Cylindrical nonaqueous electrolyte secondary battery

Abstract

Disclosed is a cylindrical nonaqueous electrolyte secondary battery (10) which is provided with: an electrode body (14) which is obtained by winding a positive electrode (11) and a negative electrode (12) with a separator (13) being interposed therebetween; a nonaqueous electrolyte; a bottomed cylindrical outer package can (16) which houses the electrode body (14) and the nonaqueous electrolyte; and a sealing body (17) which closes the opening of the outer package can (16) and has an exhaust valve. This cylindrical nonaqueous electrolyte secondary battery (10) is characterized in that: a negative electrode lead (30) is connected to an end of the negative electrode (12) on the winding start side; and the negative electrode lead (30) has a base part (31), at least a part of which is connected to the negative electrode (12), and which extends along the axial direction, an extension part (32) which is connected to a lower end part of the base part (31) in the axial direction and extends along a bottom surface 16A of the outer package can 16, and a protrusion part (33) which is connected to the extension part (32) and extends in the direction away from the extension part (32), and at least a part of which is disposed in a hollow part (28) that is provided at the inner end of the electrode body 14 in the winding direction.

Description

Cylindrical non-aqueous electrolyte secondary battery

[0001] The present disclosure relates to a cylindrical non-aqueous electrolyte secondary battery.

[0002] A cylindrical nonaqueous electrolyte 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 a cylindrical outer can with a bottom. Patent Document 1 discloses a cylindrical nonaqueous electrolyte secondary battery in which a negative electrode lead is connected to the end of the negative electrode at the winding start side.

[0003] Japanese Patent Application Laid-Open No. 2006-302734

[0004] Cylindrical non-aqueous electrolyte secondary batteries are generally provided with an exhaust valve that releases high-temperature gas from inside the battery to the outside when the internal pressure of the battery increases due to abnormal heat generation. In the event of an abnormality, it is important to operate the exhaust valve and release the high-temperature gas from inside the battery to the outside through the exhaust valve.

[0005] A cylindrical non-aqueous electrolyte secondary battery according to one aspect of the present disclosure is a cylindrical non-aqueous electrolyte secondary battery comprising: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a non-aqueous electrolyte; a bottomed cylindrical outer can that houses the electrode assembly and the non-aqueous electrolyte; and a sealing body that closes the opening of the outer can and has an exhaust valve, wherein a negative electrode lead is connected to the end of the negative electrode on the winding start side, and the negative electrode lead has: a base at least a portion of which is connected to the negative electrode and extends along the axial direction; an extension connected to the lower axial end of the base and extends along the bottom surface of the outer can; and a protrusion connected to the extension, extending in a direction away from the extension, and at least a portion of which is disposed in a hollow portion provided at the inner end of the electrode assembly in the winding direction.

[0006] Furthermore, a cylindrical non-aqueous electrolyte secondary battery according to another aspect of the present disclosure is a cylindrical non-aqueous electrolyte secondary battery including: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a non-aqueous electrolyte; a cylindrical outer can with a bottom that houses the electrode assembly and the non-aqueous electrolyte; and a sealing body that closes the opening of the outer can and has an exhaust valve; and a negative electrode lead is connected to the end of the negative electrode on the side where the winding begins, and the negative electrode lead has: a base that is connected at least in part to the negative electrode and extends along the axial direction; an extension that is connected to the lower axial end of the base and extends along the bottom surface of the outer can; and a partition that extends radially inward from the base and is located in a hollow portion that is provided at the inner end of the electrode assembly in the winding direction.

[0007] According to the cylindrical nonaqueous electrolyte secondary battery of one aspect of the present disclosure, in the event of an abnormality, high-temperature gas inside the battery can be easily exhausted through the exhaust valve, thereby improving the safety of the battery.

[0008] FIG. 1 is an axial cross-sectional view of a cylindrical nonaqueous electrolyte secondary battery according to a first embodiment; FIG. 2 is a perspective view showing a negative electrode lead constituting the cylindrical nonaqueous electrolyte secondary battery according to the first embodiment; FIG. 3 is a schematic view showing gas flow inside the cylindrical nonaqueous electrolyte secondary battery according to the first embodiment in the event of an abnormality, showing (a) a case where a protrusion is provided and (b) a case where no protrusion is provided; FIG. 4 is an axial cross-sectional view of a cylindrical nonaqueous electrolyte secondary battery according to a second embodiment; FIG. 5 is a perspective view showing a negative electrode lead constituting the cylindrical nonaqueous electrolyte secondary battery according to the second embodiment; FIG. 6 is a developed view of a negative electrode lead constituting the cylindrical nonaqueous electrolyte secondary battery according to the second embodiment; FIG. 7 is an axial cross-sectional view of a cylindrical nonaqueous electrolyte secondary battery according to a third embodiment; FIG. 8 is a perspective view showing a negative electrode lead constituting the cylindrical nonaqueous electrolyte secondary battery according to the third embodiment; FIG. 9 is an axial cross-sectional view of a cylindrical nonaqueous electrolyte secondary battery according to a fourth embodiment; FIG. 10 is a perspective view showing a negative electrode lead constituting the cylindrical nonaqueous electrolyte secondary battery according to the fourth embodiment;

[0009] Hereinafter, an example of an embodiment of a cylindrical nonaqueous electrolyte secondary battery according to the present disclosure will be described in detail 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.

[0010] First Embodiment FIG. 1 is a schematic cross-sectional view of a cylindrical nonaqueous electrolyte secondary battery (hereinafter simply referred to as battery) 10 according to a first embodiment. As shown in FIG. 1 , battery 10 includes an electrode assembly 14, a nonaqueous electrolyte (not shown), a cylindrical outer can 16 with a bottom that accommodates electrode assembly 14 and the nonaqueous electrolyte, and a sealing member 17 that closes the opening of outer can 16. As will be described in detail later, sealing member 17 has a vent valve that releases internal pressure when the internal pressure of battery 10 rises above a predetermined value. In other words, when abnormal heat generation or the like occurs in battery 10 and high-temperature gas is generated inside battery 10, the high-temperature gas is released to the outside through sealing member 17. Hereinafter, the sealing member 17 side in the axial direction (height direction) of battery 10 is referred to as the "upper" side, and the bottom surface 16A side of outer can 16 in the axial direction is referred to as the "lower" side.

[0011] The electrode assembly 14 includes a positive electrode 11, a negative electrode 12, and a separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 that make up the electrode assembly 14 are all long, strip-like 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 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in the longitudinal 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 battery 10 includes insulating plates 18 and 19 arranged above and below the electrode assembly 14, respectively.

[0012] A positive electrode lead 20 is connected to the positive electrode 11. The positive electrode lead 20 passes through a through-hole in the insulating plate 18 and extends toward the sealing body 17. The positive electrode lead 20 is connected to the lower surface of the metal plate 24 of the sealing body 17 by welding or the like. This makes the sealing body 17 a positive electrode terminal.

[0013] A negative electrode lead 30 is connected to the negative electrode 12. More specifically, the negative electrode lead 30 is connected to the end of the negative electrode 12 on the winding start side. The negative electrode lead 30 passes through a through hole 19A in the insulating plate 19 and extends toward the bottom surface 16A of the outer can 16. As will be described in detail later, the negative electrode lead 30 has a base 31, at least a portion of which is connected to the negative electrode 12, an extension 32 that extends along the bottom surface 16A of the outer can 16, and a protrusion 33 that extends in a direction away from the extension 32 and has at least a portion disposed in the hollow portion 28. The extension 32 is connected to the inner surface of the bottom surface 16A of the metal outer can 16 by welding or the like. This makes the outer can 16 a negative electrode terminal.

[0014] A substantially cylindrical hollow portion 28 is formed at the inner end in the winding direction of the electrode body 14. The hollow portion 28 corresponds to the core portion when the positive electrode 11 and the negative electrode 12 are spirally wound. When abnormal heat generation occurs in the battery 10 and high-temperature gas is generated inside the battery 10, the high-temperature gas flows into the hollow portion 28. From the viewpoint of activating an exhaust valve provided at the top of the battery 10 and releasing the high-temperature gas to the outside through the exhaust valve, it is important to guide the high-temperature gas that has flowed into the hollow portion 28 to the top of the battery 10.

[0015] As a result of investigations by the present inventors, it has become clear that the flow path of the high-temperature gas that flows into the hollow portion 28 is significantly affected by the shape of the negative electrode lead 30. Although the detailed mechanism is unclear, it is presumed that the high-temperature gas that flows into the hollow portion 28 moves along the negative electrode lead 30 connected to the end of the negative electrode 12 on the winding start side. As will be described in detail later, by providing a protrusion 33 on the negative electrode lead 30, the high-temperature gas that flows into the hollow portion 28 is guided to the upper part of the battery 10. As a result, the exhaust valve provided at the upper part of the battery 10 can be operated, and the safety of the battery 10 can be improved.

[0016] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer formed on the positive electrode core. The positive electrode core 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 contains a positive electrode active material, a conductive agent, and a binder. 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., onto the positive electrode core, drying the coating, and then compressing it to form a positive electrode mixture layer on both sides of the positive electrode core.

[0017] The positive electrode mixture layer 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 them, it is preferable to contain at least one selected from Co, Ni, Al, 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] Examples of conductive agents contained in the positive electrode mixture layer include carbon black such as acetylene black, furnace black, and ketjen black, as well as carbon materials such as graphite, carbon nanotubes (CNT), carbon nanofibers, and graphene. Examples of binders contained in the positive electrode mixture layer include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resin, and polyolefin. These resins may also be used in combination with carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), or the like.

[0019] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer formed on the negative electrode core. The negative electrode core 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. The negative electrode mixture layer contains a negative electrode active material, a binder, and, if necessary, a conductive agent. The negative electrode 12 can be fabricated by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the surface of the negative electrode core, drying the coating, and then compressing it to form a negative electrode mixture layer on both sides of the negative electrode core. In addition, an exposed portion where the negative electrode core is exposed is provided at the end of the winding start side of the negative electrode 12. A negative electrode lead 30 is connected to this exposed portion.

[0020] The negative electrode mixture layer 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 lump 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.

[0021] A suitable example of a composite material containing Si is SiO ２ Examples 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.

[0022] The binder contained in the negative electrode mixture layer can be, as in the case of the positive electrode mixture layer, fluorine-containing resin, PAN, polyimide, acrylic resin, polyolefin, etc., but styrene butadiene rubber (SBR) is preferably used. The negative electrode mixture layer preferably contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), etc. Among these, it is preferable to use SBR in combination with CMC or a salt thereof, PAA or a salt thereof, etc. The negative electrode mixture layer may contain a conductive agent such as CNT.

[0023] 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.

[0024] The non-aqueous electrolyte has ion conductivity (for example, lithium ion conductivity) and may be a liquid electrolyte (electrolytic solution) or a solid electrolyte.

[0025] 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

[0026] Examples of the solid electrolyte include solid or gel polymer electrolytes and inorganic solid electrolytes. 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. Examples of the matrix polymer include a polymer material that absorbs the non-aqueous solvent and gels. Examples of the polymer material include fluororesin, acrylic resin, and polyether resin. Examples of the inorganic solid electrolyte include materials known in all-solid-state lithium ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.).

[0027] The outer can 16 is a cylindrical metal container with a bottom that is open at the top and contains the electrode assembly 14 and the non-aqueous electrolyte. The outer can 16 has a bottom 16A and a sidewall 16B that extends upward from the outer edge of the bottom 16A. As described above, the extension 32 of the negative electrode lead 30 is welded to the inner surface of the bottom 16A.

[0028] The exterior can 16 has a grooved portion 22 formed by a portion of the side wall 16B projecting inward. The grooved portion 22 is formed in an annular shape along the circumferential direction of the exterior can 16, and supports the sealing body 17 on its top surface. In other words, the sealing body 17 is fixed to the top of the exterior can 16 by the grooved portion 22 and the open end of the exterior can 16 that is crimped to the sealing body 17.

[0029] The sealing body 17 is a disk-shaped member having an exhaust valve. The sealing body 17 has a structure in which a metal plate 24, an insulating member 25, and a valve body 26 are stacked in this order from the electrode body 14 side. The metal plate 24 and the valve body 26 are connected to each other at the radial center. A positive electrode lead 20 is connected to the metal plate 24. This allows the valve body 26 to function as an external terminal for the positive electrode 11. The outer periphery of the valve body 26 is held, via a gasket 27, between a crimped portion formed by bending the opening of the outer can 16 inward and a grooved portion 22.

[0030] In the event of an abnormality, if high-temperature gas is generated within the battery 10 and the internal pressure of the battery 10 rises excessively, the generated high-temperature gas pushes up and bulges the thin-walled portion 26A formed on the valve body 26. The thin-walled portion 26A and the portion inside it of the valve body 26 then deform so as to protrude toward the outside of the battery 10. As a result, high-temperature gas is exhausted from this bulged portion to the outside of the battery 10. In other words, the thin-walled portion 26A of the valve body 26 and the portion radially inward thereof function as an exhaust valve (explosion-proof valve). In FIG. 1 , the portion indicated by the symbol B (the thin-walled portion 26A and the portion radially inward thereof) is the exhaust valve. Note that the exhaust valve may be configured so that the thin-walled portion 26A of the valve body 26 and the portion radially inward thereof rupture when the internal pressure of the battery 10 rises excessively.

[0031] 1 , as long as the structure of the sealing body 17 has a vent valve that releases the internal pressure when the internal pressure of the battery 10 increases excessively. For example, the sealing body 17 may have a laminated structure including two valve bodies, or may have a convex cap that covers the valve body.

[0032] Next, the negative electrode lead 30 will be described in detail with further reference to Figures 2 and 3. Figure 2 is a perspective view schematically showing the negative electrode lead 30.

[0033] As shown in FIGS. 1 and 2 , the negative electrode lead 30 has a base 31, at least a portion of which is connected to the negative electrode core of the negative electrode 12, an extension 32 that extends along the bottom surface 16A of the outer can 16, and a protrusion 33 that extends in a direction away from the extension 32 and has at least a portion disposed in the hollow portion 28. The negative electrode lead 30 is a conductive member for electrically connecting the negative electrode core to the outer can 16, which serves as the negative electrode terminal. In this embodiment, the negative electrode lead 30 is formed from a single continuous member and has a bent portion 34. The extension 32 and the protrusion 33 are connected via the bent portion 34. By forming the negative electrode lead 30 having the protrusion 33 from a single member, the number of components constituting the battery 10 does not increase, and therefore an increase in the manufacturing cost of the battery 10 can be suppressed.

[0034] The negative electrode lead 30 has a substantially constant width and thickness throughout. The width and thickness of the negative electrode lead 30 can be set appropriately depending on the size and capacity of the battery 10. The width of the negative electrode lead 30 is, for example, 1 mm or more and 5 mm or less. The thickness of the negative electrode lead 30 is, for example, 50 μm or more and 250 μm or less. The negative electrode lead 30 can be made using one or more materials selected from the group consisting of aluminum, nickel, copper, and alloys containing these metals.

[0035] The base 31 extends along the axial direction and, except for a partial lower region, connects to an exposed portion of the negative electrode core at the winding start end of the negative electrode 12. The base 31 is joined to the surface of the negative electrode core by, for example, ultrasonic welding. The lower end of the base 31 passes through the through hole 19A of the insulating plate 19.

[0036] From the viewpoint of strengthening the bond between the base 31 and the negative electrode core, the axial length of the base 31 is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more of the axial length of the negative electrode 12. The upper limit of the axial length of the base 31 is, for example, 110% of the axial length of the negative electrode 12.

[0037] The extension 32 is connected to the lower end of the base 31 and extends along the bottom surface 16A of the outer can 16. The extension 32 is connected by welding to the inner surface of the bottom surface 16A of the outer can 16. A bent portion 34 is formed at the end of the extension 32 opposite the base 31, and the protrusion 33 is connected via the bent portion 34.

[0038] The length of the extension portion 32 in the extension direction is the length over which the entire extension portion 32 is disposed inside the hollow portion 28 when viewed from above the electrode body 14. From the viewpoint of reliably disposing the protrusion 33 in the hollow portion 28, the length of the extension portion 32 in the extension direction is preferably 95% or less, and more preferably 90% or less, of the radial length (diameter) of the hollow portion 28. On the other hand, if the length of the extension portion 32 is too small, it becomes difficult to weld the extension portion 32 to the inner surface of the bottom surface 16A of the outer can 16. Therefore, the length of the extension portion 32 in the extension direction is preferably 50% or more, and more preferably 60% or more, of the radial length of the hollow portion 28. Therefore, the length of the extension portion 32 is preferably 50% or more and 95% or less, and more preferably 60% or more and 90% or less, of the radial length of the hollow portion 28.

[0039] The protruding portion 33 is connected to the extending portion 32 via the bent portion 34 and extends along the axial direction. As a result, the region of the protruding portion 33 excluding the lower end portion is disposed in the hollow portion 28. In this embodiment, the protruding portion 33 is formed substantially perpendicular to the extending portion 32. That is, the extension direction of the protruding portion 33 is a direction substantially normal to the surface of the extending portion 32. Here, the substantially normal direction means a direction that is recognized as substantially the normal direction, and includes, for example, a range inclined by about 5° from the normal. Furthermore, in this embodiment, the protruding portion 33 does not abut against the inner circumferential surface of the negative electrode 12, but a portion of the protruding portion 33 may abut against the inner circumferential surface of the negative electrode 12.

[0040] 3A and 3B are diagrams showing the gas flow inside the battery 10 when an abnormality occurs in the battery 10. Fig. 3A shows the gas flow when the protrusion 33 is present, and Fig. 3B shows the gas flow when the protrusion 33 is not present.

[0041] 3, when high-temperature gas is generated inside the battery 10 due to abnormal heat generation or the like, the high-temperature gas flows into the hollow portion 28. As described above, the gas present in the hollow portion 28 tends to move along the negative electrode lead 30. Therefore, the gas present in the hollow portion 28 moves, for example, along the base 31 to the lower side of the battery 10.

[0042] 3(b), if the negative electrode lead 30 does not have a protrusion 33, the high-temperature gas that has moved to the lower side of the battery 10 may enter the gap between the electrode body 14 and the insulating plate 19 or the gap between the insulating plate 19 and the bottom surface 16A of the outer can 16. Then, the high-temperature gas moves to the outer periphery of the battery 10 through the gap. As a result, the side wall 16B of the outer can 16 may be exposed to high temperatures and may be damaged.

[0043] As shown in FIG. 3( a), when the negative electrode lead 30 has a protrusion 33, high-temperature gas that has moved to the lower side of the battery 10 is guided along the protrusion 33 to the upper side of the battery 10. This prevents gas present below the hollow portion 28 from entering the gap between the electrode body 14 and the insulating plate 19 and the gap between the insulating plate 19 and the bottom surface 16A of the outer can 16. As a result, damage to the side wall 16B of the outer can 16 can be suppressed. Furthermore, because the high-temperature gas is guided along the protrusion 33 to the upper side of the battery 10, it becomes easier to operate the exhaust valve of the sealing body 17 provided at the top of the battery 10, thereby improving the safety of the battery 10.

[0044] From the viewpoint of smoothly guiding the generated high-temperature gas to the upper side of the battery 10, the axial length of the protrusion 33 is preferably 10% or more of the axial length of the base 31, more preferably 20% or more, and even more preferably 30% or more. On the other hand, if the axial length of the protrusion 33 is too large, the protrusion 33 may be easily broken or may fall over and come into contact with the base 31, which may actually worsen the gas flow in the hollow portion 28. Therefore, the axial length of the protrusion 33 is preferably 70% or less of the axial length of the base 31, more preferably 60% or less, and even more preferably 50% or less. Therefore, the axial length of the protrusion 33 is preferably 10% or more but 70% or less of the axial length of the base 31, more preferably 20% or more but 60% or less, and even more preferably 30% or more but 50% or less.

[0045] Second Embodiment Next, a cylindrical nonaqueous electrolyte secondary battery 10A according to a second embodiment will be described with reference to Fig. 4 to Fig. 6. Fig. 4 is an axial cross-sectional view of the battery 10A according to the second embodiment, Fig. 5 is a perspective view showing a negative electrode lead 30A according to the second embodiment, and Fig. 6 is a developed view of the negative electrode lead 30A according to the second embodiment. Below, the same reference numerals are used for components common to the first embodiment, and redundant description will be omitted. Differences from the first embodiment will be mainly described.

[0046] 4 to 6, the negative electrode lead 30A of this embodiment has a base 31, an extending portion 32, and a protruding portion 33, similar to the first embodiment. The shapes of the base 31 and the extending portion 32 are similar to those of the first embodiment. On the other hand, the negative electrode lead 30A of this embodiment differs from the first embodiment in the shape of the protruding portion 33.

[0047] The protruding portion 33 has a first region 33A facing the base 31 and a pair of second regions 33B provided between the base 31 and the first region 33A. The length of the second region 33B in the extension direction of the extending portion 32 (hereinafter referred to as the "first direction") is approximately the same as the length of the extending portion 32. As a result, the lower region of the negative electrode lead 30A is surrounded by the base 31, the extending portion 32, and the protruding portion 33, and has a box shape that is open at the top.

[0048] The protruding portion 33 of the negative electrode lead 30 in the first embodiment has only the first region 33A facing the base 31. Therefore, in the event of an abnormality or the like, high-temperature gas present in the hollow portion 28 may infiltrate, via the gap between the base 31 and the protruding portion 33, into the gap between the electrode body 14 and the insulating plate 19 and the gap between the insulating plate 19 and the bottom surface 16A of the outer can 16. On the other hand, as described above, the negative electrode lead 30A in the second embodiment has a pair of second regions 33B provided between the base 31 and the first region 33A. Therefore, in the event of an abnormality or the like, high-temperature gas present in the hollow portion 28 is prevented from infiltrating, via the gap between the base 31 and the protruding portion 33, into the gap between the electrode body 14 and the insulating plate 19 and the gap between the insulating plate 19 and the bottom surface 16A of the outer can 16. As a result, damage to the side wall 16B of the outer can 16 due to exposure to high temperatures can be further suppressed.

[0049] The axial length of the second region 33B is, for example, uniform across the first direction and is approximately the same as the axial height of the first region 33A. Note that the axial length of the second region 33B may vary in the first direction. For example, the axial length of the second region 33B may increase in the first direction as it approaches the base 31.

[0050] The negative electrode lead 30 is preferably formed from a single continuous member. The negative electrode lead 30 of this embodiment can be produced, for example, by processing a metal plate made of aluminum or the like into the shape of the developed view shown in FIG. 6 and bending the boundary between the extension portion 32 and the first region 33A and the boundary between the extension portion 32 and the second region 33B. The first region 33A and the second region 33B may be joined to the base 31 or the extension portion 32 by welding or the like. The first region 33A and the second region 33B may also be joined to each other by welding or the like.

[0051] [Third Embodiment] Next, a cylindrical nonaqueous electrolyte secondary battery 10B according to a third embodiment will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is an axial cross-sectional view of the battery 10B according to the third embodiment, and Fig. 8 is a perspective view showing a negative electrode lead 30B according to the third embodiment. In the following, the same reference numerals are used for components common to the first and second embodiments, and redundant description will be omitted. Differences from the first and second embodiments will be mainly described.

[0052] 7 and 8 , the negative electrode lead 30B of this embodiment has a base 31, an extending portion 32, and a protruding portion 33, similar to the first and second embodiments. However, as will be described in detail later, the shape of the extending portion 32 of the negative electrode lead 30B is different from that of the first and second embodiments. Also, the protruding portion 33 of the negative electrode lead 30B is different from that of the first and second embodiments in that it is joined to the upper surface of the extending portion 32 by welding or the like.

[0053] Like the extending portion 32 in the first and second embodiments, the extending portion 32 of the negative electrode lead 30B is connected to the lower axial end of the base 31 and extends along the bottom surface 16A of the outer can 16. On the other hand, the length of the extending portion 32 of the negative electrode lead 30B in the extension direction is longer than the extending portion 32 of the first and second embodiments. More specifically, the length of the extending portion 32 of the negative electrode lead 30B in the extension direction is a length over which a portion of the extending portion 32 is disposed outside the hollow portion 28 in a top view of the electrode body 14. The length of the extending portion 32 in the extension direction is, for example, 110% or more of the radial length (diameter) of the hollow portion 28, preferably 130% or more of the radial length of the hollow portion 28, and more preferably 150% or more of the radial length of the hollow portion 28. By increasing the length of the extension portion 32 in the extension direction, it becomes easier to weld the extension portion 32 to the inner surface of the bottom surface 16A of the outer can 16.

[0054] [Fourth Embodiment] Next, a cylindrical nonaqueous electrolyte secondary battery 10C according to a fourth embodiment will be described with reference to Figures 9 to 11. Figure 9 is an axial cross-sectional view of the battery 10C according to the fourth embodiment, and Figure 10 is a perspective view showing a negative electrode lead 30C according to the fourth embodiment. Below, the same reference numerals are used for components common to the first to third embodiments, and redundant description will be omitted. Differences from the first to third embodiments will be mainly described.

[0055] 9 and 10 , the negative electrode lead 30C of the present embodiment has a base portion 31 and an extending portion 32, similar to the first to third embodiments. On the other hand, the negative electrode lead 30C differs from the first to third embodiments in that it does not have a protruding portion 33.

[0056] In addition to the base 31 and the extension 32, the negative electrode lead 30C has a partition 35 that extends radially inward from the base 31 and is disposed in the hollow portion 28. The provision of the partition 35 prevents high-temperature gas present in the hollow portion 28 and above the partition 35 from moving downward in the battery 10. As a result, the high-temperature gas is more likely to move upward in the battery 10, making it easier to operate the exhaust valve of the sealing body 17 provided at the top of the battery 10, thereby improving the safety of the battery 10. The partition 35 is joined to the surface of the base 31 by, for example, welding.

[0057] As described above, the partition 35 prevents the high-temperature gas present above the partition 35 from moving downwards in the battery 10. Therefore, the partition 35 is preferably provided below the axial center of the base 31.

[0058] The width of the partition 35 is, for example, approximately the same as the width of the base 31. By increasing the width of the partition 35, the high-temperature gas present in the hollow portion 28, which is present above the partition 35, is prevented from moving downward to the battery 10. On the other hand, if the width of the partition 35 is too large, the high-temperature gas present in the hollow portion 28, which is present below the partition 35, is prevented from moving upward to the battery 10. Therefore, the width of the partition 35 is preferably 50% to 150% of the width of the base 31, and more preferably 75% to 125%. An example of the width of the partition 35 is 0.5 mm to 5 mm.

[0059] The length of the partition portion 35 in the extension direction is, for example, approximately the same as the length of the extension portion 32 in the extension direction. In this embodiment, of the ends of the partition portion 35, the end portion 35A opposite to the base portion 31 does not abut against the inner circumferential surface of the negative electrode 12, but may abut against the inner circumferential surface of the negative electrode 12.

[0060] FIG. 11 is an axial cross-sectional view of a battery 10C, which is a modification of the fourth embodiment. As shown in FIG. 11 , the partition 35 may be provided so as to slope upward in the axial direction from the base 31. In this case, high-temperature gas present in the hollow portion 28 and below the partition 35 is more likely to move upward in the battery 10 along the lower surface 35B of the partition 35. In other words, the high-temperature gas present above the partition 35 is prevented from moving downward in the battery 10, while the high-temperature gas present below the partition 35 is more likely to move upward in the battery 10. This makes it easier to operate the exhaust valve of the sealing body 17 provided at the top of the battery 10, further improving the safety of the battery 10.

[0061] 11 , the inclination angle θ of the partition 35 with respect to the normal direction to the surface of the base 31 is preferably 10° or more, more preferably 15° or more, and even more preferably 20° or more, from the viewpoint of facilitating the movement of high-temperature gas present below the partition 35 to the upper side of the battery 10. Furthermore, from the viewpoint of preventing the movement of high-temperature gas present above the partition 35 to the lower side of the battery 10, the inclination angle θ is preferably 50° or less, more preferably 45° or less, and even more preferably 40° or less. Therefore, the inclination angle θ is preferably 10° or more and 50° or less, more preferably 15° or more and 45° or less, and even more preferably 20° or more and 40° or less.

[0062] The above-described embodiments can be appropriately modified in design without impairing the object of the present disclosure. For example, in the first and third embodiments, the negative electrode leads 30 and 30B may have a plurality of protrusions 33. In the fourth embodiment, the negative electrode lead 30C may have a plurality of partitions 35. In the fourth embodiment, the length of the extension portion 32 in the extension direction of the extension portion 32 may be such that a portion of the extension portion 32 is disposed outside the hollow portion 28 when viewed from above the electrode body 14, as in the third embodiment.

[0063] The present disclosure is further described by the following embodiments. Aspect 1: A cylindrical nonaqueous electrolyte secondary battery including: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a nonaqueous electrolyte; a bottomed cylindrical outer can containing the electrode assembly and the nonaqueous electrolyte; and a sealing member that closes the opening of the outer can and has a vent valve, wherein a negative electrode lead is connected to an end of the negative electrode at a winding start side, and the negative electrode lead has: a base portion at least a portion of which is connected to the negative electrode and extends along the axial direction; an extension portion connected to a lower axial end of the base and extending along a bottom surface of the outer can; and a protrusion portion connected to the extension portion, extending in a direction away from the extension portion, and at least a portion of which is disposed in a hollow portion provided at an inner end of the electrode assembly in the winding direction. Aspect 2: The cylindrical nonaqueous electrolyte secondary battery according to Aspect 1, wherein the negative electrode lead has a bent portion, and the extension portion and the protrusion portion are connected via the bent portion. Configuration 3: The cylindrical nonaqueous electrolyte secondary battery according to Configuration 1 or 2, wherein the extension direction of the protrusion is approximately normal to the surface of the extension portion.Configuration 4: The cylindrical nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 3, wherein the axial length of the protrusion is 10% to 70% of the axial length of the base.Configuration 5: The cylindrical nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 4, wherein the protrusion includes a first region facing the base and a pair of second regions provided between the base and the first region.Configuration 6: The cylindrical nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 5, wherein the extension portion is welded to the bottom surface of the outer can. Configuration 7: A cylindrical non-aqueous electrolyte secondary battery comprising: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a non-aqueous electrolyte; a bottomed cylindrical outer can that houses the electrode assembly and the non-aqueous electrolyte; and a sealing body that closes an opening of the outer can and has a vent valve, wherein a negative electrode lead is connected to an end of the negative electrode on the winding start side, and the negative electrode lead has: a base that extends in the axial direction; an extension that connects to a lower end of the base in the axial direction and extends along the bottom surface of the outer can; and a partition that extends radially inward from the base and is located in a hollow portion that is provided at an inner end of the electrode assembly in the winding direction.Aspect 8: The cylindrical nonaqueous electrolyte secondary battery according to Aspect 7, wherein the partition is provided below the axial center of the base. Aspect 9: The cylindrical nonaqueous electrolyte secondary battery according to Aspect 7 or 8, wherein the partition is provided so as to incline from the base toward the axially upper side.

[0064] 10 Non-aqueous electrolyte secondary battery (battery), 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Outer can, 16A Bottom surface, 16B Side wall, 17 Sealing body, 18, 19 Insulating plate, 19A Through hole, 20 Positive electrode lead, 22 Grooved portion, 24 Metal plate, 25 Insulating member, 26 Valve body, 26A Thin portion, 27 Gasket, 28 Hollow portion, 30, 30A, 30B, 30C Negative electrode lead, 31 Base portion, 32 Extension portion, 33 Protruding portion, 33A First region, 33B Second region, 34 Bent portion, 35 Partition portion, 35A End portion, 35B Bottom surface, B Exhaust valve, θ Tilt angle.

Claims

1. A cylindrical non-aqueous electrolyte secondary battery comprising: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a non-aqueous electrolyte; a bottomed cylindrical outer can containing the electrode assembly and the non-aqueous electrolyte; and a sealing body that closes an opening of the outer can and has a ventilation valve, wherein a negative electrode lead is connected to an end of the negative electrode at the winding start side, and the negative electrode lead has: a base at least a portion of which is connected to the negative electrode and extends along the axial direction, an extension connected to a lower axial end of the base and extends along a bottom surface of the outer can, and a protrusion connected to the extension, extending in a direction away from the extension, and at least a portion of which is disposed in a hollow portion provided at the inner end of the electrode assembly in the winding direction.

2. The cylindrical nonaqueous electrolyte secondary battery according to claim 1, wherein the negative electrode lead has a bent portion, and the extending portion and the protruding portion are connected via the bent portion.

3. The cylindrical nonaqueous electrolyte secondary battery according to claim 1, wherein the extension direction of said protrusion is substantially normal to the surface of said extension portion.

4. The cylindrical nonaqueous electrolyte secondary battery according to claim 1, wherein the axial length of said protrusion is 10% or more and 70% or less of the axial length of said base.

5. The cylindrical nonaqueous electrolyte secondary battery according to claim 1, wherein the protrusion includes a first region facing the base, and a pair of second regions provided between the base and the first region.

6. The cylindrical nonaqueous electrolyte secondary battery according to claim 1, wherein the extension is welded to the bottom surface of the exterior can.

7. A cylindrical non-aqueous electrolyte secondary battery comprising: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a non-aqueous electrolyte; a cylindrical outer can with a bottom that contains the electrode assembly and the non-aqueous electrolyte; and a sealing body that closes the opening of the outer can and has a ventilation valve, wherein a negative electrode lead is connected to an end of the negative electrode at the winding start side, and the negative electrode lead has: a base at least a portion of which is connected to the negative electrode and extends in the axial direction; an extension connected to a lower axial end of the base and extending along a bottom surface of the outer can; and a partition extending radially inward from the base and disposed in a hollow portion provided at the inner end of the electrode assembly in the winding direction.

8. The cylindrical nonaqueous electrolyte secondary battery according to claim 7, wherein the partition portion is provided below the axial center portion of the base portion.

9. The cylindrical nonaqueous electrolyte secondary battery according to claim 7, wherein the partition is inclined axially upward with respect to a normal direction to the surface of the base.

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