Non-aqueous electrolyte secondary battery

Abstract

The positive electrode active material contains a lithium-containing composite oxide; the negative electrode active material contains a silicon-containing material; the discharge capacity per 1.0 g of the negative electrode mixture layer (52) is 0.5 Ah or more; and the thickness of the negative electrode mixture layer (52) is 85 µm or less. The positive electrode (11) has one or more double-sided positive electrode current collector exposed parts (45a, 45b), and the negative electrode (12) has one or more double-sided negative electrode current collector exposed parts (55a). The one or more double-sided positive electrode current collector exposed parts (45a, 45b) include one or more lead fixing exposed parts (45a), and a negative electrode lead (21) is fixed to the double-sided negative electrode current collector exposed part (55a). The double-sided negative electrode current collector exposed part (55a) faces double-sided positive electrode current collector exposed parts (45a, 45b) through an interposed separator (13), and at least a part of a positive electrode lead (20) is fixed in a location that overlaps in the height direction with the negative electrode lead facing position in the positive electrode (11) that the negative electrode lead (21) faces via the interposed separator (13).

Description

Nonaqueous electrolyte secondary battery

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery.

[0002] A conventional nonaqueous electrolyte secondary battery is a cylindrical battery described in Patent Document 1. This cylindrical 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 the cylindrical battery of Patent Document 1, the negative electrode lead is attached to the end of the winding. However, if the negative electrode lead is attached to the middle of the winding direction instead of the end of the winding direction, the current collection path becomes shorter, reducing electrical resistance and facilitating a high-power battery. However, the present inventors discovered that if the negative electrode lead is attached to the middle of the winding direction of the negative electrode, a step is created between the exposed portion of the negative electrode current collector to which the negative electrode lead is attached and the portion where the negative electrode mixture layer is disposed in the middle of the winding direction, which tends to deteriorate the circularity of the electrode assembly and, as a result, to cause separator crushing. Separator crushing can easily cause battery reactions to become non-uniform in the winding direction and reduce the capacity retention rate. Therefore, an object of the present disclosure is to provide a non-aqueous electrolyte secondary battery that can easily achieve high power output and suppress separator crushing.

[0005] In order to solve the above problems, the non-aqueous electrolyte secondary battery according to the present disclosure includes an electrode assembly in which a positive electrode having a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and a negative electrode having a negative electrode current collector and a negative electrode mixture layer disposed on the negative electrode current collector are wound together with a separator interposed therebetween; a non-aqueous electrolyte; a bottomed cylindrical outer can that accommodates the electrode assembly and the non-aqueous electrolyte; one or more positive electrode leads that are fixed to the positive electrode current collector and include a protruding portion that protrudes from a first side in the height direction of the electrode assembly; and one or more negative electrode leads that are fixed to the negative electrode current collector and include a protruding portion that protrudes from a second side in the height direction of the electrode assembly, wherein the positive electrode mixture layer contains a lithium-containing composite oxide as a positive electrode active material, and the negative electrode mixture layer contains a silicon-containing material as a negative electrode active material, and the discharge capacity per 1.0 g of the negative electrode mixture layer is 0.5 Ah or more. the thickness of the negative electrode mixture layer is 85 μm or less; the positive electrode has one or more double-sided positive electrode current collector exposed portions where the positive electrode current collector is exposed in substantially the same region in the positive electrode longitudinal direction on both the positive electrode first surface and the positive electrode second surface, and the one or more double-sided positive electrode current collector exposed portions include one or more lead fixing exposed portions to which a positive electrode lead is fixed; the negative electrode has one or more double-sided negative electrode current collector exposed portions where the negative electrode current collector is exposed in substantially the same region in the negative electrode longitudinal direction on both the negative electrode first surface and the negative electrode second surface, and the one or more double-sided negative electrode current collector exposed portions face the one or more double-sided positive electrode current collector exposed portions via a separator, and a negative electrode lead is fixed to the one or more double-sided negative electrode current collector exposed portions, and at least a portion of the positive electrode lead is fixed to a position where the positive electrode lead overlaps in the height direction with a position of the positive electrode facing the negative electrode lead via the separator.

[0006] The nonaqueous electrolyte secondary battery according to the present disclosure can easily achieve high output and suppress separator collapse.

[0007] 1 is an axial cross-sectional view of a cylindrical nonaqueous electrolyte secondary battery according to an embodiment of the present disclosure;

[0023] FIG. 1 is a perspective view of an electrode body;

[0024] FIG. 2 is a schematic diagram showing an example of the structure of a negative electrode mixture layer;

[0025] FIG. 3 is a plan view showing an outer winding surface, a positive electrode lead, and an insulating tape in a positive electrode developed into a long shape;

[0026] FIG. 4 is a plan view showing an inner winding surface, a positive electrode lead, and an insulating tape in a negative electrode developed into a long shape;

[0027] FIG. 5 is a plan view showing an inner winding surface, a negative electrode lead, and an insulating tape in a negative electrode developed into a long shape;

[0028] FIG. 6 is an enlarged schematic cross-sectional view of the periphery of a negative electrode lead in a cross section orthogonal to the height direction of the electrode body and passing through the negative electrode lead;

[0029] FIG. 7 is a plan view showing an outer winding surface, a positive electrode lead, and an insulating tape in a positive electrode developed into a long shape of a cylindrical lithium-ion secondary battery of a first modified example;

[0029] FIG. 8 is a plan view showing an inner winding surface, a positive electrode lead, and an insulating tape in a positive electrode developed into a long shape of a cylindrical lithium-ion secondary battery of a first modified example; FIG. 1 is a plan view showing the outer winding surface, negative electrode lead, winding end side negative electrode lead, and insulating tape of a negative electrode developed into a long shape in a cylindrical lithium-ion secondary battery of a first modified example. FIG. 2 is a plan view showing the inner winding surface, negative electrode lead, winding end side negative electrode lead, and insulating tape of a negative electrode developed into a long shape in a cylindrical lithium-ion secondary battery of a first modified example. FIG. 3 is a plan view showing the outer winding surface, three positive electrode leads, and insulating tape of a positive electrode developed into a long shape in a cylindrical nonaqueous electrolyte secondary battery of a second modified example. FIG. 4 is a plan view showing the outer winding surface, three negative electrode leads, and insulating tape of a negative electrode developed into a long shape in a cylindrical nonaqueous electrolyte secondary battery of a second modified example. FIG. 5 is a plan view showing the outer winding surface, three negative electrode leads, and insulating tape of a negative electrode developed into a long shape in a cylindrical nonaqueous electrolyte secondary battery of a second modified example.

[0008] Hereinafter, with reference to the drawings, embodiments of a cylindrical nonaqueous electrolyte secondary battery according to the present disclosure will be described in detail. It is anticipated from the beginning that new embodiments can be constructed by appropriately combining the features of the embodiments and modified examples described below. In the following embodiments, the same components are denoted by the same reference numerals in the drawings, and redundant description will be omitted. The drawings are schematic views, and the dimensional ratios of the length, width, height, etc. of each component between different drawings do not necessarily match. In this specification, the side of the sealing body 17 in the axial direction of the cylindrical nonaqueous electrolyte secondary battery 10 is referred to as the "upper" side, and the side of the bottom 68 of the outer can 16 in the axial direction is referred to as the "lower" side. In this specification, when simply referring to the "height direction," this height direction refers to the height direction of the electrode body (wound body) 14.

[0009] The development views of the electrodes (negative electrode, positive electrode) in Figures 4A-4D, 6A-6D, and 7A-7D are schematic views, and the longitudinal dimensions are reduced in size in the development views. In the development views of the electrodes, the hatched area is the area where the mixture layer is disposed. In the following description, the technical concept of the present disclosure will be explained using an example in which the cylindrical nonaqueous electrolyte secondary battery is a cylindrical lithium-ion secondary battery, but the cylindrical nonaqueous electrolyte secondary battery of the present disclosure is not limited to a cylindrical lithium-ion secondary battery. Among the components described below, components not recited in the independent claims representing the highest concept are optional components and not essential components.

[0010] Fig. 1 is an axial cross-sectional view of a cylindrical nonaqueous electrolyte secondary battery 10 according to one embodiment of the present disclosure, and Fig. 2 is a perspective view of an electrode assembly 14 of the cylindrical nonaqueous electrolyte secondary battery 10. As shown in Fig. 1, the cylindrical nonaqueous electrolyte secondary battery (hereinafter simply referred to as battery) 10 includes a wound electrode assembly 14, a nonaqueous electrolyte (not shown), a cylindrical metal outer can 16 with a bottom that houses the electrode assembly 14 and the nonaqueous 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 a long positive electrode 11 and a long negative electrode 12 are wound with two long separators 13 interposed therebetween.

[0011] 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. 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, in general, 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.

[0012] 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

[0013] 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.).

[0014] The positive electrode 11 includes a positive electrode current collector 41 (see FIGS. 4A and 4B ) and positive electrode mixture layers 42 (see FIGS. 4A and 4B ) disposed on both sides of the positive electrode current collector 41. The positive electrode current collector 41 may be 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 having such a metal disposed on its surface. The positive electrode mixture layer 42 includes a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be fabricated, 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.

[0015] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Examples of metal elements contained in the 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 metal 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 11 with a large discharge capacity.

[0016] Examples of the conductive agent contained in the positive electrode mixture layer 42 include carbon materials such as carbon black, acetylene black, ketjen black, graphite, and carbon nanotubes. 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.

[0017] The negative electrode 12 has a negative electrode current collector 51 (see FIGS. 4C and 4D ) and a negative electrode mixture layer 52 (see FIGS. 4C and 4D ) 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 with 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.

[0018] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Preferred carbon materials include 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 thickness of the negative electrode mixture layer 52 is 85 μm or less. As described below, in the present disclosure, the negative electrode lead 21 is fixed to the radially central portion of the electrode body 14. Therefore, a step in the negative electrode mixture layer 52 and the outer negative electrode current collector exposed portion 57a ​​(see FIGS. 4C and 5 ) to which the negative electrode lead 21 is fixed are formed in the radially central portion. As described below, a thickness of 85 μm or less can effectively prevent separator collapse around the step. This facilitates uniform battery reaction in the winding direction, facilitating the production of an excellent battery 10 with a high capacity retention rate.

[0019] If the thickness of the negative electrode mixture layer 52 is 40 μm or more, the negative electrode 12 can be prevented from becoming excessively thin relative to the positive electrode 11, thereby enabling smooth winding of the electrode body 14. The discharge capacity per 1.0 g of the negative electrode mixture layer 52 is 0.5 Ah or more. In order to effectively increase the discharge capacity per 1.0 g of the negative electrode mixture layer 52, it is preferable that the negative electrode mixture layer 52 contains a silicon-containing material containing silicon (Si) as the negative electrode active material.

[0020] 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. 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 facilitates high 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 reduces the volume change of the negative electrode mixture layer 52 during charging and discharging, thereby suppressing the expansion and contraction of the electrode body 14 during charging and discharging, thereby facilitating excellent durability of the battery 10. The ion-conducting phase 71 may be composed of, for example, an amorphous carbon phase, a lithium silicate 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.

[0021] 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% by mass or more, and more preferably 12% by mass or more, because this increases the discharge capacity and results in high output of the battery 10. Furthermore, the weight ratio of elemental silicon to the anode mixture layer 52 is preferably 50% by mass or less, because this reduces the volume change of the anode mixture layer 52 during charging and discharging, thereby suppressing expansion and contraction of the electrode body 14 during charging and discharging, thereby improving the durability of the battery 10. 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% by mass or more and 50% by mass or less. 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.

[0022] 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.

[0023] 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.

[0024] 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 negative electrode 12. 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 through a through-hole in the insulating plate 19 and extends toward the bottom 68 of the outer can 16. The positive electrode lead 20 is connected to the underside of a sealing 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 sealing 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 68 of the metal outer can 16 by welding or the like, and the outer can 16 serves as a negative electrode terminal. In this embodiment, the positive electrode lead 20 is electrically connected to an intermediate portion, such as the center portion, of the positive electrode current collector 41 in the winding direction, and the negative electrode lead 21 is electrically connected to an intermediate portion, such as the center portion, of the negative electrode current collector 51 in the winding direction.

[0025] 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 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.

[0026] 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 68, and 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 29 of the sealing body 17 when the sealing body 17 is crimped to the outer can 16.

[0027] The sealing body 17 has a structure in which, in order from the electrode body 14 side, a sealing plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a terminal cap 27 are stacked. Each member constituting the sealing body 17 has, for example, a disk or ring shape, and each member except for the insulating member 25 is electrically connected to one another. The sealing plate 23 has at least one through-hole 23a. The lower valve body 24 and the upper valve body 26 are connected at their respective centers, with the insulating member 25 interposed between their respective peripheral edges.

[0028] 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 improving the safety of the battery 10.

[0029] The above description deals with a case in which 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 an internal 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.

[0030] Fig. 4A is a plan view showing the outer winding surface 11a, the positive electrode lead 20, and the insulating tape 60 of the positive electrode 11 developed into a long shape, and Fig. 4B is a plan view showing the inner winding surface 11b, the positive electrode lead 20, and the insulating tape 60 of the positive electrode 11 developed into a long shape. Fig. 4C is a plan view showing the outer winding surface 12a, the negative electrode lead 21, and the insulating tape 80 of the negative electrode 12 developed into a long shape, and Fig. 4D is a plan view showing the inner winding surface 12b, the negative electrode lead 21, and the insulating tape 80 of the negative electrode 12 developed into a long shape.

[0031] The outer winding surface 11a of the positive electrode 11 constitutes a positive electrode first surface, and the inner winding surface 11b of the positive electrode 11 constitutes a positive electrode second surface. The outer winding surface 12a of the negative electrode 12 constitutes a negative electrode first surface, and the inner winding surface 12b of the negative electrode 12 constitutes a negative electrode second surface. In addition, in Figures 4A and 4B, the α direction indicates the positive electrode longitudinal direction when the positive electrode 11 is developed into a long shape, and the β direction indicates the positive electrode width direction when the positive electrode 11 is developed into a long shape. In addition, in Figures 4C and 4D, the γ direction indicates the negative electrode longitudinal direction when the negative electrode 12 is developed into a long shape, and the δ direction indicates the negative electrode width direction when the negative electrode 12 is developed into a long shape.

[0032] 4A and 4B , the positive electrode 11 has two double-sided positive electrode current collector exposed portions 45a, 45b where the positive electrode current collector 41 is exposed in approximately the same region in the longitudinal direction of the positive electrode (the α direction shown in FIGS. 4A and 4B ) on both the outer winding surface 11a and the inner winding surface 11b, and does not have a portion where the positive electrode current collector is exposed on only one surface. In this embodiment, the positive electrode 11 does not have a portion where the positive electrode current collector is exposed on only one surface, but the positive electrode may have a portion where the positive electrode current collector is exposed on only one surface. The two double-sided positive electrode current collector exposed portions 45a, 45b are provided at both the winding start end and the winding end end of the positive electrode 11 at positions spaced apart in the α direction and are arranged at an interval from each other in the α direction. The two double-sided positive electrode current collector exposed portions 45a, 45b include a lead-fixed exposed portion 45a to which the positive electrode lead 20 is fixed, and a lead-unfixed exposed portion 45b that is spaced apart from the positive electrode lead 20 in the α direction and to which the positive electrode lead 20 is not fixed.

[0033] Each of the two double-sided positive electrode current collector exposed portions 45a, 45b is preferably located in a middle region when the elongated positive electrode 11 is divided into three regions of equal length in the α direction. In other words, when the coordinate (position) of the winding start end of the positive electrode 11 in the α direction is defined as 0 (reference position) and the coordinate (position) of the winding end end is defined as 1, each of the two double-sided positive electrode current collector exposed portions 45a, 45b is preferably located at a position between 1 / 3 and 2 / 3 of the way around in the α direction. Furthermore, the positive electrode lead 20 is preferably fixed at a position between 1 / 3 and 2 / 3 of the way around the radius of the electrode body 14.

[0034] The negative electrode 12 has a double-sided negative electrode current collector exposed portion 55a where the negative electrode current collector 51 is exposed in substantially the same region in the negative electrode longitudinal direction (γ direction shown in FIGS. 4C and 4D ) on both the outer winding surface 12a and the inner winding surface 12b. The double-sided negative electrode current collector exposed portion 55a is provided between, in the γ direction, two double-sided negative electrode mixture layer arranged portions 56a, 56b in the negative electrode 12, where the negative electrode mixture layer 52 is present on both the outer winding surface 12a and the inner winding surface 12b.

[0035] 5 is an enlarged schematic cross-sectional view of the periphery of the negative electrode lead 21 in a cross section perpendicular to the height direction of the electrode body 14 and passing through the negative electrode lead 21. As shown in FIG. 5 , the double-sided negative electrode current collector exposed portion 55a faces the double-sided positive electrode current collector exposed portions 45a, 45b, with the separator 13 interposed therebetween. The lead-unfixed exposed portion 45b is located closer to the winding start side than the lead-fixed exposed portion 45a. The lead-unfixed exposed portion 47b, located on the outer side of the lead-unfixed exposed portion 45b, faces the winding-inner negative electrode current collector exposed portion 57b, located on the inner side of the double-sided negative electrode current collector exposed portion 55a, with the separator 13 interposed therebetween. The positive electrode lead 20 is fixed to the winding-inner lead fixed exposed portion 48b, located on the inner side of the lead-fixed exposed portion 45a, and the negative electrode lead 21 is fixed to the winding-outer negative electrode current collector exposed portion 57a, located on the outer side of the double-sided negative electrode current collector exposed portion 55a. The outer negative electrode current collector exposed portion 57a ​​faces the inner lead fixing exposed portion 48b with the separator 13 interposed therebetween.

[0036] In this embodiment, the battery 10 has two double-sided positive current collector exposed portions 45 a, 45 b. However, the battery may have only one double-sided positive current collector exposed portion. For example, the positive current collector exposed portion 47 a located on the inner side of the unfixed lead exposed portion 45 b in FIG. 5 may not be present. In other words, a positive electrode mixture layer may be disposed on the portion of the positive current collector where the positive current collector exposed portion 47 a is present in FIG. 5 .

[0037] 1 , the positive electrode lead 20 protrudes to a first side in the height direction (upper side in the height direction), and the negative electrode lead 21 protrudes to a second side in the height direction (lower side in the height direction). The positive electrode lead 20 and the negative electrode lead 21 face each other and are positioned with a gap in the height direction, and the positive electrode lead 20 and the negative electrode lead 21 are preferably fixed at different height positions on the electrode body 14.

[0038] In this embodiment, the positive electrode lead 20 does not overlap the negative electrode lead 21 in the radial direction of the electrode body 14 via the separator 13. More specifically, when the overlapping amount of the positive electrode lead 20 over the positive electrode 11 in the height direction is A [mm], the overlapping amount of the negative electrode lead 21 over the negative electrode 12 in the height direction is B [mm], and the negative electrode width of the negative electrode 12 is C [mm], then (A + B) < C holds. It is preferable that A < (C / 2) and B < (C / 2) hold.

[0039] At least a portion of the positive electrode lead 20 is arranged at a position overlapping the negative electrode lead 21 in the height direction of the electrode body 14 at a position on the positive electrode 11 opposite the negative electrode lead 21 with the separator 13 interposed therebetween. In other words, at least a portion of the positive electrode lead 20 and at least a portion of the negative electrode lead 21 are located in the same range in the winding direction of the electrode body 14. This allows the range in the winding direction of the electrode body in which the flat electrode leads 20, 21 are located to be limited to a local range, thereby increasing the circularity of the electrode body 14 and resulting in an increase in the capacity of the battery 10. Like the positive electrode lead 20, the negative electrode lead 21 is preferably fixed at a position located at ⅓ to ⅔ of the radius of the electrode body 14.

[0040] Although the case where the positive electrode lead 20 is positioned at a distance from the negative electrode lead 21 in the height direction has been described, a configuration in which at least a portion of the positive electrode lead overlaps the negative electrode lead in the radial direction of the electrode body with a separator interposed therebetween may also be used. Furthermore, although the case where the positive electrode lead 20 and the negative electrode lead 21 are fixed at positions located at ⅓ to ⅔ of the radius of the electrode body 14 has been described, the positive electrode lead and the negative electrode lead do not necessarily have to be fixed at positions located at ⅓ to ⅔ of the radius of the electrode body 14.

[0041] 4C and 4D , in this embodiment, the outer winding surface 12a of the negative electrode 12 has an outermost negative electrode current collector exposed portion 58 where the negative electrode current collector 51 is exposed at the end on the winding end side in the γ direction, and the inner winding surface 12b of the negative electrode 12 also has an outermost negative electrode current collector exposed portion 59 where the negative electrode current collector 51 is exposed at the end on the winding end side in the γ direction. The length in the γ direction of the outermost negative electrode current collector exposed portion 58 is longer than the length in the γ direction of the negative electrode current collector exposed portion 59.

[0042] 1 , the outermost negative electrode current collector exposed portion 58 includes a portion located on the outermost peripheral surface of the electrode assembly 14. The outermost negative electrode current collector exposed portion 58 contacts the inner peripheral surface of the outer can 16 of the battery 10 and is electrically connected to the inner peripheral surface of the outer can 16. By fixing the negative electrode lead 21 to the radially intermediate portion of the electrode assembly 14 and bringing the outermost negative electrode current collector exposed portion 58 into contact with the inner peripheral surface of the outer can 16 of the battery 10, both the longitudinal intermediate portion of the negative electrode 12 and the end portion on the winding end side are electrically connected to the negative electrode terminal. This shortens the current collection path through which current flows and reduces electrical resistance.

[0043] As shown in FIGS. 4A and 4B , insulating tape 60 is applied to each of the double-sided positive electrode current collector exposed portions 45 a, 45 b on both the outer winding surface 11 a and the inner winding surface 11 b, covering the positive electrode mixture layer 42 located on both sides in the α direction. Furthermore, as shown in FIGS. 4C and 4D , insulating tape 80 is also applied to the outer negative electrode current collector exposed portion 57 a to which the negative electrode lead 21 is fixed, covering at least the negative electrode lead. The insulating tape 80 may also be applied to the inner negative electrode current collector exposed portion 57 b, covering the negative electrode mixture layer 52 located on both sides in the γ direction. The insulating tape may be applied to the inner negative electrode current collector exposed portion 57 b, or may be applied so as to cover the boundary between the other negative electrode mixture layer and the negative electrode current collector exposed portion. The insulating tapes 60, 80 are provided for the purposes of preventing short circuits and active material from falling off. The insulating tapes 60 and 80 can be made of, for example, a tape having a base material made of polyimide film and an adhesive material made of silicone, but may be made of any material as long as the tape has insulating properties and can be attached.

[0044] Example 1 In the cylindrical battery described above, the negative electrode discharge utilization rate (Ah / g), defined as the discharge capacity of the negative electrode mixture layer per 1.0 g of the negative electrode mixture layer, was set to 0.68 Ah, and the silicon element weight ratio wt %, defined as the weight ratio of silicon element to the negative electrode mixture layer, was set to 15%. The thickness of the negative electrode mixture layer was set to 79.6 μm.

[0045] The negative electrode discharge utilization rate was measured as follows. First, the fabricated battery was disassembled, and the removed negative electrode was placed opposite lithium as a positive electrode. Then, the battery was discharged from a state in which the negative electrode was 5 mV higher than the lithium to a state in which the negative electrode was 1 V higher than the lithium. The negative electrode discharge utilization rate was calculated based on the charge released during the discharge.

[0046] The silicon element weight ratio was measured by disassembling the fabricated battery and using ICP (Inductively Coupled Plasma). ICP is a type of optical emission spectroscopy. When plasma energy is applied to an analysis sample from the outside, the contained component elements (atoms) are excited. In ICP, the emission lines (spectral lines) emitted when the excited atoms return to a lower energy level are measured, and the content of the component elements (atoms) is measured based on the measured emission lines. The thickness of the negative electrode mixture layer was measured with a thickness gauge after disassembling the fabricated battery.

[0047] Example 2 In the cylindrical battery described above, the discharge capacity per 1.0 g of the negative electrode mixture layer was set to 0.90 Ah, and the silicon weight ratio wt% was set to 25%. The thickness of the negative electrode mixture layer was set to 64.9 μm. The negative electrode discharge utilization rate, silicon weight ratio, and thickness of the negative electrode mixture layer were measured in the same manner as in Example 1.

[0048] Example 3 In the cylindrical battery described above, the discharge capacity per 1.0 g of the negative electrode mixture layer was 1.13 Ah, the silicon weight ratio wt% was 35%, and the thickness of the negative electrode mixture layer was 57.9 μm. The negative electrode discharge utilization rate, the silicon weight ratio, and the thickness of the negative electrode mixture layer were measured in the same manner as in Example 1.

[0049] Comparative Example 1: In comparison with the cylindrical battery described above, the discharge capacity per 1.0 g of the negative electrode mixture layer was set to 0.35 Ah, which was less than 0.5 Ah, and the thickness of the negative electrode mixture layer was set to 117.2 μm, which was greater than 85 μm. The silicon element weight ratio wt % was set to 0%. The negative electrode discharge utilization rate, silicon element weight ratio, and thickness of the negative electrode mixture layer were measured in the same manner as in Example 1.

[0050] Comparative Example 2: In comparison with the cylindrical battery described above, the discharge capacity per 1.0 g of the negative electrode mixture layer was set to 0.42 Ah, which was less than 0.5 Ah, and the thickness of the negative electrode mixture layer was set to 99.4 μm, which was greater than 85 μm. The silicon element weight ratio wt % was set to 4%. The negative electrode discharge utilization rate, silicon element weight ratio, and thickness of the negative electrode mixture layer were measured in the same manner as in Example 1.

[0051] Comparative Example 3: In comparison with the cylindrical battery described above, the thickness of the negative electrode mixture layer was set to 104.4 μm, which was larger than 85 μm. The discharge capacity per 1.0 g of the negative electrode mixture layer was set to 0.68 Ah, and the silicon weight ratio wt % was set to 15%. The negative electrode discharge utilization rate, silicon weight ratio, and thickness of the negative electrode mixture layer were measured in the same manner as in Example 1.

[0052] (Capacity Measurement) The capacities of the batteries of Examples 1-3 and Comparative Examples 1-3 were measured. Specifically, after each battery was fabricated, it was charged at a constant current of 0.3 C at 25°C until the battery voltage reached 4.2 V, and then it was charged at a constant voltage of 4.2 V until the current value reached 0.02 C. After a 20-minute rest, 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 was calculated assuming that the capacity of the battery of Example 1 was 100.

[0053] (Separator Crush Measurement) Each of the batteries of Examples 1-3 and Comparative Examples 1-3 was subjected to 100 charge-discharge cycles in an air-cooled environment at 45°C. After reaching 4.2 V at a constant current of 0.3 C, the battery was charged at 4.2 V until the current reached 0.02 C, followed by a 20-minute pause. The battery was then discharged at a constant current of 0.5 C until the battery voltage reached 2.85 V, followed by a 20-minute pause. Subsequently, in an air-cooled environment at 45°C, the battery was charged at a constant current of 0.3 C until the voltage reached 4.2 V, followed by a constant voltage charge at 4.2 V until the current reached 0.02 C, until the battery was fully charged (SOC (State Of Charge) 100%).

[0054] The battery was then disassembled, and the separator was extracted. A scanning electron microscope (SEM) was used to measure the thickness t1 of a first location (designated 13a in FIG. 5 ) on the inner side of the winding of the double-sided negative electrode current collector exposed portion, which was radially opposed to the boundary between the double-sided negative electrode current collector exposed portion and the negative electrode mixture layer (in the radial direction of the battery). Furthermore, a thickness t2 of a second location (designated 13b in FIG. 5 ) on the inner side of the winding of the double-sided negative electrode current collector exposed portion, which was radially opposed to the center of the double-sided negative electrode current collector exposed portion in the longitudinal direction of the negative electrode, was measured, and the separator collapse amount (t2 - t1) was calculated. The separator collapse amount for each battery was calculated by setting the separator collapse amount for Example 1 to 100. A scanning electron microscope is a device that irradiates an electron beam on a sample to observe its surface. The electron beam is incident on the sample in a vacuum, and the secondary electrons generated during the incident are imaged. By using a scanning electron microscope, it is possible to obtain topographical images and compositional contrast images of the sample surface.

[0055] (Test results)

[0056] The batteries of Comparative Examples 1 and 2, in which the negative electrode discharge utilization rate was less than 0.5, had capacities of 86 and 95, respectively, which were significantly smaller by 5% or more than the capacity of the battery of Example 1, which was the smallest among the batteries of the Examples.

[0057] The separator crushing amount of the battery of Comparative Example 1-3, in which the negative electrode mixture thickness is greater than 85 μm, is greater than the separator crushing amount of the battery of Example 1, which has the largest separator crushing amount among Examples 1-3.

[0058] In particular, when the battery of Example 1 and Comparative Example 3, which were identical in negative electrode discharge utilization rate and silicon element weight ratio but differed only in negative electrode mixture thickness, the amount of separator crushing in the battery of Comparative Example 2 was increased by 2% compared to the battery of Example 1. Therefore, it was confirmed that the negative electrode mixture thickness has a decisive effect on the amount of separator crushing.

[0059] Through the above-mentioned tests and numerous other tests, the present inventors have found that when the negative electrode mixture thickness is 85 μm or less, the amount of separator crushing can be suppressed and the capacity can be increased, as long as the negative electrode discharge utilization rate is not less than 0.5. Note that, as shown in Example 1-3, when the negative electrode mixture thickness is 55 μm or more and 80 μm or less, the amount of separator crushing can be effectively suppressed and the capacity can be effectively increased.

[0060] The batteries of Examples 1 to 3 all had a silicon element weight ratio in the range of 7% to 50%. The inventors of the present invention confirmed through the above-mentioned tests and numerous other tests that a silicon element weight ratio in the range of 7% to 50% facilitates suppressing separator crushing and increasing capacity. A silicon element weight ratio of 15% or more facilitates high output from the battery 10, and a silicon element weight ratio of 25% or more significantly increases the output of the battery 10.

[0061] The present disclosure is not limited to the above-described embodiments and their modifications, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents.

[0062] For example, in the above embodiment, the outermost negative electrode current collector exposed portion 58 provided at the end of the winding of the negative electrode 12 in the longitudinal direction is in contact with the inner circumferential surface of the outer can 16. However, the outermost circumferential surface of the electrode body in the winding direction may be formed of a separator, and one negative electrode lead electrically connected to an intermediate portion, such as the center portion, of the negative electrode current collector 51 in the longitudinal direction may be electrically connected to the outer can.

[0063] Alternatively, a configuration may be adopted in which an exposed negative electrode current collector portion is provided at the end of the winding of the negative electrode, and the exposed negative electrode current collector portion and the inner surface of the outer can are electrically connected by a negative electrode lead separate from the negative electrode lead 21 fixed to the middle part of the radius of the electrode body 14. Fig. 6A is a plan view showing the outer winding surface 11a, the positive electrode lead 20, and the insulating tape 60 of the positive electrode 11 unfolded into a long shape in a cylindrical lithium-ion secondary battery of the first modified example, and Fig. 6B is a plan view showing the inner winding surface 11b, the positive electrode lead 20, and the insulating tape 60 of the positive electrode 11 unfolded into a long shape. 6C is a plan view showing the outer winding surface 12a, the negative electrode lead 21, the winding end side negative electrode lead 125, and the insulating tape 80 of the negative electrode 12 that has been developed into a long shape in the cylindrical lithium-ion secondary battery of the first modified example, and FIG. 6D is a plan view showing the inner winding surface 12b, the negative electrode lead 21, the winding end side negative electrode lead 125, and the insulating tape 80 of the negative electrode 12 that has been developed into a long shape.

[0064] 6A to 6D , the cylindrical lithium-ion secondary battery of Example 2 has a negative electrode lead 21 having one end joined to a double-sided negative electrode current collector exposed portion provided at a midpoint in the negative electrode longitudinal direction of the negative electrode 12, as well as an end-of-winding negative electrode lead 125 having one end joined to a negative electrode current collector exposed portion 151 provided at the end of the winding of the negative electrode 12. The other ends of the negative electrode lead 21 and the end-of-winding negative electrode lead 125 are joined to the inner bottom surface of the outer can 16. In the first modified example, as in the above embodiment, both the midpoint in the longitudinal direction and the end of the winding of the negative electrode 112 are electrically connected to the negative electrode terminal, thereby shortening the current collection path and reducing electrical resistance.

[0065] The above description deals with the case where the battery 10 has only one positive electrode lead 20. However, the battery may have two or more positive electrode leads. Fig. 7A is a plan view showing the outer winding surface 211a of the positive electrode 211, three positive electrode leads 20, 20, 20, and insulating tape 60, in the cylindrical nonaqueous electrolyte secondary battery of the second modified example, which is developed into a long shape. Fig. 7B is a plan view showing the inner winding surface 211b of the positive electrode 211, three positive electrode leads 20, 20, 20, and insulating tape 60, in the positive electrode 211, which is developed into a long shape. 7A and 7B , the positive electrode 211 includes a positive electrode current collector 241 and a positive electrode mixture layer 242. As shown in FIGS. 7C and 7D , the negative electrode 212 includes a negative electrode current collector 251 and a negative electrode mixture layer 252. Also, as shown in FIGS. 7C and 7D , the negative electrode 212 includes a negative electrode current collector 251 and a negative electrode mixture layer 252. As shown in FIGS. 7A and 7B , the negative electrode 211 includes a negative electrode current collector 241 and a negative electrode mixture layer 242. Also, as shown in FIGS. 7C and 7D , the negative electrode 212 includes a negative electrode current collector 251 and a negative electrode mixture layer 252. As shown in FIGS. 7B and 7C , the negative electrode 212 includes a negative electrode current collector 251 and a negative electrode mixture layer 252. As shown in FIGS. 7C and 7D , the negative electrode 212 includes a negative electrode current collector 251 and a negative electrode mixture layer 252. As shown in FIGS. 7D and 7B , the negative electrode 211 includes a negative electrode current collector 251 and a negative electrode mixture layer 252. As shown in FIGS. 7C and 7D , the negative electrode 212 includes a negative electrode current collector 251 and a negative electrode mixture layer 252. As shown in FIGS. 7D and 7C ...

[0066] 7A to 7D , the cylindrical nonaqueous electrolyte secondary battery of the second modified example has N sets (N is a natural number of 2 or more) of two sets of double-sided positive electrode current collector exposed portions 45 a, 45 b, a positive electrode lead 20, a double-sided negative electrode current collector exposed portion 55 a, and a negative electrode lead 21, which have the relative positional relationship described in detail using FIGS. 4A to 4D , spaced apart from one another in the winding direction of the electrode body. For example, as shown in FIGS. 7A to 7D , the cylindrical nonaqueous electrolyte secondary battery has three such sets. In this way, the current collection paths in each of the positive electrode 211 and the negative electrode 212 can be further shortened, thereby significantly reducing the resistance of the cylindrical nonaqueous electrolyte secondary battery.

[0067] In the above description, each current collector exposed portion is provided from one end to the other end in the width direction of the long (strip-shaped) electrode. However, the electrode body may have one or more current collector exposed portions in which the current collector is not exposed across the entire width direction of the long electrode. In this case, the one or more current collector exposed portions are arranged in only a portion in the height direction, and the mixture layer is arranged in a region that overlaps the current collector exposed portion in the height direction (width direction of the electrode), thereby increasing the capacity.

[0068] The cylindrical battery of the present disclosure may also have the following configuration: Configuration 1: An electrode assembly in which a positive electrode having a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and a negative electrode having a negative electrode current collector and a negative electrode having a negative electrode mixture layer disposed on the negative electrode current collector are wound together with a separator interposed therebetween, a non-aqueous electrolyte, a bottomed cylindrical outer can accommodating the electrode assembly and the non-aqueous electrolyte, one or more positive electrode leads fixed to the positive electrode current collector and including a protruding portion protruding from a first side in a height direction of the electrode assembly, and one or more negative electrode leads fixed to the negative electrode current collector and including a protruding portion protruding from a second side in the height direction of the electrode assembly, wherein the positive electrode mixture layer contains a lithium-containing composite oxide as a positive electrode active material, and the negative electrode mixture layer contains a silicon-containing material as a negative electrode active material, and the discharge capacity per 1.0 g of the negative electrode mixture layer is 0.5 Ah or more, and the thickness of the negative electrode mixture layer is 85 μm or less. the positive electrode has one or more double-sided positive current collector exposed portions where the positive electrode current collector is exposed in substantially the same region in the positive electrode longitudinal direction on both a positive electrode first surface and a positive electrode second surface, and the one or more double-sided positive current collector exposed portions include one or more lead fixing exposed portions to which the positive electrode lead is fixed; the negative electrode has one or more double-sided negative current collector exposed portions where the negative electrode current collector is exposed in substantially the same region in the negative electrode longitudinal direction on both a negative electrode first surface and a negative electrode second surface, and the one or more double-sided negative current collector exposed portions face the one or more double-sided positive current collector exposed portions via the separator, and the negative electrode lead is fixed to the one or more double-sided negative current collector exposed portions, and at least a portion of the positive electrode lead is fixed to a position of the positive electrode that overlaps in the height direction with a position of the negative electrode lead facing the negative electrode lead across the separator. Configuration 2: The nonaqueous electrolyte secondary battery according to Configuration 1, wherein the one or more double-sided positive electrode current collector exposed portions include two or more double-sided positive electrode current collector exposed portions, the two or more double-sided positive electrode current collector exposed portions being provided at locations spaced apart in the longitudinal direction of the positive electrode from both a winding start end and a winding end and being spaced apart from each other in the longitudinal direction of the positive electrode, and the two or more double-sided positive electrode current collector exposed portions including the fixed-lead exposed portion and a non-fixed-lead exposed portion to which the positive electrode lead is not fixed.Configuration 3: The nonaqueous electrolyte secondary battery according to Configuration 1 or 2, wherein a winding termination end of the negative electrode is provided with a negative electrode current collector exposed portion that contacts the inner circumferential surface of the outer can and exposes the negative electrode current collector.Configuration 4: The nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 3, wherein the negative electrode mixture layer has a thickness of 40 μm or more.Configuration 5: The nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 4, wherein the silicon-containing material includes an ion-conducting phase and a Si phase dispersed in the ion-conducting phase.Configuration 6: The nonaqueous electrolyte secondary battery according to Configuration 5, wherein the ion-conducting phase includes an amorphous carbon phase.Configuration 7: The nonaqueous electrolyte secondary battery according to Configuration 5 or 6, wherein the weight ratio of the Si phase in the silicon-containing material is 30% or more and 60% or less.Configuration 8: The nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 7, wherein the weight ratio of elemental silicon in the negative electrode mixture layer is 7 mass% or more. Aspect 9: The nonaqueous electrolyte secondary battery according to any one of Aspects 1 to 8, wherein the weight ratio of silicon element in the negative electrode mixture layer is 50 mass % or less. Aspect 10: The nonaqueous electrolyte secondary battery according to any one of Aspects 1 to 9, wherein the lithium-containing composite oxide has a layered rock salt structure.

[0069] REFERENCE SIGNS LIST 10 Battery, 11,211 Positive electrode, 11a,211a Outer winding surface of positive electrode, 11b,211b Inner winding surface of positive electrode, 12,112,212 Negative electrode, 12a,212a Outer winding surface of negative electrode, 12b,212b Inner winding surface of negative electrode, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18,19 Insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 23 Sealing plate, 23a Through hole, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Terminal cap, 27a Through hole, 28 Gasket, 29 Peripheral edge portion, 30 Cylindrical portion, 34 Grooved portion, 38 Shoulder portion, 41,241 Positive electrode current collector, 42,242 Positive electrode mixture layer, 45a,45b Double-sided positive electrode current collector exposed portion, 45a Lead fixed exposed portion, 45b Lead non-fixed exposed portion, 47a Positive electrode current collector exposed portion, 47b Outer winding lead non-fixed exposed portion, 48b Inner winding lead fixed exposed portion, 51,251 Negative electrode current collector, 52,252 Negative electrode mixture layer, 55a Double-sided negative electrode current collector exposed portion, 56a,56b Double-sided negative electrode mixture layer disposed portion, 57a Outer winding negative electrode current collector exposed portion, 57b Inner winding negative electrode current collector exposed portion, 58 Outermost peripheral negative electrode current collector exposed portion, 59 Negative electrode current collector exposed portion, 60,80 Insulating tape, 68 Bottom, 70 Silicon-containing material, 71 ion-conducting phase, 72 Si phase, 125 winding end side negative electrode lead, 151 exposed portion of negative electrode current collector.

Claims

1. An electrode assembly in which a positive electrode having a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and a negative electrode having a negative electrode current collector and a negative electrode having a negative electrode mixture layer disposed on the negative electrode current collector are wound with a separator interposed therebetween; a non-aqueous electrolyte; a bottomed cylindrical outer can containing the electrode assembly and the non-aqueous electrolyte; one or more positive electrode leads fixed to the positive electrode current collector and including a protrusion protruding from a first side in a height direction of the electrode assembly; and one or more negative electrode leads fixed to the negative electrode current collector and including a protrusion protruding from a second side in the height direction of the electrode assembly, wherein the positive electrode mixture layer contains a lithium-containing composite oxide as a positive electrode active material, the negative electrode mixture layer contains a silicon-containing material as a negative electrode active material, the discharge capacity per 1.0 g of the negative electrode mixture layer is 0.5 Ah or more, and the thickness of the negative electrode mixture layer is 85 μm or less, a positive electrode having one or more double-sided positive current collector exposed portions where the positive electrode current collector is exposed in substantially the same region in the negative electrode longitudinal direction on both a positive electrode first surface and a positive electrode second surface, the one or more double-sided positive current collector exposed portions including one or more lead fixed exposed portions to which the positive electrode lead is fixed; the negative electrode having one or more double-sided negative current collector exposed portions where the negative electrode current collector is exposed in substantially the same region in the negative electrode longitudinal direction on both a negative electrode first surface and a negative electrode second surface, the one or more double-sided negative current collector exposed portions facing the one or more double-sided positive current collector exposed portions via the separator, the negative electrode lead being fixed to the one or more double-sided negative current collector exposed portions, and at least a portion of the positive electrode lead being fixed to a position where the negative electrode lead faces a negative electrode lead facing position of the positive electrode across the separator, in the height direction.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the one or more double-sided positive electrode current collector exposed portions have two or more double-sided positive electrode current collector exposed portions, the two or more double-sided positive electrode current collector exposed portions are provided at locations spaced apart in the longitudinal direction of the positive electrode from both a winding start end and a winding end end and are spaced apart from each other in the longitudinal direction of the positive electrode, and the two or more double-sided positive electrode current collector exposed portions include the lead-fixed exposed portion and a lead-unfixed exposed portion to which the positive electrode lead is not fixed.

3. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein a negative electrode current collector exposed portion is provided at a winding end of the negative electrode, the negative electrode current collector being in contact with an inner peripheral surface of the outer can and exposing the negative electrode current collector.

4. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the negative electrode mixture layer has a thickness of 40 μm or more.

5. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the silicon-containing material includes an ion-conducting phase and a Si phase dispersed in the ion-conducting phase.

6. The nonaqueous electrolyte secondary battery according to claim 5, wherein the ion-conducting phase includes an amorphous carbon phase.

7. The nonaqueous electrolyte 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 nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the weight ratio of silicon in the negative electrode mixture layer is 7 mass % or more.

9. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the weight ratio of silicon in the negative electrode mixture layer is 50 mass % or less.

10. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the lithium-containing composite oxide has a layered rock salt structure.

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