Cylindrical battery

Abstract

In a cylindrical battery as an example of an embodiment, a negative electrode (12) has, on a winding start side of an electrode body (14), a non-facing portion (43) wound over a length of 0.6-0.9 weeks, and a core exposed portion (42). The negative electrode lead (21) is joined to the core exposed portion (42) such that a winding termination side end portion of the lead is located in a range in which an angle from a positive electrode start end (11x) toward a winding start side with respect to a winding center (Z) of the electrode body (14) is 60-180 degrees. In the non-facing section (43), the ratio (D2 / D1) of the maximum value (D2) to the minimum value (D1) of the inter-core distance between the non-facing section (43) and the core exposed section (42) is 1.5 or more in a range in which the angle of the non-facing section (43) from the position corresponding to the positive electrode starting end (11x) toward the winding starting side with respect to the winding center (Z) of the electrode body (14) is 60-180 degrees.

Description

Technical Field

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

[0002] A cylindrical battery includes a wound electrode body in which a positive electrode and a negative electrode are wound in a spiral shape with a separator interposed therebetween. In the core of the electrode body, a cavity extending in the axial direction is generally formed. This cavity functions as an exhaust path for guiding gas generated during an abnormality in the battery toward the safety valve. For example, in Patent Document 1, a cylindrical battery including a wound electrode body is disclosed. The electrode body has a non-opposing portion on the winding start side of the electrode body. The non-opposing portion has a negative electrode composite layer formed on at least one surface of the negative electrode core, and is wound for a length of 0.6 turns or more and 0.9 turns or less without opposing the positive electrode.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: WO 2018 / 116876 Summary of the Invention

[0006] In the cylindrical battery according to Patent Document 1, the shape stability of the core portion is improved, and the exhaust path during an abnormality is sufficiently ensured. On the other hand, when the volume change of the negative electrode during charge and discharge becomes large due to high capacity of the battery or the like, in the cylindrical battery of Patent Document 1, deformation of the electrode body is also likely to occur near the core. When a large deformation occurs in the electrode body at the portion where the positive electrode and the negative electrode oppose each other, the distance between the positive electrode and the negative electrode changes, and problems such as uneven charge and discharge reactions occur.

[0007] The cylindrical battery according to the present disclosure includes an electrode body having a positive electrode, a negative electrode including a core and a composite layer, and a separator, and the positive electrode and the negative electrode are wound with the separator interposed therebetween, and has a negative electrode lead wire joined to the negative electrode. The negative electrode has: a non-opposing portion formed on at least one surface of the core at the winding start side of the electrode body and wound for a length of 0.6 turns or more and 0.9 turns or less without opposing the positive electrode; and a core exposed portion formed from the negative electrode start end to the non-opposing portion. The negative electrode lead wire is joined to the core exposed portion such that the winding end side end thereof is located in a range of 60° or more and 180° or less from the positive electrode start end with respect to the winding center of the electrode body. In the non-opposing portion, in a range of 60° or more and 180° or less from the position corresponding to the positive electrode start end with respect to the winding center of the electrode body, the ratio of the maximum value to the minimum value of the core-to-core distance between the non-opposing portion and the core exposed portion is 1.5 or more.

[0008] According to the cylindrical battery related to the present disclosure, deformation of the electrode body at the opposed portion between the positive electrode and the negative electrode can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 FIG. is an axial sectional view of a cylindrical battery as an example of an embodiment.

[0010] Figure 2 FIG. is a view showing a part of a radial section of an electrode body as an example of an embodiment.

[0011] Figure 3 FIG. is a view for explaining an evaluation method of plate deformation. DETAILED DESCRIPTION

[0012] Hereinafter, an example of an embodiment of the cylindrical battery related to the present disclosure will be described in detail with reference to the drawings. In addition, the cylindrical battery related to the present disclosure is not limited to the embodiment described below.

[0013] Figure 1 FIG. is a sectional view of a cylindrical battery 10 as an example of an embodiment. As Figure 1 shown, the cylindrical battery 10 includes an electrode body 14, which has a positive electrode 11, a negative electrode 12, and a separator 13, and is formed by winding the positive electrode 11 and the negative electrode 12 with the separator 13 interposed therebetween. In addition, the cylindrical battery 10 includes a bottomed cylindrical outer can 16 that houses the electrode body 14, and a sealing body 17 that seals the opening of the outer can 16. In the outer can 16, an electrolyte is housed together with the electrode body 14. The outer can 16 has a groove portion 22 formed on the side wall, and the sealing body 17 is supported by the groove portion 22 and seals the opening of the outer can 16. Hereinafter, for the sake of convenience of explanation, the side of the sealing body 17 of the cylindrical battery 10 is set as the upper side, and the bottom side of the outer can 16 is set as the lower side.

[0014] Details will be described later, but the negative electrode 12 has a non-opposed portion 43 (see Figure 2 ) on the winding start side of the electrode body 14. The non-opposed portion 43 has a negative electrode composite layer 41 formed on at least one surface of the negative electrode core 40, and is wound with a length 0 of 0.6 turns or more and 0.9 turns or less in a state of not opposing the positive electrode 11. The non-opposed portion 43 ensures a core structure of the electrode body 14 with excellent shape stability, and forms a cavity along the axial direction in the core. The cavity of the core functions as an exhaust path for guiding the gas generated when an abnormality occurs in the battery toward the safety valve. By setting the length of the non-opposed portion 43 to 0.6 turns or more, the shape of the core can be stabilized, and a sufficient cavity can be ensured as an exhaust path. In addition, by setting the length of the non-opposed portion 43 to 0.9 turns or less, deformation of the electrode body 14 can be effectively suppressed.

[0015] The electrolyte may also be an aqueous electrolyte, but a non-aqueous electrolyte is used in this embodiment. The non-aqueous electrolyte has lithium ion conductivity. The non-aqueous electrolyte may be a liquid electrolyte (electrolyte solution) or a solid electrolyte. The cylindrical battery 10 is, for example, a non-aqueous electrolyte secondary battery, and preferably a lithium ion battery.

[0016] The liquid electrolyte (electrolyte solution) contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. For the non-aqueous solvent, for example, esters, ethers, nitriles, amides, and mixed solvents of two or more of them are used. As an example of the non-aqueous solvent, ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and their mixed solvents are listed. The non-aqueous solvent may also contain a halogen-substituted body obtained by substituting at least a part of the hydrogen of these solvents with a halogen atom such as fluorine (for example, fluoroethylene carbonate, etc.). For the electrolyte salt, for example, a lithium salt such as LiPF6 is used.

[0017] 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, known materials such as all-solid-state lithium ion secondary batteries (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used. The polymer electrolyte contains, for example, a lithium salt and a matrix polymer, or contains a non-aqueous solvent, a lithium salt, and a matrix polymer. As the matrix polymer, for example, a polymer material that gels by absorbing a non-aqueous solvent is used. As the polymer material, fluororesin, acrylic resin, polyether resin, etc. are listed.

[0018] As described above, the electrode body 14 has a winding structure in which the positive electrode 11 and the negative electrode 12 are wound in a spiral shape with the separator 13 interposed therebetween. The positive electrode 11, the negative electrode 12, and the separator 13 are all strip-shaped long bodies, and are alternately laminated in the radial direction of the electrode body 14 by being wound in a spiral shape. In order to prevent the precipitation of lithium, the negative electrode 12 is formed to be one turn larger than the positive electrode 11. That is, the negative electrode 12 is formed to be longer than the positive electrode 11 in the length direction and the width direction. The separator 13 is formed to be at least one turn larger than the positive electrode 11, and for example, two sheets are arranged sandwiching the positive electrode 11.

[0019] The electrode body 14 has a positive electrode lead 20 joined to the positive electrode 11 and a negative electrode lead 21 joined to the negative electrode 12. In this embodiment, the positive electrode lead 20 is provided at a position in the central portion in the length direction of the positive electrode 11, away from the winding start side end and the winding end side end of the electrode body 14. On the other hand, the negative electrode lead 21 is provided at one end portion in the length direction of the negative electrode 12 located on the winding start side of the electrode body 14. The negative electrode 12 has a first core exposed portion 42 (refer to Figure 2), the exposed portion 42 of the first core body is the portion from the negative electrode starting end 12x, which is one end in the longitudinal direction, to the non-opposing portion 43, and there is no negative electrode composite agent layer 41. The negative electrode lead 21 is joined to the exposed portion 42 of the core body.

[0020] The positive electrode 11 has a positive electrode core body 30 and a positive electrode composite agent layer 31 formed on at least one surface of the core body. For the positive electrode core body 30, foils of metals such as aluminum and aluminum alloys that are stable within the potential range of the positive electrode 11, thin films obtained by disposing such metals on the surface layer, etc. can be used. The positive electrode composite agent layer 31 contains a positive electrode active material, a conductive agent such as acetylene black, and an adhesive such as polyvinylidene fluoride (PVdF), and is preferably formed on both surfaces of the positive electrode core body 30. The thickness of the positive electrode composite agent layer 31 is, for example, 40 μm or more and 100 μm or less. For the positive electrode active material, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, etc. is used, for example. In addition, the positive electrode lead 20 is preferably directly joined to the positive electrode core body 30 by ultrasonic welding or the like.

[0021] The negative electrode 12 has a negative electrode core body 40 and a negative electrode composite agent layer 41 formed on at least one surface of the core body. For the negative electrode core body 40, foils of metals such as copper and copper alloys that are stable within the potential range of the negative electrode 12, thin films obtained by disposing such metals on the surface layer, etc. can be used. The negative electrode composite agent layer 41 contains a negative electrode active material and an adhesive such as styrene-butadiene rubber (SBR), and is preferably formed on both surfaces of the negative electrode core body 40. The thickness of the negative electrode composite agent layer 41 is, for example, 40 μm or more and 100 μm or less. For the negative electrode active material, graphite, a Si-containing material, etc. are used, for example. The negative electrode lead 21 is preferably directly joined to the negative electrode core body 40 by ultrasonic welding or the like.

[0022] The cylindrical battery 10 includes an upper insulating plate 18, which is disposed between the sealing body 17 and the electrode group and has an opening through which the positive electrode lead 20 passes. In this specification, the electrode group refers to the part of the electrode body 14 that is composed of the positive electrode 11, the negative electrode 12, and the separator 13 and excludes the positive electrode lead 20 and the negative electrode lead 21. In addition, the cylindrical battery 10 includes a lower insulating plate 19, which is disposed between the inner surface of the bottom of the outer can 16 and the electrode group and has an opening through which the negative electrode lead 21 passes.

[0023] In Figure 1 the example shown, the positive electrode lead 20 extends toward the sealing body 17 side through the opening of the upper insulating plate 18, and the negative electrode lead 21 extends toward the bottom side of the outer can 16 through the opening of the lower insulating plate 19. The positive electrode lead 20 is connected to the lower surface of the bottom plate 23 of the sealing body 17 by welding or the like, and the sealing body 17 becomes the positive terminal. The negative electrode lead 21 is connected to the inner surface of the bottom of the outer can 16 by welding or the like, and the outer can 16 becomes the negative terminal.

[0024] The negative electrode 12 is disposed on the outermost peripheral surface of the electrode body 14, and a second core body exposed portion 44 where the surface of the negative electrode core body 40 is exposed is provided. Further, the core body exposed portion 44 abuts against the inner peripheral surface of the outer can 16. The core body exposed portion 44 abuts against the inner peripheral surface of the outer can 16 which serves as a negative terminal, whereby both end portions in the longitudinal direction of the negative electrode 12 are electrically connected to the outer can 16, and good current collecting property can be ensured. The core body exposed portion 44 may be provided on a part of the outermost peripheral surface of the electrode body 14, but is preferably provided in the entire region of the outermost peripheral surface. For example, starting from the winding end of the negative electrode 12, a portion where the negative electrode composite agent layer 41 does not exist on both surfaces of the negative electrode core body 40 is provided with a length of more than one turn of the electrode body 14.

[0025] The outer can 16 is a bottomed cylindrical metal container. A gasket 28 is provided between the outer can 16 and the sealing body 17, and the inside of the battery is sealed. The outer can 16 has, for example, a groove portion 22 that supports the sealing body 17 formed by pressing the side surface portion from the outside. The groove portion 22 is preferably formed in a ring shape along the circumferential direction of the outer can 16, and the sealing body 17 is supported on its upper surface. Further, the upper end portion of the outer can 16 is bent inward and fastened to the peripheral edge portion of the sealing body 17.

[0026] The sealing body 17 has a structure in which a bottom plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a lid 27 are laminated in this order from the side of the electrode body 14. Each member constituting the sealing body 17 has, for example, a disc shape or a ring shape, and the members other than the insulating member 25 are electrically connected to each other. The lower valve body 24 and the upper valve body 26 are connected to each other at their central portions, and the insulating member 25 is interposed between the peripheral edge portions of the valve bodies. When the internal pressure of the battery rises, the lower valve body 24 deforms and breaks in a manner of pressing the upper valve body 26 toward the lid 27 side, whereby the current path between the lower valve body 24 and the upper valve body 26 is cut off. When the internal pressure further rises, the upper valve body 26 breaks, and gas is discharged from the opening portion of the lid 27.

[0027] Hereinafter, with reference to Figure 2 the electrode body 14 will be described in detail. Figure 2 is a radial cross-sectional view of the winding core of the electrode body 14 and its vicinity. In Figure 2 in order to clarify the drawing, the illustration of the separator 13 is omitted.

[0028] As shown in Figure 2As shown, the negative electrode 12 that constitutes the electrode body 14 has a non-opposing portion 43 on the winding start side of the electrode body 14. The non-opposing portion 43 has a negative electrode composite layer 41 formed on at least one surface of the negative electrode core 40, and is wound with a length of 0.6 turns or more and 0.9 turns or less in a state where it does not oppose the positive electrode 11. Although the non-opposing portion 43 has the negative electrode composite layer 41, since it does not oppose the positive electrode 11, it does not contribute to the charge and discharge of the battery. On the other hand, since the non-opposing portion 43 has the negative electrode composite layer 41, it has a relatively high rigidity, which helps to stabilize the shape of the wound core portion of the electrode body 14 and ensures an exhaust path for the gas generated when an abnormality occurs in the battery. In addition, the portion located on the winding termination side of the electrode body 14 further than the positive electrode start end 11x becomes the opposing portion of the positive and negative electrodes where the positive electrode 11 and the negative electrode 12 oppose each other with the separator 13 interposed therebetween.

[0029] In this specification, the positive electrode start end 11x refers to one end in the length direction of the positive electrode 11 located on the winding start side (wound core side) of the electrode body 14. Similarly, the negative electrode start end 12x refers to one end in the length direction of the negative electrode 12 located on the winding start side of the electrode body 14. The negative electrode start end 12x is located at a position closer to the winding center Z than the positive electrode start end 11x.

[0030] In the non-opposing portion 43, the negative electrode composite layer 41 may be formed on either the inner peripheral surface of the negative electrode core 40 facing the winding center Z or the outer peripheral surface of the negative electrode core 40 facing the side wall of the outer can 16, and is preferably formed on both the inner and outer peripheral surfaces. In this case, the shape stability of the wound core portion is further improved. The negative electrode composite layer 41 is preferably formed on both surfaces of the negative electrode core 40 at least from the position corresponding to the positive electrode start end 11x to the minimum portion P1 described later, and may also be formed on both surfaces of the negative electrode core 40 over the entire length of the non-opposing portion 43.

[0031] As described above, the non-opposing portion 43 is formed with a length of 0.6 turns or more and 0.9 turns or less. In this case, it is easy to ensure a good exhaust path in the wound core portion. In addition, when the length of the non-opposing portion 43 is less than 0.6 turns or exceeds 0.9 turns, the effect of suppressing the plate deformation caused by introducing the minimum portion P1 and the maximum portion P2 into the wound core portion is reduced.

[0032] As described above, the negative electrode 12 has a core exposed portion 42 formed from the negative electrode starting end 12x over the non-opposing portion 43. The core exposed portion 42, like the non-opposing portion 43, is a portion that does not oppose the positive electrode 11, but is different from the non-opposing portion 43 in that it does not have the negative electrode composite layer 41 and is composed only of the negative electrode core 40. In the present embodiment, a negative electrode lead 21 is joined to the core exposed portion 42. When the negative electrode lead 21 is disposed in the wound core portion of the electrode body 14, deformation is likely to occur at the opposing portion of the positive and negative electrodes during charge and discharge. However, according to the present embodiment, such deformation can be effectively suppressed.

[0033] The length of the core exposed portion 42 is not particularly limited, but from the viewpoint of ensuring the bonding area of the negative electrode lead 21 and the like, it preferably has a length of 0.5 turns or more. The core exposed portion 42 may be formed with a length of 0.5 turns or more and 1.0 turn or less. The negative electrode lead 21 is, for example, a metal thin plate mainly composed of a metal such as nickel and has a thickness of 50 μm or more and 100 μm or less. The negative electrode lead 21 is joined to the outer peripheral surface of the core exposed portion 42, for example, at a position away from the negative electrode starting end 12x and the non-opposing portion 43.

[0034] The negative electrode lead 21 is joined to the core exposed portion 42 such that the winding termination side end portion of the negative electrode lead 21 is located in the range of 60° or more and 180° or less with respect to the winding center Z of the electrode body 14 from the positive electrode starting end 11x. And in the range of 60° or more and 180° or less with respect to the winding center Z of the electrode body 14 from the positive electrode starting end 11x, the ratio of the maximum value to the minimum value of the core-to-core distance between the non-opposing portion 43 and the core exposed portion 42 is 1.5 or more. In this case, it is considered that the stress applied to the electrode body 14 during charge and discharge can be absorbed by the wound core portion, and deformation of the opposing portion of the positive and negative electrodes can be effectively suppressed.

[0035] The negative electrode 12 has a minimum portion P1 where the core-to-core distance between the non-opposing portion 43 and the core exposed portion 42 is the smallest, and a maximum portion P2 where the core-to-core distance is the largest, in the range of 60° or more and 180° or less with respect to the winding center Z of the electrode body 14 from the position corresponding to the positive electrode starting end 11x toward the winding start side. In the present embodiment, the position corresponding to the winding termination side end portion of the negative electrode lead 21 is the minimum portion P1. In addition, the maximum portion P2 is formed closer to the positive electrode starting end 11x than the minimum portion P1. Both the minimum portion P1 and the maximum portion P2 are preferably formed between the position corresponding to the positive electrode starting end 11x and the position corresponding to the winding termination side end portion of the negative electrode lead 21.

[0036] In this specification, the angle θ1 refers to the angle from the positive electrode starting end 11x (starting point) to the minimum portion P1, and the angle θ2 refers to the angle from the positive electrode starting end 11x to the maximum portion P2. The angle θ1 is preferably greater than the angle θ2.

[0037] At the opposing portion of the positive and negative electrodes of the electrode body 14, the interval between the positive and negative electrodes is substantially constant, but the interval between the non-opposing portion 43 and the core exposed portion 42 is uneven. That is, at the opposing portion of the positive and negative electrodes, the distance between the cores is substantially constant, and at the portion where the non-opposing portion 43 and the core exposed portion 42 oppose each other, the distance between the cores changes. Preferably, the distance between the cores of the non-opposing portion 43 and the core exposed portion 42 gradually increases from the position corresponding to the positive electrode starting end 11x toward the maximum portion P2, and gradually decreases from the maximum portion P2 toward the minimum portion P1. In this case, the effect of suppressing the deformation of the electrode body 14 is more remarkable.

[0038] In the present embodiment, the non-opposing portion 43 bends greatly at the position corresponding to the maximum portion P2, and the curvature becomes larger compared to other portions of the non-opposing portion 43. In addition, at the position corresponding to the maximum portion P2 of the core exposed portion 42, the degree of bending becomes gentle or substantially flat, and the curvature becomes smaller compared to other portions of the core exposed portion 42. For example, at the position corresponding to the minimum portion P1 of the core exposed portion 42, the curvature becomes larger compared to other portions of the core exposed portion 42. In addition, in this specification, the position corresponding to the minimum portion P1 means the position overlapping the minimum portion P1 in the radial direction of the electrode body 14 (the same applies to the maximum portion P2, the positive electrode starting end 11x, etc.).

[0039] The minimum portion P1 only needs to be formed such that the angle θ1 is 60° or more and 180° or less, but it is preferably formed at the position corresponding to the negative electrode lead 21 or at a position closer to the positive electrode starting end 11x side than the position corresponding to the negative electrode lead 21. The maximum portion P2 only needs to be formed such that the angle θ2 is 60° or more and 180° or less, but it is preferably formed at a position closer to the positive electrode starting end 11x side than the minimum portion P1.

[0040] As described above, the ratio (D2 / D1) of the distance D2 between the cores at the maximum portion P2 to the distance D1 between the cores at the minimum portion P1 is 1.5 or more, preferably 1.8 or more, and more preferably 2.0 or more. In this case, it is considered that the stress applied to the electrode body 14 during charge and discharge can be effectively absorbed by the wound core portion. From the viewpoint of suppressing the deformation of the electrode body 14, the upper limit value of D2 / D1 is not particularly limited, but from the viewpoints of ensuring the exhaust path, productivity, etc., D2 / D1 is preferably 2.5 or less, and particularly preferably 2.3 or less. An example of the suitable range of D2 / D1 is 1.8 or more and 2.3 or less.

[0041] The electrode body 14 is manufactured by winding the electrode plates using a core member. However, by changing the tension (acceleration) during the winding of the electrode plates, the minimum portion P1 and the maximum portion P2 can be formed, and the distance between the cores can be adjusted. Specifically, compared with the acceleration when winding a portion with a constant core-to-core distance, the acceleration is decreased at the position corresponding to the minimum portion P1 and increased at the position corresponding to the maximum portion P2.

[0042] The minimum portion P1 and the maximum portion P2 can be determined based on the CT image of the electrode body 14. The CT image of the electrode body 14 can be obtained using an X-ray CT device (manufactured by Shimadzu Corporation, SMX-225CT FPD HR).

[0043] Example

[0044] Hereinafter, the present disclosure will be further described by way of examples, but the present disclosure is not limited to these examples.

[0045] <Example 1>

[0046] [Fabrication of the positive electrode]

[0047] As the positive electrode active material, a lithium nickel oxide containing cobalt and aluminum (LiNi 0.88 Co 0.09 Al 0.03 O2) is used. The positive electrode active material, acetylene black, and polyvinylidene fluoride are mixed at a solid component mass ratio of 98:1:1, and N-methylpyrrolidone (NMP) is used as a dispersion medium to prepare a positive electrode composite agent slurry. The slurry is coated on both sides of a positive electrode core made of a long strip of aluminum foil with a thickness of 15 μm, and the coating film is dried and compressed to obtain a positive electrode having positive electrode composite agent layers formed on both sides of the positive electrode core (single-sided thickness: 90 μm, density: 3.6 g / cm 3 ). In addition, at the central portion in the length direction of the positive electrode, a core exposed portion where no positive electrode composite agent layer exists is provided, and an aluminum positive electrode lead is ultrasonically welded to the exposed portion.

[0048] [Fabrication of the negative electrode]

[0049] As the negative electrode active material, a material obtained by mixing graphite powder and a Si-containing material at a mass ratio of 95:5 is used. The negative electrode active material, a dispersion of styrene-butadiene rubber, and sodium carboxymethyl cellulose are mixed at a solid component mass ratio of 98:1:1, and water is used as a dispersion medium to prepare a negative electrode composite agent slurry. The slurry is coated on both sides of a negative electrode core made of a long strip of copper foil with a thickness of 8 μm, and the coating film is dried and compressed to obtain a negative electrode having negative electrode composite agent layers formed on both sides of the negative electrode core (single-sided thickness: 95 μm, density: 1.6 g / cm 3The negative electrode of ( ). In addition, within a given length range starting from both ends in the length direction of the negative electrode, a first core body exposed portion and a second core body exposed portion where the negative electrode composite layer does not exist are provided, and a negative electrode lead made of nickel is ultrasonically welded to the first core body exposed portion.

[0050] [Fabrication of the electrode body]

[0051] Using a cylindrical winding core member, the above-mentioned positive electrode, the above-mentioned negative electrode, and a separator made of polyethylene are wound into a spiral shape, and winding fixing tapes are pasted at both axial end portions of the outermost peripheral surface to obtain a wound-type electrode body. At this time, the negative electrode is arranged such that the first core body exposed portion of the negative electrode to which the negative electrode lead is joined is located on the winding start side of the electrode body. That is, the second core body exposed portion of the negative electrode is located on the winding end side of the electrode body. In addition, on the winding start side of the electrode body, the negative electrode extends beyond the starting end of the positive electrode, thereby providing a non-opposing portion that does not oppose the positive electrode. After forming the winding structure of the electrode body, the winding core member is removed to obtain a wound-type electrode body having a cavity formed in the winding core portion.

[0052] In Example 1, the electrode plates are wound such that the angle θ1 representing the position of the end portion on the winding end side of the negative electrode lead with respect to the position of the starting end of the positive electrode is 60°. At the position of the angle θ1, the minimum distance D1 (0.24 mm) between the first core body exposed portion and the non-opposing portion is obtained. In addition, by changing the tension (acceleration) during the winding of the electrode plates, the maximum distance D2 between the first core body exposed portion and the non-opposing portion is set to 0.48 mm, and the angle θ2 representing its position is set to 20°. That is, in the electrode body of Example 1, a minimum portion P1 is formed at a position 60° from the starting end of the positive electrode with respect to the winding center, and a maximum portion P2 is formed at a position 20° from the starting end of the positive electrode with respect to the winding center.

[0053] [Preparation of the non-aqueous electrolyte]

[0054] In 100 parts by mass of a mixed solvent obtained by mixing ethylene carbonate (EC) and dimethyl carbonate (DMC) at a volume ratio of 1:3 (25 °C), 5 parts by mass of vinylene carbonate (VC) is added, and 1.5 mol / L of LiPF6 is dissolved to prepare a non-aqueous electrolyte.

[0055] [Fabrication of the cylindrical battery]

[0056] After arranging insulating plates above and below the above-mentioned electrode body, the negative electrode lead is welded to the inner surface of the bottom of a bottomed cylindrical outer can, the positive electrode lead is welded to the internal terminal plate of the sealing body, and the electrode body is accommodated in the outer can. Then, the non-aqueous electrolyte is injected into the outer can in a reduced-pressure manner, and the opening of the outer can is sealed with the sealing body through a gasket, thereby obtaining a cylindrical battery. In addition, the second core body exposed portion of the negative electrode forms the outermost peripheral surface of the electrode body and contacts the inner peripheral surface of the outer can.

[0057] <Example 2>

[0058] Set the length of the non-opposing part of the negative electrode to 0.9 turns. Except for this, a cylindrical battery was fabricated in the same manner as in Example 1.

[0059] <Example 3>

[0060] Change the position of the winding termination side end of the negative electrode lead with respect to the positive electrode starting end, and wind the electrode plates such that the angle θ1 is 180°. Except for this, a cylindrical battery was fabricated in the same manner as in Example 2.

[0061] <Comparative Example 1>

[0062] Set the length of the non-opposing part of the negative electrode to 0.5 turns, and change the tension during electrode plate winding such that the maximum value D2 of the interval between the first core body exposed part and the non-opposing part is 0.30 mm. Except for this, a cylindrical battery was fabricated in the same manner as in Example 1.

[0063] <Comparative Example 2>

[0064] Change the tension during electrode plate winding such that the position of the winding termination side end of the negative electrode lead is changed with respect to the positive electrode starting end so that the angle θ1 is 50°, and the maximum value D2 of the interval between the first core body exposed part and the non-opposing part is 0.27 mm. Except for this, a cylindrical battery was fabricated in the same manner as in Example 1.

[0065] <Comparative Example 3>

[0066] Change the tension during electrode plate winding such that the position of the winding termination side end of the negative electrode lead is changed with respect to the positive electrode starting end so that the angle θ1 is 190°, and the maximum value D2 of the interval between the first core body exposed part and the non-opposing part is 0.30 mm. Except for this, a cylindrical battery was fabricated in the same manner as in Example 1.

[0067] <Comparative Example 4>

[0068] Set the length of the non-opposing part of the negative electrode to 1.0 turns, and change the tension during electrode plate winding such that the maximum value D2 of the interval between the first core body exposed part and the non-opposing part is 0.26 mm. Except for this, a cylindrical battery was fabricated in the same manner as in Example 3.

[0069] [Evaluation of Electrode Plate Deformation (Presence or Absence of Bending)]

[0070] The batteries of each example were charged at a constant current of 0.5C in a temperature environment of 45°C until the battery voltage reached 4.2V. Then, they were discharged at a constant current of 0.7C until the battery voltage reached 2.5V. After performing 200 cycles of such charge and discharge, the batteries were set in a charged state, and observation near the core of the electrode body was carried out using an X-ray CT device (manufactured by Shimadzu Corporation, SMX-225CT FPD HR).

[0071] As Figure 3 shown, in the part where the positive electrode and the negative electrode face each other, when deformation (bending) of the electrode plate (at least one of the positive electrode 11 and the negative electrode 12) with an angle θ of 150° or less was confirmed, it was determined that there was bending, and thus the presence or absence of bending was evaluated. The number of batteries evaluated was 100.

[0072] [Table 1]

[0073]

[0074] As shown in Table 1, in the batteries of the examples, compared with the case of the batteries of the comparative examples, it was difficult for the electrode body to bend. That is, by restricting the non-opposing part to a length of 0.6 turns or more and 0.9 turns or less, and arranging the negative electrode lead within a given angular range starting from the positive electrode starting end, and introducing a minimum part P1 and a maximum part P2 with D2 / D1 of 1.5 or more in the core part, such an electrode body can effectively suppress deformation at the opposing part of the positive and negative electrodes. On the other hand, when using the electrode body of the comparative example that does not satisfy this condition, the probability of deformation at the opposing part of the positive and negative electrodes increases.

[0075] The present disclosure will be further described by the following embodiments.

[0076] Structure 1: A cylindrical battery includes an electrode body having a positive electrode, a negative electrode including a core body and a composite agent layer, and a separator, and the positive electrode and the negative electrode are wound with the separator therebetween, and has a negative electrode lead wire joined to the negative electrode. The negative electrode has: a non-opposing portion that is formed with the composite agent layer on at least one surface of the core body on the winding start side of the electrode body and is wound with a length of 0.6 turns or more and 0.9 turns or less without opposing the positive electrode; and a core body exposed portion that is formed from the negative electrode start end over the non-opposing portion, and the negative electrode lead wire is joined to the core body exposed portion such that the winding end side end of the negative electrode lead wire is located in a range of 60° or more and 180° or less from the positive electrode start end to the winding start side with respect to the winding center of the electrode body. In the non-opposing portion, in a range of 60° or more and 180° or less from the position corresponding to the positive electrode start end to the winding start side with respect to the winding center of the electrode body, the ratio of the maximum value to the minimum value of the core body distance between the non-opposing portion and the core body exposed portion is 1.5 or more.

[0077] Structure 2: In the cylindrical battery according to Structure 1, a maximum portion representing the maximum value of the core body distance between the non-opposing portion and the core body exposed portion is formed at a position closer to the positive electrode start end side than a minimum portion representing the minimum value of the core body distance.

[0078] Structure 3: In the cylindrical battery according to Structure 2, the minimum portion is formed at a position corresponding to the winding end side end of the negative electrode lead wire.

[0079] Structure 4: In the cylindrical battery according to any one of Structures 1 to 3, in the non-opposing portion, the composite agent layer is formed on both surfaces of the core body.

[0080] Structure 5: In the cylindrical battery according to any one of Structures 1 to 4, the negative electrode lead wire is joined to the outer peripheral surface of the core body exposed portion.

[0081] -Symbol Explanation-

[0082] 10: Cylindrical battery; 11: Positive electrode; 11x: Positive electrode start end; 12: Negative electrode; 12x: Negative electrode start end; 13: Separator; 14: Electrode body; 16: Outer can; 17: Sealing body; 18: Upper insulating plate; 19: Lower insulating plate; 20: Positive electrode lead wire; 21: Negative electrode lead wire; 22: Groove portion; 23: Bottom plate; 24: Lower valve body; 25: Insulating member; 26: Upper valve body; 27: Cover; 28: Gasket; 30: Positive electrode core body; 31: Positive electrode composite agent layer; 40: Negative electrode core body; 41: Negative electrode composite agent layer; 42, 44: Core body exposed portion; 43: Non-opposing portion; P1: Minimum portion; P2: Maximum portion.

Claims

1. A cylindrical battery includes an electrode body having a positive electrode, a negative electrode including a core body and a composite agent layer, and a separator, and the positive electrode and the negative electrode are wound with the separator therebetween, and further includes a negative electrode lead wire joined to the negative electrode. The negative electrode has: a non-opposing portion formed at a winding start side of the electrode body, where the composite agent layer is formed on at least one surface of the core body and wound with a length of 0.6 turns or more and 0.9 turns or less in a state of not opposing the positive electrode; and a core body exposed portion formed from a negative electrode start end over the non-opposing portion. The negative electrode lead wire is joined to the core body exposed portion such that an end portion on a winding end side of the negative electrode lead wire is located in a range where an angle from a positive electrode start end to the winding start side with respect to a winding center of the electrode body is 60° or more and 180° or less. In the non-opposing portion, in a range where an angle from a position corresponding to the positive electrode start end to the winding start side with respect to the winding center of the electrode body is 60° or more and 180° or less, a ratio of a maximum value to a minimum value of a core body distance between the non-opposing portion and the core body exposed portion is 1.5 or more.

2. The cylindrical battery according to claim 1, wherein a maximum portion representing the maximum value of the core body distance between the non-opposing portion and the core body exposed portion is formed at a position closer to the positive electrode start end side than a minimum portion representing the minimum value of the core body distance.

3. The cylindrical battery according to claim 2, wherein the minimum portion is formed at a position corresponding to an end portion on a winding end side of the negative electrode lead wire.

4. The cylindrical battery according to any one of claims 1 to 3, wherein in the non-opposing portion, the composite agent layer is formed on both surfaces of the core body.

5. The cylindrical battery according to any one of claims 1 to 3, wherein the negative electrode lead wire is joined to an outer peripheral surface of the core body exposed portion.

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