Nonaqueous electrolyte secondary battery and method for manufacturing electrode

Abstract

The present invention is characterized in that: a first electrode (11) has a first electrode core body (30), and a first electrode mixture layer (31) and an insulating layer (33) formed on the first electrode core body (30); a mixture layer non-formation part (32) is provided to a winding start end part and / or a winding termination end part of the first electrode (11); the insulating layer (33) contains an insulating material as a main component, and has a first region (34) covering the mixture layer non-formation part (32), and a second region (35) disposed between the first electrode core body (30) and the first electrode mixture layer (31); and the thickness of the insulating layer (33) in the second region (35) is smaller than the thickness of the insulating layer (33) in the first region (34).

Description

Method for manufacturing a non-aqueous electrolyte secondary battery and electrodes

[0001] This disclosure relates to a method for manufacturing a non-aqueous electrolyte secondary battery and an electrode.

[0002] Conventionally, non-aqueous electrolyte secondary batteries are known that have electrode bodies in which a positive electrode and a negative electrode are wound with a separator in between. Generally, the positive electrode has a positive electrode core and a positive electrode mixture layer formed on the positive electrode core, and the negative electrode has a negative electrode core and a negative electrode mixture layer formed on the negative electrode core. Patent Document 1 discloses a non-aqueous electrolyte secondary battery in which an insulating layer mainly composed of an insulating material is formed on a part of the positive electrode core.

[0003] Japanese Patent Publication No. 2017-143004

[0004] In recent years, non-aqueous electrolyte secondary batteries have seen expanding applications in electric vehicles and energy storage devices for renewable energy, creating a demand for higher capacity. Furthermore, in non-aqueous electrolyte secondary batteries equipped with wound electrodes, the roundness of the electrode body may deteriorate due to steps formed at the beginning or end of the winding of the positive electrode, for example. When the roundness of the electrode body deteriorates, for example, repeated charging and discharging can cause localized deformation of at least one of the positive and negative electrodes, reducing the reliability of the battery. Therefore, there is a need to increase the capacity of non-aqueous electrolyte secondary batteries while maintaining roundness.

[0005] A non-aqueous electrolyte secondary battery according to one aspect of the present disclosure is a non-aqueous electrolyte secondary battery comprising an electrode body in which a first electrode and a second electrode having different polarities are wound along the length direction via a separator, wherein the first electrode has a first electrode core body and a first electrode mixture layer and an insulating layer formed on the first electrode core body, and at least one of the winding start end and winding end of the first electrode is provided with a mixture layer non-formed portion where the first electrode mixture layer is not formed, and the insulating layer mainly contains an insulating material and has a first region covering the mixture layer non-formed portion and a second region disposed between the first electrode core body and the first electrode mixture layer, wherein the thickness of the insulating layer in the second region is smaller than the thickness of the insulating layer in the first region.

[0006] Furthermore, an electrode manufacturing method according to one aspect of the present disclosure is a method for manufacturing an electrode having a first electrode core and a first electrode mixture layer and an insulating layer formed on the first electrode core, comprising a coating step of applying a first electrode mixture layer slurry for forming the first electrode mixture layer and an insulating layer slurry for forming the insulating layer onto the first electrode core from different discharge ports while conveying the first electrode core, and a drying step of drying the coating film produced in the coating step, characterized in that in the coating step, the first electrode mixture layer slurry is applied so as to overlap a part of the insulating layer slurry coating film.

[0007] According to a non-aqueous electrolyte secondary battery, which is one aspect of this disclosure, it is possible to increase capacity while ensuring the roundness of the electrode body.

[0008] This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery, which is an example of an embodiment. This is a plan view of the starting side of the winding when the positive electrode, which is an example of an embodiment, is unfolded. This is a cross-sectional view along line AA in Figure 2. This is a diagram corresponding to Figure 3, showing another example of a positive electrode in an embodiment.

[0009] Hereinafter, an example of an embodiment of the non-aqueous electrolyte secondary battery according to this disclosure will be described in detail with reference to the drawings. However, the non-aqueous electrolyte secondary battery according to this disclosure is not limited to the embodiments described below.

[0010] Figure 1 is an axial cross-sectional view of a non-aqueous electrolyte secondary battery 10, which is an example of an embodiment. As shown in Figure 1, the non-aqueous electrolyte secondary battery 10 comprises an electrode body 14 in which a first electrode and a second electrode are wound around a separator 13, and a bottomed cylindrical outer casing 16 that houses the electrode body 14. The non-aqueous electrolyte secondary battery 10 also comprises a non-aqueous electrolyte housed in the outer casing 16 and a sealing body 17 that closes the opening of the outer casing 16. For the sake of explanation, the side of the non-aqueous electrolyte secondary battery 10 with the sealing body 17 will be referred to as "upper," and the bottom side of the outer casing 16 will be referred to as "lower."

[0011] Non-aqueous electrolytes are lithium ion conductive. Non-aqueous electrolytes may be liquid electrolytes (electrolytes) or solid electrolytes.

[0012] A liquid electrolyte (electrolyte solution) comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. The non-aqueous solvent may also contain halogen-substituted solvents (e.g., fluoroethylene carbonate) in which at least some of the hydrogen atoms of the solvent are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include LiPF4. ６ Lithium salts such as these are used.

[0013] As the solid electrolyte, for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc., can be used. As the inorganic solid electrolyte, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used. The polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As the matrix polymer, for example, a polymer material that absorbs a non-aqueous solvent and gels is used. Examples of polymer materials include fluororesins, acrylic resins, polyether resins, etc.

[0014] The electrode body 14 has a structure in which a strip-shaped first electrode and a second electrode with opposite polarities are wound along the longitudinal direction via a separator 13. Below, we will describe the case where the first electrode is the positive electrode 11 and the second electrode is the negative electrode 12. However, the first electrode may be the negative electrode 12 and the second electrode may be the positive electrode 11.

[0015] The positive electrode 11, the negative electrode 12, and the separator 13 are all elongated strip-shaped bodies that are alternately stacked in the radial direction of the electrode body 14 by being wound in a spiral shape. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in both the length and width directions than the positive electrode 11. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and two of them are arranged, for example, so as to sandwich the positive electrode 11.

[0016] The positive electrode 11 comprises a long positive electrode core 30 and a positive electrode mixture layer 31 formed on the positive electrode core 30. The positive electrode core 30 can be made of a metal foil that is stable within the potential range of the positive electrode 11, such as aluminum, aluminum alloy, stainless steel, or titanium, or a film with the metal arranged on its surface. The positive electrode mixture layer 31 contains 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 sides of the positive electrode core 30. For example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, etc., can be used as the positive electrode active material.

[0017] The thickness of the positive electrode 11 is, for example, 10 μm or more and 300 μm or less. In this embodiment, the thickness of the positive electrode 11 is substantially constant except for the non-formed composite layer portion 32 (see Figure 3) and the region to which the positive electrode lead 20 is connected, which will be described later. The thickness of the positive electrode core 30 is, for example, 10 μm or more and 30 μm or less. The positive electrode 11 can be manufactured by applying a positive electrode composite layer slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core 30, drying the coating film, and then compressing it to form a positive electrode composite layer 31 on both sides of the positive electrode core 30.

[0018] The negative electrode 12 comprises a long negative electrode core 40 and a negative electrode mixture layer 41 formed on the negative electrode core 40. The negative electrode core 40 can be made of a metal foil that is stable within the potential range of the negative electrode 12, such as copper, copper alloy, stainless steel, nickel, or nickel alloy, or a film with the metal arranged on its surface. The negative electrode mixture layer 41 contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR), and is preferably formed on both sides of the negative electrode core 40.

[0019] Generally, carbon materials that reversibly intercept and release lithium ions are used as the negative electrode active material. Suitable examples of carbon materials include natural graphite such as flake graphite, lump graphite, and earthy graphite, as well as artificial graphite such as lump graphite (MAG) and graphitized mesophase carbon microbeads (MCMB).

[0020] Furthermore, silicon-containing materials may be used as the negative electrode active material. Any silicon-containing material is acceptable, and examples include silicon alloys, silicon compounds, and silicon-containing composite materials. Among silicon-containing materials, silicon-containing composite materials are preferred. A preferred example of a silicon-containing composite material is SiO2. ２ Examples include materials in which Si fine particles are dispersed in a phase, a silicate phase such as lithium silicate, or an amorphous carbon phase. A conductive layer, such as a carbon film, may be formed on the particle surface of the composite material.

[0021] The thickness of the negative electrode 12 is, for example, 100 μm or more and 300 μm or less. In this embodiment, the thickness of the negative electrode 12 is substantially constant except for the outer peripheral exposed portion 42 and the region to which the negative electrode lead 21 is connected, which will be described later. The thickness of the negative electrode core 40 is, for example, 5 μm or more and 15 μm or less. The thickness of the negative electrode mixture layer 41 is, for example, 50 μm or more and 150 μm or less on one side of the negative electrode core 40. The negative electrode 12 can be manufactured in the same way as the positive electrode 11 by applying a negative electrode mixture slurry containing a negative electrode active material and a binder onto the negative electrode core 40, drying the coating film, and then compressing it to form the negative electrode mixture layer 41 on both sides of the negative electrode core 40.

[0022] The electrode body 14 has a positive electrode lead 20 connected to a positive electrode 11 and a negative electrode lead 21 connected to a negative electrode 12. In this embodiment, the positive electrode lead 20 is connected to the longitudinal center of the positive electrode 11, and the negative electrode lead 21 is connected to one longitudinal end of the negative electrode 12, which is located on the winding start side of the electrode body 14.

[0023] Insulating plates 18 and 19 are positioned above and below the electrode body 14, respectively. In the example shown in Figure 1, the positive electrode lead 20 extends through a through-hole in the insulating plate 18 towards the sealing body 17, and the negative electrode lead 21 extends through a through-hole in the insulating plate 19 towards the bottom of the outer can 16. The positive electrode lead 20 is connected to the lower surface of the internal terminal plate 23 of the sealing body 17 by welding or the like, and the cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, becomes the positive electrode terminal. The negative electrode lead 21 is connected to the inner bottom surface of the outer can 16 by welding or the like, and the outer can 16 becomes the negative electrode terminal.

[0024] In this embodiment, a negative electrode 12 is arranged on the outermost surface of the electrode body 14, and an outer peripheral exposed portion 42 is provided where the surface of the negative electrode core body 40 is exposed. At least a portion of the outer peripheral exposed portion 42 is in contact with the inner peripheral surface of the outer casing 16. By the outer peripheral exposed portion 42 contacting the inner peripheral surface of the outer casing 16, both ends in the longitudinal direction of the negative electrode 12 and the outer casing 16 are electrically connected, ensuring good current collection. The outer peripheral exposed portion 42 may be provided on a part of the outermost surface of the electrode body 14, but preferably it is provided over the entire outermost surface of the electrode body 14. A separator 13 may be arranged on the outermost surface of the electrode body 14.

[0025] The outer casing 16 is a bottomed cylindrical metal container. A gasket 28 is provided between the outer casing 16 and the sealing body 17, sealing the inside of the battery. The outer casing 16 has, for example, a grooved portion 22 formed by pressing the side surface from the outside. The grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the outer casing 16, and its upper surface supports the sealing body 17. The upper end of the outer casing 16 is bent inward and crimped to the periphery of the sealing body 17.

[0026] The sealing body 17 has a structure in which an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked in order from the electrode body 14 side. Each component constituting the sealing body 17 has, for example, a disc shape or a ring shape, and each component except the insulating member 25 is electrically connected to one another. The lower valve body 24 and the upper valve body 26 are connected at their respective radial centers, with the insulating member 25 interposed between their respective peripheral edges. When the internal pressure of the battery rises due to abnormal heat generation, the lower valve body 24 deforms and ruptures, pushing the upper valve body 26 towards the cap 27. This interrupts the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further, the upper valve body 26 ruptures, and gas is discharged from the opening of the cap 27.

[0027] The configuration of the winding start side of the positive electrode 11 will be described in detail below with reference to Figures 2 and 3. Figure 2 is a plan view of the winding start side of the positive electrode 11 in an unfolded state, and Figure 3 is a cross-sectional view taken along line AA in Figure 2.

[0028] As shown in Figures 2 and 3, the positive electrode 11 comprises a positive electrode core 30 and a positive electrode mixture layer 31 formed on the positive electrode core 30. In this embodiment, the positive electrode mixture layer 31 is formed on both sides of the positive electrode core 30. The positive electrode mixture layer 31 has a substantially uniform thickness, except for the portion formed on the second region 35, which will be described later. The thickness of the positive electrode mixture layer 31 is, for example, 50 μm or more and 150 μm or less on one side of the positive electrode core 30, except for the portion formed on the second region 35.

[0029] At the winding start end 11A of the positive electrode 11, a non-compound layer formation portion 32 is provided on the positive electrode core 30 where the positive electrode compound layer 31 is not formed. In other words, the non-compound layer formation portion 32 is provided for a predetermined length from the winding start end 11A of the positive electrode 11 toward the winding end. The non-compound layer formation portion 32 is provided over the entire width of the positive electrode 11. In this embodiment, the non-compound layer formation portion 32 is provided on both sides of the positive electrode core 30.

[0030] By providing the non-formation portion 32 of the composite layer, the starting end 31A of the positive electrode composite layer 31 can be separated from the starting end 11A of the positive electrode 11, thereby reducing the step formed on the starting end 11A of the positive electrode 11. This improves the roundness of the electrode body 14. As a result, for example, deformation of the negative electrode 12 facing the starting end 11A of the positive electrode 11 can be suppressed when charging and discharging are repeated.

[0031] In the longitudinal direction of the positive electrode 11, the length of the non-formed composite layer portion 32 is preferably 0.5 mm or more, and more preferably 1.0 mm or more. By making the length of the non-formed composite layer portion 32 0.5 mm or more, the roundness of the electrode body 14 can be further improved. Furthermore, the length of the non-formed composite layer portion 32 is preferably 5.0 mm or less, and more preferably 4.5 mm or less. By making the length of the non-formed composite layer portion 32 5.0 mm or less, the area of ​​the region where the positive electrode composite layer 31 is formed can be increased, making it easier to achieve a higher battery capacity. Therefore, in the longitudinal direction of the positive electrode 11, the length of the non-formed composite layer portion 32 is preferably 0.5 mm or more, 5.0 mm or less, and more preferably 1.0 mm or more, 4.5 mm or less.

[0032] An insulating layer 33, mainly composed of an insulating material, is provided on the positive electrode core 30 at the winding start end of the positive electrode 11. The insulating layer 33 is formed from the winding start end 11A of the positive electrode 11 toward the winding end, and a portion of it is formed between the positive electrode core 30 and the positive electrode mixture layer 31. In other words, the insulating layer 33 has a first region 34 that covers the portion 32 where the mixture layer is not formed, and a second region 35 formed between the positive electrode core 30 and the positive electrode mixture layer 31.

[0033] The positive electrode core 30 has lower resistance than the positive electrode composite layer 31. Therefore, if the positive electrode core 30 in the non-composite layer portion 32 comes into contact with the opposing negative electrode 12, an internal short circuit may occur. Thus, by covering the non-composite layer portion 32 with an insulating layer 33 mainly composed of an insulating material, contact between the non-composite layer portion 32 and the negative electrode 12 is suppressed, and an internal short circuit can be suppressed.

[0034] Furthermore, by providing a portion of the insulating layer 33 between the positive electrode core 30 and the positive electrode mixture layer 31, the portion 32 where the mixture layer is not formed can be completely covered with the insulating layer 33, thereby further suppressing internal short circuits. Also, if a portion of the insulating layer 33 is not provided between the positive electrode core 30 and the positive electrode mixture layer 31, and is instead provided on the surface of the positive electrode mixture layer 31 so as to cover the winding start end 31A of the positive electrode mixture layer 31, a large step will be formed at the winding start end 31A of the positive electrode mixture layer 31. This can easily reduce the roundness of the electrode body 14.

[0035] Here, the thickness of the insulating layer 33 in the second region 35 is smaller than the thickness of the insulating layer 33 in the first region 34. This makes it easier to secure a conductive path between the positive electrode core 30 and the positive electrode mixture layer 31 on the second region 35, thereby enabling higher capacity. In other words, if the thickness of the insulating layer 33 in the second region 35 is the same as the thickness of the insulating layer 33 in the first region 34, the conductive path between the positive electrode core 30 and the positive electrode mixture layer 31 on the second region 35 is obstructed, and the battery capacity tends to decrease.

[0036] The ratio of the thickness of the insulating layer 33 in the second region 35 to the thickness of the insulating layer 33 in the first region 34 is, for example, 0.7 or less, preferably 0.6 or less, and more preferably 0.5 or less. In this case, a more conductive path is secured between the positive electrode core 30 and the positive electrode mixture layer 31, and further higher capacitance can be achieved. The lower limit of the ratio of the thickness of the insulating layer 33 in the second region 35 to the thickness of the insulating layer 33 in the first region 34 is not particularly limited, but is, for example, 0.1. The thickness of the insulating layer 33 in the first region 34 is, for example, 3 μm or more and 15 μm or less.

[0037] In the longitudinal direction of the positive electrode 11, the length of the second region 35 is preferably 0.5 mm or more, and more preferably 1.0 mm or more. By setting the length of the second region 35 to 0.5 mm or more, exposure of the positive electrode core 30 in the non-agent layer forming portion 32 can be suppressed, and internal short circuit can be further suppressed. Also, the length of the second region 35 is preferably 5.0 mm or less, and more preferably 4.5 mm or less. By setting the length of the second region 35 to 5.0 mm or less, a conduction path between the positive electrode core 30 and the positive electrode mixture layer 31 can be more ensured. Therefore, in the longitudinal direction of the positive electrode 11, the length of the second region 35 is preferably 0.5 mm or more and 5.0 mm or less, and more preferably 1.0 mm or more and 4.5 mm or less.

[0038] As described above, the insulating layer 33 contains an insulating material as a main component. Here, the main component means the component having the highest mass ratio among the constituent components of the insulating layer 33. The content of the insulating material is preferably 80% by mass or more, and more preferably 90% by mass or more of the total mass of the insulating layer 33. Also, the insulating layer 33 may be substantially composed of only the insulating material.

[0039] The insulating material constituting the insulating layer 33 preferably contains at least a resin material. When the insulating material contains a resin material, the insulating layer 33 becomes difficult to peel off from the positive electrode core 30. Also, the resin material functions, for example, as a binder for bonding the positive electrode core 30 and the positive electrode mixture layer 31. Therefore, when the insulating material contains a resin material, peeling of the positive electrode mixture layer 31 at the start end 31A of the positive electrode mixture layer 31 can be suppressed.

[0040] The resin material contained in the insulating material constituting the insulating layer 33 is preferably a polymer material. For example, fluorine-based resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), polyimide-based resins, polyamide-based resins, acrylic resins, polyolefin-based resins, styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethyl cellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts, polyvinyl alcohol (PVA), etc. can be exemplified. Among them, polyvinylidene fluoride (PVDF) is preferable. These may be used alone or in combination of two or more kinds.

[0041] The insulating material may be composed of only the resin material, or may further contain an inorganic material. Examples of the inorganic material include metal oxides, metal nitrides, metal fluorides, metal carbides, etc. Examples of the metal oxide include aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, nickel oxide, silicon oxide, manganese oxide, etc. Examples of the metal nitride include titanium nitride, boron nitride, aluminum nitride, magnesium nitride, silicon nitride, etc. Examples of the metal fluoride include aluminum fluoride, lithium fluoride, sodium fluoride, magnesium fluoride, calcium fluoride, barium fluoride, etc. Examples of the metal carbide include silicon carbide, boron carbide, titanium carbide, tungsten carbide, etc. Further, the inorganic material may be a porous aluminosilicate such as zeolite (M ２／ｎ O·Al ２ O ３ ·xSiO ２ ·yH ２ O, where M is a metal element, n is the valence of M, x≥2, y≥0), a layered silicate such as talc (Mg ３ Si ４ O １０ (OH) ２ ), a mineral such as barium titanate (BaTiO ３ ), strontium titanate (SrTiO ３ ), etc. These may be used alone or in combination of two or more kinds.

[0042] Inorganic materials are composed of particulate inorganic particles, for example. The average particle size of inorganic particles is, for example, between 0.05 μm and 2 μm. The average particle size of inorganic particles refers to the particle size at which the cumulative frequency of the smallest particle size accounts for 50% in the volume-based particle size distribution, and is also called the median diameter. The particle size distribution of inorganic particles can be measured using a laser diffraction particle size distribution analyzer (for example, Microtrac-Bell MT3000II) with water as the dispersion medium.

[0043] When the insulating material contains the above-mentioned inorganic material, the content of the inorganic material relative to the total mass of the insulating layer 33 is preferably, for example, 60% by mass or more and 95% by mass or less, and 70% by mass or more and 90% by mass or less. When the insulating material contains the above-mentioned inorganic material, it becomes easier to form the insulating layer 33 on the surface of the positive electrode core 30.

[0044] The insulating layer 33 may further contain a conductive agent in addition to the insulating material. Examples of conductive agents included in the insulating layer 33 include carbon black such as acetylene black and Ketjenblack, graphite, carbon nanotubes (CNTs), carbon nanofibers, and carbon materials such as graphene. These may be used individually or in combination of two or more.

[0045] The manufacturing method for the positive electrode 11 of this embodiment includes, for example, a coating step of applying a positive electrode mixture layer slurry that forms a positive electrode mixture layer 31 and an insulating layer slurry that forms an insulating layer 33 onto a positive electrode core body 30, and a drying step of drying the coating film produced in the coating step.

[0046] In the coating process, while the positive electrode core 30 is being transported, the positive electrode mixture layer slurry and the insulating layer slurry are applied onto the positive electrode core 30 from different discharge ports. The insulating layer slurry is prepared by mixing a resin material and an inorganic material, and adding an appropriate amount of water, N-methyl-2-pyrrolidone (NMP), etc. The solid content concentration in the insulating layer slurry is, for example, 3% by mass or more and 50% by mass or less.

[0047] Methods for applying the positive electrode mixture layer slurry and the insulating layer slurry include, for example, die coating, gravure coating, spray coating, roll coating, reverse roll coating, screen printing, and inkjet coating, with the die coating method being preferred. In this case, the positive electrode mixture layer slurry is applied so as to overlap a portion of the insulating layer slurry coating. This allows a portion of the insulating layer 33 to be interposed between the positive electrode core 30 and the positive electrode mixture layer 31.

[0048] Here, the specific gravity of the insulating layer slurry is preferably 30% to 70% of the specific gravity of the positive electrode mixture layer slurry, and more preferably 40% to 60%. When the specific gravity of the insulating layer slurry is 30% to 70% of the specific gravity of the positive electrode mixture layer slurry, when the insulating layer 33 is formed, the second region 35 of the insulating layer 33 is pressed by the positive electrode mixture layer 31, and the thickness of the second region 35 tends to become smaller than the thickness of the first region 34.

[0049] In the drying process, the coating film prepared in the coating process is dried. Drying can be carried out by known methods. After drying, a rolling process can be carried out as needed to obtain the positive electrode 11 of this embodiment.

[0050] In the above embodiment, the case in which the non-composite layer portion 32 and the insulating layer 33 are formed on the winding start side of the positive electrode 11 has been described. However, the non-composite layer portion 32 and the insulating layer 33 may be formed on the winding end side of the positive electrode 11, in addition to or instead of the winding start side. Even when the non-composite layer portion 32 and the insulating layer 33 are formed on the winding end side of the positive electrode 11, the roundness of the electrode body 14 can still be ensured.

[0051] Next, a modified example of the positive electrode 11 will be described with reference to Figure 4. Figure 4 is a diagram of the modified positive electrode 11, corresponding to Figure 3.

[0052] As shown in Figure 4, the positive electrode mixture layer 31 of this embodiment has an inclined portion 36 in which the thickness of the positive electrode mixture layer 31 decreases as it approaches the winding start end 31A of the positive electrode mixture layer 31. By providing the inclined portion 36, the step formed at the winding start end 31A of the positive electrode mixture layer 31 can be reduced. This makes it possible to further improve the roundness of the electrode body 14. As a result, for example, when charging and discharging are repeated, the deformation of the negative electrode 12 facing the winding start end 11A of the positive electrode 11 can be further suppressed.

[0053] In the longitudinal direction of the positive electrode 11, the length of the inclined portion 36 may be, for example, 0.5 mm or more and 5 mm or less, or 1 mm or more and 3 mm or less. In this case, while suppressing peeling of the positive electrode mixture layer 31, deformation of the negative electrode 12 at the winding start side of the positive electrode 11 can be further suppressed.

[0054] The inclined portion 36 can be created, for example, by reducing the amount of cathode mixture layer slurry applied as it approaches the starting end 31A of the cathode mixture layer 31.

[0055] In the example shown in Figure 4, the inclined portion 36 is provided on both sides of the positive electrode mixture layer 31, but the inclined portion 36 may be provided on only one side of the positive electrode mixture layer 31. Also, in the example shown in Figure 4, the thickness of the positive electrode mixture layer 31 decreases linearly as it approaches the winding start end 31A of the positive electrode mixture layer 31, but it may decrease non-linearly as it approaches the winding start end 31A of the positive electrode mixture layer 31.

[0056] The present disclosure is further described by the following embodiments. Configuration 1: A non-aqueous electrolyte secondary battery comprising an electrode body in which a first electrode and a second electrode having different polarities are wound along the length direction via a separator, wherein the first electrode comprises a first electrode core, a first electrode mixture layer and an insulating layer formed on the first electrode core, and at least one of the winding start end and winding end of the first electrode is provided with a mixture layer non-formed portion where the first electrode mixture layer is not formed, and the insulating layer mainly comprises an insulating material and comprises a first region covering the mixture layer non-formed portion and a second region disposed between the first electrode core and the first electrode mixture layer, wherein the thickness of the insulating layer in the second region is less than the thickness of the insulating layer in the first region. Configuration 2: The non-aqueous electrolyte secondary battery according to Configuration 1, wherein the insulating material comprises a resin material and an inorganic material, and the content of the inorganic material with respect to the total mass of the insulating layer is 60% by mass or more and 95% by mass or less. Configuration 3: The non-aqueous electrolyte secondary battery according to Configuration 2, wherein the resin material contains polyvinylidene fluoride. Configuration 4: The non-aqueous electrolyte secondary battery according to any one of Configurations 1 to 3, wherein the ratio of the thickness of the insulating layer in the second region to the thickness of the insulating layer in the first region is 0.70 or less. Configuration 5: The non-aqueous electrolyte secondary battery according to any one of Configurations 1 to 4, wherein the thickness of the insulating layer in the first region is 3 μm or more and 15 μm or less. Configuration 6: A method for manufacturing an electrode having a first electrode core and a first electrode mixture layer and an insulating layer formed on the first electrode core, comprising: a coating step of applying a first electrode mixture layer slurry for forming the first electrode mixture layer and an insulating layer slurry for forming the insulating layer onto the first electrode core from different discharge ports while conveying the first electrode core; and a drying step of drying the coating film produced in the coating step, wherein in the coating step, the first electrode mixture layer slurry is applied so as to overlap a portion of the insulating layer slurry coating film. Configuration 7: The method for manufacturing an electrode according to Configuration 6, wherein the specific gravity of the insulating layer slurry is 30% or more and 70% or less of the specific gravity of the first electrode mixture layer slurry.

[0057] 10 Non-aqueous electrolyte secondary battery, 11 Positive electrode (first electrode), 11A Winding start end, 11B Winding start end, 12 Negative electrode (second electrode), 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18 Insulating plate, 19 Insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved section, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive electrode core body (first electrode core body), 31 Positive electrode mixture layer (first electrode mixture layer), 31A Winding start end, 32B Winding start end, 32 Mixture layer non-formed section, 33 Insulating layer, 34 First region, 35 Second region, 36 Inclined section, 40 Negative electrode core body, 41 Negative electrode mixture layer, 42 Outer peripheral exposed section.

Claims

1. A non-aqueous electrolyte secondary battery comprising an electrode body in which a first electrode and a second electrode having opposite polarities are wound along the length direction via a separator, wherein the first electrode comprises a first electrode core and a first electrode mixture layer and an insulating layer formed on the first electrode core, and at least one of the winding start end and winding end of the first electrode is provided with a mixture layer non-formed portion where the first electrode mixture layer is not formed, and the insulating layer mainly comprises an insulating material and comprises a first region covering the mixture layer non-formed portion and a second region disposed between the first electrode core and the first electrode mixture layer, wherein the thickness of the insulating layer in the second region is smaller than the thickness of the insulating layer in the first region.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the insulating material comprises a resin material and an inorganic material, and the content of the inorganic material relative to the total mass of the insulating layer is 60% by mass or more and 95% by mass or less.

3. The non-aqueous electrolyte secondary battery according to claim 2, wherein the resin material comprises polyvinylidene fluoride.

4. The ratio of the thickness of the insulating layer in the second region to the thickness of the insulating layer in the first region is 0.7 or less, the non-aqueous electrolyte secondary battery according to claim 1.

5. The non-aqueous electrolyte secondary battery according to claim 1, wherein the thickness of the insulating layer in the first region is 3 μm or more and 15 μm or less.

6. A method for manufacturing an electrode, comprising a first electrode core and a first electrode mixture layer and an insulating layer formed on the first electrode core, comprising: a coating step of applying a first electrode mixture layer slurry for forming the first electrode mixture layer and an insulating layer slurry for forming the insulating layer onto the first electrode core from different discharge ports while conveying the first electrode core; and a drying step of drying the coating film produced in the coating step, wherein in the coating step, the first electrode mixture layer slurry is applied so as to overlap a portion of the insulating layer slurry coating film.

7. The method for manufacturing an electrode according to claim 6, wherein the specific gravity of the insulating layer slurry is 30% or more and 70% or less of the specific gravity of the first electrode mixture layer slurry.

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