Secondary battery and battery pack
The secondary battery design with insulating members covering the electrode winding side surfaces addresses reliability issues by preventing contact with the outer can, enhancing safety and reliability through reduced internal short circuits and electrolyte isolation.
Patent Information
- Application Number
- JP2024051119
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-03-27
- Publication Date
- 2025-10-09
Smart Images
Figure 2025150306000001_ABST
Abstract
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 obtaining high energy density. These secondary batteries have a battery element 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 / 020237 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 reliability of secondary batteries.
[0006] Therefore, a highly reliable secondary battery is desired. [Means for solving the problem]
[0007] A secondary battery according to one embodiment of the present disclosure includes an electrode winding in which a laminate including a positive electrode, a negative electrode, and a separator is wound along the longitudinal direction of the laminate and has through-holes penetrating in a width direction perpendicular to the longitudinal direction; a positive electrode current collector plate and a negative electrode current collector plate facing each other with the electrode winding sandwiched between them in the width direction; an electrolyte; and an electrolyte-permeable insulating member through which the electrolyte passes. The electrode winding has a first end face facing the positive electrode current collector plate in the width direction, a second end face facing the negative electrode current collector plate in the width direction, and a side face connecting the first end face and the second end face. The positive electrode has a positive electrode active material layer extending in both the longitudinal direction and the width direction and spaced apart from the positive electrode current collector plate, a positive electrode covered region covered by the positive electrode active material layer, and a positive electrode exposed region adjacent to the positive electrode covered region in the width direction, and a positive electrode current collector foil joined to the positive electrode current collector plate at the positive electrode exposed region. The first end surface is formed by bending the edge of the positive electrode exposed region in the wound state toward the through hole, and the insulating member covers a first end region of the side surface that is adjacent to the first end surface. [Effects of the Invention]
[0008] According to a secondary battery according to an embodiment of the present disclosure, the first end region of the side surface of the electrode winding is covered with an insulating member. This prevents contact between the inner surface of the outer can and the side surface of the electrode winding during assembly or use of the secondary battery. Furthermore, the insulating member allows electrolyte to pass through, preventing a small amount of electrolyte from remaining isolated in a portion of the electrode winding. This prevents a localized overcharge state (local battery) in the electrode winding and suppresses dissolution and precipitation of the positive electrode active material. As a result, the occurrence of an internal short circuit can be prevented.
[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 an example of a vertical cross-sectional structure of a secondary battery according to an embodiment of the present disclosure, taken along a height direction. [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 horizontal 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 6A] 6A is an exploded perspective view illustrating the appearance of the electrode winding body and the insulating member shown in FIG. [Figure 6B] FIG. 6B is a perspective view illustrating the appearance of the electrode winding body with the insulating member attached. [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. 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. 1. Secondary battery 1-1.Configuration 1-2.Operation 1-3. Manufacturing method 1-4. Action and effects 2. Application Examples 2-1.Battery pack 2-2. Energy storage system 3. Variations
[0012] <1. Secondary battery> First, a secondary battery according to an embodiment of the present disclosure will be described.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] [1-1.Configuration] (Lithium-ion secondary battery 1) Fig. 1 shows a vertical cross-sectional configuration along the height direction of a lithium-ion secondary battery 1 (hereinafter simply referred to as secondary battery 1) according to this embodiment. The secondary battery 1 shown in Fig. 1 includes a substantially cylindrical outer can 11 and an electrode winding body 20 as a battery element housed in the outer can 11. Furthermore, the secondary battery 1 includes an outer tube 50 that covers the outer peripheral surface of the outer can 11. In this specification, the height direction of the secondary battery 1 is defined as the Z-axis direction.
[0018] Specifically, the secondary battery 1 includes, for example, a pair of insulating plates 12, 13, an electrode winding 20, a positive electrode current collector 24 as a first electrode current collector, and a negative electrode current collector 25 as a second electrode current collector, inside an outer can 11. The electrode winding 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 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 thermosensitive resistor (PTC) element and a reinforcing member.
[0019] (Outer can 11) The outer can 11 is a container that houses the positive electrode current collector 24, the negative electrode current collector 25, the electrode winding 20, and the like. The outer can 11 has a bottom 11B and a sidewall 11W. The bottom 11B also serves as a negative electrode terminal connected to the negative electrode 22 via the negative electrode current collector 25. The outer can 11 has, for example, a hollow cylindrical structure with a closed lower end in the Z-axis direction and an open upper end. Therefore, the upper end of the outer can 11 is an open end 11N, and the lower end of the outer can 11 is closed by the substantially disk-shaped bottom 11B. Between the open end 11N and the bottom 11B is a sidewall 11W that surrounds the electrode winding 20. The sidewall 11W is erected in the height direction along the outer edge of the bottom 11B to surround the electrode winding 20, and includes an open end 11N on the opposite side to the bottom 11B that is open and allows the electrode winding 20 to be inserted therethrough. The constituent material of the outer can 11 includes, 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, in the Z-axis direction, the open end 11N and its vicinity may be referred to as the upper part of the secondary battery 1, and the portion where the outer can 11 is closed and its vicinity may be referred to as the lower part of the secondary battery 1.
[0020] (Outer tube 50) The outer tube 50 surrounds the side surface 11WS, which is the outer surface of the side wall portion 11W of the outer can 11. However, as shown in Fig. 1, the outer tube 50 may also cover a folded portion 11P (described later) at the upper end of the outer can 11. The outer tube 50 may also cover a part of the bottom surface 11BS, which is the outer surface of the bottom portion 11B of the outer can 11. The outer tube 50 is made of a heat-shrinkable insulating film containing, for example, a polyester-based resin, a polyamide-based resin, or a thermoplastic elastomer resin.
[0021] (Washer 55) A washer 55 is provided in the gap between the exterior tube 50 and the bent portion 11P of the exterior can 11. The washer 55 is an insulating ring member having an opening 55K in the central region within a plane perpendicular to the height direction. A protrusion 14T in the central region of the battery lid 14 is inserted into the opening 55K. The washer 55 can be made of, for example, black modified polyphenylene ether.
[0022] (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.
[0023] (Crimped structure 11R) An open end 11N of the outer can 11 has a structure in which, for example, the battery lid 14 and the safety valve mechanism 30 are crimped via a gasket 15, i.e., a crimped structure 11R. The battery lid 14 seals the outer can 11 with the electrode wound body 20 and other components housed inside. The crimped structure 11R is a so-called crimped structure and has a bent portion 11P as a so-called crimp portion. In addition, a constricted portion 11S is provided between the bent portion 11P and the insulating plate 12, where a portion of the outer can 11 protrudes inward.
[0024] (Battery cover 14) The battery lid 14 is primarily a closing member that closes the open end 11N when the electrode winding body 20 and other components are housed inside the exterior can 11. The battery lid 14 is, for example, a conductor containing the same material as the material from which the exterior can 11 is formed. The battery lid 14 closes the open end 11N of the exterior can 11 and is connected to the positive electrode current collector 24. Therefore, the battery lid 14 also serves as a positive electrode terminal that is connected to the positive electrode 21 via the positive electrode current collector 24. A central region of the battery lid 14 protrudes upward (in the +Z direction), for example. As a result, the peripheral region of the battery lid 14 other than the central region is in contact with, for example, a safety valve mechanism 30.
[0025] (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.
[0026] (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.
[0027] (Electrode winding body 20) The electrode winding body 20 is disposed between a positive electrode current collector 24 and a negative electrode current collector 25. The electrode winding body 20 has an upper end face 41 that faces the positive electrode current collector 24 in the height direction, and a lower end face 42 that faces the negative electrode current collector 25 in the height direction. The electrode winding body 20 is a power generation element that causes charge / discharge reactions to proceed, and is housed inside an 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.
[0028] FIG. 2 is a developed view of the electrode winding body 20. That is, FIG. 2 is a schematic representation of a portion of a laminate S20 in which the electrode winding body 20 is developed. The laminate S20 includes a positive electrode 21, a negative electrode 22, and a separator 23. In the laminate S20, the positive electrode 21 and the negative electrode 22 are stacked with the separator 23 interposed between them. 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 direction as the short side direction and the L direction as the long side direction.
[0029] As shown in FIG. 3 , the electrode winding body 20 is formed by winding the laminate S20 around a through-hole 26 along 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 an orientation in which the W 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. The through-hole extends in the Z-axis direction along the central axis CL and penetrates the electrode winding body 20. Therefore, the laminate S20 is wound around the through-hole .
[0030] 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, respectively. 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 one-turn portion of the positive electrode 21 in the electrode winding body 20. The negative electrode outermost portion 22out is the outermost one-turn 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, the negative electrode innermost circumferential portion 22in, which is located at the innermost periphery of the negative electrode 22 included in the electrode winding body 20, is located inside the positive electrode innermost circumferential portion 21in, which is 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.
[0031] 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 that covers a portion of 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.
[0032] The positive electrode current collector 21A includes a positive electrode covering region 211 covered with the positive electrode active material layer 21B, and a positive electrode exposed region 212 that is not covered with the positive electrode active material layer 21B and extends in the W direction. As shown in FIG. 4A , the positive electrode covering region 211 and the positive electrode exposed region 212 each extend along the L direction, which is the longitudinal direction of the positive electrode 21, from the winding center side edge 21E1 of the positive electrode 21 to the winding outer peripheral side edge 21E2 of the positive electrode 21. Here, the L 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 winding center side edge 21E1 of the positive electrode 21 to the winding outer peripheral side edge 21E2 of the positive electrode 21 in the winding direction of the electrode wound body 20. The positive electrode covering region 211 and the positive electrode exposed region 212 are adjacent to each other in the W direction, which is the short-side direction of the positive electrode 21. The W direction substantially coincides with the central axis CL. The positive electrode active material layer 21B extends in both the L direction, which is the longitudinal direction of the positive electrode 21, and the W direction, which is the width direction perpendicular to the L direction. As shown in FIG. 2, in the electrode wound body 20, the winding center side edge 21E1 of the positive electrode innermost circumferential portion 21 in is positioned more inward than the winding center side edge 22E1 of the negative electrode innermost circumferential portion 22 in. The positive electrode 21 also has a lower edge 21E3 extending in the L direction at the lower side of the electrode wound body 20. Note that FIGS. 4A and 4B schematically depict the positive electrode current collector 21A extending linearly along the W direction. 1, the positive electrode edge portion 212E of the positive electrode exposed region 212 is bent toward the central axis CL and connected to the positive electrode current collector plate 24. That is, the end portion of the positive electrode exposed region 212 in the W direction forms the upper end surface 41 and is connected to the positive electrode current collector plate 24 (see FIG. 1). The upper end surface 41 is formed by bending the positive electrode edge portion 212E of the positive electrode exposed region 212 toward the through-hole 26 in a wound state.
[0033] An insulating layer 101 may be provided near the boundary between the positive electrode covering region 211 and the positive electrode exposed region 212. Similar to the positive electrode covering region 211 and the positive electrode exposed region 212, the insulating layer 101 may extend from the winding center edge 21E1 to the winding outer periphery edge 21E2 of the electrode wound 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.
[0034] FIG. 5A is a developed view of the negative electrode 22, schematically illustrating 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 as a second electrode current collector and a negative electrode active material layer 22B that covers a portion of the negative electrode current collector 22A. The negative electrode active material layer 22B may be provided on only one surface of the negative electrode current collector 22A, or on both surfaces of the negative electrode current collector 22A. FIG. 5B illustrates a case in which the negative electrode active material layer 22B is provided on both surfaces 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 central axis CL and a negative electrode current collector outer peripheral surface 22A2 opposite the negative electrode current collector inner peripheral surface 22A1. The negative electrode 22 includes, 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.
[0035] The negative electrode 22 has a negative electrode covering region 221 in which the negative electrode current collector 22A is covered with the negative electrode active material layer 22B, and a negative electrode exposed region 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 region 221 and the negative electrode exposed region 222 each extend along the L direction. The negative electrode exposed region 222 extends from the center 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 region 221 is not provided on the center edge 22E1 or the outer peripheral edge 22E2 of the negative electrode 22. As shown in FIG. 5A , parts of the negative electrode exposed region 222 are formed to sandwich the negative electrode covering region 221 in the L direction. Specifically, the negative electrode exposed region 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 direction at the lower side of the electrode winding body 20. The first portion 222A is provided adjacent to the negative electrode covering region 221 in the W direction and extends in the L direction from the center side edge 22E1 to the outer peripheral side edge 22E2 of the negative electrode 22. That is, the first portion 222A is a region extending in the W direction from the negative electrode active material layer 22B. The second portion 222B and the third portion 222C are provided to sandwich the negative electrode covering region 221 in the L direction. The first portion 222A is located near the lower edge 22E3 of the negative electrode 22. The second portion 222B is located near the center edge 22E1 of the negative electrode 22, for example, and the third portion 222C is located near the outer peripheral edge 22E2 of the negative electrode 22. Note that FIGS. 5A and 5B schematically illustrate the negative electrode current collector 22A extending linearly along the W direction. However, in reality, the negative electrode edge 222E of the negative electrode exposed region 222 is bent toward the center axis CL as shown in FIG. 1 and connected to the negative electrode current collector 25. That is, the W-direction end of the negative electrode exposed region 222 forms the lower end surface 42 and is connected to the negative electrode current collector 25 (see FIG. 1). The lower end surface 42 is formed by bending the negative electrode edge 222E of the negative electrode exposed region 222 toward the through-hole 26 in a wound state. Note that the detailed configuration of the negative electrode 22 will be described later.
[0036] 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 region 212 and the first portion 222A of the negative electrode exposed region 222 face opposite each other along the width direction W. A fixing tape 46 is attached to a middle region 45M of a side surface 45 of the electrode winding body 20. By attaching the fixing tape 46 to the middle region 45M of the side surface 45, the end of the separator 23 of the electrode winding body 20 is fixed, preventing loosening of the winding.
[0037] In the secondary battery 1, as shown in FIG. 2 , when the width of the positive electrode exposed region 212 is A and the width of the first portion 222A of the negative electrode exposed region 222 is B, it is preferable that A>B. For example, when width A=7 (mm), width B=4 (mm). Furthermore, when the width of the portion of the positive electrode exposed region 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 region 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 width C=4.5 (mm), width D=3 (mm).
[0038] 1 , at the upper part of the secondary battery 1, a plurality of adjacent positive electrode edges 212E in the radial direction (direction R) of the electrode winding 20 in the positive electrode exposed region 212 wound around the central axis CL are bent toward the central axis CL so as to overlap with each other, thereby constituting an upper end surface 41 of the electrode winding 20. Similarly, at the lower part of the secondary battery 1, a plurality of adjacent negative electrode edges 222E in the radial direction (direction R) in the negative electrode exposed region 222 wound around the central axis CL are bent toward the central axis CL so as to overlap with each other, thereby constituting a lower end surface 42 of the electrode winding 20. Therefore, a plurality of positive electrode edges 212E of the positive electrode exposed region 212 are gathered at the upper end surface 41 of the electrode winding 20, and a plurality of negative electrode edges 222E of the negative electrode exposed region 222 are gathered at the lower end surface 42 of the electrode winding 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 region 212 and the negative electrode exposed region 222 can be joined to the positive electrode current collector plate 24 and the negative electrode current collector plate 25, respectively.
[0039] The positive electrode current collector 21A is made of, for example, aluminum foil, as described below. On the other hand, 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 region 212 is lower than that of the negative electrode exposed region 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 region 212 and the negative electrode exposed region 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 edges 212E (FIG. 1) of the positive electrode exposed region 212 are folded and overlap each other to an appropriate extent. This facilitates bonding of the positive electrode exposed region 212 and the positive electrode current collector 24. Similarly, the negative electrode edge portions 222E (FIG. 1) of the negative electrode exposed region 222 are folded and overlap each other to an appropriate degree. This facilitates joining of the negative electrode exposed region 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.
[0040] As shown in FIG. 2 , the portion of the positive electrode exposed region 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 region 212 of the positive electrode 21 that faces the negative electrode covering region 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 region 221 and the positive electrode exposed region 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 region 212 and a short circuit between the positive electrode exposed region 212 and the negative electrode 22.
[0041] (insulating members 53, 54) The secondary battery 1 further includes insulating members 53 and 54 in the gap between the outer can 11 and the electrode wound body 20. The positive electrode exposed region 212 and the negative electrode exposed region 222, which are concentrated on the upper end face 41 and the lower end face 42, are conductors such as bare metal foil. Therefore, if the positive electrode exposed region 212 and the negative electrode exposed region 222 are in close proximity 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 24 on the upper end face 41 comes close to the outer can 11, a short circuit may also occur. For this reason, it is preferable to provide the insulating members 53 and 54 as insulating members. Furthermore, providing the insulating members 53 and 54 can protect the electrode wound body 20 when inserting the electrode wound body 20 into the outer can 11 or when attaching the safety valve mechanism 30 during the manufacturing process described below. Furthermore, by providing insulating members 53, 54, when the electrode winding body 20 expands due to charging, it is possible to prevent the electrode winding body 20 from coming into contact with other components of the secondary battery 1, thereby protecting the electrode winding body 20.
[0042] The insulating member 53 covers at least an upper end region 45T of the side surface 45 that is adjacent to the upper end surface 41. The insulating member 53 may also cover a peripheral region near the outer edge of the upper end surface 41. Specifically, as shown in FIG. 6A , the insulating member 53 includes a first portion 531 and a second portion 532. As shown in FIG. 6B , the insulating member 53 is attached to the electrode wound body 20 so that the first portion 531 covers the upper end region 45T and the second portion 532 covers the peripheral region of the upper end surface 41. The first portion 531 of the insulating member 53 is sandwiched between the side surface 45 of the electrode wound body 20 and the inner surface of the outer can 11. The positive electrode current collector 24 may be sandwiched between the upper end surface 41 and the second portion 532 of the insulating member 53. The first portion 531 of the insulating member 53 is provided in the upper end region 45T of the electrode winding 20 so as to wrap around the central axis CL of the electrode winding 20. FIG. 6A is an exploded perspective view illustrating the appearance of the electrode winding 20 and the insulating members 53 and 54, and FIG. 6B is a perspective view illustrating the appearance of the electrode winding 20 with the insulating members 53 and 54 attached thereto. The insulating member 53 may be in contact with the fixing tape 46 provided in the intermediate region 45M, but it is preferable that it not overlap with the fixing tape 46. This is to avoid unnecessary space being generated between the side wall portion 11W of the outer can 11 and the side surface 45 of the electrode winding 20 and to ensure sufficient volume for the electrode winding 20. For the same reason, the thickness of the insulating member 53 is preferably equal to or less than the thickness of the fixing tape 46. The insulating member 53 may be fixed to the electrode winding 20 by adhesion, fusion, or by another insulating member. The insulating member 53 is a specific example that corresponds to an "insulating member" according to one aspect of the present disclosure. The upper end region 45T is a specific example that corresponds to a "first end region" according to one aspect of the present disclosure.
[0043] The insulating member 54 covers at least a lower end region 45B of the side surface 45 that is adjacent to the lower end surface 42. The insulating member 54 may also cover a peripheral region near the outer edge of the lower end surface 42. Specifically, as shown in FIG. 6A , the insulating member 54 includes a first portion 541 and a second portion 542. As shown in FIG. 6B , the insulating member 54 is attached to the electrode wound body 20 so that the first portion 541 covers the lower end region 45B and the second portion 542 covers the peripheral region of the lower end surface 42. The first portion 541 of the insulating member 54 is sandwiched between the side surface 45 of the electrode wound body 20 and the inner surface of the outer can 11. The negative electrode current collector 25 may be sandwiched between the lower end surface 42 and the second portion 542 of the insulating member 54. The first portion 541 of the insulating member 54 is provided in the lower end region 45B of the electrode winding 20 so as to wrap around the central axis CL of the electrode winding 20. The insulating member 54 may be in contact with the fixing tape 46 provided in the middle region 45M, but it is preferable that the insulating member 54 does not overlap with the fixing tape 46. This is to avoid unnecessary space being generated between the side wall portion 11W of the outer casing 11 and the side surface 45 of the electrode winding 20 and to ensure a sufficient volume of the electrode winding 20. For the same reason, the thickness of the insulating member 54 is preferably equal to or less than the thickness of the fixing tape 46. The insulating member 54 may also be fixed to the electrode winding 20 by adhesion, fusion, or by another insulating member. The insulating member 54 is a specific example that corresponds to a "protective member" according to one aspect of the present disclosure. The lower end region 45B is a specific example that corresponds to a "second end region" according to one aspect of the present disclosure.
[0044] The insulating members 53 and 54 are made of a material that has electrical insulation properties and electrolyte permeability, allowing the electrolyte to pass through. The insulating members 53 and 54 are, for example, stretched films, porous films, or nonwoven fabrics. The insulating members 53 and 54 have a resistance of, for example, 35 sec / 100 cm 3 ] or more 3000[sec / 100cm 3 It is recommended that the air permeability be 35 sec / 100 cm or less. 3 ] or more, the thickness will be sufficient to ensure insulation. 3] or less, good electrolyte permeability can be obtained. The insulating members 53, 54 may be made of the same material as the base material of the separator 23, specifically a polyolefin porous film.
[0045] (Positive electrode current collector 24 and negative electrode current collector 25) In a typical lithium-ion secondary battery, for example, one 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 covering region 211 on the upper end face 41 is welded to the positive electrode current collector 24 at multiple points, and the negative electrode covering region 221 on 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 located between the battery cover 14 and the upper end face 41. The positive current collector 24 is electrically connected to the battery lid 14 via, for example, a safety valve mechanism 30. The negative current collector 25 is provided between the bottom 11B and the lower end surface 42 of the outer can 11. The negative current collector 25 is electrically connected to, for example, the inner surface of the bottom 11B of the outer can 11. FIG. 7A is a developed view showing an example of the configuration of the positive current collector 24. FIG. 7B is a developed view showing an example of the configuration of the negative current collector 25. The positive current collector 24 is a metal plate made of, for example, aluminum or an aluminum alloy, or a composite material thereof. The negative 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.
[0046] As shown in FIG. 7A , the positive current collector 24 has a sector-shaped portion 31 that is substantially sector-shaped and a strip-shaped portion 32 that is substantially rectangular. However, the shape of the positive current collector 24 is not limited to the shape shown in FIG. 7A and can be selected arbitrarily. In the secondary battery 1, the positive current collector 24 is housed in the outer can 11 with the strip-shaped portion 32 folded relative to the sector-shaped portion 31, as shown in FIG. 1 . FIG. 7A shows the positive current collector 24 in an unfolded state. The sector-shaped portion 31 is a facing portion that faces and is connected to the upper end face 41. The sector-shaped portion 31 has an outer edge that includes, for example, straight and curved portions. An opening 35 is formed near the center of the sector-shaped portion 31. FIG. 7A illustrates a case in which the opening 35 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction. The strip-shaped portion 32 is connected to, for example, a straight portion of the outer edge of the sector-shaped portion 31. The strip-shaped portion 32 extends in a direction intersecting the straight portion of the sector-shaped portion 31. As shown in Fig. 1, in the secondary battery 1, the positive electrode current collector plate 24 is provided so that the opening 35 overlaps with the through-hole 26 in the Z-axis direction. That is, the opening 35 is provided at a position that overlaps with a part of the upper end surface 41 on the winding center side in the Z-axis direction.
[0047] The shaded portion in FIG. 7A is the insulating portion 32A of the strip portion 32. The insulating portion 32A is a portion of the strip portion 32 to which an insulating member is attached or to which an insulating material is applied. The portion of the strip portion 32 below the insulating portion 32A is a connection portion 32B to the sealing plate, which also serves as an external terminal. The sealing plate is electrically connected to the battery cover 14. Note that, as shown in FIG. 1, if the secondary battery 1 has a battery structure without a metal center pin in the through-hole 26, the strip portion 32 is unlikely to come into contact with a portion at the negative electrode potential. Therefore, the positive electrode current collector 24 may not have the insulating portion 32A. If the positive electrode current collector 24 does not have the insulating portion 32A, the charge / discharge capacity can be increased by increasing the width between the positive electrode 21 and the negative electrode 22 by an amount corresponding to the thickness of the insulating portion 32A.
[0048] The shape of the negative electrode current collector 25 shown in FIG. 7B is almost the same as the shape of the positive electrode current collector 24 shown in FIG. 7A. The negative electrode current collector 25 has a substantially sector-shaped fan portion 33 and a substantially rectangular strip portion 34. However, the shape of the negative electrode current collector 25 is not limited to the shape shown in FIG. 7B and can be selected arbitrarily. In the secondary battery 1, the negative electrode current collector 25 is housed in the outer can 11 with the strip portion 34 folded relative to the fan portion 33, as shown in FIG. 1. FIG. 7B shows the negative electrode current collector 25 in an unfolded state. The fan portion 33 is a facing portion that faces and is connected to the lower end surface 42. The fan portion 33 has an outer edge that includes, for example, a straight portion and a curved portion. The strip portion 34 is connected to, for example, the straight portion of the outer edge of the fan portion 33. The strip portion 34 extends in a direction that intersects with the straight portion of the fan portion 33. 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 a plurality of circular protrusions 37 indicated by circles. At least some of the protrusions 37 are welded to the bottom 11B of the outer can 11. During resistance welding, current concentrates on the protrusions 37, melting the protrusions 37 and welding the strip portion 34 to the bottom 11B of the outer can 11. Similar to the positive current collector 24, the negative current collector 25 has an opening 36 formed near the center of the sector portion 33. In the secondary battery 1, the negative current collector 25 is provided with the opening 36 overlapping the through-hole 26 in the Z-axis direction. FIG. 7B illustrates an example in which the opening 36 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction.
[0049] Due to its planar shape, the sector-shaped portion 31 of the positive current collector 24 covers only a portion of the upper end surface 41. Similarly, due to its planar shape, the sector-shaped portion 33 of the negative current collector 25 covers only a portion of the lower end surface 42. There are two reasons why the sector-shaped portions 31 and 33 do not cover the entire upper end surface 41 and the entire lower end surface 42. The first reason is to allow the electrolyte to smoothly penetrate into the electrode winding 20, for example, when assembling the secondary battery 1. In particular, in the secondary battery 1 of this embodiment, the positive current collector 24 is provided so that the opening 35 overlaps with a portion of the upper end surface 41 on the winding center side in the Z-axis direction. Therefore, a portion of the positive edge portion 212E constituting the upper end surface 41 is not covered by the sector-shaped portion 31 of the positive current collector 24 and is exposed to the opening 35. Therefore, the secondary battery 1 has a structure that allows the electrolyte to penetrate into the electrode winding 20 more quickly. The second reason is to facilitate the release of gas generated when the lithium ion secondary battery is in an abnormally high temperature state or is overcharged.
[0050] (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.
[0051] (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.
[0052] (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.
[0053] (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.
[0054] 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 single silicon, a silicon alloy, a silicon compound, a mixture of two or more of them, or a material containing one or two or more phases of them. Also, the silicon-containing material may be crystalline, amorphous, or may contain both a crystalline part and an amorphous part. However, since the single substance described here means only a general single substance, it may contain a trace amount of impurities. That is, the purity of the single substance is not necessarily limited to 100%. The silicon alloy 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 silicon compound contains, for example, any one or two or more of carbon and oxygen as constituent elements other than silicon. Note that the silicon compound may contain any one or two or more of the series of constituent elements described for the silicon alloy as constituent elements other than silicon. Specifically, the silicon alloy and the silicon compound 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), etc. However, the range of v can be arbitrarily set, and for example, 0.2 < v < 1.4 may also be possible.
[0055] (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.
[0056] 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.
[0057] (electrolyte) The electrolyte solution contains a solvent and an electrolyte salt. However, the electrolyte solution may further contain one or more other materials such as additives. The solvent contains one or more non-aqueous solvents such as organic solvents. An electrolyte solution containing a non-aqueous solvent is a so-called non-aqueous electrolyte solution. The non-aqueous solvent contains, for example, a fluorine compound and a dinitrile compound. The fluorine compound includes, for example, at least one of fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, fluorinated carboxylic acid ester, and fluorinated ether. The non-aqueous solvent may further contain a nitrile compound other than the dinitrile compound, such as at least one of a mononitrile compound and a trinitrile compound. As the dinitrile compound, succinonitrile (SN) is preferable. However, the dinitrile compound is not limited to succinonitrile, and may be other dinitrile compounds such as adiponitrile.
[0058] The electrolyte salt includes, for example, one or more salts such as lithium salts. However, the electrolyte salt may include, for example, salts other than lithium salts. The salts other than lithium include, for example, salts of light metals other than lithium. Examples of lithium salts include lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SF6), 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 deterioration due to salt consumption (decomposition) during high-load rate charging can be prevented, thereby improving high-load cycle performance. When the electrolyte solution 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 performance.
[0059] [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.
[0060] [1-3. Manufacturing method] A method for manufacturing the secondary battery 1 will be described with reference to Fig. 8 in addition to Figs. 1 to 7. Fig. 8 is a perspective view illustrating the manufacturing process of the secondary battery shown in Fig. 1.
[0061] 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. Then, an insulating layer 101 is formed on the surface of the positive electrode current collector 21A along a first edge 21BT1 of the positive electrode active material layer 21B. The above operations result in a positive electrode 21. 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, thereby forming a negative electrode 22 having a negative electrode covering region 221 and a negative electrode exposed region 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 so that the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222 are opposite each other in the W-axis direction. Thereafter, the laminate S20 is spirally wound so as to form the through-holes 26. At this time, for example, a cylindrical winding core is used as a jig, and the laminate S20 is wound around the cylindrical winding core. Furthermore, a fixing tape 46 is attached to the outermost periphery of the spirally wound laminate S20, and then the winding core is removed. In this way, the electrode wound body 20 is obtained as shown in FIG. 8(A).
[0062] Next, for example, the tip of a plate-like member having a wedge-shaped cross section 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, to locally bend a portion of the upper end face 41 and a portion of the lower end face 42 (first press). As a result, as shown in FIG. 8B, a plurality of grooves 43 extending radially from the through-holes 26 in the radial direction (R direction) are created in each of the upper end face 41 and the lower end face 42. Note that the number and arrangement of the grooves 43 shown in FIG. 8B are merely examples and the present disclosure is not limited thereto.
[0063] Next, substantially the same pressure is applied substantially simultaneously from above and below the electrode winding 20 to the upper end face 41 and the lower end face 42 in a direction approximately perpendicular to the electrode winding 20 (secondary pressing). At this time, a rod-shaped jig, for example, is inserted into the through-hole 26. By doing so, as shown in FIG. 8C , the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222 are each bent so that the upper end face 41 and the lower end face 42 each become flat. At this time, it is preferable that multiple adjacent portions of the positive electrode edge portion 212E of the positive electrode exposed region 212 located on the upper end face 41 bend toward the through-hole 26 so as to overlap with each other in the radial direction of the electrode winding 20. Similarly, it is preferable that multiple adjacent portions of the negative electrode edge portion 222E of the negative electrode exposed region 222 located on the lower end face 42 bend toward the through-hole 26 so as to overlap with each other in the radial direction of the electrode winding 20. Thereafter, the sectorial portion 31 of the positive current collector plate 24 is joined to the upper end face 41 by laser welding or the like, and the sectorial portion 33 of the negative current collector plate 25 is joined to the lower end face 42 by laser welding or the like.
[0064] 8(D), insulating members 53 and 54 are attached to predetermined positions of the electrode winding body 20. Thereafter, 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.
[0065] 8(E), the electrode winding body 20 assembled as described above is inserted into the outer can 11, and then the bottom 11B 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.
[0066] 8(F), the outer can 11 is sealed using the gasket 15, the safety valve mechanism 30, and the battery lid 14, utilizing the constricted portion 11S. Finally, the outer can 11, with the washer 55 attached to the battery lid 14, is covered with the outer tube 50, and the outer tube 50 is heated and shrunk by applying hot air to the outer tube 50, for example, and the outer tube 50 is then tightly attached to the outer surface of the outer can 11.
[0067] Through the above steps, the secondary battery 1 of this embodiment is completed.
[0068] [1-4. Actions and Effects] In this way, in the secondary battery 1 of this embodiment, the upper end region 45T and the lower end region 45B of the side surface 45 of the electrode winding body 20 are covered with insulating members 53, 54, so that when assembling the secondary battery 1 or using the secondary battery 1, contact between, for example, the inner surface of the outer can 11 and the side surface 45 of the electrode winding body 20 can be avoided.
[0069] Furthermore, because the insulating members 53 and 54 have the property of allowing the electrolyte to permeate, it is possible to prevent a small amount of electrolyte from remaining in a portion of the electrode winding 20, particularly near the outermost portion of the electrode winding 20. This prevents the occurrence of an overcharged state (local battery) in a localized portion of the electrode winding 20, and suppresses dissolution and precipitation of the positive electrode active material. Furthermore, it is possible to prevent a small amount of electrolyte from entering the gap between the side surface 45 of the electrode winding 20 and the inner surface of the outer can 11. This prevents the occurrence of an overcharged state (local battery) in a localized portion inside the secondary battery 1, which can lead to a localized overheating. As a result, dissolution and precipitation of the metal (mainly Fe) constituting the outer can 11 is suppressed. For these reasons, the secondary battery 1 of this embodiment can ensure excellent reliability while reducing the internal resistance of the secondary battery 1.
[0070] Furthermore, if the secondary battery is a lithium ion secondary battery, sufficient battery capacity can be stably obtained by utilizing the absorption and desorption of lithium, and therefore higher battery performance can be obtained.
[0071] <2. Application Examples> The secondary battery 1 according to the embodiment of the present disclosure can be used, for example, as described below.
[0072] [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.
[0073] 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.
[0074] 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).
[0075] 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. 9, it may also be provided on the - side.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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.
[0083] [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.
[0084] 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.
[0085] 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]
[0086] An embodiment of the present disclosure will be described.
[0087] [Production method] Example 1 As explained below, a cylindrical secondary battery was fabricated as shown in Figure 1. Here, a lithium-ion secondary battery with nominal dimensions of 21 mm in diameter and 70 mm in length was fabricated.
[0088] 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 region 212 adjacent to the positive electrode covering region 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 region 211 and the positive electrode exposed region 212. The positive electrode 21 was then sheared to set the width of the positive electrode covering region 211 in the W direction to 60 mm, and the width of the positive electrode exposed region 212 in the W direction to 7 mm. The length of the positive electrode 21 in the L direction was set to 1,700 mm.
[0089] 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 region 221 and a negative electrode exposed region 222 was obtained. Thereafter, the negative electrode 22 was sheared to set the width in the W direction of the negative electrode covering region 221 to 62 mm and the width in the W direction of the first portion 222A of the negative electrode exposed region 222 to 4 mm. In addition, the length in the L direction of the negative electrode 22 was set to 1760 mm.
[0090] 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 region 212 and the first portion 222A of the negative electrode exposed region 222 were on opposite sides of each other in the W 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 direction. Polyethylene sheets having a width of 65 mm and a thickness of 5 μm were used as the first separator member 23A and the second separator member 23B. The laminate S20 was then spirally wound to form through-holes 26, and a fixing tape 46 was attached to the middle region 45M of the side surface 45 of the wound laminate S20.
[0091] 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).
[0092] Next, substantially the same pressure was applied from above and below the electrode winding body 20 in a direction substantially perpendicular to the upper end face 41 and the lower end face 42 at substantially the same time. This bent the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222, respectively, to form flat surfaces on the upper end face 41 and the lower end face 42. At this time, the positive electrode edge portion 212E of the positive electrode exposed region 212 and the negative electrode edge portion 222E of the negative electrode exposed region 222 at the upper end face 41 and the lower end face 42 were folded while overlapping toward the through-holes 26. Thereafter, the sector-shaped portion 31 of the positive current collector 24 was joined to the upper end face 41 by laser welding, and the sector-shaped portion 33 of the negative current collector 25 was joined to the lower end face 42 by laser welding. The positive current collector 24 used had a sector-shaped portion 31 with an opening 35 having an inner diameter D35 of 4.0 mm.
[0093] Next, insulating members 53 and 54 were attached to predetermined positions of the electrode wound body 20. A 20 μm-thick polyolefin porous film was used as the insulating members 53 and 54. One circumference of the insulating member 53 was attached to the upper end region 45T, and one circumference of the insulating member 54 was attached to the lower end region 45B. The electrolyte permeation time of the insulating members 53 and 54 was 1 second. The electrolyte permeation time here refers to the time required for 20 μL of electrolyte solution dropped onto the surface of the insulating members 53 and 54 to permeate to the back surface of the insulating members 53 and 54. The air permeability was measured according to the Gurley test method described in JIS P8117:2009. Thereafter, 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.
[0094] Next, the electrode winding body 20 assembled as described above was inserted into the outer can 11, and then the bottom 11B of the outer can 11 was welded to the negative electrode current collector plate 25. The inner diameter D11 of the outer can 11 used was 20.80±0.05 mm.
[0095] Thereafter, a constricted portion 11S was formed near the open end 11N of the outer can 11. Furthermore, after the electrolyte was poured into the outer can 11, the strip portion 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 were welded together.
[0096] 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.
[0097] Thereafter, the gasket 15, the safety valve mechanism 30, and the battery lid 14 were used to seal the battery lid 14. Finally, the exterior can 11, on which the washer 55 was attached, was covered with the exterior tube 50. After that, the exterior tube 50 was heated and shrunk by applying hot air to the exterior tube 50, and the exterior tube 50 was tightly attached to the outer surface of the exterior can 11.
[0098] In this way, the secondary battery of Example 1 was obtained.
[0099] Example 2 Polyolefin porous films having a thickness of 20 μm were attached to each of the upper end region 45T and the lower end region 45B in two circumferences as the insulating members 53 and 54. That is, the total thickness of the insulating members 53 and 54 was 40 μm. Except for this, the secondary battery of Example 2 was obtained in the same manner as Example 1. The electrolyte permeation time of the insulating members 53 and 54 in Example 2 was 1 second.
[0100] Example 3 Polyolefin porous membranes having a thickness of 20 μm were attached 20 times around the upper end region 45T and the lower end region 45B as the insulating members 53 and 54. That is, the total thickness of the insulating members 53 and 54 was 200 μm. Except for this, the secondary battery of Example 3 was obtained in the same manner as in Example 1. The electrolyte permeation time of the insulating members 53 and 54 in Example 3 was 1 second.
[0101] Example 4 Polyolefin porous films having a thickness of 20 μm were attached to each of the upper end region 45T and the lower end region 45B for 15 turns as insulating members 53 and 54. That is, the total thickness of insulating member 53 and insulating member 53 were each 300 μm. Except for this, the secondary battery of Example 4 was obtained in the same manner as in Example 1. The electrolyte permeation time of insulating members 53 and 54 in Example 4 was 2 seconds.
[0102] Example 5 Polyolefin porous films having a thickness of 20 μm were attached to each of the upper end region 45T and the lower end region 45B for 20 turns as insulating members 53 and 54. That is, the total thickness of insulating member 53 and insulating member 53 was 400 μm. Except for this, the secondary battery of Example 5 was obtained in the same manner as in Example 1. The electrolyte permeation time of insulating members 53 and 54 in Example 5 was 3 seconds.
[0103] Example 6 A 100 μm-thick porous film made of polyethylene (PE) was attached to each of the upper end region 45T and the lower end region 45B in a round shape as insulating members 53 and 54. Except for this, the secondary battery of Example 6 was obtained in the same manner as in Example 1. The electrolyte permeation time of insulating members 53 and 54 in Example 6 was 5 seconds.
[0104] Example 7 A 150 μm-thick nonwoven fabric tape made of polyethylene terephthalate (PET) was attached to each of the upper end region 45T and the lower end region 45B in one round as insulating members 53 and 54. Except for this, the secondary battery of Example 7 was obtained in the same manner as in Example 1. The electrolyte permeation time of insulating members 53 and 54 in Example 7 was 5 seconds.
[0105] (Comparative Example 1) A 15 μm thick PI tape that is impermeable to the electrolyte was attached to each of the upper end region 45T and the lower end region 45B in one round as the insulating members 53, 54. Except for this, the secondary battery of Comparative Example 1 was obtained in the same manner as in Example 1.
[0106] (Comparative Example 2) A 15 μm thick PP tape that is impermeable to the electrolyte was attached to each of the upper end region 45T and the lower end region 45B in one round as insulating members 53, 54. Except for this, the secondary battery of Comparative Example 2 was obtained in the same manner as in Example 1.
[0107] [Evaluation of battery characteristics] The secondary batteries of Examples 1 to 6 and Comparative Examples 1 and 2 obtained as described above were evaluated for voltage characteristics when stored at 60° C. Here, each secondary battery was charged under the following charging conditions in an environment of 23° C., and then stored at 23° C. for 24 hours, and then the relationship between the elapsed time from the start of storage at 60° C. and the battery voltage was examined. (Charging conditions) Constant current-constant voltage (CC-CV) charging was performed. The battery was charged at a constant current of 1C (5A) up to a voltage of 4.2V, and then charged at a constant voltage of 4.2V. The cutoff current was set to 0.05A. The results are shown in Table 1. The evaluation index shown in Table 1 was the time (h) elapsed until the battery voltage became 4 V or less.
[0108] [Table 1]
[0109] As shown in Table 1, in all of Examples 1 to 7, a battery voltage of 4 V or higher was maintained for 1,200 hours or more. In contrast, in Comparative Examples 1 and 2, the battery voltage fell below 4 V after 500 hours and 480 hours, respectively. It is believed that because Comparative Examples 1 and 2 used insulating materials that are impermeable to electrolyte, a localized electrolyte shortage, known as electrolyte starvation, occurred inside the battery. As a result, in Comparative Examples 1 and 2, dissolution and precipitation of the positive electrode active material (mainly Ni and Co) and dissolution and precipitation of the metals constituting the outer can occurred, causing an internal voltage drop.
[0110] From the above results, it was confirmed that the secondary battery of the present disclosure uses an electrolyte-permeable insulating member, which can prevent the generation of small amounts of isolated electrolyte inside the battery and prevent the occurrence of internal short circuits, and therefore it was confirmed that the secondary battery of the present disclosure can ensure superior safety.
[0111] The present disclosure has been described above with reference to one embodiment and several examples. However, the configuration of the present disclosure is not limited to the configuration described in the above embodiment and several examples and can be modified in various ways. For example, in the above embodiment, the insulating member 54 as a protective member is also electrolyte-permeable. However, in the secondary battery of the present disclosure, the protective member does not have to be electrolyte-permeable. Furthermore, in the above embodiment, the entire insulating member 53 is made of an electrolyte-permeable material. However, the present disclosure is not limited to this. The insulating member of the present disclosure may be partially electrolyte-permeable. Furthermore, in the above embodiment, the insulating member 53 includes the first portion 531 and the second portion 532. However, the insulating member 53 may not include the second portion 532.
[0112] In addition, although the above embodiment and examples have been described with reference to a case where the electrode reactant is lithium, the electrode reactant is not particularly limited. Therefore, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.
[0113] 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.
[0114] The present disclosure may take the following forms. <1> an electrode winding body formed by winding a laminate including a positive electrode, a negative electrode, and a separator along the longitudinal direction of the laminate and having a through-hole penetrating in a width direction perpendicular to the longitudinal direction; a positive electrode current collector plate and a negative electrode current collector plate that face each other with the electrode winding body sandwiched in the width direction; An electrolyte; an electrolyte-permeable insulating member that allows the electrolyte to pass through; Equipped with the electrode winding body has a first end face facing the positive electrode current collector plate in the width direction, a second end face facing the negative electrode current collector plate in the width direction, and a side face connecting the first end face and the second end face, The positive electrode is a positive electrode active material layer extending in both the longitudinal direction and the width direction and spaced apart from the positive electrode current collector plate; a positive electrode current collecting foil including a positive electrode covering region covered with the positive electrode active material layer and a positive electrode exposed region adjacent to the positive electrode covering region in the width direction, the positive electrode current collecting foil being joined to the positive electrode current collecting plate in the positive electrode exposed region; and the first end surface is formed by bending an edge of the positive electrode exposed region in a wound state toward the through hole, The insulating member covers a first end region of the side surface that is adjacent to the first end surface. Secondary battery. <2> The insulating member is provided so as to surround the side surface of the electrode winding body. the above <1> The secondary battery described. <3> The insulating member has a resistance of 35 sec / 100 cm 3 ] or more 3000[sec / 100cm 3 ] or less air permeability the above <1> or <2> The secondary battery described. <4> The insulating member is a stretched film, a porous film, or a nonwoven fabric. the above <1> from <3> 10. The secondary battery according to claim 9, wherein the second battery is a battery having a capacitance of 100.degree. <5> The insulating member also covers the first end surface. the above <1> from <4> 10. The secondary battery according to claim 9, wherein the second battery is a battery having a capacitance of 100.degree. <6> The insulating member is fixed to the electrode winding body. the above <1> from <5> 10. The secondary battery according to claim 9, wherein the second battery is a battery having a capacitance of 100.degree. <7> Further provided is an electrolyte-permeable protective member that allows the electrolyte to pass through, The negative electrode is a negative electrode active material layer extending in both the longitudinal direction and the width direction and spaced apart from the negative electrode current collector plate; a negative electrode current collecting foil including a negative electrode covering region covered with the negative electrode active material layer and a negative electrode exposed region adjacent to the negative electrode covering region in the width direction, the negative electrode current collecting foil being joined to the negative electrode current collecting plate in the negative electrode exposed region; and the second end surface is formed by bending an edge of the negative electrode exposed region in a wound state toward the through hole, The protective member covers a second end region of the side surface that is adjacent to the second end surface. the above <1> from <6> 10. The secondary battery according to claim 9, wherein the second battery is a battery having a capacitance of 100.degree. <8> A part of the positive electrode exposed region constituting the first end surface is connected to the positive electrode current collector plate. the above <1> from <7> 10. The secondary battery according to claim 9, wherein the second battery is a battery having a capacitance of 100.degree. <9> A part of the negative electrode exposed region constituting the second end surface is connected to the negative electrode current collector plate. the above <1> from <8> 10. The secondary battery according to claim 9, wherein the second battery is a battery having a capacitance of 100.degree. <10> further comprising an outer can that accommodates the electrode winding body, The insulating member is sandwiched between the side surface of the electrode winding body and the inner surface of the outer can. the above <1> from <9> 10. The secondary battery according to claim 9, wherein the second battery is a battery having a capacitance of 100.degree. <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 [Explanation of symbols]
[0115] 1...lithium ion secondary battery, 11...outer can, 11B...bottom, 11N...open end, 11W...side wall, 12, 13...insulating plate, 14...battery lid, 15...gasket, 20...electrode winding body, S20...laminated body, 21...positive electrode, 21A...positive electrode current collector, 21B...positive electrode active material layer, 21BT1...first edge, 211...positive electrode covering region, 212...positive electrode exposed region, 22...negative electrode, 22A...negative electrode current collector, 22B...negative electrode active material layer, 221...negative electrode covering region, 222...negative electrode exposed region, 23...separator separator, 23A...first separator member, 23B...second separator member, 24...positive electrode current collector plate, 25...negative electrode current collector plate, 26...through hole, 30...safety valve mechanism, 31, 33...fan-shaped portion, 32, 34...strip-shaped portion, 35, 36...opening, 37...protrusion, 41...upper end surface, 42...lower end surface, 45...side surface, 45T...upper end region, 45B...lower end region, 45M...middle region, 46...fixing tape, 50...outer tube, 53, 54...insulating member, 55...washer, 101...insulating layer, CL...central axis.
Claims
1. an electrode winding body formed by winding a laminate including a positive electrode, a negative electrode, and a separator along the longitudinal direction of the laminate and having a through-hole penetrating in a width direction perpendicular to the longitudinal direction; a positive electrode current collector plate and a negative electrode current collector plate that face each other with the electrode winding body sandwiched in the width direction; An electrolyte; an electrolyte-permeable insulating member that allows the electrolyte to pass through; Equipped with the electrode winding body has a first end surface facing the positive electrode current collector plate in the width direction, a second end surface facing the negative electrode current collector plate in the width direction, and a side surface connecting the first end surface and the second end surface, The positive electrode is a positive electrode active material layer extending in both the longitudinal direction and the width direction and spaced apart from the positive electrode current collector plate; a positive electrode current collecting foil including a positive electrode covering region covered with the positive electrode active material layer and a positive electrode exposed region adjacent to the positive electrode covering region in the width direction, the positive electrode current collecting foil being joined to the positive electrode current collecting plate in the positive electrode exposed region; and the first end surface is formed by bending an edge of the positive electrode exposed region in a wound state toward the through hole, The insulating member covers a first end region of the side surface that is adjacent to the first end surface. Secondary battery.
2. The insulating member is provided so as to surround the side surface of the electrode winding body. The secondary battery according to claim 1 .
3. The insulating member has a resistance of 35 sec / 100 cm ３ ] or more 3000 [sec / 100cm ３ ]having an air permeability of The secondary battery according to claim 1 .
4. The insulating member is a stretched film, a porous film, or a nonwoven fabric. The secondary battery according to claim 1 .
5. The insulating member also covers the first end surface. The secondary battery according to claim 1 .
6. The insulating member is fixed to the electrode winding body. The secondary battery according to claim 1 .
7. Further provided is an electrolyte-permeable protective member that allows the electrolyte to pass through, The negative electrode is a negative electrode active material layer extending in both the longitudinal direction and the width direction and spaced apart from the negative electrode current collector plate; a negative electrode current collecting foil including a negative electrode covering region covered with the negative electrode active material layer and a negative electrode exposed region adjacent to the negative electrode covering region in the width direction, the negative electrode current collecting foil being joined to the negative electrode current collecting plate in the negative electrode exposed region; and the second end surface is formed by bending an edge of the negative electrode exposed region in a wound state toward the through hole, The protective member covers a second end region of the side surface that is adjacent to the second end surface. The secondary battery according to claim 1 .
8. A part of the positive electrode exposed region constituting the first end surface is connected to the positive electrode current collector plate. The secondary battery according to claim 1 .
9. A part of the negative electrode exposed region constituting the second end surface is connected to the negative electrode current collector plate. The secondary battery according to claim 1 .
10. further comprising an outer can that accommodates the electrode winding body, The insulating member is sandwiched between the side surface of the electrode winding body and the inner surface of the outer can. The secondary battery according to claim 1 .
11. The secondary battery according to any one of claims 1 to 10; a control unit that controls the secondary battery; an exterior body that encloses the secondary battery; A battery pack having
Citation Information
Patent Citations
Secondary battery, battery pack, electronic device, electric tool, electric airplane and electric vehicle
WO2021020237A1