in the manufacturing process of a secondary battery. [Figure 6] This is a cross-sectional view showing the configuration of a secondary battery as a second embodiment of the present disclosure. [Figure 7] This is a cross-sectional view showing the configuration of the secondary battery in Modification Example 1. [Figure 8] This is a schematic diagram illustrating the amount of winding misalignment in a secondary battery as an example. [Modes for carrying out the invention]

[0013] Hereinafter, one embodiment of this disclosure will be described in detail with reference to the drawings. The order of description is as follows. 1. Secondary battery of the first embodiment 1-1. Composition 1-2.Operation 1-3. Manufacturing method 1-4. Function and Effect 2. Secondary Battery of the Second Embodiment 2-1. Structure 2-2. Operation 2-3. Manufacturing Method 2-4. Function and Effect 3. Variation 4. Example

[0014] <1. Secondary Battery of the First Embodiment> First, the secondary battery of the first embodiment of the present disclosure will be described.

[0015] The secondary battery described here has a flat and columnar three-dimensional shape and is called a so-called coin type or button type. As will be described later, this secondary battery has a pair of bottom portions facing each other and a side wall portion located between the pair of bottom portions. In this secondary battery, the height is smaller than the outer diameter. The "outer diameter" referred to here is the maximum diameter (maximum outer diameter) of the bottom portion. In this secondary battery, the maximum diameters of each of the pair of opposing bottom portions are substantially equal to each other. Further, the "height" referred to here is the maximum distance from the upper surface of one bottom portion to the lower surface of the other bottom portion. In the present embodiment, the direction in which the pair of bottom portions face each other is defined as the height direction Z.

[0016] The charge-discharge principle of the secondary battery is not particularly limited. Hereinafter, the case where the battery capacity is obtained by utilizing the absorption and release of electrode reactants will be described. This secondary battery includes an electrolyte together with a positive electrode and a negative electrode. In this secondary battery, in order to prevent the deposition of electrode reactants on the surface of the negative electrode during charging, the charging capacity of the negative electrode is larger than the discharging capacity of the positive electrode. That is, the electrochemical capacity per unit area of the negative electrode is set to be larger than the electrochemical capacity per unit area of the positive electrode.

[0017] The types of electrode reactants are not particularly limited, but specifically, they are light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, while alkaline earth metals include beryllium, magnesium, and calcium.

[0018] In the following example, we will consider the case where lithium is the electrode reactant. A secondary battery that obtains battery capacity by utilizing the intercalation and deintercalation of lithium is a so-called lithium-ion secondary battery. In this lithium-ion secondary battery, lithium is intercalated and deintercalated in an ionic state.

[0019] <1-1. Structure> Figure 1 shows a perspective view of the secondary battery. Figure 2 shows a cross-sectional view of the secondary battery shown in Figure 1. Figure 3 shows a cross-sectional view of the battery element 40 shown in Figure 2. However, in Figure 3, only a portion of the cross-sectional view of the battery element 40 is magnified.

[0020] For convenience, in the following explanation, the upper side in Figure 1 and Figure 2 will be described as the upper side of the secondary battery, and the lower side in Figure 1 and Figure 2 will be described as the lower side of the secondary battery.

[0021] The secondary battery described here has a three-dimensional shape in which the height H is smaller than the outer diameter D, as shown in Figure 1; that is, a flat and columnar three-dimensional shape. Here, the three-dimensional shape of the secondary battery is flat and cylindrical. In this embodiment, the vertical direction of the paper in Figures 1 and 2 is defined as the height direction Z. Therefore, the height H represents the dimension in the height direction Z of the secondary battery in this embodiment. The outer diameter D represents the dimension in the direction perpendicular to the height direction Z of the secondary battery in this embodiment.

[0022] The dimensions of a secondary battery are not particularly limited, but as an example, the outer diameter D is 3mm to 30mm and the height H is 0.5mm to 70mm. However, the ratio of the outer diameter D to the height H (D / H) is greater than 1. That is, the outer diameter D is greater than the height H. There is no particular upper limit to this ratio (D / H), but it is preferably 25 or less.

[0023] As shown in Figures 1 to 3, this rechargeable battery comprises an outer casing 10, external terminals 20, and a battery element 40. In this case, the rechargeable battery further comprises a gasket 30, a negative electrode lead 52, insulating films 62 and 64, and a core material 13.

[0024] [Outer can] As shown in Figures 1 and 2, the outer casing 10 is a hollow outer component that houses the battery element 40 and the like. The outer casing 10 is made of a conductive material.

[0025] Here, the outer casing 10 has a flat and cylindrical three-dimensional shape, corresponding to the flat and cylindrical three-dimensional shape of the secondary battery. For this reason, the outer casing 10 has a pair of opposing bottoms M1 and M2, and a side wall M3 located between the bottoms M1 and M2. That is, the side wall M3 connects the bottoms M1 and M2 and surrounds the battery element 40. The upper end of the side wall M3 is connected to the bottom M1. The lower end of the side wall M3 is connected to the bottom M2. As described above, since the outer casing 10 is approximately cylindrical, the planar shapes of the bottoms M1 and M2 are approximately circular, and the surface of the side wall M3 is a convex curved surface.

[0026] Furthermore, the outer can 10 includes a storage section 11 and a lid section 12 that are welded to each other. That is, the internal space of the outer can 10 is sealed by welding the lid section 12 to the storage section 11. In this embodiment, the bottom section M1 constitutes the lid section 12, and the bottom section M2 and the side wall section M3 together constitute the storage section 11. Therefore, the outer edge of the lid section 12 is welded to the upper end of the side wall section M3.

[0027] The storage section 11 is a flat, cylindrical storage member that houses the battery element 40 and the like. The storage section 11 has a hollow structure with an open upper end and a closed lower end. That is, the storage section 11 has an opening 11K (Figure 2) at its upper end, which serves as a passage through which the battery element 40 can be inserted in the height direction Z.

[0028] As shown in Figure 2, the lid portion 12 is a substantially disc-shaped lid member that closes the opening 11K of the storage portion 11 and has a through-hole 12K. The through-hole 12K has an inner diameter of φ12K. 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 outer edge of the lid portion 12 is welded to the opening 11K of the storage portion 11. The external terminal 20 is attached to the lid portion 12 via a gasket 30. That is, the lid portion 12 supports the external terminal 20 via the gasket 30. The external terminal 20 is attached to the lid portion 12 via the gasket 30 so as to close the through-hole 12K. The external terminal 20 is electrically insulated from the outer casing 10.

[0029] Furthermore, in the completed secondary battery, as described above, the lid 12 is welded to the storage section 11. As mentioned above, the opening 11K is closed by the lid 12. Therefore, it is possible that by looking at the exterior of the secondary battery, it is not possible to confirm whether the storage section 11 had an opening 11K.

[0030] However, if the lid 12 is welded to the storage section 11, welding marks will remain on the surface of the outer can 10, more specifically at the boundary between the storage section 11 and the lid 12. Based on the presence or absence of these welding marks, it is possible to retrospectively confirm whether the storage section 11 had an opening 11K.

[0031] In other words, if welding marks remain on the surface of the outer can 10, it means that the storage compartment 11 had an opening 11K. On the other hand, if no welding marks remain on the surface of the outer can 10, it means that the storage compartment 11 did not have an opening 11K.

[0032] The lid portion 12 is bent so as to partially protrude along the height direction Z toward the interior of the storage portion 11, forming a recessed portion 12H. That is, when viewed from the outside of the outer casing 10, the lid portion 12 has a shape that is partially recessed in the height direction Z toward the battery element 40 housed inside the outer casing 10. The recessed portion 12H includes a through-hole 12K that penetrates in the height direction Z, a bottom portion 12HB that surrounds the through-hole 12K along a horizontal plane perpendicular to the height direction Z, and a wall portion 12HW that stands along the outer edge of the bottom portion 12HB. The portion of the lid portion 12 other than the recessed portion 12H is the peripheral portion 12R. The peripheral portion 12R is an annular shape that surrounds the recessed portion 12H in a horizontal plane perpendicular to the height direction Z of the secondary battery. The peripheral portion 12R is the part that surrounds the recessed portion 12H and protrudes away from the battery element 40 along the height direction Z. Therefore, in the height direction Z, the surface 12HS of the bottom 12HB of the recessed portion 12H is lower toward the interior of the storage portion 11 than the surface 12RS of the peripheral portion 12R. In other words, in the height direction Z, the distance between the surface 12HS of the bottom 12HB of the recessed portion 12H and the battery element 40 is shorter than the distance between the surface 12RS of the peripheral portion 12R and the battery element 40.

[0033] The plan view shape of the recess 12H, that is, the shape defined by the outer edge of the recess 12H when the secondary battery is viewed from above, is not particularly limited. Here, the plan view shape of the recess 12H is approximately circular. The inner diameter and depth of the recess 12H are not particularly limited and can be set arbitrarily. However, when the external terminal 20 is attached to the recess 12H via the gasket 30, the depth of the recess 12H is set such that the height position of the surface 20S of the external terminal 20 is lower than the height position of the surface 12RS of the peripheral portion 12R.

[0034] As described above, the outer can 10 is a can in which the storage section 11 and the lid section 12, which were previously physically separated from each other, are welded together; in other words, it is a welded can. As a result, the outer can 10 after welding is a single, physically integrated component, and therefore cannot be separated into the storage section 11 and the lid section 12 afterward.

[0035] The outer can 10, which is a welded can, is a different type of can from a crimped can formed using a crimping process, and is a so-called crimp-pressed can. This is because the element space volume increases inside the outer can 10, thus increasing the energy density per unit volume. This "element space volume" refers to the volume (effective volume) of the internal space of the outer can 10 that can be used to house the battery elements 40.

[0036] Furthermore, the outer can 10, which is a welded can, does not have any overlapping parts, nor does it have any overlapping parts between two or more components.

[0037] "Having no overlapping parts" means that no part of the outer casing 10 is processed (bent) in a way that allows it to overlap with other parts. Furthermore, "Having no overlapping parts between two or more components" means that, after the secondary battery is completed, the outer casing 10 is physically a single component, and therefore cannot be subsequently separated into two or more components. In other words, the state of the outer casing 10 in the completed secondary battery is not one in which two or more components are combined while overlapping each other in a way that would allow for subsequent separation.

[0038] Here, the outer casing 10 is conductive. More specifically, the storage section 11 and the lid section 12 are both conductive. The outer casing 10 is electrically connected to the negative electrode 42 of the battery element 40 via the negative electrode lead 52. Therefore, the outer casing 10 also serves as an external connection terminal for the negative electrode 42. In this embodiment, the secondary battery does not need to have an external connection terminal for the negative electrode 42 separate from the outer casing 10, thus suppressing the reduction in element space volume caused by the presence of an external connection terminal for the negative electrode 42. As a result, the element space volume increases, and therefore the energy density per unit volume increases.

[0039] Specifically, the outer can 10 is a metal can containing one or more types of conductive materials, such as metal materials and alloy materials. The conductive materials that make up the metal can include iron, copper, nickel, stainless steel, iron alloys, copper alloys, and nickel alloys. The type of stainless steel is not particularly limited, but specifically, it includes SUS304 and SUS316. However, the forming material of the storage section 11 and the forming material of the lid section 12 may be the same or different from each other.

[0040] The lid portion 12 is insulated from the external terminal 20, which serves as the external connection terminal for the positive electrode 41, via a gasket 30. This is to prevent contact, i.e., short circuits, between the outer casing 10, which is the external connection terminal for the negative electrode 42, and the external terminal 20, which is the external connection terminal for the positive electrode 41.

[0041] [External terminals] As shown in Figures 1 and 2, the external terminal 20 is a connection terminal used to connect to electronic equipment when the secondary battery is mounted on that electronic equipment. As described above, the external terminal 20 is attached to and supported by the lid 12 of the outer casing 10. The external terminal 20 is located on the opposite side of the bottom M2 when viewed from the lid 12, and overlaps with the through-hole 12K in the height direction Z.

[0042] Here, the external terminal 20 is connected to the positive electrode 41 of the battery element 40 via the core material 13. Therefore, the external terminal 20 also serves as an external connection terminal for the positive electrode 41. As a result, when the secondary battery is used, the secondary battery is connected to the electronic device via the external terminal 20, which serves as an external connection terminal for the positive electrode 41, and the outer casing 10, which serves as an external connection terminal for the negative electrode 42. Thus, the electronic device can operate using the secondary battery as a power source.

[0043] The external terminal 20 is a flat, roughly plate-shaped member that extends along a horizontal plane perpendicular to the height direction Z of the secondary battery, and is located inside the recessed portion 12H via a gasket 30. The external terminal 20 is insulated from the lid portion 12 via the gasket 30. Here, as shown in Figure 2, in the height direction Z, the position of the surface 20S of the external terminal 20 is lower toward the battery element 40 than the position of the surface 12RS of the peripheral portion 12R of the outer casing 10. That is, the external terminal 20 is housed inside the recessed portion 12H such that its upper end surface 20S is recessed toward the battery element 40 than the surface 12RS. In the secondary battery of this embodiment, the height of the secondary battery is reduced compared to the case where the external terminal 20 protrudes above the lid portion 12. As a result, the energy density per unit volume of the secondary battery increases. In addition, it is possible to prevent short circuits between the outer casing 10 and the external terminal 20 via other conductive members. Furthermore, in this embodiment, the peripheral portion of the external terminal 20 overlaps with the bottom portion 12HB of the recessed portion 12H in the height direction Z. By having an overlapping portion between the external terminal 20 and the cover portion 12, the overall mechanical strength of the secondary battery can be improved. Here, the length of the overlapping portion between the external terminal 20 and the peripheral portion along the horizontal plane perpendicular to the height direction Z is preferably greater than the thickness of the external terminal 20 and greater than the thickness of the bottom portion 12HB.

[0044] Furthermore, since the outer diameter of the external terminal 20 is smaller than the inner diameter of the recess 12H, the external terminal 20 is separated from the cover 12 in its surrounding area. As a result, the gasket 30 is placed only in a portion of the area between the external terminal 20 and the cover 12 (recess 12H), and more specifically, it is placed only in places where the external terminal 20 and the cover 12 would come into contact with each other if the gasket 30 were not present. However, it is preferable that the gasket 30 also be provided between the inner wall surface of the wall portion 12HW of the recess 12H and the outer edge 20T of the external terminal 20. It is also preferable that the cover 12 and the external terminal 20 are fixed together by the gasket 30.

[0045] Furthermore, the external terminal 20 contains 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 contains an aluminum layer and a nickel layer in order from the side closest to the gasket 30, and in this clad material, the aluminum layer and the nickel layer are roll-bonded to each other.

[0046] [gasket] As shown in Figure 2, the gasket 30 is an insulating member positioned between the outer can 10 (lid portion 12) and the external terminal 20. The external terminal 20 is fixed to the lid portion 12 via the gasket 30. The gasket 30 has a ring-shaped planar form with a through-hole at a location corresponding to the through-hole 12K. The gasket 30 also contains one or more types of insulating materials, such as insulating polymer compounds, and these insulating materials are resins such as polypropylene and polyethylene.

[0047] The installation range of the gasket 30 is not particularly limited and can be set arbitrarily. Here, the gasket 30 is positioned in the gap between the upper surface of the lid 12 and the lower surface of the external terminal 20 inside the recess 12H. However, as mentioned above, it is preferable that the gasket 30 also be provided between the inner wall surface of the wall 12HW of the recess 12H and the outer edge 20T of the external terminal 20. Furthermore, it is preferable that the lid 12H and the external terminal 20 are fixed together by the gasket 30.

[0048] [Battery element] As shown in Figures 2 and 3, the battery element 40 is a power generation element that carries out a charge-discharge reaction and is housed inside the outer casing 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 electrolyte (not shown) which is a liquid electrolyte.

[0049] The center line PC shown in Figure 2 is a line segment corresponding to the center of the battery element 40 in the direction along the outer diameter D of the secondary battery (casing 10). In other words, the position P of the center line PC corresponds to the position of the center of the battery element 40.

[0050] 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 via a separator 43. Furthermore, the stacked positive electrode 41, negative electrode 42 and separator 43 are wound around a core material 13 located at position P. The positive electrode 41 and the negative electrode 42 are wound around the core material 13 while maintaining a state of facing each other via the separator 43. In other words, a core material 13 extending in the height direction Z exists at the center of the battery element 40.

[0051] Here, the positive electrode 41, the negative electrode 42, and the separator 43 are wound such that the separator 43 is positioned at the outermost circumference and innermost circumference of the wound electrode body, respectively. The number of turns for each of the positive electrode 41, the negative electrode 42, and the separator 43 is not particularly limited and can be set arbitrarily.

[0052] The battery element 40 has a three-dimensional shape that conforms to the three-dimensional shape of the outer casing 10. Specifically, the battery element 40 has a flattened and cylindrical three-dimensional shape. Compared to the case where the battery element 40 has a three-dimensional shape different from the three-dimensional shape of the outer casing 10, when the battery element 40 is housed inside the outer casing 10, so-called dead space, specifically the gap between the outer casing 10 and the battery element 40, is less likely to occur. As a result, the internal space of the outer casing 10 is effectively utilized. Consequently, the volume of the element space increases, and the energy density per unit volume of the secondary battery increases.

[0053] (positive electrode) The positive electrode 41 is the first electrode used to carry out the charge-discharge reaction, and as shown in Figure 3, it includes a positive electrode current collector 41A and a positive electrode active material layer 41B.

[0054] The positive electrode current collector 41A has a pair of surfaces on which the positive electrode active material layer 41B is provided. This positive electrode current collector 41A contains a conductive material such as a metal material, and the metal material is aluminum, for example.

[0055] 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 intercalating and deintercalating lithium. However, the positive electrode active material layer 41B may be provided on only one side of the positive electrode current collector 41A. Furthermore, the positive electrode active material layer 41B may also contain a positive electrode binder and a positive electrode conductive agent. The method for forming the positive electrode active material layer 41B is not particularly limited, but specifically, it may be a coating method.

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

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

[0058] (Negative electrode) The negative electrode 42 is a second electrode used to advance the charge-discharge reaction, and as shown in Figure 3, it includes a negative electrode current collector 42A and a negative electrode active material layer 42B.

[0059] The negative electrode current collector 42A has a pair of surfaces on which the negative electrode active material layer 42B is provided. This negative electrode current collector 42A contains a conductive material such as a metal material, and the metal material is such as copper.

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

[0061] The negative electrode active material contains either or both carbon materials and metallic materials because they allow for high energy density. Carbon materials include easily graphitizable carbon, poorly graphitizable carbon, and graphite (natural graphite and artificial graphite). Metallic materials are materials that contain one or more metallic elements and metalloid elements capable of forming alloys with lithium, such as silicon and tin, either or both. However, metallic materials may be elements, alloys, compounds, mixtures of two or more of these, or materials containing two or more phases. Specific examples of metallic materials are TiSi2 and SiO2. x (0 <x≦2、または0.2<x<1.4)などである。

[0062] 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 both above and below the positive electrode 41. This is to prevent lithium released from the positive electrode 41 from being deposited. This "height" is the dimension corresponding to the height H of the secondary battery described above, that is, the vertical dimension in Figures 1 and 2, respectively. The definition of height explained here will remain the same throughout.

[0063] (Separator) As shown in Figures 2 and 3, the separator 43 is an insulating porous membrane placed between the positive electrode 41 and the negative electrode 42. The separator 43 allows lithium ions to pass through while preventing a short circuit between the positive electrode 41 and the negative electrode 42. The separator 43 contains a polymer compound such as polyethylene.

[0064] Here, the height of the separator 43 is greater than the height of the negative electrode 42. That is, the separator 43 should protrude both above and below the negative electrode 42.

[0065] (electrolyte) The electrolyte is impregnated into the positive electrode 41, the negative electrode 42, and the separator 43, and contains a solvent and an electrolyte salt. The solvent contains one or more non-aqueous solvents (organic solvents) such as carbonate ester compounds, carboxylic acid ester compounds, and lactone compounds, and the electrolyte containing such a non-aqueous solvent is a so-called non-aqueous electrolyte. The electrolyte salt contains one or more light metal salts such as lithium salts.

[0066] Furthermore, an insulating film 62 is placed between the lid 12 and the battery element 40. This insulates the lid 12 and the battery element 40 from each other via the insulating film 62, preventing a short circuit between the lid 12 and the positive electrode 41 of the battery element 40.

[0067] [Negative lead] The negative electrode lead 52 is housed inside the outer casing 10, as shown in Figure 2. The negative electrode lead 52 is electrically connected to both the negative electrode 42 and the outer casing 10 (storage section 11). Therefore, the storage section 11 (bottom M2) is electrically connected to the negative electrode 42 via the negative electrode lead 52. Here, the secondary battery has one negative electrode lead 52. However, the secondary battery may have two or more negative electrode leads 52.

[0068] The negative electrode lead 52 is connected to the lower end of the negative electrode 42, and 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 housing 11. The method of connecting the negative electrode lead 52 is not particularly limited, but specifically, it is one or more welding methods such as resistance welding and laser welding.

[0069] Details regarding the forming material of the negative electrode lead 52 are the same as details regarding the forming material of the negative electrode current collector 42A. However, the forming material of the negative electrode lead 52 and the forming material of the negative electrode current collector 42A may be the same or different.

[0070] The connection position of the negative electrode lead 52 to the negative electrode 42 is not particularly limited and can be set arbitrarily. Here, the negative electrode lead 52 is connected to the outermost part of the negative electrode 42 that constitutes the wound electrode body.

[0071] The negative electrode lead 52 is provided separately from the negative electrode current collector 42A. However, since the negative electrode lead 52 is physically continuous with the negative electrode current collector 42A, it may be integrated with the negative electrode current collector 42A.

[0072] [Insulating film] As shown in Figure 2, the insulating film 62 is a first insulating member positioned between the lid 12 and the battery element 40 in the height direction Z. Here, the insulating film 62 has a ring-shaped planar form with an opening 62K at a location corresponding to the through-hole 12K in the height direction Z. The opening 62K has an inner diameter of φ62K. The inner diameters of the through-hole 12K (φ12K) and the opening 62K (φ62K) are larger than the outer diameter (φ13) of the core material 13, which will be described later.

[0073] In this case, the insulating film 62 may be bonded to the lid portion 12 via an adhesive layer.

[0074] Furthermore, the insulating film 62 may contain one or more insulating materials, such as insulating polymer compounds. The insulating materials contained in the insulating film 62 are polyimide, etc.

[0075] As shown in Figure 2, the insulating film 64 is a second insulating member provided between the bottom M2 and the battery element 40 in the height direction Z. The insulating film 64 electrically insulates the core material 13 from the negative electrode lead 52 and the bottom M2.

[0076] Details regarding the material for forming the insulating film 64 are the same as those regarding the material for forming the insulating film 62. However, the material for forming the insulating film 64 and the material for forming the insulating film 62 may be the same or different from each other.

[0077] [Core material] The core material 13 is a member having a cylindrical or cylindrical appearance, for example, with the center line PC as its central axis. The core material 13 has an outer diameter φ13K. The outer diameter φ13 is substantially equal to the inner diameter of the battery element 40. The core material 13 is inserted through the through-hole 12K and the opening 62K of the insulating film 62 and fixed to the external terminal 20. In the secondary battery of this embodiment, the core material 13 is conductive and is electrically connected to the external terminal 20 and the positive electrode 41, respectively. For example, the innermost end of the positive electrode 41 in the battery element 40 is electrically connected to the core material 13. Therefore, the external terminal 20 and the positive electrode 41 are electrically connected via the core material 13. As mentioned above, since an insulating film 64 is provided between the core material 13 and the bottom M2 and the negative electrode lead 52, the core material 13 is physically separated from the bottom M2 and the negative electrode lead 52 and is electrically insulated from them.

[0078] [others] Furthermore, this secondary battery may also include one or more other components.

[0079] Specifically, the secondary battery is equipped with a safety valve mechanism. This safety valve mechanism disconnects the electrical connection between the outer casing 10 and the battery element 40 when the internal pressure of the outer casing 10 reaches a certain level. The causes of the internal pressure of the outer casing 10 reaching a certain level include a short circuit occurring inside the secondary battery and the secondary battery being heated from the outside. The location of the safety valve mechanism is not particularly limited, but it is preferable that the safety valve mechanism be provided on either the bottom M1 or M2, and more preferably on the bottom M2 where the external terminal 20 is not attached.

[0080] Furthermore, the secondary battery may have an insulator other than the insulating films 62 and 64 between the outer casing 10 and the battery element 40. This insulator includes one or more types of insulating films and insulating sheets, etc., and prevents short circuits between the outer casing 10 and the battery element 40. The installation range of the insulator is not particularly limited and can be set arbitrarily.

[0081] The outer container 10 is provided with an opening valve. This opening valve ruptures when the internal pressure of the outer container 10 reaches a certain level, thereby releasing the internal pressure. The location of the opening valve is not particularly limited, but, similar to the location of the safety valve mechanism described above, either the bottom M1 or M2 is preferred, with the bottom M2 being particularly preferred.

[0082] <1-2. Operation> During charging of the secondary battery, lithium is released from the positive electrode 41 in the battery element 40, and this lithium is absorbed into the negative electrode 42 via the electrolyte. Conversely, during discharging of the secondary battery, lithium is released from the negative electrode 42 in the battery element 40, and this lithium is absorbed into the positive electrode 41 via the electrolyte. During these charging and discharging processes, lithium is absorbed and released in an ionic state.

[0083] <1-3. Manufacturing method> Figure 4 shows a perspective view of the outer casing 10 used in the manufacturing process of secondary batteries, and corresponds to Figure 1.

[0084] Figure 4 shows the state in which the lid portion 12 is separated from the storage portion 11, before the lid portion 12 is welded to the storage portion 11.

[0085] In the following explanation, we will refer to Figures 1 to 3, which have already been explained, as well as Figure 4, from time to time.

[0086] Here, in order to form the outer container 10, a storage section 11 and a lid section 12, which are physically separated from each other, are prepared as shown in Figure 4. The storage section 11 is a roughly container-shaped member in which the bottom section M2 and the side wall section M3 are integrated with each other, and has an opening 11K. The lid section 12 is a roughly plate-shaped member corresponding to the bottom section M1, and the external terminals 20 are pre-attached to the recessed section 12H provided in the lid section 12 via a gasket 30.

[0087] However, the storage section 11 may be formed by preparing a bottom section M2 and a side wall section M3 that are physically separated from each other, and welding the side wall section M3 to the bottom section M2.

[0088] [Fabrication of the positive electrode] First, a positive electrode mixture is prepared by mixing positive electrode active material, positive electrode binder, and positive electrode conductive agent. Next, a paste-like positive electrode mixture slurry is prepared by adding the prepared positive electrode mixture to an organic solvent. Subsequently, the positive electrode mixture slurry is applied to both sides of the positive electrode current collector 41A to form a positive electrode active material layer 41B. Finally, the positive electrode active material layer 41B is compressed and molded using a roll press or the like. In this case, the positive electrode active material layer 41B may be heated, or the compression molding may be repeated multiple times. This produces the positive electrode 41.

[0089] [Fabrication of the negative electrode] The negative electrode 42 is manufactured using the same procedure as that used for manufacturing the positive electrode 41. Specifically, a negative electrode mixture, which consists of a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent, is added to an organic solvent to prepare a paste-like negative electrode mixture slurry. Then, the negative electrode mixture slurry is applied to both sides of the negative electrode current collector 42A to form a negative electrode active material layer 42B. After this, the negative electrode active material layer 42B is compressed and molded using a roll press or the like. This completes the manufacturing of the negative electrode 42.

[0090] [Preparation of electrolyte solution] The electrolyte salt is added to the solvent. This disperses or dissolves the electrolyte salt in the solvent, thus preparing the electrolyte solution.

[0091] [Assembly of rechargeable batteries] First, the first end of the negative electrode lead 52 is connected to the negative electrode 42 (negative electrode current collector 42A) using a welding method such as resistance welding. Next, the core material 13 is attached to the center of the lid portion 12 to which the external terminals 20 are attached via a gasket 30. Furthermore, the insulating film 62 is superimposed on the lid portion 12 so as to pass the core material 13 through the opening 62K. At this time, the insulating film 62 may be fixed to the bottom portion 12HB of the lid portion 12 by adhesive or the like.

[0092] Next, the positive electrode 41 and the negative electrode 42 are stacked with a separator 43 in between. Then, as shown in Figure 5, the stacked body 40S, including the positive electrode 41, the negative electrode 42, and the separator 43, is wound around the core material 13 to create a wound body 40Z (see Figure 4). The wound body 40Z has the same configuration as the battery element 40, except that the positive electrode 41, the negative electrode 42, and the separator 43 are not impregnated with electrolyte. When creating the wound body 40Z, the end of the positive electrode 41 is connected to the core material 13 by welding or the like, and then the stacked body 40S, including the positive electrode 41, the negative electrode 42, and the separator 43, is wound around the core material 13. Note that the negative electrode lead 52 is not shown in Figure 4. Also, although the external terminal 20 and the core material 13 are depicted as being spaced apart in Figure 4, in reality, the external terminal 20 and the core material 13 are connected.

[0093] Next, electrolyte is injected into the storage section 11 through the opening 11K. After that, the second end of the negative electrode lead 52 is connected to the bottom M2 of the storage section 11 by a welding method such as resistance welding, and then the lid 12 and the storage section 11 are superimposed so that the wound body 40Z is housed inside the storage section 11 through the opening 11K. At this time, the lid 12 is made to close the opening 11K. In addition, an insulating film 64 is placed between the bottom M2 and the negative electrode lead 52 and the battery element 40. As a result, the electrolyte is impregnated into the wound body 40Z, which includes the positive electrode 41, the negative electrode 42 and the separator 43, and the battery element 40, which is a wound electrode body, is manufactured. Note that the electrolyte may be impregnated into the wound body 40Z in advance before housing it in the storage section 11.

[0094] Finally, the lid portion 12 is welded to the storage portion 11 using a welding method such as laser welding. This forms the outer can 10, and the battery elements 40 and other components are housed inside the outer can 10, completing the assembly of the secondary battery.

[0095] [Stabilization of secondary batteries] The assembled secondary battery is then charged and discharged. Various conditions, such as ambient temperature, number of charge / discharge cycles, and charge / discharge conditions, can be set arbitrarily. This causes a coating to form on the surface of the negative electrode 42, etc., thereby electrochemically stabilizing the state of the secondary battery. Thus, the secondary battery is completed.

[0096] <1-4. Mechanism and Effects> Thus, in this embodiment of the secondary battery, the laminate constituting the battery element 40 is wound around the core material 13 fixed to the external terminal 20. As a result, the winding state of the battery element 40 is stabilized, and loosening or misalignment of the winding of the battery element 40 is less likely to occur. Therefore, this secondary battery can achieve high reliability. Furthermore, the volume ratio of the battery element 40 occupying the internal space of the outer casing 10 is improved.

[0097] Furthermore, in the secondary battery of this embodiment, the core material 13 is conductive, and the core material 13 is electrically connected to the external terminal 20 and the positive electrode 41, respectively, while being insulated from the bottom M2 which is conductive to the negative electrode 42. Therefore, the core material 13 can be used as a positive electrode lead connecting the external terminal 20 and the positive electrode 41, eliminating the need to provide a separate positive electrode lead. As a result, the volume ratio of the battery element 40 occupying the internal space of the outer casing 10 is improved. Thus, this secondary battery is suitable for high capacity applications. In addition, the process of connecting the positive electrode lead to the battery element 40 and the external terminal 20 can be omitted, improving ease of manufacturing. Moreover, in this secondary battery, the electrical connection between the battery element 40 and the external terminal 20 can be maintained more stably compared to the case where a positive electrode lead is used.

[0098] Furthermore, in the secondary battery of this embodiment, the outer edge of the lid portion 12, which includes a through-hole 12K through which the core material 13 fixed to the external terminal 20 is inserted, is welded to the upper end of the side wall portion M3, which is the end opposite to the bottom portion M2. As a result, the battery element 40 can be housed in the housing portion 11 with the battery element 40 wrapped around the core material 13, that is, the external terminal 20, core material 13, battery element 40, and lid portion 12 can be integrated together, and the outer edge of the lid portion 12 can be easily welded to the opening 11K of the housing portion 11, thereby sealing the battery element 40 inside the outer casing 10.

[0099] Furthermore, the recessed portion 12H includes a through-hole 12K that penetrates in the height direction Z, and a bottom portion 12HB that surrounds the through-hole 12K along a horizontal plane perpendicular to the height direction Z, with a portion of the external terminal 20 overlapping with the bottom portion 12HB of the recessed portion 12H in the height direction Z. In this way, the secondary battery of this embodiment can improve the overall mechanical strength of the secondary battery by having an overlapping portion between the external terminal 20 and the cover portion 12. In particular, the length of the overlapping portion between the external terminal 20 and the bottom portion 12HB along the horizontal plane perpendicular to the height direction Z is greater than the thickness of the external terminal 20 and greater than the thickness of the bottom portion 12HB. Therefore, the mechanical strength is further improved.

[0100] Furthermore, in this embodiment of the secondary battery, the lid portion 12 and the external terminal 20 are fixed together by a gasket 30 made of insulating resin. This increases the mechanical strength against vibration. It also prevents short circuits caused by foreign matter entering the gap between the recessed portion 12 and the external terminal 20.

[0101] Furthermore, in the secondary battery of this embodiment, a recessed portion 12H is provided in the lid portion 12, and the external terminals 20 are positioned in the recessed portion 12H. This makes it possible to reduce the height dimension of the secondary battery while ensuring sufficient battery capacity.

[0102] Furthermore, if the secondary battery is flat and columnar, that is, if the secondary battery is a coin-type or button-type secondary battery, the positive electrode lead 51 is less likely to be damaged even in small secondary batteries, which have significant size constraints, thus providing a greater advantage in terms of physical durability.

[0103] Furthermore, if the secondary battery is a lithium-ion secondary battery, sufficient battery capacity can be stably obtained by utilizing the intercalation and deintercalation of lithium.

[0104] <2. Secondary battery of the second embodiment> Next, a secondary battery as a second embodiment of the present disclosure will be described with reference to Figure 6. Figure 6 shows the cross-sectional configuration of the secondary battery as the second embodiment and corresponds to Figure 2, which represents the secondary battery of the first embodiment.

[0105] <2-1. Structure> In the secondary battery of the first embodiment described above, the core material 13 is fixed to the external terminal 20 and spaced apart from the bottom M2 of the housing 11. In contrast, in the secondary battery of this embodiment shown in Figure 6, the core material 13 is fixed to the bottom M2 and spaced apart from the external terminal 20. Therefore, in the secondary battery of Figure 6, the core material 13 is not inserted through the through-hole 12K and the opening 62K of the insulating film 62, but is inserted through the opening 64K provided in the insulating film 64. The opening 64K has an inner diameter of φ64K. The inner diameter of the opening 64K is larger than the outer diameter φ13 of the core material 13. Also, in the secondary battery of this embodiment shown in Figure 6, instead of having a negative electrode lead 52, there is a positive electrode lead 51. In the secondary battery of this embodiment, the core material 13 is conductive and is electrically connected to the bottom M2 and the negative electrode 42, respectively. For example, the innermost end of the negative electrode 42 in the battery element 40 is electrically connected to the core material 13. Therefore, the bottom M2 and the negative electrode 42 are electrically connected via the core material 13. The external terminal 20 and the positive electrode 41 are electrically connected to each other by the positive electrode lead 51. Furthermore, in the secondary battery of this embodiment, the outer casing 10 has a housing section 14 in which the bottom M1 and the side wall M3 are integrated, and a lid section 15 having an outer edge welded to the lower end of the side wall M3, instead of a housing section 11 and a lid section 12. Except for the points mentioned above, the secondary battery of this embodiment has substantially the same configuration as the secondary battery of the first embodiment.

[0106] <2-2. Operation> The operation of the secondary battery in this embodiment is the same as that of the secondary battery in the first embodiment described above.

[0107] <2-3. Manufacturing method> First, to form the outer can 10, a storage section 14 and a lid section 15, which are physically separated from each other, are prepared. The storage section 14 is a roughly container-shaped member in which the bottom section M1 and the side wall section M3 are integrated with each other, and has an opening 14K at the bottom. The lid section 15 is a roughly plate-shaped member corresponding to the bottom section M2, and an external terminal 20 is pre-attached to the recessed section 12H provided in the bottom section M1 via a gasket 30.

[0108] Next, the preparation of the positive electrode 41, the negative electrode 42, and the electrolyte can all be carried out in the same manner as the manufacturing method of the secondary battery in the first embodiment described above.

[0109] Next, the secondary battery is assembled. First, the first end of the positive electrode lead 51 is connected to the positive electrode 41 (positive electrode current collector 41A) using a welding method such as resistance welding. Next, the core material 13 is attached to the center of the lid 15. Furthermore, the insulating film 64 is placed over the lid 15 so that the core material 13 is inserted through the opening 64K. At this time, the insulating film 62 may also be fixed to the lid 15 by adhesive or other means.

[0110] Next, the positive electrode 41 and the negative electrode 42 are stacked with a separator 43 in between. Then, as shown in Figure 5, the stacked body 40S, including the positive electrode 41, the negative electrode 42, and the separator 43, is wound around the core material 13 to create a wound body 40Z (see Figure 4). When creating the wound body 40Z, the end of the negative electrode 42 is connected to the core material 13 by welding or the like, and then the stacked body 40S, including the positive electrode 41, the negative electrode 42, and the separator 43, is wound around the core material 13.

[0111] Next, electrolyte is injected into the storage section 14 through the opening 14K. After that, the second end of the positive electrode lead 51 is connected to the bottom M1 of the storage section 14 by a welding method such as resistance welding, and then the lid 15 and the storage section 14 are superimposed so that the wound body 40Z is housed inside the storage section 14 through the opening 14K. At this time, the lid 15 is made to close the opening 14K. In addition, an insulating film 62 is placed between the bottom M1 and the positive electrode lead 51 and the battery element 40. As a result, the electrolyte is impregnated into the wound body 40Z, which includes the positive electrode 41, negative electrode 42 and separator 43, and the battery element 40, which is a wound electrode body, is manufactured. Note that the electrolyte may be impregnated into the wound body 40Z in advance before housing it in the storage section 14.

[0112] Finally, the lid portion 15 is welded to the storage portion 14 using a welding method such as laser welding. This forms the outer casing 10, and the battery elements 40 and the like are housed inside the outer casing 10, completing the assembly of the secondary battery. After this, charging and discharging are performed in the same manner as the secondary battery of the first embodiment described above to stabilize it electrochemically.

[0113] <2-4. Action and Effects> As described above, in this embodiment of the secondary battery, the laminate constituting the battery element 40 is wound around the core material 13 fixed to the lid portion 15. Therefore, the winding state of the battery element 40 is stabilized, and loosening or collapse of the winding of the battery element 40 is less likely to occur. Thus, this secondary battery can achieve high reliability.

[0114] Furthermore, in the secondary battery of this embodiment, the core material 13 is conductive, and the core material 13 is electrically connected to the outer casing 10 (lid portion 15) and the negative electrode 42, respectively, while being insulated from the external terminal 20 which is conductive to the positive electrode 41. Therefore, the core material 13 can be used as a negative electrode lead connecting the outer casing 10 and the negative electrode 42, eliminating the need to provide a separate negative electrode lead. As a result, the volume ratio of the battery element 40 occupying the internal space of the outer casing 10 is improved. Thus, this secondary battery is suitable for high capacity applications. In addition, the process of connecting the negative electrode lead to the battery element 40 and the outer casing 10 can be omitted, improving ease of manufacturing. Moreover, in this secondary battery, the electrical connection between the battery element 40 and the outer casing 10 can be maintained more stably compared to the case where a negative electrode lead is used.

[0115] Furthermore, in the secondary battery of this embodiment, the outer edge of the lid portion 15 to which the core material 13 is fixed is welded to the lower end of the side wall portion M3, which is the end opposite to the bottom portion M1. As a result, the battery element 40 can be housed in the housing portion 14 with the battery element 40 wrapped around the core material 13, that is, the core material 13, the battery element 40, and the lid portion 15 can be housed as an integrated unit, and the outer edge of the lid portion 15 can be easily welded to the opening 14K of the housing portion 14, thereby sealing the battery element 40 inside the outer casing 10.

[0116] <3. Variant> The configuration of the secondary battery described above can be modified as needed, as explained below.

[0117] [Example 1] Figure 7 shows a cross-sectional configuration of a secondary battery as a modified example 1 of the first embodiment described above. In the secondary battery of Figure 2, the lid portion 12 has a recessed portion 12H. However, in the secondary battery of this disclosure, as shown in the modified example 1 of Figure 7, the lid portion 12 does not have to have a recessed portion 12H. Similarly, although the bottom portion M1 of the secondary battery of the second embodiment shown in Figure 6 has a recessed portion 12H, in this disclosure, the bottom portion M1 may not have a recessed portion 12H.

[0118] <4. Examples> Examples of the present disclosure will be described below.

[0119] (Examples 1-1 to 1-3) After fabricating the secondary battery (lithium-ion secondary battery) shown in Figure 6, the volume loss ratio of the secondary battery was evaluated. The results are shown in Table 1.

[0120] [Table 1]

[0121] The "Outer Diameter D [mm]" and "Height H [mm]" shown in Table 1 are the outer diameter D and height H of the outer casing 10, as illustrated in Figure 6. The "Outer Diameter D40 [mm]" and "Height H40 [mm]" shown in Table 1 are the outer diameter D40 and height H40 of the battery element 40, as illustrated in Figure 6. Furthermore, "D / H [-]" in Table 1 is the ratio of the outer diameter D to the height H. Also, the "Winding Misalignment Amount h [mm]" in Table 1 is the difference between the height H40 of the innermost part of the wound battery element 40 and the height H40 of the outermost part of the battery element 40, as shown, for example, in the explanatory diagram in Figure 8. Furthermore, "h / H40 [%]" in Table 1 is the ratio of the winding misalignment amount h to the height H40.

[0122] Furthermore, the "Volume Loss Ratio LS[%]" in Table 1 is a value calculated using the following formula (1). LS[%]=(H+h) / H-1 ……(1)

[0123] (Comparative Examples 1-1 to 1-3) Except for the absence of the core material 13 and the provision of a negative electrode lead for connecting the bottom M2 and the negative electrode 42, a secondary battery with the same configuration as the secondary battery shown in Figure 6 was fabricated in the same manner as in Examples 1-1 to 1-3, and the volume loss ratio of the secondary battery was evaluated. The results are shown in Table 1.

[0124] As shown in Table 1, in Examples 1-1 to 1-3, the winding misalignment amount h [mm] was reduced compared to Comparative Examples 1-1 to 1-3, and the volume loss ratio LS [%] was kept low. Therefore, in the secondary battery of this disclosure, since a core material 13 is provided, winding misalignment of the battery element 40 wound around the core material 13 is less likely to occur, and as a result, it was confirmed that the volume ratio of the battery element 40 occupying the internal space of the outer casing 10 is improved.

[0125] (Examples 2-1 to 2-3) A secondary battery (lithium-ion secondary battery) was fabricated as shown in Figure 6. Examples 2-1 to 2-3 differ from Examples 1-1 to 1-3 in that the outer diameter D of the outer casing 10 was set to 12.0 mm, the outer diameter D40 of the battery element 40 was set to 11.6 mm, the positive electrode length was set to 450 mm, and the negative electrode length was set to 500 mm. The volume loss ratio of each fabricated secondary battery was evaluated in the same manner as in Examples 1-1 to 1-3. The results are shown in Table 2.

[0126] [Table 2]

[0127] (Comparative Examples 2-1 to 2-3) Except for the absence of a core material 13 and the provision of a negative electrode lead for connecting the bottom M2 and the negative electrode 42, a secondary battery with the same configuration as the secondary battery shown in Figure 6 was fabricated in the same manner as in Examples 2-1 to 2-3, and the volume loss ratio of the secondary battery was evaluated. The results are shown in Table 2.

[0128] As shown in Table 2, in Examples 2-1 to 2-3, the winding misalignment amount h [mm] was reduced compared to Comparative Examples 2-1 to 2-3, and the volume loss ratio LS [%] was kept low. Therefore, in the secondary battery of this disclosure, since a core material 13 is provided, winding misalignment of the battery element 40 wound around the core material 13 is less likely to occur, and as a result, it was confirmed that the volume ratio of the battery element 40 occupying the internal space of the outer casing 10 is improved.

[0129] (Examples 3-1 to 3-3) A secondary battery (lithium-ion secondary battery) was fabricated as shown in Figure 6. Examples 3-1 to 3-3 differ from Examples 1-1 to 1-3 in that the outer diameter D of the outer casing 10 was set to 16.0 mm, the outer diameter D40 of the battery element 40 was set to 15.6 mm, the positive electrode length was set to 820 mm, and the negative electrode length was set to 890 mm. The volume loss ratio of each fabricated secondary battery was evaluated in the same manner as in Examples 1-1 to 1-3. The results are shown in Table 3.

[0130] [Table 3]

[0131] (Comparative Examples 3-1 to 3-3) Except for the absence of a core material 13 and the provision of a negative electrode lead for connecting the bottom M2 and the negative electrode 42, a secondary battery with the same configuration as the secondary battery shown in Figure 6 was fabricated in the same manner as in Examples 3-1 to 3-3, and the volume loss ratio of the secondary battery was evaluated. The results are shown in Table 3.

[0132] As shown in Table 3, in Examples 3-1 to 3-3, the winding misalignment amount h [mm] was reduced compared to Comparative Examples 3-1 to 3-3, and the volume loss ratio LS [%] was kept low. Therefore, in the secondary battery of this disclosure, since a core material 13 is provided, winding misalignment of the battery element 40 wound around the core material 13 is less likely to occur, and as a result, it was confirmed that the volume ratio of the battery element 40 occupying the internal space of the outer casing 10 is improved.

[0133] Although the present technology has been described above with reference to one embodiment and one example, the configuration of the present technology is not limited to the configuration described in the one embodiment and one example, and can be modified in various ways.

[0134] Specifically, the explanation described the case where the outer can is a welded can (crimped can), but the structure of the outer can is not particularly limited, and a crimped can is also acceptable. In this crimped can, the storage section and the lid section, which are separate from each other, are crimped together via a gasket.

[0135] Furthermore, while we have described the case where the electrode reactant is lithium, the electrode reactant is not particularly limited. Therefore, as mentioned above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0136] The effects described herein are illustrative only, and the effects of this disclosure are not limited to those described herein. Therefore, other effects may be obtained with respect to this disclosure.

[0137] Furthermore, this disclosure may take the following forms: <1> A core material extending in the first direction, A battery element comprising a laminate including a first electrode and a second electrode wound around the core material, An exterior member for housing the battery element, having a lid portion with a through-hole that penetrates in the first direction, a bottom portion facing the lid portion with the battery element in the first direction, and a side wall portion that connects the lid portion and the bottom portion and surrounds the battery element, An external terminal provided on the opposite side of the bottom when viewed from the lid, and in a position that overlaps with the through-hole in the first direction. Equipped with, The core material is fixed to the external terminal, The outer edge of the lid is welded to the end of the side wall opposite to the bottom. Secondary battery. <2> A core material extending in the first direction, A battery element comprising a laminate including a first electrode and a second electrode wound around the core material, An exterior member for housing the battery element, having a lid portion with a through-hole that penetrates in the first direction, a bottom portion facing the lid portion with the battery element in the first direction, and a side wall portion that connects the lid portion and the bottom portion and surrounds the battery element, An external terminal provided on the opposite side of the bottom when viewed from the lid, and in a position that overlaps with the through-hole in the first direction. Equipped with, The core material is fixed to the bottom, The outer edge of the bottom portion is welded to the end of the side wall portion opposite to the lid portion. Secondary battery. <3> The core material is conductive, electrically connected to the external terminal and the first electrode, and insulated from the bottom. The bottom portion is electrically connected to the second electrode. <1> The rechargeable battery described. <4> The core material is conductive, electrically connected to the bottom and the second electrode, and insulated from the external terminals. The external terminal is electrically connected to the first electrode. <2> The rechargeable battery described. <5> The bottom portion and the side wall portion are integrated to form a storage compartment. <1> from <4> A rechargeable battery as described in one of the following. <6> The lid portion and the external terminals are further provided with an insulator. <1> from <5> A rechargeable battery as described in one of the following. <7> The system further comprises a first insulating member provided between the lid and the battery element, The first insulating member has a first opening provided in the first direction at a position corresponding to the through-hole, The core material is inserted through the through-hole and the first opening. <1> , <3> , <5> or <6> The secondary battery described above. <8> The system further comprises a second insulating member provided between the bottom portion and the battery element, The second insulating member has a second opening provided in the first direction at a position corresponding to the through-hole, The core material is inserted through the second opening. <2> , <4> , <5> or <6> The secondary battery described above. <9> The outer diameter in the second direction perpendicular to the first direction of the exterior member is greater than the height of the exterior member in the first direction. <1> from <8> A rechargeable battery as described in one of the following. <10> The lid portion of the exterior member has a recessed portion that is recessed toward the battery element along the first direction, The aforementioned through-hole is provided in the aforementioned recess. <1> from <9> A rechargeable battery as described in one of the following. [Explanation of Symbols]

[0138] 10...Outer can, M1, M2...Bottom, M3...Side wall, 11, 14...Storage section, 11K, 14K...Opening, 12, 15...Lid, 12H...Recess, 12K...Through-hole, 12R...Peripheral section, 13...Core material, 20...External terminal, 30...Gasket, 40...Battery element, 41...Positive electrode, 41A...Positive electrode current collector, 41B...Positive electrode active material layer, 42...Negative electrode, 42A...Negative electrode current collector, 42B...Negative electrode active material layer, 43...Separator, 51...Positive electrode lead, 52...Negative electrode lead, 62, 64...Insulating film, PC...Center line.

Claims

1. A core material extending in the first direction, A battery element comprising a laminate including a first electrode and a second electrode wound around the core material, An exterior member for housing the battery element, having a lid portion with a through-hole that penetrates in the first direction, a bottom portion facing the lid portion with the battery element in the first direction, and a side wall portion that connects the lid portion and the bottom portion and surrounds the battery element, An external terminal is provided in a position opposite to the bottom when viewed from the lid and overlapping with the through-hole in the first direction, A first insulating member provided between the lid and the battery element Equipped with, The core material is fixed to the external terminal, The outer edge of the lid is welded to the end of the side wall opposite to the bottom, The first insulating member has a first opening provided in the first direction at a position corresponding to the through-hole, The core material is inserted through the through-hole and the first opening. Secondary battery.

2. A core material extending in the first direction, A battery element comprising a laminate including a first electrode and a second electrode wound around the core material, An exterior member for housing the battery element, having a lid portion with a through-hole that penetrates in the first direction, a bottom portion facing the lid portion with the battery element in the first direction, and a side wall portion that connects the lid portion and the bottom portion and surrounds the battery element, An external terminal provided on the opposite side of the bottom when viewed from the lid, and in a position that overlaps with the through-hole in the first direction. Equipped with, The core material is fixed to the bottom, The outer edge of the bottom portion is welded to the end of the side wall portion opposite to the lid portion. The core material is conductive, electrically connected to the bottom and the second electrode, and insulated from the external terminals. The external terminal is electrically connected to the first electrode. Secondary battery.

3. A core material extending in a first direction, A battery element comprising a laminate including a first electrode and a second electrode wound around the core material, An exterior member for housing the battery element, having a lid portion with a through-hole that penetrates in the first direction, a bottom portion facing the lid portion with the battery element in the first direction, and a side wall portion that connects the lid portion and the bottom portion and surrounds the battery element, An external terminal is provided in a position opposite to the bottom when viewed from the lid and overlapping with the through-hole in the first direction, A second insulating member is provided between the bottom portion and the battery element. Equipped with, The core material is fixed to the bottom, The outer edge of the bottom portion is welded to the end of the side wall portion opposite to the lid portion. The second insulating member has a second opening provided in the first direction at a position corresponding to the through-hole, The core material is inserted through the second opening. Secondary battery.

4. The core material is conductive, electrically connected to the external terminal and the first electrode, and insulated from the bottom. The bottom portion is electrically connected to the second electrode. The secondary battery according to claim 1.

5. The bottom portion and the side wall portion are integrated to form a storage compartment. A secondary battery according to any one of claims 1 to 3.

6. The lid portion and the external terminals are further provided with an insulator. A secondary battery according to any one of claims 1 to 3.

7. The outer diameter in the second direction perpendicular to the first direction of the exterior member is greater than the height of the exterior member in the first direction. A secondary battery according to any one of claims 1 to 3.

8. The lid portion of the exterior member has a recessed portion that is recessed toward the battery element along the first direction, The aforementioned through-hole is provided in the aforementioned recess. A secondary battery according to any one of claims 1 to 3.

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