Non-aqueous electrolyte secondary battery

Abstract

To provide a non-aqueous electrolyte secondary battery that can suppress damage to an electrode body near the end of an insulating tape caused by repeated charging and discharging.SOLUTION: A non-aqueous electrolyte secondary battery 10 includes an outer casing 15, a wound electrode assembly 14 housed in the outer casing 15 and formed by winding a positive electrode 11 and a negative electrode 12 with a separator 13 interposed therebetween, and an insulating tape 30 attached to the electrode assembly 14, the insulating tape 30 includes a base layer 40 having a first main surface 44a, a second main surface 44b opposite the first main surface 44a, and a side surface 46 extending from an edge of the first main surface 44a to an edge of the second main surface 44b, and an adhesive layer 42 provided on the first main surface 44a of the base layer 40, the side surface 46 of the base layer 40 is inclined at an angle ranging from 40° to 80° or from 100° to 140° relative to the first main surface 44a and the second main surface 44b of the base layer 40.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] BACKGROUND ART Non-aqueous electrolyte secondary batteries have been widely used in which a wound electrode assembly, in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, is housed in an outer casing.

[0003] Patent Documents 1 and 2 disclose an insulating tape that is attached to an electrode body so as to fix the winding end of the electrode body so that the electrode body does not become loose after winding.

[0004] Furthermore, Patent Documents 3 to 5 disclose insulating tapes that are attached to a positive electrode constituting an electrode assembly so as to cover a positive electrode lead connected to the positive electrode, in order to improve insulation between the positive electrode lead and the negative electrode. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-199974 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-216754 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-89856 [Patent Document 4] International Publication No. 2017 / 038010 [Patent Document 5] Japanese Patent Application Publication No. 2017-152372 Summary of the Invention [Problem to be solved by the invention]

[0006] When the electrode assembly repeatedly expands and contracts due to repeated charge and discharge of a nonaqueous electrolyte secondary battery, the electrode assembly is repeatedly subjected to pressure from the outer casing. When the electrode assembly is repeatedly subjected to pressure from the outer casing, stress is applied to the insulating tape attached to the electrode assembly, which may cause damage to the electrode assembly due to unevenness at the end of the insulating tape. Such damage to the electrode assembly may lead to a decrease in the reliability and safety of the battery.

[0007] Therefore, an object of the present disclosure is to provide a nonaqueous electrolyte secondary battery that can suppress damage to the electrode assembly near the end of the insulating tape that occurs due to repeated charging and discharging. [Means for solving the problem]

[0008] A nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure includes: an outer casing; a wound electrode assembly housed in the outer casing, in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; and an insulating tape attached to the electrode assembly, wherein the insulating tape includes a base layer having a first main surface, a second main surface opposite to the first main surface, and a side surface extending from an edge of the first main surface to an edge of the second main surface; and an adhesive layer provided on the first main surface of the base layer, wherein the side surface of the base layer is inclined at an angle of 40° to 80° or 100° to 140° relative to the first main surface and the second main surface of the base layer. [Effects of the Invention]

[0009] According to the nonaqueous electrolyte secondary battery according to the present disclosure, damage to the electrode assembly near the end of the insulating tape caused by repeated charging and discharging can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment; [Figure 2] FIG. 2 is a perspective view of the electrode assembly shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line L1-L1 in FIG. 2. [Figure 4] FIG. 2 is a partial top view of the positive electrode at a location where the positive electrode tab is attached, observed from one main surface side. [Figure 5] FIG. 5 is a cross-sectional view taken along line L1-L1 in FIG. [Figure 6] FIG. 2 is a partial top view of the winding start end portion of the positive electrode, observed from one main surface side. [Figure 7] FIG. 7 is a cross-sectional view taken along line L1-L1 in FIG. [Figure 8] FIG. 2 is a cross-sectional view showing an example of the configuration of an insulating tape used in the present embodiment. [Figure 9] FIG. 10 is a cross-sectional view showing another example of an insulating tape used in the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an example of an embodiment of a nonaqueous electrolyte secondary battery according to the present disclosure will be described with reference to the drawings. In the following description, specific shapes, materials, numerical values, directions, etc. are examples for facilitating understanding of the present disclosure and can be appropriately changed according to the specifications of the nonaqueous electrolyte secondary battery. Furthermore, when the following description includes multiple embodiments and modified examples, it is initially assumed that the characteristic portions thereof will be used in appropriate combination.

[0012] Fig. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment. The nonaqueous electrolyte secondary battery 10 shown in Fig. 1 includes an electrode assembly 14, a nonaqueous electrolyte (not shown), insulating plates 17 and 18 respectively disposed above and below the electrode assembly 14, an outer casing 15 that houses these components, and a sealing body 16 that closes the opening of the outer casing 15. The electrode assembly 14 has a wound structure in which a positive electrode 11 and a negative electrode 12 are wound with a separator 13 interposed therebetween. Note that although the electrode assembly 14 shown in Fig. 1 is cylindrical, it may have other shapes, such as a flat shape.

[0013] The exterior body 15 is, for example, a cylindrical metal exterior can with a bottom. However, the exterior body 15 may also be rectangular. A gasket 27 is provided between the exterior body 15 and the sealing body 16 to ensure airtightness inside the battery. The exterior body 15 has, for example, a grooved portion 21 that supports the sealing body 16, with a portion of the side surface protruding inward. The grooved portion 21 is preferably formed in an annular shape along the circumferential direction of the exterior body 15, and supports the sealing body 16 on its upper surface via the gasket 27.

[0014] The sealing body 16 includes a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26, which are stacked in this order from the electrode body 14 side. Each component of the sealing body 16 has, for example, a disk or ring shape, and all components except for the insulating member 24 are electrically connected to each other. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective centers, with the insulating member 24 interposed between their respective peripheral edges. If the internal pressure of the battery increases due to heat generation caused by an internal short circuit or the like, for example, the lower valve body 23 may rupture, causing the upper valve body 25 to bulge toward the cap 26 and separate from the lower valve body 25, thereby cutting off the electrical connection therebetween. If the internal pressure continues to increase, the upper valve body 25 may rupture, and gas may be released from the opening 26a of the cap 26.

[0015] In the nonaqueous electrolyte secondary battery 10 shown in FIG. 1 , a positive electrode tab 19 is attached to the positive electrode 11. The positive electrode tab 19 attached to the positive electrode 11 passes through a through-hole in the insulating plate 17 and is welded to the underside of a filter 22, which is the bottom plate of the sealing body 16. As a result, a cap 26, which is the top plate of the sealing body 16 and is electrically connected to the filter 22, serves as the positive electrode terminal. On the other hand, a negative electrode tab 20 is attached to the negative electrode 12. The negative electrode tab 20 attached to the negative electrode 12 passes through a through-hole in the insulating plate 18 and is welded to the inner bottom surface of the exterior body 15. As a result, the exterior body 15 serves as the negative electrode terminal.

[0016] FIG. 2 is a perspective view of the electrode body shown in FIG. 1. FIG. 3 is a cross-sectional view taken along line L1-L1 in FIG. 2. As described above, the electrode body 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The positive electrode 11, the negative electrode 12, and the separator 13 are all formed in a strip shape and spirally wound around a winding core disposed along the winding axis, resulting in a state in which they are alternately stacked in the radial direction of the electrode body 14. In the electrode body 14 shown in FIG. 2, the negative electrode 12 is wound so that it forms the outermost peripheral surface of the electrode body 14. In the electrode body 14, the longitudinal direction of the positive electrode 11 and the negative electrode 12 is the winding direction, and the strip width direction of the positive electrode 11 and the negative electrode 12 is the axial direction.

[0017] As shown in FIGS. 2 and 3 , an insulating tape 30 is attached to the outermost peripheral surface of the electrode assembly 14 so as to secure the winding end 14a of the electrode assembly 14 to the electrode assembly 14. Note that the winding end 14a of the electrode assembly 14 shown in FIG. 2 is the winding end of the negative electrode 12, which is the outermost peripheral surface of the electrode assembly 14. Therefore, in other words, the insulating tape 30 is attached to the outermost peripheral surface of the electrode assembly 14 so as to secure the winding end of the negative electrode 12 to the electrode assembly 14. However, the outermost peripheral surface and winding end 14a of the electrode assembly 14 are not limited to the negative electrode 12, but may be the separator 13 or the positive electrode 11. In such cases, the insulating tape 30 may also be applied. In either case, by attaching the insulating tape 30 to the outermost peripheral surface of the electrode assembly 14 so as to secure the winding end 14a of the electrode assembly 14 to the electrode assembly 14, loosening of the electrode assembly 14 after winding is suppressed.

[0018] The position and number of insulating tapes 30 are not particularly limited as long as they can fix the winding end portion 14a, but for example, as shown in Figure 2, one may be provided at each end of the axial direction of the electrode body 14, or one may be provided at either end of the axial direction of the electrode body 14.

[0019] The length of the insulating tape 30 is preferably close to the circumferential length (length of one circumference) of the outermost surface of the electrode body 14, and may be shorter than the outermost circumferential length of the electrode body 14 so that one end and the other end in the longitudinal direction do not overlap as shown in Figure 2.

[0020] The width of the insulating tape 30 is preferably 10% to 40% of the height of the electrode body 14. The width of the insulating tape 30 is, for example, 3 mm to 30 mm, and may be 5 mm to 15 mm.

[0021] Fig. 4 is a partial top view of the positive electrode at a location where the positive electrode tab is attached, observed from one main surface side, and Fig. 5 is a cross-sectional view taken along line L1-L1 in Fig. 4. The positive electrode 11 shown in Figs. 4 and 5 shows the state before winding. In Fig. 4, the insulating tape 30 covering the positive electrode tab 19 is shown in a see-through view with a dashed line to clarify the configuration of the positive electrode 11.

[0022] The positive electrode 11 includes a positive electrode current collector 32 and a positive electrode active material layer 34 formed on the positive electrode current collector 32. The positive electrode 11 does not have the positive electrode active material layer 34 formed thereon, and instead has an exposed portion 32a where the positive electrode current collector 32 is exposed. One end of the positive electrode tab 19 is connected to the exposed portion 32a of the positive electrode current collector 32. As described above, the other end of the positive electrode tab 19 is connected to the filter 22 of the sealing body 16 shown in FIG. 1. The method for connecting the positive electrode tab 19 and the exposed portion 32a is not particularly limited as long as the electrical connection between the positive electrode tab 19 and the positive electrode 11 is ensured, and examples thereof include ultrasonic welding.

[0023] The exposed portion 32a to which the positive electrode tab 19 is connected may be formed anywhere on the positive electrode 11, but is generally formed on the central side of the positive electrode 11 in the longitudinal direction.

[0024] As shown in FIGS. 4 and 5 , an insulating tape 30 is attached to the positive electrode 11 constituting the electrode assembly 14 so as to cover the exposed portion 32a of the positive electrode current collector 32 and the positive electrode tab 19 located on the exposed portion 32a. By covering the exposed portion 32a and the positive electrode tab 19 on the exposed portion 32a with the insulating tape 30 in this manner, it is possible to improve the insulation between the positive electrode 11 and the negative electrode 12, for example. Also, as shown in FIGS. 4 and 5 , the insulating tape 30 may extend toward the positive electrode active material layer 34 so as to cover the boundary between the positive electrode active material layer 34 and the exposed portion 32a. By covering the exposed portion 32a and the positive electrode tab 19 on the exposed portion 32a with the insulating tape 30 and also covering the boundary between the positive electrode active material layer 34 and the exposed portion 32a with the insulating tape 30 in this manner, it is possible to further improve the insulation between the positive electrode 11 and the negative electrode 12, for example.

[0025] Fig. 6 is a partial top view of the winding start end of the positive electrode observed from one main surface side, and Fig. 7 is a cross-sectional view taken along line L1-L1 in Fig. 6. The positive electrode shown in Figs. 6 and 7 is in a state before winding. In Fig. 6, insulating tape 30 is shown in a see-through view with a dashed line to clarify the configuration of positive electrode 11.

[0026] 6 and 7 , when the winding-start end of the positive electrode 11 does not have the positive electrode active material layer 34 and has an exposed portion 32a where the positive electrode current collector 32 is exposed, an insulating tape 30 may be attached to the positive electrode 11 constituting the electrode body 14 so as to cover a boundary portion 36 between the exposed portion 32a at the winding-start end of the positive electrode 11 and the positive electrode active material layer 34. By covering the boundary portion 36 between the positive electrode active material layer 34 and the exposed portion 32a with the insulating tape 30 in this way, it is possible to improve the insulation between the positive electrode 11 and the negative electrode 12, for example.

[0027] 6 and 7 show a configuration in which the exposed portion 32a is formed at the winding start end of the positive electrode 11, but the exposed portion 32a may be formed at an appropriate location depending on the battery design, etc. For example, it may be formed at the winding end end of the positive electrode 11 or at the longitudinal center of the positive electrode 11. In either case, the insulating tape 30 may be attached to the positive electrode 11 so as to cover the boundary 36 between the exposed portion 32a where the positive electrode current collector 32 is exposed and the positive electrode active material layer 34.

[0028] Although not shown in the figures, the negative electrode 12 has a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, and like the positive electrode 11, an exposed portion of the negative electrode current collector may be formed. For example, the exposed portion may be formed at the winding start end of the negative electrode 12. It is desirable to connect, for example, one end of the negative electrode tab 20 to the exposed portion at the winding start end of the negative electrode 12. Note that, as already described, the other end of the negative electrode tab 20 is connected to the bottom of the exterior body 15 shown in FIG. 1. As with the positive electrode tab 19, the method for connecting the negative electrode tab 20 to the exposed portion includes, for example, ultrasonic welding.

[0029] Furthermore, for example, an exposed portion of the negative electrode current collector may be formed at the winding end of the negative electrode 12, or the entire outermost peripheral surface of the electrode body 14 may be an exposed portion of the negative electrode current collector. This may make it easier to ensure a current path to the exterior body 15 via the outermost peripheral surface of the negative electrode 12, for example, and may improve the output characteristics of the battery.

[0030] The insulating tape 30 may be attached to the negative electrode, for example, so as to cover the boundary between the exposed portion of the negative electrode current collector and the negative electrode active material layer, or may be attached to the negative electrode so as to cover the exposed portion and the negative electrode tab 20 on the exposed portion.

[0031] The configuration of the insulating tape 30 will be described below.

[0032] Fig. 8 is a cross-sectional view showing an example of an insulating tape used in this embodiment, and Fig. 9 is a cross-sectional view showing another example of an insulating tape used in this embodiment. As shown in Figs. 8 and 9, insulating tape 30 has a base layer 40 and an adhesive layer 42 provided on base layer 40. The adhesive layer 42 serves as an adhesive surface for contacting electrode body 14.

[0033] The material constituting the base layer 40 is preferably a polymer material, for example, in terms of the flexibility and strength of the insulating tape 30. Examples include cellulose derivatives (e.g., cellulose ether, cellulose ester, etc.), polyvinyl chloride, polyolefins (e.g., polyethylene, polypropylene, etc.), polystyrene, polyesters (e.g., polyethylene terephthalate, etc.), polyimide, polyamide, polyamideimide, polycarbonate, and polyphenylene sulfide. Among these, polyimide and wholly aromatic polyamide (aramid) are preferred, with polyimide being particularly preferred. The base layer 40 may contain inorganic particles dispersed in a polymer material. The base layer 40 may have a multilayer structure, for example, including a layer containing inorganic particles and a layer containing only a polymer material. The thickness of the base layer 40 is, for example, 1 μm to 250 μm, and may be 3 μm to 180 μm.

[0034] The base layer 40 has main surfaces (44a, 44b) and side surfaces 46. The main surfaces are a pair of surfaces consisting of a surface 44a on which the adhesive layer 42 is disposed and a surface 44b opposite the surface 44a. The side surface 46 extends from an edge of one of the main surfaces 44a to an edge of the other surface 44b and is inclined non-perpendicularly with respect to the main surfaces (44a, 44b). The inclination angle of the side surface 46 of the base layer 40 with respect to the main surfaces (44a, 44b) is preferably in the range of 40° to 80° or 100° to 140°, for example, in terms of effectively suppressing damage to the electrode body 14. Opposing side surfaces 46 of the base layer 40 may be inclined in the same direction as shown in FIG. 8 or in different directions as shown in FIG. 9. The thickness of the base layer 40 is, for example, 1 μm to 125 μm, and may be 2 μm to 125 μm.

[0035] As described above, when the electrode body 14 repeatedly expands and contracts due to repeated charge and discharge, the electrode body 14 is repeatedly subjected to pressure from the exterior body 15. When pressure from the exterior body 15 is repeatedly applied, stress is applied to the insulating tape 30 attached to the electrode body 14. However, because the side surface 46 of the base layer 40 is inclined non-perpendicularly with respect to the main surfaces (44a, 44b), the shear force acting on the side surface 46 of the base layer 40 is alleviated compared to when the side surface 46 of the base layer 40 is perpendicular to the main surfaces (44a, 44b). As a result, damage to the electrode body 14 (substantially, the positive electrode 11, the negative electrode 12, or the separator 13) at the locations where the insulating tape 30 is attached is suppressed.

[0036] The material constituting the adhesive layer 42 is not particularly limited as long as it is a material that can ensure adhesion between the insulating tape 30 and the electrode body 14, and examples thereof include acrylic resin, natural rubber, synthetic rubber, silicone, epoxy resin, melamine resin, and phenolic resin. These may be used alone or in combination of two or more. Furthermore, in addition to the resin material, the material constituting the adhesive layer 42 may contain additives such as a tackifier, a crosslinking agent, an antiaging agent, a coloring agent, an antioxidant, a chain transfer agent, a plasticizer, a softener, a surfactant, and an antistatic agent, as well as a solvent, as necessary. The thickness of the adhesive layer 42 is, for example, 1 μm to 125 μm, and may be 2 μm to 125 μm.

[0037] The materials used for the positive electrode 11, the negative electrode 12, the separator 13, and the non-aqueous electrolyte will be described below.

[0038] The positive electrode current collector 32 constituting the positive electrode 11 may be a foil of a metal such as aluminum that is stable within the potential range of the positive electrode 11, or a film having such a metal disposed on its surface. The positive electrode active material layer 34 constituting the positive electrode 11 includes a positive electrode active material. The positive electrode active material layer 34 preferably includes a conductive material and a binder in addition to the positive electrode active material. The positive electrode 11 can be fabricated, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a binder, a conductive material, etc., to the positive electrode current collector 32, drying the slurry, and then rolling the positive electrode active material layer 34. The exposed portion 32a of the positive electrode current collector 32 may be formed, for example, by intermittent application in which the positive electrode mixture slurry is not applied to a portion of the positive electrode current collector 32.

[0039] Examples of positive electrode active materials include Li composite oxides containing lithium (Li) and transition metal elements such as cobalt (Co), manganese (Mn), and nickel (Ni). The Li composite oxides may contain additional elements other than Co, Mn, and Ni, such as aluminum (Al), zirconium (Zr), boron (B), magnesium (Mg), scandium (Sc), yttrium (Y), titanium (Ti), iron (Fe), copper (Cu), zinc (Zn), chromium (Cr), lead (Pb), tin (Sn), sodium (Na), potassium (K), barium (Ba), strontium (Sr), calcium (Ca), tungsten (W), molybdenum (Mo), niobium (Nb), and silicon (Si).

[0040] Examples of the conductive material contained in the positive electrode active material layer 34 include carbon powders such as carbon black, acetylene black, ketjen black, and graphite. These may be used alone or in combination of two or more.

[0041] Examples of binders contained in the positive electrode active material layer 34 include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resins, polyolefin resins, carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), etc. These may be used alone or in combination of two or more.

[0042] The negative electrode current collector constituting the negative electrode 12 may be, for example, a foil of a metal such as copper, or a film having such a metal disposed on its surface. The negative electrode active material layer constituting the negative electrode 12 includes, for example, a negative electrode active material. The negative electrode active material layer may also include a binder in addition to the negative electrode active material. The negative electrode 12 can be fabricated, for example, by applying a negative electrode mixture slurry containing the negative electrode active material, the binder, and the like to the negative electrode current collector, drying the slurry, and then rolling the negative electrode mixture layer. The exposed portion of the negative electrode current collector is formed, for example, by intermittent application in which the negative electrode mixture slurry is not applied to a portion of the negative electrode current collector.

[0043] Examples of the negative electrode active material include carbon materials capable of absorbing and releasing lithium ions, such as graphite, non-graphitizable carbon, graphitizable carbon, fibrous carbon, coke, carbon black, etc. Furthermore, examples of the non-carbon-based negative electrode active material include silicon, tin, and alloys and oxides mainly containing these.

[0044] The binder contained in the negative electrode active material layer may be the same material as that used in the positive electrode 11, or may be a styrene-butadiene copolymer (SBR) or a modified product thereof, etc. These may be used alone or in combination of two or more types.

[0045] The separator 13 may be, for example, a porous sheet having ion permeability and insulating properties. Specific examples of porous sheets include microporous membranes, woven fabrics, and nonwoven fabrics. Suitable materials for the separator 13 include olefin-based resins such as polyethylene and polypropylene, and cellulose. The separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin-based resin. Alternatively, the separator 13 may be a multilayer separator including a polyethylene layer and a polypropylene layer, and the surface of the separator 13 may be coated with a material such as an aramid-based resin or ceramic.

[0046] The non-aqueous electrolyte contains a non-aqueous solvent (organic solvent) and an electrolyte salt. Examples of the non-aqueous solvent include carbonates, lactones, ethers, ketones, and esters. These solvents may be used alone or in combination. When a mixture of two or more solvents is used, it is preferable to use a mixed solvent containing a cyclic carbonate and a chain carbonate. Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Examples of the chain carbonate include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). Examples of the electrolyte salt include LiPF6, LiBF4, LiCF3SO3, and mixtures thereof. The amount of electrolyte salt dissolved in the non-aqueous solvent can be, for example, 0.5 to 2.0 mol / L. [Explanation of symbols]

[0047] 10 non-aqueous electrolyte secondary battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 14a winding end portion, 15 outer casing, 16 sealing body, 17, 18 insulating plates, 19 positive electrode tab, 20 negative electrode tab, 21 grooved portion, 22 filter, 23 lower valve body, 24 insulating member, 25 upper valve body, 26 cap, 26a opening, 27 gasket, 30 insulating tape, 32 positive electrode current collector, 32a exposed portion, 34 positive electrode active material layer, 36 boundary portion, 40 substrate layer, 42 adhesive layer, 44a, 44b main surfaces, 46 side surface.

Claims

1. A nonaqueous electrolyte secondary battery comprising: an outer casing; a wound electrode assembly housed in the outer casing, the wound electrode assembly including a positive electrode and a negative electrode wound with a separator interposed therebetween; and an insulating tape attached to the electrode assembly, the insulating tape includes a base layer having a first main surface, a second main surface opposite to the first main surface, and a side surface extending from an edge of the first main surface to an edge of the second main surface; and an adhesive layer provided on the first main surface of the base layer; the side surface of the base layer is inclined at an angle in the range of 40° to 80°, or in the range of 100° to 140°, relative to the first main surface and the second main surface of the base layer.

2. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the side surfaces include a first side surface and a second side surface that face each other, and the first side surface and the second side surface are inclined in the same direction.

3. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the insulating tape is attached so as to fix the winding end portion of the electrode assembly to the electrode assembly.

4. At least one of the positive electrode and the negative electrode has a current collector, an active material layer formed on the current collector, and an exposed portion where the active material layer is not formed and the current collector is exposed, and an electrode tab is connected to the exposed portion; 4. The nonaqueous electrolyte secondary battery according to claim 1, wherein the insulating tape is attached so as to cover the exposed portion and the electrode tab on the exposed portion.

5. At least one of the positive electrode and the negative electrode has a current collector, an active material layer formed on the current collector, and an exposed portion where the active material layer is not formed and the current collector is exposed, 5. The nonaqueous electrolyte secondary battery according to claim 1, wherein the insulating tape is attached so as to cover a boundary between the exposed portion and the active material layer.

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