Non-aqueous electrolyte secondary battery

Abstract

A non-aqueous electrolyte secondary battery according to the present invention includes an electrode body (14) that is formed by winding a positive electrode (11) and a negative electrode (12) with a separator (13) therebetween and an outer can that accommodates the electrode body (14). The negative electrode (12) includes a negative electrode core (30) and a mixture layer (32) that includes an active material and is provided to at least one surface of the negative electrode core (30). At a negative-electrode winding-start-side end part (12a) that is closer to a winding start side than a positive-electrode start end (B1) that is a winding-start-side end of the positive electrode (11), the negative electrode (12) has a high-resistance part (D1) that can adhere to the opposing separator (13) or has a higher coefficient of static friction relative to the opposing separator than other portions. The end of the high-resistance part (D1) on the positive-electrode start end (B1) side is closer to the winding start side than the position (C1) at which the negative-electrode winding-start-side end part (12a) is opposite the positive-electrode start end (B1) with the separator (13) therebetween.

Description

Non-aqueous electrolyte secondary battery

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

[0002] Conventionally, there is a non-aqueous electrolyte secondary battery described in Patent Document 1. This non-aqueous electrolyte secondary battery includes an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween. In this non-aqueous electrolyte secondary battery, in the negative electrode, a negative electrode winding start side end portion located on the winding start side from a positive electrode start end which is the winding start side end of the positive electrode is provided, and a negative electrode tab is adhered to the negative electrode winding start side end portion.

[0003] International Publication No. 2018 / 180748

[0004] On the other hand, as in the configuration described in Patent Document 1, when a negative electrode winding start side end portion located on the winding start side from the positive electrode start end is provided in the negative electrode, stress concentrates in the vicinity of the positive electrode start end of the negative electrode winding start side end portion due to expansion of the electrode plate caused by charge and discharge, which may cause electrode plate deformation such as buckling. As a result, the start end of the positive electrode abuts against the portion where the electrode plate deformation occurs via the separator, and breakage of the separator may cause a voltage drop.

[0005] Therefore, an object of the non-aqueous electrolyte secondary battery of the present disclosure is to suppress electrode plate deformation of the negative electrode that causes voltage drop.

[0006] A non-aqueous electrolyte secondary battery according to the present disclosure includes an electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween, and an outer can that accommodates the electrode assembly. The negative electrode includes a strip-shaped negative electrode core and a mixture layer containing an active material provided on at least one surface of the negative electrode core. The negative electrode has a high resistance portion provided at the negative electrode winding start side end portion located on the winding start side from the positive electrode start end which is the winding start side end of the positive electrode, the high resistance portion being adhesive to the opposing separator or having a higher coefficient of static friction with the opposing separator than other portions. An end of the high resistance portion on the positive electrode start end side is located on the winding start side from a position facing the positive electrode start end of the negative electrode winding start side end portion via the separator. This is the non-aqueous electrolyte secondary battery.

[0007] In the non-aqueous electrolyte secondary battery according to this disclosure, by positioning the positive electrode start end of the high-resistance section at a point away from the positive electrode start end of the negative electrode winding start end, when the electrode plates expand during charging and discharging of the secondary battery, the negative electrode winding start end is more likely to bend near the positive electrode start end at the end of the high-resistance section away from the positive electrode start end. As a result, stress near the positive electrode start end of the negative electrode winding start end is relieved, and electrode plate deformation in that area can be suppressed. Furthermore, since the positive electrode does not face the positive electrode near the positive electrode start end of the high-resistance section via a separator, deformation of the negative electrode winding start end near the end of the high-resistance section does not cause a voltage drop in the secondary voltage. Therefore, electrode plate deformation of the negative electrode, which causes a voltage drop in the secondary battery, can be suppressed.

[0008] This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure. This is a schematic diagram showing the arrangement relationship of the positive electrode, negative electrode, and separator at the winding start end portion shown in Figure 1, with the positive electrode, negative electrode, and separator extended in a straight line. This is a partial cross-sectional view of the insulating tape shown in Figure 2. This is a schematic diagram showing the winding start end portion of the electrode body shown in Figure 1, with a cross-section perpendicular to the central axis of the outer casing. This diagram shows that in the electrode body constituting a comparative example of a non-aqueous electrolyte secondary battery, electrode plate deformation occurs near the positive electrode start end at the winding start end of the negative electrode when the electrode plate expands, and is a schematic diagram corresponding to a part of the circumferential direction of the cross-section perpendicular to the central axis of the outer casing. This is a diagram corresponding to Figure 2 in another example of the embodiment of a non-aqueous electrolyte secondary battery. This is a diagram corresponding to Figure 2 in another example of the embodiment of a non-aqueous electrolyte secondary battery.

[0009] It is intended from the outset that new embodiments can be constructed by appropriately combining the characteristic features of the embodiments and modifications described below. In the following embodiments, the same reference numerals are used for the same components in the drawings, and redundant explanations are omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. Furthermore, among the components described below, components that are not described in the independent claim indicating the highest-level concept are optional components and are not essential components. Moreover, this disclosure is not limited to the embodiments and modifications described below, and various improvements and modifications are possible within the scope of the claims of this application and their equivalents.

[0010] Figure 1 is an axial cross-sectional view of the non-aqueous electrolyte secondary battery 10 according to the embodiment. Figure 2 is a schematic diagram showing the arrangement of the positive electrode 11, negative electrode 12, and separator 13 at the winding start end, with the positive electrode 11, negative electrode 12, and separator 13 extended in a straight line. Figure 3 is a partial cross-sectional view of the insulating tape 34 shown in Figure 2. Figure 4 is a schematic diagram showing the winding start end of the electrode body 14 in a cross-section perpendicular to the central axis O of the outer casing 15.

[0011] As shown in Figure 1, the non-aqueous electrolyte secondary battery 10 has a strip-shaped positive electrode 11 and a negative electrode 12 with opposite polarities, and a separator 13, and comprises a wound electrode body 14 in which the positive electrode 11 and the negative electrode 12 are wound around the separator 13. The non-aqueous electrolyte secondary battery 10 also comprises a bottomed cylindrical outer casing 15 that houses the electrode body 14, and a sealing body 16 that closes the opening of the outer casing 15. The outer casing 15 contains the electrode body 14 together with the non-aqueous electrolyte.

[0012] The outer container 15 is a bottomed cylindrical metal container having a cylindrical portion 15a and a bottom portion provided at one end of the cylindrical portion 15a in the axial direction α. ​​The outer container 15 has a grooved portion 21, described later, formed on the other end in the axial direction α, which is the open end of the cylindrical portion 15a, and the sealing body 16 is supported by the grooved portion 21 and closes the opening of the outer container 15. For the sake of explanation, in the following, the sealing body 16 side of the non-aqueous electrolyte secondary battery 10 will be considered the top, and the bottom side of the outer container 15 will be considered the bottom.

[0013] The non-aqueous electrolyte has ionic conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte (non-aqueous electrolyte solution), but may also be a solid electrolyte using a gel-like polymer or the like. The non-aqueous electrolyte secondary battery 10 is preferably a lithium-ion battery. The electrolyte salt may be, for example, LiBF ４ LiPF ６ Lithium salts such as the above are used. Non-aqueous solvents include, for example, esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), as well as ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain halogen-substituted products in which at least some of the hydrogen atoms in these solvents are replaced with halogen atoms such as fluorine.

[0014] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated linear carbonates, and fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP). In terms of suppressing the deterioration of the charge-discharge cycle characteristics of non-aqueous electrolyte secondary batteries or improving the output characteristics, the non-aqueous electrolyte preferably contains 5% by mass or more of FEC relative to the mass of the non-aqueous electrolyte, and more preferably contains 5% to 15% by mass of FEC.

[0015] As solid electrolytes, for example, solid or gel-like polymer electrolytes, inorganic solid electrolytes, etc., are used. Polymer electrolytes include, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As matrix polymers, for example, polymer materials that absorb non-aqueous solvents and gel are used. As polymer materials, for example, fluororesins, acrylic resins, polyether resins, etc., are used. As inorganic solid electrolytes, for example, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) are used.

[0016] As described above, the electrode body 14 has a wound structure in which a positive electrode 11 and a negative electrode 12 are wound around a separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all elongated strip-shaped bodies that are alternately stacked in the radial direction β of the electrode body 14 by being wound in a spiral. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer than the positive electrode 11 in both the longitudinal and short-range directions of the electrode plate. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and for example, two separators are arranged so as to sandwich the positive electrode 11.

[0017] A positive electrode tab 19 and a negative electrode tab 20 are connected to the electrode body 14. The positive electrode tab 19 electrically connects the positive electrode 11 and the sealing body 16. The positive electrode tab 19 is located, for example, in the center of the electrode plate of the positive electrode 11, at a position away from the winding start end and winding end end of the electrode body 14, approximately in the center of the radial direction β of the electrode body 14. The positive electrode tab 19 is a strip-shaped conductive member. The constituent material of the positive electrode tab 19 is not particularly limited, but it is preferable that the positive electrode tab 19 be made of a metal mainly composed of aluminum.

[0018] The negative electrode tab 20 is joined to the core body exposed surface 31a (Figure 2) of the core body exposed portion 31, described later, which is provided at the negative electrode winding start end, which is one end in the longitudinal direction of the negative electrode 12. In the example shown in Figure 1, the positive electrode tab 19 extends towards the sealing body 16 through the opening of the upper insulating plate 17 and is joined to the lower surface of the sealing body 16, so that the sealing body 16 becomes the positive electrode terminal. The negative electrode tab 20 is bent along the inner surface of the bottom of the outer can 15 through the through hole of the annular lower insulating plate 18 and is connected to the inner surface of the bottom of the outer can 15 by welding or the like, so that the outer can 15 becomes the negative electrode terminal. The negative electrode tab 20 is a strip-shaped conductive member. The constituent material of the negative electrode tab 20 is not particularly limited. Preferably, the negative electrode tab 20 is made of a metal mainly composed of nickel or copper, or a metal containing both nickel and copper.

[0019] The outermost surface of the electrode body 14 has an exposed portion of the surface of the negative electrode core that constitutes the negative electrode 12, and the negative electrode core is in contact with the inner surface of the outer casing 15. As a result, both the starting end and ending end of the negative electrode 12 are electrically connected to the outer casing 15, ensuring good current collection.

[0020] Referring to Figure 2, the positive electrode 11 has a strip-shaped positive electrode core 41 and positive electrode mixture layers 42 formed on both sides of the positive electrode core 41. The positive electrode core 41 can be made of a metal foil that is stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. A preferred positive electrode core 41 is a metal foil mainly composed of aluminum or an aluminum alloy. The thickness of the positive electrode core 41 is, for example, 10 μm to 30 μm.

[0021] The positive electrode composite layer 42 preferably contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF), and is formed on both sides of the positive electrode core. The thickness of the positive electrode composite layer 42 is, for example, 40 μm to 100 μm on one side. For the positive electrode active material, for example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, etc. is used. The positive electrode tab 19 is directly joined to the positive electrode core 41 by ultrasonic welding or the like.

[0022] The positive electrode 11 is manufactured 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 core 41, followed by drying and rolling.

[0023] Examples of positive electrode active materials include lithium-containing transition metal oxides containing transition metal elements such as Co, Mn, and Ni. While lithium-containing transition metal oxides are not particularly limited, they generally have the formula Li １＋ｘ MO ２ It is preferable that the composite oxide is represented by the formula (wherein -0.2 < x ≤ 0.2, and M includes at least one of Ni, Co, Mn, and Al).

[0024] Examples of the conductive agents mentioned above include acetylene black (AB), carbon black (CB) such as Ketjenblack, and carbon materials such as graphite. Examples of the binders mentioned above include fluororesins 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 carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc. These may be used individually or in combination of two or more types.

[0025] The positive electrode tab 19 is formed on one side of the positive electrode 11 and is joined, for example, by ultrasonic welding, to the exposed surface of the positive electrode core 41 that is exposed from the positive electrode mixture layer 42. In this state, the positive electrode tab 19 extends from the upper end, which is one end in the width direction of the positive electrode core 41.

[0026] The negative electrode 12 has a strip-shaped negative electrode core 30 and negative electrode mixture layers 32 formed on both sides of the negative electrode core 30. The negative electrode core 30 can be made of a metal foil that is stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with the metal arranged on its surface. The negative electrode mixture layer 32 contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR). The thickness of the negative electrode mixture layer 32 is, for example, 40 μm to 100 μm on one side. For the negative electrode active material, for example, graphite or a Si-containing material can be used. The negative electrode tab 20 is preferably directly joined to the negative electrode core by ultrasonic welding or the like.

[0027] The negative electrode 12 is manufactured by, for example, applying a negative electrode mixture slurry containing a negative electrode active material, a binder, and water to both sides of the negative electrode core 30, followed by drying and rolling.

[0028] The negative electrode active material is not particularly limited as long as it can reversibly intercept and release lithium ions. For example, carbon materials such as natural graphite and artificial graphite, metals that alloy with lithium such as Si and Sn, or alloys and composite oxides containing these can be used. For the binder contained in the negative electrode mixture layer, for example, the same resin as in the case of the positive electrode 11 is used. When preparing the negative electrode mixture slurry with an aqueous solvent, styrene-butadiene rubber (SBR), CMC or its salts, polyacrylic acid or its salts, polyvinyl alcohol, etc. can be used. These may be used individually or in combination of two or more.

[0029] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material of the separator 13 is preferably an olefin resin such as polyethylene or polypropylene. The thickness of the separator 13 is, for example, 10 μm to 50 μm. The separator 13 is becoming thinner as batteries increase in capacity and power output. The separator 13 has a melting point of, for example, 130°C to 180°C.

[0030] An annular gasket 27 is interposed between the outer casing 15 and the sealing body 16. The sealing body 16 is crimped and fixed to the upper end, which is the open end of the outer casing 15, via the gasket 27. Specifically, the upper end of the outer casing 15 is crimped to the peripheral edge of the sealing body 16 via the gasket 27. This seals the inside of the battery.

[0031] The outer can 15 has, for example, a grooved portion 21 formed by pressing the side surface from the outside to support the sealing body 16. The grooved portion 21 is preferably formed in an annular shape along the circumferential direction of the outer can 15, and its upper surface supports the sealing body 16.

[0032] The sealing body 16 has a structure in which an internal terminal plate 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26 are stacked in order from the electrode body 14 side. Each component constituting the sealing body 16 has, for example, a disc shape or a ring shape, and each component except the insulating member 24 is electrically connected to one another. The cap 26 has an annular flange provided on its outer circumference and a hat shape with a cylindrical portion in the center whose upper end is closed. The internal terminal plate 22 has a central hole that penetrates vertically. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective central portions, and the insulating member 24 is interposed between their respective peripheral portions. The components constituting the sealing body 16 are stacked axially on the flange portion of the sealing body 16.

[0033] When the internal pressure of the battery rises to a predetermined value, the lower valve body 23 deforms and breaks, pushing the upper valve body 25 upward toward the cap 26, thereby interrupting the current path between the lower valve body 23 and the upper valve body 25. If the internal pressure rises further and reaches a predetermined value, the upper valve body 25 breaks, and gas is discharged from the opening 26a of the cap 26.

[0034] The configuration of the negative electrode winding start end 12a, which is located on the winding start side of the positive electrode 11, will be explained in detail below using Figures 2 and 3. The negative electrode winding start end 12a is on the inner circumference side of the positive electrode winding start end B1 of the positive electrode 11, and is located on the winding start side of the positive electrode start end B1. In Figure 2, the portion of the negative electrode 12 indicated by arrow A2 is the negative electrode winding start end 12a, and the portion indicated by arrow A1 is the positive electrode facing portion of the negative electrode 12 that faces the positive electrode 11 via the separator 13.

[0035] The negative electrode 12 has a core body exposed portion 31 at the negative electrode winding start end 12a, where the negative electrode mixture layer 32 is absent on both sides of the negative electrode core body 30. The core body exposed portion 31 is provided in a predetermined range from the negative electrode start end B2, which is the negative electrode winding start end, toward the winding end of the negative electrode 12. Therefore, on both sides of the core body exposed portion 31, there are core body exposed surfaces 31a and 31b where the negative electrode mixture layer 32 is absent, extending from the negative electrode start end B2 toward the winding end. Of the core body exposed surfaces 31a and 31b, the negative electrode tab 20 is joined to the outer core body exposed surface 31a facing the outer circumference by ultrasonic welding or the like. In this state, the negative electrode tab 20 extends from the lower end, which is one end in the width direction of the negative electrode core body 30.

[0036] An insulating tape 34 is attached to the exposed core surface 31a on the outer side of the winding, so as to cover the surface of the exposed core surface 31a and the negative electrode tab 20 that overlaps the exposed core surface 31a. As shown in Figure 3, the insulating tape 34 is a double-sided adhesive tape having a base layer 35 provided in the middle of the thickness direction and an adhesive layer 36 which is an adhesive layer formed on both sides of the base layer 35. Between the base layer 35 and the adhesive layer 36, a heat-resistant layer containing inorganic particles such as metal oxides can be provided. The base layer can be any insulating resin, such as PPS (polyphenylene sulfide), PEEK (polyether ether ketone), PI (polyimide), PP (polypropylene), PET (polyethylene terephthalate), PBT (polybutylene terephthalate), etc.

[0037] The adhesive layer may contain at least one of a rubber-based polymer or an acrylic-based polymer. The adhesive layer may further contain, for example, a silicone-based polymer.

[0038] The insulating tape 34 is provided from near the winding start end of the core body exposed surface 31a toward the winding end, but does not reach the negative electrode mixture layer 32 on the outside of the winding. The end B3 of the insulating tape 34 on the positive electrode start end B1 side constitutes the negative electrode winding start end 12a and is positioned on the outer surface of the portion where the negative electrode mixture layer 32 is located on the inside of the winding, which is opposite the thickness direction of the negative electrode 12.

[0039] An end B3 of the insulating tape 34 is located closer to the winding start side than a position C1, which faces the positive electrode starting end B1 of the negative electrode winding start side end portion 12a with the separator 13 interposed therebetween. In the winding direction of the negative electrode 12, the end B3 of the insulating tape 34 is preferably disposed at a position advanced 0.1 turn or more and 1 turn or less toward the winding start side from the position facing the positive electrode starting end B1.

[0040] Note that the winding end side end portion of the insulating tape 34 may extend further toward the winding end side than that shown in Figure 2 to cover a part of the outer surface of the outer wound negative electrode mixture layer 32.

[0041] Since the insulating tape 34 is a double-sided tape, an adhesive layer 36 is provided on the outer side surface of the insulating tape 34 opposite to the negative electrode core 30. The adhesive layer 36 on this outer side surface is a high-resistance portion D1 that is provided at the negative electrode winding start side end portion 12a and can be adhered to the separator 13 facing the outer peripheral side. The high-resistance portion D1 is provided over the entire length of the insulating tape 34 in the winding direction. In the preferred configuration described above, an end B3 of the high-resistance portion D1 on the positive electrode starting end B1 side is also disposed at a position advanced 0.1 turn or more and 1 turn or less toward the winding start side from the position facing the positive electrode starting end B1 in the winding direction of the negative electrode 12.

[0042] Note that in this example, the winding start side end of the inner wound negative electrode mixture layer 32 is located closer to the winding start side than the winding start side end of the outer wound negative electrode mixture layer 32; however, the winding start side ends of both the outer wound and inner wound negative electrode mixture layers 32 may be aligned in the winding direction or may differ from each other. Furthermore, in this example, the negative electrode mixture layers 32 are provided on both surfaces of the negative electrode core 30, but the negative electrode mixture layers may also be provided only on one surface of the negative electrode core 30.

[0043] As described above, in this embodiment, a high-resistance portion D1 that can be adhered to the opposing separator 13 is provided at the negative electrode winding start end 12a, which is located on the winding start side of the negative electrode 12, relative to the positive electrode start end B1. Furthermore, the end B3 of the high-resistance portion D1 on the positive electrode start end B1 side is located on the winding start side of the negative electrode winding start end 12a, relative to the opposing position C1 across the separator 13 from the positive electrode start end B1. By positioning the end B3 of the high-resistance portion D1 on the positive electrode start end B1 side of the negative electrode winding start end 12a away from the positive electrode start end B1, when the electrode plates expand during charging and discharging of the secondary battery, the high-resistance portion D1 of the negative electrode winding start end 12a is pressed against the separator 13, and the high-resistance portion D1 is fixed to the separator 13 by adhesion at that point. Therefore, the negative electrode winding start end 12a is not fixed to the separator 13 near the positive electrode start end B1 side of the high-resistance section D1 near the end B3 (for example, near E1 in Figure 2), which is far from the positive electrode start end B1, making it more prone to bending. As a result, the stress on the negative electrode winding start end 12a near the positive electrode start end B1 is relieved, and electrode plate deformation in that area can be suppressed. Furthermore, since the positive electrode 11 does not face the high-resistance section D1 near the end B3 on the positive electrode start end B1 side via the separator 13, deformation of the negative electrode winding start end 12a near the end B3 of the high-resistance section D1 does not cause a voltage drop in the secondary voltage. Therefore, electrode plate deformation of the negative electrode 12, which causes a voltage drop in the secondary battery, can be suppressed.

[0044] The effects of this embodiment will be explained in detail with reference to Figure 4. As shown in Figure 4, in this example, a high-resistance portion D1 is provided at the negative electrode winding start end 12a. The end B3 of the high-resistance portion D1 on the positive electrode start end B1 side is located on the winding start side of the negative electrode winding start end 12a, relative to the opposing position C1 via the separator 13 with respect to the positive electrode start end B1. Therefore, when the secondary battery expands due to charging and discharging, the high-resistance portion D1 of the negative electrode winding start end 12a is pressed against the separator 13 located on the outer circumference side and adhered to the inner circumference side of the separator 13, thus fixing it to the separator 13. As a result, the rigidity of the portion where the high-resistance portion D1 and the separator 13 are fixed is increased, making it less susceptible to deformation. On the other hand, near the end B3 of the high-resistance portion D1 of the negative electrode winding start end 12a on the positive electrode start end B1 side, the portion on the positive electrode start end B1 side (for example, portion E1 in Figure 4) has low rigidity and is therefore more susceptible to deformation. The high-resistance section D1 is positioned, for example, approximately 0.5 turns from the positive electrode start end B1 towards the winding start end, as shown in Figure 4. This ensures that when the electrode plates expand due to the charge-discharge cycle of the secondary battery, and a circumferential compressive stress is generated on the negative electrode 12, the negative electrode winding start end 12a deforms easily near the positive electrode start end B1 side end B3 of the high-resistance section D1, resulting in, for example, a bend. Therefore, the stress on the negative electrode 12 in the area facing the positive electrode start end B1 is relieved, and electrode plate deformation in that area is suppressed. Furthermore, the positive electrode 11 does not face the outer and inner circumference of the area facing the positive electrode start end B1 of the negative electrode 12, even with the separator 13 in between. Therefore, deformation near the end B3 of the high-resistance section D1 of the negative electrode 12 does not cause a voltage drop in the secondary battery. Consequently, electrode plate deformation of the negative electrode 12, which causes a voltage drop, can be suppressed.

[0045] On the other hand, Figure 5 shows that in the electrode body 14a constituting the comparative example non-aqueous electrolyte secondary battery, electrode plate deformation occurs near the positive electrode start end B1 at the winding start end of the negative electrode 12 when the electrode plate expands, and is a schematic diagram corresponding to a part of the circumferential direction of the cross section perpendicular to the central axis of the outer casing.

[0046] In the comparative example of FIG. 5, unlike the embodiments of FIGS. 1 to 4, no high-resistance portion is provided at the negative electrode winding start side end portion 12a. For example, a negative electrode tab (not shown) and an insulating tape covering the negative electrode tab are provided on the winding outer surface of the negative electrode winding start side end portion 12a, but no adhesive layer is provided on the outer surface of the insulating tape. For this reason, the insulating tape is simply a single-sided tape having an adhesive layer on the negative electrode core side.

[0047] In FIG. 5, the oblique lattice portions schematically show the inner peripheral side end portion 14b and the outer peripheral side portion 14c of the electrode assembly 14a. The illustration of the separator is omitted. In such a comparative example, as shown in FIG. 5(a), when the electrode plate expands during charge and discharge, pressure is applied from the inner surface of the outer can, whereby the internal pressure radially inward of the electrode assembly 14a increases, and slipping occurs in which the negative electrode winding start side end portion 12a moves to one side in the winding direction so as to reduce the inner diameter.

[0048] On the other hand, as shown in FIG. 5(b), a compressive stress in the circumferential direction indicated by the black arrow is generated in each electrode plate as the internal pressure increases. At this time, among the inner peripheral side portion of the negative electrode 12, the positive electrode facing portion shown on the right side of FIG. 5(b) is compressed by members on both radial sides and the frictional force increases, so movement in the slipping direction is inhibited. On the other hand, among the negative electrode 12, the negative electrode winding start side end portion 12a located on the winding start side from the positive electrode start end B1 is likely to move in the circumferential direction toward the positive electrode start end B1, so electrode plate deformation such as buckling occurs in the portion G of FIG. 5(b). For this reason, when the winding start side end portion of the positive electrode 11 abuts against the portion G of FIG. 5(b) via a separator (not shown) and the separator is damaged, this causes a voltage drop in the secondary battery.

[0049] According to the embodiments shown in FIGS. 1 to 4 above, when the electrode plate expands during charge and discharge, the insulating tape 34 provided on the negative electrode winding start side end portion 12a is adhesively fixed to the separator 13. As a result, the portion of the negative electrode winding start side end portion 12a that is separated from the positive electrode start end B1 toward the winding start side is easily deformed, and the stress near the positive electrode start end B1 of the negative electrode winding start side end portion 12a is relieved. Therefore, electrode plate deformation of the negative electrode 12 that causes a voltage drop in the secondary battery can be suppressed.

[0050] Furthermore, in the embodiments shown in Figures 1 to 4, it is preferable that the high-resistance portion D1 provided at the negative electrode winding start end 12a is positioned at a location that is 0.1 to 1 turn toward the winding start end from the position facing the positive electrode start end B1 in the winding direction of the negative electrode 12. This preferred configuration makes it easier to more effectively relieve the stress concentrated in the portion of the negative electrode 12 that faces the vicinity of the positive electrode start end B1. On the other hand, if the high-resistance portion D1 is provided at a location that is less than 0.1 turns toward the winding start end from the position facing the positive electrode start end B1 in the negative electrode 12, the end of the high-resistance portion D1 is more likely to be located near the portion of the negative electrode 12 that faces the vicinity of the positive electrode start end B1, which may reduce the stress relief effect near the positive electrode start end B1 at the negative electrode winding start end 12a. Furthermore, if the high-resistance portion D1 is provided in the negative electrode 12 at a position that extends more than 1.0 turn toward the winding start side from the position opposite the positive electrode start end B1, the distance in the winding direction between the end of the high-resistance portion D1 and the vicinity of the positive electrode start end B1 becomes excessive. As a result, it becomes difficult to effectively relieve the stress in the portion of the negative electrode that faces the vicinity of the positive electrode start end B1.

[0051] Figure 6 is a diagram corresponding to Figure 2, showing another embodiment of a non-aqueous electrolyte secondary battery. In this example, the end of the insulating tape 34 provided on the negative electrode winding start end 12a on the positive electrode start end B1 side is shortened, and the end B3 on the positive electrode start end B1 side is positioned on the outer core exposed surface 31a of the core exposed portion 31 of the negative electrode 12, where the negative electrode mixture layer 32 is not provided on both sides. According to this example, since the end B3 is provided on the core exposed portion 31, the negative electrode winding start end is more easily deformed near the end B3. As a result, the stress in the negative electrode 12 in the portion facing the positive electrode start end B1 is further relieved, and the deformation of the electrode plate in that portion is further suppressed. In this example, the other configurations and operations are the same as those in Figures 1 to 4.

[0052] Figure 7 is a diagram corresponding to Figure 2, showing another example of a non-aqueous electrolyte secondary battery according to the embodiment. In this example, the negative electrode winding start end 12a is not provided with a negative electrode tab or insulating tape covering the negative electrode tab. On the other hand, in this example, a textured portion 50 is provided on the core body exposed surface 31a, which is the outer side surface of the core body exposed portion 31 of the negative electrode winding start end 12a. In Figure 7, the textured portion 50 is shown by a thick black line. The textured portion 50 is a portion in which a plurality of recesses or a plurality of protrusions or both are formed by processing, for example, an embossed portion in which the irregularities are arranged regularly or in a pattern. The textured portion 50 constitutes a high-resistance portion D2 at the negative electrode winding start end 12a, which is a high-friction portion with a higher static friction coefficient between it and the opposing separator 13 than other portions. The end B3a of the high-resistance section D2 on the positive electrode starting end B1 side is located on the winding start side of the negative electrode winding start end 12a, relative to the opposing position C1 via the separator 13 with respect to the positive electrode starting end B1.

[0053] In this example, a high-resistance portion D2 is provided at the negative electrode winding start end 12a, which has a higher static friction coefficient with the opposing separator 13 than other portions. The end B3a of the high-resistance portion D2 on the positive electrode start end B1 side is located on the winding start side of the negative electrode winding start end 12a, relative to the opposing position C1 via the separator 13 with respect to the positive electrode start end B1. As a result, by positioning the end B3a of the high-resistance portion D2 on the positive electrode start end B1 side of the negative electrode winding start end 12a away from the positive electrode start end B1, when the electrode plates expand during charging and discharging of the secondary battery, the high-resistance portion D2 of the negative electrode winding start end 12a is pressed against the separator 13, increasing the frictional force in that portion. Therefore, near the end B3a of the high-resistance section D2, which is further away from the positive electrode start end B1 towards the winding start side, the static friction coefficient between the negative electrode winding start end 12a and the separator 13 is lower than the static friction coefficient between the high-resistance section D2 and the separator 13. Consequently, near the end B3a of the high-resistance section D2, which is further away from the positive electrode start end B1 towards the winding start side, the negative electrode winding start end 12a becomes more prone to bending. Therefore, the stress on the negative electrode winding start end 12a near the positive electrode start end B1 is relieved, and electrode plate deformation in that area can be suppressed. Furthermore, since the positive electrode 11 does not face the high-resistance section D2 near the end B3a on the positive electrode start end B1 side via the separator 13, deformation of the negative electrode winding start end 12a near the end B3 of the high-resistance section D2 does not cause a voltage drop in the secondary voltage. As a result, electrode plate deformation of the negative electrode 12, which causes a voltage drop in the secondary battery, can be suppressed. In this example, the other configurations and functions are the same as those in Figures 1 to 4.

[0054] Furthermore, as an alternative embodiment, in the configurations of Figures 1 to 4, or Figure 6, the insulating tape 34 can be a single-sided tape having an adhesive layer only on the negative electrode core side, and a high-resistance portion can be provided on the outer surface of the single-sided tape, which has a higher static friction coefficient with the opposing separator than other parts. The high-resistance portion can be formed, for example, by grinding the outer surface of the single-sided tape or by applying a layer that forms a high roughness. Even when such a single-sided tape is provided, when the electrode plates expand during charging and discharging of the secondary battery, the high-resistance portion formed by the single-sided tape at the negative electrode winding start end is pressed against the separator, and the frictional force at that part increases. As a result, the negative electrode winding start end is more likely to bend near the positive electrode start end, near the end of the high-resistance portion that is far from the positive electrode start end. Therefore, the stress at the negative electrode winding start end near the positive electrode start end is relieved, and electrode plate deformation at that part can be suppressed. As a result, deformation of the negative electrode plate, which causes a voltage drop in secondary batteries, can be suppressed.

[0055] In the embodiments described above, a high-resistance portion was provided on the outer surface side of the negative electrode winding start end. However, the high-resistance portion may also be provided on the inner surface side of the negative electrode winding start end, allowing it to be bonded to a separator facing its inner circumference, or the static friction coefficient between the high-resistance portion and the separator may be increased.

[0056] The present disclosure is further illustrated by the following embodiments. Configuration 1: A non-aqueous electrolyte secondary battery comprising: an electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator; and an outer can for housing the electrode body, wherein the negative electrode comprises: a strip-shaped negative electrode core; and a mixture layer containing an active material provided on at least one surface of the negative electrode core; wherein the negative electrode is provided at a negative electrode winding start end located on the winding start side of the positive electrode start end, which is the winding start end of the positive electrode, and has a high resistance portion that is adhesive to the opposing separator or has a higher static friction coefficient with the opposing separator than other portions, and the positive electrode start end end of the high resistance portion is located on the winding start side of the position of the negative electrode winding start end facing the positive electrode start end via the separator. Configuration 2: The end of the high-resistance portion on the positive electrode starting end side is positioned at a location that is 0.1 to 1 turn toward the winding start side from the position opposite to the positive electrode starting end in the winding direction of the negative electrode, as described in Configuration 1. Configuration 3: The high-resistance portion is an adhesive layer provided on the outer surface of the tape provided at the negative electrode winding start end, as described in Configuration 1 or Configuration 2. Configuration 4: The high-resistance portion is the outer surface of the tape provided at the negative electrode winding start end, and is a portion where the static friction coefficient between it and the opposing separator is higher than that of the other portions, as described in Configuration 1 or Configuration 2. Configuration 5: The high-resistance portion is an unevenly processed portion provided on the side surface of the negative electrode core at the negative electrode winding start end, as described in Configuration 1 or Configuration 2.

[0057] 10 Non-aqueous electrolyte secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14, 14a Electrode body, 15 Outer can, 15a Cylindrical part, 16 Sealing body, 17 Upper insulating plate, 18 Lower insulating plate, 19 Positive electrode tab, 20 Negative electrode tab, 21 Grooved part, 22 Internal terminal plate, 23 Lower valve body, 24 Insulating member, 25 Upper valve body, 26 Cap, 27 Gasket, 30 Negative electrode core, 31 Core body exposed part, 31a, 31b Core body exposed surface, 32 Negative electrode mixture layer, 34 Insulating tape, 35 Base layer, 36 Adhesive layer, 41 Positive electrode core, 41a, 41b Core body exposed surface, 42 Positive electrode mixture layer, 50 Textured part.

Claims

1. A non-aqueous electrolyte secondary battery comprising: an electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator in between; and an outer can for housing the electrode body, wherein the negative electrode comprises a strip-shaped negative electrode core and a composite layer containing an active material provided on at least one surface of the negative electrode core, the negative electrode is provided at a negative electrode winding start end located on the winding start side of the positive electrode start end which is the winding start end of the positive electrode, and has a high resistance portion that is adhesive to the opposing separator or has a higher static friction coefficient with the opposing separator than other portions, and the positive electrode start end end of the high resistance portion is located on the winding start side of the position of the negative electrode winding start end opposite the positive electrode start end via the separator.

2. The end of the high-resistance portion on the positive electrode starting end side is positioned at a location that is 0.1 turns or more but 1 turn or less toward the winding start side from the position opposite to the positive electrode starting end in the winding direction of the negative electrode, as described in claim 1.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the high-resistance portion is an adhesive layer provided on the outer surface of the tape provided at the negative electrode winding start end.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the high-resistance portion is the outer surface of the tape provided at the negative electrode winding start end, and the static friction coefficient between it and the opposing separator is higher than that of the other portions.

5. The non-aqueous electrolyte secondary battery according to claim 1, wherein the high-resistance portion is a textured portion provided on the side surface of the negative electrode core body at the starting end of the negative electrode winding.

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