Non-aqueous electrolyte secondary battery

Abstract

A nonaqueous electrolyte secondary battery has a nonaqueous electrolyte and an electrode body in which a positive electrode and a negative electrode are alternately stacked with a separator interposed therebetween, the positive electrode includes a core exposure portion in which a positive electrode core is exposed and a base portion in which a composite material layer is formed on at least one face of the positive electrode core, a first region in which an active material is embedded in the positive electrode core is formed in the base portion, a second region in which an average embedding depth of the active material in the positive electrode core is smaller than that of the first region is formed in the base portion, and the second region is formed adjacent to the core exposure portion.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a nonaqueous electrolyte secondary battery and a manufacturing method of a nonaqueous electrolyte secondary battery. BACKGROUND

[0002] A nonaqueous electrolyte secondary battery has a nonaqueous electrolyte and an electrode body in which a positive electrode and a negative electrode are alternately stacked with a separator interposed therebetween. The positive electrode and the negative electrode include a core-exposed portion in which a core is exposed and a base portion in which a composite material layer is formed on at least one face of the core. A manufacturing process of such a positive electrode and a negative electrode includes a coating process in which a composite material slurry including an active material and the like is coated on a long metal foil while leaving an exposed portion including the core-exposed portion, a compression process in which a coating film is dried and subjected to rolling to form the composite material layer on the metal foil, and a cutting process in which the metal foil on which the composite material layer is formed is cut into a predetermined shape (for example, Patent Literature 1).

[0003] Prior art documents

[0004] Patent documents

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2014-179217 SUMMARY

[0006] For the positive electrode and the negative electrode of the nonaqueous electrolyte secondary battery, the composite material layer is easily peeled from the core at an end face formed of the core and the composite material layer. In particular, in the cutting process of the positive electrode and the negative electrode of the nonaqueous electrolyte secondary battery, the composite material layer is easily peeled from the metal foil when the metal foil and the composite material layer are cut at a slit or the like. As a solution to this, it is considered to improve the adhesion strength (adhesion) of the core to the composite material layer to prevent peeling. However, the core strength is reduced due to the improvement of the adhesion of the core to the composite material layer.

[0007] A tab is formed in the core-exposed portion of the positive electrode and the negative electrode of the nonaqueous electrolyte secondary battery, and vibration or impact acts when the tab is joined to a current collector by welding or the like. For example, in the case where the adhesion of the core to the composite material layer is improved, a fracture is likely to occur in a portion of the composite material layer adjacent to the core-exposed portion. In addition, in the coating process of the positive electrode and the negative electrode of the nonaqueous electrolyte secondary battery, both end portions in a conveyance direction of the long metal foil are left as exposed portions and the composite material slurry is coated. In the both end portions in the conveyance direction of the metal foil, stress concentration occurs due to twisting of the metal foil or the like. In the case where the adhesion of the metal foil to the composite material layer is improved as described above, a fracture is likely to occur in a portion of the composite material layer adjacent to the exposed portion.

[0008] A nonaqueous electrolyte secondary battery according to an embodiment of the present disclosure includes a nonaqueous electrolyte and an electrode body in which a positive electrode and a negative electrode are alternately stacked with a separator interposed therebetween, each of the positive electrode and the negative electrode including a core-exposed portion in which a core is exposed and a base portion in which a composite material layer is formed on at least one face of the core, the base portion including a first region in which an active material is embedded in the core and a second region in which the active material is embedded in the core at a smaller average embedding depth than the first region, the second region being formed adjacent to the core-exposed portion.

[0009] A method of manufacturing a nonaqueous electrolyte secondary battery according to an embodiment of the present disclosure manufactures a nonaqueous electrolyte secondary battery including a nonaqueous electrolyte and an electrode body in which a positive electrode and a negative electrode are alternately stacked with a separator interposed therebetween, each of the positive electrode and the negative electrode including a core-exposed portion in which a core is exposed and a base portion in which a composite material layer is formed on at least one face of the core, the base portion including a first region in which an active material is embedded in the core and a second region in which the active material is embedded in the core at a smaller average embedding depth than the first region, the second region being formed adjacent to the core-exposed portion. In the method of manufacturing, there is a coating process in which the positive electrode or the negative electrode is produced by coating a composite material including the active material on at least one face of a metal foil forming the core in a manner to leave an exposed portion including the core-exposed portion. In the coating process, the composite material is coated in a manner to form a first coated portion and a second coated portion having a smaller coating amount per unit area than the first coated portion, the second coated portion being adjacent to the exposed portion.

[0010] According to an embodiment of the present disclosure, peeling of the core from the composite material layer can be avoided, and breakage of a portion of the composite material layer adjacent to the core-exposed portion can be avoided. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a perspective view of a nonaqueous electrolyte secondary battery that is one example of an embodiment.

[0012] Figure 2 is a perspective view of an electrode body that is one example of an embodiment.

[0013] Figure 3 is a front view of a positive electrode that is one example of an embodiment.

[0014] Figure 4 is a schematic view showing a state in which a positive electrode active material is tightly bonded to a positive electrode core in a first region.

[0015] Figure 5 is a schematic view showing a state in which a positive electrode active material is tightly bonded to a positive electrode core in a second region.

[0016] Figure 6 is a view for explaining a production process of a positive electrode that is one example of an embodiment.

[0017] Figure 7 is an AA cross-sectional view of the AA before compression. Figure 6 is an AA cross-sectional view of the AA before compression.

[0018] Figure 8 is a cross-sectional view of AA of the compressed Figure 6 DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of the present disclosure will be described using the drawings. The shapes, materials, and numbers described below are examples, and can be appropriately changed according to the specifications of the nonaqueous electrolyte secondary battery and the manufacturing method of the nonaqueous electrolyte secondary battery. Hereinafter, the same reference signs are attached to the same elements in all the drawings and are described.

[0020] [Nonaqueous electrolyte secondary battery]

[0021] Figure 1 is a perspective view of a nonaqueous electrolyte secondary battery 10 that is one example of an embodiment. As shown in Figure 1 , the nonaqueous electrolyte secondary battery 10 has an electrode body 11 (see Figure 2 ), a nonaqueous electrolyte, a bottomed square cylindrical outer can 14 that houses the electrode body 11 and the nonaqueous electrolyte, and a sealing plate 15 that plugs an opening portion of the outer can 14. The nonaqueous electrolyte secondary battery 10 is a so-called square battery. The outer can 14 is a flat and substantially rectangular parallelepiped-shaped metal container that is open at one end in the axial direction, and the sealing plate 15 has an elongated rectangular shape. The outer can 14 and the sealing plate 15 are composed of, for example, a metal material in which aluminum is a main component.

[0022] The nonaqueous electrolyte secondary battery 10 has a positive electrode terminal 12 that is electrically connected to a positive electrode 20 (see Figure 2 ) via a positive electrode current collector and a negative electrode terminal 13 that is electrically connected to a negative electrode 30 (see Figure 2 ) via a negative electrode current collector. In the present embodiment, the positive electrode terminal 12 is disposed at one end side in the length direction of the sealing plate 15, and the negative electrode terminal 13 is disposed at the other end side in the length direction of the sealing plate 15. The positive electrode terminal 12 and the negative electrode terminal 13 are external connection terminals that are electrically connected to other nonaqueous electrolyte secondary batteries 10, circuits, devices, and the like, and are attached to the sealing plate 15 with an insulating member interposed. The sealing plate 15 is provided with: a liquid injection portion 16 for injecting a nonaqueous electrolytic solution into the inside of the outer can 14 in which the electrode body 11 is housed; and a gas discharge valve 17 for opening the valve to discharge gas at the time of abnormality of the battery.

[0023] Hereinafter, for convenience of explanation, the height direction of the outer can 14 is taken as the "vertical direction" of the nonaqueous electrolyte secondary battery 10, the sealing plate 15 side is taken as the "top", and the bottom portion side of the outer can 14 is taken as the "bottom". In addition, the direction along the length direction of the sealing plate 15 is taken as the "lateral direction" of the nonaqueous electrolyte secondary battery 10.

[0024] ​[Non-aqueous electrolyte]

[0025] The non-aqueous electrolyte contains, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. As the non-aqueous solvent, for example, an ester, an ether, a nitrile, an amide, a mixed solvent of two or more of them, or the like can be used. The non-aqueous solvent can also contain a halogen-substituted body obtained by substituting at least a part of the hydrogen of these solvents with a halogen atom such as fluorine. As the electrolyte salt, for example, a lithium salt such as LiPF6is used.

[0026] [Electrode body]

[0027] Figure 2 is a perspective view of the electrode body 11. As shown in Figure 2 , the electrode body 11 is a laminated electrode body in which a plurality of positive electrodes 20 and a plurality of negative electrodes 30 are alternately laminated one by one with separators 40 interposed therebetween. The positive electrodes 20 and the negative electrodes 30 each contain a positive electrode tab 23 and a negative electrode tab 33 that protrude upward. The positive electrodes 20 are laminated and arranged so that the positive electrode tabs 23 are located on one end side in the lateral direction of the electrode body 11 and the plurality of positive electrode tabs 23 are arranged in the thickness direction of the electrode body 11. In addition, the negative electrodes 30 are laminated and arranged so that the negative electrode tabs 33 are located on the other end side in the lateral direction of the electrode body 11 and the plurality of negative electrode tabs 33 are arranged in the thickness direction of the electrode body 11.

[0028] [Positive electrode]

[0029] Figure 3 is a front view of the positive electrode 20. As shown in Figure 3 , the positive electrode 20 contains a positive electrode core 21 and a positive electrode composite material layer 22 formed on both faces of the positive electrode core 21. As the positive electrode core 21, a foil of a metal such as aluminum that is stable in the battery operating voltage range, a film in which the metal is arranged on the surface, or the like can be used. The thickness of the positive electrode core 21 is, for example, 5 μm to 20 μm, and is preferably 8 μm to 15 μm.

[0030] The positive electrode composite material layer 22 contains, for example, a positive electrode active material, a conductive material, and a binder, and is formed on both faces of the positive electrode core 21. The thickness of the positive electrode composite material layer 22 is, for example, 40 μm to 120 μm on one side of the positive electrode core 21, and is preferably 50 μm to 80 μm. The positive electrode 20 can be produced by, for example, applying a positive electrode composite material slurry containing a positive electrode active material, a conductive material, a binder, and the like onto the positive electrode core 21, drying the coating film, and compressing it, forming the positive electrode composite material layer 22 on both faces of the positive electrode core 21, and then cutting it to a predetermined shape.

[0031] As the positive electrode active material, a lithium transition metal composite oxide is used. As the metal element contained in the lithium transition metal composite oxide, Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, and the like are exemplified. Among them, at least one of Ni, Co, and Mn is preferable. As an example of the preferable composite oxide, a lithium transition metal composite oxide containing Ni, Co, and Mn, and a lithium transition metal composite oxide containing Ni, Co, and Al are exemplified.

[0032] As the conductive material contained in the positive electrode composite layer 22, a carbon material such as carbon black, acetylene black, Ketjen black, and graphite can be exemplified. As the binder material contained in the positive electrode composite layer 22, a fluorine resin such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), a polyacrylonitrile (PAN), a polyimide resin, an acrylic resin, a polyolefin resin, and the like can be exemplified. In addition, these resins can be used together with a cellulose derivative such as carboxymethyl cellulose (CMC) or a salt thereof, and polyethylene oxide (PEO), and the like.

[0033] The positive electrode 20 includes a core exposed portion 24 in which the positive electrode core 21 is exposed, and a base portion 25 in which the positive electrode composite layer 22 is formed on at least one face of the positive electrode core 21. In the present embodiment, the positive electrode composite layer 22 is formed on both faces of the positive electrode core 21. The core exposed portion 24 is formed in a band shape along the lateral direction at the upper end portion of the positive electrode 20. The positive electrode tab 23 described above is formed at the upper end portion of the core exposed portion 24. The base portion 25 is all portions of the positive electrode 20 except for the core exposed portion 24.

[0034] The base portion 25 includes a first region 26 in which the positive electrode active material is embedded in the positive electrode core 21, and a second region 27 in which the positive electrode active material is not embedded in the positive electrode core 21 as compared with the first region 26. In the first region 26, the positive electrode active material is embedded in the positive electrode core 21 at a substantially uniform depth. In the first region 26, an end face 26A other than the end face adjacent to the second region 27 is formed by the positive electrode core 21 and the positive electrode composite layer 22. At the end face 26A, the positive electrode composite layer 22 is easily peeled from the positive electrode core 21.

[0035] The second region 27 is formed adjacent to the core exposed portion 24. The second region 27 is preferably formed in a range of 10 mm or less from the side end adjacent to the core exposed portion 24. In the second region 27, vibration or impact acts when the positive electrode tab 23 is joined by welding or the like. Therefore, the second region 27 can be broken.

[0036] Figure 4 is a schematic view showing the state in which the positive electrode active material is tightly adhered to the positive electrode core 21 in the first region 26. As shown in the drawing, the positive electrode active material is embedded in the positive electrode core 21 at a substantially uniform depth in the first region 26. In the first region 26, the end face 26A other than the end face adjacent to the second region 27 is formed by the positive electrode core 21 and the positive electrode composite layer 22. At the end face 26A, the positive electrode composite layer 22 is easily peeled from the positive electrode core 21. Figure 4As shown, in the first region 26, the positive electrode active material is embedded in the positive electrode core 21. This improves the adhesion between the positive electrode core 21 and the positive electrode composite material layer 22 in the first region 26. Therefore, delamination between the core and the composite material at the end face 26A of the first region 26 formed by the positive electrode core 21 and the positive electrode composite material layer 22 can be avoided.

[0037] In region 26, the positive electrode active material is embedded in the positive electrode core 21. Therefore, the curvature of the positive electrode core 21 is preferably 110% to 150%, more preferably 130% to 140%. The curvature of the positive electrode core 21 is an indicator of the surface unevenness of the positive electrode core 21. It is the ratio of the length of the uneven surface (with the positive electrode active material embedded) to the length of the flat surface of the positive electrode core 21 (without the positive electrode active material embedded) in a cross-sectional view in the vertical or horizontal direction. The curvature of the positive electrode core 21 can be measured by observing the cross-section of the positive electrode 20 using a scanning electron microscope (SEM).

[0038] In region 27, the average embedment depth of the positive electrode active material into the positive electrode core 21 is smaller than that in region 26. The average embedment depth refers to the average embedment depth of the positive electrode active material into the positive electrode core 21. Embedment depth is the length along the thickness direction of the positive electrode core material from its surface to the portion where the positive electrode active material is most deeply embedded. The embedment depth of the positive electrode active material can be measured by observing the cross-section of the positive electrode 20 using a scanning electron microscope (SEM).

[0039] Figure 5 This is a schematic diagram showing the state in which the positive electrode active material and the positive electrode core 21 are tightly bonded in region 27. In region 27, it can be seen as follows... Figure 5 The region shown includes a portion where the positive electrode active material is not embedded in the positive electrode core 21, and may also include a portion where the average depth of the positive electrode active material embedded in the positive electrode core 21 is smaller than that of the first region 26. Furthermore, in the second region 27, preferably, the portion where the positive electrode active material is not embedded in the positive electrode core 21 is formed on the core exposed portion 24 side, and the portion where the positive electrode active material is embedded in the positive electrode core 21 is formed on the first region 26 side. Moreover, in the second region 27, the positive electrode active material may not be embedded in the positive electrode core 21 at all, or the positive electrode active material may be uniformly embedded in the positive electrode core 21.

[0040] The curvature per unit area of ​​the positive electrode core 21 in the second region 27 is preferably smaller than that of the positive electrode core 21 in the first region 26. In the first region 26, the positive electrode active material is embedded in the positive electrode core 21, therefore the curvature of the positive electrode core 21 is preferably 100% to 110%.

[0041] Thus, in the second region 27, the strength of the positive electrode core 21 can be ensured compared to the first region 26. Therefore, it is possible to avoid breakage of the second region 27 due to vibration or impact when the positive electrode tab 23 is joined to the current collector by welding or the like.

[0042] The positive electrode active material contains a large-particle-size lithium transition metal complex oxide and a small-particle-size lithium transition metal complex oxide that is smaller than the large-particle-size. For example, in the first region 26, the positive electrode active material of the large-particle-size and the small-particle-size can be embedded in the positive electrode core 21, or the positive electrode active material of the large-particle-size can be embedded in the positive electrode core 21. In addition, by mixing the positive electrode active material of the large-particle-size and the small-particle-size, the density of the positive electrode composite layer 22 can be increased.

[0043] The positive electrode active material of the large-particle-size, for example, preferably has a median particle diameter (hereinafter, referred to as "D50") of 15 μm or more, and more preferably 15 μm to 20 μm on a volume basis. The positive electrode active material of the small-particle-size, for example, preferably has a D50 of 5 μm or more, and more preferably 5 μm to 10 μm on a volume basis. The D50 on a density volume basis means a particle diameter at which the cumulative frequency becomes 50% from the smaller side in the particle size distribution on a volume basis, and is also referred to as a median diameter. The D50 can be measured using a particle size distribution measuring device of a laser diffraction type (for example, Microtrac HRA manufactured by NIKKISO CO., LTD.), with water as a dispersion medium.

[0044] [Negative electrode]

[0045] The negative electrode 30 has a structure in which a negative electrode composite layer is formed in the entire region of the surface of the negative electrode core except for the portion of the side on which the negative electrode tab 33 is formed. For the negative electrode core, a foil of a metal such as copper that is stable in the battery operating voltage range, a film in which the metal is disposed on the surface layer, or the like can be used. The thickness of the negative electrode core is, for example, 3 μm to 15 μm, and preferably 5 μm to 10 μm.

[0046] The negative electrode composite layer contains, for example, a negative electrode active material, a binder material, and is formed on both surfaces of the negative electrode core. In addition, the negative electrode composite layer can also be formed on the root portion of the negative electrode tab 33. The thickness of the negative electrode composite layer is, for example, 40 μm to 120 μm, and preferably 50 μm to 80 μm on one side of the negative electrode core. The negative electrode 30 can be produced by, for example, applying a negative electrode composite slurry containing a negative electrode active material, a binder material, and the like on the negative electrode core, drying the coating film, and compressing, forming the negative electrode composite layer on both surfaces of the negative electrode core, and then cutting to a predetermined shape.

[0047] As the negative active material, for example, a carbon-based active material that reversibly occludes or releases lithium ions is used. Preferred carbon-based active materials are natural graphite such as flaky graphite, massive graphite, earthy graphite, and the like, artificial graphite such as massive artificial graphite (MAG) and graphitized mesocarbon microbeads (MCMB), and the like. In addition, for the negative active material, a Si-based active material composed of at least one of Si and a compound containing Si can be used, or a carbon-based active material and a Si-based active material can be used together.

[0048] For the binder material contained in the negative composite material layer, similarly to the case of the positive electrode 20, a fluorine resin, PAN, polyimide, an acrylic resin, a polyolefin, or the like can be used, but it is preferable to use styrene butadiene rubber (SBR). In addition, it is preferable that the negative composite material layer further contain CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), or the like. Among them, it is preferable to use SBR together with CMC or a salt thereof, PAA or a salt thereof.

[0049] The negative electrode 30 can also include, similarly to the case of the positive electrode 20, a core-exposed portion in which the negative electrode core is exposed and a base portion in which the negative composite material layer is formed on both faces of the negative electrode core. In addition, the base portion can be formed with a first region in which the negative active material is embedded in the negative electrode core and a second region in which the negative active material is not embedded in the negative electrode core compared to the first region.

[0050] According to the nonaqueous electrolyte secondary battery 10 of the present embodiment, peeling of the positive electrode core 21 from the positive composite material layer 22 can be avoided in the first region 26, and breakage can be avoided in the second region 27.

[0051] [Manufacturing process of nonaqueous electrolyte secondary battery]

[0052] Hereinafter, one example of a manufacturing method of the nonaqueous electrolyte secondary battery 10 having the above-described structure will be described. In the manufacturing process of the nonaqueous electrolyte secondary battery 10, a process of manufacturing the positive electrode 20, a process of manufacturing the negative electrode 30, a process of manufacturing the electrode body 11 using the positive electrode 20 and the negative electrode 30, and a process of injecting the nonaqueous electrolyte into the inside of the exterior can 14 after the electrode body 11 is housed in the inside of the exterior can 14 are included. In addition, for the constituent materials of the electrode body 11 such as the positive active material, the negative active material, and the separator 40, the same materials as in the past can be used.

[0053] The manufacturing process of the positive electrode 20 includes: a coating process in which a positive electrode composite material paste including a positive electrode active material and the like is coated on a long strip-shaped metal foil 50 that is a positive electrode core 21; a compression process in which a coating film is dried and is rolled to form a positive electrode composite material layer 22 on both surfaces of the metal foil 50; and a cutting process in which the metal foil 50 is cut into a predetermined shape. Hereinafter, a direction orthogonal to a transport direction of the metal foil 50 is referred to as a width direction.

[0054] Figure 6 is a schematic view that illustrates the manufacturing process of the positive electrode 20. As shown in Figure 6 , in the coating process, a known coating device such as a gravure coater, a slit coater, a die coater, or the like is used to coat the positive electrode composite material paste on the surface of the metal foil 50. At this time, a certain region of both end portions in the width direction of the metal foil 50 is left as an exposed portion 51, and the positive electrode composite material paste is coated on the metal foil 50. The core exposed portion 24 and the positive electrode tab 23 are formed in the exposed portion 51.

[0055] In the coating process, the positive electrode composite material paste is coated on the metal foil 50 to form a coated portion 62. At this time, the first coated portion 64 and a second coated portion 65 in which the amount of coating per unit area is less than that of the first coated portion 64 are continuously formed to form the coated portion 62. Hereinafter, a description of the amount of coating simply refers to the amount of coating per unit area. The second coated portion 65 is formed adjacent to the exposed portion 51. The second coated portion 65 preferably has a size of 10 mm or less from the side end adjacent to the exposed portion 51.

[0056] Figure 7 is an AA cross-sectional view of Figure 6 . In the example shown in Figure 7 , the amount of coating of the positive electrode composite material paste is adjusted in such a manner that the cross-sectional shape in the transport direction becomes a trapezoidal shape. In this cross-sectional shape, the cross-sectional shape of the first coated portion 64 is a band-shaped rectangle, and the cross-sectional shape of the second coated portion 65 is a triangular shape. In other words, the amount of coating of the first coated portion 64 is the same in the width direction. The amount of coating of the second coated portion 65 decreases linearly from the amount of coating of the first coated portion 64 to 0.

[0057] In the compression process, after the coating film is heated and dried, the coating film is compressed using a rolling roller or the like and is transported in a predetermined direction. Figure 8 is an AA cross-sectional view of Figure 6 . In the example shown in Figure 8 , in the compression process, the first coated portion 64 is formed as the positive electrode composite material layer 22 of the above-described first region 26, and the second coated portion 65 is formed as the positive electrode composite material layer 22 of the above-described second region 27. In addition, in the compression process, the density of the second region 27 is smaller than the density of the first region 26.

[0058] At both ends in the conveyance direction of the metal foil 50, stress concentration occurs due to twisting of the metal foil 50 or the like. Therefore, in the conveyance in the compression process, a break can occur in the second region 27 adjacent to the exposed portion 51. In addition, in the cutting process, when the metal foil 50 and the positive electrode composite material layer 22 are cut at a slit or the like, the positive electrode composite material layer 22 is easily peeled from the metal foil 50.

[0059] In the present embodiment, the adhesion of the metal foil 50 to the positive electrode composite material layer 22 can be improved in the first region 26. Therefore, peeling of the positive electrode composite material layer 22 from the metal foil 50 when the metal foil 50 and the positive electrode composite material layer 22 are cut at a slit or the like in the cutting process can be avoided. In addition, the strength of the metal foil 50 can be ensured in the second region 27 compared to the first region 26. Therefore, a break of the second region 27 of the positive electrode composite material layer 22 in the conveyance in the compression process can be avoided.

[0060] It can also be that the coating amount of the positive electrode composite material slurry is adjusted in a manner that the cross-sectional shape in the conveyance direction becomes a semi-elliptical shape. In this cross-sectional shape, the cross-sectional shape of the first coating portion 64 is a rectangular band shape, and the cross-sectional shape of the second coating portion 65 is a semi-circular shape.

[0061] It can also be that the coating amount of the positive electrode composite material slurry is adjusted in a manner that the cross-sectional shape in the conveyance direction becomes a convex shape. In this cross-sectional shape, the cross-sectional shape of the first coating portion 64 is a rectangular band shape, and the cross-sectional shape of the second coating portion 65 is a rectangular shape lower than the cross-sectional shape of the first coating portion 64. In other words, it is adjusted that the coating amount is the same in the width direction in the first coating portion 64, and the coating amount is less than the coating amount of the first coating portion 64 and is the same in the width direction in the second coating portion 65.

[0062] In the cutting process, the metal foil 50 is cut by a conventionally known method such as laser irradiation, a blanking die process, or the like. Figure 6 In the cutting process, the metal foil 50 is cut by a conventionally known method such as laser irradiation, a blanking die process, or the like.

[0063] In the manufacturing process of the non-aqueous electrolyte secondary battery 10, the electrode body 11 is housed in the exterior can 14 after the respective positive electrode tabs 23 of the plurality of positive electrodes 20 are connected to the positive electrode current collector, and the respective negative electrode tabs 33 of the plurality of negative electrodes 30 are connected to the negative electrode current collector by welding or the like.

[0064] According to the manufacturing process of the nonaqueous electrolyte secondary battery 10 of the present embodiment, peeling of the positive electrode core 21 from the positive electrode composite layer 22 in the first region 26 in the cutting process can be avoided, and breakage of the second region 27 in the conveying in the compression process can be avoided.

[0065] Further, the present application is not limited to the above-described embodiments and modified examples thereof, and various changes and improvements can of course be made within the scope of the matters recited in the claims of the present application.

[0066] List of reference signs

[0067] 10, nonaqueous electrolyte secondary battery; 11, electrode body; 12, positive electrode terminal; 13, negative electrode terminal; 14, outer can; 15, sealing plate; 16, liquid injection portion; 17, gas discharge valve; 20, positive electrode; 21, positive electrode core; 22, positive electrode composite layer; 23, positive electrode tab; 24, core exposed portion; 25, base portion; 26, first region; 27, second region; 30, negative electrode; 33, negative electrode tab; 40, separator; 50, metal foil; 51, exposed portion; 62, coated portion; 64, first coated portion; 65, second coated portion.

Claims

1. A non-aqueous electrolyte secondary battery, comprising a stacked electrode body consisting of a non-aqueous electrolyte and a plurality of positive electrodes and a plurality of negative electrodes alternately stacked with separators, wherein both the positive and negative electrodes include a core-exposed portion and a base portion on at least one surface of the core having a composite material layer formed thereon, wherein, The base has a first region where the active material is embedded in the core, and a second region where the average embedment depth of the active material in the core is smaller than that of the first region. The second region is formed adjacent to the core exposed portion. The curvature of the core surface in the first region is 110% to 150%. The curvature is an indicator of the surface roughness of the core, and is the proportion of the length of the roughness of the surface with embedded active material per unit length of the flat surface of the core without embedded active material in a vertical or horizontal cross-sectional view.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The second region is formed within a range of 10 mm or less from the side end adjacent to the exposed portion of the core.

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