Secondary battery

Abstract

The present invention is characterized by being provided with: an electrode body (14) in which a first electrode and a second electrode are wound via a separator (13); a cylindrical outer casing (16) that accommodates the electrode body (14); a sealing body 17 that closes an opening of the outer casing (16); and a cylindrical member (40) that is disposed on the winding core of the central part in the radial direction of the electrode body (14) and extends along the axial direction of the electrode body (14), wherein the cylindrical member (40) is configured from an insulating material, and a hollow part (43) is formed therein in the central part in the radial direction.

Description

secondary battery

[0001] The present disclosure relates to secondary batteries.

[0002] The secondary battery includes an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, and the electrode assembly is housed in an outer can. Patent Document 1 discloses that a solid member is disposed on a winding core in the radial center of the electrode assembly.

[0003] JP 2013-073873 A

[0004] When the internal pressure of the battery increases due to abnormal heat generation or the like, the space in the winding core of the electrode assembly functions as an exhaust path for exhausting gas inside the battery to the outside. From the viewpoint of improving the reliability of the battery, it is important to maintain the space in the winding core and ensure an exhaust path for gas inside the battery in the event of an abnormality.

[0005] A secondary battery according to one aspect of the present disclosure comprises an electrode assembly in which a first electrode and a second electrode are wound with a separator interposed therebetween, a cylindrical outer can that houses the electrode assembly, a sealing body that closes the opening of the outer can, and a tubular member that is disposed on a winding core in the radial center of the electrode assembly and extends along the axial direction of the electrode assembly, the tubular member being made of an insulating material and having a hollow portion formed in the radial center.

[0006] According to the secondary battery of one aspect of the present disclosure, the space in the winding core can be maintained even in the event of an abnormality, and a gas exhaust path can be secured inside the battery, thereby providing a highly reliable secondary battery.

[0007] FIG. 1 is an axial cross-sectional view of a secondary battery that is an example of an embodiment; FIG. 2 is a perspective view of an electrode body that constitutes a secondary battery that is an example of an embodiment; FIG. 3 is a perspective view of an upper current collector plate that constitutes a secondary battery that is an example of an embodiment, viewed from above; FIG. 4 is a perspective view of a tubular member that constitutes a secondary battery that is an example of an embodiment, viewed from above; FIG. 5 is a perspective view of a tubular member that constitutes a secondary battery that is an example of an embodiment, viewed from below; FIG. 6 is an axial cross-sectional view of a secondary battery that is an example of an embodiment, showing the internal configuration of the secondary battery before a sealing body is compressed; FIG. 7 is an axial cross-sectional view of a secondary battery that is an example of an embodiment, showing the internal configuration of the secondary battery after a sealing body is compressed; FIG. 8 is an axial cross-sectional view of a secondary battery that is another example of an embodiment;

[0008] Hereinafter, an example of an embodiment of a secondary battery according to the present disclosure will be described with reference to the drawings. The embodiment described below is merely an example, and the present disclosure is not limited to the following embodiment. Furthermore, the present disclosure also includes embodiments obtained by selectively combining the components of the embodiments described below.

[0009] The configuration of a secondary battery 10, which is an example of an embodiment, will be described with reference to Figures 1 and 2. Figure 1 is a diagram schematically showing an axial cross section of the secondary battery 10, and Figure 2 is a perspective view of an electrode body 14 that constitutes the secondary battery 10.

[0010] As shown in FIGS. 1 and 2 , the secondary battery 10 includes an electrode assembly 14 in which a first electrode and a second electrode are wound with a separator 13 interposed therebetween, a nonaqueous electrolyte (not shown), an outer can 16 that houses the electrode assembly 14 and the nonaqueous electrolyte, and a sealing member 17 that closes the opening of the outer can 16. The secondary battery 10 also includes an upper current collector 30 as a current collecting member disposed between the sealing member 17 and the electrode assembly 14, and a lower current collector 20 disposed between the electrode assembly 14 and the bottom 16A of the outer can 16. In this specification, the sealing member 17 side of the secondary battery 10 is referred to as the "top" and the bottom 16A side of the outer can 16 is referred to as the "bottom." The following description will be given for a case in which the first electrode is a positive electrode 11 and the second electrode is a negative electrode 12. The first electrode may be the negative electrode 12 and the second electrode may be the positive electrode 11.

[0011] The electrode assembly 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The positive electrode 11, the negative electrode 12, and the separator 13 that constitute the electrode assembly 14 are all long, strip-shaped bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. The positive electrode 11 protrudes above the negative electrode 12 and the separator 13, and the negative electrode 12 protrudes below the positive electrode 11 and the separator 13. A space in which a tubular member 40, described below, is disposed, is formed in the winding core of the electrode assembly 14 along the axial direction (vertical direction).

[0012] The positive electrode 11 has a positive electrode core 50 and a positive electrode mixture layer 51 formed on the positive electrode core 50. The positive electrode core 50 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 the surface layer. The positive electrode mixture layer 51 contains a positive electrode active material, a conductive agent, and a binder, and is preferably formed on both sides of the positive electrode core 50 except for the positive electrode core exposed portion 52 described below. 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 50, drying the coating, and then compressing it to form the positive electrode mixture layer 51 on both sides of the positive electrode core 50.

[0013] The positive electrode mixture layer 51 contains particulate lithium metal composite oxide as a 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, or lithium metal composite oxides containing Ni, Co, and Al.

[0014] Examples of the conductive agent contained in the positive electrode mixture layer 51 include carbon black such as acetylene black and ketjen black, graphite, carbon nanotubes (CNT), carbon nanofibers, graphene, and other carbon materials. Examples of the binder contained in the positive electrode mixture layer 51 include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resin, polyolefin, and the like. Furthermore, these resins may be used in combination with carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), and the like.

[0015] The negative electrode 12 has a negative electrode core 60 and a negative electrode mixture layer 61 formed on the negative electrode core 60. For the negative electrode core 60, 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, can be used. The negative electrode mixture layer 61 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 60. The negative electrode 12 can be produced by applying a negative electrode mixture slurry containing the negative electrode active material and the binder, etc., to the surface of the negative electrode core 60, drying the coating, and then compressing it to form the negative electrode mixture layer 61 on both sides of the negative electrode core 60.

[0016] The negative electrode mixture layer 61 generally contains, as the negative electrode active material, a carbon material that reversibly absorbs and releases lithium ions. Suitable examples of the carbon material include natural graphite such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite such as massive artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB). 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 composite material containing Si is preferred.

[0017] A suitable example of a composite material containing Si is SiO ２Examples of the composite material include a material in which Si fine particles are dispersed in a silicate phase such as lithium silicate, or a material in which Si fine particles are dispersed in an amorphous carbon phase. A conductive layer such as a carbon coating is formed on the particle surface of the composite material. The combined use of a carbon material and a Si-containing composite material as the negative electrode active material is preferred from the viewpoint of achieving both high capacity and high durability of the battery.

[0018] As in the case of the positive electrode mixture layer 51, the binder contained in the negative electrode mixture layer 61 can be a fluorine-containing resin, PAN, polyimide, acrylic resin, polyolefin, or the like, but preferably styrene-butadiene rubber (SBR) is used. The negative electrode mixture layer 61 preferably contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), or the like. Among these, it is preferable to use SBR in combination with CMC or a salt thereof, PAA or a salt thereof, or the like. The negative electrode mixture layer 61 may contain a conductive agent such as CNT.

[0019] As shown in FIG. 2 , in this embodiment, the positive electrode 11 has a positive electrode core exposed portion 52 at its axial upper end, where the positive electrode mixture layer 51 is not provided and the positive electrode core 50 is exposed. The positive electrode core exposed portion 52 is provided, for example, over a range from the winding start end to the winding end end of the long positive electrode 11 in the longitudinal direction. The negative electrode 12 has a negative electrode core exposed portion 62 at its axial lower end, where the negative electrode mixture layer 61 is not provided and the negative electrode core 60 is exposed. The negative electrode core exposed portion 62 is provided, for example, over a range from the winding start end to the winding end end of the long negative electrode 12 in the longitudinal direction. Therefore, the axial upper end of the electrode body 14 is constituted by the positive electrode core exposed portion 52, and the axial lower end of the electrode body 14 is constituted by the negative electrode core exposed portion 62. The width of the positive electrode substrate exposed portion 52 is, for example, 2 mm or more and 20 mm or less, and the width of the negative electrode substrate exposed portion 62 is, for example, 2 mm or more and 20 mm or less.

[0020] 1 , the positive electrode substrate exposed portion 52 extends from the upper end surface of the electrode body 14 substantially parallel to the axial direction of the electrode body 14. The positive electrode substrate exposed portion 52 is bent radially inward at the upper end portion and joined by welding or the like to the outer circumferential portion 33 of the upper current collector plate 30 or the lower surface of the protruding portion 34. By joining the positive electrode substrate exposed portion 52 to the upper current collector plate 30, the contact area between the positive electrode substrate exposed portion 52 and the upper current collector plate 30 increases, and the internal resistance of the positive electrode 11 can be reduced.

[0021] 1 , the negative electrode substrate exposed portion 62 extends from the lower end surface of the electrode body 14 substantially parallel to the axial direction of the electrode body 14. The negative electrode substrate exposed portion 62 is bent radially inward at the lower end and joined by welding or the like to the upper surface of the lower current collector plate 20. Note that the secondary battery 10 may not include the lower current collector plate 20, and the negative electrode substrate exposed portion 62 may be joined by welding or the like to the inner surface of the bottom 16A of the outer can 16.

[0022] The separator 13 is a porous sheet having ion permeability and insulating 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.

[0023] The non-aqueous electrolyte has lithium ion conductivity and may be a liquid electrolyte (electrolytic solution) or a solid electrolyte.

[0024] 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

[0025] 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 the 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.

[0026] 1, a cylindrical member 40 is disposed on the winding core at the radial center of the electrode body 14. The cylindrical member 40 is made of an insulating material. The cylindrical member 40 has a first portion 41 extending along the axial direction of the electrode body 14 and a second portion 42 connected to the upper end of the first portion 41 and extending radially outward.

[0027] A hollow portion 43 is formed in the radial center of the first portion 41. The hollow portion 43 is formed along the axial direction and functions as a gas exhaust path in the event of an abnormality in the secondary battery 10. By disposing the hollow first portion 41 on the winding core in the radial center of the electrode body 14, it is possible to maintain space in the winding core in the event of an abnormality, and to ensure a gas exhaust path. As a result, it is possible to provide a secondary battery 10 with excellent reliability.

[0028] In this embodiment, the outer diameter of the first portion 41 is approximately the same as the diameter of the winding core of the electrode body 14, and the side surface of the first portion 41 abuts against the surface of the electrode body 14 on the winding core side. This makes it possible to suppress movement of the electrode body 14 even when the electrode body 14 expands in the radial direction due to repeated charging and discharging of the secondary battery 10. Note that the side surface of the first portion 41 does not have to abut against the surface of the electrode body 14 on the winding core side.

[0029] The first portion 41 is fixed to the secondary battery 10 by fitting its lower end into the recess 20A of the lower current collector plate 20. The axial length of the first portion 41 is longer than the axial length of the electrode body 14, and is a length that allows the upper end of the first portion 41 to be positioned above the upper end surface of the electrode body 14 when the lower end of the first portion 41 fits into the recess 20A of the lower current collector plate 20. Note that the method of fixing the tubular member 40 (first portion 41) and the lower current collector plate 20 is not limited to this, and they may be screwed together or joined with an adhesive, for example.

[0030] The second portion 42 has an annular shape and is disposed between the electrode body 14 and the upper current collector plate 30. The second portion 42 supports the upper current collector plate 30 on its upper surface. This allows the upper current collector plate 30 to be stably held inside the secondary battery 10. A through hole 44 is provided in the second portion 42. The recess 20A of the upper current collector plate 30 is disposed in the through hole 44. The configuration of the cylindrical member 40 will be described in detail below.

[0031] In this embodiment, an insulating film 21 is provided between the electrode body 14 and the outer casing 16 on the upper end side of the electrode body 14. The insulating film 21 is provided, for example, around the entire periphery of the electrode body 14. This prevents the upper end of the positive electrode 11 from coming into contact with the outer casing 16, thereby preventing an internal short circuit from occurring.

[0032] The material of the insulating film 21 is not particularly limited, and examples thereof include polyesters such as polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), polyphenylene sulfide (PPS), polyetherimide (PEI), polyamide, etc. The insulating film 21 may have an adhesive portion and be attached to the surface of the electrode body 14 or the outer can 16. The thickness of the insulating film 21 is not particularly limited, and may be, for example, 20 μm or more and 200 μm or less, or 30 μm or more and 150 μm or less.

[0033] The outer can 16 is a cylindrical metal container with a bottom and an opening on one axial side. The opening of the outer can 16 is closed by a sealing body 17. A gasket 19 is provided between the outer can 16 and the sealing body 17 to ensure airtightness inside the battery. The provision of the gasket 19 also ensures insulation between the outer can 16 and the sealing body 17. In other words, the gasket 19 serves both as a sealing member to maintain airtightness inside the battery and as an insulating member to insulate the outer can 16 from the sealing body 17.

[0034] The outer can 16 has a grooved portion 16B formed inward at a portion of its side wall that supports the sealing body 17. The grooved portion 16B is preferably formed in an annular shape along the circumferential direction of the outer can 16, and supports the sealing body 17 on its top surface. The grooved portion 16B can be formed, for example, by spinning a portion of the side wall of the outer can 16 radially inward to create a recess in the radial direction. The sealing body 17 is fixed to the top of the outer can 16 by the grooved portion 16B and the open end of the outer can 16 that is crimped to the sealing body 17.

[0035] As described above, the sealing body 17 has the function of sealing the opening of the outer can 16. In this embodiment, the sealing body 17 is composed of a single sealing plate 18. Note that the configuration of the sealing body 17 is not limited to this as long as it is capable of sealing the opening of the outer can 16. The sealing body 17 may have a structure in which multiple members are stacked in the axial direction, for example.

[0036] The sealing plate 18 has a central protrusion 18A that protrudes toward the outside of the battery. The protrusion 18A has a substantially circular shape when viewed from above. The sealing plate 18 is joined to the upper current collector plate 30 in a region radially outward of the protrusion 18A. In this embodiment, the sealing plate 18 and the upper current collector plate 30 are joined by laser welding. The number and area of ​​the welds between the sealing plate 18 and the upper current collector plate 30 are set, for example, taking into consideration the joint strength and resistance. Generally, the larger the area of ​​the weld, the higher the joint strength and the lower the resistance. From the perspective of increasing the joint strength between the sealing plate 18 and the upper current collector plate 30, it is preferable that the weld be formed in a substantially circular shape when viewed from above.

[0037] The upper current collecting plate 30 is a metal member having a through hole 31 in the radial center. As described above, the positive electrode substrate exposed portion 52 constituting the positive electrode 11 is joined to the lower surface of the upper current collecting plate 30. The upper surface of the upper current collecting plate 30 is joined to the sealing plate 18. As a result, the sealing plate 18 functions as a positive electrode terminal. The upper current collecting plate 30 has a protruding portion 34 that protrudes toward the electrode body 14, and at least a portion of the protruding portion 34 is disposed inside the through hole 44.

[0038] The lower current collector plate 20 is a metal member having a recess 20A in its radial center, into which the cylindrical member 40 fits. As described above, the negative electrode core exposed portion 62 constituting the negative electrode 12 is joined to the upper surface of the lower current collector plate 20. The lower surface of the lower current collector plate 20 is welded to the inner surface of the bottom 16A of the outer can 16. This allows the outer can 16 to function as the negative electrode terminal. The shape of the lower current collector plate 20 is not particularly limited, and may, for example, have a generally circular shape when viewed from above.

[0039] Next, the configuration of the upper current collecting plate 30 will be described in detail with reference to Fig. 3. Fig. 3 is a perspective view of the upper current collecting plate 30 as seen from above.

[0040] 3 , the upper current collecting plate 30 has a through hole 31 in the radial center and has a circular shape when viewed from above. The outer diameter of the upper current collecting plate 30 is, for example, 50% to 90% of the inner diameter of the outer can 16.

[0041] The upper current collecting plate 30 has a base 32 and an outer peripheral portion 33 that is disposed on the outer periphery of the base 32 and is located lower than the base 32. The base 32 has a circular shape in a top view. The outer diameter of the base 32 is, for example, 20% to 60% of the inner diameter of the outer can 16. In this embodiment, the outer diameter of the base 32 is approximately the same as the outer diameter of the second portion 42 of the tubular member 40.

[0042] The base 32 is provided with protrusions 34 that protrude downward. In this embodiment, the protrusions 34 have a generally rectangular shape when viewed from above, and four protrusions 34 are provided on the base 32. The four protrusions 34 are arranged at 90° intervals in the circumferential direction. The depth of the protrusions 34 is, for example, 0.5 mm or more and 5.0 mm or less. The protrusions 34 may be provided in an annular shape along the circumferential direction. As described above, the positive electrode core exposed portion 52 that constitutes the positive electrode 11 is joined to the lower surface of the protrusions 34.

[0043] In this embodiment, a thick portion 35 (see FIG. 1 ) that is thicker than other portions is provided in a region of the base 32 radially outward of the protruding portion 34. The thick portion 35 is, for example, annular. The thick portion 35 has a thickness that is, for example, 1.2 to 3.0 times the thickness of the region of the base 32 other than the thick portion 35. The thick portion 35 is a region that is joined to the sealing plate 18 by laser welding. By providing the thick portion 35, damage caused by heat or the like to components disposed below the upper current collecting plate 30 can be suppressed during laser welding. Note that the upper current collecting plate 30 does not necessarily have to have the thick portion 35.

[0044] A peripheral protrusion 36 that protrudes downward is provided in a position of the peripheral portion 33 that overlaps radially with the protrusion 34. The lower surface of the peripheral protrusion 36 and the lower surface of the protrusion 34 are disposed on approximately the same plane. A positive electrode substrate exposed portion 52 that constitutes the positive electrode 11 is joined to the lower surface of the peripheral protrusion 36.

[0045] Next, the configuration of the cylindrical member 40 will be described in detail with reference to Figures 4 and 5. Figure 4 is a perspective view of the cylindrical member 40 as seen from above, and Figure 5 is a perspective view of the cylindrical member 40 as seen from below.

[0046] 4 and 5 , the cylindrical member 40 has a first portion 41 that extends along the axial direction (vertical direction) of the electrode body 14, and a second portion 42 that connects to the upper end of the first portion 41 and extends radially outward. The first portion 41 is disposed on the winding core of the electrode body 14, and the second portion 42 is disposed between the electrode body 14 and the upper current collector plate 30.

[0047] The cylindrical member 40 is made of an insulating material. Examples of insulating materials that can be used to make the cylindrical member 40 include resin materials such as polypropylene (PP), polyphenylene sulfide (PPS), polyethylene (PE), polybutylene terephthalate (PBT), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), and polyamide (PA), as well as inorganic materials such as silicon oxide, silicon carbide, and silicon nitride. By making the cylindrical member 40 out of an insulating material, the occurrence of internal short circuits can be suppressed.

[0048] The radially outer surface of the first portion 41 is provided with recesses 45 that extend along the axial direction and are recessed radially inward. In this embodiment, four recesses 45 are arranged at 90° intervals in the circumferential direction. By providing the recesses 45 on the radially outer surface of the first portion 41, when the non-aqueous electrolyte is injected from the top of the outer can 16 during the manufacturing process of the secondary battery 10, the non-aqueous electrolyte flows downward through the recesses 45, improving the injection of the non-aqueous electrolyte. The depth of the recesses 45 is not particularly limited and is, for example, 0.5 mm or more and 5.0 mm or less.

[0049] At least one notch 46 is provided at the lower end of the first portion 41. In this embodiment, four notches 46 are arranged at approximately 90° intervals. The notches 46 are provided on extensions of the recesses 45 in the axial direction. By providing the notches 46, when the nonaqueous electrolyte is injected from the top of the outer can 16 during the manufacturing process of the secondary battery 10, the nonaqueous electrolyte flows through the notches 46, improving the injection of the nonaqueous electrolyte. Furthermore, when abnormal heat generation occurs in the secondary battery 10, gas inside the battery flows into the hollow portion 43 through the notches 46. This makes it easier for gas inside the battery to be exhausted to the outside through the tubular member 40. The circumferential length of the notches 46 is, for example, 0.5 mm or more and 5.0 mm or less. The axial length of the notches 46 is, for example, 0.5 mm or more and 5.0 mm or less.

[0050] The second portion 42 has a circular shape in a top view. The outer diameter of the second portion 42 is configured to be smaller than the outer diameter of the electrode body 14. This makes it easier for the nonaqueous electrolyte to flow downward through the space outside the second portion 42 when the nonaqueous electrolyte is injected from the top of the outer can 16 during the manufacturing process of the secondary battery 10, improving the injection of the nonaqueous electrolyte. The outer diameter of the second portion 42 is, for example, 30% to 90% of the outer diameter of the electrode body 14, or may be 40% to 80%. The thickness of the second portion 42 is, for example, 0.5 mm to 5.0 mm, excluding a region in which a groove 47 (described below) is provided.

[0051] Four through holes 44 are arranged at approximately 90° intervals in the second portion 42. As described above, the protrusion 34 of the upper current collecting plate 30 is arranged inside the through holes 44. That is, the through holes 44 are provided at positions facing the protrusions 34 and are sized to accommodate the protrusions 34. In this embodiment, the through holes 44 have a generally rectangular shape when viewed from above. Furthermore, when nonaqueous electrolyte is injected from the top of the exterior can 16 during the manufacturing process of the secondary battery 10, some of the nonaqueous electrolyte passes through the through holes 44 and flows downward.

[0052] Grooves 47 are provided on the upper surface of the second portion 42, connecting the through-holes 44 and the hollow portion 43 in the radial center. The grooves 47 extend radially. The grooves 47 improve the injectability of the non-aqueous electrolyte when the non-aqueous electrolyte is injected from the top of the exterior can 16 during the manufacturing process of the secondary battery 10. The depth of the grooves 47 is, for example, 10% to 80% of the thickness of the second portion 42, and may be 20% to 70%.

[0053] Of the upper surface of the second portion 42, the outer peripheral region 42A abuts against the lower surface of the thick portion 35 of the upper current collecting plate 30. In the present embodiment, the thick portion 35 is provided along the entire periphery, and therefore the outer peripheral region 42A of the second portion 42 abuts against the lower surface of the thick portion 35 along the entire periphery.

[0054] Next, the internal configuration of secondary battery 10 before and after compression of sealing body 17 will be described in detail with reference to Figures 6 and 7. Figure 6 is a diagram showing the internal configuration of secondary battery 10 before sealing body 17 is compressed, and Figure 7 is a diagram showing the internal configuration of secondary battery 10 after sealing body 17 is compressed.

[0055] In the manufacturing process of the secondary battery 10, the upper current collector plate 30 is placed on top of the electrode assembly 14, and after the nonaqueous electrolyte is injected, the sealing body 17 (sealing plate 18) is placed on the upper surface of the grooved portion 16B of the outer can 16 via a gasket 19. Then, as shown in FIG. 6 , the open end of the outer can 16 is bent radially inward to fix the sealing plate 18 to the top of the secondary battery 10. Thereafter, as shown in FIG. 7 , the sealing plate 18 is compressed downward along the axial direction so that the lower surface of the sealing plate 18 abuts against the upper surface of the upper current collector plate 30. The sealing plate 18 and the upper current collector plate 30 are then joined by laser welding. That is, in the manufacturing process of the secondary battery 10, when the sealing plate 18 is compressed downward, the upper current collector plate 30 is also pressed downward.

[0056] In the secondary battery 10 of this embodiment, as described above, the upper current collecting plate 30 is supported by the cylindrical member 40. Therefore, when the sealing plate 18 is compressed downward, the upper current collecting plate 30 is less likely to shift axially. As a result, there is no need to provide a space or the like inside the secondary battery 10 to accommodate movement of the upper current collecting plate 30 and other components, making it easier to miniaturize the secondary battery 10.

[0057] As described above, the secondary battery 10 of this embodiment includes a tubular member 40 that is disposed on a winding core in the radial center of the electrode body 14 and extends along the axial direction of the electrode body 14. The tubular member 40 is made of an insulating material and has a hollow portion 43 formed in the radial center. This allows the space in the winding core to be maintained even when the secondary battery 10 abnormally heats up, making it easy to ensure an exhaust path for gas inside the battery. As a result, a highly reliable secondary battery 10 can be provided.

[0058] The above-described embodiment can be modified as appropriate within the scope of the present disclosure. For example, as shown in Fig. 8 , the electrode assembly 14 may have a positive electrode lead 70 extending from the positive electrode 11 and a negative electrode lead 71 extending from the negative electrode 12. In this case, the negative electrode 12 is generally formed to be longer than the positive electrode 11 in the longitudinal direction and width direction, and the separator 13 is formed to be slightly larger than the positive electrode 11 and the negative electrode 12.

[0059] The positive electrode lead 70 is connected to the positive electrode 11 by welding or the like. The number of positive electrode leads 70 may be one or more. Increasing the number of positive electrode leads 70 can reduce resistance. The positive electrode lead 70 is connected to the underside of at least one of the outer peripheral portion 33 (outer peripheral protrusion 36) and the protrusion 34 of the upper current collector plate 30 by welding or the like. This makes the sealing body 17 a positive electrode terminal.

[0060] The negative electrode lead 71 is connected to the negative electrode 12 by welding or the like. In the example shown in FIG. 8 , the negative electrode lead 71 passes outside the insulating plate 72 and extends toward the bottom 16A of the outer can 16. The negative electrode lead 71 is joined to the inner surface of the bottom 16A of the outer can 16 by welding or the like. This makes the outer can 16 a negative electrode terminal. The negative electrode lead 71 may pass through the center of the insulating plate 72 and extend toward the bottom 16A of the outer can 16. Alternatively, the negative electrode lead 71 may be omitted, and the negative electrode core 60 may be exposed at the outermost periphery of the electrode body 14 and abut against the inner surface of the outer can 16. In the example shown in FIG. 8 , the cylindrical member 40 is joined and fixed to the insulating plate 72, but the method of fixing the cylindrical member 40 is not limited thereto.

[0061] In the secondary battery 10 of this embodiment, as described above, the upper current collector plate 30 is supported by the cylindrical member 40. Therefore, even when the positive electrode lead 70 and the negative electrode lead 71 are used, the upper current collector plate 30 is less likely to shift axially when the sealing plate 18 is compressed downward during the manufacturing process of the secondary battery 10. As a result, there is no need to provide a margin inside the secondary battery 10 to account for bending of the positive electrode lead 70 or the negative electrode lead 71 due to movement of the upper current collector plate 30, and the secondary battery 10 can be easily miniaturized.

[0062] 9, the tubular member 40 may be composed of only the first portion 41 without including the second portion 42. That is, the tubular member 40 may be a cylindrical member extending along the axial direction. Also, as shown in FIG. 9, the upper surface of the first portion 41 may abut against the lower surface of the upper current collector 30, and the upper current collector 30 may be supported by the upper surface of the first portion 41. This allows the upper current collector 30 to be stably held inside the secondary battery 10. Furthermore, when the tubular member 40 does not include the second portion 42, the shape of the upper current collector 30 is not particularly limited. For example, as shown in FIG. 9, the upper current collector 30 may have a flat plate shape.

[0063] The present disclosure is further described by the following embodiments. Aspect 1: A secondary battery comprising: an electrode assembly in which a first electrode and a second electrode are wound with a separator interposed therebetween; a cylindrical outer can containing the electrode assembly; a sealing body closing an opening of the outer can; and a tubular member disposed on a winding core in a radial center of the electrode assembly and extending along the axial direction of the electrode assembly, the tubular member being made of an insulating material and having a hollow portion formed in the radial center. Aspect 2: The secondary battery according to Aspect 1, further comprising: a current collecting member disposed between the sealing body and the electrode assembly and electrically connected to the first electrode, the surface of the tubular member facing the sealing body abutting the surface of the current collecting member facing the electrode assembly. Aspect 3: The secondary battery according to Aspect 2, in which the tubular member has a first portion extending along the axial direction of the electrode assembly and a second portion connected to an end of the first portion facing the sealing body and extending radially outward. Configuration 4: The secondary battery according to Configuration 3, wherein the outer diameter of the second portion is smaller than the outer diameter of the electrode assembly.Configuration 5: The secondary battery according to Configuration 3 or 4, wherein the second portion is provided with at least one or more through holes.Configuration 6: The secondary battery according to Configuration 5, wherein the current collecting member has a protrusion that protrudes toward the electrode assembly, and the protrusion is disposed inside the through hole.Configuration 7: The secondary battery according to Configuration 5 or 6, wherein the surface of the second portion facing the sealing body is provided with a groove that extends along the radial direction and connects the through hole to the hollow portion.Configuration 8: The secondary battery according to any one of Configurations 3 to 7, wherein the radially outer surface of the first portion is provided with a recess that extends along the axial direction of the electrode assembly and is recessed radially inward.Configuration 9: The secondary battery according to any one of Configurations 3 to 8, wherein the end of the first portion on the bottom side of the outer can is provided with at least one or more notches.

[0064] REFERENCE SIGNS LIST 10 secondary battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 16 outer can, 16A bottom, 16B grooved portion, 17 sealing body, 18 sealing plate, 18A convex portion, 19 gasket, 20 lower current collector plate, 20A concave portion, 21 insulating film, 30 upper current collector plate (current collector member), 31 through hole, 32 base portion, 33 outer periphery, 34 protruding portion, 35 thick portion, 36 outer periphery protruding portion, 40 cylindrical member, 41 first portion, 42 second portion, 43 hollow portion, 44 through hole, 45 concave portion, 46 notch, 47 groove, 50 positive electrode core, 51 positive electrode mixture layer, 52 positive electrode core exposed portion, 60 negative electrode core, 61 negative electrode mixture layer, 62 Negative electrode core exposed portion, 70 positive electrode lead, 71 negative electrode lead, 72 insulating plate

Claims

1. A secondary battery comprising: an electrode assembly in which a first electrode and a second electrode are wound with a separator interposed therebetween; a cylindrical outer can that houses the electrode assembly; a sealing body that closes the opening of the outer can; and a tubular member that is disposed on a winding core in the radial center of the electrode assembly and extends along the axial direction of the electrode assembly, wherein the tubular member is made of an insulating material and has a hollow portion formed in the radial center.

2. The secondary battery according to claim 1, further comprising a current collecting member disposed between the sealing body and the electrode body and electrically connected to the first electrode, wherein the surface of the cylindrical member facing the sealing body abuts against the surface of the current collecting member facing the electrode body.

3. The secondary battery according to claim 2, wherein the cylindrical member has a first portion extending along the axial direction of the electrode body, and a second portion connected to the end of the first portion on the sealing body side and extending radially outward.

4. The secondary battery according to claim 3, wherein the outer diameter of the second portion is smaller than the outer diameter of the electrode body.

5. The secondary battery according to claim 3, wherein the second portion is provided with at least one through hole.

6. The secondary battery according to claim 5, wherein the current collecting member has a protruding portion that protrudes toward the electrode body, and the protruding portion is disposed inside the through hole.

7. The secondary battery according to claim 5, wherein a groove extending along a radial direction is provided on the surface of the second portion facing the sealing body, the groove communicating with the through hole and the hollow portion.

8. A secondary battery according to claim 3, wherein a recess extending along the axial direction of the electrode body and recessed radially inward is provided on the radially outer surface of the first portion.

9. The secondary battery according to claim 3, wherein at least one notch is provided in the end of the first portion on the bottom side of the exterior can.

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