Cylindrical battery

Abstract

A cylindrical battery, which is an example of an embodiment of the present invention, comprises an electrode body (14) in which a positive electrode (11) and a negative electrode (12) are wound with a separator (13) in between and a bottomed cylindrical exterior can (16) accommodating the electrode body (14). The negative electrode (12) extends farther to the winding start side of the electrode body (14) than a position facing a positive electrode starting end (11x). The electrode body (14) has a negative electrode facing part where the winding inner surface and the winding outer surface of the negative electrode (12) face each other across the separator (13), and a spacer (50) disposed in the negative electrode facing part. At least a part of the spacer (50) is disposed within a range of no more than 140° from the positive electrode starting end (11x) toward the winding start side along the winding direction with respect to a winding center Z of the electrode body (14).

Description

Cylindrical battery

[0001] The present disclosure relates to cylindrical batteries.

[0002] A cylindrical battery includes a wound electrode assembly in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween. The electrode assembly generally has a cavity extending in the axial direction formed in the winding core. This cavity functions as an exhaust path that guides gas generated in the event of a battery abnormality toward a safety valve. For example, Patent Document 1 discloses a cylindrical battery including an electrode assembly in which the negative electrode extends toward the center of the winding of the electrode assembly beyond the position facing the starting end of the positive electrode, and is wound to a predetermined length or more without facing the positive electrode.

[0003] International Publication No. 2018 / 116876

[0004] The cylindrical battery of Patent Document 1 has improved shape stability of the winding core portion and ensures a sufficient exhaust path in the event of an abnormality. However, as a result of studies by the present inventors, it was found that when the volume change of the negative electrode during charge and discharge increases due to an increase in battery capacity, deformation of the negative electrode is likely to occur near the starting end of the positive electrode.

[0005] The cylindrical battery according to the present disclosure is a cylindrical battery comprising an electrode assembly including a positive electrode, a negative electrode, and a separator, the positive electrode and the negative electrode being wound with the separator interposed therebetween, and a bottomed cylindrical outer can that houses the electrode assembly, wherein the negative electrode extends toward the winding start side of the electrode assembly beyond a position facing the positive electrode starting end, which is the end of the positive electrode on the winding start side of the electrode assembly, and a negative electrode opposing portion is formed where the inner winding surface and the outer winding surface of the negative electrode face each other via the separator, the electrode assembly has a spacer arranged in the negative electrode opposing portion, and at least a portion of the spacer is arranged from the positive electrode starting end toward the winding start side along the winding direction of the electrode assembly within a range of 140° or less with respect to the winding center of the electrode assembly.

[0006] According to the cylindrical battery of the present disclosure, deformation of the negative electrode near the starting end of the positive electrode can be effectively suppressed.

[0007] 1 is a cross-sectional view of a cylindrical battery according to an embodiment of the present invention; FIG. 2 is a diagram illustrating a part of a radial cross section of an electrode assembly according to an embodiment of the present invention; FIG. 3 is a diagram illustrating a method for evaluating electrode plate deformation;

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

[0009] FIG. 1 is a schematic diagram illustrating an axial and radial cross section of a cylindrical battery 10 according to an embodiment. As shown in FIG. 1 , the cylindrical battery 10 includes a positive electrode 11, a negative electrode 12, and a separator 13. The positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween to form an electrode assembly 14, and a cylindrical outer can 16 with a bottom that houses the electrode assembly 14. The cylindrical battery 10 also includes an electrolyte housed in the outer can 16 and a sealing body 17 that closes the opening of the outer can 16. The outer can 16 has a groove 22 formed in its side wall, and the sealing body 17 is supported by the groove 22 to close the opening of the outer can 16. Hereinafter, for convenience of explanation, the sealing body 17 side of the cylindrical battery 10 will be referred to as the top, and the bottom side of the outer can 16 will be referred to as the bottom.

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

[0011] The liquid electrolyte (electrolytic solution) contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixed solvents of two or more of these. Examples of the non-aqueous solvent include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents of these. The non-aqueous solvent may contain a halogen-substituted compound (e.g., fluoroethylene carbonate) in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine. Examples of the electrolyte salt include LiPF ６ Lithium salts such as

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

[0013] As described above, the electrode assembly 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The positive electrode 11, the negative electrode 12, and the separator 13 are all long strips that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in the length direction and width direction than the positive electrode 11. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and for example, two separators 13 are arranged to sandwich the positive electrode 11.

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

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

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

[0017] The thickness of the negative electrode 12 is, for example, 170 μm or more and 210 μm or less. In the present embodiment, the thickness of the negative electrode 12 is substantially constant except for a core exposed portion described below. The thickness of the negative electrode core 40 is, for example, 5 μm or more and 15 μm or less. The thickness of the negative electrode mixture layer 41 is, for example, 70 μm or more and 110 μm or less on one surface side of the negative electrode core 40. The negative electrode 12 can be produced, similarly to the positive electrode 11, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder onto the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode mixture layers 41 on both surfaces of the negative electrode core 40.

[0018] The electrode body 14 has a positive electrode lead 20 connected to the positive electrode 11 and a negative electrode lead 21 connected to the negative electrode 12. In this embodiment, a core exposed portion where the positive electrode mixture layer 31 is not present and the surface of the positive electrode core 30 is exposed is formed in the center of the positive electrode 11 in the longitudinal direction, and the positive electrode lead 20 is connected to this exposed portion. On the other hand, the negative electrode lead 21 is provided at one end of the negative electrode 12 in the longitudinal direction, which is located at the start side of winding of the electrode body 14. At one end of the negative electrode 12 in the longitudinal direction, a first core exposed portion 42 (see FIG. 2 described below) where the negative electrode mixture layer 41 is not present and the surface of the negative electrode core 40 is exposed is formed, and the negative electrode lead 21 is connected to the core exposed portion 42.

[0019] Insulating plates 18 and 19 are disposed above and below the electrode body 14. In the example shown in Fig. 1 , the positive electrode lead 20 passes through a through hole in the insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes through a through hole in the insulating plate 19 and extends toward the bottom side of the outer can 16. The positive electrode lead 20 is connected to the underside of an internal terminal plate 23 of the sealing body 17 by welding or the like, and a cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal. The negative electrode lead 21 is connected to the inner bottom surface of the outer can 16 by welding or the like, and the outer can 16 serves as the negative electrode terminal.

[0020] The negative electrode 12 is disposed on the outermost peripheral surface of the electrode body 14, and a second core exposed portion 43 is provided where the surface of the negative electrode core 40 is exposed. The core exposed portion 43 abuts against the inner peripheral surface of the outer can 16. By abutting the core exposed portion 43 against the inner peripheral surface of the outer can 16, both ends of the negative electrode 12 in the length direction and the outer can 16 are electrically connected, ensuring good current collection. The core exposed portion 43 may be provided on a part of the outermost peripheral surface of the electrode body 14, but is preferably provided over the entire outermost peripheral surface.

[0021] The outer can 16 is a cylindrical metal container with a bottom. A gasket 28 is provided between the outer can 16 and the sealing body 17 to seal the interior of the battery. The outer can 16 has a groove 22 that supports the sealing body 17, formed, for example, by pressing the side surface from the outside. The groove 22 is preferably formed in an annular shape along the circumferential direction of the outer can 16, and supports the sealing body 17 on its top surface. The upper end of the outer can 16 is bent inward and crimped to the periphery of the sealing body 17.

[0022] The sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked. Each member constituting the sealing body 17 has, for example, a disk or ring shape, and each member except for 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, and the insulating member 25 is interposed between their respective peripheral edges. When the internal pressure of the battery increases due to abnormal heat generation, the lower valve body 24 deforms and breaks, pushing the upper valve body 26 toward the cap 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. When the internal pressure further increases, the upper valve body 26 breaks, and gas is discharged from the opening of the cap 27.

[0023] The electrode assembly 14 will be described in detail below with reference to Fig. 2. Fig. 2 is a radial cross-sectional view of the winding start side of the electrode assembly 14. To clarify the drawing, the separator 13 is omitted from Fig. 2. The positive electrode core 30 and the positive electrode mixture layer 31 are also omitted from the drawing.

[0024] As shown in FIG. 2 , the negative electrode 12 constituting the electrode assembly 14 extends further toward the winding start side of the electrode assembly 14 than the position facing the positive electrode starting end 11x, which is the end of the positive electrode 11 at the winding start side of the electrode assembly 14. The winding start side of the negative electrode 12 includes a non-facing region, for example, a region where the negative electrode 12 is wound around one or more turns without facing the positive electrode 11. A negative electrode mixture layer 41 may be formed in the non-facing region of the negative electrode 12. In this embodiment, most of the non-facing region, excluding the vicinity of the positive electrode starting end 11x, is a core exposed portion 42. A negative electrode lead 21 is connected to the core exposed portion 42 near the negative electrode starting end 12x, which is the end of the winding start side of the negative electrode 12. Furthermore, a negative electrode facing portion is formed in the non-facing region of the negative electrode 12, where the inner and outer winding surfaces of the negative electrode 12 face each other via the separator 13.

[0025] The electrode assembly 14 has a spacer 50 disposed in the negative electrode facing portion. The spacer 50 may be disposed on either the inner or outer winding surface of the negative electrode 12. In the negative electrode facing portion, a gap not occupied by the negative electrode 12 or the separator 13 exists near the positive electrode starting end 11x. As a result of studies by the inventors, it was found that repeated charging and discharging of the battery reduces this gap, making the negative electrode 12 prone to bending and deformation near the positive electrode starting end 11x. By disposing the spacer 50 within a predetermined range from the positive electrode starting end 11x, the spacing between the negative electrodes 12 can be maintained, effectively suppressing deformation of the negative electrodes 12.

[0026] At least a portion of the spacer 50 is disposed within a range of 140° or less from the positive electrode starting end 11x toward the start of winding along the winding direction of the electrode body 14 with respect to the winding center Z of the electrode body 14. In other words, of the ends of the spacer 50 in the winding direction of the electrode body 14, at least the end on the winding end side in the winding direction is located within a range of 140° or less from the positive electrode starting end 11x toward the start of winding of the electrode body 14. In this case, deformation of the negative electrode 12 near the positive electrode starting end 11x can be effectively suppressed. The entire spacer 50 may be located within an angle range of 140° or less from the positive electrode starting end 11x.

[0027] The angles θ (θ1, θ2) shown in FIG. 2 refer to angles measured from the position of the positive electrode starting end 11x, which is the starting point, toward the start of winding along the winding direction of the electrode body 14 around the winding center Z. Furthermore, angle θ1 refers to the angle along the winding direction from the positive electrode starting end 11x to the end of the winding of the spacer 50, and angle θ2 refers to the angle along the winding direction from the positive electrode starting end 11x to the end of the winding of the spacer 50. In other words, angle θ1 is the central angle of the arc (arc centered at the winding center Z) from the position of the positive electrode starting end 11x to the end of the winding of the spacer 50, and angle θ2 is the central angle of the arc from the position of the positive electrode starting end 11x to the end of the winding of the spacer 50.

[0028] As described above, the electrode body 14 has the negative electrode lead 21 connected near the negative electrode starting end 12x. In this embodiment, the negative electrode lead 21 is connected to the core exposed portion 42, which is the non-facing region of the negative electrode 12, closer to the winding start side than the spacer 50. The negative electrode lead 21 is fixed to the outer can 16, and therefore the non-facing region of the negative electrode 12 is constrained. In this case, the negative electrode 12 is more likely to deform than when the negative electrode lead 21 is not present in the non-facing region; however, by providing the spacer 50 between the negative electrode lead 21 and the positive electrode starting end 11x, deformation of the negative electrode 12 can be effectively suppressed.

[0029] The spacer 50 may be joined to the separator 13 at the portion facing the negative electrode, for example. However, from the viewpoint of improving the positioning accuracy of the spacer 50, it is preferable that the spacer 50 be joined to the negative electrode 12. In this embodiment, the spacer 50 is joined to the core exposed portion 42 at the portion facing the negative electrode. In this case, the spacer 50 can be firmly joined to the negative electrode 12, and problems such as misalignment of the spacer 50 can be suppressed.

[0030] The thickness of the spacer 50 is preferably 60% to 120% of the thickness of the positive electrode 11, and more preferably 70% to 100%. In this case, an appropriate gap can be secured between the negative electrodes 12, and deformation of the negative electrode 12 due to charging and discharging of the battery can be more effectively suppressed. The thickness of the spacer 50 may be smaller than the thickness of the positive electrode 11, or may be substantially the same as the thickness of the positive electrode 11. The thickness of the spacer 50 may be smaller immediately after manufacturing the electrode body 14, as long as it is 60% to 120% of the thickness of the positive electrode 11 in the cylindrical battery 10 state.

[0031] The material of the spacer 50 is not particularly limited, but the spacer 50 is preferably made of a flexible material that curves along the winding direction of the electrode assembly 14. The spacer 50 is bonded to the core exposed portion 42 during the manufacture of the negative electrode 12, for example, and is preferably made of an elastically deformable resin material that follows the curvature of the negative electrode 12. One example of a suitable spacer 50 is a tape having a strip-shaped substrate and an adhesive layer provided on one surface of the substrate. For example, the spacer 50 can be provided by applying a resin material to the negative electrode 12, but if the spacer 50 is a tape having an adhesive layer, the spacer 50 can be easily attached to the negative electrode 12.

[0032] The spacer 50 is preferably made of a material that increases in thickness by absorbing the nonaqueous electrolyte. For example, the spacer 50 has a small thickness when the electrode assembly 14 is manufactured, and when the nonaqueous electrolyte is injected into the outer can 16, the spacer 50 absorbs the nonaqueous electrolyte and swells, increasing in thickness by three or more times. In this case, it is easier to form a wound structure for the electrode assembly 14 than when the thickness of the spacer 50 does not change.

[0033] The spacer 50 has, for example, a tape substrate that swells upon absorption of the non-aqueous electrolyte. The tape substrate is preferably composed primarily of a resin that has a high affinity for the non-aqueous electrolyte. Suitable resins include polystyrene, a copolymer of styrene and an α-olefin, and a fluororesin such as PVdF. The tape substrate may be a porous sheet or a foam sheet having numerous pores to allow the non-aqueous electrolyte to easily penetrate.

[0034] The adhesive layer of the spacer 50 is preferably composed primarily of an adhesive (resin) with excellent electrolyte resistance. The adhesive may be a hot-melt type that becomes adhesive when heated or a thermosetting type that hardens when heated, but from the standpoint of productivity, etc., an adhesive that is adhesive at room temperature is preferred. The adhesive layer may be composed of, for example, an acrylic adhesive or a rubber adhesive.

[0035] At least a portion of the spacer 50 is preferably disposed within a range of 110° or less from the positive electrode starting end 11x to the winding start side along the winding direction of the electrode body 14 relative to the winding center Z. That is, the angle θ1 from the positive electrode starting end 11x to the winding end side of the spacer 50 is preferably 110° or less. In this case, deformation of the negative electrode 12 near the positive electrode starting end 11x can be more effectively suppressed. The lower limit of the angle θ1 is not particularly limited, but is preferably set to 30° or more from the viewpoint of reliably preventing interference between the spacer 50 and the positive electrode 11. An example of a suitable range for the angle θ1 is 30° or more and 110° or less.

[0036] The spacer 50 is preferably disposed entirely within a range not exceeding 360° from the positive electrode starting end 11x to the winding start side along the winding direction of the electrode body 14 with respect to the winding center Z. That is, the angle θ2 from the positive electrode starting end 11x to the winding start side end of the spacer 50 is preferably 360° or less. If the angle θ2 exceeds 360°, it is expected that the spacer 50 will press the non-facing region of the negative electrode 12 radially outward from the electrode body 14, promoting deformation of the negative electrode 12. Therefore, the angle θ2 is preferably set to 360° or less.

[0037] Furthermore, if the length of the spacer 50 along the winding direction of the electrode body 14 becomes too short, stress generated during charging and discharging may be concentrated at the portion where the spacer 50 is joined, potentially causing deformation of the negative electrode 12. For this reason, it is preferable that the spacer 50 have a length in the winding direction that corresponds to an angle θ of 30° or more.

[0038] The spacer 50 is preferably a strip-shaped member, and is provided so that the width direction of the spacer 50 is along the winding direction of the electrode body 14. The width of the spacer 50 is, for example, 1 mm or more and 5 mm or less. The spacer 50 is preferably joined to the negative electrode 12 so as not to protrude from both ends of the negative electrode 12 in the width direction. The length of the spacer 50 (the length along the width direction of the negative electrode 12) may be shorter than the width of the negative electrode 12, but is preferably 50% or more, and more preferably 70% or more, of the width of the negative electrode 12. The spacer 50 has, for example, substantially the same length as the width of the negative electrode 12, and is provided across the entire width of the negative electrode 12.

[0039] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to these examples.

[0040] Example 1 [Fabrication of Positive Electrode] As a positive electrode active material, lithium nickel oxide (LiNi) containing cobalt and aluminum was used. ０．８８ Co ０．０９ Al ０．０３ O ２) was used. The positive electrode active material, acetylene black, and polyvinylidene fluoride were mixed in a solid content mass ratio of 98:1:1, and N-methylpyrrolidone (NMP) was used as a dispersion medium to prepare a positive electrode mixture slurry. The slurry was applied to both sides of a positive electrode core made of a long aluminum foil with a thickness of 15 μm, and the coating was dried and compressed to obtain a positive electrode (thickness: 180 μm) in which a positive electrode mixture layer was formed on both sides of the positive electrode core. Note that a core exposed portion where no positive electrode mixture layer was present was provided in the center of the positive electrode in the longitudinal direction, and an aluminum positive electrode lead was ultrasonically welded to this exposed portion.

[0041] [Negative Electrode Fabrication] A mixture of graphite powder and a Si-containing material in a mass ratio of 95:5 was used as the negative electrode active material. The negative electrode active material, a dispersion of styrene butadiene rubber, and sodium carboxymethyl cellulose were mixed in a solids mass ratio of 98:1:1, and a negative electrode mixture slurry was prepared using water as a dispersion medium. The slurry was applied to both sides of a negative electrode core made of a long copper foil with a thickness of 8 μm and a width of 64 mm, and the coating was dried and compressed to obtain a negative electrode (thickness: 190 μm) in which a negative electrode mixture layer was formed on both sides of the negative electrode core. First and second core exposed portions, in which the negative electrode mixture layer was not present, were provided within a predetermined length range from both ends of the negative electrode in the longitudinal direction, and a nickel negative electrode lead was ultrasonically welded to the first core exposed portion.

[0042] A swelling tape (Model SAS044 manufactured by AUZON) was used as the spacer. The swelling tape had a tape substrate that increased in thickness upon absorbing the non-aqueous electrolyte and an adhesive layer on one side of the tape substrate. The swelling tape had a thickness of 44 μm, a width of 1.5 mm, and a length of 64 mm. When immersed in the non-aqueous electrolyte, its thickness became 140 μm. The width and length of the swelling tape hardly changed even when immersed in the non-aqueous electrolyte. The swelling tape was attached to the first core exposed portion of the negative electrode at a distance L1 of 5 mm from the starting end of the positive electrode along the winding direction of the electrode assembly and at an angle θ1 of 140°. The swelling tape was attached across the entire width of the negative electrode core.

[0043] [Preparation of Electrode Assembly] The positive electrode, the negative electrode, and a polyethylene separator were spirally wound around a cylindrical winding core member, and a stop tape was attached to the outermost peripheral surface to obtain a wound electrode assembly. The negative electrode was positioned so that the first core exposed portion of the negative electrode, to which the negative electrode lead and spacer were attached, was located at the start of winding of the electrode assembly. Furthermore, the negative electrode extended from the starting end of the positive electrode at the start of winding of the electrode assembly, leaving a non-facing region that did not face the positive electrode for approximately 1.5 turns. The positive electrode and negative electrode were wound with the separator interposed between them so that the distance L1 was 5 mm and the angle θ1 was 140° (angle θ2 was 185°) relative to the starting end of the positive electrode of the spacer attached to the first core exposed portion. After forming the wound structure of the electrode assembly, the winding core member was removed to obtain a wound electrode assembly with a cavity formed in the winding core portion.

[0044] [Preparation of non-aqueous electrolyte] 5 parts by mass of vinylene carbonate (VC) was added to 100 parts by mass of a mixed solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 1:3 (25°C), and LiPF ６ was dissolved in a concentration of 1.5 mol / L to prepare a non-aqueous electrolyte solution.

[0045] [Cylindrical Battery Fabrication] After placing insulating plates above and below the electrode assembly, the negative electrode lead was welded to the inner bottom surface of a cylindrical outer can with a bottom, and the positive electrode lead was welded to the internal terminal plate of the sealing body, and the electrode assembly was housed in the outer can. A nonaqueous electrolyte was then injected into the outer can under reduced pressure, and the opening of the outer can was sealed with the sealing body via a gasket, thereby obtaining a cylindrical battery. The second core exposed portion of the negative electrode formed the outermost surface of the electrode assembly and was in contact with the inner surface of the outer can.

[0046] Example 2 An electrode assembly and a cylindrical battery were fabricated in the same manner as in Example 1, except that the spacers were arranged so that the distance L1 was 4 mm and the angle θ1 was 110°.

[0047] Example 3 An electrode assembly and a cylindrical battery were fabricated in the same manner as in Example 1, except that the spacers were arranged so that the distance L1 was 3 mm and the angle θ1 was 83°.

[0048] Example 4 An electrode assembly and a cylindrical battery were fabricated in the same manner as in Example 1, except that the spacers were arranged so that the distance L1 was 1.5 mm and the angle θ1 was 42°.

[0049] Comparative Example 1 An electrode assembly and a cylindrical battery were produced in the same manner as in Example 1, except that no spacer was attached to the negative electrode.

[0050] The batteries of the Examples and Comparative Examples were evaluated by the following method, and the evaluation results, along with the attachment positions of the spacers, are shown in Table 1. The gap lengths of the negative electrode facing portions shown in Table 1 are relative values ​​when the gap length of the negative electrode facing portion of the battery of Comparative Example 1 is set to 100.

[0051] [Evaluation of Negative Electrode Deformation (Buckling)] Each battery of the Examples and Comparative Examples was charged at a constant current of 0.5 C in a temperature environment of 45° C. until the battery voltage reached 4.2 V. Thereafter, the battery was discharged at a constant current of 0.7 C until the battery voltage reached 2.5 V. After 200 cycles of this charge / discharge, the battery was placed in a charged state, and the vicinity of the winding core of the electrode body was observed using an X-ray CT device (Shimadzu Corporation, SMX-225CT FPD HR).

[0052] As shown in FIG. 3 , deformation was determined to have occurred when deformation (buckling) of the negative electrode 12 was confirmed near the starting end of the positive electrode in the CT image of the electrode body, with the angle α being 150° or less. Evaluations were performed on three batteries for each of Examples 1 to 3 and Comparative Example 1. In the CT image of the electrode body, the distance between the negative electrode cores of the negative electrode facing portion was measured at a position 0.3 mm away from the starting end of the positive electrode along the winding direction of the electrode body. The thickness of the negative electrode mixture layer and the thickness of the separator were subtracted from the distance between the negative electrode cores to calculate the gap length of the negative electrode facing portion.

[0053]

[0054] As shown in Table 1, in the batteries of the example having spacers, an appropriate gap is ensured between the negative electrodes near the starting end of the positive electrode, suppressing deformation of the negative electrode during charging and discharging of the battery. In particular, by arranging the spacers so that the angle θ1 is 110°, deformation of the negative electrode can be more reliably suppressed. On the other hand, in the battery of Comparative Example 1, which does not have a spacer, deformation of the negative electrode was confirmed in all three batteries evaluated.

[0055] The present disclosure is further described by the following embodiments. Configuration 1: A cylindrical battery including an electrode assembly including a positive electrode, a negative electrode, and a separator, the positive electrode and the negative electrode being wound with the separator interposed therebetween, and a bottomed cylindrical outer can housing the electrode assembly, wherein the negative electrode extends toward the winding start side of the electrode assembly beyond a position facing a positive electrode starting end, which is the end of the positive electrode at the winding start side of the electrode assembly, and a negative electrode facing portion is formed where the inner and outer winding surfaces of the negative electrode face each other via the separator, the electrode assembly has a spacer disposed in the negative electrode facing portion, and at least a portion of the spacer is disposed from the positive electrode starting end toward the winding start side along the winding direction of the electrode assembly within a range of 140° or less with respect to the winding center of the electrode assembly. Configuration 2: The cylindrical battery according to Configuration 1, further including a nonaqueous electrolyte housed in the outer can, the spacer being made of a material that absorbs the nonaqueous electrolyte and increases in thickness. Configuration 3: The cylindrical battery according to Configurations 1 or 2, wherein at least a portion of the spacer is disposed from the positive electrode start end along the winding direction toward the winding start side within a range of 110° or less with respect to the winding center.Configuration 4: The cylindrical battery according to any one of Configurations 1 to 3, wherein the entire spacer is disposed from the positive electrode start end along the winding direction toward the winding start side within a range of not more than 360° with respect to the winding center.Configuration 5: The cylindrical battery according to any one of Configurations 1 to 4, wherein the spacer is bonded to the negative electrode.Configuration 6: The cylindrical battery according to any one of Configurations 1 to 5, wherein the thickness of the spacer is 60% or more and 120% or less of the thickness of the positive electrode.Configuration 7: The cylindrical battery according to any one of Configurations 1 to 6, wherein the electrode body has a negative electrode lead connected to the negative electrode closer to the winding start side than the spacer.

[0056] REFERENCE SIGNS LIST 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, 21 Negative electrode lead, 22 Grooved portion, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive electrode core, 31 Positive electrode mixture layer, 40 Negative electrode core, 41 Negative electrode mixture layer, 42, 43 Core exposed portion, 50 Spacer, Z Winding center

Claims

1. A cylindrical battery comprising an electrode assembly including a positive electrode, a negative electrode, and a separator, the positive electrode and the negative electrode being wound with the separator interposed therebetween, and a bottomed cylindrical outer can housing the electrode assembly, wherein the negative electrode extends toward the start of winding of the electrode assembly beyond a position facing the positive electrode starting end, which is the end of the positive electrode at the start of winding of the electrode assembly, and a negative electrode facing portion is formed where the inner and outer winding surfaces of the negative electrode face each other via the separator, the electrode assembly has a spacer arranged in the negative electrode facing portion, and at least a portion of the spacer is arranged from the positive electrode starting end toward the start of winding along the winding direction of the electrode assembly within a range of 140° or less with respect to the center of winding of the electrode assembly.

2. The cylindrical battery according to claim 1, further comprising a non-aqueous electrolyte contained in the outer can, wherein the spacer is made of a material that absorbs the non-aqueous electrolyte and increases in thickness.

3. A cylindrical battery according to claim 1, wherein at least a portion of the spacer is disposed within a range of 110° or less from the winding center toward the winding start side from the starting end of the positive electrode along the winding direction.

4. A cylindrical battery according to claim 1, wherein the entire spacer is disposed within a range not exceeding 360° from the starting end of the positive electrode to the winding start side along the winding direction with respect to the winding center.

5. The cylindrical battery according to claim 1, wherein the spacer is bonded to the negative electrode.

6. The cylindrical battery according to claim 1, wherein the thickness of the spacer is 60% to 120% of the thickness of the positive electrode.

7. A cylindrical battery according to any one of claims 1 to 6, wherein the electrode assembly has a negative electrode lead connected to the negative electrode closer to the winding start side than the spacer.

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