Cylindrical battery

Abstract

A cylindrical battery (10) comprises: a wound-type electrode body (14) obtained by winding a positive electrode (11) and a negative electrode (12) with a separator (13) interposed therebetween; an outer can (15) which has a cylindrical shape provided with a bottom for accommodating the electrode body (14) and in which an annular groove (20) protruding inward is formed in the vicinity of an opening of the outer can; and a sealing body (16) which is aligned by the groove (20) and which closes the opening of the outer can (15). A wound outer peripheral part of the electrode body (14) is wound by shifting the separator (13) in the axial direction of the electrode body (14), and the separator (13) of the wound outer peripheral part comprises an extension part (60) one edge of which extends in the axial direction of the electrode body (14) beyond the edge of the electrode body (14). The extension part (60) bends inward in the radial direction of the electrode body (14) and is interposed between the groove (20) and the electrode body (14) so as to provide insulation therebetween.

Description

Cylindrical battery

[0001] The present invention relates to a cylindrical battery, and more particularly to the outermost separator structure of a cylindrical battery.

[0002] Conventionally, cylindrical batteries have been widely known, including a wound electrode assembly formed by spirally winding a positive electrode and a negative electrode with a separator interposed therebetween, a cylindrical outer can with a bottom that houses the electrode assembly, a sealing member that closes the opening of the outer can, and an insulating plate disposed on the electrode assembly (see, for example, Patent Document 1). Generally, the outer can of a cylindrical battery has a groove formed therein that supports the sealing member. Furthermore, a lead extending from the negative electrode of the electrode assembly is connected to the outer can, and the outer can serves as a negative electrode external terminal. For this reason, an insulating plate was required to prevent contact between the groove in the outer can and the positive electrode of the electrode assembly.

[0003] Japanese Patent Application Publication No. 06-243857

[0004] However, a battery configuration that prevents short circuits between the groove in the outer can and the electrode body by using an insulating plate placed on the electrode body has the problem of increasing the number of parts and manufacturing processes, which increases the cost of the battery.

[0005] The cylindrical battery according to the present disclosure is a cylindrical battery comprising: a wound electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; an outer can having a bottomed cylindrical shape that houses the electrode body and in which a ring-shaped groove that protrudes inward is formed near the opening; and a sealing body that is positioned by the groove and closes the opening of the outer can, wherein the outer wound periphery of the electrode body is wound with the separator shifted in the axial direction of the electrode body, and one edge of the separator on the outer wound periphery has an extension portion that extends in the axial direction of the electrode body beyond the edge of the electrode body, and the extension portion bends radially inward of the electrode body and is interposed between the groove portion and the electrode body, providing insulation between them.

[0006] According to the cylindrical battery of the present disclosure, the number of parts of the cylindrical battery can be reduced, and the manufacturing process can be simplified.

[0007] 1 is an axial cross-sectional view of a cylindrical battery according to an embodiment of the present invention; FIG. 2 is a perspective view of an electrode body according to an embodiment of the present invention; FIG. 3 is an enlarged view of part A in FIG. 1; and FIG. 4 is a diagram showing the structure of a separator on the outer periphery of a winding.

[0008] Hereinafter, with reference to the drawings, a cylindrical battery according to an embodiment of the present invention will be described in detail. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. Furthermore, the present invention also includes configurations that are formed by selectively combining multiple embodiments and modifications described below.

[0009] A cylindrical battery 10, which is an example of the present embodiment, will be described in detail using Figures 1 and 2. Figure 1 is a schematic diagram showing an axial cross section of a cylindrical battery 10, which is an example of the embodiment. Figure 2 is a perspective view showing an electrode assembly 14.

[0010] As shown in Figure 1, the cylindrical battery 10 includes an electrode assembly 14 having a wound structure, an electrolyte, and a cylindrical outer can 15 with a bottom that houses the electrode assembly 14 and the electrolyte. The electrode assembly 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and is configured such that the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The outer can 15 is a cylindrical metal container with a bottom that is open on one axial side, and the opening of the outer can 15 is closed by a sealing member 16. For ease of explanation, the sealing member 16 side of the cylindrical battery 10 will be referred to as the top, and the bottom side of the outer can 15 will be referred to as the bottom.

[0011] The electrolyte may be an aqueous electrolyte, but in this embodiment, a non-aqueous electrolyte is used. The non-aqueous electrolyte has lithium ion conductivity. The non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte. The cylindrical battery 10 is, for example, a non-aqueous electrolyte secondary battery, and preferably a lithium ion battery.

[0012] The liquid electrolyte (electrolytic solution) contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixed solvents of two or more of these. Examples of the non-aqueous solvent include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents of these. The non-aqueous solvent may contain a halogen-substituted compound (e.g., fluoroethylene carbonate) in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine. Examples of the electrolyte salt include LiPF ６ Lithium salts such as

[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, a material known in all-solid-state lithium ion secondary batteries, etc. (for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a halogen-based solid electrolyte, 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. As the polymer material, for example, a fluororesin, an acrylic resin, a polyether resin, etc. can be used.

[0014] The positive electrode 11, negative electrode 12, and separator 13 that make up the electrode assembly 14 are all strip-shaped, long bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in the length direction and width direction (short direction) than the positive electrode 11. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and two separators 13 are arranged to sandwich the positive electrode 11. The cylindrical battery 10 includes an insulating plate 17 arranged below the electrode assembly 14.

[0015] The electrode body 14 has a positive electrode lead 18 connected to the positive electrode 11 by welding or the like, and a negative electrode lead 19 connected to the negative electrode 12 by welding or the like. In this embodiment, the positive electrode lead 18 is connected to the center of the positive electrode 11 in the longitudinal direction, and the negative electrode lead 19 is connected to the end of the negative electrode 12 in the longitudinal direction that is located on the winding core side of the electrode body 14.

[0016] The positive electrode 11 has a positive electrode core 30 and a positive electrode mixture layer 31 formed on the positive electrode core 30. The positive electrode core 30 can be a foil of a metal, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on its surface. The positive electrode mixture layer 31 contains a positive electrode active material, a conductive agent, and a binder, and is preferably formed on both sides of the positive electrode core 30 except for the portion to which the positive electrode lead 18 is welded. The positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc. to the positive electrode core 30, drying the coating, and then compressing it to form the positive electrode mixture layer 31 on both sides of the positive electrode core 30.

[0017] The positive electrode mixture layer 31 generally contains particulate lithium metal composite oxide as the positive electrode active material. The lithium metal composite oxide is a composite oxide containing metal elements such as Co, Mn, Ni, and Al in addition to Li. The metal element constituting the lithium metal composite oxide is, for example, at least one selected from Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, and Bi. Among these, it is preferable to contain at least one selected from Co, Ni, and Mn. Examples of suitable composite oxides include lithium metal composite oxides containing Ni, Co, and Mn, and lithium metal composite oxides containing Ni, Co, and Al.

[0018] The negative electrode 12 has a negative electrode core 40 and a negative electrode mixture layer 41 formed on the negative electrode core 40. The negative electrode core 40 can be a foil of a metal, such as copper or a copper alloy, that is stable within the potential range of the negative electrode 12, or a film with such a metal disposed on the surface layer. The negative electrode mixture layer 41 contains a negative electrode active material, a binder, and, if necessary, a conductive agent, and is preferably formed on both sides of the negative electrode core 40 except for the portion to which the negative electrode lead 19, described below, is welded. The negative electrode 12 can be produced by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the surface of the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode mixture layer 41 on both sides of the negative electrode core 40.

[0019] The negative electrode mixture layer 41 generally contains, as the negative electrode active material, a carbon material that reversibly absorbs and releases lithium ions. A suitable example of the carbon material is graphite, such as natural graphite or artificial graphite. Furthermore, as the negative electrode active material, a material containing at least one of an element that alloys with Li, such as Si or Sn, and a material containing such an element may be used. Among these, a Si-containing composite material is preferred. A suitable Si-containing composite material is a composite particle containing an ion-conducting phase and a Si phase dispersed in the ion-conducting phase. A carbon material and a Si-containing composite material may be used together as the negative electrode active material, which is preferable from the viewpoint of achieving both high capacity and high durability of the battery. A Li metal negative electrode may be used as the negative electrode.

[0020] In the cylindrical battery 10, the negative electrode lead 19 is connected by welding or the like to the inner bottom surface of the outer can 15. The positive electrode lead 18 extends toward the sealing body 16 and is connected by welding or the like to the underside of an internal terminal plate 21, which is the bottom plate of the sealing body 16. Therefore, in this embodiment, the sealing body 16 serves as a positive electrode external terminal, and the outer can 15 serves as a negative electrode external terminal.

[0021] The separator 13 is a porous sheet having ion permeability and insulation properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator 13 include polyolefins such as polyethylene and polypropylene, and cellulose. The separator 13 may have a single-layer structure or a multi-layer structure. A highly heat-resistant resin layer such as an aramid resin may be formed on the surface of the separator 13. A filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12. As will be described in more detail below, in this embodiment, the separator 13 is arranged so as to be located at the outermost periphery of the electrode assembly 14.

[0022] As described above, the outer can 15 is a cylindrical metal container with a bottom and an opening on one axial side. A gasket 26 is provided between the outer can 15 and the sealing body 16 to ensure sealing of the battery interior and insulation between the outer can 15 and the sealing body 16. After the electrode assembly 14 is housed in the outer can 15, a groove 20 is formed in the outer can 15, with a portion of the side surface protruding inward to support the sealing body 16. The groove 20 is preferably formed in an annular shape along the circumferential direction of the outer can 15, and its top surface supports the sealing body 16. The groove 20 is formed in an annular shape around the entire circumference of the outer can 15, for example, by spinning. The sealing body 16 is fixed to the top of the outer can 15 by the groove 20 and the open end of the outer can 15, which is crimped to the sealing body 16.

[0023] The sealing body 16 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 21, a lower valve body 22, an insulating member 23, an upper valve body 24, and a cap 25 are stacked. Each member constituting the sealing body 16 has, for example, a disk or ring shape, and each member except for the insulating member 23 is electrically connected to one another. The lower valve body 22 and the upper valve body 24 are connected at their respective centers, and the insulating member 23 is interposed between their respective peripheral edges. If an abnormality occurs in the battery and the internal pressure increases, the lower valve body 22 deforms and breaks, pushing the upper valve body 24 toward the cap 25, thereby interrupting the current path between the lower valve body 22 and the upper valve body 24. If the internal pressure further increases, the upper valve body 24 breaks, and gas is discharged from the opening of the cap 25.

[0024] 2, tape 50 is attached to the outer peripheral surface of the electrode body 14. The tape 50 is attached to each axial end of the outer peripheral surface of the electrode body 14. The tape 50 is a stop tape that fixes the winding end 13x of the wound structure of the electrode body 14 and maintains the wound structure of the electrode body 14.

[0025] In this embodiment, the separator 13 forms the outer periphery of the electrode assembly 14, which is the outermost periphery, and the longitudinal end of the separator 13 is the winding end 13x of the wound structure. The tape 50 is attached to the outer periphery of the electrode assembly 14 (separator 13) so as to straddle the winding end 13x and fix the winding end 13x. The tape 50 is preferably installed so as not to come into contact with the extension 60 of the separator 13. The tape 50 is preferably installed so that its length direction follows the circumferential direction of the electrode assembly 14.

[0026] The separator 13 on the outer periphery of the winding will be described in detail with reference to FIG.

[0027] 2 , the outermost winding portion of the electrode assembly 14 is formed by winding the separator 13 while shifting it in the axial direction of the electrode assembly 14. The separator 13 at the outer winding portion has an extending portion 60, one edge of which extends further in the axial direction of the electrode assembly 14 than the edge of the electrode assembly 14. More specifically, the extending portion 60 is wound while shifting it in the axial direction of the electrode assembly 14, and extends from the edge of the electrode assembly 14 toward the annular groove 20 formed in the outer can 15.

[0028] 2 is housed in an outer can 15, the groove 20 is formed in the outer can 15, and the extension 60 of the separator 13 is pressed against the groove 20 and bent radially inward of the electrode assembly 14. As a result, the extension 60 is interposed between the electrode assembly 14 and the groove 20 of the outer can 15, which functions as the negative electrode external terminal, and functions as an insulating part that prevents electrical contact between them. In other words, the separator 13 is an element that constitutes the electrode assembly 14, and also an insulating part that prevents a short circuit between the electrode assembly 14 and the groove 20.

[0029] The extension 60 of the separator 13 at the outer periphery of the winding will be described in more detail with reference to Figures 2 and 3. Figure 3 is an enlarged view of part A in Figure 1.

[0030] When the extension portion 60 is bent radially inward of the electrode body 14, the extension portion 60 preferably extends radially inward beyond the tip P of the groove portion 20. The tip P is the portion of the groove portion 20 located at the radially innermost position. In this case, the surface of the groove portion 20 facing the electrode body 14 (the lower surface of the groove portion 20) is completely covered by the extension portion 60 of the separator 13, thereby more effectively preventing a short circuit between the electrode body 14 and the groove portion 20. The length L of the extension portion 60 along the radial direction of the electrode body 14 may be the same as the length of the groove portion 20 along the radial direction, but may also be, for example, 1.1 to 2.0 times the length of the groove portion 20 so that the entire lower surface of the groove portion 20 is more reliably covered by the extension portion 60.

[0031] When the thickness of the positive electrode 11 is tc, the thickness of the negative electrode 12 is ta, and the thickness of the separator 13 is ts, it is preferable that the length L of the extension portion 60 of the separator 13 at the outer periphery of the winding satisfy L≧tc+ta+ts. This allows the extension portion 60 to protect at least the outermost positive electrode 11 when the extension portion 60 of the separator 13 is folded.

[0032] The structure of the separator 13 at the outer periphery of the winding to form the extension portion 60 will be described in detail with reference to Fig. 4. Fig. 4 is a plan view of the separator 13 at the outer periphery of the winding.

[0033] As described above, the extension portion 60 is formed by shifting the separator 13 at the outer periphery of the winding in the axial direction of the electrode assembly 14. "Shifting" here means gradually extending the separator 13 at the outer periphery of the winding in the axial direction of the electrode assembly 14 to form a spiral extension portion 60. In this case, the separator 13 at the outer periphery of the winding is preferably wound around the outermost periphery of the electrode assembly 14 one or more times. Furthermore, in order to extend spirally, it is preferable to wind the separator 13 until the length L at the shortest position of the extension portion 60 satisfies the condition for the length L of the extension portion 60. Furthermore, when positioning the separator 13 at the outer periphery of the winding, the positive electrode 11 and the negative electrode 12 may be cut midway through winding.

[0034] 4A , a triangular overlapping portion 61 is formed at the beginning of the shifting of the separator 13. The overlapping portion 61 is formed by folding the separator 13 back into a triangle in the winding start direction, tilting the separator 13 and causing the separator 13 to extend. As a result, the separator 13 forms an extension portion 60 that extends spirally from the electrode body 14.

[0035] 4B , a triangular extension portion 62 may be formed to form the extension portion 60. The extension portion 62 is formed by winding the separator 13 while pulling it upward, and the amount of extension increases toward the bottom of the separator 13. This causes the separator 13 to form the extension portion 60 that extends spirally from the electrode body 14.

[0036] The overlapping portion 61 and the stretched portion 62 may be formed so that the edge of the separator 13 is parallel to the edge of the electrode body 14 midway through winding the extending portion 60. In other words, the extending portion 60 may be formed upside down midway through winding the extending portion 60 relative to the triangular shape formed at the beginning of the shifting of the separator 13. This allows the extending portion 60 to be formed so that the length L of the extending portion 60 is constant.

[0037] With the above configuration, the separator 13 on the outer periphery of the winding insulates the groove 20 of the outer can 15 from the electrode assembly 14. This makes it possible to omit the upper insulating plate that was previously installed to insulate the groove 20 from the electrode assembly 14. This allows for a reduction in the number of parts in the cylindrical battery 10, and simplifies the manufacturing process.

[0038] The above embodiment can be appropriately modified in design without impairing the object of the present disclosure. For example, in the above embodiment, the outer can 15 functions as a negative electrode external terminal, but the positive electrode lead 18 can also be connected to the outer can 15 to serve as a positive electrode external terminal.

[0039] Furthermore, in the above embodiment, the separator 13 at the outer periphery of the winding and the electrode assembly 14 are integrally formed to form the extension portion 60, but the extension portion 60 may also be formed using a separator piece cut from the separator 13. In this case, after cutting the positive electrode 11, the negative electrode 12, and the separator 13, the extension portion 60 can be formed by winding an additional separator piece shifted in the axial direction of the electrode assembly 14. This makes the edge of the extension portion 60 flat, and prevents the separator 13 from extending as the extension portion 60 by more than the required amount. It is preferable that the additionally wound separator piece be wound around the outermost periphery of the electrode assembly 14 for at least one full turn.

[0040] The electrode body 14 may also have a lead extending from a position facing the groove 20 toward the sealing body 16. The lead is, for example, a positive electrode lead 18. A plurality of positive electrode leads 18 may be provided in the length direction of the positive electrode 11, some of which may extend from a position facing the groove 20. In this case, the extending portion 60 of the separator 13 is disposed between the groove 20 and the positive electrode lead 18, preventing them from contacting each other. Therefore, the separator 13 and the positive electrode lead 18 are interposed between the groove 20 and the electrode body 14. In other words, using the separator 13 as an insulating portion makes it easy to provide a lead in a position facing the groove 20 of the electrode body 14.

[0041] The present disclosure is further described by the following embodiments. Configuration 1: A cylindrical battery comprising: a wound electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a cylindrical outer can housing the electrode assembly and having a bottomed, closed-end shape and formed with an annular groove protruding inward near an opening; and a sealing body positioned by the groove and closing the opening of the outer can, wherein the separator is wound around the wound outer periphery with one edge offset in the electrode assembly axial direction, and the separator at the wound outer periphery has an extension portion that extends in the electrode assembly axial direction beyond the edge of the electrode assembly, the extension portion bent radially inward in the electrode assembly and interposed between the groove portion and the electrode assembly to provide insulation therebetween. Configuration 2: The cylindrical battery according to Configuration 1, wherein the extension portion extends radially inward in the electrode assembly beyond an end of the groove portion. Configuration 3: The cylindrical battery according to Configuration 1 or 2, wherein the extension portion extends spirally from the electrode body and is formed by providing a triangular extension portion in the separator at the outer periphery of the winding.Configuration 4: The cylindrical battery according to Configuration 1 or 2, wherein the extension portion extends spirally from the electrode body and is formed by providing a triangular overlap portion in the separator at the outer periphery of the winding.Configuration 5: The cylindrical battery according to any one of Configurations 1 to 4, wherein, when the thickness of the positive electrode is tc, the thickness of the negative electrode is ta, and the thickness of the separator is ts, an extension amount L of the separator at the outer periphery of the winding satisfies L≧tc+ta+ts. Configuration 6: A cylindrical battery comprising: a wound electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; an outer can having a bottomed cylindrical shape that houses the electrode body and has an annular groove formed near an opening that protrudes inward; and a sealing body that is positioned by the groove and closes the opening of the outer can, wherein a separator piece cut from the separator is wound around the wound outer periphery of the electrode body while being shifted in the axial direction of the electrode body, and one edge of the separator piece at the wound outer periphery has an extending portion that extends in the axial direction of the electrode body beyond the edge of the electrode body, and the extending portion is bent radially inward of the electrode body and is interposed between the groove portion and the electrode body to provide insulation therebetween.

[0042] REFERENCE SIGNS LIST 10 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 13x Winding end, 14 Electrode body, 15 Outer can, 16 Sealing body, 17 Insulating plate, 18 Positive electrode lead, 19 Negative electrode lead, 20 Groove portion, 21 Internal terminal plate, 22 Lower valve body, 23 Insulating member, 24 Upper valve body, 25 Cap, 26 Gasket, 30 Positive electrode core, 31 Positive electrode mixture layer, 40 Negative electrode core, 41 Negative electrode mixture layer, 50 Tape, 60 Extension portion

Claims

1. A cylindrical battery comprising: a wound electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a cylindrical exterior can containing the electrode body and having a bottomed cylindrical shape with an annular groove formed near the opening that protrudes inward; and a sealing body positioned by the groove and closing the opening of the exterior can, wherein the wound outer periphery of the electrode body is wound with the separator shifted in the axial direction of the electrode body, and one edge of the separator on the wound outer periphery has an extension portion that extends in the axial direction of the electrode body beyond the edge of the electrode body, and the extension portion is bent radially inward of the electrode body and is interposed between the groove portion and the electrode body, providing insulation between the two.

2. The cylindrical battery according to claim 1, wherein the extension portion extends radially inwardly of the electrode body beyond the tip of the groove portion.

3. The cylindrical battery according to claim 1, wherein the extension portion extends in a spiral shape from the electrode body and is formed by providing a triangular extension portion in the separator on the outer periphery of the winding.

4. The cylindrical battery according to claim 1, wherein the extension portion extends in a spiral shape from the electrode body and is formed by providing a triangular overlapping portion on the separator at the outer periphery of the winding.

5. A cylindrical battery according to any one of claims 1 to 4, wherein, when the thickness of the positive electrode is tc, the thickness of the negative electrode is ta, and the thickness of the separator is ts, an extension amount L of the separator at the outer periphery of the winding satisfies L ≧ tc + ta + ts.

6. A cylindrical battery comprising: a wound electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; an outer can having a bottomed cylindrical shape for accommodating the electrode body and having an annular groove formed near an opening thereof that protrudes inward; and a sealing body positioned by the groove and closing the opening of the outer can, wherein a separator piece cut from the separator is wound around the wound outer periphery of the electrode body and shifted in the axial direction of the electrode body, and one edge of the separator piece at the wound outer periphery has an extension portion that extends in the axial direction of the electrode body beyond the edge of the electrode body, and the extension portion is bent radially inward of the electrode body and is interposed between the groove portion and the electrode body to provide insulation between them.

Images