Current collector, electrode, battery, and method for manufacturing an electrode

Abstract

The adhesion between the current collector and the electrode layer is improved, while reducing resistance at the interface between the current collector and the electrode layer. [Solution] The current collector 100 of this disclosure comprises a substrate 101 and a coating layer 102. The coating layer 102 includes a conductive material 103 and a binder 104. The conductive material 103 includes a carbon material. In the Raman spectrum of the coating layer 102, the G / D ratio, which is the ratio of the peak intensity of the G band to the peak intensity of the D band, is greater than 0.80 and less than 3.09.

Description

[Technical Field]

[0001] This disclosure relates to a current collector, an electrode, a battery, and a method for manufacturing an electrode. [Background technology]

[0002] Current collectors are essential components of batteries. An electrode layer, such as an active material layer, is placed on top of the current collector. The adhesion between the current collector and the electrode layer affects the battery's performance. Current collectors equipped with a substrate and a coating layer are known to improve adhesion.

[0003] Patent Document 1 describes an electrode sheet for an all-solid-state secondary battery, which includes a primer layer to improve adhesion between the current collector (metal foil) and the electrode active material layer. The primer layer includes a binder and conductive particles. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2019 / 074076 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In conventional technology, it is desirable to improve the adhesion between the current collector and the electrode layer while reducing the resistance at the interface between the current collector and the electrode layer. [Means for solving the problem]

[0006] This disclosure is, circuit board and A coating layer comprising a binder and a conductive material, which covers the substrate, A current collector equipped with, The conductive material includes a carbon material, Satisfying at least one selected from the group consisting of the following requirements (a), (b), (c), (d), and (e): Current collector. (a) In the Raman spectrum of the coating layer, the G / D ratio, which is the ratio of the peak intensity of the G band to the peak intensity of the D band, is greater than 0.80 and less than 3.09. (b) The basis weight of the coating layer is 0.20 g / m² 2 More than 1.93g / m 2 Less than, (c) The value X calculated based on the following formula (i) is 9.8 mg / cm³ 2 A larger 70 mg / cm³ 2 The following is: X = mβ / (S × mα) ... (i) Here, S is the specific surface area of ​​the conductive material (unit: m²). 2 mα represents the mass of the conductive material contained in the coating layer per unit area (unit: g / m²), where mα is the mass of the conductive material contained in the coating layer per unit area (unit: g / m²). 2 mβ represents the mass of the binder contained in the coating layer per unit area (unit: mg / m²). 2 ) represents, (d) The rate of change of surface roughness ΔSa, shown by the following formula (ii), is -29% or more and -16% or less. ΔSa=100×(S2-S1) / S1 (ii) Here, S1 represents the surface roughness of the coating layer before the electrode layer is bonded to the current collector, and S2 represents the surface roughness of the coating layer after the electrode layer is bonded to the current collector. (e) The binder contains a resin with a heat of fusion of 50 J / g or more. [Effects of the Invention]

[0007] According to the technology disclosed herein, it is possible to improve the adhesion between the current collector and the electrode layer while reducing the resistance at the interface between the current collector and the electrode layer. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view of a current collector according to Embodiment 1. [Figure 2] Figure 2 is a cross-sectional view of a current collector according to Modified Example 1. [Figure 3]Figure 3 is a cross-sectional view of the electrode according to Embodiment 2. [Figure 4] Figure 4 is a cross-sectional view of the battery according to Embodiment 3. [Figure 5] Figure 5 is a cross-sectional view of the battery according to Embodiment 4. [Figure 6] Figure 6 shows cross-sectional views of the positive electrodes of samples 1 to 7. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to the embodiments described below.

[0010] (Embodiment 1) Figure 1 is a cross-sectional view of a current collector 100 according to Embodiment 1. The current collector 100 comprises a substrate 101 and a coating layer 102. The substrate 101 is covered by the coating layer 102. The substrate 101 is made of a conductive material, and is typically a metal foil. The coating layer 102 is in contact with the substrate 101. The coating layer 102 contains a conductive material 103 and a binder 104. The coating layer 102 improves the adhesion between the electrode layer, such as an active material layer, and the current collector 100. The conductive material 103 contains a carbon material.

[0011] According to this embodiment, the conductive material 103 and the binder 104 are dispersed in the coating layer 102. Therefore, the electron conduction paths formed by the conductive material 103 are less likely to be blocked by the binder 104. This improves the contact between the current collector 100 having the coating layer 102 and the electrode layer, making it possible to construct an interface that combines high peel strength and low contact resistance. As a result, the resistance of the battery can be reduced, and the charge and discharge characteristics of the battery can be improved.

[0012] Peel strength is an indicator of the adhesion between the current collector 100 and the electrode layer. Contact resistance is an indicator of the resistance at the interface between the current collector 100 and the electrode layer.

[0013] The current collector 100 satisfies at least one selected from the following plurality of requirements: [G / D ratio], [basis weight], [value X: ratio of the mass of the binder to the total surface area of the conductive material], [change rate of surface roughness ΔSa], and [heat of fusion of the binder]. As a result, the effects of improving adhesion and reducing resistance can be achieved simultaneously. The explanations regarding each requirement can be applied to each other.

[0014] [G / D ratio] The inventors of the present invention have intensively studied a method for reducing the resistance of a solid-state battery. As a result, it has been found that by using a current collector in which the intensity ratio of two Raman bands characteristic of carbon is controlled, the peel strength between the current collector and the electrode layer increases, and the contact resistance at the interface between the current collector and the electrode layer can be reduced. It is presumed that when the intensity ratio of the Raman bands derived from the conductive material is appropriately controlled, the formation of the conductive network by the conductive material and the formation of the adhesive interface by the binder are achieved in good balance.

[0015] That is, in the Raman spectrum of the coating layer 102 of the current collector 100, the G / D ratio, which is the ratio of the peak intensity of the G band to the peak intensity of the D band, can be greater than 0.80 and less than 3.09. The Raman spectrum is a spectrum obtained by performing Raman spectroscopic analysis. The G band is a peak that appears around a Raman shift value of 1580 cm -1 and is derived from the graphite structure. The D band is a peak that appears around a Raman shift value of 1350 cm -1 and is derived from the disorder and defects of the graphite structure.

[0016] When the G / D ratio is small, the crystallinity of the conductive material 103 tends to be low and the specific surface area of ​​the conductive material 103 tends to be large. In this case, the contact frequency between carbon particles that form electron conduction paths by the conductive material 103 increases, thereby reducing the contact resistance at the interface between the current collector 100 and the electrode layer. However, if the specific surface area of ​​the conductive material 103 is too large, the binder 104 is excessively adsorbed on the surface of the conductive material 103, and the peel strength between the current collector 100 and the electrode layer decreases. When the G / D ratio is large, the crystallinity of the conductive material 103 tends to be high and the specific surface area of ​​the conductive material 103 tends to be small. In this case, high peel strength can be achieved, but contact resistance also increases. Therefore, by adjusting the G / D ratio to be greater than 0.80 and less than 3.09, it is possible to provide a current collector 100 that can provide high peel strength and low contact resistance at the interface between the current collector 100 and the electrode layer.

[0017] The G / D ratio of the coating layer 102 is preferably greater than 0.80 and 2.00 or less, and more preferably greater than 0.88 and 2.00 or less. With this configuration, the proportion of highly crystalline conductive material 103 is not too high, and an electron conduction path can be constructed using the conductive material 103 while ensuring a sufficient amount of binder 104. Therefore, it is easy to achieve both the effect of improving peel strength and the effect of reducing contact resistance.

[0018] The conductive material 103 may contain at least one selected from the group consisting of graphite and carbon black. If the conductive material 103 contains graphite, it is easy to reduce the amount of binder 104. By reducing the amount of binder 104, the contact resistance at the interface between the current collector 100 and the electrode layer can be reduced. As a result, the charge and discharge characteristics of the battery can be improved. If the conductive material 103 contains carbon black, a conductive network is easily formed by the conductive material 103. This is because carbon black tends to exhibit better electronic conductivity than graphite. A good conductive network can reduce the contact resistance at the interface between the current collector 100 and the electrode layer. As a result, the charge and discharge characteristics of the battery can be improved.

[0019] The conductive material 103 may contain graphite. Graphite has high crystallinity and a small specific surface area. Therefore, using graphite reduces the amount of binder 104 adsorbed on the surface of the conductive material 103 when constructing electron conduction paths in the coating layer 102. As a result, high peel strength can be achieved. Examples of graphite include natural graphite, artificial graphite, flake graphite, spheroidal graphite, coke, graphitized carbon, and amorphous carbon. At least one type of graphite selected from these can be used. From the viewpoint of reducing contact resistance by reducing the amount of binder 104, the use of flake graphite is recommended.

[0020] The conductive material 103 may contain carbon black. Carbon black has low crystallinity and a large specific surface area. Therefore, using carbon black increases the frequency of contact between particles of the conductive material 103 when constructing electron conduction paths in the coating layer 102. This allows for the achievement of low contact resistance. Examples of carbon black include furnace black, acetylene black, and Ketjen black. At least one type of carbon black selected from these can be used. If the carbon black contains acetylene black, it is easier to improve the electrical conductivity of the coating layer 102.

[0021] The conductive material 103 may contain multiple types of carbon materials. When multiple types of carbon materials are included, the binder 104 and the multiple types of carbon materials are dispersed in the coating layer 102. Therefore, the electron conduction paths formed by the multiple types of carbon materials can exist without being blocked by the binder 104. As a result, the contactability of the interface between the current collector 100 and the electrode layer is improved, and a current collector 100 can be provided that provides high peel strength and low contact resistance at the interface between the current collector 100 and the electrode layer. The current collector 100 can reduce the resistance of the battery, and thus improve the charge and discharge characteristics of the battery.

[0022] Furthermore, if the conductive material 103 contains multiple types of carbon materials, the G / D ratio can be easily adjusted. The multiple types of carbon materials may be a mixture. In one example, the conductive material 103 includes a first conductive material 13a and a second conductive material 13b. The first conductive material 13a and the second conductive material 13b may each be carbon materials. The structure and electrical properties of the first conductive material 13a differ from those of the second conductive material 13b. "Electrical properties" refer to, for example, electrical conductivity.

[0023] In one example, the conductive material 103 includes a mixture of graphite and carbon black. The graphite is the first conductive material 13a, and the carbon black is the second conductive material 13b. With this configuration, a good conductive network can be easily formed by the carbon black, and the amount of binder 104 can be reduced by the graphite. This makes it possible to achieve both high peel strength and low contact resistance. As a result, the charge and discharge characteristics of the battery can be improved.

[0024] The proportion of graphite in the conductive material 103 is not particularly limited. Similarly, the proportion of carbon black in the conductive material 103 is not particularly limited. The amounts of graphite and carbon black can be adjusted so that the G / D ratio falls within the range described above. Increasing the proportion of graphite increases the G / D ratio. Decreasing the proportion of graphite decreases the G / D ratio. The ratio of the mass of graphite M1 to the sum of the mass of graphite M1 and the mass of carbon black M2 (M1 / (M1+M2)) is, for example, 0.01 to 0.99, and preferably 0.10 to 0.50.

[0025] If the first conductive material 13a is graphite, the first conductive material 13a may contain graphite as its main component, but may also contain unavoidable impurities such as starting materials, by-products, and decomposition products. The first conductive material 13a may contain 100% graphite by mass ratio to the whole of the first conductive material 13a, excluding unavoidable impurities. The first conductive material 13a may consist only of graphite. In this disclosure, "main component" means the component that is present in the largest amount by mass ratio.

[0026] If the second conductive material 13b is carbon black, the second conductive material 13b may contain carbon black as its main component, but may also contain unavoidable impurities such as starting materials, by-products, and decomposition products. The second conductive material 13b may contain 100% carbon black by mass ratio to the total amount of the second conductive material 13b, excluding unavoidable impurities. The second conductive material 13b may consist solely of carbon black.

[0027] The average particle diameter of the first conductive material 13a is, for example, in the range of 10 nm to 300 μm. The average particle diameter of the second conductive material 13b is, for example, in the range of 10 nm to 100 nm. The average particle diameter is calculated, for example, using an image obtained by a transmission electron microscope (TEM image). The equivalent diameters of a sufficient number of particles (e.g., 10 or more) are calculated by image processing. The average value of the calculated equivalent diameters is considered to be the average particle diameter. The equivalent diameter means the diameter of a circle having an area equal to the area of ​​the particle in question.

[0028] It is not essential that the conductive material 103 contains multiple types of carbon materials. The G / D ratio can also be adjusted using only one type of carbon material. For example, the G / D ratio can be adjusted by heat-treating, classifying, or finely grinding graphite.

[0029] The shape of the conductive material 103 is not particularly limited. The particles of the conductive material 103 may have shapes such as fibrous, needle-shaped, spherical, ellipsoidal, or flaky.

[0030] The conductive material 103 may contain materials other than graphite and carbon black. Examples of such materials include fibrous carbon such as vapor-phase carbon fibers, carbon nanotubes, and carbon nanofibers; metal fibers; carbon fluoride; metal powders such as aluminum; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymer compounds such as polyaniline, polypyrrole, and polythiophene. With such a configuration, the electrical conductivity of the coating layer 102 can be improved.

[0031] [Gross weight] The inventors diligently researched methods for reducing the resistance of solid-state batteries. As a result, they found that by using a current collector with a controlled amount of coating layer, the peel strength between the current collector and the electrode layer can be increased, and the contact resistance at the interface between the current collector and the electrode layer can be reduced. Furthermore, they found that using such a current collector also improves the short-circuit resistance of the electrodes. In solid-state batteries, when cracks occur in the electrodes due to foreign matter or external pressure, components of the current collector's coating layer can penetrate the cracks, causing current to flow between the positive and negative electrodes. In this specification, this type of resistance to conduction is referred to as "short-circuit resistance."

[0032] In other words, the basis weight of the coating layer 102 is 0.20 g / m². 2 More than 1.93g / m 2 It may be less than [a certain value]. The basis weight refers to the mass of the coating layer 102 per unit area. When the basis weight of the coating layer 102 is adjusted to the above range, a good balance is achieved at the interface between the coating layer 102 and the electrode layer between the conductive network formed by the conductive material 103 and the adhesive interface formed by the binder 104. Furthermore, by appropriately adjusting the basis weight, high short-circuit resistance can be achieved while maintaining high peel strength and low contact resistance.

[0033] The basis weight of the coating layer 102 is preferably 0.40 g / m². 2 More than 1.50g / m 2 The following, and more preferably 0.70 g / m² 2 More than 1.50g / m 2 The following applies: When the basis weight is adjusted to this range, it is easier to maintain high peel strength and low contact resistance, and short-circuit resistance is also improved.

[0034] In particular, when the conductive material 103 contains graphite and carbon black, high peel strength and low contact resistance are easily maintained even if the basis weight is reduced to improve short-circuit resistance.

[0035] The basis weight of the coating layer 102 can be adjusted by the thickness of the coating layer 102. Specifically, the thickness of the coating layer 102 can be adjusted to a desired value by selecting conditions such as the amount of solution or dispersion containing the material of the coating layer 102 applied, the solid content ratio in the solution or dispersion, and the application method.

[0036] [Value X: Ratio of binder mass to total surface area of ​​conductive material] The inventors diligently researched methods for reducing the resistance of solid-state batteries. As a result, they found that by using a current collector in which the ratio of binder mass to the total surface area of ​​the conductive material (= value X) is controlled, the peel strength between the current collector and the electrode layer can be increased, and the contact resistance at the interface between the current collector and the electrode layer can be reduced.

[0037] In other words, in the current collector 100, the value X calculated based on the following formula (i) is 9.8 mg / cm³. 2 A larger 70 mg / cm³ 2 The following is possible. Here, S is the specific surface area of ​​the conductive material 103 (unit: m²). 2 mα represents the mass of conductive material 103 contained in a unit area of ​​the coating layer 102 (unit: g / m). 2 mβ represents the mass of binder 104 contained in a unit area of ​​coating layer 102 (unit: mg / m). 2 ) represents.

[0038] X = mβ / (S × mα) ... (i)

[0039] The value X calculated based on equation (i) corresponds to the mass of the binder 104 normalized by the total surface area (S × mα) of the conductive material 103. As the value X increases, the peel strength between the current collector 100 and the electrode layer also increases. However, the excess binder 104 disrupts the conductive network formed by the conductive material 103, thus increasing the contact resistance. On the other hand, a small value X is advantageous for the formation of a conductive network by the conductive material 103. However, as the value X decreases, the binder 104 becomes insufficient, and the peel strength between the current collector 100 and the electrode layer also decreases. As in this embodiment, when the value X is appropriately adjusted, a good balance is achieved between the formation of a conductive network by the conductive material 103 and the formation of an adhesive interface by the binder 104. As a result, high peel strength and low contact resistance can be achieved, and consequently, the charge and discharge characteristics of the battery can be improved.

[0040] The value X is preferably 20 mg / cm³. 2 A larger 70 mg / cm³ 2 The following, and more preferably 30 mg / cm³ 2 More than 70mg / cm 2 The following is true. In particular, when the conductive material 103 contains graphite and carbon black, high peel strength and low contact resistance are easily achieved.

[0041] The specific surface area of ​​the conductive material 103, the mass of the conductive material 103 contained in a unit area of ​​the coating layer 102, and the mass of the binder 104 contained in a unit area of ​​the coating layer 102 can be determined by separating the conductive material 103 from the binder 104. If the conductive material 103 is a carbon material, the conductive material 103 is insoluble in most organic solvents. Therefore, the conductive material 103 and the binder 104 can be separated by dissolving the binder 104 in a suitable organic solvent. The specific surface area of ​​the recovered conductive material 103 can be calculated using the BET formula from the isothermal adsorption curve of nitrogen gas at liquid nitrogen temperature (77K).

[0042] When the conductive material 103 includes a first conductive material 13a and a second conductive material 13b, equation (i) is expressed as X = mβ / ((S1 × m1) + (S2 × m2)). S1 is the specific surface area of ​​the first conductive material 13a (unit: m²). 2 S2 represents the specific surface area (unit: m²) of the second conductive material 13b. 2 m1 represents the mass of the first conductive material 13a contained in a unit area of ​​the coating layer 102 (unit: g / m). 2 m² represents the mass of the second conductive material 13b contained in the coating layer 102 per unit area (unit: g / m²). 2 Equation (i) represents the same result. Equation (i) can also be applied when the conductive material 103 contains three or more types of carbon materials.

[0043] [Percentage change of surface roughness ΔSa] The inventors diligently researched methods for reducing the resistance of solid-state batteries. As a result, they found that controlling the rate of change in the surface roughness of the coating layer on the current collector increases the peel strength between the current collector and the electrode layer.

[0044] In other words, the electrode layer can be bonded to the current collector 100 such that the rate of change ΔSa of surface roughness, shown by the following formula (ii), is between -29% and -16%. S1 represents the surface roughness of the coating layer 102 before the electrode layer is bonded to the current collector 100. S2 represents the surface roughness of the coating layer 102 after the electrode layer is bonded to the current collector 100.

[0045] ΔSa=100×(S2-S1) / S1 (ii)

[0046] A rate of change in surface roughness that is too large means that the change in the thickness of the coating layer 102 on the current collector 100 is excessive. In this case, cracking of the battery using the current collector 100 may occur. On the other hand, a rate of change in surface roughness that is too small means that the adhesion between the current collector 100 and the electrode layer is insufficient. In this case, the electrode layer may peel off from the current collector 100 or the contact resistance may increase. As in this embodiment, when the rate of change in surface roughness ΔSa is adjusted to a range of -29% to -16%, the contact performance at the interface between the coating layer 102 and the electrode layer is improved. As a result, a good balance is achieved between the formation of a conductive network by the conductive material 103 and the formation of an adhesive interface by the binder 104 at the interface between the coating layer 102 and the electrode layer. As a result, high peel strength and low contact resistance can be achieved, and consequently, the charge and discharge characteristics of the battery can be improved.

[0047] Surface roughness refers to the arithmetic mean height Sa as defined in ISO 25178. Since it is not possible to measure the surface roughness S2 of the coating layer 102 with the electrode layer adhered to the current collector 100, in this specification, the surface roughness of the coating layer 102 after the electrode layer (active material layer) has been peeled off from the current collector 100 by a 90-degree peel test is considered to be "the surface roughness S2 of the coating layer 102 after the electrode layer has been adhered to the current collector 100".

[0048] [Heat of fusion of the binder] The inventors diligently researched methods to improve the handling and reliability of batteries. As a result, they discovered that the peel strength between the current collector and the electrode layer largely depends on the resin component contained in the coating layer of the current collector.

[0049] In other words, the binder 104 may contain a resin with a heat of fusion of 50 J / g or more. When the binder 104 contains such a resin, the resin melts at a temperature above its melting point. This facilitates the adhesion of the electrode layer to the current collector 100. The heat of fusion can be measured using a differential scanning calorimeter (DSC).

[0050] There is no particular upper limit to the heat of fusion of the resin contained in the binder 104; for example, it is 300 J / g.

[0051] The resin contained in the binder 104 may be crystalline. In this case, the resin crystallizes at a temperature below its melting point, ensuring high adhesion.

[0052] Examples of resins with a heat of fusion of 50 J / g or more include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyacetal, polyoxymethylene, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyether ether ketone, polyimide, polyacrylonitrile, polyacrylic acid, polyacrylic acid ester, and liquid crystal polymer. A mixture of two or more of these materials may also be used. Copolymers of two or more crystalline materials can also be used as binder 104.

[0053] Resins with a heat of fusion of 50 J / g or more may contain polyolefins. Polyolefins are a general term for high-molecular-weight compounds whose raw material monomers are olefins. Polyolefins are composed only of carbon and hydrogen atoms and do not have functional groups. Therefore, polyolefins do not react easily with other materials such as the substrate 101, conductive material 103, and components contained in the electrode layer, and exhibit high stability when used in batteries. In addition, coating solutions can be easily prepared by dissolving polyolefins in an organic solvent or dispersing them in water as an emulsion. Therefore, polyolefins as binders 104 improve productivity when forming the coating layer 102.

[0054] For example, the melting point and crystallinity of polyolefins vary depending on their molecular weight and molecular structure. For instance, the melting point of polyethylene is at most 140°C, and the melting point of polypropylene is at most 160°C. Therefore, using these resins as binder 104 eliminates the need to apply high temperatures exceeding 200°C when bonding the electrode layer to the current collector 100. This is desirable from the standpoint of preventing deterioration of battery characteristics. The heat of fusion of perfectly crystalline polyethylene is 286.7 J / g, and that of perfectly crystalline polypropylene is 209 J / g. The degree of crystallinity of the resin can be calculated from these heats of fusion values.

[0055] The melting point of the resin contained in the binder 104 may be in the range of 80°C to 140°C. When such a resin is used as the binder 104, it is not necessary to apply high temperatures exceeding 200°C when bonding the electrode layer to the current collector 100. This is desirable from the standpoint of preventing deterioration of the battery's characteristics. As a result, bonding the electrode layer to the current collector 100 becomes easier, and the resin crystallizes at temperatures below its melting point, ensuring high adhesion.

[0056] With the above configuration, the binder 104 contained in the coating layer 102 is interposed between the current collector 100 and the electrode layer, thus achieving high peel strength.

[0057] When manufacturing electrodes using the current collector 100, the electrode layer may be bonded to the current collector 100 by applying a temperature of 80°C to 140°C to the current collector 100 and the electrode layer. Bonding the electrode layer to the current collector 100 at such a temperature can prevent deterioration of the battery's characteristics. At temperatures above 80°C, the resin can be sufficiently melted, thus reducing the pressure applied between the current collector 100 and the electrode layer. This is advantageous in preventing defects such as electrode cracking and electrode end breakage. Furthermore, since the peel strength between the current collector 100 and the electrode layer can be increased, the handling of the battery during manufacturing or use, battery performance, battery shock resistance, battery vibration resistance, and battery heat resistance can also be improved.

[0058] Let's explain the current collector 100 in more detail.

[0059] <Current collector> The current collector 100 has, for example, a plate-like or foil-like shape. The thickness of the current collector 100 may be 0.1 μm or more and 1 mm or less, 1 μm or more and 100 μm or less, or 10 μm or more and 50 μm or less. When the thickness of the current collector 100 is 0.1 μm or more, the strength of the current collector 100 is improved, and damage to the current collector 100 is suppressed. When the thickness of the current collector 100 is 1 mm or less, the energy density of the battery can be improved by reducing the weight of the current collector 100. In other words, by appropriately adjusting the thickness of the current collector 100, batteries can be manufactured stably and the energy density of the battery can be improved.

[0060] <Circuit board> The substrate 101 may have a plate-like or foil-like shape. The substrate 101 may be made of a single metal or an alloy. Examples of single metals include aluminum, iron, nickel, and copper. Examples of alloys include aluminum alloys and stainless steel (SUS). The substrate 101 may also contain aluminum or an aluminum alloy.

[0061] The substrate 101 may contain aluminum as its main component. "The substrate 101 contains aluminum as its main component" means that the aluminum content in the substrate 101 is 50% by mass or more. Aluminum is a lightweight metal with high electrical conductivity. Therefore, electrodes equipped with a substrate 101 containing aluminum as its main component can improve the mass energy density of the battery. The substrate 101 containing aluminum as its main component may further contain elements other than aluminum. However, if the substrate 101 consists only of aluminum, i.e., if the aluminum content in the substrate 101 is 100%, the strength of the substrate 101 may decrease. Therefore, the substrate 101 may contain elements other than aluminum. The aluminum content in the substrate 101 may be 99.9% by mass or less, or 90% by mass or less.

[0062] The substrate 101 may contain an aluminum alloy. Aluminum alloys are lightweight and have high strength. Therefore, a current collector 100 equipped with a substrate 101 containing an aluminum alloy can provide a battery that achieves both high mass energy density and high durability. The aluminum alloy is not particularly limited and examples include Al-Cu alloy, Al-Mn alloy, Al-Mn-Cu alloy, Al-Fe-Cu alloy, etc.

[0063] An Al-Mn alloy may be used as the material for the substrate 101. Al-Mn alloys have high strength, as well as excellent formability and corrosion resistance. Therefore, a current collector 100 equipped with an Al-Mn alloy substrate 101 can improve the battery's cycle characteristics.

[0064] The thickness of the substrate 101 is not particularly limited and may be, for example, 0.1 μm or more and 50 μm or less, or 1 μm or more and 30 μm or less. When the thickness of the substrate 101 is 0.1 μm or more, the strength of the substrate 101 is improved, and thus damage to the substrate 101 is suppressed. When the thickness of the substrate 101 is 50 μm or less, the mass of the substrate 101 is reduced, and the mass energy density of the battery can be improved.

[0065] <Coating layer> The coating layer 102 may cover the entire main surface of the substrate 101, or it may partially cover the main surface of the substrate 101. "Main surface" refers to the surface of the substrate 101 that has the largest surface area. The shape of the coating layer 102 may be dot-shaped, striped, or the like.

[0066] <Conductive material> Examples of conductive materials 103 included in the coating layer 102 include graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black (AB) and Ketjenblack (KB), conductive fibers such as carbon fiber (CF), vapor-deposited carbon (VGCF (a registered trademark of Resonaq Corporation)), and carbon nanotubes (CNT), and nanocarbons such as graphene. One of these selected materials may be used alone as the conductive material 103, or a mixture of two or more selected materials may be used.

[0067] The conductive material 103 may include the first conductive material 13a and the second conductive material 13b described above.

[0068] <Binder> The binder 104 is included for the purpose of improving the adhesion between the particles of the conductive material 103 and for improving the adhesion between the current collector 100 and the active material layer. Examples of binder 104 include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, and carboxymethylcellulose. Furthermore, copolymers of two or more materials selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene can also be used as binder 104. Alternatively, a mixture of two or more materials selected from the above materials may be used as binder 104.

[0069] Binder 104 may contain polyolefin. Using polyolefin makes it easier to achieve both improved peel strength and reduced contact resistance. Examples of polyolefins include polyethylene, polypropylene, and poly-α-olefin. One of these may be used alone, or two or more may be used in combination.

[0070] In the coating layer 102, the ratio of the mass Mb of the binder 104 to the mass Mc of the conductive material 103 (Mb / Mc) is, for example, in the range of 0.01 to 99, and preferably in the range of 1 to 50.

[0071] The coating layer 102 can be formed by applying a solution or dispersion containing the material for the coating layer 102 to the main surface of the substrate 101 to form a coating film, and then drying the coating film. The solution or dispersion can be applied to the substrate 101 using a coating device such as a gravure coater or a die coater.

[0072] The current collector 100 can be used as an electrode in a battery. The battery may be a non-aqueous electrolyte battery or a solid-state battery. The current collector 100 is particularly suitable for all-solid-state batteries.

[0073] (Variation 1) Figure 2 is a cross-sectional view of a current collector 200 according to Modification 1. The current collector 200 comprises a substrate 101, a coating layer 102, and a coating layer 102. The coating layer 102 is provided on each of the two main surfaces of the substrate 101. "Main surface" refers to the surface having the largest area.

[0074] (Embodiment 2) Figure 3 is a cross-sectional view of the positive electrode 300 according to Embodiment 2. The positive electrode 300 comprises a current collector 100 and a positive electrode active material layer 310. The positive electrode active material layer 310 is supported by the current collector 100. The positive electrode active material layer 310 is in contact with the current collector 100. The positive electrode active material layer 310 may include a positive electrode active material 311, a binder 313, a conductive material 315, and a solid electrolyte 316. The positive electrode active material 311 may include a coating layer 312.

[0075] The current collector 100 may be used as the negative electrode. In that case, the positive electrode active material layer 310 is replaced with the negative electrode active material layer.

[0076] Instead of the current collector 100, the current collector 200 described with reference to Figure 2 may be used. In this case, the positive electrode active material layer 310 may be placed on each of the two main surfaces of the current collector 200.

[0077] (Cathode active material) As the positive electrode active material 311, materials that can be used as positive electrode active materials for all-solid-state lithium-ion batteries can be used.

[0078] As the positive electrode active material 311, LiCoO2, LiNi x Me 1-x O2, LiNi x Co 1-x O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, hetero-element substituted Li-Mn spinel, lithium titanate, lithium metal phosphate, transition metal oxide, etc. may be mentioned. In LiNi x Me 1-x O2, x satisfies 0.1 ≦ x < 1, and Me contains at least one or more selected from the group consisting of Co, Mn and Al. In LiNi x Co 1-x O2, x satisfies 0 < x < 0.5. As the hetero-element substituted Li-Mn spinel, LiMn 1.5 Ni 0.5 O4, LiMn 1.5 Al 0.5 O4, LiMn 1.5 Mg 0.5 O4, LiMn 1.5 Co 0.5 O4, LiMn 1.5 Fe 0.5 O4, LiMn 1.5 Zn 0.5 O4, etc. may be mentioned. As the lithium titanate, Li4Ti5O 12 may be mentioned. As the lithium metal phosphate, LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4, etc. may be mentioned. As the transition metal oxide, V2O5, MoO3, etc. may be mentioned.

[0079] The positive electrode active material 311 may be a lithium-containing composite oxide such as LiCoO2, LiNi x Me 1-x O2, LiNi x Co 1-x O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, hetero-element substituted Li-Mn spinel, lithium metal phosphate, etc.

[0080] When the positive electrode active material 311 is a lithium-containing composite oxide, the positive electrode active material 311 may have a layered rock salt structure. In a layered rock salt structure, the transition metal and lithium are regularly arranged to form a two-dimensional plane, thus enabling two-dimensional diffusion of lithium. Therefore, the energy density of the battery can be improved.

[0081] (covering layer) The coating layer 312 is in direct contact with the positive electrode active material 311.

[0082] Hereinafter, the material constituting the coating layer 312 will be referred to as the "coating material." The coating active material 317 in Embodiment 2 includes the positive electrode active material 311 and the coating layer 312. The coating material is present on at least a portion of the surface of the positive electrode active material 311 to form the coating layer 312.

[0083] The coating layer 312 may uniformly cover the positive electrode active material 311. With this configuration, the positive electrode active material 311 and the coating layer 312 are in close contact, which can further reduce the resistance of the battery.

[0084] The coating layer 312 may cover only a portion of the surface of the positive electrode active material 311. Direct contact between the particles of the positive electrode active material 311 through the portion not covered by the coating layer 312 improves the electron conductivity between the particles of the positive electrode active material 311. As a result, the battery can operate at high power.

[0085] The coating of the positive electrode active material 311 with the coating layer 312 suppresses the formation of an oxide film due to the oxidative decomposition of other solid electrolytes during battery charging. As a result, the charge and discharge efficiency of the battery is improved. An example of another solid electrolyte is solid electrolyte 316.

[0086] The coating layer 312 may contain a halide solid electrolyte. The halide solid electrolyte is, for example, a material containing Li, Ti, M, and X. M is at least one selected from the group consisting of metallic elements and metalloid elements other than Li and Ti. X is a halogen atom. Such materials have excellent ionic conductivity and oxidation resistance. Therefore, the coating active material 317 having the coating layer 312 improves the charge-discharge efficiency and thermal stability of the battery.

[0087] M may include at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr. With such a configuration, the halide solid electrolyte exhibits high ionic conductivity.

[0088] M may contain Al (=aluminum). That is, the halide solid electrolyte may contain Al as a metallic element. When M contains Al, the halide solid electrolyte exhibits high ionic conductivity.

[0089] To further increase the ionic conductivity of the halide solid electrolyte, M may be Al. The halide solid electrolyte is represented, for example, by the following compositional formula (1). In compositional formula (1), α, β, γ, and δ are each independently greater than 0.

[0090] Li α Ti β M γ X δ ...Equation (1)

[0091] The halide solid electrolyte represented by compositional formula (1) has higher ionic conductivity compared to halide solid electrolytes such as LiI, which consists only of Li and halogen elements. Therefore, when the halide solid electrolyte represented by compositional formula (1) is used in a battery, the charge and discharge efficiency of the battery can be improved.

[0092] The halide solid electrolyte may substantially consist of Li, Ti, Al, and X. Here, "the halide solid electrolyte substantially consists of Li, Ti, Al, and X" means that the molar ratio (i.e., mole fraction) of the total amount of the substance of Li, Ti, Al, and X to the total amount of the substance of all the elements constituting the halide solid electrolyte is 90% or more. As an example, the molar ratio (i.e., mole fraction) may be 95% or more. The halide solid electrolyte may consist only of Li, Ti, Al, and X.

[0093] In order to further increase the ionic conductivity, in the halide solid electrolyte, the ratio of the amount of substance of Li to the total amount of the substances of Ti and Al may be 1.12 or more and 5.07 or less.

[0094] The halide solid electrolyte may be represented by the following compositional formula (2).

[0095] Li 6-(4-x)b (Ti 1-x Al x ) b F6 ··· Formula (2)

[0096] In the compositional formula (2), 0 < x < 1 and 0 < b ≤ 1.5 are satisfied. The halide solid electrolyte having such a composition has high ionic conductivity.

[0097] In order to further increase the ionic conductivity of the halide solid electrolyte, in the compositional formula (2), 0.1 ≤ x ≤ 0.9 may be satisfied.

[0098] In the compositional formula (2), 0.1 ≤ x ≤ 0.7 may be satisfied.

[0099] The upper and lower limit values of the range of x in the compositional formula (2) may be defined by any combination selected from the numerical values of 0.1, 0.3, 0.4, 0.5, 0.6, 0.67, 0.7, 0.8, and 0.9.

[0100] To further increase the ionic conductivity of the halide solid electrolyte, the condition 0.8 ≤ b ≤ 1.2 may be satisfied in composition formula (2).

[0101] The upper and lower limits of the range of b in composition formula (2) can be defined by any combination selected from the values ​​0.8, 0.9, 0.94, 1.0, 1.06, 1.1, and 1.2.

[0102] The halide solid electrolyte may be crystalline or amorphous.

[0103] The thickness of the coating layer 312 is, for example, 1 nm or more and 500 nm or less. If the thickness of the coating layer 312 is appropriately adjusted, contact between the positive electrode active material 311 and the solid electrolyte 316 can be sufficiently suppressed. The thickness of the coating layer 312 can be determined by thinning the coating active material 317 using a method such as ion milling and observing the cross-section of the coating active material 317 with a transmission electron microscope. The average value of the thickness measured at any multiple locations (e.g., 5 points) can be considered as the thickness of the coating layer 312.

[0104] Halide solid electrolytes may also be solid electrolytes that do not contain sulfur. In this case, the generation of sulfur-containing gases such as hydrogen sulfide gas from the solid electrolyte can be avoided. A sulfur-free solid electrolyte means a solid electrolyte represented by a composition formula that does not contain the element sulfur. Therefore, solid electrolytes that contain a very small amount of sulfur, for example, solid electrolytes with a sulfur content of 0.1% by mass or less, belong to the category of sulfur-free solid electrolytes. Halide solid electrolytes may also contain oxygen as anion other than the halogen element.

[0105] The shape of the halide solid electrolyte is not particularly limited. The shape of the halide solid electrolyte may be, for example, needle-shaped, spherical, or ellipsoidal. For example, the shape of the halide solid electrolyte may be particulate.

[0106] If the shape of the halide solid electrolyte is, for example, particulate (e.g., spherical), the halide solid electrolyte may have a median diameter of 0.01 μm or more and 100 μm or less.

[0107] The coating material can be manufactured by the following method. Here, we will illustrate a method for manufacturing a halide solid electrolyte represented by composition formula (1).

[0108] Prepare the raw material powder for the halide according to the desired composition. The halide may be a compound consisting of three elements, including a halogen element. For example, Li 2.7 Ti 0.3 Al 0.7 When preparing F6, LiF, TiF4, and AlF3 are prepared as raw material powders in a molar ratio of approximately 2.7:0.3:0.7. By appropriately selecting the types of raw material powders, the elemental species of "M" and "X" in compositional formula (1) can be determined. The values ​​of "α," "β," "γ," and "δ" in compositional formula (1) can be adjusted by controlling the types of raw material powders, their mixing ratios, and the synthesis process. The raw material powders may also be mixed in a pre-adjusted molar ratio to counteract any compositional changes that may occur during the synthesis process.

[0109] After mixing and grinding the raw material powders, the powders are reacted with each other using a mechanochemical milling method to obtain a reactant. The reactant may be calcined in a vacuum or an inert atmosphere. Alternatively, the raw material powders may be mixed and ground first, and then calcined in a vacuum or an inert atmosphere to obtain the reactant. Calcination is carried out, for example, at a temperature of 100°C or higher and 400°C or lower for at least one hour. To suppress any compositional changes that may occur during calcination, the raw material powders may be calcined in a sealed container such as quartz. Through these steps, a halogen solid electrolyte is obtained.

[0110] The composition of the crystalline phase (i.e., the crystalline structure) of a halide solid electrolyte can be controlled and determined by the reaction method and conditions of the raw material powders.

[0111] Here, the coated active material 317 can be manufactured, for example, by the following method. First, a coating layer 312 is formed on the surface of the particles of the positive electrode active material 311. The method for forming the coating layer 312 is not particularly limited. Methods for forming the coating layer 312 include solid-phase coating, liquid-phase coating, and gas-phase coating.

[0112] A mixture is obtained by mixing the powder of the positive electrode active material 311 and the powder of the solid electrolyte of the coating layer 312 in an appropriate ratio. The mixture is milled to impart mechanical energy to it. A mixing device such as a ball mill can be used for the milling process. To suppress oxidation of the materials, the milling process may be carried out in a dry and inert atmosphere.

[0113] The coating active material 317 may be manufactured by a dry particle compounding method. The dry particle compounding method involves applying at least one mechanical energy selected from the group consisting of impact, compression, and shear to the positive electrode active material 311 and the solid electrolyte of the coating layer 312. The positive electrode active material 311 and the solid electrolyte of the coating layer 312 are mixed in an appropriate ratio.

[0114] The apparatus used in the production of the coating active material 317 is not particularly limited and may be any apparatus capable of applying impact, compression, and shear mechanical energy to the mixture of the positive electrode active material 311 and the solid electrolyte of the coating layer 312. Examples of apparatus capable of applying mechanical energy include ball mills, compression and shear processing apparatuses (particle compounding apparatuses) such as "Mechanofusion" (manufactured by Hosokawa Micron Corporation) and "Nobilta" (manufactured by Hosokawa Micron Corporation).

[0115] "Mechanofusion" is a particle compounding device that uses a dry mechanical compounding technology, which involves applying strong mechanical energy to multiple different raw material powders. In mechanofusion, mechanical energy in the form of compression, shear, and friction is applied to the raw material powders fed between a rotating container and a press head. This causes the compounding of particles.

[0116] "Nobilta" is a particle compounding device that uses dry mechanical compounding technology, an advanced particle compounding technology, to compound nanoparticles as raw materials. Nobilta manufactures composite particles by applying mechanical energy such as impact, compression, and shear to multiple types of raw material powders.

[0117] In "Nobilta," a rotor rotates at high speed within a horizontal cylindrical mixing container, positioned to have a predetermined gap between itself and the inner wall of the container. This process repeatedly forces the raw material powder through the gap. This applies impact, compression, and shear forces to the mixture, enabling the creation of composite particles of the positive electrode active material 311 and the solid electrolyte of the coating layer 312. By adjusting conditions such as the rotor's rotation speed, processing time, and the amount of material to be charged, the thickness of the coating layer 312 and the coverage rate of the positive electrode active material 311 by the solid electrolyte of the coating layer 312 can be controlled.

[0118] However, processing using the above-mentioned apparatus is not mandatory. The coating active material 317 may be manufactured by mixing the positive electrode active material 311 with the solid electrolyte of the coating layer 312 using a mortar and pestle, mixer, or the like. The solid electrolyte of the coating layer 312 may also be deposited on the surface of the positive electrode active material 311 by various methods such as spraying, spray dry coating, electrodeposition, immersion, or mechanical mixing using a disperser.

[0119] (solid electrolyte) The solid electrolyte 316 may include at least one selected from the group consisting of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, and complex hydride solid electrolytes.

[0120] The solid electrolyte 316 may include at least one selected from the group consisting of sulfide solid electrolytes and halide solid electrolytes. With the above configuration, the output characteristics of the battery can be improved.

[0121] The solid electrolyte 316 may be a mixture of a sulfide solid electrolyte and a halide solid electrolyte.

[0122] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 These are some examples. Sulfide solid electrolytes with an argyrodite structure, such as Li6PS5Cl, Li6PS5Br, and Li6PS5I, can also be used. These sulfide solid electrolytes include LiX, Li2O, and MO q Li p MO q The following may be added. Here, X is at least one selected from the group consisting of F, Cl, Br, and I. M is at least one selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. p and q are natural numbers, respectively. One or more sulfide solid electrolytes selected from the above materials may be used.

[0123] With the above configuration, the ionic conductivity of the sulfide solid electrolyte can be further improved. This, in turn, can improve the charge and discharge efficiency of the battery.

[0124] Halide solid electrolytes are represented, for example, by the following compositional formula (3).

[0125] Li α M β X γ ...Equation (3)

[0126] Here, α, β, and γ are each independently greater than 0. γ could be, for example, 4 or 6. M includes at least one element selected from the group consisting of metallic and metalloid elements other than Li. X includes at least one element selected from the group consisting of F, Cl, Br, and I.

[0127] In this disclosure, “metalloid elements” refers to B, Si, Ge, As, Sb, and Te. “Metallic elements” refers to all elements in groups 1 through 12 of the periodic table, excluding hydrogen, and all elements in groups 13 through 16 of the periodic table, excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. In other words, “metalloid elements” or “metallic elements” are the group of elements that can become cations when forming inorganic compounds with halogen elements.

[0128] The halide solid electrolyte represented by composition formula (3) has higher ionic conductivity compared to halide solid electrolytes such as LiI, which consists of Li and halogen elements. Therefore, the halide solid electrolyte represented by composition formula (1) can further improve the ionic conductivity of the halide solid electrolyte. Consequently, using a solid electrolyte 316 containing such a halide solid electrolyte in a battery can further improve the battery's charge and discharge efficiency.

[0129] In compositional formula (3), M may be at least one element selected from the group consisting of metallic elements and metalloid elements other than Li.

[0130] In compositional formula (3), X may be at least one selected from the group consisting of F, Cl, Br, and I.

[0131] The composition formula (3) may also satisfy 2.5 ≤ α ≤ 3, 1 ≤ β ≤ 1.1, and γ = 6. With the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved.

[0132] In compositional formula (3), M may also contain Y (=yttrium). That is, the halide solid electrolyte may contain Y as a metallic element. With the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved.

[0133] A halide solid electrolyte containing Y may be represented, for example, by the following compositional formula (4).

[0134] Li a Me b Y c X6...Formula (4)

[0135] Here, a + mb + 3c = 6 and c > 0 are satisfied. Me is at least one element selected from the group consisting of metallic elements and metalloid elements, excluding Li and Y. m is the valence of element Me. If element Me contains multiple elements, mb is the sum of the values ​​obtained by multiplying the composition ratio of each element by the valence of that element. For example, if Me contains elements Me1 and Me2, and the composition ratio of element Me1 is b1 and the valence of element Me1 is m1, and the composition ratio of element Me2 is b2 and the valence of element Me2 is m2, then mb = m1b1 + m2b2. X is at least one element selected from the group consisting of F, Cl, Br, and I.

[0136] Me may be, for example, at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0137] With the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved. Therefore, using a solid electrolyte 316 containing such a halide solid electrolyte in a battery can further improve the battery's charge and discharge efficiency.

[0138] As a halide solid electrolyte, for example, the following materials can be used. The following configuration can further improve the ionic conductivity of the halide solid electrolyte.

[0139] The halide solid electrolyte may be a material represented by the following compositional formula (A1).

[0140] Li 6-3d Y d X6...Formula (A1)

[0141] In the compositional formula (A1), X is at least one selected from the group consisting of F, Cl, Br, and I. Also, 0 < d < 2 is satisfied.

[0142] The halide solid electrolyte may be a material represented by the following compositional formula (A2).

[0143] Li3YX6 ··· Formula (A2)

[0144] In the compositional formula (A2), X is at least one selected from the group consisting of F, Cl, Br, and I.

[0145] The halide solid electrolyte may be a material represented by the following compositional formula (A3).

[0146] Li 3-3δ Y 1+δ Cl6 ··· Formula (A3)

[0147] In the compositional formula (A3), 0 < δ ≦ 0.15 is satisfied.

[0148] The halide solid electrolyte may be a material represented by the following compositional formula (A4).

[0149] Li 3-3δ Y 1+δ Br6 ··· Formula (A4)

[0150] In the compositional formula (A4), 0 < δ ≦ 0.25 is satisfied. <00​​​​​​​​​​​​​​​​​​​​​​In the compositional formula (A5), Me contains at least one selected from the group consisting of Mg, Ca, Sr, Ba, and Zn. Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, and Zn.

[0154] In the compositional formula (A5), -1 < δ < 2, 0 < a < 3, 0 < (3 - 3δ + a), 0 < (1 + δ - a), 0 ≤ x ≤ 6, 0 ≤ y ≤ 6, and (x + y) ≤ 6 are satisfied.

[0155] The halide solid electrolyte may be a material represented by the following compositional formula (A6).

[0156] Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (A6)

[0157] In the compositional formula (A6), Me contains at least one selected from the group consisting of Al, Sc, Ga, and Bi. Me may be at least one selected from the group consisting of Al, Sc, Ga, and Bi.

[0158] In the compositional formula (A6), -1 < δ < 1, 0 < a < 2, 0 < (1 + δ - a), 0 ≤ x ≤ 6, 0 ≤ y ≤ 6, and (x + y) ≤ 6 are satisfied.

[0159] The halide solid electrolyte may be a material represented by the following compositional formula (A7).

[0160] Li 3-3δ-a Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (A7)

[0161] In the compositional formula (A7), Me contains at least one selected from the group consisting of Zr, Hf, and Ti. Me may be at least one selected from the group consisting of Zr, Hf, and Ti.

[0162] In the compositional formula (A7), -1 < δ < 1, 0 < a < 1.5, 0 < (3 - 3δ - a), 0 < (1 + δ - a), 0 ≤ x ≤ 6, 0 ≤ y ≤ 6, and (x + y) ≤ 6 are satisfied.

[0163] The halide solid electrolyte may be a material represented by the following compositional formula (A8).

[0164] Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (A8)

[0165] In the compositional formula (A8), Me contains at least one selected from the group consisting of Ta and Nb. Me may be at least one selected from the group consisting of Ta and Nb.

[0166] In the compositional formula (A8), -1 < δ < 1, 0 < a < 1.2, 0 < (3 - 3δ - 2a), 0 < (1 + δ - a), 0 ≤ x ≤ 6, 0 ≤ y ≤ 6, and (x + y) ≤ 6 are satisfied.

[0167] As the halide solid electrolyte, more specifically, for example, Li3YX6, Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, Li3(Al, Ga, In)X6, etc. can be used. Here, X is at least one selected from the group consisting of F, Cl, Br, and I.

[0168] In the present disclosure, the notation "(A, B, C)" in the chemical formula means "at least one selected from the group consisting of A, B, and C". For example, "(Al, Ga, In)" is synonymous with "at least one selected from the group consisting of Al, Ga, and In". The same applies to other elements.

[0169] Examples of oxide solid electrolytes include NASICON-type solid electrolytes represented by LiTi2(PO4)3 and its elemental substitutions, (LaLi)TiO3-based perovskite-type solid electrolytes, and Li 14 ZnGe4O 16 , LiSICON-type solid electrolytes such as Li4SiO4, LiGeO4 and their elemental substitutions, Li7La3Zr2O 12 Garnet-type solid electrolytes, such as those represented by their elemental substitutions, Li-BO compounds such as Li3N and its H-substituted derivatives, Li3PO4 and its N-substituted derivatives, LiBO2, and Li3BO3, can be used as a base, with Li2SO4, Li2CO3, etc., added as a base, or glass ceramics.

[0170] As a polymeric solid electrolyte, for example, a compound of a polymer compound and a lithium salt can be used. The polymer compound may have an ethylene oxide structure. Polymeric compounds having an ethylene oxide structure can contain a large amount of lithium salt. Therefore, the ionic conductivity can be further increased. Examples of lithium salts that can be used include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. One or more lithium salts selected from the above lithium salts can be used.

[0171] Examples of complex hydride solid electrolytes that can be used include LiBH4-LiI and LiBH4-P2S5.

[0172] The solid electrolyte 316 does not necessarily have to contain sulfur. With the above configuration, the generation of hydrogen sulfide gas can be suppressed. Therefore, it becomes possible to provide a battery with improved safety.

[0173] The shape of the solid electrolyte 316 is not particularly limited. The shape of the solid electrolyte 316 may be, for example, needle-shaped, spherical, or ellipsoidal. For example, the shape of the solid electrolyte 316 may be particulate.

[0174] For example, if the solid electrolyte 316 is particulate (e.g., spherical), the median diameter of the solid electrolyte 316 may be 100 μm or less. When the median diameter of the solid electrolyte 316 is 100 μm or less, the positive electrode active material 311 and the solid electrolyte 316 can form a good dispersion state in the positive electrode active material layer 310. This improves the charge and discharge characteristics of the battery.

[0175] The median diameter of the solid electrolyte 316 may be 10 μm or less. With the above configuration, the positive electrode active material 311 and the solid electrolyte 316 can form a good dispersion state in the positive electrode active material layer 310.

[0176] The median diameter of the solid electrolyte 316 may be smaller than the median diameter of the positive electrode active material 311. With the above configuration, the positive electrode active material 311 and the solid electrolyte 316 can form a better dispersion state in the positive electrode active material layer 310.

[0177] The shape of the positive electrode active material 311 is not particularly limited. The shape of the positive electrode active material 311 may be, for example, needle-shaped, spherical, or ellipsoidal. For example, the shape of the positive electrode active material 311 may be particulate.

[0178] The median diameter of the positive electrode active material 311 may be 0.1 μm or more and 100 μm or less. When the median diameter of the positive electrode active material 311 is 0.1 μm or more, the positive electrode active material 311 and the solid electrolyte 316 can form a good dispersion state in the positive electrode active material layer 310. This improves the charge and discharge characteristics of the battery. When the median diameter of the positive electrode active material 311 is 100 μm or less, the diffusion rate of lithium within the positive electrode active material 311 is sufficiently ensured. This allows the battery to operate at high power.

[0179] The median diameter of the positive electrode active material 311 may be larger than the median diameter of the solid electrolyte 316. This allows the positive electrode active material 311 and the solid electrolyte 316 to form a good dispersion state.

[0180] In this disclosure, median diameter means particle size (d50) when the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is measured, for example, by a laser diffraction analyzer or an image analyzer.

[0181] In the positive electrode active material layer 310, the solid electrolyte 316 and the positive electrode active material 311 may be in contact with each other.

[0182] The positive electrode active material layer 310 may contain a plurality of solid electrolyte particles 316 and a plurality of positive electrode active material particles 311.

[0183] In the positive electrode active material layer 310, the content of the solid electrolyte 316 and the content of the positive electrode active material 311 may be the same or different. In the positive electrode active material layer 310, the ratio "v1:100-v1" of the volume of the positive electrode active material 311 to the volume of the solid electrolyte 316 may satisfy 30≦v1≦95. If 30≦v1 is satisfied, the energy density of the battery is sufficiently ensured. If v1≦95 is satisfied, the battery can operate at high power.

[0184] (binder) The positive electrode active material layer 310 may contain a binder 313 for the purpose of improving the adhesion between particles. The binder 313 is used to improve the binding properties of the materials constituting the positive electrode. Examples of binders 313 include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl polyacrylate, polyethyl polyacrylate, polyhexyl polyacrylate, polymethacrylic acid, polymethyl polymethacrylate, polyethyl polymethacrylate, polyhexyl polymethacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polycarbonate, polyethersulfone, polyetherketone, polyetheretherketone, polyphenylene sulfide, hexafluoropolypropylene, styrene-butadiene rubber, carboxymethylcellulose, and ethylcellulose. Copolymers of two or more monomers selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, butadiene, styrene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid esters, acrylic acid, and hexadiene may also be used. One of these may be used alone, or two or more may be used in combination.

[0185] For the reason of excellent binding properties, binder 313 may be an elastomer. An elastomer is a polymer that has rubber elasticity. The elastomer used as binder 313 may be a thermoplastic elastomer or a thermosetting elastomer. Binder 313 may contain a thermoplastic elastomer. Examples of thermoplastic elastomers include styrene-ethylene-butylene-styrene (SEBS), styrene-ethylene-propylene-styrene (SEPS), styrene-ethylene-ethylene-propylene-styrene (SEEPS), butylene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), styrene-butylene rubber (SBR), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), hydrogenated isoprene rubber (HIR), hydrogenated butyl rubber (HIIR), hydrogenated nitrile rubber (HNBR), hydrogenated styrene-butylene rubber (HSBR), polyvinylidene fluoride (PVdF), and polytetrafluoroethylene (PTFE). One of these may be used alone, or two or more may be used in combination.

[0186] (Conductive material) The positive electrode active material layer 310 may contain a conductive material 315 to improve electronic conductivity. Examples of conductive materials 315 include graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black and Ketjen black, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymer compounds such as polyaniline, polypyrrole, and polythiophene. When a carbon material is used as the conductive material 315, the cost of the positive electrode 300 can be reduced.

[0187] The conductive material 315 may include a first conductive material 315a and a second conductive material 315b. The first conductive material 315a is, for example, graphite. The second conductive material 315b is, for example, carbon black.

[0188] The thickness of the positive electrode active material layer 310 may be 1 μm or more and 500 μm or less. When the thickness of the positive electrode active material layer 310 is 1 μm or more, sufficient energy density can be ensured. When the thickness of the positive electrode active material layer 310 is 500 μm or less, the battery can operate at high power.

[0189] (Method of manufacturing electrodes) The positive electrode 300 is obtained by placing a positive electrode active material layer 310 on a current collector 100. For example, a positive electrode slurry containing the material for the positive electrode active material layer 310 is prepared. The positive electrode slurry is applied to the current collector 100 to form a coating film. The coating film is dried to form the positive electrode active material layer 310. The current collector 100 and the positive electrode active material layer 310 are pressed together at a predetermined pressure to adhere the positive electrode active material layer 310 to the current collector 100. Alternatively, the positive electrode active material layer 310 may be formed on a support and then transferred from the support to the current collector 100. The positive electrode active material layer 310 may also be adhered to the current collector 100 while heating the positive electrode active material layer 310 and the current collector 100 to a temperature higher than room temperature. Such methods can increase the peel strength between the current collector 100 and the positive electrode active material layer 310. Preferably, the positive electrode active material layer 310 and the current collector 100 may be heated to a temperature of 50°C to 180°C while pressure is applied to adhere the positive electrode active material layer 310 to the current collector 100. The "temperature of 50°C to 180°C" may be, for example, the surface temperature of the positive electrode active material layer 310.

[0190] When bonding the positive electrode active material layer 310 to the current collector 100, pressure may be applied to the current collector 100 and the positive electrode active material layer 310. The method of applying pressure is not particularly limited and may be a uniaxial press or a roll press. When a uniaxial press is used, the pressure applied to the current collector 100 and the positive electrode active material layer 310 is, for example, in the range of 5 MPa to 160 MPa. When a roll press is used, the pressure applied to the current collector 100 and the positive electrode active material layer 310 is, for example, in the range of 0.1 t / cm to 10 t / cm. By using such a method, the peel strength between the current collector 100 and the positive electrode active material layer 310 can be increased.

[0191] As described in Embodiment 1, the process of bonding the positive electrode active material layer 310 to the current collector 100 may be carried out such that the rate of change of surface roughness ΔSa, shown by the following formula (ii), falls within the range of -29% to -16%. S1 represents the surface roughness of the coating layer 102 before bonding the positive electrode active material layer 310 to the current collector 100. S2 represents the surface roughness of the coating layer 102 after bonding the positive electrode active material layer 310 to the current collector 100. Specifically, the pressure and temperature applied to the current collector 100 and the positive electrode active material layer 310 can be adjusted so that the rate of change of surface roughness ΔSa falls within the range of -29% to -16%.

[0192] ΔSa=100×(S2-S1) / S1 (ii)

[0193] By appropriately controlling the rate of change ΔSa of surface roughness, the contact properties at the interface between the coating layer 102 and the positive electrode active material layer 310 are improved. This allows for a good balance between the formation of a conductive network by the conductive material 103 and the formation of an adhesive interface by the binder 104 at the interface between the coating layer 102 and the positive electrode active material layer 310. As a result, high peel strength and low contact resistance can be achieved, which in turn improves the charge and discharge characteristics of the battery.

[0194] (Embodiment 3) Figure 4 is a cross-sectional view of a battery 500 according to Embodiment 3. The battery 500 comprises a positive electrode 300, a negative electrode 400, and an electrolyte layer 501. The electrolyte layer 501 is located between the positive electrode 300 and the negative electrode 400.

[0195] (positive electrode) The positive electrode 300 may be the positive electrode 300 described with reference to Figure 3.

[0196] (electrolyte layer) The electrolyte layer 501 is a layer containing an electrolyte. This electrolyte is, for example, a solid electrolyte. That is, the electrolyte layer 501 may be a solid electrolyte layer. As the solid electrolyte contained in the electrolyte layer 501, the material exemplified as the solid electrolyte 316 in Embodiment 2 may be used. That is, the electrolyte layer 501 may contain a solid electrolyte having the same composition as the solid electrolyte 316. With the above configuration, the charge and discharge efficiency of the battery 500 can be further improved.

[0197] The electrolyte layer 501 may contain a solid electrolyte having a different composition from that of the solid electrolyte 316.

[0198] The electrolyte layer 501 may contain a sulfide solid electrolyte. With the above configuration, the charge and discharge characteristics of the battery 500 can be further improved.

[0199] The electrolyte layer 501 may contain only one solid electrolyte selected from the materials listed as solid electrolytes.

[0200] The electrolyte layer 501 may contain two or more solid electrolytes selected from the materials listed as solid electrolytes. In this case, the multiple solid electrolytes may have different compositions from each other. For example, the electrolyte layer 501 may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0201] The thickness of the electrolyte layer 501 may be 1 μm or more and 300 μm or less. When the thickness of the electrolyte layer 501 is 1 μm or more, short circuits between the positive electrode 300 and the negative electrode 400 are less likely to occur. When the thickness of the electrolyte layer 501 is 300 μm or less, the battery 500 can operate at high output.

[0202] (Negative electrode) The negative electrode 400 comprises a negative electrode active material layer 502 and a negative electrode current collector 503. The negative electrode active material layer 502 is supported by the negative electrode current collector 503. The negative electrode active material layer 502 is in contact with the negative electrode current collector 503.

[0203] The negative electrode active material layer 502 includes a material having the property of intercalating and releasing metal ions (e.g., lithium ions). The negative electrode active material layer 502 includes, for example, a negative electrode active material.

[0204] The negative electrode active material can be a metallic material, a carbon material, an oxide, a nitride, a tin compound, a silicon compound, etc. The metallic material may be a pure metal or an alloy. Examples of metallic materials include lithium metal and lithium alloys. Examples of carbon materials include natural graphite, coke, carbon in the process of graphitization, carbon fibers, spheroidal carbon, artificial graphite, and amorphous carbon. The capacity density can be improved by using silicon (Si), tin (Sn), silicon compounds, tin compounds, etc.

[0205] The negative electrode active material layer 502 may contain a solid electrolyte. With the above configuration, the lithium ion conductivity inside the negative electrode active material layer 502 is increased, and the battery 500 can operate at high power. As the solid electrolyte contained in the negative electrode active material layer 502, the material exemplified as the solid electrolyte 316 in Embodiment 2 may be used. That is, the negative electrode active material layer 502 may contain a solid electrolyte having the same composition as the solid electrolyte 316.

[0206] The shape of the solid electrolyte contained in the negative electrode active material layer 502 is not particularly limited. The shape of the solid electrolyte contained in the negative electrode active material layer 502 may be, for example, needle-shaped, spherical, or ellipsoidal. For example, the shape of the solid electrolyte contained in the negative electrode active material layer 502 may be particulate.

[0207] When the solid electrolyte contained in the negative electrode active material layer 502 is particulate (for example, spherical), the median diameter of the solid electrolyte may be 100 μm or less. When the median diameter of the solid electrolyte is 100 μm or less, the negative electrode active material and the solid electrolyte can form a good dispersion state in the negative electrode active material layer 502. This improves the charge and discharge characteristics of the battery 500.

[0208] The median diameter of the solid electrolyte contained in the negative electrode active material layer 502 may be 10 μm or less, or 1 μm or less. With the above configuration, the negative electrode active material and the solid electrolyte can form a good dispersion state in the negative electrode active material layer 502.

[0209] The median diameter of the solid electrolyte contained in the negative electrode active material layer 502 may be smaller than the median diameter of the negative electrode active material. With this configuration, the negative electrode active material and the solid electrolyte can form a better dispersion state in the negative electrode active material layer 502.

[0210] The shape of the negative electrode active material is not particularly limited. The shape of the negative electrode active material may be, for example, needle-shaped, spherical, or ellipsoidal. For example, the shape of the negative electrode active material may be particulate.

[0211] The median diameter of the negative electrode active material may be 0.1 μm or more and 100 μm or less. When the median diameter of the negative electrode active material is 0.1 μm or more, the negative electrode active material and the solid electrolyte can form a good dispersion state in the negative electrode active material layer 502. This improves the charge and discharge characteristics of the battery 500. When the median diameter of the negative electrode active material is 100 μm or less, a sufficient lithium diffusion rate is ensured within the negative electrode active material. This allows the battery 500 to operate at high power.

[0212] The median diameter of the negative electrode active material may be larger than the median diameter of the solid electrolyte contained in the negative electrode active material layer 502. This allows the negative electrode active material and the solid electrolyte to form a good dispersion state.

[0213] The volume ratio "v2:100-v2" of the negative electrode active material to the solid electrolyte contained in the negative electrode active material layer 502 may satisfy the condition 30≦v2≦95. Here, v2 represents the volume ratio of the negative electrode active material when the total volume of the negative electrode active material and solid electrolyte contained in the negative electrode active material layer 502 is set to 100. If 30≦v2 is satisfied, the energy density of the battery 500 can be sufficiently secured. If v2≦95 is satisfied, the battery 500 can operate at high power.

[0214] The thickness of the negative electrode active material layer 502 may be 1 μm or more and 500 μm or less. When the thickness of the negative electrode active material layer 502 is 1 μm or more, the energy density of the battery 500 can be sufficiently ensured. When the thickness of the negative electrode active material layer 502 is 500 μm or less, the battery 500 can operate at high power.

[0215] At least one selected from the group consisting of the positive electrode active material layer 310, the electrolyte layer 501, and the negative electrode active material layer 502 may contain a binder for the purpose of improving the adhesion between particles. Examples of the binder include materials that may be contained in the positive electrode active material layer 310 as the binder 313.

[0216] The negative electrode active material layer 502 may contain a conductive material for the purpose of improving the electron conductivity. Examples of the conductive material include materials that may be contained in the positive electrode active material layer 310 as the conductive material 315.

[0217] Examples of the shape of the battery 500 in Embodiment 2 include coin type, cylindrical type, rectangular type, sheet type, button type, flat type, laminated type, and the like.

[0218] (Embodiment 4) FIG. 5 is a cross-sectional view of a battery 600 according to Embodiment 4. The battery 500 includes a positive electrode 300, an electrolyte layer 501, a negative electrode 400, an electrolyte layer 501, and a positive electrode 300 in this order. That is, the battery 600 includes two sets of cells. The negative electrode current collector 503 is shared by the two sets of cells. Each cell has the same structure as the battery 500 described with reference to FIG. 4. The technology of the present disclosure can also be applied to a battery 600 having such a structure.

[0219] As the current collector 100 in the positive electrode 300 of the battery 600, the current collector 200 described with reference to FIG. 2 may be used. In this case, the positive electrode active material layer 310 can be disposed on both sides of the current collector 200. That is, it is possible to construct a multi-layered battery including three or more sets of cells.

[0220] (Other Embodiments) (Supplementary Note) The following techniques are disclosed by the description of the above embodiments.

[0221] (Technique 1) A substrate, A coating layer that includes a binder and a conductive material and covers the substrate, A current collector provided with: The conductive material includes a carbon material, The current collector satisfies at least one selected from the group consisting of the following requirements (a), (b), (c), (d), and (e). Current collector. (a) In the Raman spectrum of the coating layer, the G / D ratio, which is the ratio of the peak intensity of the G band to the peak intensity of the D band, is greater than 0.80 and less than 3.09. (b) The basis weight of the coating layer is 0.20 g / m 2 or more and less than 1.93 g / m 2 (c) The value X calculated based on the following formula (i) is greater than 9.8 mg / cm and less than or equal to 70 mg / cm 2 X = mβ / (S × mα) ··· (i) 2 (d) The change rate ΔSa of the surface roughness represented by the following formula (ii) is -29% or more and -16% or less. [[ID=三十一]] X = mβ / (S × mα) ··· (i) Here, S represents the specific surface area of the conductive material (unit: m 2 / g), mα represents the mass of the conductive material contained in the coating layer per unit area (unit: g / m 2 ), and mβ represents the mass of the binder contained in the coating layer per unit area (unit: mg / m 2 2 (e) The binder includes a resin having a heat of fusion of 50 J / g or more. ΔSa = 100 × (S2 - S1) / S1 ··· (ii) Here, S1 represents the surface roughness of the coating layer before the electrode layer is adhered to the current collector, and S2 represents the surface roughness of the coating layer after the electrode layer is adhered to the current collector. (e) The binder includes a resin having a heat of fusion of 50 J / g or more.

[0222] According to the current collector of this disclosure, it is possible to improve the adhesion between the current collector and the electrode layer while reducing the resistance at the interface between the current collector and the electrode layer.

[0223] (Technology 2) A current collector as described in Technical 1, wherein the G / D ratio is greater than 0.80 and 2.00 or less. With such a configuration, it is easy to achieve both the effect of improving peel strength and the effect of reducing contact resistance.

[0224] (Technology 3) A current collector as described in Technical 1, wherein the G / D ratio is greater than 0.88 and less than or equal to 2.00. With such a configuration, it is easy to achieve both the effect of improving peel strength and the effect of reducing contact resistance.

[0225] (Technology 4) The basis weight of the aforementioned coating layer is 0.40 g / m². 2 More than 1.50g / m 2 The current collector described in any one of the following technical sections 1 to 3. When the basis weight is adjusted to such a range, it is easier to maintain high peel strength and low contact resistance, and short-circuit resistance is also improved.

[0226] (Technology 5) The current collector according to Technology 4, wherein the conductive material comprises graphite and carbon black. When the conductive material comprises graphite and carbon black, high peel strength and low contact resistance are easily maintained even if the basis weight is reduced to improve short-circuit resistance.

[0227] (Technology 6) A current collector according to any one of the Art 1 to 5, wherein the binder comprises a polyolefin. Using a polyolefin makes it easier to achieve both improved peel strength and reduced contact resistance.

[0228] (Technology 7) A current collector according to any one of the technologies 1 to 6, wherein the conductive material includes multiple types of carbon materials. With such a configuration, it is easy to achieve both the effect of improving peel strength and the effect of reducing contact resistance.

[0229] (Technology 8) The conductive material includes a first conductive material and a second conductive material, and the formula (i) is represented by X = mβ / ((S1×m1)+(S2×m2)), where S1 represents the specific surface area of the first conductive material (unit: m 2 / g), S2 represents the specific surface area of the second conductive material (unit: m 2 / g), m1 represents the mass of the first conductive material contained in the coating layer per unit area (unit: g / m 2 ), and m2 represents the mass of the second conductive material contained in the coating layer per unit area (unit: g / m 2 ). The current collector according to any one of Technologies 1 to 7. The formula (i) can also be applied when the conductive material includes a plurality of surrounding carbon materials.

[0230] (Technology 9) The current collector according to any one of Technologies 1 to 8, wherein the melting point of the resin is in the range of 80°C to 140°C. When such a resin is used as a binder, it is not necessary to apply a high temperature exceeding 200°C when adhering the electrode layer to the current collector.

[0231] (Technology 10) The current collector according to any one of Technologies 1 to 9, wherein the conductive material includes at least one selected from the group consisting of graphite and carbon black. When the conductive material includes graphite, it is easy to reduce the amount of the binder. When the conductive material includes carbon black, a conductive network is easily formed by the conductive material.

[0232] (Technology 11) The current collector according to any one of Technologies 1 to 10, an electrode layer supported by the current collector, and an electrode comprising the same.

[0233] According to the electrode of the present disclosure, it is possible to improve the adhesion between the current collector and the electrode layer while reducing the resistance at the interface between the current collector and the electrode layer.

[0234] (Technology 12) A method for manufacturing electrodes as described in Technical 11, This includes bonding the electrode layer to the current collector at a temperature of 50°C to 180°C. A method for manufacturing electrodes.

[0235] According to the electrode manufacturing method of this disclosure, it is possible to improve the adhesion between the current collector and the electrode layer while reducing the resistance at the interface between the current collector and the electrode layer.

[0236] (Technology 13) A method for manufacturing an electrode according to Technology 12, wherein when the electrode layer is bonded to the current collector, a pressure of 5 MPa to 160 MPa is applied to the current collector and the electrode layer. By such a method, the peel strength between the current collector and the electrode layer can be increased.

[0237] (Technology 14) A method for manufacturing electrodes as described in Technical 11, The method includes adhering the electrode layer to the current collector such that the rate of change ΔSa of surface roughness, as shown in the following formula (ii), falls within the range of -29% to -16%. A method for manufacturing electrodes. ΔSa=100×(S2-S1) / S1 (ii) Here, S1 represents the surface roughness of the coating layer before the electrode layer is bonded to the current collector, and S2 represents the surface roughness of the coating layer after the electrode layer is bonded to the current collector.

[0238] According to the electrode manufacturing method of this disclosure, it is possible to improve the adhesion between the current collector and the electrode layer while reducing the resistance at the interface between the current collector and the electrode layer.

[0239] (Technology 15) Positive electrode and, The negative electrode and, An electrolyte layer located between the positive electrode and the negative electrode, Equipped with, At least one selected from the group consisting of the positive electrode and the negative electrode includes the electrode described in Technical 11. battery.

[0240] The battery of this disclosure makes it possible to improve the adhesion between the current collector and the electrode layer while reducing resistance at the interface between the current collector and the electrode layer. [Examples]

[0241] (Sample 1) [Preparation of sulfide solid electrolytes] In an argon glove box with a dew point of -60°C or lower, the raw material powders Li2S, P2S5, LiBr, and LiI were weighed in a molar ratio of 85(1.5Li2S:0.5P2S5)·7.5LiBr·7.5LiI. The raw material powders were ground and mixed in a mortar to obtain a mixture. The mixture was then milled using a planetary ball mill (Fritsch, P-7 type) at 510 rpm for 10 hours. This yielded a glassy solid electrolyte. The obtained solid electrolyte was heat-treated in an inert atmosphere at 270°C for 2 hours. This produced a glass-ceramic sulfide solid electrolyte, Li2S-P2S5-LiBr-LiI (hereinafter referred to as LPSBI).

[0242] [Fabrication of coating material] In an argon glove box with a dew point of -60°C or lower, the raw material powders LiF, TiF4, and AlF3 were weighed in a molar ratio of LiF:TiF4:AlF3 = 2.5:0.5:0.5. These were ground and mixed in a mortar to obtain a mixture. The mixture was then milled using a planetary ball mill at 500 rpm for 12 hours. This yielded a powder of a halide solid electrolyte to be used as a coating material for the coating layer. The coating material is Li 2.5 Ti 0.5 Al 0.5 It had a composition represented by F6 (hereinafter referred to as LTAF).

[0243] [Preparation of coated active material] As the positive electrode active material, Li(NiCoAl)O2 (hereinafter referred to as NCA) powder was prepared. Next, a coating layer made of LTAF was formed on the surface of the NCA. The coating layer was formed by compression shearing using a particle compounding device (NOB-MINI, manufactured by Hosokawa Micron Corporation). Specifically, NCA and LTAF were weighed in a volume ratio of 98:2 and processed under the conditions of blade clearance: 2 mm, rotation speed: 6000 rpm, and processing time: 50 min. This yielded a coated active material. Hereafter, the coated active material will be referred to as "LTAF-NCA".

[0244] [Fabrication of cathode materials] Carbon fiber (VGCF-H, manufactured by Resonaq Corporation) was used as the first conductive material. Acetylene black (Li435, manufactured by Denka Corporation) was used as the second conductive material. In an argon glove box with a dew point of -60°C or lower, the binder, solvent, and Li435 were mixed and dispersed using a homogenizer. LTAF-NCA was then added and mixed, and dispersed using a homogenizer. Furthermore, LPSBI and VGCF-H were added and mixed, and dispersed using a homogenizer. This prepared the cathode slurry.

[0245] [Fabrication of the positive electrode active material layer] A positive electrode slurry was applied to an aluminum (A1N30) support substrate to form a coating film. The positive electrode active material layer was fabricated by drying the coating film using a hot plate at 120°C for 30 minutes.

[0246] [Manufacturing of a current collector with a coating layer] (Sample 1) A coating was prepared by kneading conductive carbon, a binder, and a solvent to achieve a solid content of 18% by mass. Graphite (Gr: UP-type graphite, manufactured by Nippon Graphite Industries Co., Ltd.) and carbon black (CB: manufactured by Denka Co., Ltd.) were used as the conductive carbon. Polyolefin was used as the binder. Deionized water was used as the solvent. Next, a coating film was formed by applying the coating in the MD direction to one side (first side) of the substrate using a gravure coater. Aluminum alloy foil (A1N30-H18, thickness: 15 μm) was used as the substrate. The coating film was dried at 150°C to form a protective layer.

[0247] (Sample 2) The current collector for Sample 2 was fabricated using the same method as for Sample 1, except that graphite with an average particle diameter of 20 μm was used as the conductive material, and the amount of binder was adjusted.

[0248] (Sample 3) The current collector for Sample 3 was fabricated using the same method as for Sample 1, except that graphite with an average particle diameter of 5 μm was used as the conductive material, and the amount of binder was adjusted.

[0249] (Sample 4) The current collector for Sample 4 was manufactured using the same method as for Sample 1, except that the type of binder was changed and the amount of binder was adjusted.

[0250] (Sample 5) The current collector for Sample 5 was fabricated using the same method as for Sample 1, except that only carbon black was used as the conductive material and the amount of binder was adjusted.

[0251] (Sample 6) The current collector for Sample 6 was fabricated using the same method as for Sample 1, except that graphite was used as the conductive material.

[0252] (Sample 7) The current collector for Sample 7 was fabricated using the same method as for Sample 1, except that only graphite was used as the conductive material. Note that the crystalline properties of the graphite used in Sample 7 differed from those of the graphite used in Sample 6.

[0253] [Raman spectroscopy] Raman spectra were obtained from the surface of the coating layer of current collectors 1 to 7 using micro-Raman spectroscopy. A laser Raman spectrophotometer (JASCO Corporation, NRS-5500) was used for the measurements. Raman mapping measurements were performed at 360 locations within a 100 μm × 100 μm area on the surface of the current collector coating layer. The average spectrum was calculated from all obtained spectra. After applying background correction to the average spectrum, the corrected average spectrum was obtained.

[0254] Corrected average spectrum at 1580 cm⁻¹ -1 The maximum intensity of the nearby Raman band (G band), and 1370 cm -1 The maximum intensity of the nearby Raman band (D band) was read, and the G / D ratio, which is the ratio of Raman band intensities, was calculated. Using the same method, Raman mapping was performed on three different fields of view, and the average of the obtained G / D ratios was calculated. The results are shown in Table 1.

[0255] [Fabrication of the positive electrode] A pre-fabricated positive electrode active material layer was placed on each side of an Al current collector (SDX-PT, manufactured by Resonaq Corporation) equipped with a carbon coating layer on each side, and roll pressing was performed at 175°C and 2 t / cm. The support substrate was removed from the positive electrode active material layer, and the positive electrode active material layer was transferred to the Al current collector. This resulted in a laminate with positive electrode active material layers on both sides of the Al current collector. Subsequently, the laminate was roll-pressed again at 175°C and 5 t / cm. Then, the current collectors of Sample 1 were placed on both sides of the laminate, and uniaxial pressing was performed at 140°C, 80 MPa, and 5 minutes. This resulted in obtaining the positive electrode of Sample 1. The positive electrodes of Samples 2 through 7 were obtained using the same method.

[0256] [Preparation of a reference positive electrode] A pre-fabricated positive electrode active material layer was placed on each side of an aluminum current collector (SDX-PT, manufactured by Resonaq Corporation) equipped with a carbon coating layer on each side, and roll pressing was performed at 175°C and 5 t / cm. As a result, a reference positive electrode was obtained in which aluminum foil (A1N30) was provided on both sides, replacing the current collectors of samples 1 to 7.

[0257] Figure 6 is a cross-sectional view of the positive electrode 700 of samples 1 to 7. The positive electrode 700 had, in this order, one current collector 100 of any of samples 1 to 7, a positive electrode active material layer 310, an Al current collector 701 with a carbon coating layer, another positive electrode active material layer 310, and one current collector 100 of any of samples 1 to 7. The reference positive electrode had a structure in which the current collector 100 was replaced with aluminum foil (A1N30).

[0258] [Measurement of contact resistance] The total resistance R1 of the positive electrode of samples 1 to 7 was measured by DC polarization. The total resistance R0 of the reference positive electrode was measured by DC polarization. Then, using the following equation (x), the contact resistance (R) at the interface between the current collector and the positive electrode active material layer of samples 1 to 7 was calculated. int The result was calculated. The results are shown in Table 1.

[0259] R int =(R1-R0) / 2...Equation (x)

[0260] In the DC polarization method, the current flowing when a constant voltage of 0.10V, 0.15V, or 0.20V was applied to the positive electrode was read, and the total resistances R1 and R0 were calculated using Ohm's law.

[0261] [Measurement of peel strength] The peel strength of the positive electrodes of samples 1 to 7 was measured using a universal material testing machine (A&D Corporation, RTH-1310) by the following method. The measurements were performed in a dry room with a dew point of -50°C or lower. First, a positive electrode cut to a width of 10 mm was attached to a test plate with double-sided tape. More specifically, the positive electrode active material layer was attached to the test plate via double-sided tape. Next, using a universal material testing machine equipped with a jig for a 90-degree peel test of adhesive tape, the positive electrode active material layer was peeled from the current collector at a peel angle of 90 degrees and a peel speed of 5 mm / min. After the start of measurement, the measurement value of the first 5 mm length peeled from the current collector was not used. Subsequently, the measurement values ​​(unit: N) for the positive electrode active material layer over a 5 mm length peeled from the current collector were recorded continuously. The average value (Av) of these measurements was considered to be the peel strength (unit: N / cm) between the positive electrode active material layer and the current collector. The results are shown in Table 1. In Table 1, peel strength and contact resistance are expressed as relative values ​​based on the values ​​for Sample 1.

[0262] [Table 1]

[0263] ≪Consideration≫ As shown in Table 1, the G / D ratios for current collectors of samples 1 to 7 were 1.01, 1.15, 1.75, 1.28, 0.80, 3.09, and 5.43, respectively.

[0264] As shown in Table 1, the positive electrode of Sample 5, which used only carbon black as the conductive material, exhibited low contact resistance. This is likely because the use of carbon black with a large specific surface area increased the frequency of contact between carbon black particles. When the frequency of contact between carbon black particles increases, the electronic conductivity of the coating layer improves, increasing the frequency of contact between the current collector and the positive electrode active material layer, and thus achieving low contact resistance. However, in terms of peel strength, Sample 5 exhibited the lowest peel strength. This is likely because the use of carbon black with a large specific surface area caused the binder to adsorb onto the carbon black, reducing the amount of binder present at the interface between the current collector and the positive electrode active material layer. In other words, it is thought that there was insufficient binder to maintain adhesion between the current collector and the positive electrode active material layer.

[0265] Samples 6 and 7, using graphite with a smaller specific surface area, showed the opposite results to sample 5. In other words, the current collectors of samples 6 and 7 exhibited sufficiently high peel strength. However, it is thought that the formation of a conductive network in the coating layer was insufficient with graphite alone, resulting in high contact resistance.

[0266] In contrast, in the range where the G / D ratio is greater than 0.80 and less than 3.09, it is believed that high peel strength and low contact resistance could be achieved by a coating layer that utilizes the characteristics of graphite and carbon black. Among these, when the G / D ratio was 2.00 or less, even higher peel strength and lower contact resistance could be achieved.

[0267] (Sample 11) [Manufacturing of a current collector with a coating layer] The paint used to prepare the current collector of Sample 4 was diluted with deionized water. This resulted in a paint with a solid content of 11.8% by mass. Using this paint, the current collector of Sample 11 was prepared in the same manner as Sample 1.

[0268] (Sample 12) The paint used to prepare the current collector of Sample 4 was diluted with deionized water. This resulted in a paint with a solid content of 14.5% by mass. Using this paint, the current collector of Sample 12 was prepared in the same manner as Sample 1.

[0269] (Sample 13) Using the same materials as the paint used to fabricate the current collector of Sample 4, a paint with a solid content of 20.4% by mass was prepared. Using this paint, the current collector of Sample 13 was fabricated in the same manner as Sample 1.

[0270] (Sample 14) The current collector in sample 14 was identical to that in sample 4.

[0271] (Sample 15) Using the same paint used to produce the current collector for Sample 4, the current collector for Sample 15 was manufactured using a mass production machine.

[0272] (Sample 16) The current collector in sample 16 was identical to that in sample 5.

[0273] (Sample 17) The paint for Sample 17 was prepared in the same manner as for Sample 1, except that only graphite was used as the conductive material. Using this paint, the current collector for Sample 17 was fabricated in the same manner as for Sample 1.

[0274] (Sample 18) Aside from increasing the capacity of the gravure-printed cup and applying paint to the substrate, the current collector for Sample 18 was manufactured using the same paint as for Sample 13 and in the same manner as for Sample 1.

[0275] (Sample 19) Aside from increasing the capacity of the gravure-printed cup and applying paint to the substrate, the current collector for Sample 19 was manufactured using the same paint as that used for Sample 1 and in the same manner as for Sample 1.

[0276] [Gross weight] The basis weight of the coating layer of the current collectors for samples 11 to 19 was calculated by subtracting the mass of the substrate from the mass of the current collector. The results are shown in Table 2.

[0277] [Fabrication of the positive electrode] The positive electrodes for samples 11 through 19 were fabricated using the method described earlier.

[0278] [Preparation of a reference positive electrode] A reference positive electrode was fabricated using the method described earlier.

[0279] [Measurement of contact resistance] The total resistance R1 of the positive electrode of samples 11 to 19 was measured by DC polarization. The total resistance R0 of the reference positive electrode was measured by DC polarization. Then, using the equation (x) described earlier, the contact resistance (R) at the interface between the current collector and the positive electrode active material layer of samples 11 to 19 was calculated. int The contact resistance was calculated. The results are shown in Table 2. In Table 2, the contact resistance is expressed as a relative value based on the value of Sample 1.

[0280] [Measurement of peel strength] The peel strength of the positive electrodes of samples 11 to 19 was measured using the method described above. The results are shown in Table 2. In Table 2, the peel strength is expressed as a relative value with respect to the value of sample 1.

[0281] [Preparation of a battery for measuring self-discharge rate] A battery having the structure described in Figure 5 was fabricated using the method described below.

[0282] A negative electrode slurry was applied to each side of an Al current collector (SDX-PT, manufactured by Resonaq Corporation) which had a carbon coating layer on each side, to form a coating film. The coating film was dried to obtain the negative electrode. The negative electrode slurry contained Li4Ti5O as the negative electrode active material. 12 It contained a sulfide solid electrolyte as a solid electrolyte, a conductive additive, a binder, and a solvent.

[0283] A solid electrolyte slurry was applied to an aluminum (A1N30) support substrate to form a coating film. The coating film was dried to obtain a solid electrolyte sheet. The solid electrolyte slurry contained a sulfide solid electrolyte LPSBI as the solid electrolyte, a binder, and a solvent.

[0284] The positive electrode slurry was applied to an aluminum (A1N30) support substrate to form a coating film. The coating film was dried to obtain the positive electrode active material layer. The positive electrode slurry was the same as that used in Sample 1.

[0285] Solid electrolyte sheets were placed on each side of the negative electrode to form a laminate, and roll pressing was performed at 175°C and 3 t / cm. The support substrate was removed from the solid electrolyte sheet, and the solid electrolyte layer was transferred to the negative electrode. A positive electrode active material layer was placed on each of the two solid electrolyte layers, and roll pressing was performed at 175°C and 5 t / cm. The support substrate was removed from the positive electrode active material layer, and the positive electrode active material layer was transferred to the laminate. A current collector of sample 11 was placed on each of the two positive electrode active material layers. A stainless steel wire with a diameter of 40 μm and a length of 2 mm was placed as a foreign object so as to be in contact with the substrate of the current collector. Then, uniaxial pressing of the laminate was performed at 140°C and 80 MPa. This obtained the sample 11 battery for self-discharge measurement. The sample 11 battery was sealed in aluminum laminate packaging.

[0286] Batteries for samples 12 through 19 were fabricated using the same method as for sample 11.

[0287] [Measurement of self-discharge rate] The self-discharge rate of batteries 11 to 19 was measured. Specifically, the batteries were placed in a constant temperature bath at 25°C and connected to a charge / discharge device. Constant current charging was performed at a rate of 0.1C until the voltage reached 2.515V, corresponding to a state of charge (SOC) of 85%. After reaching 2.515V, constant voltage charging was performed until the current value decreased to 0.01C. After charging was completed, the open-circuit voltage was maintained, and the voltage drop during the period from 48 hours to 72 hours was calculated as the self-discharge rate (mV / day). The results are shown in Table 2.

[0288] [Table 2]

[0289] ≪Consideration≫ As shown in Table 2, the basis weight of the current collectors for samples 11 to 19 was 0.21 g / m², respectively. 2 , 0.75g / m 2 1.45 g / m 2 1.15g / m 2 1.08 g / m 2 , 0.66 g / m 2 , 0.94g / m 2 1.93g / m 2 , and 2.64 g / m 2 That was the case.

[0290] The self-discharge rates shown in Table 2 can be used as an indicator of short-circuit resistance. A high self-discharge rate indicates low short-circuit resistance. A low self-discharge rate indicates high short-circuit resistance.

[0291] As shown in Table 2, the self-discharge rates of batteries in samples 18 and 19 were high. In other words, when the basis weight of the coating layer was too high, the short-circuit resistance of the battery was insufficient.

[0292] The self-discharge rates of batteries 11 through 17 were low. Batteries 11 through 17 also showed excellent short-circuit resistance.

[0293] Scanning electron microscope examination of cross-sections of several samples revealed cracks caused by the stainless steel wire W. For samples with a large coating layer, it is thought that the coating components flowed deep into the cracks, resulting in a high self-discharge rate for the battery. For samples with a small coating layer, it is thought that the coating components did not flow easily into the cracks, resulting in a low self-discharge rate for the battery.

[0294] As shown in Table 2, the positive electrode using the current collector of Sample 11 exhibited low peel strength and high contact resistance. As shown in Samples 12 to 15, contact resistance decreased and peel strength increased with increasing basis weight. This is thought to be because a coating layer of sufficient thickness existed between the current collector and the positive electrode active material layer, thus forming a good interface between the current collector and the positive electrode active material layer.

[0295] The positive electrodes using current collectors from Sample 16, which used only carbon black as the conductive material, and Sample 17, which used only graphite as the conductive material, tended to exhibit low peel strength and high contact resistance. This result indicates that using a mixture of graphite and carbon black as the conductive material can achieve both high peel strength and low contact resistance.

[0296] Based on these results, the basis weight of the coating layer is 0.20 g / m². 2 More than 1.93g / m 2 It is preferable that it be less than 0.40 g / m². 2 More than 1.50g / m 2 It is more preferable that the following is true: 0.70 g / m 2 More than 1.50g / m 2 The following is most desirable: If the conductive material contained in the coating layer is a mixture of graphite and carbon black, short-circuit resistance can be improved while maintaining high peel strength and low contact resistance.

[0297] (Sample 21) [Manufacturing of a current collector with a coating layer] Sample 21 paint was prepared by reducing the binder content in the paint used to fabricate the current collector of Sample 4. Specifically, the ratio of the binder mass in Sample 21 paint to the binder mass in Sample 4 paint was 68% by mass. A current collector for Sample 21 was fabricated using the paint for Sample 21 in the same manner as for Sample 1.

[0298] (Sample 22) Sample 22 paint was prepared by reducing the binder content in the paint used to fabricate the current collector of Sample 4. Specifically, the ratio of the binder mass in Sample 22 paint to the binder mass in Sample 4 paint was 85% by mass. A current collector for Sample 22 was fabricated using the paint for Sample 22 in the same manner as for Sample 1.

[0299] (Sample 23) Sample 23 was prepared by increasing the binder content in the paint used to fabricate the current collector of Sample 4. Specifically, the ratio of the binder mass in Sample 23 paint to the binder mass in Sample 4 paint was 120% by mass. A current collector for Sample 23 was fabricated using the paint for Sample 23 in the same manner as for Sample 1.

[0300] (Sample 24) Sample 24 paint was prepared by increasing the binder content in the paint used to fabricate the current collector of Sample 4. Specifically, the ratio of the binder mass in Sample 24 paint to the binder mass in Sample 4 paint was 138% by mass. A current collector for Sample 24 was fabricated using the paint for Sample 24 in the same manner as for Sample 1.

[0301] (Sample 25) Sample 25 paint was prepared by increasing the binder content in the paint used to fabricate the current collector of Sample 4. Specifically, the ratio of the binder mass in Sample 25 paint to the binder mass in Sample 4 paint was 155% by mass. A current collector for Sample 25 was fabricated using the paint for Sample 25 in the same manner as for Sample 1.

[0302] (Sample 26) The current collector in sample 26 was identical to that in sample 4.

[0303] (Sample 27) The current collector in sample 27 was identical to that in sample 15.

[0304] (Sample 28) Sample 28 paint was prepared by increasing the binder content in the paint used to fabricate the current collector of Sample 4. Specifically, the ratio of the binder mass in Sample 28 paint to the binder mass in Sample 4 paint was 200% by mass. A current collector for Sample 28 was fabricated using the paint for Sample 28 in the same manner as for Sample 1.

[0305] (Sample 29) The current collector in sample 29 was identical to that in sample 5.

[0306] [Gross weight] The basis weight of the coating layer on current collectors for samples 21 to 29 was calculated by subtracting the mass of the substrate from the mass of the current collector. The results are shown in Table 3.

[0307] [Fabrication of the positive electrode] The positive electrodes for samples 21 to 29 were fabricated using the method described earlier.

[0308] [Preparation of a reference positive electrode] A reference positive electrode was fabricated using the method described earlier.

[0309] [Measurement of contact resistance] The total resistance R1 of the positive electrode of samples 21 to 29 was measured by DC polarization. The total resistance R0 of the reference positive electrode was measured by DC polarization. Then, using the equation (x) described earlier, the contact resistance (R) at the interface between the current collector and the positive electrode active material layer of samples 21 to 29 was calculated. int The result was calculated. The results are shown in Table 3.

[0310] [Measurement of peel strength] The peel strength of the positive electrodes of samples 21 to 29 was measured using the method described earlier. The results are shown in Table 3.

[0311] [Calculation of value X] The specific surface area of ​​graphite, the conductive material used in the coating layer, was calculated. Specifically, graphite was placed in a test tube and connected to a specific surface area and pore distribution analyzer (Microtrac-Bel, BELSORP MAX). Subsequently, a nitrogen gas adsorption test was conducted under conditions of adsorption temperature of 77K and upper limit of adsorption relative pressure of 0.995 (P / P0). Using the analysis software Belmaster 7, the specific surface area was calculated by performing an analysis using the BET method in the linear region of the adsorption isotherm. The specific surface area of ​​carbon black, the conductive material used in the coating layer, was calculated using the same method.

[0312] The specific surface area of ​​the conductive material, the mass of the conductive material, and the mass of the binder were substituted into equation (i) to calculate the current collector value X for samples 21 to 29. The results are shown in Table 3.

[0313] [Table 3]

[0314] ≪Consideration≫ As shown in Table 3, the values ​​X for the current collectors of samples 21 to 29 are 20 g / m², respectively. 2 30g / m 2 50g / m 2 60g / m 2 70g / m 2 38.83 g / m 2 38.83 g / m 2 77.67 g / m 2 9.8g / m 2 That was the case.

[0315] As shown in Table 3, the positive electrode using the current collector of Sample 29 exhibited the lowest peel strength. The coating layer of the current collector of Sample 29 contained only carbon black as the conductive material. Therefore, it also showed a slightly higher contact resistance.

[0316] As the results for samples 21 to 28 show, as the value X increases, there is a tendency for both contact resistance and peel strength to increase. This is because a sufficient amount of binder in the coating layer is present between the current collector and the positive electrode active material layer, resulting in the formation of a good interface between the current collector and the positive electrode active material layer.

[0317] From these results, it is possible to provide a current collector that combines low contact resistance and high peel strength by appropriately controlling the value X. Furthermore, by using multiple types of carbon materials as conductive materials in the coating layer, it was possible to reduce contact resistance and improve peel strength.

[0318] From the results shown in Table 3, the desirable range for value X is 9.8 mg / cm³. 2 A larger 70 mg / cm³ 2 The following applies. When the value X falls within this range, high peel strength and low contact resistance can be achieved. The value X is preferably 20 mg / cm². 2 A larger 70 mg / cm³ 2 The following, and more preferably 30 mg / cm³ 2 More than 70mg / cm 2 The following applies:

[0319] (Sample 31) [Manufacturing of a current collector with a coating layer] The current collector in sample 31 was identical to that in sample 12.

[0320] (Sample 32) The current collector in sample 32 was identical to that in sample 13.

[0321] (Sample 33) The current collector in sample 33 was identical to that in sample 18.

[0322] (Sample 34) The current collector in sample 34 was identical to that in sample 4.

[0323] (Sample 35) The current collector in sample 35 was identical to that in sample 15.

[0324] (Sample 36) The current collector in sample 36 was identical to that in sample 19.

[0325] [Gross weight] The basis weight of the coating layer of the current collectors for samples 31 to 36 was calculated by subtracting the mass of the substrate from the mass of the current collector. The results are shown in Table 4.

[0326] [Fabrication of the positive electrode] The positive electrodes for samples 31 to 36 were fabricated using the method described earlier.

[0327] [Preparation of a reference positive electrode] A reference positive electrode was fabricated using the method described earlier.

[0328] [Measurement of contact resistance] The total resistance R1 of the positive electrode of samples 31 to 36 was measured by DC polarization. The total resistance R0 of the reference positive electrode was measured by DC polarization. Then, using the equation (x) described earlier, the contact resistance (R) at the interface between the current collector and the positive electrode active material layer of samples 31 to 36 was calculated. int The result was calculated. The results are shown in Table 4.

[0329] [Measurement of peel strength] The peel strength of the positive electrodes of samples 31 to 36 was measured using the method described above. The results are shown in Table 4.

[0330] [Surface roughness measurement] The surface roughness S1 of the coating layer before the positive electrode active material layer was bonded to the current collector, and the surface roughness S2 of the coating layer after the positive electrode active material layer was bonded to the current collector were measured. The surface roughness of the coating layer after the positive electrode active material layer was peeled off from the current collector by a 90-degree peel test was considered as "surface roughness S2". A laser microscope (Keyence Corporation, VK-X3000) was used for measurement. A 50x objective lens was used for observation. The surface roughness of five arbitrary regions was measured, and the average value of these measurements was adopted.

[0331] The amount of change and the rate of change were calculated from the surface roughness S1 and surface roughness S2. The results are shown in Table 4.

[0332] [Table 4]

[0333] ≪Consideration≫ As shown in Table 4, the rate of change ΔSa of surface roughness in the current collectors of samples 31 to 36 was 7.61%, -20.54%, -28.30%, -16.02%, -16.89%, and -29.13%, respectively.

[0334] As shown in Table 4, the current collector of sample 31 exhibited the largest rate of change ΔSa and the lowest peel strength. The reason for the low peel strength is thought to be that the amount of change in the shape of the coating layer during the bonding process, in which heat and pressure were applied, was small, resulting in insufficient adhesion between the current collector and the positive electrode active material layer.

[0335] As the results for samples 32 to 35 show, there was a tendency for peel strength to increase with decreasing rate of change ΔSa. This result indicates that the shape of the coating layer changed sufficiently during the bonding process in which heat and pressure were applied, and the adhesion between the current collector and the positive electrode active material layer improved. In other words, the high peel strength of samples 32 to 35 is thought to be due to the sufficient reduction in the surface roughness of the coating layer of the current collector after the bonding process.

[0336] As the results for sample 36 show, when the rate of change ΔSa was too small, the basis weight and contact resistance were high.

[0337] Based on the above, it is considered that high peel strength and low contact resistance can be achieved by controlling the rate of change of the surface roughness ΔSa of the coating layer to between -29% and -16%.

[0338] (Sample 41) [Manufacturing of a current collector with a coating layer] The current collector of Sample 41 was identical to that of Sample 1. The basis weight of the coating layer on the current collector of Sample 41 was 1.3 g / m². 2 That was the case.

[0339] [Measurement of heat of fusion] Using a differential scanning calorimeter (manufactured by Hitachi High-Tech Corporation), the heat of fusion and melting point of polyethylene, the binder used in the fabrication of the current collector, were measured in advance. The temperature of the sample (polyethylene) was increased from -50°C to 250°C at a heating rate of 5°C / min, and the melting point (peak temperature) and heat of fusion were measured. As shown in Table 5, the melting point of the polyethylene used in sample 41 was 94°C, and the heat of fusion was 100 J / g.

[0340] [Fabrication of the positive electrode] A pre-fabricated positive electrode active material layer was placed on each side of an Al current collector (manufactured by Resonac, SDX-PT) equipped with a carbon coating layer on each side, and roll pressing was performed at 175°C and 2 t / cm. The support substrate was removed from the positive electrode active material layer, and the positive electrode active material layer was transferred to the Al current collector. This resulted in a laminate with positive electrode active material layers on both sides of the Al current collector. Subsequently, the laminate was roll-pressed again at 175°C and 5 t / cm. Then, the current collectors of Sample 1 were placed on both sides of the laminate, and uniaxial pressing was performed at an bonding temperature of 140°C, a bonding pressure of 80 MPa, and for 5 minutes. This resulted in obtaining the positive electrode of Sample 41. The bonding temperature and bonding pressure shown in Table 5 are the temperature and pressure conditions for uniaxial pressing.

[0341] The binder used to prepare the positive electrode active material layer was amorphous styrene resin. Amorphous styrene resin has no melting point, and its heat of fusion was 0 J / g.

[0342] (Sample 42) The positive electrode of sample 42 was prepared in the same manner as sample 41, except that polyethylene with a melting point of 92°C and a heat of fusion of 75 J / g was used as the binder for the coating layer of the current collector.

[0343] (Sample 43) The cathode of sample 43 was fabricated using the same method as sample 42, except that the bonding pressure in the uniaxial press was changed to 45 MPa.

[0344] (Sample 44) The cathode of sample 44 was fabricated using the same method as sample 42, except that the bonding pressure in the uniaxial press was changed to 6 MPa.

[0345] (Sample 45) The cathode of sample 45 was prepared using the same method as sample 42, except that the bonding temperature in the uniaxial press was changed to 80°C.

[0346] (Sample 46) The positive electrode of sample 46 was prepared in the same manner as sample 41, except that amorphous polyimide was used as the binder for the current collector coating layer. As shown in Table 5, the amorphous polyimide had no melting point that could be determined by DSC, and therefore had a heat of fusion of 0 J / g.

[0347] (Sample 47) The cathode for sample 47 was prepared using the same method as for sample 46, except that the bonding temperature in the uniaxial press was changed to 190°C.

[0348] [Measurement of peel strength] The peel strength of the positive electrodes of samples 41 to 47 was measured using the method described earlier. The results are shown in Table 5.

[0349] [Table 5]

[0350] ≪Consideration≫ As shown in Table 5, the positive electrodes of samples 41 to 45 showed high peel strength. Under temperature and pressure conditions that were unlikely to adversely affect the positive electrode active material layer, the positive electrode active material layer could not be adhered to the current collector of sample 46. The positive electrode active material layer could be adhered to the current collector of sample 47, but the peel strength was low. In other words, by including a resin with a heat of fusion of 50 J / g or more as a binder in the coating layer, the resin melts at temperatures above its melting point, making adhesion easier, while at temperatures below its melting point, the resin crystallizes, ensuring high adhesion. [Industrial applicability]

[0351] The current collector of this disclosure is useful for solid-state batteries. [Explanation of symbols]

[0352] 13a First conductive material 13b Second conductive material 100,200 current collector 101 circuit board 102 Covering layer 103 Conductive material 104 Binder 300 positive electrode 310 Cathode active material layer 311 Cathode active material 312 Covering layer 313 Binder 315 Conductive material 316 Solid electrolyte 317 Coated active material 400 negative electrode 500,600 batteries 501 Electrolyte layer 502 Negative electrode active material layer 503 Negative electrode current collector

Claims

1. circuit board and A coating layer comprising a binder and a conductive material, which covers the substrate, A current collector equipped with, The conductive material includes a carbon material, Satisfying at least one selected from the group consisting of the following requirements (a), (b), (c), (d), and (e): Current collector. (a) In the Raman spectrum of the coating layer, the G / D ratio, which is the ratio of the peak intensity of the G band to the peak intensity of the D band, is greater than 0.80 and less than 3.

09. (b) The basis weight of the coating layer is 0.20 g / m² 2 1.93g / m or more 2 Less than, (c) The value X calculated based on the following formula (i) is 9.8 mg / cm³ 2 Larger 70 mg / cm 2 The following is: X=mβ / (S×mα)...(i) Here, S is the specific surface area (unit: m²) of the conductive material. 2 mα represents the mass of the conductive material contained in the coating layer per unit area (unit: g / m²), where mα is the mass of the conductive material contained in the coating layer per unit area (unit: g / m²). 2 mβ represents the mass of the binder contained in the coating layer per unit area (unit: mg / m²). 2 ) represents, (d) The rate of change ΔSa of surface roughness, as shown in formula (ii) below, is -29% or more and -16% or less. ΔSa=100×(S2-S1) / S1...(ii) Here, S1 represents the surface roughness of the coating layer before the electrode layer is bonded to the current collector, and S2 represents the surface roughness of the coating layer after the electrode layer is bonded to the current collector. (e) The binder contains a resin with a heat of fusion of 50 J / g or more.

2. The aforementioned G / D ratio is greater than 0.80 and less than or equal to 2.

00. The current collector according to claim 1.

3. The aforementioned G / D ratio is greater than 0.88 and less than or equal to 2.

00. The current collector according to claim 1.

4. The basis weight of the coating layer is 0.40 g / m 2 or more and 1.50 g / m 2 or less, The current collector according to claim 1.

5. The conductive material includes graphite and carbon black. The current collector according to claim 4.

6. The binder contains a polyolefin. The current collector according to claim 1.

7. The conductive material includes a plurality of types of carbon materials, The current collector according to claim 1.

8. The conductive material includes a first conductive material and a second conductive material. The above equation (i) is expressed as X = mβ / ((S1 × m1) + (S2 × m2)), Here, S1 is the specific surface area (unit: m²) of the first conductive material. 2 S2 represents the specific surface area (unit: m²) of the second conductive material, where S2 is the specific surface area (unit: m²) of the second conductive material. 2 m1 represents the mass of the first conductive material contained in the coating layer per unit area (unit: g / m²), where m1 is the mass of the first conductive material contained in the coating layer per unit area (unit: g / m²). 2 ) represents the mass of the second conductive material contained in the coating layer per unit area (unit: g / m²). 2 ) represents, The current collector according to claim 1.

9. The melting point of the aforementioned resin is in the range of 80°C to 140°C. The current collector according to claim 1.

10. The conductive material includes at least one selected from the group consisting of graphite and carbon black. The current collector according to claim 1.

11. The current collector according to claim 1, The electrode layer supported by the current collector, Equipped with electrodes.

12. A method for manufacturing an electrode according to claim 11, This includes bonding the electrode layer to the current collector at a temperature of 50°C to 180°C. A method for manufacturing electrodes.

13. When the electrode layer is bonded to the current collector, a pressure of 5 MPa to 160 MPa is applied to the current collector and the electrode layer. The method for manufacturing an electrode according to claim 12.

14. A method for manufacturing an electrode according to claim 11, The method includes adhering the electrode layer to the current collector such that the rate of change ΔSa of the surface roughness, as shown in the following formula (ii), falls within the range of -29% to -16%. A method for manufacturing electrodes. ΔSa=100×(S2-S1) / S1...(ii) Here, S1 represents the surface roughness of the coating layer before the electrode layer is bonded to the current collector, and S2 represents the surface roughness of the coating layer after the electrode layer is bonded to the current collector.

15. Positive electrode and, The negative electrode and, An electrolyte layer located between the positive electrode and the negative electrode, Equipped with, At least one selected from the group consisting of the positive electrode and the negative electrode includes the electrode described in claim 11. battery.

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