Cylindrical battery

Abstract

In this cylindrical battery according to an example of an embodiment, an electrode body (14) has a wound structure in which a positive electrode (11) and a negative electrode (12) are wound in a spiral shape with a separator (13) interposed therebetween, and includes a positive electrode lead (20) connected to the positive electrode (11). A negative electrode core (40) constituting the negative electrode (12) has an extension part (45) that extends further toward the winding end side of the electrode body (14) than a position facing the outside of a positive electrode terminating end (11x). The inner surface of the extension part (45) is provided with a second negative electrode mixture layer (46) at least at a position overlapping the positive electrode lead (20) in the radial direction of the electrode body (14).

Description

Cylindrical battery

[0001] The present disclosure relates to a cylindrical battery, and more particularly to a cylindrical battery provided with a wound electrode assembly.

[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 (see, for example, Patent Document 1). As disclosed in Patent Document 1, electrode plates (the positive electrode and the negative electrode) constituting the wound electrode assembly include a core body and a mixture layer formed on the core body. A lead is generally connected to the core body of the electrode plate. The positive electrode lead connected to the positive electrode is connected radially inward of the outermost peripheral surface of the electrode assembly.

[0003] Japanese Unexamined Patent Publication No. 2001-185201

[0004] As a result of studies by the present inventors, it has been found that deformation is likely to occur in a portion of the electrode plate constituting the wound electrode assembly that is located radially outward of the positive electrode lead in the electrode assembly and radially overlaps the positive electrode lead. Since deformation of the electrode plate may lead to non-uniform battery reaction, occurrence of local short circuit, and the like, suppressing deformation of the electrode plate is an important issue.

[0005] A cylindrical battery according to the present disclosure is a cylindrical battery including: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; and a bottomed cylindrical outer can that accommodates the electrode assembly, wherein the electrode assembly has a positive electrode lead connected to the positive electrode, the positive electrode includes a positive electrode core body and a positive electrode mixture layer formed on the positive electrode core body, the negative electrode includes a negative electrode core body and a negative electrode mixture layer formed on the negative electrode core body, the negative electrode core body has an extending portion extending toward a winding end side of the electrode assembly beyond a position facing a radially outer side of the electrode assembly at a terminal end of the positive electrode mixture layer, which is an end of the positive electrode mixture layer on the winding end side of the electrode assembly, and a second negative electrode mixture layer is provided on an inner surface of the extending portion facing radially inward of the electrode assembly, at least at a position overlapping the positive electrode lead in a radial direction of the electrode assembly.

[0006] According to the cylindrical battery of the present disclosure, deformation of the electrode plate can be effectively suppressed in a wound electrode assembly including a positive electrode lead.

[0007] This is an axial cross-sectional view of a cylindrical battery, which is an example of an embodiment. This is a radial cross-sectional view of an electrode body, which is an example of an embodiment. This is a diagram showing a part of the radial cross-section of an electrode body, which is an example of an embodiment. This is a diagram showing a modified example of an electrode body.

[0008] Hereinafter, an example of an embodiment of the cylindrical battery according to this disclosure will be described in detail with reference to the drawings. Note that the cylindrical battery according to this disclosure is not limited to the embodiments described below. Furthermore, forms obtained by selectively combining the various components of the multiple embodiments and modifications described below are also included in this disclosure.

[0009] Figure 1 is a schematic diagram showing an axial cross-section including the central axis of a cylindrical battery 10, which is an example of an embodiment. As shown in Figure 1, the cylindrical battery 10 includes a positive electrode 11, a negative electrode 12, and a separator 13, and comprises an electrode body 14 in which the positive electrode 11 and the negative electrode 12 are wound around the separator 13, and a bottomed cylindrical outer casing 16 that houses the electrode body 14. The cylindrical battery 10 also includes an electrolyte housed in the outer casing 16 and a sealing body 17 that closes the opening of the outer casing 16. The outer casing 16 has grooves 22 formed in its side wall, and the sealing body 17 is supported by the grooves 22 and closes the opening of the outer casing 16. In the following description, for convenience, the side of the cylindrical battery 10 with the sealing body 17 will be considered the top, and the bottom side of the outer casing 16 will be considered 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 (electrolyte solution) or a solid electrolyte. The cylindrical battery 10 is, for example, a non-aqueous electrolyte secondary battery, and among these, a lithium-ion battery is preferred.

[0011] A liquid electrolyte (electrolyte solution) comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. The non-aqueous solvent may also contain halogen-substituted solvents (e.g., fluoroethylene carbonate) in which at least some of the hydrogen atoms of the solvent are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include LiPF4. ６ Lithium salts such as these are used.

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

[0013] As described above, the electrode body 14 has a wound structure in which a positive electrode 11 and a negative electrode 12 are wound in a spiral shape via a separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all elongated strip-shaped bodies that are alternately stacked in the radial direction of the electrode body 14 by being wound in a spiral shape. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in both the length and width directions 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 are arranged so as to sandwich the positive electrode 11.

[0014] The positive electrode 11 comprises a long positive electrode core 30 and a positive electrode mixture layer 31 formed on the positive electrode core 30. The positive electrode core 30 can be made of a metal foil that is stable within the potential range of the positive electrode 11, such as aluminum, aluminum alloy, stainless steel, or titanium, or a film with the metal arranged on its surface. 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, and is preferably formed on both sides of the positive electrode core 30, except for the core exposed portion described later. For example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, etc., can be used as the positive electrode active material.

[0015] The thickness of the positive electrode 11 is, for example, 150 μm to 230 μm. In this embodiment, the thickness of the positive electrode 11 is substantially constant except for the core body exposed portion. The thickness of the positive electrode core body 30 is, for example, 10 μm to 30 μm. The thickness of the positive electrode mixture layer 31 is, for example, 70 μm to 100 μm on one side of the positive electrode core body 30. The positive electrode 11 can be manufactured by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core body 30, drying the coating film, and then compressing it to form the positive electrode mixture layer 31 on both sides of the positive electrode core body 30.

[0016] The negative electrode 12 comprises a long negative electrode core 40 and a negative electrode mixture layer 41 formed on the negative electrode core 40. The negative electrode core 40 can be made of a metal foil that is stable within the potential range of the negative electrode 12, such as copper, copper alloy, stainless steel, nickel, or nickel alloy, or a film with the metal arranged on its surface. 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, except for the core exposed portion described later. For the negative electrode active material, for example, graphite or silicon-containing material can be used.

[0017] The thickness of the negative electrode 12 is, for example, 145 μm to 235 μm. In this embodiment, the thickness of the negative electrode 12 is substantially constant except for the exposed core portion. The thickness of the negative electrode core 40 is, for example, 5 μm to 15 μm. The thickness of the negative electrode mixture layer 41 is, for example, 70 μm to 110 μm on one side of the negative electrode core 40. The negative electrode 12 can be manufactured in the same way as 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 film, and then compressing it to form the negative electrode mixture layer 41 on both sides of the negative electrode core 40.

[0018] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator 13 include polyethylene, polyolefins such as polypropylene, and cellulose. The separator 13 may have a single-layer structure or a multi-layer structure. Furthermore, a highly heat-resistant resin layer, such as aramid resin, may be formed on the surface of the separator 13.

[0019] The electrode body 14 has a positive electrode lead 20 connected to a positive electrode 11 and a negative electrode lead 21 connected to a negative electrode 12. In this embodiment, the positive electrode mixture layer 31 is absent in the longitudinal center of the positive electrode 11, and a core exposure portion is formed where the surface of the positive electrode core body 30 is exposed. The positive electrode lead 20 is connected to this exposed portion. On the other hand, the negative electrode lead 21 is provided at one longitudinal end of the negative electrode 12, which is located on the winding start side of the electrode body 14. At one longitudinal end of the negative electrode 12, the negative electrode mixture layer 41 is absent, and a first core exposure portion 47A (see Figure 2, described later) is formed where the surface of the negative electrode core body 40 is exposed. The negative electrode lead 21 is connected to this core exposure portion.

[0020] Insulating plates 18 and 19 are positioned above and below the electrode body 14, respectively. In the example shown in Figure 1, the positive electrode lead 20 extends through a through-hole in the insulating plate 18 towards the sealing body 17, and the negative electrode lead 21 extends through a through-hole in the insulating plate 19 towards the bottom of the outer can 16. The positive electrode lead 20 is connected to the lower surface of the internal terminal plate 23 of the sealing body 17 by welding or the like, and the cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, becomes the positive electrode terminal. The negative electrode lead 21 is connected to the inner bottom surface of the outer can 16 by welding or the like, and the outer can 16 becomes the negative electrode terminal.

[0021] The outermost surface of the electrode body 14 is provided with a negative electrode 12 and a second core exposure portion 47B where the surface of the negative electrode core 40 is exposed. The core exposure portion 47B is in contact with the inner surface of the outer casing 16. By the core exposure portion 47B contacting the inner surface of the outer casing 16, both ends of the negative electrode 12 in the longitudinal direction are electrically connected to the outer casing 16, ensuring good current collection on the negative electrode side. In addition, a winding stopper tape may be attached to the outermost surface of the electrode body 14 to maintain the winding structure.

[0022] The outer casing 16 is a bottomed cylindrical metal container. A gasket 28 is provided between the outer casing 16 and the sealing body 17 to seal the inside of the battery. The outer casing 16 has a grooved portion 22 that supports the sealing body 17, which is formed, for example, by pressing the side wall of the outer casing 16 from the outside. The grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the outer casing 16, and its upper surface supports the sealing body 17. The upper end of the outer casing 16 is bent inward and crimped to the periphery of the sealing body 17.

[0023] The sealing body 17 has a structure in which an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked in order from the electrode body 14 side. Each component constituting the sealing body 17 has, for example, a disc shape or a ring shape, and each component except the insulating member 25 is electrically connected to one another. The lower valve body 24 and the upper valve body 26 are connected at their respective centers, with the insulating member 25 interposed between their respective peripheries. When the internal pressure of the battery rises due to abnormal heat generation, the lower valve body 24 deforms and ruptures, pushing the upper valve body 26 towards the cap 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further, the upper valve body 26 ruptures, and gas is discharged from the opening of the cap 27.

[0024] The structure of the electrode body 14 will be described in detail below with reference to Figures 2 and 3.

[0025] Figure 2 shows a radial cross-section of the electrode body 14 cut in a direction perpendicular to the central axis. Note that in Figure 2, the separator 13 is omitted from the illustration for clarity. As shown in Figure 2, the electrode body 14 has a winding structure in which the negative electrode 12 extends toward the end of the winding of the electrode body 14 beyond the positive electrode end 11x, which is the end of the positive electrode 11 at the end of the winding of the electrode body 14. As described above, the negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition, and the negative electrode mixture layer 41 is always positioned in the area facing the positive electrode mixture layer 31 via the separator 13. That is, the end of the negative electrode mixture layer 41 is located toward the end of the winding of the electrode body 14 than the end of the positive electrode mixture layer 31.

[0026] The electrode body 14 has a hollow portion 14z extending axially towards the winding start side. The electrode body 14 is manufactured, for example, by winding a positive electrode 11 and a negative electrode 12 in a spiral shape with a separator 13 in between using a cylindrical winding core. After winding, the winding core is removed, forming a hollow portion 14z in the electrode body 14. It is also possible to leave the winding core in place. In either case, a hollow portion 14z is formed in the center of the electrode body 14. Furthermore, a first core body exposure portion 47A is formed at the winding start end of the negative electrode 12 that faces or is located near the hollow portion 14z, and the negative electrode lead 21 is connected to the core body exposure portion 47A.

[0027] The hollow portion 14z contains the winding center Z of the electrode body 14. The winding center Z refers to the position through which the central axis of the electrode body 14 passes in the radial cross-section of the electrode body 14. The central axis is the rotational axis when manufacturing the winding structure of the electrode body 14. In the radial cross-section of the electrode body 14, the center of the circumscribed circle of the electrode body 14 is approximately the winding center Z. In this specification, the center of the circumscribed circle is defined as the winding center Z.

[0028] The positive electrode lead 20 is positioned in the radially intermediate part of the electrode body 14. As described above, the positive electrode lead 20 is connected to a core exposed portion formed in the longitudinal center of the positive electrode 11. The core exposed portion is formed on both sides in the thickness direction of the positive electrode 11, and the positive electrode lead 20 is connected to one of the core exposed portions. Protective tape covering the positive electrode lead 20 and the core exposed portion may be attached to the positive electrode 11. The thickness of the positive electrode lead 20 is greater than, for example, the thickness of the positive electrode mixture layer 31. In the portion of the electrode body 14 where the positive electrode lead 20 is positioned, the thickness of the electrode plate changes, forming a step. As a result, deformation of the electrode plate is more likely to occur in the portion of the electrode body 14 located radially outside the positive electrode lead 20.

[0029] The positive electrode lead 20 is positioned closer to the outermost surface than the winding center Z in the radial direction of the electrode body 14. For example, the positive electrode lead 20 is positioned in a range of 55% to 80% or 60% to 75% of the radius of the electrode body 14 from the winding center Z. In this case, since the positive electrode lead 20 is connected to the longitudinal center of the positive electrode 11 or its vicinity, it is easier to ensure good current collection on the positive electrode side. However, compared to the case where the positive electrode lead 20 is connected to both longitudinal ends of the positive electrode 11, deformation of the electrode plate due to the positive electrode lead 20 is more likely to occur.

[0030] It is preferable that the positive electrode lead 20 is not positioned on a straight line L1 from point C on the outermost surface of the electrode body 14, which overlaps radially with the positive electrode end 11x, to the winding center Z, in a radial cross-sectional view of the electrode body 14. By positioning the positive electrode lead 20 while avoiding the straight line L, deformation of the electrode plate can be suppressed more effectively. Furthermore, in a radial cross-sectional view of the electrode body 14, if we define a straight line L4 extending from the winding center Z through the center of the width direction of the positive electrode lead 20 to the outermost surface of the electrode body 14, and the intersection of the straight line L4 and the outermost surface as point D, then the central angle θ of the inferior arc CD is, for example, 90° ± 30°. In this case, deformation of the electrode plate can be suppressed more effectively.

[0031] In this embodiment, when straight lines L2 and L3 are defined as extending from the winding center Z of the electrode body 14 through both ends of the positive electrode lead 20 in the width direction to the outermost surface of the electrode body 14, and the intersection points of straight lines L2 and L3 with the outermost surface are defined as points A and B in order of furthest from point C, the negative electrode end 12x, which is the end of the negative electrode 12 at the winding end of the electrode body 14, is located on the superior arc AC along the outermost surface of the electrode body 14. Furthermore, as will be described in more detail later, a second negative electrode mixture layer 46, which functions as a buffer layer, is provided inside the inferior arc AB.

[0032] Figure 3 is a magnified view of a portion of the radial cross-section of the electrode body 14 (the end of the winding of the electrode body 14).

[0033] As shown in Figure 3, the negative electrode 12 and separator 13 extend beyond the positive electrode end 11x toward the winding end of the electrode body 14. That is, the negative electrode 12 and separator 13 extend toward the winding end beyond the position where the positive electrode end 11x faces the radially outer side of the electrode body 14. Since the negative electrode mixture layer 41 is always positioned in the area facing the positive electrode mixture layer 31, the negative electrode mixture layer 41 is positioned to sandwich the positive electrode end 11x from both radial sides of the electrode body 14.

[0034] As described above, the positive electrode end 11x is the end of the positive electrode 11 at the winding end of the electrode body 14. In this embodiment, the positive electrode mixture layer end, which is the end of the positive electrode mixture layer 31 at the winding end of the electrode body 14, and the positive electrode end 11x, which is the end of the positive electrode 11, coincide. That is, there is no exposed portion of the positive electrode core 30 at the winding end of the electrode body 14, and the positive electrode end 11x can be rephrased as the positive electrode mixture layer end. In the following, for the sake of convenience, the radially outer side of the electrode body 14 may be simply referred to as the "outside," and the radially inner side of the electrode body 14 may be simply referred to as the "inside."

[0035] The negative electrode core 40 has an extension portion 45 that extends from the position facing the outside of the positive electrode end 11x via the separator 13 toward the winding end of the electrode body 14. The extension portion 45 extends from the position facing the outside of the positive electrode end 11x to a position where it overlaps radially with the positive electrode lead 20 and the electrode body 14. A second negative electrode mixture layer 46 is provided on the inner surface of the extension portion 45 facing radially inward with the electrode body 14, at least at a position where it overlaps radially with the positive electrode lead 20 and the electrode body 14. The second negative electrode mixture layer 46 does not contribute to the charging and discharging of the battery, but functions as a buffer layer and effectively suppresses deformation of the electrode plate.

[0036] The negative electrode 12 includes, in order from the winding start side of the electrode body 14 toward the negative electrode end 12x, a double-sided compound layer forming portion 44, a first single-sided compound layer forming portion 43A, a first double-sided exposed portion 42A, a second single-sided compound layer forming portion 43B, and a second double-sided exposed portion 42B. The double-sided compound layer forming portion 44 is the portion on which the negative electrode compound layer 41 is formed on both sides of the negative electrode core body 40. The single-sided compound layer forming portions 43A and 43B are portions on which the outer surface of the negative electrode core body 40 facing radially outward from the electrode body 14 is exposed, and on which the negative electrode compound layers 41 and 46 are formed on the inner surface of the negative electrode core body 40 facing radially inward from the electrode body 14, respectively.

[0037] The double-sided exposed portions 42A and 42B are parts of the negative electrode core body 40 where the negative electrode mixture layer 41 is not present on either side, and which are composed of the negative electrode core body 40. The double-sided exposed portions 42A and 42B constitute the second core body exposed portion 47B at the winding end of the negative electrode 12 and are located on the outermost surface of the electrode body 14. The core body exposed portion 47B forms, for example, 0.5 turns or more of the outermost surface of the electrode body 14. If the surface of the negative electrode core body 40 is in contact with the inner surface of the outer casing can 16 for a length of 0.5 turns or more on the outermost surface of the electrode body 14, good current collection performance on the negative electrode side can be ensured. The single-sided mixture layer forming portion 43B is also located on the outermost surface of the electrode body 14 and constitutes a part of the core body exposed portion 47B.

[0038] The single-sided compound layer forming portion 43A is formed in a region where the positive electrode 11 is not present on the radially inner side of the electrode body 14, via the separator 13, and where the positive electrode 11 is not present on the radially outer side of the electrode body 14. In this embodiment, the single-sided compound layer forming portion 43A is positioned inside the positive electrode end 11x, slightly towards the end of the winding from the position where it faces the positive electrode end 11x via the separator 13, and has a length of approximately one full turn. The end of the single-sided compound layer forming portion 43A at the end of the winding is located outside the positive electrode end 11x, slightly towards the end of the winding from the position where it faces the outside of the positive electrode end 11x via the separator 13.

[0039] The double-sided composite layer forming section 44 is formed on both radial sides of the electrode body 14 via the separator 13, in a range facing the positive electrode 11. Specifically, the double-sided composite layer forming section 44 is positioned at least from a position facing the positive electrode composite layer start end, which is the end of the positive electrode composite layer 31 on the winding start side of the electrode body 14, via the separator 13, to a position radially inward of the electrode body 14 beyond the positive electrode end 11x, and facing the positive electrode end 11x via the separator 13. The positive electrode end 11x is sandwiched from both radial sides of the electrode body 14 via the separator 13 by the single-sided composite layer forming section 43A and the double-sided composite layer forming section 44.

[0040] The separator 13 includes a first separator 13A and a second separator 13B. The two separators 13 are wound with the positive electrode 11 interposed therebetween. The first separator 13A is disposed at a position directly facing the outside of the positive electrode terminal end 11x, and the second separator 13B is disposed at a position directly facing the inside of the positive electrode terminal end 11x, respectively. For the first separator 13A and the second separator 13B, the same type of porous sheet having the same width as each other can be used.

[0041] The electrode assembly 14 has a structure in which a single-sided mixture layer forming portion 43A is disposed outside the positive electrode terminal end 11x with the second separator 13B interposed therebetween, and a double-sided mixture layer forming portion 44 is disposed inside the positive electrode terminal end 11x with the first separator 13A interposed therebetween. The negative electrode mixture layers 41 of the single-sided mixture layer forming portion 43A and the double-sided mixture layer forming portion 44 that sandwich the positive electrode terminal end 11x are disposed slightly extending toward the winding end side of the electrode assembly 14 beyond the position facing the outside of the positive electrode terminal end 11x with the separator 13 interposed therebetween, in order to more reliably prevent lithium precipitation.

[0042] In the present embodiment, the terminal end of the single-sided mixture layer forming portion 43A on the winding end side of the electrode assembly 14 and the terminal end of the double-sided mixture layer forming portion 44 are disposed substantially aligned in the radial direction of the electrode assembly 14. The terminal ends of the single-sided mixture layer forming portion 43A and the double-sided mixture layer forming portion 44 are located, for example, in a range of not less than 0.1 turn and not more than 0.2 turn from the position facing the outside of the positive electrode terminal end 11x with the separator 13 interposed therebetween toward the winding end side of the electrode assembly 14. Note that the terminal end of the first single-sided mixture layer forming portion 43A is the start end of the first double-sided exposed portion 42A, and the terminal end of the double-sided mixture layer forming portion 44 is also the start end of the first single-sided mixture layer forming portion 43A.

[0043] The electrode assembly 14 further has a structure in which the second separator 13B is wound one or more turns from the position facing the positive electrode terminal end 11x toward the winding end side of the electrode assembly 14. The entire outer peripheral surface of the single-sided mixture layer forming portion 43A is covered by the second separator 13B.

[0044] Here, for example, the phrase "the second separator 13B is wound one turn from the position facing the positive electrode terminal end 11x toward the winding end side of the electrode assembly 14" means that the second separator 13B is wound 360° around the winding center Z of the electrode assembly 14 from the position facing the positive electrode terminal end 11x.

[0045] The first separator 13A and the second separator 13B have different lengths from each other, and the length of the first separator 13A is shorter than the length of the second separator 13B. The terminal end of the first separator 13A on the winding end side of the electrode assembly 14 is located at a position slightly extending toward the winding end side from a position facing the positive electrode terminal end 11x inside the positive electrode terminal end 11x, and is located at or near a position facing the terminal end of the double-sided mixture layer forming portion 44.

[0046] In the electrode assembly 14, it is not necessary to extend the separator significantly further toward the winding end side of the electrode assembly 14 than the positive electrode terminal end 11x, but the second separator 13B extends extra for one or more turns from the position facing the positive electrode terminal end 11x toward the winding end side. In this case, two or more layers of the second separator 13B are arranged outside the positive electrode terminal end 11x, and deformation of the negative electrode 12 (the portion where the negative electrode mixture layer 41 is formed) in the vicinity of the positive electrode terminal end 11x is effectively suppressed. It is considered that the second separator 13B functions as a buffer layer and reduces the pressure acting on the negative electrode 12 in the vicinity of the positive electrode terminal end 11x.

[0047] The second separator 13B is preferably wound beyond one turn from the position facing the positive electrode terminal end 11x toward the winding end side of the electrode assembly 14. In this case, the second separator 13B functions more effectively as a buffer layer, and the effect of suppressing deformation of the negative electrode 12 becomes more remarkable. The second separator 13B only needs to be wound from the position directly facing the positive electrode terminal end 11x to the position facing the positive electrode terminal end 11x via the single-sided mixture layer forming portion 43A, but in the present embodiment, the second separator 13B extends beyond the position facing the positive electrode terminal end 11x to a position covering the outer surface of the double-sided exposed portion 42A.

[0048] An example of a suitable length of the second separator 13B extending from the position facing the positive electrode terminal end 11x toward the winding end side of the electrode assembly 14 is more than 1.0 turns and not more than 2.0 turns, more than 1.0 turns and not more than 1.5 turns, or more than 1.1 turns and not more than 1.5 turns in the winding direction of the electrode assembly 14. Even if the second separator 13B is wound beyond 2.0 turns, the effect of suppressing deformation of the negative electrode 12 will level off, while the volumetric energy density of the electrode assembly 14 will decrease. For this reason, the upper limit of the above length of the second separator 13B is set to 2.0 turns, for example.

[0049] The exposed core portion 47B of the negative electrode 12 abuts against the inner circumferential surface of the outer casing 16 and constitutes more than 50% of the circumference of the outermost surface of the electrode body 14. In this case, good current collection performance on the negative electrode side can be ensured. In this embodiment, the exposed core portion 47B extends beyond the position outside the second separator 13B where it faces the positive electrode end 11x and the end of the second separator 13B, towards the winding end, and the outermost surface of the electrode body 14 is formed by the exposed core portion 47B, except for the portion to which the winding stopper tape is attached.

[0050] The extension portion 45 of the negative electrode core body 40 will be described in more detail below.

[0051] As described above, the extension portion 45 is the portion that extends toward the winding end of the electrode body 14 beyond the position facing the outside of the positive electrode end 11x, and in this embodiment, the entire area of ​​the extension portion 45 is a core body exposed portion 47B in which the negative electrode mixture layer 41 does not exist on the outer surface of the negative electrode core body 40. The extension portion 45 includes a second single-sided mixture layer forming portion 43B in which the second negative electrode mixture layer 46 is formed only on the inner surface of the negative electrode core body 40. The extension portion 45 has, in order from the starting end side of the extension portion 45 facing the outside of the positive electrode end 11x via the second separator 13B, a first single-sided mixture layer forming portion 43A, a first double-sided exposed portion 42A, a second single-sided mixture layer forming portion 43B, and a second double-sided exposed portion 42B.

[0052] The second negative electrode mixture layer 46 of the single-sided mixture layer forming section 43B suppresses deformation of the portions of the positive electrode 11 and negative electrode 12 that are located radially outward from the positive electrode lead 20 on the electrode body 14. Steps are formed on the electrode body 14 due to, for example, the thickness of the positive electrode lead 20, the exposed core portion to which the positive electrode lead 20 is connected, and the protective tape covering the positive electrode lead 20. As a result, electrode plate deformation is likely to occur on the outside of the positive electrode lead 20. The second negative electrode mixture layer 46 functions as a buffer layer and effectively suppresses electrode plate deformation caused by the positive electrode lead 20.

[0053] The negative electrode mixture layer 46 is provided at a position that overlaps radially with at least the positive electrode lead 20 and the electrode body 14, i.e., inside the inferior arc AB. Since the positive electrode mixture layer 31 does not exist in the area facing the negative electrode mixture layer 46, the negative electrode mixture layer 46 does not contribute to the charging and discharging of the battery and functions solely as a buffer layer. Preferably, the negative electrode mixture layer 46 is provided on the inner surface of the extension portion 45 at a position that overlaps radially with the center of the positive electrode lead 20 in the width direction and the electrode body 14, i.e., on a straight line L4. The negative electrode mixture layer 46 effectively suppresses deformation of the portion of the negative electrode 12 that faces the negative electrode mixture layer 46 via the second separator 13B (the first single-sided mixture layer forming portion 43A).

[0054] The negative electrode mixture layer 46, like the negative electrode mixture layer 41, contains a negative electrode active material and a binder, and is formed by coating the negative electrode mixture slurry onto the negative electrode core body 40. From the viewpoint of improving productivity, it is preferable that the negative electrode mixture layers 41 and 46 are formed using the same negative electrode mixture slurry. That is, the negative electrode mixture layers 41 and 46 are made of the same material. The thickness of the negative electrode mixture layer 46 may be greater than or less than the thickness of the negative electrode mixture layer 41, but it is preferable that it has substantially the same thickness as the negative electrode mixture layer 41.

[0055] The negative electrode mixture layer 46 is preferably provided in a region that overlaps radially with the entire positive electrode lead 20 and the electrode body 14, and more preferably in a region that exceeds the region that overlaps radially with the positive electrode lead 20. The negative electrode mixture layer 46 is positioned inside the inferior arc AB and along the inferior arc AB. The length of the negative electrode mixture layer 46 along the circumferential direction of the electrode body 14 is preferably 2.0 to 5.0 times the length of the inferior arc AB, and more preferably 2.5 to 3.5 times. In this case, the amount of negative electrode material that does not contribute to charging and discharging can be suppressed, and the negative electrode mixture layer 46 can be more reliably positioned in a region that overlaps radially with the entire positive electrode lead 20 and the electrode body 14, thereby efficiently suppressing deformation of the electrode plate.

[0056] The extension portion 45 has a first double-sided exposed portion 42A on the winding start side of the electrode body 14, compared to the single-sided combined material layer forming portion 43B, which is the portion where the second negative electrode combined material layer 46 is provided. That is, a double-sided exposed portion 42A is formed between the starting end of the extension portion 45 and the single-sided combined material layer forming portion 43B. The central angle θ of the inferior arc CD, which indicates the positional relationship between the positive electrode terminal 11x and the positive electrode lead 20, is, for example, 90° ± 30°, so the starting end of the extension portion 45 and the negative electrode combined material layer 46 are separated to some extent. In the extension portion 45, if the negative electrode combined material layer 46 is placed in a region that overlaps radially with the positive electrode lead 20 and the electrode body 14, deformation of the electrode plate can be effectively suppressed, but if the negative electrode combined material layer is placed inside the superior arc AC, it does not substantially contribute to suppressing deformation of the electrode plate. Therefore, by providing the first double-sided exposed portion 42A, the amount of negative electrode material that does not contribute to charging and discharging can be suppressed, and deformation of the electrode plate can be efficiently suppressed.

[0057] The extension portion 45 further has a second double-sided exposed portion 42B on the winding end side of the electrode body 14, which is provided on the single-sided composite layer forming portion 43B where the negative electrode composite layer 46 is provided. That is, the single-sided composite layer forming portion 43B, which includes the negative electrode composite layer 46, is sandwiched between the two double-sided exposed portions 42A and 42B. In this case, deformation of the electrode plate can be suppressed more efficiently while suppressing the amount of negative electrode material that does not contribute to charging and discharging. The double-sided exposed portion 42B is provided on the outermost circumferential surface of the electrode body 14, extending from point B, which is the winding end end at a position that radially overlaps with the positive electrode lead 20, or slightly further towards the winding end than point B, beyond the position facing the positive electrode end 11x to the negative electrode end 12x.

[0058] Figure 4 shows an example of a modified electrode body 14C of the above embodiment. In the following, we will omit redundant explanations of content common to the above embodiment and mainly explain the differences.

[0059] As shown in Figure 4, the electrode body 14C differs from the electrode body 14 in that both the first separator 13A and the second separator 13B are wound around the end of the electrode body 14 at least once, starting from a position opposite the positive electrode end 11x. In the electrode body 14C, the first separator 13A and the second separator 13B directly face each other and directly overlap each other at the end of the electrode body 14C, beyond the positive electrode end 11x. In the electrode body 14C, outside the positive electrode end 11x, the second separator 13B, the first single-sided composite layer forming portion 43A, the first separator 13A, the second separator 13B, and the double-sided exposed portion 42 are stacked in order from the positive electrode end 11x side.

[0060] The end positions of the first separator 13A and the second separator 13B may be far apart, but in the electrode body 14C, the end positions of each separator are aligned. In this case, the first separator 13A and the second separator 13B can be cut at the same position, improving the productivity of the electrode body 14C. The first separator 13A is wound more than one turn from the position opposite the positive electrode end 11x toward the winding end of the electrode body 14C. A suitable length of the separator 13 extending from the position directly opposite the positive electrode end 11x toward the winding end of the electrode body 14C is, for example, more than 1.1 turns but no more than 1.5 turns in the winding direction of the electrode body 14C.

[0061] In the electrode body 14C, three or more separators 13, which function as buffer layers, are arranged outside the positive electrode end 11x, thereby more effectively suppressing deformation of the negative electrode 12 near the positive electrode end 11x. In the electrode body 14C, the end positions of the double-sided exposed portions 42 coincide with the end positions of the first separator 13A and the second separator 13B, and the outermost surface of the electrode body 14 is formed by the core exposed portion 47B, except for the portion to which the winding stopper tape is attached. The end positions of the double-sided exposed portions 42 may be located on the winding end side of the electrode body 14C than the end positions of the separators 13, similar to the case of the electrode body 14.

[0062] The electrode body 14C is similar to the electrode body 14 in that it has a second negative electrode mixture layer 46C provided at the extension portion 45 of the negative electrode core body 40, where it overlaps radially with the positive electrode lead 20 and the electrode body 14. On the other hand, the second negative electrode mixture layer 46C differs from the electrode body 14 in that it is provided from the starting end of the extension portion 45 and is continuous with the negative electrode mixture layer 41 which is formed on the winding start side of the electrode body 14, rather than the positive electrode end 11x. In this case as well, electrode plate deformation caused by the positive electrode lead 20 can be effectively suppressed. The negative electrode mixture layers 41 and 46C are formed continuously using the same material and with the same thickness, but in the electrode body 14C, the starting end position of the extension portion 45 is set as the boundary position between the negative electrode mixture layers 41 and 46.

[0063] As described above, with the electrode bodies 14 and 14C having the above configuration, the second negative electrode mixture layer 46 provided on the inner surface of the extension portion 45 effectively suppresses deformation of the electrode plate in the portion located radially outward from the positive electrode lead 20 and overlapping radially with the positive electrode lead 20 and the electrode body 14. In particular, deformation of the single-sided mixture layer forming portion 43A of the negative electrode 12, which is the portion facing the negative electrode mixture layer 46, is effectively suppressed. The negative electrode mixture layer 46 is considered to function as a buffer layer capable of reducing the pressure that tends to concentrate in the portion where the positive electrode lead 20 and the electrode body 14 overlap radially during charging and discharging of the battery.

[0064] In electrode bodies 14 and 14C, at least two layers of separator 13 are further arranged outside the positive electrode terminal 11x. As a result, deformation of the portion of the negative electrode 12 where the negative electrode mixture layer 41 is formed is effectively suppressed near the positive electrode terminal 11x. The separator 13 arranged outside the positive electrode terminal 11x is thought to function as a buffer layer that reduces the pressure that tends to concentrate near the positive electrode terminal 11x during battery charging and discharging, similar to the second negative electrode mixture layer 46.

[0065] The above embodiments can be modified as appropriate without impairing the purpose of this disclosure. For example, in the electrode body 14, the second separator 13B is wound around the electrode body for one or more turns from a position facing the end of the positive electrode mixture layer toward the end of the winding, but the separator wound for one or more turns may be the first separator 13A. Also, the second core body exposed portion 47B does not extend to a position that overlaps with the positive electrode end 11x in the radial direction of the electrode body 14, and it is also possible to configure the outermost periphery of the electrode bodies 14, 14C with the core body exposed portion 47B and the separator 13. However, even in this case, it is preferable that the core body exposed portion 47B has a length of 0.5 turns or more of the outermost periphery of the electrode bodies 14, 14C.

[0066] Each electrode body 14, 14C has one positive electrode lead 20, but the number of positive electrode leads 20 is not limited to one and may be multiple. In this case as well, it is preferable that a second negative electrode mixture layer is provided on the inner surface of the extension portion 45 at a position that overlaps each positive electrode lead 20 and the electrode body in the radial direction. Furthermore, it is preferable that the positive electrode terminal 11x and each positive electrode lead 20 are arranged so that they do not overlap each other in the radial direction of the electrode bodies 14, 14C.

[0067] The present disclosure will be further described by the following embodiments. Configuration 1: A cylindrical battery comprising an electrode body in which a positive electrode and a negative electrode are wound with a separator between them, and a bottomed cylindrical outer casing for housing the electrode body, wherein the electrode body has a positive electrode lead connected to the positive electrode, the positive electrode has a positive electrode core and a positive electrode mixture layer formed on the positive electrode core, the negative electrode has a negative electrode core and a negative electrode mixture layer formed on the negative electrode core, the negative electrode core has an extension portion that extends toward the end of the electrode body beyond a position opposite to the radially outer side of the electrode body at the end of the positive electrode mixture layer which is the end of the positive electrode mixture layer on the winding end side of the electrode body, and a second negative electrode mixture layer is provided on the inner surface of the extension portion facing radially inward of the electrode body at a position that overlaps radially with the positive electrode lead and the electrode body. Configuration 2: The cylindrical battery according to Configuration 1, wherein the second negative electrode mixture layer is provided at a position that overlaps at least the widthwise central portion of the positive electrode lead with the radial portion of the electrode body. Configuration 3: The cylindrical battery according to Configuration 2, wherein the second negative electrode mixture layer is provided in a region that overlaps the entire positive electrode lead with the radial portion of the electrode body. Configuration 4: The cylindrical battery according to any one of Configurations 1 to 3, wherein the extension portion has a double-sided exposed portion on the side of the electrode body closer to the winding start of the electrode body than the portion where the second negative electrode mixture layer is provided, in which both sides of the negative electrode core body are exposed. Configuration 5: The cylindrical battery according to any one of Configurations 1 to 4, wherein the extension portion has a second double-sided exposed portion on the side of the electrode body closer to the winding end of the electrode body than the portion where the second negative electrode mixture layer is provided, in which both sides of the negative electrode core body are exposed. Configuration 6: The cylindrical battery according to any one of Configurations 1 to 5, wherein the separator includes a first separator located inside the end of the positive electrode mixture layer in the radial direction of the electrode body, and a second separator located outside the end of the positive electrode mixture layer, and at least one of the first and second separators is wound around the electrode body at least once from a position opposite to the end of the positive electrode mixture layer toward the end of the winding.

[0068] 10 Cylindrical battery, 11 Positive electrode, 11x Positive electrode terminal, 12 Negative electrode, 12x Negative electrode terminal, 13 Separator, 13A First separator, 13B Second separator, 14, 14C 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 section, 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 Double-sided exposed section, 42A First double-sided exposed section, 42B Second double-sided exposed section, 43A First single-sided mixture layer forming section, 43B Second single-sided compound layer forming section, 44 double-sided compound layer forming section, 45 extension section, 46, 46C second negative electrode compound layer, 47A first core body exposed section, 47B second core body exposed section

Claims

1. A cylindrical battery comprising an electrode body in which a positive electrode and a negative electrode are wound with a separator between them, and a bottomed cylindrical outer casing for housing the electrode body, wherein the electrode body has a positive electrode lead connected to the positive electrode, the positive electrode has a positive electrode core and a positive electrode mixture layer formed on the positive electrode core, the negative electrode has a negative electrode core and a negative electrode mixture layer formed on the negative electrode core, the negative electrode core has an extension portion that extends toward the end of the electrode body beyond a position opposite to the radially outer side of the electrode body at the end of the positive electrode mixture layer which is the end of the positive electrode mixture layer on the winding end side of the electrode body, and a second negative electrode mixture layer is provided on the inner surface of the extension portion facing radially inward of the electrode body at a position that overlaps the positive electrode lead and the electrode body in the radial direction.

2. The cylindrical battery according to claim 1, wherein the second negative electrode mixture layer is provided at a position that overlaps at least the widthwise central portion of the positive electrode lead with the radial portion of the electrode body.

3. The cylindrical battery according to claim 3, wherein the second negative electrode mixture layer is provided in a region that overlaps radially with the entire positive electrode lead and the electrode body.

4. The cylindrical battery according to claim 1, wherein the extension portion has a double-sided exposed portion on the side of the electrode body winding start that is closer to the portion where the second negative electrode mixture layer is provided, and both sides of the negative electrode core body are exposed.

5. The cylindrical battery according to claim 4, wherein the extension portion has a second double-sided exposed portion on the winding end side of the electrode body, where both sides of the negative electrode core body are exposed, relative to the portion where the second negative electrode mixture layer is provided.

6. The cylindrical battery according to any one of claims 1 to 5, wherein the separator includes a first separator located inside the end of the positive electrode mixture layer in the radial direction of the electrode body and a second separator located outside the end of the positive electrode mixture layer, and at least one of the first and second separators is wound around the electrode body at least once from a position opposite to the end of the positive electrode mixture layer toward the winding end side.

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