Battery electrode and battery

Abstract

The battery 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. A cross-section parallel to the thickness direction of the negative electrode active material layer includes a first region and a second region. In the thickness direction, the first region is disposed between the second region and the substrate. The first region includes a first active material and a first binder. The second region includes a second active material and a second binder. The relationship of 'A2lt, A1' and 'B2lt, B1' is satisfied, or the relationship of 'A2gt, A1' and 'B2gt, B1' is satisfied. A1 represents the aspect ratio of the first active material. A2 represents the aspect ratio of the second active material. B1 represents the area fraction of the first adhesive in the first region. B2 represents the area fraction of the second binder in the second region.

Description

Technical Field

[0001] The present disclosure relates to a battery electrode and a battery. Background Art

[0002] Japanese Patent Application Laid-Open No. 10-284059 discloses an electrode in which a binder is distributed more at an interface between a negative electrode material layer and a current collector than at an outer surface of the negative electrode material layer. Summary of the invention

[0003] Research has been conducted on orienting active materials in the negative electrode active material layer. For example, by using active materials with a large aspect ratio, the active materials can be oriented in the negative electrode active material layer. By orienting the active materials, it is expected that the rate performance will be improved. However, in general, during the manufacturing process of the electrode, the negative electrode active material layer is subjected to pressurization. During the pressurization, the active material is crushed, and the orientation state of the active material may be destroyed.

[0004] The present disclosure is directed to improvement of rate performance.

[0005] The following describes the structure and effects of the technology disclosed in the present invention. However, the mechanism of action includes assumptions. The mechanism of action does not limit the technical scope of the present invention.

[0006] 1. A battery electrode comprises a substrate and a negative electrode active material layer. The negative electrode active material layer is disposed on the surface of the substrate. A cross section parallel to the thickness direction of the negative electrode active material layer comprises a first region and a second region. In the thickness direction, the first region is disposed between the second region and the substrate. The first region comprises a first active material and a first binder. The second region comprises a second active material and a second binder. The relationship between the following formula (1) and formula (2) is satisfied, or the relationship between the following formula (3) and formula (4) is satisfied. A2 <A1 (1) B2<B1 (2) A2> A1 (3) B2>B1 (4) In formulas (1) to (4), A1 represents the aspect ratio of the first active material, A2 represents the aspect ratio of the second active material, B1 represents the area fraction of the first binder in the first region, and B2 represents the area fraction of the second binder in the second region.

[0007] The first region is closer to the substrate than the second region. The aspect ratio of the active material is different between the first region and the second region. The area fraction of the binder at the cross section of the negative electrode active material layer represents the amount of binder present. The amount of binder present is different between the first region and the second region. As shown in the relationship between the above-mentioned formula (1) and formula (2), or the relationship between the above-mentioned formula (3) and formula (4), in the first region and the second region, the area where the aspect ratio of the active material is relatively large, the amount of binder present is relatively large. In the area containing the active material with a large aspect ratio, the active material can be oriented more strongly. In this area, by making the amount of binder present more, it can be expected that the orientation state of the active material is more strongly fixed. Furthermore, for the area on the other side, the aspect ratio of the active material is relatively small, and the amount of binder present is relatively small, so it can function as a buffer during press processing. As a result, the load on the oriented active material can be reduced. That is, during press processing, it can be expected that the orientation state of the active material is difficult to destroy. By maintaining the orientation state of the active material, it can be expected to promote ion conduction.

[0008] The binder may hinder ion conduction. If the amount of binder in the negative electrode active material layer is too large, the rate performance may be reduced. In the first region and the second region, by reducing the amount of binder in one region, the desired ion conduction can be expected as a whole of the negative electrode active material layer. Through the complementary effects of the above, the rate performance can be expected to be improved.

[0009] 2. The battery electrode described in the above-mentioned "1" may have the following configuration, for example. The negative electrode active material layer has a curvature of 1.8 or less.

[0010] The smaller the curvature, the more improvement in rate performance can be expected. In the negative electrode active material layer, by making the orientation state of the active material good, a curvature of 1.8 or less can be achieved.

[0011] 3. The battery electrode described in the above-mentioned "1" or "2" may include the following configuration, for example. The following relationship of formula (5) is also satisfied. 0.05≤I 110 / I 002 (5) In formula (5), I 110 It represents the diffraction intensity of the (110) plane in the X-ray diffraction spectrum of the negative electrode active material layer. 002 It shows the diffraction intensity of the (002) plane in the X-ray diffraction pattern of the negative electrode active material layer.

[0012] “I 110 / I 002" is an indicator of the orientation state. 110 / I 002 ” is also called “orientation degree”. The larger the value of the orientation degree is, the more improvement in rate performance can be expected. In the negative electrode active material layer, by making the orientation state of the active material good, an orientation degree of 0.05 or more can be achieved.

[0013] 4. The battery electrode described in any one of the above “1” to “3” may have the following configuration, for example. Among the relationship between the above-mentioned formula (1) and formula (2) and the relationship between the above-mentioned formula (3) and formula (4), only the relationship between formula (1) and formula (2) is satisfied.

[0014] By arranging the active material with a large aspect ratio in the first region, the active material can be strongly oriented in the first region. During the press working, the first region (lower layer) does not directly contact the roller. Therefore, during the press working, it can be expected that the orientation state of the first region is difficult to be destroyed.

[0015] 5. The battery electrode described in any one of the above “1” to “4” may have the following configuration, for example. The first active material and the second active material each independently include artificial graphite.

[0016] 6. The battery electrode described in any one of the above “1” to “5” may have the following configuration, for example. The negative electrode active material layer has a 20 mg / cm 2 The negative electrode active material layer has a mass per unit area of ​​1.1 g / cm 3 Up to 1.6g / cm 3 density.

[0017] High density electrodes can have 20mg / cm 2 The mass per unit area and 1.1g / cm 3 Up to 1.6g / cm 3 In a high-density electrode, a large load is applied to the active material during press processing, so there is a tendency for the orientation state of the active material to be easily destroyed. According to the above-mentioned structure of "1", a good orientation state can be expected even in a high-density electrode.

[0018] 7. The battery electrode described in any one of the above “1” to “6” may have the following configuration, for example. The following relationship (6) is also satisfied. 0.5≤Tx / (T1+T2)≤0.7 (6) In formula (6), T1 represents the thickness of the first region. T2 represents the thickness of the second region. When the relationship of formula (1) is satisfied, Tx represents the thickness of the first region. When the relationship of formula (3) is satisfied, Tx represents the thickness of the second region.

[0019] In the region containing the active material with a large aspect ratio, the active material can be strongly oriented. By making the ratio of the thickness of the region where the active material is strongly oriented more than 50% of the whole, it can be expected that the rate performance can be improved. In the region where the active material is strongly oriented, the amount of binder present is also large. By making the ratio of this region less than 70%, it can be expected that the amount of binder present is within an appropriate range.

[0020] 8. The battery electrode described in any one of the above “1” to “7” may have the following configuration, for example. The following relationship (7) is also satisfied. 1.8%≤|B1-B2| (7)

[0021] When the absolute value of the difference between the area fraction of the binder in the first region and the area fraction of the binder in the second region is 1.8% or more, a desired alignment state tends to be easily achieved.

[0022] 9. The battery electrode described in any one of the above “1” to “8” may have the following configuration, for example. The following relationship (8) is also satisfied. 1.8≤Ax (8) In the formula (8), when the relationship of the formula (1) is satisfied, Ax represents the aspect ratio of the first active material. When the relationship of the formula (3) is satisfied, Ax represents the aspect ratio of the second active material.

[0023] When the active material has an aspect ratio of 1.8 or more, a desired orientation state tends to be easily achieved.

[0024] 10. A battery comprising the battery electrode described in any one of "1" to "9" above.

[0025] The following describes an embodiment of the present disclosure (hereinafter may be referred to as "the present embodiment") and an example of the present disclosure (hereinafter may be referred to as "the present example"). However, the present embodiment and the present example do not limit the technical scope of the present disclosure. The present embodiment and the present example are illustrative in all aspects. The present embodiment and the present example are non-restrictive. The technical scope of the present disclosure includes all changes within the meaning and scope equivalent to the description of the claims. For example, it is intended from the outset to extract arbitrary structures from the present embodiment and combine them arbitrarily.

[0026] The above and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of the present disclosure when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic cross-sectional view showing an example of the battery electrode in this embodiment. Figure 2 This is an example of mapping analysis of a cross section of a negative electrode active material layer. Figure 3 This is a schematic flowchart of the method for producing a battery electrode in this embodiment. Figure 4 This is a conceptual diagram showing an example of a battery in this embodiment. Figure 5 : is a table showing the first battery configuration. Figure 6 : is a table showing the second battery configuration. Figure 7 : is a table showing the third battery configuration. Figure 8 is a table showing the experimental results. Fig. 9 This is a cross-sectional SEM image of the first region and the second region in No. 1-1. Fig.10 This is the discharge curve when discharging at 1C. DETAILED DESCRIPTION

[0028] <Terms and Phrases> "Having", "including", "having" and their variations are open terms. In addition to the essential elements, an open term may or may not contain additional elements. The statement "consisting of..." is a closed term. However, even a composition expressed in a closed term may contain commonly accompanying impurities or additional elements that are not related to the target technology. The statement "consisting essentially of..." is a semi-closed term. In a semi-closed term, it is allowed to add elements that do not substantially affect the basic and novel characteristics of the target technology.

[0029] The expressions "may" and "might" are used in a permissive sense, meaning "may", rather than in an obligatory sense, meaning "must".

[0030] The multiple steps, actions and operations included in various methods are not limited to the order of recording unless otherwise specified. For example, multiple steps can also be performed simultaneously. For example, multiple steps can also be performed in sequence.

[0031] Geometric terms should not be interpreted in a strict sense. Examples of geometric terms include "parallel", "perpendicular", and "orthogonal". For example, "parallel" may deviate slightly from "parallel" in the strict sense. Geometric terms may include tolerances and errors in design, operation, and manufacturing. There are cases where the dimensional relationships in the drawings are inconsistent with the actual dimensional relationships. In order to help readers understand, there are cases where the dimensional relationships in the drawings are changed. For example, there are cases where the length, width, thickness, etc. are changed. There are also cases where part of the structure is omitted.

[0032] Numerical ranges such as "m% to n%" include upper and lower limits unless otherwise specified. That is, "m% to n%" means a numerical range of "above m% and below n%". In addition, "above m% and below n%" includes "more than m% and less than n%". "Above" and "below" are represented by inequality signs "≤, ≥" with equal signs. "Exceeding" and "less than" are represented by inequality signs "<, >" that do not include equal signs. A numerical value arbitrarily selected from the numerical range can be used as a new upper limit or lower limit. For example, a new numerical range can be set by arbitrarily combining a numerical value within the numerical range with a numerical value recorded in other parts, tables, figures, etc. in this specification.

[0033] All numerical values ​​are modified by the term "about". The term "about" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximate values ​​that may vary depending on how the disclosed technology is used. All numerical values ​​may be represented by significant figures. Unless otherwise specified, the measured value may be an average value from multiple measurements. The number of measurements may be more than 3 times, more than 5 times, or more than 10 times. Generally, the more measurements are made, the more reliability of the average value can be expected to improve. The measured value may be rounded off based on the number of significant figures. The measured value may, for example, include errors associated with the detection limit of the measuring device, etc.

[0034] The "aspect ratio" is measured by the following method. A cross-section sample is prepared by cutting the negative electrode active material layer. The cross-section sample includes a cross section parallel to the thickness direction of the negative electrode active material layer. For example, the observed object portion can be purified using a CROSS SECTIONPOLISHER (registered trademark, cross-section polisher) or the like. A cross-section SEM image is obtained by observing the cross-section sample using a SEM (Scanning Electron Microscope). More than 5 cross-section SEM images can be prepared. In each cross-section SEM image, more than 10 active materials (particles) are randomly extracted. Among the extracted particles, the major axis diameter and the minor axis diameter are measured. The major axis diameter The diameter between the two points on the particle's contour that are the farthest apart. The aspect ratio is the ratio of the major axis to the minor axis. The arithmetic average of more than 50 aspect ratios is used.

[0035] The "area fraction" is measured by the following method. For example, in the cross-section sample of the negative electrode active material layer, the dyeing treatment of the binder can be implemented. For example, styrene-butadiene rubber (SBR) can be dyed with osmium oxide. Using SEM-EDX (Scanning Electron Microscope-Energy dispersive X-ray spectrometry), a mapping analysis of the binder is performed in the cross-section sample. Figure 2 This is an example of mapping analysis of a cross section of a negative electrode active material layer. In the negative electrode active material layer 220, white pixels correspond to the binder. Figure 2 In the example, the adhesive tends to be more in the area (first area 221) close to the substrate 210 than in the area (second area 222) far from the substrate 210. For example, in the first area 221, the pixels corresponding to the adhesive are counted. By dividing the number of pixels corresponding to the adhesive by the number of pixels in the first area 221 as a whole, the area fraction of the adhesive in the first area 221 is calculated. The area fraction is expressed as a percentage (%). The same is true for the area fraction of the adhesive in the second area 222.

[0036] The "degree of curvature" indicates a value obtained by the following formula. τ=(R ion ·A·K·ε) / 2d τ: curvature R ion :Ionic resistance A: Area of ​​negative electrode active material layer K: Conductivity of the electrolyte ε: Porosity of the negative electrode active material layer d: thickness of the negative electrode active material layer "Ionic resistance" is measured using the following steps. Impedance measurement of a symmetrical monomer is performed. A symmetrical monomer refers to a monomer in which two equivalent electrodes are symmetrically arranged in the monomer. The real component of the impedance at the extreme low frequency is measured. The value of three times the real component is regarded as the ionic resistance. The conductivity represents the measured value at 25°C. An electrolyte is sealed in a monomer having lithium (Li). In the monomer, the resistance at 10kHz is measured using the AC method. The conductivity is calculated based on the resistance.

[0037] The "degree of orientation" is measured using the following method. XRD (X-ray diffraction) is used to measure the XRD spectrum of the negative electrode active material layer. The X-ray source is CuKα line. The measurement range is "10°≤2θ≤90°". In the XRD spectrum, 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 002 ,I 110 ). As shown in the above formula (5), by I 110 Divide by I 002 , find the orientation degree (I 110 / I 002 ).

[0038] The stoichiometric composition formula represents a representative example of a compound. A compound may also have a non-stoichiometric composition. For example, "Al2O3" is not limited to a compound having a molar ratio (molar ratio) of "Al / O = 2 / 3". Unless otherwise specified, "Al2O3" represents a compound containing Al and O in any molar ratio. For example, the compound may be doped with trace elements. Al and O may also be partially replaced by other elements.

[0039] "Derivative" means a compound that has been changed by at least one selected from the group consisting of the introduction of a substituent, substitution of atoms, oxidation, reduction and other chemical reactions in a part of a compound as a parent. The change site can be either one or multiple. "Substituent" can include, for example, at least one selected from the group consisting of alkyl, alkenyl, alkynyl, cycloalkyl, unsaturated cycloalkyl, aromatic, heterocyclic, halogen (F, Cl, Br, I, etc.), OH, SH, CN, SCN, OCN, nitro, alkoxy, unsaturated alkoxy, amino, alkylamino, dialkylamino, aryloxy, acyl, alkoxycarbonyl, acyloxy, aryloxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, arylthio, sulfonyl, sulfinyl, urea, phosphoramido, sulfo, carboxyl, hydroxamic acid, sulfinyl, hydrazine, imino and silyl. These substituents may also be further substituted. In the case of two or more substituents, the substituents may be the same or different. Multiple substituents may also be bonded to each other to form a ring. In addition, derivatives of polymer compounds (resin materials) may also be referred to as "modified bodies".

[0040] The "copolymer" includes at least one selected from the group consisting of random type, statistical type, random type, alternating type, periodic type, block type and graft type.

[0041] "D50" represents a particle size at which the cumulative distribution of volume-based particle size distribution (cumulative distribution) reaches 50%. The particle size distribution can be measured by a laser diffraction method.

[0042] The "BET specific surface area" refers to a specific surface area measured by a gas adsorption method (BET single-point method). Nitrogen was used as the adsorption gas.

[0043] <Battery Electrodes> Hereinafter, the battery electrode may be referred to as "electrode". The electrode is in sheet form. The electrode may be applied to any purpose as long as it is for battery. For example, the electrode may be for monopolar battery (single-phase battery), bipolar battery, non-aqueous battery, lithium ion battery, etc.

[0044] Figure 1 2 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. Figure 1 The cross section 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 .

[0045] The substrate 210 supports the negative electrode active material layer 220. The substrate 210 may be, for example, in the form of a sheet. The thickness of the substrate 210 may be, for example, 1 μm to 50 μm, 3 μm to 30 μm, or 5 μm to 15 μm. The substrate 210 is conductive. The substrate 210 may include, for example, a metal foil. The substrate 210 may include, for example, at least one selected from the group consisting of 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, and the like. The substrate 210 may have, for example, a multilayer structure. For example, the substrate 210 may be formed by laminating a Cu foil and an Al foil.

[0046] 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 only on one side of the substrate 210. The negative electrode active material layer 220 may also 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 (surface) of the substrate 210, and the positive electrode active material layer (not shown) may be disposed on the other side (back side).

[0047] 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, for example, 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 μm to 400 μm.

[0048] The mass per unit area of ​​the negative electrode active material layer 220 may be, for example, 5 mg / cm 2 Above, 10mg / cm 2 Above, 15mg / cm 2 Above, 20mg / cm 2 Above, 25mg / cm 2 Above, 30mg / cm 2 Above, 40mg / cm 2 Above or 50mg / cm 2 The mass per unit area of ​​the negative electrode active material layer 220 may be, for example, 100 mg / cm 2 Below, 75mg / cm 2 Below, 50mg / cm 2 Below, 40mg / cm 2 Below or 30mg / cm 2 the following.

[0049] The density (apparent density) of the negative electrode active material layer 220 can be, for example, 0.8 g / cm 3 Above, 1.0g / cm 3 Above, 1.2g / cm 3 Above, 1.4g / cm 3 Above, 1.6g / cm 3 Above or 1.8g / cm 3 The density of the negative electrode active material layer 220 may be, for example, 2.0 g / cm 3 Below, 1.8g / cm 3 Below, 1.6g / cm 3 Below, 1.4g / cm 3 Below, 1.2g / cm 3 Below or 1.0g / cm 3 the following.

[0050] <First Area, Second Area> The cross section of the negative electrode active material layer 220 includes a first region 221 and a second region 222. The first region 221 may also be referred to as a "lower layer". In the thickness direction (Z direction), the first region 221 is arranged between the second region 222 and the substrate 210. The first region 221 may, for example, be in direct contact with the substrate 210. The first region 221 may, for example, include an interface between the substrate 210 and the negative electrode active material layer 220. The second region 222 may also be referred to as an "upper layer". The second region 222 may, for example, include the surface of the negative electrode active material layer 220.

[0051] The negative electrode active material layer 220 only needs to include the first region 221 and the second region 222, and may also include additional regions (third region, fourth region, etc.). The additional region can be distinguished from the first region 221 and the second region 222 by at least one of the composition and structure. For example, the additional region can be arranged between the substrate 210 and the first region 221. For example, the additional region can also be arranged between the first region 221 and the second region 222. For example, the additional region can also be arranged between the surface of the negative electrode active material layer 220 and the second region 222.

[0052] The first region 221 contains a first active material 12 and a first binder 14. The second region 222 contains a second active material 22 and a second binder 24. The first active material 12 and the second active material 22 are negative electrode active materials. The chemical composition of the first active material 12 may be the same as or different from the chemical composition of the second active material 22. The first active material 12 and the second active material 22 may each independently contain at least one selected from the group consisting of natural graphite and artificial graphite. The negative electrode active material layer 220 only needs to contain the first active material 12 and the second active material 22, and may also contain other negative electrode active materials. The negative electrode active material layer 220 may, for example, contain at least one selected from the group consisting of silicon (Si), silicon oxide (SiO), silicon-carbon composite material (Si-C), silicon-based alloy, tin, tin oxide and lithium titanate. For example, Si-C can be formed by dispersing Si particles in carbon particles. The mass fraction of other negative electrode active materials relative to the total of the negative electrode active materials may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 1% or less.

[0053] The first active material 12 and the second active material 22 may each independently have a D50 of, for example, 1 μm to 50 μm, 5 μm to 30 μm, or 10 μm to 25 μm. The first active material 12 and the second active material 22 may each independently have a D50 of 0.5 μm to 1 μm. 2 / g to 5m 2 / g, 1m 2 / g to 4m2 / g or 1.5m 2 / g to 3m 2 / g BET specific surface area.

[0054] The chemical composition of the first adhesive 14 may be the same as or different from the chemical composition of the second adhesive 24. The first adhesive 14 and the second adhesive 24 may, for example, independently include at least one selected from the group consisting of SBR, acrylic butadiene rubber (ABR), polyacrylonitrile (PAN), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), acrylic resin (acrylate copolymer), methacrylic resin (methacrylate copolymer), polyvinyl alcohol (PVA) and their derivatives. The amount of the adhesive may be, for example, 0.1 to 10 parts by mass, 1 to 6.5 parts by mass, 2 to 6.5 parts by mass, 3 to 6.5 parts by mass, 4 to 6.5 parts by mass or 5 to 6.5 parts by mass relative to 100 parts by mass of the active material.

[0055] A specific relationship is satisfied between the first region 221 and the second region 222 regarding the aspect ratio of the active material and the area fraction of the binder. In one embodiment of the present invention, the following relationship of formula (1) and formula (2) is satisfied. A2 <A1 (1) B2 <B1 (2) A1: Aspect ratio of the first active material 12 A2: Aspect ratio of the second active material 22 B1: Area fraction of the first adhesive 14 in the first region 221 B2: Area fraction of the second adhesive 24 in the second region 222

[0056] exist Figure 1 As an example, the present embodiment that satisfies the relationship between the above-mentioned formula (1) and formula (2) is schematically shown. In the first region 221, the aspect ratio of the first active material 12 is large, and the area fraction of the first binder 14 is large. By arranging the active material with a larger aspect ratio in the first region 221 (lower layer), it can be expected that the orientation state is easily maintained.

[0057] In another embodiment, the relationship between the above-mentioned equations (1) and (2) is replaced by the relationship between the following equations (3) and (4). By arranging the active material with a larger aspect ratio in the second region 222 (upper layer), it is expected that ion diffusion will be promoted in the thickness direction of the negative electrode active material layer 220. A2>A1 (3) B2>B1 (4)

[0058] As long as the above relationship is satisfied, the first active material 12 and the second active material 22 may have any particle shape. The first active material 12 and the second active material 22 may each independently include at least one selected from the group consisting of spherical particles, flaky particles, needle-like particles, and massive particles.

[0059] The thickness of each region may satisfy the relationship of the following formula (6), for example. 0.5≤Tx / (T1+T2)≤0.7 (6) T1: thickness of the first region 221 T2: thickness of the second region 222 Tx: The thickness of the region of the first region 221 and the second region 222 in which the active material has a larger aspect ratio. The thickness ratio {Tx / (T1+T2)} may be, for example, 0.6 or more or 0.6 or less.

[0060] The area fractions (B1, B2) of the binder may satisfy, for example, the relationship of the following formula (7). 1.8%≤|B1-B2| (7) B1: Area fraction of the first adhesive 14 in the first region 221 B2: Area fraction of the second adhesive 24 in the second region 222 The absolute value of the difference between B1 and B2 (|B1-B2|) may be, for example, 2% or more, 2.5% or more, or 3% or more. |B1-B2| may be, for example, 4% or less, 3% or less, or 2.5% or less.

[0061] The larger value of B1 and B2 may be, for example, 3.5% or more, 4% or more, or 5% or more. The larger value of B1 and B2 may be, for example, 10% or less, 8% or less, or 6% or less. The smaller value of B1 and B2 may be, for example, less than 3.5%, less than 3%, less than 2.5%, less than 2%, less than 1.5%, or less than 1%. The smaller value of B1 and B2 may be, for example, 0.5%, more than 1%, more than 1.5%, more than 2%, or more than 3%.

[0062] The aspect ratios (A1, A2) of the active materials may satisfy the relationship of the following formula (8), for example. 1.8≤Ax (8) Ax: The larger value of A1 and A2 Ax may be, for example, 2 or more, 2.5 or more, 3 or more, 3.5 or more, 4 or more, 4.5 or more, 5 or more, 5.5 or more, 6 or more, 6.5 or more, or 7 or more. Ax may be, for example, 8 or less, 7.5 or less, 7 or less, 6.5 or less, 6 or less, 5.5 or less, 5 or less, 4.5 or less, 4 or less, 3.5 or less, or 3 or less.

[0063] The smaller value (Ay) of A1 and A2 may be, for example, less than 1.8, less than 1.7, less than 1.6, less than 1.5, less than 1.4, less than 1.3, less than 1.2, or less than 1.1. Ay may be, for example, greater than 1, greater than 1.1, greater than 1.2, greater than 1.3, greater than 1.4, greater than 1.5, or greater than 1.6.

[0064] <Optional Ingredients> The negative electrode active material layer 220 may include a thickening material, for example. The thickening material can impart viscosity to the slurry. The thickening material may include, for example, at least one selected from the group consisting of sodium alginate, carboxymethyl cellulose (CMC), polyacrylic acid (PAA) and polyvinyl pyrrolidone (PVP). CMC and PAA, for example, may be in the form of Na salt, Li salt, NH4 salt, etc. The amount of the thickening material 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 relative to 100 parts by mass of the active material.

[0065] The negative electrode active material layer 220 may include, for example, a conductive material. The conductive material is capable of forming an electron conduction path. 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 flakes (GF). CNT may include at least one selected from the group consisting of single-layer CNT (SWCNT) and multilayer CNT (MWCNT). The amount of the conductive material may be, for example, 0.1 to 10 parts by mass relative to 100 parts by mass of the active material.

[0066] 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 (montmorillonite, montmorillonite, bentonite, hectorite, etc.), an inorganic filler (solid alumina, hollow silica, boehmite, etc.), a polysiloxane compound, etc.

[0067] <Orientation Degree> Orientation degree (I 110 / I 002) is larger, the more ion conduction can be expected to be promoted. In this embodiment, a larger orientation degree can be achieved. The orientation degree (I 110 / I 002 ) can be, for example, 0.03 or more, 0.05 or more, 0.08 or more, 0.10 or more, or 0.12 or more. That is, the relationship of the following formula (5) can be satisfied. 0.05≤I 110 / I 002 (5) I 110 : Diffraction intensity of (110) plane in XRD spectrum I 002 : Diffraction intensity of (002) plane in XRD spectrum The degree of orientation may be, for example, 0.30 or less, 0.25 or less, 0.20 or less, 0.15 or less, 0.12 or less, 0.10 or less, 0.08 or less, or 0.05 or less.

[0068] <Degree of curvature> The smaller the curvature, the more ion conduction can be expected to be promoted. In this embodiment, a smaller curvature can be achieved. The curvature of the negative electrode active material layer 220 can be, for example, less than 2.8, less than 2.5, less than 2.0, or less than 1.8. The curvature can be, for example, greater than 0.1, greater than 0.5, greater than 1.0, or greater than 1.5.

[0069] <Method for producing battery electrode> Figure 3 This is a schematic flow chart of the method for manufacturing a battery electrode in the present embodiment. The "method for manufacturing a battery electrode in the present embodiment" may be referred to as "the present manufacturing method" hereinafter. The present manufacturing method includes "(a) lower layer coating", "(b) upper layer coating", "(c) magnetic field application", "(d) drying" and "(e) pressurization".

[0070] <(a) Lower layer coating> The manufacturing method includes forming a first region 221 by applying a first slurry on the surface of a substrate 210. The first slurry includes a first active material 12, a first adhesive 14, and a dispersion medium. For example, the first slurry can be formed by mixing the first active material 12, the first adhesive 14, a thickening material, and a dispersion medium. The amount of the first adhesive 14 can be determined based on the size relationship between the aspect ratios of the first active material 12 and the second active material 22. Any mixing device can be used. For example, a planetary mixer can be used. The viscosity of the first slurry can be, for example, 10000 Pa·s to 30000 mPa·s.

[0071] The first region 221 (lower layer) can be formed by coating the first slurry on the surface of the substrate 210. Any coating device can be used, such as a die coater or a roll coater.

[0072] <(b) Upper layer coating> The manufacturing method includes forming a second region 222 by applying a second slurry on the first region 221. The second slurry includes a second active material 22, a second binder 24, and a dispersion medium. For example, the second slurry can be formed by mixing the second active material 22, the second binder 24, a thickening material, and a dispersion medium. The amount of the second binder 24 can be determined according to the relationship between the aspect ratios of the first active material 12 and the second active material 22. The viscosity of the second slurry can be, for example, 10000 Pa·s to 30000 mPa·s.

[0073] The second region 222 (upper layer) can be formed by coating the second slurry on the first region 221. At this stage, the first region 221 and the second region 222 (coating film) are in a wet state. That is, the first region 221 and the second region 222 contain a dispersion medium.

[0074] <(c) Magnetic Field Orientation> The present manufacturing method includes applying a magnetic field to the first region 221 and the second region 222. For example, the magnetic field may be applied before the first region 221 is completely dried. By applying the magnetic field before the first region 221 is dried, it is expected that a desired orientation state will be formed.

[0075] The magnetic field can be applied, for example, along the thickness direction of the first region 221 and the second region 222. The active material contained in the first region 221 and the second region 222 can be oriented in response to the magnetic field. The active material can be oriented in a manner such that the major axis is along the thickness direction (Z direction). There is a tendency that the larger the aspect ratio of the active material, the easier it is to orient. The magnetic flux density and application time of the magnetic field can be adjusted to obtain the desired orientation state. The magnetic flux density can be, for example, 100mT to 1000mT. The application time can be, for example, 1 minute to 60 minutes.

[0076] <(d) Drying> The manufacturing method includes forming the negative electrode active material layer 220 by drying the first region 221 and the second region 222. The dispersion medium can be removed by drying. Any drying device can be used. For example, a hot air drying device can be used. The drying temperature can be, for example, 40°C to 80°C or 40°C to 60°C. By removing the dispersion medium, the electrode 200 can be completed.

[0077] <(e) Pressurization> The manufacturing method may also include, for example, compressing the negative electrode active material layer 220. For example, the negative electrode active material layer 220 may be compressed using a rolling mill or the like. During the press processing, the active material can be expected to maintain its orientation state by having a region where the aspect ratio of the active material is relatively small and the amount of the binder present is relatively small function as a buffer.

[0078] <Battery> Figure 4 1 is a conceptual diagram showing an example of a battery in this embodiment. Battery 1000 may be, for example, a monopolar lithium ion battery. Battery 1000 includes an outer casing 900. Outer casing 900 accommodates power generation element 500 and an electrolyte (not shown).

[0079] <Exterior body> The outer casing 900 may have any form. The outer casing 900 may be, for example, a metal shell, a bag made of a laminated film, or the like. The shell may have any shape. The shell may be, for example, cylindrical, square, flat, coin-shaped, or the like. The outer casing 900 may contain, for example, Al, or the like. The outer casing 900 may contain, for example, one or more power generation elements 500. The plurality of power generation elements 500 may form, for example, a series circuit or a parallel circuit. In the outer casing 900, the plurality of power generation elements 500 may be stacked in the thickness direction of the battery 1000.

[0080] <Power Generation Elements> The power generation element 500 may also be referred to as an "electrode group", "electrode body", etc. The power generation element 500 includes an electrode 200 and a counter electrode 100. In the present embodiment, the electrode 200 is a negative electrode. The counter electrode 100 is a positive electrode. The power generation element 500 may also include a separator 300. The separator 300 is arranged between the positive electrode and the negative electrode. The power generation element 500 may have any form. The power generation element 500 may be, for example, a stacked type. For example, the power generation element 500 may be formed by alternately stacking the positive electrode and the negative electrode while sandwiching the separator 300 between the positive electrode and the negative electrode. The power generation element 500 may be, for example, a wound type. For example, a stacked body may be formed by stacking a strip-shaped positive electrode, a strip-shaped separator 300, and a strip-shaped negative electrode. The power generation element 500 may also be formed by spirally winding the stacked body. The wound power generation element 500 may also be formed into a flat shape after winding.

[0081] <Positive electrode> 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 has electrical conductivity. The substrate supports the positive electrode active material layer. The substrate may be, for example, in the form of a sheet. The substrate may have a thickness of, for example, 5 μm to 50 μm. The substrate may include, for example, a metal foil. The substrate may include, for example, at least one selected from the group consisting of Al, Mn, Ti, Fe, and Cr. The substrate may include, for example, Al foil, Al alloy foil, Ti foil, stainless steel (SUS) foil, etc.

[0082] An intermediate layer may also 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 μm to 5 μm. The intermediate layer may contain, for example, a conductive material, an insulating material, an adhesive, etc. The conductive material may contain, for example, carbon black, etc. The insulating material may contain, for example, aluminum oxide, boehmite, aluminum hydroxide, etc. The adhesive may contain, for example, PVdF, etc.

[0083] The positive electrode active material layer is arranged on the surface of the substrate. The positive electrode active material layer can be arranged only on one side of the substrate. The positive electrode active material layer can also be arranged on both sides of the substrate. The thickness of the positive electrode active material layer can be, for example, 10 μm to 1000 μm, 50 μm to 500 μm, or 100 μm to 300 μm. The positive electrode active material layer contains a positive electrode active material. The positive electrode active material layer can also contain, for example, a conductive material and a binder.

[0084] The amount of the conductive material may be, for example, 0.1 to 10 parts by mass relative to 100 parts by mass of the 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, Ketjen black, VGCF, CNT, and GF.

[0085] The amount of the binder may be, for example, 0.1 to 10 parts by mass relative to 100 parts by mass of the 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 ethers, and derivatives thereof.

[0086] The positive electrode active material layer may further 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 positive electrode active material layer may include, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, a silane coupling agent, MoS2, WO3, etc.

[0087] The positive electrode active material can be, for example, particulate. The D50 of the positive electrode active material can be, for example, from 1 μm to 30 μm, from 10 μm to 20 μm, or from 1 μm to 10 μm. The positive electrode active material can contain any components. The positive electrode active material can contain, for example, transition metal oxides, polyanion compounds, etc. Within one particle (positive electrode active material), the composition can be uniform or non-uniform. For example, the composition can be inclined from the surface of the particle towards the center. The change in the composition can be continuous or discontinuous (stepwise).

[0088] <Transition metal oxide (space group R-3m)> The transition metal oxide can have any crystal structure. The transition metal oxide can contain, for example, a crystal structure belonging to the space group R-3m, etc. For example, a compound represented by the general formula "LiMO2" may have a crystal structure belonging to the space group R-3m. The transition metal oxide can be represented by the following general formula, for example. Li 1-a Ni x M 1-x O2 In the formula, the relationship of -0.5 ≤ a ≤ 0.5 and 0 ≤ x ≤ 1 is satisfied. M can contain, for example, at least one selected from the group consisting of Co, Mn, and Al. For example, the relationship of 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 can be satisfied. For example, the relationship of -0.4 ≤ a ≤ 0.4, -0.3 ≤ a ≤ 0.3, -0.2 ≤ a ≤ 0.2, or -0.1 ≤ a ≤ 0.1 can be satisfied.

[0089] The transition metal oxide can contain, for example, at least one selected from the group consisting of LiCoO2, LiMnO2, LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 O2, and LiNiO2.

[0090] <ncm> Transition metal oxides can be represented, for example, by the following general formula. Compounds represented by the following general formula may also be referred to as "NCM". Li 1-a Ni x Co y Mn z O2 In the formula, the relationships of -0.5 ≤ a ≤ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationships of 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 may be satisfied. For example, the relationships of 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 may be satisfied. For example, the relationships of 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 may be satisfied.

[0091] NCM may contain, for example, those selected from the group consisting of 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 0.6 Co 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 At least one of the group consisting of O2.

[0092] <nca> Transition metal oxides can be represented, for example, by the following general formula. Compounds represented by the following general formula may also be referred to as "NCA". Li 1-a Ni x Co y Al z O2 In the formula, the relationships of -0.5 ≤ a ≤ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationships of 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 can be satisfied. For example, the relationships of 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 can be satisfied. For example, the relationships of 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 can be satisfied.

[0093] NCA can contain, for example, at least one selected from the group consisting of 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 O2.

[0094] <Multi-component system> The positive electrode active material can contain, for example, two or more types of NCM or the like. The positive electrode active material can contain, for example, NCM (0.6 ≤ x) and NCM (x < 0.6). "NCM (0.6 ≤ x)" means that in the general formula "Li 1-a Ni x Co y Mn z O2" is a compound with x (Ni ratio) of 0.6 or more. NCM (0.6≤x) can also be called "high nickel material". NCM (0.6≤x) contains, for example, LiNi 0.8 Co 0.1 Mn 0.1 O2, etc. "NCM (x < 0.6)" means that in the general formula "Li 1-a Ni x Co y Mn z O2" compounds with x (Ni ratio) less than 0.6. NCM (x<0.6) for example contains LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc. The mixing ratio (mass ratio) of NCM (0.6≤x) and NCM (x<0.6) can be, 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".

[0095] 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, "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 that of NCM. The Ni ratio of NCA may also be lower than that of NCM.

[0096] <Transition Metal Oxides (Space Group C2 / m)> The transition metal oxide may include, for example, a crystal structure belonging to the space group C2 / m, etc. The transition metal oxide may be represented by, for example, the following general formula. Li2MO3 In the formula, M may include at least one selected from the group consisting of 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), etc.

[0097] <Transition Metal Oxides (Space Group Fd-3m)> The transition metal oxide may include, for example, a crystal structure belonging to the space group Fd-3m, etc. The transition metal oxide may be represented by, for example, the following general formula. LiMn 2-x M x O4 In the formula, the relationship of 0≤x≤2 is satisfied. M may include, for example, at least one selected from the group consisting of Ni, Fe, and Zn.

[0098] LiM2O4 (space group Fd-3m) may include, for example, LiMn2O4 and LiMn 1.5 Ni 0.5 At least one of the group consisting of O4. The positive electrode active material may, for example, include 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, for example, be "LiMO2 / LiM2O4=9 / 1 to 1 / 9", "LiMO2 / LiM2O4=9 / 1 to 5 / 5" or "LiMO2 / LiM2O4=9 / 1 to 7 / 3".

[0099] <Polyanionic compounds> The polyanionic compound may include, for example, phosphate (eg, LiFePO 4 , etc.), silicate, borate, etc. The polyanionic compound may be represented by, for example, the following general formula group. LiMPO4 Li 2-x MPO4F Li2MSiO4 LiMBO3 In the above general formula group, M may include at least one selected from the group consisting of Fe, Mn and Co. 2-x In "MPO4F", for example, the relationship 0≤x≤2 can be satisfied.

[0100] 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".

[0101] <Adulteration> Dopants may also 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 biased on the particle surface. The dopant may be either a substitutional solid solution atom or an intrusive 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 dopants may also be added. Two or more dopants may also form a composite.

[0102] The dopant may, for example, include at least one selected from the group consisting of 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 actinide elements.

[0103] 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.

[0104] <Surface coating> The positive electrode active material can also form composite particles. The composite particles can, for example, include core particles and coating layers. The core particles include 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 can, for example, be 1nm to 3000nm, 5nm to 2000nm, 10nm to 1000nm, 10nm to 100nm or 10nm to 50nm. The thickness of the coating layer can be measured, for example, in an SEM image of a particle cross section. That is, a sample is prepared by embedding the composite particles with a resin material. The sample is sectioned using an ion milling device. The cross section of the sample is observed using an SEM. For 10 composite particles, the thickness of the coating layer is measured in 20 fields of view respectively. The arithmetic average of the thickness at a total of 200 locations is used.

[0105] The proportion of the surface of the core particle that is covered by the coating layer is also referred to as "coverage". The coverage can be, for example, 1% or more, 10% or more, 30% or more, 50% or more, or 70% or more. The coverage can be, for example, 100% or less, 90% or less, or 80% or less.

[0106] The coverage rate can be measured, for example, by XPS (X-ray Photoelectron Spectroscopy). A powder sample composed of composite particles is placed in XPS. A narrow scan analysis is performed. The measured data is processed using analytical software. By analyzing the measured data, a variety of elements are detected. Based on the area of ​​each peak, the ratio of each detected element is calculated. The coverage rate is calculated according to the following formula. γ={I1 / (I0+I1)}×100 γ: Coverage [%] I0: Ratio of elements originating from core particles I1: Ratio of elements originating from the coating layer For example, when the core particle includes NCM, I0 represents the total element ratio of "Ni, Co, Mn". For example, when the core particle includes NCA, I0 represents the total element ratio of "Ni, Co, Al". For example, when the coating layer includes P and B, I1 represents the total element ratio of "P, B".

[0107] The coating layer may contain any component, such as a simple substance, an organic substance, an inorganic acid salt, an organic acid salt, a hydroxide, an oxide, a carbide, a nitride, a sulfide, a halide, or the like. The coating layer may, for example, include at least one selected from the group consisting of 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, LiTiAlF6, LiYBr6, LiYCl6, etc.).

[0108] <Hollow particles / Solid particles> Hollow particles and solid particles are both secondary particles. In the cross-sectional image of "hollow particles", the proportion of the area of ​​the hollow in the center is more than 30% of the cross-sectional area of ​​the entire particle. The proportion of the hollow in the hollow particles can be, for example, more than 40%, more than 50% or more than 60%. In the cross-sectional image of the particle, the proportion of the area of ​​the hollow in the center is less than 30% of the cross-sectional area of ​​the entire particle. The proportion of the hollow in the solid particles can be, for example, less than 20%, less than 10% or less than 5%. The positive electrode active material can be either hollow particles or solid particles. A mixture of hollow particles and solid particles can also be used. The mixing ratio (mass ratio) of hollow particles and solid particles can be, 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".

[0109] <Large Particles / Small Particles> The active material may have, for example, a unimodal particle size distribution (based on the number of particles). The active material may have, for example, a multimodal particle size distribution. The active material may have, for example, a bimodal particle size distribution. That is, the active material may also contain large particles and small particles. When the particle size distribution is bimodal, the particle size corresponding to the peak with the larger particle size is regarded as the particle size of the large particle (d L The particle size corresponding to the peak with the smaller particle size is regarded as the particle size of the small particle (d S ). Particle size ratio (d L / d S ) can be, for example, 2 to 10, 2 to 5 or 2 to 4. L For example, it may be 8 μm to 20 μm or 8 μm to 15 μm. S For example, it may be 1 μm to 10 μm or 1 μm to 5 μm.

[0110] For example, the peak separation process of the particle size distribution can be performed using waveform analysis software. The peak area (S L ) and the peak area originating from small particles (S S ) can be, 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 =7 / 3 to 9 / 1”.

[0111] The particle size distribution based on the number is measured by microscopy. Multiple cross-section samples are collected from the active material layer. The cross-section sample may, for example, include a cross-section perpendicular to the surface of the active material layer. For example, the observation object surface is purified by ion milling or the like. The cross-section sample is observed using an SEM. The observation magnification is adjusted so that 10 to 100 particles are within the observation field of view. The Feret diameter of all particles in the image is measured. "Ferret diameter" represents the distance between the two farthest points on the contour line of the particle. By observing multiple cross-section samples, a total of more than 1,000 Feret diameters are obtained. Based on more than 1,000 Feret diameters, a particle size distribution based on the number is generated.

[0112] A bimodal particle size distribution can be formed by mixing two kinds of particles. The two kinds of particles have different particle size distributions from each other. For example, the two kinds of particles can have different D50s from each other. The measurement sample is a powder. For example, the D50 of large particles can be 8μm to 20μm or 8μm to 15μm. For example, the D50 of small particles can be 1μm to 10μm or 1μm to 5μm. The ratio of the D50 of large particles to the D50 of small particles can be, for example, 2 to 10, 2 to 5 or 2 to 4. The mixing ratio (mass ratio) of large particles to small particles can be, for example, "large particles / small particles = 1 / 9 to 9 / 1", "large particles / small particles = 5 / 5 to 9 / 1" or "large particles / small particles = 7 / 3 to 9 / 1".

[0113] In addition, the large particles and the small particles may have the same composition or different compositions. For example, the large particles may be NCA and the small particles may be NCM. For example, the large particles may be NCM (0.6≤x) and the small particles may be NCM (x<0.6).

[0114] <Electrolyte> The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute can be, for example, 0.5 mol / L to 1 mol / L, 1 mol / L to 1.5 mol / L, 1.5 mol / L to 2 mol / L, 2 mol / L to 2.5 mol / L, or 2.5 mol / L to 3 mol / L. "mol / L" is sometimes also denoted as "M". The solute contains a supporting salt (Li salt). The solute can contain, for example, an inorganic acid salt, an imide salt, an oxalate, a halide, and the like. The solute may, for example, include at least one selected from the group consisting of 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 their derivatives.

[0115] The electrolyte may include, for example, a carbonate-based solvent. The solvent may include, for example, a cyclic carbonate, a chain carbonate, a fluorinated carbonate, 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 carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, propylene fluorocarbonate, difluoropropylene carbonate, and their derivatives.

[0116] The solvent may also include cyclic carbonates (EC, PC, FEC, etc.) and chain carbonates (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of cyclic carbonate and chain carbonate may be, for example, "cyclic carbonate / chain carbonate = 1 / 9 to 4 / 6", "cyclic carbonate / chain carbonate = 2 / 8 to 3 / 7", or "cyclic carbonate / chain carbonate = 3 / 7 to 4 / 6".

[0117] The solvent may also include cyclic carbonates (EC, PC, etc.) and fluorinated cyclic carbonates (FEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates and fluorinated cyclic carbonates 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".

[0118] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy the relationship represented by the following formula, for example. V EC +V FEC +V EMC +V DMC +V DEC =10 In the above formula, V EC 、V FEC 、V EMC 、V DMC 、V DEC They represent the volume ratios of EC, FEC, EMC, DMC and DEC respectively. Satisfying the relationship 1≤V EC ≤4,0≤V FEC ≤3, V EC +V FEC ≤4,0≤V EMC ≤9,0≤V DMC ≤9,0≤V DEC ≤9,6≤V EMC +V DMC +V DEC ≤9. For example, it can satisfy 1≤V EC ≤2 or 2≤V EC The relationship is ≤3. For example, it can satisfy 1≤V FEC ≤2 or 2≤V FEC The relationship is ≤4. For example, 3≤V EMC ≤4 or 6≤V EMC The relationship is ≤8. For example, 3≤V DMC ≤4 or 6≤V DMC The relationship is ≤8. For example, 3≤V DEC ≤4 or 6≤V DEC The relationship is ≤8.

[0119] The solvent can have a composition of "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", "EC / FEC / DMC / EMC=1 / 2 / 3 / 4", etc. in a volume ratio, for example.

[0120] The electrolyte may also contain an ether solvent. For example, the electrolyte may contain 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), ethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and derivatives thereof.

[0121] The electrolyte may contain any additives. The amount of addition (relative to the mass fraction of the entire electrolyte) may be, for example, 0.01% to 5%, 0.05% to 3%, or 0.1% to 1%. The additives may include, for example, SEI (Solid Electrolyte Interphase) formation promoters, SEI formation inhibitors, gas generators, overcharge prevention agents, flame retardants, antioxidants, electrode protective agents, surfactants, etc.

[0122] The additives may include, for example, vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), vinyl sulfite (ES), propane sultone (PS), vinyl sulfate (DTD), γ-butyrolactone, phosphazene compounds, carboxylates (e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (M P), diethyl malonate (DEM), etc.], fluorobenzenes [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.], fluorotoluenes (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3 fluorotoluene (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), trifluorotoluene (e.g., trifluorotoluene, 2-fluoro-m-xylene, 3-fluoro-m-xylene, 4-fluoro-m-xylene, 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 (such as benzothiazole, 2-methylbenzothiazole, tetrathiafulvalene, etc.), nitrile compounds (such as adiponitrile, succinonitrile, etc.), phosphates (such as trimethylphosphoric acid, triethylphosphoric acid, etc.), carboxylic anhydrides (such as acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, etc.), alcohols (such as methanol, ethanol, n-propanol, ethylene glycol, diethylene glycol monomethyl ether, etc.) and their derivatives. At least one of the group consisting of.

[0123] The above-mentioned components as solute and solvent can be used as trace components (additives). The additive can 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 their derivatives.

[0124] The electrolyte solution may contain an ionic liquid. For example, the ionic liquid may contain at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, phosphonium salts, imidazolium salts, and derivatives thereof.

[0125] <Colloidal Electrolyte> The battery 1000 may also include a colloidal electrolyte. The colloidal electrolyte may include an electrolyte solution 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.

[0126] <Spacer> The separator 300 can separate the positive electrode from the negative electrode. The separator 300 has electrical insulation. The separator 300 may include, for example, at least one selected from the group consisting of 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.

[0127] The resin film is porous. The resin film may include, for example, a microporous film, a non-woven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be, for example, continuous in a network. Pores are formed in the gaps of the resin skeleton. The resin film allows electrolyte to pass through. The resin film may, for example, have an average pore size of less than 1 μm. The average pore size of the resin film may, for example, be 0.01 μm to 1 μm or 0.1 μm to 0.5 μm. The "average pore size" may be measured using a mercury penetration method. The Gurley value of the resin film may, for example, be 50 s / 100 cm 3 Up to 250s / 100cm 3 The "Gurley value" can be determined using the Gurley test method.

[0128] The resin film may include, for example, at least one selected from olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin film may include, for example, at least one selected from the group consisting of 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, and the like. The thickness of the resin film may be, for example, 5 μm to 50 μm or 10 μm to 25 μm.

[0129] The resin film may have a single-layer structure, for example. The resin film may be composed of a PE layer, for example. The skeleton of the PE layer is formed by PE. The PE layer can have a shutdown function. The resin film may also have a multilayer structure, for example. The resin film may include a PP layer and a PE layer, for example. The skeleton of the PP layer is formed by PP. The resin film may also have a three-layer structure, for example. The resin film may be formed by stacking a PP layer, a PE layer, and a PP layer in this order. The thickness of the PE layer may be, for example, 5 μm to 20 μm. The thickness of the PP layer may be, for example, 3 μm to 10 μm.

[0130] The inorganic particle layer may be formed on the surface of the resin film. The inorganic particle layer may be formed only on one side of the resin film, or may be formed on both sides. The inorganic particle layer may be formed on the side opposite to the positive electrode, or may be formed on the side opposite to the negative electrode. In addition, the inorganic particle layer may be formed on the surface of the positive electrode, or may be formed on the surface of the negative electrode.

[0131] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles can also be called "inorganic fillers". Pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer can be, for example, 0.5 μm to 10 μm or 1 μm to 5 μm. The inorganic particles can, for example, contain heat-resistant materials. The inorganic particle layer containing heat-resistant materials is also called "HRL (Heat Resistance Layer)". The inorganic particles can contain at least one selected from the group consisting of boehmite, aluminum oxide, zirconium oxide, titanium dioxide, magnesium oxide and silicon dioxide. The inorganic particles can have any shape. The inorganic particles can be, for example, spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles can be, for example, 0.1 μm to 10 μm or 0.5 μm to 3 μm. The inorganic particle layer can also contain a binder. The binder may include, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluorine resins, aromatic polyether resins, and liquid crystal polyester resins.

[0132] The spacer 300 may include an organic particle layer, for example. The spacer 300 may include an organic particle layer instead of a resin film, for example. The spacer 300 may include an organic particle layer instead of an inorganic particle layer, for example. The spacer 300 may include both a resin film and an organic particle layer. The spacer 300 may include both an inorganic particle layer and an organic particle layer. The spacer 300 may include a resin film, an inorganic particle layer, and an organic particle layer.

[0133] The thickness of the organic particle layer can be, for example, 0.1 μm to 50 μm, 0.5 μm to 20 μm, 0.5 μm to 10 μm, or 1 μm to 5 μm. The organic particle layer contains organic particles. The organic particles can also be called "organic fillers". The organic particles can contain heat-resistant materials. The organic particles can, for example, contain at least one selected from the group consisting of PE, PP, PTFE, PI, PAI, PA, and aromatic polyamide. The organic particles can, for example, be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the organic particles can, for example, be 0.1 μm to 10 μm or 0.5 μm to 3 μm.

[0134] The spacer 300 may include, for example, a mixed layer. The mixed layer includes both inorganic particles and organic particles.

[0135] <Battery composition> Figure 5 : is a table showing the first battery configuration. Figure 6 : is a table showing the second battery configuration. Figure 7 is a table showing the third battery configuration. In each table, when a plurality of materials are recorded in a cell, the record includes each material alone and their combination. For example, when the material "α, β, γ" is recorded in a cell, the record means "at least one selected from the group consisting of α, β and γ". Any elements can be extracted from each of the first battery configuration, the second battery configuration and the third battery configuration, and can be arbitrarily combined. [Example]

[0136] <Preparation of Evaluation Electrode> Figure 8 TABLE 2 is a table showing the experimental results. Various electrodes (negative electrodes) for evaluation were produced by the following procedures.

[0137] <No.1-1> Negative electrode manufacturing Prepare the following materials. Active materials: Graphite A (scaly particles, artificial graphite), Graphite B (spherical particles, artificial graphite) Binder: SBR Thickening material: CMC Dispersion medium: water Substrate: Cu foil (thickness: 15μm)

[0138] (a) Lower coating The first slurry is prepared by mixing graphite A, SBR, CMC and water. The solid content is formulated as "graphite A / CMC / SBR = 95.8 / 0.6 / 3.6 (mass ratio)". The first region (lower layer) is formed by applying the first slurry to the substrate. The first region is formed to have a unit area mass of 13 mg / cm after drying. 2 .

[0139] (b) Top coating The second slurry is prepared by mixing graphite B, SBR, CMC and dispersion medium. The solid content formula is "graphite B / CMC / SBR = 98.2 / 0.6 / 1.2 (mass ratio)". The second region (upper layer) is formed by overlapping and coating the second slurry on the first slurry. The second region is formed so that the unit area mass after drying is 13 mg / cm 2 .

[0140] (c) Magnetic field orientation A magnetic field is applied to the coating film (the first region and the second region).

[0141] (d) Drying The coating film is dried to form a negative electrode active material layer.

[0142] (e) Pressurization The negative electrode active material layer was compressed. After compression, the density of the negative electrode active material layer was 1.2 g / cm 3 A negative electrode was manufactured according to the above. In the cross-sectional sample of the negative electrode active material layer, the aspect ratio of the active material and the area fraction of the binder were measured for each region. The orientation degree and curvature of the negative electrode active material layer were also measured.

[0143] <No.1-2> The negative electrode of No. 1-2 is the product of No. 1-1 before pressurization.

[0144] <No.1-3> No.1-3 is the product before the magnetic field is applied in No.1-1.

[0145] <No.2> The slurry was prepared by mixing graphite A, SBR, CMC and water. The solid content was prepared as "graphite A / CMC / SBR = 97 / 0.6 / 2.4 (mass ratio)". The slurry was applied to a substrate to form a coating (single layer). The negative electrode active material layer was formed to have a mass per unit area of ​​26 mg / cm after drying. 2 A magnetic field is applied to the coating film. The coating film is dried to form a negative electrode active material layer. The negative electrode active material layer is compressed. After compression, the density of the negative electrode active material layer is 1.2 g / cm 3 According to the above, a negative electrode was manufactured.

[0146] <No.3> A negative electrode was produced in the same manner as in No. 2 except that the solid content formula was changed to "graphite A / CMC / SBR=95.8 / 0.6 / 3.6 (mass ratio)".

[0147] <No.4> A negative electrode was produced in the same manner as in No. 2 except that the solid content formula was changed to "graphite B / CMC / SBR=98.2 / 0.6 / 1.2 (mass ratio)".

[0148] <No.5> A negative electrode was produced in the same manner as in No. 2 except that no magnetic field was applied to the coating film.

[0149] <Production of Evaluation Monomer> A single cell for evaluation (laminated cell) including the negative electrode obtained in the above manner was produced. The rated capacity of the single cell for evaluation was 155 mAh.

[0150] Preparation of positive electrode Prepare the following materials. Positive electrode active material: LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM) Conductive material: AB Adhesive: PVdF Dispersion medium: N-methylpyrrolidone (NMP) Substrate: Al foil (thickness: 30 μm)

[0151] The slurry is prepared by mixing NCM, AB, PVdF and NMP. The solid content formula is "NCM / AB / PVdF=97.8 / 0.8 / 1.4 (mass ratio)". The positive electrode active material layer is formed by applying the slurry to a substrate. The positive electrode active material layer is dried. The positive electrode is manufactured by compressing the positive electrode active material layer.

[0152] Assembly Prepare the following materials. Spacer: PE porous sheet Electrolyte: 1.0mol / L LiPF6, EC+DMC+EMC Outer body: Bag made of Al laminated film

[0153] A power generation element is formed by laminating a positive electrode, a spacer, and a negative electrode in this order. An evaluation cell is manufactured by enclosing the power generation element and an electrolyte in an exterior body.

[0154] <Evaluation> In the evaluation cell, the discharge capacity was measured at 0.1C and 1C. The ambient temperature during discharge was 25°C. The ratio of the capacity at 1C discharge (1C discharge capacity) to the capacity at 0.1C discharge (0.1C discharge capacity) (1C discharge capacity / 0.1C discharge capacity) was calculated. The larger the 1C discharge capacity / 0.1C discharge capacity, the better the rate performance is considered to be.

[0155] <Results> From the degree of orientation of No.1-1, No.1-2, and No.1-3, it can be seen that the degree of orientation tends to increase due to the application of a magnetic field. From the degree of orientation of No.1-1 and No.1-2, it is known that in No.1-1, the oriented state is maintained even after pressurization. In No.1-1, the relationships of "A2 < A1" and "B2 < B1" are satisfied. It is considered that by making the second region with a relatively small aspect ratio of the active material and a relatively small amount of the binder present function as a buffer, the oriented state is difficult to be destroyed.

[0156] Fig. 9 It is a cross-sectional SEM image of the first region and the second region in No.1-1. In the first region (lower layer), flaky particles with a relatively large aspect ratio are oriented in the thickness direction. In the second region (upper layer), spherical particles with a relatively small aspect ratio are distributed.

[0157] Fig.10 It is a discharge curve at 1C discharge. No.1-1 and No.2 tend to have excellent rate performance compared to No.5. No.1-1 and No.2 have a larger degree of orientation compared to No.5. No.1-1 tends to have excellent rate performance compared to No.2. No.1-1 has a smaller degree of curvature compared to No.2. The negative electrode active material layer of No.1-1 includes a first region and a second region. The negative electrode active material layer of No.2 is composed of a single region.< / nca> < / ncm>

Claims

1. A battery electrode, It comprises a substrate and a negative electrode active material layer. The negative electrode active material layer is disposed on the surface of the substrate. A cross section parallel to the thickness direction of the negative electrode active material layer includes a first region and a second region, In the thickness direction, the first region is arranged between the second region and the substrate, The first region comprises a first active material and a first adhesive, The second region comprises a second active material and a second binder, Satisfying the relationship between the following formula (1) and formula (2), or satisfying the relationship between the following formula (3) and formula (4), A2 <A1 (1) B2 <B1 (2) A2>A1 (3) B2>B1 (4) In the above formula (1) to the above formula (4), A1 represents the aspect ratio of the first active material, A2 represents the aspect ratio of the second active material, B1 represents the area fraction of the first adhesive in the first region, and B2 represents the area fraction of the second binder in the second region.

2. The battery electrode according to claim 1, wherein The negative electrode active material layer has a curvature of 1.8 or less.

3. The battery electrode according to claim 1, wherein It also satisfies the following relationship (5): 0.05≤I 110 / I 002 (5) In the formula (5), I 110 represents the diffraction intensity of the (110) plane in the X-ray diffraction pattern of the negative electrode active material layer, and I 002 The diffraction intensity of the (002) plane in the X-ray diffraction pattern of the negative electrode active material layer is shown.

4. The battery electrode according to any one of claims 1 to 3, wherein Of the relationship between the equation (1) and the equation (2) and the relationship between the equation (3) and the equation (4), only the relationship between the equation (1) and the equation (2) is satisfied.

5. The battery electrode according to any one of claims 1 to 3, wherein The first active material and the second active material each independently include artificial graphite.

6. The battery electrode according to any one of claims 1 to 3, wherein The negative electrode active material layer has a 20 mg / cm 2 The unit area mass is 1.1 g / cm 3 Up to 1.6g / cm 3 density.

7. The battery electrode according to any one of claims 1 to 3, wherein It also satisfies the following relationship (6): 0.5≤Tx / (T1+T2)≤0.7 (6) In the formula (6), T1 represents the thickness of the first region, T2 represents the thickness of the second region, When the relationship of the above formula (1) is satisfied, Tx represents the thickness of the first region, and when the relationship of the above formula (3) is satisfied, Tx represents the thickness of the second region.

8. The battery electrode according to any one of claims 1 to 3, wherein It also satisfies the following relationship (7): 1.8%≤|B1-B2| (7).

9. The battery electrode according to any one of claims 1 to 3, wherein It also satisfies the following relationship (8): 1.8≤Ax (8) In the formula (8), When the relationship of the above formula (1) is satisfied, Ax represents the aspect ratio of the first active material, and when the relationship of the above formula (3) is satisfied, Ax represents the aspect ratio of the second active material.

10. A battery, It comprises the battery electrode according to any one of claims 1 to 3.

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