Cylindrical battery

Abstract

In a cylindrical battery as an example of an embodiment, a negative electrode (12) has: a non-facing portion (43) wound at a winding start side of an electrode body (14) by 0.75 cycles or more; a minimum section (X) in which the inter-core distance between the non-facing section (43) and a second region (45) facing the non-facing section (43) on the outside in the radial direction of the electrode body (14) is minimum in a range in which the angle (theta) from the positive electrode start end (11x) toward the winding start side with respect to the winding center (Z) of the electrode body (14) is 150 DEG or less; and a maximum portion (Y) in which the inter-core distance between the non-facing portion (43) and the second region (45) is maximum in a range in which the angle (theta) is 150 DEG or less. The minimum portion (X) is positioned closer to the positive electrode starting end (11x) side than the maximum portion (Y). The inter-core distance (D2) at the maximum portion (Y) is 1.4 times or more of the inter-core distance (D1) at the minimum portion (X).

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 a 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 given length or more 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. However, as a result of research by the present inventors, it has been found that when the volume change of the negative electrode during charge and discharge increases due to high capacity of the battery or the like, the non-opposing portion contacts a portion located outside the non-opposing portion of the negative electrode, and deformation of the electrode body is likely to occur in the portion where the positive electrode and the negative electrode oppose each other. On the other hand, when the space of this portion is increased so that the non-opposing portion does not contact the portion located outside it, lithium is likely to precipitate near the positive electrode start end.

[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. The negative electrode has: a non-opposing portion, on the winding start side of the electrode body, a composite layer is formed on at least one surface of the core, and it is wound for 0.75 turns or more without opposing the positive electrode; a minimum portion, in a range where the angle from the positive electrode start end to the winding start side with respect to the winding center of the electrode body is 150° or less, the distance between the non-opposing portion and the core of the second region is the smallest, and the second region opposes the non-opposing portion on the radially outer side of the electrode body; and a maximum portion, in a range where the angle from the positive electrode start end to the winding start side with respect to the winding center of the electrode body is 150° or less, the distance between the non-opposing portion and the core of the second region is the largest, the minimum portion is located closer to the positive electrode start end side than the maximum portion, and the core distance at the maximum portion is 1.4 times or more the core distance at the minimum portion.

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

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

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

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

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

[0013] Figure 1 is a cross-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 sealing body 17 side 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 for 0.75 turns or more without facing 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 in 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 0.75 turns or more, the shape of the core can be stabilized, and a sufficient cavity can be ensured as an exhaust path.

[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 a mixed solvent of two or more thereof are used. As an example of the non-aqueous solvent, ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and a mixed solvent thereof are listed. The non-aqueous solvent may also contain a halogen substituent 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 size 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 size 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 center of 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 of 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 (see Figure 2), the exposed portion 42 of the first core 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.

[0020] The positive electrode 11 has a positive electrode core 30 and a positive electrode composite agent layer 31 formed on at least one surface of the core. For the positive electrode core 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 a binder such as polyvinylidene fluoride (PVdF), and is preferably formed on both surfaces of the positive electrode core 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 30 by ultrasonic welding or the like.

[0021] The negative electrode 12 has a negative electrode core 40 and a negative electrode composite agent layer 41 formed on at least one surface of the core. For the negative electrode core 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 a binder such as styrene-butadiene rubber (SBR), and is preferably formed on both surfaces of the negative electrode core 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, Si-containing materials, etc. are used, for example. The negative electrode lead 21 is preferably directly joined to the negative electrode core 40 by ultrasonic welding or the like.

[0022] The cylindrical battery 10 includes an upper insulating plate 18 that 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 portion 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 that 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 passes through the opening of the upper insulating plate 18 and extends toward the sealing body 17 side, and the negative electrode lead 21 passes through the opening of the lower insulating plate 19 and extends toward the bottom side of the outer can 16. 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 formed by exposing the surface of the negative electrode core body 40 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 electrode 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 termination 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 stamping 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 an annular 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 wound 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 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 more than 0.75 turns in a state where it does not oppose the positive electrode 11. The non-opposing portion 43 has the negative electrode composite layer 41, but 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 higher 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 during abnormal conditions of the battery. In addition, the portion located on the winding end side of the electrode body 14 relative to 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 in between.

[0029] In this specification, the positive electrode start end 11x refers to one end in the longitudinal 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 longitudinal 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 near the winding center Z closer 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 circumferential surface of the negative electrode core 40 facing the winding center Z or the outer circumferential surface of the negative electrode core 40 facing the side wall of the outer can 16, and is preferably formed on both the inner circumferential surface and the outer circumferential surface. 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 from at least the position corresponding to the positive electrode start end 11x to the maximum portion Y 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. The non-opposing portion 43 is preferably formed with a length of more than 0.75 turns and less than 1.5 turns, more preferably with a length of more than 0.90 turns and less than 1.4 turns, and particularly preferably with a length of more than 1.0 turn and less than 1.3 turns. In this case, it is easy to ensure a good exhaust path in the wound core portion.

[0031] As described above, the negative electrode 12 has a core exposed portion 42 from the negative electrode start end 12x to 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 only composed of the negative electrode core 40. In this 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 in the opposing portion of the positive and negative electrodes during charge and discharge. However, according to this embodiment, such deformation can be effectively suppressed.

[0032] The length of the exposed portion 42 of the core 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 exposed portion 42 of the core may also 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 thin metal 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 exposed portion 42 of the core, for example, at a position away from the negative electrode starting end 12x and the non-opposing portion 43.

[0033] As Figure 2 shown, the negative electrode 12 has a minimum portion X and a maximum portion Y within a range where the angle θ from the positive electrode starting end 11x with respect to the winding center Z of the electrode body 14 is 150° or less. The minimum portion X is the portion where the core-to-core distance between the non-opposing portion 43 and the second region 45 opposed to the non-opposing portion 43 on the radially outer side of the electrode body 14 is the smallest. The maximum portion Y is the portion where the core-to-core distance between the non-opposing portion 43 and the second region 45 is the largest. The minimum portion X is located closer to the positive electrode starting end 11x side than the maximum portion Y. There is no positive electrode 11 between the non-opposing portion 43 and the second region 45.

[0034] Figure 2 The angle θ shown is the angle that advances from the position overlapping the positive electrode starting end 11x in the radial direction of the electrode body 14 toward the winding start side of the electrode body 14. In addition, the angle θ1 is the angle from the positive electrode starting end 11x (starting point) to the minimum portion X, and the angle θ2 is the angle from the positive electrode starting end 11x to the maximum portion Y.

[0035] At the opposing portion of the positive electrode 11 and the negative electrode 12 of the electrode body 14, the distance between the positive and negative electrodes is substantially constant, but the distance between the non-opposing portion 43 and the second region 45 is not uniform. That is, at the opposing portion of the positive and negative electrodes, the core-to-core distance is substantially constant, and at the portion where the non-opposing portion 43 is opposed to the second region 45, the core-to-core distance changes.

[0036] The distance (core-to-core distance) between the non-opposing portion 43 and the second region 45 preferably gradually decreases from the position corresponding to the positive electrode starting end 11x toward the minimum portion X. The non-opposing portion 43 is gently curved so that it gets closer to the second region 45 as it gets closer to the minimum portion X from the position corresponding to the positive electrode starting end 11x. In addition, the distance between the non-opposing portion 43 and the second region 45 preferably gradually increases from the minimum portion X toward the maximum portion Y. Within the range where the angle θ is 150° or less, the distance between the non-opposing portion 43 and the second region 45 temporarily decreases toward the winding start side of the electrode body 14 and then increases again. The non-opposing portion 43, for example, has a larger curvature at the portion opposed to the minimum portion X than at other portions.

[0037] In this case, it is possible to suppress the precipitation of lithium due to the stabilization of the interval between the positive and negative electrodes near the positive electrode starting end 11x, and it is possible to suppress the deformation of the electrode plate caused by the strong contact between the non-opposing portion 43 and the second region 45. Merely making the interval between the non-opposing portion 43 and the second region 45 uneven does not achieve such an effect. However, by sequentially forming the minimum portion X and the maximum portion Y from the positive electrode starting end 11x side within the range where the angle θ is 150° or less, it is possible to achieve both the suppression of lithium precipitation and the suppression of electrode plate deformation.

[0038] The minimum portion X only needs to be formed such that the angle θ1 is 150° or less. The angle θ1 is preferably 90° or less, more preferably 80° or less. In addition, the minimum portion X is preferably formed at a position far from the positive electrode starting end 11x. Specifically, the angle θ1 is preferably 30° or more, more preferably 40° or more. An example of a suitable range of the angle θ1 is 40° or more and 80° or less, or 50° or more and 70° or less. If the angle θ1 is within this range, the above effects are more significant.

[0039] The maximum portion Y only needs to be formed such that the angle θ2 is 150° or less. The angle θ2 is preferably 95° or more, more preferably 100° or more. Further, the angle θ2 is preferably 145° or less, more preferably 140° or less. An example of a suitable range of the angle θ2 is 100° or more and 140° or less, or 110° or more and 130° or less. If the angle θ2 is within this range, the above effects are more significant.

[0040] The distance D2 between the cores at the maximum portion Y is preferably 1.4 times or more the distance D1 between the cores at the minimum portion X. In this case, the above effects are more significant. Depending on other conditions such as the angles θ1 and θ2, it may vary somewhat, but the distance D2 between the cores is more preferably 1.5 times or more the distance D1 between the cores, and particularly preferably 1.6 times or more. The upper limit of the ratio D2 / D1 is not particularly limited, but from the viewpoints of ensuring the exhaust path, productivity, etc., the distance D2 between the cores is preferably 2.2 times or less the distance D1 between the cores, more preferably 2.1 times or less. An example of a suitable range of D2 / D1 is 1.4 or more and 2.2 or less.

[0041] The distance D1 between the cores at the minimum portion X is preferably 190 μm or less, more preferably 180 μm or less, and particularly preferably 170 μm or less. In this case, it is easy to suppress the precipitation of lithium. On the other hand, at the minimum portion X, the non-opposing portion 43 preferably does not contact the second region 45, and the distance D1 between the cores is preferably more than twice the thickness of the negative electrode composite agent layer 41. An example of a suitable range of the distance D1 between the cores is 120 μm or more and 180 μm or less, or 130 μm or more and 170 μm or less.

[0042] The inter-core distance D2 at the majority part Y is preferably 210 μm or more, more preferably 220 μm or more, and particularly preferably 230 μm or more. In this case, deformation of the electrode body 14 is easily suppressed. On the other hand, from the viewpoints of ensuring the exhaust path, productivity, etc., the inter-core distance D2 is preferably 330 μm or less. An example of a suitable range of the inter-core distance D2 is 220 μm or more and 330 μm or less, or 230 μm or more and 320 μm or less.

[0043] The electrode body 14 is manufactured by winding a plate electrode using a core winding member. However, by changing the tension (acceleration) during winding of the plate electrode, the minimum part X and the maximum part Y can be formed, and the inter-core distance can be adjusted. Specifically, compared with the acceleration when winding a part with a constant inter-core distance, the acceleration is decreased at the position corresponding to the maximum part Y, and the acceleration is increased at the position corresponding to the minimum part X. The inter-core distances D1 and D2 can be adjusted according to this acceleration. For example, the greater the acceleration, the smaller the inter-core distance.

[0044] The minimum part X and the maximum part Y 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).

[0045] Examples

[0046] Hereinafter, the present disclosure will be further described by experimental examples, but the present disclosure is not limited to these experimental examples.

[0047] <Experimental Example 1>

[0048] [Manufacture of Positive Electrode]

[0049] 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-shaped aluminum foil with a thickness of 15 μm, and the coating film is dried and compressed to obtain a positive electrode having a positive electrode composite agent layer (single-sided thickness: 90 μm, density: 3.6 g / cm 3 ) formed on both sides of the positive electrode core. In addition, at the central part in the length direction of the positive electrode, a core exposed part where the positive electrode composite agent layer is not present is provided, and an aluminum positive electrode lead is ultrasonically welded to the exposed part.

[0050] [Manufacture of Negative Electrode]

[0051] As the negative electrode active material, a material obtained by mixing graphite powder and a Si-containing material in 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 in a solid component mass ratio of 98:1:1, and water is used as the dispersion medium to prepare a negative electrode composite agent slurry. The slurry is coated on both sides of a negative electrode core body composed of a strip-shaped copper foil with a thickness of 8 μm, and the coating film is dried and compressed to obtain a negative electrode having a negative electrode composite agent layer formed on both sides of the negative electrode core body (thickness on one side: 95 μm, density: 1.6 g / cm 3 ). In addition, within a given length range 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 agent layer does not exist are provided, and a negative electrode lead made of nickel is ultrasonically welded to the first core body exposed portion.

[0052] [Fabrication of Electrode Body]

[0053] Using a cylindrical winding core member, the above-mentioned positive electrode, the above-mentioned negative electrode, and a polyethylene separator are wound into a vortex shape, and winding fixing tapes are pasted on 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, so that a non-opposing portion that does not oppose the positive electrode is provided. 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.

[0054] In Experimental Example 1, by changing the tension (acceleration) during plate winding, a minimum portion X with a minimum core body distance D1 (210 μm) was formed such that the angle θ1 was 60°, and a maximum portion Y with a maximum core body distance D2 (300 μm) was formed such that the angle θ2 was 120°.

[0055] [Preparation of Non-Aqueous Electrolyte]

[0056] In 100 parts by mass of a mixed solvent obtained by mixing ethylene carbonate (EC) and dimethyl carbonate (DMC) in 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.

[0057] [Fabrication of Cylindrical Battery]

[0058] After disposing the insulating plates above and below the above electrode body, the negative electrode lead is welded to the inner surface of the bottom of the 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. Thereafter, a 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. Further, the exposed portion of the second core body of the negative electrode forms the outermost circumferential surface of the electrode body and contacts the inner circumferential surface of the outer can.

[0059] <Experimental Examples 2 to 9>

[0060] Change the tension during winding of the electrode plates so that the positions (angles θ1, θ2) of the minimum portion X and the maximum portion Y and the core-to-core distances D1, D2 are the values shown in Table 1. Except for this, a cylindrical battery is produced in the same manner as in Experimental Example 1.

[0061] <Experimental Example 10>

[0062] Wind the electrode plates so that the core-to-core distance is constant and the minimum portion X and the maximum portion Y are not formed. Except for this, a cylindrical battery is produced in the same manner as in Experimental Example 1.

[0063] <Experimental Example 11>

[0064] Change the tension during winding of the electrode plates so that Figure 2 the indicated angle θ ranges from 0° to 150°, and the core-to-core distance gradually decreases. Except for this, a cylindrical battery is produced in the same manner as in Experimental Example 1. In the electrode body of Experimental Example 11, the distance between the non-opposing portion and the core body in the second region at the position where the angle θ is 60° is 210 μm, and the core-to-core distance at the position where the angle θ is 150° is 150 μm.

[0065] [Evaluation of Deformation (Bending) of Electrode Plates]

[0066] In a temperature environment of 45°C, each battery of the experimental examples is charged with a constant current of 0.5C until the battery voltage reaches 4.2V. Thereafter, it is discharged with a constant current of 0.7C until the battery voltage reaches 2.5V. After performing 200 cycles of this charge and discharge, the battery is set to the charged state, and the vicinity of the wound core of the electrode body is observed using an X-ray CT apparatus (manufactured by Shimadzu Corporation, SMX-225CT FPD HR).

[0067] As Figure 3 shown, in the portion where the positive electrode and the negative electrode are opposed, when deformation (bending) of the electrode plates (at least one of the positive electrode 11 and the negative electrode 12) with an angle θ of 150° or less is confirmed, it is determined that there is bending, and thus the presence or absence of bending is evaluated. The number of batteries evaluated is 100.

[0068] Evaluation of Li precipitation

[0069] Disassemble each battery after the above cyclic test to confirm whether there is a white precipitate (metallic lithium) near the starting end of the positive electrode.

[0070] [Table 1]

[0071]

[0072] As shown in Table 1, in the batteries of Experimental Examples 1 to 9, compared with the battery of Experimental Example 10, it is difficult to produce Li precipitation. In addition, in the batteries of Experimental Examples 1 to 9, compared with the battery of Experimental Example 11, it is difficult to produce bending of the electrode body. That is, according to the cylindrical batteries of Experimental Examples 1 to 9, Li precipitation can be suppressed, and at the same time, deformation of the electrode body at the facing portion of the positive electrode and the negative electrode can be effectively suppressed. When the distance between the core bodies near the wound core is constant (Experimental Example 10), Li precipitation is likely to occur near the starting end of the positive electrode. In addition, when the distance between the core bodies gradually decreases in the direction from the position corresponding to the starting end of the positive electrode toward the winding center (Experimental Example 11), compared with the battery of Experimental Example 10, Li precipitation is suppressed, but on the other hand, bending of the electrode plate is likely to occur.

[0073] The present disclosure will be further described by the following embodiments.

[0074] Structure 1: A cylindrical battery includes an electrode body, the 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 interposed therebetween. The negative electrode has: a non-facing portion, on the winding start side of the electrode body, the composite agent layer is formed on at least one surface of the core body and is wound for more than 0.75 turns in a state of not facing the positive electrode; a minimum portion, in a range where the angle from the starting end of the positive electrode to the winding start side with respect to the winding center of the electrode body is 150° or less, the distance between the non-facing portion and the core body in the second region is the smallest, and the second region faces the non-facing portion on the radially outer side of the electrode body; and a maximum portion, in a range where the angle from the starting end of the positive electrode to the winding start side with respect to the winding center of the electrode body is 150° or less, the distance between the non-facing portion and the core body in the second region is the largest, the minimum portion is located closer to the starting end side of the positive electrode than the maximum portion, and the distance between the core bodies at the maximum portion is 1.4 times or more the distance between the core bodies at the minimum portion.

[0075] Structure 2: In the cylindrical battery according to Structure 1, the minimum portion is formed in a range where the angle from the starting end of the positive electrode to the winding start side with respect to the winding center of the electrode body is 40° or more and 80° or less.

[0076] Structure 3: In the cylindrical battery according to Structure 1 or 2, the maximum portion is formed in a range where the angle from the positive electrode starting end to the winding starting side with respect to the winding center of the electrode body is 100° or more and 140° or less.

[0077] Structure 4: In the cylindrical battery according to any one of Structures 1 to 3, the distance between the cores at the minimum portion is 170 μm or less, and the distance between the cores at the maximum portion is 230 μm or more.

[0078] Structure 5: In the cylindrical battery according to any one of Structures 1 to 4, the distance between the cores at the maximum portion is 2.2 times or less the distance between the cores at the minimum portion.

[0079] Structure 6: In the cylindrical battery according to any one of Structures 1 to 5, the electrode body has a negative electrode lead wire, and the negative electrode lead wire is joined to the core exposed portion, which is the portion from the negative electrode starting end to the non-opposing portion and where the composite agent layer is absent.

[0080] -Symbol Explanation-

[0081] 10: Cylindrical battery; 11: Positive electrode; 11x: Positive electrode starting end; 12: Negative electrode; 12x: Negative electrode starting 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: Lid; 28: Gasket; 30: Positive electrode core; 31: Positive electrode composite agent layer; 40: Negative electrode core; 41: Negative electrode composite agent layer; 42, 44: Core exposed portion; 43: Non-opposing portion; 45: Second region; X: Minimum portion; Y: Maximum portion.

Claims

1. A cylindrical battery comprising an electrode body, wherein the electrode body comprises a positive electrode, a negative electrode including a core body and a composite material layer, and a separator, wherein the positive electrode and the negative electrode are wound with the separator interposed therebetween. The negative electrode has: The non-opposing portion is formed with the composite agent layer on at least one surface of the core body at the winding start side of the electrode body, and is wound for more than 0.75 turns in a state of not facing the positive electrode; A minimum portion, wherein the distance between the non-opposing portion and the core body of the second region is minimum within a range of an angle of 150° or less from the positive electrode starting end to the winding starting side relative to the winding center of the electrode body, and the second region is opposed to the non-opposing portion on the radially outer side of the electrode body; and The maximum portion has a maximum distance between the core body of the non-opposing portion and the second region within a range of an angle of 150° or less from the positive electrode starting end to the winding starting side relative to the winding center of the electrode body, The minimum portion is located closer to the positive electrode starting end than the maximum portion. The distance between the cores at the maximum portion is at least 1.4 times the distance between the cores at the minimum portion.

2. The cylindrical battery according to claim 1, wherein: The minimum portion is formed in a range where an angle from the positive electrode start end to the winding start side relative to the winding center of the electrode body is 40° or more and 80° or less.

3. The cylindrical battery according to claim 1, wherein: The large portion is formed in a range where an angle from the positive electrode start end to the winding start side relative to the winding center of the electrode body is 100° or more and 140° or less.

4. The cylindrical battery according to claim 1, wherein: The distance between the cores at the extremely small part is less than 170 μm. The distance between the cores at the maximum portion is greater than 230 μm.

5. The cylindrical battery according to claim 1, wherein The distance between the cores at the maximum portion is less than or equal to 2.2 times the distance between the cores at the minimum portion.

6. The cylindrical battery according to any one of claims 1 to 5, wherein The electrode body has a negative electrode lead, The negative electrode lead is joined to a core exposed portion, which is a portion from a negative electrode start end to the non-opposing portion and where the composite agent layer does not exist.

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