Electrode

Abstract

To improve cycle endurance.SOLUTION: An electrode includes a substrate and a negative electrode active material layer. The negative electrode active material layer is disposed on a surface of the substrate. The negative electrode active material layer includes a first active material particle and a second active material particle. The first active material particle includes graphite. The second active material particle includes silicon. In a cross section parallel to a thickness direction of the negative electrode active material layer, the first active material particle has a first orientation angle of 50° or more. The second active material particle has a second orientation angle of 35° or more. The first orientation angle indicates an angle formed between a major axis of the first active material particle and the surface of the substrate. The second orientation angle indicates an angle formed between a major axis of the second active material particle and the surface of the substrate.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an electrode.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2017-050203 discloses a negative electrode containing a silicon alloy containing titanium and graphite.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a negative electrode active material layer, a technique for magnetically orienting graphite is known. By applying a magnetic field, graphite can be oriented so that the long axis of the particles is along the thickness direction of the negative electrode active material layer. Due to the orientation of graphite, the tortuosity (also referred to as the "curvature factor") of the ion diffusion path can be reduced. By reducing the tortuosity, ion diffusion can be promoted in the thickness direction of the negative electrode active material layer. As a result, for example, an improvement in cycle durability is expected.

[0005] For increasing the capacity, a mixed system of graphite and silicon (Si) has been studied. Compared with a single system of graphite, a mixed system of graphite and Si tends to have a smaller effect of improving performance by applying a magnetic field.

[0006] An object of the present disclosure is to improve cycle durability.

Means for Solving the Problems

[0007] 1. The electrode includes a substrate and a negative electrode active material layer. The negative electrode active material layer is disposed on the surface of the substrate. The negative electrode active material layer includes first active material particles and second active material particles. The first active material particles contain graphite. The second active material particles contain silicon. In a cross-section parallel to the thickness direction of the negative electrode active material layer, the first active material particles have a first orientation angle of 50° or more. The second active material particles have a second orientation angle of 35° or more. The first orientation angle indicates the angle formed by the long axis of the first active material particles and the surface of the substrate. The second orientation angle indicates the angle formed by the long axis of the second active material particles and the surface of the substrate.

[0008] The "orientation angle" is an index of the orientation state. The orientation angle can take a value from 0 to 90°. The closer the orientation angle is to 90°, the stronger the orientation of the particles in the thickness direction of the negative electrode active material layer.

[0009] In the mixed system of graphite and Si, it is considered that one of the reasons for the small effect of improving performance by applying a magnetic field is that Si is difficult to respond to the magnetic field. That is, since Si is not sufficiently oriented, it is considered that the degree of bending is difficult to be reduced as a whole. Therefore, the first active material particles (graphite) are given an orientation angle of 50° or more, and the second active material particles (Si) are also given an orientation angle of 35° or more. As a result, even in the mixed system of graphite and Si, the degree of bending can be reduced. That is, an improvement in cycle durability is expected.

[0010] 2. The electrode described in the above "1" may include, for example, the following configuration. The second active material particles include core particles and a magnetic material. The core particles contain silicon. The magnetic material is attached to at least a part of the core particles.

[0011] By attaching the magnetic material to the core particles, an improvement in magnetic field responsiveness is expected.

[0012] 3. The electrode described in the above "2" may include, for example, the following configuration. The magnetic material includes at least one selected from the group consisting of titanium, zirconium, and vanadium. The ratio of the adhesion area of the magnetic material to the surface area of the second active material particles is 35% or more.

[0013] Titanium (Ti), zirconium (Zr), and vanadium (V) may have magnetic field responsiveness. Hereinafter, the ratio of the adhesion area of the magnetic material to the surface area of the second active material particles is also referred to as the "coating rate". When the coating rate is 35% or more, an improvement in magnetic field responsiveness is expected.

[0014] 4. The electrode according to any one of the above items "1" to "3" may include, for example, the following configuration. The first active material particles have an aspect ratio of 4.3 to 9.5.

[0015] When the aspect ratio of the first active material particles (graphite) is 4.3 or more, an improvement in magnetic field responsiveness is expected. As the aspect ratio of the first active material particles increases, the first active material particles tend to shift more easily during charge and discharge cycles. That is, due to the intense expansion of the second active material particles (Si), the thin first active material particles (graphite) are pushed back, and the position of the first active material particles tends to shift in the in-plane direction. The in-plane direction indicates any direction orthogonal to the thickness direction. Due to the shift of the first active material particles, the degree of bending may increase. When the aspect ratio of the first active material particles is 9.5 or less, the first active material particles can have an appropriate thickness. When the first active material particles have an appropriate thickness, it is expected that the first active material particles are difficult to shift.

[0016] 5. The electrode according to any one of the above items "1" to "4" may include, for example, the following configuration. The first orientation angle is 58° or more. The ratio of the first orientation angle to the second orientation angle is 1.40 or less.

[0017] When the first orientation angle is 58° or more, a reduction in the degree of bending is expected. Hereinafter, the ratio of the first orientation angle to the second orientation angle is also referred to as the "orientation angle ratio". When the orientation angle ratio is 1.40 or less, a reduction in the degree of bending is expected.

[0018] Hereinafter, embodiments of the present disclosure (hereinafter may be abbreviated as "the present embodiments"), and examples of the present disclosure (hereinafter may be abbreviated as "the present examples") will be described. However, the present embodiments and the present examples do not limit the technical scope of the present disclosure. The present embodiments and the present examples are illustrative in all respects. The present embodiments and the present examples are non-limiting. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the description of the claims. For example, any configurations are extracted from the present embodiments and their arbitrary combinations are also planned from the beginning.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0020] <Main Terms> "Aspect ratio" indicates the ratio of the major axis diameter to the minor axis diameter. The major axis diameter indicates the maximum Feret diameter. The minor axis diameter indicates the minimum Feret diameter. The maximum Feret diameter and the minimum Feret diameter of the particles are measured in a cross-sectional SEM (Scanning Electron Microscope) image of the negative electrode active material layer. The maximum Feret diameter and the minimum Feret diameter can be specified by image analysis software. The cross-section is parallel to the thickness direction of the negative electrode active material layer. The observation magnification can be adjusted according to the size of the particles. The observation magnification is, for example, 700 times.

[0021] "Orientation angle" is measured by the following procedure. Five cross-sectional SEM images of the negative electrode active material layer are prepared. The five cross-sectional SEM images are taken at different positions. Figure 1 is an explanatory diagram of the orientation angle. In the image, the major axis L of the particle is specified. The major axis L is the maximum Feret diameter F of the particle maxIt is a straight line passing through. The angle θ formed by the major axis L and the surface of the base material 10 is the orientation angle. The orientation angle is on the acute angle side. The orientation angle can take values from 0 to 90°. The orientation angle can be specified by image analysis software. In 5 cross-sectional SEM images, the average value of the orientation angles of the first active material particles is the "first orientation angle (θ1)". In 5 cross-sectional SEM images, the average value of the orientation angles of the second active material particles is the "second orientation angle (θ2)". Note that particles for which it is difficult to specify the major axis due to particle deformation (crushing, cracking, etc.) can be excluded from the measurement targets. The same applies to "particle size" and the like below.

[0022] "Particle size" indicates the average value of the maximum Feret diameter. For example, in 5 cross-sectional SEM images, the average value of the maximum Feret diameters of the first active material particles is regarded as the "particle size of the first active material particles". The same applies to the particle size of the second active material particles.

[0023] "Coating rate" indicates the ratio of the adhesion area of the magnetic material to the surface area of the second active material particles. The coating rate is measured by the following procedure. An SEM image of the second active material particles is prepared. Black is assigned to (a) Si and (b) voids in the SEM image. Binarization processing is performed on the SEM image according to the threshold values determined by (a) and (b). In the image after binarization processing, the coating rate (S2 / S1) is obtained by subtracting the area (S2) of the magnetic material in the same region from the area (S1) of the region surrounded by the contour line of the particles. The coating rate is expressed as a percentage. The average value of the coating rates of 10 or more second active material particles is adopted.

[0024] Elements expressed in the singular form include the plural form as well, unless otherwise specified. For example, "particle" includes not only "one particle" but also "a plurality of particles (particle group)" and "an aggregate of particles (powder)".

[0025] The stoichiometric composition formula shows representative examples of compounds. The compound may have a non-stoichiometric composition. For example, "SiO" is not limited to a compound having a molar ratio of "Si:O = 1:1". "SiO" indicates a compound containing Si and O in an arbitrary molar ratio, unless otherwise specified. For example, the compound may be doped with trace elements. A part of Si and O may be substituted with another element.

[0026] Geometric terms should not be construed in a strict sense. Examples of geometric terms include, for example, "parallel", "perpendicular", "orthogonal", etc. For example, "parallel" may deviate somewhat from "parallel" in the strict sense. Geometric terms may include, for example, tolerances, errors, etc. in design, work, manufacturing, etc. The dimensional relationships in each figure may not match the actual dimensional relationships. The dimensional relationships in each figure may be changed to assist the reader's understanding. For example, the length, width, thickness, etc. may be changed. Some configurations may be omitted.

[0027] A numerical range such as "from m to n%" includes the upper limit value and the lower limit value, unless otherwise specified. That is, "from m to n%" indicates a numerical range of "m% or more and n% or less". Also, "m% or more and n% or less" includes "more than m% and less than n%". "Or more" and "or less" are represented by the inequality sign "≦" with an equal sign. "More than" and "less than" are represented by the inequality sign "<" that does not include an equal sign.

[0028] <Electrode> FIG. 2 is a conceptual diagram showing the electrode in the present embodiment. In FIG. 2, the Z-axis direction is the thickness direction. The X-axis direction and the Y-axis direction are each an example of an in-plane direction. The electrode 100 is for a battery. The electrode 100 may be, for example, a negative electrode for a monopolar battery. The electrode 100 may be, for example, for a bipolar battery. The electrode 100 may be, for example, for a liquid-based lithium-ion battery. The electrode 100 may be, for example, for an all-solid-state lithium-ion battery. The electrode 100 includes a base material 10 and a negative electrode active material layer 20.

[0029] ·Base material The substrate 10 supports the negative electrode active material layer 20. The substrate 10 may be, for example, sheet-shaped. The thickness of the substrate 10 may be, for example, from 1 to 50 μm, or from 5 to 30 μm. The substrate 10 has conductivity. The substrate 10 may contain, for example, a metal foil or the like. The substrate 10 may contain at least one selected from the group consisting of copper (Cu), nickel (Ni), zinc (Zn), lead (Pb), aluminum (Al), Ti, iron (Fe), silver (Ag), gold (Au), and a conductive resin. The substrate 10 may contain, for example, a Cu foil, a Cu alloy foil, or the like. The substrate 10 may have, for example, a multilayer structure. For example, the substrate 10 may be formed by laminating a Cu foil and an Al foil.

[0030] ·Negative electrode active material layer The negative electrode active material layer 20 is disposed on the surface of the substrate 10. The negative electrode active material layer 20 may be disposed on only one side of the substrate 10. The negative electrode active material layer 20 may be disposed on both sides of the substrate 10. When the electrode 100 is for a bipolar battery, the negative electrode active material layer 20 may be disposed on one surface (front surface) of the substrate 10, and a positive electrode active material layer (not shown) may be disposed on the other surface (back surface). The thickness of the negative electrode active material layer 20 may be, for example, from 10 to 1000 μm, or from 100 to 500 μm.

[0031] The negative electrode active material layer 20 contains first active material particles 21 and second active material particles 22. The first active material particles 21 and the second active material particles 22 are negative electrode active materials. The mass fraction of the second active material particles 22 with respect to the total mass of the first active material particles 21 and the second active material particles 22 may be, for example, 1% or more, 3% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more. The same mass fraction may be, for example, 75% or less, 50% or less, 25% or less, or 10% or less.

[0032] ·First active material particles The first active material particle 21 contains graphite. The first active material particle 21 may contain natural graphite or artificial graphite. As long as the first active material particle 21 contains graphite, it may contain additional components. The first active material particle 21 may further contain, for example, soft carbon, hard carbon, and amorphous carbon. For example, amorphous carbon may be attached to the surface of the graphite. The mass fraction of graphite in the first active material particle 21 may be, for example, 50% or more, 75% or more, 90% or more, or 95% or more.

[0033] The first active material particle 21 is oriented in the thickness direction. The first active material particle 21 has a first orientation angle (θ1). The first orientation angle (θ1) is 50° or more. The first orientation angle (θ1) may be, for example, 52° or more, 54° or more, 58° or more, 62° or more, 63° or more, or 66° or more. The first orientation angle (θ1) may be, for example, 90° or less, 80° or less, or 70° or less.

[0034] The aspect ratio of the first active material particle 21 may be, for example, 1.3 or more, 4.3 or more, 8.2 or more, 9.5 or more, or 13.5 or more. The aspect ratio of the first active material particle 21 may be, for example, 20 or less, 15 or less, 13.5 or less, or 9.5 or less.

[0035] The particle size of the first active material particle 21 may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, 30 μm or more, 45 μm or more, or 60 μm or more. The particle size of the first active material particle 21 may be, for example, 75 μm or less, 60 μm or less, 45 μm or less, or 30 μm or less.

[0036] · The second active material particle The second active material particles 22 contain Si. As long as the second active material particles 22 contain Si, they may contain additional components. The second active material particles 22 may contain, for example, at least one selected from the group consisting of Si, Si-based alloys, silicon oxide (SiO), and Si-C. "Si-C" refers to a composite material containing Si and carbon (C). In Si-C, Si may or may not form a compound with C. C may be amorphous or crystalline. For example, carbon particles may carry Si. The molar fraction of Si in the second active material particles 22 may be, for example, 5% or more, 10% or more, 25% or more, 50% or more, 75% or more, 90%, or 95% or more.

[0037] The second active material particles 22 may contain, for example, core particles 1 and a magnetic material 2. The core particles 1 may contain, for example, at least one selected from the group consisting of Si, Si-based alloys, SiO, and Si-C. The core particles 1 may be primary particles or secondary particles. The magnetic material 2 has magnetic field responsiveness. The magnetic material 2 may contain, for example, at least one selected from the group consisting of Ti, Zr, and V. The magnetic material 2 is attached to at least a part of the core particles 1. The magnetic material 2 may be, for example, encapsulated in the core particles 1 (secondary particles). The magnetic material 2 may, for example, coat the surface of the core particles 1. The magnetic material 2 may be, for example, in the form of a film or in the form of particles (islands). For example, the core particles 1 may be coated with the magnetic material 2 by the barrel sputtering method. The coating rate may be, for example, 12% or more, 35% or more, 38% or more, 41% or more, or 43% or more. The coating rate may be, for example, 100% or less, 75% or less, or 50% or less.

[0038] The second active material particles 22 are also oriented in the thickness direction. The second active material particles 22 have a second orientation angle (θ2). The second orientation angle (θ2) is 35° or more. The second orientation angle (θ2) may be, for example, 37° or more, 43° or more, 46° or more, 47° or more, 49° or more, or 51° or more. The second orientation angle (θ2) may be, for example, 90° or less, 80° or less, 70° or less, or 60° or less.

[0039] The orientation angle ratio (θ1 / θ2) may be, for example, 1.41 or less, 1.40 or less, 1.27 or less, 1.26 or less, or 1.24 or less. The orientation angle ratio (θ1 / θ2) may be, for example, 1 or more, 1.1 or more, 1.2 or more, or 1.24 or more.

[0040] The aspect ratio of the second active material particles 22 may be, for example, greater than 1, 1.1 or more, 1.2 or more, 1.5 or more, 2 or more, 3 or more, 4 or more, or 5 or more. The aspect ratio of the second active material particles 22 may be, for example, 10 or less, 7.5 or less, or 5 or less.

[0041] For example, the second active material particles 22 may have a smaller particle size than the first active material particles 21. The particle size of the second active material particles 22 may be, for example, 0.5 μm or more, 1 μm or more, 1.5 μm or more, 3 μm or more, or 4.5 μm or more. The particle size of the second active material particles 22 may be, for example, 12 μm or less, 9 μm or less, or 6 μm or less.

[0042] · Other components In addition to the negative electrode active material, the negative electrode active material layer 20 may further contain a conductive material, a thickening material, a binder, and the like. The conductive material can form an electron conduction path. The conductive material may contain, for example, at least one selected from the group consisting of acetylene black (AB), ketjen black (registered trademark), vapor grown carbon fiber (VGCF), carbon nanotube (CNT), and graphene flake (GF). The blending amount of the conductive material may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material.

[0043] The thickening agent can impart viscosity to the negative electrode paste. The thickening agent may include, for example, at least one selected from the group consisting of sodium alginate, carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and polyvinylpyrrolidone (PVP). The blending amount of the thickening agent may be, for example, from 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material.

[0044] The binder can bind solids together. The binder may include, for example, at least one selected from the group consisting of styrene butadiene rubber (SBR), acrylate butadiene rubber (ABR), polyacrylonitrile (PAN), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), acrylic resin (acrylate copolymer), methacrylic resin (methacrylate copolymer), and polyvinyl alcohol (PVA). The blending amount of the binder may be, for example, from 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material.

Examples

[0045] <Preparation of Samples> ·No.1 As the first active material particles, graphite (aspect ratio: 3.1) was prepared. As the second active material particles, a Si-based material (Si or SiO) was prepared. A negative electrode paste was prepared by mixing the first active material particles, the second active material particles, SBR, CMC, and ion-exchanged water. The solid content was blended as "graphite: Si-based material: SBR: CMC = (98.3 - a): a: 0.5: 1.2 (mass ratio)". As the substrate, a Cu foil (thickness: 10 μm, long strip) was prepared. A coating film was formed by applying the negative electrode paste to both sides of the substrate. A negative electrode active material layer was formed by drying the coating film. An electrode (negative electrode sheet) was prepared by compressing the negative electrode active material layer. In the negative electrode sheet, the first orientation angle (θ1), the second orientation angle (θ2), etc. were measured by the above-described procedure.

[0046] An evaluation cell (lithium-ion battery) was fabricated according to the following procedure. LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2 (particle size: 5 μm), AB, PVdF, and N-methyl-2-pyrrolidone were mixed to prepare a positive electrode paste. The composition of the solid content was "LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2:AB:PVdF = 92:5:3 (mass ratio)". As the substrate, an Al foil (thickness: 15 μm, long strip) was prepared. The positive electrode paste was applied to both sides of the substrate to form a coating film. The coating film was dried to produce a positive electrode active material layer. The positive electrode active material layer was compressed to produce a counter electrode (positive electrode sheet).

[0047] A separator was prepared. The separator included a resin porous membrane and a heat-resistant layer. The resin porous membrane (thickness: 24 μm) had a three-layer structure (polyethylene layer / polypropylene layer / polyethylene layer). The heat-resistant layer (thickness: 4 μm) was formed on one side of the resin porous membrane.

[0048] A laminate was formed by laminating the positive electrode sheet, the separator, the negative electrode sheet, and the separator. The laminate was wound in a spiral shape to form a wound power generation element (also referred to as an "electrode body"). The power generation element was flattened by being crushed in the radial direction. An external terminal was connected to the power generation element. The power generation element was housed in a metal case. An electrolytic solution was injected into the metal case. After the injection of the electrolytic solution, the metal case was sealed. Thus, the evaluation cell was fabricated. The composition of the electrolytic solution was as follows.

[0049] Solvent: "Ethylene carbonate:dimethyl carbonate:ethyl methyl carbonate = 3:3:4 (volume ratio)" Solute: LiPF6 (concentration: 1 mol / L)

[0050] The first charge and discharge (activation treatment) was carried out under the following conditions. Ambient temperature: 25°C Charging: Constant current - constant voltage method, current during constant current: 1 / 3C, voltage during constant voltage: 4.2V, cut-off current: 1 / 50C Discharging: Constant current method, current: 1 / 3C, cut-off voltage: 3V

[0051] · No.2 Figure 3 is a table showing the experimental results. In No.2, graphite (aspect ratio: 4.3) was used as the first active material particles. A negative electrode paste was prepared in the same manner as in No.1. By applying the negative electrode paste to both sides of the substrate, a coating film was formed. In No.2, after the formation of the coating film, a magnetic field was applied to the coating film by passing the coating film through the gap between a pair of neodymium magnets. The magnetic flux density of the magnet was 0.5T. After the application of the magnetic field, the coating film was dried to produce a negative electrode active material layer. Except for these, electrodes and evaluation cells were produced in the same manner as in No.1.

[0052] · No.3 In No.3, graphite (aspect ratio: 13.3) was used as the first active material particles. The second active material particles were coated with a magnetic material by the barrel sputtering method. The coating rate was 12%. Except for using the coated second active material particles, electrodes and evaluation cells were produced in the same manner as in No.2.

[0053] · No.4 to No.8 As shown in Figure 3, except that the aspect ratio of the first active material particles and the coating rate of the second active material particles were changed, electrodes and evaluation cells were produced in the same manner as in No.3.

[0054] <Evaluation> · Measurement of initial capacity The initial capacity (initial discharge capacity) was measured by charge and discharge under the following conditions. Charging: Constant current - constant voltage method, current during constant current: 1 / 3C, voltage during constant voltage: 4.1V, cut-off current: 1 / 50C Discharging: Constant current method, current: 1 / 3C, cut-off voltage: 3V

[0055] · Cycle characteristics The charge and discharge under the following conditions were taken as one cycle, and the charge and discharge were carried out for 300 cycles. Ambient temperature: 25 °C Current: 0.5C Range of state of charge (SOC): 0% to 100%

[0056] After 300 cycles, the capacity after cycling was measured in the same manner as the initial capacity. The capacity retention rate was obtained by dividing the capacity after cycling by the initial capacity. The higher the capacity retention rate, the better the cycle durability is considered to be.

[0057] <Results> In the table of Fig. 3, Nos. 3 to 8 have improved cycle durability compared to Nos. 1 and 2. In Nos. 3 to 8, the first orientation angle (θ1) is 50° or more, and the second orientation angle (θ2) is 35° or more.

[0058] In Nos. 3 to 8, when the aspect ratio of the first active material particles is from 4.3 to 9.5, there is a tendency for the cycle durability to improve.

[0059] In Nos. 3 to 8, when the first orientation angle is 58° or more, there is a tendency for the cycle durability to improve.

[0060] In Nos. 3 to 8, when the coating rate is 35% or more, there is a tendency for the cycle durability to improve.

[0061] In Nos. 3 to 8, when the orientation angle ratio is 1.40 or less, there is a tendency for the cycle durability to improve.

Explanation of symbols

[0062] 1 Core particle, 2 Magnetic material, 10 Substrate, 20 Negative electrode active material layer, 21 First active material particle, 22 Second active material particle, 100 Electrode, F max Maximum ferrite diameter, L Long axis.

Claims

1. comprising a substrate and a negative electrode active material layer, wherein the negative electrode active material layer is disposed on the surface of the substrate, the negative electrode active material layer includes first active material particles and second active material particles, the first active material particles include graphite, the second active material particles include silicon, in a cross-section parallel to the thickness direction of the negative electrode active material layer, the first active material particles have a first orientation angle of 50° or more, the second active material particles have a second orientation angle of 35° or more, the first orientation angle indicates the angle formed by the major axis of the first active material particles and the surface of the substrate, and the second orientation angle indicates the angle formed by the major axis of the second active material particles and the surface of the substrate, an electrode.

2. the second active material particles include core particles and a magnetic material, the core particles include silicon, and the magnetic material is attached to at least a part of the core particles, the electrode according to Claim 1.

3. the magnetic material includes at least one selected from the group consisting of titanium, zirconium, and vanadium, and the ratio of the adhesion area of the magnetic material to the surface area of the second active material particles is 35% or more, the electrode according to Claim 2.

4. the first active material particles have an aspect ratio of 4.3 to 9.5, the electrode according to Claim 1.

5. the first orientation angle is 58° or more, and the ratio of the first orientation angle to the second orientation angle is 1.40 or less, the electrode according to any one of Claims 1 to 4.

Images