Cylindrical battery

Abstract

A first electrode (11) has a core body (30) and a mixture layer (31) disposed on a surface of the core body (30) and is characterized in that a mixture layer uncoated part (32) in which the mixture layer (31) is not disposed is provided on the surface of the core body (30), that a strip-shaped electrode tab (20) is joined to the mixture layer uncoated part (32), that a protective layer (33) is provided in a region of the surface of the mixture layer uncoated part (32) to which the electrode tab (20) is not joined, and that the protective layer (33) is provided so as not to cover a first surface (20A) adjacent to the electrode tab (20) and joined to the mixture layer uncoated part (30) of the surface of the electrode tab (20), and a second surface (20B) facing the first surface (20A) in the thickness direction of the electrode tab (20).

Description

Cylindrical battery

[0001] This disclosure relates to cylindrical batteries.

[0002] Conventionally, cylindrical batteries are known that have an electrode body in which a positive electrode and a negative electrode are wound with a separator in between. Patent documents 1 and 2 disclose a cylindrical battery in which an uncoated portion of the positive electrode core body is provided in the longitudinal middle of the positive electrode, and an electrode tab is joined to the uncoated portion of the positive electrode core body.

[0003] Patent Document 1 discloses a technique for suppressing breakage of the uncoated portion of the composite layer by interposing a protective layer between the uncoated portion of the composite layer and the electrode tab. Patent Document 2 discloses a technique for suppressing internal short circuits caused by the electrode tab by covering the electrode tab with an insulating protective layer.

[0004] Japanese Patent Publication No. 6070067, Japanese Unexamined Patent Publication No. 2010-55906

[0005] While the technology described in Patent Document 1 can suppress the tearing of the uncoated portion of the composite layer, it may reduce the bonding strength between the electrode tab and the uncoated portion of the composite layer. Furthermore, in the technology described in Patent Document 2, the thickness of the area where the electrode tab is placed increases, leading to increased surface pressure on the uncoated portion of the composite layer near the electrode tab, which may cause tearing of the uncoated portion. Therefore, there is a need for a technology that can suppress tearing of the uncoated portion of the composite layer while ensuring the bonding strength between the electrode tab and the uncoated portion of the composite layer.

[0006] A cylindrical battery according to one aspect of the present disclosure comprises an electrode body in which a first electrode and a second electrode having opposite polarities are wound longitudinally via a separator, and a bottomed cylindrical outer casing for housing the electrode body, wherein the first electrode has a core body and a composite layer disposed on the surface of the core body, and at least one uncoated composite layer portion is provided in the longitudinal middle portion of the first electrode where the composite layer is not disposed on the surface of the core body, a strip-shaped electrode tab is joined to the uncoated composite layer portion, a protective layer is provided in the area of ​​the surface of the uncoated composite layer portion to which the electrode tab is not joined, and the protective layer is provided such that it does not cover a first surface adjacent to the electrode tab and joined to the uncoated composite layer portion on the surface of the electrode tab, and a second surface facing the first surface in the thickness direction of the electrode tab.

[0007] According to a cylindrical battery in one aspect of this disclosure, it is possible to ensure the bonding strength between the electrode tab and the uncoated portion of the composite layer while suppressing the breakage of the uncoated portion of the composite layer.

[0008] This is an axial cross-sectional view of a cylindrical battery according to the first embodiment. This is a front view showing the positive electrode of the cylindrical battery according to the first embodiment in an unfolded state. This is a cross-sectional view taken along line A-A in Figure 2. This is a diagram showing an example of a method for manufacturing a protective layer. This is a diagram of the positive electrode of the cylindrical battery according to the second embodiment, corresponding to Figure 2. This is a diagram of the positive electrode of the cylindrical battery according to the third embodiment, corresponding to Figure 3.

[0009] In the following, an example of an embodiment of the cylindrical battery according to this disclosure will be described in detail with reference to the drawings. In the following description, specific shapes, materials, numerical values, directions, etc., are examples to facilitate understanding of the present invention and can be appropriately modified according to the specifications of the cylindrical battery. Furthermore, if the following description includes multiple embodiments and modifications, it is intended from the outset that their characteristic parts may be used in appropriate combinations.

[0010] [First Embodiment] Figure 1 is an axial cross-sectional view of a cylindrical battery 10 according to the first embodiment. As shown in Figure 1, the cylindrical battery 10 comprises a wound electrode body 14, a non-aqueous electrolyte (not shown), and an outer casing 16 that houses the electrode body 14 and the non-aqueous electrolyte. The outer casing 16 is a bottomed cylindrical metal container with one side open in the axial direction, and the opening of the outer casing 16 is sealed by a sealing body 17. For the sake of explanation, the side of the cylindrical battery 10 with the sealing body 17 will be referred to as "upper," and the bottom side of the outer casing 16 will be referred to as "lower."

[0011] The electrode body 14 has a structure in which a strip-shaped first electrode and a second electrode with opposite polarities are wound along the longitudinal direction via a separator 13. Below, we will describe the case where the first electrode is the positive electrode 11 and the second electrode is the negative electrode 12.

[0012] The positive electrode 11, the negative electrode 12, and the separator 13 are wound in a spiral shape so that they are alternately stacked in the radial direction of the electrode body 14. In the electrode body 14, the longitudinal direction of the positive electrode 11 and the negative electrode 12 is the winding direction, and the width direction of the positive electrode 11 and the negative electrode 12 is the axial direction. The cylindrical battery 10 further includes a positive electrode tab 20 connected to the positive electrode 11 by welding or the like and protruding from the upper end of the electrode body 14, and a negative electrode tab 21 connected to the negative electrode 12 by welding or the like and protruding from the lower end of the electrode body 14.

[0013] The positive electrode 11 comprises a 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 made of a metal foil that is stable within the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal disposed on its surface. The positive electrode mixture layer 31 contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be manufactured, for example, 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.

[0014] The positive electrode composite layer 31 contains particulate lithium-containing composite oxide as the positive electrode active material. The lithium-containing composite oxide is a composite oxide containing metal elements such as Co, Mn, Ni, and Al in addition to Li. The metal elements constituting the lithium-containing composite oxide are, 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, Al, and Mn. Examples of suitable composite oxides include lithium-containing composite oxides containing Ni, Co, and Mn, and lithium-containing composite oxides containing Ni, Co, and Al.

[0015] Examples of conductive agents included in the positive electrode mixture layer 31 include carbon black such as acetylene black and Ketjenblack, graphite, carbon nanotubes (CNTs), carbon nanofibers, and graphene. Examples of binders included in the positive electrode mixture layer 31 include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resins, and polyolefins. In addition, these resins may be used in combination with carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0016] The negative electrode 12 comprises a 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 metal foil that is stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with the metal disposed on its surface. The negative electrode mixture layer 41 contains a negative electrode active material, a binder, and optionally a conductive agent. The negative electrode 12 can be manufactured by applying a negative electrode mixture slurry containing the negative electrode active material and binder to the surface of the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode mixture layer 41 on both sides of the negative electrode core 40.

[0017] The negative electrode mixture layer 41 generally contains a carbon material that reversibly intercepts and releases lithium ions as the negative electrode active material. A suitable example of the carbon material is graphite such as natural graphite like flake graphite, lump graphite, or clay graphite, or artificial graphite such as lump graphite (MAG) or graphitized mesophase carbon microbeads (MCMB). Alternatively, a material containing at least one of elements that alloy with Li, such as Si and Sn, and a material containing such elements may be used as the negative electrode active material.

[0018] As the binder included in the negative electrode mixture layer 41, similar to the case of the positive electrode mixture layer 31, fluororesin, PAN, polyimide, acrylic resin, polyolefin, etc. may be used, but styrene-butadiene rubber (SBR) is preferred. Furthermore, the negative electrode mixture layer 41 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 41 may also contain a conductive agent such as CNT.

[0019] The separator 13 is made of a porous sheet having ion permeability and insulating properties. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator 13 include polyethylene, polyolefins such as polypropylene, and cellulose. The separator 13 may have a single-layer structure or a multi-layer structure. Furthermore, a heat-resistant resin layer, such as aramid resin, may be formed on the surface of the separator 13.

[0020] Non-aqueous electrolytes are lithium ion conductive. Non-aqueous electrolytes may be liquid electrolytes (electrolytes) or solid electrolytes.

[0021] A liquid electrolyte (electrolyte solution) comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. The non-aqueous solvent may also contain halogen-substituted solvents (e.g., fluoroethylene carbonate) in which at least some of the hydrogen atoms in the solvent are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include LiPF4. ６ Lithium salts such as these are used.

[0022] As the solid electrolyte, for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc., can be used. As the inorganic solid electrolyte, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used. The polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As the matrix polymer, for example, a polymer material that absorbs a non-aqueous solvent and gels is used. Examples of polymer materials include fluororesins, acrylic resins, polyether resins, etc.

[0023] Insulating plates 18 and 19 are positioned above and below the electrode body 14, respectively. In the example shown in Figure 1, the positive electrode tab 20 extends towards the sealing body 17 through a through hole in the insulating plate 18, and the negative electrode tab 21 extends towards the bottom of the outer can 16 through a through hole in the insulating plate 19. The positive electrode tab 20 is connected to the lower surface of the internal terminal plate 23 of the sealing body 17 by welding or the like, and the cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, becomes the positive electrode terminal. The negative electrode tab 21 is connected to the inner bottom surface of the outer can 16 by welding or the like, and the outer can 16 becomes the negative electrode terminal.

[0024] As described above, the outer container 16 is a bottomed cylindrical metal container with one end open in the axial direction, and the opening of the outer container 16 is sealed by the sealing body 17.

[0025] A gasket 28 is provided between the outer casing 16 and the sealing body 17 to ensure airtightness inside the battery. The outer casing 16 has a grooved portion 22 formed on its side surface, which protrudes inward to support the sealing body 17. The grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the outer casing 16, and its upper surface supports the sealing body 17. The sealing body 17 is fixed to the upper part of the outer casing 16 by the grooved portion 22 and the open end of the outer casing 16 which is crimped to the sealing body 17.

[0026] The sealing body 17 has a structure in which 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 in order from the electrode body 14 side. Each component constituting the sealing body 17 has, for example, a disc shape or a ring shape, and each component except the insulating member 25 is electrically connected to one another. The lower valve body 24 and the upper valve body 26 are connected at their respective centers, with the insulating member 25 interposed between their respective peripheries. When the internal pressure of the battery rises due to abnormal heat generation, the lower valve body 24 deforms and breaks, pushing the upper valve body 26 towards the cap 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further, the upper valve body 26 breaks, and gas is discharged from the vent hole in the cap 27.

[0027] Next, the positive electrode 11 will be described in detail with reference to Figures 2 and 3. Figure 2 is a front view showing the positive electrode 11 in an unfolded state, and Figure 3 is a cross-sectional view taken along line A-A in Figure 2.

[0028] As shown in Figures 2 and 3, the positive electrode 11 has a positive electrode core 30 and positive electrode mixture layers 31 arranged on both sides of the positive electrode core 30. 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 layers 31 is, for example, 50 μm or more and 100 μm or less on one side of the positive electrode core 30.

[0029] In the longitudinal middle portion of the positive electrode 11, there is an uncoated portion 32 where the positive electrode mixture layer 31 is not applied. In this embodiment, the uncoated portion 32 has a rectangular shape in plan view, and is in contact only with the upper end 11X in the width direction of the positive electrode 11, but not with the lower end 11Y in the width direction of the positive electrode 11. Furthermore, the positive electrode mixture layer 31 is applied to the surface of the region of the positive electrode core 30 that overlaps with the uncoated portion 32 in the width direction of the positive electrode 11. This makes it possible to increase the area of ​​the positive electrode mixture layer 31, and facilitates increasing the capacity of the cylindrical battery 10. The length of the uncoated portion 32 along the longitudinal direction of the positive electrode 11 is, for example, 5 mm or more and 50 mm or less. The uncoated portion 32 can be manufactured by intermittent coating, in which the positive electrode mixture slurry is not applied to a part of the positive electrode core 30.

[0030] A strip-shaped positive electrode tab 20 is joined to at least one surface of the uncoated portion 32 of the composite layer. The positive electrode tab 20 may be placed on either the outer or inner surface of the winding of the positive electrode 11. The positive electrode tab 20 is joined to the uncoated portion 32 of the composite layer by, for example, ultrasonic welding.

[0031] The positive electrode tab 20 is made of a metal, for example, aluminum as its main component. The thickness of the positive electrode tab 20 is generally greater than the thickness of the positive electrode mixture layer 31, for reasons such as reducing electrical resistance. In other words, the positive electrode tab 20 is configured to protrude from the surface of the positive electrode 11 in the direction of the thickness of the positive electrode 11. The thickness of the positive electrode tab 20 is, for example, 50 μm or more and 200 μm or less.

[0032] An insulating tape member 50 is provided on the surface of the positive electrode 11, covering the uncoated portion 32 of the mixture layer. The tape member 50 covers the entire uncoated portion 32 of the mixture layer, a part of the positive electrode tab 20, and the positive electrode mixture layer 31 around the uncoated portion 32. By providing the tape member 50, contact between the uncoated portion 32 of the mixture layer or the positive electrode tab 20 and the negative electrode 12 can be suppressed if the separator 13 is damaged. In this embodiment, the tape member 50 is provided on both sides of the positive electrode 11.

[0033] The tape member 50 is, for example, an adhesive tape having a base layer and an adhesive layer formed on one surface of the base layer. A heat-resistant layer containing inorganic particles such as metal oxides may be provided between the base layer and the adhesive layer. The base layer can be any insulating resin, such as PPS (polyphenylene sulfide), PEEK (polyether ether ketone), PI (polyimide), PP (polypropylene), PET (polyethylene terephthalate), PBT (polybutylene terephthalate), etc. The thickness of the base layer 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 layer is the portion for adhering the tape member 50 to the surface of the positive electrode 11. The thickness of the adhesive layer is, for example, 1 μm or more and 30 μm or less, preferably 5 μm or more and 25 μm or less. The adhesive portion may contain at least one of a rubber-based polymer and an acrylic-based polymer. Since rubber-based polymers and acrylic-based polymers are adhesive, they can adhere the tape member 50 to the surface of the positive electrode 11. The adhesive layer may further contain, for example, a silicone-based polymer.

[0035] Generally, the tape member 50 is attached to the surface of the positive electrode 11 and then pressed against the surface side of the positive electrode 11 by a roller or the like to bond it. As a result, as shown in Figure 3, the tape member 50 takes on a recessed shape towards the positive electrode core 30 in the region between the positive electrode mixture layer 31 and the positive electrode tab 20.

[0036] As shown in Figures 2 and 3, a protective layer 33 is provided on the surface of the uncoated portion 32 of the composite layer where the positive electrode tab 20 is not joined. The protective layer 33 is provided adjacent to the positive electrode tab 20 on both sides in the width direction of the positive electrode tab 20. Furthermore, the protective layer 33 is provided so as not to cover the first surface 20A of the surface of the positive electrode tab 20 that is joined to the uncoated portion 32 of the composite layer. In other words, the protective layer 33 is not interposed between the positive electrode tab 20 and the positive electrode core 30. In addition, the protective layer 33 is provided so as not to cover the second surface 20B of the surface of the positive electrode tab 20 that is opposite the first surface 20A in the thickness direction.

[0037] As described above, by providing the protective layer 33, when the positive electrode 11 is pressed against the tape member 50 due to the expansion of the negative electrode 12 during charging, the stress applied from the tape member 50 does not concentrate on the positive electrode tab 20, but is distributed to the protective layer 33 as well. This suppresses the concentration of stress in the area of ​​the uncoated mixture layer 32 that faces the positive electrode tab 20, especially the area facing the corner of the outer edge of the positive electrode tab 20. As a result, the breakage of the positive electrode core 30 in the uncoated mixture layer 32 can be suppressed. In other words, if the protective layer 33 is not provided, when the positive electrode 11 is pressed against the tape member 50 due to the expansion of the negative electrode 12 during charging, excessive stress may concentrate in the area facing the corner of the outer edge of the positive electrode tab 20, which may cause the positive electrode core 30 to break.

[0038] In addition, when the protective layer 33 covers the first surface 20A of the positive electrode tab 20, the contact area between the positive electrode tab 20 and the uncoated portion 32 of the mixture layer decreases, and the bonding strength between the positive electrode tab 20 and the uncoated portion 32 of the mixture layer decreases. Further, when the protective layer 33 covers the second surface 20B of the positive electrode tab 20, the thickness of the region where the positive electrode tab 20 is disposed excessively increases, and stress is likely to concentrate on the positive electrode tab 20. As a result, the positive electrode core 30 may be cut.

[0039] The protective layer 33 is, for example, an insulating layer containing a resin material. Examples of the resin material contained in the protective layer 33 include fluororesins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), polyimide resins, polyamide resins, acrylic resins, polyolefin resins, styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethyl cellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts, polyvinyl alcohol (PVA), and the like. These may be used alone or in combination of two or more.

[0040] Further, the protective layer 33 may contain inorganic particles. Examples of the inorganic particles contained in the protective layer 33 include metal oxide particles, metal nitride particles, metal fluoride particles, metal carbide particles, and the like. Examples of the metal oxide particles include aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, nickel oxide, silicon oxide, manganese oxide, and the like. Examples of the metal nitride particles include titanium nitride, boron nitride, aluminum nitride, magnesium nitride, silicon nitride, and the like. Examples of the metal fluoride particles include aluminum fluoride, lithium fluoride, sodium fluoride, magnesium fluoride, calcium fluoride, barium fluoride, and the like. Examples of the metal carbide particles include silicon carbide, boron carbide, titanium carbide, tungsten carbide, and the like. Further, the inorganic particles are zeolite (M ２／ｎ O·Al ２ O ３ ·xSiO ２ ·yH ２O and M are metal elements, n is the valence of M, x ≥ 2, y ≥ 0), etc. of porous aluminosilicates, talc (Mg ３ Si ４ O １０ (OH) ２ ) etc. of layered silicates, barium titanate (BaTiO ３ ), strontium titanate (SrTiO ３ ) etc. of minerals may be used. These may be used alone or in combination of two or more.

[0041] As shown in FIG. 3, the maximum thickness of the protective layer 33 is preferably equal to or less than the thickness of the positive electrode tab 20. When the maximum thickness of the protective layer 33 exceeds the thickness of the positive electrode tab 20, when the positive electrode 11 is pressed by the tape member 50, the stress applied to the positive electrode core 30 may increase.

[0042] Further, the protective layer 33 preferably abuts on the tape member 50. When the protective layer 33 abuts on the tape member 50, the stress applied from the tape member 50 does not concentrate on the positive electrode tab 20 and is easily dispersed by the protective layer 33. As a result, breakage of the positive electrode core 30 in the uncoated portion 32 of the mixture layer can be more effectively suppressed.

[0043] In the example shown in FIG. 3, the thickness of the protective layer 33 is maximum at the portion adjacent to the positive electrode tab 20 and decreases as it moves away from the positive electrode tab 20. In this case, in the cross-section in the thickness direction of the protective layer 33, the angle θ formed by the side surface 20C of the positive electrode tab 20 and the surface 33A of the protective layer 33 is preferably 60° or more and 90° or less. When the θ is 60° or more and 90° or less, the protective layer 33 abuts on the tape member 50, the stress applied from the tape member 50 does not concentrate on the positive electrode tab 20 and is easily dispersed by the protective layer 33. As a result, breakage of the positive electrode core 30 in the uncoated portion 32 of the mixture layer can be more effectively suppressed.

[0044] As shown in FIG. 3, the length L along the longitudinal direction of the positive electrode 11 from the outer end of the positive electrode tab 20 to the outer end of the protective layer 33 is, for example, 0.1 mm or more and 10 mm or less, and may be 0.2 mm or more and 5 mm or less. When the length L is 0.1 mm or more and 10 mm or less, breakage of the positive electrode core 30 can be more effectively suppressed.

[0045] The method for manufacturing the protective layer 33 is not particularly limited, but for example, it can be manufactured by applying a coating liquid containing a dispersed resin material to the surface of the uncoated portion 32 of the composite layer where the positive electrode tab 20 is not bonded. The solid content concentration in the coating liquid is, for example, 3% by mass or more and 50% by mass or less. Examples of methods for applying the coating liquid include gravure coating, spray coating, die coating, roll coating, reverse roll coating, screen printing, and inkjet coating. The manufactured coating film may also be subjected to a drying treatment to remove the solvent. The drying treatment method is not particularly limited and may be performed by, for example, natural drying, aeration drying with hot air, heat drying, reduced pressure / vacuum drying, or a combination thereof.

[0046] Alternatively, as shown in Figure 4, a protective layer 33 may be created by placing a substrate 34 containing resin material or the like on the surface of the area of ​​the uncoated mixture layer 32 where the positive electrode tab 20 is not joined, and then pressing the tape member 50 from the surface side to spread the substrate 34. This method allows for the formation of the protective layer 33 along with the attachment of the tape member 50.

[0047] Alternatively, a protective layer 33 may be formed on the side surface of the positive electrode tab 20 in advance, and then the positive electrode tab 20 with the protective layer 33 formed on it may be joined to the uncoated portion 32 of the mixture layer. One method for forming the protective layer 33 on the side surface of the positive electrode tab 20 in advance is to apply a coating liquid containing dispersed resin material or the like to the side surface of the positive electrode tab 20.

[0048] [Second Embodiment] Next, the positive electrode 11 constituting the cylindrical battery 10 of the second embodiment will be described with reference to Figure 5. Figure 5 is a diagram of the positive electrode 11 of the second embodiment, corresponding to Figure 2. In the following, components common to the first embodiment will be given the same reference numerals and redundant explanations will be omitted, and the differences from the first embodiment will be explained in detail.

[0049] As shown in Figure 5, the arrangement of the uncoated portion 32 of the composite layer in the positive electrode 11 of the second embodiment differs from that of the positive electrode 11 of the first embodiment. Specifically, the uncoated portion 32 of the composite layer in the positive electrode 11 of the second embodiment is formed over the width direction of the positive electrode 11 and is in contact with the upper end 11X and lower end 11Y in the width direction of the positive electrode 11.

[0050] Even when the uncoated portion 32 of the composite layer extends across the width of the positive electrode 11, by providing the protective layer 33 adjacent to the positive electrode tab 20 and not covering the first surface 20A and the second surface 20B of the positive electrode tab 20, the stress applied from the tape member 50 does not concentrate on the positive electrode tab 20 but is distributed to the protective layer 33 as well. As a result, breakage of the positive electrode core 30 in the uncoated portion 32 of the composite layer can be suppressed.

[0051] [Third Embodiment] Next, the positive electrode 11 constituting the cylindrical battery 10 of the third embodiment will be described with reference to Figure 6. Figure 6 is a diagram of the positive electrode 11 of the third embodiment, corresponding to Figure 3. In the following, components common to the first embodiment will be given the same reference numerals and redundant explanations will be omitted, and the differences from the first embodiment will be mainly described.

[0052] As shown in Figure 6, the shape of the protective layer 33 of the positive electrode 11 in the third embodiment differs from that of the positive electrode 11 in the first embodiment. Specifically, the protective layer 33 of the third embodiment has a raised shape in the middle portion in the width direction of the protective layer 33, and its thickness is maximum at a position a predetermined length away from the positive electrode tab 20. The length along the longitudinal direction of the positive electrode 11 from the end of the positive electrode tab 20 to the position where the protective layer 33 has maximum thickness is, for example, 0.05 mm or more and 1 mm or less.

[0053] Even if the protective layer 33 has the shape shown in Figure 6, the stress applied from the tape member 50 does not concentrate on the positive electrode tab 20, but is also distributed to the protective layer 33. As a result, breakage of the positive electrode core 30 in the uncoated portion 32 of the composite layer can be suppressed. It is also preferable that the protective layer 33 is in contact with the tape member 50, even if the protective layer 33 has the shape shown in Figure 6.

[0054] Each of the embodiments described above can be modified as appropriate without altering the purpose of this disclosure. For example, although the above embodiments describe a case where there is one positive electrode tab 20, multiple positive electrode tabs 20 may be provided. That is, the positive electrode 11 may have multiple uncoated portions 32 of the composite layer. The multiple uncoated portions 32 of the composite layer are arranged, for example, at approximately equal intervals in the longitudinal direction of the positive electrode 11. When the positive electrode 11 has multiple uncoated portions 32 of the composite layer, it is preferable to provide a protective layer 33 on all of the uncoated portions 32 of the composite layer, but there may be uncoated portions 32 of the composite layer that do not have a protective layer 33.

[0055] Furthermore, although the above embodiments described the case in which the protective layer 33 is an insulating layer containing a resin material, the protective layer 33 may also be a conductive layer containing metal particles or the like.

[0056] Furthermore, although the above embodiment described the case where the first electrode is a positive electrode 11 and the second electrode is a negative electrode 12, the first electrode may be a negative electrode 12 and the second electrode may be a positive electrode 11. That is, a protective layer 33 may be provided on the negative electrode 12.

[0057] This disclosure is further illustrated by the following embodiments. Configuration 1: A cylindrical battery comprising an electrode body in which a first electrode and a second electrode having opposite polarities are wound longitudinally via a separator, and a bottomed cylindrical outer casing for housing the electrode body, wherein the first electrode has a core body and a composite layer disposed on the surface of the core body, and at least one uncoated composite layer portion is provided in the longitudinal middle portion of the first electrode where the composite layer is not disposed on the surface of the core body, a strip-shaped electrode tab is bonded to the uncoated composite layer portion, and a protective layer is provided on the surface of the uncoated composite layer portion where the electrode tab is not bonded, and the protective layer is provided such that it does not cover a first surface of the electrode tab that is adjacent to the electrode tab and bonded to the uncoated composite layer portion, and a second surface that faces the first surface in the thickness direction of the electrode tab. Configuration 2: The cylindrical battery according to Configuration 1, wherein the maximum thickness of the protective layer is less than or equal to the thickness of the electrode tab. Configuration 3: The cylindrical battery according to Configuration 1 or 2, wherein the uncoated portion of the mixture layer is covered by a tape member, and the protective layer is in contact with the tape member. Configuration 4: The cylindrical battery according to any one of Configurations 1 to 3, wherein the thickness of the protective layer is greatest in the portion adjacent to the electrode tab, and the angle between the side surface of the electrode tab and the surface of the protective layer in the thickness direction cross-section of the protective layer is 60° or more and 90° or less. Configuration 5: The cylindrical battery according to any one of Configurations 1 to 4, wherein the protective layer includes a resin material. Configuration 6: The cylindrical battery according to any one of Configurations 1 to 5, wherein the length along the longitudinal direction of the first electrode from the outer end of the electrode tab to the outer end of the protective layer is 0.1 mm or more and 10 mm or less. Configuration 7: The cylindrical battery according to any one of Configurations 1 to 6, wherein the first electrode is the positive electrode and the second electrode is the negative electrode.

[0058] 10 Cylindrical battery, 11 Positive electrode (first electrode), 11X Upper end, 11Y Lower end, 12 Negative electrode (second electrode), 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18 Insulating plate, 19 Insulating plate, 20 Positive electrode tab (electrode tab), 20A First surface, 20B Second surface, 20C Side, 21 Negative electrode tab, 22 Grooved section, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive electrode core body, 31 Positive electrode mixture layer, 32 Uncoated part of mixture layer, 33 Protective layer, 33A Surface, 34 Substrate, 40 Negative electrode core body, 41 Negative electrode mixture layer, 50 Tape member

Claims

1. A cylindrical battery comprising: an electrode body in which a first electrode and a second electrode having opposite polarities are wound longitudinally via a separator; and a bottomed cylindrical outer casing for housing the electrode body, wherein the first electrode has a core body and a composite layer disposed on the surface of the core body; at least one uncoated composite layer portion is provided in the longitudinal middle portion of the first electrode where the composite layer is not disposed on the surface of the core body; a strip-shaped electrode tab is joined to the uncoated composite layer portion; a protective layer is provided on the surface of the uncoated composite layer portion where the electrode tab is not joined; and the protective layer is provided so as not to cover a first surface of the electrode tab that is adjacent to the electrode tab and joined to the uncoated composite layer portion, and a second surface that is opposite the first surface in the thickness direction of the electrode tab.

2. The cylindrical battery according to claim 1, wherein the maximum thickness of the protective layer is less than or equal to the thickness of the electrode tab.

3. The cylindrical battery according to claim 1, wherein the uncoated portion of the mixture layer is covered by a tape member, and the protective layer is in contact with the tape member.

4. The cylindrical battery according to claim 1, wherein the thickness of the protective layer is greatest in the portion adjacent to the electrode tab, and the angle between the side surface of the electrode tab and the surface of the protective layer in a cross-section in the thickness direction of the protective layer is 60° or more and 90° or less.

5. The cylindrical battery according to claim 1, wherein the protective layer comprises a resin material.

6. The cylindrical battery according to claim 1, wherein the length of the first electrode along its longitudinal direction from the outer end of the electrode tab to the outer end of the protective layer is 0.1 mm or more and 10 mm or less.

7. The cylindrical battery according to claim 1, wherein the first electrode is a positive electrode and the second electrode is a negative electrode.

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