Non-aqueous electrolyte secondary battery

Abstract

This non-aqueous electrolyte secondary battery comprises an electrode body in which a band-shaped first electrode and a band-shaped second electrode are wound. A first current collector exposed portion formed along the longitudinal direction is joined to a first current collector plate at one end of the electrode body in the winding axis direction. A tab joined to the second electrode extends at the other end of the electrode body in the winding axis direction. A first fixing tape and a second fixing tape are attached respectively to one end side and the other end side in the winding axis direction on the outermost peripheral surface of the electrode body. The length L1 of the first fixing tape and the length L2 of the second fixing tape satisfy L1 < L2. L1 and L2 satisfy respectively the relationships C × 0.1 ≤ L1 ≤ C × 0.5 and L2 ≥ C × 0.5, with respect to the perimeter C of the outermost peripheral surface of the electrode body.

Description

Nonaqueous electrolyte secondary battery

[0001] This disclosure relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery comprising a wound electrode body.

[0002] Non-aqueous electrolyte secondary batteries, which house a wound electrode body consisting of a strip-shaped positive electrode and a strip-shaped negative electrode wound around a separator, have been widely used. In such batteries, the outermost surface of the electrode body is fixed to prevent the winding from loosening after winding, and the end of the winding of the electrode body is sometimes fixed with tape to prevent the outermost surface from peeling off, especially when inserting the electrode body into the outer casing. Patent Document 1 describes an embodiment in which the fixing tape is attached to various positions on the outermost surface of the electrode body, but generally, the fixing tape is attached to both ends in the winding axis direction of the electrode body, with a length of about one full turn around the outermost surface.

[0003] Furthermore, in order to collect current from an electrode included in a wound electrode body, in addition to the method of connecting one end of a tab to the exposed current collector portion of the electrode while extending the other end of the tab from the end of the electrode body, there is also a method of providing an exposed current collector portion on the entire surface of the end of the electrode body in the direction of the winding axis, and connecting the exposed current collector portion to a current collector plate to collect current by so-called end-face current collection (see, for example, Patent Document 2).

[0004] Japanese Patent Publication No. 2009-199974, International Publication No. 2023 / 286600

[0005] In non-aqueous electrolyte secondary batteries, current is sometimes collected at one end of the electrode body by a tab, while at the other end by end-face current collection. Through our research, we have found that when different current collection structures are used at both ends of such an electrode body, and fixing tape is attached to both ends in the direction of the winding axis of the electrode body, fracture may occur at the end of the electrode winding near the end of the electrode body on the end-face current collection side. When the electrode body expands and contracts due to charging and discharging, the different current collection structures at both ends cause a difference in expansion and contraction in the direction of the winding axis. It is presumed that the area near the end of the electrode body on the end-face current collection side is fixed to the current collection plate, so stress is applied due to the difference in expansion and contraction compared to the area near the tab end of the electrode body, causing fracture at the end of the electrode winding.

[0006] The object of this disclosure is to provide a non-aqueous electrolyte secondary battery that suppresses breakage at the end of the electrode winding.

[0007] A non-aqueous electrolyte secondary battery according to one aspect of the present disclosure comprises an electrode body in which strip-shaped first and second electrodes having opposite polarities are wound longitudinally via a separator, and an outer casing housing the electrode body, wherein a first current collector exposed portion is formed along the longitudinal direction at one end of the electrode body in the winding axis direction, and the current collector of the first electrode is exposed, and the first current collector exposed portion is joined to a first current collector plate, and a tab joined to the second electrode extends from the other end of the electrode body in the winding axis direction The electrode body is provided with a first fixing tape attached to one end in the winding axis direction on the outermost surface, and a second fixing tape attached to the other end in the winding axis direction. The lengths L1 of the first fixing tape and L2 of the second fixing tape satisfy L1 < L2, and L1 satisfies the relationship C × 0.1 ≤ L1 ≤ C × 0.5 with respect to the circumference C of the outermost surface of the electrode body, and L2 satisfies the relationship L2 ≥ C × 0.5 with respect to C.

[0008] The non-aqueous electrolyte secondary battery according to this disclosure can suppress breakage at the end of the electrode winding.

[0009] This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery, which is an example of an embodiment. This is a front view showing the positive and negative electrodes included in the electrode body of the non-aqueous electrolyte secondary battery of Figure 1 in an unfolded state. This is a perspective view of the electrode body of the non-aqueous electrolyte secondary battery of Figure 1. This is a diagram showing the vicinity of the outermost periphery of the cross-section when the electrode body shown in Figure 3 is cut radially on the first fixing tape.

[0010] An example of an embodiment of this disclosure is described in detail below. In the following description, specific shapes, materials, directions, and numerical values ​​are illustrative examples to facilitate understanding of this disclosure and can be modified as appropriate to suit the application, purpose, and specifications. Furthermore, if the following description includes multiple embodiments and modifications, it is intended from the outset that their characteristic features may be combined as appropriate.

[0011] Figure 1 is an axial cross-sectional view of a non-aqueous electrolyte secondary battery 10, which is an example of an embodiment. In the secondary battery 10 shown in Figure 1, the electrode body 14 and the non-aqueous electrolyte (not shown) are housed in an outer casing 15. For the sake of explanation, the side with the sealing body 16 will be referred to as "upper" and the bottom side of the outer casing 15 will be referred to as "lower".

[0012] The electrode body 14 has a wound-type structure in which a strip-shaped positive electrode 11 and a negative electrode 12 are wound longitudinally via a separator 13. For the separator 13, for example, a porous sheet having ion permeability and insulating properties can be used. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator include polyethylene, olefin resins such as 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 resin. Alternatively, it may be a multilayer separator containing a polyethylene layer and a polypropylene layer, or a separator 13 with a surface coated with a material such as an aramid resin or ceramic may be used.

[0013] Non-aqueous electrolytes include, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. As the non-aqueous solvent (organic solvent), carbonates, lactones, ethers, ketones, and esters can be used, and two or more of these solvents can be used in mixture form. When using a mixture of two or more solvents, it is preferable to use a mixed solvent containing a cyclic carbonate and a linear carbonate. For example, ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC) can be used as cyclic carbonates, and dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) can be used as linear carbonates. As the electrolyte salt, LiPF ６ LiBF ４ , and LiCF ３ SO ３These and mixtures thereof can be used. The solubility of the electrolyte salt in the non-aqueous solvent can be, for example, 0.5 mol / L or more and 2.0 mol / L or less. The non-aqueous electrolyte is not limited to a liquid electrolyte, but may also be a solid electrolyte using a gel polymer or the like.

[0014] The opening of the outer casing 15 is sealed by the sealing body 16, thereby creating a sealed interior for the secondary battery 10. An insulating plate 17 is provided on the upper side of the electrode body 14. The positive electrode tab 18 extends upward through a through-hole in the insulating plate 17 and is welded to the lower surface 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 electrically connected to the filter 22, becomes the positive electrode terminal. The positive electrode tab 18 is made of aluminum, for example.

[0015] In the example shown in Figure 1, three positive electrode tabs 18 extend from the upper end of the electrode body 14. The number of positive electrode tabs 18 extending from the electrode body 14 is not particularly limited, but by extending multiple positive electrode tabs 18 from the electrode body 14, the connection resistance between the positive electrode 11 and the sealing body 16 can be suppressed, and the output characteristics of the secondary battery 10 can be improved. The more positive electrode tabs 18 there are, the more the connection resistance is suppressed, but the cost of the secondary battery 10 increases. Therefore, from the viewpoint of balancing the effect of suppressing connection resistance and cost, the number of positive electrode tabs 18 may be, for example, 3 to 10, or 3 to 8.

[0016] A metal current collector plate 20, made of nickel or a nickel alloy, is provided on the lower side of the electrode body 14. As will be described later, a negative electrode current collector exposed portion 44 is formed at the lower end of the electrode body 14, where the negative electrode current collector is exposed. The negative electrode current collector exposed portion 44 is joined to the current collector plate 20, and the current collector plate 20 is joined to the inner surface of the bottom plate of the outer casing 15. As a result, the outer casing 15, to which the negative electrode current collector exposed portion 44 is electrically connected via the current collector plate 20, becomes the negative electrode terminal. The end face of the electrode body 14 is joined to the current collector plate 20 in a state where the negative electrode current collector exposed portion 44 is bent and flattened.

[0017] The outer casing 15 is, for example, a metal outer casing in the shape of a bottomed cylindrical can. A gasket 27 is provided between the outer casing 15 and the sealing body 16 to ensure airtightness inside the secondary battery 10. The outer casing 15 has grooves 21 that support the sealing body 16, which are formed, for example, by pressing the side surface from the outside. The grooves 21 are preferably formed in an annular shape along the circumferential direction of the outer casing 15, and their upper surface supports the sealing body 16.

[0018] The sealing body 16 has 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 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 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 peripheries. If the internal pressure of the battery rises due to abnormal heat generation, for example, the lower valve body 23 may rupture, causing the upper valve body 25 to bulge towards the cap 26 and separate from the lower valve body 23, thereby interrupting the electrical connection between the two. If the internal pressure rises further, the upper valve body 25 may rupture, and gas may be discharged from the opening 26a of the cap 26.

[0019] Next, with reference to Figures 2 to 4, the electrode body 14 and the positive electrode 11 and negative electrode 12 included in the electrode body 14 will be described. In the following, an example will be described in which the negative electrode 12 is the first electrode and the positive electrode 11 is the second electrode. Note that this embodiment is not limited to this example, and the positive electrode 11 may be the first electrode and the negative electrode 12 may be the second electrode.

[0020] First, the positive electrode 11 and the negative electrode 12 will be described with reference to Figure 2. Figure 2 is a front view showing the positive electrode 11 and the negative electrode 12 in an unfolded state, which are included in the electrode body 14 of the non-aqueous electrolyte secondary battery 10 of Figure 1. The negative electrode 12 is larger than the positive electrode 11 in both the longitudinal and transverse directions from the viewpoint of preventing lithium deposition during charging.

[0021] The positive electrode 11 includes, for example, a strip-shaped positive electrode current collector 30 and a positive electrode mixture layer 32 formed on both sides of the positive electrode current collector 30. The positive electrode current collector 30 can be, for example, a metal foil such as aluminum, or a film with the metal arranged on its surface. The positive electrode mixture layer 32 may contain, for example, a positive electrode active material, a binder, and a conductive agent. The positive electrode active material is the main component of the positive electrode mixture layer and accounts for, for example, 90% or more of the total mass of the positive electrode mixture layer. In this specification, "main component" means the component with the highest mass ratio. The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a binder, and a conductive agent to the surface of the positive electrode current collector, drying it to form a positive electrode mixture layer, and then rolling this positive electrode mixture layer.

[0022] The positive electrode active material is composed mainly of, for example, a lithium transition metal composite oxide. Elements other than Li contained in the lithium transition metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, Si, and P. A suitable example of a lithium transition metal composite oxide is a composite oxide containing at least one of Ni, Co, and Mn. Specific examples include lithium transition metal composite oxides containing Ni, Co, and Mn, and lithium transition metal composite oxides containing Ni, Co, and Al.

[0023] Examples of conductive agents included in the positive electrode mixture layer include acetylene black (AB) and carbon black (CB) such as Ketjenblack, as well as carbon-based particles such as carbon nanotubes (CNT), graphene, and graphite. These may be used individually or in combination of two or more. Examples of binders included in the positive electrode mixture layer include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyimide resins, acrylic resins, polyolefin resins, and polyacrylonitrile (PAN). These may be used individually or in combination of two or more.

[0024] As shown in Figure 2, the surface of the positive electrode 11 has multiple exposed positive electrode current collector portions 34 at its upper end, and a positive electrode mixture layer 32 exists between these exposed positive electrode current collector portions 34. The exposed positive electrode current collector portions 34 are the parts of the surface of the positive electrode current collector 30 that are not covered by the positive electrode mixture layer 32, and are provided, for example, by intermittent coating, where the positive electrode mixture slurry is not applied to a part of the positive electrode current collector 30.

[0025] One of the positive electrode leads 19 is connected to each of the exposed positive electrode current collector portions 34. By connecting the positive electrode leads 19 to the positive electrode 11 in this manner, the area of ​​the positive electrode mixture layer 32 can be increased, thereby improving the output characteristics of the secondary battery 10. Note that the configuration of the positive electrode 11 is not limited to the example shown in Figure 2; for example, the exposed positive electrode current collector portion 34 may be formed to penetrate the positive electrode 11 in the short direction from one end along the longitudinal direction to the other end.

[0026] The negative electrode 12 includes, for example, a strip-shaped negative electrode current collector 40 and a negative electrode mixture layer 42 formed on both sides of the negative electrode current collector 40. The negative electrode current collector 40 can be, for example, a metal foil such as copper, or a film with the metal arranged on its surface. The negative electrode mixture layer 42 may include, for example, a negative electrode active material and a binder. The negative electrode active material is the main component of the negative electrode mixture layer and accounts for, for example, 90% or more of the total mass of the negative electrode mixture layer. The negative electrode 12 can be manufactured, for example, by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, a thickener, etc., to the surface of the negative electrode current collector and drying it to form a negative electrode mixture layer, and then rolling this negative electrode mixture layer.

[0027] 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 oxides containing these can be used.

[0028] The binder contained in the negative electrode mixture layer 42 can be, for example, fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resins, or polyolefin resins. 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 types.

[0029] As shown in Figure 2, on the surface of the negative electrode 12, a negative electrode current collector exposed portion 44 is formed along the longitudinal direction at the lower end. The negative electrode current collector exposed portion 44 is the part of the surface of the negative electrode current collector 40 that is not covered by the negative electrode mixture layer 42, and is provided, for example, by intermittent coating, in which the negative electrode mixture slurry is not applied to a part of the negative electrode current collector 40.

[0030] Next, with reference to Figures 3 and 4, a method for fixing the end 14E of the electrode body 14 with fixing tapes 51 and 52 will be described. Figure 3 is a perspective view of the electrode body 14 provided in the non-aqueous electrolyte secondary battery 10 of Figure 1. Figure 4 is a diagram showing the vicinity of the outermost outer surface in a cross-section when the electrode body 14 shown in Figure 3 is cut radially on the first fixing tape 51.

[0031] As shown in Figure 3, the electrode body 14 has a wound structure in which a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 are wound in a spiral shape via a separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all formed in a strip shape and are wound in a spiral shape around a winding core arranged along the winding axis, resulting in an alternate stacking in the radial direction of the electrode body 14. In the example shown in Figure 3, the separator 13 is arranged on the outermost circumference of the electrode body 14, and the winding end 14E of the electrode body 14 is the winding end of the separator 13. In the electrode body 14, the longitudinal direction of the positive electrode 11 and the negative electrode 12 is the winding direction, and the short direction of the positive electrode 11 and the negative electrode 12 is the winding axis direction. In the winding direction, the side facing the winding axis is called the winding start side, and the opposite side is called the winding end side. Also, in the positive electrode 11, the negative electrode 12, and the electrode body 14, the end on the winding end side is called the winding end.

[0032] At the upper end of the electrode body 14, the positive electrode tab 18 extends in the direction of the winding axis. Furthermore, a negative electrode current collector exposed portion 44 is formed at the lower end of the electrode body 14.

[0033] On the outermost surface of the electrode body 14, a first fixing tape 51 is attached to the lower end side, and a second fixing tape 52 is attached to the upper end side. Both the first fixing tape 51 and the second fixing tape 52 are attached to the outermost surface of the electrode body 14 so as to straddle the end 14E of the winding of the electrode body 14 in order to fix the end 14E of the winding of the electrode body 14.

[0034] The fixing tapes 51 and 52 each have, for example, a base layer and an adhesive layer formed on the surface of the base layer. The base layer can be appropriately selected from viewpoints such as strength, resistance to electrolytes, processability, and cost, and for example, PP (polypropylene), PI (polyimide), PET (polyethylene terephthalate), and PPS (polyphenylene sulfide) can be used. The adhesive layer is preferably made of a resin that is adhesive at room temperature, and for example, acrylic resins and rubber resins can be used. In the example shown in Figure 3, the first fixing tape 51 and the second fixing tape 52 have the same material and structure. However, the material and thickness of the base layer and adhesive layer of the first fixing tape 51 and the second fixing tape 52 may differ from each other.

[0035] The lengths L1 of the first fixing tape 51 and L2 of the second fixing tape 52 satisfy L1 < L2, and L1 satisfies the relationship C × 0.1 ≤ L1 ≤ C × 0.5 with respect to the circumference C of the outermost surface of the electrode body 14, while L2 satisfies the relationship L2 ≥ C × 0.5 with respect to C. This suppresses breakage at the end of the electrode winding. By setting L1 < L2 and setting L1 and L2 to the predetermined lengths described above, the restraining force by the first fixing tape 51 is made smaller than the restraining force by the second fixing tape 52, and it is presumed that breakage at the end of the electrode winding is suppressed by relaxing the stress near the end of the electrode body 14 on the current-collecting side. In this specification, "electrode" means positive electrode or negative electrode. The circumference C of the outermost surface is the length of one rotation of the outermost surface of the electrode body 14 in a cross-section of the electrode body 14 perpendicular to the winding axis. Furthermore, as long as the above effects are achieved, fixing tapes other than the first fixing tape 51 and the second fixing tape 52 may be attached to the outermost surface of the electrode body 14.

[0036] L1 may satisfy the relationship C × 0.2 ≤ L1 ≤ C × 0.5, or C × 0.2 ≤ L1 ≤ C × 0.3. L2 may, for example, satisfy the relationship C × 0.5 ≤ L2 ≤ C × 1.5, and C × 0.5 ≤ L2 ≤ C × 1.2.

[0037] L1 and L2 satisfy, for example, the relationship 1 < L2 / L1 ≤ 10. L1 and L2 may also satisfy the relationship 1.1 ≤ L2 / L1 ≤ 8, or 1.8 ≤ L2 / L1 ≤ 6. This makes the effect of suppressing breakage at the end of the electrode winding more pronounced.

[0038] The width W1 of the first fixing tape 51 and the width W2 of the second fixing tape 52 both satisfy the relationship H × 0.05 ≤ W1 and W2 ≤ H × 0.2 with respect to the height H in the winding axis direction of the electrode body 14. H is the distance between one end and the other end of the electrode body 14 in the axial direction.

[0039] The distance D between the first fixed tape 51 and the second fixed tape 52 satisfies, for example, the relationship D≧H×0.5 with respect to the height H in the winding axis direction of the electrode body 14. Thereby, the charge-discharge cycle characteristics are improved. By setting D≧H×0.5, it becomes possible for the fixed tapes 51 and 52 to apply sufficient restraining force to the electrode body 14, and it is presumed that this is because the distance between the positive electrode 11 and the negative electrode 12 after the charge-discharge cycle could be maintained below a predetermined value. It is more preferable that D and H satisfy the relationship D≧H×0.8. D is the distance between the center of the width W1 of the first fixed tape 51 and the center of the width W2 of the second fixed tape 52.

[0040] As shown in FIG. 4, it is preferable that the first fixed tape 51 does not overlap with both the winding end 11E of the positive electrode 11 and the winding end 12E of the negative electrode 12 in the radial direction of the electrode body 14. Thereby, the pressure applied near the winding ends 11E and 12E during charging and discharging of the battery is reduced, and the effect of suppressing breakage of the winding ends 11E and 12E of the electrode becomes more prominent.

[0041] Hereinafter, the present disclosure will be further described by way of examples, but the present disclosure is not limited to these examples.

[0042] <Experimental Example 1> [Production of positive electrode] As the positive electrode active material, lithium nickel cobalt aluminum oxide (LiNi ０．８８ Co ０．０９ Al ０．０３ O ２ ) was used. The positive electrode active material, graphite, and polyvinylidene fluoride were mixed at a solid content mass ratio of 100:1:0.9, and a positive electrode mixture slurry was prepared using N-methyl-2-pyrrolidone (NMP) as a dispersion medium. Next, the positive electrode mixture slurry was applied to both sides of a positive electrode current collector made of aluminum foil by the doctor blade method, the coating film was dried, and rolled using a roller. Thereafter, the positive electrode current collector was cut to a predetermined electrode size to obtain a positive electrode having positive electrode active material layers formed on both sides of the positive electrode current collector. Also, on the surface of the positive electrode, as shown in FIG. 2, three positive electrode current collector exposed portions were formed at the upper end portion. Aluminum positive electrode tabs were connected to each of the positive electrode current collector exposed portions by ultrasonic welding.

[0043] [Fabrication of the negative electrode] As the negative electrode active material, a mixture of 65 parts by mass of graphite powder and 35 parts by mass of SiC was used. 100 parts by mass of this negative electrode active material, 3 parts by mass of styrene-butadiene rubber (SBR) as a binder, and 1 part by mass of carboxymethyl cellulose (CMC) as a thickener were mixed, and further an appropriate amount of water was added to prepare a negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to both sides of a negative electrode current collector made of a copper foil by the doctor blade method, the coating film was dried, and rolled using a roller. Thereafter, the negative electrode current collector was cut into a predetermined electrode size to obtain a negative electrode having negative electrode active material layers formed on both sides of the negative electrode current collector. Also, as shown in FIG. 2, a negative electrode current collector exposed portion was formed along the longitudinal direction at the lower end on the surface of the negative electrode.

[0044] [Fabrication of the electrode body] The fabricated positive electrode and negative electrode were wound in a spiral shape through a separator so that the separator was located at the outermost periphery to fabricate a wound type electrode body. The separator used was one having a heat-resistant layer formed by dispersing fillers of polyamide and alumina on one side of a microporous membrane made of polyethylene. The first fixing tape and the second fixing tape were attached to both axial ends of the electrode body so as to straddle the winding end of the electrode body as shown in FIG. 3 to fix the electrode body. At this time, the winding end of the electrode body was positioned approximately at the center in the longitudinal direction of the first fixing tape and the second fixing tape. Also, as shown in FIG. 4, the first fixing tape was made not to overlap with either the winding end of the positive electrode or the winding end of the negative electrode. The first fixing tape and the second fixing tape had the same material and configuration, and the widths W1 and W2 were 0.1H. The values of L1, L2, and D were as shown in Table 1.

[0045] [Preparation of the non-aqueous electrolyte] Ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1:3 (25 ° C), and then vinylene carbonate was added to the mixed solvent at a concentration of 5% by mass and LiPF ６ was added so as to have a concentration of 1 mol / L to obtain a non-aqueous electrolyte.

[0046] [Fabrication of the secondary battery] The exposed negative electrode current collector at the lower end of the electrode body was welded to the current collector plate. An insulating plate was placed beneath the electrode body, the current collector plate was welded to the bottom of the casing, the positive electrode tab was welded to the sealing body, and the electrode body was housed in a bottomed cylindrical metal casing. Then, a non-aqueous electrolyte was injected into the inside of the casing. Furthermore, the open end of the casing was sealed with a sealing body via a gasket to fabricate a cylindrical non-aqueous electrolyte secondary battery.

[0047] <Examples 2-7 and Comparative Examples> For Examples 2-7 and the Comparative Examples, secondary batteries were manufactured in the same manner as in Example 1, except that the first and second fixing tapes were attached so that L1, L2, and D were the values ​​shown in Table 1. For Examples 4 and 5, compared to Example 1, D was adjusted by changing the position of the first fixing tape while keeping the position of the second fixing tape unchanged.

[0048] [Evaluation of Charge / Discharge Cycle Characteristics] The above secondary battery was charged with a constant current of 0.3C at a temperature of 25°C until the battery voltage reached 4.2V, and then charged with a constant voltage until the current value reached 0.02C at 4.2V. After a 20-minute pause, the battery was discharged with a constant current of 1C until the battery voltage reached 3.0V, followed by another 20-minute pause. This charge / discharge cycle was considered one cycle, and the cycle was repeated 200 times. The capacity retention rate was calculated using the following formula: Capacity retention rate = (Discharge capacity at cycle 200 / Discharge capacity at cycle 1) × 100

[0049] The charge-discharge cycle characteristics of the examples were evaluated relative to the comparative example's capacity retention rate, which was set to 100. A capacity retention rate of less than 100 was marked with ×, a capacity retention rate of 100 or more but less than 105 was marked with △, and a capacity retention rate of 105 or more was marked with ○.

[0050] [Evaluation of electrode winding end fracture] For each of the secondary batteries in the examples and comparative examples, 50 test cells were disassembled after the above charge-discharge cycle, and evaluated by the number of defective secondary batteries with fracture at the electrode winding end. ○ indicates no defective secondary batteries, △ indicates a defect rate of 5% or less, and × indicates a defect rate of more than 5%. In this experiment, all electrodes in which fracture at the winding end was observed were negative electrodes.

[0051] Table 1 shows the evaluation results for the examples and comparative examples.

[0052]

[0053] In Examples 1 to 6, no breakage was observed at the end of the electrode winding, and in Example 7, the rate of defective secondary batteries was lower compared to the comparative example. In particular, the secondary batteries of Examples 2 and 3 also exhibited good charge-discharge cycle characteristics.

[0054] This disclosure is further illustrated by the following embodiments. Configuration 1: A non-aqueous electrolyte secondary battery comprising an electrode body in which strip-shaped first and second electrodes having opposite polarities are wound longitudinally via a separator, and an outer casing housing the electrode body, wherein a first current collector exposed portion is formed along the longitudinal direction at one end of the electrode body in the winding axis direction, the current collector of the first electrode being exposed, and the first current collector exposed portion is joined to a first current collector plate, and a tab joined to the second electrode extends from the other end of the electrode body in the winding axis direction, and a first fixing tape is attached to the outermost outer surface of the electrode body on the side of one end in the winding axis direction, and a second fixing tape is attached to the side of the other end in the winding axis direction. A non-aqueous electrolyte secondary battery in which the length L1 of the first fixing tape and the length L2 of the second fixing tape satisfy L1 < L2, and L1 satisfies the relationship C × 0.1 ≤ L1 ≤ C × 0.5 with respect to the circumference C of the outermost surface of the electrode body, and L2 satisfies the relationship L2 ≥ C × 0.5 with respect to C. Configuration 2: The non-aqueous electrolyte secondary battery according to Configuration 1, wherein L1 and L2 satisfy the relationship 1 < L2 / L1 ≤ 10. Configuration 3: The non-aqueous electrolyte secondary battery according to Configuration 1 or 2, wherein the distance D between the first fixing tape and the second fixing tape satisfies the relationship D ≥ H × 0.5 with respect to the height H in the winding axis direction of the electrode body. Configuration 4: The non-aqueous electrolyte secondary battery according to any one of Configurations 1 to 3, wherein the width W1 of the first fixing tape and the width W2 of the second fixing tape both satisfy the relationship H × 0.05 ≤ W1 and W2 ≤ H × 0.2 with respect to H. Configuration 5: The non-aqueous electrolyte secondary battery according to any one of Configurations 1 to 4, wherein the first fixing tape does not overlap with both the winding end of the positive electrode and the winding end of the negative electrode in the radial direction of the electrode body.

[0055] 10 (Non-aqueous electrolyte) secondary battery, 11 Positive electrode, 11E End of winding for positive electrode, 12 Negative electrode, 12E End of winding for negative electrode, 13 Separator, 14 Electrode body, 14E End of winding for electrode body, 15 Outer casing, 16 Sealing body, 17 Insulating plate, 18 Positive electrode tab, 20 Current collector plate, 21 Grooved section, 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, 34 Exposed part of positive electrode current collector, 40 Negative electrode current collector, 42 Negative electrode mixture layer, 44 Exposed part of negative electrode current collector, 51 First fixing tape, 52 Second fixing tape, O Winding shaft

Claims

1. A non-aqueous electrolyte secondary battery comprising an electrode body in which strip-shaped first and second electrodes having opposite polarities are wound longitudinally via a separator, and an outer casing housing the electrode body, wherein a first current collector exposed portion is formed along the longitudinal direction at one end of the electrode body in the winding axis direction, the current collector of the first electrode is exposed, and the first current collector exposed portion is joined to a first current collector plate, and a tab joined to the second electrode extends from the other end of the electrode body in the winding axis direction, and a first fixing tape is attached to the outermost outer surface of the electrode body on the side of one end in the winding axis direction, and a second fixing tape is attached to the side of the other end in the winding axis direction. A non-aqueous electrolyte secondary battery in which the length L1 of the first fixing tape and the length L2 of the second fixing tape satisfy L1 < L2, and L1 satisfies the relationship C × 0.1 ≤ L1 ≤ C × 0.5 with respect to the circumference C of the outermost surface of the electrode body, and L2 satisfies the relationship L2 ≥ C × 0.5 with respect to C.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein L1 and L2 satisfy the relationship 1 < L2 / L1 ≤ 10.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the distance D between the first fixing tape and the second fixing tape satisfies the relationship D ≥ H × 0.5 with respect to the height H in the winding axis direction of the electrode body.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the width W1 of the first fixing tape and the width W2 of the second fixing tape both satisfy the relationship H × 0.05 ≤ W1 and W2 ≤ H × 0.2 with respect to H.

5. The non-aqueous electrolyte secondary battery according to claim 1, wherein the first fixing tape does not overlap with both the winding end of the first electrode and the winding end of the second electrode in the radial direction of the electrode body.

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