Nonaqueous electrolyte secondary battery

Abstract

Provided is a nonaqueous electrolyte secondary battery in which the risk of short circuit is reduced. A non-aqueous electrolyte secondary battery according to one embodiment of the present application is provided with an electrode body in which a belt-shaped first electrode and a second electrode having mutually different polarities are wound in the longitudinal direction with a separator interposed therebetween, and an exterior body that accommodates the electrode body, the first electrode having a current collector and a mixture layer formed on the surface of the current collector, and the mixture layer being formed on the surface of the first electrode. An exposed portion from which the current collector is exposed is formed on the first electrode, a protective tape is bonded so as to cover the exposed portion and the mixture layer around the exposed portion, the protective tape has a base material layer and an adhesive layer, and an end portion of the adhesive layer is positioned further toward the inside of the protective tape than an end portion of the base material layer in the longitudinal direction of the first electrode. And is positioned further toward the end of the substrate layer than the end of the exposed portion.

Description

Technical Field

[0001] This application relates to a non-aqueous electrolyte secondary battery. Background Technology

[0002] Non-aqueous electrolyte secondary batteries have long been widely used, which house wound electrode bodies consisting of a strip-shaped positive electrode and a strip-shaped negative electrode sandwiched between spacers within an outer packaging. Patent Document 1 discloses a technique where exposed portions of the current collector are formed at both the positive and negative electrodes, and after leads are soldered to these exposed portions, the leads are covered with protective tape. Patent Document 2 discloses a technique where the adhesive layer does not cover the surface of the binder layer, thereby preventing a reaction between the adhesive layer and the binder layer of the protective tape.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2004-311282

[0006] Patent Document 2: Japanese Patent Application Publication No. 2010-55906 Summary of the Invention

[0007] The technology disclosed in Patent Document 2 has a safety concern because the adhesive layer does not cover the surface of the adhesive layer, which could allow foreign matter to get into the exposed portion. Furthermore, according to the researchers' findings, the electrode body repeatedly expands and contracts due to the charging and discharging of the battery, resulting in peeling and cracking of the adhesive layer starting from the end of the protective tape's adhesive layer, potentially leading to a short circuit. The technology disclosed in Patent Document 1 does not address the risk of short circuits and therefore has room for improvement.

[0008] The purpose of this application is to provide a non-aqueous electrolyte secondary battery that reduces the risk of short circuits.

[0009] As one aspect of this application, the non-aqueous electrolyte secondary battery is characterized by comprising an electrode body formed by winding a strip-shaped first electrode and a second electrode with different polarities along the length direction with a spacer between them, and an outer packaging body for housing the electrode body. The first electrode has a current collector and an adhesive layer formed on the surface of the current collector. An exposed portion of the current collector is formed on the surface of the first electrode, and a protective tape is attached to cover the exposed portion and the adhesive layer around the exposed portion. The protective tape has a substrate layer and an adhesive layer. In the length direction of the first electrode, the end of the adhesive layer is located inside the protective tape compared to the end of the substrate layer, and is located at the end side of the substrate layer compared to the end of the exposed portion.

[0010] The non-aqueous electrolyte secondary battery of this application suppresses the risk of short circuit and has excellent safety. Attached Figure Description

[0011] Figure 1 This is an axial cross-sectional view of a cylindrical secondary battery as an example of an implementation method.

[0012] Figure 2 yes Figure 1 The diagram shows a three-dimensional view of the wound-type electrode body of the secondary battery.

[0013] Figure 3 This is a front view showing the positive and negative electrodes of the constituent electrode body as an example of an implementation method in an unfolded state.

[0014] Figure 4 yes Figure 3 A cross-sectional view at line AA.

[0015] Figure 5 It is Figure 3 An enlarged image of the area surrounding the exposed positive electrode.

[0016] Figure 6 This is another example of the implementation method. Figure 5 The corresponding diagram. Detailed Implementation

[0017] Hereinafter, with reference to the accompanying drawings, a detailed description of one embodiment of the cylindrical secondary battery of this application will be provided. In the following description, specific shapes, materials, values, orientations, etc., are examples used to facilitate understanding of the invention and can be appropriately varied depending on the specifications of the cylindrical secondary battery. Furthermore, in the following description, where multiple embodiments and modifications are included, it is initially conceived that their characteristic parts are appropriately combined.

[0018] 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 contains an 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 strip-shaped positive electrode 11 and a strip-shaped negative electrode 12, separated by a spacer 13. 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 used in combination. When using two or more solvents in combination, 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 relative to 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 sealing body 16 side will be referred to as "upper" and the bottom side of the outer packaging body 15 as "lower" in the following description.

[0019] The opening of the outer packaging 15 is sealed by the sealing body 16, thereby sealing the interior of the secondary battery 10. Insulating plates 17 and 18 are respectively provided above and below the electrode body 14. The positive electrode lead 19 passes through the through hole of the insulating plate 17 and extends upwards, and is welded to the lower surface of the filter 22, which serves as the bottom plate of the sealing body 16. In the 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. On the other hand, the negative electrode lead 20 passes through the through hole of the insulating plate 18 and extends towards the bottom side of the outer packaging 15, and is welded to the inner bottom surface of the outer packaging 15. In the secondary battery 10, the outer packaging 15 becomes the negative terminal. It should be noted that when the negative electrode lead 20 is located at the outer end of the winding, the negative electrode lead 20 passes through the outside of the insulating plate 18 and extends towards the bottom side of the outer packaging 15, and is welded to the inner bottom surface of the outer packaging 15.

[0020] The outer packaging 15 is, for example, a bottomed cylindrical metal can. A gasket 27 is provided between the outer packaging 15 and the sealing body 16 to ensure the airtightness of the interior of the secondary battery 10. The outer packaging 15 has a slotted portion 21 that supports the sealing body 16, for example, formed by pressing the side portion from the outside. The slotted portion 21 is preferably formed in a ring shape along the circumference of the outer packaging 15, and its upper surface supports the sealing body 16.

[0021] 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, causing the upper valve body 25 to bulge towards the cover 26 and detach from the lower valve body 23, thereby blocking the electrical connection between the two. When the internal pressure rises further, the upper valve body 25 breaks, and gas is discharged from the opening 26a of the cover 26.

[0022] Below, in reference Figure 2 The electrode body 14 will be described at the same time. 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 positive electrode 11 and a negative electrode 12 in a spiral shape with a spacer 13 between them. The positive electrode 11, the negative electrode 12, and the spacer 13 are all formed in the shape of strips, and are arranged in a spiral shape around a core arranged along the winding shaft 28, so as to be in a state of alternating layers along the radial direction of the electrode body 14. In the radial direction, the side on the winding shaft 28 is called the inner peripheral side, and the side opposite to it is called the outer peripheral side. In the electrode body 14, the length direction of the positive electrode 11 and the negative electrode 12 is the winding direction, and the width direction of the positive electrode 11 and the negative electrode 12 is the axial direction. The positive electrode lead 19 extends axially from approximately the center in the radial direction between the center and the outermost periphery at the upper end of the electrode body 14. In addition, the negative electrode lead 20 extends axially from near the winding shaft 28 at the lower end of the electrode body 14.

[0023] The spacer 13 is made of a porous sheet material that is both ion-permeable and insulating. Specific examples of porous sheets include microporous films, woven fabrics, and nonwoven fabrics. The preferred material for the spacer 13 is an olefin resin such as polyethylene or polypropylene. The thickness of the spacer 13 is, for example, 10 μm to 50 μm.

[0024] Below, in reference Figures 3-6 The positive electrode 11 and negative electrode 12 of the secondary battery 10 will be described in detail below. An example in which the positive electrode 11 is the first electrode and the negative electrode 12 is the second electrode will be described below. It should be noted that this embodiment is not limited to this example. For example, the negative electrode 12 may be the first electrode. Alternatively, the second electrode may have the same characteristics as the first electrode, and both the positive electrode 11 and the negative electrode 12 may have the characteristics of the first electrode.

[0025] Figure 3 This is a front view showing the positive and negative electrodes constituting an electrode body in an unfolded state, as an example of an implementation method. Figure 3As shown, in order to prevent lithium deposition, the negative electrode 12 is usually formed with a size that is slightly larger than that of the positive electrode 11. That is, the negative electrode 12 is formed to be longer in both the length and width directions compared to the positive electrode 11.

[0026] The positive electrode 11 has a positive current collector 30 and a positive electrode flux layer 32 formed on the surface of the positive current collector 30. The positive current collector 30 can be a foil of a metal such as aluminum that is stable in the potential range of the positive electrode, or a film of the metal disposed on the surface.

[0027] The positive electrode mixture layer 32 includes, for example, a positive electrode active material, a conductive agent, and a binder. The content of the positive electrode active material in the positive electrode mixture layer 32 is, for example, 85% to 99% by mass relative to the total mass of the positive electrode mixture layer. For example, a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc., is coated on both sides of the positive electrode current collector 30. After the coating film dries, it is calendered using a roller or similar device, thereby producing a positive electrode. The positive electrode mixture layer 32 is preferably formed on both sides of the positive electrode current collector 30.

[0028] Examples of positive electrode active materials contained in the positive electrode additive layer 32 include lithium transition metal composite oxides containing transition metal elements such as Co, Mn, and Ni. Lithium transition metal composite oxides are, for example, Li. x CoO2, Li x NiO2, Li x MnO2, Li x Co y Ni 1-y O2, Li x Co y M 1-y O z Li x Ni 1-y M y O z Li x Mn2O4, Li x Mn 2-y M y O4, LiMPO4, Li2MPO4F (M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B, 0 < x ≤ 1.2, 0 < y ≤ 0.9, 2.0 ≤ z ≤ 2.3). They can be used alone or in combination.

[0029] From the perspective of achieving high capacity in the secondary battery 10, the positive electrode active material preferably comprises a lithium-nickel composite oxide. Examples of lithium-nickel composite oxides include Li... x NiO2, Li x Co y Ni 1-yO2, Li x Ni 1-y M y O z (M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B, where 0 < x ≤ 1.2, 0 < y ≤ 0.9, and 2.0 ≤ z ≤ 2.3). The higher the Ni content in lithium-nickel composite oxides, the higher the capacity.

[0030] Conductive agents contained in the positive electrode layer 32 can include, for example, acetylene black, carbon black such as Ketjen black, graphite, carbon nanotubes (CNTs), carbon nanofibers, graphene, metal fibers, metal powders, and conductive whiskers. They can be used alone or in combination of two or more.

[0031] Examples of binders contained in the positive electrode binder layer 32 include fluorinated resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. One type may be used alone, or two or more may be used in combination.

[0032] On the surface of the positive electrode 11, a positive electrode exposure portion 34 is formed, exposing the positive electrode current collector 30, and a positive electrode lead 19 is connected to the positive electrode exposure portion 34. The positive electrode exposure portion 34 is provided, for example, by intermittent coating of a portion of the positive electrode current collector 30 without coating the positive electrode slurry. Multiple positive electrode exposure portions 34 may be formed on the surface of the positive electrode 11.

[0033] In this embodiment, the exposed positive electrode portion 34 contacts only one end 11a of the two ends of the positive electrode 11 in the width direction, and does not extend to the other end 11b in the width direction of the positive electrode 11. As a result, a positive electrode binder layer 32 exists between the other end 11b in the width direction of the positive electrode 11 and the exposed positive electrode portion 34, thereby increasing the battery capacity of the secondary battery 10.

[0034] On the surface of the positive electrode 11, a protective tape 36 is adhered to cover the exposed positive electrode portion 34 and the positive electrode adhesive layer 32 surrounding the exposed positive electrode portion 34. Specifically, the entire surface of the exposed positive electrode portion 34, the positive electrode lead 19, and the portion of the positive electrode adhesive layer 32 adjacent to the exposed positive electrode portion 34 are covered by the protective tape 36. The protective tape 36 is an insulating component used to prevent the positive electrode lead 19 and the exposed positive electrode portion 34 from short-circuiting with the opposite negative electrode adhesive layer in the event of a breakage of the spacer 13.

[0035] The negative electrode 12 has a negative electrode current collector 40 and a negative electrode flux layer 42 formed on the surface of the negative electrode current collector 40. The negative electrode current collector 40 can be a foil of a metal that is stable in the potential range of the negative electrode, such as copper, or a film of the metal disposed on the surface.

[0036] The negative electrode mixture layer 42, for example, contains a negative electrode active material and a binder. The content of the negative electrode active material in the negative electrode mixture layer 42 relative to the total mass of the negative electrode mixture layer 42 is, for example, 80% to 99% by mass. For example, a negative electrode mixture slurry containing a negative electrode active material, a binder, etc., is coated onto the surface of the negative electrode current collector 40. After the coating film dries, it is calendered using a roller or similar device, thereby producing the negative electrode 12. The negative electrode mixture layer 42 is preferably formed on both sides of the negative electrode current collector 40.

[0037] As the negative electrode active material contained in the negative electrode additive layer 42, there are no particular limitations as long as it can reversibly absorb, store, and release lithium ions. Carbon materials such as graphite are usually used. Graphite can be any of the following: natural graphite such as flake graphite, block graphite, and amorphous graphite, block artificial graphite, and artificial graphite such as graphitized mesophase carbon microspheres.

[0038] As negative electrode active materials, metals alloyed with Li such as Si and Sn, metal compounds containing Si and Sn, and lithium-titanium composite oxides can be used. For example, SiO2 can also be used. x (0.5≤x≤1.6) represents Si-containing compounds, and Li represents... 2y SiO （2＋y） (0<y<2) indicates that Si-containing compounds in which Si particles are dispersed in a lithium silicate phase or Si-containing compounds in which Si are dispersed in a carbon material are used in combination with graphite.

[0039] Examples of binders contained in the negative electrode binder layer 42 include styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), carboxymethyl cellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts (PAA-Na, PAA-K, etc., and also partially neutralized salts), polyvinyl alcohol (PVA), etc. One of these can be used alone, or two or more can be used in combination.

[0040] On the surface of the negative electrode 12, a negative electrode exposure portion 44 is formed, exposing the negative electrode current collector 40, and a negative electrode lead 20 is connected to the negative electrode exposure portion 44. The negative electrode exposure portion 44 is provided, for example, by intermittently coating a portion of the negative electrode current collector 40 without coating it with the negative electrode slurry. Figure 3 In the example shown, the negative electrode 12 has a negative electrode exposed portion 44 at the inner end of the winding in the length direction.

[0041] Figure 4 yes Figure 3A cross-sectional view at line AA. A positive electrode binder layer 32 is formed on both sides of the positive electrode current collector 30, and a positive electrode exposed portion 34 is formed on both sides of the positive electrode 11, facing each other with the positive electrode current collector 30 sandwiched between them. In this embodiment, the positive electrode lead 19 is connected to the inner peripheral surface of the positive electrode current collector 30. Protective tape 36 is adhered to both the inner and outer peripheral surfaces of the positive electrode 11 to cover the positive electrode exposed portion 34. It should be noted that the positive electrode lead 19 may also be connected to the outer peripheral surface of the positive electrode current collector 30. Furthermore, the protective tape 36 described later may only be adhered to either the inner or outer peripheral surface of the positive electrode 11. That is, ordinary protective tape may be adhered to either the inner or outer peripheral surface of the positive electrode 11. Since the electrode body 14 expands and contracts during charging and discharging, applying tensile stress to the outer peripheral surface, the protective tape 36 described later is preferably adhered to the outer peripheral surface of the positive electrode 11.

[0042] The protective tape 36 has a substrate layer 38 and an adhesive layer 39 formed on one surface of the substrate layer 38. A heat-resistant layer containing inorganic particles such as metal oxides can be provided between the substrate layer 38 and the adhesive layer 39. The substrate layer 38 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. From the viewpoint of protecting the exposed positive electrode portion 34, PI with higher hardness is preferred. The thickness of the substrate layer 38 is, for example, 5 μm or more and 50 μm or less.

[0043] The adhesive layer 39 is used to adhere the protective tape 36 to the positive electrode 11. The thickness of the adhesive layer 39 is, for example, 1 μm or more and 30 μm or less. The adhesive layer 39 may contain at least one of a rubber-based polymer and an acrylic polymer. Because rubber-based polymers and acrylic polymers have adhesive properties, they can adhere the protective tape 36 to the surface of the positive electrode 11. For example, a silicone-based polymer may be further added to the adhesive layer 39.

[0044] Along the length of the positive electrode 11, the end 39E of the adhesive layer 39 is located inside the protective tape 36 compared to the end 38E of the substrate layer 38, and is located on the side of the end 38E of the substrate layer 38 compared to the end 34E of the exposed positive electrode portion 34. According to the research of the present inventors, peeling and cracking of the positive electrode adhesive layer 32 occur near the end 39E of the adhesive layer 39. This can be attributed to the tensile stress applied near the end 39E of the adhesive layer 39 when the electrode body 14 expands and contracts due to charging and discharging. Based on the above configuration, since the area near the end 39E of the adhesive layer 39 is covered by the substrate layer 38, even if peeling and cracking of the positive electrode adhesive layer 32 occurs near the end 39E, the risk of short circuits can be reduced. Furthermore, since the length of the adhesive layer 39 is shorter along its length, the tensile stress on the positive electrode adhesive layer 32 is reduced, further reducing the risk of peeling and cracking. In addition, since the adhesive layer 39 not only covers the entire surface of the positive electrode exposed portion 34, but also covers the positive electrode binder layer 32 around it, the risk of foreign matter being mixed into the positive electrode exposed portion 34 can be reduced.

[0045] Figure 5 It is Figure 3 The image shows an enlarged view of the periphery of the exposed positive electrode portion 34. The distance g1 between the end 39E of the adhesive layer 39 along the length of the positive electrode 11 and the end 38E of the substrate layer 38 is, for example, 1 mm or more. The upper limit of g1 is, for example, 10 mm. Furthermore, the distance g2 between the end 39E of the adhesive layer 39 along the length of the positive electrode 11 and the end 34E of the exposed positive electrode portion 34 is, for example, 0.5 mm or more. The upper limit of g2 is, for example, 10 mm.

[0046] The ratio W2 of the exposed portion 34 of the positive electrode 11 in the width direction to the total length W1 of the positive electrode 11 in the width direction, W2 / W1, is, for example, 5% to 50%. Alternatively, it can be like... Figure 6 As shown in the example, the positive electrode exposed portion 34 extends from one end 11a to the other end 11b in the width direction of the positive electrode 11. In this case, the protective tape 36 is also applied in such a way that it covers the entire surface of the positive electrode exposed portion 34, the positive electrode lead 19, and the portion of the positive electrode adhesive layer 32 adjacent to the positive electrode exposed portion 34.

[0047] As described above, the non-aqueous electrolyte secondary battery according to this application can reduce the risk of short circuits even if peeling or cracking occurs in the positive electrode adhesive layer starting from near the end of the adhesive layer of the protective tape.

[0048] This application is further illustrated by the following embodiments.

[0049] Component 1:

[0050] A non-aqueous electrolyte secondary battery comprises an electrode body formed by winding strip-shaped first and second electrodes of different polarities along its length, separated by a spacer, and an outer packaging body that houses the electrode body.

[0051] The first electrode described above has a current collector and an agent layer formed on the surface of the current collector.

[0052] On the surface of the first electrode, an exposed portion is formed that exposes the current collector, and a protective tape is attached to cover the exposed portion and the adhesive layer surrounding the exposed portion.

[0053] The aforementioned protective tape has a substrate layer and an adhesive layer.

[0054] Along the length of the first electrode, the end of the adhesive layer is located inside the protective tape compared to the end of the substrate layer, and is located on the end side of the substrate layer compared to the end of the exposed portion.

[0055] Composition 2:

[0056] According to the non-aqueous electrolyte secondary battery described in configuration 1, the distance between the end of the adhesive layer and the end of the substrate layer in the length direction of the first electrode is 1 mm or more.

[0057] Composition 3:

[0058] According to configuration 1 or 2, the non-aqueous electrolyte secondary battery, wherein the exposed portion contacts only one of the two ends of the first electrode in the width direction.

[0059] Composition 4:

[0060] According to any one of the non-aqueous electrolyte secondary batteries described in 1 to 3, the first electrode mentioned above is the positive electrode.

[0061] Explanation of reference numerals in the attached figures

[0062] 10 Secondary battery, 11 Positive electrode, 11a One end, 11b The other end, 12 Negative electrode, 13 Spacer, 14 Electrode body, 15 Outer packaging body, 16 Sealing body, 17, 18 Insulating plate, 19 Positive electrode lead, 20 Negative electrode lead, 21 Slotted part, 22 Filter, 23 Lower valve body, 24 Insulating component, 25 Upper valve body, 26 Cover, 26a Opening, 27 Gasket, 28 Winding shaft, 30 Positive electrode current collector, 32 Positive electrode binder layer, 34 Positive electrode exposed part, 36 Protective tape, 38 Substrate layer, 39 Adhesive layer, 40 Negative electrode current collector, 42 Negative electrode binder layer, 44 Negative electrode exposed part.

Claims

1. A non-aqueous electrolyte secondary battery, comprising an electrode body formed by winding strip-shaped first and second electrodes of different polarities together along its length, separated by a spacer, and an outer packaging body for housing the electrode body. The first electrode has a current collector and an agent layer formed on the surface of the current collector. On the surface of the first electrode, an exposed portion is formed that exposes the current collector, and a protective tape is attached to cover the exposed portion and the adhesive layer surrounding the exposed portion. The protective tape has a substrate layer and an adhesive layer. Along the length of the first electrode, the end of the adhesive layer is located inside the protective tape relative to the end of the substrate layer, and is located on the end side of the substrate layer relative to the end of the exposed portion.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The distance between the end of the adhesive layer and the end of the substrate layer in the length direction of the first electrode is more than 1 mm.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The exposed portion contacts only one of the two ends of the first electrode in the width direction.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The first electrode is the positive electrode.

Images