Patent Description:
Conventionally widely used is a non-aqueous electrolyte secondary battery comprising: a wound electrode assembly in which a band-shaped positive electrode and a band-shaped negative electrode are wound with a separator interposed therebetween, and the outermost circumference surface thereof is wound and fixed with a fixing tape; and an exterior housing body that houses the electrode assembly. In such a battery, a negative electrode lead, which is projected from a winding initial end part of the negative electrode, is connected to the exterior housing body to allow the exterior housing body to be a negative electrode terminal. Patent Literature <NUM> discloses a non-aqueous electrolyte secondary battery in which: a negative electrode lead provided on a winding initial end part of a negative electrode is connected to an exterior housing body; and a current collector exposed part that is in contact with an inner wall surface of the exterior housing body is provided on a winding terminal end part of the negative electrode, for improvement in output characteristics of the battery.

A relevant aqueous electrolyte secondary battery is also disclosed in <CIT>.

PATENT LITERATURE <NUM>: International Publication No.<CIT>.

Although the non-aqueous electrolyte secondary battery described in Patent Literature <NUM> requires not less than a certain contacting pressure between the electrode assembly and the exterior housing body, the electrode assembly with repeated charging and discharging expands, which results in increased contacting pressure. Since the fixing tape is attached to the outermost circumference surface of the electrode assembly, deformation such as flexure may occur on a positive electrode or negative electrode constituting the electrode assembly from an end part of the fixing tape, where the stress is likely to concentrate.

An object of the present disclosure is to provide a non-aqueous electrolyte secondary battery that can prevent the deformation, such as flexure, of the positive electrode and negative electrode from the fixing tape when the electrode assembly expands.

The non-aqueous electrolyte secondary battery of an aspect of the present disclosure is a non-aqueous electrolyte secondary battery, comprising: a wound electrode assembly in which a band-shaped positive electrode and a band-shaped negative electrode are wound with a separator interposed therebetween; and a metallic exterior housing body that houses the electrode assembly. The positive electrode or the negative electrode is exposed on the outermost circumference surface of the electrode assembly, the fixing tape having a substrate layer and an adhesive layer is attached to the positive electrode or the negative electrode by means of the adhesive layer, and the substrate layer has a surface roughness (Sa) of <NUM> or more on a region having a width of at least <NUM> from the end part.

The non-aqueous electrolyte secondary battery according to the present disclosure can prevent the deformation, such as flexure, of the positive electrode and negative electrode from the fixing tape when the electrode assembly expands.

Hereinafter, an example of an embodiment of a cylindrical secondary battery according to the present disclosure will be described in detail with reference to the drawings. In the following description, specific shapes, materials, values, directions, and the like, which are examples for facilitating understanding of the present invention, may be appropriately modified with specifications of cylindrical secondary batteries. The exterior housing body is not limited to being in cylindrical form, and may be in rectangular form or the like. When a plurality of embodiments and modified examples are included in the following description, use in appropriate combination of characteristic portions thereof are anticipated in advance.

<FIG> is an axial sectional view of a cylindrical secondary battery <NUM> of an example of an embodiment. In the secondary battery <NUM> illustrated in <FIG>, an electrode assembly <NUM> and a non-aqueous electrolyte (not illustrated) are housed in an exterior housing body <NUM>. The electrode assembly <NUM> has a wound structure in which a positive electrode <NUM> and a negative electrode <NUM> are wound with a separator <NUM> interposed therebetween. For a non-aqueous solvent of the non-aqueous electrolyte (organic solvent), carbonates, lactones, ethers, ketones, esters, and the like may be used, and two or more of these solvents may be mixed to be used. When two or more of the solvent are mixed to be used, a mixed solvent including a cyclic carbonate and a chain carbonate is preferably used. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and the like may be used as the cyclic carbonate, and dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and the like may be used as the chain carbonate. For an electrolyte salt in the non-aqueous electrolyte, LiPF<NUM>, LiBF<NUM>, LiCF<NUM>SO<NUM>, and the like, and a mixture thereof may be used. An amount of the electrolyte salt dissolved in the non-aqueous solvent may be, for example, <NUM> to <NUM> mol/L. Hereinafter, for convenience of description, the sealing assembly <NUM> side will be described as "the upper side", and the bottom side of the exterior housing body <NUM> will be described as "the lower side".

An opening end of the exterior housing body <NUM> is capped with the sealing assembly <NUM> to seal inside the secondary battery <NUM>. Insulating plates <NUM> and <NUM> are provided on the upper and lower sides of the electrode assembly <NUM>, respectively. A positive electrode lead <NUM> extends upward through a through hole of the insulating plate <NUM>, and welded with the lower face of a filter <NUM>, which is a bottom plate of the sealing assembly <NUM>. In the secondary battery <NUM>, a cap <NUM>, which is a top plate of the sealing assembly <NUM> electrically connected to the filter <NUM>, becomes a positive electrode terminal. Meanwhile, a negative electrode lead <NUM> extends through a through hole of the insulating plate <NUM> toward the bottom side of the exterior housing body <NUM>, and welded with a bottom inner face of the exterior housing body <NUM>. In the secondary battery <NUM>, the exterior housing body <NUM> becomes a negative electrode terminal.

The exterior housing body <NUM> is a bottomed cylindrical metallic exterior housing can. The exterior housing body <NUM> is hard and barely deforms when an external stress is applied to the battery, and may protect the inside. Meanwhile, since the metallic exterior housing body <NUM> is hard and barely deforms, a contacting pressure generated between an electrode assembly <NUM> and the exterior housing body <NUM> increases when the electrode assembly <NUM> expands due to repeated charges and discharges.

As described above, the exterior housing body <NUM> may be in rectangular form. It is to be noted that the exterior housing body <NUM> in cylindrical form has a disc-shaped cross section in the horizontal direction, resulting in uniform distribution of stress inside the battery. Thus, the exterior housing body <NUM> in cylindrical form is less likely to expand as compared with a rectangular exterior housing body having an easily-expandable plain part, and the contacting pressure between the electrode assembly <NUM> and the exterior housing body <NUM> is likely to increase. Accordingly, the exterior housing body <NUM> in cylindrical form is likely to cause deformation, such as flexure, of the positive electrode <NUM> and negative electrode <NUM> from the fixing tape, and therefore easily exerts the effect of the present disclosure.

A gasket <NUM> is provided between the exterior housing body <NUM> and the sealing assembly <NUM> to achieve sealability inside the secondary battery <NUM>. The exterior housing body <NUM> has a grooved part <NUM> formed by, for example, pressing the side part thereof from the outside to support the sealing assembly <NUM>. The grooved part <NUM> is preferably formed circularly along the circumferential direction of the exterior housing body <NUM>, and supports the sealing assembly <NUM> with the gasket <NUM> interposed therebetween and with the upper face of the grooved part <NUM>.

The sealing assembly <NUM> has a stacked structure of a filter <NUM>, a lower vent member <NUM>, an insulating member <NUM>, an upper vent member <NUM>, and a cap <NUM> in this order from the electrode assembly <NUM> side. Each member constituting the sealing assembly <NUM> has, for example, a disk shape or a ring shape, and each member except for the insulating member <NUM> is electrically connected each other. The lower vent member <NUM> and the upper vent member <NUM> are connected each other at each of central parts thereof, and the insulating member <NUM> is interposed between each of the circumferential parts of the vent members <NUM> and <NUM>. If the internal pressure of the battery increases with abnormal heat generation, for example, the lower vent member <NUM> breaks and the upper vent member <NUM> expands toward the cap <NUM> side to be separated from the lower vent member <NUM>, resulting in cutting off of an electrical connection between the both members. If the internal pressure further increases, the upper vent member <NUM> breaks, and gas is discharged through an opening 26a of the cap <NUM>.

Next, the electrode assembly <NUM> will be described with reference to <FIG> is a perspective view of the electrode assembly <NUM>. As described above, the electrode assembly <NUM> has a wound structure in which the positive electrode <NUM> and the negative electrode <NUM> are spirally wound with the separator <NUM> interposed therebetween. Any of the positive electrode <NUM>, the negative electrode <NUM>, and the separator <NUM> is formed in a band shaped, and spirally wound around a winding core disposed along a winding axis to be alternately stacked in the radial direction of the electrode assembly <NUM>. In the radial direction, the winding axial side is referred to as the inner peripheral side, and the opposite side is referred to as the outer peripheral side. In the electrode assembly <NUM>, the longitudinal direction of the positive electrode <NUM> and negative electrode <NUM> corresponds to a winding direction, and the width direction of the positive electrode <NUM> and negative electrode <NUM> corresponds to an axial direction. The positive electrode lead <NUM> extends, on the upper end of the electrode assembly <NUM> toward the axial direction, from a substantial center between the center and the outermost circumference in the radial direction. The negative electrode lead <NUM> extends, on the lower end of the electrode assembly <NUM>, toward the axial direction from near the winding axis.

The negative electrode <NUM> is exposed on the outermost circumference surface of the electrode assembly <NUM>, and a fixing tape <NUM> is attached through both ends in the axial direction to the negative electrode <NUM>. The fixing tape <NUM>, which is a member for winding and fixing the electrode assembly <NUM>, is attached so as to cover at least a part of a winding terminal end part 12a of the negative electrode <NUM>. A width of the fixing tape <NUM> is not particularly limited, and for example, <NUM> to <NUM>, and may be <NUM> to <NUM>. A position and number of the fixing tape <NUM> is not particularly limited as long as it is attached so as to cover a part of the winding terminal end part 12a, which is exposed on the outermost circumference surface of the electrode assembly <NUM>, and for example, the fixing tape <NUM> may be attached along the axial direction.

For the separator <NUM>, a porous sheet having an ion permeation property and an insulation property is used. Specific examples of the porous sheet include a fine porous thin film, a woven fabric, and a nonwoven fabric. As a material of the separator <NUM>, an olefin resin such as polyethylene and polypropylene is preferable. A thickness of the separator <NUM> is, for example, <NUM> to <NUM>. The separator <NUM> has tended to be thinned as higher capacity and higher output of the battery. The separator <NUM> has a melting point of, for example, approximately <NUM> to <NUM>.

Next, the positive electrode <NUM> and negative electrode <NUM> constituting the electrode assembly <NUM> will be described with reference to <FIG> illustrates the positive electrode <NUM> and the negative electrode <NUM> with an unwound state. The negative electrode <NUM> is formed to be larger than the positive electrode <NUM> to prevent precipitation of lithium on the negative electrode <NUM> in the electrode assembly <NUM>. Specifically, a length in the width direction (axial direction) of the negative electrode <NUM> is larger than a length in the width direction of the positive electrode <NUM>. In addition, a length in the longitudinal direction of the negative electrode <NUM> is larger than a length in the longitudinal direction of the positive electrode <NUM>. As a result, an entirety of at least a portion on which the positive electrode mixture layer <NUM> of the positive electrode <NUM> is formed is disposed opposite to a portion on which negative electrode mixture layer <NUM> of the negative electrode <NUM> is formed with the separator <NUM> interposed therebetween when wound as the electrode assembly <NUM>.

The positive electrode <NUM> has a band-shaped positive electrode current collector <NUM> and a positive electrode mixture layer <NUM> formed on both surfaces of the inner peripheral side and outer peripheral side of the positive electrode current collector <NUM>. For the positive electrode current collector <NUM>, a foil of a metal, such as aluminum, a film in which such a metal is disposed on a surface layer thereof, and the like are used, for example. A preferable positive electrode current collector <NUM> is a foil of aluminum or of a metal mainly composed of an aluminum alloy. A thickness of the positive electrode current collector <NUM> is, for example, <NUM> to <NUM>.

The positive electrode mixture layer <NUM> is preferably formed on an entire region of both surfaces of the positive electrode current collector <NUM> except for a positive electrode current collector exposed part <NUM>, described later. The positive electrode mixture layer <NUM> preferably includes a positive electrode active material, a conductive agent, and a binder. The positive electrode <NUM> is produced by: applying a positive electrode mixture slurry including the positive electrode active material, the conductive agent, the binder, and a solvent such as N-methyl-<NUM>-pyrrolidone (NMP) on both surfaces of the positive electrode current collector <NUM>; and then drying and compressing the positive electrode mixture layer <NUM>.

Examples of the positive electrode active material may include a lithium-containing transition metal oxide containing a transition metal element such as Co, Mn, and Ni. The lithium-containing transition metal oxide is not particularly limited, and preferably a composite oxide represented by the general formula Li<NUM>+xMO<NUM> (in the formula, -<NUM> < x ≤ <NUM> and M includes at least one of the group consisting of Ni, Co, Mn, and Al).

Examples of the conductive agent include carbon materials such as carbon black (CB), acetylene black (AB), Ketjenblack, and graphite. Examples of the binder include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), a polyimide (PI), an acrylic resin, and a polyolefin resin. With these resins, carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), and the like may be used in combination. These materials may be used singly, or may be used in combination of two or more thereof.

In the example illustrated in <FIG>, the positive electrode current collector exposed part <NUM> is provided on a central part in the longitudinal direction of the positive electrode <NUM> and over an entire length in the width direction. The positive electrode current collector exposed part <NUM> is a portion where a surface of the positive electrode current collector <NUM> is uncovered with the positive electrode mixture layer <NUM>. The positive electrode current collector exposed part <NUM> is provided by, for example, intermittent application in which the positive electrode mixture slurry is not applied on a part of the positive electrode current collector <NUM>.

Onto the positive electrode current collector exposed part <NUM>, one end of the positive electrode lead <NUM> is connected with ultrasonic welding or the like. The positive electrode current collector exposed part <NUM> is preferably provided on both surfaces of the positive electrode <NUM> to be stacked in the thickness direction of the positive electrode <NUM> from a viewpoint of operability of connecting the positive electrode lead <NUM>. The positive electrode lead <NUM> is preferably provided at a position of substantially same distance from the winding initial end part and the winding terminal end part 11a from a viewpoint of current collectability. The other end of the positive electrode lead <NUM> extends upward from the end surface in the width direction at a medial position in the radial direction of the electrode assembly <NUM> when wound as the electrode assembly <NUM>. The position of the positive electrode lead <NUM> to be disposed is not particularly limited to the example illustrated in <FIG>, and the positive electrode current collector exposed part <NUM> may be provided corresponding to the position of the positive electrode lead <NUM> to be disposed.

The negative electrode <NUM> has the band-shaped negative electrode current collector <NUM> and the negative electrode mixture layer <NUM> formed on both surfaces of the negative electrode current collector <NUM>. For the negative electrode current collector <NUM>, a foil of a metal such as copper, a film in which such a metal is disposed on a surface layer thereof, or the like is used, for example. A thickness of the negative electrode current collector <NUM> is, for example, <NUM> to <NUM>.

The negative electrode mixture layer <NUM> is preferably formed on an entire region of both surfaces of the negative electrode current collector <NUM> except for a negative electrode current collector exposed part <NUM>, described later. The negative electrode mixture layer <NUM> preferably includes a negative electrode active material and a binder. For example, the negative electrode <NUM> is produced by: applying a negative electrode mixture slurry including the negative electrode active material, the binder, water, and the like on both surfaces of the negative electrode current collector <NUM>; and drying and compressing the negative electrode mixture layer <NUM>.

The negative electrode active material is not particularly limited as long as it may reversibly occlude and release lithium ions, and for example, carbon materials such as natural graphite and artificial graphite, metals that form an alloy with lithium such as Si and Sn, or an alloy or oxide including them may be used. For the binder included in the negative electrode mixture layer <NUM>, the resin similar to the positive electrode <NUM> is used, for example. When the negative electrode mixture slurry is prepared in an aqueous solvent, styrene-butadiene rubber (SBR), CMC or a salt thereof, polyacrylic acid or a salt thereof, polyvinyl alcohol, and the like may be used. These materials may be used singly, and may be used in combination of two or more thereof.

In the example illustrated in <FIG>, the negative electrode current collector exposed part <NUM> is provided on the winding initial end part and winding terminal end part 12a in the longitudinal direction of the negative electrode <NUM> and over an entire length in the width direction of the current collector. The negative electrode current collector exposed part <NUM> is a portion where a surface of the negative electrode current collector <NUM> is uncovered with the negative electrode mixture layer <NUM>. The negative electrode current collector exposed part <NUM> is provided by, for example, intermittent application in which the negative electrode mixture slurry is not applied on a part of the negative electrode current collector <NUM>.

Onto the negative electrode current collector exposed part <NUM> of the winding initial end part, one end of the negative electrode lead <NUM> is connected with ultrasonic welding or the like. The negative electrode current collector exposed part <NUM> is preferably provided on both surfaces of the negative electrode <NUM> to be stacked in the thickness direction of the negative electrode <NUM> from a viewpoint of operability of connecting the negative electrode lead <NUM>. The other end of the negative electrode lead <NUM> extends downward from the end surface in the width direction near the winding axial center of the electrode assembly <NUM> when wound as the electrode assembly <NUM>. The position of the negative electrode lead <NUM> to be disposed is not particularly limited to the example illustrated in <FIG>, and the negative electrode current collector exposed part <NUM> may be provided corresponding to the position of the negative electrode lead <NUM> to be disposed.

The negative electrode current collector exposed part <NUM> of the winding terminal end part 12a is positioned on the outermost circumference surface of the electrode assembly <NUM>, and is in contact with the exterior housing body <NUM>. Thus, a current pathway to the negative electrode terminal is achieved in addition to the negative electrode lead <NUM>, resulting in improvement in output characteristics of the battery.

On the outermost circumference surface of the electrode assembly <NUM>, the negative electrode <NUM> is exposed to achieve the current pathway to the negative electrode terminal of the winding terminal end part 12a, but the negative electrode current collector <NUM> is preferably exposed as an example of an embodiment. The negative electrode current collector <NUM> is more preferably exposed on an entire surface of the outermost circumference surface of the electrode assembly <NUM>. Thus, a contacting area of the negative electrode current collector exposed part <NUM> and the exterior housing body <NUM> increases, resulting in improvement in output characteristics of the battery. When the negative electrode current collector <NUM> is exposed on the entire surface of the outermost circumference surface of the electrode assembly <NUM>, a length in the longitudinal direction of the negative electrode current collector exposed part <NUM> may be larger than a length of the outermost circumference of the electrode assembly <NUM>.

Although a case where the exterior housing body <NUM> is the negative electrode terminal in <FIG> is described above, the positive electrode <NUM> may be exposed on the outermost circumference surface of the electrode assembly <NUM> when the exterior housing body <NUM> is the positive electrode terminal. As a result, a current pathway of the winding terminal end part 11a of the positive electrode <NUM> to the positive electrode terminal is achieved. The fixing tape <NUM> is attached so as to cover at least a part of the winding terminal end part 11a of the positive electrode <NUM> exposed to the outermost circumference surface of the electrode assembly <NUM>. Similar to the case where the negative electrode <NUM> is exposed to the outermost circumference surface of the electrode assembly <NUM>, it is preferable that the positive electrode current collector exposed part <NUM> be provided on the winding terminal end part 11a of the positive electrode <NUM>, and the positive electrode current collector <NUM> be exposed on the outermost circumference surface of the electrode assembly <NUM>.

Next, the fixing tape <NUM>, which is a member for winding and fixing the electrode assembly <NUM>, will be described with reference to <FIG> is a sectional view of the fixing tape <NUM> of an example of an embodiment. The fixing tape <NUM> has a substrate layer <NUM> and an adhesive layer <NUM>, and is attached to the positive electrode <NUM> or negative electrode <NUM> exposed to the outermost circumference surface of the electrode assembly <NUM> by means of the adhesive layer <NUM>.

The substrate layer <NUM> has an uneven shape on the surface thereof as illustrated in <FIG>. An interval of the uneven shape on the surface of the substrate layer <NUM> may be regular, and may be irregular. On the surface of the substrate layer <NUM>, the unevenness may be present in a specific direction, but is preferably present in all the direction.

The substrate layer <NUM> has a surface roughness (Sa) of <NUM> or more on a region having a width of at least <NUM> from the end part. Setting the surface roughness (Sa) near the end part of the fixing tape <NUM>, which is likely to concentrate a stress due to the contacting pressure between the electrode assembly <NUM> and the exterior housing body <NUM>, to be <NUM> or more relaxes the stress, and may prevent the deformation, such as flexure, of the positive electrode <NUM> and negative electrode <NUM>. Here, the surface roughness (Sa) is defined by ISO25178, and may be measured with a commercially available microscope such as VR-<NUM> manufactured by KEYENCE.

An entire surface of the substrate layer <NUM> preferably has the surface roughness (Sa) of <NUM> or more. As a result, not only a surface near the end part of the substrate layer <NUM> but also the entire surface of the substrate layer <NUM> relaxes the stress; thus, the deformation, such as flexure, of the positive electrode <NUM> and negative electrode <NUM> is more certainly prevented.

The surface roughness (Sa) on the substrate layer <NUM> is preferably <NUM> or less from a viewpoint of maintenance of battery characteristics. A larger surface roughness (Sa) on the substrate layer <NUM> increases a thickness of the fixing tape <NUM>, resulting in a decreased space for housing the electrode assembly <NUM> and the electrolyte in the exterior housing body <NUM>.

The substrate layer <NUM> may be appropriately selected from viewpoints of strength, resistance against the electrolyte liquid, processability, cost, and the like, and for example, PP (polypropylene), PI (polyimide), PET (polyethylene terephthalate), or the like may be used. The adhesive layer <NUM> is preferably a resin having adhesiveness at room temperature, and for example, an acrylic resin and a rubber resin may be used.

In <FIG>, t represents a thickness of the fixing tape <NUM>. The numeral t represents a thickness from a top of the substrate layer <NUM> to a surface of the adhesive layer <NUM>. The numeral t is, for example, <NUM> to <NUM>, and preferably <NUM> to <NUM>.

A method of producing the uneven shape on the surface of the substrate layer <NUM> is not particularly limited, and the uneven shape may be produced by, for example, pressing the fixing tape <NUM> in which a laminated paper is adhered to the adhesive layer <NUM> against a roller having an uneven shape on a surface thereof. The surface roughness (Sa) on the substrate layer <NUM> may be regulated with a surface roughness (Sa) of the roller and a pressing pressure of the roller. For example, pressing a roller having a surface roughness (Sa) of <NUM> to <NUM> with a linear pressure of <NUM> kgf/cm to <NUM> kgf/cm enables to produce the fixing tape <NUM> having the surface roughness (Sa) of <NUM> or more.

The present disclosure will be further described below with Examples, but the present disclosure is not limited to these Examples.

Mixing of <NUM> parts by mass of graphite, <NUM> parts by mass of SiO, <NUM> part by mass of carboxymethyl cellulose (CMC), and <NUM> part by mass of styrene-butadiene rubber (SBR) was performed, and an appropriate amount of water was added thereto to prepare a negative electrode mixture slurry. Then, the negative electrode mixture slurry was applied on one surface of a band-shaped negative electrode current collector made with a copper foil having a thickness of <NUM>, and then the applied film was dried. The dried applied film was compressed by using a roller, and then cut to a predetermined electrode size to produce a negative electrode in which a negative electrode mixture layer was formed on the one surface of the negative electrode current collector.

An adhesive layer of an acrylic adhesive was applied with <NUM> on a substrate layer made with polypropylene (PP) having a thickness of <NUM> to produce a flat-plate tape. Then, a polypropylene (PP) laminated paper on which a mold releasing agent was applied was adhered on the adhesive layer side, a roller having a unevenness with a surface roughness of <NUM> was pressed from the substrate layer side with a linear pressure of <NUM> kgf/cm, and then the pressed tape was cut to a <NUM>-mm width to produce a fixing tape having an uneven shape on an entire surface on the substrate layer side.

The fixing tape in which the laminated paper was peeled was attached to a side of the negative electrode on which the negative electrode mixture layer was not formed to produce a specimen.

A specimen was produced in the same manner as in Example <NUM> except that the linear pressure of compressing the flat-plate tape with the roller was changed to <NUM> kgf/cm.

A specimen was produced in the same manner as in Example <NUM> except that the flat-plate tape was not compressed with a roller.

Before the fixing tape was attached to the negative electrode, surface roughnesses (Sa) of the fixing tapes produced in Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM> were measured by using VR-<NUM> manufactured by KEYENCE under a condition of magnification of <NUM>.

On the specimens of Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM>, a stress application test was performed by using a stress applying apparatus illustrated in <FIG> to evaluate possibility of occurrence of the deformation, such as flexure, of the positive electrode and negative electrode derived from the fixing tape. Details of the stress application test are as follows.

<FIG> is a plan view of a stress applying apparatus <NUM>, and <FIG> is a sectional view from the arrow direction on the A-A line in <FIG>. The stress applying apparatus <NUM> has a specimen stage <NUM>, a chloroprene rubber sheet <NUM> as a buffer, and an indenter <NUM>. As illustrated in <FIG>, a specimen <NUM> was disposed on the chloroprene rubber sheet <NUM> so that the negative electrode mixture layer <NUM> directed downward and the fixing tape <NUM> directed upward. As illustrated in <FIG>, in the specimen <NUM>, the fixing tape <NUM> with a <NUM>-mm width covers a part of the negative electrode current collector <NUM>. After the specimen <NUM> was disposed, a stress of <NUM> kN was applied for <NUM> seconds by the indenter with <NUM>-mm square to a range including a boundary line between the negative electrode current collector <NUM> and the fixing tape <NUM>. In this test, a larger stress is applied to the specimen <NUM> than an actual stress that will be applied from the exterior housing body <NUM> to the outermost circumference surface of the electrode assembly <NUM>. Thus, a fixing tape <NUM> having a large impact to the deformation, such as flexure, of the positive electrode and negative electrode will break the negative electrode current collector <NUM> at a breakage evaluating portion <NUM> corresponding to the boundary line between the negative electrode current collector <NUM> and the fixing tape <NUM>. Meanwhile, a fixing tape <NUM> having a small impact to the deformation, such as flexure, of the positive electrode and negative electrode will prevent the breakage of the negative electrode current collector <NUM> at the breakage evaluating portion <NUM>. Thus, in this test, presence/absence of a breakage of the negative electrode current collector <NUM> at the breakage evaluating portion <NUM> after the test was observed to evaluate the possibility of occurrence of the deformation, such as flexure, of the positive electrode and negative electrode derived from the fixing tape <NUM>.

A surface roughness (Sa) of each of the fixing tapes used in Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM> and a presence/absence of the breakage of each specimen after the test are shown in Table <NUM>.

In Comparative Examples <NUM> to <NUM>, which had a small surface roughness (Sa) of the fixing tape, the negative electrode current collector was broken at the breakage evaluating portion. Meanwhile, in Examples <NUM> to <NUM>, which had a large surface roughness (Sa) of the fixing tape, the negative electrode current collector was not broken. In other words, in Examples <NUM> to <NUM>, the fixing tape has a small impact to the deformation, such as flexure, of the positive electrode and negative electrode, resulting in a low possibility of occurrence of the deformation of the positive electrode and negative electrode derived from the fixing tape. From the results, it is found that a large surface roughness (Sa) of the fixing tape may prevent the deformation, such as flexure, of the negative electrode and positive electrode even when the contacting pressure occurs between the electrode assembly and the exterior housing body.

Claim 1:
A non-aqueous electrolyte secondary battery (<NUM>), comprising:
a wound electrode assembly (<NUM>) in which a band-shaped positive electrode (<NUM>) and a band-shaped negative electrode (<NUM>) are wound with a separator (<NUM>) interposed therebetween; and
a metallic exterior housing body (<NUM>) that houses the electrode assembly (<NUM>), wherein
the positive electrode (<NUM>) or the negative electrode (<NUM>) is exposed on an outermost circumference surface of the electrode assembly (<NUM>), and a fixing tape (<NUM>) having a substrate layer (<NUM>) and an adhesive layer (<NUM>) is attached to the positive electrode (<NUM>) or the negative electrode (<NUM>) by means of the adhesive layer (<NUM>);
the fixing tape (<NUM>) is attached so as to cover at least a part of a winding terminal end part of the positive electrode (<NUM>) or the negative electrode (<NUM>) exposed on the outermost circumference surface of the electrode assembly (<NUM>); and
the substrate layer (<NUM>) has a surface roughness (Sa) of <NUM> or more on a region having a width of at least <NUM> from the end part, where the surface roughness is defined by ISO25178.