Method for manufacturing electrode material and electrode material

Abstract

A method for manufacturing an electrode material, the electrode material being used in a non-aqueous electrolyte secondary battery, the method comprising a granulation step, the granulation step comprising: mixing an aqueous solution of an inorganic binder containing an inorganic binder comprising phosphate as a component with a suspension of an active material dispersed in an organic solvent to obtain a mixture; subjecting the mixture to heat treatment to evaporate the water in the mixture; obtaining granules containing the inorganic binder and the active material, wherein the solid content concentration of the aqueous solution of the inorganic binder is more than 1% by mass and less than 30% by mass.

Description

Technical Field

[0001] This invention relates to a method for manufacturing electrode materials and electrode materials, and more specifically, to a method for manufacturing electrode materials for non-aqueous electrolyte secondary batteries and electrode materials for non-aqueous electrolyte secondary batteries. Background Technology

[0002] In related fields, for electrode materials used in non-aqueous secondary batteries, such as lithium-ion batteries, techniques are known to form granular bodies by combining active material particles such as Si particles with binders to improve capacity and cycle characteristics (e.g., Patent Document 1). Additionally, as a method for forming Si particles into fine particles, a wet grinding method is known to pulverize a suspension containing dispersed Si particles using a bead mill (e.g., Patent Document 2).

[0003] Patent Document 1: JP2013-235682A

[0004] Patent Document 2: JP2020-17389A Summary of the Invention

[0005] When active material particles (e.g., Si particles) are granulated using wet milling, the active material particles are dispersed to form a suspension, and a fluid material, including liquids (e.g., water or organic solvents), is used as the dispersion medium. When the dispersion medium is water and the active material is an alloy or a material that may react with water, hydrogen is sometimes generated as the active material is dispersed in the dispersion medium. The same problem arises when water is used as a solvent or dispersion medium in the binder. Therefore, when a binder using water as a solvent or dispersion medium (aqueous binder) is used with alloy materials, water decomposes to generate hydrogen, which is very difficult to handle and makes it difficult to obtain a uniform electrode. Furthermore, while hydrogen is generated, an oxide film easily forms on the surface of the alloy material, causing a decrease in capacitance and an increase in internal resistance. The generation of hydrogen and the formation of the oxide film occur, for example, according to the following formula 1.

[0006] Si + 2H2O → SiO2 + 2H2↑ Formula 1

[0007] To prevent hydrogen generation, organic solvents can be chosen as the dispersion medium. Examples of organic solvents include various solvents such as hydrocarbon-based organic solvents, alcohol-based organic solvents, ketone-based organic solvents, ester-based organic solvents, glycol-based organic solvents, glycol ether-based organic solvents, halogen-based organic solvents, and nitrogen-based organic solvents. Considering that they can prevent the deterioration of active materials and hydrogen generation, have minimal impact on human health and the environment, and are inexpensive, alcohol-based organic solvents are preferred.

[0008] Specific examples of methods for preparing electrode active materials composed of Si particles using alcohol-based solvents as dispersion media include methods in which Si particles containing median particle size (D) are dispersed in alcohol-based solvents. 50 A mixture of 5 μm Si powder and ethanol was fed into a bead mill (using 20 μm diameter zirconia beads) and processed for 10 minutes to readily produce a dispersion with a median particle size (D). 50 The sample was a suspension of Si with a wavelength of 300 nm. In this case, corresponding to the use of ethanol as the dispersion medium, no hydrogen was observed to be generated from the suspension, and it was assumed that no oxidation reaction of Si as described in Formula 1 occurred. Note that when water is used instead of ethanol, the Si can be pulverized, but a large amount of hydrogen is generated from the suspension.

[0009] Particulate matter containing active material and granulating binder can be manufactured by mixing the granulating binder with active material powder and then drying the mixture. The active material powder is obtained by removing the ethanol, which serves as a dispersion medium, from the suspension containing ethanol and Si particles obtained above. However, this method requires a step of removing the dispersion medium from the suspension to produce the active material powder before the granulation step, which increases the number of production steps.

[0010] If granules can be manufactured by directly adding a granulating binder to a suspension, granules can be manufactured efficiently without removing the organic solvent that serves as the dispersion medium. However, in this case, the granulating binder used must not generate hydrogen and must not lose its fluidity and binder function even when in contact with the organic solvent contained in the suspension.

[0011] In view of the above, the object of the present invention is to provide a method for manufacturing an electrode material and an electrode material that can be manufactured in this manner, the method being able to efficiently and safely manufacture granules containing active material using a suspension obtained by dispersing an active material in an organic solvent, while preventing the generation of hydrogen gas.

[0012] To solve the above-mentioned problems, the electrode material manufacturing method and the electrode material according to the present invention have the following configuration.

[0013] [1] A method for manufacturing an electrode material, wherein the electrode material is an electrode material for a non-aqueous electrolyte secondary battery, the manufacturing method comprising a granulation step, the granulation step comprising:

[0014] A mixture is obtained by mixing an aqueous solution of an inorganic binder containing an inorganic binder with phosphate as a component and a suspension in which the active material is dispersed in an organic solvent;

[0015] Heat treatment of the mixture is used to evaporate the water in the mixture;

[0016] Obtain granular material containing inorganic binder and active material, wherein

[0017] The solid content concentration of the inorganic binder aqueous solution is above 1% by mass and below 30% by mass.

[0018] [2] According to the manufacturing method of the electrode material described in [1] above, the phosphate contains aluminum phosphate represented by the condensed formula Al2O3·nP2O5·mH2O (0.5≤n≤4, 0≤m≤8).

[0019] [3] According to the manufacturing method of the electrode material described in [1] or [2] above, wherein,

[0020] The solids content concentration of the suspension is above 1% by mass and below 30% by mass.

[0021] The suspension also contains water, and

[0022] The concentration of water in the suspension relative to the organic solvent is 10% by mass or more.

[0023] [4] The method for manufacturing the electrode material according to any one of [1] to [3] above, wherein the organic solvent is a water-soluble organic solvent.

[0024] [5] In the method for manufacturing the electrode material described in [4] above, the water-soluble organic solvent is an alcohol-based organic solvent.

[0025] [6] The method for manufacturing the electrode material according to any one of [1] to [5], wherein the above-mentioned mixture is heat-treated under conditions of 100°C or higher and 500°C or lower.

[0026] [7] A method for manufacturing an electrode material according to any one of [1] to [6], wherein the active material comprises a median particle size (D). 50 () refers to a single particle with a diameter greater than 10 nm and a diameter less than 1 μm.

[0027] [8] The method for manufacturing an electrode material according to any one of [1] to [7] above, wherein the active material comprises a material capable of forming an alloy phase with an alkali metal.

[0028] [9] In the method for manufacturing electrode material according to [8] above, the material that can form an alloy phase with the alkali metal is a Si-based material.

[0029]

[10] The method for manufacturing the electrode material according to any one of [1] to [9] above, wherein the mixture further contains carbon.

[0030]

[11] The method for manufacturing the electrode material according to any one of [1] to

[10] above, wherein the granules are spherical and the median particle size (D) 50 The size ranges from 0.5 μm to 50 μm.

[0031]

[12] The method for manufacturing the electrode material according to any one of [1] to

[11] , wherein the heat treatment includes spray drying.

[0032]

[13] An electrode material, which is an electrode material for a non-aqueous electrolyte secondary battery, wherein...

[0033] The electrode material is a granular body containing active materials and an inorganic binder, wherein the inorganic binder contains phosphate as a component, and

[0034] The content of inorganic binder is more than 1% by mass and less than 30% by mass.

[0035]

[14] According to the electrode material described in

[13] above, wherein the phosphate comprises aluminum phosphate represented by the condensed form Al2O3·nP2O5·mH2O (0.5 ≤ n ≤ 4 and 0 ≤ m ≤ 8).

[0036]

[15] The electrode material according to

[13] or

[14] above, wherein the active material comprises a Si-based material.

[0037]

[16] According to the electrode material described in

[15] above, the Si-based material includes Si particles and SiX compound particles, where X is at least one element selected from Fe, Co, Ni, Zr, Ti, Cr, V and Nb.

[0038]

[17] According to the electrode material described in

[16] above, wherein

[0039] In the active material, the mass proportion of Si particles is more than 10% and less than 90%, and the mass proportion of SiX compound particles is more than 5% and less than 90%.

[0040]

[18] According to the electrode material described in

[17] above, wherein

[0041] In the active material, the mass proportion of Si particles is more than 20% and less than 50%, and the mass proportion of SiX compound particles is more than 30% and less than 85%.

[0042]

[19] The electrode material according to any one of

[16] to

[18] above, wherein the Si-based material further comprises YCu compound particles, where Y is at least one element selected from Sn, Al, In and Bi.

[0043] In the method for manufacturing the electrode material according to the present invention having the above configuration [1], an aqueous solution of an inorganic binder containing an inorganic binder and a suspension in which the active material is dispersed in an organic solvent are directly mixed, and the mixture is heat-treated to obtain granules containing an inorganic binder and an active material. Since there is no need to remove the organic solvent constituting the suspension, the electrode material can be manufactured efficiently. Here, since an inorganic binder containing phosphate as a component is used, the oxidation of the active material and the generation of hydrogen during the manufacturing process of the electrode material can be prevented. Therefore, the manufacturing of granules can be carried out safely. Here, since the solid content concentration in the aqueous solution of the inorganic binder is set to 1% by mass or more, the high effect of preventing hydrogen generation and improving the mechanical strength of the manufactured granules can be obtained. In addition, since it is set to 30% by mass or less, the aggregation or precipitation of phosphate in the aqueous solution of the inorganic binder is not likely to occur, and it is easy to manufacture homogeneous granules. Furthermore, the electrode material obtained by this manufacturing method has excellent flame retardancy and is not prone to hydrogen generation due to contact with water. Furthermore, non-aqueous electrolyte secondary batteries using this electrode material exhibit excellent cycle characteristics, can operate stably at high temperatures, and have low electrode resistance. Additionally, they are less prone to thermal runaway, thus improving safety.

[0044] In the aspect described above [2], the phosphate comprises aluminum phosphate represented by the condensation formula Al2O3·nP2O5·mH2O having specified m and n. In this case, granules with high mechanical strength can be obtained, and flame retardancy is also improved.

[0045] In the above [3] aspect, the concentration of solids in the suspension is 1% by mass or more and 30% by mass or less, and the suspension also contains water, the concentration of water in the suspension relative to the organic solvent is 10% by mass or more. Since the suspension contains water in the above range in addition to the organic solvent, the suspension and the inorganic binder aqueous solution are easy to mix, and the aggregation or precipitation of the inorganic binder is not likely to occur.

[0046] In aspect [4] above, the organic solvent is a water-soluble organic solvent. In this case, the suspension and the aqueous solution of the inorganic binder are not easily separated. In aspect [5] above, the water-soluble organic solvent is an alcohol-based organic solvent. In this case, the volatility of the solvent is appropriate, and the impact on the environment and human health is reduced.

[0047] In the aspect described above [6], the heat treatment is performed at a temperature above 100°C and below 500°C. In this case, the mechanical strength of the granules is effectively improved by drying and curing the phosphate, and dephosphorization due to overheating is prevented.

[0048] In the aspects mentioned above [7], the active material includes a median particle size (D).50 The particles are single particles with a diameter of 10 nm or more and a diameter of 1 μm or less. In this case, excellent cycle characteristics and output characteristics can be obtained in the battery formed using the electrode material according to the present invention.

[0049] In aspect [8] above, the active material includes a material capable of forming an alloy phase with an alkali metal. Furthermore, in aspect [9] above, a Si-based material is used as the material capable of forming an alloy phase with an alkali metal. In these cases, a large theoretical capacity can be obtained in a non-aqueous electrolyte secondary battery formed using the manufactured electrode material.

[0050] In the aspect described above

[10] , the mixture also contains carbon. In this case, the resulting granules contain carbon, which functions as a conductive additive, in addition to the active material and the inorganic binder, thereby improving the conductivity of the granules.

[0051] In the aspects mentioned above

[11] , the median particle size (D) was obtained. 50 The particles are spherical particles with a diameter of 0.5 μm or larger and 50 μm or smaller. In this case, by making the particles into spherical shapes, the density may increase when forming electrodes from electrode materials, and uneven charging and discharging may be avoided. In addition, when the particles have the above-mentioned particle size, the workability of the granular powder is improved, and it is possible to manufacture uniform electrodes.

[0052] In the aspect described above

[12] , the heat treatment includes spray drying. In this case, spherical particles are easily obtained, and the particle size is also easily controlled.

[0053] The electrode material according to the invention having the configuration described above

[13] is formed as a granular body containing an active material and an inorganic binder, wherein the inorganic binder contains phosphate as a component and the content of the inorganic binder is 1% by mass or more and 30% by mass or less. The electrode material can be suitably manufactured by any of the manufacturing methods described above [1] to

[12] . Therefore, the electrode material according to the invention can be efficiently produced using a suspension in which the active material is dispersed in an organic solvent, and oxidation of the active material and generation of hydrogen are prevented during the production process. In addition, the electrode material has excellent flame retardancy and is not prone to generating hydrogen due to contact with water. Furthermore, the non-aqueous electrolyte secondary battery using the electrode material has excellent cycle characteristics, can operate stably in high-temperature environments, and has low electrode resistance. In addition, thermal runaway of the battery is less likely to occur, and safety is also improved.

[0054] In the above

[14] scheme, since the phosphate contained in the granules contains aluminum phosphate with a condensation formula Al2O3·nP2O5·mH2O having specified m and n, the mechanical strength and flame retardancy of the granules are improved.

[0055] In the aspects mentioned above

[15] , since the active material contains Si-based materials, a large theoretical capacity can be obtained in the non-aqueous electrolyte secondary battery formed using this electrode material.

[0056] Furthermore, in the aspects described above

[16] , since the Si-based material contains Si particles and SiX compound particles, high cycle performance can be obtained in the non-aqueous electrolyte secondary battery formed using this electrode material. In particular, in the aspects described above

[17] and

[18] , when the mass ratio of Si particles to SiX compound particles in the active material is set to a specified range, high cycle performance and high discharge performance can be obtained.

[0057] In the aspects mentioned above

[19] , since the Si-based materials also contain YCu compound particles, the improvement in cycle characteristics is particularly excellent. Attached Figure Description

[0058] Figure 1 This is a schematic diagram illustrating a method for manufacturing an electrode material according to an embodiment of the present invention. The area inside the dashed lines is an enlarged view of the granular material.

[0059] Figure 2 This is a surface scanning electron microscope (SEM) image of the electrode mixture layer in Example 1.

[0060] Figure 3 This is a surface SEM image of the electrode mixture layer in Example 2.

[0061] Figure 4 This is a surface SEM image of the electrode mixture layer in Example 3.

[0062] Figure 5 This is a surface SEM image of the electrode mixture layer in Example 4.

[0063] Figure 6 This is a surface SEM image of the electrode mixture layer in Example 5.

[0064] Figure 7 This is a surface SEM image of the electrode mixture layer in Example 6.

[0065] Figure 8 This is a surface SEM image of the electrode mixture layer in Comparative Example 1.

[0066] Figure 9 This is a surface SEM image of the electrode mixture layer in Comparative Example 2.

[0067] Figure 10 This is the differential scanning calorimetry (DSC) curve for Example 1.

[0068] Figure 11 This is the DSC curve for Example 2.

[0069] Figure 12 This is the DSC curve for Example 3.

[0070] Figure 13 This is the DSC curve from Example 4.

[0071] Figure 14 This is the DSC curve from Example 5.

[0072] Figure 15 This is the DSC curve from Example 6.

[0073] Figure 16 This is the DSC curve of Comparative Example 1.

[0074] Figure 17 This is the DSC curve of Comparative Example 2. Detailed Implementation

[0075] Hereinafter, a method for manufacturing electrode materials according to embodiments of the present invention and electrode materials according to embodiments of the present invention will be described in detail.

[0076] [1] Manufacturing methods and overview of electrode materials

[0077] The electrode material manufacturing method according to an embodiment of the present invention is a method for manufacturing electrode materials for non-aqueous electrolyte secondary batteries. The electrode material according to an embodiment of the present invention is an electrode material for non-aqueous electrolyte secondary batteries, which can be manufactured by the above-described manufacturing method. According to the electrode material manufacturing method according to an embodiment of the present invention described below, electrode materials composed of granules containing active materials can be manufactured efficiently, and oxidation of the active materials and generation of hydrogen can be prevented during the manufacturing process of the electrode material.

[0078] It should be noted that, in this specification, granular material refers to secondary particles obtained by forming and combining active material (single particles) as raw materials and granulation binders into particles larger than the active material raw materials (single particles). Active material refers to electrode active material, and is defined as a substance capable of reversibly undergoing chemical changes through charging and discharging, as well as adsorption or release of a carrier. Granulation binder is a material with the property of binding active materials together and improving the mechanical strength of the granular material.

[0079] In the method for manufacturing the electrode material according to this embodiment, such as Figure 1As schematically shown, as a granulation step, an aqueous solution 4 containing an inorganic binder 1 composed of phosphate (e.g., Al₂O₃·3P₂O₅) is mixed with a suspension 6 in which the active material 2 is dispersed in an organic solvent 5, and then the mixture 7 is heat-treated, for example, using a spray dryer. By heat treatment, granules 3 containing the inorganic binder 1 containing phosphate, the active material 2, and optional conductive additives are prepared. Hereinafter, specific raw materials, etc., will be described in turn. The manufacturing method according to this embodiment does not include the step of removing the organic solvent 5 from the suspension 6 before preparing the mixture 7.

[0080] [2] Suspension containing active materials

[0081] In this manufacturing method, as described above, a suspension in which the active material is dispersed in an organic solvent as the dispersion medium is used as the raw material for manufacturing the electrode material. The dispersion medium used in the suspension is an organic solvent. This is because by using an organic solvent, the surface of the active material is less likely to be oxidized and the active material is less likely to be altered. Then, the suspension containing the organic solvent and the active material is mixed with an aqueous solution of an inorganic binder containing phosphate as a component, and then dried, thereby combining the active material and the inorganic binder to obtain granules. By using an organic solvent, in the electrode using the manufactured electrode material, a decrease in reversible capacity due to alteration of the active material and an increase in resistance can be prevented, and the generation of hydrogen gas during the electrode material manufacturing step can be prevented. The suspension can be appropriately prepared by wet milling using a bead mill or similar method.

[0082] The active materials contained in the suspension are not particularly limited, as long as they are active materials used in non-aqueous electrolyte secondary batteries. For example, in the case of lithium-ion batteries, the active materials are not particularly limited, as long as they can adsorb and release the lithium ions used. Examples of such active materials include known active materials, including alkali metal / transition metal composite oxide active materials, vanadium-based active materials, sulfur-based active materials, solid solution active materials (lithium-rich, sodium-rich, potassium-rich active materials), carbon-based active materials, organic active materials, graphite, hard carbon, soft carbon, lithium titanate, alloy materials, conversion materials, etc. These active materials can be used alone or in combination of two or more. From the viewpoint of high theoretical capacity, materials that can form alloy phases with alkali metals are preferred, especially tin (Sn)-based materials, silicon (Si)-based materials, aluminum (Al)-based materials, germanium (Ge)-based materials, silver (Ag)-based materials, and other alloy materials. Among these, materials with high capacity, such as Si and SiO, are preferred. x(x is a real number greater than 0.3 and less than 1.4), Si-based materials of Si-M alloys. That is, the active material preferably contains particles containing Si. The Si-M alloy can be any of a fully solid solution alloy, a eutectic alloy, a hypoeutectic alloy, a hypereutectic alloy, and a peritectic alloy, and M is a metallic element, and examples include iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), yttrium (Y), aluminum (Al), vanadium (V), tin (Sn), manganese (Mn), zirconium (Zr), titanium (Ti), copper (Cu), niobium (Nb), and molybdenum (Mo). The surface of the active material particles can be coated with a material with excellent electronic conductivity, such as carbon or ceramics.

[0083] A preferred specific example of a Si-based material constituting the active material comprising a Si-M alloy is a material comprising Si particles and SiX compound particles. Here, element X is at least one element selected from Fe, Co, Ni, Zr, Ti, Cr, V, and Nb. All of these elements X are capable of forming compounds (silicides) with Si. Element X preferably contains at least Fe. The Si particles may contain only Si as the main component, except for unavoidable impurities, or they may contain an alloy in which element X is dispersed within the Si as the main component. Si preferably accounts for 95% or more by mass of the Si particles. The SiX compound particles may contain an intermetallic compound of Si and element X as the main component. The SiX intermetallic compound preferably accounts for 95% or more by mass of the SiX compound particles. When the Si-based material constituting the active material also contains SiX compound particles in addition to Si particles, the electrode material exhibits excellent cycle characteristics. This is because the SiX compound particles are less prone to volume changes during charge and discharge.

[0084] The content ratio of Si particles and SiX compound particles in the active material is not particularly limited. The mass ratio of Si particles (relative to the total mass ratio of the active material) is preferably in the range of 10% to 90%, and the mass ratio of SiX compound particles is preferably in the range of 5% to 90%. This results in a high degree of improvement in cycle characteristics. Furthermore, the electrode material exhibits high discharge characteristics; that is, it exhibits high discharge capacity even at high discharge rates. Specifically, the mass ratio of Si particles is more preferably in the range of 20% to 50%, and the mass ratio of SiX compound particles is more preferably in the range of 30% to 85%. When the mass ratios are within the above ranges, the effect of improving discharge characteristics is improved. Furthermore, the mass ratio of Si particles is more preferably in the range of 25% to 40%, and the mass ratio of SiX compound particles is more preferably in the range of 55% to 75%.

[0085] When the Si-based active material comprises Si particles and SiX compound particles, the Si-based material may further comprise YCu compound particles. Here, element Y is at least one element selected from Sn, Al, In, and Bi. Element Y does not form compounds with Si, but can form compounds with copper (Cu). Element Y preferably comprises at least Sn. The YCu compound particles contain an intermetallic compound of element Y and Cu as the main component. The YCu intermetallic compound preferably accounts for 95% or more by mass of the YCu compound particles. When the Si-based active material comprises YCu compound particles in addition to Si particles and SiX compound particles, the improvement in cycling performance is further enhanced. This is because the YCu compound particles exhibit a buffering effect that reduces the difference in volume expansion coefficients between Si particles and SiX compound particles. The content of YCu compound particles in the active material is not particularly limited, but the mass percentage of YCu compound particles in the active material is preferably in the range of 0.1% or more and 1% or less.

[0086] In the case of Si-based materials comprising Si particles, SiX compound particles, and YCu compound particles as needed, each of the Si particles, SiX compound particles, and YCu compound particles constitutes an independent particle. Then, a mixture of these particles is combined and bonded together using a phosphate-based inorganic binder to form granules.

[0087] To manufacture active materials containing Si-based materials, Si alloy powder can be prepared, for example, using atomization methods such as gas atomization. By using atomization to produce powder containing Si and desired metallic elements such as X, Y, and Cu, a metal powder can be obtained in which the Si phase, as well as the SiX compound phase and YCu compound phase corresponding to the composition, are crystallized. When the obtained metal powder is pulverized using a bead mill or similar method, the multiple phases separate, and the Si particles, SiX compound particles, and YCu compound particles become independent particles. The resulting particle mixture can then be used as a raw material active material and subjected to the granulation step described later.

[0088] The shape of the active material particles is not particularly limited and can be any shape, such as spherical, elliptical, fragmented, faceted, ribbon-like, fibrous, sheet-like, donut-shaped, or amorphous. Furthermore, each shape can be solid or hollow. However, from the viewpoint that the density of the electrode mixture layer can be easily increased by compressing the electrodes using a press, and from the viewpoint that it is difficult to cause uneven charging and discharging in the electrodes, the shape is preferably spherical and solid.

[0089] From the perspective of excellent battery cycle and output characteristics, active materials are preferably composed of median particle size (D). 50It consists of single particles with a diameter greater than 10 nm and less than 1 μm. It should be noted that a single particle is different from a granular body formed by the aggregation or linkage of multiple particles; it refers to a particle in a dispersed state where the primary particle is a single particle. In this specification, the median particle size (D...) 50 The term "particle size" refers to the volumetric reference particle size in laser diffraction / scattering particle size distribution measurement. Laser diffraction / scattering particle size distribution measurement utilizes the phenomenon that the intensity distribution of diffracted and scattered light varies with particle size when a laser beam is applied to a particle to measure particle size. In cases where the active material comprises Si particles, SiX compound particles, and, if necessary, YCu compound particles, each particle can be composed of a single particle having the aforementioned median diameter.

[0090] In addition to the active materials mentioned above, the suspension may also contain ceramics such as alumina, silicon dioxide, and zirconium oxide, as well as transition metal oxides containing alkali metals such as lithium niobate, sodium niobate, and lithium silicate, as fillers to mitigate the volume changes that accompany charging and discharging.

[0091] There are no particular limitations on the organic solvents used as dispersion media, and examples include: hydrocarbon-based organic solvents, such as toluene, xylene, dipentene, cyclohexane, methylcyclohexane, ethylcyclohexane, n-hexane, isohexane, n-pentane, and styrene monomer; alcohol-based organic solvents, such as methanol, ethanol, n-propanol, isopropanol (IPA), n-butanol, isobutanol, octanol, benzyl alcohol, and diacetone alcohol; and ester-based organic solvents, such as ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, methoxybutyl acetate, methyl methoxybutyl acetate, and ethyl-3-ethoxypropionate. Propylene glycol monomethyl ether propionate, diester, dimethyl carbonate; ketone organic solvents, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl hexyl ketone, diisobutyl ketone, cyclohexanone, isophorone; ethylene glycol ether organic solvents, such as butyl ethylene glycol, methyl diethylene glycol, ethyl diethylene glycol, butyl diethylene glycol, 1-methoxy-2-propanol, methyl dipropylene glycol, 3-methoxybutanol, 3-methyl-3-methoxybutanol, and tetrahydrofuran; nitrogen-based organic solvents, such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone (NMP); and halogen-based organic solvents, such as halogenated alkanes, trichloroethylene, chloroform, hydrofluorocarbons, and hydrochlorofluorocarbons.

[0092] The organic solvent may be soluble or insoluble in water, and is preferably a water-soluble organic solvent, more preferably a water-miscible organic solvent, because it does not separate from the aqueous solution of the phosphate-based inorganic binder used in the granulation step. A water-miscible organic solvent is one that can be mixed with water in any proportion. From the viewpoint that the solvent's volatility is neither too high nor too low, and its impact on the environment and human health is minimal, the solvent is particularly preferred to be an alcohol-based organic solvent such as ethanol, 1-propanol, or IPA, or a nitrogen-based organic solvent such as NMP.

[0093] From the viewpoint of facilitating mixing with the aqueous solution of the phosphate-based inorganic binder, the suspension preferably further contains water. When the suspension contains water as described above, if the organic solvent used in the suspension is a non-polar solvent, the suspension is likely to separate, making it difficult to mix with the phosphate-based inorganic binder. Therefore, water-soluble organic solvents such as alcohols and nitrogen-based solvents are preferred as the organic solvent constituting the suspension. Among these, as described above, alcohol-based organic solvents such as ethanol, 1-propanol, and IPA, and nitrogen-based organic solvents such as NMP are more preferred. Furthermore, when the suspension contains water, the concentration of water in the suspension relative to the organic solvent is preferably 10% by mass or more, because when the suspension and the aqueous solution of the phosphate-based inorganic binder are mixed, the inorganic binder is less likely to aggregate or precipitate. Specifically, the mass ratio of organic solvent to water is preferably 1:9 to 9:1, more preferably 2:8 to 7:3. From the viewpoint of ensuring a sufficient amount of active material and improving the dispersibility of the active material, the solid content concentration of the suspension is preferably 1% by mass or more and 30% by mass or less. It should be noted that the solid content concentration in the suspension refers to the proportion of solid active materials in the overall suspension.

[0094] [3] Inorganic binder aqueous solution

[0095] In the manufacturing method according to this embodiment, as described above, an aqueous solution of inorganic binder (a phosphate-based inorganic binder aqueous solution) containing an inorganic binder with phosphate as a component is used together with the above-mentioned suspension as a raw material for manufacturing the electrode material. By using a phosphate-based inorganic binder as a granulating binder, an electrode material with high flame retardancy can be manufactured, and the generation of hydrogen and oxidation of the active material can be prevented during the electrode material manufacturing step.

[0096] Typically, granules manufactured using reactive silicon-based materials as the active material and resin-based binders as the granulation binders may not possess sufficient flame retardancy. Even polyimide (PI), which is used as a resin-based binder with excellent flame retardancy, still exhibits some degree of flammability.

[0097] In contrast, phosphate-based inorganic binders are known to exhibit superior flame retardancy compared to resin-based binders such as PI. Furthermore, phosphate-based inorganic binders are characterized by their high melting point, resistance to thermal decomposition, and chemical stability. For example, phosphate-based inorganic binders have higher melting points than resin-based binders, thus allowing for long-term use in applications requiring fire resistance. Additionally, their strong agglomeration during drying facilitates the production of dense granules. Moreover, when using silicon-based materials as the active material, the specific gravity of phosphate-based inorganic binders is close to that of silicon, making it easy to maintain a homogeneous mixture if the suspension and the inorganic binder aqueous solution are thoroughly and uniformly mixed. Furthermore, phosphate-based inorganic binders do not easily lose their flowability and binder function even when in contact with organic solvents contained in the suspension.

[0098] Besides phosphate-based inorganic binders, representative inorganic binders include silicate-based inorganic binders (such as lithium silicate, sodium silicate, potassium silicate, and ammonium silicate). However, when using aqueous solutions of silicate-based inorganic binders, hydrogen is generated when the aqueous solution comes into contact with alloy materials. Therefore, not all inorganic binders, including silicate-based inorganic binders, can be used in this invention aimed at preventing hydrogen generation. As a result of research on various inorganic binders, the inventors have discovered that in the case of aqueous solutions of phosphate-based inorganic binders, the effect of preventing hydrogen generation can be obtained when the aqueous solution comes into contact with active materials. Therefore, in the manufacturing method of this embodiment, a phosphate-based inorganic binder is used as the inorganic binder for granulation.

[0099] The reason why hydrogen generation can be suppressed when the inorganic binder aqueous solution comes into contact with the active material by using phosphate-based inorganic binders is that phosphates, such as aluminum phosphate, are acidic solutes, and therefore have the function of acidifying the water near the electrode material when the electrode material comes into contact with water. Since hydrogen generation is prevented in acidic water, it is believed that oxidation of active materials such as Si alloys caused by water is also prevented.

[0100] However, phosphates, as components of inorganic binders, are almost insoluble in organic solvents. For example, even when aluminum phosphate (Al₂O₃·3P₂O₅·5H₂O) is added as powder to a suspension containing ethanol and Si-based materials (solid content concentration: 40% by mass), a homogeneous mixture of fine particles cannot be obtained. When a homogeneous mixture of fine particles cannot be obtained, the particles are heterogeneous, and in electrodes prepared from these particles, the cycling characteristics and stability at high temperatures tend to deteriorate, and the electrode impedance tends to increase. This also leads to significant variations in the properties of individual electrodes.

[0101] Therefore, in the manufacturing method according to this embodiment, a phosphate-based inorganic binder is mixed with a suspension as an aqueous solution with a solid content concentration of 30% by mass or less. Thus, a homogeneous mixture of fine particles can be obtained by mixing with the suspension. The reason for setting the solid content concentration to 30% by mass or less is that when the solid content concentration is greater than 30% by mass, due to a phenomenon called salting out or alcohol precipitation, the water of hydrated phosphate ions hydrates with the organic solvent (e.g., alcohol) constituting the suspension, and the phosphate ions are released as phosphate. Depending on various conditions such as the solid content concentration and solvent type, liquid temperature, and dripping rate in the mixture, the released substance can manifest as non-uniform lumpy aggregates, powdery precipitates, or uniform gel-like substances. For example, even when attempting to produce granules by adding an aqueous solution of aluminum phosphate (Al₂O₃·3P₂O₅) with a solid content concentration of 35% by mass to a suspension containing ethanol and Si-based materials (solid content concentration: 40% by mass), large lumpy aggregates are immediately generated after adding the aluminum phosphate aqueous solution to the ethanol-containing suspension. Therefore, controlling the particle size of granules is extremely difficult, and it is also difficult to obtain homogeneous granules.

[0102] However, when the solid content concentration in the aluminum phosphate aqueous solution is reduced to below 30% by mass, even if the release of phosphate due to salting out cannot be completely prevented when the aluminum phosphate aqueous solution is mixed with the suspension, it is obviously unlikely that phosphate aggregation or precipitation will occur, and a homogeneous mixture of fine particles or a gel-like mixture can be obtained. Thus, homogeneous granules can be manufactured, and the manufacturing efficiency of the electrode material is improved. This also applies to other phosphates. However, when the solid content concentration in the phosphate-based inorganic binder aqueous solution is less than 1% by mass, the effect of the phosphate-based inorganic binder cannot be fully utilized, for example, preventing hydrogen generation or producing granules with high mechanical strength. Therefore, in the manufacturing method according to this embodiment, the solid content concentration in the phosphate-based inorganic binder aqueous solution is set to 1% by mass or more and 30% by mass or less. The solid content concentration is preferably 3% by mass or more and 20% by mass or less. It should be noted that the solid content concentration in the phosphate-based inorganic binder aqueous solution refers to the proportion of the solid component of the phosphate-based inorganic binder in the total aqueous solution.

[0103] The solid content concentration in the aqueous solution of the phosphate-based inorganic binder can be appropriately determined within the range of 1% by mass or more and 30% by mass or less, as described above. In the manufactured granules, the lower the proportion of the granulating binder and the higher the proportion of the active material, the easier it is to obtain an electrode material that provides an electrode with excellent output characteristics and high energy density. On the other hand, the mechanical strength and flame retardancy of the granules tend to decrease. When the granules are brittle, they may collapse and fail to maintain their shape during the mixing step of the slurry when forming the electrode from the granules, or during charging and discharging on the produced electrode, which may lead to an increase in electrode impedance. Furthermore, when the proportion of the non-flammable phosphate-based inorganic binder is low, the granules are prone to heating or ignition. Therefore, from the viewpoints of ensuring strength to maintain the shape of the granules, ensuring sufficient flame retardancy, and ensuring the required output characteristics of the electrode, it is sufficient to set the mixing ratio of the active material and the phosphate-based inorganic binder based on the solid content concentration in the aqueous solution of the phosphate-based inorganic binder and the mixing ratio of the aqueous solution of the phosphate-based inorganic binder to the suspension containing the active material. Specifically, in the case where the active material is the median diameter (D) 50 When the particles are Si-based single particles with a diameter of 10 nm or more and a diameter of 1 μm or less, the proportion of the granulation binder relative to the entire granule is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 15% by mass or less, depending on the type and particle size of the active material.

[0104] The phosphate constituting the phosphate-based inorganic binder is not particularly limited, but aluminum phosphate is preferred. In particular, aluminum phosphate represented by the condensation formula Al₂O₃·nP₂O₅·mH₂O (0.5 ≤ n ≤ 4 and 0 ≤ m ≤ 8) is preferred. When n is a real number between 0.5 and 4, even with a reduced amount of granulating binder, granules with high mechanical strength and improved flame retardancy can be obtained. Furthermore, within the above range, the smaller n is, the higher the water resistance of the heat-treated granules. When the water resistance of the granules is high, aqueous binders are readily used as electrode binders (binders used when forming electrodes from granules). Additionally, when the phosphate is heat-treated, aluminum tetramethonium phosphate (Al₄(P₄O₅)) is readily formed at values ​​of n. 12 )3), when the value of n is large, aluminum orthophosphate (AlPO4) is easily generated.

[0105] The phosphate constituting the phosphate-based inorganic binder can also replace Al2O3, or contain B2O3, SiO2, GeO2, Fe2O3, TiO2, MnO, CaO, MgO, V2O5, As2O3, TeO2, ZnO, or PbO in addition to Al2O3. However, the presence of a large amount of such metal oxides may lead to a decrease in battery strength and an increase in irreversible capacity. Therefore, even when the phosphate contains these metal oxides, their amount is preferably less than that of Al2O3. More preferably, the total amount of phosphate constituting the phosphate-based inorganic binder is the aforementioned aluminum phosphate.

[0106] The phosphate constituting the phosphate-based inorganic binder can be anhydrous (m = 0) or hydrated (m > 0). However, in the case of hydrated form, as mentioned above, the hydration number m in aluminum phosphate is a real number of 10 or less. Furthermore, when the hydration number m is a real number greater than 8, the mechanical strength of the granules decreases, and therefore the structure of the granules may easily collapse during the slurry manufacturing process, which may not adequately improve flame retardancy, and irreversible capacity may increase. Therefore, the hydration number m in aluminum phosphate is preferably 8 or less, more preferably 6 or less.

[0107] The aforementioned phosphates, such as aluminum phosphate, possess the following properties: they solidify upon drying and are subsequently dehydrated by heat treatment at high temperatures to form phosphate metal bonds, such as aluminum phosphate bonds, and transform into a robust substance. Specifically, the hydration number m is 6 to 8 at heating temperatures of 100°C to 150°C, 5 to 6 at 150°C to 200°C, 2 to 5 at 200°C to 300°C, and essentially 0 at 450°C to 500°C. Thus, through heating and drying at temperatures above 450°C, although the hydrated water contained in the phosphate completely disappears, dephosphorization occurs at temperatures above 1000°C, and the value of n decreases. From this perspective, in the heat treatment following mixing an aqueous solution of a phosphate-based inorganic binder with a suspension containing active materials, the heating temperature is preferably 100°C to 500°C.

[0108] In preparing aqueous solutions of phosphate-based inorganic binders, phosphates can be prepared by dissolving pre-prepared phosphates in water, or by reacting orthophosphoric acid (H3PO4) with a metal source such as aluminum. For example, aluminum phosphate can be generated by mixing 1 mol of orthophosphoric acid and 3 mol of aluminum hydroxide and reacting them. In cases of poor reactivity, there is a tendency for reactivity to increase with heating. Since orthophosphoric acid is soluble in water, alcohol, or ether, it can be added to suspensions containing organic solvents and active materials.

[0109] In addition to phosphate, the inorganic binder aqueous solution may further contain alkali metal oxides (A₂O, where A is an alkali metal element) or alkali metal salts. When the inorganic binder aqueous solution contains alkali metal oxides or alkali metal salts, a reduction in resistance is expected in the battery made using this electrode material. However, when an excessive amount of alkali metal oxides or alkali metal salts is present, the strength of the particles decreases; therefore, it is preferable to contain them in an amount of 20% by mass or less relative to phosphate. When the amount added is about 0.1% by mass or more, the desired effect can be sufficiently obtained.

[0110] In addition to phosphates, inorganic binder aqueous solutions may also contain boron compounds such as boric acid (B(OH)3), metaboric acid (HBO2), and boron oxide (B2O3). The presence of boron compounds provides a non-hygroscopic effect on the electrode material, thus preventing moisture degradation of the electrolyte or electrolyte solution in the battery. In this case, it is preferable to contain 20% by mass or less of boron compounds compared to phosphates. The desired effect can be achieved when the added amount is approximately 0.1% by mass or more.

[0111] Besides phosphates, the inorganic binder aqueous solution may contain organic nitrogen compounds such as ammonium salts, urea, and urea phosphate. When organic nitrogen compounds are included, the electrode material is less prone to moisture absorption, thus preventing moisture degradation of the electrolyte or electrolyte solution in the battery. In this case, it is preferable to contain less than 20% by mass of organic nitrogen compounds compared to phosphates. When the amount added is about 0.1% by mass or more, the desired effect can be achieved.

[0112] Besides phosphate-based inorganic binders, aqueous solutions of inorganic binders may also contain resin-based binders as granulation binders. Known resin-based binders can be used as resin-based binders. For example, resin-based binders commonly used for positive or negative electrodes can be used. From the viewpoints of chemical stability, heat resistance, and reduction resistance of the granules, polybenzimidazole, styrene-butadiene rubber, polyvinylidene fluoride, carboxymethyl cellulose salt, polyvinyl alcohol, polyacrylic acid, polyacrylate, cellulose nanofibers, polyimide, polyamic acid, polyamide, and polyamide-imide are preferred. However, from the viewpoint of maintaining high flame retardancy of the granules, the content of resin-based binders can be reduced to less than 100% relative to phosphate-based inorganic binders. When maintaining particularly high heat resistance of the granules is required, it is preferable not to add resin-based binders.

[0113] In addition to phosphate-based inorganic binders, the aqueous solution of the inorganic binder may further contain ceramic particles as a granulating binder. Known ceramic particles can be used as the ceramic particles. Examples include silica, alumina, zirconium oxide, titanium dioxide, and yttrium oxide. When ceramic particles are added, the amount added is preferably 0.1% or more and 20% or less relative to the phosphate. Note that when the aqueous solution of the inorganic binder contains solid components other than the phosphate-based inorganic binder (e.g., alkali metal compounds, boron compounds, organic nitrogen compounds, resin-based binders, and ceramic particles listed herein), the solid content concentration of the aforementioned 1% by mass and 30% by mass or more of the phosphate-based inorganic binder is defined as the solid content concentration of the phosphate-based inorganic binder only, excluding solid components other than the phosphate-based inorganic binder.

[0114] [4] Granulation steps

[0115] As described above, the manufacturing method of this embodiment includes: as a granulation step, mixing an aqueous solution of an inorganic binder containing phosphate as a component with a suspension in which the active material is dispersed in an organic solvent to obtain a mixture, subjecting the mixture to heat treatment to evaporate the water, and then obtaining granules. The mixing method of the inorganic binder aqueous solution and the suspension is not particularly limited, as long as a homogeneous mixture composed of the various materials can be obtained. For example, known mixing or stirring methods such as multi-axis planetary mixers, roller mills, vibratory mills, planetary mills, oscillating mills, horizontal mills, grinders, jet mills, mills, ultrasonic homogenizers, stirring homogenizers, fluidizers, paint mixers, mixers, and magnetic stirrers can be used.

[0116] Alternatively, the mixture may consist only of an aqueous solution of an inorganic binder containing phosphate and a suspension in which the active material is dispersed in an organic solvent, with carbon preferably added as a conductive additive. Adding carbon improves the cycling characteristics and input / output characteristics of the manufactured electrode. Carbon can be added in any of the following ways: by dispersing carbon in an aqueous solution of an inorganic binder containing phosphate; by dispersing carbon in a suspension in which the active material is dispersed in an organic solvent; and by dispersing carbon in a mixture containing an aqueous solution of the inorganic binder and a suspension.

[0117] There are no particular limitations on the carbon used, as long as it improves the conductivity of the granules, and carbon known as an electrode conductive additive can be used. Examples include graphite, furnace black, channel black, acetylene black, thermal cracking black, lamp black, disc black, roll black, carbon black, soft carbon, hard carbon, glassy carbon, carbon nanotubes, carbon nanofibers (e.g., vapor-grown carbon fibers such as “VGCF” (registered trademark)), graphene, and carbon nanofibers, and one or more of these can be used.

[0118] When the total content of active material, inorganic binder, and carbon in the granules is 100% by mass, the carbon content is preferably 1% to 40% by mass. Carbon materials (graphite, soft carbon, hard carbon, etc.) also exist that function as both conductive additives and active materials. When using materials other than these carbon materials (e.g., materials capable of forming alloy phases with alkali metals) as active materials, when the carbon content exceeds 40% by mass, the proportion of active material in the battery decreases accordingly, and therefore the electrode capacity density may decrease.

[0119] The heat treatment method for obtaining granules containing both the inorganic binder and the active material after preparing a mixture by mixing an aqueous solution of an inorganic binder and a suspension containing an active material is not particularly limited. For example, known heat treatment methods such as heating drying, hot air drying, vacuum heating drying, far-infrared drying, spray drying, and fluidized bed drying can be used. However, from the viewpoint that the obtained granules are easily spherical and the particle size is easily controlled, heat treatment including spray drying is preferred. As described in the section on the aqueous solution of the inorganic binder above, the heating temperature during heat treatment is preferably 100°C or higher and 500°C or lower.

[0120] In spray drying, a mixture is formed into fine droplets, which are then instantaneously dried to remove the liquid components, thereby forming granules of active material bound together by an inorganic binder. For example, in a greenhouse heated to 50°C to 300°C, a mixture of active material dispersed in an aqueous solution of an inorganic binder is sprayed from above at a rate of 1 mL / min to 30 mL / min and a pressure of 0.01 MPa to 5 MPa to form aggregated particles. These aggregated particles are then dried to obtain granules. The granules obtained by spray drying can be further subjected to vacuum drying.

[0121] The median particle size (D) of the granules manufactured by the manufacturing method of this embodiment is... 50 The median diameter of the particles is preferably 0.5 μm or more and 50 μm or less. Setting the median diameter of the particles to 0.5 μm or more prevents deterioration of powder handling properties due to scattering or agglomeration of the granular powder. On the other hand, when the median diameter of the particles is 50 μm or less, non-uniformity of the electrode surface is prevented during electrode fabrication, and a uniform electrode can be fabricated. To adjust the particle size, sieving, cyclone grading, gravimetric grading, inertial grading, centrifugal grading, and precipitation grading are preferred.

[0122] The resulting granules can be further coated with carbon, metal oxides, solid electrolytes, etc. In this case, the amount of coating material relative to the granules is preferably 0.1% by mass or more and 20% by mass or less. For example, when a carbon film is formed on the surface of the granules by CVD, electrolyte decomposition is prevented in batteries manufactured using electrode materials, and very good cycle characteristics can be obtained.

[0123] By means of a granulation step, granular material, which is the electrode material according to this embodiment, can be obtained. The granular material contains an active material and an inorganic binder composed of phosphate. Furthermore, the granular material may contain additives such as carbon as conductive additives, as needed. In the electrode material, the content of the phosphate-based inorganic binder is preferably 1% by mass or more and 30% by mass or less. When the content of the phosphate-based inorganic binder is within this range, the mechanical strength and flame retardancy of the granular material are significantly improved by using the phosphate-based inorganic binder, and the precipitation and aggregation of the phosphate-based inorganic binder during the manufacturing process are easily avoided, thereby obtaining homogeneous granular material. More preferably, the content of the phosphate-based inorganic binder is 3% by mass or more, and even more preferably 10% by mass or more. Additionally, it is preferably 20% by mass or less, and more preferably 15% by mass or less. Note that the content of the phosphate-based inorganic binder in the electrode material refers to the proportion of the phosphate-based inorganic binder in the total solid content of the electrode material.

[0124] In the manufacturing method according to this embodiment, granules containing active materials and binders can be efficiently manufactured while suppressing hydrogen generation and surface oxidation of the active material. The electrode material obtained thus according to this embodiment has high flame retardancy and thermal stability, and also has high cycle characteristics. In addition, when a slurry is formed, the slurry has high coatability. Generally, in granules used as electrode materials, as the particle size increases, granules with excellent flame retardancy can be obtained, and the scattering of the electrode material also decreases. Therefore, although the processability is excellent, the input / output characteristics may be reduced. In addition, when the active material includes a material in which a large volume change occurs with charging and discharging (e.g., an alloying material that can form an alloy phase with an alkali metal), the cycle characteristics of the battery to be manufactured deteriorate. However, the granules manufactured by the manufacturing method of this embodiment, as shown in the examples described later, provide an electrode with high flame retardancy and high thermal stability, and can be used to manufacture an electrode with high input / output characteristics and high cycle characteristics.

[0125] [5] Applications of electrode materials

[0126] The electrode material obtained according to this embodiment, as described above, can be used as the positive or negative electrode material for a non-aqueous electrolyte secondary battery. Specifically, the electrode can be manufactured by molding the electrode material together with an electrode binder onto a current collector.

[0127] Electrode binders can be any substance that can be dispersed or dissolved in water or organic solvents and has the function of binding current collectors to granular materials containing active materials. The electrode material according to this embodiment has the characteristic that it does not easily generate hydrogen even when in contact with water. Therefore, the electrode binder can be an aqueous binder. As electrode binders, resin-based binders such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide, polyamide-imide, polyacrylic acid, styrene-butadiene rubber (SBR), ethylene-vinyl acetate copolymer (EVA), styrene-ethylene-butene-styrene copolymer (SEBS), carboxymethyl cellulose (CMC), xanthan gum, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), ethylene vinyl alcohol, polyethylene (PE), polypropylene (PP), polyacrylic acid, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, methyl acrylate, ethyl acrylate, polyacrylamide, polyacrylate, epoxy resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), nylon, vinyl chloride, silicone rubber, nitrile rubber, cyanoacrylate, urea resin, melamine resin, phenolic resin, latex, polyurethane, silylated polyurethane, nitrocellulose, dextrin, and polyvinylpyrrolidone can be used. Vinyl acetate, polystyrene, allyl chloride, resorcinol resin, polyaromatic compounds, modified organosilicon, methacrylic resin, polybutene, butyl rubber, 2-acrylic acid, cyanoacrylate, methyl methacrylate, glycidyl methacrylate, acrylic oligomers, 2-hydroxyethyl acrylate, polyacetal, alginate, starch, sucrose, paint, glue, casein, and cellulose nanofibers, or inorganic binders such as lithium silicate (Li₂O·nSiO₂, n = 0.5 to 6), sodium silicate (Na₂O·nSiO₂, n = 0.5 to 6), potassium silicate (K₂O·nSiO₂, n = 0.5 to 6), colloidal silica, cement, or aluminum phosphate (Al₂O₃·nP₂O₅, n = 0.5 to 6). These electrode binders can be used alone or in combination of two or more of them.

[0128] When forming an electrode, electrode material is mixed with an electrode binder to prepare an electrode slurry. In the electrode slurry, when the total solid content is 100% by mass, the content of the electrode binder is preferably from 0.1% to 30% by mass. When the content of the electrode binder is 0.1% by mass or more, the flexibility of the electrode is improved, and peeling or falling off is less likely to occur during the pressing pressure adjustment step or the winding step. On the other hand, when the binder content is reduced to 30% by mass or less, the electrode exhibits high ionic conductivity and low resistance, sufficiently ensuring the proportion of active material for the battery, and increasing the electrode capacity density.

[0129] The electrode slurry preferably further contains conductive additives. When the total amount of solid components in the electrode slurry is set to 100% by mass, the conductive additive is preferably contained in an amount of 0.5% by mass or more and 20% by mass or less. There are no particular limitations on the conductive additive for the electrode, as long as it has electronic conductivity; for example, the same carbon as the granulated conductive additive described above can be used.

[0130] The current collector used for the electrode can be a material that is electronically conductive and capable of energizing the held active material. For example, it is desirable to use a current collector made of Cu, Ni, Ti, Al, stainless steel (SUS), carbon, or an alloy or coating material containing these elements. Examples of current collector shapes include wire, rod, plate, foil, porous, etc., and any of these can be used. The electrode slurry is formed into the desired shape on the surface of the current collector by coating or the like, and then dried appropriately, thus preparing the electrode.

[0131] The electrodes thus obtained can be used as the positive or negative electrodes of a non-aqueous electrolyte secondary battery. A non-aqueous electrolyte secondary battery is a battery that includes a positive electrode, a negative electrode, and a non-aqueous electrolyte between the positive and negative electrodes, and examples of such batteries include lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, lithium-ion capacitors, sodium-ion capacitors, and potassium-ion capacitors.

[0132] When using the prepared electrode as the positive electrode of a secondary battery, the secondary battery can be prepared by combining the prepared electrode with an electrode whose charging / discharging potential is lower than that of the prepared electrode. Conversely, when using the prepared electrode as the negative electrode of a secondary battery, the secondary battery can be prepared by combining the prepared electrode with an electrode whose charging / discharging potential is higher than that of the prepared electrode. For example, when using the prepared electrode as the positive electrode, there are no particular restrictions on the opposite electrode (negative electrode), as long as it can be used as the negative electrode of the secondary battery.

[0133] The electrolyte used in a secondary battery can be a liquid or solid (such as a lithium-supported salt) capable of moving alkali metal ions or fluoride compound anions from the positive electrode to the negative electrode or vice versa. That is, the same electrolyte used in secondary batteries employing known non-aqueous electrolytes can be used. Examples include electrolytes, gel electrolytes, solid electrolytes, ionic liquids, and molten salts. Here, an electrolyte refers to the state in which the electrolyte is dissolved in a solvent.

[0134] There are no particular limitations on the structure of secondary batteries; existing forms and structures such as stacked and wound types can be used. In these forms, an electrode assembly in which the positive and negative electrodes are laminated or wound together facing each other with a separator inserted between them is sealed while immersed in an electrolyte to form a secondary battery. Alternatively, a secondary battery is formed by stacking or winding the positive and negative electrodes together with an electrode assembly in which the electrodes face each other via a solid electrolyte.

[0135] Aside from the main difference in the operation of the opposing electrodes, lithium-ion capacitors can be manufactured in the same manner as lithium-ion batteries. Specifically, for example, a battery can be manufactured in the same manner as a battery, except that the electrode according to this embodiment is used as the positive electrode and the negative electrode of a lithium-ion capacitor in the related art is used as the negative electrode. Alkali metal ion batteries, other than lithium-ion batteries, can be manufactured in the same manner as lithium-ion batteries, except that lithium, which serves as the charge carrier in a lithium-ion battery, is replaced with sodium or potassium. Specifically, a sodium-ion battery can be manufactured in the same manner as a battery, except that the electrode prepared as described above is used as the positive electrode, the negative electrode of a sodium-ion battery in the related art is used as the negative electrode, and a sodium-supported salt is used as the electrolyte. A potassium-ion battery can be manufactured in the same manner as a lithium-ion battery, except that the electrode prepared as described above is used as the positive electrode, the negative electrode of a potassium-ion battery in the related art is used as the negative electrode, and a potassium-supported salt is used as the electrolyte.

[0136] As described above, the electrode material according to this embodiment possesses high flame retardancy and high thermal stability, and the electrode prepared using this electrode material exhibits high input / output characteristics and high cycle performance. As illustrated in the examples described later, the flame retardancy and thermal stability of the electrode material can each be evaluated using a Class 2 hazardous material test and differential scanning calorimetry (DSC). It should be noted that the input / output characteristics and cycle performance of the electrode can be evaluated by fabricating a lithium-ion battery using this electrode material and conducting charge-discharge tests.

[0137] Example

[0138] The present invention will now be described with examples. Note that the present invention is not limited to these examples.

[0139] [1]. Sample Preparation 1

[0140] [Preparation of Si Alloys]

[0141] A fine-powdered Si alloy was prepared by using gas atomization to produce a powder from a molten alloy composed of Si (70 wt%) and Fe (30 wt%). The powder was then pulverized using a bead mill and further classified using a sieve to a particle size below 150 μm. Note that an argon atmosphere was used during both the preparation of the molten alloy and the gas atomization process. It should be noted that during gas atomization, high-pressure (4 MPa) argon gas was injected into the molten alloy as it fell in a rod-like pattern within the atomization chamber.

[0142] [Preparation of Si alloy suspension]

[0143] Using a wet bead mill, the fine powdered Si alloy obtained above and ethanol were stirred together with zirconia beads (0.3 mm in diameter) until the median particle size of the Si alloy (D) was reached. 50 To prepare a Si alloy suspension with a solid content concentration of 40% by mass, the particle size was 700 nm (circumferential velocity: 10 m / s). Here, the median particle size (D) of the Si alloy was... 50 The particle size is a volume-based measurement using a laser diffraction / scattering particle size distribution measuring device (Partica LA-960V2 manufactured by HORIBA, Ltd).

[0144] [Preparation of Electrode Materials]

[0145] (Example 1)

[0146] As an example of the electrode material, granules containing active material and an inorganic binder containing phosphate were prepared by the following method.

[0147] Water was added to the Si alloy suspension prepared above to achieve a solid content concentration of 10% by mass, and then the mixture was prepared to prepare suspension A. Meanwhile, an aqueous solution of aluminum phosphate (Al₂O₃·3P₂O₅) and carbon black (CB, average primary particle size: 35 nm, specific surface area: 70 m²) were mixed. 2 (g) was added together with water to make the solid content concentration of aluminum phosphate 10% by mass, and then mixed to prepare suspension B. Further, suspension A and suspension B were mixed to make the solid content composition Si alloy: Al2O3·3P2O5:CB = 93:5:2% by mass to prepare a mixture for spray drying. At this time, when checking for the presence or absence of hydrogen by visual observation, no bubbles were observed, therefore no hydrogen was observed in the mixture. It should be noted that suspension A, suspension B, and the mixture for spray drying were all obtained by mixing for 10 minutes at atmospheric pressure and 2000 rpm using a rotary mixer (Awatori Rentaro ARE-310, manufactured by THINKY Corporation).

[0148] Furthermore, the spray-drying mixture obtained above was spray-dried using a spray dryer (ADL311S-A, manufactured by Yamato Scientific Co., Ltd.), followed by vacuum drying (300°C, 12 hours) to obtain granules as electrode materials. The spray-drying conditions were an inlet drying temperature of 170°C, an outlet drying temperature of 70°C to 90°C, a pressure of 0.04 MPa to 0.05 MPa, and a pressure of 0.1 m... 3 / min to 0.2m 3 Average dry air flow rate / min.

[0149] (Examples 2-6)

[0150] The electrode materials in Examples 2 through 6 were prepared in the same manner as in Example 1, except that the solid content composition of the spray-drying mixture obtained by mixing suspension A and suspension B is as follows. In any of Examples 2 through 6, as in Example 1, no hydrogen generation from the mixture was observed.

[0151] Example 2: Si alloy: Al2O3·3P2O5:CB = 88:10:2 (mass%)

[0152] Example 3: Si alloy: Al2O3·3P2O5:CB = 91:7:2 (mass%)

[0153] Example 4: Si alloy: Al2O3·3P2O5:CB = 88:7:5 (mass%)

[0154] Example 5: Si alloy: Al2O3·3P2O5:CB = 85:5:10 (mass%)

[0155] Example 6: Si alloy: Al2O3·3P2O5:CB = 90:5:5 (mass%)

[0156] (Comparative Example 1)

[0157] The electrode material of Comparative Example 1 was prepared using a resin-based binder instead of a phosphate-based inorganic binder. Specifically, water was added to a Si alloy suspension to a solid content concentration of 5% by mass, and then mixed to prepare suspension A. On the other hand, an aqueous solution of polyimide (UPIA-LB2001 manufactured by UBE Corporation) and CB were mixed with water to a polyimide solid content concentration of 5% by mass to prepare suspension B. Furthermore, suspension A and suspension B were mixed to a solid content composition of Si alloy:polyimide:CB = 93:5:2% by mass to prepare a spray-drying mixture. Except as described above, the electrode material of Comparative Example 1 was prepared under the same conditions as in Example 1.

[0158] (Comparative Example 2)

[0159] As the electrode material in Comparative Example 2, the Si alloy suspension was simply dried under reduced pressure to obtain Si alloy fine powder.

[0160] (Comparative Example 3)

[0161] Water was added to a Si alloy suspension to achieve a solid content concentration of 35% by mass, and then mixed to prepare suspension A. On the other hand, an aqueous solution of aluminum phosphate (Al₂O₃·3P₂O₅) and CB were added together with water to achieve a solid content concentration of aluminum phosphate of 35% by mass, and then mixed to prepare suspension B. Further, when suspensions A and B were mixed with a solid content composition of Si alloy:Al₂O₃·3P₂O₅:CB = 93:5:2% by mass, aggregates of approximately several millimeters in size were formed as precipitates. Even after diluting and mixing the mixture with water, these aggregates did not disappear, nor did they appear to disappear or decrease. When the mixture for spray drying contained aggregates in the millimeter range, the spray nozzle for spray drying became clogged. Therefore, in the manufacturing method of Comparative Example 3, it was impossible to prepare a mixture for spray drying. Note that the conditions not described are the same as those in Example 1.

[0162] [2] Evaluation methods and evaluation results 1

[0163] [Evaluation of the manufacturing steps for electrode materials]

[0164] As described above, in Examples 1 to 6, suspension A and suspension B were mixed to prepare a mixture for spray drying. In suspension A, the Si alloy, serving as the active material, was suspended in an organic solvent, and suspension B contained an aqueous solution of an inorganic binder containing phosphate as a component. In these Examples 1 to 6, no hydrogen generation from the mixture was observed, and the generation of the electrode material could be safely advanced. Furthermore, in Comparative Example 3, where the solid content concentration of phosphate in suspension B was greater than 30% by mass, aggregates formed due to precipitation, and spray drying could not be performed. However, in Examples 1 to 6, where the solid content concentration of phosphate in suspension B was reduced to below 30% by mass, no precipitation occurred, and spray drying could be performed normally. Therefore, by keeping the solid content concentration in the inorganic binder aqueous solution below 30% by mass, phosphate precipitation is prevented, and the manufacture of granular materials as electrode materials can be efficiently advanced. It should be noted that in the following evaluations, the electrode material of Comparative Example 3, which did not yield a mixture suitable for spray drying, was not used.

[0165] [Observation of Electrode Materials]

[0166] To examine the particulate structure of the electrode materials, the samples in Examples 1 to 6 and Comparative Examples 1 and 2 were observed using a scanning electron microscope (SEM). Electrode mixture layers for SEM observation were prepared by embedding the granules obtained as electrode materials in each of the above examples and comparative examples in resin, followed by mechanical polishing. Figures 2 to 7 SEM images of the surface of the electrode mixture layers in Examples 1 through 6 are shown respectively. Figure 8 and 9 Surface SEM images of the electrode mixture layers in Comparative Examples 1 and 2 are shown respectively.

[0167] Depend on Figures 2-9 It is clearly observed that spherical particles were observed in Examples 1 to 6 and Comparative Example 1, but no spherical particles were observed in Comparative Example 2, which did not use a binder; only fine particles were observed. This indicates that granular particles were formed by bonding the active material using a binder.

[0168] [Evaluation of flame retardancy]

[0169] To evaluate the flame retardancy of each electrode material, a small gas flame ignition test was conducted on each electrode material in Examples 1 to 6 and Comparative Examples 1 and 2, according to the Class 2 hazardous substance test. In the small gas flame ignition test, the ambient temperature was 20°C, the ambient humidity was 50%, the atmospheric pressure was constant, there was no wind, and the flame contact area was 2 cm². 2 Under the condition of a flame contact angle of 30°, the flame is brought into contact with the electrode material (3 mL) set in a hemispherical shape on the heat insulation plate for 10 seconds to check the ignition ease of the electrode material.

[0170] Table 1 shows the results of flame retardancy determination. Electrode materials that ignite within 3 seconds of contact with a flame are rated "C", those that ignite after more than 3 seconds but less than 10 seconds are rated "B", and those that do not ignite even after more than 10 seconds of contact are rated "A". Even in cases where the electrode material ignites, if the time until ignition is longer than 3 seconds, the electrode material can be considered to have sufficiently high flame retardancy.

[0171] [Table 1]

[0172]

[0173] As can be clearly seen from Table 1, Examples 1 to 6 are powder electrode materials that are less prone to ignition than Comparative Examples 1 and 2. In particular, in Example 2 containing 10% by mass of aluminum phosphate, since the electrode material did not ignite even after 10 seconds, it is speculated that the higher the aluminum phosphate content, the less prone the electrode material is to ignition.

[0174] [Evaluation of thermal stability]

[0175] To examine the thermal stability of the electrode materials, differential scanning calorimetry (DSC) measurements were performed on each electrode material in Examples 1 to 6 and Comparative Examples 1 and 2. DSC measurements were performed by enclosing each electrode material (6.3 mg to 8.5 mg) in an open aluminum dish. During the DSC measurements, air flowed at a rate of 5 mL / min, and the temperature increased at a rate of 10 °C / min over a measurement range of 50 °C to 450 °C.

[0176] Figures 10 to 15 The DSC measurement results of the electrode materials in Examples 1 to 6 are shown. Figure 16 and Figure 17 The DSC measurement results for the electrode materials of Comparative Examples 1 and 2 are shown. In each figure, the solid line is the DSC curve, and an upward shift in the curve indicates that the electrode material is self-heating. Note that the dashed line in the figure is the baseline representing the DSC value at 50°C. Figures 10 to 17 It is clear that Examples 1 to 6 are powder electrode materials that are less prone to overheating compared to Comparative Examples 1 and 2. Specifically, in Examples 1 to 6 where aluminum phosphate is used to form granules, the total heat generation of the electrode material is low and the onset temperature of heating is high, indicating that aluminum phosphate has the effect of improving the thermal stability of the electrode material.

[0177] Note that in Comparative Example 2, the onset temperature of heating was higher than that in Comparative Example 1, but a large heating reaction was observed above 270°C. On the other hand, in Examples 1 to 6, no large heating reaction as observed in Comparative Example 2 was observed.

[0178] [3] Sample preparation 2

[0179] [Electrode fabrication]

[0180] Electrodes were prepared using the electrode materials from Examples 1 to 6 and Comparative Examples 1 and 2. The electrodes were prepared by applying a slurry consisting of 90% by mass of the electrode material, 3% by mass of acetylene black (Denka Black, manufactured by Denka Company Limited), 1% by mass of vapor-grown carbon fiber (VGCF-H, manufactured by Showa Denko KK), and 6% by mass of polyimide (UPIA-LB 1001, manufactured by UBECorporation) onto a nickel-plated steel foil (Super Nickel, thickness: 10 μm, manufactured by NIPPON STEEL CORPORATION) serving as the current collector, followed by vacuum drying (300°C, 12 hours). The reversible capacity per unit area was 3 mAh / cm². 2 Note that the slurry was prepared by mixing for 6 minutes at atmospheric pressure and 2000 rpm using a planetary centrifugal mixer (Awatori Rentaro ARE-310, manufactured by THINKY Corporation).

[0181] [Battery Manufacturing]

[0182] Each of the electrodes obtained using the electrode materials from Examples 1 to 6 and Comparative Examples 1 and 2 described above was used as a test electrode. A coin-shaped battery (R2032) was fabricated using a lithium metal relative electrode (lithium foil with a thickness of 500 μm manufactured by Honjo Metal Co., Ltd.), a PP / PE / PP three-layer microporous membrane (Celgard 2325), a glass filter (ADVANTEC GA100), and a non-aqueous electrolyte. The non-aqueous electrolyte used was a solution in which 1% by mass of fluoroethylene carbonate (FEC) was added to a solvent obtained by adding 1% by mass of ethylene carbonate (FEC) to a mixture of ethylene carbonate (EC): diethyl carbonate (DEC) = 1:1 (volume ratio), and LiPF6 was dissolved at a concentration of 1 mol / L. Note that the battery was prepared in a drying chamber (NS drying chamber, dew point: -80°C, manufactured by NihonSpindle Manufacturing Co., Ltd.).

[0183] [4] Evaluation methods and evaluation results 2

[0184] [Charge-discharge cycle characteristics]

[0185] Charge and discharge tests were performed on batteries using the electrode materials described in Examples 1 to 6 and Comparative Examples 1 and 2. The charge-discharge cycle tests were conducted at 30°C under conditions of repeated charge-discharge cycles at a cutoff voltage of 0.001V to 1.5V and a rate of 0.1C.

[0186] Table 2 shows the measured discharge capacity and capacity retention for the first and 60th cycles, representing the cycling characteristics of each test electrode. Note that discharge capacity was determined by dividing the electrode's capacitance obtained during discharge by the mass of the electrode material. Capacity retention is expressed as a relative discharge capacity based on the discharge capacity (100%) in the first cycle.

[0187] [Table 2]

[0188]

[0189] In Comparative Example 2, since the electrode material does not contain granulating binder and granulating conductive additive, the initial discharge capacity is as high as 1664.6 mAh / g, but the discharge capacity in the 60th cycle is less than the initial discharge capacity, and the capacity retention rate is as low as 76.6%. On the other hand, in Examples 1 to 6 and Comparative Example 1, which use granulating binder and granulating conductive additive to form spherical particles, the initial discharge capacity is smaller than that in Comparative Example 2, but the capacity retention rate is larger than that in Comparative Example 2.

[0190] [High-speed discharge characteristics]

[0191] High-rate discharge tests were conducted on batteries using the electrode materials described in Examples 1 to 6 and Comparative Examples 1 and 2. The high-rate discharge tests were conducted under the following conditions: five cycles of charging and discharging were repeated at a cutoff voltage of 0.001 V to 1.5 V and a rate of 0.1 C at 30°C, followed by discharge at rates of 0.2 C, 0.5 C, 1 C, and 3 C.

[0192] Table 3 shows the electrode capacity obtained at each discharge rate based on the discharge capacity at a rate of 0.1 C for each test electrode.

[0193] [Table 3]

[0194]

[0195] According to Table 3, at low rates below 0.5 C, the samples exhibited almost identical discharge capacities. However, when discharging at a rate of 3 C, it was found that the discharge capacities of Examples 1 to 6 using aluminum phosphate as a granulation binder were greater than those of Comparative Examples 1 and 2.

[0196] [5] Study on the composition of active materials

[0197] Furthermore, electrode materials were prepared by changing the composition of the Si alloy used as the active material, and their properties were evaluated.

[0198] [Sample Preparation]

[0199] Electrode materials according to Examples 7 to 14 were prepared in the same manner as described in item [1] above. In the preparation of the Si alloy, the alloy composition of the molten alloy used as raw material in the gas atomization method is shown in the left column of Table 4 below. The powder obtained by the gas atomization method was pulverized using a bead mill to obtain Si alloy powder containing Si particles, Si2Fe compound particles and SnCu compound particles. The proportion of compounds in the obtained alloy powder, i.e., the proportion of Si phase, Si2Fe phase and SnCu compound phase, is shown in the right column of Table 4 below.

[0200] The compound proportions were determined by calculation based on the results of X-ray diffraction (XRD) measurements. The calculation method for the compound proportions is explained using Example 7 as an example. (1) First, the constituent phases in the alloy powder were examined by XRD analysis. In Example 7, the Si phase, the Si2Fe phase as the SiX compound phase, and the SnCu phase (Sn5Cu6) as the YCu compound phase were observed. (2) Next, assuming that all element X contained in the alloy composition constitutes the SiX compound phase observed in (1), the mass proportion of the SiX compound phase in the alloy powder was determined based on the mass ratio of Si in the SiX compound phase to element X. The mass ratio of Si to Fe in the Si2Fe phase is Si:Fe = 50.1:49.9. In the alloy composition of Example 7, the Fe content is 44.6% by mass, and the amount of Si that constitutes the Si2Fe phase with Fe is 44.6 × 50.1 / 49.9 = 44.8% by mass. The compound proportion of the SiX compound phase composed of Si2Fe is the total mass of Si and Fe constituting Si2Fe, which is 44.6 + 44.8 = 89.4% by mass in Example 7. (3) In addition, the compound proportion of the Si phase is determined by subtracting the amount of Si constituting the SiX compound phase determined in (2) from the Si content in the alloy composition. In Example 7, the compound proportion of the Si phase is 54.9 - 44.8 = 10.1% by mass. Finally, the compound proportion of the YCu compound phase is determined as the total content of elements Y and Cu in the alloy composition. In Example 7, the compound proportion of the SnCu phase is 0.3 + 0.2 = 0.5% by mass.

[0201] [Table 4]

[0202]

[0203] In sample preparation, the steps following the preparation of the Si alloy were performed in the same manner as in Example 1. Except for the composition of the Si alloy powder, the composition of the spray drying mixture was also the same as in Example 1, resulting in granules with the compositions shown in Table 5 below, which were used as electrode materials. Furthermore, a carbon film was formed on the surface of the obtained granules using a thermal CVD method. In the thermal CVD method, acetylene gas, as an organic gas, was supplied to the furnace, while the granules were held in the furnace at 700°C for 1 hour.

[0204] [Evaluation of flame retardancy]

[0205] The flame retardancy of each of the obtained electrode materials was evaluated in the same manner as in the evaluation of the above-mentioned item [2]. Table 5 below shows the evaluation results of flame retardancy and the composition of the granules.

[0206] [Table 5]

[0207]

[0208] According to Table 5, Examples 7 to 14 all achieved a high flame retardancy rating of "B," similar to Example 1. This demonstrates that even when the granules contain a specified amount of an inorganic binder composed of phosphates, high flame retardancy is achieved even when the composition of the Si-based material constituting the active material changes.

[0209] [Evaluation of charge / discharge characteristics and high-rate discharge characteristics]

[0210] Using the electrode materials from Examples 7 to 14, electrodes and batteries were fabricated in the same manner as described in item [3] above. Then, charge-discharge cycle characteristics and high-rate discharge characteristics were evaluated in the same manner as described in item [4] above. The evaluation results of charge-discharge cycle characteristics are shown in Table 6 below, and the evaluation results of high-rate discharge characteristics are shown in Table 7 below.

[0211] [Table 6]

[0212]

[0213] [Table 7]

[0214]

[0215] According to Table 6, in all samples, a capacity retention rate of over 80% was obtained at the 60th cycle, indicating high cycling performance. In particular, in Examples 7 to 13, where the Si phase content ranged from 10% to 90% and the Si2Fe phase content ranged from 5% to 90%, the capacity retention rate was over 83%. In the discharge characteristics results in Table 7, Examples 7 to 13 also showed high discharge performance with a discharge capacity of over 80% at 3C rate. Furthermore, in Examples 8 and 9, where the Si phase content ranged from 20% to 50% and the Si2Fe phase content ranged from 30% to 85%, the capacity retention rate at the 60th cycle in Table 6 and the discharge capacity at 3C rate in Table 7 both achieved large values ​​in a balanced manner, indicating excellent cycling and discharge performance. Specifically, in Example 8, the capacity retention rate at the 60th cycle was the second largest, and the discharge capacity at 3C rate was the largest among Examples 7 to 14, thus achieving a high degree of balance between cycling and discharge performance.

[0216] Although preferred embodiments and examples of the invention have been described above, various additions, modifications, or deletions can be made without departing from the spirit of the invention. Therefore, such modifications are also included within the scope of the invention. Furthermore, in this specification, the numbers described in the general formulas of compounds may simply be represented as integers, but only those that satisfy electrical neutrality; where substantially the same, they are included within the scope of the invention.

[0217] This application is based on Japanese Patent Application No. 2024-233217, filed on December 29, 2024, and Japanese Patent Application No. 2025-163573, filed on September 30, 2025, the contents of which are incorporated herein by reference.

[0218] List of reference numerals

[0219] 1 Inorganic binders

[0220] 2. Active materials

[0221] 3. Granular bodies

[0222] 4. Inorganic binder aqueous solution

[0223] 5. Organic solvents

[0224] 6. Suspension

[0225] 7. Mixture.

Claims

1. A method for manufacturing an electrode material, wherein the electrode material is an electrode material for a non-aqueous electrolyte secondary battery, the manufacturing method comprising a granulation step, the granulation step comprising: A mixture is obtained by mixing an aqueous solution of an inorganic binder and a suspension, wherein the aqueous solution of the inorganic binder contains an inorganic binder containing phosphate as a component, and the active material is dispersed in an organic solvent in the suspension; The mixture is heat-treated to evaporate the water in the mixture; Particulate matter containing the inorganic binder and the active material is obtained, wherein The solid content concentration of the inorganic binder aqueous solution is above 1% by mass and below 30% by mass.

2. The method for manufacturing electrode material according to claim 1, wherein, The phosphate includes aluminum phosphate represented by the condensed form Al2O3·nP2O5·mH2O, wherein 0.5 ≤ n ≤ 4 and 0 ≤ m ≤ 8.

3. The method for manufacturing electrode material according to claim 1 or 2, wherein, The solid content concentration of the suspension is above 1% by mass and below 30% by mass. The suspension also contains water, and The concentration of water in the suspension relative to the organic solvent is 10% by mass or more.

4. The method for manufacturing electrode material according to claim 1 or 2, wherein, The organic solvent is a water-soluble organic solvent.

5. The method for manufacturing electrode material according to claim 4, wherein, The water-soluble organic solvent is an alcohol-based organic solvent.

6. The method for manufacturing electrode material according to claim 1 or 2, wherein, The mixture is subjected to the heat treatment at a temperature above 100°C and below 500°C.

7. The method for manufacturing electrode material according to claim 1 or 2, wherein, The active material contains median particle size (D) 50 () refers to single particles with a diameter greater than 10 nm and a diameter less than 1 μm.

8. The method for manufacturing electrode material according to claim 1 or 2, wherein, The active material includes materials capable of forming alloy phases with alkali metals.

9. The method for manufacturing electrode material according to claim 8, wherein, The material that can form an alloy phase with alkali metals is a Si-based material.

10. The method for manufacturing electrode material according to claim 1 or 2, wherein, The mixture also contains carbon.

11. The method for manufacturing electrode material according to claim 1 or 2, wherein, The granules are spherical, and the median particle size (D) of the granules is... 50 The size ranges from 0.5 μm to 50 μm.

12. The method for manufacturing electrode material according to claim 1 or 2, wherein, The heat treatment includes spray drying.

13. An electrode material for use in non-aqueous electrolyte secondary batteries, wherein, The electrode material is a granular material containing active material and an inorganic binder composed of phosphate. The content of the inorganic binder is more than 1% by mass and less than 30% by mass.

14. The electrode material according to claim 13, wherein, The phosphate comprises aluminum phosphate represented by the condensed form Al2O3·nP2O5·mH2O, wherein 0.5 ≤ n ≤ 4 and 0 ≤ m ≤ 8.

15. The electrode material according to claim 13 or 14, wherein, The active material comprises Si-based materials.

16. The electrode material according to claim 15, wherein, The Si-based material comprises Si particles and SiX compound particles, wherein X is at least one element selected from Fe, Co, Ni, Zr, Ti, Cr, V and Nb.

17. The electrode material according to claim 16, wherein, In the active material, the mass proportion of Si particles is more than 10% and less than 90%, and the mass proportion of SiX compound particles is more than 5% and less than 90%.

18. The electrode material according to claim 17, wherein, In the active material, the mass proportion of Si particles is more than 20% and less than 50%, and the mass proportion of SiX compound particles is more than 30% and less than 85%.

19. The electrode material according to claim 16, wherein, The Si-based material also contains YCu compound particles, wherein Y is at least one element selected from Sn, Al, In and Bi.

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