Cylindrical secondary battery

Abstract

A battery (10) includes a wound electrode body (14), a nonaqueous electrolyte, and a bottomed cylindrical outer can. A discharge capacity per 1.0 g of a negative-electrode mixture layer (52) is 0.50 Ah or more. A negative electrode (12) includes a both-side mixture disposition part (60) in which the negative-electrode mixture layer (52) is disposed on both a winding inner surface and a winding outer surface of a negative-electrode current collector (51). The negative electrode (12) has a positive-electrode facing part (65) in which both a winding inner side and a winding outer side of the both-side mixture disposition part (60) face a positive electrode in a radial direction. When a total length in a negative-electrode longitudinal direction in the positive-electrode facing part (65) is assumed to be x, an average aw1 of the length a negative-electrode width direction of the negative-electrode mixture layer (52) from a winding-start end to x / 4 in the positive-electrode facing part (65) is set to 1.0025 times or more and less than 1.0100 times of an average aw2 of a length in the negative-electrode width direction of the negative-electrode mixture layer (52) from a winding-end end of the positive-electrode facing part (65) to x / 4.

Description

Cylindrical secondary battery

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

[0002] A conventional cylindrical secondary battery is described in Patent Document 1. This cylindrical secondary battery includes an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, a bottomed cylindrical outer can that houses the electrode assembly, and a sealing body that is crimped and fixed to the opening of the outer can via a gasket. One end of a positive electrode lead is joined to a middle portion of the positive electrode in the winding direction, and the other end of the positive electrode lead is joined to the inner surface of the sealing body. Furthermore, one end of a negative electrode lead is joined to the end of the winding end of the negative electrode, and the other end of the negative electrode lead is joined to the inner bottom surface of the outer can.

[0003] Re-table No. 2019-044770

[0004] In cylindrical secondary batteries, radial stress on the electrode assembly increases as the negative electrode expands during charging. Therefore, the electrode, which is subjected to an inward force due to the radial stress on the inner side of the electrode assembly around the hollow portion, may bend toward the hollow portion, which may result in damage to the separator. Therefore, an object of the present disclosure is to provide a cylindrical secondary battery that can suppress bending of the electrode on the inner side of the electrode assembly.

[0005] In order to solve the above problems, a cylindrical secondary battery according to the present disclosure includes an electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween, a non-aqueous electrolyte, and a bottomed cylindrical outer can that accommodates the electrode assembly and the non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, the negative electrode has a negative electrode current collector and a negative electrode mixture layer disposed on the negative electrode current collector, and the discharge capacity per 1.0 g of the negative electrode mixture layer is 0.50 Ah or more, and the negative electrode has a winding inner surface of the negative electrode current collector and a winding inner surface of the negative electrode current collector. The negative electrode includes a double-sided mixture arrangement portion in which a negative electrode mixture layer is arranged on both outer surfaces, and the negative electrode has positive electrode facing portions on both the inside and outside of the double-sided mixture arrangement portion that face the positive electrode in the radial direction, and when the total length of the positive electrode facing portion in the negative electrode longitudinal direction is x, the average length aw1 of the negative electrode mixture layer in the negative electrode width direction from the winding start end of the positive electrode facing portion to x / 4 is 1.0025 to 1.0100 times the average length aw2 of the negative electrode mixture layer in the negative electrode width direction from the winding end of the positive electrode facing portion to x / 4. Note that the above radial direction is the radial direction of the cylindrical secondary battery and the radial direction of the outer can.

[0006] According to the cylindrical secondary battery according to the present disclosure, bending of the electrodes on the inside of the wound electrode body can be suppressed.

[0007] FIG. 1 is an axial cross-sectional view of a cylindrical cylindrical secondary battery according to an embodiment of the present disclosure. FIG. 2 is a perspective view of an electrode body of a cylindrical secondary battery. FIG. 3 is a schematic diagram showing an example of the structure of a negative electrode mixture layer. FIG. 4 is a schematic top view of the inner side of the electrode body as viewed from above in the axial direction. FIG. 5 is a diagram showing the relationship between strain and stress when a tensile test is performed on an example negative electrode current collector. FIG. 6 is a top view showing the position of the inner side of the negative electrode and the position of the outer side of the negative electrode as viewed from above in the axial direction. FIG. 7 is a schematic half cross-sectional view of the periphery of the electrode body in the axial direction of a battery after repeated charging and discharging of the battery, showing a state in which the inner side of the negative electrode has elongated. FIG. 8 is a diagram showing an example of the relationship between the radial position of an outer can and the width of the negative electrode. FIG. 9 is a diagram explaining the bending angle of the electrode.

[0008] An embodiment of a cylindrical secondary battery according to the present disclosure will be described in detail below with reference to the drawings. The cylindrical secondary battery according to the present disclosure may be a battery using an aqueous electrolyte or a battery using a nonaqueous electrolyte. Hereinafter, a cylindrical lithium-ion secondary battery using a nonaqueous electrolyte will be described as an example of a cylindrical secondary battery 10 according to one embodiment, but the cylindrical secondary battery according to the present disclosure is not limited to this. It is anticipated from the beginning that new embodiments may be constructed by appropriately combining the features of the embodiments and variations described below. In the following embodiments, identical components are designated by the same reference numerals in the drawings, and redundant description will be omitted. Furthermore, multiple drawings include schematic views, and the dimensional ratios of the length, width, height, etc. of each component between different drawings do not necessarily match. Furthermore, in this specification, the side of the sealing body 17 in the axial direction (height direction) of the cylindrical cylindrical secondary battery 10 will be referred to as "upper," and the side of the bottom 55 of the outer can 16 in the axial direction will be referred to as "lower." Among the components described below, components not recited in the independent claims representing the highest concepts are optional and not essential. Furthermore, the present disclosure is not limited to the following embodiments and their modifications, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents. Furthermore, if a cylindrical secondary battery satisfies the requirements set forth in the claims of the present application at any time from the time of manufacture to the time of disposal (including the time from disposal to the time of disappearance), the cylindrical secondary battery will constitute an infringement of the patent. For example, if a cylindrical secondary battery satisfies the conditions set forth in the claims of the present application at the time of shipment, the cylindrical secondary battery will constitute an infringement of the patent, and if a cylindrical secondary battery satisfies the conditions set forth in the claims of the present application during use after shipment, the cylindrical secondary battery will constitute an infringement of the patent.

[0009] Fig. 1 is an axial cross-sectional view of a cylindrical secondary battery 10 according to an embodiment of the present disclosure, and Fig. 2 is a perspective view of an electrode assembly 14 of the cylindrical secondary battery 10. As shown in Fig. 1, the cylindrical secondary battery (hereinafter simply referred to as battery) 10 includes a wound electrode assembly 14, a non-aqueous electrolyte (not shown), a cylindrical metal outer can 16 with a bottom that houses the electrode assembly 14 and the non-aqueous electrolyte, and a sealing body 17 that closes the opening of the outer can 16. As shown in Fig. 2, the electrode assembly 14 has a wound structure in which an elongated positive electrode 11 and an elongated negative electrode 12 are wound with two elongated separators 13 interposed therebetween.

[0010] The negative electrode 12 is formed to have dimensions slightly larger than the positive electrode 11 to prevent lithium precipitation. That is, the negative electrode 12 is formed to be longer in the longitudinal direction and width direction (short direction) than the positive electrode 11. Furthermore, the two separators 13 are formed to have dimensions at least slightly larger than the positive electrode 11 and are arranged to sandwich the positive electrode 11, for example. The negative electrode 12 may form the winding start end of the electrode assembly 14. However, generally, the separator 13 extends beyond the winding start end of the negative electrode 12, and the winding start end of the separator 13 becomes the winding start end of the electrode assembly 14.

[0011] The non-aqueous electrolyte has ion conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte. The liquid electrolyte (electrolytic solution) includes 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] Examples of the solid electrolyte include solid or gel polymer electrolytes and inorganic solid electrolytes. 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. Examples of the matrix polymer include a polymer material that absorbs the non-aqueous solvent and gels. Examples of the polymer material include fluororesin, acrylic resin, and polyether resin. Examples of the inorganic solid electrolyte include materials known in all-solid-state lithium ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.).

[0013] The positive electrode 11 has a positive electrode current collector 41 (see FIG. 4 ) and positive electrode mixture layers 42 (see FIG. 4 ) disposed on both sides of the positive electrode current collector 41. The positive electrode current collector 41 can be made of a metal foil, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on its surface. The positive electrode mixture layer 42 contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and the like onto the positive electrode current collector 41, drying the coating, and then compressing it to form the positive electrode mixture layers 42 on both sides of the positive electrode current collector 41.

[0014] The positive electrode active material is composed mainly of a lithium-containing composite oxide. Examples of metal elements contained in the lithium-containing composite oxide (lithium-containing metal composite oxide) include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. An example of a preferred lithium-containing composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al. The lithium-containing composite oxide may have a spinel structure or an olivine structure. However, it is preferable that the lithium-containing composite oxide have a layered rock salt structure, as this facilitates the production of a positive electrode with a large discharge capacity.

[0015] Examples of the conductive agent contained in the positive electrode mixture layer 42 include carbon black such as acetylene black and ketjen black, and carbon materials such as graphite. Examples of the binder contained in the positive electrode mixture layer 42 include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resin, acrylic resin, and polyolefin resin. These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), and the like.

[0016] The negative electrode 12 has a negative electrode current collector 51 (see FIG. 4 ) and a negative electrode mixture layer 52 (see FIG. 4 ) disposed on both sides of the negative electrode current collector 51. The negative electrode current collector 51 can be made of a metal foil, such as copper or a copper alloy, that is stable within the potential range of the negative electrode 12, or a film having such a metal disposed on its surface. The negative electrode mixture layer 52 contains a negative electrode active material and a binder. The negative electrode 12 can be produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the negative electrode current collector 51, drying the coating, and then compressing it to form the negative electrode mixture layer 52 on both sides of the negative electrode current collector 51.

[0017] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Preferred carbon materials are graphites such as natural graphite, such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite, such as lump artificial graphite and graphitized mesophase carbon microbeads. The discharge capacity per 1.0 g of the negative electrode mixture layer 52 is 0.50 Ah or more. To effectively increase the discharge capacity per 1.0 g of the negative electrode mixture layer, the negative electrode mixture layer 52 preferably contains a silicon-containing material containing silicon (Si) as the negative electrode active material.

[0018] FIG. 3 is a schematic diagram illustrating an example of the structure of the negative electrode mixture layer 52. As shown in FIG. 3, the negative electrode mixture layer 52 preferably includes graphite 60 and a silicon-containing material 70. The silicon-containing material 70 includes, for example, an ion-conducting phase 71 and an Si phase 72 dispersed in the ion-conducting phase 71. Because this increases the discharge capacity and facilitates high output of the battery 10, the weight ratio of the Si phase 72 in the silicon-containing material 70 is preferably 30% or more. Furthermore, since this reduces the volume change of the negative electrode mixture layer 52 during charging and discharging, bending of the electrodes 11 and 12 on the inner side of the electrode body winding, which will be described in detail below, can be effectively suppressed. The ion-conducting phase 71 may be composed of, for example, an amorphous carbon phase, a lithium silicate phase, a lithium aluminate phase, a silicon oxide phase, a titanium oxide phase, a zirconium oxide phase, or the like. However, in order to suppress the volume change of the negative electrode active material during charge and discharge and to increase the charge and discharge efficiency, it is preferable that the ion-conducting phase 71 contains an amorphous carbon phase.

[0019] From the viewpoint of the weight ratio of elemental silicon to the anode mixture layer 52, the weight ratio of elemental silicon to the anode mixture layer 52 is preferably 7 mass% or more, and more preferably 12 mass% or more, because this increases the discharge capacity and results in high output for the battery 10. Furthermore, since the volume change of the anode mixture layer 52 during charging and discharging can be reduced, bending of the electrodes 11, 12 on the inside of the electrode body can be effectively suppressed. Therefore, the weight ratio of elemental silicon to the anode mixture layer 52 is preferably less than 50 mass%. When the anode mixture layer 52 contains a silicon-containing material 70, the mass of the elemental silicon may be approximately the same as the mass of the Si phase 72. That is, the weight ratio of the Si phase 72 to the anode mixture layer 52 may be 7 mass% or more and less than 50 mass%. The anode active material may be a metal other than Si that alloys with lithium, an alloy containing such a metal, a compound containing such a metal, or the like.

[0020] As in the case of the positive electrode 11, fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like may be used as the binder contained in the negative electrode mixture layer 52, but styrene-butadiene rubber (SBR) or a modified product thereof is preferably used. In addition to SBR or the like, the negative electrode mixture layer 52 may also contain, for example, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

[0021] 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. Preferred materials for the separator 13 include polyolefin resins such as polyethylene and polypropylene, and cellulose. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer or the like may be disposed on the surface of the separator 13.

[0022] As shown in FIG. 1 , a positive electrode lead 20 is joined to the positive electrode 11, and a negative electrode lead 21 is joined to the end of the negative electrode 12 on the longitudinal winding end side. The battery 10 has an insulating plate 18 above the electrode body 14 and an insulating plate 19 below the electrode body 14. 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 outside the insulating plate 19 and extends toward the bottom 55 of the outer can 16. The positive electrode lead 20 is connected to the underside of a terminal plate 23 of the sealing body 17 by welding or the like. A terminal cap 27 constituting the top plate of the sealing body 17 is electrically connected to the terminal plate 23, and the terminal cap 27 serves as a positive electrode terminal. The negative electrode lead 21 is connected to the inner surface of the bottom 55 of the metal outer can 16 by welding or the like, and the outer can 16 serves as a negative electrode terminal.

[0023] The positive electrode 11 has a positive electrode current collector exposed portion where the positive electrode current collector 41 is exposed in an intermediate portion such as the center portion in the longitudinal direction of the positive electrode, and the positive electrode lead 20 is joined and electrically connected to the positive electrode current collector exposed portion by ultrasonic welding or the like. The negative electrode 12 has a negative electrode current collector exposed portion where the negative electrode current collector 51 is exposed at the end portion on the winding end side in the winding direction, and the negative electrode lead 21 is joined and electrically connected to the negative electrode current collector exposed portion by ultrasonic welding or the like.

[0024] The battery may have a plurality of positive electrode leads, and the positive electrode may have a plurality of exposed positive electrode current collector portions spaced apart in the longitudinal direction of the positive electrode and to which one end of the positive electrode leads is joined. The battery may also include current collector plates to which the other end of each positive electrode lead is joined. The current collector plates may be electrically connected to a terminal cap.

[0025] Alternatively, the strip-shaped positive electrode may have a strip-shaped positive electrode current collector exposed portion at one end of the width direction of the positive electrode, extending in the longitudinal direction of the positive electrode from one end to the other end in the longitudinal direction of the positive electrode. Furthermore, a wide range of the strip-shaped positive electrode current collector exposed portion in the longitudinal direction of the positive electrode may be joined to the current collector plate by laser welding or resistance welding. The current collector plate to which the positive electrode current collector exposed portion is joined may then be electrically connected to a terminal cap. By adopting these variations, the current collection path on the positive electrode side can be shortened, thereby reducing electrical resistance.

[0026] The negative electrode may have a first negative electrode current collector exposed portion where the negative electrode current collector is exposed at an end portion on the winding start side in the negative electrode longitudinal direction, and a second negative electrode current collector exposed portion where the negative electrode current collector is exposed at an end portion on the winding end side in the negative electrode longitudinal direction. The second negative electrode current collector exposed portion may have an outermost peripheral surface portion included in the outermost peripheral surface of the electrode assembly. One end of the negative electrode lead may be joined to the first negative electrode current collector exposed portion, and the other end of the negative electrode lead may be joined to the inner bottom surface of the outer can. The outermost peripheral surface portion may contact the inner circumferential surface of the outer can.

[0027] Alternatively, two negative electrode leads may be joined to the electrode body, one end of one negative electrode lead electrically connected to the end of the negative electrode current collector at the winding start side in the longitudinal direction of the negative electrode, and one end of the other negative electrode lead electrically connected to the end of the negative electrode current collector at the winding end side in the longitudinal direction of the negative electrode, and the other end of each negative electrode lead may be electrically connected to the bottom of the outer can.

[0028] Alternatively, the strip-shaped negative electrode may have a strip-shaped negative electrode current collector exposed portion at one end of the negative electrode width direction, extending in the negative electrode longitudinal direction from one end to the other end in the negative electrode longitudinal direction. Furthermore, a wide range of the strip-shaped negative electrode current collector exposed portion in the negative electrode longitudinal direction may be joined to the current collector plate by laser welding or resistance welding. Furthermore, the current collector plate may be joined to the bottom of the outer can by laser welding or the like, thereby being electrically connected. By adopting these variations, the current collection path on the negative electrode side can be shortened, thereby reducing electrical resistance.

[0029] As shown in Fig. 1 , the battery 10 further includes a resin gasket 28 disposed between the exterior can 16 and the sealing body 17. The sealing body 17 is fixed to the opening side of the exterior can 16 by crimping via the gasket 28, thereby sealing the internal space of the battery 10. The gasket 28 is sandwiched between the exterior can 16 and the sealing body 17, and insulates the sealing body 17 from the exterior can 16. The gasket 28 serves as a sealing material to maintain airtightness inside the battery and as an insulating material to insulate the exterior can 16 and the sealing body 17.

[0030] The outer can 16 accommodates the electrode assembly 14 and the non-aqueous electrolyte. The outer can 16 has a cylindrical portion 30 and a bottom portion 55. The cylindrical portion 30 includes a shoulder portion 38 and a grooved portion 34. The grooved portion 34 can be formed, for example, by spinning a portion of the side surface of the outer can 16 radially inward to form an annular recess radially inward. The shoulder portion 38 is formed by bending the upper end of the outer can 16 inward toward the peripheral edge portion 48 of the sealing body 17 when the sealing body 17 is crimped to the outer can 16.

[0031] Sealing body 17 has a structure in which, in order from the electrode body 14 side, terminal plate 23, lower valve body 24, insulating member 25, upper valve body 26, and terminal cap 27 are stacked. Each member constituting sealing body 17 has, for example, a disk or ring shape, and each member except for insulating member 25 is electrically connected to each other. Terminal plate 23 has at least one through-hole 23a. Furthermore, lower valve body 24 and upper valve body 26 are connected at their respective centers, with insulating member 25 interposed between their respective peripheral edges.

[0032] When the battery 10 generates abnormal heat and the internal pressure of the battery 10 rises, the lower valve body 24 deforms and breaks, pushing the upper valve body 26 toward the terminal cap 27, cutting off 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 breaks and gas is released from the through-hole 27a of the terminal cap 27. This gas release prevents the internal pressure of the battery 10 from rising excessively, which could cause the battery 10 to explode, thereby increasing the safety of the battery 10.

[0033] In the above description, the sealing body 17 has a laminated structure including two rupture plates (lower valve body 24 and upper valve body 26) and a convex terminal cap 27 that covers the rupture plate. However, the sealing body may be composed of only a rupture plate, or may have a structure in which a terminal plate, an insulating plate, and a rupture plate are laminated in this order from the electrode body side. Alternatively, the sealing body may not have a rupture plate, and the bottom of the outer can may have a thin, easily breakable portion that breaks when the battery generates abnormal heat. In this case, the sealing body may include a current collector plate and a terminal cap having an outer periphery joined to the outer periphery of the current collector.

[0034] Fig. 4 is a schematic top view of the inner side of the electrode assembly 14 as viewed from above in the axial direction. Note that the separator 13 is not shown in Fig. 4. As shown in Fig. 4, the negative electrode 12 includes a double-side mixture arrangement portion 60 in which a negative electrode mixture layer 52 is arranged on both the inner and outer sides of the negative electrode current collector 51. Furthermore, the negative electrode 12 has a positive electrode facing portion 65 in which both the inner and outer sides of the double-side mixture arrangement portion 60 face the positive electrode 11 in the radial direction (the radial direction of the outer can 16).

[0035] When the total length of the positive electrode opposing portion 65 in the negative electrode longitudinal direction is x, the average aw1 of the length in the negative electrode width direction of the negative electrode mixture layer 52 from the winding start end of the positive electrode opposing portion 65 to x / 4 is 1.0025 to less than 1.0100 times the average aw2 of the length in the negative electrode width direction of the negative electrode mixture layer 52 from the winding end of the positive electrode opposing portion 65 to x / 4.

[0036] Next, an example of a method for producing an electrode assembly 14 in which aw1 is 1.0025 to less than 1.0100 times aw2 will be described. A positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc. is uniformly (evenly) applied to a strip-shaped positive electrode current collector 41 in the same area in the positive electrode width direction, the coating is dried, and then compressed to form positive electrode mixture layers 42 on both sides of the positive electrode current collector 41, thereby producing a positive electrode 11. Also, a negative electrode mixture slurry containing a negative electrode active material, a binder, etc. is uniformly (evenly) applied to a strip-shaped negative electrode current collector 51 in the same area in the negative electrode width direction, the coating is dried, and then compressed to form negative electrode mixture layers 52 on both sides of the negative electrode current collector 51, thereby producing a negative electrode 12.

[0037] The negative electrode current collector 51 is a negative electrode current collector that is softer and more stretchable than a typical negative electrode current collector. Specifically, the negative electrode current collector 51 has a 1% yield strength of 100 MPa to 400 MPa, which is lower than the 1% yield strength of a typical negative electrode current collector. The negative electrode current collector 51 also has an elongation rate in a tensile test of 3% to 20%, which is more stretchable than a typical negative electrode current collector. When the negative electrode current collector 51 is made of copper foil, if the average crystal grain size of the copper in the copper foil is large, the negative electrode current collector 51 is more likely to elongate. By making the negative electrode current collector 51 of copper foil with an average crystal grain size of 2 μm to 20 μm, the negative electrode current collector 51 having the above-described physical properties can be easily produced. Although this is well known and will not be described in detail, when the negative electrode current collector 51 is made of copper foil, the average crystal grain size of the copper in the copper foil can be adjusted with high precision by adjusting the heat treatment temperature of the negative electrode current collector or by adjusting the impurities mixed into the constituent materials of the negative electrode current collector.

[0038] The negative electrode current collector 51 does not have to be made of copper foil having an average crystal grain size of 2 μm or more and 20 μm or less. Any known material may be used as the material for the negative electrode current collector. By adjusting the thickness of the negative electrode current collector 51, the negative electrode current collector 51 having the above-mentioned physical properties can be easily produced. The negative electrode mixture layer 52 is made to contain a silicon-containing material that increases the negative electrode expansion during charging.

[0039] The silicon-containing material contains an ion-conducting phase and a Si phase dispersed in the ion-conducting phase, and the weight ratio of the Si phase in the silicon-containing material is set to 30% or more and 60% or less. The weight ratio of silicon element in the negative electrode mixture layer is set to 12% by mass or more and less than 50% by mass. The negative electrode 12 is set so that the peel strength of the negative electrode mixture layer 52 is 9 N / m or more and 80 N / m or less. The peel strength of the negative electrode mixture layer 52 can be adjusted with high precision by adjusting the amount of binder mixed in the negative electrode mixture layer 52.

[0040] The 1% yield strength of the negative electrode current collector is the yield strength (1%) measured according to JIS Z 2241, a tensile testing method for metallic materials. Figure 5 shows the relationship between strain and stress when a tensile test is performed on an example negative electrode current collector. The 1% yield strength is the stress value at a strain of 1%. More specifically, the 1% yield strength is calculated by drawing a line parallel to the elastic modulus from the 1% point on the strain axis to find the intersection with the stress-strain curve, and then calculating the stress value at that intersection. The elastic modulus is defined as the slope of stress versus strain in the region where strain and stress are proportional. The 1% yield strength of the negative electrode current collector can be adjusted with high precision, for example, by adjusting the crystal grain size of the material of the negative electrode current collector. The elongation of the negative electrode current collector during the tensile test is the strain value at which the negative electrode current collector breaks in Figure 5.

[0041] The peel strength of the negative electrode mixture layer was calculated in accordance with the T-peel method of JIS K6854 (test method for peel adhesion strength). Specifically, a 1 cm x 15 cm piece of negative electrode was cut, and 15 cm of 1 cm-wide adhesive tape was prepared. The electrode piece and adhesive tape were firmly bonded together, with their ends aligned, for a length of 10 cm. A protective paper strip was attached to the remaining adhesive tape to prevent the adhesive from being exposed. The portion of the electrode piece without the adhesive tape and the paper strip were each fixed to the sample holder of a tensile tester and pulled at a rate of 2.5 cm per second. The average tension was taken as the peel strength. Measurements were performed while maintaining the portion of the electrode piece bonded to the adhesive tape at a constant 90° angle to the pulling direction.

[0042] A temporary electrode body is produced by winding the fabricated positive electrode 11 and negative electrode 12 with two separators 13 interposed therebetween. Then, a cylindrical secondary battery is fabricated using the fabricated temporary electrode body by the method described with reference to FIGS. 1 to 4 . The fabricated cylindrical secondary battery is charged and discharged before shipping. This charging and discharging elongates the inner side of the negative electrode winding in the temporary electrode body in the negative electrode width direction, producing an electrode body 14 in which aw1 is 1.0025 to less than 1.0100 times aw2. Alternatively, the inner side of the negative electrode winding elongates in the negative electrode width direction based on the use of the battery after shipping, producing an electrode body 14 in which aw1 is 1.0025 to less than 1.0100 times aw2.

[0043] FIG. 6 is a top view of the electrode assembly 14, showing the positions of the inner winding portion 12a and the outer winding portion 12b of the negative electrode, as viewed from above in the axial direction. FIG. 7 is a schematic half-sectional view in the axial direction of the periphery of the electrode assembly in a battery after repeated charge and discharge, showing the state in which the inner winding portion 12a of the negative electrode has expanded. In FIG. 7 , the gray elongated region represents the positive electrode 11, and the white elongated region represents the negative electrode 12. The separator is not shown in FIG. 7 . As shown in FIG. 7 , by performing charge and discharge one or more times using the above-described negative electrode current collector and negative electrode mixture layer as the negative electrode current collector 51 and negative electrode mixture layer 52, the inner winding portion of the negative electrode expands in the negative electrode width direction.

[0044] The expansion of the negative electrode in the width direction on the inner side of the winding due to charging and discharging is presumed to occur according to the mechanism described below. Expansion and contraction during discharge occurs in the negative electrode 12. The negative electrode 12 expands in the radial and axial directions during charging. In this context, the inner side of the winding of the electrode body 14 is close to the hollow portion of the electrode body 14, so the radial stress during expansion of the negative electrode tends to be small, and the expansion of the negative electrode tends to be large. As a result, it is presumed that the negative electrode 12 tends to expand in the width direction on the inner side of the winding.

[0045] Next, the effects of the battery 10 of the present disclosure will be described. During charging, radial stress on the electrode body increases as the negative electrode expands. Therefore, in conventional cylindrical secondary batteries, the electrode, which is subjected to an inward force due to the radial stress on the inner side of the wound electrode around the hollow portion of the electrode body, may bend toward the hollow portion, which may result in damage to the separator.

[0046] In contrast, in the battery 10 of the present disclosure, the inner side of the negative electrode winding of the electrode assembly 14 expands during charging and discharging. Therefore, the mass of the negative electrode mixture layer per unit surface area of ​​the negative electrode current collector on the inner side of the negative electrode winding is reduced, resulting in less radial expansion of the negative electrode on the inner side of the negative electrode winding. Therefore, the radial stress caused by the expansion of the negative electrode on the inner side of the electrode assembly winding is reduced, effectively suppressing or preventing bending of the electrode toward the hollow portion. As a result, damage to the separator 13 can be effectively suppressed, enabling the production of a highly reliable battery 10.

[0047] Example 1 A battery having a value of [(aw1 / aw2)-1] x 100 of 0.28%, a value of aw1-aw2 of 0.16 mm, a discharge capacity per 1 g of negative electrode mixture of 0.52 Ah / g, a 1% proof stress of the negative electrode current collector of 350 MPa, and a negative electrode current collector elongation of 5% was designated as the battery of Example 1. Note that the values ​​of [(aw1 / aw2)-1] x 100 and aw1-aw2 for the battery of Example 1, as well as the batteries of Examples 2-4 and Comparative Examples 1-5 below, were determined after 10 cycles of charge-discharge cycles were performed in an air-cooled environment at 45°C, in which the battery voltage reached 4.2 V at a constant current of 0.3 C, followed by constant-voltage charging at a voltage of 4.2 V until the current value reached 0.02 C, and then constant-current discharging at a constant current of 0.5 C until the battery voltage reached 2.85 V.

[0048] 8 is a diagram showing an example of the relationship between the radial position of the outer can and the negative electrode width. As shown in FIG. 8, in Examples 1-4 and Comparative Examples 1-5, aw1 and aw2 were each approximately calculated by averaging the negative electrode width direction lengths of the negative electrode mixture layer at multiple representative points (six representative points in this example) that included both ends of the negative electrode longitudinal direction range of the respective positive electrode facing portions and were arranged at equal intervals in the negative electrode longitudinal direction. The position of the negative electrode mixture layer in the negative electrode width direction is known. Therefore, the position of the negative electrode mixture layer can be determined if the position of the negative electrode is known.

[0049] The elongation of the negative electrode can be determined, for example, by a computed tomography (CT) image of the axial cross section of the electrode assembly, or by measurement after removing the negative electrode through destructive testing. In Examples 1-4 and Comparative Examples 1-5, the 1% proof stress and elongation of the negative electrode current collector were calculated by the above-mentioned methods.

[0050] Example 2 A battery in which the value of [(aw1 / aw2)-1]×100 was 0.35%, the value of aw1-aw2 was 0.20 mm, the discharge capacity per 1 g of negative electrode mixture was 0.52 Ah / g, the 1% yield strength of the negative electrode current collector was 200 MPa, and the elongation rate of the negative electrode current collector was 10% was designated as the battery of Example 2.

[0051] Example 3 A battery in which the value of [(aw1 / aw2)-1]×100 was 0.35%, the value of aw1-aw2 was 0.20 mm, the discharge capacity per 1 g of negative electrode mixture was 0.90 Ah / g, the 1% yield strength of the negative electrode current collector was 350 MPa, and the elongation rate of the negative electrode current collector was 5% was designated as the battery of Example 3.

[0052] Example 4 A battery in which the value of [(aw1 / aw2)-1]×100 was 0.50%, the value of aw1-aw2 was 0.29 mm, the discharge capacity per 1 g of negative electrode mixture was 0.90 Ah / g, the 1% yield strength of the negative electrode current collector was 200 MPa, and the elongation rate of the negative electrode current collector was 10% was designated as the battery of Example 4.

[0053] <Comparative Example 1> A battery in which the value of [(aw1 / aw2)-1] × 100 was 0.18%, the value of aw1-aw2 was 0.10 mm, the discharge capacity per 1 g of negative electrode mixture was 0.52 Ah / g, the 1% yield strength of the negative electrode current collector was 600 MPa, and the elongation rate of the negative electrode current collector was 2% was designated as the battery of Comparative Example 1.

[0054] <Comparative Example 2> A battery in which the value of [(aw1 / aw2)-1] × 100 was 0.22%, the value of aw1-aw2 was 0.13 mm, the discharge capacity per 1 g of negative electrode mixture was 0.90 Ah / g, the 1% yield strength of the negative electrode current collector was 600 MPa, and the elongation rate of the negative electrode current collector was 2% was designated as the battery of Comparative Example 2.

[0055] <Comparative Example 3> A battery in which the value of [(aw1 / aw2)-1] × 100 was 0.21%, the value of aw1-aw2 was 0.12 mm, the discharge capacity per 1 g of negative electrode mixture was 0.52 Ah / g, the 1% yield strength of the negative electrode current collector was 350 MPa, and the elongation rate of the negative electrode current collector was 5% was designated as the battery of Comparative Example 3.

[0056] <Comparative Example 4> A battery in which the value of [(aw1 / aw2)-1]×100 was 1.10%, the value of aw1-aw2 was 0.64 mm, the discharge capacity per 1 g of negative electrode mixture was 0.90 Ah / g, the 1% yield strength of the negative electrode current collector was 350 MPa, and the elongation rate of the negative electrode current collector was 5% was designated as the battery of Comparative Example 4.

[0057] <Comparative Example 5> A battery in which the value of [(aw1 / aw2)-1]×100 was 0.18%, the value of aw1-aw2 was 0.10 mm, the discharge capacity per 1 g of negative electrode mixture was 0.35 Ah / g, the 1% yield strength of the negative electrode current collector was 200 MPa, and the elongation rate of the negative electrode current collector was 10% was designated as the battery of Comparative Example 5.

[0058] (Electrode Plate Deformation Measurement Test) For each of the batteries of Examples 1-4 and Comparative Examples 1-5, in an air-cooled environment at 45°C, constant voltage charging was performed at a constant current of 0.3 C until the voltage reached 4.2 V, followed by constant voltage charging at a voltage of 4.2 V until the current value reached 0.02 C, and then constant current discharging at a constant current of 0.5 C until the battery voltage reached 2.85 V. This charge-discharge cycle was repeated 300 times. The bending angle of the electrode bent furthest toward the hollow portion of the electrode body on the inner side of the winding, indicated by θ in FIG. 9, was measured using CT images of a cross section parallel to the radial direction of the electrode body. A case in which θ was 170° or more was designated A, a case in which θ was greater than 150° and less than 170° was designated B, and a case in which θ was 150° or less was designated C.

[0059] (Foil Breakage Test) For each of the batteries of Examples 1-4 and Comparative Examples 1-5, a charge-discharge cycle was repeated 300 times in an air-cooled environment at 45°C, in which after the voltage reached 4.2 V at a constant current of 0.3 C, constant voltage charging was performed at a voltage of 4.2 V until the current value reached 0.02 C, and then constant current discharging was performed at a constant current of 0.5 C until the battery voltage reached 2.85 V. Thereafter, the presence or absence of foil breakage was confirmed based on CT images of the axial cross section of the electrode body.

[0060] (Capacity Measurement) The capacity of each of the batteries of Examples 1-5 and Comparative Examples 1 and 2 was measured. Specifically, after each battery was fabricated, it was charged at a constant current of 0.2 C at an ambient temperature of 25° C. until the battery voltage reached 2.5 V, and then it was charged at a constant voltage of 4.2 V until the current value reached 0.02 C. Thereafter, it was discharged at a constant current of 0.2 C until the battery voltage reached 2.5 V, and the capacity (discharge capacity) was measured. The capacity of each battery is shown as a relative value when the capacity of the battery of Example 1 is set to 100.

[0061]

[0062] The values ​​of the above-mentioned physical properties of each battery are shown in Table 1, and the test results are shown in Table 2. As shown in Tables 1 and 2, in the battery of Comparative Example 1-3 in which aw1 was less than 1.0025 of aw2, the electrode plate change was B or C, confirming that bending of the electrode on the inside of the electrode body winding was likely to occur.

[0063] In addition, in the battery of Comparative Example 5, in which the discharge capacity per 1 g of negative electrode mixture was less than 0.50 Ah, the electrode plate change was A and no bending of the electrode on the inside of the electrode body winding occurred, but the capacity was extremely small at 90, and it was confirmed that a high-performance battery could not be produced.

[0064] In the battery of Comparative Example 4, in which aw1 was 1.0100 times or more of aw2, the electrode on the inner side of the electrode body was excessively stretched, and foil breakage was observed in the negative electrode current collector.

[0065] In contrast, in the battery of Example 1-4 in which aw1 was 1.0025 to less than 1.0100 times aw2 and the discharge capacity per 1 g of negative electrode mixture was 0.50 Ah or more, no electrode bending occurred on the inside of the electrode body winding, no foil breakage occurred, and a high-capacity battery could be produced.

[0066] [Preferred configuration for use in the battery of the present disclosure] It is preferable that 0.15 mm < (aw1 - aw2) be satisfied, since this effectively reduces the stress on the inside of the electrode body winding when the negative electrode expands. Furthermore, if (aw1 - aw2) ≥ 0.50 mm, the axial length of the electrode body before charge and discharge must be reduced in consideration of the expansion of the negative electrode on the inside of the electrode body winding, making it difficult to increase the battery capacity. In other words, it is preferable that (aw1 - aw2) < 0.50 mm, since this makes it easier to increase the battery capacity.

[0067] Because this effectively reduces stress on the inside of the electrode assembly when the negative electrode expands, it is preferable that the average thickness at1 of the negative electrode mixture layer from the winding start end to x / 4 of the positive electrode facing portion 65 be less than 0.9975 times the average thickness at2 of the negative electrode mixture layer from the winding end to x / 4 of the positive electrode facing portion 65. Furthermore, because this prevents the negative electrode on the inside of the electrode assembly from excessively stretching, making it easier to increase the battery capacity, it is preferable that at1 be 0.9900 times or more at2.

[0068] Since this makes it easier to increase the capacity, it is preferable that the negative electrode mixture layer 52 contains a silicon-containing material. Furthermore, if the negative electrode mixture layer 52 contains a silicon-containing material, the expansion of the negative electrode mixture layer 52 during charging becomes large, and therefore, if the configuration of the present disclosure is not adopted, electrode deformation on the inside of the electrode body winding when the negative electrode expands is likely to occur. In other words, the effect of the present disclosure, which is the suppression effect of electrode deformation by reducing stress on the inside of the electrode body winding when the negative electrode expands, becomes exceptionally and significantly.

[0069] The weight ratio of the Si phase 72 in the silicon-containing material 70 is preferably 30% or more because this increases the discharge capacity and tends to increase the output of the battery 10. Furthermore, the weight ratio of the Si phase 72 in the silicon-containing material 70 is preferably 60% or less because this can reduce the volume change of the negative electrode mixture layer 52 during charging and discharging and effectively suppress bending of the electrodes 11, 12 on the inside of the electrode body winding.

[0070] The weight ratio of silicon element to the negative electrode mixture layer 52 is preferably 7% by mass or more, and more preferably 12% by mass or more, because this increases the discharge capacity and provides high output to the battery 10. Furthermore, the weight ratio of silicon element to the negative electrode mixture layer 52 is preferably less than 50% by mass, because this can reduce the volume change of the negative electrode mixture layer 52 during charging and discharging and effectively suppress bending of the electrodes 11, 12 on the inside of the electrode body winding.

[0071] The 1% yield strength of the negative electrode current collector is preferably 400 MPa or less, since this effectively reduces the stress on the inside of the electrode body winding when the negative electrode expands. Also, the 1% yield strength of the negative electrode current collector is preferably 100 MPa or more, since this prevents the negative electrode on the inside of the electrode body winding from excessively elongating, making it easier to increase the battery capacity.

[0072] The elongation percentage of the negative electrode current collector 51 during a tensile test is preferably 3% or more, since this effectively reduces the stress on the inside of the electrode body winding when the negative electrode expands. Furthermore, the elongation percentage of the negative electrode current collector 51 during a tensile test is preferably 20% or less, since this prevents the negative electrode on the inside of the electrode body winding from excessively elongating, making it easier to increase the battery capacity.

[0073] The negative electrode current collector 51 is preferably made of copper having an average crystal grain size of 2 μm or more, since this effectively reduces the stress on the inside of the electrode body winding when the negative electrode expands. Furthermore, the negative electrode current collector 51 is preferably made of copper having an average crystal grain size of 20 μm or less, since this prevents the negative electrode on the inside of the electrode body winding from excessively elongating, making it easier to increase the battery capacity.

[0074] The peel strength of the negative electrode 12 is preferably 9 N / m or more because this makes it difficult for the negative electrode mixture layer 52 to peel off from the negative electrode current collector 51 and allows the length of the negative electrode mixture layer 52 on the inside of the negative electrode winding in the negative electrode width direction to be reliably extended to a length that effectively reduces stress on the inside of the electrode winding. Furthermore, the peel strength of the negative electrode is preferably 80 N / m or less because this prevents the negative electrode mixture layer 52 from becoming excessively hard, making it easy to increase the capacity and reduce the electrical resistance.

[0075] [Modifications] The present disclosure is not limited to the above-described embodiment and modifications thereof, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents.

[0076] For example, in the above embodiment, the negative electrode current collector 51 is made of an easily stretchable material, and the negative electrode 12 is intentionally stretched in the negative electrode width direction on the inner side of the electrode body winding, thereby suppressing electrode deformation on the inner side of the electrode body winding. However, in the present disclosure, the negative electrode current collector may be made of any known material. Even if the negative electrode current collector is made of a hard material and the negative electrode does not stretch or is difficult to stretch in the negative electrode width direction on the inner side of the electrode body winding, a battery of the present disclosure can be fabricated by applying the negative electrode mixture slurry to the inner side of the negative electrode current collector winding more thinly than to the outer side of the winding and more widely in the negative electrode width direction during negative electrode fabrication.

[0077] The cylindrical secondary battery of the present disclosure may also have the following configurations: Configuration 1: An electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween, a non-aqueous electrolyte, and a bottomed cylindrical outer can that accommodates the electrode assembly and the non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, the negative electrode has a negative electrode current collector and a negative electrode mixture layer disposed on the negative electrode current collector, and the discharge capacity per 1.0 g of the negative electrode mixture layer is 0.50 Ah or more, and the negative electrode has the negative electrode mixture layer disposed on both the inner and outer winding surfaces of the negative electrode current collector. the negative electrode has positive electrode facing portions on both the inner and outer sides of the positive electrode facing portion that face the positive electrode in the radial direction, and when the total length of the positive electrode facing portion in the negative electrode longitudinal direction is x, an average length aw1 of the negative electrode mixture layer in the negative electrode width direction from the winding start end of the positive electrode facing portion to x / 4 of the length is 1.0025 to 1.0100 times an average length aw2 of the negative electrode mixture layer in the negative electrode width direction from the winding end of the positive electrode facing portion to x / 4 of the length. Configuration 3: The cylindrical secondary battery according to Configuration 1 or 2, wherein the average thickness at1 of the negative electrode mixture layer from the winding start end to x / 4 of the positive electrode facing portion is 0.9900 to less than 0.9975 times the average thickness at2 of the negative electrode mixture layer from the winding end to x / 4 of the positive electrode facing portion. Configuration 4: The cylindrical secondary battery according to any one of Configurations 1 to 3, wherein the negative electrode mixture layer contains a silicon-containing material. Configuration 5: The cylindrical secondary battery according to Configuration 4, wherein the silicon-containing material contains an ion-conducting phase and a Si phase dispersed in the ion-conducting phase. Configuration 6: The cylindrical secondary battery according to Configuration 5, wherein the ion-conducting phase contains an amorphous carbon phase. Configuration 7: The cylindrical secondary battery according to Configuration 5 or 6, wherein the weight ratio of the Si phase in the silicon-containing material is 30% to 60%. Configuration 8: The cylindrical secondary battery according to any one of Configurations 4 to 7, wherein the weight ratio of elemental silicon in the negative electrode mixture layer is 7 mass% or more. Configuration 9: The cylindrical secondary battery according to any one of Configurations 4 to 8, wherein the weight ratio of elemental silicon in the negative electrode mixture layer is 50 mass% or less.Configuration 10: A cylindrical secondary battery according to any one of Configurations 1 to 9, wherein the negative electrode current collector has a 1% yield strength of 100 MPa or more and 400 MPa or less.Configuration 11: A cylindrical secondary battery according to any one of Configurations 1 to 10, wherein the negative electrode current collector has an elongation percentage in a tensile test of 3% or more and 20% or less.Configuration 12: A cylindrical secondary battery according to any one of Configurations 1 to 11, wherein the negative electrode current collector is made of copper having an average crystal grain size of 2 μm or more and 20 μm or less.Configuration 13: A cylindrical secondary battery according to any one of Configurations 1 to 12, wherein the negative electrode mixture layer has a peel strength of 9 N / m or more and 80 N / m or less.

[0078] REFERENCE SIGNS LIST 10 Battery, 11 Positive electrode, 12 Negative electrode, 12a Inner winding portion, 12b Outer winding portion, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18, 19 Insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 23 Terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Terminal cap, 28 Gasket, 30 Cylindrical portion, 34 Grooved portion, 38 Shoulder portion, 41 Positive electrode current collector, 42 Positive electrode mixture layer, 48 Peripheral portion, 51 Negative electrode current collector, 52 Negative electrode mixture layer, 55 Bottom portion, 60 Both-side mixture placement portion, 65 Positive electrode facing portion, 70 Silicon-containing material, 71 Ion conducting phase, 72 Si phase.

Claims

1. A cylindrical secondary battery comprising: an electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween; a non-aqueous electrolyte; and a bottomed cylindrical exterior can containing the electrode body and the non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, the negative electrode has a negative electrode current collector and a negative electrode mixture layer disposed on the negative electrode current collector, the discharge capacity per 1.0 g of the negative electrode mixture layer is 0.50 Ah or more, the negative electrode includes both-side mixture disposed portions where the negative electrode mixture layer is disposed on both the inner winding surface and the outer winding surface of the negative electrode current collector, the negative electrode has positive electrode facing portions where both the inner side and the outer side in the winding direction of the both-side mixture disposed portions face the positive electrode in the radial direction, and when the total length of the length of the negative electrode in the longitudinal direction in the positive electrode facing portion is x, the average aw1 of the length in the negative electrode width direction of the negative electrode mixture layer from the start end of winding to x / 4 in the positive electrode facing portion is 1.0025 times or more and less than 1.0100 times the average aw2 of the length in the negative electrode width direction of the negative electrode mixture layer from the end end of winding to x / 4 in the positive electrode facing portion.

2. The cylindrical secondary battery according to claim 1, wherein 0.15 mm < (aw1 - aw2) < 0.5 mm.

3. The cylindrical secondary battery according to claim 1, wherein the average at1 of the thickness of the negative electrode mixture layer from the start end of winding to x / 4 in the positive electrode facing portion is 0.9900 times or more and less than 0.9975 times the average at2 of the thickness of the negative electrode mixture layer from the end end of winding to x / 4 in the positive electrode facing portion.

4. The cylindrical secondary battery according to claim 1, wherein the negative electrode mixture layer contains a silicon-containing material.

5. The cylindrical secondary battery according to claim 4, wherein the silicon-containing material includes an ion conductive phase and Si phases dispersed in the ion conductive phase.

6. The cylindrical secondary battery according to claim 5, wherein the ion conductive phase includes an amorphous carbon phase.

7. The cylindrical secondary battery according to claim 5, wherein the weight ratio of the Si phase in the silicon-containing material is 30% or more and 60% or less.

8. The cylindrical secondary battery according to claim 4, wherein the weight ratio of silicon element in the negative electrode mixture layer is 7% by mass or more.

9. The cylindrical secondary battery according to claim 4, wherein the weight ratio of silicon element in the negative electrode mixture layer is 50% by mass or less.

10. The cylindrical secondary battery according to claim 1, wherein the 1% proof stress of the negative electrode current collector is 100 MPa or more and 400 MPa or less.

11. The cylindrical secondary battery according to claim 1, wherein the elongation rate during the tensile test of the negative electrode current collector is 3% or more and 20% or less.

12. The cylindrical secondary battery according to claim 1, wherein the negative electrode current collector is made of copper having an average crystal grain size of 2 μm or more and 20 μm or less.

13. The cylindrical secondary battery according to claim 1, wherein the peel strength of the negative electrode mixture layer is 9 N / m or more and 80 N / m or less.

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