Secondary battery, method for producing the same and battery pack

Abstract

A secondary battery with higher reliability is provided. The secondary battery includes an electrode bobbin, a first electrode current collecting plate, and a second electrode current collecting plate. The electrode bobbin includes a stacked body having a first electrode and a second electrode stacked with a separator interposed therebetween. The stacked body is wound around a central axis extending in a first direction. The electrode bobbin has a first end surface and a second end surface opposite to each other in the first direction. The first electrode current collecting plate faces the first end surface of the electrode bobbin and is connected to the first electrode. The second electrode current collecting plate faces the second end surface of the electrode bobbin and is connected to the second electrode.The first electrode includes a first electrode covering portion in which a first electrode current collector is covered with a first electrode active material layer, and a first electrode exposing portion in which the first electrode current collector is exposed without being covered by the first electrode active material layer. The first electrode exposing portion includes a plurality of first edge portions adjacent to each other in the radial direction of the electrode coil body. The plurality of first edge portions are bent toward the central axis and overlap each other to form the first end surface. The plurality of first edge portions each have an end having a first curved surface.

Description

Technical area

[0001] The disclosure relates to a secondary battery, a method for manufacturing the secondary battery, and a battery pack comprising the secondary battery. Technical background

[0002] Various types of electronic devices, including mobile phones, are widely used. This widespread use has promoted the development of secondary batteries as energy sources, which are more compact and lightweight, and enable higher energy density. The secondary battery includes a positive electrode, a negative electrode, and an electrolyte housed within an outer casing member. The configuration of the secondary battery has been studied in various ways (see, for example, PTL 1).

[0003] PTL 1 proposes a secondary battery using a so-called tabless structure to reduce the internal resistance and enable charging and discharging with a relatively large current. Citation listPatent literature

[0004] PTL 1: International Publication No. WO 2021 / 020237 Brief description of the invention

[0005] The performance of a secondary battery has been studied in various ways. However, there is still room for improvement in secondary battery performance.

[0006] Therefore, a secondary battery with higher performance is sought.

[0007] A secondary battery according to an embodiment of the disclosure includes an electrode coil, a first electrode current collecting plate, and a second electrode current collecting plate. The electrode coil includes a stacked body including a first electrode and a second electrode stacked with a separator interposed therebetween. The stacked body is wound around a central axis extending in a first direction. The electrode coil has a first end face and a second end face opposite to each other in the first direction. The first electrode current collecting plate faces the first end face of the electrode coil and is connected to the first electrode. The second electrode current collecting plate faces the second end face of the electrode coil and is connected to the second electrode.The first electrode includes a first electrode covering portion in which a first electrode current collector is covered with a first electrode active material layer, and a first electrode exposing portion in which the first electrode current collector is exposed without being covered by the first electrode active material layer. The first electrode exposing portion includes a plurality of first edge portions adjacent to each other in the radial direction of the electrode coil body. The plurality of first edge portions are bent toward the central axis and overlap each other to form the first end surface. The plurality of first edge portions each have an end having a first curved surface.

[0008] The secondary battery according to an embodiment of the disclosure improves the tight contact between the plurality of first edge portions of the first electrode current collector and the first electrode current collecting plate to achieve a favorable connection state without causing deformation of the electrode coil body. This reduces the internal resistance and consequently enables higher output power.

[0009] It should be noted that the effects of the disclosure are not necessarily limited to those described above, but may also include a number of other effects described below in connection with the disclosure. Short description of the drawings [ Fig. 1] Fig. 1 is a sectional view illustrating a configuration of a secondary battery according to an embodiment of the disclosure. [ Fig. 2] Fig. 2 is a schematic diagram showing a configuration example of a stacked body including a positive electrode, a negative electrode, and a separator as shown in Fig. 1 shown, illustrated. [ Fig. 3] Fig. 3 is a sectional view showing a configuration example of a cross-sectional structure of an electrode coil body shown in Fig. 1 shown, illustrated. [ Fig. 4A] Fig. 4A is a settlement of the Fig. 1 shown positive electrode. [ Fig. 4B] Fig. 4B is a sectional view of the Fig. 1 shown positive electrode. [ Fig. 4C] Fig. Figure 4C is an enlarged sectional view showing an enlarged view of the Fig. 4B illustrates the edge regions of the positive electrode. [ Fig. 5A] Fig. 5A is a settlement of the Fig. 1 shown negative electrode. [ Fig. 5B] Fig. 5B is a sectional view of the Fig. 1 shown negative electrode. [ Fig. 5C] Fig. Figure 5C is an enlarged sectional view showing an enlarged view of the Fig. 5B illustrates the edge regions of the negative electrode. [ Fig. 6A] Fig. 6A is a plan view of the Fig. 1 shown positive electrode current collecting plate. [ Fig. 6B] Fig. 6B is a plan view of the Fig. Negative electrode current collecting plate shown in Figure 1. [ Fig. 7] Fig. 7 is a perspective view showing a manufacturing process of the Fig. 1 shows the secondary battery. [ Fig. 8A] Fig. 8A is a schematic diagram showing a step of cutting a positive electrode current collector in the manufacturing process of the Fig. 7 shown secondary battery. [ Fig. 8B] Fig. 8B is a schematic diagram showing an enlarged view of a sectional surface of the Fig. 8A illustrates a sectioned positive electrode current collector. [ Fig. 9A] Fig. 9A is a schematic diagram showing a step of cutting a negative electrode current collector in the manufacturing process of the Fig. 7 shown secondary battery. [ Fig. 9B] Fig. 9B is a schematic diagram showing an enlarged view of a sectional surface of the Fig. 9A illustrates a sectioned negative electrode current collector. [ Fig. 10] Fig. 10 is a block diagram illustrating a circuit configuration of a battery pack in which the secondary battery according to an embodiment of the disclosure is applied. [ Fig. 11A] Fig. 11A is an enlarged sectional view illustrating an enlarged view of the peripheral portions of the positive electrode of Comparative Example 1. [ Fig. 11B] Fig. 11B is an enlarged sectional view illustrating an enlarged view of the peripheral portions of the negative electrode of Comparative Example 1. Modes for carrying out the invention

[0010] Some embodiments of the disclosure will be described in detail below with reference to the drawings. The description will be made in the following order. 0. Background 1. Secondary battery 1-1. Configuration 1-2. Operation 1-3. Manufacturing process 1-4. Effects and effects 1-5. Modification example 2. Application Examples 2-1. Battery pack 2-2. Electrical power storage system [0. Background]

[0011] A secondary battery having a positive electrode terminal (a positive electrode tab) and a negative electrode terminal (a negative electrode tab) for power output is widely used. The positive electrode terminal and the negative electrode terminal are respectively electrically coupled to a positive electrode and a negative electrode, which are constituent parts of a battery device. Such a secondary battery is referred to herein as a tab-structured secondary battery. However, in the tab-structured secondary battery, the positive electrode terminal and the negative electrode terminal each typically have a long, narrow strip shape, so that the connection area of the positive electrode terminal to the positive electrode and the connection area of the negative electrode terminal to the negative electrode have a small area.Consequently, the electrical resistance at these junctions is high, which can lead to increased internal resistance of the battery. In recent years, there has been an increasing demand for charging and discharging at higher load levels. However, in secondary batteries with a tab structure, the high internal resistance causes the temperature inside the battery to rise slightly when charging at high load levels.

[0012] To address this problem, the applicant has developed a secondary battery with a so-called tabless structure, which does not have an electrode terminal (tab) for connecting to the positive electrode or the negative electrode of the battery device (see, for example, PTL 1 described above). In the secondary battery with the tabless structure, a positive electrode current collecting plate and a negative electrode current collecting plate are used instead of the positive electrode tab and the negative electrode tab. The positive electrode current collecting plate and the negative electrode current collecting plate are respectively connected to the positive electrode and the negative electrode of the battery device via a larger contact area. Therefore, the secondary battery with the tabless structure enables a significantly reduced internal resistance compared to the secondary battery with the tab structure and allows charging and discharging at a relatively high current.

[0013] As described above, the secondary battery with the tabless structure has the characteristic of significantly reducing internal resistance compared to the secondary battery with the tab structure, which can suppress a temperature rise of the battery during charging at a high load level. The applicant conducted further research, which led to the proposal of a secondary battery with a tabless structure that enables an even further reduction in internal resistance. Such a secondary battery is described in detail below. [1. Secondary battery]

[0014] First, a secondary battery according to an embodiment of the disclosure will be described.

[0015] In this embodiment, a cylindrical lithium-ion secondary battery with an outer cylindrical shape is described as an example. However, the secondary battery of the disclosure is not limited to the cylindrical lithium-ion secondary battery, but may also be a lithium-ion secondary battery with an outer shape other than the cylindrical shape, or a battery using an electrode reactant other than lithium.

[0016] Although the charging and discharging principle of the secondary battery is not particularly limited, the following description will consider a case where the battery capacity is achieved by the storage and extraction of the electrode reactant. The secondary battery includes a positive electrode, a negative electrode, and an electrolyte. In the secondary battery, to prevent the electrode reactant from deposition on the surface of the negative electrode during charging, the charging capacity of the negative electrode is designed to be larger than the discharging capacity of the positive electrode. In other words, the electrochemical capacity per unit area of the negative electrode is designed to be larger than the electrochemical capacity per unit area of the positive electrode.

[0017] As described above, the type of electrode reactant is not particularly limited, but it is specifically a light metal such as an alkali metal or an alkaline earth metal. Examples of alkali metals include lithium, sodium, and potassium. Examples of alkaline earth metals include beryllium, magnesium, and calcium.

[0018] The following describes a case where the electrode reactant is lithium as an example. A secondary battery in which the battery capacity is achieved by the storage and extraction of lithium is called a lithium-ion secondary battery. In a lithium-ion secondary battery, lithium is stored and extracted in the ionic state. [1-1. Configuration][Lithium-ion secondary battery 1]

[0019] Fig. 1 illustrates a sectional configuration of a lithium-ion secondary battery 1 (hereinafter simply referred to as secondary battery 1) according to the embodiment along a height direction. Fig. In the secondary battery 1 shown in Figure 1, an electrode winding body 20 as a battery device is housed within an outer packaging can 11 having a cylindrical shape.

[0020] Specifically, the secondary battery 1 includes, for example, a pair of insulating plates 12 and 13, the electrode coil 20, a positive electrode current collecting plate 24, and a negative electrode current collecting plate 25 within the outer packaging can 11. The electrode coil 20 is a structure in which a positive electrode 21 and a negative electrode 22 are stacked and wound with a separator 23 interposed therebetween. The electrode coil 20 is impregnated with an electrolyte solution. The electrolyte solution is a liquid electrolyte. Note that the secondary battery 1 may further include a thermosensitive resistance device (PTC component), a reinforcing member, or both within the outer packaging can 11. [Outer packaging can 11]

[0021] The outer packaging can 11 has, for example, a hollow cylindrical structure having a lower end portion and an upper end portion in the Z-axis direction. The Z-axis direction corresponds to the height direction. The lower end portion is closed, and the upper end portion is open. Accordingly, the upper end portion of the outer packaging can 11 is an open end portion 11N. The outer packaging can 11 has, for example, a metal material such as iron as a constituent part. Note that a surface of the outer packaging can 11 may be plated with, for example, a metal material such as nickel. The insulating plate 12 and the insulating plate 13 are arranged opposite each other so that the electrode coil body 20 is positioned therebetween in the Z-axis direction.In the present specification, the open end portion 11N and the adjacent portion in the Z-axis direction may be referred to as an upper part of the secondary battery 1, while a portion in which the outer packaging can 11 is closed and the adjacent portion in the Z-axis direction may be referred to as a lower part of the secondary battery 1. [Insulation plates 12 and 13]

[0022] Each of the insulating plates 12 and 13 is, for example, a bowl-shaped plate with a surface that is perpendicular to a central axis CL of the electrode winding body 20, that is, perpendicular to the Z-axis in Fig. 1. The insulating plates 12 and 13 are arranged so that the electrode winding body 20 is positioned therebetween. [Crimped structure 11R]

[0023] For example, at the open end portion 11N of the outer packaging can 11, a structure is provided in which a battery cover 14 and a safety valve mechanism 30 are crimped with a gasket 15 interposed therebetween, that is, a crimped structure 11R. The outer packaging can 11 is closed by the battery cover 14, with the electrode winding body 20 and other components contained within the outer packaging can 11. The crimped structure 11R is a so-called crimp structure and has a bent portion 11P serving as a crimped part. [Battery cover 14]

[0024] The battery cover 14 is a closure member that mainly closes the open end portion 11N of the outer packaging can 11 in a state where the electrode coil body 20 and other components are contained within the outer packaging can 11. The battery cover 14 has, for example, a similar material to the material of the outer packaging can 11. A central portion of the battery cover 14 protrudes upward, for example, in the +Z direction. As a result, a peripheral portion (i.e., a portion outside the central portion) of the battery cover 14 is in contact with, for example, the safety valve mechanism 30. [Poem 15]

[0025] The gasket 15 is a sealing member mainly disposed between the bent portion 11P of the outer packaging can 11 and the battery cover 14. The gasket 15 seals the gap between the bent portion 11P and the battery cover 14. Note that a surface of the gasket 15 may be coated with, for example, asphalt. The gasket 15 comprises, for example, one or more insulating materials. The type of the insulating material is not particularly limited, and examples include a polymer material such as polybutylene terephthalate (PBT) or polypropylene (PP). Polybutylene terephthalate is particularly preferred. One reason for this is that it sufficiently seals the gap between the bent portion 11P and the battery cover 14 while keeping the outer packaging can 11 and the battery cover 14 electrically separated from each other. [Safety valve mechanism 30]

[0026] The safety valve mechanism 30 is designed to release the sealed state of the outer packaging can 11 to reduce the internal pressure of the outer packaging can 11 when necessary, particularly when the internal pressure increases. One cause of the increase in the internal pressure of the outer packaging can 11 may be, for example, a gas generated by a decomposition reaction of the electrolyte during charging and discharging. The internal pressure of the outer packaging can 11 may also increase due to external heating. [Electrode winding body 20]

[0027] The electrode winding body 20 is a power generation device that enables charging and discharging reactions and is housed within the outer packaging can 11. The electrode winding body 20 includes the positive electrode 21, the negative electrode 22, the separator 23, and the electrolyte solution as the liquid electrolyte.

[0028] Fig. 2 is a developed view of the electrode coil former 20 and schematically illustrates a portion of a stacked body S20 including the positive electrode 21, the negative electrode 22, and the separator 23. In the stacked body S20, which corresponds to the electrode coil former 20 in a developed state, the positive electrode 21 and the negative electrode 22 are stacked with the separator 23 interposed therebetween. The separator 23 includes, for example, two base materials, namely a first separator element 23A and a second separator element 23B. Accordingly, the electrode coil former 20 includes the stacked body S20 having four layers. In the four-layered stacked body S20, the positive electrode 21, the first separator element 23A, the negative electrode 22, and the second separator element 23B are stacked in this order.Each of the positive electrode 21, the first separator element 23A, the negative electrode 22 and the second separator element 23B is a substantially belt-shaped element, wherein a W-axis direction corresponds to the transverse direction and an L-axis direction corresponds to the longitudinal direction.

[0029] As in Fig. 3, the electrode winding body 20 has the stack body S20 wound around the central axis CL extending in the Z-axis direction (see Fig. 1), so that a spiral shape is formed in a cross-section that is orthogonal to the Z-axis direction. Here, the stacked body S20 is wound in an orientation in which the W-axis direction essentially coincides with the Z-axis direction. It should be noted that Fig. 3 shows a configuration example of the electrode winding body 20 along a horizontal cross section orthogonal to the Z-axis direction. For better visibility, Fig. 3, the illustration of the separator 23 is omitted. The electrode winding body 20 has a substantially circular cylindrical outer shape overall. The positive electrode 21 and the negative electrode 22 are wound in a state in which they face each other with the separator 23 interposed therebetween. The electrode winding body 20 has a through-hole 26 as an internal cavity at its center. The through-hole 26 is an opening into which a winding core for assembling the electrode winding body 20 and an electrode rod for welding are inserted.

[0030] The positive electrode 21, the negative electrode 22, and the separator 23 are wound such that the separator 23 is located both in the outermost winding of the electrode winding body 20 and in the innermost winding of the electrode winding body 20. Furthermore, in the outermost winding of the electrode winding body 20, the negative electrode 22 is positioned on the outside relative to the positive electrode 21. In other words, as shown in Fig. 3, an outermost positive electrode winding section 21 out, which is located in the outermost winding of the positive electrode 21 in the electrode winding body 20, is positioned on the inside relative to an outermost negative electrode winding section 22 out, which is located in the outermost winding of the negative electrode 22 in the electrode winding body 20. Here, the outermost positive electrode winding section 21 out corresponds to the outermost winding of the positive electrode 21 in the electrode winding body 20, while the outermost negative electrode winding section 22 out corresponds to the outermost winding of the negative electrode 22 in the electrode winding body 20. In contrast, in the innermost winding of the electrode winding body 20, the negative electrode 22 is positioned on the inside relative to the positive electrode 21. In other words, as in Fig. 3B, an innermost negative electrode winding portion 22in located in the innermost winding of the negative electrode 22 in the electrode winding body 20 is positioned on the inner side relative to an innermost positive electrode winding portion 21in located in the innermost winding of the positive electrode 21 in the electrode winding body 20. Here, the innermost positive electrode winding portion 21in corresponds to the innermost winding of the positive electrode 21 in the electrode winding body 20, while the innermost negative electrode winding portion 22in corresponds to the innermost winding of the negative electrode 22 in the electrode winding body 20. The number of windings of the positive electrode 21, the negative electrode 22, and the separator 23 is not particularly limited and can be selected as needed.

[0031] Fig. 4A is a development of the positive electrode 21 and schematically illustrates a state before winding. Fig. Figure 4B shows a sectional configuration of the positive electrode 21. It should be noted that Fig. 4B shows a cross section of the positive electrode 21 in the direction of the arrow along the line IVB-IVB in Fig. 4A. The positive electrode 21 includes, for example, a positive electrode current collector 21A and a positive electrode active material layer 21B formed on the positive electrode current collector 21A. The positive electrode active material layer 21B may be formed, for example, only on one of the two opposite surfaces of the positive electrode current collector 21A or on both opposite surfaces of the positive electrode current collector 21A. Fig. 4B shows a case where the positive electrode active material layer 21B is formed on both opposite surfaces of the positive electrode current collector 21A. Specifically, the positive electrode current collector 21A has an inward positive electrode current collector surface 21A1 positioned toward the winding center side of the electrode bobbin 20, that is, toward the central axis CL, and an outward positive electrode current collector surface 21A2 positioned on the side of the electrode bobbin 20 opposite the winding center.The positive electrode 21 includes, as positive electrode active material layers 21B, an inner coil-side positive electrode active material layer 21B1 covering all or part of the inward positive electrode current collector surface 21A1, and an outer coil-side positive electrode active material layer 21B2 covering all or part of the outward positive electrode current collector surface 21A2. Note that in the present specification, the inner coil-side positive electrode active material layer 21B1 and the outer coil-side positive electrode active material layer 21B2 may be collectively referred to as the positive electrode active material layer 21B without distinguishing between them.

[0032] The positive electrode 21 has a positive electrode covering region 211 in which the positive electrode current collector 21A is covered with the positive electrode active material layer 21B, and a positive electrode exposing region 212 in which the positive electrode current collector 21A is exposed without being covered by the positive electrode active material layer 21B. As shown in Fig. 4A, the positive electrode covering portion 211 and the positive electrode exposing portion 212 each extend from an inner winding-side edge 21E1 to an outer winding-side edge 21E2 along the L-axis direction, that is, the longitudinal direction of the positive electrode 21, in the electrode winding body 20. Here, the L-axis direction corresponds to the winding direction of the electrode winding body 20. In other words, the positive electrode current collector 21A in the positive electrode 21 is covered with the positive electrode active material layer 21B from the inner winding-side edge 21E1 to the outer winding-side edge 21E2 of the positive electrode 21 in the winding direction of the electrode winding body 20. The positive electrode covering region 211 and the positive electrode exposing region 212 are adjacent to each other in the W-axis direction, that is, the transverse direction of the positive electrode 21. The W-axis direction substantially coincides with the central axis CL.Furthermore, as in . Fig. 2, in the electrode winding body 20, the inner winding-side edge 21E1 of the innermost positive electrode winding section 21in is positioned offset inward relative to the inner winding-side edge 22E1 of the innermost negative electrode winding section 22in.

[0033] Fig. 4A and Fig. 4B each schematically illustrates the positive electrode current collector 21A in a state where it is stretched along the W-axis direction. In fact, however, as shown in Fig. 1, the positive electrode edge portions 212E of the positive electrode exposure portion 212 are bent toward the central axis CL and connected to the positive electrode current collecting plate 24. As shown in Fig. 4C, the plurality of positive electrode edge portions 212E overlap and each have one end having a curved surface 21RS serving as a second curved surface. Fig. 4C is an enlarged sectional view illustrating an enlarged view of the positive electrode edge portions 212E of the positive electrode 21. The curved surface 21RS is a depression surface formed by, for example, shearing. The curved surface 21RS faces the positive electrode current collecting plate 24. The end of each of the plurality of positive electrode edge portions 212E further includes a protrusion 21PR serving as a second protrusion. The protrusion 21PR protrudes toward a side opposite the positive electrode current collecting plate 24. The protrusion 21PR is a ridge formed by, for example, shearing. An insulating layer 101 is preferably formed in a region including a boundary between the positive electrode covering portion 211 and the positive electrode exposing portion 212 and the vicinity of this boundary.Like the positive electrode covering portion 211 and the positive electrode exposing portion 212, the insulating layer 101 preferably extends from the inner winding-side edge 21E1 to the outer winding-side edge 21E2 in the electrode winding body 20. Furthermore, it is preferable that the insulating layer 101 be adhered to the first separator member 23A, the second separator member 23B, or both. One reason for this is that this can prevent the positive electrode 21 and the separator 23 from being displaced from each other. Furthermore, the insulating layer 101 preferably comprises a resin containing polyvinylidene fluoride (PVDF). One reason for this is that when the insulating layer 101 contains PVDF, it can be swelled by a solvent contained in the electrolytic solution, thereby improving the adhesion of the insulating layer 101 to the separator 23. It should be noted that a detailed configuration of the positive electrode 21 will be described later.

[0034] Fig. 5A is a development of the negative electrode 22 and schematically illustrates a state before winding. Fig. Figure 5B shows a sectional configuration of the negative electrode 22. It should be noted that Fig. 5B shows a cross section of the negative electrode 22 in the direction of the arrow along the line VB-VB in Fig. 5A. The negative electrode 22 includes, for example, a negative electrode current collector 22A and a negative electrode active material layer 22B formed on the negative electrode current collector 22A. The negative electrode active material layer 22B may be formed, for example, only on one of the two opposite surfaces of the negative electrode current collector 22A or on both opposite surfaces of the negative electrode current collector 22A. Fig. 5B shows a case where the negative electrode active material layer 22B is formed on both opposite surfaces of the negative electrode current collector 22A. Specifically, the negative electrode current collector 22A has an inward-facing negative electrode current collector surface 22A1 positioned toward the winding center side of the electrode bobbin 20, that is, toward the central axis CL, and an outward-facing negative electrode current collector surface 22A2 positioned on the side of the electrode bobbin 20 opposite the winding center.The negative electrode 22 includes, as negative electrode active material layers 22B, an inner coil-side negative electrode active material layer 22B1 covering all or part of the inward-facing negative electrode current collector surface 22A1, and an outer coil-side negative electrode active material layer 22B2 covering all or part of the outward-facing negative electrode current collector surface 22A2. Note that in the present specification, the inner coil-side negative electrode active material layer 22B1 and the outer coil-side negative electrode active material layer 22B2 may be collectively referred to as the negative electrode active material layer 22B, without distinguishing between them.

[0035] The negative electrode 22 has a negative electrode covering region 221 in which the negative electrode current collector 22A is covered with the negative electrode active material layer 22B, and a negative electrode exposing region 222 in which the negative electrode current collector 22A is exposed without being covered by the negative electrode active material layer 22B. As shown in Fig. 5A, the negative electrode covering portion 221 and the negative electrode exposing portion 222 each extend along the L-axis direction, that is, the longitudinal direction of the negative electrode 22. The negative electrode exposing portion 222 extends from the inner winding-side edge 22E1 of the negative electrode 22 to the outer winding-side edge 22E2 of the negative electrode 22 in the winding direction of the electrode winding body 20. In contrast, the negative electrode covering portion 221 is provided neither at the inner winding-side edge 22E1 of the negative electrode 22 nor at the outer winding-side edge 22E2 of the negative electrode 22. As shown in Fig. 5A, portions of the negative electrode exposure region 222 are arranged so that the negative electrode covering region 221 is sandwiched therebetween in the L-axis direction, that is, the longitudinal direction of the negative electrode 22. Specifically, the negative electrode exposure region 222 includes a first portion 222A, a second portion 222B, and a third portion 222C. The first portion 222A is arranged adjacent to the negative electrode covering region 221 in the W-axis direction and extends from the inner coil-side edge 22E1 of the negative electrode 22 to the outer coil-side edge 22E2 of the negative electrode 22 in the L-axis direction. The second portion 222B and the third portion 222C are arranged so that the negative electrode covering region 221 is sandwiched therebetween in the L-axis direction.The second portion 222B is positioned, for example, in a region including the inner coil-side edge 22E1 of the negative electrode 22 and its surroundings. The third portion 222C is positioned, for example, in a region including the outer coil-side edge 22E2 of the negative electrode 22 and its surroundings. Note that . Fig. 5A and Fig. 5B each schematically illustrate the negative electrode current collector 22A in a state in which it is stretched along the W-axis direction. In fact, however, as shown in Fig. 1, the negative electrode edge portions 222E of the negative electrode exposure portion 222 are bent toward the central axis CL and connected to the negative electrode current collecting plate 25. A detailed configuration of the negative electrode 22 will be described later.

[0036] In the stacked body S20 of the electrode coil body 20, the positive electrode 21 and the negative electrode 22 are stacked with the separator 23 interposed therebetween such that the positive electrode exposure portion 212 and the first portion 222A of the negative electrode exposure portion 222 are aligned in opposite directions along the W-axis direction, that is, the transverse direction. In the electrode coil body 20, one end portion of the separator 23 is fixed by attaching a fixing band 46 to a side surface portion 45 of the electrode coil body 20, thereby preventing winding loosening.

[0037] In the secondary battery 1, as in Fig. 2, preferably satisfies the condition A>B, where A is a width of the positive electrode exposure region 212 and B is a width of the first portion 222A of the negative electrode exposure region 222. For example, when the width A is 7 (mm), the width B is 4 (mm). Further, preferably, the condition C>D is satisfied, where C is a width of a portion of the positive electrode exposure region 212 that protrudes beyond an outer edge in the width direction of the separator 23, and D is a protruding length of the first portion 222A of the negative electrode exposure region 222 measured from an opposite outer edge in the width direction of the separator 23. For example, when the width C is 4.5 (mm), the width D is 3 (mm).

[0038] As in Fig. 1, in the upper part of the secondary battery 1, the plurality of positive electrode edge portions 212E of the positive electrode exposure portion 212 wound around the central axis CL, which are adjacent to each other in a radial direction (an R direction) of the electrode bobbin 20, are bent toward the central axis CL to overlap each other, thereby forming an end surface 41 of an upper part of the electrode bobbin 20. Similarly, in the lower part of the secondary battery 1, the plurality of negative electrode edge portions 222E of the negative electrode exposure portion 222 wound around the central axis CL, which are adjacent to each other in the radial direction (the R direction), are bent toward the central axis CL to overlap each other, thereby forming an end surface 42 of a lower part of the electrode bobbin 20.Accordingly, the plurality of positive electrode edge portions 212E of the positive electrode exposure portion 212 are congregated on the end surface 41 of the upper part of the electrode bobbin 20, and the plurality of negative electrode edge portions 222E of the negative electrode exposure portion 222 are congregated on the end surface 42 of the lower part of the electrode bobbin 20. To achieve better contact between the positive electrode current collecting plate 24, which is provided for current output, and the plurality of positive electrode edge portions 212E, the plurality of positive electrode edge portions 212E are bent toward the central axis CL and form a flat surface. Likewise, the plurality of negative electrode edge portions 222E are bent toward the central axis CL and form a flat surface to achieve better contact between the negative electrode current collecting plate 25, which is provided for current output, and the plurality of negative electrode edge portions 222E.It should be noted that the term “flat surface” here includes not only a completely flat surface, but also a surface having certain unevenness or surface roughness, as long as the connection of the positive electrode exposure region 212 to the positive electrode current collecting plate 24 and the connection of the negative electrode exposure region 222 to the negative electrode current collecting plate 25 is possible.

[0039] As in Fig. 5C, each end of the overlapping plurality of negative electrode edge portions 222E has a curved surface 22RS serving as a first curved surface. Fig. 5C is an enlarged sectional view illustrating an enlarged view of the negative electrode edge portions 222E of the negative electrode 22. The curved surface 22RS is a depression surface formed by, for example, shearing. The curved surface 22RS faces the negative electrode current collecting plate 25. The end of each of the plurality of negative electrode edge portions 222E further includes a protrusion 22PR serving as a first protrusion. The protrusion 22PR protrudes toward a side opposite the negative electrode current collecting plate 25. The protrusion 22PR is a burr formed by, for example, shearing.

[0040] The positive electrode current collector 21A comprises, for example, an aluminum foil, as described later. In contrast, the negative electrode current collector 22A comprises, for example, a copper foil, as described later. In this case, the positive electrode current collector 21A is softer than the negative electrode current collector 22A. In other words, the positive electrode exposure region 212 has a lower elastic modulus than the negative electrode exposure region 222. Accordingly, in one embodiment, it is preferable that the widths A to D satisfy the relationships A>B and C>D.In such a case, when the positive electrode exposure region 212 and the negative electrode exposure region 222 are bent simultaneously with equal pressure from the respective electrode sides, the bent region in the positive electrode 21 and the bent region in the negative electrode 22 may sometimes have approximately equal heights as measured from the respective ends of the separator 23. In this case, the plurality of positive electrode edge regions 212E (. Fig. 1) of the positive electrode exposure portion 212 by bending it in a suitable manner. This enables easy connection of the positive electrode exposure portion 212 to the positive electrode current collecting plate 24. Likewise, the plurality of negative electrode edge portions 222E ( Fig. 1) The negative electrode exposure portion 222 is bent in an appropriate manner. This allows for easy joining of the negative electrode exposure portion 222 to the negative electrode current collecting plate 25. Note that the term "joining" herein includes coupling by, for example, laser welding; however, the joining method is not limited to laser welding.

[0041] As in Fig. As shown in FIG. 2, a portion of the positive electrode exposure region 212 of the positive electrode 21, which faces the negative electrode 22 with the separator 23 interposed therebetween, is covered with the insulating layer 101. The insulating layer 101 has, for example, a width of 3 mm in the W-axis direction. The insulating layer 101 completely covers the portion of the positive electrode exposure region 212 of the positive electrode 21, which faces the negative electrode covering region 221 of the negative electrode 22 with the separator 23 interposed therebetween. The insulating layer 101 makes it possible to effectively prevent an internal short circuit of the secondary battery 1 when, for example, foreign matter gets between the negative electrode covering region 221 and the positive electrode exposure region 212.Furthermore, when the secondary battery 1 is subjected to an impact, the insulating layer 101 absorbs the impact, thereby making it possible to effectively prevent deformation of the positive electrode exposure region 212 and a short circuit between the positive electrode exposure region 212 and the negative electrode 22. [Insulating tapes 53 and 54].

[0042] The secondary battery 1 may further include insulating tapes 53 and 54 in a gap between the outer packaging can 11 and the electrode bobbin 20. The positive electrode exposure region 212, whose portions gather at the end face 41, and the negative electrode exposure region 222, whose portions gather at the end face 42, are electrical conductors such as metal foils that are exposed. Accordingly, a short circuit may occur between the positive electrode 21 and the negative electrode 22 via the outer packaging can 11 when the positive electrode exposure region 212 and the negative electrode exposure region 222 are located near the outer packaging can 11. A short circuit may also occur when the positive electrode current collecting plate 24 at the end face 41 and the outer packaging can 11 approach each other. To prevent this, it is preferable to provide the insulating tapes 53 and 54 as insulating members.Each of the insulating tapes 53 and 54 is an adhesive tape comprising a base layer and an adhesive layer formed on a surface of the base layer. The base layer comprises, for example, one of the following materials: polypropylene, polyethylene terephthalate, or polyimide. To prevent the provision of the insulating tapes 53 and 54 from resulting in a reduced capacity of the electrode coil body 20, the insulating tapes 53 and 54 are arranged so as not to overlap with the fixing tape 46 attached to the side surface portion 45, and their thickness is set to a value equal to or less than the thickness of the fixing tape 46 [positive electrode current collecting plate 24 and negative electrode current collecting plate 25].

[0043] For example, in a typical lithium-ion secondary battery, a lead for current output is welded to a location of each of the positive electrode and the negative electrode. However, such a structure increases the internal resistance of the lithium-ion secondary battery and causes the lithium-ion secondary battery to generate heat and heat up during discharge; therefore, this structure is unsuitable for high-current discharge. To address this problem, in the secondary battery 1 according to the present embodiment, the positive electrode current collecting plate 24 is disposed so as to oppose the end face 41, and the negative electrode current collecting plate 25 is disposed so as to oppose the end face 42.Furthermore, the positive electrode edge portions 212E of the positive electrode exposure portion 212 provided on the end surface 41 and the positive electrode current collecting plate 24 are connected to each other at multiple points; likewise, the negative electrode edge portions 222E of the negative electrode exposure portion 222 provided on the end surface 42 and the negative electrode current collecting plate 25 are connected to each other at multiple points. The connection of the positive electrode edge portions 212E to the positive electrode current collecting plate 24 and the connection of the negative electrode edge portions 222E to the negative electrode current collecting plate 25 are performed, for example, by laser welding. This achieves a reduced internal resistance of the secondary battery 1. Each of the end surfaces 41 and 42 is a flat surface, as described above, which also contributes to resistance reduction.The positive electrode current collecting plate 24 is electrically connected to the battery cover 14, for example, via the safety valve mechanism 30. The negative electrode current collecting plate 25 is electrically connected to the outer packaging can 11, for example. Fig. 6A is a schematic diagram illustrating a configuration example of the positive electrode current collecting plate 24. Fig. 6B is a schematic diagram illustrating a configuration example of the negative electrode current collecting plate 25. The positive electrode current collecting plate 24 is a metal plate comprising, for example, aluminum or an aluminum alloy, or a composite material of aluminum and the aluminum alloy, as a single component. The negative electrode current collecting plate 25 is a metal plate comprising, for example, nickel, a nickel alloy, copper, or a copper alloy, or a composite material of two or more of these materials, as a single component.

[0044] As in Fig. 6A, the positive electrode current collecting plate 24 has a shape in which a band-shaped portion 32 having a substantially rectangular shape is connected to a fan-shaped portion 31 having a substantially fan-shaped shape. The fan-shaped portion 31 has a through-hole 35 near its center. In the secondary battery 1, the positive electrode current collecting plate 24 is arranged so that the through-hole 35 overlaps with the through-hole 26 in the Z-axis direction. A hatched area in Fig. 6A illustrates an insulating region 32A of the band-shaped portion 32. The insulating region 32A is a part of the band-shaped portion 32 to which either an insulating tape or an insulating material has been applied. Of the band-shaped portion 32, a region below the insulating region 32A is a connecting region 32B, which is coupled to a sealing plate that also serves as an external terminal. It should be noted that when the secondary battery 1 has a battery configuration without a metallic center pin in the through-hole 26, as shown in Fig. 1, there is a low probability that the band-shaped portion 32 will come into contact with a region of negative electrode potential. In such a case, the positive electrode current collecting plate 24 does not need to have the insulating region 32A. If the positive electrode current collecting plate 24 does not have the insulating region 32A, it is possible to increase the width of the positive electrode 21 and the negative electrode 22 by an amount corresponding to the thickness of the insulating region 32A, thereby increasing the charging and discharging capacity.

[0045] The Fig. The negative electrode current collecting plate 25 shown in Fig. 6B has a similar shape to that shown in Fig. 6A. Note that the negative electrode current collecting plate 25 has a band-shaped portion 34 different from the band-shaped portion 32 of the positive electrode current collecting plate 24. The band-shaped portion 34 of the negative electrode current collecting plate 25 is shorter than the band-shaped portion 32 of the positive electrode current collecting plate 24 and does not have a portion corresponding to the insulating portion 32A of the positive electrode current collecting plate 24. The band-shaped portion 34 is provided with protrusions 37, each having a round shape and illustrated as a plurality of circles. During resistance welding, the current is concentrated on the protrusions 37, causing the protrusions 37 to melt and the band-shaped portion 34 to be welded to the bottom of the outer packaging can 11.Like the positive electrode current collecting plate 24, the negative electrode current collecting plate 25 has a through-hole 36 near the center of a fan-shaped portion 33. In the secondary battery 1, the negative electrode current collecting plate 25 is arranged so that the through-hole 36 overlaps with the through-hole 26 in the Z-axis direction.

[0046] The fan-shaped portion 31 of the positive electrode current collecting plate 24 covers only a part of the end surface 41 due to the planar shape of the fan-shaped portion 31. Similarly, the fan-shaped portion 33 of the negative electrode current collecting plate 25 covers only a part of the end surface 42 due to the planar shape of the fan-shaped portion 33. Reasons why the fan-shaped portion 31 does not cover the entire end surface 41 and why the fan-shaped portion 33 does not cover the entire end surface 42 include, for example, the following two reasons. A first reason is to allow the electrolyte solution to smoothly penetrate into the electrode bobbin 20 during assembly of the secondary battery 1. A second reason is to allow gas generated upon abnormal heating or overcharging of the lithium-ion secondary battery to be more easily discharged to the outside. [Positive electrode current collector 21A]

[0047] The positive electrode current collector 21A comprises, for example, an electrically conductive material such as aluminum. The positive electrode current collector 21A is, for example, a metal foil comprising aluminum or an aluminum alloy. [Positive electrode active material layer 21B]

[0048] The positive electrode active material layer 21B includes, as the positive electrode active material, one or more positive electrode materials into which lithium can be incorporated and from which lithium can be extracted. Note that the positive electrode active material layer 21B may further include one or more other materials. Examples of these other materials include a positive electrode binder and a positive electrode conductor. It is preferable that the positive electrode material be a lithium-containing compound, specifically, a lithium-containing compound oxide or a lithium-containing phosphoric acid compound. The lithium-containing compound oxide is an oxide comprising lithium and one or more other elements, that is, one or more elements other than lithium, as constituents.The lithium-containing composite oxide has any crystal structure, including, but not limited to, a layered rock salt crystal structure and a spinel crystal structure. The lithium-containing phosphoric acid compound is a phosphoric acid compound comprising lithium and one or more other elements as constituents, and has, for example, an olivine crystal structure. The positive electrode active material layer 21B preferably comprises, in particular, at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide as the positive electrode active material. The positive electrode binder comprises, for example, one or more materials, including, but not limited to, synthetic rubber and a polymer material. Examples of synthetic rubber include styrene-butadiene rubber, fluororubber, and ethylene propylene diene.Examples of the polymer material include polyvinylidene fluoride and polyimide. The positive electrode conductor comprises, for example, one or more materials, including but not limited to a carbon material. Examples of the carbon material include graphite, carbon black, acetylene black, and Ketjen black. Note that the positive electrode conductor may be one of the electrically conductive materials, and may be, for example, a metal material or an electrically conductive polymer. [Negative electrode current collector 22A]

[0049] The negative electrode current collector 22A comprises, for example, an electrically conductive material such as copper. The negative electrode current collector 22A is, for example, a metal foil comprising nickel, a nickel alloy, copper, or a copper alloy.

[0050] A surface of the negative electrode current collector 22A is preferably roughened. One reason for this is to improve the adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A through the so-called anchor effect. In this case, the surface of the negative electrode current collector 22A needs to be roughened at least in a region opposite to the negative electrode active material layer 22B. Examples of a roughening method include a method of forming microparticles through electrolytic treatment. In the electrolytic treatment, the microparticles are formed on the surface of the negative electrode current collector 22A by an electrolytic process in an electrolysis tank. This provides the surface of the negative electrode current collector 22A with unevenness.A copper foil produced by the electrolytic process is commonly called electrolytic copper foil. [Negative electrode current collector 22A]

[0051] The negative electrode current collector 22A comprises, for example, an electrically conductive material such as copper. The negative electrode current collector 22A is, for example, a metal foil comprising nickel, a nickel alloy, copper, or a copper alloy. A surface of the negative electrode current collector 22A is preferably roughened. One reason for this is that the adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A is thereby improved by the so-called anchor effect. In this case, the surface of the negative electrode current collector 22A is to be roughened at least in a region opposite the negative electrode active material layer 22B. Examples of a roughening method include a method in which microparticles are formed by electrolytic treatment.In the electrolytic treatment, the microparticles are formed on the surface of the negative electrode current collector 22A by an electrolytic process in an electrolytic tank. This provides the surface of the negative electrode current collector 22A with unevenness. A copper foil produced by the electrolytic process is generally referred to as an electrolytic copper foil. [Negative electrode active material layer 22B]

[0052] The negative electrode active material layer 22B includes, as a negative electrode active material, one or more negative electrode materials into which lithium can be intercalated and from which lithium can be extracted. Note that the negative electrode active material layer 22B may further include one or more other materials. Examples of these other materials include a negative electrode binder and a negative electrode conductor. The negative electrode material is, for example, a carbon material. One reason for this is that the carbon material exhibits very little change in crystal structure during the intercalation and extraction of lithium, and thus a high energy density can be stably achieved. Another reason is that the carbon material also serves as a negative electrode conductor, thereby improving the electrical conductivity of the negative electrode active material layer 22B.Examples of the carbon material include graphitizable carbon, non-graphitizable carbon, and graphite. Note that the (002) plane pitch of the non-graphitizable carbon is preferably 0.37 nm or greater. The (002) plane pitch of the graphite is preferably 0.34 nm or less. More specific examples of the carbon material include pyrolytic carbons, coke, glassy carbon fibers, an organic polymer compound residue obtained by pyrolysis or carbonization, activated carbon, and carbon black. Examples of coke include pitch coke, needle coke, and petroleum coke. The organic polymer compound residue is a product obtained by firing or carbonizing a polymer compound such as a phenolic resin or a furan resin at an appropriate temperature.In addition to the above examples, the carbon material may also be low-crystalline carbon heat-treated at a temperature of about 1000°C or lower, or amorphous carbon. Note that the carbon material may have a fibrous shape, a spherical shape, a granular shape, or a plate-like shape. In the secondary battery 1, when an open-circuit voltage in a fully charged state, that is, a battery voltage, is 4.25 V or higher, the amount of extracted lithium per unit mass increases compared to an open-circuit voltage of 4.20 V, even if the same positive electrode active material is used. Therefore, the amount of the positive electrode active material and the amount of the negative electrode active material are adjusted accordingly. This makes it possible to achieve a high energy density.

[0053] The negative electrode active material layer 22B may contain, as the negative electrode active material, a silicon-containing material comprising at least one of silicon, silicon oxide, a carbon-silicon compound, or a silicon alloy. The term "silicon-containing material" is a generic term for a material containing silicon as a constituent element. Note that the silicon-containing material may contain only silicon as a constituent element. A single silicon-containing material may be used, or two or more silicon-containing materials may be used. The silicon-containing material is capable of forming an alloy with lithium and may be a silicon element, a silicon alloy, a silicon compound, a mixture of two or more thereof, or a material comprising one or more phases thereof.Furthermore, the silicon-containing material may be crystalline or amorphous, or contain both a crystalline and an amorphous portion. It should be noted that the element described here generally refers to a chemically pure element. However, the element may contain a small amount of impurities. In other words, the purity of the element is not limited to 100%. The silicon alloy contains, as one or more constituent elements other than silicon, one or more of the following elements, including but not limited to: tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium. The silicon compound contains, as one or more constituent elements other than silicon, one or more of the following elements, including but not limited to: carbon and oxygen.It should be noted that the silicon compound may contain, as one or more constituent elements other than silicon, one or more of the elements described above in connection with the silicon alloy. Specific examples of the silicon alloy and the silicon compound include SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, and SiO. v (where 0 < v ≤ 2). Note that v can be set within any desired range and can, for example, be in the following range: 0.2 < v < 1.4. [Separator 23]

[0054] The separator 23 is arranged between the positive electrode 21 and the negative electrode 22. The separator 23 allows the passage of lithium ions and prevents a current short circuit caused by contact between the positive electrode 21 and the negative electrode 22. The separator 23 comprises, for example, one or more types of porous films, each containing, for example, a synthetic resin or a ceramic, and may comprise a stacked film of two or more types of porous films. Examples of synthetic resin include polytetrafluoroethylene, polypropylene, and polyethylene. Note that the separator 23 preferably comprises base materials, each comprising a single-layer porous polyolefin film containing polyethylene. One reason for this is that an advantageous high-performance property can be achieved compared with a stacked film.When the first separator element 23A and the second separator element included in the separator 23 each include a single-layer porous film comprising polyolefin, the thickness of the porous film is preferably at least 10 µm and at most 15 µm. Internal short circuiting can be sufficiently prevented when the single-layer porous film comprising polyolefin has a thickness of at least 10 µm. A more favorable discharge capacity characteristic can be achieved when the thickness of the single-layer porous film comprising polyolefin is at most 15 µm. Furthermore, the porous film preferably has an areal density of at least 6.3 g / m. 2 and a maximum of 8.3 g / m 2 An internal short circuit can be sufficiently avoided if the areal density of the single-layer porous film with polyolefin is at least 6.3 g / m 2A more favorable discharge capacity property can be achieved if the areal density of the single-layer porous film with polyolefin is at most 8.3 g / m 2 amounts.

[0055] Specifically, the separator 23 may include, for example, the porous film as any of the above-described base materials, and a polymer substance layer formed on one or both opposite surfaces of each of the base layers. One reason for this is that the adhesion of the separator 23 to the positive electrode 21 and the negative electrode 22 improves, thereby suppressing distortion of the electrode coil body 20. This suppresses a decomposition reaction of the electrolytic solution and also prevents leakage of the electrolytic solution impregnated into the base layers. This prevents a simple increase in resistance even upon repeated charging and discharging and also suppresses battery swelling. The polymer substance layer contains, for example, a polymer substance such as polyvinylidene fluoride.One reason for this is that the polymer substance such as polyvinylidene fluoride has superior physical strength and is electrochemically stable. It should be noted that the polymer substance can also be a substance other than polyvinylidene fluoride. To form the polymer substance layer, for example, a solution in which the polymer substance is dissolved in a solvent such as an organic solvent can be coated on the base layer and then dried. Alternatively, the base layer can be immersed in the solution and then dried. The polymer substance layer may contain one or more types of insulating particles such as inorganic particles. Examples of the type of inorganic particles include aluminum oxide and aluminum nitride. [Electrolyte solution]

[0056] The electrolytic solution comprises a solvent and an electrolytic salt. Note that the electrolytic solution may further contain one or more other materials. Examples of these other materials include an additive. The solvent comprises one or more non-aqueous solvents, including but not limited to an organic solvent. An electrolytic solution containing a non-aqueous solvent is referred to as a non-aqueous electrolytic solution. The non-aqueous solvent includes, for example, a fluorine compound and a dinitrile compound. The fluorine compound includes, for example, at least one of fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, a fluorinated carboxylic acid ester, or a fluoroether. The non-aqueous solvent may further contain at least one of nitrile compounds other than the dinitrile compound.Examples of nitrile compounds other than dinitrile include mononitrile and trinitrile. For example, succinonitrile (SN) is preferred as a dinitrile compound. Note that dinitrile compounds are not limited to succinonitrile, but can also include other dinitrile compounds such as adiponitrile.

[0057] The electrolyte salt includes, for example, one or more salts, including but not limited to a lithium salt. Note that the electrolyte salt may contain a salt other than the lithium salt. Examples of a salt other than the lithium salt include a salt of a light metal other than lithium.

[0058] Examples of the lithium salt include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SF6), lithium chloride (LiCl), and lithium bromide (LiBr). In particular, the lithium salt is preferably one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, or lithium hexafluoroarsenate, with lithium hexafluorophosphate being particularly preferred. Although not particularly limited, the content of the electrolyte salt is preferably in a range of 0.3 mol / kg to 3 mol / kg inclusive, based on the solvent. If the electrolyte solution contains LiPF6 as the electrolyte salt, the concentration of LiPF6 in the electrolyte solution is preferably at least 1.25 mol / kg and at most 1.45 mol / kg.One reason for this is that it can more effectively prevent the deterioration in cycling life caused by the consumption or decomposition of the salt during high-load charging, thereby enabling a further improvement in the high-load cycling life. When the electrolyte solution contains LiBF4 in addition to LiPF6 as the electrolyte salt, the concentration of LiBF4 in the electrolyte solution is preferably at least 0.001 weight percent (wt%) and at most 0.1 weight percent (wt%). One reason for this is that it can more effectively prevent the deterioration in cycling life caused by the consumption or decomposition of the salt during high-load charging, thereby enabling a further improvement in the high-load cycling life. [1-2. Operation]

[0059] In the secondary battery 1 according to the present embodiment, for example, during charging, lithium ions are extracted from the positive electrode 21, and the extracted lithium ions are stored in the negative electrode 22 via the electrolyte solution. In the secondary battery 1, for example, during discharging, lithium ions are extracted from the negative electrode 22, and the extracted lithium ions are stored in the positive electrode 21 via the electrolyte solution. [1-3. Manufacturing process]

[0060] A method of manufacturing the secondary battery 1 will be described with reference to Fig. 7 to Fig. 9B and Fig. 1 to Fig. 5B. Fig. 7 is a perspective view showing a manufacturing process of the Fig. 1 shows the secondary battery. Fig. 8A and Fig. 8B are schematic diagrams describing a step of shearing the positive electrode current collector 21A to a predetermined width dimension. Fig. 9A and Fig. 9B are schematic diagrams describing a step of shearing the negative electrode current collector 22A to a predetermined width dimension.

[0061] First, the positive electrode current collector 21A is provided, and the positive electrode active material layer 21B is selectively formed on the surface of the positive electrode current collector 21A to form the positive electrode 21 having the positive electrode covering region 211 and the positive electrode exposing region 212. Subsequently, the positive electrode current collector 21A is cut in the positive electrode exposing region 212 so that the width A (see Fig. 2) of the positive electrode exposure region 212 has a predetermined dimension. Specifically, as shown in Fig. 8A, for example, with a lower blade (LB) pressed against the inward-facing positive electrode current collector surface 21A1 and an upper blade (UB) pressed against the outward-facing positive electrode current collector surface 21A2, pressure is applied in the directions indicated by arrows, so that the positive electrode current collector 21A is cut. This forms a cut surface extending in the L-axis direction. The cut surface is a portion that forms the plurality of positive electrode edge regions 212E in the electrode winding body 20. As shown in Fig. 8B, the positive electrode edge portion 212E includes the curved surface 21RS, which is a depression surface, and the protrusion 21PR, which is a ridge.

[0062] Subsequently, the negative electrode current collector 22A is provided, and the negative electrode active material layer 22B is selectively formed on the surface of the negative electrode current collector 22A to form the negative electrode 22 having the negative electrode covering portion 221 and the negative electrode exposing portion 222. Thereafter, the negative electrode current collector 22A is cut in the negative electrode exposing portion 222 so that the width B (see Fig. 2) of the first portion 222A of the negative electrode exposure region 222 has a predetermined dimension. Specifically, as shown in Fig. 9A, for example, with a lower blade (LB) pressed against the inward-facing negative electrode current collector surface 22A1 and an upper blade (UB) pressed against the outward-facing negative electrode current collector surface 22A2, pressure is applied in the directions indicated by arrows, so that the negative electrode current collector 22A is cut. This forms a cut surface extending in the L-axis direction. The cut surface is a portion that forms the plurality of negative electrode edge regions 222E in the electrode winding body 20. As shown in Fig. 9B, the negative electrode edge portion 222E includes the curved surface 22RS, which is a depression surface, and the protrusion 22PR, which is a ridge.

[0063] The positive electrode 21 and negative electrode 22 manufactured in the manner described above may be subjected to a drying process. Subsequently, the positive electrode 21 and the negative electrode 22 are stacked, with the first separator element 23A and the second separator element 23B being arranged on the positive electrode 21 and the negative electrode 22, respectively, so that the positive electrode exposure region 212 and the first portion 222A of the negative electrode exposure region 222 are on opposite sides of each other in the W-axis direction. This forms the stacked body S20. Subsequently, the stacked body S20 is wound in a spiral shape to form the through-hole 26. Further, the fixing tape 46 is attached to the outermost winding of the spirally wound stacked body S20. This obtains the electrode winding body 20 as shown in part (A) of Fig. 7 shown.

[0064] Then, as described in part (B) of Fig. 7, the end surfaces 41 and 42 of the electrode winding body 20 are each locally bent by pressing a flat plate, for example, 0.5 millimeters thick, vertically, ie, in the Z-axis direction, against each of the end surfaces 41 and 42. This forms grooves 43 which radiate in radial directions (the R directions) from the through-hole 26. It should be noted that the number and arrangement of the grooves shown in part (B) of Fig. 7 are merely an example and the disclosure is not limited thereto.

[0065] Then, as described in part (C) of Fig. 7, substantially equal pressures are simultaneously applied in nearly vertical directions from above and below to the end surfaces 41 and 42 of the electrode coil body 20. For example, a rod-shaped tool is inserted into the through-hole 26 in advance. This action bends the positive electrode exposure portion 212 and the negative electrode edge portions 222E of the negative electrode exposure portion 222, so that each of the end surfaces 41 and 42 is converted into a flat surface. At this time, the positive electrode edge portions 212E of the positive electrode exposure portion 212 at the end surface 41 are bent toward the through-hole 26, overlapping each other, just as the negative electrode edge portions 222E of the negative electrode exposure portion 222 at the end surface 42 are bent toward the through-hole 26, overlapping each other.Subsequently, the fan-shaped portion 31 of the positive electrode current collecting plate 24 is joined to the end face 41 by a method such as laser welding, and the fan-shaped portion 33 of the negative electrode current collecting plate 25 is joined to the end face 42 by a method such as laser welding.

[0066] Then the insulating tapes 53 and 54 are applied to the designated positions of the electrode winding body 20. Then, as described in part (D) of Fig. 7, the band-shaped portion 32 of the positive electrode current collecting plate 24 is bent and inserted through a hole 12H of the insulating plate 12. Further, the band-shaped portion 34 of the negative electrode current collecting plate 25 is bent and inserted through a hole 13H of the insulating plate 13.

[0067] Thereafter, the electrode winding body 20 assembled in the manner described above is inserted into the position shown in part (E) of Fig. 7 is inserted into the outer packaging can 11. Subsequently, a bottom portion of the outer packaging can 11 and the negative electrode current collecting plate 25 are welded together. After that, a narrow portion 11S is formed near the open end portion 11N of the outer packaging can 11. Further, the electrolytic solution is poured into the outer packaging can 11, and then the band-shaped portion 32 of the positive electrode current collecting plate 24 and the safety valve mechanism 30 are welded together.

[0068] Then, as described in part (F) of Fig. 7, sealing is performed with the gasket 15, the safety valve mechanism 30 and the battery cover 14 using the narrow portion 11S.

[0069] The secondary battery 1 according to the present embodiment is completed in the manner described above. [1-4. Effects and effects]

[0070] As described above, in the secondary battery 1 according to the present embodiment, the plurality of positive electrode edge portions 212E of the positive electrode exposure portion 212, which are adjacent to each other in the radial direction of the electrode bobbin 20, are bent toward the central axis CL to overlap each other, thereby forming the end surface 41. Furthermore, in the secondary battery 1 according to the present embodiment, the plurality of negative electrode edge portions 222E of the negative electrode exposure portion 222, which are adjacent to each other in the radial direction of the electrode bobbin 20, are bent toward the central axis CL to overlap each other, thereby forming the end surface 42. Here, each of the plurality of positive electrode edge portions 212E includes the curved surface 21RS, and each of the plurality of negative electrode edge portions 222E includes the curved surface 22RS.Accordingly, the contact area between the plurality of positive electrode edge portions 212E of the positive electrode current collector 21A and the positive electrode current collecting plate 24 increases without causing deformation of the electrode coil body 20. This improves the contact area between the plurality of positive electrode edge portions 212E and the positive electrode current collecting plate 24, thus achieving a favorable connection state. Likewise, the contact area between the plurality of negative electrode edge portions 222E of the negative electrode current collector 22A and the negative electrode current collecting plate 25 increases without causing deformation of the electrode coil body 20. This improves the contact area between the plurality of negative electrode edge portions 222E and the negative electrode current collecting plate 25, thus achieving a favorable connection state.This makes it possible to reduce the internal resistance of the secondary battery 1 and consequently to achieve a higher output power.

[0071] In contrast, for example, if the plurality of positive electrode edge regions 212E do not have a curved surface 21RS, but instead have a sharp edge or protrusion facing the positive electrode current collecting plate 24, a point contact would occur between the positive electrode edge regions 212E and the positive electrode current collecting plate 24. Likewise, if the plurality of negative electrode edge regions 222E do not have a curved surface 22RS, but instead have a sharp edge or protrusion facing the negative electrode current collecting plate 25, a point contact would occur between the negative electrode edge regions 222E and the negative electrode current collecting plate 25.In such a case, the contact areas between the positive electrode edge regions 212E and the positive electrode current collecting plate 24 and between the negative electrode edge regions 222E and the negative electrode current collecting plate 25 would be relatively small compared to the present embodiment.

[0072] In the present embodiment, the curved surfaces 21RS are directed toward the positive electrode current collecting plate 24, and the curved surfaces 22RS are directed toward the negative electrode current collecting plate 25. This increases the contact area between the positive electrode edge portions 212E and the positive electrode current collecting plate 24, as well as the contact area between the negative electrode edge portions 222E and the negative electrode current collecting plate 25, so that favorable connection states can be achieved. This leads to a reduction in contact resistance at the interface between the positive electrode edge portions 212E and the positive electrode current collecting plate 24, and at the interface between the negative electrode edge portions 222E and the negative electrode current collecting plate 25.

[0073] Furthermore, in the present embodiment, when manufacturing the electrode winding body 20, the stacked body is wound so that the protrusions 21PR are directed toward the side opposite the positive electrode current collecting plate 24 and the protrusions 22PR are directed toward the side opposite the negative electrode current collecting plate 25. In other words, the stacked body is wound so that the protrusions 21PR and 22PR face the central axis CL, and then the positive electrode edge portions 212E and the negative electrode edge portions 222E are bent. This contributes to preventing the positive electrode edge portions 212E and the negative electrode edge portions 222E from being accidentally bent or bent, thereby making it easier to achieve uniform planarity of the end surfaces 41 and 42.

[0074] When the electrode coil body 20 is manufactured such that the protrusions 21PR and 22PR face the outside of the electrode coil body 20, accidental kinks or bends are likely to occur when the positive electrode edge portions 212E and the negative electrode edge portions 222E are bent. This makes it difficult to achieve a large contact area between the positive electrode edge portions 212E and the positive electrode current collecting plate 24, and a large contact area between the negative electrode edge portions 222E and the negative electrode current collecting plate 25. In addition, during laser welding to connect the positive electrode edge portions 212E to the positive electrode current collecting plate 24 and the negative electrode edge portions 222E to the negative electrode current collecting plate 25, perforations may occur in the positive electrode current collecting plate 24 and the negative electrode current collecting plate 25, resulting in a reduction in the contact area.Therefore, it is desirable that the projections 21PR face the side opposite the positive electrode current collecting plate 24 and the projections 22PR face the side opposite the negative electrode current collecting plate 25. [2. Application examples]

[0075] Examples of applications of the secondary battery 1 according to the above embodiment of the disclosure are described below. [2-1. Battery pack]

[0076] Fig. 10 is a block diagram illustrating an example of a circuit configuration in which a battery according to an embodiment of the invention, which may be referred to as a secondary battery hereinafter, is applied to a battery pack 300. The battery pack 300 includes an assembled battery 301, an outer casing, a switch 304, a current detection resistor 307, a temperature detection device 308, and a controller 310. The switch 304 includes a charge control switch 302a and a discharge control switch 303a.

[0077] The battery pack 300 includes a positive electrode terminal 321 and a negative electrode terminal 322. During charging, the positive electrode terminal 321 and the negative electrode terminal 322 are respectively coupled to a positive electrode terminal and a negative electrode terminal of a charger to perform charging. During operation of an electronic device, the positive electrode terminal 321 and the negative electrode terminal 322 are respectively coupled to a positive electrode terminal and a negative electrode terminal of the electronic device to perform discharging.

[0078] The interconnected battery 301 includes a plurality of secondary batteries 301a connected in series or parallel. The secondary battery 1 described above is applicable to each of the secondary batteries 301a. Note that Fig. 10 shows an example in which six secondary batteries 301a are coupled in a two-parallel and three-series (2P3S) configuration. However, the secondary batteries 301a may also be coupled in any other configuration, for example, in any n-parallel and m-series configuration (where n and m are each an integer).

[0079] The switch 304 includes the charge control switch 302a, a diode 302b, the discharge control switch 303a, and a diode 303b, and is controlled by the controller 310. The diode 302b has a polarity that is reverse-biased with respect to a charging current flowing in the direction from the positive electrode terminal 321 to the interconnected battery 301, and a polarity that is forward-biased with respect to a discharging current flowing in the direction from the negative electrode terminal 322 to the interconnected battery 301. The diode 303b has a polarity that is forward-biased with respect to the charging current and reverse-biased with respect to the discharging current. It should be noted that the switch 304 in Fig. 10 is shown on the positive side, but can also be arranged on the negative side.

[0080] The charge control switch 302a is controlled by a charge and discharge controller to turn off when the battery voltage reaches an overcharge voltage, thereby preventing the charging current from flowing through the current path of the interconnected battery 301. After the charge control switch 302a is turned off, only discharge via the diode 302b is possible. Furthermore, the charge control switch 302a is controlled by the controller 310 to turn off when a high current flows during charging, thereby blocking the charging current through the current path of the interconnected battery 301. The discharge control switch 303a is controlled by the controller 310 to turn off when the battery voltage reaches a deep discharge detection voltage, thereby preventing the discharging current from flowing through the current path of the interconnected battery 301.After the discharge control switch 303a is turned off, charging is only possible via the diode 303b. Furthermore, the discharge control switch 303a is controlled by the controller 310 to turn off when a high current flows during discharging, thereby blocking the discharge current through the current path of the interconnected battery 301.

[0081] The temperature detection device 308 is, for example, a thermistor. The temperature detection device 308 is arranged near the interconnected battery 301, measures a temperature of the interconnected battery 301, and transmits the measured temperature to the controller 310. A voltmeter 311 measures a voltage of the interconnected battery 301 and a voltage of each of the secondary batteries 301a included in the interconnected battery 301, performs A / D conversion of the measured voltages, and transmits the converted voltages to the controller 310. An ammeter 313 measures a current using the current measuring resistor 307 and transmits the measured current to the controller 310. A switch controller 314 controls the charge control switch 302a and the discharge control switch 303a of the switch 304 based on the voltages input from the voltmeter 311 and the current input from the ammeter 313.

[0082] When the voltage of one of the plurality of secondary batteries 301a reaches or falls below the overcharge voltage, the overdischarge detection voltage, or when a large current suddenly flows, the switch regulator 314 sends a control signal to the switch 304 to prevent overcharge and overdischarge, as well as overcurrent charging and discharging. For example, the overcharge voltage of a lithium-ion secondary battery is typically 4.20 V ± 0.05 V, and the overdischarge detection voltage is 2.4 V ± 0.1 V.

[0083] For example, semiconductor switches such as MOSFETs can be used as charge and discharge switches. In this case, the parasitic diodes of the MOSFETs serve as diodes 302b and 303b. When P-channel FETs are used as charge and discharge switches, the switch controller 314 sends control signals DO and CO to the gate of the charge control switch 302a and the discharge control switch 303a, respectively. If the charge control switch 302a and the discharge control switch 303a are P-channel types, they are turned on by a gate potential that is a certain value lower than the source potential. This means that during normal charge and discharge operations, the control signals CO and DO are set to a low level to turn on the charge control switch 302a and the discharge control switch 303a.

[0084] For example, in the event of overcharging or overdischarging, the control signals CO and DO are set to a high level to turn off the charge control switch 302a and the discharge control switch 303a.

[0085] A memory 317 includes a RAM and a ROM. For example, the memory 317 includes an erasable programmable read-only memory (EPROM) as non-volatile memory. Values such as numerical values calculated by the controller 310 and the internal resistance value of each of the secondary batteries 301a in the initial state, measured during the manufacturing process, are stored in advance in the memory 317 and can be overwritten as needed. Furthermore, by storing the full charge capacity of the secondary battery 301a, the controller 310 can calculate, for example, the remaining capacity.

[0086] A temperature meter 318 measures a temperature using the temperature detecting device 308, performs charge and discharge control when abnormal heat generation occurs, and performs correction in the calculation of the remaining capacity. [2-2. Electric Power Storage System]

[0087] The secondary battery according to the above embodiment of the disclosure can be mounted in or used for power supply of devices including, but not limited to, electronic devices, an electric vehicle, an electric aircraft, and an electric power storage system.

[0088] Examples of electronic devices include laptops, smartphones, tablet terminals, PDAs (i.e., mobile information devices), mobile phones, portable terminals, cordless telephone handsets, portable video recording and playback devices, digital still cameras, e-books, electronic dictionaries, music players, radios, headphones, game consoles, navigation systems, memory cards, pacemakers, hearing aids, power tools, electric razors, refrigerators, air conditioners, televisions, stereo systems, water heaters, microwave ovens, dishwashers, washing machines, clothes dryers, lighting devices, toys, medical devices, robots, road conditioners, and traffic lights.

[0089] Examples of electric vehicles include rail cars, golf carts, electric trolleys, and electric cars, including hybrid electric vehicles. The secondary battery can be used as a motive power source or as an auxiliary power source for one of these electric vehicles. Examples of electric power storage systems include an electrical energy storage source for structures, including homes, or for power generation facilities. Examples

[0090] Examples of the revelation are described. [Example 1]

[0091] As described below, the Fig. 1 was manufactured, after which a battery characteristic evaluation of the secondary battery 1 was performed. The manufactured secondary battery 1 was a lithium-ion secondary battery with a diameter of 21 mm and a length of 70 mm. [Fabrication Method]

[0092] First, a 12 µm-thick aluminum foil was prepared as a 21A positive electrode current collector. Then, a positive electrode mixture was prepared by mixing a layered lithium oxide as the positive electrode active material with a positive electrode binder and a conductive additive. The layered lithium oxide contained lithium nickel cobalt aluminum oxide (NCA) with a nickel content of 85% or more. The positive electrode binder contained polyvinylidene fluoride. The conductive additive contained a mixture of carbon black, acetylene black, and Ketjen black. The mixing ratio of the positive electrode active material, the positive electrode binder, and the conductive additive was set to 96.4:2:1.6.Next, the positive electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a positive electrode mixed slurry in a paste form. Subsequently, the positive electrode mixed slurry was coated onto predetermined areas of the two opposite surfaces of the positive electrode current collector 21A using a coating device, and then dried to form the positive electrode active material layers 21B. Furthermore, a coating material containing polyvinylidene fluoride (PVDF) was coated onto the surfaces of the positive electrode exposure region 212 at respective adjacent positions to the positive electrode covering region 211. The coated coating material was dried to form the insulating layers 101 having a width of 3 mm and a thickness of 8 μm.Subsequently, the positive electrode active material layers 21B were compacted using a roller press. This obtained the positive electrode 21 including the positive electrode covering portion 211 and the positive electrode exposing portion 212. Subsequently, the positive electrode 21 was sheared so that the positive electrode covering portion 211 had a width of 60 mm in the W-axis direction and the positive electrode exposing portion 212 had a width of 7 mm in the W-axis direction. A cross-section of the positive electrode edge portion 212E of the positive electrode exposing portion 212 after shearing was observed with a VHX-6000 microscope manufactured by Keyence Corporation at a magnification ranging from about 500 times to about 2000 times to confirm the formation of the curved surface 21RS and the protrusion 21PR. The length of the positive electrode 21 in the L-axis direction was set to 1700 mm.

[0093] In addition, a copper foil with a thickness of 8 μm was provided as a 22A negative electrode current collector. Then, a negative electrode mixture was prepared by mixing the negative electrode active material with a negative electrode binder and a conductive additive. The negative electrode active material contained a mixture of a carbon material and SiO. The carbon material contained graphite. The negative electrode binder contained polyvinylidene fluoride. The conductive additive contained a mixture of carbon black, acetylene black, and Ketjen black. The mixing ratio between the negative electrode active material, the negative electrode binder, and the conductive additive was set to 96.1:2, 9:1.0. Furthermore, the mixing ratio between graphite and SiO in the negative electrode active material was set to 95:5.Next, the negative electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a negative electrode mixed slurry in a paste form. The negative electrode mixed slurry was then coated onto predetermined areas of the two opposite surfaces of the negative electrode current collector 22A using a coating device, and then dried to form the negative electrode active material layers 22B. Subsequently, the negative electrode active material layers 22B were compacted using a roller press. Thus, the negative electrode 22 having the negative electrode covering portion 221 and the negative electrode exposing portion 222 was obtained.Subsequently, the negative electrode 22 was sheared so that the negative electrode covering region 221 had a width of 62 mm in the W-axis direction and the first portion 222A of the negative electrode exposure region 222 had a width of 4 mm in the W-axis direction. A cross-section of the negative electrode edge region 222E of the negative electrode exposure region 222 after shearing was observed with a VHX-6000 microscope manufactured by Keyence Corporation at a magnification ranging from about 500 times to about 2000 times to confirm the formation of the curved surface 22RS and the protrusion 22PR. The length of the negative electrode 22 in the L-axis direction was set to 1760 mm.

[0094] Subsequently, the positive electrode 21 and the negative electrode 22 were stacked, with the first separator member 23A and the second separator member 23B disposed on the positive electrode 21 and the negative electrode 22, respectively, such that the positive electrode exposure region 212 and the first portion 222A of the negative electrode exposure region 222 were located on opposite sides of each other in the W-axis direction. Thus, the stacked body S20 was manufactured. At this time, the stacked body S20 was manufactured such that the positive electrode active material layers 21B did not protrude beyond the negative electrode active material layers 22B in the W-axis direction. A polyethylene film with a width of 65 mm and a thickness of 14 μm was used as the first separator member 23A and the second separator member 23B, respectively.Subsequently, the stacked body S20 was spirally wound to form the through-hole 26 and a recess near the central axis CL. The fastening tape 46 was attached to the outermost winding of the thus wound stacked body S20. Thus, the electrode winding body 20 was obtained.

[0095] Thereafter, the end surfaces 41 and 42 of the electrode coil body 20 were each locally bent by pressing a 0.5-millimeter-thick flat plate perpendicularly, i.e., in the Z-axis direction, against each of the end surfaces 41 and 42. This formed the grooves 43 radiating in the radial directions (the R directions) from the through-hole 26.

[0096] Subsequently, substantially equal pressures were simultaneously applied in nearly perpendicular directions from above and below to the end surfaces 41 and 42 of the electrode coil body 20. This bent the positive electrode exposure portion 212 and the first portion 222A of the negative electrode exposure portion 222, so that each of the end surfaces 41 and 42 was converted into a flat surface. At this time, the positive electrode edge portions 212E of the positive electrode exposure portion 212 at the end surface 41 were bent toward the through-hole 26, overlapping each other, just as the negative electrode edge portions 222E of the negative electrode exposure portion 222 at the end surface 42 were bent toward the through-hole 26, overlapping each other.Subsequently, the fan-shaped portion 31 of the positive electrode current collecting plate 24 was joined to the end face 41 by laser welding, and the fan-shaped portion 33 of the negative electrode current collecting plate 25 was joined to the end face 42 by laser welding.

[0097] Subsequently, the insulating tapes 53 and 54 were attached to the designated locations of the electrode coil body 20. Next, the tape-shaped portion 32 of the positive electrode current collecting plate 24 was bent and inserted through the hole 12H of the insulating plate 12, while the tape-shaped portion 34 of the negative electrode current collecting plate 25 was bent and inserted through the hole 13H of the insulating plate 13.

[0098] Next, the electrode coil body 20 assembled as described above was inserted into the outer packaging can 11. Then, the bottom portion of the outer packaging can 11 and the negative electrode current collecting plate 25 were welded together. After that, the narrow portion 11S was formed near the open end portion 11N of the outer packaging can 11. Further, the electrolytic solution was poured into the outer packaging can 11, and then the band-shaped portion 32 of the positive electrode current collecting plate 24 and the safety valve mechanism 30 were welded together.

[0099] The electrolyte solution used was a solution containing a solvent prepared by adding fluoroethylene carbonate (FEC) and succinonitrile (SN) to a main solvent, namely ethylene carbonate (EC) and dimethyl carbonate (DMC). The solution also contained LiBF4 and LiPF6 as electrolyte salts. In the lithium-ion secondary battery of this example, the content ratio (weight percent) of EC, DMC, FEC, SN, LiBF4, and LiPF6 in the electrolyte solution was set to 12.7:56.2:12.0:1.0:1.0:17.1.

[0100] Finally, the sealing with the gasket 15, the safety valve mechanism 30 and the battery cover 14 was performed using the narrow area 11S.

[0101] This resulted in the secondary battery of Example 1. [Comparison example 1]

[0102] A secondary battery according to Comparative Example 1 was manufactured in a similar manner to Example 1, except that the projections 21PR were oriented to face the positive electrode current collecting plate 24 as shown in Fig. 11A, and the projections 22PR were aligned to face the negative electrode current collecting plate 25, as shown in Fig. 11B. [Evaluation of battery characteristics]

[0103] As a battery characteristic of the secondary battery of Example 1 obtained as described above and the secondary battery of Comparative Example 1, a DC resistance value was measured. The obtained results are shown in Table 1. Specifically, the DC resistance value was determined by calculating the gradient of the voltage when a discharge current was increased from 0 [A] to 100 [A] within five seconds. Note that in Table 1, the DC resistance value of the secondary battery of Example 1 is expressed as a relative value, with the DC resistance value of the secondary battery of Comparative Example 1 being assumed to be 1. [Table 1] Table 1 Gleichstromwi derstandswert Beispiel 1 0.93 Vergleichs beispiel 1 1

[0104] As shown in Table 1, in Example 1, a reduction of the DC resistance value by about 7% was achieved compared to the DC resistance value of Comparative Example 1. From this result, it was confirmed that the secondary battery according to the disclosure increased the contact areas between the positive electrode 21 and the positive electrode current collecting plate 24 and between the negative electrode 22 and the negative electrode current collecting plate 25, thereby achieving favorable connection states and thus reducing the internal resistance.

[0105] Although the disclosure has been described herein with reference to some embodiments and an example, the configuration of the disclosure is not limited to the configurations illustrated in the above-described embodiments and the example, and therefore can be modified in various ways. For example, in the above embodiment, the plurality of positive electrode edge portions 212E constituting the end surface 41 each include the curved surface 21RS, and the plurality of negative electrode edge portions 222E constituting the end surface 42 each include the curved surface 22RS; however, the disclosure is not limited thereto. For example, in the disclosure, only the plurality of positive electrode edge portions 212E each include the curved surface 21RS, or only the plurality of negative electrode edge portions 222E each include the curved surface 22RS.Alternatively, only some of the plurality of positive electrode edge regions 212E may each have the curved surface 21RS, or only some of the plurality of negative electrode edge regions 222E may each have the curved surface 22RS.

[0106] Furthermore, in the secondary battery according to the disclosure, the positive electrode and the negative electrode are not necessarily arranged in the Fig. 4A and Fig. 5A. For example, one or more slits may be provided in the positive electrode exposure region 212 or the negative electrode exposure region 222. These one or more slits may extend, for example, in the W-axis direction or in an oblique direction to both the W-axis direction and the L-axis direction.

[0107] Furthermore, in the above embodiments and examples, the case where the electrode reaction material is lithium was described; however, the electrode reaction material is not particularly limited thereto. Accordingly, the electrode reaction material may be another alkali metal such as sodium or potassium, or an alkaline earth metal such as beryllium, magnesium, or calcium, as described above. In addition, the electrode reaction material may be another light metal such as aluminum.

[0108] The effects described herein are merely examples, and the effects of the disclosure are not limited thereto.

[0109] The disclosure may have the following embodiments. <1>

[0110] Secondary battery comprising: an electrode winding body, the electrode winding body comprising a stacked body having a first electrode and a second electrode stacked with a separator disposed therebetween, the stacked body being wound around a central axis extending in a first direction, and the electrode winding body having a first end face and a second end face opposite to each other in the first direction; a first electrode current collecting plate facing the first end face of the electrode coil body and connected to the first electrode; and a second electrode current collecting plate facing the second end face of the electrode coil body and connected to the second electrode, wherein the first electrode has a first electrode covering region in which a first electrode current collector is covered with a first electrode active material layer, and a first electrode exposing region in which the first electrode current collector is exposed without being covered by the first electrode active material layer, the first electrode exposure region has a plurality of first edge regions adjacent to each other in a radial direction of the electrode winding body, the plurality of first edge regions being bent toward the central axis and overlapping each other to form the first end surface, and the plurality of first edge regions each having an end having a first curved surface. <2>

[0111] Secondary battery after <1> wherein the end of each of the plurality of first edge portions has a first projection extending toward a side opposite the first electrode current collecting plate. <3>

[0112] Secondary battery after <1> or <2> , where the second electrode has a second electrode covering region in which a second electrode current collector is covered with a second electrode active material layer, and a second electrode exposing region in which the second electrode current collector is exposed without being covered by the second electrode active material layer, and the second electrode exposure portion has a plurality of second edge portions adjacent to each other in the radial direction of the electrode winding body, the plurality of second edge portions being bent toward the central axis and overlapping each other to form the second end surface, and the plurality of second edge portions each having an end having a second curved surface. <4>

[0113] Secondary battery after <3> wherein the end of each of the plurality of second edge portions has a second projection extending toward a side opposite the second electrode current collecting plate. <5>

[0114] Secondary battery according to one of <1> until <4> , wherein the first electrode comprises a negative electrode and the second electrode comprises a positive electrode. <6>

[0115] Secondary battery according to one of <1> until <5> , where the second electrode has a second electrode covering region in which a second electrode current collector is covered with a second electrode active material layer, and a second electrode exposing region in which the second electrode current collector is exposed without being covered by the second electrode active material layer and is connected to the second electrode current collecting plate, and the first electrode current collector comprises a copper foil or a copper alloy foil and the second electrode current collector comprises an aluminum foil or an aluminum alloy foil. <7>

[0116] Secondary battery according to one of <1> until <6> , wherein the first electrode current collecting plate and the first end face are connected to each other by welding. <8>

[0117] Secondary battery according to one of <1> until <7> , where the first electrode current collecting plate comprises nickel, a nickel alloy, copper, a copper alloy or a composite material thereof, and the second electrode current collecting plate comprises aluminum or an aluminum alloy. <9>

[0118] Secondary battery after <6> , wherein the second electrode active material layer comprises a negative electrode active material, wherein the negative electrode active material comprises at least one of silicon, silicon oxide, a carbon-silicon compound, or a silicon alloy. <10>

[0119] Secondary battery after <5> , wherein the first electrode active material layer comprises a positive electrode active material, wherein the positive electrode active material comprises at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide. <11>

[0120] Battery pack comprising: the secondary battery according to one of <1> until <10> ; a controller that controls the secondary battery; and an outer casing that houses the secondary battery. <12>

[0121] A method for producing a secondary battery, the method comprising: Manufacturing a first electrode by selectively forming a first electrode active material layer on a first electrode current collector, the first electrode having a first electrode covering region in which the first electrode current collector is covered with the first electrode active material layer, and a first electrode exposing region in which the first electrode current collector is exposed without being covered by the first electrode active material layer, the first electrode covering region and the first electrode exposing region being adjacent to each other in a first direction and the first electrode extending in a second direction orthogonal to the first direction; Forming a cut surface by cutting the first electrode current collector in the first electrode exposure region along the second direction, the cut surface having a first curved surface and extending in the second direction; Producing a second electrode by selectively forming a second electrode active material layer on a second electrode current collector; Manufacturing an electrode winding body by Producing a stacked body by stacking the first electrode, a first separator, the second electrode and a second separator in this order, and Wrapping the stack body around a central axis extending in the first direction; Forming a first end surface in which a plurality of first edge portions of the wound cut surface of the first electrode, which are adjacent to each other in the radial direction of the electrode winding body, overlap each other by bending the plurality of first edge portions toward the central axis; Connecting a first electrode current collecting plate to the first end face; and connecting a second end face of the electrode winding body to a second electrode current collecting plate, the second end face being located on a side opposite the first end face in the first direction. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2021 / 020237

[0004]

Claims

[1] Secondary battery comprising: an electrode winding body, the electrode winding body comprising a stacked body having a first electrode and a second electrode stacked with a separator disposed therebetween, the stacked body being wound around a central axis extending in a first direction, and the electrode winding body having a first end face and a second end face opposite to each other in the first direction; a first electrode current collecting plate facing the first end face of the electrode coil body and connected to the first electrode; and a second electrode current collecting plate facing the second end face of the electrode coil body and connected to the second electrode, wherein the first electrode has a first electrode covering region in which a first electrode current collector is covered with a first electrode active material layer, and a first electrode exposing region in which the first electrode current collector is exposed without being covered by the first electrode active material layer, the first electrode exposure region has a plurality of first edge regions adjacent to each other in a radial direction of the electrode winding body, the plurality of first edge regions being bent toward the central axis and overlapping each other to form the first end surface, and the plurality of first edge regions each having an end having a first curved surface. [2] The secondary battery according to claim 1, wherein the end of each of the plurality of first edge portions has a first projection extending toward a side opposite to the first electrode current collecting plate. [3] A secondary battery according to claim 1, wherein the second electrode has a second electrode covering region in which a second electrode current collector is covered with a second electrode active material layer, and a second electrode exposing region in which the second electrode current collector is exposed without being covered by the second electrode active material layer, and the second electrode exposure portion has a plurality of second edge portions adjacent to each other in the radial direction of the electrode winding body, the plurality of second edge portions being bent toward the central axis and overlapping each other to form the second end surface, and the plurality of second edge portions each having an end having a second curved surface. [4] The secondary battery according to claim 3, wherein the end of each of the plurality of second edge portions has a second projection extending toward a side opposite to the second electrode current collecting plate. [5] A secondary battery according to any one of claims 1 to 4, wherein the first electrode comprises a negative electrode and the second electrode comprises a positive electrode. [6] Secondary battery according to one of claims 1 to 4, wherein the second electrode has a second electrode covering region in which a second electrode current collector is covered with a second electrode active material layer, and a second electrode exposing region in which the second electrode current collector is exposed without being covered by the second electrode active material layer and is connected to the second electrode current collecting plate, and the first electrode current collector comprises a copper foil or a copper alloy foil and the second electrode current collector comprises an aluminum foil or an aluminum alloy foil. [7] A secondary battery according to any one of claims 1 to 4, wherein the first electrode current collecting plate and the first end face are joined together by welding. [8] Secondary battery according to one of claims 1 to 4, wherein the first electrode current collecting plate comprises nickel, a nickel alloy, copper, a copper alloy or a composite material thereof, and the second electrode current collecting plate comprises aluminum or an aluminum alloy. [9] The secondary battery according to claim 6, wherein the second electrode active material layer comprises a negative electrode active material, the negative electrode active material comprising at least one of silicon, silicon oxide, a carbon-silicon compound, or a silicon alloy. [10] The secondary battery according to claim 5, wherein the first electrode active material layer comprises a positive electrode active material, the positive electrode active material comprising at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide. [11] Battery pack comprising: the secondary battery according to any one of claims 1 to 4; a controller that controls the secondary battery; and an outer casing that houses the secondary battery. [12] A method for producing a secondary battery, the method comprising: Manufacturing a first electrode by selectively forming a first electrode active material layer on a first electrode current collector, the first electrode having a first electrode covering region in which the first electrode current collector is covered with the first electrode active material layer, and a first electrode exposing region in which the first electrode current collector is exposed without being covered by the first electrode active material layer, the first electrode covering region and the first electrode exposing region being adjacent to each other in a first direction and the first electrode extending in a second direction orthogonal to the first direction; Forming a cut surface by cutting the first electrode current collector in the first electrode exposure region along the second direction, the cut surface having a first curved surface and extending in the second direction; Producing a second electrode by selectively forming a second electrode active material layer on a second electrode current collector; Producing an electrode winding body by producing a stacked body by stacking the first electrode, a first separator, the second electrode and a second separator in this order, and Winding the stacked body around a central axis extending in the first direction; Forming a first end surface in which a plurality of first edge portions of the wound cut surface of the first electrode, which are adjacent to each other in the radial direction of the electrode winding body, overlap each other by bending the plurality of first edge portions toward the central axis; Connecting a first electrode current collecting plate to the first end face; and Connecting a second end face of the electrode coil body to a second electrode current collecting plate, the second end face being located on a side opposite the first end face in the first direction.

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