Cylindrical battery

Abstract

A negative electrode (12) in a cylindrical battery according to an embodiment includes, in order from a negative electrode terminal (12e) side: a both-surfaces-exposed part (42) in which both surfaces of a negative electrode core body (40) are exposed; a mixture-layer-formed-on-one-surface part (43) in which the outer surface of the negative electrode core body (40) facing outward in the radial direction of an electrode body (14A) is exposed and a negative electrode mixture layer (41) is formed on the inner surface of the negative electrode core body (40) facing inward in the radial direction; and a mixture-layer-formed-on-both-surfaces part (44) in which the negative electrode mixture layer (41) is formed on both surfaces of the negative electrode core body (40). At least one among a first separator (13x) and a second separator (13y) is wound one or more turns from a position facing a positive electrode terminal (11e) to the winding end side of the electrode body (14A).

Description

Cylindrical battery

[0001] The present disclosure relates to a cylindrical battery, and more particularly to a cylindrical battery having 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, the positive electrode and negative electrode constituting the wound electrode assembly have a core and a mixture layer formed on the core. Note that a negative electrode mixture layer is always disposed in an area facing the positive electrode mixture layer in the radial direction of the electrode assembly. Therefore, 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 assembly, is sandwiched from both radial sides of the electrode assembly by the negative electrode mixture layer via a separator.

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

[0004] As a result of the inventors' investigations, it was found that the negative electrode is prone to deformation near the end of the positive electrode mixture layer. Generally, the negative electrode extends beyond the end of the positive electrode mixture layer toward the end of the winding of the electrode assembly, and a large gap corresponding to the thickness of the positive electrode mixture layer is formed between the negative electrodes facing each other in the radial direction of the electrode assembly near the end of the positive electrode mixture layer. The electrode assembly expands and contracts during charging and discharging of the battery. At this time, stress is concentrated near the end of the positive electrode mixture layer where the gap exists, which is thought to result in deformation of the negative electrode. Since deformation of the negative electrode can lead to uneven battery reactions and local short circuits, suppressing deformation of the negative electrode is an important issue.

[0005] The cylindrical battery according to the present disclosure is a cylindrical battery including a positive electrode, a negative electrode, and a separator, and including an electrode assembly in which the positive electrode and the negative electrode are wound with the separator interposed therebetween, and a bottomed cylindrical outer can that houses the electrode assembly, 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 cylindrical battery includes, in order from a negative electrode termination side that is the end of the negative electrode on the winding end side of the electrode assembly, a double-sided exposed portion in which both surfaces of the negative electrode core are exposed and which constitutes 0.5 or more circumferences of the outermost peripheral surface of the electrode assembly, a double-sided exposed portion in which the outer surface of the negative electrode core facing radially outward of the electrode assembly is exposed and which constitutes an inner surface of the negative electrode core facing radially inward, The negative electrode core body includes a single-sided mixture layer forming section on which the negative electrode mixture layer is formed, and a double-sided mixture layer forming section on which the negative electrode mixture layer is formed on both sides of the negative electrode core body, and the single-sided mixture layer forming section and the double-sided mixture layer forming section are arranged to sandwich a positive electrode mixture layer terminal end, which is an end of the positive electrode mixture layer on the winding end side of the electrode body, from both radial sides of the electrode body, and the separators include a first separator arranged on the radially inner side of the positive electrode mixture layer terminal end and a second separator arranged on the radially outer side of the positive electrode mixture layer terminal end, and at least one of the first and second separators is wound around one or more times from a position facing the positive electrode mixture layer terminal end towards the winding end side of the electrode body.

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

[0007] Fig. 1 is an axial cross-sectional view of a cylindrical battery that is an example of an embodiment; Fig. 2 is a view showing a part of a radial cross-section of an electrode body of a first embodiment; Fig. 3 is a view showing a part of a radial cross-section of an electrode body of a second embodiment; Fig. 4 is a view showing a part of a radial cross-section of an electrode body of a third embodiment; Fig. 5 is a view showing a part of a radial cross-section of an electrode body of a fourth embodiment;

[0008] Hereinafter, an example of an embodiment of a cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. Note that the cylindrical battery according to the present disclosure is not limited to the embodiment described below. Furthermore, the present disclosure also includes configurations that selectively combine the components of the multiple embodiments and variations described below.

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

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

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

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

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

[0014] The positive electrode 11 has a long positive electrode core 30 and a positive electrode mixture layer 31 formed on the positive electrode core 30. The positive electrode core 30 can be a foil of a metal that is stable within the potential range of the positive electrode 11, such as aluminum, an aluminum alloy, stainless steel, or titanium, or a film with such a metal disposed on the surface. 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 with some exceptions. The positive electrode active material can be, for example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, or the like.

[0015] The thickness of the positive electrode 11 is, for example, 150 μm or more and 230 μm or less. In this embodiment, the thickness of the positive electrode 11 is substantially constant except for the core exposed portion to which the positive electrode lead 20 is connected. The thickness of the positive electrode core 30 is, for example, 10 μm or more and 30 μm or less. The thickness of the positive electrode mixture layer 31 is, for example, 70 μm or more and 100 μm or less on one side of the positive electrode core 30. The positive electrode 11 can be produced by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core 30, drying the coating, and then compressing it to form the positive electrode mixture layer 31 on both sides of the positive electrode core 30.

[0016] The negative electrode 12 has a long negative electrode core 40 and a negative electrode mixture layer 41 formed on the negative electrode core 40. For the negative electrode core 40, a foil of a metal that is stable within the potential range of the negative electrode 12, such as copper, a copper alloy, stainless steel, nickel, or a nickel alloy, or a film having such a metal disposed on its surface can be used. The negative electrode mixture layer 41 contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR), and is preferably formed on both sides of the negative electrode core 40 with some exceptions. For example, graphite, a silicon-containing material, or the like is 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 the present embodiment, the thickness of the negative electrode 12 is substantially constant except for a portion including a core exposed portion described below. The thickness of the negative electrode core 40 is, for example, 5 μm or more and 15 μm or less. The thickness of the negative electrode mixture layer 41 is, for example, 70 μm or more and 110 μm or less on one surface side of the negative electrode core 40. The negative electrode 12 can be produced, similarly to the positive electrode 11, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder onto the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode mixture layers 41 on both surfaces of the negative electrode core 40.

[0018] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator 13 include polyolefins such as polyethylene and 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 an 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 the positive electrode 11 and a negative electrode lead 21 connected to the negative electrode 12. In this embodiment, a core exposed portion where the positive electrode mixture layer 31 is not present and the surface of the positive electrode core 30 is exposed is formed in the center of the positive electrode 11 in the longitudinal direction, and the positive electrode lead 20 is connected to this exposed portion. On the other hand, the negative electrode lead 21 is provided at one end in the longitudinal direction of the negative electrode 12 located at the start side of winding of the electrode body 14. At one end in the longitudinal direction of the negative electrode 12, a first core exposed portion (not shown) where the negative electrode mixture layer 41 is not present and the surface of the negative electrode core 40 is exposed is formed, and the negative electrode lead 21 is connected to this core exposed portion.

[0020] Insulating plates 18 and 19 are disposed above and below the electrode body 14. In the example shown in Fig. 1 , the positive electrode lead 20 passes through a through hole in the insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes through a through hole in the insulating plate 19 and extends toward the bottom side of the outer can 16. The positive electrode lead 20 is connected to the underside of an internal terminal plate 23 of the sealing body 17 by welding or the like, and a cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal. The negative electrode lead 21 is connected to the inner bottom surface of the outer can 16 by welding or the like, and the outer can 16 serves as the negative electrode terminal.

[0021] The negative electrode 12 is disposed on the outermost peripheral surface of the electrode body 14, and a double-sided exposed portion 42, which is a second core exposed portion where the surface of the negative electrode core 40 is exposed, is provided. The double-sided exposed portion 42 abuts against the inner peripheral surface of the outer can 16. The abutment of the double-sided exposed portion 42 with the inner peripheral surface of the outer can 16 electrically connects both longitudinal ends of the negative electrode 12 to the outer can 16, ensuring good current collection on the negative electrode side. A stop tape for maintaining the wound structure may be attached to the outermost peripheral surface of the electrode body 14.

[0022] The outer can 16 is a cylindrical metal container with a bottom. A gasket 28 is provided between the outer can 16 and the sealing body 17 to seal the interior of the battery. The outer can 16 has a groove 22 that supports the sealing body 17, formed, for example, by pressing the side surface from the outside. The groove 22 is preferably formed in an annular shape along the circumferential direction of the outer can 16, and supports the sealing body 17 on its top surface. The upper end of the outer can 16 is bent inward and crimped to the periphery of the sealing body 17.

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

[0024] Electrode assembly embodiments will be described in detail below with reference to Figures 2 to 5. Figures 2 to 5 are diagrams showing portions of radial cross sections of electrode assemblies 14A to 14D of the first to fourth embodiments, showing cross sections at the end of winding. Note that any of the electrode assemblies 14A to 14D can be used as the electrode assembly 14 of the cylindrical battery 10 shown in Figure 1.

[0025] 2 , the electrode body 14A of the first embodiment has a wound structure in which the negative electrode 12 and separator 13 extend beyond the positive electrode terminal end 11e, which is the end of the positive electrode 11 at the winding end side of the electrode body 14A. 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 disposed in an area facing the positive electrode mixture layer 31 with the separator 13 interposed between them. The negative electrode mixture layer 41 is disposed so as to sandwich the positive electrode terminal end 11e from both radial sides of the electrode body 14A.

[0026] In this embodiment, the positive electrode mixture layer terminal end, which is the end of the positive electrode mixture layer 31 on the winding end side of the electrode body 14A, coincides with the positive electrode terminal end 11e, which is the end of the positive electrode 11. In other words, no exposed portion of the positive electrode core 30 is provided on the winding end side of the electrode body 14A, and the positive electrode terminal end 11e can be rephrased as the positive electrode mixture layer terminal end. Hereinafter, for convenience of explanation, the radially outer side of the electrode body may be simply referred to as the "outside" and the radially inner side of the electrode body may be simply referred to as the "inside".

[0027] The negative electrode 12 includes, in order along the winding direction from the negative electrode terminal end 12e, which is the end of the negative electrode 12 on the winding end side of the electrode body 14A, a double-sided exposed portion 42, a single-sided mixture layer formed portion 43, and a double-sided mixture layer formed portion 44. The double-sided exposed portion 42 exposes both surfaces of the negative electrode core 40 and constitutes at least 0.5 of the circumference of the outermost surface of the electrode body 14A. As described above, the double-sided exposed portion 42 abuts the inner circumferential surface of the outer can 16, electrically connecting the negative electrode 12 and the outer can 16 at the winding end side of the electrode body 14A. If the double-sided exposed portion 42 covers at least 0.5 of the circumference of the outermost surface of the electrode body 14A, good current collection properties on the negative electrode side can be ensured.

[0028] The single-sided mixture layer forming portion 43 is a portion where the outer surface of the negative electrode core 40 facing radially outward of the electrode body 14A is exposed and where the negative electrode mixture layer 41 is formed on the inner surface of the negative electrode core 40 facing radially inward of the electrode body 14A. The single-sided mixture layer forming portion 43 is formed in a range that faces the positive electrode 11 radially inward of the electrode body 14A with the separator 13 interposed between them and that does not include the positive electrode 11 radially outward of the electrode body 14A. In this embodiment, the single-sided mixture layer forming portion 43 is arranged slightly toward the winding end side of the position facing the positive electrode terminal end 11e with the separator 13 interposed between them, for a length of approximately one turn.

[0029] The double-sided mixture layer forming portion 44 is a portion where the negative electrode mixture layer 41 is formed on both sides of the negative electrode core 40. The double-sided mixture layer forming portion 44 is formed in a range facing the positive electrode 11 on both radial sides of the electrode body 14A with the separator 13 interposed therebetween. Specifically, the double-sided mixture layer forming portion 44 is arranged from a position inside the positive electrode terminal end 11e slightly toward the winding end side of the position facing the positive electrode terminal end 11e with the separator 13 interposed therebetween, to a position facing at least the positive electrode mixture layer starting end, which is the end of the positive electrode mixture layer 31 on the winding start side of the electrode body 14A, with the separator 13 interposed therebetween. The single-sided mixture layer forming portion 43 and the double-sided mixture layer forming portion 44 are arranged to sandwich the positive electrode terminal end 11e from both radial sides of the electrode body 14A, as described above.

[0030] The electrode assembly 14A includes a first separator 13x and a second separator 13y as separators 13. The two separators are wound around the positive electrode 11, with the first separator 13x positioned radially inside the electrode assembly 14A facing the positive electrode terminal end 11e, and the second separator 13y positioned radially outside the electrode assembly 14A facing the positive electrode terminal end 11e. The first separator 13x and the second separator 13y may be made of the same type of porous sheet having the same width. As will be described in detail later, in this embodiment, the first separator 13x and the second separator 13y have different lengths, with the second separator 13y being longer than the first separator 13x.

[0031] As described above, the electrode body 14A has a structure in which the single-sided mixture layer forming portion 43 is disposed on the outer side of the positive electrode terminal end 11e with the second separator 13y interposed therebetween, and the double-sided mixture layer forming portion 44 is disposed on the inner side of the positive electrode terminal end 11e with the first separator 13x interposed therebetween. The negative electrode mixture layers 41 of the single-sided mixture layer forming portion 43 and the double-sided mixture layer forming portion 44, which sandwich the positive electrode terminal end 11e, are disposed slightly toward the winding end side of the electrode body 14A from the position facing the positive electrode terminal end 11e with the separator 13 interposed therebetween, in order to more reliably prevent lithium deposition.

[0032] In this embodiment, the end of the single-sided mixture layer forming portion 43 and the end of the double-sided mixture layer forming portion 44 on the winding termination side of the electrode body 14A are arranged substantially side by side in the radial direction of the electrode body 14A. The ends of the single-sided mixture layer forming portion 43 and the double-sided mixture layer forming portion 44 are located, for example, in a range of 0.1 to 0.2 turns from a position facing the positive electrode terminal end 11e with the separator 13 interposed therebetween toward the winding termination side of the electrode body 14A. Note that the double-sided exposed portion 42, single-sided mixture layer forming portion 43, and double-sided mixture layer forming portion 44 of the negative electrode 12 are formed successively in this order from the negative electrode terminal end 12e side, and therefore the end of the single-sided mixture layer forming portion 43 is the start end of the double-sided exposed portion 42, and the end of the double-sided mixture layer forming portion 44 is the start end of the single-sided mixture layer forming portion 43.

[0033] The electrode body 14A further has a structure in which a second separator 13y is wound one or more times from a position facing the positive electrode terminal end 11e toward the winding end side of the electrode body 14A. The second separator 13y preferably extends beyond the position facing the positive electrode terminal end 11e outside the single-sided mixture layer forming portion 43 toward the winding end side of the electrode body 14A. In this embodiment, the entire outer peripheral surface of the single-sided mixture layer forming portion 43 is covered by the second separator 13y, and the second separator 13y constitutes part of the outermost peripheral surface of the electrode body 14A. Meanwhile, the end of the first separator 13x on the winding end side of the electrode body 14A is located opposite or near the end of the double-sided mixture layer forming portion 44.

[0034] Here, for example, "the second separator 13y is wound one turn from the position facing the positive electrode terminal end 11e toward the winding end side of the electrode body 14A" means that, in the radial cross section of the electrode body 14A, the second separator 13y is wound 360° around the winding center of the electrode body 14A from the position facing the positive electrode terminal end 11e. In this case, the end of the second separator 13y is disposed outside the positive electrode terminal end 11e in the radial direction of the electrode body 14A.

[0035] In the electrode assembly 14A, it is not necessary to extend the separator farther toward the winding end of the electrode assembly 14A than the positive electrode terminal end 11e to prevent short circuits between the positive and negative electrodes. However, the second separator 13y extends one or more turns from the position facing the positive electrode terminal end 11e toward the winding end. In this case, two or more layers of the second separator 13y are arranged outside the positive electrode terminal end 11e, which effectively suppresses deformation of the negative electrode mixture layer 41 near the positive electrode terminal end 11e. The second separator 13y functions as a buffer layer and is thought to reduce the pressure acting on the negative electrode 12 near the positive electrode terminal end 11e.

[0036] The second separator 13y is preferably wound more than one turn from the position facing the positive electrode terminal end 11e toward the winding end side of the electrode body 14A. In this case, the second separator 13y functions more effectively as a buffer layer, and the effect of suppressing deformation of the negative electrode 12 becomes more pronounced. The second separator 13y may be wound from the position directly facing the positive electrode terminal end 11e to the position facing the positive electrode terminal end 11e via the single-side mixture layer forming portion 43. In this embodiment, however, the second separator 13y extends beyond the position facing the positive electrode terminal end 11e to a position covering the outer surfaces of the both-side exposed portion 42.

[0037] An example of a suitable length of the second separator 13y extending from the position facing the positive electrode terminal end 11e toward the winding end of the electrode assembly 14A is more than 1.0 laps but not more than 2.0 laps, more than 1.0 laps but not more than 1.5 laps, or more than 1.1 laps but not more than 1.5 laps in the winding direction of the electrode assembly 14A. If the second separator 13y is wound more than 2.0 laps, the effect of suppressing deformation of the negative electrode 12 will plateau, while the volumetric energy density of the electrode assembly 14A will decrease. For this reason, the upper limit of the length of the second separator 13y is set to, for example, 2.0 laps.

[0038] The exposed portion 42 of the negative electrode 12 abuts against the inner peripheral surface of the outer can 16 and forms at least 0.5 of the circumference of the outermost peripheral surface of the electrode body 14A. In this case, good current collection performance on the negative electrode side can be ensured. In this embodiment, the exposed portion 42 does not extend radially of the electrode body 14A to a position where it overlaps with the positive electrode terminal end 11e, and the outermost peripheral surface of the electrode body 14A is formed by the exposed portion 42 and the second separator 13y.

[0039] [Second Embodiment] As shown in Figure 3, the electrode assembly 14B of the second embodiment differs from the electrode assembly 14A in that both the first separator 13x and the second separator 13y are wound one or more times from a position facing the positive electrode terminal 11e toward the winding end of the electrode assembly 14A. Below, we will omit redundant description of the content common to the above embodiment and focus on the differences (this also applies to the following embodiments). In the electrode assembly 14B, the first separator 13x and the second separator 13y directly face each other and overlap each other on the winding end side of the electrode assembly 14B relative to the positive electrode terminal 11e. The second separator 13y, the single-sided mixture layer forming portion 43, the first separator 13x, and the second separator 13y are stacked in this order on the outside of the positive electrode terminal 11e.

[0040] Although the terminal positions of the first separator 13x and the second separator 13y may be apart, in the electrode assembly 14B, the terminal positions of the separators are aligned. In this case, the first separator 13x and the second separator 13y can be cut at the same position, improving the productivity of the electrode assembly 14B. The first separator 13x is wound from a position facing the positive electrode terminal end 11e toward the winding end of the electrode assembly 14B for more than one turn, extending to a position covering the outer surfaces of the both-side exposed portion 42. A suitable length of the separator 13 extending from a position directly facing the positive electrode terminal end 11e toward the winding end of the electrode assembly 14B is, for example, more than 1.1 turns and not more than 1.5 turns in the winding direction of the electrode assembly 14B.

[0041] According to the electrode body 14B, three or more layers of separators 13 functioning as buffer layers are arranged on the outside of the positive electrode terminal end 11e, and deformation of the negative electrode 12 in the vicinity of the positive electrode terminal end 11e is more effectively suppressed.

[0042] [Third Embodiment] As shown in Figure 4, the electrode assembly 14C of the third embodiment differs from the electrode assembly 14A in that the negative electrode 12 is wound one or more times from a position facing the positive electrode terminal end 11e via the second separator 13y toward the winding termination side of the electrode assembly 14C. In the electrode assembly 14C, the both-side exposed portion 42 of the negative electrode 12 is wound to a position facing the positive electrode terminal end 11e via at least the second separator 13y and the single-side mixture layer forming portion 43. In this case, the both-side exposed portion 42 functions as a buffer layer together with the second separator 13y, effectively suppressing deformation of the portion of the negative electrode 12 where the negative electrode mixture layer 41 is formed. Furthermore, extending the both-side exposed portion 42 increases the contact area between the negative electrode 12 and the outer can 16, improving current collection performance.

[0043] The double-sided exposed portion 42 is preferably further wound beyond a position facing the positive electrode terminal end 11e via the second separator 13y and the single-sided mixture layer forming portion 43. In the electrode body 14C, the double-sided exposed portion 42 is wound more than one turn from the end of the single-sided mixture layer forming portion 43. Furthermore, it is preferable that the end position of the double-sided exposed portion 42 coincides with the end position of the second separator 13y or is located closer to the end of the winding of the electrode body 14C than the end position of the second separator 13y. In this case, the second separator 13y is not disposed on the outermost peripheral surface of the electrode body 14C, and the improvement in current collection performance is more pronounced.

[0044] 5 , an electrode assembly 14D of the fourth embodiment is similar to the electrode assembly 14B in that both the first separator 13x and the second separator 13y are wound one or more times from a position facing the positive electrode terminal end 11e toward the winding termination side of the electrode assembly 14A. The electrode assembly 14D is also similar to the electrode assembly 14C in that the electrode assembly 14D has a structure in which the both-side exposed portion 42 of the negative electrode 12 is wound to a position facing the positive electrode terminal end 11e via the separator 13 and the single-side mixture layer forming portion 43. In other words, the electrode assembly 14D has four or more buffer layers arranged on the outside of the positive electrode terminal end 11e: one or more layers of the first separator 13x, two or more layers of the second separator 13y, and one or more layers of the both-side exposed portion 42.

[0045] The first separator 13x, the second separator 13y, and the double-sided exposed portion 42 are preferably wound beyond the position where they overlap the positive electrode terminal end 11e outside the positive electrode terminal end 11e, and further beyond the end position of the single-sided mixture layer forming portion 43. As in the case of the electrode body 14C, the end position of the double-sided exposed portion 42 preferably coincides with the end positions of the first separator 13x and the second separator 13y, or is located closer to the end of winding of the electrode body 14D than the end positions.

[0046] As described above, with the electrode assemblies 14A to 14D having the above-described configuration, at least two layers of separator 13 are arranged on the outside of the positive electrode terminal 11e, which effectively suppresses deformation of the portion of the negative electrode 12 where the negative electrode mixture layer 41 is formed near the positive electrode terminal 11e. The separator 13 arranged on the outside of the positive electrode terminal 11e is thought to function as a buffer layer that reduces pressure that tends to concentrate near the positive electrode terminal 11e during charging and discharging of the battery.

[0047] In the electrode bodies 14C and 14D, a double-sided exposed portion 42 of the negative electrode 12 is further disposed outside the positive electrode terminal end 11e. That is, two or more layers of separator 13 and one or more layers of negative electrode core 40 are laminated and disposed outside the positive electrode terminal end 11e. Furthermore, the separator 13 is not exposed on the outermost peripheral surface of the electrode bodies 14C and 14D, and the double-sided exposed portion 42 is disposed along the entire periphery. In this case, the effect of suppressing negative electrode deformation is enhanced, and the contact area between the negative electrode 12 and the outer can 16 is increased, improving current collection performance.

[0048] For example, in the above embodiment, in the configuration in which only one of the first separator 13x and the second separator 13y is wound one or more times from a position facing the end of the positive electrode mixture layer toward the winding end side of the electrode assembly (electrode assemblies 14A and 14C), the separator that extends one or more times is the second separator 13y, but this may be the first separator 13x.

[0049] The present disclosure will be further described by the following embodiments. Configuration 1: A cylindrical battery including an electrode assembly including a positive electrode, a negative electrode, and a separator, the positive electrode and the negative electrode being wound with the separator interposed therebetween, and a bottomed cylindrical outer can accommodating the electrode assembly, the positive electrode having a positive electrode core and a positive electrode mixture layer formed on the positive electrode core, the negative electrode having a negative electrode core and a negative electrode mixture layer formed on the negative electrode core, and the battery includes, in order from a negative electrode termination side that is the end of the negative electrode on the winding end side of the electrode assembly, a double-sided exposed portion in which both surfaces of the negative electrode core are exposed and that constitutes 0.5 or more circumferences of the outermost peripheral surface of the electrode assembly, an outer surface of the negative electrode core facing radially outward of the electrode assembly being exposed, and a negative electrode mixture layer formed on an inner surface of the negative electrode core facing radially inward. a single-sided mixture layer forming section on which an electrode mixture layer is formed, and a double-sided mixture layer forming section on which the negative electrode mixture layer is formed on both sides of the negative electrode core, the single-sided mixture layer forming section and the double-sided mixture layer forming section being arranged to sandwich a positive electrode mixture layer terminal end, which is an end of the positive electrode mixture layer on the winding end side of the electrode body, from both radial sides of the electrode body, the separators including a first separator located radially inward of the positive electrode mixture layer terminal end and a second separator located radially outward of the positive electrode mixture layer terminal end, at least one of the first and second separators being wound one or more times from a position facing the positive electrode mixture layer terminal end toward the winding end side of the electrode body. Configuration 3: The cylindrical battery according to Configuration 1 or 2, wherein the negative electrode is wound one or more times from a position facing the end of the positive electrode mixture layer via the second separator toward the winding end side of the electrode body.Configuration 4: The cylindrical battery according to any one of Configurations 1 to 3, wherein the both-side exposed portion is disposed in a position facing the outside of the end of the positive electrode mixture layer via the separator and the single-side mixture layer forming portion.Configuration 5: The cylindrical battery according to any one of Configurations 1 to 4, wherein at least one of the first and second separators is wound more than one time from a position facing the end of the positive electrode mixture layer toward the winding end side of the electrode body.

[0050] REFERENCE SIGNS LIST 10 Cylindrical battery, 11 Positive electrode, 11e Positive electrode terminal, 12 Negative electrode, 12e Negative electrode terminal, 13 Separator, 13x First separator, 13y Second separator, 14, 14A, 14B, 14C, 14D Electrode body, 16 Outer can, 17 Sealing body, 18 Upper insulating plate, 19 Lower insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved portion, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive electrode core, 31 Positive electrode mixture layer, 40 Negative electrode core, 41 Negative electrode mixture layer, 42 Double-sided exposed portion, 43 Single-sided mixture layer forming portion, 44 Double-sided mixture layer forming portion

Claims

1. A cylindrical battery comprising an electrode assembly including a positive electrode, a negative electrode, and a separator, the positive electrode and the negative electrode being wound with the separator interposed therebetween, and a bottomed cylindrical outer can accommodating the electrode assembly, 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 battery includes, in order from a negative electrode termination side which is the end of the negative electrode on the winding end side of the electrode assembly, a double-sided mixture layer forming portion in which both sides of the negative electrode core are exposed and which constitutes 0.5 or more of the outermost circumference of the electrode assembly, a single-sided mixture layer forming portion in which the outer surface of the negative electrode core facing radially outward of the electrode assembly is exposed and the negative electrode mixture layer is formed on the inner surface of the negative electrode core facing radially inward, and a double-sided mixture layer forming portion in which the negative electrode mixture layer is formed on both sides of the negative electrode core, a cylindrical battery in which the single-sided mixture layer forming section and the double-sided mixture layer forming section are arranged to sandwich a positive electrode mixture layer terminal end, which is an end of the positive electrode mixture layer on the winding end side of the electrode body, from both radial sides of the electrode body, and the separators include a first separator located radially inward of the positive electrode mixture layer terminal end and a second separator located radially outward of the positive electrode mixture layer terminal end, and at least one of the first and second separators is wound one or more times from a position facing the positive electrode mixture layer terminal end toward the winding end side of the electrode body.

2. A cylindrical battery according to claim 1, wherein the first and second separators are wound one or more times from the positions facing the ends of the positive electrode mixture layer toward the winding end of the electrode body.

3. A cylindrical battery as described in claim 1 or 2, wherein the negative electrode is wound one or more times from a position opposite the end of the positive electrode mixture layer via the second separator toward the end of the winding of the electrode body.

4. A cylindrical battery according to claim 3, wherein the double-sided exposed portion is positioned opposite the outer end of the positive electrode mixture layer via the separator and the single-sided mixture layer forming portion.

5. A cylindrical battery as described in claim 1 or 2, wherein at least one of the first and second separators is wound more than one turn from the position opposite the end of the positive electrode mixture layer toward the end of the winding of the electrode body.

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