Electrode mixture, electrode layer, battery and method for manufacturing electrode layer

Abstract

To provide an electrode mixture capable of reducing initial resistance in an electrode layer even when a content of a conductive material in the electrode layer is reduced.SOLUTION: In the present disclosure, an electrode mixture contains an electrode active material, fibrous carbon as a conductive material, and a solid electrolyte. In a case where a specific surface area of the fibrous carbon is X (m2 / g) and a solid content ratio of the fibrous carbon in the electrode mixture is Y (mass%), a product of the X and the Y is greater than 42 and smaller than 2,200, and the Y is 2.0 mass% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, the development of batteries has been actively pursued. For example, in the automotive industry, development of batteries for use in electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), or hybrid electric vehicles (HEVs) is underway. The electrode layer used in a battery usually contains an electrode active material and may further contain a conductive material to improve electronic conductivity.

[0003] For example, Patent Document 1 discloses a positive electrode having a positive electrode current collector, an adhesive layer, and a positive electrode layer in this order. Patent Document 1 also discloses that the positive electrode layer contains a positive electrode active material and further contains spherical carbon and fibrous carbon as conductive materials. Meanwhile, Patent Document 2 discloses a positive electrode layer containing S, Li2S, P2S5, and single-walled carbon nanotubes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-109298 [Patent Document 2] Japanese Patent Publication No. 2022-156238 Summary of the Invention [Problem to be solved by the invention]

[0005] The conductive material has the function of improving the electronic conductivity of the electrode layer and reducing the resistance of the electrode layer. On the other hand, when a conductive material with high electronic conductivity reacts with an electrolyte, electrochemical degradation of the electrolyte occurs. Therefore, particularly when the content of the conductive material in the electrode layer is high, the resistance of the electrode layer is likely to increase over time. Conversely, when the content of the conductive material in the electrode layer is low, it is difficult to sufficiently reduce the initial resistance of the electrode layer.

[0006] The present disclosure has been made in consideration of the above-described circumstances, and has as its main object to provide an electrode mixture that can reduce the initial resistance of an electrode layer even when the content of a conductive material in the electrode layer is reduced. [Means for solving the problem]

[0007] [1] An electrode mixture containing an electrode active material and fibrous carbon as a conductive material, The specific surface area of ​​the above fibrous carbon is X (m 2 / g) and the solid content ratio of the fibrous carbon in the electrode mixture is Y (mass%), The product of the above X and the above Y is greater than 42 and less than 2200, The electrode mixture, wherein the Y is 2.0 mass % or less.

[0008] [2] The electrode mixture according to [1], wherein the product of X and Y is greater than 120 and less than 2000.

[0009] [3] The above X is 350m 2 / g or more.

[0010] [4] The electrode mixture according to any one of [1] to [3], wherein the fibrous carbon is a single-walled carbon nanotube.

[0011] [5] The electrode mixture according to any one of [1] to [4], further comprising a solid electrolyte.

[0012] [6] The electrode mixture according to any one of [1] to [5], wherein the electrode active material has a layered rock salt type crystal structure.

[0013] [7] An electrode layer comprising the electrode mixture according to any one of [1] to [6].

[0014] [8] The electrode layer according to [7], wherein the electrode layer has a packing ratio of less than 93%.

[0015] [9] The electrode layer according to [7] or [8], wherein the electrode layer has a packing ratio of 75% or more.

[0016]

[10] The electrode layer according to any one of [7] to [9], wherein the electrode layer is a positive electrode layer.

[0017]

[11] A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, The battery, wherein the positive electrode layer or the negative electrode layer is the electrode layer according to any one of [7] to

[10] .

[0018]

[12] The battery according to

[11] , wherein the electrolyte layer contains a solid electrolyte.

[0019]

[13] The battery according to

[11] or

[12] , wherein the positive electrode layer is the electrode layer.

[0020]

[14] A method for manufacturing an electrode layer, comprising: A preparation step of preparing the electrode mixture according to any one of [1] to [6]; a pressing step of pressing the electrode mixture at a temperature of 0°C or higher and 30°C or lower to obtain the electrode layer; A method for manufacturing an electrode layer, comprising:

[0021]

[15] The method for producing an electrode layer according to

[14] , wherein the electrode layer has a packing ratio of less than 93%.

[0022]

[16] The method for producing an electrode layer according to

[14] or

[15] , wherein the electrode layer has a packing ratio of 75% or more. [Effects of the Invention]

[0023] The electrode mixture according to the present disclosure has the effect of reducing the initial resistance of the electrode layer even when the content of the conductive material in the electrode layer is reduced. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. [Figure 2] FIG. 1 is a flow diagram illustrating a method for manufacturing an electrode layer in the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0025] The electrode mixture, electrode layer, battery, and method for manufacturing the electrode layer according to the present disclosure will be described in detail below.

[0026] A. Electrode composite material The electrode mixture in the present disclosure is an electrode mixture containing an electrode active material and fibrous carbon as a conductive material, and the specific surface area of ​​the fibrous carbon is X (m 2 / g) and the solid content ratio of the fibrous carbon in the electrode mixture is Y (mass%), the product of X and Y is greater than 42 and less than 2200, and Y is 2.0 mass% or less.

[0027] According to the present disclosure, when the product of X and Y is within a predetermined range, the electrode mixture can reduce the initial resistance of the electrode layer even when the content of the conductive material in the electrode layer is reduced. As described above, the conductive material has the function of improving the electronic conductivity of the electrode layer and reducing the resistance of the electrode layer. On the other hand, when a conductive material with high electronic conductivity reacts with an electrolyte, electrochemical degradation of the electrolyte occurs. Therefore, particularly when the content of the conductive material in the electrode layer is high, the resistance of the electrode layer is likely to increase over time. Conversely, when the content of the conductive material in the electrode layer is low, it is difficult to sufficiently reduce the initial resistance of the electrode layer. This is because it is difficult to sufficiently ensure an electron conduction path in the electrode layer. In contrast, the present disclosure employs fibrous carbon as the conductive material, focuses on its specific surface area X and its solid content ratio Y (content), and sets the product thereof within a predetermined range, thereby making it possible to reduce the initial resistance of the electrode layer even when the content of the conductive material in the electrode layer is low.

[0028] 1. Fibrous carbon The fibrous carbon in the present disclosure functions as a conductive material. In addition, in the present disclosure, the specific surface area of ​​the fibrous carbon is defined as X (m 2 / g), and the solid content ratio of the fibrous carbon in the electrode mixture is Y (mass %). As will be described later, the electrode mixture may or may not contain a dispersion medium. Since the proportion of fibrous carbon in the electrode mixture varies greatly depending on the presence or absence of a dispersion medium, in the present disclosure, the proportion of fibrous carbon in the electrode mixture is defined as a solid content ratio. Furthermore, the specific surface area in the present disclosure can be determined by the BET method.

[0029] The product of X and Y (XY) is usually greater than 42 and less than 2200. XY may be 100 or greater, greater than 120, 150 or greater, 180 or greater, or 200 or greater. XY may be 2100 or less, less than 2000, 1500 or less, 1000 or less, 800 or less, or 600 or less.

[0030] The above X is, for example, 350m 2 / g or more, and 2 / g or more, and 2 / g or more, and 2 / g or more, and 2 / g or more, and 2 / g or more, and 2 / g or more, and 2 On the other hand, the X may be, for example, 2600 m 2 / g or less.

[0031] The above Y is usually 2.0% by mass or less, may be 1.5% by mass or less, 1.0% by mass or less, 0.7% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.2% by mass or less, while the above Y is, for example, 0.01% by mass or more.

[0032] The diameter of the fibrous carbon is not particularly limited, but may be, for example, 0.1 nm or more and 200 nm or less. It is 0.2 nm or more and 100 nm or less. It may be 0.3 nm or more and 50 nm or less. On the other hand, the length of the fibrous carbon is not particularly limited, but may be, for example, 0.5 μm or more and 100 μm or less, or 1 μm or more and 50 μm or less. The aspect ratio (length / diameter) of the fibrous carbon is not particularly limited, but may be, for example, 100 or more and 5000 or less, or 500 or more and 4000 or less.

[0033] The G / D ratio of the fibrous carbon is preferably high, for example, 10 or more, or may be 30 or more, 50 or more, 70 or more, or 90 or more. The purity of the fibrous carbon is also preferably high. The purity of the fibrous carbon determined by thermogravimetry is, for example, 90% or more, or may be 95% or more, or may be 99% or more.

[0034] Specific examples of fibrous carbon include carbon nanotubes (CNTs) such as single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs); and carbon fibers (CNFs). The theoretical specific surface area of ​​SWCNTs is approximately 2600 m. 2 / g.

[0035] The electrode mixture in the present disclosure typically contains the above-described fibrous carbon as the main component of the conductive material. The proportion of the above-described fibrous carbon to all conductive materials in the electrode mixture is, for example, 80 mass % or more, or may be 90 mass % or more, or 95 mass % or more, or may be 100 mass %. Examples of conductive materials other than the fibrous carbon include particulate carbon such as acetylene black (AB) and ketjen black (KB).

[0036] 2. Electrode active material The electrode active material in the present disclosure may be a positive electrode active material or a negative electrode active material, and examples of the electrode active material in the present disclosure include oxide active materials, Si-based active materials, and carbon-based active materials.

[0037] The crystal structure of the oxide active material is not particularly limited, but examples thereof include layered rock salt type, spinel type, and olivine type. Examples of the oxide active material include compounds containing Li, M, and O elements (lithium composite oxides). Here, M is a metal (including metalloids) other than Li. The oxide active material may contain only one M element, or two or more M elements.

[0038] M may be a transition metal or a metal (including metalloids) belonging to Groups 13 to 16 of the periodic table. M preferably contains at least Ni. Examples of M other than Ni include at least one of Co, Mn, Al, V, and Fe. The molar ratio of Ni to M (Ni / M) is not particularly limited, but may be, for example, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more. Meanwhile, Ni / M may be 100% or less. The oxide active material may contain a nonmetallic element such as P in addition to Li, M, and O.

[0039] An example of the composition of the oxide active material is LiNi x Co y Al z O2 (0≦x≦1, 0≦y≦1, 0≦z≦1, x+y+z=1). x may be 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. On the other hand, x may be less than 1. y may be 0 or more than 0. Also, y is, for example, 0.20 or less. z may be 0 or more than 0. Also, z is, for example, 0.10 or less.

[0040] Other examples of oxide active material compositions include LiNi a Co b Mn c O2 (0≦a≦1, 0≦b≦1, 0≦c≦1, a+b+c=1). a may be 0.3 or more, 0.5 or more, 0.7 or more, or 0.9 or more. On the other hand, a may be less than 1. b may be 0 or more than 0. Also, b is, for example, 0.40 or less. c may be 0 or more than 0. Also, c is, for example, 0.40 or less.

[0041] The electrode active material may be a Si-based active material. The Si-based active material is an active material whose main component is Si. The Si-based active material may be simple Si, a Si alloy, or a Si oxide. The Si-based active material may have a diamond-type crystalline phase, a clathrate I crystalline phase, or a clathrate II crystalline phase. In the clathrate I or II crystalline phase, multiple Si elements form a polyhedron (cage) containing pentagons or hexagons. This polyhedron has spaces inside that can encapsulate Li ions, thereby suppressing volume changes due to charge and discharge. The Si-based active material may also have voids within its primary particles. The porosity of the primary particles is, for example, 4% or more and 40% or less.

[0042] The electrode active material may be a carbon-based active material. The carbon-based active material is preferably used as, for example, a negative electrode active material. Examples of the carbon-based active material include graphite, hard carbon, and soft carbon.

[0043] The electrode active material is, for example, in the form of particles. 50 is, for example, 100 nm or more, may be 1 μm or more, or may be 5 μm or more. 50 is, for example, 50 μm or less, and may be 20 μm or less. 50 corresponds to the particle size equivalent to a cumulative 50% by volume measured using a laser diffraction particle size distribution analyzer.

[0044] The electrode active material may be coated with a coating layer. By providing a coating layer, it is possible to suppress the reaction between the electrode active material and the electrolyte, which would otherwise cause the electrolyte to deteriorate. In particular, when the electrode active material is an oxide active material and the electrode composite contains a sulfide solid electrolyte, it is preferable that the electrode active material be coated with a coating layer. It is preferable that the coating layer contains a Li-ion conductive oxide. Examples of Li-ion conductive oxides include compounds containing Li element and a PO4 structure (LPO, for example, Li3PO4), compounds containing Li element, B element, and a PO4 structure (LBPO, for example, LiBPO4), and compounds containing Li element, Nb element, and O element (for example, LiNbO3).

[0045] The thickness of the coating layer is not particularly limited, but may be, for example, 1 nm or more and 100 nm or less, or may be 5 nm or more and 50 nm or less, or may be 10 nm or more and 30 nm or less. The thickness of the coating layer is determined, for example, as the average thickness of multiple samples (e.g., 100 or more samples) observed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The coverage of the coating layer with respect to the electrode active material is, for example, 70% or more, or may be 80% or more, or may be 90% or more.

[0046] The solid content ratio of the electrode active material in the electrode mixture is, for example, 20% by mass or more, or may be 30% by mass or more, or 40% by mass or more. If the solid content ratio of the electrode active material is too low, sufficient energy density may not be obtained. On the other hand, the solid content ratio of the electrode active material is, for example, 80% by mass or less, or may be 70% by mass or less, or may be 60% by mass or less. If the solid content ratio of the electrode active material is too high, the ionic conductivity and electronic conductivity of the electrode mixture may relatively decrease.

[0047] 3.Solid electrolyte The electrode composite material may further contain a solid electrolyte. The solid electrolyte may be an organic solid electrolyte such as a gel electrolyte, or an inorganic solid electrolyte such as a sulfide solid electrolyte, a halide solid electrolyte, or an oxide solid electrolyte. Among them, the solid electrolyte is preferably a sulfide solid electrolyte because of its high ionic conductivity.

[0048] The sulfide solid electrolyte usually contains at least Li element and S element. The sulfide solid electrolyte preferably further contains a Me element (Me is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, In). Also, the sulfide solid electrolyte may contain a halogen element such as F, Cl, Br, I.

[0049] The sulfide solid electrolyte may be a glass-based (amorphous) sulfide solid electrolyte, a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. The sulfide solid electrolyte may have a crystalline phase. Examples of the crystalline phase include, for example, Thio-LISICON type crystalline phase, argyrodite type crystalline phase, and LGPS type crystalline phase.

[0050] The composition of the sulfide solid electrolyte is not particularly limited, and examples include, for example, xLi2S·(1-x)P2S5 (0.5≦x<1), yLiI·zLiBr·(100-y-z)(xLi2S·(1-x)P2S5) (0.5≦x<1, 0≦y≦30, 0≦z≦30). In these compositions, x preferably satisfies 0.7≦x≦0.8. Also, as other examples of the composition of the sulfide solid electrolyte, Li 7-x-2y PS 6-x-y X y is mentioned. X is at least one of F, Cl, Br, I, and x and y satisfy 0≦x, 0≦y. Also, as other examples of the composition of the sulfide solid electrolyte, Li 4-x Me 1-x P x S4 (0<x<1) is mentioned. Me is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0051] The solid content ratio of the solid electrolyte in the electrode mixture is, for example, 10 mass % or more and 50 mass % or less, and may be 20 mass % or more and 40 mass % or less.

[0052] 4. Other ingredients The electrode mixture may further contain a binder. Examples of binders include rubber-based binders such as butadiene rubber (BR) and styrene-butadiene rubber (SBR), and fluoride-based binders such as polyvinylidene fluoride (PVdF). The solid content of the binder in the electrode mixture is, for example, 0.1% by mass or more and 5% by mass or less.

[0053] The electrode mixture may or may not further contain a dispersion medium. Examples of the dispersion medium include butyl acetate, butyl butyrate, mesitylene, tetralin, heptane, and N-methyl-2-pyrrolidone (NMP). When the electrode mixture contains a dispersion medium, the solid content of the electrode mixture is, for example, 20% by mass or more and 80% by mass or less.

[0054] 5.Electrode composite material The electrode mixture in the present disclosure may be a positive electrode mixture containing a positive electrode active material as the electrode active material, or a negative electrode mixture containing a negative electrode active material as the electrode active material, but the former is preferred. The electrode mixture in the present disclosure is used, for example, in a battery. Batteries will be described later in "C. Batteries."

[0055] B. Electrode layer The electrode layer in the present disclosure contains the electrode mixture described above in "A. Electrode mixture."

[0056] According to the present disclosure, by using the above-described electrode mixture, an electrode layer can be obtained that can reduce the initial resistance even if the content of the conductive material in the electrode layer is reduced. The electrode mixture contained in the electrode layer is the same as that described above in "A. Electrode mixture." In the present disclosure, the electrode layer may be a positive electrode layer or a negative electrode layer.

[0057] The filling rate of the electrode layer is not particularly limited, but may be, for example, less than 93%, 92% or less, or 90% or less. Here, in the electrode layer of a solid-state battery, electrons and ions are conducted through the solid-solid interface, so from the viewpoint of ensuring a conduction path, a high filling rate of the electrode layer is generally preferable. On the other hand, in order to increase the filling rate, for example, it is necessary to increase the pressing temperature, which requires equipment. In contrast, by using the above-described electrode composite, even when the filling rate of the electrode layer is low, the initial resistance can be reduced in the same way as when the filling rate of the electrode layer is high. Therefore, it is possible to reduce equipment costs and simplify the manufacturing process. On the other hand, the filling rate of the electrode layer is, for example, 75% or more, and may be 77% or more, or 79% or more.

[0058] The thickness of the electrode layer is not particularly limited, but is, for example, 0.1 μm or more and 1000 μm or less, or may be 1 μm or more and 500 μm or less, or may be 5 μm or more and 100 μm or less. The electrode layer in the present disclosure is used, for example, in a battery. Batteries will be described later in "C. Batteries."

[0059] C.Battery Fig. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. The battery 10 shown in Fig. 1 includes a positive electrode layer 1, a negative electrode layer 2, an electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 that collects current from the positive electrode layer 1, and a negative electrode current collector 5 that collects current from the negative electrode layer 2. In the present disclosure, the positive electrode layer 1 or the negative electrode layer 2 is the electrode layer described above in "B. Electrode Layer."

[0060] According to the present disclosure, by using the above-described electrode layer, a battery having reduced initial resistance can be obtained even if the content of the conductive material in the electrode layer is reduced. As described above, the electrode layer may be a positive electrode layer or a negative electrode layer.

[0061] 1. Positive electrode layer The positive electrode layer in the present disclosure may be the electrode layer described above in "B. Electrode Layer." The electrode layer is the same as that described above in "B. Electrode Layer," and therefore will not be described here. On the other hand, when the negative electrode layer described below is the electrode layer described above in "B. Electrode Layer," any positive electrode layer can be used as the positive electrode layer.

[0062] 2. Negative electrode layer The negative electrode layer in the present disclosure may be the electrode layer described above in "B. Electrode Layer." The electrode layer is the same as that described above in "B. Electrode Layer," and therefore will not be described here. On the other hand, when the positive electrode layer is the electrode layer described above in "B. Electrode Layer," any negative electrode layer can be used as the negative electrode layer.

[0063] 3. Electrolyte layer The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and contains at least an electrolyte. The electrolyte may be a solid electrolyte or a liquid electrolyte (electrolytic solution). In particular, the electrolyte layer preferably contains a solid electrolyte, and more preferably contains a solid electrolyte as the main component of the electrolyte.

[0064] The solid electrolyte is the same as that described above in "A. Electrode Composite," and therefore will not be described here. On the other hand, the electrolyte preferably contains a supporting salt and a solvent. Examples of supporting salts (lithium salts) for the lithium-ion conductive electrolyte include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6, and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3. Examples of solvents used in the electrolyte include cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and chain esters (chain carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The electrolyte preferably contains two or more solvents.

[0065] The thickness of the electrolyte layer is not particularly limited, but is, for example, 0.1 μm or more and 1000 μm or less, or may be 1 μm or more and 500 μm or less, or may be 5 μm or more and 100 μm or less.

[0066] 4. Other configurations The battery according to the present disclosure preferably includes a positive electrode current collector that collects current from the positive electrode layer and a negative electrode current collector that collects current from the negative electrode layer. Examples of materials for the positive electrode current collector include stainless steel, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of materials for the negative electrode current collector include stainless steel, copper, nickel, and carbon.

[0067] The battery of the present disclosure may further include a restraining jig that applies a restraining pressure to the positive electrode layer, electrolyte layer, and negative electrode layer in the thickness direction. In particular, when the electrolyte layer contains a solid electrolyte, applying a restraining pressure is preferable to form a good ion conduction path. The restraining pressure is, for example, 0.1 MPa or more, or may be 1 MPa or more, or may be 5 MPa or more. Meanwhile, the restraining pressure is, for example, 100 MPa or less, or may be 50 MPa or less, or may be 20 MPa or less.

[0068] 5.Battery The type of battery in the present disclosure is not particularly limited, but is typically a lithium-ion battery. The battery in the present disclosure may be a liquid battery containing an electrolytic solution as an electrolyte layer, or a solid battery having a solid electrolyte layer as an electrolyte layer. The solid battery may be a semi-solid battery or an all-solid battery. The battery in the present disclosure may be a primary battery or a secondary battery, but a secondary battery is preferred because it can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery.

[0069] Examples of uses of the battery include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, it is preferable to use the battery as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery may also be used as a power source for mobile objects other than vehicles (for example, trains, ships, and aircraft), and may also be used as a power source for electrical appliances such as information processing devices.

[0070] D. Manufacturing method of electrode layer Fig. 2 is a flow diagram illustrating a method for manufacturing an electrode layer according to the present disclosure. In the method for manufacturing an electrode layer shown in Fig. 2, first, the electrode mixture described above in "A. Electrode mixture" is prepared (preparation step). Next, the electrode mixture is pressed at a temperature of 0°C or higher and 30°C or lower to obtain an electrode layer (pressing step).

[0071] According to the present disclosure, by using the above-described electrode mixture, an electrode layer with reduced initial resistance can be obtained even when pressed at a temperature near room temperature.

[0072] 1. Preparation process The preparation step in the present disclosure is a step of preparing the electrode mixture described above. The electrode mixture is the same as that described above in "A. Electrode mixture." The electrode mixture may or may not contain a dispersion medium.

[0073] 2. Pressing process The pressing step in the present disclosure is a step of pressing the electrode mixture at a temperature of 0° C. or higher and 30° C. or lower to obtain the electrode layer.

[0074] For example, when the electrode mixture contains a dispersion medium (when the electrode mixture is a slurry), the slurry is applied and dried to form a precursor layer, and the precursor layer is pressed. The precursor layer is formed, for example, on an electrode current collector. On the other hand, when the electrode mixture does not contain a dispersion medium, the powder electrode mixture is pressed. The powder electrode mixture is placed, for example, on an electrode current collector.

[0075] Methods for pressing the electrode mixture include, for example, roll pressing and plate pressing. The pressure for pressing the electrode mixture is not particularly limited, and is preferably selected so as to obtain a predetermined packing ratio.

[0076] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0077] [Example 1] (Preparation of positive electrode active material) 2.5 L of an aqueous ammonia solution with a concentration of 5 g / L was prepared in a reaction vessel, and while the temperature in the vessel was maintained at 40°C, an initial aqueous solution was prepared using an aqueous sodium hydroxide solution so that the pH was 11.5 at a liquid temperature of 25°C. Next, nickel sulfate, cobalt sulfate, and aluminum sulfate were dissolved in pure water to give a molar ratio of Ni:Co:Al = 0.82:0.15:0.03, to prepare a mixed aqueous solution with a concentration of 2.0 mol / L.

[0078] The mixed aqueous solution was added dropwise to the initial aqueous solution in the reaction vessel at a constant rate to form a precipitate. The recovered slurry was filtered, washed, and then dried to obtain a precursor. The resulting precursor was mixed with Li2CO3 in a molar ratio of Li:(Ni+Co+Al) = 1.1:1 and calcined in an oxygen atmosphere at 750°C for 10 hours. This yielded a positive electrode active material.

[0079] (Preparation of coated positive electrode active material) 10.8 g of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in 166.0 g of ion-exchanged water. Next, lithium hydroxide monohydrate was added to obtain a coating solution with a molar ratio of Li:P = 0.45:1. Next, 53.7 g of the coating solution was added to 50.0 g of the positive electrode active material to prepare a slurry, which was then spray-dried to obtain a coated positive electrode active material.

[0080] (Preparation of positive electrode) Coated cathode active material and sulfide solid electrolyte (Li2S-P2S5 glass ceramics containing LiI, D 50 The coated positive electrode active material and the sulfide solid electrolyte were weighed out to a volume ratio of 75:25, and then mixed with a conductive material (single-walled carbon nanotubes, specific surface area = 2000 m 2 The conductive material was added to tetralin together with 0.1% by mass of the conductive material in the solid content of the positive electrode mixture.

[0081] The obtained positive electrode mixture was thoroughly dispersed using an ultrasonic homogenizer (UH-50 manufactured by SMT), then coated onto a positive electrode current collector (aluminum foil) and dried at 100°C for 30 minutes. 2 The positive electrode was obtained by punching out a piece of the sheet.

[0082] (Preparation of negative electrode) In the kneading vessel of the Filmix device (30-L type manufactured by Primix), a sulfide solid electrolyte (Li2S-P2S5 type glass ceramics containing LiI, D 50 = 0.8 μm), 1 mass % of conductive material (vapor grown carbon fiber), 2 mass % of binder (butadiene rubber), and dispersion medium (heptane) were added and stirred at 20,000 rpm for 30 minutes. 12 particle, D 50 =1 μm) was placed in a kneading vessel so that the volume ratio with the sulfide solid electrolyte was 70:30, and the mixture was stirred in a Filmix device at 15,000 rpm for 60 minutes to obtain a negative electrode mixture.

[0083] The obtained negative electrode mixture was applied onto a negative electrode current collector (copper foil) and dried at 100°C for 30 minutes. 2 The negative electrode was obtained by punching out the material into a size of 100 mm.

[0084] (Fabrication of solid electrolyte layer) Inner diameter cross-sectional area 1cm 2 The cylindrical ceramics are filled with sulfide solid electrolyte (Li2S-P2S5 glass ceramics containing LiI, D 50 Then, 64.8 mg of 1 ton / cm2 (=2.5 μm) was added and smoothed. 2 The solid electrolyte layer was obtained by pressing the substrate at a pressure of 1000 kJ / cm.

[0085] (Battery construction) A positive electrode was placed on one side of the obtained solid electrolyte layer, and a negative electrode was placed on the other side. The resulting solid electrolyte layer was then heated at room temperature (25°C) and subjected to a load of 6 ton / cm. 2 Then, a stainless steel rod was placed on each electrode and the electrodes were confined under a pressure of 1 ton to obtain an all-solid-state battery.

[0086] [Example 2] An all-solid-state battery was obtained in the same manner as in Example 1, except that the proportion of the conductive material in the solid content of the positive electrode mixture was changed to 0.3 mass %.

[0087] [Example 3] An all-solid-state battery was obtained in the same manner as in Example 1, except that the proportion of the conductive material in the solid content of the positive electrode mixture was changed to 1.0 mass %.

[0088] [Example 4] The conductive material added to the positive electrode is a material with a specific surface area of ​​400m 2 / g of single-walled carbon nanotubes, and further, the proportion of the conductive material in the solid content of the positive electrode mixture was changed to 0.3 mass %.

[0089] [Comparative Example 1] An all-solid-state battery was obtained in the same manner as in Example 1, except that the proportion of the conductive material in the solid content of the positive electrode mixture was changed to 1.1 mass %.

[0090] Comparative Example 2 The conductive material added to the positive electrode is a material with a specific surface area of ​​13m 2 / g, and further, the proportion of the conductive material in the solid content of the positive electrode mixture was changed to 2.0 mass %.

[0091] Comparative Example 3 An all-solid-state battery was obtained in the same manner as in Comparative Example 2, except that the proportion of the conductive material in the solid content of the positive electrode mixture was changed to 3.2 mass %.

[0092] Comparative Example 4 An all-solid-state battery was obtained in the same manner as in Comparative Example 2, except that the pressing temperature was changed from room temperature to 150°C during battery production.

[0093] [evaluation] (Battery evaluation) The all-solid-state batteries obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were subjected to two cycles of constant current-constant voltage charge and discharge at a set voltage of 2.8 V or 1.5 V and a 1 / 3 C rate. The batteries were then adjusted to an SOC of 40% at a 1 / 3 C rate. The batteries were discharged at a direct current equivalent to a 2.5 C rate in a thermostatic chamber maintained at 25°C, and the resistance values ​​were calculated from the voltage drop at 5 seconds relative to 0 seconds and the applied current. The results are shown in Table 1. In Table 1, the resistance values ​​of Comparative Example 2 were set as the reference value of 1.00, and the resistance values ​​of each Example and Comparative Example were evaluated relative to this value.

[0094] Next, a cycle test was conducted at 60°C, 1C, SOC: 0% to 100%, and 100 cycles. After the cycle test, the discharge resistance was measured again, and the resistance increase rate before and after the cycle test was calculated. The results are shown in Table 1. In Table 1, the resistance increase rate of Comparative Example 2 was set as the reference of 1.00, and the resistance increase rates of each Example and Comparative Example were evaluated relative to each other.

[0095] (Measurement of filling rate) The positive electrodes (1 cm ) prepared in Examples 1 to 4 and Comparative Examples 1 to 4 2The mass of the cathode (punched to the size of ) was measured, and the thickness of the cathode pressed under the same conditions as when the battery was fabricated was measured with a film thickness meter to determine the density of the cathode composite. The packing ratio of the cathode layer was calculated from the true density of each inserted component and the composition of the cathode composite. The results are shown in Table 1.

[0096] [Table 1]

[0097] As shown in Table 1, it was confirmed that Examples 1 to 4 had lower initial resistances and the resistance increase rates were similar or lower than those of Comparative Example 2. In particular, Examples 1 and 2 had significantly lower initial resistances and resistance increase rates than Comparative Example 2. On the other hand, Comparative Example 1 had a lower initial resistance but a higher resistance increase rate than Comparative Example 2. This is thought to be because, when a conductive material with a large specific surface area X is used, unless the solid content ratio Y is made smaller, the effect of deterioration of the solid electrolyte due to the reaction between the conductive material and the solid electrolyte becomes apparent.

[0098] Furthermore, Comparative Example 2 had a higher initial resistance than Examples 1 to 4. This is thought to be due to a lack of electron conduction paths in the positive electrode layer. On the other hand, Comparative Example 3 had a lower initial resistance than Comparative Example 2. This is thought to be due to the fact that the solid content ratio Y in Comparative Example 3 was higher than that in Comparative Example 2. However, since the solid content ratio Y in Comparative Example 3 was higher than that in Comparative Example 2, deterioration of the solid electrolyte occurred due to a reaction between the conductive material and the solid electrolyte, which is thought to have resulted in an increased rate of increase in resistance.

[0099] Furthermore, in Comparative Example 4, the pressing temperature was 150°C, and the filling factor was higher than in Examples 1 to 4 and Comparative Examples 1 to 3. In the electrode layer of a solid-state battery, electrons and ions are conducted through the solid-solid interface, so from the viewpoint of ensuring a conduction path, a high filling factor of the electrode layer is generally preferable. On the other hand, in order to increase the filling factor, for example, it is necessary to increase the pressing temperature, which requires equipment for this. In contrast, in Examples 1 to 3, despite the pressing temperature being room temperature, a significant effect was obtained in that the initial resistance was similar to that of Comparative Example 4. In particular, in Examples 1 and 2, despite the pressing temperature being room temperature, an even more significant effect was obtained in that the initial resistance and resistance increase rate were similar to those of Comparative Example 4. [Explanation of symbols]

[0100] 1...Positive electrode layer 2...Anode layer 3...electrolyte layer 4...Positive electrode current collector 5...Negative electrode current collector 10...battery

Claims

1. An electrode mixture containing an electrode active material and fibrous carbon as a conductive material, The specific surface area of ​​the fibrous carbon is X (m ２ / g) and the solid content ratio of the fibrous carbon in the electrode mixture is Y (mass%), the product of X and Y is greater than 42 and less than 2200; The electrode mixture, wherein the Y is 2.0 mass% or less.

2. 2. The electrode composite of claim 1, wherein the product of X and Y is greater than 120 and less than 2000.

3. The X is 350 m ２ The electrode mixture according to claim 1, wherein the SiO 2 content is 1 / g or more.

4. The electrode mixture according to claim 1 , wherein the fibrous carbon is a single-walled carbon nanotube.

5. The electrode mixture according to claim 1 , further comprising a solid electrolyte.

6. The electrode mixture according to claim 1 , wherein the electrode active material has a layered rock salt type crystal structure.

7. An electrode layer comprising the electrode mixture according to any one of claims 1 to 6.

8. The electrode layer according to claim 7 , wherein the fill factor of the electrode layer is less than 93%.

9. The electrode layer according to claim 7 , wherein the electrode layer has a packing ratio of 75% or more.

10. The electrode layer according to claim 7 , wherein the electrode layer is a positive electrode layer.

11. A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, A battery, wherein the positive electrode layer or the negative electrode layer is the electrode layer according to claim 7 .

12. 12. The battery of claim 11, wherein the electrolyte layer comprises a solid electrolyte.

13. 12. The battery of claim 11, wherein the positive electrode layer is the electrode layer.

14. A method for manufacturing an electrode layer, comprising: a preparation step of preparing the electrode mixture according to any one of claims 1 to 6; a pressing step of pressing the electrode mixture at a temperature of 0°C or higher and 30°C or lower to obtain the electrode layer; A method for manufacturing an electrode layer, comprising:

15. The method for manufacturing an electrode layer according to claim 14 , wherein the electrode layer has a fill factor of less than 93%.

16. The method for manufacturing an electrode layer according to claim 14 , wherein the electrode layer has a packing ratio of 75% or more.

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