Nonaqueous electrolyte secondary battery

Abstract

Provided is a nonaqueous electrolyte secondary battery which is capable of reducing the risk of short circuit of a core body even if stress is applied to an end part of a protective tape in a charge / discharge cycle in a configuration that comprises a wound electrode body. The nonaqueous electrolyte secondary battery comprises an electrode body that is obtained by winding a first electrode and a second electrode having different polarities from each other with a separator being interposed therebetween, wherein: the first electrode (a positive electrode (11)) has a core body (a positive electrode core body (31)) and a mixture layer (a positive electrode mixture layer (30)) that is formed on the surface of the core body; a core body exposed part (a positive electrode core body exposed part (31a)) is formed on the surface of the first electrode; a protective tape (40) is adhered to the first electrode (the positive electrode (11)) so as to cover the core body exposed part and the mixture layer around the core body exposed part; and a protective layer (42) is formed between the mixture layer and the core body on a perpendicular line from an end of the protective tape (40) toward the core body.

Description

Nonaqueous electrolyte secondary battery

[0001] This disclosure relates to a non-aqueous electrolyte secondary battery.

[0002] Conventionally, non-aqueous electrolyte secondary batteries are known to have an electrode body and an outer casing that houses the electrode body, and the electrode body is a wound type in which the positive electrode and negative electrode are wound around a separator. The positive electrode and negative electrode each have a composite layer containing an active material and a binder formed on both sides of a core body (current collector). The non-aqueous electrolyte secondary battery includes, for example, rectangular plate-shaped electrode tabs connected to the positive electrode and negative electrode, respectively, as lead wires for electrically connecting the electrode body to external terminals.

[0003] Patent Document 1 discloses a method for manufacturing a non-aqueous electrolyte secondary battery, in which core body exposed portions are formed on both the positive and negative electrodes, electrode tabs are joined to these core body exposed portions by welding or other means, and then the electrode tabs, core body exposed portions, and the composite layer surrounding the core body exposed portions are covered with protective tape.

[0004] Japanese Patent Publication No. 2004-311282

[0005] In non-aqueous electrolyte secondary batteries, repeated charging and discharging can generate stress due to the expansion and contraction of the positive and negative electrodes. In particular, with the recent increase in the capacity of non-aqueous electrolyte secondary batteries, the volume changes due to the expansion and contraction of the positive and negative electrodes during charging and discharging have become larger. When the volume changes of the positive and negative electrodes during charging and discharging become large, stress is applied, especially to the overlapping portion of the protective tape on the inner electrode and the composite layer, which can cause partial cracking in the composite layer. If cracks occur in the composite layer, there is a possibility that these cracks will reach the core and increase the risk of a short circuit in the exposed core.

[0006] The object of this disclosure is to provide a non-aqueous electrolyte secondary battery that can reduce the risk of short-circuiting the core even when stress is applied to the end of the protective tape during a charge-discharge cycle in a configuration that includes a wound electrode body.

[0007] This disclosure relates to a non-aqueous electrolyte secondary battery comprising a wound electrode body in which a first electrode and a second electrode having opposite polarities are wound around a separator, wherein the first electrode has a core body and a composite layer formed on the surface of the core body, a core body exposed portion is formed on the surface of the first electrode in which the core body is exposed, a protective tape is attached so as to cover the core body exposed portion and the composite layer surrounding the core body exposed portion, and a protective layer is formed between the composite layer and the core body on a perpendicular line from the end of the protective tape toward the core body.

[0008] This disclosure relates to a non-aqueous electrolyte secondary battery comprising a wound electrode body in which a first electrode and a second electrode having opposite polarities are wound around a separator, wherein the first electrode comprises a core body and a composite layer formed on the surface of the core body, a core body exposed portion is formed on the surface of the first electrode in which the core body is exposed, a protective tape is attached to the first electrode so as to cover a part of the core body exposed portion, a protective layer is formed between the protective tape and the core body on a perpendicular line from the end of the protective tape toward the core body, and the core body exposed portion is covered by the protective tape and the protective layer.

[0009] The non-aqueous electrolyte secondary battery according to this disclosure provides a non-aqueous electrolyte secondary battery that can reduce the risk of short-circuiting of the core even when stress is applied to the end of the protective tape during a charge-discharge cycle in a configuration that includes a wound electrode body.

[0010] This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure. This is a schematic plan view of an example of the longitudinal middle portion of the positive electrode, when the positive electrode of Figure 1, which is the first electrode, is viewed in the thickness direction while unfolded along the planar direction. This is a cross-sectional view taken along line A-A' in Figure 2. This is a schematic plan view of the longitudinal middle portion of the positive electrode, when the positive electrode, which is the first electrode in a conventional non-aqueous electrolyte secondary battery, is viewed in the thickness direction while unfolded along the planar direction. This is a cross-sectional view taken along line A-A' in Figure 4. This is a schematic plan view of another example of the longitudinal middle portion of the positive electrode, when the positive electrode of Figure 1, which is the first electrode, is viewed in the thickness direction while unfolded along the planar direction. This is a cross-sectional view taken along line A-A' in Figure 6.

[0011] Embodiments of this disclosure will be described below. These embodiments are examples of implementing this disclosure, and this disclosure is not limited to these embodiments.

[0012] Hereinafter, embodiments of the non-aqueous electrolyte secondary battery according to this disclosure will be described in detail with reference to the drawings.

[0013] It is intended from the outset that new embodiments can be constructed by appropriately combining the characteristic features of the embodiments and modifications described below. In the following embodiments, the same reference numerals are used for the same components in the drawings, and redundant explanations are omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. Furthermore, among the components described below, components that are not described in the independent claim indicating the highest-level concept are optional components and are not essential components. Moreover, this disclosure is not limited to the embodiments and modifications described below, and various improvements and changes are possible within the scope of the claims of this application and to an equal extent.

[0014] Figure 1 is an axial cross-sectional view of a non-aqueous electrolyte secondary battery 10, which is an example of an embodiment. Figure 2 is a schematic plan view of the longitudinal middle portion of the positive electrode 11 when viewed in the thickness direction while the positive electrode 11 is unfolded along the planar direction.

[0015] As shown in Figure 1, the non-aqueous electrolyte secondary battery 10 has a strip-shaped positive electrode 11 and a negative electrode 12, and a separator 13, and comprises a wound electrode body 14 in which the positive electrode 11 and the negative electrode 12 are wound longitudinally via the separator 13. The non-aqueous electrolyte secondary battery 10 also comprises a bottomed cylindrical outer casing 15 that houses the electrode body 14, and a sealing body 16 that closes the opening of the outer casing 15. The outer casing 15 houses the electrode body 14 together with the non-aqueous electrolyte. In the example in Figure 1, the positive electrode 11 corresponds to the first electrode, and the negative electrode 12 corresponds to the second electrode.

[0016] The outer casing 15 is a bottomed cylindrical metal container, and has a cylindrical portion 15a and a bottom provided at one end of the cylindrical portion 15a in the winding axis direction α of the electrode body 14. The outer casing 15 has a grooved portion 21 formed at the open end of the outer casing 15 on the other end of the cylindrical portion 15a in the winding axis direction α. ​​The grooved portion 21 is formed in an annular shape along the circumferential direction of the outer casing 15 by pressing the cylindrical portion 15a from the outside, and supports the sealing body 16 on its upper surface. For the sake of explanation, in the following, the side of the non-aqueous electrolyte secondary battery 10 with the sealing body 16 will be referred to as the upper side, and the bottom side of the outer casing 15 will be referred to as the lower side.

[0017] Non-aqueous electrolytes have ionic conductivity (for example, lithium ion conductivity). A non-aqueous electrolyte comprises a non-aqueous solvent (also called an organic solvent) and an electrolyte salt dissolved in the non-aqueous solvent. Non-aqueous electrolytes are not limited to liquid electrolytes (non-aqueous electrolyte solutions), but may also be solid electrolytes using gel-like polymers or the like. A non-aqueous electrolyte secondary battery 10 is, for example, a lithium-ion battery.

[0018] Examples of electrolyte salts include lithium tetrafluoroborate (LiBF). ４ ), lithium hexafluorophosphate (LiPF) ６ Examples include lithium salts such as )

[0019] Examples of non-aqueous solvents include esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), as well as ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may also contain halogen-substituted solvents in which at least some of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine atoms.

[0020] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated linear carbonates, and fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP). In terms of suppressing the deterioration of the charge-discharge cycle characteristics of non-aqueous electrolyte secondary batteries or improving the output characteristics, the non-aqueous electrolyte preferably contains 5% by mass or more of FEC relative to the mass of the non-aqueous electrolyte, and more preferably contains 5% to 15% by mass of FEC.

[0021] Examples of solid electrolytes include solid or gel-like polymer electrolytes and inorganic solid electrolytes. Polymer electrolytes include, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. Examples of matrix polymers include polymer materials that absorb non-aqueous solvents and gel. Examples of polymer materials include fluororesins, acrylic resins and polyether resins. Examples of inorganic solid electrolytes include materials known from all-solid-state lithium-ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.).

[0022] As described above, the electrode body 14 has a wound structure in which a positive electrode 11 and a negative electrode 12 are wound around a separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all elongated strip-shaped bodies, and are alternately stacked in the radial direction β of the electrode body 14 by being wound in a spiral in the longitudinal direction. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to suppress lithium deposition. That is, the negative electrode 12 is formed to be longer than the positive electrode 11 in both the longitudinal and short-range directions of the electrode plate. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and for example, two separators are arranged so as to sandwich the positive electrode 11.

[0023] Examples of the separator 13 include porous sheets having ion permeability and insulation properties. Examples of the porous sheet include a microporous thin film, woven fabric, non-woven fabric, and the like. Examples of the material of the separator 13 include resins such as olefin resins including polyethylene and polypropylene. The thickness of the separator 13 is, for example, 10 μm to 50 μm.

[0024] A positive electrode tab 19 and a negative electrode tab 20 are connected to the electrode assembly 14. The positive electrode tab 19 electrically connects the positive electrode 11 and the sealing body 16. The positive electrode tab 19 is located at a substantially intermediate portion of the positive electrode 11 in the longitudinal direction of the electrode plate, at a position separated from the winding start side end and the winding end side end of the electrode assembly 14, and is joined to the exposed portion of the positive electrode core provided at a substantially central portion in the radial direction β of the electrode assembly 14. In the example shown in FIG. 1, the positive electrode tab 19 extends toward the sealing body 16 through the opening of the upper insulating plate 17 and is joined to the lower surface of the sealing body 16, so that the sealing body 16 serves as the positive electrode terminal. The positive electrode tab 19 corresponds to an electrode tab. The positive electrode tab 19 is, for example, a rectangular plate-shaped conductive member, and has a thickness larger than that of a positive electrode core described later. The thickness of the positive electrode tab 19 is, for example, 120 to 150 μm. The constituent material of the positive electrode tab is not particularly limited. The positive electrode tab 19 is made of, for example, a metal containing aluminum as a main component (for example, 95% by mass or more of the entire mass).

[0025] The negative electrode tab 20 is joined to the exposed portion of the negative electrode core provided at the winding start side end, which is one end portion in the longitudinal direction of the electrode plate of the negative electrode 12 located on the winding start side of the negative electrode 12. In the example shown in FIG. 1, the negative electrode tab 20 passes through the through hole of the annular lower insulating plate 18, is bent along the inner surface of the bottom of the outer casing 15, and is connected to the inner surface of the bottom of the outer casing 15 by welding or the like, so that the outer casing 15 serves as the negative electrode terminal. The negative electrode tab 20 is, for example, a rectangular plate-shaped conductive member, and has a thickness larger than that of a negative electrode core described later. The thickness of the negative electrode tab 20 is, for example, 80 to 100 μm. The constituent material of the negative electrode tab 20 is not particularly limited. The negative electrode tab 20 is made of, for example, a metal containing nickel or copper as a main component (for example, 95% by mass or more of the entire mass), or a metal containing both nickel and copper.

[0026] On the outermost peripheral surface of the electrode assembly 14, the negative electrode 12 is disposed, and a portion where the surface of the negative electrode core constituting the negative electrode 12 is exposed is in contact with the inner peripheral surface of the exterior body 15. As a result, together with the winding start side end portion of the negative electrode 12 to which the negative electrode tab 20 is connected, the winding end side end portion of the negative electrode 12 is electrically connected to the exterior body 15, and good current collectibility can be ensured.

[0027] An annular gasket 27 is interposed between the exterior body 15 and the sealing body 16. The sealing body 16 is caulked and fixed between the upper end portion of the exterior body 15 and the grooved portion 21 via the gasket 27. Thereby, the inside of the battery is sealed.

[0028] The sealing body 16 has a structure in which an inner terminal plate 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26 are stacked in this order from the electrode assembly 14 side. Each member constituting the sealing body 16 has a disk shape or a ring shape, and each member excluding the insulating member 24 is electrically connected to each other. The cap 26 has an annular flange on the outer peripheral side, and has a hat shape in which a cylindrical portion with a closed upper end is provided at the center. The inner terminal plate 22 has a central hole penetrating vertically. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective central portions, and the insulating member 24 is interposed between their respective peripheral edge portions. Each member constituting the sealing body 16 is superimposed in the axial direction on the flange portion of the sealing body 16.

[0029] When the internal pressure of the battery rises, the lower valve body 23 deforms so as to push the upper valve body 25 toward the cap 26 side and breaks, thereby cutting off the current path between the lower valve body 23 and the upper valve body 25. When the internal pressure further rises, the upper valve body 25 breaks, and gas is discharged from the opening 26a of the cap 26.

[0030] FIG. 2 is a schematic plan view showing an example of a middle portion in the longitudinal direction when the positive electrode 11 of FIG. 1, which is the first electrode, is viewed in the thickness direction in an unfolded state along the planar direction. FIG. 3 shows an A-A' cross-sectional view of FIG. 2.

[0031] The positive electrode 11 includes a strip-shaped positive electrode core body 31 and positive electrode mixture layers 30 formed on both surfaces of the positive electrode core body 31. Although FIG. 2 shows only the positive electrode mixture layer 30 formed on one surface in the thickness direction of the positive electrode core body 31, as shown in FIG. 3, the positive electrode mixture layer 30 is similarly formed on the other surface in the thickness direction of the positive electrode core body 31 as well.

[0032] Examples of the positive electrode core body 31 include foils of metals that are as stable as possible in the potential range of the positive electrode 11, such as aluminum and aluminum alloys, or films such as resins having the metal disposed on the surface layer. The positive electrode core body 31 is preferably a metal foil containing aluminum or an aluminum alloy as a main component (for example, 95 mass% or more of the entire core body). The thickness of the positive electrode core body 31 is, for example, 5 μm to 30 μm.

[0033] The positive electrode mixture layer 30 contains, for example, a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF), and is preferably formed on both surfaces of the positive electrode core body. The thickness of the positive electrode mixture layer 30 is, for example, 40 μm to 100 μm.

[0034] Examples of the positive electrode active material contained in the positive electrode mixture layer 30 include lithium transition metal composite oxides containing transition metal elements such as Co, Mn, and Ni. Examples of the lithium transition metal composite oxide include Li ｘ CoO ２ , Li ｘ NiO ２ , Li ｘ MnO ２ , Li ｘ Co ｙ Ni １－ｙ O ２ , Li ｘ Co ｙ M １－ｙ O ｚ , Li ｘ Ni １－ｙ M ｙ O ｚ , Li ｘ Mn ２ O ４ , Li ｘ Mn ２－ｙ M ｙ O ４ , LiMPO ４ , Li２ MPO ４ Examples include F (where M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, or B, with 0 < x ≤ 1.2, 0 < y ≤ 0.9, and 2.0 ≤ z ≤ 2.3). These may be used individually or in combination of two or more types.

[0035] In terms of being able to increase the capacity of the non-aqueous electrolyte secondary battery 10, it is preferable that the positive electrode active material contains a lithium nickel composite oxide. As for the lithium nickel composite oxide, Li ｘ NiO ２ Li ｘ Co ｙ Ni １－ｙ O ２ Li ｘ Ni １－ｙ M ｙ O ｚ Examples include (where M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B, with 0 < x ≤ 1.2, 0 < y ≤ 0.9, and 2.0 ≤ z ≤ 2.3). The higher the Ni content of lithium nickel composite oxide, the higher the capacity.

[0036] Examples of conductive agents included in the positive electrode mixture layer 30 include carbon black such as acetylene black and Ketjenblack, graphite, carbon nanotubes (CNTs), carbon nanofibers, graphene, metal fibers, metal powders, and conductive whiskers. These may be used individually or in combination of two or more types.

[0037] Examples of binders included in the positive electrode mixture layer 30 include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), and resins such as polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These may be used individually or in combination of two or more types.

[0038] A positive electrode core exposed portion 31a is formed on a part of the surface of the positive electrode 11, and a positive electrode tab 19 is connected to the positive electrode core exposed portion 31a.

[0039] The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc., to the surface of the positive electrode core 31, drying the coating, and then rolling the coating using a roller or the like. The exposed portion 31a of the positive electrode core is provided, for example, by intermittent coating, where the positive electrode mixture slurry is not applied to a part of the positive electrode core 31. The positive electrode tab 19 can be directly joined to the exposed portion 31a of the positive electrode core by, for example, ultrasonic welding.

[0040] The negative electrode 12 comprises a strip-shaped negative electrode core and negative electrode mixture layers formed on both sides of the negative electrode core. Examples of the negative electrode core include a metal foil that is as stable as possible within the potential range of the negative electrode 12, such as copper or a copper alloy, or a film of resin or other material with that metal arranged on its surface. The negative electrode core is preferably a metal foil with copper or a copper alloy as its main component (for example, 95% or more by mass). The thickness of the negative electrode core is, for example, 5 μm to 30 μm.

[0041] The negative electrode mixture layer preferably comprises, for example, a negative electrode active material and a binder such as styrene-butadiene rubber (SBR), and is formed on both sides of the negative electrode core. The thickness of the negative electrode mixture layer is, for example, 40 μm to 100 μm. As the negative electrode active material, a material capable of reversibly intercalating and releasing lithium ions can be used, such as carbon materials and silicon materials.

[0042] Examples of carbon materials used as negative electrode active materials include graphite. Examples of graphite include natural graphite such as flake graphite, lump graphite, and earthy graphite, as well as artificial graphite such as lump graphite and graphitized mesophase carbon microbeads.

[0043] As the negative electrode active material, metals that alloy with Li such as Si and Sn, metal compounds containing Si and Sn, silicon materials such as lithium titanium composite oxide, and tin materials may be used. For example, SiO ｘ Si-containing compounds represented by (0.5 ≤ x ≤ 1.6), Li ２ｙSiO （２＋ｙ） A Si-containing compound in which fine Si particles are dispersed in a lithium silicate phase represented by (0 < y < 2), or a Si-containing compound in which Si is dispersed in a carbon material, may be used in combination with a carbon material such as graphite.

[0044] Examples of binders included in the negative electrode mixture layer include styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethylcellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts (such as PAA-Na, PAA-K, or partially neutralized salts), and polyvinyl alcohol (PVA). These may be used individually or in combination of two or more types.

[0045] The negative electrode 12 can be manufactured, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the surface of the negative electrode core, drying the coating, and then rolling the coating using a roller or the like.

[0046] A portion of the surface of the negative electrode 12 is formed where the negative electrode core is exposed, and a negative electrode tab 20 is connected to this exposed portion. The exposed portion of the negative electrode core is formed, for example, by intermittent coating, where the negative electrode mixture slurry is not applied to a portion of the negative electrode core. The negative electrode tab 20 may be directly joined to the negative electrode core by, for example, ultrasonic welding.

[0047] As shown in Figures 2 and 3, a positive electrode core exposed portion 31a is formed on a part of the positive electrode 11 in the longitudinal direction X, for example, approximately in the middle, with a predetermined width in the longitudinal direction X and extending over a part or all of the short direction Y, that is, for a predetermined length from the side from which the positive electrode tab 19 extends in the short direction Y, where the surface of the metal constituting the positive electrode core 31 is exposed. The positive electrode core exposed portion 31a is formed on both sides of the positive electrode 11, facing each other with the positive electrode core 31 in between. The positive electrode core exposed portion 31a is the part to which the positive electrode tab 19 is joined, and is the part where the surface of the positive electrode core 31 is not covered by the positive electrode mixture layer 30. The longitudinal direction X of the positive electrode 11 corresponds to the winding direction of the electrode body 14, and the short direction Y of the positive electrode 11 corresponds to the winding axis direction α (Figure 1) of the electrode body.

[0048] In the example shown in Figure 2, the exposed positive electrode core portion 31a is in contact with only one end of the positive electrode 11 in the short-side direction Y (the side from which the positive electrode tab 19 extends, the upper end in the example of Figure 2), and does not extend to the other end of the positive electrode 11 in the short-side direction Y (the lower end in the example of Figure 2). As a result, the positive electrode mixture layer 30 exists between the other end of the positive electrode 11 in the short-side direction Y and the exposed positive electrode core portion 31a, thereby increasing the battery capacity of the non-aqueous electrolyte secondary battery 10.

[0049] The ratio W2 / W1 of the length W2 of the exposed portion 31a of the positive electrode core in the short direction Y of the positive electrode 11 to the total length W1 in the short direction Y of the positive electrode 11 is, for example, 5% to 50%, and may be 5% to 30%.

[0050] The exposed positive electrode core portion 31a may be in contact with one end of the positive electrode 11 in the short-side direction Y of the electrode plate (the side from which the positive electrode tab 19 extends, the upper end in the example of Figure 2) and may extend to the other end of the positive electrode 11 in the short-side direction Y of the electrode plate (the lower end in the example of Figure 2).

[0051] The exposed portion 31a of the positive electrode core 31 may be formed at a location other than approximately the middle of the longitudinal direction X of the electrode plate, for example, it may be formed near the end of the longitudinal direction X of the electrode plate.

[0052] The positive electrode tab 19 is joined to the exposed portion 31a of the positive electrode core by welding, such as ultrasonic welding. The positive electrode tab 19 extends from one end (upper end) of the electrode plate in the short-side direction Y of the positive electrode core 31. In the example shown in Figure 3, the positive electrode tab 19 is joined to the surface that becomes the inner circumference side of the positive electrode core 31 when wound. As shown in Figure 3, the positive electrode tab 19 is formed in a strip shape with a substantially rectangular cross-section when unfolded along the planar direction of the positive electrode 11, for example. As described above, the positive electrode tab 19 has a thickness greater than the thickness of the positive electrode core 31.

[0053] The protective tape 40 is attached to the positive electrode 11 so as shown in Figures 2 and 3, for example, on both the inner and outer surfaces of the positive electrode 11 when wound, covering the exposed positive electrode core portion 31a and the positive electrode mixture layer 30 surrounding the exposed positive electrode core portion 31a. Specifically, the protective tape 40 is attached to the positive electrode 11 so as to cover the surface of at least the portion of the positive electrode tab 19 that is on the inner circumference side of the positive electrode 11 when wound, the entire surface of the exposed positive electrode core portion 31a, and the portion of the positive electrode mixture layer 30 adjacent to the exposed positive electrode core portion 31a. In addition, the protective tape 40 is attached to the positive electrode 11 so as to cover the entire surface of the exposed positive electrode core portion 31a that is on the outer circumference side of the positive electrode 11 when wound, and the portion of the positive electrode mixture layer 30 adjacent to the exposed positive electrode core portion 31a.

[0054] As shown in Figures 2 and 3, in this embodiment, a protective layer 42 is formed between the positive electrode compound layer 30 and the positive electrode core 31 on a perpendicular line from the end of the protective tape 40 toward the positive electrode core 31, on both the inner and outer circumference sides of the winded positive electrode 11. With this configuration, even if stress is applied to the end of the protective tape 40 during a charge-discharge cycle and a crack occurs in the overlapping portion between the end of the protective tape 40 and the compound layer (e.g., positive electrode compound layer 30), it is possible to suppress the crack from reaching the core (e.g., positive electrode core 31) and exposing the core. Therefore, the risk of a short circuit of the core is reduced.

[0055] In the conventional technology, as shown in Figures 4 and 5, the positive electrode core exposed portion 31a and the positive electrode mixture layer 30 surrounding the positive electrode core exposed portion 31a are attached to both the inner and outer surfaces of the wound positive electrode 11. Therefore, if a crack occurs in the positive electrode mixture layer 30, it is not possible to prevent the positive electrode core 31 from being exposed as in this embodiment.

[0056] A similar phenomenon to that in the positive electrode 11 may occur in the negative electrode 12 due to the protective tape. In this case, the first electrode is designated as the negative electrode 12, and a protective layer can be formed between the negative electrode mixture layer and the negative electrode core on a perpendicular line from the end of the protective tape toward the negative electrode core.

[0057] As shown in Figures 6 and 7, the protective tape 40 may be attached to either the inner or outer surface of the positive electrode 11 when it is wound, so as to cover a portion of the exposed positive electrode core 31a. In this case, the protective tape 40 is attached to the positive electrode 11 so as not to cover the positive electrode mixture layer 30. With this configuration, even if stress is applied to the end of the protective tape 40 during the charge-discharge cycle, cracking of the positive electrode mixture layer 30 does not occur, and the risk of short-circuiting the positive electrode core 31 is reduced. As shown in Figures 6 and 7, a protective layer 42 is formed between the protective tape 40 and the positive electrode core 31 on a perpendicular line from the end of the protective tape 40 toward the positive electrode core 31. The exposed positive electrode core 31a is covered by the protective tape 40 and the protective layer 42.

[0058] Similar phenomena to those occurring at the positive electrode 11 due to the protective tape may also occur at the negative electrode 12. In this case, the first electrode is designated as the negative electrode 12, and a protective layer can be formed between the protective tape and the negative electrode core on a perpendicular line from the end of the protective tape toward the negative electrode core.

[0059] The protective layer 42 may be formed before the compound layer is formed by a gravure coating method of the slurry for the protective layer 42, such that it is positioned between the positive electrode compound layer 30 or the protective tape 40 and the positive electrode core 31 on a perpendicular line from the end of the protective tape 40 toward the positive electrode core 31, or between the negative electrode compound layer or the protective tape and the negative electrode core on a perpendicular line from the end of the protective tape 40 toward the negative electrode core.

[0060] The protective layer 42 includes, for example, resin materials such as fluororesins like polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), polyimide resins, polyamide resins, acrylic resins, polyolefin resins, styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethylcellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts, and polyvinyl alcohol (PVA). In addition to the resin materials, the protective layer 42 may also contain inorganic particles such as metal oxides, metal nitrides, metal fluorides, and metal carbides. It is preferable that the resin material contained in the protective layer 42 is the same material as the binder contained in the composite layer.

[0061] The thickness of the protective layer 42 is, for example, 5 μm to 25 μm.

[0062] Preferably, the peel strength of the protective layer 42 against the positive electrode core 31 is higher than the peel strength of the positive electrode mixture layer 30 against the positive electrode core 31. Furthermore, preferably, the peel strength of the protective layer 42 against the negative electrode core is higher than the peel strength of the negative electrode mixture layer against the negative electrode core.

[0063] The peel strength of the protective layer 42 to the core and the peel strength of the composite layer to the core can be measured, for example, by attaching adhesive tape to the surface of the composite layer or the protective layer 42, attaching the end of the tape to a spring scale and applying a tensile force, and measuring the tensile load when the adhesive tape peels off.

[0064] The electrical resistivity of the protective layer 42 is preferably higher than that of the positive electrode core 31. Furthermore, the electrical resistivity of the protective layer 42 is preferably higher than that of the negative electrode core.

[0065] The electrical resistivity of the protective layer 42 and the core can be measured, for example, by the two-terminal method.

[0066] The protective tape 40 is an insulating tape having insulating properties. The protective tape 40 is an insulating member that prevents the positive electrode tab 19 and the exposed portion 31a of the positive electrode core from short-circuiting with the negative electrode mixture layer of the opposing negative electrode 12 via the separator 13.

[0067] The protective tape 40 has, for example, a base layer and an adhesive layer formed on one surface of the base layer. A heat-resistant layer containing inorganic particles such as metal oxides may be provided between the base layer and the adhesive layer.

[0068] The base layer can be any insulating resin, such as PPS (polyphenylene sulfide), PEEK (polyether ether ketone), PI (polyimide), PP (polypropylene), PET (polyethylene terephthalate), and PBT (polybutylene terephthalate). Among these, PI, which has relatively high hardness, is preferred from the standpoint of protecting the exposed portion 31a of the positive electrode core. The thickness of the base layer is, for example, 5 μm to 50 μm.

[0069] The adhesive layer is the portion for attaching the protective tape 40 to the positive electrode 11. The adhesive layer includes, for example, at least one of a rubber-based polymer and an acrylic-based polymer. Since the rubber-based polymer and the acrylic-based polymer are adhesive, the protective tape 40 can be adhered to the surface of the positive electrode 11. The adhesive layer may further include, for example, a silicone-based polymer. The thickness of the adhesive layer is, for example, 1 μm to 30 μm.

[0070] As described above, the non-aqueous electrolyte secondary battery of this disclosure reduces the risk of short-circuiting of the core even when stress is applied to the ends of the protective tape during charge-discharge cycles in a configuration that includes a wound electrode body.

[0071] The present invention includes the following embodiments: (1) A non-aqueous electrolyte secondary battery comprising a wound electrode body in which a first electrode and a second electrode having opposite polarities are wound with a separator between them, wherein the first electrode comprises a core and a composite layer formed on the surface of the core, a core exposed portion is formed on the surface of the first electrode in which the core is exposed, a protective tape is attached to the first electrode so as to cover the core exposed portion and the composite layer surrounding the core exposed portion, and a protective layer is formed between the composite layer and the core on a perpendicular line from the end of the protective tape toward the core.

[0072] (2) A non-aqueous electrolyte secondary battery comprising a wound electrode body in which a first electrode and a second electrode having opposite polarities are wound around a separator, wherein the first electrode comprises a core body and a composite layer formed on the surface of the core body, a core body exposed portion is formed on the surface of the first electrode in which the core body is exposed, a protective tape is attached to the first electrode so as to cover a part of the core body exposed portion, a protective layer is formed between the protective tape and the core body on a perpendicular line from the end of the protective tape toward the core body, and the core body exposed portion is covered by the protective tape and the protective layer.

[0073] (3) The non-aqueous electrolyte secondary battery according to (1) or (2), wherein the peel strength of the protective layer against the core is higher than the peel strength of the composite layer against the core.

[0074] (4) The non-aqueous electrolyte secondary battery according to any one of (1) to (3), wherein the electrical resistivity of the protective layer is higher than the electrical resistivity of the core.

[0075] (5) The protective layer comprises a resin material, the non-aqueous electrolyte secondary battery according to any one of (1) to (4).

[0076] 10 Non-aqueous electrolyte secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Outer casing, 15a Cylindrical part, 16 Sealing body, 17 Upper insulating plate, 18 Lower insulating plate, 19 Positive electrode tab, 20 Negative electrode tab, 21 Grooved part, 22 Internal terminal plate, 23 Lower valve body, 24 Insulating member, 25 Upper valve body, 26 Cap, 26a Opening, 27 Gasket, 30 Positive electrode mixture layer, 31 Positive electrode core body, 31a Positive electrode core body exposed part, 40 Protective tape, 42 Protective layer.

Claims

1. A non-aqueous electrolyte secondary battery comprising a wound electrode body in which a first electrode and a second electrode having opposite polarities are wound around a separator, wherein the first electrode comprises a core body and a composite layer formed on the surface of the core body, a core body exposed portion is formed on the surface of the first electrode in which the core body is exposed, a protective tape is attached to the first electrode so as to cover the core body exposed portion and the composite layer surrounding the core body exposed portion, and a protective layer is formed between the composite layer and the core body on a perpendicular line from the end of the protective tape toward the core body.

2. A non-aqueous electrolyte secondary battery comprising a wound electrode body in which a first electrode and a second electrode having opposite polarities are wound around a separator, wherein the first electrode comprises a core body and a composite layer formed on the surface of the core body, a core body exposed portion is formed on the surface of the first electrode in which the core body is exposed, a protective tape is attached to the first electrode so as to cover a part of the core body exposed portion, a protective layer is formed between the protective tape and the core body on a perpendicular line from the end of the protective tape toward the core body, and the core body exposed portion is covered by the protective tape and the protective layer.

3. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the peel strength of the protective layer against the core is higher than the peel strength of the composite layer against the core.

4. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the electrical resistivity of the protective layer is higher than the electrical resistivity of the core.

5. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the protective layer comprises a resin material.

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