Electrode material, electrode, energy storage element, and method for manufacturing electrode material

Abstract

To provide an electrode material with suppressed agglomeration, an electrode and a power storage element using such an electrode material, and a method of manufacturing such an electrode material.SOLUTION: An electrode material contains an active material, a solid electrolyte, and graphite. The active material and the solid electrolyte are compounded.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrode material, an electrode, an energy storage element, and a method for manufacturing an electrode material. [Background technology]

[0002] Due to their high energy density, lithium ion secondary batteries are widely used in electronic devices such as personal computers and communication terminals, automobiles, etc. The lithium ion secondary batteries generally have a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte interposed between the electrodes, and are configured to charge and discharge by transferring lithium ions between the electrodes. In addition to lithium ion secondary batteries, capacitors such as lithium ion capacitors are also widely used as energy storage elements. Energy storage elements using a solid electrolyte as the non-aqueous electrolyte, such as all-solid-state batteries, have also been developed.

[0003] Because solid electrolytes do not have fluidity, electrodes of energy storage elements that use solid electrolytes are prone to voids between the active material and the solid electrolyte. Such voids in the electrode increase the resistance of the electrode. Therefore, various composite particles in which an active material is coated with a solid electrolyte have been developed to reduce the resistance. Patent Document 1 describes a composite active material in which the surfaces of active material particles containing at least one of cobalt, nickel, and manganese and further containing lithium and oxygen are coated with an oxide-based solid electrolyte and a sulfide-based solid electrolyte. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-154407 Summary of the Invention [Problem to be solved by the invention]

[0005] When an active material and a solid electrolyte are composited, the composite may be difficult or excessive aggregation may occur depending on the shape of the active material, etc. If the composite particles are excessively aggregated, the active material layer formed using such composite particles may become uneven, and voids may easily occur in the active material layer, which may affect the charge / discharge performance of the energy storage element, such as the discharge capacity, capacity retention rate, and output.

[0006] The present invention has been made in light of the above circumstances, and aims to provide an electrode material in which an active material and a solid electrolyte are composited and in which aggregation is suppressed, an electrode and an energy storage element using such an electrode material, and a method for manufacturing such an electrode material. [Means for solving the problem]

[0007] An electrode material according to one aspect of the present invention contains an active material, a solid electrolyte, and graphite, in which the active material and the solid electrolyte are composited.

[0008] An electrode according to another aspect of the present invention contains the electrode material according to the aspect of the present invention.

[0009] An energy storage device according to another aspect of the present invention includes the electrode according to the aspect of the present invention.

[0010] A method for producing an electrode material according to another aspect of the present invention includes compounding an active material and a solid electrolyte in the presence of graphite. [Effects of the Invention]

[0011] According to one aspect of the present invention, it is possible to provide an electrode material in which an active material and a solid electrolyte are composited and in which aggregation is suppressed, an electrode and an energy storage element using such an electrode material, and a method for manufacturing such an electrode material. [Brief explanation of the drawings]

[0012] [Figure 1]FIG. 1 is a schematic cross-sectional view of an energy storage device (all-solid-state battery) according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an energy storage device configured by assembling a plurality of energy storage elements according to one embodiment of the present invention. [Figure 3A] FIG. 3A is an image of the electrode material of Example 1 observed with a scanning electron microscope (SEM). [Figure 3B] FIG. 3B is an image mapping the distribution of nickel element in the image field of FIG. 3A. [Figure 3C] FIG. 3C is an image mapping the distribution of elemental sulfur in the image field of FIG. 3A. [Figure 4] FIG. 4 shows charge / discharge curves of the energy storage elements using the electrode materials of Example 1 and Comparative Example 1. [Figure 5] FIG. 5 is a graph showing the capacity retention rate per cycle of the energy storage elements using the electrode materials of Example 1 and Comparative Example 1. [Figure 6] FIG. 6 is a planar plot of the complex impedance of the energy storage elements using the electrode materials of Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0013] First, an outline of the electrode material, electrode, energy storage element, and method for manufacturing the electrode material disclosed in this specification will be described.

[0014] An electrode material according to one aspect of the present invention contains an active material, a solid electrolyte, and graphite, in which the active material and the solid electrolyte are composited.

[0015] An electrode material according to one aspect of the present invention is an electrode material in which an active material and a solid electrolyte are composited, and aggregation is suppressed. The reason for this effect is unclear, but the following reason is presumed. When an active material and a solid electrolyte are used as raw materials to composite them, it is thought that aggregation occurs when another active material adheres to the solid electrolyte adhered to the surface of the active material, causing the active materials to bond together via the solid electrolyte. Graphite has good lubricity due to, for example, the layered crystal structure. Therefore, by having graphite present when combining the active material and the solid electrolyte, the graphite acts as a lubricant and suppresses the active materials from bonding together via the solid electrolyte. It is presumed that aggregation is suppressed in the electrode material according to one aspect of the present invention due to the lubricating effect of the graphite.

[0016] "Active material" refers to a material other than graphite that can absorb and release charge carrier ions (such as lithium ions). "Graphite" refers to the graphite that has an average lattice spacing (d 002 The term "a state in which lithium ions capable of being absorbed and desorbed during charging and discharging have been sufficiently released" refers to a state in which the open circuit voltage is 0.7 V or higher in a single-electrode battery using an electrode containing a carbon material as the working electrode and metallic Li as the counter electrode. "Composited" refers to the formation of particles containing an active material and a solid electrolyte (composite particles of an active material and a solid electrolyte). For example, it includes the formation of composite particles in which a solid electrolyte is attached to at least a portion of the surface of an active material particle. The composite particles may further contain graphite. That is, at least a portion of the graphite may be composited with the active material and the solid electrolyte. Furthermore, particles that do not contain either the active material or the solid electrolyte may exist. That is, an active material and a solid electrolyte that are not composited may exist.

[0017] The active material is preferably secondary particles having a ratio of secondary particle size to primary particle size of 3 or less, or substantially non-aggregated primary particles (hereinafter, "secondary particles having a ratio of secondary particle size to primary particle size of 3 or less, or substantially non-aggregated primary particles" are collectively referred to as "single-particle particles"). Single-particle particles have advantages such as being less susceptible to cracking during the manufacturing process or charge / discharge, and maintaining good charge / discharge performance. On the other hand, single-particle particles have a high surface smoothness, making them difficult to composite with a solid electrolyte by conventional methods. Furthermore, if treatment is performed for a long time or at a high intensity in order to forcibly promote composite formation, they are likely to aggregate. In contrast, in an electrode material according to one aspect of the present invention, even when the active material is single-particle particles, they are well composited and aggregation is suppressed, and the electrode material can be used as an electrode material in which the advantages of single-particle particles can be fully exhibited by composite formation.

[0018] The "primary particle diameter" of an active material is the average particle diameter of any 50 primary particles that make up the active material observed under SEM. Primary particles are particles for which no grain boundaries are observed externally under SEM observation. The particle diameter of a primary particle is determined as follows: The shortest diameter passing through the center of the smallest circumscribing circle of the primary particle is defined as the minor diameter, and the diameter passing through the center and perpendicular to the minor diameter is defined as the major diameter. The particle diameter is defined as the average of the major and minor diameters. If there are two or more shortest diameters, the longest diameter that intersects at right angles is defined as the minor diameter. The "secondary particle diameter" of an active material is the value (D50: median diameter) at which the volume-based cumulative distribution is 50% as calculated in accordance with JIS-Z-8819-2 (2001) based on the particle size distribution measured by laser diffraction / scattering in accordance with JIS-Z-8815 (2013) for a diluted solution of the active material with a solvent. The term "primary particles that are not substantially agglomerated" refers to primary particles in which, when observed with an SEM, a plurality of primary particles are present independently without agglomeration, or primary particles in which the primary particles are not generally directly bonded to other primary particles.

[0019] The solid electrolyte is preferably a sulfide solid electrolyte, in which case the active material and the solid electrolyte are particularly well combined and the aggregation is further suppressed to provide an electrode material.

[0020] An electrode according to another aspect of the present invention contains the electrode material according to the aspect of the present invention. Because the electrode contains the electrode material according to the aspect of the present invention, an energy storage device including the electrode has good charge / discharge performance.

[0021] An energy storage device according to another aspect of the present invention includes the electrode according to the aspect of the present invention. The energy storage device has good charge / discharge performance because it includes the electrode containing the electrode material according to the aspect of the present invention.

[0022] A method for producing an electrode material according to one aspect of the present invention includes compounding an active material and a solid electrolyte in the presence of graphite. The method makes it possible to obtain an electrode material in which the active material and the solid electrolyte are compounded and in which aggregation is suppressed.

[0023] Hereinafter, an electrode material and a manufacturing method thereof, an electrode, an energy storage element and a manufacturing method thereof, an energy storage device, and other embodiments according to one embodiment of the present invention will be described in detail. Note that the names of the components (elementary components) used in each embodiment may differ from the names of the components (elementary components) used in the background art.

[0024] <Electrode material> An electrode material according to one embodiment of the present invention contains an active material, a solid electrolyte, and graphite. The electrode material may be an electrode material for an energy storage device. The electrode material is usually particulate. The electrode material may be a material used in a positive electrode (positive electrode material) or a material used in a negative electrode (negative electrode material), but is preferably a positive electrode material.

[0025] (active material) When the electrode material is a positive electrode material, the active material is a positive electrode active material, and when the electrode material is a negative electrode material, the active material is a negative electrode active material.

[0026] The positive electrode active material can be appropriately selected from known positive electrode active materials commonly used in lithium ion secondary batteries and all-solid-state batteries. A material capable of absorbing and releasing lithium ions is usually used as the positive electrode active material. Examples of the positive electrode active material include lithium transition metal composite oxides having an α-NaFeO2 crystal structure, lithium transition metal composite oxides having a spinel crystal structure, polyanion compounds, chalcogen compounds, and sulfur. Examples of lithium transition metal composite oxides having an α-NaFeO2 crystal structure include Li[Li x Ni (1-x) ]O2(0≦x<0.5), Li[Li x Ni γ Co (1-x-γ) ]O2(0≦x<0.5, 0<γ<1), Li[Li x Co (1-x) ]O2(0≦x<0.5), Li[Li x Ni γ Mn (1-x-γ) ]O2(0≦x<0.5, 0<γ<1), Li[Li x Ni γ Mn β Co (1-x-γ-β) ]O2(0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1), Li[Li x Ni γ Co β Al (1-x-γ-β) ]O2 (0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1). Lithium transition metal composite oxides with spinel crystal structure include Li x Mn2O4, Li x Ni γ Mn (2-γ) Examples of polyanion compounds include LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, and Li2CoPO4F. Examples of chalcogen compounds include titanium disulfide, molybdenum disulfide, and molybdenum dioxide. Atoms or polyanions in these materials may be partially substituted with atoms or anion species of other elements.

[0027] The positive electrode active material is preferably a lithium transition metal composite oxide, more preferably a lithium transition metal composite oxide containing at least one of nickel, cobalt, and manganese, even more preferably a lithium transition metal composite oxide containing at least two of nickel, cobalt, and manganese, and even more preferably a lithium transition metal composite oxide containing nickel, cobalt, and manganese. This lithium transition metal composite oxide preferably has an α-NaFeO2 crystal structure. Use of such a lithium transition metal composite oxide can increase the energy density, etc.

[0028] The lithium transition metal composite oxide is preferably a compound represented by the following formula 1. Li 1+α Me 1-α O2···1 In formula 1, Me is a metal (excluding Li) containing at least one of Ni, Co, and Mn, and 0≦α<1.

[0029] It is preferable that Me in formula 1 is substantially composed of the three elements Ni, Co, and Mn, although Me may contain other metals.

[0030] From the viewpoint of achieving a larger electric capacity, the preferred contents (composition ratios) of the constituent elements in the compound represented by formula 1 are as follows: Note that the molar ratio is equal to the atomic ratio.

[0031] In formula 1, the lower limit of the molar ratio of Ni to Me (Ni / Me) is preferably 0.1, and in some cases, 0.2, 0.3, or 0.4 is more preferable, while the upper limit of this molar ratio (Ni / Me) is preferably 0.9, and in some cases, 0.8, 0.7, or 0.6 is more preferable.

[0032] In formula 1, the lower limit of the molar ratio of Co to Me (Co / Me) is preferably 0.05, and in some cases, 0.1 or 0.2 is more preferable, while the upper limit of this molar ratio (Co / Me) is preferably 0.7, and in some cases, 0.5, 0.4, or 0.3 is more preferable.

[0033] In formula 1, the lower limit of the molar ratio of Mn to Me (Mn / Me) is preferably 0.05, and in some cases, 0.1 or 0.2 is more preferable, while the upper limit of this molar ratio (Mn / Me) is preferably 0.6, and in some cases, 0.5 or 0.4 is more preferable.

[0034] In formula 1, the upper limit of the molar ratio of Li to Me (Li / Me), ie, (1+α) / (1−α), is preferably 1.6, and in some cases is more preferably 1.4 or 1.2.

[0035] The composition ratio of the lithium transition metal composite oxide refers to the composition ratio when the element is fully discharged using the following method. First, the storage element is discharged at a constant current of 0.05 C to the lower limit voltage for normal use. "Normal use" refers to the case where the non-aqueous electrolyte storage element is used under the charge / discharge conditions recommended or specified for non-aqueous electrolyte storage elements. The element is disassembled, the positive electrode is removed, and a test battery is assembled with metallic Li as the counter electrode. The positive electrode potential is measured at a discharge current of 10 mA per 1 g of positive electrode active material until the positive electrode potential reaches 3.0 V vs. Li / Li. + The positive electrode is then fully discharged by discharging at a constant current until the positive electrode reaches a constant current of 0.05V. The device is then disassembled again and the positive electrode is removed. Dimethyl carbonate is used to thoroughly wash away any components (electrolyte, etc.) adhering to the removed positive electrode, and the electrode is then dried under reduced pressure at room temperature for 24 hours, after which the lithium transition metal composite oxide, the active material for the positive electrode, is extracted. The extracted lithium transition metal composite oxide is then subjected to measurement. All operations from disassembling the energy storage element to extracting the lithium transition metal composite oxide for measurement are carried out in an argon atmosphere with a dew point of -60°C or below.

[0036] Suitable lithium transition metal composite oxides include, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 3 / 5Co 1 / 5 Mn 1 / 5 O2, LiNi 1 / 2 Co 1 / 5 Mn 3 / 10 O2, LiNi 1 / 2 Co 3 / 10 Mn 1 / 5 O2, LiNi 8 / 10 Co 1 / 10 Mn 1 / 10 Examples include O2.

[0037] The negative electrode active material can be appropriately selected from known negative electrode active materials other than graphite that are commonly used in lithium ion secondary batteries and all-solid-state batteries. Materials capable of absorbing and releasing lithium ions are typically used as the negative electrode active material. Examples of the negative electrode active material include metallic Li; metals or semimetals such as Si and Sn; metal oxides or semimetal oxides such as Si oxide, Ti oxide, and Sn oxide; and Li4Ti5O 12 , LiTiO 2、 Examples include titanium-containing oxides such as TiNb2O7; polyphosphate compounds; silicon carbide; and carbon materials other than graphite, such as non-graphitic carbon (easily graphitizable carbon or non-graphitizable carbon).

[0038] "Non-graphitic carbon" refers to carbon that has an average lattice spacing (d 002 ) is 0.34 nm or more and 0.42 nm or less. Non-graphitic carbon includes non-graphitizable carbon and easily graphitizable carbon. Examples of non-graphitic carbon include resin-derived materials, petroleum pitch or petroleum pitch-derived materials, petroleum coke or petroleum coke-derived materials, plant-derived materials, and alcohol-derived materials. The "discharged state" of a carbon material refers to a state in which the carbon material, which is the negative electrode active material, is discharged so that lithium ions that can be absorbed and released during charging and discharging are sufficiently released.

[0039] "Non-graphitizable carbon" means the above d 002 This refers to carbon materials with a particle size of 0.36 nm or more and 0.42 nm or less.

[0040] "Graphitizable carbon" means the above d002 This refers to carbon materials with a particle size of 0.34 nm or more and less than 0.36 nm.

[0041] The active material is in particulate form. The active material is preferably monoparticulate. In one embodiment of the present invention, the active material may be monoparticulate particles of a lithium transition metal composite oxide.

[0042] An example of the monoparticle particles is secondary particles A having a ratio of secondary particle diameter to primary particle diameter of 3 or less. This ratio of secondary particle diameter to primary particle diameter is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. When the ratio of secondary particle diameter to primary particle diameter of secondary particles A is equal to or less than the above upper limit, the advantages of monoparticle particles, such as resistance to cracking, can be fully exhibited.

[0043] The lower limit of the ratio of the secondary particle diameter to the primary particle diameter of secondary particles A may be 1. Note that, due to differences in the methods for measuring the primary particle diameter and the secondary particle diameter, the lower limit of the ratio of the secondary particle diameter to the primary particle diameter of secondary particles A may be less than 1, for example, 0.9.

[0044] Another example of a single-particle particle is a primary particle B that is not substantially aggregated (a particle in which one primary particle exists independently). Such a primary particle B can also fully exhibit the advantages of a single-particle particle, such as being less susceptible to cracking. The secondary particles A and the primary particles B may be mixed. For example, among any 50 particles of an active material observed under SEM, the number of primary particles B is preferably more than 25, more preferably 30 or more, and even more preferably 40 or more.

[0045] The primary particle diameter of the active material is, for example, preferably 0.1 μm to 30 μm, more preferably 0.5 μm to 15 μm, and even more preferably 2 μm to 8 μm. The secondary particle diameter of the active material is, for example, preferably 0.1 μm to 30 μm, more preferably 0.5 μm to 15 μm, and even more preferably 2 μm to 8 μm. By keeping the particle diameters (primary particle diameter and secondary particle diameter) of the active material within the above ranges, the conductivity of the electrode material is improved.

[0046] Single-particle particles having a predetermined particle size can be produced by known methods, and the primary particle size and the like can be controlled by the production conditions. Alternatively, commercially available single-particle particles having a predetermined particle size may be used. In the production process of the active material, the particle size can be increased by growing multiple primary particles, for example, by increasing the firing temperature or prolonging the firing time. Alternatively, primary particles can be obtained by crushing secondary particles.

[0047] In another embodiment of the present invention, the active material may be secondary particles having a ratio of secondary particle size to primary particle size of greater than 3.

[0048] The content of the active material in the electrode material is preferably 70% by mass to 99% by mass, more preferably 80% by mass to 98% by mass, even more preferably 90% by mass to 97% by mass, and even more preferably 92% by mass to 96% by mass. By setting the content of the active material in the electrode material within this range, the active material can be well combined with the solid electrolyte, thereby enabling a well-balanced display of various performance characteristics such as discharge capacity, capacity retention rate, and output.

[0049] (solid electrolyte) The solid electrolyte may be a conventionally known solid electrolyte, such as a sulfide solid electrolyte, an oxide solid electrolyte, a dry polymer electrolyte, a gel polymer electrolyte, or a quasi-solid electrolyte, and is preferably a sulfide solid electrolyte.

[0050] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-Li3N, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S 2n (where m and n are positive numbers, and Z is Ge, Zn, or Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In.) Li 10 GeP2S 12 As the sulfide solid electrolyte, an argyrodite-type solid electrolyte can be suitably used.

[0051] The content of the solid electrolyte in the electrode material is preferably 1% by mass to 20% by mass, more preferably 2% by mass to 10% by mass, and even more preferably 3% by mass to 7% by mass. By setting the content of the solid electrolyte in the electrode material within this range, the solid electrolyte can be well combined with the active material, thereby enabling a well-balanced display of various performance characteristics such as discharge capacity, capacity retention rate, and output.

[0052] The content of the solid electrolyte relative to 100 parts by mass of the active material in the electrode material is preferably from 1 to 20 parts by mass, more preferably from 2 to 10 parts by mass, and even more preferably from 3 to 7 parts by mass. By setting the content of the solid electrolyte relative to the active material in the electrode material within the above range, the solid electrolyte can be well combined with the active material, and various performance characteristics such as discharge capacity, capacity retention rate, and output can be exhibited in a well-balanced manner.

[0053] (graphite) As described above, graphite has a lubricating effect that can suppress aggregation when the active material and the solid electrolyte are combined. Graphite is also preferable as a component of the electrode material because of its electrical conductivity.

[0054] Conventionally known graphite can be used as the graphite. The graphite may be any of spherical graphite, massive graphite, flake graphite, etc. Furthermore, the graphite may be any of natural graphite and artificial graphite. Among these, flake graphite is preferred because it has a particularly excellent lubricating effect.

[0055] The lower limit of the aspect ratio of graphite, such as flake graphite, is preferably 2, more preferably 3, and even more preferably 5. The upper limit of the aspect ratio of graphite may be, for example, 100, 50, or 30. The aspect ratio of graphite is measured as follows: The graphite is observed from a side view using an SEM. 50 randomly selected graphite particles are measured for their minor and major diameters. The ratio of the major diameter to the minor diameter is calculated, and the average of these ratios for the 50 particles is taken as the aspect ratio. The minor and major diameters of graphite are defined in the same way as the minor and major diameters when calculating the primary particle diameter of the active material described above. Note that the "side view" refers to a view from the side of a single piece of graphite placed on a horizontal surface.

[0056] The average major axis of the graphite (the average value of the major axes of the 50 graphite particles) is preferably 0.1 μm or more and 20 μm or less, and more preferably 1 μm or more and 10 μm or less. From the viewpoint of lubrication, the lower limit of the average minor axis of the graphite (the average value of the minor axes of the 50 graphite particles) may be the thickness of a graphene monolayer, that is, about 0.35 nm. The average minor axis of the graphite is preferably 50 nm or more and 2 μm or less. When the average minor axis of the graphite is in the above range, in addition to the lubrication effect, the effect of improving crack resistance is also obtained.

[0057] The graphite content in the electrode material is preferably 0.1% by mass to 10% by mass, more preferably 0.3% by mass to 4% by mass, and even more preferably 0.5% by mass to 2% by mass. By setting the graphite content in the electrode material to the above lower limit or higher, sufficient lubrication is achieved, and the active material and the solid electrolyte are particularly effectively composited with sufficiently suppressed aggregation. On the other hand, by setting the graphite content in the electrode material to the above upper limit or lower, the energy density of the electrode material can be increased.

[0058] (Other ingredients, etc.) The electrode material may contain components other than the active material, solid electrolyte, and graphite. Examples of other components include conductive agents (excluding graphite), binders, fillers, etc. However, the total content of the active material, solid electrolyte, and graphite in the electrode material is preferably 90% by mass or more, more preferably 99% by mass or more, and even more preferably 99.9% by mass or more, and may be 100% by mass.

[0059] (compound) In this electrode material, the active material and the solid electrolyte are composited. That is, the active material and the solid electrolyte form composite particles. The active material and the solid electrolyte may be chemically or physically bonded. In one embodiment of the present invention, the composite particles have active material particles that serve as cores (base materials) and a solid electrolyte that coats at least a portion of the surface of the particles. The composite particles may further have graphite that coats at least a portion of the surface of the active material particles together with the solid electrolyte. The composite particles may be particles that essentially consist of an active material and a solid electrolyte, or particles that essentially consist of an active material, a solid electrolyte, and graphite. The electrode material may contain an active material, a solid electrolyte, and graphite that are not composited, each of which is present independently.

[0060] In the composite particles, the solid electrolyte may cover at least a portion of the surface of the active material particles. The solid electrolyte may form a film on the surface of the active material particles, or may be scattered in the form of particles. In the composite particles, the solid electrolyte preferably covers 30% or more, and more preferably 50% or more, of the surface of the active material particles in terms of area. By sufficiently covering the surface of the active material particles with the solid electrolyte, the conductivity of the electrode material can be increased.

[0061] The average particle size of the composite particles is, for example, preferably 0.1 μm or more and 30 μm or less, more preferably 0.5 μm or more and 15 μm or less, and even more preferably 2 μm or more and 10 μm or less. By setting the average particle size of the composite particles within the above range, the conductivity of the electrode material is improved. The average particle size of the composite particles means D50 (median diameter) measured in the same manner as the secondary particle size of the active material described above.

[0062] (Application) The electrode material can be used in various types of energy storage elements, and is particularly suitable for use in all-solid-state energy storage elements. When the electrode material is used in an all-solid-state energy storage element, the active material and the solid electrolyte are composited in a good state, and effects such as good electrical conductivity are particularly fully exhibited. The electrode material can also be applied to energy storage elements in which a solid electrolyte and an electrolytic solution are used in combination as the electrolyte.

[0063] <Electrode material manufacturing method> A method for producing an electrode material according to one embodiment of the present invention comprises compounding an active material and a solid electrolyte in the presence of graphite. Examples of the compounding method include mixing a particulate or powdered active material, a solid electrolyte, and graphite while applying impact, compression, and shear forces. The compounding method may also include mixing the solid electrolyte, the active material, and the graphite while plastically deforming the solid electrolyte. This method allows the graphite to act as a lubricant, and the solid electrolyte to adhere uniformly to the surfaces of the active material particles, resulting in compounding.

[0064] The above-mentioned composite treatment can be carried out, for example, by treatment using an apparatus equipped with an impeller (also called a rotating blade, impeller, etc.). Specifically, the above treatment is a treatment using a mechanical kneading method in which an impeller inside a container is rotated to apply impact, compression, and shear forces to a mixture of an active material, a solid electrolyte, and graphite between the impeller and the wall of the container. The above treatment may be carried out in a dry or wet manner, but is preferably carried out in a dry manner.

[0065] The rotation speed of the impeller in the above treatment is adjusted appropriately depending on the size of the impeller, etc., but is preferably 1,000 rpm or more and 10,000 rpm or less, more preferably 2,000 rpm or more, 4,000 rpm or more, or even more preferably 6,000 rpm or more. The treatment time in the above treatment is preferably 0.5 minutes or more and 30 minutes or less, more preferably 1 minute or more and 20 minutes or less, and even more preferably 2 minutes or more and 10 minutes or less. The treatment may be carried out in multiple steps, in which case the total treatment time is preferably within the above range.

[0066] The active material, solid electrolyte, and graphite may be mixed in advance before the treatment using the impeller-equipped device, or the active material, solid electrolyte, and graphite may be separately charged into the impeller-equipped device.

[0067] Specific and preferred examples of the active material, solid electrolyte, and graphite used as raw materials in the manufacturing method of the electrode material are the same as the specific and preferred examples of the active material, solid electrolyte, and graphite described as each component of the electrode material according to one embodiment of the present invention. Specific and preferred amounts of the active material, solid electrolyte, and graphite mixed are also the same as the contents of each component in the electrode material described above.

[0068] <Electrode> An electrode according to one embodiment of the present invention contains the electrode material according to one embodiment of the present invention. The electrode may be an electrode for an energy storage device. The electrode has a substrate and an active material layer disposed on the substrate directly or via an intermediate layer. The electrode may be a positive electrode or a negative electrode, but is preferably a positive electrode.

[0069] (base material) The substrate is electrically conductive. Whether or not it is "electrically conductive" is determined by whether the volume resistivity measured in accordance with JIS-H-0505 (1975) is 10 7 The threshold value is Ω·cm.

[0070] When the electrode is a positive electrode, the material of the substrate (positive electrode substrate) is a metal such as aluminum, titanium, tantalum, stainless steel, or an alloy thereof. Among these, aluminum or an aluminum alloy is preferred from the viewpoints of potential resistance, high conductivity, and cost. Examples of the positive electrode substrate include foil, vapor deposition film, mesh, and porous material, with foil being preferred from the viewpoint of cost. Therefore, aluminum foil or aluminum alloy foil is preferred as the positive electrode substrate. Examples of aluminum or aluminum alloy include A1085, A3003, and A1N30 specified in JIS-H-4000 (2014) or JIS-H4160 (2006).

[0071] The average thickness of the positive electrode substrate is preferably 3 μm to 50 μm, more preferably 5 μm to 40 μm, even more preferably 8 μm to 30 μm, and particularly preferably 10 μm to 25 μm. By setting the average thickness of the positive electrode substrate within the above range, the strength of the positive electrode substrate can be increased while increasing the energy density per volume of the energy storage device. The "average thickness" of the positive electrode substrate and the negative electrode substrate described below refers to the value obtained by dividing the punched mass when a substrate of a predetermined area is punched out by the true density and punched area of ​​the substrate.

[0072] When the electrode is a negative electrode, the material of the substrate (negative electrode substrate) may be a metal such as copper, nickel, stainless steel, nickel-plated steel, or aluminum, or an alloy thereof, or a carbonaceous material. Among these, copper or a copper alloy is preferred. Examples of the negative electrode substrate include foil, a vapor-deposited film, a mesh, and a porous material, with foil being preferred from the viewpoint of cost. Therefore, copper foil or a copper alloy foil is preferred as the negative electrode substrate. Examples of copper foil include rolled copper foil and electrolytic copper foil.

[0073] The average thickness of the negative electrode substrate is preferably 2 μm to 35 μm, more preferably 3 μm to 30 μm, even more preferably 4 μm to 25 μm, and particularly preferably 5 μm to 20 μm. By setting the average thickness of the negative electrode substrate within the above range, the strength of the negative electrode substrate can be increased while increasing the energy density per volume of the energy storage element.

[0074] (middle class) The intermediate layer is a layer disposed between the substrate and the active material layer. The intermediate layer contains a conductive agent such as carbon particles to reduce the contact resistance between the substrate and the active material layer. The configuration of the intermediate layer is not particularly limited, and may contain, for example, a binder and a conductive agent.

[0075] (active material layer) The active material layer contains an electrode material according to one embodiment of the present invention. The active material layer contains optional components such as a solid electrolyte, a conductive agent, a binder, a thickener, and a filler, as needed. The active material layer may be formed from a mixture (positive electrode mixture or negative electrode mixture) containing the electrode material and the like.

[0076] The content of the electrode material in the active material layer is preferably 50% by mass to 99% by mass, more preferably 60% by mass to 98% by mass, even more preferably 70% by mass to 95% by mass, and even more preferably 75% by mass to 90% by mass. By setting the content of the electrode material within the above range, both high energy density and manufacturability of the energy storage element can be achieved.

[0077] The content of the active material in the active material layer is preferably 50% by mass to 99% by mass, more preferably 60% by mass to 95% by mass, even more preferably 65% ​​by mass to 90% by mass, and even more preferably 70% by mass to 85% by mass. By setting the content of the active material within the above range, the energy density, conductivity, manufacturability, etc. of the energy storage element can be optimized.

[0078] As the solid electrolyte, the same materials as those explained as one component of the electrode material can be used, and a sulfide solid electrolyte is preferred.

[0079] When the active material layer contains a solid electrolyte, the content of the solid electrolyte is preferably 1% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 30% by mass or less, and even more preferably 10% by mass or more and 20% by mass or less. By setting the content of the solid electrolyte within the above range, the electric capacity of the storage element can be increased. Note that the content of the solid electrolyte in this active material layer does not include the content of the solid electrolyte forming the electrode material. When an electrode according to one embodiment of the present invention is applied to a non-aqueous electrolyte storage element, the active material layer may not contain a solid electrolyte.

[0080] The conductive agent is not particularly limited as long as it is a material having electrical conductivity. Examples of such conductive agents include carbonaceous materials, metals, and conductive ceramics. Examples of carbonaceous materials include graphite, non-graphitic carbon, and graphene-based carbon. Examples of non-graphitic carbon include carbon nanofibers, pitch-based carbon fibers, and carbon black. Examples of carbon black include furnace black, acetylene black, and ketjen black. Examples of graphene-based carbon include graphene, carbon nanotubes (CNTs), and fullerenes. The conductive agent may be in the form of powder or fiber. As the conductive agent, one of these materials may be used alone, or two or more may be mixed. These materials may also be used in combination. For example, a composite of carbon black and CNTs may be used. Among these, carbon black is preferred from the viewpoint of electronic conductivity, and acetylene black is particularly preferred.

[0081] The content of the conductive agent in the active material layer is preferably 0.1% by mass to 10% by mass, more preferably 1% by mass to 5% by mass. Note that the content of the conductive agent in this active material layer does not include the content of graphite that forms the electrode material. By setting the content of the conductive agent within the above range, the energy density, conductivity, etc. of the energy storage element can be increased.

[0082] Examples of binders include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyacrylic, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.

[0083] The binder content in the active material layer is preferably 0.1% by mass to 10% by mass, more preferably 1% by mass to 5% by mass. By setting the binder content within this range, the electrode material and the like can be stably held.

[0084] Examples of thickeners include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. When the thickener has a functional group that reacts with lithium or the like, the functional group may be deactivated in advance by methylation or the like. In one embodiment of the present invention, the content of the thickener in the active material layer may be 1% by mass or less, or 0.1% by mass or less, or the active material layer may be substantially free of thickener.

[0085] The filler is not particularly limited. Examples of fillers include polyolefins such as polypropylene and polyethylene; inorganic oxides such as silicon dioxide, alumina, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicates; hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide; carbonates such as calcium carbonate; sparingly soluble ionic crystals such as calcium fluoride, barium fluoride, and barium sulfate; nitrides such as aluminum nitride and silicon nitride; mineral-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica; and artificial products thereof. In one embodiment of the present invention, the filler content in the active material layer may be 1% by mass or less, or 0.1% by mass or less, or may be substantially filler-free.

[0086] The active material layer may contain typical non-metallic elements such as B, N, P, F, Cl, Br, and I; typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba; and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, and W as components other than the electrode material, solid electrolyte, conductive agent, binder, thickener, and filler.

[0087] The average thickness of the active material layer is preferably 10 μm or more and 1,000 μm or less, and more preferably 30 μm or more and 500 μm or less. By setting the average thickness of the active material layer to the above lower limit or more, it is possible to obtain an energy storage element with a high energy density. By setting the average thickness of the active material layer to the above upper limit or less, it is possible to achieve miniaturization of the energy storage element. The average thickness of the active material layer is the average value of thicknesses measured at any five positions. Furthermore, when active material layers are provided on both sides of the substrate, the average thickness of the active material layer on one side is taken as the average thickness of the active material layer. The same applies to the average thickness of the isolation layer described below.

[0088] <Energy storage element> An all-solid-state battery will be described below as a specific example of an energy storage element according to one embodiment of the present invention. The energy storage element 10 of FIG. 1 is an all-solid-state battery, and is a secondary battery in which a positive electrode 1 and a negative electrode 2 are arranged with an isolation layer 3 between them. The positive electrode 1 has a positive electrode substrate 4 and a positive electrode active material layer 5, with the positive electrode substrate 4 being the outermost layer of the positive electrode 1. The negative electrode 2 has a negative electrode substrate 7 and a negative electrode active material layer 6, with the negative electrode substrate 7 being the outermost layer of the negative electrode 2. In the energy storage element 10 shown in FIG. 1, the negative electrode active material layer 6, the isolation layer 3, the positive electrode active material layer 5, and the positive electrode substrate 4 are stacked in this order on the negative electrode substrate 7. At least one of the positive electrode 1 and the negative electrode 2 in the energy storage element 10 is an electrode according to one embodiment of the present invention.

[0089] (positive electrode) The positive electrode 1 includes a positive electrode substrate 4 and a positive electrode active material layer 5 disposed on the positive electrode substrate 4 directly or via an intermediate layer. In one embodiment of the present invention, the electrode according to one embodiment of the present invention described above is used for the positive electrode 1. In this case, specific and preferred forms of the positive electrode substrate 4 and positive electrode active material layer 5 of the positive electrode 1 are as described above for the substrate (positive electrode substrate) and active material layer (positive electrode active material layer) provided in the electrode according to one embodiment of the present invention.

[0090] In another embodiment of the present invention, when an electrode according to one embodiment of the present invention is used for the negative electrode 2, the positive electrode 1 may be a conventionally known positive electrode. Examples of such a positive electrode 1 include a positive electrode similar to the electrode (positive electrode) according to one embodiment of the present invention described above, except that conventionally known active material or composite particles of an active material and a solid electrolyte are used.

[0091] (Negative electrode) The negative electrode 2 includes a negative electrode substrate 7 and a negative electrode active material layer 6 disposed on the negative electrode substrate 7 directly or via an intermediate layer. In one embodiment of the present invention, the electrode according to one embodiment of the present invention described above is used for the negative electrode 2. In this case, specific and preferred forms of the negative electrode substrate 7 and negative electrode active material layer 6 of the negative electrode 2 are as described above for the substrate (negative electrode substrate) and active material layer (negative electrode active material layer) provided in the electrode according to one embodiment of the present invention.

[0092] In another embodiment of the present invention, when the electrode according to one embodiment of the present invention is used as the positive electrode 1, the negative electrode 2 may be a conventionally known negative electrode. Examples of such negative electrodes 2 include negative electrodes similar to the electrode (negative electrode) according to one embodiment of the present invention, except that conventionally known active material particles or composite particles of an active material and a solid electrolyte are used. In another embodiment, the negative electrode active material layer 6 may be a layer essentially consisting of metallic Li or a Li alloy. In this case, the lithium content in the negative electrode active material layer 6 may be 90% by mass or more, 99% by mass or more, or even 100% by mass. In this case, the negative electrode active material layer 6 may be a metallic Li foil or a Li alloy foil.

[0093] (isolation layer) The separator 3 usually contains a solid electrolyte. The above-mentioned conventionally known solid electrolytes can be used as the solid electrolyte contained in the separator 3, and a sulfide solid electrolyte is preferred. The content of the solid electrolyte in the separator 3 is preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 99% by mass or more, and in some cases even more preferably substantially 100% by mass.

[0094] In addition to the solid electrolyte, the isolation layer 3 may contain optional components such as oxides, halogen compounds, binders, thickeners, and fillers. The optional components such as binders, thickeners, and fillers can be selected from the materials exemplified as components in the active material layer. Furthermore, the isolation layer 3 may contain a woven fabric, a nonwoven fabric, a porous resin film, or the like to increase mechanical strength.

[0095] The average thickness of the separator 3 is preferably 1 μm or more and 200 μm or less, and more preferably 3 μm or more and 100 μm or less. By setting the average thickness of the separator 3 to be equal to or greater than the above-mentioned lower limit, it is possible to reliably insulate the positive electrode 1 from the negative electrode 2. By setting the average thickness of the separator 3 to be equal to or less than the above-mentioned upper limit, it is possible to increase the energy density of the energy storage element 10.

[0096] <Method of manufacturing an energy storage element> The energy storage device according to one embodiment of the present invention can be manufactured by a conventionally known method, for example, by preparing the above-described energy storage device 10, which is an all-solid-state battery, including (1) preparing a positive electrode mixture, (2) preparing a material for an isolating layer, (3) preparing a negative electrode mixture, and (4) stacking a positive electrode, a isolating layer, and a negative electrode.

[0097] (1) Positive electrode mixture preparation process In this step, a positive electrode mixture for forming a positive electrode active material layer is usually prepared. The method for preparing the positive electrode mixture is not particularly limited and can be appropriately selected depending on the purpose. For example, mechanical milling of the positive electrode mixture material, compression molding of the positive electrode mixture material, etc. can be mentioned.

[0098] (2) Preparation of materials for the isolation layer In this step, a material for forming an isolation layer is usually prepared. The isolation layer material is usually a solid electrolyte. The solid electrolyte as an isolation layer material can be prepared by a conventionally known method. For example, it can be obtained by processing a predetermined material by a mechanical milling method. The isolation layer material may also be prepared by heating predetermined materials to above their melting temperature by a melt quenching method, melt-mixing them in a predetermined ratio, and then quenching. Other methods for synthesizing isolation layer materials include, for example, a solid-phase method in which the material is sintered under reduced pressure, a liquid-phase method such as solution deposition, a vapor-phase method (PLD), and sintering in an argon atmosphere after mechanical milling.

[0099] (3) Negative electrode mixture preparation process In this step, a negative electrode mixture for forming a negative electrode active material layer is usually prepared. The specific method for preparing the negative electrode mixture is the same as that for preparing the positive electrode mixture.

[0100] (4)Lamination process In this process, for example, a positive electrode having a positive electrode substrate and a positive electrode active material layer, a separator, and a negative electrode having a negative electrode substrate and a negative electrode active material layer are laminated. In this process, the positive electrode, separator, and negative electrode may be formed sequentially in this order, or vice versa; the order of forming each layer is not particularly important. For example, the positive electrode is formed by pressure molding a positive electrode substrate and a positive electrode mixture, the separator is formed by pressure molding an separator material, and the negative electrode is formed by pressure molding a negative electrode substrate and a negative electrode mixture. The positive electrode, separator, and negative electrode may be laminated by pressure molding the positive electrode substrate, the positive electrode mixture, the separator material, the negative electrode mixture, and the negative electrode substrate all at once. The positive electrode and the negative electrode may be molded in advance, and then pressure molded and laminated with the separator.

[0101] <Electricity storage device> An energy storage element according to one embodiment of the present invention can be mounted as an energy storage unit (battery module) comprising a collection of a plurality of energy storage elements in an automobile power source such as an electric vehicle (EV), a hybrid electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV), a power source for electronic devices such as a personal computer or a communication terminal, or a power source for power storage, etc. In this case, the technology of the present invention may be applied to at least one energy storage element included in the energy storage unit.

[0102] 2 shows an example of an energy storage device 30 in which energy storage units 20, each of which is an assembly of two or more electrically connected energy storage elements 10, are further assembled. The energy storage device 30 may include a bus bar (not shown) that electrically connects two or more energy storage elements 10, a bus bar (not shown) that electrically connects two or more energy storage units 20, etc. The energy storage units 20 or the energy storage device 30 may include a status monitoring device (not shown) that monitors the status of one or more energy storage elements 10.

[0103] <Other embodiments> The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, or part of the configuration of one embodiment can be replaced with the configuration of another embodiment or well-known technology. Furthermore, part of the configuration of one embodiment can be deleted. Also, well-known technology can be added to the configuration of one embodiment.

[0104] In the above embodiment, the energy storage element is described as a chargeable and dischargeable all-solid-state battery. However, the type, shape, size, capacity, etc. of the energy storage element are arbitrary. The present invention can also be applied to various secondary batteries and capacitors such as electric double layer capacitors and lithium ion capacitors. For example, the energy storage element according to the present invention may include layers other than the positive electrode, separator, and negative electrode. The structures of the positive electrode, separator, and negative electrode are not limited to those described above. Furthermore, the energy storage element according to the present invention may contain a liquid in one or more of the layers. The energy storage element according to the present invention may also be a nonaqueous electrolyte storage element in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween and a nonaqueous electrolyte is used as the electrolyte.

[0105] <Example> The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0106] [Example 1] (Preparation of electrode materials) LiNi, the positive electrode active material 3 / 5 Co 1 / 5 Mn 1 / 5 Single-particle particles of O2 (primary particles that are substantially unagglomerated; secondary particle diameter (D50) 4.9 μm), an argyrodite-type solid electrolyte, which is a sulfide solid electrolyte, and flake graphite (major axis 3 μm) were mixed in a mortar at a mass ratio of 95:4:1. The mixture was compounded using a Hosokawa Micron "Nobilta MINI" impeller-equipped device. The compound was compounded twice for 2 minutes at a rotation speed of 7,000 rpm to obtain the electrode material of Example 1. FIG. 3A shows an SEM image of the obtained electrode material (composite particles) of Example 1. FIG. 3B shows an image of the distribution of nickel element in the field of view of the SEM image of FIG. 3A, mapped by energy dispersive X-ray analysis (EDX), and FIG. 3C shows an image of the distribution of sulfur element. In FIG. 3B, the white areas indicate the locations where nickel element is present, and in FIG. 3C, the white areas indicate the locations where sulfur element is present. Nickel is an element that constitutes the positive electrode active material, and sulfur is an element that constitutes the solid electrolyte. As shown in FIGS. 3A and 3B, the electrode material of Example 1 shows that the solid electrolyte is adhered to the entire particle surface of the positive electrode active material, forming a composite.

[0107] Each of the electrode materials of Comparative Examples 1 to 3 was obtained in the same manner as in Example 1, except that the raw materials and mass ratios used were as shown in Table 1.

[0108] [Table 1]

[0109] When the obtained electrode materials of Example 1 and Comparative Examples 1 to 3 were observed with an SEM, excessive aggregation occurred in each of the electrode materials of Comparative Example 1, which did not use graphite, and Comparative Examples 2 and 3, which used other carbon materials instead of graphite. In contrast, aggregation was suppressed in the electrode material of Example 1. It can be seen that the use of graphite effectively composites the active material and solid electrolyte while suppressing aggregation.

[0110] (Fabrication of energy storage element) Using the electrode material of Example 1 or Comparative Example 1, an electricity storage element (all-solid-state battery) was produced in the following manner. A positive electrode mixture was prepared by mixing the electrode material of Example 1 or Comparative Example 1, an argyrodite-type solid electrolyte, acetylene black as a conductive agent, and styrene-butadiene rubber (SBR) as a binder in a mass ratio of 80:16:2:2. An argyrodite-type solid electrolyte was also prepared as a separator material. A three-layer structure of a positive electrode, separator, and negative electrode was fabricated using the positive electrode mixture, aluminum foil as a positive electrode substrate, separator material, and SUS316L as a negative electrode substrate, and metallic lithium foil bonded to the negative electrode substrate. A charge-discharge test was carried out on each of the obtained energy storage elements at 50°C as follows. Constant-current, constant-voltage charging was carried out at a current of 0.1 C with a charge cut-off voltage of 4.35 V. The charge was terminated until the current reached 0.05 C. A 10-minute rest period was then provided. Subsequently, constant-current discharging was carried out at a current of 0.1 C with a discharge cut-off voltage of 2.85 V. A 10-minute rest period was then provided. This charge-discharge cycle was repeated for 7 cycles for the energy storage element using the electrode material of Example 1, and for 16 cycles for the energy storage element using the electrode material of Comparative Example 1. The charge-discharge curves obtained up to the fourth cycle are shown in FIG. 4, and a graph showing the capacity retention rate for each cycle is shown in FIG. 5. Furthermore, for each energy storage element, during the rest period after each charge cycle, a 10 mV amplitude, 10 mV frequency range, and 10 mV frequency range were provided. 6 From 10 -2 The AC impedance was measured at 50°C. The complex impedance was plotted as shown in Figure 6.

[0111] As shown in Figures 4 and 5, the energy storage element using the electrode material of Example 1 has a large discharge capacity and a high capacity retention rate. Furthermore, as shown in Figure 6, the energy storage element using the electrode material of Example 1 also has low resistance. These results are presumably due to the fact that, in the electrode material of Example 1, the active material and the solid electrolyte are highly uniformly composited and aggregation is suppressed. [Industrial Applicability]

[0112] The present invention is applicable to power storage elements used as power sources for electronic devices such as personal computers and communication terminals, automobiles, etc., and electrodes provided therefor. [Explanation of symbols]

[0113] 1 positive electrode 2 negative electrode 3 isolation layer 4. Positive electrode substrate 5 Cathode active material layer 6 Negative electrode active material layer 7. Negative electrode substrate 10 Energy storage element (all-solid-state battery) 20 Energy storage unit 30 Energy storage device

Claims

1. The battery contains graphite, an active material other than the graphite, and a solid electrolyte, Composite particles containing the active material, the solid electrolyte, and the graphite, The content of the solid electrolyte is 7% by mass or less, An electrode material having a graphite content of 0.5 mass% or more.

2. 2. The electrode material according to claim 1, wherein the active material is in the form of secondary particles having a ratio of secondary particle size to primary particle size of 3 or less, or substantially non-aggregated primary particles.

3. 3. The electrode material according to claim 1, wherein the solid electrolyte is a sulfide solid electrolyte.

4. An electrode comprising the electrode material according to any one of claims 1 to 3.

5. An energy storage element comprising the electrode according to claim 4.

6. The method for producing an electrode material according to claim 1 , comprising: forming a composite of the active material, which is a material other than the graphite, and the solid electrolyte in the presence of the graphite.

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