Electrode for battery, battery, and method of producing electrode for battery

Abstract

An electrode for a battery comprises 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 comprises graphite and a binder. A first layer and a second layer are formed within the negative electrode active material layer. The first layer is formed between the substrate and the second layer. The relationships “1.2 ≤ A ≤ 4”, “1 < m2 / m1”, and “1 < θ2 / θ1” are satisfied. A represents the aspect ratio of graphite. m1 represents the mass fraction of the binder in the first layer. m2 represents the mass fraction of the binder in the second layer. θ1 represents the orientation angle of the graphite in the first layer. θ2 represents the orientation angle of the graphite in the second layer.

Description

Technology Field

[0001] The present disclosure relates to an electrode for a battery, a battery, and a method for manufacturing an electrode for a battery. Background Technology

[0002] Japanese Patent Publication No. 2014-096201 discloses a negative electrode active material layer having a low amount of binder on the side closer to the metal foil.

[0003] In the side closer to the substrate (lower side), the adhesion between the substrate and the negative electrode active material layer may be reduced as the binder is reduced. Due to the reduced adhesion, stress concentration at the boundary between the substrate and the negative electrode active material layer can be alleviated. As a result, for example, an improvement in cycle performance is expected.

[0004] On the other hand, the ion diffusivity tends to be low on the upper side of the negative electrode active material layer, which has a relatively large amount of binder. Because the ion diffusivity is low on the upper side, there is a possibility that the desired rate performance cannot be obtained.

[0005] The purpose of the present disclosure is to improve rate performance.

[0006] The technical configuration and effects of the present disclosure are described below. However, the mechanism of action includes presumptions. The mechanism of action does not limit the technical scope of the present disclosure.

[0007] 1. The electrode for the battery comprises 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 comprises graphite and a binder. A first layer and a second layer are formed within the negative electrode active material layer. The first layer is formed between the substrate and the second layer. The electrode for the battery satisfies the relationships of the following formulas (1) to (3).

[0008]

[0009]

[0010]

[0011] In the above equations (1) to (3), A represents the aspect ratio of graphite. m1 represents the mass fraction of the binder in the first layer. m2 represents the mass fraction of the binder in the second layer. θ1 represents the orientation angle of graphite in the first layer. θ2 represents the orientation angle of graphite in the second layer.

[0012] As shown in Equation (3) above, compared to the first layer (lower layer), the graphite in the second layer (upper layer) is strongly oriented. That is, the long axis of the graphite follows the thickness direction. Because the graphite is strongly oriented in the second layer, the diffusion of ions in the thickness direction can be promoted. Therefore, as shown in Equation (2) above, even if the binder in the second layer is large, an improvement in rate performance is expected.

[0013] On the other hand, in the first layer, the long axis of the graphite follows the surface of the substrate. As the contact area between the graphite and the substrate is increased, it is expected that the negative electrode active material layer and the substrate will adhere sufficiently with a small amount of binder. In addition, in the first layer, it is expected that ion diffusion will be promoted due to the small amount of binder.

[0014] As shown in the above equation (1), graphite has an aspect ratio of 1.2 to 4. When the aspect ratio is less than 1.2, there is a possibility that the desired rate performance may not be obtained even if the graphite is oriented. Even if the aspect ratio exceeds 4, there is a possibility that sufficient ion diffusivity may not be obtained. Generally, the negative electrode active material layer is manufactured through press processing. When particles with a large aspect ratio undergo press processing while oriented in the thickness direction, there is a possibility that the frequency of occurrence of, for example, cracking and breakage of the particles may increase. Cracking of particles in the second layer (upper layer) may reduce the reaction area. Due to the reduction in the reaction area, there is a possibility that the desired rate performance may not be obtained.

[0015] During press processing, the first layer (lower layer) can function as a cushion. This is because the amount of binder in the first layer is small. As the first layer functions as a cushion, the load applied to the second layer (upper layer) during press processing can be relieved. Due to the relief of the load, it is expected that the orientation state of the second layer will not be easily disrupted. In addition, due to the large amount of binder in the second layer, it is expected that the orientation state of the second layer will be firmly fixed.

[0016] 2. The battery electrode described in "1" above may include, for example, the following configuration. The battery electrode further satisfies the relationship of the following formula (4).

[0017]

[0018] Among the above equation (4), I 110 Silver represents the diffraction intensity of the (110) plane in the X-ray diffraction profile of the negative electrode active material layer. 002 represents the diffraction intensity of the (002) plane in the X-ray diffraction profile of the negative electrode active material layer.

[0019] In the X-ray diffraction (XRD) profile, the intensity ratio (I 110 / I 002 ) is an indicator of the orientation state of graphite. I 110 / I 002 The larger θ is, the more the long axis of the graphite is thought to follow the thickness direction. I of the negative electrode active material layer 110 / I 002 It is thought that it reflects the average of the orientation state of the first layer and the orientation state of the second layer.

[0020] 3. The electrode for a battery described in "1" or "2" above may include, for example, the following composition. The negative electrode active material layer has a thickness of 100 to 400 μm.

[0021] The technology of "1" above is suitable for a thick negative electrode active material layer, particularly a negative electrode active material layer having a thickness of 100 μm or more. When the thickness of the negative electrode active material layer is 400 μm or less, the balance between rate performance and capacity is good.

[0022] 4. The battery electrode described in any one of the above “1” to “3” may include, for example, the following configuration. The battery electrode further satisfies the relationship of the following formula (5).

[0023]

[0024] In the above equation (5), T1 represents the thickness of the first layer. T2 represents the thickness of the second layer.

[0025] When the relationship of the above equation (5) is satisfied, an improvement in rate performance is expected.

[0026] 5. The battery includes a battery electrode described in any one of claims 1 to 4 above.

[0027] 6. A method for manufacturing an electrode for a battery comprises the following (a) to (d) in this order.

[0028] (a) A first layer is formed by applying a first slurry to the surface of the substrate.

[0029] (b) A second layer is formed by applying a second slurry on top of the first layer.

[0030] (c) Apply a magnetic field to the first and second layers.

[0031] (d) By drying the first and second layers, a negative electrode active material layer is formed.

[0032] Each of the first slurry and the second slurry comprises graphite, a binder, and a dispersion medium.

[0033] The manufacturing method satisfies the relationship between the following formulas (6) and (7).

[0034]

[0035]

[0036] In the above equations (6) and (7), η1 represents the viscosity of the first slurry. η2 represents the viscosity of the second slurry. r1 represents the mixing ratio of the binder in the solid content of the first slurry. r2 represents the mixing ratio of the binder in the solid content of the second slurry.

[0037] By applying a magnetic field to a slurry containing graphite, the graphite can be oriented. Since the viscosity of the second slurry is lower than that of the first slurry, the orientation angle of the second layer is expected to be larger than that of the first layer. In addition, since the mixing ratio of the binder in the second slurry is large, it is expected that the graphite in the second layer will be fixed while oriented.

[0038] Embodiments of the present disclosure (hereinafter abbreviated as “present embodiments”) are described below. However, present embodiments do not limit the technical scope of the present disclosure. Present embodiments are illustrative in all respects. Present embodiments are non-limiting. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the description in the claims. For example, any configuration may be derived from present embodiments, and any combination thereof is also intended from the outset.

[0039] The above and other objects, features, aspects, and advantages of the present disclosure will become apparent from the following detailed description of the present disclosure as understood in conjunction with the accompanying drawings. Brief explanation of the drawing

[0040] Figure 1 is a conceptual diagram showing the method for measuring the orientation angle. Figure 2 is an example of an XRD profile. FIG. 3 is a schematic cross-sectional view showing an example of a battery electrode in the present embodiment. Figure 4 is a graph showing the relationship between the XRD intensity ratio and the binder abundance ratio. FIG. 5 is a schematic flowchart of a method for manufacturing a battery electrode in the present embodiment. FIG. 6 is a conceptual diagram showing an example of a battery in the present embodiment. Figure 7 is a table showing the configuration of the first battery. Figure 8 is a table showing the configuration of the second battery. Figure 9 is a table showing the configuration of the third battery. Figure 10 is a table showing the experimental results. Figure 11 is a graph showing the relationship between the XRD intensity ratio and the discharge rate. Figure 12 is a graph showing the relationship between the aspect ratio of graphite and the discharge rate. Specific details for implementing the invention

[0041] < Terms and Phrases >

[0042] "Equipped with," "includes," "possesses," and variations thereof are open-ended terms. Open-ended terms may include additional elements in addition to essential elements, or they may not. The description "consists of" is a closed-ended term. However, even if a configuration is expressed in a closed-ended term, additional elements that are incidental in normal practice or unrelated to the subject technology may be included. The description "substantially consists of..." is a semi-closed term. In the case of semi-closed terms, the addition of elements that do not substantially affect the fundamental and novel characteristics of the subject technology is permitted.

[0043] Expressions such as "may" and "can" are used not in an obligatory sense meaning "must do," but in a permissive sense meaning "having the possibility to do."

[0044] Geometric terms should not be interpreted strictly in their original sense. Examples of geometric terms include "parallel," "perpendicular," and "orthogonal." For instance, "parallel" may deviate somewhat from the strict definition of "parallel." Geometric terms may include tolerances and errors arising from design, operation, or manufacturing, for instance. The dimensional relationships within the drawings may not correspond to the actual dimensions. To aid the reader's understanding, dimensional relationships within the drawings may be altered. For instance, lengths, widths, thicknesses, etc., may be changed. Some components may also be omitted.

[0045] Numerical ranges such as "m to n%" include upper and lower limits unless specifically stated otherwise. That is, "m to n%" indicates a numerical range of "m% or more and n% or less." Furthermore, "m% or more and n% or less" includes "greater than m% and less than n%." "greater than" and "less than" are indicated by the inequality sign "≤" with an equal sign. "greater than" and "less than" are indicated by the inequality sign "<" without an equal sign. A numerical value arbitrarily selected from within the numerical range may serve as a new upper or lower limit. For example, a new numerical range may be established by arbitrarily combining a numerical value within the numerical range with a numerical value described in other parts of this specification, tables, drawings, etc.

[0046] All numerical values ​​are modified by the term "approximately." The term "approximately" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximations that may vary depending on the form of use of the present disclosure. All numerical values ​​may be expressed in significant figures. Unless otherwise specified, the measured value may be the average of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. Generally, the reliability of the average value is expected to improve as the number of measurements increases. The measured value may be rounded to the nearest whole number based on the number of significant figures. The measured value may include errors, for example, due to the detection limit of the measuring device.

[0047] "Orientation angle" represents a value measured by the following method. FIG. 1 is a conceptual diagram illustrating the method of measuring the orientation angle. A cross-sectional sample is prepared by cutting the negative electrode active material layer. The cross-sectional sample includes a cross section parallel to the thickness direction of the negative electrode active material layer. For example, the part to be observed may be cleaned by a cross-section polisher (registered trademark), etc. An SEM image is acquired by observing the cross-sectional sample with a Scanning Electron Microscope (SEM). In the SEM image, the graphite (particle) has a major axis diameter (φ1) and a minor axis diameter (φ2). The diameter connecting the two furthest points on the outline of the graphite is the "major axis diameter." The diameter perpendicular to the major axis diameter at the midpoint of the major axis diameter is the "minor axis diameter." The orientation angle (θ) represents the angle (acute angle side) formed by the surface of the substrate (210) and the major axis diameter. The orientation angle (θ) can take a value from 0 to 90°. Ten particles are randomly selected from the target location of the SEM image (e.g., the first layer). For each particle, the orientation angle is measured. The arithmetic mean of the orientation angles of the ten particles is used.

[0048] "Aspect ratio" represents the ratio (φ1 / φ2) of the major axis (φ1) to the minor axis (φ2). The aspect ratio can also be measured in an SEM image used to measure the orientation angle. Ten particles are randomly selected from the target location of the SEM image (e.g., the first layer). The aspect ratio is measured for each particle. The arithmetic mean of the aspect ratios for the ten particles is used.

[0049] "D50" represents the particle size at which the accumulation is 50% in the volume-based particle size distribution (integration distribution). The particle size distribution can be measured by laser diffraction.

[0050] "BET specific surface area" refers to the specific surface area measured by the gas adsorption method (BET 1-point method). Nitrogen is used as the adsorbed gas.

[0051] The XRD profile is measured by an XRD device. The X-ray source is CuKα rays. The measurement range is “10° ≤ 2θ ≤ 90°”. FIG. 2 is an example of an XRD profile. The diffraction peak of the (002) plane can be detected in the range of “25° ≤ 2θ ≤ 30°”. The diffraction peak of the (110) plane can be detected in the range of “75° ≤ 2θ ≤ 80°”. The diffraction intensity (I) of each peak 002 , I 110 ) are measured respectively.

[0052] "Viscosity" is 10s at 25℃ -1 It is measured by the shear rate. Viscosity can be measured by a rotational viscometer. For example, a rotational viscometer described in JIS K 7117:1999 “Method for measuring viscosity at a constant shear rate by a rotational viscometer for plastics—liquid, emulsifiable, or dispersed resins” may be used.

[0053] The “mixing ratio” of the binder in the slurry indicates the ratio of the mass of the binder to the total mass of the solids. The solids refer to components other than the dispersion medium.

[0054] The stoichiometric composition formula represents a representative example of the compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to a compound having a substance ratio (molar ratio) of "Al / O = 2 / 3". Unless otherwise specified, "Al2O3" refers to a compound containing Al and O in any molar ratio. For example, the compound may be doped with trace elements. Some of the Al and O may be substituted with other elements.

[0055] "Derivative" refers to a compound in which a part of the parent compound is modified by at least one selected from the group consisting of the introduction of a substituent, substitution of an atom, oxidation, reduction, and other chemical reactions. The modification site may be one site or multiple sites. "Substituents" are, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (F, Cl, Br, I, etc.), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphate amide groups, sulfo groups, carboxyl groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and, It may include at least one selected from the group consisting of silyl groups, etc. These substituents may be additionally substituted. If there are two or more substituents, the substituents may be the same or different. Multiple substituents may be combined to form a ring. In addition, derivatives of polymer compounds (resin materials) may also be called "modified materials."

[0056] The “copolymer” includes at least one type selected from the group consisting of unspecified type, statistical type, random type, alternating type, periodic type, block type, and graft type.

[0057] < Electrode for battery >

[0058] Hereinafter, the electrode for a battery may be abbreviated as "electrode." The electrode is in the form of a sheet. The electrode may be applied to any application as long as it is for a battery. The electrode may be, for example, for a monopolar battery (unipolar battery), a bipolar battery, a non-aqueous battery, a lithium-ion battery, etc.

[0059] FIG. 3 is a schematic cross-sectional view showing an example of a battery electrode in the present embodiment. The electrode (200) may be, for example, a negative electrode of a monopolar lithium-ion battery. The cross-section of FIG. 1 is parallel to the thickness direction (Z direction) of the electrode (200). The electrode (200) includes a substrate (210) and a negative electrode active material layer (220).

[0060] The substrate (210) supports the negative electrode active material layer (220). The substrate (210) may be in the form of a sheet, for example. The thickness of the substrate (210) may be, for example, 1 to 50 μm, 3 to 30 μm, or 5 to 15 μm. The substrate (210) is conductive. The substrate (210) may include, for example, a metal foil, etc. The substrate (210) may include at least one selected from the group consisting of, for example, Cu, Ni, Zn, Pb, Al, Ti, Fe, Ag, Au, and a conductive resin. The substrate (210) may include, for example, a Cu foil, a Cu alloy foil, etc. The substrate (210) may have a multilayer structure, for example. For example, the substrate (210) may be formed by joining a Cu foil and an Al foil together.

[0061] The negative electrode active material layer (220) is disposed on the surface of the substrate (210). The negative electrode active material layer (220) may be disposed on only one side of the substrate (210). The negative electrode active material layer (220) may be disposed on both sides of the substrate (210). When the electrode (200) is for a bipolar battery, the negative electrode active material layer (220) may be disposed on one side (front side) of the substrate (210), and a positive electrode active material layer (not shown) may be disposed on the other side (back side). The thickness of the negative electrode active material layer (220) may be, for example, 10 μm or more, 50 μm or more, 100 μm or more, 150 μm or more, 200 μm or more, 300 μm or more, 400 μm or more, or 500 μm or more. The thickness of the negative electrode active material layer (220) may be any of 1000 μm or less, 500 μm or less, 400 μm or less, 300 μm or less, or 200 μm or less. The thickness of the negative electrode active material layer (220) may be, for example, 100 to 400 μm.

[0062] A first layer (221) and a second layer (222) are formed within the negative electrode active material layer (220). The first layer (221) is a lower layer. The first layer (221) is formed between the substrate (210) and the second layer (222). The first layer (221) may be in direct contact with the substrate (210). The first layer (221) may include the interface between the substrate (210) and the negative electrode active material layer (220). The second layer (222) is an upper layer. The second layer (222) may be directly laminated on the first layer (221). The second layer (222) may include the surface of the negative electrode active material layer (220). The orientation state of the graphite (10) is different between the first layer (221) and the second layer (222). In addition, the amount of binder (20) differs between the first layer (221) and the second layer (222).

[0063] Regarding the thickness (T1) of the first layer (221) and the thickness (T2) of the second layer (222), for example, the relationship (5) below may be satisfied.

[0064]

[0065] The thickness ratio (T1 / (T1+T2)) may be, for example, 0.2 or greater or 0.3 or greater. The thickness ratio (T1 / (T1+T2)) may be, for example, 0.3 or less or 0.2 or less.

[0066] The negative electrode active material layer (220) comprises a negative electrode active material and a binder. The negative electrode active material can generate a negative electrode reaction. The negative electrode active material comprises graphite. The graphite may include at least one selected from the group consisting of artificial graphite and natural graphite. For example, the surface of the graphite may be coated with amorphous carbon. As long as the negative electrode active material includes graphite, it may further include other negative electrode active materials. In addition to graphite, the negative electrode active material may include at least one selected from the group consisting of, for example, silicon (Si), silicon oxide (SiO), silicon-carbon composite material (Si-C), silicon-based alloy, tin, tin oxide, and lithium titanate. For example, Si-C may be formed by dispersing Si fine particles within carbon particles. The mass fraction of graphite to the total of the negative electrode active material may be, for example, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more.

[0067] Graphite is a particle group (powder). The D50 of the graphite may be, for example, 1 to 50 μm, 5 to 30 μm, or 10 to 25 μm. The BET specific surface area of ​​the graphite may be, for example, 0.5 to 5 m² / g, 1 to 4 m² / g, or 1.5 to 3 m² / g.

[0068] Graphite has an aspect ratio (A) of 1.2 to 4. That is, the relationship of the following equation (1) is satisfied.

[0069]

[0070] The aspect ratio (A) may be, for example, 1.5 or more, 2 or more, 2.5 or more, 3 or more, or 3.5 or more. The aspect ratio (A) may be, for example, 3.8 or less, 3.5 or less, 3 or less, 2.5 or less, 2 or less, or 1.5 or less.

[0071] In the first layer (221) and the second layer (222), the graphite has a specific orientation state. That is, the relationship of the following formula (3) is satisfied.

[0072]

[0073] The orientation angle (θ1) in the first layer (221) may be, for example, 0° or more, 5° or more, 10° or more, or 20° or more. The orientation angle (θ1) may be, for example, 30° or less, 20° or less, 10° or less, or 5° or less. The orientation angle (θ2) in the second layer (222) may be, for example, 60° or more, 70° or more, or 80° or more. The orientation angle (θ2) may be, for example, 90° or less, 80° or less, or 70° or less. The orientation angle ratio (θ2 / θ1) may be, for example, 1.1 or more, 1.5 or more, 2 or more, 5 or more, 10 or more, 30 or more, 50 or more, or 100 or more. The orientation angle ratio (θ2 / θ1) may be any of 1000 or less, 500 or less, 100 or less, 50 or less, 30 or less, or 10 or less.

[0074] The relationship of the following equation (4) may be satisfied.

[0075]

[0076] XRD intensity ratio (I 110 / I 002 ) is thought to reflect the average of the orientation states of the first layer (221) and the second layer (222). XRD intensity ratio (I 110 / I 002 ) may be, for example, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, or 0.08 or more. XRD intensity ratio (I 110 / I 002 ) may be any of, for example, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, or 0.03 or less.

[0077] The binder binds solids together. The binder may include any component. 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 (acrylic acid ester copolymer), methacrylic resin (methacrylic acid ester copolymer), polyvinyl alcohol (PVA), and derivatives thereof. The amount of binder may be, for example, 0.1 to 10 parts by mass, 0.5 to 5 parts by mass, 1 to 4 parts by mass, or 2 to 3 parts by mass with respect to 100 parts by mass of negative electrode active material.

[0078] The negative electrode active material layer (220) may include a thickening agent. The thickening agent can impart viscosity to the slurry. The thickening agent may include at least one selected from the group consisting of, for example, sodium alginate, carboxymethylcellulose (CMC), polyacrylic acid (PAA), and polyvinylpyrrolidone (PVP). CMC and PAA, etc., may be in the form of, for example, Na salts, Li salts, NH4 salts, etc. The amount of the thickening agent may be, for example, 0.1 to 2 parts by mass, or 0.1 to 1 part by mass, or 0.1 to 0.5 parts by mass, with respect to 100 parts by mass of the negative electrode active material.

[0079] The negative electrode active material layer (220) may include a conductive material. The conductive material can form an electron conduction path within the negative electrode active material layer (220). The conductive material may include, 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 CNT may include at least one selected from the group consisting of single-layer CNT (SWCNT) and multi-layer CNT (MWCNT). The 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.

[0080] The negative electrode active material layer (220) may include, for example, an inorganic filler, an organic filler, a solid electrolyte, a surface modifier, a dispersant, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The negative electrode active material layer (220) may include, for example, a layered silicate (smectite, montmorillonite, bentonite, hectorite, etc.), an inorganic filler (solid alumina, hollow silica, boehmite, etc.), a polysiloxane compound, etc.

[0081] Between the first layer (221) and the second layer (222), the relationship of the following equation (2) is satisfied.

[0082]

[0083] The mass fraction (m1) of the binder in the first layer (221) may be, for example, 0.5 to 2.5%, 1 to 2%, or 1 to 1.5%. The mass fraction (m2) of the binder in the second layer (222) may be, for example, 1 to 5%, 1.5 to 3%, or 1.5 to 2%. The binder abundance ratio (m2 / m1) in the first layer (221) and the second layer (222) may be, for example, 1.2 or more, 1.5 or more, 2 or more, 2.5 or more, or 3 or more. The binder abundance ratio (m2 / m1) may be 5 or less, 4 or less, 3 or less, 2.5 or less, 2 or less, or 1.5 or less.

[0084] A binder abundance ratio (m2 / m1) greater than 1 may be confirmed, for example, by mapping analysis using SEM-EDX (Scanning Electron Microscope-Energy dispersive X-ray spectrometry). For example, a binder staining treatment may be performed on a cross-sectional sample of the negative electrode active material layer (220). For example, SBR may be stained with osmium oxide. A binding mapping analysis is performed on a cross-sectional sample. For example, pixels corresponding to the binder are counted within the first layer (221). By dividing the number of pixels corresponding to the binder by the total number of pixels in the first layer (221), the area fraction (S1) of the binder in the first layer (221) is obtained. Likewise, the area fraction (S2) of the binder in the second layer (222) is obtained. The area fraction ratio (S2 / S1) is considered to be substantially the same as the binder abundance ratio (m2 / m1).

[0085] FIG. 4 is a graph showing the relationship between the XRD intensity ratio and the binder abundance ratio. The XRD intensity ratio can be increased by applying a magnetic field to the slurry film. The white circle plot (point 1) indicates that the film is formed by a single slurry. The use of a single slurry indicates that the negative electrode active material layer (220) has a single-layer structure. In the black circle plot (point 3), two types of slurries with different viscosities are used. The use of two types of slurries indicates that the negative electrode active material layer (220) has a two-layer structure. The two-layer structure shows a tendency for the XRD intensity ratio to increase more easily than the single-layer structure. Furthermore, in the two-layer structure, the XRD intensity ratio tends to increase further as the binder abundance ratio increases. This is thought to be because the lower layer functions as a cushion during pressing, making it difficult for the orientation state to be disrupted.

[0086] Method for manufacturing electrodes for batteries >

[0087] FIG. 5 is a schematic flowchart of a method for manufacturing an electrode for a battery according to the present embodiment. Hereinafter, "method for manufacturing an electrode for a battery according to the present embodiment" may be abbreviated as "the present manufacturing method." The present manufacturing method includes "(a) formation of a first layer," "(b) formation of a second layer," "(c) magnetic field orientation," and "(d) drying" in this order. The present manufacturing method may further include, for example, "(e) compression," etc.

[0088] (a) Formation of the first layer

[0089] The present manufacturing method comprises forming a first layer (221) by applying a first slurry to the surface of a substrate (210). The first slurry comprises graphite, a binder, and a dispersion medium. For example, the first slurry may be formed by mixing graphite, a binder, a thickening agent, and a dispersion medium. Any mixing device may be used. For example, a planetary mixer may be used. The viscosity of the slurry may be adjusted, for example, by the solid content concentration, the amount of thickening agent mixed, the stirring speed, and the mixing time. The viscosity of the first slurry may be, for example, 15,000 mPa·s or more, 20,000 mPa·s or more, 25,000 mPa·s or more, or 30,000 mPa·s or more. The viscosity of the first slurry may be, for example, 40,000 mPa·s or less, 35,000 mPa·s or less, 30,000 mPa·s or less, or 25,000 mPa·s or less.

[0090] A first layer (221) (coating film) can be formed by applying a first slurry to the surface of the substrate (210). Any coating device may be used. For example, a die coater, a roll coater, etc. may be used. The graphite included in the first slurry tends to be oriented along the surface of the substrate (210).

[0091] (b) Formation of the second layer

[0092] The present manufacturing method comprises forming a second layer (222) by applying a second slurry on top of a first layer (221). The second slurry comprises graphite, a binder, and a dispersion medium. For example, the second slurry may be formed by mixing graphite, a binder, a thickener, and a dispersion medium.

[0093] The viscosity of the second slurry may be, for example, 5000 mPa·s or more, 10000 mPa·s or more, or 15000 mPa·s or more. The viscosity of the second slurry may be, for example, 20000 mPa·s or less, 15000 mPa·s or less, or 10000 mPa·s or less.

[0094] In the present manufacturing method, the relationship of the following equation (6) is satisfied with respect to the viscosity (η1) of the first slurry and the viscosity (η2) of the second slurry.

[0095]

[0096] The viscosity ratio (η1 / η2) may be, for example, 2.08 or more, 2.5 or more, or 3 or more. The viscosity ratio (η1 / η2) may be, for example, 5 or less, 4 or less, 3 or less, or 2.5 or less.

[0097] In the present manufacturing method, the relationship of the following formula (7) is satisfied with respect to the mixing ratio (r1) of the binder in the solid content of the first slurry and the mixing ratio (r2) of the binder in the solid content of the second slurry.

[0098]

[0099] "r2 / r1" in the above equation (7) is substantially the same as "m2 / m1" in the above equation (2).

[0100] A second layer (222) (coating) can be formed by applying a second slurry over the first layer (221). At this stage, the first layer (221) and the second layer (222) are in a wet state. That is, the first layer (221) and the second layer (222) contain a dispersion medium.

[0101] (c) Magnetic field orientation

[0102] The present manufacturing method includes applying a magnetic field to the first layer (221) and the second layer (222). The magnetic field may be applied, for example, along the thickness direction of the first layer (221) and the second layer (222). Graphite contained in the first layer (221) and the second layer (222) may be oriented in response to the magnetic field. Since the viscosity of the first layer (221) (first slurry) is higher than the viscosity of the second layer (222) (second slurry), it is thought that the graphite in the first layer (221) is more difficult to orient than the graphite in the second layer (222). As a result, it is thought that there is a difference in the orientation state between the first layer (221) and the second layer (222). That is, within the first layer (221), the graphite is thought to be easily oriented in the planar direction (XY direction). On the other hand, within the second layer (222), the graphite is thought to be easily oriented in the thickness direction (Z direction). The magnetic flux density of the magnetic field and the application time can be adjusted so that a desired orientation state is obtained. The magnetic flux density may be, for example, 100 to 1000 mT. The application time may be, for example, 1 to 60 minutes.

[0103] (d) Drying

[0104] The present manufacturing method includes forming a negative electrode active material layer (220) by drying the first layer (221) and the second layer (222). The dispersion medium may be removed by drying. Any drying device may be used. For example, a hot air drying device may be used. The drying temperature may be, for example, 40 to 80°C, or 40 to 60°C. The electrode (200) may be completed by removing the dispersion medium.

[0105] (e) compression

[0106] The present manufacturing method may include, for example, compressing the negative electrode active material layer (220). For example, the negative electrode active material layer (220) may be compressed by a rolling mill, etc. Since the aspect ratio of the graphite is 4 or less, cracking, breakage, etc. of the graphite on the surface of the negative electrode active material layer (220) (second layer (222)) can be reduced. In addition, it is thought that the orientation state of the graphite can be maintained during compression because a large amount of binder is placed in the second layer (222).

[0107] For example, the negative electrode active material layer (220) may be compressed so that the density (apparent density) of the negative electrode active material layer (220) is 1.30 g / cm³ or less. Because the density is 1.30 g / cm³ or less, the orientation state of the graphite tends to be easily maintained. The density may be, for example, 1.25 g / cm³ or less, 1.2 g / cm³ or less, or 1.15 g / cm³ or less. The density may be, for example, 1.05 g / cm³ or more, 1.10 g / cm³ or more, or 1.15 g / cm³ or more. After compression, the electrode (200) may be cut into a predetermined size.

[0108] < Battery >

[0109] FIG. 6 is a conceptual diagram showing an example of a battery in the present embodiment. The battery (1000) may be, for example, a monopolar lithium-ion battery. The battery (1000) includes an outer body (900). The outer body (900) houses a power generation element (500) and an electrolyte (not shown).

[0110] < External body >

[0111] The outer body (900) may have any shape. The outer body (900) may be, for example, a metal case, a laminated film pouch, etc. The case may have any shape. The case may be, for example, cylindrical, prismatic, flat, coin-shaped, etc. The outer body (900) may contain, for example, Al, etc. The outer body (900) may house, for example, one or more power generation elements (500). The multiple power generation elements (500) may form, for example, a series circuit or a parallel circuit. Within the outer body (900), the multiple power generation elements (500) may be stacked in the thickness direction of the battery (1000).

[0112] < Development Factors >

[0113] The power generation element (500) may also be called an "electrode group," "electrode body," etc. The power generation element (500) includes an electrode (200) and a counter electrode (100). In this embodiment, the electrode (200) is the negative electrode. The counter electrode (100) is the positive electrode. The power generation element (500) may further include a separator (300). The separator (300) is placed between the positive electrode and the negative electrode. The power generation element (500) may have any shape. For example, the power generation element (500) may be a stacked type. For example, the power generation element (500) may be formed by alternately stacking the positive electrode and the negative electrode while inserting the separator (300) between the positive electrode and the negative electrode. For example, the power generation element (500) may be a wound type. For example, a laminate may be formed by stacking a strip-shaped positive electrode, a strip-shaped separator (300), and a strip-shaped negative electrode. A power generation element (500) may be formed by winding the laminate in a swirling shape. The wound power generation element (500) may be formed into a flat shape after winding.

[0114] Straight Drama

[0115] The positive electrode is in the form of a sheet. The positive electrode may include a substrate and a positive electrode active material layer. The substrate is conductive. The substrate supports the positive electrode active material layer. The substrate may, for example, be in the form of a sheet. The substrate may, for example, have a thickness of 5 to 50 μm. The substrate may, for example, include a metal foil. The substrate may, for example, include at least one material selected from the group consisting of Al, Mn, Ti, Fe, and Cr. The substrate may, for example, include an Al foil, an Al alloy foil, a Ti foil, a stainless steel (SUS) foil, etc.

[0116] An intermediate layer may be formed between the substrate and the positive electrode active material layer. The intermediate layer does not contain the positive electrode active material. The intermediate layer may have a thickness of, for example, 0.1 to 5 μm. The intermediate layer may include, for example, a conductive material, an insulating material, a binder, etc. The conductive material may include, for example, carbon black, etc. The insulating material may include, for example, alumina, boehmite, aluminum hydroxide, etc. The binder may include, for example, PVdF, etc.

[0117] The positive electrode active material layer is disposed on the surface of the substrate. The positive electrode active material layer may be disposed on only one side of the substrate. The positive electrode active material layer may be disposed on both sides of the substrate. The thickness of the positive electrode active material layer may be, for example, 10 to 1000 μm, 50 to 500 μm, or 100 to 300 μm. The positive electrode active material layer comprises a positive electrode active material. The positive electrode active material layer may further comprise, for example, a conductive material and a binder.

[0118] The amount of conductive material may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of positive electrode active material. The conductive material may include any component. The conductive material may include, for example, at least one selected from the group consisting of graphite, AB, Ketjenblack, VGCF, CNT, and GF.

[0119] The amount of binder may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of positive electrode active material. The binder may include any component. The binder may include, for example, at least one selected from the group consisting of PVdF, vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), PTFE, CMC, PAA, PVA, PVP, polyoxyethylene alkyl ether, and derivatives thereof.

[0120] The positive electrode active material layer may further include, for example, inorganic fillers, organic fillers, solid electrolytes, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The positive electrode active material layer may also include, for example, polyoxyethyleneallylphenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0121] The positive electrode active material may be in the form of particles, for example. The D50 of the positive electrode active material may be, for example, 1 to 30 μm, 10 to 20 μm, or 1 to 10 μm. The positive electrode active material may include any component. The positive electrode active material may include, for example, transition metal oxides, polyanion compounds, etc. Within a single particle (positive electrode active material), the composition may be either uniform or non-uniform. For example, the composition may be inclined from the surface of the particle toward the center. The change in composition may be either continuous or discontinuous (step-by-step).

[0122] < Transition Metal Oxide (Space Group R-3m) >

[0123] Transition metal oxides may have any crystal structure. Transition metal oxides may include, for example, crystal structures belonging to the space group R-3m. For example, a compound represented by the general formula "LiMO2" may have a crystal structure belonging to the space group R-3m. Transition metal oxides may be represented, for example, by the following formula.

[0124]

[0125] Among the above formulas, the relationships -0.5≤a≤0.5 and 0≤x≤1 are satisfied. M may include, for example, at least one type selected from the group consisting of Co, Mn and Al. Among the above formulas, x may satisfy, for example, the relationships 0<x≤0.1, 0.1≤x≤0.2, 0.2≤x≤0.3, 0.3≤x≤0.4, 0.4≤x≤0.5, 0.5≤x≤0.6, 0.6≤x≤0.7, 0.7≤x≤0.8, 0.8≤x≤0.9, or 0.9≤x≤1. a may satisfy, for example, the relationships -0.4≤a≤0.4, -0.3≤a≤0.3, -0.2≤a≤0.2, or -0.1≤a≤0.1.

[0126] Transition metal oxides are, for example, LiCoO2, LiMnO2, LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 It may include at least one selected from the group consisting of O2 and LiNiO2.

[0127] < NCM >

[0128] Transition metal oxides may be represented, for example, by the following formula. Compounds represented by the following formula may also be called "NCM".

[0129]

[0130] Among the above equations, the relationships -0.5≤a≤0.5, 0<x<1, 0<y<1, 0<z<1, and x+y+z=1 are satisfied. x may satisfy, for example, the relationships 0<x≤0.1, 0.1≤x≤0.2, 0.2≤x≤0.3, 0.3≤x≤0.4, 0.4≤x≤0.5, 0.5≤x≤0.6, 0.6≤x≤0.7, 0.7≤x≤0.8, 0.8≤x≤0.9, or 0.9≤x<1. y may satisfy, for example, 0<y≤0.1, 0.1≤y≤0.2, 0.2≤y≤0.3, 0.3≤y≤0.4, 0.4≤y≤0.5, 0.5≤y≤0.6, 0.6≤y≤0.7, 0.7≤y≤0.8, 0.8≤y≤0.9, or 0.9≤y<1. z may satisfy, for example, 0<z≤0.1, 0.1≤z≤0.2, 0.2≤z≤0.3, 0.3≤z≤0.4, 0.4≤z≤0.5, 0.5≤z≤0.6, 0.6≤z≤0.7, 0.7≤z≤0.8, 0.8≤z≤0.9, or 0.9≤z<1.

[0131] NCM is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, and, LiNi 0.9 Co 0.05 Mn 0.05 It may include at least one type selected from the group consisting of O2.

[0132] < NCA >

[0133] Transition metal oxides may be represented, for example, by the following formula. A compound represented by the following formula may also be called "NCA".

[0134]

[0135] Among the above equations, the relationships -0.5≤a≤0.5, 0<x<1, 0<y<1, 0<z<1, and x+y+z=1 are satisfied. x may satisfy, for example, the relationships 0<x≤0.1, 0.1≤x≤0.2, 0.2≤x≤0.3, 0.3≤x≤0.4, 0.4≤x≤0.5, 0.5≤x≤0.6, 0.6≤x≤0.7, 0.7≤x≤0.8, 0.8≤x≤0.9, or 0.9≤x<1. y may satisfy, for example, 0<y≤0.1, 0.1≤y≤0.2, 0.2≤y≤0.3, 0.3≤y≤0.4, 0.4≤y≤0.5, 0.5≤y≤0.6, 0.6≤y≤0.7, 0.7≤y≤0.8, 0.8≤y≤0.9, or 0.9≤y<1. z may satisfy, for example, 0<z≤0.1, 0.1≤z≤0.2, 0.2≤z≤0.3, 0.3≤z≤0.4, 0.4≤z≤0.5, 0.5≤z≤0.6, 0.6≤z≤0.7, 0.7≤z≤0.8, 0.8≤z≤0.9, or 0.9≤z<1.

[0136] NCA is, for example, LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1 Al 0.1 O2, LiNi 0.8 Co 0.17 Al 0.03 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, and, LiNi 0.9 Co 0.05 Al 0.05 It may include at least one type selected from the group consisting of O2.

[0137] Multicomponent system

[0138] The positive electrode active material may include, for example, two or more types of NCM, etc. The positive electrode active material may include, for example, NCM (0.6 ≤ x), NCM (x < 0.6). "NCM (0.6 ≤ x)" is the above formula "Li 1-a Ni x Co y Mn z In "O2," it refers to a compound where x (Ni ratio) is 0.6 or higher. NCM (0.6 ≤ x) can also be called, for example, "high-nickel materials." NCM (0.6 ≤ x) is, for example, LiNi 0.8 Co 0.1 Mn 0.1 Includes O2, etc. "NCM(x<0.6)" is the above formula "Li 1-a Ni x Co y Mn z In "O2", it represents a compound where x (Ni ratio) is less than 0.6. NCM(x<0.6) is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 It includes O2, etc. The mixing ratio (mass ratio) of NCM (0.6≤x) and NCM (x<0.6) may be any of, for example, “NCM(0.6≤x) / NCM(x<0.6)=9 / 1 to 1 / 9”, “NCM(0.6≤x) / NCM(x<0.6)=9 / 1 to 4 / 6”, or “NCM(0.6≤x) / NCM(x<0.6)=9 / 1 to 3 / 7”.

[0139] The positive electrode active material may include, for example, NCA and NCM. The mixing ratio (mass ratio) of NCA and NCM may be, for example, any of “NCA / NCM = 9 / 1 to 1 / 9”, “NCA / NCM = 9 / 1 to 4 / 6”, or “NCA / NCM = 9 / 1 to 3 / 7”. The Ni ratio between NCA and NCM may be the same or different. The Ni ratio of NCA may be higher than the Ni ratio of NCM. The Ni ratio of NCA may be lower than the Ni ratio of NCM.

[0140] < Transition Metal Oxides (Space Group C2 / m) >

[0141] Transition metal oxides may include, for example, crystal structures belonging to the space group C2 / m. Transition metal oxides may be represented, for example, by the following formula.

[0142]

[0143] In the above formula, M may include at least one selected from the group consisting of, for example, Ni, Co, Mn, and Fe. The positive electrode active material may include, for example, a mixture of LiMO2 (space group R-3m) and Li2MO3 (space group C2 / m). The positive electrode active material may include, for example, a solid solution of LiMO2 and Li2MO3 (Li2MO3-LiMO2).

[0144] < Transition metal oxide (space group Fd-3m) >

[0145] Transition metal oxides may include, for example, crystal structures belonging to the space group Fd-3m. Transition metal oxides may be represented, for example, by the following formula.

[0146]

[0147] Among the above formulas, the relationship 0≤x≤2 is satisfied. M may include at least one type selected from the group consisting of, for example, Ni, Fe, and Zn.

[0148] LiM2O4 (space group Fd-3m) is, for example, LiMn2O4, and, LiMn 1.5 Ni 0.5It may include at least one selected from the group consisting of O4. The positive electrode active material may include, for example, a mixture of LiMO2 (space group R-3m) and LiM2O4 (space group Fd-3m). The mixing ratio (mass ratio) of LiMO2 (space group R-3m) and LiM2O4 (space group Fd-3m) may be, for example, any of “LiMO2 / LiM2O4 = 9 / 1 to 1 / 9”, “LiMO2 / LiM2O4 = 9 / 1 to 5 / 5”, or “LiMO2 / LiM2O4 = 9 / 1 to 7 / 3”.

[0149] Polyanion compounds

[0150] Polyanion compounds may include, for example, phosphates (e.g., LiFePO4, etc.), silicates, borates, etc. Polyanion compounds may be represented, for example, by the group of formulas below.

[0151]

[0152]

[0153]

[0154]

[0155] Among the above formula group, M may include at least one selected from the group consisting of, for example, Fe, Mn, and Co. The above formula "Li 2-x Among MPO4F, for example, the relationship 0≤x≤2 may be satisfied.

[0156] The positive electrode active material may include, for example, a mixture of LiMO2 (space group R-3m) and a polyanion compound. The mixing ratio (mass ratio) of LiMO2 (space group R-3m) and the polyanion compound may be, for example, “LiMO2 / polyanion compound = 9 / 1 to 1 / 9”, “LiMO2 / polyanion compound = 9 / 1 to 5 / 5”, or “LiMO2 / polyanion compound = 9 / 1 to 7 / 3”.

[0157] Dopant

[0158] A dopant may be added to the positive electrode active material. The dopant may be diffused throughout the particle or locally distributed. For example, the dopant may be localized on the particle surface. The dopant may be a substitutional solid solution atom or an interstitial solid solution atom. The amount of dopant added (molar fraction relative to the total positive electrode active material) may be, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1%. One or more types of dopants may be added. Two or more types of dopants may form a complex.

[0159] The dopant may include at least one selected from the group consisting of, for example, B, C, N, halogen, Si, Na, Mg, Al, Mn, Co, Cr, Sc, Ti, V, Cu, Zn, Ga, Ge, Se, Sr, Y, Zr, Nb, Mo, In, Pb, Bi, Sb, Sn, W, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and actinoid.

[0160] For example, the group of "Zr, Mg, W, Sm", the group of "Ti, Mn, Nb, Si, Mo", or the group of "Er, Mg" may be added to NCA. For example, Ti may be added to NCM. For example, the group of "Zr, W", the group of "Si, W", or the group of "Zr, W, Al, Ti, Co" may be added to NCM.

[0161] < Surface coating >

[0162] The positive electrode active material may form composite particles. The composite particles may include, for example, a core particle and a coating layer. The core particle contains the positive electrode active material. The coating layer covers at least a portion of the surface of the core particle. The thickness of the coating layer may be, for example, 1 to 3000 nm, 5 to 2000 nm, 10 to 1000 nm, 10 to 100 nm, or 10 to 50 nm. The thickness of the coating layer may be measured, for example, from an SEM image of the particle cross-section. That is, a sample is prepared by embedding the composite particle in a resin material. Cross-sectional processing is performed on the sample using an ion milling device. The cross-section of the sample is observed by SEM. For 10 composite particles, the thickness of the coating layer is measured at 20 fields of view for each. The arithmetic mean of the thicknesses at a total of 200 locations is used.

[0163] The proportion of the surface of the core particle that is covered by the coating layer is also called the “coverage rate.” The coverage rate may be, for example, 1% or more, 10% or more, 30% or more, 50% or more, or 70% or more. The coverage rate may be, for example, 100% or less, 90% or less, or 80% or less.

[0164] The coverage rate can be measured, for example, by XPS (X-ray Photoelectron Spectroscopy). A powder sample consisting of composite particles is set in the XPS. Narrow scan analysis is performed. The measurement data is processed by interpretation software. As the measurement data is interpreted, multiple types of elements are detected. The ratio of each detected element is calculated from the area of ​​each peak. The coverage rate is calculated by the following formula.

[0165]

[0166] γ: Coverage rate [%]

[0167] I0: Ratio of elements originating from the core particle

[0168] I1: Proportion of elements originating from the cladding layer

[0169] For example, if the core particles contain NCM, I0 represents the total elemental ratio of "Ni, Co, Mn". For example, if the core particles contain NCA, I0 represents the total elemental ratio of "Ni, Co, Al". For example, if the coating layer contains P and B, I1 represents the total elemental ratio of "P and B".

[0170] The coating layer may include any component. The coating layer may include, for example, elements, organic materials, inorganic salts, organic salts, hydroxides, oxides, carbides, nitrides, sulfides, halides, etc. The coating layer is, for example, B, Al, W, Zr, Ti, Co, F, lithium compounds (e.g., Li2CO3, LiHCO3, LiOH, Li2O, etc.), tungsten oxide (e.g., WO3, etc.), titanium oxide (e.g., TiO2, etc.), zirconium oxide (e.g., ZrO2), boron oxide, boron phosphate (e.g., BPO4, etc.), aluminum oxide (e.g., Al2O3, etc.), boehmite, aluminum hydroxide, phosphates [e.g., Li3PO4, (NH4)3PO4, AlPO4], borates (e.g., Li2B4O7, LiBO3, etc.), polyacrylates (Li salts, Na salts, NH4 salts, etc.), acetates (e.g., Li salts, etc.), CMC (CMC-Na, CMC-Li, CMC-NH4, etc.), LiNbO3, Li2TiO3, and Li-containing halides (e.g., LiAlCl4, It may include at least one selected from the group consisting of LiTiAlF6, LiYBr6, LiYCl6, etc.

[0171] < Hollow Particles / Solid Particles >

[0172] Both hollow particles and solid particles are secondary particles. For "hollow particles," the ratio of the central cavity area in the cross-sectional image is 30% or more of the total cross-sectional area of ​​the particle. The ratio of the cavity in the hollow particles may be, for example, 40% or more, 50% or more, or 60% or more. For "solid particles," the ratio of the central cavity area in the cross-sectional image of the particle is less than 30% of the total cross-sectional area of ​​the particle. The ratio of the cavity in the solid particles may be, for example, 20% or less, 10% or less, or 5% or less. The positive electrode active material may be a hollow particle or a solid particle. A mixture of hollow particles and solid particles may also be used. The mixing ratio (mass ratio) between hollow particles and solid particles may be any of, for example, “hollow particles / solid particles = 1 / 9 to 9 / 1”, “hollow particles / solid particles = 2 / 8 to 8 / 2”, “hollow particles / solid particles = 3 / 7 to 7 / 3”, or “hollow particles / solid particles = 4 / 6 to 6 / 4”.

[0173] < Large particle / Elementary particle >

[0174] "Electrode active material" is a general term for positive electrode active material and negative electrode active material. The electrode active material may, for example, have a unimodal particle size distribution (based on number). The electrode active material may, for example, have a multimodal particle size distribution. The electrode active material may, for example, have a bimodal particle size distribution. That is, the electrode active material may contain large particles and small particles. When the particle size distribution is bimodal, the particle size corresponding to the peak top of the larger particle size is the particle size of the large particle (d L It is considered to be ). The particle size corresponding to the peak top on the smaller particle size side is the particle size of the small particle (d S It is considered as ). Particle size ratio (d L / d S ) may be, for example, any of 2 to 10, 2 to 5, or 2 to 4. dL It may be, for example, 8 to 20 μm, or 8 to 15 μm. d S For example, it may be either 1 to 10 μm or 1 to 5 μm.

[0175] For example, peak separation processing of the particle size distribution may be performed by waveform analysis software. Peak area originating from large particles (S L ) and peak area derived from small particles (S S The ratio with ) is, for example, "S L / S S = 1 / 9 to 9 / 1」, 「S L / S S = 5 / 5 to 9 / 1」 or 「S L / S S It may be any of =7 / 3 to 9 / 1.

[0176] The particle size distribution based on the number is measured by microscopy. Multiple cross-sectional samples are taken from the electrode active material layer. The cross-sectional samples may include, for example, a cross-section perpendicular to the surface of the electrode active material layer. For example, the surface to be observed is cleaned by ion milling or the like. The cross-sectional samples are observed by SEM. The magnification is adjusted so that 10 to 100 particles are included within the field of view. The ferret diameter of all particles within the image is measured. "Ferret diameter" represents the distance between the two furthest points on the particle's outline. By observing multiple cross-sectional samples, a total of 1,000 or more ferret diameters are obtained. A particle size distribution based on the number is created from the 1,000 or more ferret diameters.

[0177] A two-dimensional particle size distribution can be formed by mixing two types of particles. The two types of particles have different particle size distributions. For example, the two types of particles may have different D50s. The measurement sample is a powder. For example, the D50 of the large particles may be either 8 to 20 μm or 8 to 15 μm. For example, the D50 of the small particles may be either 1 to 10 μm or 1 to 5 μm. The ratio of the D50 of the large particles to the D50 of the small particles may be, for example, 2 to 10, 2 to 5, or 2 to 4. The mixing ratio (mass ratio) of the big particle and the small particle may be any of, for example, “big particle / small particle = 1 / 9 to 9 / 1”, “big particle / small particle = 5 / 5 to 9 / 1”, or “big particle / small particle = 7 / 3 to 9 / 1”.

[0178] In addition, the algebra and the subparticle may have the same composition or different compositions. For example, the algebra may be NCA and the subparticle may also be NCM. For example, the algebra may be NCM (0.6 ≤ x) and the subparticle may also be NCM (x < 0.6).

[0179] < Electrolyte >

[0180] The electrolyte is a liquid electrolyte. The electrolyte comprises a solute and a solvent. The concentration of the solute may be, for example, 0.5 to 1 mol / L, 1 to 1.5 mol / L, 1.5 to 2 mol / L, 2 to 2.5 mol / L, or 2.5 to 3 mol / L. "mol / L" may also be denoted as "M". The solute comprises a support salt (Li salt). The solute may comprise, for example, an inorganic salt, an imide salt, an oxalato complex, a halide, etc. The solute may include at least one selected from the group consisting of, for example, LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2 "LiFSI", LiN(SO2CF3)2 "LiTFSI", LiB(C2O4)2 "LiBOB", LiBF2(C2O4) "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0181] The electrolyte may include, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may include, for example, cyclic carbonates, chain carbonates, fluorinated carbonates, etc. The solvent may include, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and derivatives thereof.

[0182] The solvent may include cyclic carbonates (EC, PC, FEC, etc.) and chain carbonates (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonates and chain carbonates may be, for example, any of “cyclic carbonates / chain carbonates = 1 / 9 to 4 / 6”, “cyclic carbonates / chain carbonates = 2 / 8 to 3 / 7”, or “cyclic carbonates / chain carbonates = 3 / 7 to 4 / 6”.

[0183] The solvent may include a cyclic carbonate (EC, PC, etc.) and a fluorinated cyclic carbonate (FEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate and the fluorinated cyclic carbonate may be, for example, “cyclic carbonate / fluorinated cyclic carbonate = 99 / 1 to 90 / 10”, “cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 1 / 9”, “cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 7 / 3”, or “cyclic carbonate / fluorinated cyclic carbonate = 3 / 7 to 1 / 9”.

[0184] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy the relationship represented by, for example, the following formula.

[0185]

[0186] Among the above formulas, V EC , V FEC , V EMC , V DMC , V DEC represents the volume ratios of EC, FEC, EMC, DMC, and DEC, respectively.

[0187] 1≤V EC ≤4, 0≤V FEC ≤3, V EC +V FEC ≤4,

[0188] 0≤V EMC ≤9, 0≤V DMC ≤9, 0≤V DEC≤9, 6≤V EMC +V DMC +V DEC ≤9

[0189] The relationship is satisfied.

[0190] For example, 1≤V EC ≤2, or 2≤V EC It is acceptable if the relationship ≤3 is satisfied.

[0191] For example, 1≤V FEC ≤2, or 2≤V FEC It is acceptable if the relationship ≤4 is satisfied.

[0192] For example, 3≤V EMC ≤4, or 6≤V EMC It is acceptable if the relationship ≤8 is satisfied.

[0193] For example, 3≤V DMC ≤4, or 6≤V DMC It is acceptable if the relationship ≤8 is satisfied.

[0194] For example, 3≤V DEC ≤4, or 6≤V DEC It is acceptable if the relationship ≤8 is satisfied.

[0195] The solvent may have a composition in volume ratio such as, for example, “EC / EMC = 3 / 7”, “EC / DMC = 3 / 7”, “EC / FEC / DEC = 1 / 2 / 7”, “EC / DMC / EMC = 3 / 4 / 3”, “EC / DMC / EMC = 3 / 3 / 4”, “EC / FEC / DMC / EMC = 2 / 1 / 4 / 3”, “EC / FEC / DMC / EMC = 1 / 2 / 4 / 3”, “EC / FEC / DMC / EMC = 2 / 1 / 3 / 4”, and “EC / FEC / DMC / EMC = 1 / 2 / 3 / 4”.

[0196] The electrolyte may include an ether-based solvent. The electrolyte may include, for example, at least one selected from the group consisting of tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylglyme, triglyme, tetraglyme, and derivatives thereof.

[0197] The electrolyte may contain any additives. The amount of additive (mass fraction relative to the total electrolyte) may be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additives may include, for example, solid electrolyte interphase (SEI) formation promoters, SEI formation inhibitors, gas generators, overcharge prevention agents, flame retardants, antioxidants, electrode protective agents, surfactants, etc.

[0198] Additives include, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), 1,3-propanesulfone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), propanesulfone (PS), ethylene sulfate (DTD), γ-butyrolactone, phosphazene compounds, carboxylic acid esters [e.g., methyl formate (MF), methyl acetate (MA), methylpropionate (MP), diethyl malonate (DEM), etc.], fluorobenzene [e.g., monofluorobenzene (FB), 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, etc.), fluorotoluene (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzotrifluoride (e.g., benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, 2-methylbenzotrifluoride, 3-methylbenzotrifluoride, 4-methylbenzotrifluoride, etc.), fluoroxylene (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methylbenzothiazole, tetrathiafulvalene, etc.), nitrile compounds (e.g., adiponitrile, succinonitrile, etc.), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate, etc.), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, etc.), alcohols (e.g., methanol, ethanol,It may include at least one selected from the group consisting of n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether, etc.), and derivatives thereof.

[0199] The aforementioned components as solutes and solvents may be used as trace components (additives). The additive may include, for example, at least one selected from the group consisting of LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and derivatives thereof.

[0200] The electrolyte may contain an ionic liquid. The ionic liquid may contain, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholium salts, phosphonium salts, imidazolium salts, and derivatives thereof.

[0201] Gel Electrolyte >

[0202] The battery (1000) may include a gel electrolyte. The gel electrolyte may include an electrolyte and a polymer material. The polymer material may form a polymer matrix. The polymer material may include, for example, at least one selected from the group consisting of PVdF, PVdF-HFP, PAN, PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0203] Separator

[0204] The separator (300) can separate the positive electrode from the negative electrode. The separator (300) has electrical insulation properties. The separator (300) may include at least one selected from the group consisting of, for example, a resin film, an inorganic particle layer, and an organic particle layer. The separator (300) may include, for example, a resin film and an inorganic particle layer.

[0205] The resin film is porous. The resin film may include, for example, a microporous film, a nonwoven fabric, etc. The resin film includes a resin backbone. The resin backbone may be continuous in a network form, for example. Pores are formed in the gaps of the resin backbone. The resin film can permeate an electrolyte. The resin film may have, for example, an average pore diameter of 1 μm or less. The resin film may have, for example, an average pore diameter of 0.01 to 1 μm or 0.1 to 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The resin film may have, for example, a Gurley value of 50 to 250 s / 100 cm³. The "Gurley value" can be measured by the Gurley test method.

[0206] The resin film may comprise at least one selected from the group consisting of, for example, olefin resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin, acrylic resin, and polyester resin. The resin film may comprise at least one selected from the group consisting of, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamideimide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film may be formed, for example, by a stretching method, a phase separation method, etc. The thickness of the resin film may be, for example, 5 to 50 μm or 10 to 25 μm.

[0207] The resin film may, for example, have a single-layer structure. The resin film may, for example, be composed of a PE layer. The framework of the PE layer is formed by PE. The PE layer may have a shutdown function. The resin film may, for example, have a multi-layer structure. The resin film may, for example, include a PP layer and a PE layer. The framework of the PP layer is formed by PP. The resin film may, for example, have a three-layer structure. The resin film may, for example, be formed by stacking a PP layer, a PE layer, and a PP layer in this order. The thickness of the PE layer may, for example, be 5 to 20 μm. The thickness of the PP layer may, for example, be 3 to 10 μm.

[0208] The inorganic particle layer may be formed on the surface of the resin film. The inorganic particle layer may be formed on only one side of the resin film or on both sides. The inorganic particle layer may be formed on the surface facing the positive electrode or on the surface facing the negative electrode. Additionally, the inorganic particle layer may be formed on the surface of the positive electrode or on the surface of the negative electrode.

[0209] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles may also be called "inorganic fillers." Pores are formed in the spaces between the inorganic particles. The thickness of the inorganic particle layer may be, for example, 0.5 to 10 μm or 1 to 5 μm. The inorganic particles may include, for example, a heat-resistant material. An inorganic particle layer containing a heat-resistant material is also called a "Heat Resistance Layer (HRL)." The inorganic particles may include at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles may have any shape. The inorganic particles may be, for example, spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles may be, for example, 0.1 to 10 μm or 0.5 to 3 μm. The inorganic particle layer may further include a binder. The binder may include at least one selected from the group consisting of, for example, acrylic resin, polyamide resin, fluorine resin, aromatic polyether resin, and liquid crystal polyester resin.

[0210] The separator (300) may include, for example, an organic particle layer. The separator (300) may include, for example, an organic particle layer instead of a resin film. The separator (300) may include, for example, an organic particle layer instead of an inorganic particle layer. The separator (300) may include both a resin film and an organic particle layer. The separator (300) may include both an inorganic particle layer and an organic particle layer. The separator (300) may include a resin film, an inorganic particle layer, and an organic particle layer.

[0211] The thickness of the organic particle layer may be, for example, 0.1 to 50 μm, 0.5 to 20 μm, 0.5 to 10 μm, or 1 to 5 μm. The organic particle layer comprises organic particles. The organic particles may also be referred to as "organic fillers." The organic particles may include a heat-resistant material. The organic particles may include at least one selected from the group consisting of, for example, PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be, for example, spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the organic particles may be, for example, 0.1 to 10 μm, or 0.5 to 3 μm.

[0212] The separator (300) may, for example, include a mixing layer. The mixing layer includes both inorganic particles and organic particles.

[0213] < Battery Composition >

[0214] FIG. 7 is a table showing a first battery configuration. FIG. 8 is a table showing a second battery configuration. FIG. 9 is a table showing a third battery configuration. In each table, if multiple types of materials are listed in a column, said listing includes each material alone and combinations thereof. For example, if materials “α, β, γ” are listed in a column, said listing indicates “at least one type selected from the group consisting of α, β, and γ.” Any element may be extracted from each of the first battery configuration, the second battery configuration, and the third battery configuration, and may also be arbitrarily combined.

[0215] [Example]

[0216] < Production of Test Cells >

[0217] Figure 10 is a table showing the experimental results. Test cells (monopolar cells) related to No. 1 to No. 18 were manufactured in the following order.

[0218] Manufacturing of negative poles

[0219] The following materials have been prepared.

[0220] Graphite: Artificial graphite (D50: 22 µm, aspect ratio: see Fig. 10)

[0221] Binder: SBR

[0222] Thickener: CMC

[0223] Dispersion medium: water

[0224] Substrate: Cu foil (thickness: 15 µm)

[0225] (a) Formation of the first layer

[0226] A first slurry was prepared by mixing graphite, a binder, a thickener, and a dispersion medium. The composition of the solids was “graphite / binder / thickener = 98.4 / 1.2 / 0.4 (mass ratio)”. That is, the composition ratio of the binder in the first slurry was 1.2. The viscosity of the first slurry was adjusted to 25,000 mPa·s. A first layer was formed by applying the first slurry to a substrate using a doctor blade.

[0227] (b) Formation of the second layer

[0228] A second slurry was prepared by mixing graphite, a binder, a thickener, and a dispersion medium. The composition of the solids was “graphite / binder / thickener = 97.8 / 1.8 / 0.4 (mass ratio).” That is, the composition ratio of the binder in the second slurry was 1.8. The viscosity of the second slurry was adjusted to 12,000 mPa·s. A second layer was formed by applying the second slurry over the first slurry using a doctor blade.

[0229] (c) Magnetic field orientation

[0230] A magnetic field was applied to the film (layer 1 and layer 2) for 10 minutes.

[0231] (d) Drying

[0232] A negative electrode active material layer was formed by drying the film at 50°C.

[0233] (e) compression

[0234] The negative electrode active material layer was compressed. After compression, the density of the negative electrode active material layer was 1.25 g / cm³. The thickness of the negative electrode active material layer is shown in Fig. 10. The basis weight of the first layer was 7 mg / cm². The basis weight of the second layer was 20 mg / cm².

[0235] A negative electrode was manufactured from the above. XRD measurements of the negative electrode were performed. In the cross-section of the negative electrode active material layer, the orientation angle of each layer was measured.

[0236] production of straight plays

[0237] The following materials have been prepared.

[0238] Positive electrode active material: LiNi 0.8 Co 0.1 Mn 0.1 O2

[0239] Conductive material: CNT

[0240] Binder: PVdF

[0241] Dispersion medium: N-methyl-pyrrolidone

[0242] Substrate: Aluminum foil (Thickness: 30 µm)

[0243] A slurry was prepared by mixing a positive electrode active material, a conductive material, a binder, and a dispersion medium. The composition of the solids was “positive electrode active material / conductive material / binder = 97.8 / 0.8 / 1.4 (mass ratio).” A positive electrode active material layer was formed by applying the slurry to a substrate using a doctor blade. The positive electrode active material layer was dried. The drying temperature was 90°C, and the drying time was 10 minutes. A positive electrode was manufactured by compressing the positive electrode active material layer. After compression, the density of the positive electrode active material layer was 3.3 g / cm³. The basis weight of the positive electrode active material layer was adjusted so that the ratio of the negative electrode capacity to the positive electrode capacity was 1.1.

[0244] assembly

[0245] The following materials have been prepared.

[0246] Separator: 3-layer structure (PP layer / PE layer / PP layer), Thickness: 16 µm

[0247] Electrolyte: 1.1M LiPF6, EC / DMC / EMC = 3 / 4 / 3 (volume ratio)

[0248] Exterior: Pouch made of Al laminate film

[0249] A power generation element was formed by stacking the positive electrode, separator, and negative electrode in this order. A test cell was manufactured by encapsulating the power generation element in an outer casing.

[0250] Charge / Discharge Test >

[0251] Activation processing

[0252] As an initial charge, a constant current-constant voltage charging method was performed. Specifically, constant current charging was performed up to 4.25 V using a current of 0.1 C. After reaching 4.25 V, constant voltage charging was performed for 3 hours. After charging was completed, constant current discharge was performed down to 3.0 V using a current of 0.1 C. "C" is a symbol representing the time rate of the current. A current of 1 C discharges the theoretical capacity of the test cell in 1 hour.

[0253] Measurement of discharge rate

[0254] Constant current charging was performed up to 4.25 V with a current of 0.1 C. After reaching 4.25 V, constant voltage charging was performed for 3 hours. After charging was completed, constant current discharge was performed down to 3.0 V with a current of 1 C, and the discharge capacity was measured. The discharge rate was calculated by dividing the discharge capacity by the theoretical capacity.

[0255] < Result >

[0256] In FIG. 10, when the relationships of the following equations (1) to (3) are satisfied, a high discharge rate is observed.

[0257]

[0258]

[0259]

[0260] In addition, in the item "Orientation Angle Ratio" of FIG. 10, ">1" indicates that "θ2 / θ1" is greater than 1. In FIG. 10, the sample No. satisfying the above equations (1) to (3) is marked with a "*".

[0261] Figure 11 is a graph showing the relationship between the XRD intensity ratio and the discharge rate. As the XRD intensity ratio increases, the discharge rate tends to improve. When the XRD intensity ratio is 0.02 or higher, the discharge rate tends to improve easily.

[0262] Figure 12 is a graph showing the relationship between the aspect ratio of graphite and the discharge rate. When the aspect ratio exceeds 4, there is a tendency for the discharge rate to be difficult to improve. This is thought to be due to the influence of grain cracking during press processing. When the aspect ratio is less than 1.2, there is also a tendency for the discharge rate to be difficult to improve.

Claims

Claim 1 The apparatus comprises 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 comprises graphite and a binder, a first layer and a second layer are formed within the negative electrode active material layer, the first layer is formed between the substrate and the second layer, and satisfies the relationships of formulas (1) to (3). 1.5 ≤ m2 / m1 (2) Among the above formulas (1) to (3), A represents the aspect ratio of the graphite, m1 represents the mass fraction of the binder in the first layer, m2 represents the mass fraction of the binder in the second layer, θ1 represents the orientation angle of the graphite in the first layer, and θ2 represents the orientation angle of the graphite in the second layer, an electrode for a battery. Claim 2 In claim 1, further satisfying the relationship of Equation (4), and Among the above equation (4), I 110 E represents the diffraction intensity of the (110) plane in the X-ray diffraction profile of the above negative electrode active material layer, and also, I 002 A battery electrode, which represents the diffraction intensity of the (002) plane in the X-ray diffraction profile of the negative electrode active material layer. Claim 3 An electrode for a battery according to claim 1 or 2, wherein the negative electrode active material layer has a thickness of 100 to 400 μm. Claim 4 In claim 1 or 2, further satisfying the relationship of formula (5), and In the above equation (5), T1 represents the thickness of the first layer, and T2 represents the thickness of the second layer, an electrode for a battery. Claim 5 A battery comprising a battery electrode as described in claim 1 or 2. Claim 6 (a) forming a first layer by applying a first slurry to the surface of a substrate, (b) forming a second layer by applying a second slurry on top of the first layer, (c) applying a magnetic field to the first layer and the second layer, and (d) forming a negative electrode active material layer by drying the first layer and the second layer, wherein each of the first slurry and the second slurry comprises graphite, a binder, and a dispersion medium, and satisfies the relationships of formulas (1), (6), and (7). 1.5 ≤ r2 / r1 (7) In the above formulas (1), (6) and (7), A represents the aspect ratio of the graphite, η1 represents the viscosity of the first slurry, η2 represents the viscosity of the second slurry, r1 represents the mixing ratio of the binder in the solid content of the first slurry, and r2 represents the mixing ratio of the binder in the solid content of the second slurry, a method for manufacturing an electrode for a battery.

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