Cylindrical battery

Abstract

In this cylindrical battery, which is an example of an embodiment, a terminal end (Xb), which is an end of a positive electrode mixture layer (31) on the winding end side of an electrode body, is located on the winding end side beyond a position facing a terminal end (Y2), which is an end of a negative electrode mixture layer (41) on the outside to a positive electrode (11) in the winding of the electrode body. In the positive electrode mixture layer (31), at least a region from the position facing the terminal end (Y2) of the negative electrode mixture layer (41) to the terminal end (Xb) of the positive electrode mixture layer (31) is configured of a second mixture layer (31B) that is a non-reactive portion not involved in a charge / discharge reaction.

Description

Cylindrical battery

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

[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 (see, for example, Patent Document 1). As disclosed in Patent Document 1, the positive electrode and the negative electrode constituting the wound electrode body have a core body and a mixture layer formed on the core body. In order to prevent metal deposition on the surface of the negative electrode, a negative electrode mixture layer is always disposed in a range facing the positive electrode mixture layer in the radial direction of the electrode body. Therefore, the positive electrode mixture layer terminal, which is the end of the positive electrode mixture layer on the winding end side of the electrode body, is sandwiched from both sides in the radial direction of the electrode body by the negative electrode mixture layer via the separator.

[0003] Japanese Patent Application Laid-Open No. 2001-185201

[0004] As a result of investigations by the present inventors, it has been found that deformation of the negative electrode located on the outer side of the winding of the electrode body rather than the positive electrode is likely to occur in the vicinity of the positive electrode mixture layer terminal. The negative electrode mixture layer extends to the winding end side of the electrode body beyond the positive electrode mixture layer terminal, and a large gap corresponding to the thickness of the positive electrode is formed between the negative electrode mixture layers facing each other in the radial direction of the electrode body in the vicinity of the positive electrode mixture layer terminal. The electrode body expands and contracts during charging and discharging of the battery. At this time, stress concentrates in the vicinity of the positive electrode mixture layer terminal where the gap exists, and as a result, it is considered that large deformation occurs in the negative electrode located on the outer side of the winding of the positive electrode mixture layer terminal. Since the occurrence of deformation of the negative electrode may lead to non-uniformity of the charge-discharge reaction, occurrence of local short circuits, etc., suppressing such deformation of the negative electrode is an important issue.

[0005] The cylindrical battery according to this disclosure comprises an electrode body in which the positive electrode and the negative electrode are wound around the separator, and a bottomed cylindrical outer casing for housing the electrode body, wherein the positive electrode has a positive electrode core and a positive electrode mixture layer formed on the positive electrode core, and the negative electrode has a negative electrode core and a negative electrode mixture layer formed on the negative electrode core, and the positive electrode mixture layer end, which is the end of the positive electrode mixture layer on the winding end side of the electrode body, is located on the winding end side beyond the position facing the negative electrode mixture layer end, which is the end of the negative electrode mixture layer on the winding end side of the electrode body, and the positive electrode mixture layer is characterized in that at least the region from the position facing the negative electrode mixture layer end to the positive electrode mixture layer end is composed of a non-reactive portion that does not participate in the charge-discharge reaction.

[0006] According to the cylindrical battery of this disclosure, deformation of the negative electrode, which is located on the outer side of the electrode body than the positive electrode, can be effectively suppressed near the end of the positive electrode mixture layer.

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

[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 an axial cross-sectional view of a cylindrical battery 10, which is an example of an embodiment, cut along a plane containing its central axis. 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. For convenience of explanation, in the following, 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 non-aqueous electrolyte 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 in dimensions than the positive electrode 11. 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 in dimensions 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 (PVdF), and is preferably formed on both sides of the positive electrode core 30. For example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, etc., can be used as the positive electrode active material. As will be described in detail later, the positive electrode mixture layer 31 comprises a first mixture layer containing the positive electrode active material and a second mixture layer not containing 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 exposed core portion (not shown) to which the positive electrode lead 20 is connected. The thickness of the positive electrode core 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 30. The positive electrode 11 can be manufactured by applying a positive electrode mixture slurry onto the positive electrode core 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 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, with some exceptions. For example, graphite or silicon-containing materials can be used as the negative electrode active material.

[0017] The thickness of the negative electrode 12 is, for example, 145 μm or more and 235 μm or less. In this embodiment, the thickness of the negative electrode 12 is substantially constant, except for the portion including the core body exposed portion described later. The thickness of the negative electrode core body 40 is, for example, 5 μm or more and 15 μm or less. The thickness of the negative electrode mixture layer 41 is, for example, 70 μm or more and 110 μm or less on one side of the negative electrode core body 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 body 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 body 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, and a filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12.

[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 exposed portion is formed where the surface of the positive electrode core 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 exposed portion (not shown) is formed where the surface of the negative electrode core 40 is exposed. The negative electrode lead 21 is connected to this core exposed 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 body exposed portion, which is a single-sided exposed portion 42 and a double-sided exposed portion 43 (see Figure 2 below for details), where the surface of the negative electrode core body 40 is exposed. At least the double-sided exposed portion 43 is in contact with the inner surface of the outer casing 16. By the double-sided exposed portion 43 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. 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 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 electrode body 14 will be described in detail below with reference to Figure 2. Figure 2 is a diagram showing a part of the radial cross-section of the electrode body 14, specifically the cross-section at the end of the winding.

[0025] As shown in Figure 2, in the electrode body 14, the end Xb (end of positive electrode mixture layer), which is the end of the positive electrode mixture layer 31 at the winding end, is located on the winding end side, beyond the position facing the end Y2 (end of negative electrode mixture layer), which is the end of the negative electrode mixture layer 41 located on the winding side of the electrode body 14, which is on the winding side of the positive electrode 11. As a result, a large gap is not formed near the end of the positive electrode mixture layer 31 between the end Y2 of the negative electrode mixture layer 41, which is located on the winding side of the positive electrode 11, and the negative electrode mixture layer 41, which is located on the winding side, and deformation of the negative electrode 12 due to the charging and discharging of the battery is effectively suppressed. As a result, for example, uniformity of the charge and discharge reaction and reduction of the risk of short circuits can be achieved.

[0026] In conventional cylindrical batteries, as described above, in order to prevent lithium deposition, the negative electrode mixture layer is always placed in the area facing the positive electrode mixture layer via a separator. Therefore, the negative electrode mixture layer is formed beyond the position facing the end of the positive electrode mixture layer. In this case, a large gap is formed between the radially opposing negative electrode mixture layers near the end of the positive electrode mixture layer, and it is thought that this gap causes significant deformation of the negative electrode located on the outer side of the winding of the end of the positive electrode mixture layer. In contrast, in the electrode body 14 of this embodiment, the positive electrode mixture layer 31 is placed at the position facing the end Y2 of the negative electrode mixture layer 41, and the gap is filled by the positive electrode mixture layer 31. That is, the electrode body 14 does not have the gap that causes negative electrode deformation. On the other hand, in this case, lithium deposition may be a problem, so a part of the positive electrode mixture layer 31 is composed of a non-reactive portion, which will be described later.

[0027] In this embodiment, the end Xb of the positive electrode mixture layer 31 is the end of the second mixture layer 31B, which is a non-reactive portion, and coincides with the end of the positive electrode core 30. No exposed portion of the positive electrode core 30 is provided on the winding end side of the electrode body 14, and the end Xb of the positive electrode mixture layer 31 coincides with the end of the positive electrode 11. On the other hand, in the negative electrode 12, the end Y2 of the negative electrode mixture layer 41 and the end of the negative electrode core 40 do not coincide, and a double-sided exposed portion 43 is formed on the winding end side of the electrode body 14, where both sides of the negative electrode core 40 are exposed.

[0028] The negative electrode 12 further has a negative electrode mixture layer 41 formed only on the inner surface of the negative electrode core 40, i.e., the surface facing radially inward of the electrode body 14, and a single-sided exposed portion 42 where the outer surface of the negative electrode core 40, i.e., the surface facing radially outward of the electrode body 14, is exposed. The end Y2 of the negative electrode mixture layer 41 is the end of the negative electrode mixture layer 41 formed on the inner surface of the negative electrode core 40, and the end Y1 of the negative electrode mixture layer 41 formed on the outer surface of the negative electrode core 40 is located on the winding side of the electrode body 14 than the positive electrode 11. In the example shown in Figure 2, the single-sided exposed portion 42 has a length equivalent to one full circumference of the electrode body 14, and the ends Y1 and Y2 substantially overlap in the radial direction of the electrode body 14.

[0029] As described above, the positive electrode mixture layer 31 has a second mixture layer 31B, which is a non-reactive portion that does not participate in the charge-discharge reaction. The positive electrode mixture layer 31 has a first mixture layer 31A, which is a reactive portion, and a second mixture layer 31B, which is a non-reactive portion, and at least the region from the position facing the end Y2 of the negative electrode mixture layer 41 to the end of the positive electrode 11 is composed of the second mixture layer 31B. By providing the second mixture layer 31B, even if the positive electrode mixture layer 31 extends beyond the position facing the end Y2 towards the winding end, the deposition of lithium on the surface of the negative electrode 12 can be prevented. Note that the end of the first mixture layer 31A on the winding end side of the electrode body 14 is the end Xa, and the end of the second mixture layer 31B is the end Xb.

[0030] The first composite layer 31A includes a positive electrode active material that serves as a lithium ion supply source, a conductive agent that forms conductive paths, and a binder that binds particles of the positive electrode active material together to form a layer structure, and is formed over a wide area of ​​the positive electrode core 30, excluding the end of the winding. The surface of the positive electrode core 30 is covered by the first composite layer 31A or the second composite layer 31B, except for the core exposed portion to which the positive electrode lead 20 is connected. The first composite layer 31A is formed, for example, by applying a positive electrode composite slurry containing a positive electrode active material, a conductive agent, a binder, and a dispersion medium to disperse them to the surface of the positive electrode core 30, drying the coating, and then compressing it.

[0031] The first composite layer 31A is formed on the winding start side of the electrode body 14, rather than at a position facing the end Y2 of the negative electrode composite layer 41. That is, the end Xa of the first composite layer 31A is on the winding start side of the position facing the end Y2. The end Xa is located, for example, in a range of 3 mm to 10 mm from the end Y2 along the winding direction (circumferential direction) of the electrode body 14. In this case, lithium deposition can be prevented more reliably without causing a decrease in capacity. The thickness of the first composite layer 31A is, for example, approximately constant throughout its entire surface, and as described above, is 70 μm to 100 μm on one side of the positive electrode core 30. Furthermore, the thickness of the first composite layer 31A is approximately constant on each surface of the positive electrode core 30.

[0032] The second composite layer 31B is composed of a composite material that does not contain positive electrode active material. As a result, lithium ions are not released from the second composite layer 31B during charging, and lithium deposition does not occur even if the negative electrode composite layer 41 is not present opposite the second composite layer 31B. The second composite layer 31B is formed, for example, by applying a positive electrode composite slurry containing at least a binder and a dispersion medium to the surface of the positive electrode core 30, drying the coating, and then compressing it. The binder may be dissolved in the dispersion medium. The second composite layer 31B can also be composed of only one type of binder, but even in that case, it is formed using a binder and a dispersion medium, so it is assumed to be composed of a composite material. As will be described in detail later, preferably the second composite layer 31B is composed of non-conductive particles and a binder.

[0033] It is possible to form the second compounding layer 31B thinner or thicker than the first compounding layer 31A, but preferably the first compounding layer 31A and the second compounding layer 31B are formed with similar thicknesses. Furthermore, it is preferable that the second compounding layer 31B be formed on both sides of the positive electrode core 30, similar to the first compounding layer 31A. The thickness of the second compounding layer 31B is, for example, 70 μm to 100 μm on one side of the positive electrode core 30. Also, the thickness of the second compounding layer 31B is approximately constant on each surface of the positive electrode core 30.

[0034] As described above, the second mixture layer 31B is formed on the winding end side of the electrode body 14, starting at least from a position facing the end Y2 of the negative electrode mixture layer 41. It is more preferable that the second mixture layer 31B is formed at least 3 mm from the winding start side of the electrode body 14 beyond the position facing the end Y2. In this case, lithium deposition can be prevented more reliably. On the other hand, extending the second mixture layer 31B too far toward the winding start side beyond the position facing the end Y2 can lead to a decrease in capacity, so it is preferable to form the second mixture layer 31B within a range not exceeding 10 mm from the position facing the end Y2 toward the winding start side. That is, it is preferable that the second mixture layer 31B is formed with a length of 3 mm to 10 mm in the range facing the negative electrode mixture layer 41.

[0035] The second compounding layer 31B is preferably continuous with the first compounding layer 31A and formed so that there are no gaps or steps between it and the first compounding layer 31A. The thickness difference between the first compounding layer 31A and the second compounding layer 31B is preferably 10% or less, and more preferably 5% or less. The second compounding layer 31B is formed, for example, with substantially the same thickness as the first compounding layer 31A. The thickness of the second compounding layer 31B is substantially constant throughout its entire surface, but for example, the thickness can be varied along the length of the positive electrode 11 and gradually decreased towards the end Xb. It is also preferable that the second compounding layer 31B is formed over the entire width of the positive electrode core 30, similar to the first compounding layer 31A.

[0036] The second compound layer 31B may be formed from the starting side of the electrode body 14 beyond the position facing the end Y2 of the negative electrode compound layer 41, and significantly beyond the position facing the end Y2. The end Xb of the second compound layer 31B is located, for example, within 0.5 turns from the position facing the end Y2 toward the end of the electrode body 14. Even if the second compound layer 31B is provided with a length exceeding 0.5 turns of the electrode body 14, the deformation suppression effect of the negative electrode 12 will no longer be improved, so it is preferable to keep the length within 0.5 turns from the viewpoint of reducing material costs, etc.

[0037] If the length of the second mixture layer 31B is too short, manufacturing variations in the electrode body 14 may result in the second mixture layer 31B not being present at the position opposite the end Y2 of the negative electrode mixture layer 41. For this reason, considering the manufacturing tolerances of the electrode body 14, it is preferable to extend the second mixture layer 31B by 3 mm or more from the position opposite the end Y2 toward the end of the winding of the electrode body 14. A preferred example of the length of the second mixture layer 31B extending from the position opposite the end Y2 toward the end of the winding is 3 mm to 10 mm. The second mixture layer 31B is formed with the same length on both the beginning and end sides of the winding of the electrode body 14, centered on the position opposite the end Y2.

[0038] In this embodiment, the ends Y1 and Y2 of the negative electrode mixture layer 41 overlap the electrode body 14 in the radial direction. Therefore, the end Xb of the second mixture layer 31B is located within 0.5 turns from the position opposite to the end Y1 toward the end of the winding of the electrode body 14. Furthermore, it is preferable that the second mixture layer 31B has a length of 3 mm to 10 mm along the winding direction from the position opposite to the end Y1. Note that the end Y1 of the negative electrode mixture layer 41 only needs to extend toward the end of the winding of the electrode body 14 beyond the position opposite to the end Xa of the first mixture layer 31A, and may also extend toward the end of the winding beyond the position opposite to the end Xb of the second mixture layer 31B.

[0039] Preferably, the second composite layer 31B does not contain a positive electrode active material or a conductive agent and is composed of non-conductive particles that do not participate in the charge-discharge reaction and a binder. By using non-conductive particles that do not participate in the charge-discharge reaction, lithium deposition can be prevented, and the second composite layer 31B of the same thickness can be easily formed in the same manner as the first composite layer 31A. Examples of non-conductive particles that do not participate in the charge-discharge reaction include, for example, particles that do not function as a positive electrode active material, and at least one selected from aluminum oxide, titanium oxide, zirconium oxide, and silicon oxide. Resin particles composed of polyolefins, fluororesins, etc., can also be used as the non-conductive particles.

[0040] The second additive layer 31B is formed by applying a second positive electrode additive slurry, different from the first positive electrode additive slurry that forms the first additive layer 31A, to the surface of the positive electrode core 30, drying the coating, and then compressing it. The second positive electrode additive slurry does not contain positive electrode active material or conductive agent, but contains non-conductive particles such as aluminum oxide, a binder, and a dispersion medium. The binder and dispersion medium of the second positive electrode additive slurry can be the same as those used in the first positive electrode additive slurry. Furthermore, the second positive electrode additive slurry can be coated in the same manner as the first positive electrode additive slurry.

[0041] Figure 3 shows a part of the radial cross-section of an electrode body 140, which is another example of the embodiment, and shows the cross-section at the end of the winding.

[0042] As shown in Figure 3, the electrode body 140 shares with the electrode body 14 the fact that the end X of the positive electrode mixture layer 32 is located beyond the position facing the end Y2 of the negative electrode mixture layer 41 on the outer side of the winding of the electrode body 14, and is closer to the end of the winding, thus effectively suppressing deformation of the negative electrode 12. Also, similar to the electrode body 14, the positive electrode mixture layer 32 is composed of a non-reactive portion that does not participate in the charge-discharge reaction, at least from the position facing the end Y2 of the negative electrode mixture layer 41 to the end X. This prevents the deposition of lithium on the surface of the negative electrode 12.

[0043] On the other hand, the non-reactive portion of the positive electrode mixture layer 32 differs from the positive electrode mixture layer 31 of the electrode body 14 in that it is composed of a mixture containing the positive electrode active material and is a portion covered by a tape 35 that covers the surface of the mixture. The tape 35 functions as an ion-impermeable shielding layer. That is, the non-reactive portion of the positive electrode mixture layer 32 has the same layer structure as the first mixture layer 31A, but has a tape 35 that covers the surface of the first mixture layer 31A and shields against the release of lithium ions from the positive electrode active material. In this case, a coating film can be formed using one type of positive electrode mixture slurry, and then the tape 35 can be attached to the surface of the mixture layer. Alternatively, an ion-impermeable material can be coated onto the surface of the mixture to form a shielding layer.

[0044] The tape 35 only needs to be able to transmit lithium ions, can be adhered to the surface of the mixture, and has electrolyte resistance. For example, it is composed of polyolefin such as polypropylene, polyimide, etc. The tape 35 is adhered to the surface of the mixture so as to cover the entire area of the portion of the surface of the positive electrode mixture layer 32 that extends from the end Y2 of the negative electrode mixture layer 41 to the winding end side. Since the positive electrode mixture layer 32 is formed on both sides of the positive electrode core 30, two tapes 35 may be separately adhered to the mixture surfaces on both sides, but it is preferable to fold one tape 35 at the end X of the positive electrode mixture layer 32 and adhere it to the mixture surfaces on both sides.

[0045] The tape 35 has, for example, a thickness of 10 μm or more and 30 μm or less, and includes a label base material and an adhesive layer formed on one side of the label base material. The end Xb of the positive electrode mixture layer 32, that is, the end of the tape 35, is located, for example, within a range of within 0.5 turns from the position facing the end Y2 of the negative electrode mixture layer 41 to the winding end side of the electrode body 14. Similar to the case of the electrode body 14, the length of the positive electrode mixture layer 32 extending from the position facing the end Y2 to the winding end side is preferably 3 mm or more and 10 mm or less. Further, the tape 35 is preferably adhered from 3 mm or more from the position facing the end Y2 and from the winding start side of the electrode body 14, and is more preferably adhered with a length of 3 mm or more and 10 mm or less in the range facing the negative electrode mixture layer 41.

[0046] As described above, according to the cylindrical battery having the above configuration, deformation of the negative electrode 12 located on the outer side of the winding of the electrode bodies 14 and 140 can be effectively suppressed in the vicinity of the ends of the positive electrode mixture layers 31 and 32, compared with the positive electrodes 11 and 110. In a conventional cylindrical battery, a large gap is formed between the negative electrode mixture layers in the vicinity of the end of the positive electrode mixture layer, and it is considered that a large deformation occurs in the negative electrode on the outer side of the winding due to this gap. However, in the configuration of the above embodiment, the positive electrode mixture layers 31 and 32 are present at the position facing the end Y2 of the negative electrode mixture layer 41, and there is no gap that causes deformation of the negative electrode 12. Further, among the positive electrode mixture layers 31 and 32, the portion that does not face the negative electrode mixture layer 41 is composed of a non-reactive portion that does not participate in the charge-discharge reaction, so the problem of lithium precipitation does not occur.

[0047] Incidentally, the above-described embodiment can be appropriately modified in design without impairing the object of the present disclosure. For example, in the above-described embodiment, the second binder layer 31B, which is a non-reactive portion, is formed on both surfaces of the positive electrode core 30, but the second binder layer 31B may be formed on only one surface of the positive electrode core 30. Also in this case, compared with the case where the second binder layer 31B does not exist, the gap between the negative electrode binder layers can be reduced, and deformation of the negative electrode 12 can be suppressed.

[0048] Further, in the above-described embodiment, the negative electrode 12 has a single-sided exposed portion 42 and a double-sided exposed portion 43. For example, the end of the negative electrode binder layer formed on the inner surface of the negative electrode core and the end of the negative electrode core may coincide. In this case, the double-sided exposed portion does not exist. Furthermore, the negative electrode may not have a core exposed portion on the winding end side of the electrode body, and negative electrode binder layers may be formed on both surfaces over the end of the negative electrode core.

[0049] The present disclosure is further described by the following embodiments. Configuration 1: A cylindrical battery comprising an electrode body in which the positive electrode and the negative electrode are wound via the separator, the positive electrode and the negative electrode being wound via the separator, and a bottomed cylindrical outer casing for housing the electrode body, wherein 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 positive electrode mixture layer end, which is the end of the positive electrode mixture layer on the winding end side of the electrode body, is located on the winding end side beyond the position facing the negative electrode mixture layer end, which is the end of the negative electrode mixture layer on the winding end side of the electrode body, and the positive electrode mixture layer is composed of a non-reactive portion that does not participate in the charge-discharge reaction, at least from the position facing the negative electrode mixture layer end to the positive electrode mixture layer end. Configuration 2: The cylindrical battery according to Configuration 1, wherein the non-reactive portion is formed on both sides of the positive electrode core. Configuration 3: The cylindrical battery according to Configuration 1 or 2, wherein the non-reactive portion is composed of a mixture that does not contain a positive electrode active material. Configuration 4: The cylindrical battery according to Configuration 3, wherein the non-reactive portion is composed of non-conductive particles that do not participate in the charge-discharge reaction and a binder. Configuration 5: The cylindrical battery according to any one of Configurations 1 to 4, wherein the non-reactive portion is a portion provided with an ion-impermeable shielding layer that covers the surface of the positive electrode mixture layer. Configuration 6: The cylindrical battery according to any one of Configurations 1 to 5, wherein the end of the positive electrode mixture layer is located within 0.5 turns from the position opposite the end of the negative electrode mixture layer toward the end of the winding of the electrode body.

[0050] 10 Cylindrical battery, 11, 110 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18 Upper insulating plate, 19 Lower insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved 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, 32 Positive electrode mixture layer, 31A First mixture layer, 31B Second mixture layer, 35 Tape, 40 Negative electrode core, 41 Negative electrode mixture layer, 42 Single-sided exposed section, 43 Double-sided exposed section, X End of positive electrode mixture layer, Xa End of first mixture layer, Xb End of second mixture layer, Y1, Y2 End of negative electrode mixture layer

Claims

1. A cylindrical battery comprising an electrode body including a positive electrode, a negative electrode, and a separator, wherein the positive electrode and the negative electrode are wound around the separator, and a bottomed cylindrical outer casing for housing the electrode body, wherein 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 positive electrode mixture layer end, which is the end of the positive electrode mixture layer on the winding end side of the electrode body, is located on the winding end side beyond the position facing the negative electrode mixture layer end, which is the end of the negative electrode mixture layer on the winding end side of the electrode body, and the positive electrode mixture layer is composed of a non-reactive portion that does not participate in the charge-discharge reaction, at least from the position facing the negative electrode mixture layer end to the positive electrode mixture layer end.

2. The cylindrical battery according to claim 1, wherein the non-reactive portion is formed on both sides of the positive electrode core.

3. The cylindrical battery according to claim 1 or 2, wherein the non-reactive portion is composed of a mixture that does not contain a positive electrode active material.

4. The cylindrical battery according to claim 3, wherein the non-reactive portion is composed of non-conductive particles that do not participate in the charge-discharge reaction and a binder.

5. The cylindrical battery according to claim 1 or 2, wherein the non-reactive portion is a portion provided with an ion-impermeable shielding layer covering the surface of the positive electrode mixture layer.

6. The cylindrical battery according to claim 1 or 2, wherein the end of the positive electrode mixture layer is located within 0.5 turns from the position opposite to the end of the negative electrode mixture layer toward the end of the winding of the electrode body.

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