Cylindrical battery

Abstract

A negative electrode (12) has a non-facing part (43) wound in a state of not facing a positive electrode (11). The non-facing part (43) includes a mixture layer formation part (44) and a mixture layer non-formation part (45) in which negative electrode mixture layers (41) are not formed on both surfaces of a negative electrode core body (40). A reinforcement material (50) is disposed on at least one surface of the mixture layer non-formation part (45), the reinforcement material (50) including a first reinforcement material (51) disposed so as to straddle a winding start end (44X) of the mixture layer formation part (44). The mixture layer non-formation part (45) is characterized in having an exposed part (47) in which both surfaces of the negative electrode core body (40) are exposed, between a position overlapping a winding start end (51X) of the first reinforcement material (51) and a winding termination end 46Y of a lead connection part (46).

Description

Cylindrical battery

[0001] The present disclosure relates to cylindrical batteries.

[0002] Conventionally, cylindrical batteries have been known that include an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, and a bottomed cylindrical outer can that houses the electrode assembly. Patent Document 1 discloses a cylindrical battery in which a negative electrode lead is provided at the winding start side of the negative electrode. Patent Document 1 also discloses a method for reducing the risk of internal short circuits by applying insulating tape across the surface of the negative electrode lead.

[0003] International Publication No. 2018 / 180748

[0004] As the capacity of cylindrical batteries has increased in recent years, the volume change of the negative electrode during charge and discharge has become larger. As a result of studies by the present inventors, it has become clear that in the technology disclosed in Patent Document 1, when the volume change of the negative electrode during charge and discharge becomes large, the negative electrode is more likely to deform near the winding start end of the positive electrode. Deformation of the negative electrode near the winding start end of the positive electrode may cause an internal short circuit.

[0005] a non-facing portion at the winding start side of the electrode body where the negative electrode is wound so as not to face the positive electrode with the separator interposed therebetween; a mix layer-forming portion in which a negative electrode mix layer is formed on at least one surface of the negative electrode core; and a mix layer-non-forming portion that is disposed closer to the winding start side of the electrode body than the mix layer-forming portion and in which the negative electrode mix layer is not formed on both surfaces of the negative electrode core; at least one reinforcing material is disposed on the surface of the mix layer-non-forming portion, and the reinforcing material includes a first reinforcing material that is disposed so as to straddle the winding start end of the mix layer-forming portion; the mix layer-non-forming portion has a lead connection portion to which a negative electrode lead is joined on at least one surface of the negative electrode core; and an exposed portion in which both surfaces of the negative electrode core are exposed is provided between a position overlapping with the winding start end of the first reinforcing material and the winding end end of the lead connection portion.

[0006] According to a cylindrical battery according to one aspect of the present disclosure, deformation of the negative electrode near the winding start end of the positive electrode can be suppressed, thereby suppressing the occurrence of internal short circuits.

[0007] Fig. 1 is an axial cross-sectional view of a cylindrical battery according to an embodiment; Fig. 2 is a diagram showing a portion of a radial cross-section of an electrode body according to an embodiment; Fig. 3 is a plan view of the winding start side of the outer surface of a rolled electrode in a state in which a positive electrode and a negative electrode according to an embodiment are deployed; Fig. 4 is a diagram showing a portion of a radial cross-section of an electrode body according to another embodiment;

[0008] Hereinafter, an example of an embodiment of a cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. Note that the cylindrical battery according to the present disclosure is not limited to the embodiment described below.

[0009] Fig. 1 is an axial cross-sectional view of a cylindrical battery 10 according to an embodiment. As shown in Fig. 1, the cylindrical battery 10 includes a positive electrode 11, a negative electrode 12, and a separator 13. The positive electrode 11 and the negative electrode 12 are wound together with the separator 13 interposed therebetween, and a cylindrical outer can 16 with a bottom that houses the electrode assembly 14. The cylindrical battery 10 also includes an electrolyte housed in the outer can 16 and a sealing member 17 that closes the opening of the outer can 16. For ease of explanation, the sealing member 17 side of the cylindrical battery 10 will be referred to as the "top" and the bottom side of the outer can 16 as the "bottom."

[0010] The electrolyte may be an aqueous electrolyte, but in this embodiment, a non-aqueous electrolyte is used. The non-aqueous electrolyte has lithium ion conductivity. The non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte. The cylindrical battery 10 is, for example, a non-aqueous electrolyte secondary battery, and preferably a lithium ion battery.

[0011] 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

[0012] As the solid electrolyte, for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc. can be used. As the inorganic solid electrolyte, a material known in all-solid-state lithium ion secondary batteries, etc. (for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a halogen-based solid electrolyte, etc.) can be used. The polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer. As the matrix polymer, for example, a polymer material that absorbs a non-aqueous solvent and gels is used. As the polymer material, for example, a fluororesin, an acrylic resin, a polyether resin, etc. can be used.

[0013] As described above, the electrode assembly 14 has a wound 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 are all long strips 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 both the length and width directions than the positive electrode 11. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and for example, two separators 13 are arranged to sandwich the positive electrode 11.

[0014] The positive electrode 11 has a long positive electrode core 30 and a positive electrode mixture layer 31 disposed on the positive electrode core 30. The positive electrode core 30 can be a foil of a metal that is stable within the potential range of the positive electrode 11, such as aluminum, an aluminum alloy, stainless steel, or titanium, or a film with such a metal disposed on the surface layer. The positive electrode mixture layer 31 contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF), and is preferably formed on both sides of the positive electrode core 30. For example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, or the like is used as the positive electrode active material.

[0015] The thickness of the positive electrode 11 is, for example, 160 μm or more and 200 μm or less. In this embodiment, the thickness of the positive electrode 11 is substantially constant except for the core exposed portion to which the positive electrode lead 20 is connected. The thickness of the positive electrode core 30 is, for example, 10 μm or more and 30 μm or less. The thickness of the positive electrode mixture layer 31 is, for example, 70 μm or more and 100 μm or less on one side of the positive electrode core 30. The positive electrode 11 can be produced by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core 30, drying the coating, and then compressing it to form the positive electrode mixture layer 31 on both sides of the positive electrode core 30.

[0016] The negative electrode 12 has a long negative electrode core 40 and a negative electrode mixture layer 41 disposed on the negative electrode core 40. The negative electrode core 40 can be made of a foil of a metal that is stable within the potential range of the negative electrode 12, such as copper, a copper alloy, stainless steel, nickel, or a nickel alloy, or a film having such a metal disposed on its surface. The negative electrode mixture layer 41 contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR), and is preferably formed on both sides of the negative electrode core 40.

[0017] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Suitable examples of the carbon material include natural graphite such as flake graphite, massive graphite, and amorphous graphite, and artificial graphite such as massive artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB).

[0018] Furthermore, it is preferable to use a silicon-containing material for the negative electrode active material. Using a silicon-containing material for the negative electrode active material facilitates achieving high capacity. Furthermore, silicon-containing materials undergo a larger volume change during charge and discharge than carbon materials. Therefore, when a silicon-containing material is used for the negative electrode active material, deformation of the negative electrode 12 is likely to occur near the winding start end 11X (see FIG. 2) of the positive electrode 11. In other words, when a silicon-containing material is used for the negative electrode active material, the effect of suppressing deformation of the negative electrode 12, described below, is significant. The content of the silicon-containing material may be, for example, 3% by mass or more and 30% by mass or less, or 5% by mass or more and 25% by mass or less, of the total mass of the negative electrode active material.

[0019] The silicon-containing material may be any material containing Si, and examples thereof include silicon alloys, silicon compounds, and composite materials containing Si. Among these, composite materials containing Si are preferred. A suitable example of a composite material containing Si is SiO ２ Examples of such composite materials include a material in which Si fine particles are dispersed in a silicon dioxide phase, a silicate phase such as lithium silicate, or an amorphous carbon phase. A conductive layer such as a carbon coating may be formed on the particle surface of the composite material.

[0020] The thickness of the negative electrode 12 is, for example, 170 μm or more and 210 μm or less. In the present embodiment, the thickness of the negative electrode 12 is substantially constant except for an outer peripheral exposed portion 42 and a mixture layer non-forming portion 45 (see FIG. 2 ), which will be described later. The thickness of the negative electrode core 40 is, for example, 5 μm or more and 15 μm or less. The thickness of the negative electrode mixture layer 41 is, for example, 70 μm or more and 110 μm or less on one side of the negative electrode core 40. The negative electrode 12 can be produced, similarly to the positive electrode 11, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder onto the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode mixture layer 41 on both sides of the negative electrode core 40.

[0021] The electrode body 14 has a positive electrode lead 20 connected to the positive electrode 11 and a negative electrode lead 21 connected to the negative electrode 12. In this embodiment, a core exposed portion where the positive electrode mixture layer 31 is not present and the surface of the positive electrode core 30 is exposed is formed in the center of the positive electrode 11 in the longitudinal direction, and the positive electrode lead 20 is connected to this core exposed portion. In addition, the negative electrode lead 21 is connected to one end of the negative electrode 12 in the longitudinal direction, which is located at the start side of the winding of the electrode body 14.

[0022] Insulating plates 18 and 19 are disposed above and below the electrode body 14. In the example shown in Fig. 1 , the positive electrode lead 20 passes through a through hole in the insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes through a through hole in the insulating plate 19 and extends toward the bottom side of the outer can 16. The positive electrode lead 20 is connected to the underside of an internal terminal plate 23 of the sealing body 17 by welding or the like, and a cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal. The negative electrode lead 21 is connected to the inner bottom surface of the outer can 16 by welding or the like, and the outer can 16 serves as the negative electrode terminal.

[0023] The negative electrode 12 is disposed on the outermost peripheral surface of the electrode assembly 14, and an outer peripheral exposed portion 42 is provided where the surface of the negative electrode core 40 is exposed. At least a portion of the outer peripheral exposed portion 42 abuts against the inner peripheral surface of the outer can 16. By abutting the outer peripheral exposed portion 42 against the inner peripheral surface of the outer can 16, both longitudinal ends of the negative electrode 12 and the outer can 16 are electrically connected, ensuring good current collection. The outer peripheral exposed portion 42 may be provided on a portion of the outermost peripheral surface of the electrode assembly 14, but is preferably provided over the entire outermost peripheral surface of the electrode assembly 14. A separator 13 may be disposed on the outermost peripheral surface of the electrode assembly 14.

[0024] The outer can 16 is a cylindrical metal container with a bottom. A gasket 28 is provided between the outer can 16 and the sealing body 17, sealing the inside of the battery. The outer can 16 has a groove 22 that supports the sealing body 17, formed, for example, by pressing the side surface from the outside. The groove 22 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 upper end of the outer can 16 is also bent inward and crimped to the periphery of the sealing body 17.

[0025] The sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked. Each component constituting the sealing body 17 has, for example, a disk or ring shape, and all components except for the insulating member 25 are electrically connected to each other. The lower valve body 24 and the upper valve body 26 are connected at their respective radial centers, with the insulating member 25 interposed between their respective peripheral edges. When abnormal heat generation causes an increase in the internal pressure of the battery, the lower valve body 24 deforms and ruptures, pushing the upper valve body 26 toward the cap 27. This interrupts the current path between the lower valve body 24 and the upper valve body 26. When the internal pressure further increases, the upper valve body 26 ruptures, and gas is discharged from the opening of the cap 27.

[0026] The electrode assembly 14 will be described in detail below with reference to Figures 2 and 3. Figure 2 is a radial cross-sectional view of the winding start side of the electrode assembly 14, and Figure 3 is a plan view showing the winding start side of the outer surface of the winding in a state in which the positive electrode 11 and negative electrode 12 are unfolded. Note that in Figure 2, the separator 13, positive electrode core 30, and positive electrode mixture layer 31 are omitted for clarity.

[0027] 2 and 3 , the negative electrode 12 constituting the electrode assembly 14 has a non-facing portion 43 at the winding start side of the electrode assembly 14 where the negative electrode 12 is wound without facing the positive electrode 11 via the separator 13. In other words, the negative electrode 12 extends toward the winding start side of the electrode assembly 14 beyond the position where it faces the winding start end 11X of the positive electrode 11 via the separator 13.

[0028] The non-facing portion 43 includes a mixture layer forming portion 44 in which the negative electrode mixture layer 41 is formed on at least one surface of the negative electrode core 40, and a mixture layer non-forming portion 45 in which the negative electrode mixture layer 41 is not formed on either surface of the negative electrode core 40. In the present embodiment, the negative electrode mixture layer 41 is formed on either surface of the negative electrode core 40 in the mixture layer forming portion 44.

[0029] The mixture layer forming section 44 is preferably wound 0.5 or more times, and more preferably 0.75 or more times. By winding the mixture layer forming section 44 0.5 or more times, the rigidity of the winding start side of the electrode body 14 is improved, making it easier to maintain the shape of the winding core portion. As a result, in the event of abnormal heat generation in the battery, gas generated inside the battery can be smoothly vented to the outside of the battery via the winding core portion. There is no particular upper limit to the length of the mixture layer forming section 44, but it is, for example, a length corresponding to three windings.

[0030] The mixture layer non-forming portion 45 is disposed closer to the winding start side of the electrode body 14 than the mixture layer forming portion 44, and is provided toward one longitudinal end of the negative electrode 12. The mixture layer non-forming portion 45 is wound, for example, 0.3 to 3 turns.

[0031] The portion 45 without a mixture layer has a lead connection portion 46 to which the negative electrode lead 21 is joined on at least one surface of the negative electrode core 40. An exposed portion 47 in which both surfaces of the negative electrode core 40 are exposed is provided in the portion 45 without a mixture layer between a winding start end 51X of a first reinforcing member 51 (described later) and a winding end end 46Y of the lead connection portion 46. The exposed portion 47 is formed across the entire width of the negative electrode 12. In this embodiment, the negative electrode lead 21 is joined to the outer winding surface of the lead connection portion 46. Note that the negative electrode lead 21 may also be joined to the inner winding surface of the lead connection portion 46.

[0032] As shown in Figures 2 and 3, a reinforcing material 50 is disposed on at least one surface of the portion 45 where no mixture layer is formed. The reinforcing material 50 has, for example, a rectangular shape in a plan view. The thickness of the reinforcing material 50 is, for example, 10 µm or more and 70 µm or less, and preferably 20 µm or more and 60 µm or less. By disposing the reinforcing material 50 on the surface of the portion 45 where no mixture layer is formed, the rigidity of the portion 45 where no mixture layer is formed can be improved. As a result, the shape of the winding core portion can be easily maintained, and in the event of abnormal heat generation in the battery, gas generated inside the battery can be more easily vented to the outside of the battery via the winding core portion.

[0033] An example of the reinforcing material 50 is insulating tape, which is attached to at least one surface of the composite layer non-forming portion 45. The insulating tape has, for example, a base portion and an adhesive portion formed on one surface of the base portion. A layer containing inorganic particles such as metal oxide may be provided between the base portion and the adhesive portion. The base portion may be made of any insulating resin, such as polypropylene (PP), polyethylene terephthalate (PET), polyimide (PI), polyphenylene sulfide (PPS), polyamide (PA), etc. These resins may be used alone or in combination of two or more. The thickness of the base portion is, for example, 5 μm or more and 50 μm or less, preferably 10 μm or more and 30 μm or less.

[0034] The adhesive portion is a portion for adhering the insulating tape serving as the reinforcing material 50 to the surface of the portion 45 or the like where the composite layer is not formed. The adhesive portion contains, for example, at least one of a rubber-based polymer and an acrylic-based polymer. The rubber-based polymer and the acrylic-based polymer have adhesive properties, allowing the insulating tape to adhere to the surface of the portion 45 or the like where the composite layer is not formed. The adhesive portion may further contain a silicone-based polymer. The thickness of the adhesive portion is, for example, 1 μm or more and 30 μm or less, and preferably 5 μm or more and 25 μm or less.

[0035] The reinforcing material 50 is not limited to the insulating tape described above. For example, the reinforcing material 50 may be a resin layer formed on the surface of the portion 45 where no composite layer is formed. The resin layer is formed, for example, by applying a resin solution to the surface of the portion 45 where no composite layer is formed and then drying the resulting coating. Examples of resin materials contained in the resin layer include synthetic resins such as epoxy resin, melamine resin, phenolic resin, polyolefin resin, and polyimide resin. One type of these resins may be used alone, or two or more types may be used in combination.

[0036] In the present embodiment, the reinforcing material 50 is composed of two members, and includes a first reinforcing material 51 and a second reinforcing material 52 that is arranged closer to the winding start side of the electrode body 14 than the first reinforcing material 51. The first reinforcing material 51 and the second reinforcing material 52 are both arranged on the outer winding surface of the mixture layer non-forming portion 45. Note that at least one of the first reinforcing material 51 and the second reinforcing material 52 may be arranged on the inner winding surface of the mixture layer non-forming portion 45. Furthermore, the second reinforcing material 52 may be arranged on the surface opposite to the surface to which the negative electrode lead 21 is joined.

[0037] The first reinforcing material 51 is arranged so as to straddle the winding start end 44X of the mixture layer forming portion 44. The first reinforcing material 51 is also arranged so that an exposed portion 47 is formed between a position of the mixture layer non-forming portion 45 that overlaps with the winding start end 51X of the first reinforcing material 51 and the winding end end 46Y of the lead connection portion 46. In other words, the first reinforcing material 51 is arranged so as not to overlap the lead connection portion 46. The first reinforcing material 51 is wound, for example, 0.2 to 1.5 turns inclusive. Increasing the length of the first reinforcing material 51 improves the rigidity of the winding start side of the electrode body 14, making it easier to maintain the shape of the winding core portion.

[0038] The second reinforcing material 52 is disposed at a distance from the first reinforcing material 51 in the length direction of the negative electrode 12. That is, the second reinforcing material 52 is disposed so as not to overlap the first reinforcing material 51 in the thickness direction. The second reinforcing material 52 is also disposed so as to straddle the winding end 46Y of the lead connection portion 46. Therefore, an exposed portion 47 in which both surfaces of the negative electrode core 40 are exposed is provided between the first reinforcing material 51 and the second reinforcing material 52. The second reinforcing material 52 is wound, for example, 0.05 to 0.5 turns inclusive.

[0039] Near winding start end 11X of positive electrode 11, there is a gap that is not occupied by negative electrode 12 and separator 13. Therefore, when the volume of positive electrode 11 and negative electrode 12 changes due to repeated charge and discharge, stress concentration occurs near winding start end 11X of positive electrode 11, making negative electrode 12 particularly prone to bending and deformation.

[0040] In the present embodiment, when the exposed portion 47, in which both surfaces of the negative electrode core 40 are exposed, is provided in the mixture layer non-forming portion 45, the exposed portion 47 deforms preferentially when volume changes occur in the positive electrode 11 and the negative electrode 12 due to repeated charge and discharge. This is because the exposed portion 47 does not have the negative electrode lead 21 or the reinforcing material 50 disposed on its surface and is therefore less rigid than the surrounding portions. The preferential deformation of the exposed portion 47 alleviates stress concentration near the winding start end 11X of the positive electrode 11, thereby suppressing deformation of the negative electrode 12 near the winding start end 11X of the positive electrode 11. As a result, the occurrence of an internal short circuit can be suppressed. As described above, since the exposed portion 47 is provided in the non-facing portion 43 that does not face the positive electrode 11 via the separator 13, even if the exposed portion 47 deforms, an internal short circuit due to the deformation of the exposed portion 47 does not occur.

[0041] The exposed portion 47 is preferably wound 0.05 or more times, more preferably 0.1 or more times. In this case, the amount of deformation of the exposed portion 47 when a volume change occurs in the positive electrode 11 and the negative electrode 12 can be increased, and stress concentration near the winding start end 11X of the positive electrode 11 can be further alleviated. As a result, the occurrence of an internal short circuit due to deformation of the negative electrode 12 near the winding start end 11X of the positive electrode 11 can be further suppressed.

[0042] Furthermore, the exposed portion 47 is preferably wound 0.3 turns or less, and more preferably 0.25 turns or less. In this case, the length of the reinforcing material 50 disposed on the surface of the mixture layer non-forming portion 45 can be sufficiently ensured, the rigidity of the winding start side of the electrode body 14 is further improved, and it becomes easier to maintain the shape of the winding core portion. Therefore, the exposed portion 47 is preferably wound 0.05 turns or more and 0.3 turns or less, and more preferably 0.1 turns or more and 0.25 turns or less.

[0043] In the embodiment shown in FIGS. 2 and 3 , the reinforcing material 50 includes a first reinforcing material 51 and a second reinforcing material 52. However, as shown in FIG. 4 , the reinforcing material 50 may be composed of only the first reinforcing material 51 without including the second reinforcing material 52. Even in this case, when the volume of the positive electrode 11 and the negative electrode 12 changes due to repeated charge and discharge, the exposed portion 47 formed between the winding start end 51X of the first reinforcing material 51 and the winding end end 46Y of the lead connection portion 46 deforms preferentially. As a result, stress concentration near the winding start end 11X of the positive electrode 11 is alleviated, and deformation of the negative electrode 12 near the winding start end 11X of the positive electrode 11 can be suppressed. Furthermore, the reinforcing material 50 may be composed of three or more components. For example, the reinforcing material 50 may include, in addition to the above-mentioned first reinforcing material 51 and second reinforcing material 52 arranged on the outer winding surface of the negative electrode 12, a third reinforcing material arranged on the inner winding surface of the negative electrode 12 in a position overlapping the first reinforcing material 51 in the thickness direction of the negative electrode 12, and a fourth reinforcing material arranged in a position overlapping the second reinforcing material 52 in the thickness direction of the negative electrode 12.

[0044] 2 and 3, the second reinforcing material 52 is arranged so as to straddle the winding end 46Y of the lead connection portion 46, but the second reinforcing material 52 does not have to straddle the winding end 46Y of the lead connection portion 46. By arranging the second reinforcing material 52 so as to straddle the winding end 46Y of the lead connection portion 46, when a volume change occurs in the positive electrode 11 and the negative electrode 12 and the exposed portion 47 is deformed, the deformed portion can be separated from the lead connection portion 46. As a result, deformation and damage to the lead connection portion 46 due to deformation of the exposed portion 47 can be suppressed.

[0045] The present disclosure will be further described by the following embodiments. Configuration 1: An electrode assembly including a strip-shaped positive electrode and a strip-shaped negative electrode wound lengthwise with a separator interposed therebetween, and a bottomed cylindrical outer can that houses the electrode assembly, wherein the negative electrode has a non-facing portion wound at a winding start side of the electrode assembly so as not to face the positive electrode with the separator interposed therebetween, the non-facing portion including a mixture layer forming portion in which a negative electrode mixture layer is formed on at least one surface of a negative electrode core, and a negative electrode mixture layer formed on both surfaces of the negative electrode core, the non-facing portion being disposed on the winding start side of the electrode assembly relative to the mixture layer forming portion A cylindrical battery comprising: a negative electrode core having a negative electrode mix layer-free portion on which a mixture layer is not formed; at least one reinforcing material disposed on the surface of the negative electrode core having a first reinforcing material disposed so as to straddle a winding start end of the negative electrode mix layer-free portion; the negative electrode core having a lead connection portion to which a negative electrode lead is joined on at least one surface of the negative electrode core; and an exposed portion in which both surfaces of the negative electrode core are exposed is provided between a position overlapping with the winding start end of the first reinforcing material and a winding end end of the lead connection portion. Aspect 2: The cylindrical battery according to Aspect 1, wherein the reinforcing material further comprises a second reinforcing material disposed at a distance from the first reinforcing material in the length direction of the negative electrode. Aspect 3: The cylindrical battery according to Aspect 2, wherein the second reinforcing material is disposed so as to straddle a winding end end of the lead connection portion. Aspect 4: The cylindrical battery according to any one of Aspects 1 to 3, wherein the exposed portion is wound 0.05 to 0.3 times. Configuration 5: The cylindrical battery according to any one of Configurations 1 to 4, wherein the mixture layer-forming portion is wound 0.5 or more times. Configuration 6: The cylindrical battery according to any one of Configurations 1 to 5, wherein the reinforcing material is an insulating tape attached to at least one surface of the mixture layer-free portion. Configuration 7: The cylindrical battery according to any one of Configurations 1 to 6, wherein the negative electrode mixture layer contains a silicon-containing material as a negative electrode active material.

[0046] REFERENCE SIGNS LIST 10 Cylindrical battery, 11 Positive electrode, 11X Winding start end, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18 Insulating plate, 19 Insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved portion, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive electrode core, 31 Positive electrode mixture layer, 40 Negative electrode core, 41 Negative electrode mixture layer, 42 Outer periphery exposed portion, 43 Non-facing portion, 44 Mixture layer formed portion, 44X Winding start end, 45 Mixture layer non-formed portion, 46 Lead connection portion, 46Y Winding end end, 47 Exposed portion, 50 Reinforcing material, 51 First reinforcing material, 51X Winding start end, 52 Second reinforcing material

Claims

1. An electrode assembly comprising a strip-shaped positive electrode and a strip-shaped negative electrode wound lengthwise with a separator interposed therebetween; and a bottomed cylindrical outer can accommodating the electrode assembly, wherein the negative electrode has a non-facing portion wound at the winding start side of the electrode assembly so as not to face the positive electrode with the separator interposed therebetween, the non-facing portion including a mix layer-forming portion in which a negative electrode mix layer is formed on at least one surface of a negative electrode core, and a mix layer-non-forming portion that is located closer to the winding start side of the electrode assembly than the mix layer-forming portion and in which the negative electrode mix layer is not formed on both surfaces of the negative electrode core, at least one reinforcing material is located on the surface of the mix layer-non-forming portion, the reinforcing material including a first reinforcing material that is located so as to straddle the winding start end of the mix layer-forming portion, and the mix layer-non-forming portion has a lead connection portion to which a negative electrode lead is joined on at least one surface of the negative electrode core, a cylindrical battery, wherein an exposed portion where both surfaces of the negative electrode core are exposed is provided between a position overlapping with the winding start end of the first reinforcing material and the winding end end of the lead connection portion.

2. The cylindrical battery according to claim 1, wherein the reinforcing member further includes a second reinforcing member spaced apart from the first reinforcing member in the longitudinal direction of the negative electrode.

3. The cylindrical battery according to claim 2, wherein the second reinforcing member is positioned so as to straddle the winding end of the lead connection portion.

4. The cylindrical battery according to claim 1, wherein the exposed portion is wound 0.05 to 0.3 times.

5. The cylindrical battery according to claim 1, wherein the mixture layer forming portion is wound 0.5 or more times.

6. The cylindrical battery according to claim 1, wherein the reinforcing material is an insulating tape attached to at least one surface of the portion where the mixture layer is not formed.

7. The cylindrical battery according to claim 1, wherein the negative electrode mixture layer contains a silicon-containing material as a negative electrode active material.

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