Battery

Abstract

A battery according to the present disclosure comprises a wound electrode group including a first electrode, a second electrode, and a separator. The first electrode includes a current collector, an active material layer, and a lead. The lead is joined to an exposed portion of the current collector where the active material layer is not provided. The electrode group further includes an insulating member attached to the exposed portion, and a protective tape covering at least a portion of the insulating member and at least a portion of the lead. The exposed portion is covered by at least one selected from the group consisting of the protective tape and the insulating member.

Description

battery

[0001] The present disclosure relates to batteries.

[0002] In non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries, for example, a configuration including an electrode group in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween, and an outer can containing the electrode group and an electrolyte solution, has been known. In recent years, there has been a strong demand for higher capacity secondary batteries. As the capacity increases, the amount of heat generated in the event of an internal short circuit in the battery increases, and therefore, there is a need to reduce the risk of an internal short circuit. The positive electrode plate of a battery has an exposed portion where the surface of the positive electrode current collector is exposed, and a positive electrode lead for current collection is joined to this exposed portion. A configuration is used in which insulating tape is placed to cover the positive electrode lead and the exposed portion of the positive electrode current collector to prevent a short circuit due to contact between the positive electrode and the negative electrode.

[0003] For example, Patent Document 1 describes that an insulating protective tape is attached to the positive electrode plate, covering the current collecting tab, and that the protective tape has a tensile strength and puncture strength equal to or greater than a predetermined value, which is said to improve safety even under severe conditions such as when the battery is crushed from above.

[0004] Japanese Patent Application Laid-Open No. 2009-245650

[0005] In conventional non-aqueous electrolyte secondary batteries, foreign matter may be mixed into the battery. As a result, the electrodes or separator may be damaged. This is undesirable from the viewpoint of improving the safety of the battery. The present disclosure provides a technology for making it difficult for foreign matter to be mixed into the electrode assembly.

[0006] The present disclosure provides a battery comprising a wound electrode group including a first electrode, a second electrode, and a separator, wherein the first electrode includes a current collector, an active material layer, and a lead, the current collector includes an exposed portion where the active material layer is not provided, the lead is joined to the exposed portion, the electrode group further includes an insulating member attached to the exposed portion, and a protective tape covering at least a portion of the insulating member and at least a portion of the lead, and the exposed portion is covered with at least one selected from the group consisting of the protective tape and the insulating member.

[0007] According to the present disclosure, it is possible to prevent foreign matter from being mixed into the electrode assembly.

[0008] FIG. 1 is a cross-sectional view of a battery according to an embodiment of the present disclosure. FIG. 2 is a partial plan view of a positive electrode in a state in which the electrode group has been disassembled. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. FIG. 5 is a partial plan view of a positive electrode in a state in which the electrode group has been disassembled according to a reference example. FIG. 6A is a cross-sectional view taken along line VIA-VIA in FIG. 5. FIG. 6B is a cross-sectional view taken along line VIB-VIB in FIG. 5. FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 5.

[0009] (Knowledge Forming the Basis of the Present Disclosure) As described in Patent Document 1, a battery has been known that includes a positive electrode in which an insulating protective tape is disposed so as to cover exposed portions of the positive electrode lead and the positive electrode current collector. FIG. 5 is a partial plan view of a positive electrode 15 according to a reference example, with the electrode assembly unwrapped. FIG. 6A is a cross-sectional view taken along the line VIA-VIA in FIG. 5. FIG. 6B is a cross-sectional view taken along the line VIB-VIB in FIG. 5. FIG. 7 is a cross-sectional view taken along the line VII-VII in FIG. 5. As can be seen from FIGS. 6B and 7 , in the positive electrode 15, the exposed portion E in which the positive electrode lead 15c is not present is made up of the protective tape 20, the positive electrode current collector 15a, and the positive electrode active material layer 15b, creating an open gap. Such a gap can serve as an entrance for conductive foreign matter, such as spatter generated during welding during the battery manufacturing process, to enter the electrode assembly from the bottom of the battery's outer can. If foreign matter gets mixed into the electrode group, the electrodes or separator may be damaged, which is undesirable from the viewpoint of improving the safety of the battery.

[0010] Based on the above findings, the present inventors have conducted extensive research and have come up with the idea of ​​the battery of the present disclosure, in which foreign matter is less likely to be mixed into an electrode group having a wound structure.

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0012] (Embodiment) FIG. 1 is a cross-sectional view of a battery according to an embodiment of the present disclosure.

[0013] The battery 100 includes a cylindrical container 1 with a bottom and an electrode group 4. The electrode group 4 is housed in the container 1. The electrode group 4 has a wound structure. The electrode group 4 includes a positive electrode 5, a negative electrode 6, and a pair of separators 7. That is, the electrode group 4 is formed by stacking the positive electrode 5 and the negative electrode 6 with the separator 7 disposed between the positive electrode 5 and the negative electrode 6, and then spirally winding the stack. The electrode group 4 is impregnated with an electrolytic solution, which is a non-aqueous electrolyte. The opening of the container 1 is closed by a sealing plate 2. The positive electrode 5 includes a positive electrode current collector 5a and a positive electrode active material layer 5b. One end of a positive electrode lead 5c is connected to the positive electrode 5. The other end of the positive electrode lead 5c is connected to the back surface of the sealing plate 2. An insulating gasket 3 is disposed around the sealing plate 2. The negative electrode 6 includes a negative electrode current collector 6a and a negative electrode active material layer 6b. One end of a negative electrode lead 6c is connected to the negative electrode 6. The other end of the negative electrode lead 6c is connected to the bottom surface of the container 1. An insulating ring 8 is disposed on each of the upper and lower surfaces of the electrode group 4.

[0014] In the battery 100, the positive electrode 5 and the negative electrode 6 are the first electrode and the second electrode, respectively, that face each other. However, the positions of the positive electrode 5 and the negative electrode 6 may be interchanged. In this case, the positive electrode 5 and the negative electrode 6 are the second electrode and the first electrode, respectively. The technology of the present disclosure is applicable to both the positive electrode 5 and the negative electrode 6.

[0015] When the electrode group 4 is unfolded and viewed in a plan view, the positive electrode 5 and the negative electrode 6 have a strip-like shape. The width of the negative electrode 6 may be wider than the width of the positive electrode 5. The outer edge of the positive electrode 5 in the width direction may overlap the negative electrode 6, or the positive electrode 5 may be contained within the negative electrode 6 in the width direction. The width of the separator 7 may be wider than the width of the positive electrode 5 and the width of the negative electrode 6. With this configuration, the safety of the battery 100 is improved.

[0016] The positive electrode current collector 5a can be a sheet or film made of a metal material such as aluminum, stainless steel, titanium, or an alloy thereof. Aluminum and its alloys are suitable materials for the positive electrode current collector 5a because they are inexpensive and easy to form into thin films. The sheet or film may be porous or non-porous. Metal foil, metal mesh, or the like may be used as the sheet or film. A carbon material such as carbon may be applied to the surface of the positive electrode current collector 5a as a conductive auxiliary material.

[0017] The positive electrode active material layer 5b contains a positive electrode active material. The positive electrode active material is not particularly limited as long as it is a material that can reversibly absorb and release lithium ions. Typically, a lithium-containing transition metal compound can be used as the positive electrode active material. Examples of the lithium-containing transition metal compound include composite oxides containing lithium and at least one element selected from the group consisting of cobalt, manganese, nickel, chromium, iron, and vanadium. Specific examples include LiCoO2, LiMnO2, LiNiO2, and LiNiO3. x M (1-x) O2 (wherein M is at least one selected from the group consisting of Co, Mn, Fe, Mg, Ti, and Al, and x satisfies 0.3≦x≦0.95), LiCrO2, αLiFeO2, LiVO2, and the like.

[0018] The positive electrode active material layer 5b may contain other materials such as a conductive additive, an ion conductor, and a binder.

[0019] The conductive additive and the ion conductor are used to reduce the resistance of the positive electrode 5. Examples of the conductive additive include carbon materials and conductive polymer compounds. Examples of the carbon materials include carbon black, graphite, acetylene black, carbon nanotubes, carbon nanofibers, graphene, fullerene, and graphite oxide. Examples of the conductive polymer compounds include polyaniline, polypyrrole, and polythiophene. Examples of the ion conductor include gel electrolytes, organic solid electrolytes, and inorganic solid electrolytes. Examples of the gel electrolyte include polymethyl methacrylate and polymethyl methacrylate. Examples of the organic solid electrolyte include polyethylene oxide. Examples of the inorganic solid electrolyte include Li7La3Zr2O 12 Examples include:

[0020] The binder is used to improve the binding property of the material constituting the positive electrode 5. As the binder, polymer materials such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, styrene-butadiene copolymer rubber, polypropylene, polyethylene, and polyimide can be used.

[0021] The negative electrode current collector 6a may be a sheet or film made of a metal material such as stainless steel, nickel, copper, or an alloy thereof. The sheet or film may be porous or non-porous. Examples of the sheet or film include metal foil and metal mesh. A carbon material such as carbon may be applied to the surface of the negative electrode current collector 6a as a conductive auxiliary material.

[0022] The negative electrode active material layer 6b includes a negative electrode active material. The negative electrode active material is not particularly limited as long as it is a material that can reversibly absorb and release lithium ions. Typically, a carbon material containing graphite having a graphite crystal structure can be used as the negative electrode active material. Examples of such carbon materials include natural graphite, spherical or fibrous artificial graphite, non-graphitizable carbon (hard carbon), and easily graphitizable carbon (soft carbon). Examples of materials other than carbon materials include lithium titanate. In addition, from the viewpoint of increasing the energy density of the battery 100, high-capacity materials such as silicon, tin, silicon alloys, tin alloys, silicon oxide, silicon nitride, tin oxide, and composites of silicon and carbon can also be suitably used as the negative electrode active material.

[0023] The negative electrode active material layer 6b may contain at least one selected from the group consisting of graphite and silicon as the negative electrode active material. Graphite may be the only negative electrode active material contained in the negative electrode active material layer 6b. Graphite is recommended because it is less likely to deteriorate even when repeatedly charged and discharged at a deep depth. Carbon materials other than graphite may also be used as the negative electrode active material. Silicon exhibits a larger capacity than graphite and is therefore advantageous for increasing the capacity of the battery 100.

[0024] The negative electrode active material layer 6b may contain other materials such as a conductive additive, an ion conductor, a binder, etc. Materials that can be used as the conductive additive, the ion conductor, and the binder for the positive electrode active material layer 5b can also be used for the negative electrode active material layer 6b.

[0025] The separator 7 is permeable to lithium ions. The material of the separator 7 is not particularly limited as long as it allows the passage of lithium ions. The material of the separator 7 can be at least one selected from the group consisting of a gel electrolyte, an ion exchange resin membrane, a semipermeable membrane, and a porous membrane. Making the separator 7 from these materials can adequately ensure the safety of the battery 100. Examples of gel electrolytes include gel electrolytes containing fluororesins such as PVdF. Examples of ion exchange resin membranes include cation exchange membranes and anion exchange membranes. Examples of porous membranes include porous membranes made of polyolefin resins and porous membranes containing glass paper obtained by weaving glass fibers into nonwoven fabric.

[0026] The electrolyte is a non-aqueous electrolyte impregnated into the positive electrode 5, the negative electrode 6, and the separator 7. The electrolyte may fill the internal space of the container 1. The electrolyte allows lithium ions to move between the positive electrode 5 and the negative electrode 6.

[0027] The electrolyte solution contains, for example, a non-aqueous solvent and a lithium salt.

[0028] Examples of non-aqueous solvents are cyclic carbonate ester solvents, chain carbonate ester solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, or fluorine-containing solvents. Examples of cyclic carbonate ester solvents are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of chain carbonate ester solvents are dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of chain ether solvents are 1,2-dimethoxyethane or 1,2-diethoxyethane. An example of a cyclic ester solvent is γ-butyrolactone. An example of a chain ester solvent is methyl acetate. Examples of fluorine-containing solvents are fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, or fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone, or a mixture of two or more non-aqueous solvents selected from these may be used.

[0029] Examples of lithium salts include lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bisperfluoroethylsulfonylimide (LiN(SO2C2F5)2), LiAsF6, LiCF3SO3, and lithium difluoro(oxalato)borate. One selected from these lithium salts may be used, or two or more may be used in combination.

[0030] The container 1 is made of a metal such as aluminum or stainless steel, and may have a cylindrical shape or a rectangular tube shape.

[0031] The electrode group 4 may be wound into a cylindrical shape or an oval shape.

[0032] The positive electrode lead 5c and the negative electrode lead 6c are strip-shaped members. The positive electrode lead 5c is made of a metal material such as aluminum, stainless steel, titanium, or an alloy thereof. The negative electrode lead 6c is made of a metal material such as nickel, a nickel alloy, titanium, a titanium alloy, copper, or a copper alloy.

[0033] Hereinafter, an example will be described in which the first electrode in the battery of the present disclosure is a positive electrode.

[0034] Fig. 2 is a partial plan view of the positive electrode 5 with the electrode group 4 unfolded. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 2.

[0035] The positive electrode lead 5c is joined to an exposed portion E of the positive electrode current collector 5a formed on at least a portion of the positive electrode 5 in the longitudinal direction. Specifically, the positive electrode lead 5c is welded to the exposed portion E and connected to the positive electrode 5 so as to protrude from the positive electrode current collector 5a. The exposed portion E is a portion of the surface of the positive electrode current collector 5a that is not covered with the positive electrode active material layer 5b, i.e., a portion where the surface of the metal constituting the positive electrode current collector 5a is exposed. The exposed portion E has a rectangular shape in a plan view. The exposed portion E is formed on at least a portion of the positive electrode 5 in the longitudinal direction, for example, in approximately the center. In FIG. 2, the exposed portion E is formed over the entire length of the positive electrode 5 in the lateral direction.

[0036] The exposed portion E may be formed in a portion other than the longitudinal center of the positive electrode 5, for example, near an end portion in the longitudinal direction. The exposed portion E is provided, for example, by intermittent application of a positive electrode mixture containing a positive electrode active material to a portion of the positive electrode current collector 5a.

[0037] The electrode group 4 further includes an insulating member 9 attached to the exposed portion E. That is, the insulating member 9 covers at least a portion of the exposed portion E. The insulating member 9 may be disposed on the exposed portion E at a position where the positive electrode lead 5c is not present in a plan view. By avoiding overlap between the positive electrode lead 5c and the insulating member 9, the thickness of the positive electrode 5 can be reduced, and miswinding of the electrode group 4 can also be prevented. The insulating member 9 is disposed so as to block the entrance (opening) of the gap between the protective tape 10 and the positive electrode current collector 5a, into which foreign matter may enter, as described above for the conventional positive electrode. The insulating member 9 may be in contact with the positive electrode lead 5c. Specifically, the side surface of the insulating member 9 may be in contact with the positive electrode lead 5c.

[0038] The insulating member 9 is in direct contact with the protective tape 10 and the exposed portion E. Specifically, the insulating member 9 has a main surface that is in direct contact with the protective tape 10 and another main surface that faces the main surface and is in direct contact with the exposed portion E. According to the above configuration, the insulating member 9 can fill the gap or space defined by the protective tape 10 and the positive electrode current collector 5a and block the entrance for foreign matter to enter, thereby reducing the possibility of foreign matter entering the electrode group 4 from, for example, the bottom of the container 1.

[0039] In this specification, the direction along the winding axis of the positive electrode 5 is defined as the up-down direction VD. The side located on the bottom side of the container 1 containing the electrode group 4 is defined as the lower side, and the opposite side is defined as the upper side. As shown in FIG. 2 , the lower end of the insulating member 9 may be located lower than the lower end of the positive electrode lead 5c. Furthermore, the upper end of the insulating member 9 may be located lower than the lower end of the positive electrode lead 5c. This configuration makes it more difficult for foreign matter to enter the electrode group 4 from the bottom of the container 1, i.e., from the lower part of the electrode group 4, thereby improving the safety of the battery. Furthermore, by avoiding overlap between the positive electrode lead 5c and the insulating member 9, the thickness of the positive electrode 5 can be reduced, preventing miswinding of the electrode group 4. Here, the up-down direction VD (winding axis direction) coincides with the short-side direction of the positive electrode 5. Referring to FIG. 1 , the side where the sealing plate 2 is located is the upper side, and the side where the bottom of the container 1 is located is the lower side.

[0040] The electrode group 4 may have a region A in the up-down direction VD where the space between the protective tape 10 and the exposed portion E is filled with the insulating member 9. In FIG. 2 , the region between the protective tape 10 and the exposed portion E and below the lower end of the positive electrode lead 5c is the region A filled with the insulating member 9. Alternatively, the space between the protective tape 10 and the exposed portion E may be filled with the positive electrode lead 5c and the insulating member 9. The insulating member 9 may be surrounded by the positive electrode current collector 5a (exposed portion E), the protective tape 10, and the positive electrode active material layer 5b, or may be surrounded by and in contact with at least one of the group consisting of these.

[0041] The electrode group 4 further includes a protective tape 10 that covers at least a portion of the insulating member 9 and at least a portion of the positive electrode lead 5c. The protective tape 10 has a rectangular shape in a plan view and covers the insulating member 9, the portion of the positive electrode lead 5c that overlaps the exposed portion E, and the exposed portion E. Figure 2 shows an example configuration in which the protective tape 10 is attached to the positive electrode 5 so as to cover portions of the surface of the positive electrode active material layer 5b arranged on both sides of the exposed portion E in the longitudinal direction of the positive electrode 5, the entire insulating member 9, the entire portion of the positive electrode lead 5c that overlaps the exposed portion E, and the entire exposed portion E. In the electrode group 4, the main surface of the positive electrode 5 on the side where the protective tape 10 is arranged faces the main surface of the negative electrode 6 with the separator 7 interposed therebetween.

[0042] According to the above configuration, the insulating member 9 fills the gap between the protective tape 10 and the positive electrode current collector 5a, blocking the entrance for conductive foreign matter, such as spatter generated during welding during the manufacturing process of the battery 100, thereby reducing the possibility of foreign matter entering the electrode group 4 from the bottom of the container 1. As a result, the safety of the battery can be further improved. Furthermore, the provision of the insulating member 9 can reduce the difference in the distance between the exposed portion E of the positive electrode current collector 5a and the protective tape 10, i.e., the thickness of the positive electrode 5, between the location where the positive electrode lead 5c is located and the location where it is not, thereby potentially preventing misalignment during the manufacturing of the electrode group.

[0043] In a plan view, the insulating member 9 is contained within the range where the exposed portion E is provided. With this configuration, it is possible to prevent the insulating member 9 from overlapping the positive electrode active material layer 5b.

[0044] The lower end of the protective tape 10 may be located below the lower end of the insulating member 9. The upper end of the protective tape 10 may be located above the upper end of the insulating member 9. Fig. 2 shows an example of a configuration in which the protective tape 10 covers the entire insulating member 9. However, this embodiment is not limited to this, and the protective tape 10 does not have to cover the entire insulating member 9. For example, the protective tape 10 does not have to cover the vicinity of the lower end of the insulating member 9.

[0045] The lower end of the insulating member 9 may be located lower than the lower end of the positive electrode current collector 5a. The lower end of the insulating member 9 may be located lower than the lower end of the positive electrode current collector 5a, and the lower end of the protective tape 10 may be located lower than the lower end of the insulating member 9. In other words, the protective tape 10 and the insulating member 9 may each have a protrusion that protrudes downward from the positive electrode current collector 5a, and the length of the protrusion of the protective tape 10 may be longer than the length of the protrusion of the insulating member 9.

[0046] The thickness T1 of the insulating member 9 may be equal to or less than the thickness T2 of the positive electrode lead 5c. As shown in FIG. 4 , the thickness T1 of the insulating member 9 may be substantially the same as the thickness T2 of the positive electrode lead 5c. "The thickness T1 of the insulating member 9 being substantially the same as the thickness T2 of the positive electrode lead 5c" means, for example, that the ratio of the thickness T1 of the insulating member 9 to the thickness T2 of the positive electrode lead 5c is 0.8 or more and 1.1 or less. The ratio T1 / T2 of the thickness T1 of the insulating member 9 to the thickness T2 of the positive electrode lead 5c may be 0.8 or more and 1.0 or less, 0.9 or more and 1.1 or less, or 0.9 or more and 1.0 or less. This configuration can reduce the gap between the protective tape 10 and the positive electrode current collector 5a, further reducing the possibility of foreign matter being mixed into the electrode assembly 4. It can also prevent misalignment during the production of an electrode assembly having a wound structure. The thickness T1 of the insulating member 9 is, for example, 50 μm or more and 200 μm or less. In this specification, the thickness is the length in the stacking direction in which the positive electrode current collector 5a and the positive electrode active material layer 5b are stacked on top of each other.

[0047] The width W1 of the insulating member 9 may be equal to or greater than the width W2 of the positive electrode lead 5c and equal to or less than the width W3 of the exposed portion E of the positive electrode current collector 5a. In this specification, the width W1 of the insulating member 9, the width W2 of the positive electrode lead 5c, and the width W3 of the exposed portion E are the respective lengths in the longitudinal direction of the positive electrode 5. This configuration can further reduce the possibility of foreign matter being mixed into the electrode assembly. As shown in FIG. 2 , the width W1 of the insulating member 9 may be substantially the same as the width W3 of the exposed portion E of the positive electrode current collector 5a. "The width W1 of the insulating member 9 is substantially the same as the width W3 of the exposed portion E of the positive electrode current collector 5a" means, for example, that the ratio W1 / W3 of the width W1 of the insulating member 9 to the width W3 of the exposed portion E of the positive electrode current collector 5a is 0.8 or greater and 1.1 or less. The ratio W1 / W3 may be 0.8 or greater and 1.0 or less, 0.9 or greater and 1.1 or less, or 0.9 or greater and 1.0 or less. According to the above configuration, the gap between the protective tape 10 and the positive electrode current collector 5 a can be filled, and the possibility of foreign matter being mixed into the electrode group 4 can be further reduced. In addition, it is possible to easily prevent the insulating member 9 from overlapping with the positive electrode active material layer 5 b.

[0048] The insulating member 9 is made of a material that has excellent insulating properties, chemical resistance, and processability. The insulating member 9 includes, for example, a resin. The resin is, for example, polyimide. Because polyimide has excellent heat resistance, the insulating member 9 is unlikely to melt even if the positive electrode 5 generates heat during use of the battery 100.

[0049] The insulating member 9 may be an adhesive tape. This allows the insulating member 9 to be easily attached to the positive electrode 5. The insulating member 9 may be an adhesive tape including a substrate and an adhesive layer provided on at least one surface of the substrate. The substrate may be a resin film such as a polyimide film. The adhesive layer may be provided on one surface or both surfaces of the substrate. The adhesive included in the adhesive layer is selected to be, for example, one that swells in the electrolyte solution and has ion permeability. The adhesive included in the adhesive layer may be, for example, an acrylic adhesive, a rubber adhesive, or a silicone adhesive. The insulating member 9 may be formed only from the substrate.

[0050] The protective tape 10 has insulating properties. A material having excellent chemical resistance, insulating properties, and processability is used for the protective tape 10. The protective tape 10 is desirably thin to avoid an increase in the volume occupied by the electrode group 4. The protective tape 10 may contain a resin film. Examples of resin films include those having excellent insulating properties, such as polyimide film. The protective tape 10 and the insulating member 9 may contain the same material.

[0051] Next, an example of a method for manufacturing the battery 100 will be described.

[0052] First, the electrode group 4 is fabricated. Specifically, a positive electrode 5, a negative electrode 6, a separator 7, and a protective tape 10 are prepared. An insulating member 9 and a protective tape 10 are attached to a predetermined position of the positive electrode 5. The positive electrode 5, the negative electrode 6, and a pair of separators 7 provided with the insulating member 9 and the protective tape 10 are stacked and wound so as to form a spirally wound electrode group 4. In this way, the electrode group 4 is obtained.

[0053] The positive electrode 5 is fabricated, for example, as follows: A positive electrode mixture is applied to one or both surfaces of a positive electrode current collector 5a, followed by drying and rolling. The positive electrode mixture is obtained by kneading and uniformly dispersing materials such as a positive electrode active material, a binder, and a conductive material using a dispersion medium.

[0054] The positive electrode mixture is applied intermittently, for example, so as to form an exposed portion E on the surface of the positive electrode current collector 5a. The applied positive electrode mixture may be dried naturally or using a drying device.

[0055] After drying, the positive electrode 5 is rolled so that the positive electrode active material layer 5b has a predetermined thickness. The rolling may be performed multiple times using a roll press.

[0056] After rolling, a positive electrode lead 5c for extracting power is welded to the exposed portion E of the positive electrode current collector 5a. Then, adhesive tape, which is an insulating member 9, is attached to a predetermined position of the exposed portion E. For example, as shown in FIG. 2 , the adhesive tape is placed below the positive electrode lead 5c in the exposed portion E. The order of attaching the positive electrode lead 5c and the adhesive tape is not particularly limited, and the positive electrode lead 5c may be welded to the exposed portion E after the adhesive tape is placed on the exposed portion E.

[0057] The protective tape 10 is attached to the positive electrode 5 so as to cover the exposed portion E, the insulating member 9, and the portion of the positive electrode lead 5c that overlaps the exposed portion E. Alternatively, after the positive electrode lead 5c is attached, instead of attaching the above-mentioned adhesive tape, an adhesive tape having a thicker base at the position where the insulating member 9 is located in a plan view can be attached so as to cover the entire exposed portion E and the portion of the positive electrode lead 5c that overlaps the exposed portion E. This makes it possible to provide the insulating member 9 and the protective tape 10, which are made of the same material and connected to each other, as an integrated unit.

[0058] The negative electrode 6 can be produced, for example, by applying a negative electrode mixture to one or both surfaces of a negative electrode current collector 6 a, followed by drying and rolling. The negative electrode mixture is obtained by kneading and uniformly dispersing materials such as a negative electrode active material, a binder, and a conductive material using a dispersion medium.

[0059] A dry method may be used instead of the above-described wet method to form the negative electrode 6. Examples of dry film formation methods include vapor deposition, sputtering, and CVD (chemical vapor deposition).

[0060] Next, the electrode group 4 is placed in the container 1, and then an electrolyte solution is poured into the container 1. Finally, the container 1 is sealed.

[0061] Through the above steps, the battery 100 shown in FIG. 1 is obtained.

[0062] Although the above description has been given using an example in which the first electrode is a positive electrode, in the battery of the present disclosure, the first electrode may be a negative electrode and the second electrode may be a positive electrode. In addition, an insulating member and a protective tape may also be provided on the second electrode.

[0063] The battery of the present disclosure is not limited to a lithium secondary battery, but may be other batteries such as a sodium secondary battery or a magnesium secondary battery.

[0064] (Other Embodiments) (Additional Notes) The above description of the embodiments discloses the following techniques.

[0065] (Technology 1) A battery comprising a wound electrode group including a first electrode, a second electrode, and a separator, wherein the first electrode includes a current collector, an active material layer, and a lead, the current collector includes an exposed portion where the active material layer is not provided, the lead is joined to the exposed portion, the electrode group further includes an insulating member attached to the exposed portion, and a protective tape covering at least a portion of the insulating member and at least a portion of the lead, and the exposed portion is covered with at least one selected from the group consisting of the protective tape and the insulating member.

[0066] The above configuration makes it difficult for foreign matter to get into the electrode assembly, thereby improving the safety of the battery. Furthermore, by providing the insulating member, it is possible to reduce the difference in the distance between the exposed portion of the current collector and the protective tape, i.e., the thickness of the first electrode, between the portion where the lead is located and the portion where it is not, and it is also possible to prevent misalignment during winding of the electrode assembly during production.

[0067] (Technology 2) The battery according to Technology 1, wherein the insulating member is an adhesive tape.

[0068] (Technology 3) The battery according to Technology 1 or 2, wherein the thickness of the insulating member is equal to or less than the thickness of the lead. With this configuration, the gap between the protective tape and the current collector can be reduced, further reducing the possibility of foreign matter being mixed into the electrode assembly. Also, it is possible to prevent the electrode assembly from being miswound.

[0069] (Technology 4) The battery according to any one of Technologies 1 to 3, wherein the width of the insulating member is equal to or greater than the width of the lead and equal to or less than the width of the exposed portion. This configuration makes it more difficult for foreign matter to be mixed into the electrode group, which can further improve the safety of the battery. In addition, it is easy to prevent the insulating member from overlapping with the active material layer.

[0070] (Technology 5) The battery according to any one of Technologies 1 to 4, wherein the insulating member is disposed at a position where the lead is not present in a plan view. With this configuration, foreign matter is less likely to be mixed into the electrode group, and the safety of the battery can be further improved.

[0071] (Technology 6) The battery according to any one of Technologies 1 to 5, wherein the insulating member is in direct contact with the protective tape and the exposed portion. With this configuration, foreign matter is less likely to be mixed into the electrode group, and the safety of the battery can be further improved.

[0072] (Technology 7) The battery according to any one of Technologies 1 to 6, further comprising a bottomed cylindrical container that houses the electrode group, wherein when the direction along the winding axis of the first electrode is defined as the up-down direction, the side of the container that is located on the bottom side is defined as the lower side, and the opposite side is defined as the upper side, a lower end of the insulating member is located lower than a lower end of the lead. With this configuration, foreign matter is less likely to be mixed into the electrode group, which can further improve the safety of the battery.

[0073] (Technology 8) The battery according to Technology 7, wherein the upper end of the insulating member is located lower than the lower end of the lead. This configuration makes it more difficult for foreign matter to get into the electrode assembly, which can further improve the safety of the battery. In addition, by avoiding overlapping between the lead and the insulating member, it is also possible to prevent misalignment of the electrode assembly.

[0074] (Technology 9) The battery according to Technology 7 or 8, wherein a lower end of the protective tape is located below a lower end of the insulating member. With this configuration, the insulating member can be protected by the protective tape.

[0075] (Technology 10) The battery according to any one of Techniques 7 to 9, wherein a lower end of the insulating member is located lower than a lower end of the current collector. With this configuration, foreign matter is less likely to be mixed into the electrode group, and the safety of the battery can be further improved.

[0076] (Technology 11) The battery according to any one of Techniques 7 to 10, wherein the electrode group has a region in the vertical direction where a space between the protective tape and the exposed portion is filled with the insulating member. With this configuration, foreign matter is further prevented from being mixed into the electrode group, and the safety of the battery can be further improved.

[0077] (Technology 12) The battery according to any one of Technologies 1 to 11, wherein the insulating member includes polyimide. With this configuration, the insulating member is less likely to melt even if the first electrode generates heat during use of the battery.

[0078] (Technology 13) The battery according to any one of technologies 1 to 12, wherein the first electrode is a positive electrode and the second electrode is a negative electrode. The technology of the present disclosure is particularly useful when the first electrode is a positive electrode.

[0079] The technology of the present disclosure is useful for non-aqueous electrolyte secondary batteries such as lithium secondary batteries.

Claims

1. A battery comprising a wound electrode group including a first electrode, a second electrode, and a separator, wherein the first electrode includes a current collector, an active material layer, and a lead, the current collector includes an exposed portion where the active material layer is not provided, the lead is joined to the exposed portion, the electrode group further includes an insulating member attached to the exposed portion, and a protective tape covering at least a portion of the insulating member and at least a portion of the lead, and the exposed portion is covered with at least one selected from the group consisting of the protective tape and the insulating member.

2. The battery according to claim 1, wherein the insulating member is an adhesive tape.

3. The battery according to claim 1, wherein the thickness of the insulating member is equal to or less than the thickness of the leads.

4. The battery according to claim 1, wherein the width of the insulating member is equal to or greater than the width of the lead and equal to or less than the width of the exposed portion.

5. The battery according to claim 1, wherein the insulating member is disposed in a position where the lead is not present in a plan view.

6. The battery according to claim 5, wherein the insulating member is in direct contact with the protective tape and the exposed portion.

7. The battery according to claim 1, further comprising a bottomed cylindrical container that houses the electrode group, wherein when the direction along the winding axis of the first electrode is defined as the up-down direction, the side facing the bottom of the container is defined as the lower side, and the opposite side is defined as the upper side, the lower end of the insulating member is positioned lower than the lower end of the lead.

8. The battery according to claim 7, wherein the upper end of the insulating member is located lower than the lower end of the lead.

9. The battery according to claim 7, wherein the lower end of the protective tape is located below the lower end of the insulating member.

10. The battery according to claim 7, wherein the lower end of the insulating member is located below the lower end of the current collector.

11. The battery according to claim 7, wherein the electrode group has a region in the vertical direction between the protective tape and the exposed portion where the insulating member is filled.

12. The battery of claim 1, wherein the insulating member comprises polyimide.

13. The battery of claim 1, wherein the first electrode is a positive electrode and the second electrode is a negative electrode.

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