Cylindrical battery

Abstract

This cylindrical battery comprises an electrode assembly in which a positive electrode (11) and a negative electrode (12) are wound with a separator (13) interposed therebetween. The negative electrode has a negative electrode tab (21) that is connected to an intermediate winding turn, and the negative electrode tab is connected to the bottom of an outer can. In the cylindrical battery, at least one permeable member (50) having higher permeability to an electrolytic solution than the separator is disposed in a positive-negative electrode opposed portion where the positive electrode and the negative electrode are opposed to each other with the separator interposed therebetween. R1 and R2 satisfy R1 / (R1 + R2) > 0.5, where R1 is the ratio of the total volume of the permeable member to the area of a portion of the positive–negative electrode opposed portion that is located in an inner circumferential region on the winding-start side with respect to the position of the winding inner surface of the negative electrode at the turn to which the negative electrode tab is connected, and R2 is the ratio of the total volume of the permeable member to the area of a portion of the positive–negative electrode opposed portion that is located in an outer circumferential region, which is a region other than the inner circumferential region.

Description

Cylindrical battery

[0001] The present disclosure relates to a cylindrical battery.

[0002] Conventionally, as an electrode body that can be used for a cylindrical battery, there is one described in Patent Document 1. In this electrode body, a positive electrode and a negative electrode are wound with a separator interposed therebetween. In a battery having this electrode body, a plurality of resin non-woven fabric buffer materials are intermittently wound together with the constituent members of the electrode body. Thereby, it is said that a pressing force can be uniformly applied to the electrode surface of the electrode body.

[0003] Japanese Patent Laid-Open No. 10-302842

[0004] In a cylindrical battery, a negative electrode tab may be connected to an intermediate circumference between the innermost circumference and the outermost circumference of the negative electrode, and a portion of the negative electrode tab led out from the electrode body may be connected to the bottom of the outer can. However, in this case, when the electrode body expands and contracts with the charge and discharge cycle, the inner circumferential portion between the start side end of the winding and the negative electrode tab in the electrode body is likely to be tightened, the liquid circulation property of the electrolytic solution in the inner circumferential portion deteriorates, and there is a risk that the charge and discharge cycle characteristics deteriorate.

[0005] Patent Document 1 does not disclose anything about the possibility of the winding of the electrode body caused by the arrangement of the negative electrode tab.

[0006] An object of the present disclosure is to provide a cylindrical battery capable of suppressing deterioration of the liquid circulation property of the electrolytic solution in the charge and discharge cycle in a configuration where a negative electrode tab is connected to an intermediate circumference of the negative electrode.

[0007] The cylindrical battery according to this disclosure comprises an electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound via a separator, and a bottomed cylindrical outer casing that houses the electrode body and electrolyte. The negative electrode has a negative electrode tab connected to an intermediate circumference between the innermost and outermost circumferences, and the portion of the negative electrode tab that extends outward from the electrode body is connected to the bottom of the outer casing. At least one permeable member with higher permeability to the electrolyte than the separator is arranged in the positive-negative electrode opposing portion where the positive and negative electrodes face each other via a separator. When R1 is the ratio of the total volume of the permeable member to the area in the inner circumference region of the positive-negative electrode opposing portion where the negative electrode tab is connected, on the winding side from the position of the inner surface of the negative electrode, and R2 is the ratio of the total volume of the permeable member to the area in the outer circumference region of the positive-negative electrode opposing portion excluding the inner circumference region, R1 and R2 satisfy R1 / (R1+R2)>0.5.

[0008] According to the cylindrical battery described herein, in a configuration in which a negative electrode tab is connected to the intermediate circumference of the negative electrode, deterioration of the electrolyte's flow during the charge-discharge cycle can be suppressed.

[0009] This is a cross-sectional view along the axial direction of a cylindrical battery according to an embodiment of the present disclosure. This is a cross-sectional view (a) perpendicular to the axial direction of the electrode body of the cylindrical battery shown in Figure 1, and an enlarged view of part A in (a). In the embodiment, this is a diagram showing the outer surface (a) and inner surface (b) of the positive electrode and the outer surface (c) and inner surface (d) of the negative electrode unfolded in the longitudinal direction. This is a diagram showing a method for measuring the liquid absorption rate of a material used in a permeable member. This is a diagram corresponding to Figure 2(a) in a comparative example of a cylindrical battery. This is a diagram corresponding to Figure 2(a) in another example of the embodiment of a cylindrical battery. This is a diagram corresponding to Figure 3(a) in another example of the embodiment of a cylindrical battery.

[0010] Hereinafter, embodiments of the cylindrical battery according to this disclosure will be described in detail with reference to the drawings. The cylindrical battery of this disclosure may be a primary battery or a secondary battery. It may also be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. In the following, a non-aqueous electrolyte secondary battery (lithium-ion battery) using a non-aqueous electrolyte will be given as an example of a cylindrical battery 10, which is one embodiment, but the cylindrical battery of this disclosure is not limited to this, and the electrolyte may also be an aqueous electrolyte.

[0011] It is intended from the outset that new embodiments can be constructed by appropriately combining the characteristic features of the embodiments and modifications described below. In the following embodiments, the same components are denoted by the same reference numerals in the drawings, and redundant explanations are omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. In this specification, the side of the cylindrical battery 10 with the sealing body 17 in the axial direction (height direction) is referred to as "upper," and the side of the outer casing 16 with the bottom 31 in the axial direction is referred to as "lower."

[0012] Figure 1 is a cross-sectional view along the axial direction α of a cylindrical battery 10 according to one embodiment of the present disclosure. As shown in Figure 1, the cylindrical battery 10 comprises an electrode body 14, a bottomed cylindrical outer casing 16 that houses the electrode body 14, and a sealing body 17 that closes the opening of the outer casing 16. The outer casing 16 contains a non-aqueous electrolyte, which is a liquid non-aqueous electrolyte, together with the electrode body 14. Hereinafter, the non-aqueous electrolyte will be referred to as the electrolyte.

[0013] The outer can 16 is generally made of a metal mainly composed of iron, for example, iron plated with nickel, but it may also be made of a metal mainly composed of aluminum or the like. The outer can 16 has a cylindrical portion 32 and a bottom portion 31, and the cylindrical portion 32 includes an annular grooved portion 22 and an annular shoulder portion 29. The shoulder portion 29 is bent inward in the radial direction β from the upper end of the cylindrical portion 32 and extends inward. The grooved portion 22 is formed by spinning a part of the cylindrical portion 32 to create a recess inward in the radial direction β. The sealing body 17 is supported by the grooved portion 22 and closes the opening of the outer can 16.

[0014] The cylindrical battery 10 further includes a gasket 28 interposed between the outer casing 16 and the sealing body 17. The gasket 28 is a ring-shaped resin member attached to the outer circumference of the sealing body 17, and insulates the sealing body 17 from the outer casing 16. The gasket 28 seals the gap between the outer casing 16 and the sealing body 17, thereby sealing the inside of the battery. The gasket 28 is made of, for example, polyolefin.

[0015] The electrolyte has ionic conductivity (e.g., lithium ion conductivity). The electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The cylindrical battery 10 is preferably a lithium-ion battery. The electrolyte salt is, for example, LiBF ４ LiPF ６ Lithium salts such as the above are used. Non-aqueous solvents include, for example, esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), as well as ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain halogen-substituted products in which at least some of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine.

[0016] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated linear carbonates, and fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP). In terms of suppressing the deterioration of the charge-discharge cycle characteristics of non-aqueous electrolyte secondary batteries or improving the input characteristics, the non-aqueous electrolyte preferably contains 5% by mass or more of FEC relative to the mass of the non-aqueous electrolyte, and more preferably contains 5% to 15% by mass of FEC.

[0017] The electrode body 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound in a spiral shape via the separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all elongated strip-shaped bodies, and 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 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in the longitudinal 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.

[0018] A positive electrode tab 20 and a negative electrode tab 21 are connected to the electrode body 14. The positive electrode tab 20 electrically connects the positive electrode 11 to the sealing body 17. The negative electrode tab 21 is connected by a joint to the intermediate circumference between the innermost and outermost circumferences of the negative electrode 12, and electrically connects this intermediate circumference to the bottom 31 of the outer container 16.

[0019] In the example shown in Figure 1, the positive electrode tab 20 extends through the opening in the upper insulating plate 71 towards the sealing body 17 and is joined to the lower surface of the sealing body 17. The portion of the negative electrode tab 21 that is led outward from the lower end of the electrode body 14 is bent towards the hollow portion 14a of the electrode body 14 through a through-hole in the annular lower insulating plate 18. The lower bent portion of the negative electrode tab 21 is resistance welded using a welding rod inserted through the hollow portion 14a of the electrode body 14 and joined to the inner surface of the bottom 31 of the outer can 16. As a result, the portion of the negative electrode tab 21 that is led outward from the electrode body 14 is connected to the bottom 31 of the outer can 16.

[0020] The exposed portion 12d (Figure 3(c)) of the negative electrode core 12a, located at least a part of the outermost circumference of the electrode body 14, is in contact with the inner surface of the outer casing 16. This electrically connects the outermost circumference of the negative electrode 12 to the inner surface of the outer casing 16.

[0021] Figure 2(a) is a cross-sectional view of the electrode body 14 perpendicular to the axial direction α of the cylindrical battery 10. Figure 2(b) is an enlarged view of part A in Figure 2(a). Figure 3 is a diagram showing the outer surface (a) and inner surface (b) of the winding of the positive electrode 11, and the outer surface (c) and inner surface (d) of the winding of the negative electrode 12, unfolded in the longitudinal direction. In Figure 3, the sandy area indicates the positive electrode mixture layer 11b or the negative electrode mixture layer 12b. In Figure 3, the oblique grid area indicates the permeable member 50.

[0022] As shown in Figures 2 and 3, the positive electrode 11 has a positive electrode core 11a and a positive electrode mixture layer 11b formed on both sides of the positive electrode core 11a. The positive electrode core 11a can be made of a metal foil that is stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. The positive electrode mixture layer 11b contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF). For the positive electrode active material, for example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, etc. is used. The positive electrode tab 20 is joined to the exposed portion 11c1 of the positive electrode core 11a where the positive electrode mixture layer 11b is not formed, by ultrasonic welding or the like. The exposed portion 11c1 is provided in the middle of the positive electrode longitudinal direction, corresponding to the middle of the winding direction of the positive electrode 11. The joint portion of the positive electrode tab 20 with respect to the exposed portion 11c1 is covered with insulating tape 40.

[0023] As shown in Figure 3, the positive electrode 11 has an exposed portion 11c1 to which the positive electrode tab 20 is joined, and an exposed portion 11c2 on the opposite side in the thickness direction, and the exposed portion 11c2 is also covered with insulating tape 40. In addition, exposed portions 11d are provided on both sides in the thickness direction at different positions in the longitudinal direction of the positive electrode from the exposed portions 11c1 and 11c2, and each exposed portion 11d is also covered with insulating tape 40. In the electrode body 14, the portion where one of the exposed portions 11c1 and 11c2 is covered with insulating tape 40 and the portion where one of the exposed portions 11d is covered with insulating tape 40 are opposite to the portion where the negative electrode tab 21 or the exposed portion 12c2 described later is covered with insulating tape 41, via a separator 13. This prevents the positive electrode mixture layer 11b, which releases Li ions during charging, from being positioned opposite the negative electrode tab 21 or exposed portions 12c1 and 12c2 via the separator 13, thereby preventing the deposition of Li.

[0024] Furthermore, as will be explained in more detail later, a permeable member 50 is placed between the portion of the positive electrode 11 located on the winding start side of the exposed portion 11d and the separator 13.

[0025] The negative electrode 12 comprises a negative electrode core 12a and negative electrode mixture layers 12b formed on both sides of the negative electrode core 12a. The negative electrode core 12a can be made of a metal foil that is stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with the metal arranged on its surface. The negative electrode mixture layer 12b contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR) or PVdF. For the negative electrode active material, graphite or a silicon-containing compound can be used. The negative electrode tab 21 is joined to the exposed portion 12c1 of the negative electrode core 12a where the negative electrode mixture layer 12b is not formed, by ultrasonic welding or the like. The exposed portion 12c1 is located in the middle of the negative electrode longitudinal direction, corresponding to the middle of the winding direction of the negative electrode 12, and is positioned to be sandwiched in the winding direction by the negative electrode mixture layer 12b. The joint portion of the negative electrode tab 21 with respect to the exposed portion 12c1 is covered with insulating tape 41.

[0026] As shown in Figure 3, the negative electrode 12 has an exposed portion 12c1 to which the negative electrode tab 21 is attached, and an exposed portion 12c2 on the opposite side in the thickness direction, and the exposed portion 12c2 is also covered with insulating tape 41.

[0027] In the case of the negative electrode 12, the negative electrode mixture layer 12b formed on both sides of the negative electrode core 12a extends, for example, 1 / 5 of a turn or more, preferably 1 / 2 of a turn or more, and more preferably 1 turn or more, from a position radially opposite to the electrode body 14 via the separator 13 with respect to the winding start end of the positive electrode 11, towards the winding start side of the electrode body 14. This makes it easier to maintain the shape of the hollow portion 14a, which is a cylindrical space formed in the winding core of the electrode body 14.

[0028] As shown in Figure 1, the sealing body 17 is fixed to the outer can 16 by crimping, with a gasket 28 between the shoulder portion 29 and the grooved portion 22. The grooved portion 22 is formed at a predetermined distance from the upper end of the outer can 16.

[0029] The sealing body 17 has a structure in which an internal terminal plate 23, a lower valve body 24, an insulating plate 25, an upper valve body 26, and a sealing plate 27 are stacked in this 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 plate 25 is electrically connected to one another. The sealing plate 27 has a convex shape with the central part β in the radial direction protruding outward. One or more ventilation holes 27a are formed in the cylindrical wall of the convex part of the sealing plate 27.

[0030] The lower valve body 24, the insulating plate 25, and the upper valve body 26 constitute a current interruption mechanism. The lower valve body 24 and the upper valve body 26 are connected at their respective centers, with the insulating plate 25 interposed between their respective peripheries. When an abnormality occurs in the cylindrical battery 10 and the internal pressure rises to a predetermined value, the lower valve body 24 deforms and ruptures, pushing the upper valve body 26 towards the sealing plate 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further and reaches a predetermined value, the upper valve body 26 ruptures, and gas is discharged from the vent hole 27a of the sealing plate 27.

[0031] In this embodiment, the positive electrode tab 20 is connected to the lower surface of the internal terminal plate 23 by laser welding or ultrasonic welding, and the sealing plate 27, which is the top plate of the sealing body 17 electrically connected to the internal terminal plate 23, becomes the positive electrode terminal. The outer can 16 to which the negative electrode tab 21 is attached becomes the negative electrode terminal.

[0032] In this embodiment, in a configuration in which a negative electrode tab 21 is connected to an intermediate circumference between the innermost and outermost circumferences of the negative electrode 12, in order to suppress deterioration of electrolyte circulation during the charge-discharge cycle, a permeable member 50 with higher permeability to the electrolyte than the separator 13 is placed in the inner circumference region IA on the winding start side of the position of the inner surface of the negative electrode winding where the negative electrode tab 21 is connected, within the positive-negative electrode opposing region where the positive electrode 11 and the negative electrode 12 face each other via the separator 13.

[0033] As shown in Figure 2(a), the negative electrode tab 21 is connected to the intermediate circumference between the innermost and outermost circumferences of the negative electrode 12. As shown in Figures 2(b) and 3(c), the negative electrode tab 21 is joined to the exposed portion 12c1 of the outer surface of the winding of the negative electrode core 12a. This makes it easier for the electrode body 14 to tighten between the winding start end and the negative electrode tab 21. As the electrode body expands and contracts with the charge-discharge cycle, it becomes easier for the electrode body 14 to tighten between the winding start end and the negative electrode tab 21, which may worsen the fluidity of the electrolyte and reduce the charge-discharge cycle characteristics. The connection position of the negative electrode tab 21 is not particularly limited as long as it is on the intermediate circumference of the negative electrode 12, but for example, it is connected to the winding start side from the longitudinal center of the negative electrode 12. When multiple negative electrode tabs 21 are connected to the negative electrode 12, the inner circumference region IA is determined based on the negative electrode tab 21 located closest to the winding start.

[0034] In this embodiment, in order to prevent deterioration of the electrolyte's flowability, as shown in Figures 2(b) and 3, a permeable member 50 with higher permeability to the electrolyte than the separator 13 is placed in the inner circumferential region IA of the positive and negative electrode opposing portions of the electrode body 14. The permeable member 50 can be placed anywhere within the inner circumferential region IA.

[0035] The permeable member 50 may be placed between the positive electrode 11 and the separator 13, or between the negative electrode 12 and the separator 13, as long as it is positioned in the area opposite the positive and negative electrodes. Figures 2 and 3 show the case where the permeable member 50 is placed between the outer surface of the winding of the positive electrode 11 and the separator 13. The permeable member 50 may also be attached to the outer surface of the winding of the positive electrode 11. The permeable member 50 may also be placed between the inner surface of the winding of the positive electrode 11 and the separator 13. The permeable member 50 is, for example, a rectangular sheet with a width approximately the same as the vertical width of the positive electrode 11.

[0036] As the permeable member 50, for example, a nonwoven fabric made of resin fibers such as polyolefin fibers such as polypropylene (PP) or polyethylene (PE) can be used. As the permeable member, for example, a highly heat-resistant fiber having aramid fibers may be used. Alternatively, as the permeable member, a ceramic layer coated on the surface of the positive electrode mixture layer or the negative electrode mixture layer may be used. Furthermore, the permeable member may be made of resin in the form of a sponge or mesh.

[0037] The permeability of the permeable member 50 to the electrolyte can be evaluated by the following method. As shown in Figure 4, the electrolyte 53 is placed in a container 52 with an open top, such as a circular container. Two types of test pieces 54 are prepared by cutting out rectangular portions of the same area from the separator 13 and the permeable member 50, respectively. The lower ends of the two test pieces 54 are placed vertically so that they are immersed in the electrolyte 53 for a predetermined length, and the height of the electrolyte that rises in the test pieces 54 due to capillary action after a predetermined time is compared. By performing such an electrolyte absorption rate test, the level of permeability can be determined. Note that an organic solvent such as ethanol may be used instead of the electrolyte 53 in the electrolyte absorption rate test.

[0038] In this example, the permeable member 50 is positioned only in the inner circumference region IA, which is the area on the winding start side of the position of the winding inner surface of the negative electrode 12 in the portion where the negative electrode tab 21 is connected, among the positive and negative electrode opposing portions.

[0039] The permeable member 50 may be placed in the outer peripheral region OA, which is the part of the positive and negative electrode opposing region excluding the inner peripheral region IA. In this case, when R1 is the ratio of the total volume of the permeable member 50 to the area of ​​the inner peripheral region IA of the positive and negative electrode opposing region, and R2 is the ratio of the total volume of the permeable member to the area of ​​the outer peripheral region OA, R1 and R2 are configured to satisfy R1 / (R1+R2)>0.5. When the permeable member 50 is placed only in the inner peripheral region IA of the positive and negative electrode opposing region, R1 / (R1+R2)=1. A configuration satisfying R1 / (R1+R2)>0.8 is also acceptable.

[0040] The area of the inner peripheral region IA is the sum of the area of the opposing portion between the inner winding surface of the negative electrode 12 and the outer winding surface of the positive electrode 11 via the separator 13 in the inner peripheral region IA and the area of the opposing portion between the outer winding surface of the negative electrode 12 and the inner winding surface of the positive electrode 11 via the separator 13. The area of the outer peripheral region OA is the sum of the area of the opposing portion between the inner winding surface of the negative electrode 12 and the outer winding surface of the positive electrode 11 via the separator 13 in the outer peripheral region OA and the area of the opposing portion between the outer winding surface of the negative electrode 12 and the inner winding surface of the positive electrode 11 via the separator 13.

[0041] According to the above configuration, in the configuration in which the negative electrode tab 21 is connected to the intermediate circumference of the negative electrode 12, a permeability member 50 having a higher permeability to the electrolytic solution than the separator 13 is disposed in the inner peripheral region IA, which is the region on the winding start side from the position of the inner winding surface of the negative electrode 12 at the portion where the negative electrode tab 21 is connected among the positive and negative electrode opposing portions of the electrode body 14. Also, the ratios R1 and R2 satisfy R1 / (R1 + R2) > 0.5. Thereby, for example, although the region inside the winding shown by the oblique lattice in FIG. 2 is likely to be tightened, the electrolytic solution easily penetrates into this region inside the winding. Thereby, deterioration of the liquid circulation property of the electrolytic solution in the charge and discharge cycles of the cylindrical battery 10 can be suppressed.

[0042] FIG. 5 is a view corresponding to FIG. 2(a) in the cylindrical battery of the comparative example. That is, FIG. 5 shows a cross section of the electrode body 14b. In the comparative example, different from the embodiments of FIGS. 1 to 3, no permeability member is disposed inside the electrode body 14b. In such a comparative example, for example, in the electrode body 14b, in the region inside the broken line δ, which is the region inside the winding from the surface where the negative electrode tab 21 is connected in the negative electrode, etc., the winding is likely to be tightened, so that the liquid circulation property of the electrolytic solution in the charge and discharge cycles deteriorates. According to the configuration of FIGS. 1 to 3, such inconvenience can be prevented.

[0043] FIG. 6 is a view corresponding to FIG. 2(a) in the cylindrical battery of another example of the embodiment. FIG. 7 is a view corresponding to FIG. 3(a) in the cylindrical battery of the another example.

[0044] In the configuration of this example, in the inner peripheral region IA of the positive and negative electrode facing portion of the electrode body 14c, two permeable members 60 and 61 are arranged so as to be located at different intermediate circumferences between the positive electrode 70 and the separator 13 (see FIG. 1). The permeable member 60 is arranged on the inner side of the winding of the permeable member 61. The two permeable members 60 and 61 may have the same length and the same volume and be made of the same material, or may be configured to have different lengths or different volumes, or may be made of different materials.

[0045] Each of the two permeable members 60 and 61 has a length less than half a turn in the winding direction inside the electrode body 14c. Each of the two permeable members 60 and 61 preferably has a length less than a quarter turn in the winding direction inside the electrode body 14c, as shown in FIG. 6.

[0046] Each of the two permeable members 60 and 61 is arranged so as to intersect at least one semi - straight line (broken line U extending from the battery center O in FIG. 6 toward the permeable members 60 and 61) extending in the radial direction of the battery in the cross - section of the electrode body 14c.

[0047] According to the above configuration, by appropriately setting the arrangement positions and dimensions of each of the permeable members 60 and 61, the roundness of the electrode body 14c can be improved. In the configurations of FIGS. 6 and 7, the case where there are two permeable members 60 and 61 has been described, but three or more permeable members may be arranged in the electrode body.

[0048] Next, a basic experiment using a specific sheet - like test piece will be described to confirm an appropriate configuration for the permeable members 50, 60, and 61 that can be used in each of the above examples. The test piece used was a test piece 1 obtained by cutting a part of the non - woven fabric, which is the permeable member of the embodiment, and a test piece 2 obtained by cutting a part of the separator constituting the electrode body so as to have the same area as the test piece 1. For the test piece 1, a non - woven fabric made of polypropylene with a thickness of 0.22 mm was used. For the test piece 2, a microporous membrane made of polyethylene with a thickness of 13.5 μm was used.

[0049] Using the above-mentioned test specimens 1 and 2, an electrolyte absorption rate test was conducted as shown in Figure 4. This time, ethanol was used instead of the electrolyte 53. Test specimens 1 and 2, each 250 mm long and 25 mm wide, were held vertically in a container 52 containing ethanol, with the lower ends of each specimen submerged in the ethanol by 5 mm. The height to which the ethanol rose due to capillary action was measured after 10 minutes. In test specimen 2, the ethanol rose to a height of 60 mm, while in test specimen 1, the ethanol rose to a height of 840 mm. It can be inferred that the relative relationship of the electrolyte rise heights for test specimens 1 and 2 remains unchanged even when an electrolyte is used instead of ethanol. Therefore, it was confirmed that the nonwoven fabric corresponding to test specimen 1 is appropriate to be used as a permeable member with higher permeability to the electrolyte than a separator.

[0050] This disclosure is further illustrated by the following embodiments. Configuration 1: A cylindrical battery comprising an electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound via a separator, and a bottomed cylindrical outer container housing the electrode body and electrolyte, wherein the negative electrode has a negative electrode tab connected to an intermediate circumference between the innermost circumference and the outermost circumference, the portion of the negative electrode tab leading outward from the electrode body is connected to the bottom of the outer container, at least one permeable member having higher permeability to the electrolyte than the separator is disposed in the positive-negative electrode opposing portion where the positive electrode and the negative electrode face each other via the separator, and when R1 is the ratio of the total volume of the permeable member to the area in the inner circumference region on the winding side of the position of the inner surface of the negative electrode winding in the portion of the positive-negative electrode opposing portion to which the negative electrode tab is connected, and R2 is the ratio of the total volume of the permeable member to the area in the outer circumference region of the positive-negative electrode opposing portion excluding the inner circumference region, R1 and R2 satisfy R1 / (R1+R2)>0.5. Configuration 2: The cylindrical battery according to Configuration 1, wherein R1 and R2 satisfy R1 / (R1+R2)=1. Configuration 3: The cylindrical battery according to Configuration 1 or Configuration 2, wherein a plurality of the permeable members are arranged in the inner circumferential region, each of the plurality of the permeable members has a length of less than half a circumference in the winding direction, and each of the plurality of the permeable members is arranged to intersect with at least one half-line extending in the radial direction of the battery in the cross-section of the electrode body. Configuration 4: The cylindrical battery according to any one of Configurations 1 to 3, wherein the permeable member is a nonwoven fabric.

[0051] 10 Cylindrical battery, 11 Positive electrode, 11a Positive electrode core, 11b Positive electrode mixture layer, 11c1, 11c2 Exposed part, 11d Exposed part, 12 Negative electrode, 12a Negative electrode core, 12b Negative electrode mixture layer, 12c1, 12c2, 12d Exposed part, 13 Separator, 14 Electrode body, 14a Hollow part, 14b, 14c Electrode body, 15 Outer can, 16 Outer can, 17 Sealing body, 18 Lower insulating plate, 20 Positive electrode tab, 21 Negative electrode tab, 22 Grooved part, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating plate, 26 Upper valve body, 27 Sealing plate, 27a Ventilation hole, 28 Gasket, 29 Shoulder part, 31 Bottom part, 32 Cylindrical part, 40 Insulating tape, 41 Insulating tape, 50, 60, 61 Penetrating material, 52 Container, 53 Electrolyte, 54 Test piece, 70 Positive electrode, 71 Upper insulating plate.

Claims

1. A cylindrical battery comprising: an electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound via a separator; and a bottomed cylindrical outer container housing the electrode body and an electrolyte, wherein the negative electrode has a negative electrode tab connected to an intermediate circumference between the innermost circumference and the outermost circumference, the portion of the negative electrode tab leading outward from the electrode body is connected to the bottom of the outer container, at least one permeable member having higher permeability to the electrolyte than the separator is disposed in the positive-negative electrode opposing portion where the positive electrode and the negative electrode face each other via the separator, and when R1 is the ratio of the total volume of the permeable member to the area in the inner circumference region of the positive-negative electrode opposing portion where the negative electrode tab is connected, on the winding side from the position of the inner surface of the negative electrode, and R2 is the ratio of the total volume of the permeable member to the area in the outer circumference region of the positive-negative electrode opposing portion excluding the inner circumference region, R1 and R2 satisfy R1 / (R1+R2)>0.

5.

2. The cylindrical battery according to claim 1, wherein R1 and R2 satisfy R1 / (R1+R2)=1.

3. The cylindrical battery according to claim 1, wherein a plurality of the permeable members are arranged in the inner circumferential region, each of the plurality of permeable members has a length of less than half a circumference in the winding direction, and each of the plurality of permeable members is arranged to intersect with at least one half-line extending in the radial direction of the battery in the cross-section of the electrode body.

4. The cylindrical battery according to claim 1, wherein the permeable member is a nonwoven fabric.

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