Cylindrical battery

Abstract

In this cylindrical battery, a negative electrode mixture layer of a negative electrode extends to a winding start side beyond a winding start side end (41) of a positive electrode (11). In the positive electrode (11), a winding start side end portion (52) on a winding outer side including a positive electrode mixture layer (11b1) on the winding outer side is covered with an outer protective member (50), and a winding start side end portion (54) on a winding inner side including a positive electrode mixture layer (11b2) on the winding inner side is covered with an inner protective member (51). Of the outer protective member (50) and the inner protective member (51), at least the inner protective member (51) is adhered to the positive electrode mixture layer (11b2). The adhesive force of the outer protective member (50) to the positive electrode mixture layer (11b1) on the winding outer side is less than the adhesive force of the inner protective member (51) to the positive electrode mixture layer (11b2) on the winding inner side.

Description

Cylindrical battery

[0001] The present disclosure relates to a cylindrical battery.

[0002] Conventionally, as a cylindrical battery, there is one described in Patent Document 1. This cylindrical battery includes an electrode body in which a positive electrode and a negative electrode are wound via a separator. In this cylindrical battery, at the starting end portion of the positive electrode winding, the surface of the positive electrode mixture layer is covered with an insulating protective member. The protective member has a base material layer and an adhesive layer and is adhered to the positive electrode. It is said that this can suppress a voltage drop due to deformation of the negative electrode.

[0003] Japanese Unexamined Patent Application Publication No. 2022-153675

[0004] The inventor of the present case has found that when a protective member is adhered to both surfaces of the positive electrode mixture layer at the starting end portion of the positive electrode winding, in the positive electrode mixture layer on the outer side of the positive electrode winding, which has a greater elongation during winding compared to the positive electrode mixture layer on the inner side of the winding, cracks may occur in the positive electrode mixture layer between the portion where the protective member is adhered and the portion where the protective member is not adhered.

[0005] Therefore, an object of the present disclosure is to provide a cylindrical battery that can suppress a voltage drop associated with charge and discharge and can suppress the occurrence of cracks in the positive electrode mixture layer.

[0006] The cylindrical battery according to the present disclosure includes an electrode body in which a strip-shaped positive electrode having a positive electrode core and a positive electrode mixture layer and a strip-shaped negative electrode having a negative electrode core and a negative electrode mixture layer are wound via a separator, a bottomed cylindrical outer can that houses the electrode body, and a sealing body that closes the opening of the outer can. The negative electrode mixture layer extends to the starting side from the inner side of the starting end of the positive electrode core, and in the positive electrode, the starting end portion on the outer side of the winding including the positive electrode mixture layer on the outer side of the winding is covered with an outer protective member, and the starting end portion on the inner side of the winding including the positive electrode mixture layer on the inner side of the winding is covered with an inner protective member. At least the inner protective member among the outer protective member and the inner protective member is adhered to the positive electrode mixture layer, and the adhesive force of the outer protective member with respect to the positive electrode mixture layer on the outer side of the winding is smaller than the adhesive force of the inner protective member with respect to the positive electrode mixture layer on the inner side of the winding.

[0007] According to the cylindrical battery of this disclosure, the separator is prevented from being pressed from near the center of the winding axis at the winding start end of the positive electrode, thereby suppressing voltage drop associated with charging and discharging. Furthermore, at the winding start end of the positive electrode, the outer positive electrode mixture layer, which has greater elongation during winding, is covered with an outer protective member that has less adhesion to the positive electrode mixture layer compared to the inner protective member. As a result, differences in elongation between the portion covered by the protective member and the portion not covered by the protective member in the outer positive electrode mixture layer are suppressed, thereby suppressing crack formation in the positive electrode mixture layer.

[0008] This is a cross-sectional view along the axial direction of a cylindrical battery according to an embodiment of the present disclosure. In the embodiment, this is a cross-sectional view perpendicular to the winding axis direction of the electrode body, showing the vicinity of the winding start end of the positive electrode. This is an enlarged cross-sectional view of the winding start end of the positive electrode shown in Figure 2. This is a view showing the outer surface of the winding start end of the positive electrode unfolded in the longitudinal direction. This is a cross-sectional view taken along line A-A in Figure 3. This is a view corresponding to Figure 4 in another cylindrical battery of the embodiment.

[0009] Hereinafter, embodiments of the cylindrical battery according to this disclosure will be described in detail with reference to the drawings. The cylindrical battery of this disclosure may be a primary battery or a secondary battery. It may also be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. In the following, a non-aqueous electrolyte secondary battery (lithium-ion battery) using a non-aqueous electrolyte will be given as an example of a cylindrical battery 10, which is one embodiment, but the cylindrical battery of this disclosure is not limited to this, and the electrolyte may also be an aqueous electrolyte.

[0010] It is intended from the outset that new embodiments can be constructed by appropriately combining the characteristic features of the embodiments and modifications described below. In the following embodiments, the same reference numerals are used for the same components in the drawings, and redundant explanations are omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. In this specification, the side of the cylindrical battery 10 with the sealing body 17 in the axial direction (height direction) is referred to as "upper," and the side of the outer casing 16 with the bottom 31 in the axial direction is referred to as "lower." Furthermore, among the components described below, components that are not described in the independent claim indicating the highest-level concept are optional components and are not essential components.

[0011] Figure 1 is a cross-sectional view along the axial direction of a cylindrical battery 10 according to one embodiment of the present disclosure. As shown in Figure 1, the cylindrical battery 10 comprises an electrode body 14, a bottomed cylindrical outer casing 16 that houses the electrode body 14, and a sealing body 17 that closes the opening of the outer casing 16. The outer casing 16 houses a non-aqueous electrolyte together with the electrode body 14. The outer casing 16 has a shoulder portion 29 at its upper end that is bent radially inward and extends inward. The outer casing 16 has a grooved portion 22 formed in its side wall, and the sealing body 17 is supported by the grooved portion 22 and closes the opening of the outer casing 16.

[0012] The cylindrical battery 10 further includes a gasket 28 interposed between the outer casing 16 and the sealing body 17. The gasket 28 is a ring-shaped resin member attached to the outer circumference of the sealing body 17, and insulates the sealing body 17 from the outer casing 16. The gasket 28 seals the gap between the outer casing 16 and the sealing body 17, thereby sealing the inside of the battery. The gasket 28 is made of, for example, polyolefin.

[0013] The non-aqueous electrolyte has ionic conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte (non-aqueous electrolyte solution), but may also be a solid electrolyte using a gel-like polymer or the like. The cylindrical battery 10 is preferably a lithium-ion battery. The electrolyte salt may be, for example, LiBF ４ LiPF ６Lithium salts such as the above are used. Non-aqueous solvents include, for example, esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), as well as ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain halogen-substituted products in which at least some of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine.

[0014] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated linear carbonates, and fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP). In terms of suppressing the deterioration of the charge-discharge cycle characteristics of non-aqueous electrolyte secondary batteries or improving the input characteristics, the non-aqueous electrolyte preferably contains 5% by mass or more of FEC relative to the mass of the non-aqueous electrolyte, and more preferably contains 5% to 15% by mass of FEC.

[0015] As solid electrolytes, for example, solid or gel-like polymer electrolytes, inorganic solid electrolytes, etc., are used. Polymer electrolytes include, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As matrix polymers, for example, polymer materials that absorb non-aqueous solvents and gel are used. As polymer materials, for example, fluororesins, acrylic resins, polyether resins, etc., are used. As inorganic solid electrolytes, for example, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) are used.

[0016] The electrode body 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound in a spiral shape via the separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all elongated strip-shaped bodies, and are alternately stacked in the radial direction of the electrode body 14 by being wound in a spiral shape. The negative electrode 12 is formed to be slightly larger in dimensions 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 and width directions than the positive electrode 11. The separator 13 is formed to be at least slightly larger in dimensions than the positive electrode 11, and for example, two separators are arranged so as to sandwich the positive electrode 11.

[0017] The electrode body 14 is connected to a positive electrode lead 20 and two negative electrode leads 21a and 21b. The positive electrode lead 20 electrically connects the positive electrode 11 to the sealing body 17. The first negative electrode lead 21a is joined to the winding start end of the negative electrode 12, electrically connecting this winding start end to the bottom 31 of the outer container 16. The second negative electrode lead 21b is joined to the winding end of the negative electrode 12, electrically connecting this winding end to the bottom 31 of the outer container 16.

[0018] In the example shown in Figure 1, the positive electrode lead 20 extends through the opening in the upper insulating plate 18 toward the sealing body 17 and is joined to the lower surface of the sealing body 17. The first negative electrode lead 21a is bent toward the hollow portion 14a of the electrode body 14, passing through a through hole in the annular lower insulating plate 19. The second negative electrode lead 21b is bent so as to overlap the first negative electrode lead 21a, passing outside the lower insulating plate 19. The overlapping portion of the first negative electrode lead 21a and the second negative electrode lead 21b is resistance welded using a welding rod inserted through the hollow portion 14a of the electrode body 14 and joined to the inner surface of the bottom 31 of the outer can 16.

[0019] By joining the negative electrode leads 21a and 21b to both ends of the negative electrode 12 in the longitudinal direction, the current collection path of the negative electrode 12 is shortened, thereby reducing the internal resistance of the cylindrical battery 10. Alternatively, the negative electrode leads may be joined only to the end of the negative electrode at the end of the winding in the longitudinal direction. Or, the negative electrode leads may be joined only to the end of the negative electrode at the beginning of the winding in the longitudinal direction, and the outermost core exposed portion of the negative electrode core, located at least a part of the outermost circumference of the electrode body, may be in contact with the inner surface of the outer casing 16.

[0020] Figure 2 is a cross-sectional view of the electrode body 14 perpendicular to the winding axis direction, showing the vicinity of the winding start end 40 of the positive electrode 11. Figure 3 is an enlarged cross-sectional view of the winding start end 40 of the positive electrode 11. Figure 4 is a view showing the outer surface of the winding start end 40 of the positive electrode 11 unfolded in the longitudinal direction. Figure 5 is a cross-sectional view taken along line A-A in Figure 3. In Figures 2, 3, and 5, the cross-section of the positive electrode 11 is shown by the areas where the sandy areas are covered with diagonal lines. In Figure 2, the separator 13 is shown with a dashed line. In Figure 4, the exposed portion of the positive electrode mixture layer 11b1 is shown by the high-density sandy area, and the portion of the positive electrode mixture layer 11b1 covered by the outer protective member 50 is shown by the low-density sandy area.

[0021] As shown in Figures 2 to 5, the positive electrode 11 comprises a positive electrode core 11a, a positive electrode mixture layer 11b1 formed on the outer surface of the winding of the positive electrode core 11a, and a positive electrode mixture layer 11b2 formed on the inner surface of the winding of the positive electrode core 11a. The positive electrode core 11a can be made of a metal foil that is stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. The positive electrode mixture layers 11b1 and 11b2 contain a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF). For the positive electrode active material, for example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, etc., is used. The positive electrode lead 20 is connected to the positive electrode 11, but it is preferable that it is directly joined to the positive electrode core 11a by ultrasonic welding or the like, and it is preferable that the joint portion with respect to the positive electrode core 11a is covered with insulating tape.

[0022] The negative electrode 12 comprises a negative electrode core 12a and a negative electrode mixture layer 12b formed on both sides of the negative electrode core 12a. The negative electrode core 12a 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 arranged on its surface. The negative electrode mixture layer 12b contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR) or PVdF. For example, graphite or a silicon-containing compound can be used as the negative electrode active material. The negative electrode leads 21a and 21b are preferably directly joined to the negative electrode core 12a by ultrasonic welding or the like, and the joint portion with respect to the negative electrode core 12a is preferably covered with insulating tape.

[0023] The negative electrode mixture layer 12b, formed on at least one side of the negative electrode core 12a, has an extended portion 38 that extends from a radially opposing position A1 of the electrode body 14 via a separator 13 to the winding start side of the electrode body 14. The extended portion 38 extends, for example, 1 / 5 of a turn or more, preferably 1 / 2 of a turn or more, and more preferably 1 turn or more towards the winding start side. When this extended portion 38 is wound from the winding start side 41 of the positive electrode for a predetermined length or more, for example 1 / 2 of a turn or more, towards the winding start side of the electrode body 14, it becomes easier to maintain the shape of the hollow portion 14a formed in the winding core of the electrode body 14.

[0024] Referring to Figure 1, the outer can 16 is generally made of a metal mainly composed of iron, for example, iron plated with nickel, but it may also be made of a metal mainly composed of aluminum or the like. The outer can 16 has a cylindrical portion 39 and a bottom portion 31, and the cylindrical portion 39 includes an annular grooved portion 22 and an annular shoulder portion 29. The grooved portion 22 is formed by spinning a part of the cylindrical portion 39 to create a recess on the radially inward side. The shoulder portion 29 is formed when the upper end (one end in the axial direction) of the cylindrical portion 39 is bent radially inward and crimped to the peripheral edge 33 of the sealing body 17, and extends radially inward at the upper end of the cylindrical portion 39.

[0025] The sealing body 17 is fixed to the outer can 16 by crimping, with a gasket 28 between the shoulder portion 29 and the grooved portion 22. The grooved portion 22 is formed at a predetermined distance from the upper end of the outer can 16. The predetermined length is, for example, 1% to 20% of the winding axial length of the outer can 16.

[0026] The sealing body 17 has a structure in which an internal terminal plate 23, a lower valve body 24, an insulating plate 25, an upper valve body 26, and a sealing plate 27 are stacked in this 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 plate 25 is electrically connected to one another. The sealing plate 27 has a convex shape with its radial center portion protruding outward. The convex portion 27a of the sealing plate 27 includes an annularly formed inclined portion and a flat top portion surrounded by the inclined portion. One or more ventilation holes 27b are formed in the top portion.

[0027] The lower valve body 24, the insulating plate 25, and the upper valve body 26 constitute a current interruption mechanism. The lower valve body 24 and the upper valve body 26 are connected at their respective centers, with the insulating plate 25 interposed between their respective peripheries. When an abnormality occurs in the cylindrical battery 10 and the internal pressure rises to a predetermined value, the lower valve body 24 deforms and ruptures, pushing the upper valve body 26 towards the sealing plate 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further and reaches a predetermined value, the upper valve body 26 ruptures, and gas is discharged from the vent hole 27b of the sealing plate 27.

[0028] In this embodiment, the positive lead 20 is connected to the lower surface of the internal terminal plate 23 by laser welding or ultrasonic welding, and the sealing plate 27, which is the top plate of the sealing body 17 electrically connected to the internal terminal plate 23, becomes the positive terminal. The outer casing 16 to which the negative leads 21a and 21b are joined becomes the negative terminal.

[0029] In this embodiment, in order to suppress the voltage drop associated with charging and discharging of the cylindrical battery 10 and to suppress the occurrence of cracks in the positive electrode mixture layers 11b1 and 11b2, the outer end 52 (Figure 3) of the positive electrode 11, which includes the outer positive electrode mixture layer 11b1, is covered with an outer protective member 50, and the inner end 54 (Figure 3), which includes the inner positive electrode mixture layer 11b2, is covered with an inner protective member 51. Furthermore, the adhesive force of the outer protective member 50 to the outer positive electrode mixture layer 11b1 is smaller than the adhesive force of the inner protective member 51 to the inner positive electrode mixture layer 11b2.

[0030] In the positive electrode 11, the positive electrode core 11a extends toward the winding start side from the winding start end 52, 54 of each positive electrode mixture layer 11b1, 11b2. Therefore, the positive electrode core 11a is exposed on both the outer and inner surfaces of the winding start end 40 of the positive electrode. The winding start end 52, 54 of each positive electrode mixture layer 11b1, 11b2 decreases in thickness toward the winding start end 41 of the positive electrode 11. Therefore, inclined surfaces 53, 55 are formed on each positive electrode mixture layer 11b1, 11b2. Note that each positive electrode mixture layer 11b1, 11b2 may be formed up to the winding start end 41 of the positive electrode 11.

[0031] The inclined surface 53 of the winding start end 54 of the outer positive electrode mixture layer 11b1 and the exposed outer surface of the positive electrode core 11a are continuously covered by the outer protective member 50. The inclined surface 55 of the winding start end 52 of the inner positive electrode mixture layer 11b2 and the exposed inner surface of the positive electrode core 11a are continuously covered by the inner protective member 51. The outer protective member 50 and the inner protective member 51 are preferably insulating adhesive tapes. Each protective member 50, 51 has a base layer 60 and an adhesive layer 61 provided on one side of the base layer 60.

[0032] As shown in Figure 5, in the inner protective member 51, an adhesive layer 61 is provided over the entire surface of one side of the base material layer 60 (the upper side in Figure 5). On the other hand, in the outer protective member 50, an adhesive layer 61 is not provided over the entire surface of one side of the base material layer 60 (the lower side in Figure 5). Of the one side of the base material layer 60 of the outer protective member 50, the outer surface of the positive electrode mixture layer 11b1 on the outside of the winding and the portion facing the positive electrode core body 11a do not have an adhesive layer. The adhesive layer 61 is provided only on the ends in the positive electrode width direction (both ends in the left and right directions in Figure 5), which are different from the portion facing this opposing part. The positive electrode width direction coincides with the winding axis direction of the electrode body 14.

[0033] Of the two protective members 50 and 51, both ends in the positive electrode width direction protrude outward beyond the positive electrode width direction ends of the positive electrode 11, and the protruding portions are bonded to each other. As a result, the portion of the outer protective member 50 that protrudes outward beyond the positive electrode 11 overlaps with the inner protective member 51 and is bonded to the inner protective member 51.

[0034] In Figure 4, the oblique grid shows the portions where the outer protective member 50 and the inner protective member 51 protrude from the positive electrode 11 in the positive electrode width direction and face each other. At this time, the inner protective member 51 has an adhesive layer 61 on the portion facing the positive electrode mixture layer 11b2 on the inside of the winding, so the inner protective member 51 is adhered to the positive electrode mixture layer 11b2 on the inside of the winding. Note that the outer protective member 50 does not have an adhesive layer 61 on the portion facing the positive electrode mixture layer 11b1 on the outside of the winding, so the adhesive area of ​​the outer protective member 50 to the positive electrode mixture layer 11b1 is zero, and is smaller than the adhesive area of ​​the inner protective member 51 to the positive electrode mixture layer 11b2 on the inside of the winding. The outer protective member 50 and the inner protective member 51 are made of the same material, but the adhesive force of the outer protective member 50 to the positive electrode mixture layer 11b1 on the outside of the winding is smaller than the adhesive force of the inner protective member 51 to the positive electrode mixture layer 11b2 on the inside of the winding.

[0035] Between the base layer 60 and the adhesive layer 61 of each protective member 50, 51, a heat-resistant layer containing inorganic particles such as metal oxides can be provided. The base layer 60 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.

[0036] The adhesive layer 61 may contain at least one of a rubber-based polymer or an acrylic-based polymer. The adhesive layer may also contain, for example, a silicone-based polymer.

[0037] During charging and discharging of the cylindrical battery 10, the electrode body 14 tends to bulge more near the center in the winding axis direction than near both ends in the winding axis direction, and the pressure tends to be higher near the center in the winding axis direction. In this embodiment, the outer surface and inner surface of the winding start end 40 of the positive electrode 11 are covered by the outer protective member 50 and the inner protective member 51, respectively. As a result, even if the separator 13 is pressed from near the center L1 in the positive electrode width direction of the winding start end 40 of the positive electrode, the voltage drop associated with charging and discharging of the cylindrical battery 10 is suppressed.

[0038] Furthermore, as shown in Figure 3, the winding start end 52 of the outer positive electrode mixture layer 11b1, which has a large elongation during winding, is covered by the outer protective member 50, and the winding start end 54 of the inner positive electrode mixture layer 11b2, which has a small elongation, is covered by the inner protective member 51. The inner protective member 51 is bonded to the positive electrode mixture layer 11b2. In addition, the adhesive force of the outer protective member 50 to the outer positive electrode mixture layer 11b1 is smaller than the adhesive force of the inner protective member 51 to the inner positive electrode mixture layer 11b2. This makes it possible to suppress the difference in elongation between the portion of the outer positive electrode mixture layer 11b1 covered by the outer protective member 50 and the portion not covered by the outer protective member 50. Therefore, it is possible to suppress the occurrence of cracks in the positive electrode mixture layers 11b1 and 11b2.

[0039] In this example, both ends of each protective member 50, 51 in the positive electrode width direction protrude from the positive electrode mixture layers 11b1, 11b2, and the two protective members 50, 51 are bonded together at the protruding portions. The embodiment is not limited to this configuration; in other cases, only one end of each protective member 50, 51 in the positive electrode width direction may protrude from the positive electrode mixture layers 11b1, 11b2, and the two protective members 50, 51 may be bonded together at the protruding portions.

[0040] [Another Embodiment] Figure 6 is a diagram corresponding to Figure 4, showing an alternative embodiment of a cylindrical battery. In this embodiment, the outer protective member 50a and the inner protective member 51a do not protrude from the positive electrode mixture layers 11b1 and 11b2 at both ends in the positive electrode width direction. In this embodiment, the winding start end of each protective member 50a and 51a extends from the winding start end 41 of the positive electrode 11 toward the winding start, and the two protective members 50a and 51a are bonded together at the overlapping portion. In Figure 6, the oblique grid shows the portions where the outer protective member 50a and the inner protective member 51a protrude from the positive electrode 11 toward the winding start and face each other.

[0041] In this example, as in the configurations shown in Figures 1 to 5, the inner protective member 51a has an adhesive layer on the portion facing the positive electrode mixture layer on the inside of the winding, and is therefore adhered to the positive electrode mixture layer on the inside of the winding. On the other hand, of one side of the base layer 60 of the outer protective member 50a, the portion facing the outer surface of the positive electrode mixture layer 11b1 on the outside of the winding and the positive electrode core 11a does not have an adhesive layer. The adhesive layer 61 is provided only on one end in the longitudinal direction of the positive electrode (the right end in Figure 6), which is a different portion from this opposing portion. As a result, the adhesive area of ​​the outer protective member 50 to the positive electrode mixture layer 11b1 on the outside of the winding is smaller than the adhesive area of ​​the inner protective member 51a to the positive electrode mixture layer on the inside of the winding. Consequently, the adhesive force of the outer protective member 50a to the positive electrode mixture layer 11b1 on the outside of the winding is smaller than the adhesive force of the inner protective member 51a to the positive electrode mixture layer on the inside of the winding.

[0042] In this example, as with the configurations shown in Figures 1 to 5, the voltage drop associated with charging and discharging can be suppressed, and the occurrence of cracks in the positive electrode mixture layer can also be suppressed. In this example, the other configurations and functions are the same as those shown in Figures 1 to 5.

[0043] In addition, in each of the above examples, in the base material layer 60 of the outer protective members 50 and 50a, an adhesive layer may not be provided at the portion facing the positive electrode mixture layer 11b1, and an adhesive layer may be provided at the portion facing the positive electrode core 11a.

[0044] Also, in each of the above examples, in the base material layer 60 of the outer protective members 50 and 50a, by providing an adhesive layer only at a part of the portion facing the positive electrode mixture layer 11b1, the adhesion area of the outer protective member 50 to the positive electrode mixture layer 11b1 on the outer side of the winding may be made smaller than the adhesion area of the inner protective member 51a to the positive electrode mixture layer on the inner side of the winding.

[0045] Also, in each of the above examples, with a configuration in which the adhesion area of the outer protective member to the positive electrode mixture layer 11b1 on the outer side of the winding is the same as the adhesion area of the inner protective member to the positive electrode mixture layer on the inner side of the winding, by making the material of the adhesive layer different between the outer protective member and the inner protective member, the adhesion force of the outer protective member to the positive electrode mixture layer 11b1 on the outer side of the winding may be made smaller than the adhesion force of the inner protective member 51a to the positive electrode mixture layer on the inner side of the winding. The comparison of the adhesion forces of each protective member to the positive electrode mixture layer can be performed, for example, in the unfolded state of the positive electrode, by gradually increasing the force one by one on each protective member from the positive electrode mixture layer to which each protective member is adhered using a suction component or the like, and measuring the resistance to peeling when peeling off. At this time, by comparing the forces immediately before the resistance suddenly decreases, the adhesion forces of each protective member to the positive electrode mixture layer can be compared.

[0046] Also, in each of the above examples, the outer protective members 50 and 50a may be sheet-like members composed only of the base material layer without being an insulating tape having an adhesive layer, and may be adhered to the inner protective members 51 and 51a at the portion overlapping with the inner protective members 51 and 51a.

[0047] 10 Cylindrical battery, 11 Positive electrode, 11a Positive electrode core, 11a1 Core exposed portion, 11b Positive electrode mixture layer, 12 Negative electrode, 12a Negative electrode core, 12b Negative electrode mixture layer, 13 Separator, 14 Electrode body, 14a Hollow portion, 15 Insulating tape, 16 Outer can, 17 Sealing body, 18 Upper insulating plate, 19 Lower insulating plate, 20 Positive electrode lead, 21a First negative electrode lead, 21b Second negative electrode lead, 22 Grooved portion, 23 Terminal plate, 24 Lower valve body, 25 Insulating plate, 26 Upper valve body, 27 Sealing plate, 27a Protrusion, 27b Ventilation hole, 28 Gasket, 29 Shoulder portion, 31 Bottom portion, 33 Peripheral portion, 38 Extension portion, 39 Cylindrical portion, 40 End of positive electrode winding start side, 41 End of positive electrode winding start side, 50, 50a Outer protective member, 51, 51a Inner protective member, 52 End of positive electrode mixture layer on the outside of winding start side, 53 Inclined surface, 54 End of positive electrode mixture layer on the inside of winding start side, 55 Inclined surface, 60 Base layer, 61 Adhesive layer.

Claims

1. A cylindrical battery comprising: an electrode body in which a strip-shaped positive electrode having a positive electrode core and a positive electrode mixture layer, and a strip-shaped negative electrode having a negative electrode core and a negative electrode mixture layer are wound via a separator; a bottomed cylindrical outer can containing the electrode body; and a sealing body that closes the opening of the outer can, wherein the negative electrode mixture layer extends from the inside of the winding to the winding start side of the winding start end 2. The cylindrical battery according to claim 1, wherein the outer protective member and the inner protective member are insulating adhesive tapes having a base layer and an adhesive layer.

3. The cylindrical battery according to claim 2, wherein the adhesive area of ​​the outer protective member to the winding start end on the outer side of the positive electrode is smaller than the adhesive area of ​​the inner protective member to the winding start end on the inner side of the positive electrode.

4. The cylindrical battery according to claim 3, wherein the outer protective member does not have the adhesive layer on at least the portion facing the positive electrode mixture layer on the outer side of the winding, and the portion of the outer protective member that extends beyond the positive electrode mixture layer is adhered to the inner protective member.

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