Non-aqueous electrolyte secondary battery

Abstract

The object of the present invention is to provide a non-aqueous electrolyte secondary battery capable of suppressing the deformation of the outermost plate of the electrode body caused by charge-discharge cycles. The non-aqueous electrolyte secondary battery (10) comprises: a wound electrode body (14) formed by winding a strip-shaped positive electrode (11) and a strip-shaped negative electrode (12) separated by a spacer (13), and a metal outer casing (15) for housing the electrode body (14). On the outermost circumferential surface of the electrode body (14), the negative electrode (12) is exposed and a fixing strip (30) for fixing the wound end of the negative electrode (12) is attached to it. The fixing strip (30) has a laminated structure comprising two or more independent layers.

Description

Technical Field

[0001] This invention relates to non-aqueous electrolyte secondary batteries. Background Technology

[0002] In the past, non-aqueous electrolyte secondary batteries have been widely used, in which a wound electrode body, consisting of a strip-shaped positive electrode and a strip-shaped negative electrode wound together with spacers, is housed in an outer casing. In this type of battery, the outermost periphery of the electrode body is fixed in a way that prevents the wound from unraveling, and in particular, to prevent the outermost periphery from rolling up when the electrode body is inserted into the outer casing, an end with a fixed electrode body is sometimes used (see Patent Documents 1 and 2).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-199974

[0006] Patent Document 2: Japanese Patent Application Publication No. 2005-216754 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, the electrode bodies of non-aqueous electrolyte secondary batteries sometimes expand during charging, and the outermost periphery is subjected to pressure from the outer casing. Furthermore, due to repeated charging and discharging, the electrode bodies expand significantly compared to their initial size, thus increasing this pressure. Because a fixing band is attached to the outermost circumferential surface of the electrode body, repeated charging and discharging can sometimes cause deformation of the outermost plates constituting the electrode body, starting from the end of the fixing band where stress tends to concentrate. If the deformation of the plates becomes excessive, there is a risk of internal short circuits; therefore, suppressing plate deformation is an important issue.

[0009] Therefore, the object of the present invention is to provide a non-aqueous electrolyte secondary battery capable of suppressing the deformation of the outermost plates of the electrode body caused by charge-discharge cycles.

[0010] means for solving problems

[0011] As one aspect of the present invention, a non-aqueous electrolyte secondary battery comprises: a wound electrode body formed by winding a strip-shaped positive electrode and a strip-shaped negative electrode with a spacer between them, and a metal outer casing for housing the electrode body, wherein the negative electrode is exposed on the outermost circumferential surface of the electrode body, and a fixing strip for fixing the wound end portion of the negative electrode is attached thereto, the fixing strip having a laminated structure comprising two or more mutually independent layers.

[0012] Invention Effects

[0013] The non-aqueous electrolyte secondary battery according to the present invention can suppress the deformation of the outermost plates of the electrode body caused by charge-discharge cycles. Attached Figure Description

[0014] Figure 1 This is an axial cross-sectional view of a cylindrical secondary battery as an example of an implementation method.

[0015] Figure 2 yes Figure 1 The diagram shows a three-dimensional view of the electrodes of a secondary battery.

[0016] Figure 3 This is a cross-sectional view of the fixing strap in one embodiment.

[0017] Figure 4 This is an enlarged view of the area near the fixed band in the non-aqueous electrolyte secondary battery of the present invention after repeated charging and discharging.

[0018] Figure 5 It is the existing non-aqueous electrolyte secondary battery and Figure 4 The corresponding diagram. Detailed Implementation

[0019] Hereinafter, an example of an embodiment of the cylindrical secondary battery of the present invention will be described in detail with reference to the accompanying drawings. In the following description, specific shapes, materials, values, orientations, etc., are examples used to facilitate understanding of the present invention and can be appropriately modified accordingly to the specifications of the cylindrical secondary battery. Furthermore, the outer casing is not limited to a cylindrical shape; for example, it can be square. Also, in the following description, where multiple embodiments and modifications are included, it is envisioned from the outset that their characteristic portions be appropriately combined.

[0020] Figure 1 This is an axial cross-sectional view of a cylindrical secondary battery 10 as an example of an implementation. Figure 1The secondary battery 10 shown houses the electrode body 14 and a non-aqueous electrolyte (not shown) within an outer casing 15. The electrode body 14 has a wound structure formed by winding a positive electrode 11 and a negative electrode 12 with a spacer 13 between them. The non-aqueous solvent (organic solvent) for the non-aqueous electrolyte can be carbonates, lactones, ethers, ketones, esters, etc., and two or more of these solvents can be mixed. When two or more solvents are mixed, a mixed solvent containing cyclic carbonates and chain carbonates is preferred. For example, ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), etc., can be used as cyclic carbonates, and dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), etc., can be used as chain carbonates. The electrolyte salt for the non-aqueous electrolyte can be LiPF6, LiBF4, LiCF3SO3, etc., and mixtures thereof. The solubility of the electrolyte salt in the non-aqueous solvent can be, for example, 0.5 to 2.0 mol / L. It should be noted that, for ease of explanation, the side of the sealing body 16 will be referred to as "upper" and the bottom side of the outer body 15 as "lower" in the following explanation.

[0021] The interior of the secondary battery 10 is sealed by the sealing body 16, which closes the opening end of the outer casing 15. Insulating plates 17 and 18 are respectively provided above and below the electrode body 14. The positive electrode lead 19 extends upward through the through hole of the insulating plate 17 and is welded to the lower surface of the filter element 22, which serves as the bottom plate of the sealing body 16. In the secondary battery 10, the top plate, i.e., the cover 26, of the sealing body 16, which is electrically connected to the filter element 22, becomes the positive terminal. On the other hand, the negative electrode lead 20 extends to the bottom side of the outer casing 15 through the through hole of the insulating plate 18 and is welded to the inner bottom surface of the outer casing 15. In the secondary battery 10, the outer casing 15 becomes the negative terminal.

[0022] The outer casing 15 is a bottomed cylindrical metal outer casing. As a result, it is hard and not easily deformed when the battery is subjected to external stress, thus protecting the internal components. On the other hand, when the electrode body 14 expands due to repeated charging and discharging, the hardness and resistance of the metal outer casing 15 prevents the electrode body 14 from experiencing increased pressure from the outer casing 15.

[0023] As described above, the outer casing 15 can also be square. However, since the cylindrical outer casing 15 has a circular cross-section in the horizontal direction, the stress inside the battery is evenly distributed. Therefore, compared with a square outer casing that has a flat portion that is prone to expansion, it is less likely to expand, and the pressure on the electrode body 14 from the outer casing 15 is more likely to increase. As a result, when the outer casing 15 is cylindrical, the electrode plates constituting the outermost periphery of the electrode body, starting from the end of the fixing band, are more likely to deform, and thus the effects of the present invention are more easily realized.

[0024] A sealing gasket 27 is provided between the outer casing 15 and the sealing body 16 to ensure the internal airtightness of the secondary battery 10. The outer casing 15, for example, has a groove portion 21 formed by pressing the side portion from the outside to support the sealing body 16. The groove portion 21 is preferably formed in a ring shape along the circumference of the outer casing 15, and the sealing body 16 is supported on its upper surface by the sealing gasket 27.

[0025] The sealing body 16 comprises a filter element 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cover 26, stacked sequentially from the electrode body 14 side. Each component constituting the sealing body 16 is, for example, circular or annular in shape, and all components except 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 central portions, with the insulating member 24 sandwiched between their respective peripheral portions. If the internal pressure of the battery rises due to abnormal heating, for example, the lower valve body 23 breaks, thereby causing the upper valve body 25 to bulge towards the cover 26 and separate from the lower valve body 23, thus severing the electrical connection between them. If the internal pressure rises further, the upper valve body 25 breaks, and gas is discharged from the opening 26a of the cover 26.

[0026] Next, refer to Figure 2 The electrode body 14 will be described. Figure 2 This is a perspective view of the electrode body 14. As described above, the electrode body 14 has a spiral structure formed by winding a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 together with a spacer 13. The positive electrode 11, negative electrode 12, and spacer 13 are all formed in strip shape and are wound into a spiral shape around a core arranged along the winding axis, thus forming an alternating layered state in the radial direction of the electrode body 14. In the radial direction, the side facing the winding axis is called the inner circumferential side, and the opposite side is called the outer circumferential side. In the electrode body 14, the length direction of the positive electrode 11 and the negative electrode 12 is called the winding direction, and the width direction of the strips of the positive electrode 11 and the negative electrode 12 is called the axial direction. Figure 2 As shown, the negative electrode 12 is exposed on the outermost circumferential surface of the electrode body 14.

[0027] The positive electrode 11 comprises: a strip-shaped positive current collector and positive electrode flux layers formed on both sides of the positive current collector. The positive current collector may be, for example, a foil of a metal such as aluminum, or a film of that metal disposed on its surface. The positive electrode flux layers may, for example, contain a positive active material, a binder, a conductive agent, etc. The positive electrode 11 may be manufactured, for example, by coating a positive electrode flux slurry containing a positive active material, a binder, a conductive agent, etc., onto the positive current collector and drying it, thereby forming the positive electrode flux layer and then calendering the positive electrode flux layer.

[0028] Examples of lithium-containing transition metal oxides containing transition metal elements such as Co, Mn, and Ni can be cited as positive electrode active materials. There are no particular limitations on lithium-containing transition metal oxides, but those with the general formula Li are preferred. 1+xMO2 (where -0.2 < x ≤ 0.2, and M includes at least one of Ni, Co, Mn, and Al) represents a composite oxide.

[0029] Examples of conductive agents include carbon black (CB), acetylene black (AB), Ketjen black, and graphite. Examples of binders include fluorinated resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resins, and polyolefin resins. Furthermore, these resins can be used in combination with carboxymethyl cellulose (CMC) or its salts, polyethylene oxide (PEO), etc. Both conductive agents and binders can be used individually or in combination of two or more.

[0030] A portion of the positive electrode 11 has an exposed portion where the surface of the positive current collector is not covered by the positive electrode flux layer. This exposed portion can be formed, for example, by intermittently coating a portion of the positive current collector without applying the positive electrode flux slurry. One end of the positive electrode lead 19 is connected to the exposed portion via ultrasonic welding or the like, and the other end of the positive electrode lead 19 is... Figure 2 As shown, at the upper end of the electrode body 14, it extends axially from approximately the center in the radial direction between the center and the outermost periphery.

[0031] The negative electrode 12 has: a strip-shaped negative electrode current collector and negative electrode binder layers formed on both sides of the negative electrode current collector. The negative electrode current collector can be, for example, a foil of a metal such as copper, or a film of the metal disposed on its surface. The negative electrode binder layers can, for example, contain a negative electrode active material, a binder, etc. The negative electrode 12 can be manufactured, for example, by coating a negative electrode binder slurry containing a negative electrode active material, a binder, a thickener, etc., onto the negative electrode current collector and drying it to form a negative electrode binder layer, and then calendering the negative electrode binder layer.

[0032] Examples of carbon materials that can absorb and release lithium ions as negative electrode active materials include graphite, non-graphitizable carbon, easily graphitizable carbon, fibrous carbon, coke, and carbon black. In addition, examples of non-carbon-based negative electrode active materials include silicon, tin, alloys based on these materials, and oxides.

[0033] As a binder, similar to the case of the positive electrode, PTFE or styrene-butadiene copolymer (SBR) or its modified form can be used. As a thickener, carboxymethyl cellulose (CMC) or its salts can be used. Both binders and thickeners can be used individually or in combination.

[0034] Near the starting end of the winding of the negative electrode 12, there is an exposed portion of the negative electrode current collector whose surface is not covered by the negative electrode binder layer. This exposed portion is formed, for example, by intermittently coating a portion of the negative electrode current collector without applying the negative electrode binder slurry. One end of the negative electrode lead 20 is connected to this exposed portion by ultrasonic welding or the like, and the other end of the negative electrode lead 20 is... Figure 2 As shown, the lower end of the electrode body 14 extends axially from near the winding shaft.

[0035] Preferably, a negative electrode current collector exposure portion is also provided near the winding end portion 12a of the negative electrode 12, and more preferably, the entire outermost circumferential surface of the electrode body 14 is a negative electrode current collector exposure portion. As a result, the current path toward the outer casing 15 via the outermost circumferential surface of the negative electrode 12 is ensured, thereby improving the output characteristics of the battery.

[0036] The spacer 13 can be made of porous sheets, for example, that have ion permeability and insulation properties. Specific examples of porous sheets include microporous membranes, woven fabrics, and nonwoven fabrics. Preferably, the material of the spacer is polyethylene, polypropylene, or other olefin-based resins, or cellulose. The spacer 13 can be a laminate containing a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin-based resin. Alternatively, it can be a multilayer spacer containing a polyethylene layer and a polypropylene layer, or a spacer with an aromatic polyamide resin, ceramic, or other material coated on its surface can be used.

[0037] exist Figure 2 In the example shown, the negative electrode 12 is exposed on the outermost circumferential surface of the electrode body 14, and a fixing strap 30 for fixing the winding end portion 12a of the negative electrode 12 is attached thereto. The position and number of the fixing straps 30 are not particularly limited as long as they can fix the winding end portion 12a; for example, they can be arranged as follows: Figure 2 One electrode can be provided at each of the two ends of the electrode body 14 along the axial direction as shown, or it can be provided at any end of the electrode body 14 along the axial direction.

[0038] The length of the fixing band 30 is preferably close to the circumference (length of one circumference) of the outermost circumference of the electrode body 14, or it can be as follows: Figure 2 As shown, the length of the electrode body 14 is shorter than its outermost circumference in such a way that one end of the length does not overlap with the other end. If the contact area of ​​the fixing band 30 is biased, the pressure from the outer casing 15 will be locally concentrated when the electrode body 14 expands, reducing the effect of suppressing the deformation of the negative electrode 12. Therefore, it is preferable to use a method where... Figure 2 The distance between one end and the other end of the fixing strap 30 shown in the longitudinal direction is relatively short.

[0039] The width of the fixing band 30 is preferably 10% to 40% of the height of the electrode body 14. Furthermore, the sum of the widths of the fixing bands 30 on the outermost circumferential surface of the electrode body 14 is preferably 20% or more of the height of the electrode body 14. By setting the width of the fixing band 30 within this range, a balance can be achieved between the frictional force between the outer casing 15 and the fixing band 30 and the adhesive force between the layers constituting the fixing band 30. As shown later, when the electrode body 14 expands due to repeated charging and discharging, each layer can easily slide independently, significantly suppressing the deformation of the negative electrode 12. Specific examples of the width of the fixing band 30 are 3mm to 30mm, and can also be 5mm to 15mm.

[0040] Next, refer to Figure 3 The structure of the fixing belt 30 will be explained. Figure 3 This is a cross-sectional view of the fixing band 30 in one embodiment. The fixing band 30 has a laminated structure comprising two or more independent layers. Figure 3 In the example shown, the fixing strip 30 has a first layer 34 comprising a first substrate layer 32 and a first adhesive layer 33, and a second layer 38 comprising a second substrate layer 36 and a second adhesive layer 37. Here, a laminated structure comprising two or more independent layers refers to a structure where each layer has two ends in the length direction; for example, it is not a structure formed by overlapping a strip consisting of a substrate layer and an adhesive layer. By making each layer constituting the laminated structure independent, as described later, when the electrode body 14 expands due to repeated charging and discharging, each layer can easily slide independently, suppressing deformation of the negative electrode 12. In the fixing strip 30, the second layer 38 is laminated on the first layer 34, and the first adhesive layer 33 of the first layer 34 is adhered to the outermost circumferential surface of the electrode body 14. The number of layers constituting the fixing strip 30 is not particularly limited as long as it is 2 or more, for example, 2 or more and 4 or less.

[0041] The first substrate layer 32 and the second substrate layer 36 can be appropriately selected from the perspectives of strength, resistance to electrolyte, processability, and cost. For example, PP (polypropylene), PI (polyimide), PET (polyethylene terephthalate), and PPS (polyphenylene sulfide) can be used. The selection is not limited to the first substrate layer 32 and the second substrate layer 36; multiple substrate layers can be made of the same material or different materials. Furthermore, the thicknesses of the multiple substrate layers can be the same or different. For example, the thickness of the substrate layers can be 1 μm to 250 μm, or 3 μm to 180 μm.

[0042] The first adhesive layer 33 and the second adhesive layer 37 are preferably resins that have adhesive properties at room temperature, such as acrylic resins and rubber resins. The first adhesive layer 33 and the second adhesive layer 37 are not limited to a single material; multiple adhesive layers can be made of the same material or different materials. Furthermore, the thicknesses of the multiple adhesive layers can be the same or different. The thickness of the adhesive layers can be, for example, 1 μm to 125 μm, or 2 μm to 125 μm.

[0043] Next, refer to Figure 4 and Figure 5 The effects of the fixing strap 30 of the present invention will be explained. Figure 4 This is an enlarged view of the area around the fixed band 30 in the non-aqueous electrolyte secondary battery of the present invention after repeated charge and discharge cycles. Figure 5 It is the existing non-aqueous electrolyte secondary battery and Figure 4 The corresponding diagram shows that the electrode body 14 expands due to repeated charging and discharging. Therefore, the fixing band 30 attached to the negative electrode 12 is forcefully pressed against the outer casing 15, increasing the pressure on the electrode body 14 from the outer casing 15. During use... Figure 5 In the case of the existing strip consisting only of the first layer 34, the first adhesive layer 33 is firmly attached to the negative electrode 12 without shifting. Therefore, the negative electrode 12 deforms near the end of the strip. Near the end of the strip, the larger the angle θ2 between the outer casing 15 and the negative electrode 12, the greater the deformation of the negative electrode 12. On the other hand, Figure 4 The two-layer fixing band 30 of the present invention, as shown, slides the second adhesive layer 37 on the first substrate layer 32 during charging and discharging, shifting between the first layer 34 and the second layer 38. Thus, after repeated charging and discharging... Figure 4 In the middle, the fixing band 30 becomes stepped, and with Figure 5 Compared to θ2, the angle θ1 between the outer casing 15 and the negative electrode 12 is smaller, thus suppressing the deformation of the negative electrode 12. The material of the aforementioned adhesive layer is easier to adhere to the negative electrode 12 than the aforementioned substrate layer; therefore, even if the same material is used in the first adhesive layer 33 and the second adhesive layer 37, the non-aqueous electrolyte secondary battery after charging and discharging will become... Figure 4 The shape shown. Additionally, for the fixing strap 30, it can be as follows: Figure 3 The multi-layered strip shown is attached to the negative electrode 12. Alternatively, the strip forming the first layer 34 can be attached to the negative electrode 12, and a second layer 38 can be further attached to it.

[0044] Example

[0045] The present invention will be further illustrated below by way of examples, but the present invention is not limited to these examples.

[0046] <Example 1>

[0047] [The production of the positive electrode]

[0048] As the positive electrode active material, LiNi is used 0.88 Co 0.09 Al 0.03 O2 represents a lithium nickel cobalt aluminum composite oxide. 100 parts by mass of this positive electrode active material, 1 part by mass of acetylene black (AB) as a conductive agent, and 1 part by mass of polyvinylidene fluoride (PVDF) as a binder were mixed, and N-methyl-2-pyrrolidone (NMP) was added in appropriate amounts to prepare a positive electrode slurry. Next, the positive electrode slurry was coated on both sides of a positive electrode current collector formed from aluminum foil, dried in a dryer, cut into specified electrode sizes, and rolled using rollers to obtain a strip-shaped positive electrode. Additionally, an uncoated portion without active material was formed at the center of the positive electrode along its length, and aluminum positive electrode leads were fixed to the uncoated portion by ultrasonic welding.

[0049] [Making the negative electrode]

[0050] As the negative electrode active material, a mixture of 95 parts by mass of graphite powder and 5 parts by mass of silicon oxide is used. 100 parts by mass of this negative electrode active material, 1 part by mass of styrene-butadiene rubber (SBR) as a binder, and 1 part by mass of carboxymethyl cellulose (CMC) as a thickener are mixed, and water is added as needed to prepare a negative electrode slurry. Next, the negative electrode slurry is coated onto both sides of a negative electrode current collector formed from copper foil, dried in a dryer, cut into specified electrode sizes, and calendered using rollers to obtain a strip-shaped positive electrode. Additionally, an uncoated portion without active material is formed at one end along the length of the negative electrode, and a nickel negative electrode lead is fixed to this uncoated portion by ultrasonic welding. An uncoated portion without active material is also formed at the other end along the length of the negative electrode.

[0051] [Electrode fabrication]

[0052] The positive and negative electrodes are wound into a spiral shape with the negative electrode on the outermost periphery, separated by a spacer, to create a wound electrode body. At this point, the end of the negative electrode without a negative lead is positioned on the inner periphery (the starting side of winding), and the uncoated portion of the other end of the negative electrode faces outwards. The spacer is a heat-resistant layer formed on one side of a microporous membrane made of polyethylene, with polyamide and aluminum fillers dispersed therein.

[0053] [Fixing the end portion of the electrode body]

[0054] Two single-layer tapes coated with 10μm acrylic adhesive are overlapped on a polypropylene film measuring 62mm in length, 9mm in width, and 20μm in thickness to form a fixing tape. This fixing tape is then... Figure 2The electrode body is fixed by attaching it to both axial ends of the electrode body, which contains the negative electrode, as shown.

[0055] [Preparation of non-aqueous electrolytes]

[0056] A non-aqueous electrolyte was prepared by adding LiPF6 at a concentration of 1 mol / L to a mixed solvent consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of EC:EMC:DMC = 3:3:4.

[0057] [Making a Second-hand Battery]

[0058] Insulating plates are placed above and below the aforementioned electrode body. The negative electrode lead is soldered to the bottom of the outer casing, and the positive electrode lead is soldered to the sealing body. The electrode body is then housed within the bottomed cylindrical outer casing. A non-aqueous electrolyte is then injected into the interior of the outer casing. Finally, the opening of the outer casing is sealed with the sealing body through a gasket, thus fabricating a cylindrical non-aqueous electrolyte secondary battery. The battery has a capacity of 4600 mAh.

[0059] <Example 2>

[0060] In fixing the end of the electrode, three single-layer tapes are overlapped to form a fixing tape. Otherwise, the secondary battery is made in the same way as in Example 1.

[0061] <Example 3>

[0062] In fixing the end of the electrode body, four single-layer tapes are overlapped to form a fixing tape. Otherwise, the secondary battery is made in the same way as in Example 1.

[0063] <Comparative Example 1>

[0064] In fixing the end of the electrode body, the single-layer tapes are not overlapped, but a single-layer tape is used as the fixing tape. Otherwise, the secondary battery is manufactured in the same way as in Example 1.

[0065] <Comparative Example 2>

[0066] In fixing the end of the electrode body, a single-layer tape coated with 10μm of acrylic adhesive on a polypropylene film with a length of 124mm, a width of 9mm, and a thickness of 20μm is used as a fixing tape, and then it is bonded in a way that is stacked in the radial direction of the electrode body. Otherwise, the secondary battery is manufactured in the same way as in technical solution 1.

[0067] The number of layers, length, and width of each fixing strap used in the embodiments and comparative examples are shown in Table 1.

[0068] [Table 1]

[0069]

[0070] [Evaluation of the deformation of the negative electrode]

[0071] The secondary batteries fabricated in the examples and comparative examples were charged at a constant current of 0.3C at 25°C until the battery voltage reached 4.2V, and then charged at a constant voltage of 4.2V until the current value reached 0.02C. Then, after a 20-minute pause, they were discharged at a constant current of 1C until the battery voltage reached 3.0V, followed by another 20-minute pause. This charge-discharge cycle was counted as one cycle and repeated 500 times. After 500 cycles, the secondary batteries were charged at a constant current of 0.3C at 25°C until the battery voltage reached 4.2V, and then charged at a constant voltage of 4.2V until the current value reached 0.02C. The batteries were then disassembled, and the deformation of the negative electrode near the fixing band was evaluated by visual observation on the outermost circumference of the electrode body.

[0072] In Examples 1-3, no negative electrode deformation was observed. However, in Comparative Examples 1 and 2, negative electrode deformation was observed. In Comparative Example 2, although the fixing tape had a two-layer structure, unlike Example 1, it did not have a structure consisting of independently stacked single-layer tapes. That is, the upper layer of the fixing tape was connected to the lower layer, thus restricting the free movement of the upper layer. It can be inferred that this prevented the suppression of negative electrode deformation in Comparative Example 2.

[0073] Explanation of reference numerals in the attached figures

[0074] 10 Secondary battery, 11 Positive electrode, 12 Negative electrode, 12a End portion, 13 Spacer, 14 Electrode body, 15 Outer body, 16 Sealing body, 17, 18 Insulating plate, 19 Positive lead, 20 Negative lead, 21 Groove, 22 Filter element, 23 Lower valve body, 24 Insulating component, 25 Upper valve body, 26 Cover, 26a Opening, 27 Sealing gasket, 30 Fixing strap, 32 First substrate layer, 33 First adhesive layer, 34 First layer, 36 Second substrate layer, 37 Second adhesive layer, 38 Second layer

Claims

1. A non-aqueous electrolyte secondary battery, comprising: a wound electrode body formed by winding a strip-shaped positive electrode and a strip-shaped negative electrode with a spacer between them, and a metal outer casing for housing the electrode body, wherein, On the outermost circumferential surface of the electrode body, the negative electrode is exposed and is fitted with a fixing strap to secure the end portion of the coil for fixing the negative electrode. The fixing strip has a laminated structure, which includes a first layer adhered to the negative electrode and a second layer adhered to the first layer. The first layer includes a first substrate layer and a first adhesive layer, and the second layer includes a second substrate layer and a second adhesive layer. In the winding direction of the electrode body, the two ends of the stacked structure are stepped.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The negative electrode comprises: a negative electrode current collector and a negative electrode additive layer formed on the surface of the negative electrode current collector. The negative current collector is exposed on the outermost circumferential surface of the electrode body.

3. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein, The fixing strap is attached to both ends of the electrode body along its axial direction.

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