Secondary battery
A secondary battery design with a narrowed-width bent portion on the positive electrode lead addresses the risk of internal short circuits by reducing contact with the electrode body, enhancing safety and maintaining low resistance.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD
- Filing Date
- 2025-10-28
- Publication Date
- 2026-06-04
AI Technical Summary
Conventional secondary batteries face the risk of internal short circuits due to the potential contact between the upper region of the positive electrode lead and the electrode body, especially when the electrode body vibrates, as the insulating tape may not adhere properly in this region.
The positive electrode lead is designed with a bent portion that narrows its width in the upper region, reducing the area that protrudes through the insulating plate and minimizing contact with the electrode body, thereby suppressing internal short circuits.
The bent portion effectively reduces the likelihood of internal short circuits by minimizing the protrusion of the positive electrode lead into the insulating plate's through-hole, even without additional insulating tape, while maintaining low resistance.
Smart Images
Figure JP2025037873_04062026_PF_FP_ABST
Abstract
Description
Secondary battery
[0001] The present invention relates to a secondary battery.
[0002] A secondary battery includes, for example, an electrode body, an exterior body that houses the electrode body, and a sealing body that seals an opening of the exterior body. In such a secondary battery, an insulating plate is disposed between the electrode body and the sealing body to maintain insulation therebetween. The insulating plate is formed with through-holes for passing electrode leads drawn from the electrode body. As the electrode leads, for example, electrode leads combining a flat bar and a round bar (for example, Patent Document 1), electrode leads with cuts (for example, Patent Documents 2 and 3) for improving flexibility and heat dissipation, etc. are known.
[0003] Conventionally, one end of the positive electrode lead is connected to the positive electrode constituting the electrode body, and the positive electrode lead extending from the positive electrode passes through the through-hole of the insulating plate, and the other end of the positive electrode lead is connected to the sealing body. In the positive electrode lead, an insulating tape is adhered to a region from one end of the positive electrode lead to the position of the through-hole of the insulating plate to ensure insulation between the positive electrode lead and the electrode body. However, in the positive electrode lead, there is a portion where the insulating tape is not adhered in a region extending from the position of the through-hole toward the sealing body side and reaching the sealing body (hereinafter sometimes referred to as the upper region). For example, when the opening of the exterior can is sealed by the sealing body, if the upper region of the positive electrode lead protrudes from the through-hole of the insulating plate toward the electrode body side, there is a risk that the portion where the insulating tape in the upper region is not adhered contacts the electrode body. Also, when an external impact is applied to the secondary battery and the electrode body vibrates up and down, if the upper end of the electrode body protrudes from the through-hole of the insulating plate toward the sealing body side, there is a risk that the electrode body contacts the portion where the insulating tape in the upper region is not adhered. In any case, since there is a risk of developing an internal short circuit in the secondary battery, a countermeasure is necessary.
[0004] Japanese Unexamined Patent Application Publication No. 2012 - 169161, Japanese Unexamined Patent Application Publication No. 2012 - 74387, Japanese Unexamined Patent Application Publication No. 2020 - 170603
[0005] Therefore, an object of the present disclosure is to provide a secondary battery in which contact between the upper region of the positive electrode lead and the electrode body is suppressed and internal short circuit is unlikely to occur.
[0006] A secondary battery according to one aspect of the present disclosure comprises an electrode body having a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; an outer casing having an opening and housing the electrode body; a sealing body sealing the opening of the outer casing; an insulating plate having a through hole and disposed between the sealing body and the electrode body; and a positive electrode lead connected to the positive electrode, extending through the through hole of the insulating plate to the sealing body and connected to the sealing body, wherein the positive electrode lead has an upper region extending from the through hole toward the sealing body and reaching the sealing body, and the upper region is provided with a bent portion that narrows the width of the positive electrode lead in the width direction in the upper region when viewed from the sealing body side.
[0007] According to this disclosure, it is possible to provide a secondary battery that is less prone to internal short circuits by suppressing contact between the upper region of the positive electrode lead and the electrode body.
[0008] Figure 7(b) is a schematic cross-sectional view of a secondary battery 10, which is an example of an embodiment. Figure 7(a) is a schematic plan view of the positive electrode lead 20 before it is connected to the positive electrode 11 and the sealing body 17, and is a schematic cross-sectional view of the upper region 32 before the bent portion 32a is formed, and Figure 7(b) is a schematic cross-sectional view of the upper region 32 along the line L1-L1 in Figure 2. Figure 7(b) is a schematic plan view showing the positive electrode lead 20 and insulating plate 18 as seen from the sealing body 17 side. Figure 7(b) is a schematic cross-sectional view of the upper region 32 with the bent portion 32a formed. (a) is a schematic plan view of the upper region 32 and lower region 31 before the bending portion 32a is formed, and (b) is a schematic plan view of the upper region 32 and lower region 31 after the bending portion 32a is formed. This is a schematic plan view of the upper region 32 and lower region 31 after the bending portion 32a is formed. This is a schematic cross-sectional view of the upper region 32 after the bending portion 32a is formed. This is a schematic perspective view of the upper region 32 after the bending portion 32a is formed. This is a partially schematic plan view observed from one main surface side of the positive electrode 11. This is a cross-sectional view along the line L1-L1 in Figure 12.
[0009] An example of a secondary battery, which is one aspect of this disclosure, is described below. The drawings referenced in the following description of the embodiments are schematic representations, and the dimensional ratios of the components depicted in the drawings may differ from those of the actual product.
[0010] Figure 1 is a cross-sectional view of a secondary battery, which is an example of an embodiment. The secondary battery 10 shown in Figure 1 comprises a wound electrode body 14 in which a positive electrode 11 and a negative electrode 12 are wound along the longitudinal direction of the electrodes via a separator 13, an electrolyte, insulating plates 18 and 19 arranged above and below the electrode body 14, respectively, a battery case 15, a positive electrode lead 20, and a negative electrode lead 21. The battery case 15 is composed of an outer casing 16 having an opening and housing the electrode body 14, etc., and a sealing body 17 that closes the opening of the outer casing 16. Note that other forms of electrode bodies may be used instead of the wound electrode body 14, such as a stacked electrode body in which the positive electrode and negative electrode are alternately stacked via a separator. The battery case 15 is, for example, a cylindrical or rectangular metal case.
[0011] The electrolyte, for example, has lithium ion conductivity. The electrolyte may be a liquid electrolyte (electrolyte solution) or a solid electrolyte.
[0012] A liquid electrolyte (electrolyte solution) comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. The non-aqueous solvent may also contain halogen-substituted solvents (e.g., fluoroethylene carbonate) in which at least some of the hydrogen atoms in the solvent are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include LiPF4. ６ Lithium salts such as these are used.
[0013] As the solid electrolyte, for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc., can be used. As the inorganic solid electrolyte, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used. The polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As the matrix polymer, for example, a polymer material that absorbs a non-aqueous solvent and gels is used. Examples of polymer materials include fluororesins, acrylic resins, polyether resins, etc. Although the electrolytes exemplified above are non-aqueous electrolytes, the electrolyte is not limited to non-aqueous electrolytes and may also be an aqueous electrolyte.
[0014] The outer casing 16 is, for example, a metal container in the shape of a bottomed cylinder. A gasket 28 is provided between the outer casing 16 and the sealing body 17 to ensure airtightness inside the battery. The outer casing 16 has, for example, a protruding portion 22 that supports the sealing body 17, which is a part of the side surface that protrudes inward. The protruding portion 22 is preferably formed in an annular shape along the circumferential direction of the outer casing 16, and its upper surface supports the sealing body 17.
[0015] The sealing body 17 has a structure in which a filter 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked in order from the electrode body 14 side. Each component constituting the sealing body 17 has, for example, a disc shape or a ring shape, and each component except the insulating member 25 is electrically connected to one another. The lower valve body 24 and the upper valve body 26 are connected to each other at their respective centers, with the insulating member 25 interposed between their respective peripheral edges. When the internal pressure of the secondary battery 10 rises due to heat generation caused by an internal short circuit or the like, for example, the lower valve body 24 deforms and breaks, pushing the upper valve body 26 towards the cap 27, thus interrupting the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further, the upper valve body 26 breaks, and gas is discharged from the opening of the cap 27.
[0016] In the secondary battery 10 shown in Figure 1, an insulating plate 18 is placed between the electrode body 14 and the sealing body 17, and an insulating plate 19 is placed between the electrode body 14 and the bottom of the outer casing 16. One end of the positive electrode lead 20 is connected to the positive electrode 11 by welding or the like. The positive electrode lead 20 connected to the positive electrode 11 extends through a through hole 18a provided in the insulating plate 18 to the sealing body 17 and is connected by welding or the like to the lower surface of the filter 23, which is the bottom plate of the sealing body 17. As a result, the cap 27, which is the top plate of the sealing body 17 and is electrically connected to the filter 23, becomes the positive electrode terminal. In addition, one end of the negative electrode lead 21 is connected to the negative electrode 12 by welding or the like. The negative electrode lead 21 connected to the negative electrode 12 extends through the outside of the insulating plate 19 to the bottom of the outer casing 16 and is connected by welding or the like to the inner surface of the bottom of the outer casing 16. As a result, the outer casing 16 becomes the negative electrode terminal.
[0017] For example, the positive electrode lead 20 can be made of a metal such as aluminum, titanium, or nickel, or an alloy thereof. Similarly, the negative electrode lead 21 can be made of a metal such as nickel or copper, or an alloy thereof.
[0018] The positive lead 20 will be explained in more detail below.
[0019] Figure 2 is a schematic plan view of the positive electrode lead 20 before it is connected to the positive electrode 11 and the sealing body 17. As shown in Figure 2, the positive electrode lead 20 has a positive electrode side connection region 30, which is the region from position A, one end of the positive electrode lead in the longitudinal direction, to position B; a lower region 31, which is from position B to position C; an upper region 32, which is from position C to position D; and a sealing body side connection region 33, which is from position D to position E, the other end of the positive electrode lead 20 in the longitudinal direction. The positive electrode side connection region 30 is the region of the positive electrode lead 20 that is in contact with the positive electrode 11. The positive electrode side connection region 30 is connected to the positive electrode 11 (specifically, the exposed portion described later) by welding or the like. Position C of the lower region 31 corresponds to the position of the through hole 18a of the insulating plate 18 after the secondary battery is assembled. That is, the lower region 31 is the region that extends from the positive electrode side connection region 30 towards the insulating plate 18 and reaches the through hole 18a of the insulating plate 18. Position D of the upper region 32 is the boundary with the sealing body side connection region 33. That is, the upper region 32 is the region that extends from the through hole 18a toward the sealing body 17 and reaches the sealing body 17. The upper region 32 is provided with a bent portion, which will be described later. The sealing body side connection region 33 is the region of the positive electrode lead 20 that is in contact with the sealing body 17. The sealing body side connection region 33 is connected to the sealing body 17 (filter 23 in Figure 1) by welding or the like.
[0020] Figure 3(a) is a schematic cross-sectional view of the upper region 32 before the formation of the bent portion 32a, and Figure 3(b) is a schematic cross-sectional view of the upper region 32 along the line L1-L1 in Figure 2, and is a cross-sectional view of the upper region 32 where the bent portion 32a is formed. The upper region 32 of the positive electrode lead 20 is provided with a bent portion 32a that narrows the width of the positive electrode lead in the width direction when viewed from the sealing body 17 side. The bent portion 32a shown in Figure 3(b) is formed by bending both ends (33a, 33b) in the width direction of the upper region 32 inward in the width direction (in the direction of arrow A shown in Figure 3(a)) in the flat plate-shaped upper region 32 shown in Figure 3(a). The bent ends (33a, 33b) are in contact with each other. The bent portion 32a may be formed only in a part of the upper region 32, but it is desirable that it be formed over the entire upper region 32. Although not shown in the diagram, the bent portion 32a may be formed by bending only one end 33a in the width direction of the upper region 32 shown in Figure 3(a) inward in the width direction.
[0021] Here, when viewed from the sealing body 17 side, the bent portion that narrows the width of the positive electrode lead in the upper region 32 means that, when viewed from the sealing body 17 side, the width of the positive electrode lead in the upper region 32 after the formation of the bent portion 32a is narrower than the width of the positive electrode lead in the upper region 32 before the formation of the bent portion 32a. Also, when viewed from the sealing body 17 side, if the sealing body 17 is considered "up" and the insulating plate 18 is considered "down", then the view is from the center of the sealing body 17 toward the insulating plate 18 in the vertical direction. In Figure 3(a), the width R of the upper region before the formation of the bent portion 32a is shown. ０ However, this is the width in the width direction of the positive electrode lead in the upper region 32 before the bent portion 32a is formed. And, in Figure 3(b), the direction of arrow X is the direction viewed from the sealing body 17 side, and the width R of the upper region 32 after the bent portion 32a is formed is the width in the width direction of the positive electrode lead in the upper region 32 after the bent portion 32a is formed, as viewed from the sealing body 17 side. And, as shown in Figure 3(b), by forming the bent portion 32a in the upper region 32, the width R of the upper region 32 after the bent portion 32a is formed is equal to the width R of the upper region 32 before the bent portion 32a was formed. ０It becomes narrower. Therefore, the bent portion 32a shown in Figure 3(b) is a bent portion that narrows the width in the width direction of the positive electrode lead in the upper region 32 when viewed from the sealing body 17 side.
[0022] Figure 4 is a schematic plan view showing the positive electrode lead 20 and insulating plate 18 as seen from the sealing body 17 side. Note that in Figure 4, the sealing body side connection region 33 of the positive electrode lead 20 is not shown. The upper region 32 is provided with a bent portion 32a that narrows the width of the positive electrode lead in the width direction when viewed from the sealing body 17 side. As described above, the bent portion 32a shown in Figure 4 is formed by bending both ends of the upper region 32 in the width direction inward. The width R of the upper region 32 after the formation of the bent portion 32a shown in Figure 4 is the width of the positive electrode lead in the width direction in the upper region 32 after the formation of the bent portion 32a when viewed from the sealing body 17 side, and corresponds to the width R of the upper region 32 shown in Figure 3(b). In a positive electrode lead 20 with a bent portion 32a formed in the upper region 32, the width R of the upper region 32 as viewed from the sealing body 17 side is narrow, so the area of the upper region 32 that protrudes into the through hole 18a side of the insulating plate 18 is reduced. As a result, for example, when the opening of the outer casing 16 is sealed by the sealing body 17, or when the secondary battery 10 is subjected to an external impact and the electrode body 14 vibrates up and down, the probability of the upper region 32 and the electrode body 14 coming into contact through the through hole 18a is reduced, and the occurrence of an internal short circuit in the secondary battery is suppressed. Normally, insulating tape is attached to the positive electrode lead 20 to ensure insulation between the electrode body 14 and the negative electrode 12, but due to the welding relationship between the positive electrode lead 20 and the sealing body 17, insulating tape is not attached to the upper region 32, or only a part of the upper region 32 is covered with insulating tape. In this embodiment, even if the upper region 32 is not protected by insulating tape, the area of the upper region 32 that protrudes into the through-hole 18a side of the insulating plate 18 is small, so the probability of the upper region 32 and the electrode body 14 coming into contact through the through-hole 18a is suppressed, and the occurrence of an internal short circuit in the secondary battery is suppressed. Furthermore, since the bent portion 32a is formed by bending the upper region 32, the cross-sectional area of the upper region 32 with the bent portion 32a formed is the same as the cross-sectional area of the upper region 32 before the bent portion 32a is formed, so the increase in the battery resistance of the secondary battery 10 is suppressed.
[0023] Figure 5 is a schematic plan view showing a conventional positive electrode lead 34 and insulating plate 18 as seen from the sealing body 17 side. A conventional positive electrode lead 34 is a positive electrode lead in which the aforementioned bent portion 32a is not formed in the upper region 32. In Figure 5, the sealing body side connection region 33 of the conventional positive electrode lead 34 is not shown. In the conventional positive electrode lead 34, the width of the upper region 32 as seen from the sealing body 17 side as shown in Figure 5 is wide, so a large area of the upper region 32 protrudes into the through hole 18a side of the insulating plate 18. This increases the probability that the upper region 32 protruding into the through hole 18a side of the insulating plate 18 and the electrode body will come into contact through the through hole 18a, which may lead to an internal short circuit in the secondary battery 10. Generally, the insulating plate 18 is provided with multiple through holes 18b in addition to the through hole 18a.
[0024] Other forms of the bent portion 32a will be described below.
[0025] Figure 6 is a schematic cross-sectional view of the upper region 32 in which the bent portion 32a is formed. As shown in Figure 6, the bent portion 32a is formed by bending both ends (32a, 32b) in the width direction of the upper region 32 inward in the width direction, but the bent ends (32a, 32b) do not come into contact with each other and are spaced apart. As shown in Figure 6, because the bent ends (32a, 32b) do not come into contact with each other, there is no risk of the ends (32a, 32b) being damaged by rubbing against each other. As a result, the occurrence of internal short circuits caused by the damaged portion becoming conductive foreign matter and mixing into the electrode body 14 is suppressed.
[0026] Figure 7(a) is a schematic cross-sectional view of the upper region 32 before the bent portion 32a is formed, and Figure 7(b) is a schematic cross-sectional view of the upper region 32 after the bent portion 32a has been formed. As shown in Figure 7(a), the upper region 32 is provided with a notch 35. The notch 35 extends in the longitudinal direction of the upper region 32 (i.e., the longitudinal direction of the positive electrode lead 20). The bent portion 32a shown in Figure 7(b) is formed by bending both ends (33a, 33b) in the width direction of the upper region 32 shown in Figure 7(a) inward in the width direction (in the direction of arrow A shown in Figure 7(a)), starting from the notch 35. Although not explained in the figures, the bent portion 32a may also be formed by bending only one end 33a in the width direction of the upper region 32 shown in Figure 7(a), starting from the notch 35, inward in the width direction. By forming the notched portion 35, the formation of the bent portion 32a becomes easier.
[0027] When forming the bent portion 32a by bending the end of the upper region 32 inward in the width direction, it is desirable to bend the end of the upper region 32 inward in the width direction so that, when viewed from the sealing body 17 side, the width of the positive electrode lead in the upper region 32 where the bent portion 32a is formed is narrowed by 10% or more compared to the width of the positive electrode lead in the upper region 32 before the bending portion 32a is formed.
[0028] When viewed from the sealing body side, it is desirable that the bent portion 32a be provided at the end of the upper region 32 closer to the through hole of the sealing body, which is one of the two ends of the positive electrode lead in the width direction in the upper region 32. When viewed from the sealing body side, if the shortest distance from one end of the positive electrode lead in the width direction in the upper region 32 to the through hole is the same as the shortest distance from the other end of the positive electrode lead in the width direction in the upper region 32 to the through hole, it is desirable that the bent portion 32a be provided at both ends of the positive electrode lead in the width direction in the upper region 32, when viewed from the sealing body side.
[0029] Figure 8(a) is a schematic plan view of the upper region 32 and the lower region 31 before the formation of the bent portion 32a, and Figure 8(b) is a schematic plan view of the upper region 32 and the lower region 31 after the bent portion 32a has been formed. The bent portion 32a shown in Figure 8(b) is formed by rotating the upper region 32 around the longitudinal axis C of the positive electrode lead shown in Figure 8(a). The bent portion 32a may be formed, for example, by fixing the lower region 31 and rotating the entire upper region 32, or by fixing a part of the upper region 32 and rotating the upper region 32 other than the fixed part. When the entire upper region 32 is rotated, the entire upper region 32 becomes the bent portion 32a, and when a part of the upper region 32 is rotated, the rotated part becomes the bent portion 32a. In any case, as the upper region 32 is rotated, the upper region 32 tilts when viewed from the sealing body 17 side, so the width of the positive lead in the upper region 32 narrows, and the width of the positive lead in the upper region 32 before rotation (R shown in Figure 8(a)) ０ ) becomes narrower. The bent portion 32a shown in Figure 8(b) is formed by rotating the upper region 32 by 90° around the longitudinal axis C of the positive electrode lead. In this case, when viewed from the sealing body 17 side, the width in the width direction of the positive electrode lead in the upper region 32 that has been rotated by 90° is not visible (only the width in the thickness direction of the positive electrode lead is visible), and the width in the width direction of the positive electrode lead in the upper region becomes zero. Furthermore, when the rotation angle of the upper region 32 exceeds 90°, the width in the width direction of the positive electrode lead in the upper region 32 increases, but even so, it is still narrower than the width in the width direction of the positive electrode lead in the upper region 32 before rotation.
[0030] The rotation angle of the upper region 32 is preferably such that, in order to effectively suppress the occurrence of internal short circuits due to contact between the upper region 32 and the electrode body 14, the width in the width direction of the positive electrode lead in the upper region where the bent portion 32a is formed is narrowed by 10% or more compared to the width of the upper region 32 before the bent portion 32a was formed, when viewed from the sealing body 17 side. Specifically, it is preferable that the rotation angle of the upper region 32 be 15° or more.
[0031] Although a diagrammatic explanation is omitted, in terms of ease of welding and connection strength between the positive electrode lead 20 and the sealing body 17, when the rotation angle of the upper region 32 is less than 90°, it is preferable that the upper region 32 near the sealing body side connection region 33 is rotated in the opposite direction to the rotation direction at the bent portion 32a, so that one main surface of the sealing body side connection region 33 is parallel to the connection surface on the sealing body 17 side. Furthermore, when the rotation angle of the upper region 32 is 90° or more and less than 180°, it is preferable that the upper region 32 near the sealing body side connection region 33 is further rotated in the same direction as the rotation direction of the upper region 32 at the bent portion 32a, so that one main surface of the sealing body side connection region 33 is parallel to the connection surface on the sealing body 17 side.
[0032] Figure 9 is a schematic plan view of the upper region 32 on which the bent portion 32a is formed. The bent portion 32a shown in Figure 9 is formed by rotating the upper region 32 by 180° around the longitudinal axis C of the positive electrode lead shown in Figure 8(a). The rotation angle of the upper region 32 is not limited to 180°, but may be a multiple of 180° (360°, 540°, 720°, etc.). When the upper region 32 is rotated by 180° or a multiple of 180°, the twisted portion of the upper region 32 becomes the bent portion 32a, which narrows the width in the width direction of the positive electrode lead in the upper region 32 when viewed from the sealing body 17 side. Note that as the upper region 32 is rotated by a multiple of 180°, the twist of the upper region 32 increases, resulting in a spiral bent portion 32a.
[0033] Figure 10 is a schematic cross-sectional view of the upper region 32 where the bent portion 32a is formed. The bent portion 32a shown in Figure 10 is formed by folding the upper region 32 in a convex mountain fold when viewed from the sealing body 17 side (in Figure 10, the direction of arrow X is the direction viewed from the sealing body 17 side). By forming the bent portion 32a with a convex mountain fold, the width R in the width direction of the positive electrode lead in the upper region 32 after the formation of the bent portion 32a is narrower than the width in the width direction of the positive electrode lead in the upper region 32 before the formation of the bent portion 32a when viewed from the sealing body 17 side. In addition, although not explained in the figure, the bent portion 32a may also be formed by folding the upper region 32 in a concave valley fold when viewed from the sealing body 17 side. In the bent portion 32a shown in Figure 10, the upper region 32 is folded in a mountain fold along a single mountain fold line along the longitudinal direction of the positive electrode lead 20, resulting in an inverted V shape in cross-sectional view, but the shape is not particularly limited. For example, the upper region 32 may be bent along a pair of mountain fold lines parallel to the longitudinal direction of the positive electrode lead 20 to form a rectangular bent portion 32a in cross-sectional view. When forming a bent portion 32a that is convex (mountain fold) or concave (valley fold), it is desirable to fold the upper region 32 in a mountain or valley fold such that, when viewed from the sealing body 17 side, the width in the width direction of the positive electrode lead in the upper region 32 where the bent portion 32a is formed is narrowed by 10% or more compared to the width in the width direction of the positive electrode lead in the upper region 32 before the bent portion 32a was formed.
[0034] Figure 11 is a schematic perspective view of the upper region 32 on which the bent portion 32a is formed. The bent portion 32a shown in Figure 11 may be formed by bending the upper region 32 in an arc shape so that it is convex when viewed from the sealing body 17 side (in Figure 11, the direction of arrow X is the direction viewed from the sealing body 17 side). By forming the bent portion 32a by bending the upper region in an arc shape, the width R in the width direction of the positive electrode lead in the upper region 32 after the formation of the bent portion 32a is narrower than the width in the width direction of the positive electrode lead in the upper region 32 before the formation of the bent portion 32a when viewed from the sealing body 17 side. In addition, although not explained in the figure, the bent portion 32a may also be formed by bending the upper region 32 in an arc shape so that it is concave when viewed from the sealing body 17 side. When bending the upper region 32 into an arc shape to form the bent portion 32a, it is desirable to bend the upper region 32 into an arc shape so that, when viewed from the sealing body 17 side, the width in the width direction of the positive electrode lead in the upper region 32 where the bent portion 32a is formed is narrowed by 10% or more compared to the width in the width direction of the positive electrode lead in the upper region 32 before the bending portion 32a is formed.
[0035] It is desirable that the sealing body side connection region 33 of the positive electrode lead 20 does not have the aforementioned bent portion 32a. If the sealing body side connection region 33 of the positive electrode lead 20 has a bent portion 32a, for example, the connection strength between the positive electrode lead 20 and the sealing body 17 may decrease.
[0036] Figure 12 is a partially schematic plan view of the positive electrode 11 as observed from one main surface side, and Figure 13 is a cross-sectional view along the line L1-L1 in Figure 12. In Figure 12, the insulating tape 50, which will be described later, is shown in a transmission view to clarify the configuration of the positive electrode 11 and the positive electrode lead 20. In Figures 12 and 13, arrow X indicates the longitudinal direction of the positive electrode 11, arrow Y indicates the short direction of the positive electrode 11, and arrow Z indicates the thickness direction of the positive electrode 11. The longitudinal direction of the positive electrode 11 is the winding direction of the electrode body 14, and the short direction of the positive electrode 11 is the winding axis direction of the electrode body 14.
[0037] As shown in Figure 13, the positive electrode 11 comprises a positive electrode current collector 52 and a positive electrode composite layer 54 disposed on the positive electrode current collector 52. The positive electrode 11 has an exposed portion 56 where the surface of the positive electrode current collector 52 is exposed and not covered by the positive electrode composite layer 54. The exposed portion 56 is formed, for example, in the middle of the longitudinal direction of the positive electrode 11. The positive electrode side connection region 30 of the positive electrode lead 20 is positioned on the exposed portion 56 on the positive electrode 11 and connected to the exposed portion 56 of the positive electrode 11 by welding or the like.
[0038] In this embodiment, the insulating tape 50 is attached to the positive electrode composite layer 54 of the positive electrode 11 so as to cover the exposed portion 56 and the positive electrode side connection region 30 of the positive electrode lead 20 located on the exposed portion 56. The insulating tape 50 is also wrapped around the lower region 31 of the positive electrode lead 20 and attached to the lower region 31. In order to suppress internal short circuits of the electrode body 14, it is desirable that the insulating tape 50 be attached to the entire lower region 31, but it is also acceptable for the insulating tape 50 to be attached to only a part of the lower region 31.
[0039] It is desirable that the lower region 31 of the positive electrode lead 20 is provided with the aforementioned bent portion 32a. The bent portion 32a may be provided over the entire lower region 31, or it may be provided in a part of the lower region 31.
[0040] In the positive electrode connection region 30 of the positive electrode lead 20, it is desirable that no bending portion that narrows the width in the width direction of the positive electrode lead in the positive electrode connection region 30 is provided in a plan view of the positive electrode connection region 30. Further, when a bending portion that narrows the width in the width direction of the positive electrode lead in the positive electrode connection region 30 is provided in the positive electrode connection region 30 of the positive electrode lead 20 in a plan view, it is desirable that the bending portion is not provided in the range from the lower end portion of the positive electrode connection region 30 (that is, one end in the longitudinal direction of the positive electrode lead 20) to 2 / 3 of the total length of the connection region. The shape of the bending portion may be the same as the bending portion described above. Also, the bending portion that narrows the width in the width direction of the positive electrode lead in the positive electrode connection region 30 means that, in a plan view of the positive electrode connection region 30, the width in the width direction of the positive electrode lead in the positive electrode connection region 30 after forming the bending portion is narrower than the width in the width direction of the positive electrode lead in the positive electrode connection region 30 before forming the bending portion. Note that if a bending portion is provided in the positive electrode connection region 30 of the positive electrode lead 20, for example, the connection strength between the positive electrode lead 20 and the positive electrode 11 may decrease.
[0041] For the positive electrode current collector 52, for example, a foil of a metal stable within the potential range of the positive electrode such as aluminum, a film having the metal disposed on the surface layer, or the like is used. The thickness of the positive electrode current collector 52 is, for example, 10 μm or more and 30 μm or less.
[0042] The positive electrode composite layer 54 is preferably formed over the entire region excluding the exposed portion 56 of the positive electrode current collector 52. The positive electrode composite layer 54 preferably contains, for example, a positive electrode active material, a conductive material, and a binder. The positive electrode 11 is produced, for example, by compressing the positive electrode composite layer 54 formed by applying and drying a positive electrode composite slurry containing a positive electrode active material or the like on both surfaces of the positive electrode current collector 52. Note that the exposed portion 56 can be produced, for example, by removing a part of the positive electrode composite layer 54 after production. Also, the exposed portion 56 may be produced, for example, by masking a part of the positive electrode current collector 52 to form an uncoated portion of the positive electrode composite slurry.
[0043] Examples of positive electrode active materials include lithium (Li) and Li composite oxides containing transition metal elements such as cobalt (Co), manganese (Mn), and nickel (Ni). Li composite oxides may also contain other additive elements besides Co, Mn, and Ni, such as aluminum (Al), zirconium (Zr), boron (B), magnesium (Mg), scandium (Sc), yttrium (Y), titanium (Ti), iron (Fe), copper (Cu), zinc (Zn), chromium (Cr), lead (Pb), tin (Sn), sodium (Na), potassium (K), barium (Ba), strontium (Sr), calcium (Ca), tungsten (W), molybdenum (Mo), niobium (Nb), and silicon (Si).
[0044] Examples of conductive materials include carbon black, acetylene black, Ketjen black, and carbon powders such as graphite. These may be used individually or in combination of two or more types.
[0045] Examples of binders include fluoropolymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resins, polyolefin resins, styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), and polyethylene oxide (PEO). These may be used individually or in combination of two or more.
[0046] The insulating tape 50 has, for example, a base material layer and an adhesive layer provided on the base material layer. The base material layer is not particularly limited as long as it is a layer mainly composed of an organic material. Here, being mainly composed of an organic material means that the proportion of the organic material is the highest among the materials constituting the base material layer. However, the content of the organic material is preferably, for example, 80% by mass or more, more preferably 90% by mass or more, based on the total mass of the base material layer, in terms of the strength of the insulating tape 50 and the like. Examples of the organic material include polyolefins (e.g., polyethylene, polypropylene, etc.), polystyrene, polyesters (e.g., polyethylene terephthalate, etc.), polyimide, polyamide, polyamideimide, polycarbonate, polyphenylene sulfide, and the like.
[0047] The adhesive layer is formed, for example, by coating an adhesive on one surface of the base material. Examples of the adhesive include acrylic resins, natural rubbers, synthetic rubbers, silicones, epoxy resins, melamine resins, phenol resins, and the like. These may be used alone or in combination of two or more. Further, the adhesive layer may contain additives such as tackifiers, crosslinking agents, anti-aging agents, coloring agents, antioxidants, chain transfer agents, plasticizers, softening agents, surfactant materials, antistatic agents, etc., as necessary.
[0048] The thickness of the insulating tape 50 is not particularly limited, but may be, for example, in the range of 10 μm or more and 60 μm or less.
[0049] The negative electrode 12 includes a strip-shaped negative electrode current collector and negative electrode composite layers disposed on both surfaces of the negative electrode current collector. For the negative electrode current collector, a foil of a metal stable within the potential range of the negative electrode such as copper, or a film having the metal disposed on the surface layer can be used. An exposed portion where the surface of the negative electrode current collector is exposed is formed on the negative electrode 12. The exposed portion is formed, for example, at the longitudinal end of the negative electrode 12.
[0050] Although the description in the figure is omitted, the secondary battery 10 includes a first protective layer disposed on the negative electrode 12 so as to cover one exposed portion of the pair of exposed portions and the negative electrode lead 21, and a second protective layer disposed on the negative electrode 12 so as to cover the other exposed portion of the pair of exposed portions.
[0051] The negative electrode composite layer preferably contains, for example, a negative electrode active material and a binder. The negative electrode 12 is manufactured by compressing the negative electrode composite layer, which is formed by coating and drying a negative electrode composite slurry containing a negative electrode active material, etc., on both sides of a negative electrode current collector.
[0052] The negative electrode active material is not particularly limited as long as it can reversibly intercept and release lithium ions, for example, carbon materials such as natural graphite and artificial graphite, lithium titanium composite oxide, metals that alloy with lithium such as Si and Sn, or alloys and composite oxides containing these. The binder is the same material as in the positive electrode. The negative electrode composite layer may contain conductive materials as needed.
[0053] For the separator 13, for example, a porous sheet having ion permeability and insulating properties can be used. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator 13 include polyethylene, olefin resins such as polypropylene, and cellulose. The separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin. Alternatively, it may be a multilayer separator containing a polyethylene layer and a polypropylene layer, or a separator with a material such as aramid resin or ceramic coated on its surface may be used.
[0054] This disclosure is further illustrated by the following embodiments. Configuration 1: A secondary battery comprising an electrode body having a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; an outer casing having an opening and housing the electrode body; a sealing body sealing the opening of the outer casing; an insulating plate having a through hole and disposed between the sealing body and the electrode body; and a positive electrode lead connected to the positive electrode, extending through the through hole of the insulating plate to the sealing body and connected to the sealing body, wherein the positive electrode lead has an upper region extending from the through hole toward the sealing body and reaching the sealing body, and the upper region is provided with a bent portion that narrows the width of the positive electrode lead in the width direction in the upper region when viewed from the sealing body side. Configuration 2: The secondary battery according to Configuration 1, wherein the positive electrode lead has a sealing body side connection region that is in contact with the sealing body, and the sealing body side connection region is not provided with the bent portion. Configuration 3: The secondary battery according to Configuration 1 or 2, wherein the positive electrode lead has a positive electrode side connection region in contact with the positive electrode, and a lower region from the positive electrode side connection region to the through hole, and the bent portion is provided in the lower region. Configuration 4: The secondary battery according to any one of Configurations 1 to 3, wherein the positive electrode lead has a positive electrode side connection region in contact with the positive electrode, and the positive electrode side connection region does not have a bent portion that narrows the width of the positive electrode lead in the width direction in the positive electrode side connection region when viewed from above. Configuration 5: The secondary battery according to any one of Configurations 1 to 3, wherein the positive electrode lead has a positive electrode side connection region in contact with the positive electrode, and the range from the lower end of the positive electrode side connection region to 2 / 3 of the total length of the positive electrode side connection region does not have a bent portion that narrows the width of the positive electrode lead in the width direction in the positive electrode side connection region when viewed from above. Configuration 6: The secondary battery according to any one of Configurations 1 to 5, wherein the bent portion of the upper region is formed by folding one or both ends of the upper region in the width direction inward in the width direction. Configuration 7: The secondary battery according to Configuration 6, wherein the bent portion of the upper region is formed by folding both ends of the upper region in the width direction inward in the width direction, and the two ends do not come into contact with each other.Configuration 8: The secondary battery according to Configuration 6, wherein the bent portion is provided at the end of the positive electrode lead in the width direction in the upper region that is closer to the through hole in the insulating plate, as viewed from the sealing body side. Configuration 9: The secondary battery according to any one of Configurations 1 to 5, wherein the bent portion of the upper region is formed by rotating the upper region about the longitudinal axis of the positive electrode lead. Configuration 10: The secondary battery according to Configuration 9, wherein when the rotation angle of the upper region is less than 90°, the upper region near the sealing body side connection area that is in contact with the sealing body is rotated in the opposite direction to the rotation direction of the bent portion, and one main surface of the sealing body side connection area is parallel to the connection surface of the sealing body. Configuration 11: The secondary battery according to Configuration 9, wherein the rotation angle of the upper region in the bent portion is 180° or a multiple of 180°. Configuration 12: The secondary battery according to any one of Configurations 1 to 5, wherein the bent portion is formed by folding the upper region in a convex mountain fold or a concave valley fold when viewed from the sealing body side. Configuration 13: The secondary battery according to any one of Configurations 1 to 5, wherein the bent portion is formed by folding the upper region in an arc shape so that it is convex or concave when viewed from the sealing body side. Configuration 14: The secondary battery according to any one of Configurations 1 to 5, wherein the bent portion has a notch extending in the longitudinal direction of the positive electrode lead, and is formed by folding one or both ends of the upper region in the width direction inward in the width direction starting from the notch.
[0055] 10 Secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Battery case, 16 Outer casing, 17 Sealing body, 18, 19 Insulating plate, 18a Through hole, 20 Positive electrode lead, 21 Negative electrode lead, 22 Protruding part, 23 Filter, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive electrode side connection area, 31 Lower area, 32 Upper area, 32a Bent part, 33 Sealing body side connection area, 34 Conventional positive electrode lead, 35 Notched part, 36 Exposed part, 50 Insulating tape, 52 Positive electrode current collector, 54 Positive electrode composite layer, 56 Exposed part.
Claims
1. A secondary battery comprising: an electrode body having a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; an outer casing having an opening and housing the electrode body; a sealing body sealing the opening of the outer casing; an insulating plate having a through hole and disposed between the sealing body and the electrode body; and a positive electrode lead connected to the positive electrode, extending through the through hole of the insulating plate to the sealing body and connected to the sealing body, wherein the positive electrode lead has an upper region extending from the through hole toward the sealing body and reaching the sealing body, and the upper region is provided with a bent portion that narrows the width of the positive electrode lead in the width direction when viewed from the sealing body side.
2. The secondary battery according to claim 1, wherein the positive electrode lead has a sealing body side connection region that is in contact with the sealing body, and the sealing body side connection region does not have the bent portion.
3. The secondary battery according to claim 1 or 2, wherein the positive electrode lead has a positive electrode side connection region that is in contact with the positive electrode, and a lower region from the positive electrode side connection region to the through hole, and the bent portion is provided in the lower region.
4. The secondary battery according to claim 1 or 2, wherein the positive electrode lead has a positive electrode side connection region that is in contact with the positive electrode, and the positive electrode side connection region is not provided with a bent portion that narrows the width of the positive electrode lead in the width direction in the positive electrode side connection region when viewed in plan.
5. The secondary battery according to claim 1 or 2, wherein the positive electrode lead has a positive electrode side connection region that is in contact with the positive electrode, and in the range from the lower end of the positive electrode side connection region to 2 / 3 of the total length of the positive electrode side connection region, there is no bent portion that narrows the width of the positive electrode lead in the width direction in the positive electrode side connection region when viewed in plan of the positive electrode side connection region.
6. The secondary battery according to claim 1 or 2, wherein the bent portion is formed by bending one or both ends of the upper region in the width direction inward in the width direction.
7. The secondary battery according to claim 6, wherein the bent portion is formed by folding both ends of the upper region in the width direction inward in the width direction, and the ends are not in contact with each other.
8. The secondary battery according to claim 6, wherein the bent portion is provided at the end of the positive electrode lead in the width direction in the upper region, as viewed from the sealing body side, that is closer to the through hole in the insulating plate.
9. The secondary battery according to claim 1 or 2, wherein the bent portion is formed by rotating the upper region about the longitudinal axis of the positive electrode lead.
10. The secondary battery according to claim 9, wherein, when the rotation angle of the upper region is less than 90°, in the positive electrode lead, the upper region near the sealing body side connection region that is in contact with the sealing body is rotated in the opposite direction to the rotation direction at the bent portion, and one main surface of the sealing body side connection region is parallel to the connection surface on the sealing body side.
11. The secondary battery according to claim 9, wherein the rotation angle of the upper region in the bent portion is 180° or a multiple of 180°.
12. The secondary battery according to claim 1 or 2, wherein the bent portion is formed by folding the upper region with a mountain fold that is convex or a valley fold that is concave when viewed from the sealing body side.
13. The secondary battery according to claim 1 or 2, wherein the bent portion is formed by bending the upper region in an arc shape so that it is convex or concave when viewed from the sealing body side.
14. The secondary battery according to claim 1 or 2, wherein the bent portion has a notch extending in the longitudinal direction of the positive electrode lead, and is formed by bending one or both ends of the upper region in the width direction starting from the notch in the width direction.