Non-aqueous electrolyte secondary battery

Abstract

Provided is a non-aqueous electrolyte secondary battery with further improved safety. A non-aqueous electrolyte secondary battery according to one aspect of the present disclosure comprises: a wound electrode body in which a belt-like positive electrode and a belt-like negative electrode are wound with a separator therebetween; and an exterior body that accommodates the electrode body. The negative electrode has a negative electrode current collector and a negative electrode mixture layer formed on the surface of the negative electrode current collector. The positive electrode has a positive electrode current collector, a positive electrode mixture layer formed on the surface of the positive electrode current collector, and a reinforcement layer applied to the surface of the positive electrode current collector on the winding start side beyond the winding start end of the positive electrode mixture layer. The reinforcement layer includes a non-facing part that is not facing the negative electrode mixture layer with the separator therebetween.

Description

Non-aqueous electrolyte secondary battery

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery including a wound electrode assembly.

[0002] Conventionally, non-aqueous electrolyte secondary batteries have been widely used, in which a wound electrode assembly, in which strip-shaped positive and negative electrodes are stacked and wound, is housed in an exterior body. Patent Document 1 discloses a technology in which a cylindrical exhaust path is formed by making the negative electrode 1.25 times longer than the positive electrode near the end on the winding start side, and thereby allowing gas generated inside the battery to be exhausted when the internal pressure of the battery increases due to abnormal heat generation or the like.

[0003] International Publication No. 2018 / 116876

[0004] When the electrode assembly expands with charge / discharge cycles, pressure is applied to the electrode assembly from the exterior packaging. This can cause deformation, such as bending, of the negative electrode facing the inner end of the positive electrode mixture layer, potentially resulting in an internal short circuit. The technology disclosed in Patent Document 1 does not take into consideration deformation of the negative electrode that occurs when the electrode assembly expands, and therefore there is still room for improvement in terms of suppressing internal short circuits.

[0005] An object of the present disclosure is to provide a non-aqueous electrolyte secondary battery with improved safety.

[0006] A nonaqueous electrolyte secondary battery according to one aspect of the present disclosure includes a wound electrode assembly in which strip-shaped positive and negative electrodes are wound with a separator interposed therebetween, and an exterior housing that houses the electrode assembly, wherein the negative electrode has a negative electrode current collector and a negative electrode mixture layer formed on the surface of the negative electrode current collector, and the positive electrode has a positive electrode current collector, a positive electrode mixture layer formed on the surface of the positive electrode current collector, and a reinforcing layer coated on the surface of the positive electrode current collector on the winding start side relative to the winding start end of the positive electrode mixture layer, and the reinforcing layer includes a non-facing portion that does not face the negative electrode mixture layer via the separator.

[0007] The nonaqueous electrolyte secondary battery according to the present disclosure can suppress deformation of the negative electrode, which can be a cause of an internal short circuit, while ensuring an exhaust path when the internal pressure of the battery increases.

[0008] Fig. 2 is an axial cross-sectional view of a cylindrical secondary battery according to an example of an embodiment. Fig. 3 is a perspective view of a wound electrode body provided in the secondary battery shown in Fig. 1. Fig. 4 is a front view showing, in a developed state, the positional relationship between a positive electrode and a negative electrode constituting the electrode body according to an example of an embodiment. Fig. 5 is a radial cross-sectional view of the vicinity of the winding axis of the electrode body according to an example of an embodiment.

[0009] Hereinafter, an example of an embodiment of a cylindrical secondary battery according to the present disclosure will be described in detail with reference to the drawings. In the following description, specific shapes, materials, numerical values, directions, etc. are examples for facilitating understanding of the present invention and can be appropriately changed according to the specifications of the cylindrical secondary battery. Furthermore, when the following description includes multiple embodiments and modified examples, it is assumed from the beginning that the characteristic portions of those embodiments and modified examples can be appropriately combined and used.

[0010] FIG. 1 is an axial cross-sectional view of a cylindrical secondary battery 10 according to an embodiment. The secondary battery 10 shown in FIG. 1 includes an electrode assembly 14 and a nonaqueous electrolyte (not shown) housed in an outer casing 15. The electrode assembly 14 has a wound structure in which a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 are wound with a separator 13 interposed therebetween. Examples of nonaqueous solvents (organic solvents) for the nonaqueous electrolyte include carbonates, lactones, ethers, ketones, esters, and the like. Two or more of these solvents can be mixed together. When two or more solvents are mixed together, a mixed solvent containing a cyclic carbonate and a chain carbonate is preferably used. For example, ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC) can be used as the cyclic carbonate, and dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) can be used as the chain carbonate. The electrolyte salt of the non-aqueous electrolyte is LiPF ６ , LiBF ４ , LiCF ３ SO ３etc., and mixtures thereof can be used. The amount of electrolyte salt dissolved in the non-aqueous solvent can be, for example, 0.5 mol / L or more and 2.0 mol / L or less. For convenience of explanation, the following description will be given with the sealing body 16 side as the "upper" and the bottom side of the exterior body 15 as the "lower".

[0011] The opening of the exterior body 15 is closed with the sealing body 16, thereby sealing the interior of the secondary battery 10. Insulating plates 17 and 18 are provided above and below the electrode body 14. The positive electrode tab 19 extends upward through a through-hole in the insulating plate 17 and is welded to the underside of the filter 22, which is the bottom plate of the sealing body 16. In the secondary battery 10, the cap 26, which is the top plate of the sealing body 16 and is electrically connected to the filter 22, serves as the positive electrode terminal. On the other hand, the negative electrode tab 20 extends through a through-hole in the insulating plate 18 toward the bottom of the exterior body 15 and is welded to the inner bottom surface of the exterior body 15. In addition, the negative electrode 12 is located on the outermost peripheral surface of the electrode body 14 and is in contact with the exterior body 15. In the secondary battery 10, the exterior body 15 serves as the negative electrode terminal.

[0012] The exterior body 15 is, for example, a cylindrical metal exterior can with a bottom. A gasket 27 is provided between the exterior body 15 and the sealing body 16 to ensure the airtightness of the interior of the secondary battery 10. The exterior body 15 has a grooved portion 21 that supports the sealing body 16, formed, for example, by pressing the side surface from the outside. The grooved portion 21 is preferably formed in an annular shape along the circumferential direction of the exterior body 15, and supports the sealing body 16 on its upper surface.

[0013] The sealing body 16 includes a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26, which are stacked in this order from the electrode body 14 side. Each component of the sealing body 16 has, for example, a disk or ring shape, and all components except for the insulating member 24 are electrically connected to each other. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective centers, with the insulating member 24 interposed between their respective peripheral edges. If the internal pressure of the battery increases due to abnormal heat generation, for example, the lower valve body 23 may rupture, causing the upper valve body 25 to bulge toward the cap 26 and separate from the lower valve body 25, thereby cutting off the electrical connection between them. If the internal pressure continues to increase, the upper valve body 25 may rupture, allowing gas to be released from the opening 26a of the cap 26.

[0014] Next, the electrode assembly 14 will be described with reference to Fig. 2. Fig. 2 is a perspective view of the electrode assembly 14. As described above, the electrode assembly 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The positive electrode 11, the negative electrode 12, and the separator 13 are all formed in a strip shape, and are spirally wound around a winding axis, thereby being alternately stacked in the radial direction of the electrode assembly 14. The separator 13 is formed to be at least one size larger than the positive electrode 11, and, for example, two separators 13 are arranged to sandwich the positive electrode 11.

[0015] The separator 13 may be, for example, a porous sheet having ion permeability and insulating properties. Specific examples of porous sheets include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator include olefin-based resins such as polyethylene and polypropylene, and cellulose. The separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin-based resin. Alternatively, the separator 13 may be a multilayer separator including a polyethylene layer and a polypropylene layer, and the surface of the separator 13 may be coated with a material such as an aramid-based resin or ceramic.

[0016] In the radial direction β, the side of the winding axis is referred to as the inner winding side, and the opposite side is referred to as the outer winding side. In the electrode body 14, the longitudinal direction of the positive electrode 11 and the negative electrode 12 is the winding direction γ, and the short direction of the positive electrode 11 and the negative electrode 12 is the axial direction α. ​​In the winding direction γ, the side of the winding axis is referred to as the winding start side, and the opposite side is referred to as the winding end side. The ends of the positive electrode 11 and the negative electrode 12 on the winding axis side are referred to as the winding start end, and the opposite end is referred to as the winding end. Similarly, both ends of the current collector, mixture layer, and reinforcing layer described below in the winding direction γ are also referred to as the winding start end and the winding end end. The positive electrode tab 19 extends in the axial direction α from approximately the center in the radial direction from the center to the outermost periphery at the upper end of the electrode body 14. The negative electrode tab 20 extends in the axial direction α from near the winding axis at the lower end of the electrode body 14.

[0017] Next, the positive electrode 11 and the negative electrode 12 will be described in detail with reference to Figures 3 and 4. Figure 3 is a front view showing the positive electrode 11 and the negative electrode 12 constituting the electrode body 14 according to one example of the embodiment in a developed state. Generally, the negative electrode 12 is formed to be slightly larger in size than the positive electrode 11, but in this embodiment, the winding start end 11s of the positive electrode 11 is located closer to the winding start side than the winding start end 12s of the negative electrode 12.

[0018] The negative electrode 12 has a strip-shaped negative electrode current collector 40 and a negative electrode mixture layer 42 formed on the surface of the negative electrode current collector 40. The negative electrode current collector 40 may be, for example, a foil of a metal such as copper, or a film having such a metal disposed on its surface. The thickness of the negative electrode current collector 40 is, for example, 5 μm or more and 30 μm or less.

[0019] The negative electrode mixture layer 42 is preferably formed on both sides of the negative electrode current collector 40. The thickness of the negative electrode mixture layer 42 is, for example, 10 μm or more and 150 μm or less on one side of the negative electrode current collector 40. The negative electrode mixture layer 42 contains, for example, a negative electrode active material and a binder. The negative electrode mixture layer 42 is produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, and a solvent such as water to both sides of the negative electrode current collector 40, followed by drying and rolling.

[0020] The negative electrode active material is not particularly limited as long as it can reversibly absorb and release Li ions, and generally, a carbon material such as graphite is used. The graphite may be any of natural graphite such as flake graphite, lump graphite, and amorphous graphite, or artificial graphite such as lump artificial graphite and graphitized mesophase carbon microbeads. Furthermore, metals that alloy with Li, such as Si and Sn, metal compounds containing Si and Sn, and lithium-titanium composite oxides may also be used as the negative electrode active material. For example, SiO ｘ (x is 0.5 to 1.6), silicon oxide represented by the formula Li ２ｙ SiO （２＋ｙ） A silicon-containing material in which fine particles of Si are dispersed in a lithium silicate phase represented by (0<y<2), a silicon-containing material in which fine particles of Si are dispersed in a carbon phase, or the like may be used in combination with graphite.

[0021] The negative electrode mixture layer 42 contains, for example, graphite as a negative electrode active material and a silicon-containing material. By including the silicon-containing material in the negative electrode 12 together with graphite, the battery capacity can be increased. The content of the silicon-containing material in the negative electrode active material may be 3% by mass or more. In this case, the amount of expansion of the negative electrode 12 due to charge and discharge increases, making the effects of the present disclosure more pronounced. The upper limit of the content of the silicon-containing material in the negative electrode active material is, for example, 30% by mass.

[0022] Examples of the binder contained in the negative electrode mixture layer 42 include styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), carboxymethyl cellulose (CMC) or its salts (CMC-Na, CMC-K, CMC-NH ４ and the like, which may be a partially neutralized salt), polyacrylic acid (PAA) or a salt thereof (PAA-Na, PAA-K, and the like, which may be a partially neutralized salt), polyvinyl alcohol (PVA), etc. These may be used alone or in combination of two or more.

[0023] In the example shown in FIG. 3 , negative electrode current collector exposed portions 48, where the negative electrode current collector 40 is exposed, are formed near the winding start end 12 s and the winding end on the surface of the negative electrode 12. The negative electrode current collector exposed portions 48 are portions of the surface of the negative electrode current collector 40 that are not covered with the negative electrode mixture layer 42. For example, the negative electrode current collector exposed portions 48 are formed by intermittent application of the negative electrode mixture slurry to a portion of the negative electrode current collector 40. A negative electrode tab 20 is connected to the negative electrode current collector exposed portion 48 near the winding start end 12 s. The negative electrode current collector exposed portion 48 near the winding end is in direct contact with the outer casing 15. The negative electrode current collector exposed portions 48 are preferably provided on both sides of the negative electrode 12 so as to overlap in the thickness direction of the negative electrode 12. The negative electrode tab 20 is joined to the negative electrode current collector exposed portion 48 by, for example, ultrasonic welding.

[0024] The positive electrode 11 includes a strip-shaped positive electrode current collector 30, and a positive electrode mixture layer 32 and a reinforcing layer 34 formed on the surface of the positive electrode current collector 30. The positive electrode current collector 30 may be, for example, a foil of a metal such as aluminum, or a film having such a metal disposed on its surface. A suitable positive electrode current collector 30 is a foil of a metal whose main component is aluminum or an aluminum alloy. The thickness of the positive electrode current collector 30 is, for example, 10 μm or more and 30 μm or less.

[0025] The positive electrode mixture layer 32 is formed smaller in the widthwise and lengthwise directions than the negative electrode mixture layer 42 from the viewpoint of preventing lithium deposition. The positive electrode mixture layer 32 is preferably formed on both sides of the positive electrode current collector 30. The thickness of the positive electrode mixture layer 32 is, for example, 10 μm or more and 150 μm or less on one side of the positive electrode current collector 30. The positive electrode mixture layer 32 includes, for example, a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 is produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and a solvent such as N-methyl-2-pyrrolidone (NMP) to both sides of the positive electrode current collector 30, followed by drying and rolling.

[0026] As the positive electrode active material, a lithium-containing transition metal oxide containing a transition metal element such as Co, Mn, or Ni can be used. The lithium-containing transition metal oxide is not particularly limited, but may be any of the following oxides represented by the general formula: Li １＋ｘ MO ２ (wherein, −0.2<x≦0.2, and M contains at least one of Ni, Co, Mn, and Al) is preferred.

[0027] Examples of the conductive agent contained in the positive electrode mixture layer 32 include carbon black (CB) such as acetylene black (AB) and Ketjen black, and carbon materials such as graphite. Examples of the binder contained in the positive electrode mixture layer 32 include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide (PI), acrylic resins, and polyolefin resins. These resins may also be used in combination with carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), or the like. These may be used alone or in combination of two or more.

[0028] The reinforcing layer 34 is applied to the surface of the positive electrode current collector 30 closer to the winding start side than the winding start end 32s of the positive electrode mixture layer 32. By arranging the reinforcing layer 34 closer to the winding start side than the winding start end 32s of the positive electrode mixture layer 32, the stress that the inner end of the positive electrode mixture layer 32 applies to the opposing negative electrode 12 can be reduced, and deformation such as bending can be suppressed. In addition, the reinforcing layer 34 includes a non-facing portion 36 that does not face the negative electrode mixture layer 42 across the separator 13, and the non-facing portion 36 forms a cylindrical exhaust path, so that gas generated inside the battery can be exhausted when the internal pressure of the battery increases due to abnormal heat generation or the like.

[0029] The reinforcing layer 34 is preferably formed on both sides of the positive electrode current collector 30. The thickness of the reinforcing layer 34 is, for example, 1 μm or more and 50 μm or less on one side of the positive electrode current collector 30. In this embodiment, the winding end of the reinforcing layer 34 coincides with the winding start end 32 s of the positive electrode mixture layer 32. However, the reinforcing layer 34 may be present between the positive electrode mixture layer 32 and the positive electrode current collector 30 near the winding start end 32 s of the positive electrode mixture layer 32. This embodiment can be achieved, for example, by forming the reinforcing layer 34 and then forming the positive electrode mixture layer 32 so as to overlap the reinforcing layer 34. Alternatively, the reinforcing layer 34 may be present on the surface of the positive electrode mixture layer 32 near the winding start end 32 s of the positive electrode mixture layer 32. This embodiment can be achieved, for example, by forming the positive electrode mixture layer 32 and then forming the reinforcing layer 34 so as to overlap the positive electrode mixture layer 32.

[0030] The resistivity per area of ​​the surface of the reinforcing layer 34 is 10 ６ Ω mm ２ or more. This suppresses short circuits between the reinforcing layer 34 and the negative electrode 12, thereby further improving the safety of the battery. The resistivity per area of ​​the surface of the reinforcing layer 34 can be measured, for example, using an electrode resistance meter (device name: XF057) manufactured by Hioki E.E. Corporation under conditions of a measurement current of 100 μA and a voltage range of 0.5 V.

[0031] The reinforcing layer 34 contains, for example, a binder and inorganic particles. The binder contained in the reinforcing layer 34 can be the same material as the binder contained in the positive electrode mixture layer 32. The binder used in the reinforcing layer 34 and the binder used in the positive electrode mixture layer 32 may be the same material, for example, polyvinylidene fluoride (PVDF). Examples of inorganic particles contained in the reinforcing layer 34 include metal oxide particles, metal nitride particles, metal fluoride particles, and metal carbide particles. Examples of metal oxide particles include aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, nickel oxide, silicon oxide, and manganese oxide. Examples of metal nitride particles include titanium nitride, boron nitride, aluminum nitride, magnesium nitride, and silicon nitride. Examples of metal fluoride particles include aluminum fluoride, lithium fluoride, sodium fluoride, magnesium fluoride, calcium fluoride, and barium fluoride. Examples of the metal carbide particles include silicon carbide, boron carbide, titanium carbide, and tungsten carbide. Inorganic particles include zeolite (M ２／ｎ O.Al ２ O ３ xSiO ２ ・yH ２ O, M is a metal element, n is the valence of M, x≧2, y≧0), porous aluminosilicates such as talc (Mg ３ Si ４ O １０ (OH) ２ ), layered silicates such as barium titanate (BaTiO ３ ), strontium titanate (SrTiO ３ ) or other minerals. These may be used alone or in combination of two or more. The inorganic material contained in the reinforcing layer 34 is preferably metal oxide particles, and among the metal oxide particles, one or more selected from the group consisting of aluminum oxide, titanium oxide, magnesium oxide, and zirconium oxide are more preferred. In addition, the reinforcing layer 34 preferably does not contain a positive electrode active material.

[0032] The reinforcing layer 34 is produced, for example, in the same manner as the positive electrode mixture layer 32, by applying a reinforcing layer slurry containing a binder, inorganic particles, and a solvent such as N-methyl-2-pyrrolidone (NMP) to both surfaces of the positive electrode current collector 30, followed by drying and rolling.

[0033] A positive electrode current collector exposed portion 38, in which the positive electrode current collector 30 is exposed, is formed on the surface of the positive electrode 11. The positive electrode current collector exposed portion 38 is a portion of the surface of the positive electrode current collector 30 that is not covered with the positive electrode mixture layer 32, and is provided, for example, by intermittent application of the positive electrode mixture slurry to a portion of the positive electrode current collector 30. The positive electrode current collector exposed portion 38 is preferably provided on both sides of the positive electrode 11 so as to overlap in the thickness direction of the positive electrode 11.

[0034] 3, a positive electrode current collector exposed portion 38 is provided over the entire length in the short direction at approximately the center in the longitudinal direction of the positive electrode 11. The position of the positive electrode current collector exposed portion 38 is not limited to this example, but from the viewpoint of current collection performance, the positive electrode current collector exposed portion 38 is preferably provided at a position approximately equidistant from both ends of the winding start side and the winding end side.

[0035] One end of the positive electrode tab 19 is connected to the positive electrode current collector exposed portion 38. The positive electrode tab 19 is joined to the positive electrode current collector exposed portion 38 by, for example, ultrasonic welding. Note that this is not limited to the example shown in Fig. 3 , and for example, a plurality of positive electrode current collector exposed portions 38 may be formed on the surface of the positive electrode 11, and a positive electrode tab 19 may be connected to each of the positive electrode current collector exposed portions 38.

[0036] In this embodiment, the reinforcing layer 34 is formed up to the winding start end 11s of the positive electrode 11, and the winding start end 34s of the reinforcing layer 34 and the winding start end 11s of the positive electrode 11 coincide with each other. However, this is not limited to this example, and for example, the positive electrode current collector exposed portion 38 may be formed closer to the winding start side than the winding start end 34s of the reinforcing layer 34.

[0037] Next, the positional relationship of the components of the positive electrode 11 and the negative electrode 12 will be described with reference to Fig. 4. Fig. 4 is a radial cross-sectional view of the electrode body 14 according to one example of the embodiment, near the winding axis O. Fig. 4 does not show the separator 13, and only shows the cross-sectional structures of the positive electrode 11 and the negative electrode 12.

[0038] The winding start end 34s of the reinforcing layer 34 is preferably located in a range of 0.5 to 1 turn, and more preferably in a range of 0.5 to 0.75 turns, from the winding start end 32s of the positive electrode mixture layer 32 in the longitudinal direction of the positive electrode 11. By locating the winding start end 34s of the reinforcing layer 34 in the above position, the safety of the battery is further improved.

[0039] The winding starting end 42s of the negative electrode mixture layer 42 is preferably located within a range of 0.5 turns toward the winding start side of the position facing the winding starting end 32s of the positive electrode mixture layer 32 in the longitudinal direction of the negative electrode 12. In other words, the winding starting end 42s of the negative electrode mixture layer 42 is located toward the winding start side of the winding starting end 32s of the positive electrode mixture layer 32, but the distance between the winding starting end 42s and the winding starting end 32s is preferably 0.5 turns or less.

[0040] As described above, in the nonaqueous electrolyte secondary battery according to the present disclosure, the reinforcing layer formed on the positive electrode can ensure an exhaust path when the internal pressure of the battery increases, while suppressing deformation of the negative electrode, which may be a cause of an internal short circuit.

[0041] The present disclosure is further described by the following embodiments. Aspect 1: A nonaqueous electrolyte secondary battery including a wound electrode assembly in which strip-shaped positive and negative electrodes are wound with a separator interposed therebetween, and an exterior housing that houses the electrode assembly, wherein the negative electrode has a negative electrode current collector and a negative electrode mixture layer formed on the surface of the negative electrode current collector, the positive electrode has a positive electrode current collector, a positive electrode mixture layer formed on the surface of the positive electrode current collector, and a reinforcing layer coated on the surface of the positive electrode current collector on a winding start side relative to a winding start end of the positive electrode mixture layer, and the reinforcing layer includes a non-facing portion that does not face the negative electrode mixture layer across the separator. Aspect 2: The nonaqueous electrolyte secondary battery according to Aspect 1, wherein the reinforcing layer contains inorganic particles. Aspect 3: The nonaqueous electrolyte secondary battery according to Aspect 1 or 2, wherein the winding start end of the reinforcing layer is located in a range of 0.5 to 0.75 turns from the winding start end of the positive electrode mixture layer in the longitudinal direction of the positive electrode. Configuration 4: The nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 3, wherein the winding start end of the negative electrode mixture layer is located within 0.5 turns toward the winding start side of a position facing the winding start end of the positive electrode mixture layer in the longitudinal direction of the negative electrode.

[0042] REFERENCE SIGNS LIST 10 secondary battery, 11 positive electrode, 11s winding start end, 12 negative electrode, 12s winding start end, 13 separator, 14 electrode body, 15 exterior body, 16 sealing body, 17, 18 insulating plate, 19 positive electrode tab, 20 negative electrode tab, 21 grooved portion, 22 filter, 23 lower valve body, 24 insulating member, 25 upper valve body, 26 cap, 26a opening, 27 gasket, 30 positive electrode current collector, 32 positive electrode mixture layer, 32s winding start end, 34 reinforcing layer, 34s ​​winding start end, 36 non-facing portion, 38 positive electrode current collector exposed portion, 40 negative electrode current collector, 42 negative electrode mixture layer, 42s winding start end, 48 negative electrode current collector exposed portion, O winding axis

Claims

1. A non-aqueous electrolyte secondary battery comprising a wound electrode body in which a strip-shaped positive electrode and a negative electrode are wound with a separator interposed therebetween, and an exterior body that houses the electrode body, wherein the negative electrode has a negative electrode current collector and a negative electrode mixture layer formed on the surface of the negative electrode current collector, the positive electrode has a positive electrode current collector, a positive electrode mixture layer formed on the surface of the positive electrode current collector, and a reinforcing layer coated on the surface of the positive electrode current collector on the winding start side of the winding start end of the positive electrode mixture layer, and the reinforcing layer includes a non-facing portion that does not face the negative electrode mixture layer through the separator.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the reinforcing layer contains inorganic particles.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the winding start end of the reinforcing layer is arranged in a range of 0.5 turns or more and 0.75 turns or less from the winding start end of the positive electrode mixture layer in the longitudinal direction of the positive electrode.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the winding start end of the negative electrode mixture layer is arranged in a range of 0.5 turns or less on the winding start side from a position facing the winding start end of the positive electrode mixture layer in the longitudinal direction of the negative electrode.

Images