Nonaqueous electrolyte secondary battery

Abstract

Provided is a nonaqueous electrolyte secondary battery (10) provided with an electrode body (14) in which a belt-shaped positive electrode plate (11) and a belt-shaped negative electrode plate (12) are wound in a spiral shape in the longitudinal direction of the electrode plate with a separator (13) interposed therebetween, the positive electrode plate (11) having a positive electrode core (11A) and a positive electrode mixture layer (11B) formed on the surface of the positive electrode core (11A), and the positive electrode mixture layer (11B) being formed in the middle of the positive electrode plate (11) in the longitudinal direction of the electrode plate. A rectangular exposed portion (11C) for exposing the positive electrode core (11A) is formed at a portion in contact with only one of both ends in the width direction of the electrode plate, the exposed portion (11C) and a portion of the positive electrode mixture layer (11B) adjacent to an outer edge portion of the exposed portion (11C) are covered by an adhesive tape (30), and a corner portion of the adhesive tape (30) on the other end side in the width direction of the electrode plate is chamfered.

Description

TECHNICAL FIELD

[0001] The present application relates to a nonaqueous electrolyte secondary battery. BACKGROUND

[0002] As a nonaqueous electrolyte secondary battery, for example, a lithium ion battery is known. The nonaqueous electrolyte secondary battery has an electrode body obtained by winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween. The positive electrode plate has a positive electrode core and a positive electrode mixture layer formed on a surface of the positive electrode core.

[0003] For example, in the nonaqueous electrolyte secondary battery disclosed in Patent Literature 1, a rectangular exposed portion in which the positive electrode core is exposed is formed in a portion that contacts only one of both ends in the electrode plate width direction of the positive electrode plate, a positive electrode tab for collecting current is joined to the exposed portion, and the exposed portion is covered with a tape.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2004-311282 SUMMARY

[0007] In the nonaqueous electrolyte secondary battery of Patent Literature 1, the tape is attached not only to the exposed portion but also to the positive electrode mixture layer around the exposed portion. At the time of charge and discharge of the battery, the portion of the positive electrode mixture layer to which the tape is attached is subjected to a tensile stress from the tape in association with expansion or contraction of the positive electrode plate. In particular, in the portion of the positive electrode mixture layer to which the corner portion of the tape is attached, the tensile stress is concentrated, and there is a case where peeling or cracking of the positive electrode mixture layer occurs. In this case, the battery characteristics of the nonaqueous electrolyte secondary battery can possibly be reduced.

[0008] Thus, an object of the present application is to provide a nonaqueous electrolyte secondary battery that can prevent a case where a tensile stress of a tape on a mixture layer is locally concentrated in association with expansion or contraction of an electrode plate.

[0009] The nonaqueous electrolyte secondary battery of the present application is characterized by including an electrode body obtained by winding a first electrode plate in a strip shape and a second electrode plate in a strip shape with a separator interposed therebetween in a spiral shape along an electrode plate length direction, the first electrode plate including a first core and a first mixture layer formed on a surface of the first core, a first core exposed portion in which the first core is exposed being formed in a portion that contacts only one of both ends in an electrode plate width direction at a middle portion of the first electrode plate in the electrode plate length direction, a portion of the first mixture layer that is adjacent to an outer edge portion of the first core exposed portion being covered with a tape, and a corner portion of the tape on the other side in the electrode plate width direction being chamfered.

[0010] The non-aqueous electrolyte secondary battery according to this application can prevent localized concentration of tensile stress caused by the tape, which occurs with the expansion or contraction of the electrode plates. Attached Figure Description

[0011] Figure 1 This is a cross-sectional view along the axial direction of a non-aqueous electrolyte secondary battery as an example of an implementation.

[0012] Figure 2 This is a schematic unfolded view of a positive electrode plate with adhesive tape attached, as an example of an implementation method.

[0013] Figure 3 This is a schematic unfolded view of a positive electrode plate with adhesive tape attached, as another example of the implementation method. Detailed Implementation

[0014] The following is a detailed description of an example of an embodiment of this application. In the following description, the specific shapes, materials, orientations, values, etc., are examples used to make this application easy to understand, and can be appropriately changed according to the use, purpose, specifications, etc.

[0015] [Non-aqueous electrolyte secondary battery]

[0016] use Figure 1 The non-aqueous electrolyte secondary battery 10, which is one example of an implementation method, will be described.

[0017] The non-aqueous electrolyte secondary battery 10 includes a wound electrode body 14, a non-aqueous electrolyte (not shown), an outer packaging can 15, and a sealing body 16. The wound electrode body 14 has a strip-shaped positive electrode plate 11 serving as a first electrode plate, a strip-shaped negative electrode plate 12 serving as a second electrode plate, and a strip-shaped spacer 13. The positive electrode plate 11 and the negative electrode plate 12 are wound into a spiral shape with the spacer 13 in between. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte and may also be a solid electrolyte using a gel polymer or the like.

[0018] The following sometimes uses axial ( Figure 1 (middle arrow α) and radial ( Figure 1 The middle arrow β) describes each component. In addition, sometimes the axial side of the electrode body 14 is referred to as "upper" and the other axial side as "lower".

[0019] The positive electrode 11, serving as the first electrode plate, has a strip-shaped positive electrode core 11A and a positive electrode connector 19 joined to the positive electrode core 11A (see reference). Figure 2The positive electrode connector 19 is a conductive member used to electrically connect the positive electrode core 11A to the positive terminal, extending axially to one side (above) from the upper end of the positive electrode core 11A in the electrode body 14. The positive electrode connector 19 is, for example, located approximately at the radial center of the electrode body 14. The positive electrode connector 19 is a strip-shaped conductive member. The material of the positive electrode connector 19 is not particularly limited. The positive electrode connector 19 is preferably made of a metal with aluminum as the main component. Furthermore, the positive electrode plate 11 has a positive electrode compound layer 11B formed on the inner (radial inner surface) and outer (radial outer surface) of the positive electrode core 11A (see reference). Figure 2 ).

[0020] The negative electrode plate 12, serving as the second electrode plate, has a strip-shaped negative electrode core and a negative electrode connector 20 joined to the negative electrode core. The negative electrode connector 20 is a conductive member for electrically connecting the negative electrode core to the outer packaging can 15 (described later), and extends axially from the lower end of the negative electrode core in the electrode body 14 to the other side (downward). The outer packaging can 15 serves as the negative terminal. The negative electrode connector 20 is, for example, provided in the inner winding portion (inner circumferential portion) of the electrode body 14. The negative electrode connector 20 is a strip-shaped conductive member. The constituent material of the negative electrode connector 20 is not particularly limited. The negative electrode connector 20 is preferably made of a metal with nickel or copper as the main component, or a metal containing both nickel and copper. Furthermore, the negative electrode plate 12 has negative electrode binder layers formed on the inner winding surface (radial inner surface) and the outer winding surface (radial outer surface) of the negative electrode core, respectively.

[0021] Furthermore, the negative electrode core is exposed on the outermost circumferential surface of the electrode body 14 and contacts the inner side of the cylindrical portion 15A of the outer packaging can 15, thereby electrically connecting it to the outer packaging can 15. This electrical connection between the negative electrode plate 12 and the cylindrical portion 15A of the outer packaging can 15 ensures better current collection.

[0022] As described above, the electrode body 14 has a spiral structure formed by winding the positive electrode plate 11 and the negative electrode plate 12 in a spiral shape with the spacer 13 in between. The positive electrode plate 11, the negative electrode plate 12 and the spacer 13 are all formed in the shape of strips and are spirally wound to form an alternating layered state along the radial direction of the electrode body 14.

[0023] Figure 1 In the example shown, an outer packaging can 15 and a sealing body 16 constitute a metal battery casing that houses the electrode body 14 and the non-aqueous electrolyte. Insulating plates 17 and 18 are respectively provided above and below the electrode body 14. The positive terminal 19 passes through a through hole in the upper insulating plate 17 and extends towards the sealing body 16, and is welded to the lower surface of the filter 22, which serves as the bottom plate of the sealing body 16. In the non-aqueous electrolyte secondary battery 10, the cover 26, which is electrically connected to the filter 22 and serves as the top plate of the sealing body 16, becomes the positive terminal.

[0024] The outer packaging can 15 is a bottomed cylindrical metal container with an opening, such as a bottomed cylindrical shape. A gasket 27 is provided between the outer packaging can 15 and the sealing body 16 to ensure the airtightness of the outer packaging can 15. The outer packaging can 15 has a slotted portion 21, for example, formed by spinning the side portion from the outside to the radially inward side. The slotted portion 21 is preferably formed in a ring shape along the circumference of the outer packaging can 15, and its upper surface supports the sealing body 16. The sealing body 16 seals the opening of the outer packaging can 15.

[0025] The sealing body 16 comprises a filter sheet 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, 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. When the internal pressure of the battery rises due to abnormal heating, for example, the lower valve body 23 breaks, and the upper valve body 25 bulges towards the cover 26 and detaches from the lower valve body 23, thereby breaking the electrical connection between them. When the internal pressure rises further, the upper valve body 25 breaks, and gas is discharged from the opening 26A of the cover 26.

[0026] [Positive plate]

[0027] use Figure 2 The positive electrode plate 11 with adhesive tape 30 attached, as an example of an embodiment, will be described.

[0028] The positive electrode plate 11 has a strip-shaped positive electrode core 11A and positive electrode flux layers 11B formed on both surfaces of the positive electrode core 11A. Hereinafter, the positive electrode plate 11 will sometimes be described using the length direction (arrow γ in the figure) and the width direction (arrow δ in the figure). In this case, the length direction (arrow γ in the figure) is the winding direction of the positive electrode plate 11, and the width direction (arrow δ in the figure) is the axial direction.

[0029] The positive electrode core 11A may be made of a foil of metal such as aluminum, or a film of such metal disposed on its surface. A suitable positive electrode core 11A is a foil of metal with aluminum or aluminum alloy as the main component. The thickness of the positive electrode core 11A is, for example, 10 μm to 30 μm.

[0030] The positive electrode mixture layer 11B preferably includes a positive electrode active material, a conductive agent, and a binder. The positive electrode plate 11 is manufactured by coating both sides of the positive electrode core 11A with a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and a solvent such as N-methyl-2-pyrrolidone (NMP), followed by drying and calendering.

[0031] 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. While there are no particular limitations on lithium-containing transition metal oxides, those with the general formula Li are preferred. 1＋x MO2 (where -0.2 < x ≤ 0.2, and M includes at least one of Ni, Co, Mn, and Al) represents a composite oxide.

[0032] Examples of the aforementioned conductive agents include acetylene black (AB), carbon black (CB) such as Ketjen black, and carbon materials such as graphite. Examples of the aforementioned 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. They can be used individually or in combination of two or more.

[0033] A rectangular exposed portion 11C, serving as the positive electrode core exposed portion, is formed in the portion that contacts only one end of the positive electrode plate 11 in the width direction. The exposed portion 11C is the portion that connects to the positive electrode connector 19, and is the portion of the surface of the positive electrode core 11A that is not covered by the positive electrode binder layer 11B. Preferably, the exposed portion 11C is formed on both sides of the positive electrode core 11A in a manner that they overlap in the thickness direction. The length of the exposed portion 11C in the width direction is preferably 5% to 50% of the length of the positive electrode plate 11 in the width direction.

[0034] [adhesive tape]

[0035] The exposed portion 11C is covered by tape 30. To ensure the tape 30 completely covers the exposed portion 11C, the positive electrode adhesive layer 11B surrounding the exposed portion 11C is adhered to the tape 30. That is, the portion of the positive electrode adhesive layer 11B adjacent to the outer edge of the exposed portion 11C is covered by the tape 30 along with the exposed portion 11C. When the tape 30 is adhered to the exposed portion 11C that connects to the positive electrode connector 19, the tape 30 covers a portion of the positive electrode connector 19. The tape 30 protects the exposed portion 11C from short-circuiting with the opposing negative electrode plate 12.

[0036] Tape 30 is an adhesive tape having a substrate layer and an adhesive layer formed on one surface of the substrate layer. Between the substrate layer and the adhesive layer, for example, a heat-resistant layer containing inorganic particles such as metal oxides can be provided. The substrate layer can be any insulating resin, such as PPS (polyphenylene sulfide), PEEK (polyether ether ketone), PI (polyimide), PP (polypropylene), PET (polyethylene terephthalate), PBT (polybutylene terephthalate), etc.

[0037] The adhesive layer is provided for attaching the tape 30 to the surface of the positive electrode plate 11. The adhesive layer may contain at least one of a rubber-based polymer and an acrylic polymer. For example, a silicone-based polymer may be further added to the adhesive layer.

[0038] The tape 30 is formed in a generally rectangular shape. The corner of the tape 30 at the other end in the electrode width direction is chamfered to form an inclined portion 30A. Here, chamfering refers to removing the apex of the right angle of the rectangular tape, for example, forming the corner into a straight line inclined relative to the electrode width direction, or a curve protruding outwards from the tape 30. It should be noted that even though the corner of the tape 30 is chamfered, the positive electrode adhesive layer 11B adjacent to the outer edge of the exposed portion 11C is still covered by the tape 30.

[0039] On the other end of the tape 30 in the electrode width direction, by chamfering the tape 30, at least a right angle will not be formed. Therefore, even when the adhesive portion of the tape 30 of the positive electrode layer 11B is stretched due to the expansion or contraction of the positive electrode plate 11, the tensile stress will not be locally concentrated at the corner of the adhesive portion of the tape 30 of the positive electrode layer 11B, thus preventing peeling or cracking of the positive electrode layer 11B. It should be noted that the tilt angle of the inclined portion 30A relative to the electrode width direction in this embodiment is set to approximately 45°. However, the tilt angle of the inclined portion 30A in this application is not particularly limited.

[0040] [Other Implementation Methods]

[0041] use Figure 3 The following describes tape 40 as another example of the embodiment. Hereinafter, when describing tape 40, only the configurations that are different from those of tape 30 described above will be described, and the configurations that are the same as those of tape 30 will be omitted.

[0042] The tape 40 is formed in a generally rectangular shape. The corner of the tape 40 at the other end in the electrode width direction is chamfered to form a curved portion 40A. It should be noted that even though the corner of the tape 40 is chamfered, the positive electrode adhesive layer 11B adjacent to the outer edge of the exposed portion 11C is still covered by the tape 30. Because the other end of the tape 40 in the electrode width direction is chamfered into a curved shape, no right-angle corner is formed. Therefore, even when the adhesive portion of the tape 40 covering the positive electrode adhesive layer 11B is stretched due to the expansion and contraction of the positive electrode plate 11, there are no areas of tensile stress concentration on the outer periphery of the adhesive portion of the tape 40 covering the positive electrode adhesive layer 11B, thus preventing peeling or cracking of the positive electrode adhesive layer 11B.

[0043] It should be noted that this application is not limited to the above-described embodiments and their variations. Of course, various modifications and improvements can be made within the scope of the claims of this application. For example, it can be configured as follows: a rectangular negative electrode core material exposure portion is formed in the part that only contacts one end of the negative electrode plate in the electrode width direction, exposing the negative electrode core; adhesive tape is attached to the negative electrode core material exposure portion, and the corner of the adhesive tape on the other side in the electrode width direction is chamfered.

[0044] Explanation of reference numerals in the attached figures

[0045] 10 Non-aqueous electrolyte secondary battery, 11 Positive plate (first plate), 11A Positive core (first core), 11B Positive flux layer (first flux layer), 11C Exposed part (exposed part of first core), 12 Negative plate (second plate), 13 Spacer, 14 Electrode body, 15 Outer packaging can, 15A Cylindrical part, 16 Sealing body, 17 Insulating plate, 18 Insulating plate, 19 Positive terminal, 20 Negative terminal, 21 Grooved part, 22 Filter, 23 Lower valve body, 24 Insulating component, 25 Upper valve body, 26 Cover, 26A Opening, 27 Gasket, 30 Adhesive tape, 30A Inclined part, 40 Adhesive tape, 40A Curved part.

Claims

1. A non-aqueous electrolyte secondary battery, comprising an electrode body formed by winding a strip-shaped first electrode plate and a strip-shaped second electrode plate in a spiral shape along the length of the electrode plates, with a spacer between them. The first electrode plate has a first core and a first compound layer formed on the surface of the first core. In the middle portion of the first electrode plate along its length, a rectangular first core exposed portion is formed in the part that contacts only one end of the electrode plate along its width. The portion of the first core exposed part and the portion of the first compound layer adjacent to the outer edge of the first core exposed part are covered with tape. The corner of the tape at the other end of the electrode in the width direction is chamfered.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The corners of the tape are chamfered into outward-convex curves.

3. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein, The first electrode plate is the positive electrode plate.

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