Battery electrode, battery, and method for producing battery electrode

Abstract

As an example of an embodiment, a battery electrode comprises a core body and an active material layer provided on the surface of the core body. The core body comprises a base portion whose surface is covered by the active material layer and a pole ear portion protruding from the base portion. A notch is formed in the core body from the root of the pole ear portion to the base portion, or a notch is formed in a portion of the base portion adjacent to the pole ear portion. The edge of the notch is formed by a first curve and a second curve or a first curve and a straight line, the first curve is composed of a first arc, and the second curve is composed of a second arc having a curvature smaller than that of the first arc. With this structure, a battery electrode can be provided that can fully suppress the generation of cracks at the root of the pole ear portion of the core body and in the vicinity thereof.

Description

Technical Field

[0001] The present disclosure relates to a battery electrode, a battery, and a method for producing the battery electrode. Background Art

[0002] A battery electrode generally comprises a metal core and an active material layer disposed on the surface of the core. The core, for example, comprises a base whose surface is covered with an active material layer and a pole ear protruding from the base. Patent document 1 discloses a battery electrode having a notch formed at the root of the pole ear and its vicinity. In addition, Patent document 1 states that after the notch is provided at the root of the pole ear and its vicinity, by compressing the active material layer, cracks in the core can be effectively suppressed.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2017 / 204184 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In addition, if the active material layer is compressed with a strong force to increase the packing density of the active material layer, the volume energy density of the battery can be increased. However, if the active material layer is strongly compressed, cracks may occur at the root of the pole ear portion of the core and its vicinity. In addition, due to the expansion and contraction of the active material layer accompanying the charging and discharging of the battery, cracks may also occur at the root of the pole ear portion of the core and its vicinity. According to the electrode disclosed in Patent Document 1, the effect of suppressing the occurrence of such cracks can be expected, but as a result of the research of the present inventors, it can be seen that there is still room for improvement.

[0008] Solutions for solving problems

[0009] A battery electrode according to a technical solution of the present disclosure is a battery electrode having a core and an active material layer provided on the surface of the core, wherein the core has a base whose core surface is covered by the active material layer and a pole ear protruding from the base. A notch is formed in the core from the root of the pole ear to the base, or a notch is formed in a portion of the base adjacent to the pole ear. The edge of the notch is formed by a first curve and a second curve or a first curve and a straight line, wherein the first curve is formed by a first arc, and the second curve is formed by a second arc having a curvature smaller than that of the first arc.

[0010] A battery according to one aspect of the present disclosure includes the above-mentioned battery electrode.

[0011] A method for manufacturing a battery electrode according to a technical solution of the present disclosure is a method for manufacturing a battery electrode as follows, the battery electrode comprising a core body and an active material layer provided on the surface of the core body, the core body having a base portion whose core surface is covered by the active material layer and a lug portion protruding from the base portion, in which the active material layer is provided at least on the surface of the base portion or on the surface of a portion to be the base portion, a notch is formed from the root of the lug portion or the portion to be the lug portion to the base portion or a notch is formed in a portion of the base portion adjacent to the lug portion or a portion to be the adjacent portion, at which time the edge of the notch is formed by a first curve and a second curve or a first curve and a straight line, the first curve being composed of a first arc, the second curve being composed of a second arc having a curvature smaller than that of the first arc, and after the notch is formed, the active material layer is compressed.

[0012] Effects of the Invention

[0013] According to the battery electrode of one aspect of the present disclosure, it is possible to sufficiently suppress the occurrence of cracks at the base of the lug portion of the core body and in the vicinity thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a cross-sectional view of a battery according to an example of an embodiment.

[0015] Figure 2 This is an exploded perspective view of an electrode body according to an example of the embodiment.

[0016] Figure 3 This is a diagram showing an enlarged view of a positive electrode lug portion and its vicinity in a positive electrode according to an example of the embodiment.

[0017] Figure 4 It is a diagram showing a modified example of the notch.

[0018] Figure 5 It is a diagram showing a modified example of the notch.

[0019] Figure 6 This is a diagram showing the notch of Comparative Example 1.

[0020] Figure 7 This is a diagram showing the notch of Comparative Example 2. DETAILED DESCRIPTION

[0021] In recent years, as a driving power source for electric vehicles (EV), hybrid electric vehicles (HEV, PHEV), etc., secondary batteries such as lithium-ion batteries are used, and the volume energy density of the battery is required to be increased compared to the past. As described above, as a method of increasing the volume energy density of the battery, a method of compressing the active material layer with a strong force to increase the packing density of the active material layer is considered. However, in this case, there is a case where cracks are generated at the root of the lug portion of the core and in the vicinity thereof.

[0022] When the active material layer is compressed with a strong force, not only the active material layer but also the core body is strongly compressed, so the core body is rolled. At this time, although the portion of the core body provided with the active material layer (base) is rolled, the exposed portion of the core body (ear part) is thinner than the portion provided with the active material layer, so no compressive load is applied and thus it is not rolled. Therefore, for the core body, there is a difference in length between the portion provided with the active material layer and the exposed portion of the core body where no active material layer is present, which causes cracks to form at the root of the ear part of the core body and its vicinity. In addition, due to the expansion and contraction of the active material layer accompanying the charging and discharging of the battery, cracks may also form at the root of the ear part of the core body and its vicinity.

[0023] The inventors have conducted intensive research to suppress the occurrence of the cracks, and as a result, have created an electrode structure in which a notch is provided from the root of the pole ear to the base, which is formed by cutting the first curve and the second curve or the first curve and the straight line, or a notch is provided in the portion of the base adjacent to the pole ear, which is formed by cutting the first curve and the second curve or the first curve and the straight line, wherein the first curve is formed by a first arc, and the second curve is formed by a second arc having a curvature smaller than that of the first arc. As described in detail below, the notch significantly suppresses the occurrence of the cracks.

[0024] An example of an embodiment of the present disclosure is described in detail below. In addition, the battery electrode, battery, and method for manufacturing a battery electrode of the present disclosure are not limited to the embodiment described below. The drawings referred to in the description of the embodiment are schematic descriptions, so the dimensional ratios of the components depicted in the drawings should be judged with reference to the following description. Figure 1 to Figure 3 In the embodiment, the stacking direction of the electrodes constituting the electrode body 3 (the thickness direction of the electrodes) is set as the z direction, the direction in which the positive electrode terminal 7 and the negative electrode terminal 9 are arranged is set as the x direction, and the direction orthogonal to the x and z directions is set as the y direction. For the sake of convenience, the x direction is sometimes referred to as the lateral direction, and the y direction is sometimes referred to as the vertical direction.

[0025] Figure 1 FIG. 1 is a cross-sectional view of a battery 1 according to an embodiment of the present invention. Figure 1As shown in the example, the battery 1 includes an outer shell 4 having a bottom and an opening and a sealing plate 5 that blocks the opening. The outer shell 4 is a square cylindrical container with a bottom, and the laminated electrode body 3 is accommodated in the outer shell 4 together with the electrolyte (not shown). The sealing plate 5 is a cover that blocks the opening of the outer shell 4, and is provided with a positive terminal 7, a negative terminal 9, a gas discharge valve 14, an electrolyte injection hole 15 for injecting an electrolyte, and a sealing plug 16 that seals the electrolyte injection hole 15. The gas discharge valve 14 has a function of breaking when the pressure inside the battery becomes above a predetermined value, so that the gas inside the battery is discharged to the outside of the battery.

[0026] The electrolyte may be any of an aqueous electrolyte and a non-aqueous electrolyte. In the present embodiment, a non-aqueous electrolyte is used. Battery 1 is, for example, a non-aqueous electrolyte secondary battery such as a lithium ion battery. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. For the non-aqueous solvent, for example, esters, ethers, nitriles, amides, and mixed solvents of two or more thereof may be used. The non-aqueous solvent may also contain a halogen substitution body obtained by replacing at least a portion of the hydrogen of these solvents with a halogen atom such as fluorine. In addition, the non-aqueous electrolyte is not limited to a liquid electrolyte, but may also be a solid electrolyte. The electrolyte salt may be, for example, a lithium salt such as LiPF6.

[0027] The positive terminal 7 has the function of electrically connecting an external element to the positive electrode. The negative terminal 9 has the function of electrically connecting an external element to the negative electrode. The positive terminal 7 is mounted on the sealing plate 5 at the positive terminal mounting hole 5a provided on the sealing plate 5 in a state of being electrically insulated from the sealing plate 5 by the insulating members 10 and 11. In addition, the negative terminal 9 is mounted on the sealing plate 5 at the negative terminal mounting hole 5b provided on the sealing plate 5 in a state of being electrically insulated from the sealing plate 5 by the insulating members 12 and 13.

[0028] The electrode body 3 is housed in the outer shell 4 in a state where the side and bottom surfaces are covered by the insulating sheet 17. The insulating sheet 17 can be, for example, a member bent into a box shape along the inner wall of the outer shell 4, or a bag-shaped member covering the electrode body 3. In the present embodiment, the stacked electrode body 3 is housed in the metal square outer shell 4, but the electrode body may be a wound type, or the outer shell may be composed of a stacked film.

[0029] The electrode body 3 is arranged in the outer shell 4 in such a way that the positive pole ear portion 24 and the negative pole ear portion 34 extend toward the sealing plate 5 side. The positive pole ear portion 24 is arranged at one end side of the outer shell 4 in the x direction, arranged in the y direction with the positive terminal 7, and electrically connected to the terminal by means of the positive electrode collector 6. The negative pole ear portion 34 is arranged at the other end side of the outer shell 4 in the x direction, arranged in the y direction with the negative terminal 9, and electrically connected to the terminal by means of the negative electrode collector 8. A current blocking mechanism can be provided in the conductive path between the positive electrode and the positive terminal 7 or the conductive path between the negative electrode and the negative terminal 9. The current blocking mechanism has the function of operating and cutting off the conductive path when the pressure inside the battery becomes above a predetermined value.

[0030] Figure 2 3 is an exploded perspective view of the electrode body 3. Figure 2 As shown in the example, the electrode body 3 has a stacked structure in which a plurality of positive electrodes 20 and a plurality of negative electrodes 30 are alternately stacked one by one through a separator 40. The stacked electrode body 3 does not have curved electrodes like a wound electrode body in which a positive electrode and a negative electrode are wound, and has a smaller dead zone than a wound electrode body. Therefore, in the stacked electrode body 3, the packing density of the active material layer can be increased compared to a wound electrode body, and the energy density of the battery can be easily increased.

[0031] The positive electrode 20 includes a positive electrode core 21 and a positive electrode active material layer 22 provided on the surface of the positive electrode core 21. The positive electrode active material layer 22 is preferably provided on both surfaces of the positive electrode core 21. The positive electrode core 21 includes a positive electrode base 23 whose core surface is covered with the positive electrode active material layer 22 and a positive electrode ear 24 protruding from the positive electrode base 23. The positive electrode ear 24 has an exposed portion 24a where the positive electrode active material layer 22 is not provided and the core surface is exposed.

[0032] The negative electrode 30 includes a negative electrode core 31 and a negative electrode active material layer 32 provided on the surface of the negative electrode core 31. The negative electrode active material layer 32 is preferably provided on both surfaces of the negative electrode core 31. The negative electrode core 31 includes a negative electrode base 33 whose core surface is covered with the negative electrode active material layer 32 and a negative electrode tab 34 protruding from the negative electrode base 33. The negative electrode tab 34 has an exposed portion 34a where the negative electrode active material layer 32 is not provided and the core surface is exposed.

[0033] In the present embodiment, the positive electrode active material layer 22 is provided on the entire area of ​​both surfaces of the positive electrode base 23. Generally, after the positive electrode active material layer 22 is provided on the surface of the metal foil or the like that becomes the positive electrode core 21, the metal foil or the like is cut into the shape and size of the electrode to manufacture the positive electrode 20, so the positive electrode active material layer 22 is slightly present at the root of the positive electrode ear 24. Similarly, the negative electrode active material layer 32 is provided on the entire area of ​​both surfaces of the negative electrode base 33, and the negative electrode active material layer 32 is slightly present at the root of the negative electrode ear 34.

[0034] The positive electrode base 23, the positive electrode tab 24, the negative electrode base 33, and the negative electrode tab 34 are all formed in a substantially quadrilateral shape, for example. Figure 2 In the example shown, when the positive electrode 20 is observed from the thickness direction (z direction), the positive electrode ear 24 protrudes from one end side of one side (upper side) of the positive electrode base 23. In addition, the negative electrode ear 34 protrudes from the other end side of one side (upper side) of the negative electrode base 33. In other words, the ear portions of the positive electrode 20 and the negative electrode 30 extend in the same direction (the direction of the sealing plate 5), and the positive electrode ear 24 and the negative electrode ear 34 are arranged in a manner that they are located on opposite sides of each other in the x direction. In addition, in the case of a lithium ion battery, in order to prevent the precipitation of lithium ions, the negative electrode base 33 is formed to have an area larger than the area of ​​the positive electrode base 23, and the positive electrode 20 and the negative electrode 30 are arranged in a manner that the entire positive electrode active material layer 22 is opposite to the negative electrode active material layer 32.

[0035] The positive electrode core 21 has a notch 25 formed from the root of the positive electrode ear 24 to the positive electrode base 23. In the positive electrode 20, the notch 25 is used to sufficiently suppress cracks that are easily generated at the root of the positive electrode ear 24 and its vicinity. In the present embodiment, the notch 25 is formed only in the positive electrode core 21, but the notch 25 may also be formed in the negative electrode core 31. The battery electrode having the notch of the present disclosure may be applied only to the positive electrode or only to the negative electrode, or may be applied to both the positive electrode and the negative electrode.

[0036] Hereinafter, the positive electrode 20 , the negative electrode 30 , and the separator 40 constituting the electrode body 3 , particularly the positive electrode 20 having the notch 25 , will be described in detail.

[0037] [positive electrode]

[0038] The positive electrode 20 includes a positive electrode core 21 and a positive electrode active material layer 22 provided on both sides of the positive electrode core 21 as described above. The positive electrode core 21 can be made of a foil of a metal such as aluminum or aluminum alloy that is stable within the potential range of the positive electrode, or a film in which the metal is arranged on the surface. The positive electrode active material layer 22 includes a positive electrode active material, a binding material, and a conductive material. The positive electrode 20 can be manufactured, for example, by applying a positive electrode composite material slurry including a positive electrode active material, a binding material, a conductive material, etc. on the positive electrode core 21, and after drying the coating, the dried coating, i.e., the positive electrode active material layer 22, is compressed with a roller.

[0039] The positive electrode active material is composed of a lithium-containing metal composite oxide as a main component. As the metal elements contained in the lithium-containing metal composite oxide, Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, Ca, Sb, Pb, Bi, Ge, etc. can be exemplified. An example of a preferred lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0040] As the conductive material contained in the positive electrode active material layer 22, carbon materials such as carbon black, acetylene black, Ketjen black, and graphite can be exemplified. As the binding material contained in the positive electrode active material layer 22, fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resin, polyolefin, etc. can be exemplified. These resins can also be used together with carboxymethyl cellulose (CMC) or its salt, polyethylene oxide (PEO), etc.

[0041] The packing density of the positive electrode active material layer 22 can be appropriately changed according to the application of the battery 1, but in the positive electrode, the packing density can be increased by utilizing the function of the notch 25. The packing density of the positive electrode active material layer 22 is, for example, 3.65 g / cm 3 Above, also available at 3.65g / cm 3 ~3.85g / cm 3 The effect of the notch 25 is more significant when the filling density of the positive electrode active material layer 22 is high. In addition, the thickness of the positive electrode active material layer 22 is not particularly limited, but as an example, it is 10 μm to 150 μm, or 30 μm to 80 μm on one side of the positive electrode core 21.

[0042] In the present embodiment, a protective layer 28 is provided at the root of the positive electrode ear 24. The protective layer 28 is a portion of the root of the positive electrode ear 24 where the positive electrode active material layer 22 is not provided, and is provided in a range opposite to the negative electrode 30 via the separator 40. In addition, there is no gap between the protective layer 28 and the positive electrode active material layer 22, and the protective layer 28 is provided adjacent to the positive electrode active material layer 22. By providing the protective layer 28, it is possible to suppress a low-resistance short circuit that may occur, for example, due to the mixing of conductive foreign matter between the positive electrode ear 24 and the negative electrode 30, and to reinforce the root of the positive electrode ear 24 to suppress the breakage of the positive electrode core 21. The protective layer 28 is provided on both sides of the positive electrode ear 24 at the root of the positive electrode ear 24. The thickness of the protective layer 28 is thinner than the thickness of the positive electrode active material layer 22, for example, 1 μm to 10 μm on one side of the positive electrode core 21.

[0043] The protective layer 28 may also be composed of only resin, but preferably contains inorganic particles and a binding material. The protective layer 28 having inorganic particles as the main component is difficult to break even if it strongly contacts with the conductive foreign matter mixed in. As specific examples of inorganic particles, at least one selected from aluminum oxide (alumina), titanium oxide (titania), manganese oxide and silicon oxide (silicon dioxide) is listed. Among them, aluminum oxide or titanium oxide is preferably used. The binding material contained in the protective layer 28 can use the same type of material as the binding material used for the positive electrode active material layer 22. In addition, a conductive material can also be added to the protective layer 28.

[0044] Below, refer to Figure 3 , and the notch 25 formed at the root of the positive electrode ear portion 24 and its vicinity will be described in detail. Figure 3 This is a diagram showing an enlarged view of the positive electrode lug portion 24 and its vicinity in the positive electrode 20 .

[0045] like Figure 3 As shown in the example, in the positive electrode core 21, a notch 25 is formed from the root of the positive electrode ear 24 to the positive electrode base 23. In addition, the edge of the notch 25 is formed by a curve 26 (first curve) and a straight line 27, wherein the curve 26 (first curve) is composed of an arc (first arc). That is, when the positive electrode 20 is observed from the thickness direction (z direction), a notch 25 formed by cutting edges using the curve 26 and the straight line 27 is formed at the root of the positive electrode ear 24 and its vicinity. In addition, instead of the straight line 27, a second curve composed of a second arc having a curvature smaller than that of the first arc can be used. For example, the curvature of the second curve may be less than 50% of the curvature of the first curve, and the second curve may be a slightly curved curve close to the straight line 27.

[0046] The notch 25 suppresses cracking at the root of the positive electrode ear 24 and its vicinity when the positive electrode active material layer 22 is compressed or when charging and discharging. If the active material layer is strongly compressed without the notch 25, the part of the core body where the active material layer exists extends, and the part where the active material layer does not exist does not extend, so there is a situation where, for example, a large stress acts on the boundary between the parts, and cracks enter the core body from the corner between the ear and the base. Considering forming the notch 25 in the positive electrode core body 21, it is possible to alleviate the stress generated by the difference in the extension of the positive electrode core body 21, and suppress the generation of cracks.

[0047] The inventors' research results have revealed that the probability of crack generation greatly changes depending on the shape of the notch 25. Compared with, for example, a notch formed by cutting only with the curve 26, a notch 25 formed by cutting with the curve 26 and the straight line 27 greatly reduces the probability of crack generation. If the packing density of the positive electrode active material layer 22 increases, cracks are more likely to occur, so the effect of the notch 25 is more significant when the packing density is high.

[0048] The notch 25 is formed at the root of the positive electrode ear 24 and its vicinity. The notch 25 is formed in the portion of the upper end of the positive electrode base 23 adjacent to the positive electrode ear 24, and extends toward the lateral end side of the positive electrode core 21 beyond the imaginary line α obtained by extending the side edge of the positive electrode ear 24. Here, the side edge refers to the edge of the positive electrode ear 24 along the up and down direction (y direction) where the positive electrode ear 24 protrudes. The edge of the notch 25 is continuous without interruption from the root of the positive electrode ear 24 to the positive electrode base 23 on the way, forming a cutting portion. Therefore, in the positive electrode core 21, there is no sharp corner at the boundary between the positive electrode ear 24 and the positive electrode base 23.

[0049] The notch 25 suppresses cracking of the positive electrode core 21 and is formed to a size that does not cause problems such as resistance increase. As described above, the positive electrode ear 24 is formed in a roughly quadrilateral shape, so the width of the positive electrode ear 24 is thinner at the root where the notch 25 is formed compared to the top. The width W1 (x direction, lateral length) of the positive electrode ear 24 in the portion where the notch 25 is not formed is, for example, 10mm to 30mm, or 15mm to 25mm. The width W2 of the positive electrode ear 24 in the portion where the notch 25 is formed, that is, the minimum width of the positive electrode ear 24 is, for example, 5mm to 25mm, or 10mm to 20mm. If the widths W1 and W2 are within this range, problems such as resistance increase generally do not occur, heat generation during high-speed charging and discharging can be suppressed, and the generation of wrinkles and deflections of the positive electrode ear 24 accompanying charging and discharging can be suppressed.

[0050] Preferably, the notches 25 are formed from both sides of the width direction of the positive electrode ear 24 to the positive electrode base 23. The notch 25 can be formed only on one side of the width direction of the positive electrode ear 24, but it is preferably formed on both sides of the width direction of the positive electrode ear 24. The two notches 25 are formed, for example, to be axially symmetrical with respect to an imaginary line (not shown) passing through the center of the width direction of the positive electrode ear 24. That is, the width W3 (x direction, lateral length) of the notch 25, the width W4 of the portion cut inward from the side edge of the positive electrode ear 24, and the lengths L1 and L2 described later are approximately the same in the two notches 25.

[0051] The width W3 of the notch 25 is, for example, 10% to 60% or 15% to 40% of the width W1 of the positive electrode ear 24, and as a specific example, it is 3 mm to 15 mm. The width W4 of the cut is, for example, 1% to 25% or 5% to 20% of the width W1 of the positive electrode ear 24, and as a specific example, it is 1 mm to 10 mm. If the widths W3 and W4 are within this range, the capacity reduction caused by the reduction of the positive electrode active material layer 22 can be suppressed, and the generation of cracks at the root of the positive electrode ear 24 and its vicinity can be fully suppressed.

[0052] At the edge of the notch 25, there is a first end P1 on the positive electrode ear 24 side and a second end P2 of the positive electrode base 23. The first end P1 is located at the intersection of the side edge of the positive electrode ear 24 and the edge of the notch 25, and the second end P2 is located at the intersection of the upper edge of the positive electrode base 23 and the edge of the notch 25. The length L1 along the up-down direction (y direction) from the first end P1 to the lower end of the notch 25 is, for example, 1% to 30% of the length of the positive electrode ear 24, and as a specific example, is 1.5 mm to 7.5 mm. The length L2 along the up-down direction from the upper edge of the positive electrode base 23 to the lower end of the notch 25 is, for example, 0.5% to 15% of the length of the positive electrode ear 24, and as a specific example, is 0.5 mm to 3.0 mm.

[0053] The longer the above-mentioned lengths L1 and L2 are, especially the longer the length L2 is, the easier it is to suppress the generation of cracks at the root of the positive electrode ear 24 and its vicinity. On the other hand, if the length L2 is lengthened, the area where the positive electrode active material layer 22 is cut off becomes larger, so the battery capacity is reduced. Therefore, it is important to determine the size of the notch 25 in consideration of the suppression of cracks and the capacity. The straight line 27 forming a part of the edge of the notch 25 not only helps to suppress cracks, but also greatly helps to suppress the reduction in capacity. If the lengths L1 and L2 are within this range, the reduction in capacity caused by the reduction of the positive electrode active material layer 22 can be suppressed, and the generation of cracks at the root of the positive electrode ear 24 and its vicinity can be fully suppressed.

[0054] In this embodiment, a protective layer 28 is provided at the root of the positive electrode ear 24, and a portion of the notch 25 is formed at the portion of the positive electrode ear 24 where the protective layer 28 is provided. By forming the notch 25 at the portion where the protective layer 28 is provided, it is possible to prevent the positive electrode core 21 from breaking from the edge of the notch 25. Figure 3 In the example shown, the first end P1 of the notch 25 is located at the portion where the protective layer 28 is provided. In addition, in the positive electrode tab 24, the entire notch 25 is formed in the portion where the protective layer 28 is provided and the portion where the positive electrode active material layer 22 is provided. In other words, the notch 25 is not formed in the exposed portion 24a.

[0055] A straight line 27 constituting a part of the edge of the notch 25 is formed from the second end P2 on the positive electrode base 23 side. In addition, a curved line 26 constituting a part of the edge of the notch 25 is formed from the first end P1 on the positive electrode ear 24 side. The curved line 26 is formed with a length from the first end P1 to the positive electrode base 23, and is connected to the straight line 27. The intersection of the curved line 26 and the straight line 27 is located, for example, at the lower end of the notch 25. Here, the lower end of the notch 25 refers to the position with the longest length from the upper end of the notch 25, that is, the first end P1, in the up-down direction.

[0056] Curve 26 is composed of a portion of the first arc. The first arc can be an arc of a perfect circle or an arc of an ellipse, but in order to suppress the reduction in capacity and effectively prevent the occurrence of cracks, an arc of an ellipse is preferably an arc of an ellipse. For example, the major axis of the ellipse is along the lateral direction (x direction) of the positive electrode 20, and the center of the ellipse is located at a position closer to the second end P2 side than the intersection Q. Here, the intersection Q is the intersection of the imaginary line α and the imaginary line β obtained by extending the upper edge of the positive electrode base 23, and is the position where the corner is formed when there is no notch 25. The perfect circle or ellipse corresponding to the first arc may also be a perfect circle or ellipse with the intersection Q as the center.

[0057] The straight line 27 is formed from the second end P2 of the notch 25 to a length not exceeding the imaginary line α obtained by extending the side edge of the positive electrode ear portion 24. In other words, the portion of the positive electrode base 23 that overlaps with the positive electrode ear portion 24 in the vertical direction does not form the straight line 27, but only forms the curve 26. The curve 26 is greatly bent toward the center side of the width direction of the positive electrode ear portion 24. The straight line 27 intersects the upper edge of the positive electrode base 23 at an obtuse angle, and the straight line 27 is formed obliquely from the second end P2 toward the lower end of the notch 25. The angle formed by the upper edge of the positive electrode base 23 and the straight line 27 is, for example, 100° to 160°, or 110° to 150°.

[0058] In addition, other curves or straight lines may exist at the edge of the notch 25 in addition to the curve 26 and the straight line 27 within the scope not impairing the purpose of the present disclosure. For example, a second straight line may be formed from the first end P1 of the notch 25 .

[0059] exist Figure 4 and Figure 5 , notches 25x and 25y are shown as another example of the embodiment. Figure 4A portion of the edge of the illustrated notch 25x is formed by a curve 26 formed by a portion of an elliptical arc from the root of the positive electrode ear 24 to the positive electrode base 23, which is common to the notch 25. On the other hand, the remaining portion of the edge of the notch 25x is formed by a straight line 27x that intersects the upper edge of the positive electrode base 23 approximately perpendicularly, which is different from the notch 25. The straight line 27x is formed from the upper edge of the positive electrode base 23 to the lower end of the notch 25x, and the angle between the straight line 27x and the upper edge of the positive electrode base 23 is approximately 90°. In this case, compared to Figure 3 The illustrated embodiment can reduce the cut-out area of ​​the positive electrode active material layer 22 .

[0060] Figure 5 The illustrated notch 25y is formed by cutting the edges with the curve 26y and the straight line 27y, which is common to the notches 25 and 25x. On the other hand, the notch 25y is formed only in the portion of the positive electrode base 23 adjacent to the positive electrode ear 24, and is not formed at the root of the positive electrode ear 24, which is different from the notches 25 and 25y. The curve 26y is formed to be connected to the side edge of the positive electrode ear 24. In this case, the width of the positive electrode ear 24 is constant from the top to the root.

[0061] Here, an example of a method for producing the positive electrode 20 having the above-mentioned structure will be described in detail.

[0062] The positive electrode 20 is manufactured by the following process, that is, the positive electrode active material layer 22 is provided at least on the surface of the positive electrode base 23 of the positive electrode core 21 or the surface of the part to be the positive electrode base 23, and the notch 25 is formed from the root of the positive electrode ear 24 or the root of the part to be the positive electrode ear 24 to the positive electrode base 23 or the part to be the positive electrode base 23, and after the notch 25 is formed, the positive electrode active material layer 22 is compressed. When the notch 25 is formed, the edge of the notch 25 is formed by a first curve and a second curve or a first curve and a straight line, wherein the first curve is composed of a first arc and the second curve is composed of a second arc having a curvature smaller than that of the first arc. The notch 25 can also be formed after the positive electrode active material layer 22 is compressed, but in order to suppress the cracks of the positive electrode core 21 that may be generated when the active material layer is compressed, it is preferred to form the notch 25 before compressing the active material layer. In addition, from the viewpoint of productivity, etc., it is preferred to form the notch 25 after the positive electrode active material layer 22 is provided.

[0063] The positive electrode 20 is manufactured by cutting a strip body (hereinafter referred to as "strip body Z") having positive electrode active material layers 22 on both sides of a strip core body that will become a positive electrode core body 21 in a subsequent process into a predetermined shape and size. An example of a manufacturing process of the positive electrode 20 includes: a first process, in which a positive electrode composite material slurry is applied to both sides of the strip core body, and the coating is dried to provide the positive electrode active material layer 22; a second process, in which the strip body Z having positive electrode active material layers 22 on both sides of the strip core body is cut to form a positive electrode ear 24 and a notch 25; a third process, in which the positive electrode active material layer 22 (strip body Z) is compressed; and a fourth process, in which the strip body Z is cut into a predetermined size to obtain the positive electrode 20.

[0064] In the first step, the positive electrode composite material slurry is applied in a manner that a strip-shaped core exposed portion along the length direction of the long core remains, thereby providing the positive electrode active material layer 22. The exposed portion is formed with a substantially constant width from one end in the width direction of the long core, and becomes an exposed portion 24a present in the positive electrode ear portion 24 in a subsequent step. When the protective layer 28 is provided, the slurry for the protective layer 28 is applied to both sides of the long core at the same time as the positive electrode composite material slurry is applied, or in another step.

[0065] In the second step, the positive electrode ear portion 24 is formed by cutting the portion of the elongated body Z where the positive electrode active material layer 22 is provided along the exposed portion, and cutting the exposed portion at a substantially constant period. The notch 25 can be formed simultaneously with the positive electrode ear portion 24, or can be formed after the positive electrode ear portion 24. The elongated body Z can be cut using a conventionally known method, such as die stamping, a cutting machine, laser irradiation, and the like. In addition, the elongated body Z can also be cut along the boundary between the portion where the positive electrode active material layer 22 is provided and the exposed portion, but in this case, since an exposed portion of the core surface is formed in a portion other than the positive electrode ear portion 24 due to a slight offset of the cutting position, it is not preferred.

[0066] In addition, the positive electrode ear 24 and the notch 25 may be formed by different methods. For example, the positive electrode ear 24 may be formed by stamping and then the notch 25 may be formed by irradiation of energy lines such as laser. When the notch 25 is formed by irradiation of laser, the edge of the notch 25 is smooth, which is advantageous in suppressing cracks.

[0067] In the second step, a portion of the strip Z is cut off in such a manner as to form a curve 26 and a straight line 27 formed by a first arc, thereby forming a notch 25 at the root of the positive electrode ear 24 (or the portion to be the root of the positive electrode ear 24) and the positive electrode base 23 (or the portion to be the positive electrode base 23). In the present embodiment, the curve 26 is formed from the portion of the root of the positive electrode ear 24 where the protective layer 28 is provided to the positive electrode base 23, and the straight line 27 is formed from the upper edge of the positive electrode base 23 to be connected to the curve 26. The curve 26 is formed as a portion of the first arc of the ellipse, and is greatly bent toward the center side in the width direction of the positive electrode ear 24. The straight line 27 intersects the upper edge of the positive electrode base 23 at an obtuse angle, and the straight line 27 is formed obliquely from the upper edge of the positive electrode base 23 toward the lower end of the curve 26 (notch 25).

[0068] In the third step, rollers are used to compress the positive electrode active material layer 22 provided on both sides of the long core body. The positive electrode active material layer 22 can be compressed by a conventionally known method, for example, by passing the long strip Z between a pair of rollers for compression. The packing density of the positive electrode active material layer 22 can be adjusted by the composition of the positive electrode composite material slurry, the coating amount, the pressure when compressing the positive electrode active material layer 22, etc. The packing density of the positive electrode active material layer 22 is adjusted to 3.65 g / cm, for example. 3 As described above, if the packing density becomes higher, cracks are likely to occur at the base of the positive electrode lug portion 24 and in the vicinity thereof.

[0069] In this manufacturing process, after forming the notch 25, the positive electrode active material layer 22 is compressed, thereby significantly reducing the probability of cracks in the third step. As described above, the notch 25 formed by cutting the edges with the curve 26 and the straight line 27 in the third step relieves the stress acting on the positive electrode ear portion 24 and its vicinity and suppresses the occurrence of cracks.

[0070] [negative electrode]

[0071] As described above, the negative electrode 30 includes a negative electrode core 31 and a negative electrode active material layer 32 provided on both surfaces of the negative electrode core 31. The negative electrode core 31 can be made of a foil of a metal such as copper or a copper alloy that is stable within the potential range of the negative electrode 30, or a film that arranges the metal on the surface. The negative electrode active material layer 32 includes a negative electrode active material and a binder. The negative electrode 30 can be manufactured, for example, by applying a negative electrode composite material slurry including a negative electrode active material, a binder, etc. on the negative electrode core 31, and after drying the coating, the dried coating, i.e., the negative electrode active material layer 32, is compressed with a roller.

[0072] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Preferred carbon materials are natural graphites such as flaky graphite, block graphite, and earthy graphite, as well as graphites such as block artificial graphite and artificial graphites such as graphitized mesophase carbon microbeads. The negative electrode active material layer 32 may also include a Si-containing compound as the negative electrode active material. In addition, the negative electrode active material may also use a metal other than Si that alloys with lithium, an alloy containing the metal, a compound containing the metal, and the like.

[0073] The binder contained in the negative electrode active material layer 32 can use fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, etc., as in the case of the positive electrode 20, but preferably styrene-butadiene rubber (SBR) or its modified body. In addition to containing SBR, the negative electrode active material layer may also contain CMC or its salt, polyacrylic acid (PAA) or its salt, polyvinyl alcohol, etc.

[0074] [Diaphragm]

[0075] The separator 40 uses a porous sheet having ion permeability and insulation. Specific examples of the porous sheet include microporous films, woven fabrics, nonwoven fabrics, etc. As the material of the separator 40, olefin resins such as polyethylene, polypropylene, copolymers containing at least one of ethylene and polypropylene, cellulose, etc. are preferred. The separator 40 can be any one of a single-layer structure and a laminated structure. A heat-resistant layer, etc. can also be formed on the surface of the separator 40.

[0076] Example

[0077] Hereinafter, the present disclosure will be further described based on examples, but the present disclosure is not limited to these examples.

[0078] <Example 1>

[0079] Nickel-lithium-cobalt-manganese composite oxide is used as the positive electrode active material. The positive electrode active material, PVdF and acetylene black are mixed in a mass ratio of 97.5:1:1.5, and N-methyl-2-pyrrolidone (NMP) is added in an appropriate amount to prepare a positive electrode composite material slurry. The positive electrode composite material slurry is applied on both sides of a long core body composed of aluminum foil with a thickness of 12 μm in such a way that a predetermined core body exposure portion remains, and the coating is dried to obtain a long strip Z having a positive electrode active material layer on both sides of the long core body. In addition, a protective layer containing aluminum oxide and PVdF is formed on a portion of the exposed portion of the core body adjacent to the positive electrode active material layer.

[0080] Next, the portion of the strip Z with the positive electrode active material layer was cut along the exposed portion of the core, and the exposed portion of the core was cut at a substantially constant period, thereby forming a 20 mm wide and 19.6 mm long ear portion. Then, from the widthwise ends of the root of the ear portion to the base of the core, a curved and straight line was formed. Figure 3 The notch is of the shape shown. The curve forming a part of the edge of the notch is composed of a part of the arc of an ellipse with a long diameter of 8 mm and a short diameter of 4 mm. The straight line forming a part of the edge of the notch is formed from the upper edge of the base with a length of 3.5 mm. The angle formed by the straight line and the upper edge of the base is 150°. In addition, the width W2 of the root of the notched ear portion is 14.6 mm, the width W3 of the notch is 8 mm, the width W4 is 2.7 mm, the length L1 is 4 mm, and the length L2 is 2 mm.

[0081] Next, the notched strip Z was passed between a pair of rollers to compress the positive electrode active material layer. In addition, by adjusting the amount of positive electrode composite material slurry applied and the compressive force of the strip Z, a packing density of the positive electrode active material layer was set to 3.71 g / cm 3 The positive electrode (1) and the packing density of the positive electrode active material layer are set to 3.8 g / cm 3 For each positive electrode, the presence or absence of cracks in the lug portion and its vicinity was checked, and the evaluation results are shown in Table 1.

[0082] <Comparative Example 1>

[0083] In addition to forming Figure 6 The notch shown (which is formed by cutting the curved line formed by a part of the arc of the ellipse) is replaced by Figure 3 Except for the notch shown, two positive electrodes with different packing densities of the positive electrode active material layer were manufactured in the same manner as in Example 1, and the above evaluation was performed. In addition, the width W2 of the root of the notched ear portion was 14.6 mm, the width W3 of the notch was 8 mm, the width W4 was 2.7 mm, the length L1 was 4 mm, and the length L2 was 2 mm.

[0084] <Comparative Example 2>

[0085] In addition to forming Figure 7 The notch shown (a notch formed by cutting the edge of a curve formed by a part of the arc of a perfect circle) is replaced by Figure 3 Except for the notch shown, two positive electrodes with different packing densities of the positive electrode active material layer were manufactured in the same manner as in Example 1, and the above evaluation was performed. In addition, the width W2 of the root of the notched pole ear portion was 14.6 mm, the width W3 of the notch was 6 mm, the width W4 was 2.7 mm, the length L1 was 6 mm, and the length L2 was 3 mm.

[0086] [Table 1]

[0087]

[0088] As shown in Table 1, in Example 1, no cracks were confirmed for the positive electrode (1) (crack generation rate 0%), and the probability of crack generation was also suppressed to a low level (30%) for the positive electrode (2) with a higher filling density of the active material layer. On the other hand, in Comparative Example 2, cracks were confirmed for the positive electrode (1). In Comparative Example 1, although no cracks were confirmed in the positive electrode (1), the probability of crack generation was high (83%) for the positive electrode (2). From this result, it can be understood that the probability of crack generation at the root of the ear and its vicinity is highly dependent on the shape of the notch, and the notch of Example 1 formed by cutting with curves and straight lines greatly suppresses the generation of the cracks. Moreover, the positive electrode of Example 1 has less influence on the capacity than the positive electrodes of Comparative Examples 1 and 2.

[0089] Description of Reference Numerals

[0090] 1. Battery; 3. Electrode body; 4. Outer shell; 5. Sealing plate; 5a. Positive terminal mounting hole; 5b. Negative terminal mounting hole; 6. Positive electrode collector; 7. Positive terminal; 8. Negative electrode collector; 9. Negative terminal; 10-13. Insulating member; 14. Gas discharge valve; 15. Electrolyte injection hole; 16. Sealing plug; 17. Insulating sheet; 20. Positive electrode; 21. Positive electrode core; 22. Positive electrode active material layer; 23. Positive electrode base; 24. Positive electrode ear; 24a, 34a, exposed portion; 25. Notch; 26. Curve; 27. Straight line; 28. Protective layer; 30. Negative electrode; 31. Negative electrode core; 32. Negative electrode active material layer; 33. Negative electrode base; 34. Negative electrode ear; 40. Diaphragm.

Claims

1. A battery electrode comprising a core body and an active material layer provided on a surface of the core body, wherein: The core body has a base portion whose surface is covered by the active material layer and a tab portion protruding from the base portion. The core body has a notch formed from the root of the pole lug to the base, or a notch formed at a portion of the base adjacent to the pole lug. The edge of the notch is formed by a first curve and a straight line, wherein the first curve is formed by a first circular arc, and the straight line is connected to the first circular arc. The edge of the notch has a first end on the lug side and a second end on the base side. The first arc is formed from the first end of the notch, and the straight line is formed from the second end of the notch.

2. The battery electrode according to claim 1, wherein The notch is formed from the root of the pole lug to the base, The width of the lug portion is thinner at the root portion than at the tip portion.

3. The battery electrode according to claim 1 or 2, wherein The notches are formed from both ends in the width direction of the root of the lug portion to the base portion, or the notches are formed in portions of the base portion adjacent to both ends in the width direction.

4. The battery electrode according to claim 1 or 2, wherein The straight line is formed from the second end to a length not exceeding a line obtained by extending the side edge of the lug portion.

5. The battery electrode according to claim 1 or 2, wherein The first arc is an arc of an ellipse.

6. The battery electrode according to claim 1 or 2, wherein The packing density of the active material layer is 3.65 g / cm 3 above.

7. The battery electrode according to claim 1 or 2, wherein The battery electrode further comprises a protective layer provided at the base of the lug portion. A portion of the notch is formed at a portion where the protective layer is provided.

8. A battery, wherein: This battery comprises the battery electrode according to any one of claims 1 to 7.

9. The battery according to claim 8, wherein The battery electrode is a positive electrode.

10. A method for manufacturing a battery electrode, the battery electrode comprising a core and an active material layer provided on the surface of the core, the core having a base portion whose surface is covered by the active material layer and a lug portion protruding from the base portion, wherein: The active material layer is provided at least on the surface of the base or the portion to be the base, A notch is formed from the root of the pole ear or the part to be the pole ear to the base or the part to be the base, or a notch is formed in the part of the base adjacent to the pole ear or the part to be the adjacent part. At this time, the edge of the notch is formed by a first curve and a straight line, the first curve is composed of a first arc, the straight line is connected to the first arc, and the edge of the notch has a first end on the pole ear side and a second end on the base side, and the first arc is connected to the first end of the notch, and the straight line is connected to the second end of the notch. After the notch is formed, the active material layer is compressed.

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