Secondary batteries and battery packs

Abstract

Provided is a secondary battery having excellent operational reliability. This secondary battery comprises an electrode wound body including a positive electrode and a negative electrode, a positive electrode current collector, and a negative electrode current collector. In a state in which the electrode wound body is deployed, a negative electrode active material layer includes a third negative electrode edge that is at a position retracted inward of a first intersection at which an extension line of a first negative electrode edge and an extension line of a second negative electrode edge intersect, and that connects the first negative electrode edge and the second negative electrode edge. A second intersection at which the first negative electrode edge and the third negative electrode edge intersect is positioned between the first intersection and a third intersection at which the first negative electrode edge and a second positive electrode edge intersect.

Description

[Technical Field]

[0001] The present disclosure relates to a secondary battery and a battery pack including the same. [Background technology]

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

[0003] Patent Document 1 proposes a secondary battery that employs a so-called tabless structure to reduce internal resistance and enable charging and discharging at a relatively large current. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 153231 [Patent Document 2] International Publication No. 2021 / 176906 Summary of the Invention [Problem to be solved by the invention]

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

[0006] Therefore, a secondary battery with improved operational reliability is desired. [Means for solving the problem]

[0007] A secondary battery according to an embodiment of the present disclosure includes an electrode winding, a positive electrode current collector, and a negative electrode current collector. The electrode winding is formed by winding a laminate having a longitudinal direction in a first direction and including, in order, a positive electrode, a first separator, a negative electrode, and a second separator, around a central axis extending in a second direction perpendicular to the first direction. The electrode winding has a first end face and a second end face facing each other in the second direction. The positive electrode current collector faces the first end face of the electrode winding and is connected to the positive electrode. The negative electrode current collector faces the second end face of the electrode winding and is connected to the negative electrode. The negative electrode has a negative electrode covering portion in which the negative electrode current collector is covered with a negative electrode active material layer, and a negative electrode exposed portion in which the negative electrode current collector is exposed and not covered by the negative electrode active material layer. The positive electrode has a positive electrode covered portion in which a positive electrode current collector is covered with a positive electrode active material layer, and a positive electrode exposed portion in which the positive electrode current collector is exposed and not covered with the positive electrode active material layer. When the electrode winding body is unfolded, a first negative electrode edge portion on the second end face side extending in the first direction of the negative electrode active material layer is located closer to the second end face than a first positive electrode edge portion on the second end face side extending in the first direction of the positive electrode active material layer. When the electrode winding body is unfolded, a second negative electrode edge portion on the central axis side in the first direction of the negative electrode active material layer is located closer to the central axis than a second positive electrode edge portion on the central axis side in the first direction of the positive electrode active material layer. The negative electrode active material layer further includes a third negative electrode edge portion that connects the first negative electrode edge portion and the second negative electrode edge portion and is located in a position recessed inward from a first intersection point where an extension of the first negative electrode edge portion and an extension of the second negative electrode edge portion intersect. The second intersection point where the first negative electrode edge portion and the third negative electrode edge portion intersect is located between the first intersection point and a third intersection point where an extension of the first negative electrode edge portion and the second negative electrode edge portion intersect. [Effects of the Invention]

[0008] In a secondary battery according to one embodiment of the present disclosure, the negative electrode active material layer includes a first negative electrode edge portion, a second negative electrode edge portion, and a third negative electrode edge portion connecting the first and second negative electrode edge portions, and the third negative electrode edge portion is located in a position recessed inward from a first intersection point where an extension of the first negative electrode edge portion intersects with an extension of the second negative electrode edge portion. This makes it difficult for the negative electrode active material layer to peel off from the negative electrode current collector. This allows for a stable battery reaction over a long period of time, ensuring high reliability.

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

[0010] [Figure 1] FIG. 1 is a cross-sectional view illustrating a configuration of a secondary battery according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing an example of the configuration of a laminate including the positive electrode, negative electrode, and separator shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view showing an example of the cross-sectional structure of the electrode winding body shown in FIG. [Figure 4A] FIG. 4A is a development view of the positive electrode shown in FIG. [Figure 4B] FIG. 4B is a cross-sectional view of the positive electrode shown in FIG. [Figure 5A] FIG. 5A is a development view of the negative electrode shown in FIG. [Figure 5B] FIG. 5B is a cross-sectional view of the negative electrode shown in FIG. [Figure 6] FIG. 6 is an enlarged plan view showing a part of the laminate shown in FIG. [Figure 7A] FIG. 7A is a plan view of the positive electrode current collector plate shown in FIG. [Figure 7B] FIG. 7B is a plan view of the negative electrode current collector plate shown in FIG. [Figure 8] FIG. 8 is a perspective view illustrating a manufacturing process of the secondary battery shown in FIG. [Figure 9] FIG. 9 is a block diagram showing a circuit configuration of a battery pack to which the secondary battery according to an embodiment of the present disclosure is applied. [Figure 10] FIG. 10 is an enlarged plan view showing a part of the laminate of Comparative Example 1. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present disclosure will be described in detail 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 method 1-4. Action and effects 1-5. Variations 2. Application Examples 2-1.Battery pack 2-2. Energy storage system

[0012] <0. Background> Conventionally, secondary batteries have been widely used, each having a positive electrode terminal (positive electrode tab) and a negative electrode terminal (negative electrode tab) for current extraction, electrically connected to the positive and negative electrodes that constitute the battery element. Here, we refer to these as tab-structure secondary batteries. However, in tab-structure secondary batteries, the positive and negative electrode terminals generally have elongated, rectangular shapes, and the areas at the connection points between the positive electrode terminal and the positive electrode and the negative electrode terminal and the negative electrode are small. This increases the electrical resistance at these connections, which can ultimately cause an increase in the battery's internal resistance. In recent years, there has been a demand for charging and discharging at higher load rates. However, when tab-structure secondary batteries are charged at high load rates, the internal temperature of the battery easily rises due to their high internal resistance.

[0013] Therefore, the present applicant has developed a secondary battery with a so-called tabless structure that does not use electrode terminals (tabs) connected to the positive and negative electrodes of the battery element (see, for example, the above-mentioned Patent Document 1). In this tabless structure secondary battery, instead of using positive and negative electrode tabs, a positive electrode current collector plate and a negative electrode current collector plate are used, and these positive and negative electrode current collector plates are connected to the positive and negative electrodes of the battery element over a larger contact surface. Therefore, compared to tab-structure secondary batteries, the internal resistance is very small, making it possible to charge and discharge with a relatively large current.

[0014] In this way, a secondary battery with a tabless structure has the characteristic that its internal resistance is much smaller than that of a secondary battery with a tab structure, and therefore, it is possible to suppress an increase in battery temperature during charging at a high load rate.

[0015] In a secondary battery with a tabless structure, the widthwise end of the positive electrode is bent to form a bonding surface (first end surface) for bonding to the positive electrode current collector plate, and the widthwise end of the negative electrode is bent to form a bonding surface (second end surface) for bonding to the negative electrode current collector plate. In this case, the negative electrode active material layer is subjected to stress, particularly at the widthwise end of the negative electrode. Therefore, the present applicant conducted further research and has proposed a secondary battery with a tabless structure that can alleviate the stress applied to the negative electrode active material layer when the second end surface is formed. This secondary battery is described in detail below.

[0016] <1. Secondary battery> First, a secondary battery according to an embodiment of the present disclosure will be described.

[0017] In this embodiment, a cylindrical lithium-ion secondary battery having a cylindrical external shape will be described as an example. However, the secondary battery of the present disclosure is not limited to a cylindrical lithium-ion secondary battery, and may be a lithium-ion secondary battery having an external shape other than a cylindrical shape, or may be a battery using an electrode reactant other than lithium.

[0018] The charge / discharge principle of a secondary battery is not particularly limited, but the following description focuses on a case where battery capacity is obtained by utilizing the absorption / desorption of an electrode reactant. This secondary battery includes a positive electrode, a negative electrode, and an electrolyte. In this secondary battery, the charge capacity of the negative electrode is larger than the discharge capacity of the positive electrode to prevent deposition of the electrode reactant on the surface of the negative electrode during charging. In other words, the electrochemical capacity per unit area of ​​the negative electrode is set to be larger than the electrochemical capacity per unit area of ​​the positive electrode.

[0019] The type of electrode reactant is not particularly limited as described above, but specifically includes light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, and alkaline earth metals include beryllium, magnesium, and calcium.

[0020] In the following, we will take the case where the electrode reactant is lithium as an example. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is called a lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and desorbed in the ionic state.

[0021] [1-1.Configuration] (Lithium-ion secondary battery 1) 1 shows a cross-sectional configuration along the height direction of a lithium-ion secondary battery 1 (hereinafter simply referred to as secondary battery 1) according to the present embodiment. In the secondary battery 1 shown in FIG. 1, a cylindrical outer can 11 houses an electrode winding body 20 as a battery element.

[0022] Specifically, the secondary battery 1 includes, for example, a pair of insulating plates 12, 13, an electrode winding body 20, a positive electrode current collector 24, and a negative electrode current collector 25 inside an outer can 11. The electrode winding body 20 is a structure in which, for example, a positive electrode 21 and a negative electrode 22 are stacked and wound with a separator 23 interposed therebetween. The electrode winding body 20 is impregnated with an electrolytic solution, which is a liquid electrolyte. The secondary battery 1 may further include, inside the outer can 11, one or more of a positive temperature coefficient (PTC) element and a reinforcing member.

[0023] (Outer can 11) The outer can 11 has, for example, a hollow cylindrical structure with a closed lower end in the Z-axis direction (height direction) and an open upper end. Therefore, the upper end of the outer can 11 is an open end 11N. The outer can 11 is made of a material containing, for example, a metal material such as iron. However, the surface of the outer can 11 may be plated with a metal material such as nickel. The insulating plates 12 and 13 are disposed, for example, facing each other in the Z-axis direction with the electrode winding body 20 sandwiched between them. In this specification, the open end 11N and its vicinity in the Z-axis direction may be referred to as the upper part of the secondary battery 1, and the closed portion of the outer can 11 and its vicinity may be referred to as the lower part of the secondary battery 1.

[0024] (insulating plates 12, 13) Each of the insulating plates 12 and 13 is, for example, a dish-shaped plate having a surface perpendicular to the central axis CL of the wound electrode body 20, i.e., a surface perpendicular to the Z axis in Fig. 1. The insulating plates 12 and 13 are arranged so as to sandwich the wound electrode body 20 therebetween.

[0025] (Crimped structure 11R) At the open end 11N of the outer can 11, for example, a structure in which the battery lid 14 and the safety valve mechanism 30 are crimped via a gasket 15, i.e., a crimped structure 11R, is formed. The outer can 11 is sealed by the battery lid 14 with the electrode wound body 20 and the like housed inside the outer can 11. The crimped structure 11R is a so-called crimped structure and has a bent portion 11P as a so-called crimp portion.

[0026] (Battery cover 14) The battery lid 14 is mainly a closing member that closes the open end 11N when the electrode winding body 20 and the like are housed inside the exterior can 11. The battery lid 14 contains, for example, the same material as the material from which the exterior can 11 is formed. For example, the central region of the battery lid 14 protrudes upward (in the +Z direction). As a result, the peripheral region of the battery lid 14 other than the central region is in contact with, for example, the safety valve mechanism 30.

[0027] (Gasket 15) The gasket 15 is a sealing member interposed mainly between the folded portion 11P of the outer can 11 and the battery lid 14. The gasket 15 seals the gap between the folded portion 11P and the battery lid 14. However, the surface of the gasket 15 may be coated with, for example, asphalt. The gasket 15 contains, for example, one or more types of insulating materials. The type of insulating material is not particularly limited, but examples include polymer materials such as polybutylene terephthalate (PBT) and polypropylene (PP). Among these, polybutylene terephthalate is preferable as the insulating material. This is because the gap between the folded portion 11P and the battery lid 14 is sufficiently sealed while electrically isolating the outer can 11 and the battery lid 14 from each other.

[0028] (Safety valve mechanism 30) The safety valve mechanism 30 is mainly configured to release the internal pressure of the outer can 11 by releasing the sealed state of the outer can 11 as necessary when the pressure inside the outer can 11 (internal pressure) increases. The internal pressure of the outer can 11 increases, for example, due to gas generated by a decomposition reaction of the electrolyte during charging and discharging. The internal pressure of the outer can 11 may also increase due to external heating.

[0029] (Electrode winding body 20) The electrode winding body 20 is a power generating element that promotes charge / discharge reactions, and is housed inside the outer can 11. The electrode winding body 20 includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolytic solution that is a liquid electrolyte.

[0030] FIG. 2 is a developed view of the electrode winding body 20, and schematically illustrates a portion of a laminate S20 including a positive electrode 21, a negative electrode 22, and a separator 23. In the laminate S20 obtained by developing the electrode winding body 20, the positive electrode 21 and the negative electrode 22 are stacked together with the separator 23 interposed therebetween. The separator 23 has, for example, two base materials, namely, a first separator member 23A and a second separator member 23B. Therefore, the electrode winding body 20 has a four-layer laminate S20 in which the positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are stacked in this order. The positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are all substantially strip-shaped members with the W-axis direction as the short side direction and the L-axis direction as the long side direction.

[0031] As shown in FIG. 3 , the electrode winding body 20 is formed by winding the laminate S20 around a central axis CL extending in the Z-axis direction so as to form a spiral shape in a horizontal cross section perpendicular to the Z-axis direction. The laminate S20 is wound in a position in which the W-axis direction roughly coincides with the Z-axis direction. Note that FIG. 3 shows an example of the configuration of the electrode winding body 20 along a horizontal cross section perpendicular to the Z-axis direction. However, in FIG. 3 , the separator 23 is omitted for improved visibility. The electrode winding body 20 has an overall substantially cylindrical appearance. The positive electrode 21 and the negative electrode 22 are wound while maintaining a state in which they face each other with the separator 23 interposed therebetween. A through-hole 26 is formed at the center of the electrode winding body 20 as an internal space. The through-hole 26 is a hole for inserting a winding core for assembling the electrode winding body 20 and an electrode rod for welding.

[0032] The positive electrode 21, the negative electrode 22, and the separator 23 are wound such that the separator 23 is disposed at the outermost and innermost peripheries of the electrode winding body 20. At the outermost periphery of the electrode winding body 20, the negative electrode 22 is disposed outside the positive electrode 21. That is, as shown in FIG. 3 , a positive electrode outermost portion 21out located at the outermost periphery of the positive electrode 21 included in the electrode winding body 20 is disposed inside a negative electrode outermost portion 22out located at the outermost periphery of the negative electrode 22 included in the electrode winding body 20. Here, the positive electrode outermost portion 21out is the outermost portion of the positive electrode 21 in the electrode winding body 20, which corresponds to one full turn. The negative electrode outermost portion 22out is the outermost portion of the negative electrode 22 in the electrode winding body 20. Meanwhile, at the innermost periphery of the electrode winding body 20, the negative electrode 22 is disposed inside the positive electrode 21. That is, as shown in FIG. 3 , a negative electrode innermost circumferential portion 22in located at the innermost periphery of the negative electrode 22 included in the electrode winding body 20 is located inside a positive electrode innermost circumferential portion 21in located at the innermost periphery of the positive electrode 21 included in the electrode winding body 20. Here, the positive electrode innermost circumferential portion 21in is the innermost one-circumferential portion of the positive electrode 21 in the electrode winding body 20. The negative electrode innermost circumferential portion 22in is the innermost one-circumferential portion of the negative electrode 22 in the electrode winding body 20. The number of windings of each of the positive electrode 21, the negative electrode 22, and the separator 23 is not particularly limited and can be set as desired.

[0033] FIG. 4A is a developed view of the positive electrode 21, and schematically illustrates the state before winding. FIG. 4B illustrates a cross-sectional configuration of the positive electrode 21. Note that FIG. 4B illustrates a cross section taken along line IVB-IVB in FIG. 4A as viewed from the arrow direction. The positive electrode 21 includes, for example, a positive electrode current collector 21A and a positive electrode active material layer 21B provided on the positive electrode current collector 21A. The positive electrode active material layer 21B may be provided on only one side of the positive electrode current collector 21A, or on both sides of the positive electrode current collector 21A. FIG. 4B illustrates a case in which the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A. More specifically, the positive electrode current collector 21A includes a positive electrode current collector inner peripheral surface 21A1 facing the winding center of the electrode wound body 20, i.e., facing the central axis CL, and a positive electrode current collector outer peripheral surface 21A2 facing the side opposite the winding center of the electrode wound body 20, i.e., on the opposite side of the positive electrode current collector inner peripheral surface 21A1. The positive electrode 21 has, as the positive electrode active material layer 21B, a positive electrode inner peripheral side active material layer 21B1 covering at least a portion of the positive electrode current collector inner peripheral surface 21A1, and a positive electrode outer peripheral side active material layer 21B2 covering at least a portion of the positive electrode current collector outer peripheral surface 21A2. Note that, in this specification, the positive electrode inner peripheral side active material layer 21B1 and the positive electrode outer peripheral side active material layer 21B2 may be collectively referred to as the positive electrode active material layer 21B without distinction.

[0034] The positive electrode 21 has a positive electrode covering portion 211 in which a positive electrode active material layer 21B is covering a positive electrode current collector 21A, and a positive electrode exposed portion 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 exposed portion 212 each extend along the L-axis direction, which is the longitudinal direction of the positive electrode 21, from the central axis side edge 21E1 to the outer peripheral edge 21E2 of the positive electrode 21. Here, the L-axis direction corresponds to the winding direction of the electrode wound body 20. That is, in the positive electrode 21, the positive electrode active material layer 21B covers the positive electrode current collector 21A from the central axis side edge 21E1 to the outer peripheral edge 21E2 of the positive electrode 21 in the winding direction of the electrode wound body 20. The positive electrode covering portion 211 and the positive electrode exposed portion 212 are adjacent to each other in the W-axis direction, which is the short-side direction of the positive electrode 21. The W-axis direction substantially coincides with the central axis CL. As shown in FIG. 2, in the electrode winding body 20, the central axis side edge 21E1 of the positive electrode innermost circumferential portion 21in is located in a position receding inward from the central axis side edge 22E1 of the negative electrode innermost circumferential portion 22in. The positive electrode 21 also has a lower edge 21E3 extending in the L-axis direction at the lower side of the electrode winding body 20.

[0035] An insulating layer 101 may be provided near the boundary between the positive electrode covering portion 211 and the positive electrode exposed portion 212. Similar to the positive electrode covering portion 211 and the positive electrode exposed portion 212, the insulating layer 101 may extend from the central axis side edge 21E1 to the outer peripheral side edge 21E2 of the electrode winding body 20. The insulating layer 101 may be bonded to at least one of the first separator member 23A and the second separator member 23B. This is because misalignment between the positive electrode 21 and the separator 23 can be prevented. The insulating layer 101 may contain a resin containing polyvinylidene fluoride (PVDF). The PVDF content of the insulating layer 101 allows the insulating layer 101 to swell with, for example, a solvent contained in the electrolyte solution, thereby enabling good adhesion to the separator 23. The detailed configuration of the positive electrode 21 will be described later.

[0036] FIG. 5A is a developed view of the negative electrode 22, and schematically illustrates the state before winding. FIG. 5B illustrates a cross-sectional configuration of the negative electrode 22. Note that FIG. 5B illustrates a cross section taken along 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 provided on the negative electrode current collector 22A. The negative electrode active material layer 22B may be provided on only one side of the negative electrode current collector 22A, or on both sides of the negative electrode current collector 22A. FIG. 5B illustrates a case where the negative electrode active material layer 22B is provided on both sides of the negative electrode current collector 22A. More specifically, the negative electrode current collector 22A includes a negative electrode current collector inner peripheral surface 22A1 facing the winding center of the electrode wound body 20, i.e., facing the central axis CL, and a negative electrode current collector outer peripheral surface 22A2 facing the side opposite the winding center of the electrode wound body 20, i.e., on the opposite side of the negative electrode current collector inner peripheral surface 22A1. The negative electrode 22 has, as the negative electrode active material layer 22B, a negative electrode inner peripheral side active material layer 22B1 covering at least a portion of the negative electrode current collector inner peripheral surface 22A1, and a negative electrode outer peripheral side active material layer 22B2 covering at least a portion of the negative electrode current collector outer peripheral surface 22A2. Note that in this specification, the negative electrode inner peripheral side active material layer 22B1 and the negative electrode outer peripheral side active material layer 22B2 may be collectively referred to as the negative electrode active material layer 22B without distinction.

[0037] The negative electrode 22 has a negative electrode covering portion 221 in which the negative electrode current collector 22A is covered with the negative electrode active material layer 22B, and a negative electrode exposed portion 222 in which the negative electrode current collector 22A is exposed without being covered with the negative electrode active material layer 22B. As shown in FIG. 5A , the negative electrode covering portion 221 and the negative electrode exposed portion 222 each extend along the L-axis direction, which is the longitudinal direction of the negative electrode 22. The negative electrode exposed portion 222 extends from the central axis side edge 22E1 to the outer peripheral edge 22E2 of the negative electrode 22 in the winding direction of the electrode wound body 20. In contrast, the negative electrode covering portion 221 is not provided on the central axis side edge 22E1 or the outer peripheral edge 22E2 of the negative electrode 22. As shown in FIG. 5A , parts of the negative electrode exposed portion 222 are formed to sandwich the negative electrode covering portion 221 in the L-axis direction, which is the longitudinal direction of the negative electrode 22. Specifically, the negative electrode exposed portion 222 includes a first portion 222A, a second portion 222B, and a third portion 222C. The negative electrode 22 further has a lower edge 22E3 extending in the L-axis direction at the lower side of the electrode winding body 20. The first portion 222A is provided adjacent to the negative electrode covering portion 221 in the W-axis direction, and extends in the L-axis direction from the central axis side edge 22E1 to the outer periphery side edge 22E2 of the negative electrode 22. The second portion 222B and the third portion 222C are provided so as to sandwich the negative electrode covering portion 221 in the L-axis direction. The first portion 222A is located near the lower edge 22E3 of the negative electrode 22. The second portion 222B is, for example, Outer peripheral edge 22E2 The third portion 222C is located in the vicinity of the negative electrode 22. Center shaft side edge 22E1 5A and 5B, the negative electrode current collector 22A is shown schematically as extending linearly along the W-axis direction. However, in reality, the negative electrode edge portion 222E of the negative electrode exposed portion 222 is bent toward the central axis CL as shown in FIG. 1 and connected to the negative electrode current collector plate 25. The detailed configuration of the negative electrode 22 will be described later.

[0038] In the laminate S20 of the electrode winding body 20, the positive electrode 21 and the negative electrode 22 are laminated with the separator 23 interposed between them so that the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 face opposite each other along the W-axis direction, which is the width direction. The electrode winding body 20 has the end of the separator 23 fixed by attaching a fixing tape 46 to its side surface portion 45, preventing loosening of the winding.

[0039] In the secondary battery 1, as shown in FIG. 2 , when the width of the positive electrode exposed portion 212 is A and the width of the first portion 222A of the negative electrode exposed portion 222 is B, it is preferable that A>B. For example, when the width A=7 (mm), the width B=4 (mm). Furthermore, when the width of the portion of the positive electrode exposed portion 212 that protrudes from the outer edge of the separator 23 in the width direction is C and the length of the first portion 222A of the negative electrode exposed portion 222 that protrudes from the outer edge on the opposite side in the width direction of the separator 23 is D, it is preferable that C>D. For example, when the width C=4.5 (mm), the width D=3 (mm).

[0040] 1 , at the upper part of the secondary battery 1, of the positive electrode exposed portion 212 wound around the central axis CL, multiple positive electrode edge portions 212E adjacent in the radial direction (R direction) of the electrode wound body 20 are bent toward the central axis CL so as to overlap with each other, thereby constituting an upper end surface 41 of the electrode wound body 20. Similarly, at the lower part of the secondary battery 1, of the negative electrode exposed portion 222 wound around the central axis CL, multiple negative electrode edge portions 222E adjacent in the radial direction (R direction) are bent toward the central axis CL so as to overlap with each other, thereby constituting a lower end surface 42 of the electrode wound body 20. Therefore, the multiple positive electrode edge portions 212E of the positive electrode exposed portion 212 are gathered at the upper end surface 41 of the electrode wound body 20, and the multiple negative electrode edge portions 222E of the negative electrode exposed portion 222 are gathered at the lower end surface 42 of the electrode wound body 20. To improve contact between the positive electrode current collector plate 24 for extracting current and the positive electrode edge portion 212E, the multiple positive electrode edge portions 212E are bent toward the central axis CL and have flat surfaces. Similarly, to improve contact between the negative electrode current collector plate 25 for extracting current and the negative electrode edge portion 222E, the multiple negative electrode edge portions 222E are bent toward the central axis CL and have flat surfaces. Note that the flat surface referred to here does not only include a completely flat surface, but also includes a surface that has some unevenness or surface roughness to the extent that the positive electrode exposed portion 212 and the negative electrode exposed portion 222 can be joined to the positive electrode current collector plate 24 and the negative electrode current collector plate 25, respectively.

[0041] The positive electrode current collector 21A is made of, for example, aluminum foil, as described below. Meanwhile, the negative electrode current collector 22A is made of, for example, copper foil, as described below. In this case, the positive electrode current collector 21A is softer than the negative electrode current collector 22A. That is, the Young's modulus of the positive electrode exposed portion 212 is lower than that of the negative electrode exposed portion 222. For this reason, in one embodiment, it is more preferable that the widths A to D satisfy the relationship A>B and C>D. In this case, when the positive electrode exposed portion 212 and the negative electrode exposed portion 222 are folded simultaneously from both electrode sides with the same pressure, the heights of the folded portions measured from the tip of the separator 23 may be approximately the same for the positive electrode 21 and the negative electrode 22. At this time, the multiple positive electrode edge portions 212E (FIG. 1) of the positive electrode exposed portion 212 are folded and overlap each other appropriately. This facilitates joining of the positive electrode exposed portion 212 and the positive electrode current collector 24. Similarly, the multiple negative electrode edge portions 222E (FIG. 1) of the negative electrode exposed portion 222 are folded and overlap each other to an appropriate degree. This facilitates joining of the negative electrode exposed portion 222 and the negative electrode current collector plate 25. The joining here means joining by, for example, laser welding, but the joining method is not limited to laser welding.

[0042] As shown in FIG. 2 , the portion of the positive electrode exposed portion 212 of the positive electrode 21 that faces the negative electrode 22 across the separator 23 is covered with an insulating layer 101. The insulating layer 101 has a width of, for example, 3 mm in the W-axis direction. The insulating layer 101 covers the entire region of the positive electrode exposed portion 212 of the positive electrode 21 that faces the negative electrode covering portion 221 of the negative electrode 22 with the separator 23 interposed therebetween. The insulating layer 101 can effectively prevent an internal short circuit in the secondary battery 1, for example, when a foreign object enters between the negative electrode covering portion 221 and the positive electrode exposed portion 212. Furthermore, when an impact is applied to the secondary battery 1, the insulating layer 101 absorbs the impact and can effectively prevent bending of the positive electrode exposed portion 212 and a short circuit between the positive electrode exposed portion 212 and the negative electrode 22.

[0043] FIG. 6 is an enlarged plan view showing a part of the laminate S20 in the state where the electrode winding body 20 is unfolded, particularly the vicinity of the central axis side end edge 22E1 of the negative electrode 22. As shown in FIG.

[0044] As shown in FIG. 6 , when the electrode winding body 20 is unfolded, the positive electrode active material layer 21B is defined by an outline including a first positive electrode edge portion 21BE1 on the lower end face 42 side and a second positive electrode edge portion 21BE2 on the central axis CL side. The first positive electrode edge portion 21BE1 extends in the L-axis direction. The second positive electrode edge portion 21BE2 extends in the W-axis direction. Note that the first positive electrode edge portion 21BE1 coincides with the lower edge 21E3, and the second positive electrode edge portion 21BE2 coincides with the central axis-side edge 21E1. Both the first positive electrode edge portion 21BE1 and the second positive electrode edge portion 21BE2 extend linearly. However, the first positive electrode edge portion 21BE1 and the second positive electrode edge portion 21BE2 may have a curved shape or may be serpentine. The first positive electrode edge portion 21BE1 and the second positive electrode edge portion 21BE2 are connected to each other so as to be perpendicular to each other at an intersection point P4, for example.

[0045] On the other hand, when the electrode wound body 20 is unfolded, the negative electrode active material layer 22B is defined by an outline including a first negative electrode edge portion 22BE1 on the lower end face 42 side, a second negative electrode edge portion 22BE2 on the central axis CL side, and a third negative electrode edge portion 22BE3 connecting the first negative electrode edge portion 22BE1 and the second negative electrode edge portion 22BE2. The first negative electrode edge portion 22BE1 extends in the L-axis direction. The second negative electrode edge portion 22BE2 extends in the W-axis direction. The first negative electrode edge portion 22BE1 and the second negative electrode edge portion 22BE2 both extend linearly. The third negative electrode edge portion 22BE3 has a curved shape in the example of FIG. 6. However, the first negative electrode edge portion 22BE1 and the second negative electrode edge portion 22BE2 may have a curved shape or may be serpentine. The third negative electrode edge portion 22BE3 may extend linearly or may be serpentine.

[0046] 6, in the unfolded state of the electrode wound body 20, the formation area of ​​the negative electrode active material layer 22B is larger than the formation area of ​​the positive electrode active material layer 21B. For example, the formation area of ​​the negative electrode active material layer 22B protrudes from the formation area of ​​the positive electrode active material layer 21B in both the L-axis direction and the W-axis direction. Therefore, the first negative electrode edge portion 22BE1 of the negative electrode active material layer 22B is located closer to the lower end surface 42 than the first positive electrode edge portion 21BE1 of the positive electrode active material layer. Furthermore, the second negative electrode edge portion 22BE2 of the negative electrode active material layer 22B is located closer to the central axis CL than the second positive electrode edge portion 21BE2 of the positive electrode active material layer.

[0047] 6, the third negative electrode edge portion 22BE3 passes through a position recessed inward from the intersection point P1 where an extension of the first negative electrode edge portion 22BE1 and an extension of the second negative electrode edge portion 22BE2 intersect. Furthermore, the intersection point P2 where the first negative electrode edge portion 22BE1 and the third negative electrode edge portion 22BE3 intersect is located between the intersection points P1 and P3. The intersection point P3 is the point where the extension of the first negative electrode edge portion 22BE1 and the second positive electrode edge portion 21BE2 intersect.

[0048] The laminate S20 may further satisfy the following conditional expression (1). 0.60≦L2 / L1≦15.00 ……(1) However, as shown in FIG. 6, L1 represents the first distance between the intersection point P1 and the intersection point P2, and L2 represents the second distance between the intersection point P2 and the intersection point P3.

[0049] The first distance L1 may be, for example, 0.2 mm or more and 5.0 mm or less, and the second distance L2 may be, for example, 2 mm or more and 25 mm or less.

[0050] (Insulating tape 53, 54) The secondary battery 1 may further include insulating tapes 53, 54 in the gap between the outer can 11 and the electrode winding body 20. The positive electrode exposed portion 212 and the negative electrode exposed portion 222, which are gathered at the upper end surface 41 and the lower end surface 42, are conductors such as bare metal foil. Therefore, if the positive electrode exposed portion 212 and the negative electrode exposed portion 222 are close to the outer can 11, a short circuit may occur between the positive electrode 21 and the negative electrode 22 through the outer can 11. Furthermore, if the positive electrode current collector plate 24 on the upper end surface 41 comes close to the outer can 11, a short circuit may also occur. For this reason, it is preferable to provide insulating tapes 53, 54 as insulating members. The insulating tapes 53, 54 are, for example, adhesive tapes whose base layer is made of one of polypropylene, polyethylene terephthalate, and polyimide and whose base layer has an adhesive layer on one surface. In order to prevent the installation of the insulating tapes 53, 54 from reducing the volume of the electrode winding body 20, the insulating tapes 53, 54 are positioned so as not to overlap with the fixing tape 46 attached to the side portion 45, and the thickness of the insulating tapes 53, 54 is set to be equal to or less than the thickness of the fixing tape 46.

[0051] (Positive electrode current collector 24 and negative electrode current collector 25) In a typical lithium-ion secondary battery, for example, a lead for current extraction is welded to each of the positive and negative electrodes. However, this increases the internal resistance of the lithium-ion secondary battery and causes the lithium-ion secondary battery to heat up and reach high temperatures during discharge, making it unsuitable for high-rate discharge. Therefore, in the secondary battery 1 of this embodiment, the positive electrode current collector 24 is positioned opposite the upper end face 41, and the negative electrode current collector 25 is positioned opposite the lower end face 42. The positive electrode coating 211 at the upper end face 41 is welded to the positive electrode current collector 24 at multiple points, and the negative electrode coating 221 at the lower end face 42 is welded to the negative electrode current collector 25 at multiple points. This reduces the internal resistance of the secondary battery 1. The flat surfaces of the upper end face 41 and the lower end face 42, as described above, also contribute to the low resistance. The positive electrode current collector 24 is electrically connected to the battery lid 14, for example, via a safety valve mechanism 30. The negative electrode current collector 25 is electrically connected to, for example, the outer can 11. FIG. 7A is a schematic diagram showing an example of the configuration of the positive electrode current collector 24. FIG. 7B is a schematic diagram showing an example of the configuration of the negative electrode current collector 25. The positive electrode current collector 24 is a metal plate made of, for example, aluminum or an aluminum alloy, or a composite material thereof. The negative electrode current collector 25 is a metal plate made of, for example, nickel, a nickel alloy, copper, or a copper alloy, or a composite material of two or more of these.

[0052] As shown in FIG. 7A , the positive electrode current collector 24 has a shape in which a substantially rectangular strip portion 32 is connected to a substantially sector-shaped sector portion 31. A through-hole 35 is formed near the center of the sector portion 31. In the secondary battery 1, the positive electrode current collector 24 is provided such that the through-hole 35 overlaps the through-hole 26 in the Z-axis direction. The hatched portion in FIG. 7A is an insulating portion 32A of the strip portion 32. The insulating portion 32A is a portion of the strip portion 32 to which insulating tape is attached or an insulating material is applied. The portion of the strip portion 32 below the insulating portion 32A is a connecting portion 32B to the sealing plate, which also serves as an external terminal. Note that, as shown in FIG. 1 , if the secondary battery 1 has a battery structure in which the through-hole 26 does not have a metal center pin, the strip portion 32 is unlikely to come into contact with a portion of the negative electrode potential. Therefore, the positive electrode current collector 24 does not need to have the insulating portion 32A. When the positive electrode current collector 24 does not have the insulating portion 32A, the charge / discharge capacity can be increased by widening the width between the positive electrode 21 and the negative electrode 22 by an amount corresponding to the thickness of the insulating portion 32A.

[0053] The shape of the negative current collector 25 shown in FIG. 7B is almost the same as the shape of the positive current collector 24 shown in FIG. 7A. However, the strip portion 34 of the negative current collector 25 is different from the strip portion 32 of the positive current collector 24. The strip portion 34 of the negative current collector 25 is shorter than the strip portion 32 of the positive current collector 24 and does not have a portion corresponding to the insulating portion 32A of the positive current collector 24. The strip portion 34 has round protrusions 37 indicated by multiple circles. During resistance welding, current concentrates on the protrusions 37, melting the protrusions 37 and welding the strip portion 34 to the bottom of the outer can 11. Like the positive current collector 24, the negative current collector 25 has a through hole 36 formed near the center of the sector portion 33. In the secondary battery 1, the negative current collector 25 is provided so that the through hole 36 overlaps with the through hole 26 in the Z-axis direction.

[0054] Due to its planar shape, the sectorial portion 31 of the positive current collector plate 24 covers only a portion of the upper end surface 41. Similarly, due to its planar shape, the sectorial portion 33 of the negative current collector plate 25 covers only a portion of the lower end surface 42. There are two reasons why the sectorial portions 31 and 33 do not cover the entire upper end surface 41 and the entire lower end surface 42. First, this is to allow the electrolyte to smoothly penetrate into the electrode winding body 20 when assembling the secondary battery 1, for example. Second, this is to facilitate the release of gas generated when the lithium-ion secondary battery is subjected to an abnormally high temperature or is overcharged.

[0055] (Positive electrode current collector 21A) The positive electrode current collector 21A contains a conductive material such as aluminum, etc. The positive electrode current collector 21A is, for example, a metal foil made of aluminum or an aluminum alloy.

[0056] (Positive electrode active material layer 21B) The positive electrode active material layer 21B contains, as a positive electrode active material, one or more types of positive electrode materials capable of absorbing and releasing lithium. However, the positive electrode active material layer 21B may further contain one or more types of other materials, such as a positive electrode binder and a positive electrode conductor. The positive electrode material is preferably a lithium-containing compound, more specifically, a lithium-containing composite oxide or a lithium-containing phosphate compound. The lithium-containing composite oxide is an oxide containing lithium and one or more other elements, i.e., elements other than lithium, as constituent elements. The lithium-containing composite oxide has, for example, a layered rock salt type or a spinel type crystal structure. The lithium-containing phosphate compound is a phosphate compound containing lithium and one or more other elements as constituent elements, and has, for example, an olivine type crystal structure. The positive electrode active material layer 21B preferably contains, as a positive electrode active material, at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. The positive electrode binder contains, for example, one or more of synthetic rubber and polymer compounds. Examples of synthetic rubber include styrene-butadiene rubber, fluorine-based rubber, and ethylene propylene diene. Examples of polymer compounds include polyvinylidene fluoride and polyimide. The positive electrode conductive agent contains, for example, one or more of carbon materials. Examples of carbon materials include graphite, carbon black, acetylene black, and ketjen black. However, the positive electrode conductive agent may also be a metal material or a conductive polymer, as long as it is a conductive material.

[0057] (Negative electrode current collector 22A) The negative electrode current collector 22A contains a conductive material such as copper. The negative electrode current collector 22A is a metal foil made of, for example, nickel, a nickel alloy, copper, or a copper alloy. The surface of the negative electrode current collector 22A is preferably roughened. This is because the so-called anchor effect improves the adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A. In this case, it is sufficient that the surface of the negative electrode current collector 22A is roughened at least in the region facing the negative electrode active material layer 22B. The roughening method may be, for example, a method of forming fine particles using an electrolytic process. In the electrolytic process, fine particles are formed on the surface of the negative electrode current collector 22A by electrolysis in an electrolytic bath, resulting in an uneven surface of the negative electrode current collector 22A. Copper foil produced by an electrolytic process is generally called electrolytic copper foil.

[0058] (Negative electrode active material layer 22B) The negative electrode active material layer 22B contains, as the negative electrode active material, one or more types of negative electrode materials capable of absorbing and releasing lithium. However, the negative electrode active material layer 22B may further contain one or more types of other materials, such as a negative electrode binder and a negative electrode conductor. The negative electrode material is, for example, a carbon material. This is because a high energy density can be stably obtained because the crystal structure changes very little during lithium absorption and release. In addition, the carbon material also functions as a negative electrode conductor, thereby improving the conductivity of the negative electrode active material layer 22B. Examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite. However, the interplanar spacing of the (002) plane of non-graphitizable carbon is preferably 0.37 nm or more. The interplanar spacing of the (002) plane of graphite is preferably 0.34 nm or less. More specifically, carbon materials include, for example, pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound calcined bodies, activated carbon, and carbon blacks. Examples of cokes include pitch coke, needle coke, and petroleum coke. Organic polymer compound calcined bodies are obtained by calcining (carbonizing) polymer compounds such as phenolic resins and furan resins at an appropriate temperature. Alternatively, the carbon material may be low-crystalline carbon heat-treated at temperatures below approximately 1000°C, or amorphous carbon. The carbon material may be fibrous, spherical, granular, or flake-shaped. In the secondary battery 1, when the open-circuit voltage at full charge, i.e., the battery voltage, is 4.25 V or higher, the amount of lithium released per unit mass is greater than when the open-circuit voltage at full charge is 4.20 V, even when the same positive electrode active material is used. Therefore, the amounts of positive and negative electrode active materials are adjusted accordingly. This results in a high energy density.

[0059] Further, the negative electrode active material layer 22B may contain, as a negative electrode active material, a silicon-containing material containing at least one of silicon, silicon oxide, carbon-silicon compound, and silicon alloy. The silicon-containing material is a general term for materials containing silicon as a constituent element. However, the silicon-containing material may contain only silicon as a constituent element. Note that the type of the silicon-containing material may be only one type or two or more types. The silicon-containing material can form an alloy with lithium, and may be a simple substance of silicon, an alloy of silicon, a compound of silicon, a mixture of two or more of them, or a material containing one or two or more phases of them. Further, the silicon-containing material may be crystalline, amorphous, or may contain both a crystalline part and an amorphous part. However, since the simple substance described here means a general simple substance, it may contain a trace amount of impurities. That is, the purity of the simple substance is not necessarily limited to 100%. The alloy of silicon contains, for example, any one or two or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as constituent elements other than silicon. The compound of silicon contains, for example, any one or two or more of carbon and oxygen as constituent elements other than silicon. Note that the compound of silicon may contain any one or two or more of the series of constituent elements described for the alloy of silicon as a constituent element other than silicon. Specifically, the alloy of silicon and the compound of silicon are, for example, SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, and SiO v (0 < v ≤ 2) and the like. However, the range of v can be arbitrarily set, and for example, 0.2 < v < 1.4 may also be used.

[0060] (Separator 23) The separator 23 is interposed between the positive electrode 21 and the negative electrode 22. The separator 23 allows lithium ions to pass through while preventing current short-circuiting due to contact between the positive electrode 21 and the negative electrode 22. The separator 23 is made of, for example, one or more types of porous membranes, such as synthetic resins and ceramics, or may be a laminated membrane of two or more types of porous membranes. Examples of synthetic resins include polytetrafluoroethylene, polypropylene, and polyethylene. However, the separator 23 preferably has a substrate made of a single-layer polyolefin porous membrane containing polyethylene. This is because better high-output characteristics can be obtained compared to laminated membranes. When the first separator member 23A and the second separator member constituting the separator 23 are each a single-layer porous membrane made of polyolefin, the thickness of the porous membrane may be, for example, 10 μm or more and 15 μm or less. When the single-layer porous membrane made of polyolefin has a thickness of 10 μm or more, internal short-circuiting can be sufficiently avoided. If the thickness of the single-layer porous film made of polyolefin is 15 μm or less, better discharge capacity characteristics can be obtained. In addition, the surface density of the porous film is, for example, 6.3 g / m 2 More than 8.3g / m 2 The surface density of the single-layer porous film made of polyolefin is preferably 6.3 g / m or less. 2 If the surface density of the single-layer porous film made of polyolefin is 8.3 g / m or more, internal short circuits can be sufficiently avoided. 2 If the content is less than this, better discharge capacity characteristics can be obtained.

[0061] In particular, the separator 23 may include, for example, the porous membrane as the substrate described above and a polymer compound layer provided on one or both sides of the substrate layer. This is because the separator 23 improves adhesion to each of the positive electrode 21 and the negative electrode 22, thereby suppressing distortion of the electrode winding body 20. This suppresses decomposition reactions of the electrolyte and also suppresses leakage of the electrolyte impregnated in the substrate layer, thereby making it difficult for resistance to increase even with repeated charge and discharge, and suppressing battery swelling. The polymer compound layer includes, for example, a polymer compound such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable. However, the polymer compound may be other than polyvinylidene fluoride. To form this polymer compound layer, for example, a solution in which a polymer compound is dissolved in an organic solvent or the like is applied to the substrate layer, and the substrate layer is then dried. Alternatively, the substrate layer may be immersed in the solution and then dried. The polymer compound layer may contain one or more types of insulating particles such as inorganic particles, for example, aluminum oxide and aluminum nitride.

[0062] (electrolyte) The electrolytic solution contains a solvent and an electrolyte salt. However, the electrolytic solution may further contain one or more of other materials such as additives. The solvent contains one or more of non-aqueous solvents such as organic solvents. An electrolytic solution containing a non-aqueous solvent is a so-called non-aqueous electrolytic solution. The non-aqueous solvent contains, for example, a fluorine compound and a dinitrile compound. The fluorine compound contains, for example, at least one of fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, fluorinated carboxylic acid ester, and fluorine ether. In addition, the non-aqueous solvent may contain a nitrile compound other than a dinitrile compound, such as a mononitrile compound or TrinitrileThe dinitrile compound may further contain at least one of the compounds. For example, succinonitrile (SN) is preferable as the dinitrile compound. However, the dinitrile compound is not limited to succinonitrile, and may be other dinitrile compounds such as adiponitrile.

[0063] The electrolyte salt contains, for example, one or more salts such as lithium salts. However, the electrolyte salt may contain, for example, a salt other than lithium salt. The salt other than lithium is, for example, a salt of a light metal other than lithium. Examples of lithium salts 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), and dilithium hexafluorosilicate (Li2S i Examples of suitable electrolyte salts include lithium hexafluorophosphate (LiPF6), lithium chloride (LiCl), and lithium bromide (LiBr). Among these, one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate are preferred, with lithium hexafluorophosphate being more preferred. The content of the electrolyte salt is not particularly limited, but is preferably 0.3 mol / kg to 3 mol / kg relative to the solvent. When the electrolyte solution contains LiPF6 as the electrolyte salt, the LiPF6 concentration in the electrolyte solution is preferably 1.25 mol / kg to 1.45 mol / kg. This is because cycle degradation due to salt consumption (decomposition) during high-load rate charging can be prevented, thereby improving high-load cycle characteristics. When the electrolyte salt further contains LiBF4 in addition to LiPF6, the LiBF4 concentration in the electrolyte solution is preferably 0.001 (wt%) to 0.1 (wt%). This is because cycle deterioration due to salt consumption (decomposition) during high-load rate charging can be more effectively prevented, thereby further improving high-load cycle characteristics.

[0064] [1-2. Operation] In the secondary battery 1 of the present embodiment, for example, during charging, lithium ions are released from the positive electrode 21 and are absorbed into the negative electrode 22 via the electrolyte. In addition, in the secondary battery 1, for example, during discharging, lithium ions are released from the negative electrode 22 and are absorbed into the positive electrode 21 via the electrolyte.

[0065] [1-3. Manufacturing method] A method for manufacturing the secondary battery 1 will be described with reference to Figure 8 in addition to Figures 1 to 7B. Figure 8 is a perspective view illustrating the manufacturing process of the secondary battery shown in Figure 1.

[0066] First, a positive electrode current collector 21A is prepared, and a positive electrode active material layer 21B is selectively formed on the surface of the positive electrode current collector 21A to form a positive electrode 21 having a positive electrode covering portion 211 and a positive electrode exposed portion 212. Next, a negative electrode current collector 22A is prepared, and a negative electrode active material layer 22B is selectively formed on the surface of the negative electrode current collector 22A to form a negative electrode 22 having a negative electrode covering portion 221 and a negative electrode exposed portion 222. A drying process may be performed on the positive electrode 21 and the negative electrode 22. Next, a laminate S20 is produced by stacking the positive electrode 21 and the negative electrode 22 with the first separator member 23A and the second separator member 23B interposed between them such that the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 are opposite each other in the W-axis direction. When producing the laminate S20, the central axis side end of the first separator member 23A and the central axis side end of the second separator member are folded back so that these central axis side ends are sandwiched between the central axis side edge 21E1 of the positive electrode 21 and the negative electrode 22. Then, the laminate S20 is spirally wound so as to form through-holes 26. Furthermore, a fixing tape 46 is attached to the outermost periphery of the spirally wound laminate S20. In this way, the electrode roll 20 is obtained as shown in FIG. 8(A).

[0067] Next, as shown in Fig. 8(B), for example, the edge of a 0.5 mm thick flat plate is pressed perpendicularly against the upper end face 41 and the lower end face 42 of the electrode winding body 20, i.e., in the Z-axis direction, thereby locally bending a portion of the upper end face 41 and a portion of the lower end face 42. As a result, grooves 43 are formed that extend radially from the through-holes 26 in the radial direction (R direction). Note that the number and arrangement of grooves 43 shown in Fig. 8(B) are merely examples and the present disclosure is not limited thereto.

[0068] Next, as shown in FIG. 8C , substantially the same pressure is applied substantially simultaneously from above and below the electrode winding body 20 in a direction approximately perpendicular to the upper end face 41 and the lower end face 42. At this time, for example, a rod-shaped jig is inserted into the through-hole 26. By doing so, the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 are bent so that the upper end face 41 and the lower end face 42 each become flat. At this time, the positive electrode edge portion 212E of the positive electrode exposed portion 212 and the negative electrode edge portion 222E of the negative electrode exposed portion 222 at the upper end face 41 and the lower end face 42 are bent while overlapping toward the through-hole 26. Thereafter, the sector-shaped portion 31 of the positive electrode current collector plate 24 is joined to the upper end face 41 by laser welding or the like, and the sector-shaped portion 33 of the negative electrode current collector plate 25 is joined to the lower end face 42 by laser welding or the like.

[0069] Next, insulating tapes 53 and 54 are attached to predetermined positions of the electrode winding body 20. Thereafter, as shown in Figure 8 (D), the strip portion 32 of the positive current collector plate 24 is bent and inserted into the hole 12H of the insulating plate 12. In addition, the strip portion 34 of the negative current collector plate 25 is bent and inserted into the hole 13H of the insulating plate 13.

[0070] Next, the electrode winding body 20 assembled as described above is inserted into the outer can 11 shown in Figure 8(E), and then the bottom of the outer can 11 is welded to the negative electrode current collector plate 25. After that, a constricted portion 11S is formed near the open end 11N of the outer can 11. Furthermore, after the electrolyte is poured into the outer can 11, the strip portion 32 of the positive electrode current collector plate 24 is welded to the safety valve mechanism 30.

[0071] Next, as shown in FIG. 8(F), the gasket 15, the safety valve mechanism 30, and the battery lid 14 are sealed using the constricted portion 11S.

[0072] Through the above steps, the secondary battery 1 of this embodiment is completed.

[0073] [1-4. Actions and Effects] As described above, in the secondary battery 1 of the present embodiment, when the electrode wound body 20 is unfolded, the negative electrode active material layer 22B includes the first negative electrode edge portion 22BE1, the second negative electrode edge portion 22BE2, and the third negative electrode edge portion 22BE3. The third negative electrode edge portion 22BE3 is located in a position recessed inward from the intersection point P1 where an extension of the first negative electrode edge portion 22BE1 intersects with an extension of the second negative electrode edge portion 22BE2. This reduces the likelihood of peeling or falling off of the negative electrode active material layer 22B from the negative electrode current collector 22A, for example, when the first portion 222A of the negative electrode exposed portion 222 is bent to form the lower end surface 42. For example, when the first negative electrode edge portion 22BE1 and the second negative electrode edge portion 22BE2 perpendicularly intersect at a corner, stress is concentrated at the corner when the first portion 222A of the negative electrode exposed portion 222 is bent. In contrast, in the edge portion of the anode active material layer 22B of the secondary battery 1 of this embodiment, the first anode edge portion 22BE1 and the second anode edge portion 22BE2 are connected by a third anode edge portion 22BE3 that intersects obliquely with both the first anode edge portion 22BE1 and the second anode edge portion 22BE2, which are perpendicular to each other. This reduces stress concentration at the edge portion of the anode active material layer 22B. This allows for a stable battery reaction over a long period of time, ensuring high reliability.

[0074] In particular, if the above-mentioned conditional formula (1) is satisfied, peeling or falling off of the negative electrode active material layer 22B from the negative electrode current collector 22A can be further suppressed, and higher reliability can be ensured.

[0075] <2. Application Examples> The secondary battery 1 according to the embodiment of the present disclosure can be used, for example, as described below.

[0076] [2-1. Battery pack] 9 is a block diagram showing an example of a circuit configuration when a battery according to an embodiment of the present invention (hereinafter referred to as a secondary battery) is applied to a battery pack 300. The battery pack 300 includes a battery pack 301, an exterior, a switch unit 304 including a charge control switch 302a and a discharge control switch 303a, a current detection resistor 307, a temperature detection element 308, and a control unit 310.

[0077] The battery pack 300 includes a positive terminal 321 and a negative terminal 322. When charging, the positive terminal 321 and the negative terminal 322 are connected to the positive terminal and the negative terminal of a charger, respectively, for charging. When using an electronic device, the positive terminal 321 and the negative terminal 322 are connected to the positive terminal and the negative terminal of the electronic device, respectively, for discharging.

[0078] The battery pack 301 is made up of a plurality of secondary batteries 301a connected in series or parallel. The secondary batteries 301a can be the above-described secondary battery 1. Note that, although Fig. 9 shows an example in which six secondary batteries 301a are connected in 2-parallel-3-series (2P3S) configuration, any other connection method may be used, such as n-parallel-m-series (n and m are integers).

[0079] Switch unit 304 includes charge control switch 302a and diode 302b, as well as discharge control switch 303a and diode 303b, and is controlled by control unit 310. Diode 302b has a polarity opposite to the charge current flowing from positive terminal 321 to battery pack 301 and a polarity forward to the discharge current flowing from negative terminal 322 to battery pack 301. Diode 303b has a polarity forward to the charge current and opposite to the polarity of the discharge current. Although switch unit 304 is provided on the + side in FIG. 10, it may also be provided on the - side.

[0080] The charge control switch 302a is controlled by the charge / discharge control unit so that it is turned off when the battery voltage reaches the overcharge detection voltage and so that no charging current flows in the current path of the battery pack 301. After the charge control switch 302a is turned off, only discharging is possible via the diode 302b. Furthermore, the control unit 310 controls the switch so that it is turned off when a large current flows during charging and so that the charging current flows in the current path of the battery pack 301. The discharge control switch 303a is controlled by the control unit 310 so that it is turned off when the battery voltage reaches the overdischarge detection voltage and so that no discharging current flows in the current path of the battery pack 301. After the discharge control switch 303a is turned off, only charging is possible via the diode 303b. Furthermore, the control unit 310 controls the switch so that it is turned off when a large current flows during discharging and so that the discharging current flows in the current path of the battery pack 301.

[0081] Temperature detection element 308 is, for example, a thermistor that is provided near battery pack 301 and measures the temperature of battery pack 301, supplying the measured temperature to control unit 310. Voltage detection unit 311 measures the voltage of battery pack 301 and each secondary battery 301a that constitutes it, A / D converts the measured voltage, and supplies the result to control unit 310. Current measurement unit 313 measures the current using current detection resistor 307 and supplies the measured current to control unit 310. Switch control unit 314 controls charge control switch 302a and discharge control switch 303a of switch unit 304 based on the voltage and current input from voltage detection unit 311 and current measurement unit 313.

[0082] When the voltage of any of the multiple secondary batteries 301a falls below the overcharge detection voltage or the overdischarge detection voltage, or when a large current suddenly flows, the switch control unit 314 sends a control signal to the switch unit 304 to prevent overcharging, overdischarging, and overcurrent charging / discharging. Here, for example, if the secondary battery is a lithium-ion secondary battery, the overcharge detection voltage is set to, for example, 4.20V±0.05V, and the overdischarge detection voltage is set to, for example, 2.4V±0.1V.

[0083] The charge / discharge switches can be semiconductor switches such as MOSFETs. In this case, the parasitic diodes of the MOSFETs function as diodes 302b and 303b. When P-channel FETs are used as the charge / discharge switches, switch control unit 314 supplies control signals DO and CO to the gates of charge control switch 302a and discharge control switch 303a, respectively. When charge control switch 302a and discharge control switch 303a are P-channel, they are turned on by a gate potential that is lower than the source potential by a predetermined value or more. That is, in normal charge and discharge operations, control signals CO and DO are set to low level, and charge control switch 302a and discharge control switch 303a are turned on.

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

[0085] The memory 317 is made up of RAM and ROM, such as non-volatile memory such as EPROM (Erasable Programmable Read Only Memory). The memory 317 stores in advance values ​​calculated by the control unit 310 and the internal resistance value of each secondary battery 301a in its initial state measured during the manufacturing process, and can be rewritten as needed. Furthermore, by storing the full charge capacity of the secondary battery 301a, it is possible to calculate, for example, the remaining capacity together with the control unit 310.

[0086] The temperature detection unit 318 measures the temperature using the temperature detection element 308, and controls charging and discharging when abnormal heat is generated, and corrects the calculation of the remaining capacity.

[0087] [2-2. Energy storage system] The secondary battery according to the embodiment of the present disclosure described above can be mounted on devices such as electronic devices, electric vehicles, electric aircraft, and power storage devices, or can be used to supply power.

[0088] Examples of electronic devices include notebook computers, smartphones, tablet devices, PDAs (personal digital assistants), mobile phones, wearable devices, cordless phone handsets, video movie players, digital still cameras, e-books, electronic dictionaries, music players, radios, headphones, game consoles, navigation systems, memory cards, pacemakers, hearing aids, power tools, electric shavers, refrigerators, air conditioners, televisions, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, lighting equipment, toys, medical equipment, robots, road conditioners, and traffic lights.

[0089] Examples of electric vehicles include railcars, golf carts, electric carts, electric vehicles (including hybrid vehicles), and the like, and the device is used as a driving power source or auxiliary power source for these. Examples of power storage devices include power storage power sources for buildings such as homes, or for power generation facilities. [Example]

[0090] An embodiment of the present disclosure will be described.

[0091] Example 1 As described below, a cylindrical secondary battery 1 shown in Fig. 1 was fabricated, and then its battery characteristics were evaluated. Here, a lithium ion secondary battery having dimensions of 21 mm in diameter and 70 mm in length was fabricated.

[0092] [Production method] First, a 12 μm-thick aluminum foil was prepared as the positive electrode current collector 21A. Next, a layered lithium oxide having a Ni ratio of 85% or more in lithium nickel cobalt aluminum oxide (NCA) was used as the positive electrode active material. A positive electrode binder made of polyvinylidene fluoride was mixed with a conductive additive containing carbon black, acetylene black, and ketjen black to obtain a positive electrode mixture. The mixture ratio of the positive electrode active material, positive electrode binder, and conductive additive was 96.4:2:1.6. Next, the positive electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone) and stirred to prepare a paste-like positive electrode mixture slurry. Next, the positive electrode mixture slurry was applied to predetermined areas on both sides of the positive electrode current collector 21A using a coating device, and the positive electrode mixture slurry was then dried to form the positive electrode active material layer 21B. Furthermore, a coating material containing polyvinylidene fluoride (PVDF) was applied to the surface of the positive electrode exposed portion 212 adjacent to the positive electrode covering portion 211, and the coating material was dried to form an insulating layer 101 having a width of 3 mm and a thickness of 8 μm. The positive electrode active material layer 21B was then compression-molded using a roll press. This resulted in a positive electrode 21 having the positive electrode covering portion 211 and the positive electrode exposed portion 212. The positive electrode 21 was then sheared to set the width of the positive electrode covering portion 211 in the W-axis direction to 60 mm, and the width of the positive electrode exposed portion 212 in the W-axis direction to 7 mm. The length of the positive electrode 21 in the L-axis direction was set to 1,700 mm.

[0093] Additionally, an 8 μm-thick copper foil was prepared as the negative electrode current collector 22A. Next, a negative electrode active material, which was a mixture of a carbon material made of graphite and SiO, a negative electrode binder made of polyvinylidene fluoride, and a conductive additive, which was a mixture of carbon black, acetylene black, and ketjen black, was mixed to obtain a negative electrode mixture. The mixing ratio of the negative electrode active material, the negative electrode binder, and the conductive additive was 96.1:2.9:1.0. The mixing ratio of graphite to SiO in the negative electrode active material was 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 paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to predetermined regions on both sides of the negative electrode current collector 22A using a coating device, and the negative electrode mixture slurry was then dried to form the negative electrode active material layer 22B. Thereafter, the negative electrode active material layer 22B was compression-molded using a roll press. As a result, a negative electrode 22 having a negative electrode covering portion 221 and a negative electrode exposed portion 222 was obtained. Thereafter, the negative electrode 22 was sheared to set the width of the negative electrode covering portion 221 in the W-axis direction to 62 mm and the width of the first portion 222A of the negative electrode exposed portion 222 in the W-axis direction to 4 mm. In addition, the length of the negative electrode 22 in the L-axis direction was set to 1760 mm.

[0094] Next, the positive electrode 21 and the negative electrode 22 were stacked with the first separator member 23A and the second separator member 23B interposed therebetween so that the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 were on opposite sides of each other in the W-axis direction, thereby producing a laminate S20. The laminate S20 was produced so that the positive electrode active material layer 21B did not protrude from the negative electrode active material layer 22B in the W-axis direction. As shown in Table 1 below, the laminate S20 was produced so that the first distance L1 and the second distance L2 were each 3 mm. Polyethylene sheets having a width of 65 mm and a thickness of 14 μm were used as the first separator member 23A and the second separator member 23B. Then, through-holes 26 were formed. I'll As shown, the laminate S20 was spirally wound, and a fixing tape 46 was attached to the outermost periphery of the wound laminate S20. In this way, the electrode wound body 20 was obtained.

[0095] Next, the edges of a 0.5 mm thick flat plate were pressed against the upper end face 41 and the lower end face 42 of the electrode winding body 20 in the Z-axis direction, thereby locally bending the upper end face 41 and the lower end face 42, and creating grooves 43 extending radially from the through hole 26 in the radial direction (R direction).

[0096] Next, substantially the same pressure was applied from above and below the electrode winding body 20 in a direction approximately perpendicular to the upper end face 41 and the lower end face 42 at substantially the same time. As a result, the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 were each folded, making the upper end face 41 and the lower end face 42 flat. At this time, the positive electrode edge portion 212E of the positive electrode exposed portion 212 and the negative electrode edge portion 222E of the negative electrode exposed portion 222 at the upper end face 41 and the lower end face 42 were folded while overlapping toward the through hole 26. Thereafter, the sector-shaped portion 31 of the positive electrode current collector plate 24 was joined to the upper end face 41 by laser welding, and the sector-shaped portion 33 of the negative electrode current collector plate 25 was joined to the lower end face 42 by laser welding.

[0097] Next, insulating tapes 53, 54 were attached to predetermined positions of the electrode winding body 20, and then the strip portion 32 of the positive electrode current collector 24 was bent to insert the strip portion 32 into the hole 12H of the insulating plate 12, and the strip portion 34 of the negative electrode current collector 25 was bent to insert the strip portion 34 into the hole 13H of the insulating plate 13.

[0098] Next, the electrode winding body 20 assembled as described above was inserted into the outer can 11, and the bottom of the outer can 11 and the negative electrode current collector plate 25 were welded together. After that, a constricted portion 11S was formed near the open end 11N of the outer can 11. Furthermore, an electrolyte was poured into the outer can 11, and the strip portion 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 were welded together.

[0099] The electrolyte used was a solvent containing ethylene carbonate (EC) and dimethyl carbonate (DMC) as the main solvent, to which fluoroethylene carbonate (FEC) and succinonitrile (SN) were added, and LiBF4 and LiPF6 were used as electrolyte salts. In the lithium-ion secondary battery of this example, the respective contents (by weight) of EC, DMC, FEC, SN, LiBF4, and LiPF6 in the electrolyte were 12.7:56.2:12.0:1.0:1.0:17.1.

[0100] Finally, the gasket 15, the safety valve mechanism 30, and the battery lid 14 were used to seal the necked portion 11S.

[0101] In this way, a secondary battery serving as Example 1-1 was obtained.

[0102] (Comparative Example 1-1) The secondary battery of Comparative Example 1-1 was fabricated in the same manner as in Example 1-1, except that the first negative electrode edge portion 22BE1 and the second negative electrode edge portion 22BE2 were configured to form a corner portion that intersects perpendicularly with each other at the intersection point P1, as in the laminate S120 shown in Figure 10, i.e., except that the negative electrode active material layer 22B did not have the third negative electrode edge portion 22BE3.

[0103] [Evaluation of battery characteristics] As the battery characteristics of the secondary battery of Example 1-1 and the secondary battery of Comparative Example 1-1 obtained as described above, evaluation of the open circuit voltage and the presence or absence of peeling of the negative electrode active material layer were carried out.

[0104] (Open circuit voltage evaluation) To evaluate the open-circuit voltage, 1,000 secondary batteries were fabricated for each of Example 1-1 and Comparative Example 1-1. Each secondary battery was charged to 4.2 V, and the difference |V2-V1| between the voltage V1 immediately after charging to 4.2 V and the voltage V2 two weeks later was measured. Next, the average value and variance of the difference |V2-V1| for the 1,000 secondary batteries in Example 1-1 and Comparative Example 1-1 were calculated. In each of Example 1-1 and Comparative Example 1-1, if even one sample out of the 1,000 batteries had a measured difference |V2-V1| greater than {(average value - 6) × variance}, it was determined to have an open-circuit voltage defect. The results are shown in Table 1.

[0105] [Table 1]

[0106] (Evaluation of the Presence or Absence of Peeling of the Negative Electrode Active Material Layer) The 1,000 secondary batteries for which the open circuit voltage evaluation was performed in Example 1-1 and Comparative Example 1-1 were disassembled, and the presence or absence of peeling of the anode active material layer 22B at the first anode edge portion 22BE1 and the presence or absence of peeling of the anode active material layer 22B at the second anode edge portion 22BE2 were visually confirmed. The results are also shown in Table 1.

[0107] As shown in Table 1, in Example 1-1, no open-circuit voltage failure occurred, and neither peeling of the anode active material layer 22B at the first anode edge portion 22BE1 nor peeling of the anode active material layer 22B at the second anode edge portion 22BE2 occurred. In contrast, in Comparative Example 1-1, open-circuit voltage failure occurred, and peeling of the anode active material layer 22B at the first anode edge portion 22BE1 and peeling of the anode active material layer 22B at the second anode edge portion 22BE2 also occurred. From these results, it was confirmed that, in the secondary battery of the present disclosure, the presence of the third anode edge portion 22BE alleviates stress concentration at the edge portion of the anode active material layer 22B, enabling a stable battery reaction to be obtained over a long period of time, and ensuring high reliability.

[0108] (Examples 2-1 to 2-8) As shown in Table 2 below, laminates S20 were produced so that the first distance L1 varied within a range of 0.1 mm to 5.5 mm. Except for this, secondary batteries of Examples 2-1 to 2-8 were produced in the same manner as in Example 1-1, and evaluated in the same manner as in Example 1-1. The results are shown in Table 2. The first distance L1 can be adjusted by the coating and drying conditions in the coating process for the positive electrode and negative electrode, the viscosity of the negative electrode slurry, the shape of the slurry discharge port of the coating equipment, and the like.

[0109] [Table 2]

[0110] As shown in Table 2, in Examples 2-1, 2-2, and 2-8, no open-circuit voltage defects occurred, but at least one of peeling of the anode active material layer 22B at the first anode edge 22BE1 and peeling of the anode active material layer 22B at the second anode edge 22BE2 was observed. In contrast, in Examples 2-3 to 2-7, no open-circuit voltage defects occurred, and peeling of the anode active material layer 22B at the first anode edge 22BE1 and peeling of the anode active material layer 22B at the second anode edge 22BE2 did not occur. Therefore, it was found that it is desirable to set L2 / L1 to 0.60 or more and 15.00 or less. It was also found that it is desirable for the first distance L1 to be 0.2 mm or more and 5.0 mm or less.

[0111] (Examples 3-1 to 3-12) As shown in Table 3 below, the laminate S20 was produced so that the second distance L2 varied between 0.0 mm and 27.0 mm. Except for this, the secondary batteries of Examples 3-1 to 3-12 were produced in the same manner as in Example 1-1, and were evaluated in the same manner as in Example 1-1. The results are shown in Table 3. The second distance L2 can be adjusted by changing the positional relationship of the positive electrode 21 with respect to the negative electrode 22 in the electrode winding step.

[0112] [Table 3]

[0113] As shown in Table 3, in Examples 3-1, 3-2, 3-11, and 3-12, no open-circuit voltage defects occurred, but at least one of peeling of the anode active material layer 22B at the first anode edge 22BE1 and peeling of the anode active material layer 22B at the second anode edge 22BE2 was observed. In contrast, in Examples 3-3 to 3-10, no open-circuit voltage defects occurred, and peeling of the anode active material layer 22B at the first anode edge 22BE1 and peeling of the anode active material layer 22B at the second anode edge 22BE2 did not occur. Therefore, it was found that it is desirable to set L2 / L1 to 0.67 or more and 8.33 or less. It was also found that it is desirable for the second distance L2 to be 2.0 mm or more and 25.0 mm or less.

[0114] The present disclosure has been described above with reference to an embodiment and examples, but the configuration of the present disclosure is not limited to the configuration described in the embodiment and examples, and various modifications are possible.

[0115] For example, in the above embodiment and example, the electrode reactant is lithium, but the electrode reactant is not particularly limited. Therefore, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0116] The effects described in this specification are merely examples, and the effects of the present disclosure are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present disclosure.

[0117] The present disclosure may take the following forms. <1> an electrode winding body formed by winding a laminate having a longitudinal direction in a first direction, the laminate including a positive electrode, a first separator, a negative electrode, and a second separator in that order, around a central axis extending in a second direction perpendicular to the first direction, the electrode winding body having a first end face and a second end face opposing each other in the second direction; a positive electrode current collector plate connected to the positive electrode while facing the first end surface of the electrode winding body; a negative electrode current collector plate connected to the negative electrode while facing the second end surface of the electrode winding body; Equipped with the negative electrode has a negative electrode covering portion in which a negative electrode current collector is covered with a negative electrode active material layer, and a negative electrode exposed portion in which the negative electrode current collector is exposed without being covered with the negative electrode active material layer, the positive electrode has a positive electrode covering portion in which a positive electrode current collector is covered with a positive electrode active material layer, and a positive electrode exposed portion in which the positive electrode current collector is exposed without being covered with the positive electrode active material layer, in a state in which the electrode winding body is unfolded, a first negative electrode edge portion of the negative electrode active material layer on the second end face side extending in the first direction is located closer to the second end face than a first positive electrode edge portion of the positive electrode active material layer on the second end face side extending in the first direction, in a state in which the electrode winding body is unfolded, a second negative electrode edge portion of the negative electrode active material layer that extends in the second direction and is closer to the central axis in the first direction is located closer to the central axis than a second positive electrode edge portion of the positive electrode active material layer that extends in the second direction and is closer to the central axis in the first direction, the negative electrode active material layer further includes a third negative electrode edge portion that is located in a position recessed inward from a first intersection point where an extension line of the first negative electrode edge portion and an extension line of the second negative electrode edge portion intersect, and that connects the first negative electrode edge portion and the second negative electrode edge portion, A second intersection point where the first negative electrode edge portion and the third negative electrode edge portion intersect is located between the first intersection point and a third intersection point where the first negative electrode edge portion and an extension line of the second positive electrode edge portion intersect. Secondary battery. <2> The following condition (1) is satisfied: the above <1> The secondary battery described. 0.60≦L2 / L1≦15.00 ……(1) however, L1: The first distance between the first intersection and the second intersection L2: The second distance between the second and third intersections <3> A first distance between the first intersection point and the second intersection point is 0.2 mm or more and 5.0 mm or less. the above <1> or <2> The secondary battery described. <4> A second distance between the second intersection point and the third intersection point is 2 mm or more and 25 mm or less. the above <1> from <3> 10. The secondary battery according to claim 9, wherein the second electrode is a conductor. <5> The positive electrode current collector is an aluminum foil or an aluminum alloy foil, and the negative electrode current collector is a copper foil or a copper alloy foil. the above <1> from <4> 10. The secondary battery according to claim 9, wherein the second electrode is a conductor. <6> The positive electrode current collector and the first end surface are joined by welding, and the negative electrode current collector and the second end surface are joined by welding. the above <1> from <5> 10. The secondary battery according to claim 9, wherein the second electrode is a conductor. <7> the positive electrode current collector plate comprises aluminum or an aluminum alloy; The negative electrode current collector plate contains nickel, a nickel alloy, copper, a copper alloy, or a composite material thereof. the above <1> from <6> 10. The secondary battery according to claim 9, wherein the second electrode is a conductor. <8> The positive electrode active material layer contains a positive electrode active material containing at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. the above <1> from <7> 10. The secondary battery according to claim 9, wherein the second electrode is a conductor. <9> The negative electrode active material layer includes a negative electrode active material containing at least one of silicon, silicon oxide, a carbon silicon compound, and a silicon alloy. the above <1> from <8> 10. The secondary battery according to claim 9, wherein the second electrode is a conductor. <10> The third negative electrode edge portion has a curved shape. the above <1> from <9> 10. The secondary battery according to claim 9, wherein the second electrode is a conductor. <11> the above <1> from <10> a secondary battery according to any one of the above items; a control unit that controls the secondary battery; an exterior body that houses the secondary battery; A battery pack having

Claims

1. An electrode winding body, which is formed by winding a laminate having a first direction as its longitudinal direction and which includes a positive electrode, a first separator, a negative electrode, and a second separator in that order around a central axis extending in a second direction perpendicular to the first direction, and which has a first end face and a second end face which face each other in the second direction; a positive electrode current collector plate connected to the positive electrode while facing the first end surface of the electrode winding body; a negative electrode current collector plate connected to the negative electrode while facing the second end surface of the electrode winding body; Equipped with the negative electrode has a negative electrode covering portion in which a negative electrode current collector is covered with a negative electrode active material layer, and a negative electrode exposed portion in which the negative electrode current collector is exposed without being covered with the negative electrode active material layer, the positive electrode has a positive electrode covering portion in which a positive electrode current collector is covered with a positive electrode active material layer, and a positive electrode exposed portion in which the positive electrode current collector is exposed without being covered with the positive electrode active material layer, in a state in which the electrode winding body is unfolded, a first negative electrode edge portion of the negative electrode active material layer on the second end surface side extending in the first direction is located closer to the second end surface than a first positive electrode edge portion of the positive electrode active material layer on the second end surface side extending in the first direction, in a state in which the electrode winding body is unfolded, a second negative electrode edge portion of the negative electrode active material layer that extends in the second direction and is located closer to the central axis in the first direction is located closer to the central axis than a second positive electrode edge portion of the positive electrode active material layer that extends in the second direction and is located closer to the central axis in the first direction, the negative electrode active material layer further includes a third negative electrode edge portion that is located in a position recessed inward from a first intersection point where an extension line of the first negative electrode edge portion and an extension line of the second negative electrode edge portion intersect, and that connects the first negative electrode edge portion and the second negative electrode edge portion, a second intersection point where the first negative electrode edge portion and the third negative electrode edge portion intersect is located between the first intersection point and a third intersection point where the first negative electrode edge portion and an extension line of the second positive electrode edge portion intersect, The following conditional expression (1) is satisfied: Secondary battery. 0.60≦L2 / L1≦15.00 ……(1) however, L1: First distance between the first intersection and the second intersection L2: Second distance between the second intersection and the third intersection

2. An electrode winding body, which is formed by winding a laminate having a first direction as its longitudinal direction and which includes a positive electrode, a first separator, a negative electrode, and a second separator in that order around a central axis extending in a second direction perpendicular to the first direction, and which has a first end face and a second end face which face each other in the second direction; a positive electrode current collector plate connected to the positive electrode while facing the first end surface of the electrode winding body; a negative electrode current collector plate connected to the negative electrode while facing the second end surface of the electrode winding body; Equipped with the negative electrode has a negative electrode covering portion in which a negative electrode current collector is covered with a negative electrode active material layer, and a negative electrode exposed portion in which the negative electrode current collector is exposed without being covered with the negative electrode active material layer, the positive electrode has a positive electrode covering portion in which a positive electrode current collector is covered with a positive electrode active material layer, and a positive electrode exposed portion in which the positive electrode current collector is exposed without being covered with the positive electrode active material layer, in a state in which the electrode winding body is unfolded, a first negative electrode edge portion of the negative electrode active material layer on the second end surface side extending in the first direction is located closer to the second end surface than a first positive electrode edge portion of the positive electrode active material layer on the second end surface side extending in the first direction, in a state in which the electrode winding body is unfolded, a second negative electrode edge portion of the negative electrode active material layer that extends in the second direction and is located closer to the central axis in the first direction is located closer to the central axis than a second positive electrode edge portion of the positive electrode active material layer that extends in the second direction and is located closer to the central axis in the first direction, the negative electrode active material layer further includes a third negative electrode edge portion that is located in a position recessed inward from a first intersection point where an extension line of the first negative electrode edge portion and an extension line of the second negative electrode edge portion intersect, and that connects the first negative electrode edge portion and the second negative electrode edge portion, a second intersection point where the first negative electrode edge portion and the third negative electrode edge portion intersect is located between the first intersection point and a third intersection point where the first negative electrode edge portion and an extension line of the second positive electrode edge portion intersect, a first distance between the first intersection point and the second intersection point is 0.2 mm or more and 5.0 mm or less; Secondary battery.

3. An electrode winding body, which is formed by winding a laminate having a first direction as its longitudinal direction and which includes a positive electrode, a first separator, a negative electrode, and a second separator in that order, around a central axis extending in a second direction perpendicular to the first direction, and which has a first end face and a second end face which face each other in the second direction; a positive electrode current collector plate connected to the positive electrode while facing the first end surface of the electrode winding body; a negative electrode current collector plate connected to the negative electrode while facing the second end surface of the electrode winding body; Equipped with the negative electrode has a negative electrode covering portion in which a negative electrode current collector is covered with a negative electrode active material layer, and a negative electrode exposed portion in which the negative electrode current collector is exposed without being covered with the negative electrode active material layer, the positive electrode has a positive electrode covering portion in which a positive electrode current collector is covered with a positive electrode active material layer, and a positive electrode exposed portion in which the positive electrode current collector is exposed without being covered with the positive electrode active material layer, in a state in which the electrode winding body is unfolded, a first negative electrode edge portion of the negative electrode active material layer on the second end surface side extending in the first direction is located closer to the second end surface than a first positive electrode edge portion of the positive electrode active material layer on the second end surface side extending in the first direction, in a state in which the electrode winding body is unfolded, a second negative electrode edge portion of the negative electrode active material layer that extends in the second direction and is located closer to the central axis in the first direction is located closer to the central axis than a second positive electrode edge portion of the positive electrode active material layer that extends in the second direction and is located closer to the central axis in the first direction, the negative electrode active material layer further includes a third negative electrode edge portion that is located in a position recessed inward from a first intersection point where an extension line of the first negative electrode edge portion and an extension line of the second negative electrode edge portion intersect, and that connects the first negative electrode edge portion and the second negative electrode edge portion, a second intersection point where the first negative electrode edge portion and the third negative electrode edge portion intersect is located between the first intersection point and a third intersection point where the first negative electrode edge portion and an extension line of the second positive electrode edge portion intersect, a second distance between the second intersection point and the third intersection point is 2 mm or more and 25 mm or less; Secondary battery.

4. The positive electrode current collector is an aluminum foil or an aluminum alloy foil, and the negative electrode current collector is a copper foil or a copper alloy foil. The secondary battery according to claim 1 .

5. The positive electrode current collector and the first end surface are joined by welding, and the negative electrode current collector and the second end surface are joined by welding. The secondary battery according to claim 1 .

6. the positive electrode current collector plate comprises aluminum or an aluminum alloy; The negative electrode current collector plate contains nickel, a nickel alloy, copper, a copper alloy, or a composite material of two or more of these. The secondary battery according to claim 1 .

7. The positive electrode active material layer contains a positive electrode active material containing at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. The secondary battery according to claim 1 .

8. The negative electrode active material layer includes a negative electrode active material containing at least one of silicon, silicon oxide, a carbon silicon compound, and a silicon alloy. The secondary battery according to claim 1 .

9. The third negative electrode edge portion has a curved shape. The secondary battery according to claim 1 .

10. The secondary battery according to any one of claims 1 to 3; a control unit that controls the secondary battery; an exterior body that houses the secondary battery; A battery pack having

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