Battery

Abstract

To provide a battery which has the equal quality to that of an existing lithium ion battery and uses less Ni elements and Co elements.SOLUTION: The battery (the battery does not include a positive electrode active material of elemental sulfur) includes a positive electrode, a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode. The positive electrode includes a Li element, an S element, a P element, and a positive electrode active material including a crystal phase with an argyrodite-type crystal structure. The total amount of the Ni element and the Co element in the positive electrode active material is equal to or smaller than 0.1 mass%. The amount of rare metal (excluding a Li element) in the positive electrode active material is equal to or smaller than 0.1 mass%.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a battery with a reduced amount of rare metal used.

Background Art

[0002] As a positive electrode active material in a lithium-ion battery, generally, a compound containing a so-called rare metal is used. Most typically, as the positive electrode active material, a lithium transition metal composite oxide called NCM or LMNO, which contains lithium and manganese, nickel and / or cobalt, can be mentioned. In addition, for example, in Patent Document 1, it has been proposed to use a sulfide containing titanium and niobium, which are rare metals, as the positive electrode active material.

Prior Art Documents

Brief Description of Drawings

[0006] [Figure 1] FIG. 1 is an initial charge-discharge curve of the battery obtained in Example 1. [Figure 2] FIG. 2 is an initial charge-discharge curve of the battery obtained in Example 2. [Figure 3] FIG. 3 is an initial charge-discharge curve of the battery obtained in Example 6. [Figure 4] FIG. 4 is an initial charge-discharge curve of the battery obtained in Comparative Example 1. [Figure 5] FIG. 5 is an initial charge-discharge curve of the battery obtained in Comparative Example 4. [Figure 6] FIG. 6 is a graph showing the cycle characteristics of the batteries obtained in the examples and comparative examples.

Mode for Carrying Out the Invention

[0007] Hereinafter, the present invention will be described based on its preferred embodiments. The present invention relates to a battery. The battery of the present invention has a positive electrode and a negative electrode. Further, the battery of the present invention has a solid electrolyte layer disposed between the positive electrode and the negative electrode. One of the features of the battery of the present invention is that the positive electrode constituting this uses materials that are industrially inexpensive and easily available, without using industrially rare metals as much as possible.

[0008] Until now, the positive electrode of batteries, particularly the positive electrode of lithium-ion batteries, has used rare metal elements such as lithium (Li), nickel (Ni), and cobalt (Co) as positive electrode active materials. However, rare metals are expensive and subject to significant price fluctuations due to their relatively low abundance in the Earth's crust and high mining and refining costs. Furthermore, there is a risk that they may be used in resource strategies between nations. Therefore, there is a strong demand for the development of batteries that do not use rare metals as battery materials. This invention addresses these demands.

[0009] In the battery of the present invention, the content of rare metals in the positive electrode active material used in the positive electrode, particularly the content of Ni and Co elements, is reduced compared to conventional batteries. Specifically, the total amount of Ni and Co elements contained in the positive electrode active material is preferably at a low level of 0.1% by mass or less. In the battery of the present invention, rare metals are used as little as possible as the positive electrode active material, and instead, the positive electrode active material is composed of raw materials that have a stable supply and little price fluctuation. Specifically, a positive electrode active material containing lithium (Li), sulfur (S), and phosphorus (P) elements is used. S and P elements are readily available, inexpensive, and stable in price. Although Li is classified as a rare metal, it is relatively easy to obtain and relatively inexpensive compared to other rare metals. By composing the positive electrode active material from these elements, the manufacturing cost of the battery of the present invention is reduced. Furthermore, since only Li is a valuable metal that needs to be recovered during battery recycling, recovery is easy. Moreover, the amount of carbon dioxide generated during recycling can be reduced compared to the recycling of conventional batteries containing multiple types of rare metals. This is advantageous because it reduces the environmental impact.

[0010] In the present invention, the positive electrode active material more preferably contains 0.05% by mass or less of Ni and Co elements in total, even more preferably 0.01% by mass or less, and even more preferably substantially zero. This is because the effects of the present invention become more pronounced. "Substantially zero" means that when 0.5 g of the sample is weighed, dissolved in an acid solution, and the volume is adjusted to 25 ml, the content of the solution is below the detection limit when measured by ICP emission spectrometry.

[0011] The content of Ni and Co elements in the positive electrode active material can be measured by subjecting a solution obtained by dissolving the positive electrode active material in, for example, an acid, to ICP emission spectrometry.

[0012] Conventional lithium-ion batteries use a lithium transition metal composite oxide called NCM as a positive electrode active material. NCM contains manganese (Mn) in addition to nickel (Ni) and cobalt (Co). On the other hand, in the positive electrode active material of the present invention, the total content of Ni and Co is within a predetermined range, and it is preferable that the content of Mn is also within a predetermined range. Specifically, in the positive electrode active material of the present invention, the total content of Ni, Co, and Mn is preferably, for example, 0.1% by mass or less, more preferably 0.05% by mass or less, even more preferably 0.01% by mass or less, and even more preferably substantially zero. This is because the effects of the present invention become more pronounced. The definition of "substantially zero" can be the same as described above, so it is omitted here.

[0013] In the present invention, the positive electrode active material is preferable from the viewpoint of reducing manufacturing costs, recycling costs, and environmental impact during recycling, as it reduces the amount of other rare metals (excluding Li) used in addition to the Ni, Co, and Mn elements mentioned above. These are nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), and niobium (Nb). As defined by the Special Subcommittee on Comprehensive Measures for Rare Metals of the Mining Council, Ministry of Economy, Trade and Industry, Japan. What are rare metals?This refers to "31 mineral species, including tungsten, cobalt, nickel, and rare earth elements (counted as one mineral species encompassing 17 rare earth elements), which are rare on Earth or difficult to extract for technical or economic reasons, but for which there is currently (and is expected to be) industrial demand, making the securing of a stable supply important from a policy perspective." Specifically, these include lithium (Li), beryllium (Be), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), gallium (Ga), germanium (Ge), selenium (Se), rubidium (Rb), strontium (Sr), zirconium (Zr), niobium (Nb), molybdenum (Mo), palladium (Pd), indium (In), antimony (Sb), tellurium (Te), cesium (Cs), barium (Ba), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), platinum (Pt), thallium (Tl), and bismuth (Bi), as well as rare earth elements. Rare earth elements include scandium (Sc), yttrium (Y), and lanthanide elements with atomic numbers 57 to 71. In this invention, Nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), and niobium (Nb) The total content is preferably, for example, 0.1% by mass or less, more preferably 0.05% by mass or less, even more preferably 0.01% by mass or less, and even more preferably substantially zero. This is because the effects of the present invention become more pronounced. The definition of "substantially zero" can be the same as described above, so its description is omitted here.

[0014] The positive electrode active material in the battery of the present invention is rare metal-free (except for Li), and preferably contains Li, S, and P elements as described above, instead of rare metals (except for Li). This positive electrode active material preferably has a crystalline phase having an argyrodite-type crystal structure. Whether or not the positive electrode active material contains a crystalline phase having an argyrodite-type crystal structure can be determined by analyzing the positive electrode active material by X-ray diffraction. For example, CuKα1 rays can be used as characteristic X-rays.

[0015] The positive electrode active material containing a crystalline phase having an argyrodite-type crystal structure may contain a halogen (X) element. As the halogen (X) element, at least one of the elements of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I) can be used. From the viewpoint of improving ionic conductivity, it is particularly preferable to use a combination of Cl and Br as the halogen elements.

[0016] A positive electrode active material containing a crystalline phase having an argyrodite-type crystal structure is, for example, a material with the composition formula (I):Li a PS b X c It is particularly preferable from the viewpoint of further improving ionic conductivity that the compound be represented by (X is at least one of the elements fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). It is preferable that X is one or two of the elements Cl and Br.

[0017] In the above compositional formula (I), the molar ratio of Li element, a, is preferably 4.5 or more, more preferably 5.0 or more, and even more preferably 5.4 or more. Furthermore, a is preferably 8 or less, more preferably 7.5 or less, and even more preferably 7.0 or less. When a is within this range, the cubic argyrodite crystal structure is stable near room temperature (25°C), and the conductivity of lithium ions can be enhanced.

[0018] In the above compositional formula (I), b is a value indicating how little Li2S component there is relative to the stoichiometric composition. From the viewpoint of ensuring a stable argyrodite crystal structure near room temperature (25°C) and high lithium ion conductivity, b is preferably, for example, 3.5 or more, more preferably 4.0 or more, and even more preferably 4.4 or more. On the other hand, b is preferably, for example, 7.0 or less, more preferably 6.5 or less, and even more preferably 6.0 or less.

[0019] In the above compositional formula (I), c may be greater than 0, 0.1 or more, or 0.2 or more. On the other hand, c is preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.6 or less, even more preferably less than 1.0, and most preferably 0.8 or less. This is because a high-capacity battery can be obtained.

[0020] The positive electrode active material preferably has peaks at positions 2θ = 25.5° ± 1.50° and 30.1° ± 1.50° in the X-ray diffraction pattern measured using CuKα1 rays. These peaks originate from the argyrodite-type crystalline phase.

[0021] The positive electrode active material, in the X-ray diffraction pattern measured using CuKα1 rays, is located at positions 2θ = 25.5° ± 1.50° and 30.1° ± 1.50°, as well as one or more positions selected from 2θ = 15.6° ± 1.50°, 17.9° ± 1.50°, 31.3° ± 1.50°, 44.7° ± 1.50°, 47.7° ± 1.50°, and 52.2° ± 1.50°, with the positions 2θ = 25.5° ± 1.50° and 30.1° ± 1.50°. It is even more preferable to have peaks at the following positions, and even more preferable to have peaks at all of the following positions in addition to 2θ = 25.5° ± 1.50° and 30.1° ± 1.50°: 2θ = 15.6° ± 1.50°, 17.9° ± 1.50°, 31.3° ± 1.50°, 44.7° ± 1.50°, 47.7° ± 1.50° and 52.2° ± 1.50°. These peaks originate from the argyrodite-type crystal phase.

[0022] The peak position mentioned above is expressed as median ±1.50°, but it is preferable that it be median ±1.00°, and even more preferable that it be median ±0.50°.

[0023] In the battery of the present invention, the positive electrode preferably contains a conductive material. From the viewpoint of improving the performance of the battery, the positive electrode preferably contains a composite material in which a positive electrode active material and a conductive material are combined. From the viewpoint of further improving the performance of the battery, it is preferable that this composite material consists of a main part of a compound containing Li, S, and P elements and a crystalline phase having an argyrodite-type crystal structure (hereinafter, for convenience, this compound will also be called an "argyrodite-type compound") and a conductive part dispersed on and / or inside the main part and containing a conductive material.

[0024] The main component comprises an argyrodite-type compound and may contain other materials or components as needed. For example, the main component may consist of a single phase composed of a crystalline phase with an argyrodite-type crystal structure, or it may contain other phases in addition to the said phase. For example, the main component may contain a Li2S phase, Li3PS4 phase, Li4P2S6 phase, LiCl or LiBr phase in addition to the crystalline phase with an argyrodite-type crystal structure. In particular, it is preferable for the main component to contain a Li2S phase in addition to the crystalline phase with an argyrodite-type crystal structure because it increases the capacity of the positive electrode active material.

[0025] The proportion of the argyrodite-type crystal structure crystalline phase contained in the main part may be, for example, 5% by mass or more, 10% by mass or more, or 20% by mass or more, relative to the total crystalline phase constituting the main part. On the other hand, the proportion may be, for example, 50% by mass or less, 40% by mass or less, or 30% by mass or less. By having the proportion of the argyrodite-type crystal structure crystalline phase within the above range, the lithium-ion conductivity of the positive electrode active material in the present invention can be increased, and as a result, the rate characteristics of the battery in the present invention can be improved.

[0026] The main part may contain a Li2S phase in addition to the crystalline phase having an argyrodite-type crystal structure. The proportion of the Li2S phase contained in the main part is preferably, for example, 10% by mass or more, more preferably 20% by mass or more, and even more preferably 50% by mass or more, relative to the total crystalline phase constituting the main part. On the other hand, the above proportion may be, for example, 95% by mass or less, 90% by mass or less, or 80% by mass or less. By having the proportion of the Li2S phase within the above range, the large capacity of Li2S can be expressed in the positive electrode active material of the present invention, and as a result, the charge and discharge capacity of the battery of the present invention can be improved.

[0027] The proportion of the crystalline phase mentioned above can be confirmed, for example, by examining the X-ray diffraction pattern.

[0028] In addition to the other materials and components mentioned above, the main part may also contain impurities in an amount that does not adversely affect the effects of the present invention, for example, less than 5% by mass, and especially less than 3% by mass.

[0029] The main part containing the argyrodite-type compound has the form of particles, and a conductive part containing the conductive material described above may be arranged on the surface or inside the particles. Any material having electronic conductivity can be used as the conductive material without particular limitations. Examples of conductive materials include various metallic materials and conductive nonmetallic materials. Either one of the metallic material or the conductive nonmetallic material may be used, or both may be used in combination. Examples of the metallic material include various noble metal elements, such as silver (Ag). Examples of various transition metal elements include copper (Cu), iron (Fe), and tin (Sn). These metallic elements may be used individually, or two or more may be used in combination. In the present invention, transition metal elements are more preferred as the conductive material, and more specifically, at least one of Cu, Fe, and Sn is preferred. As the conductive nonmetallic material, for example, carbon materials can be used. Examples include graphite, acetylene black, carbon black, carbon nanofibers, carbon nanotubes, nanographene, and fullerene nanowhiskers. These carbon materials may be used individually or in combination of two or more. Of these carbon materials, carbon black is preferred in terms of improving the initial capacity and cycle characteristics of the battery. From the viewpoint of making this advantage even more pronounced, it is preferable to use Ketjen black as the carbon black, and among these, furnace black is preferred, and in particular oil furnace black is preferred.

[0030] The conductive portion containing the various conductive materials described above plays a role as an electron conduction path when lithium is deabsorbed from the main portion, so it is preferable that it be uniformly dispersed and in close contact with the surface and interior.

[0031] In the present invention, the composite material, which is a composite of a positive electrode active material and a conductive material, is usually in the form of particles. From the viewpoint of uniformly dispersing the conductive portion containing the conductive material on the surface or inside the main portion, it is preferable that the size of the conductive material is smaller than the size of the main portion. Specifically, when the particle size of the main portion is D1 and the particle size of the conductive material is D2, the value of D1 / D2 is preferably, for example, 2 or more, more preferably 5 or more, and even more preferably 10 or more. On the other hand, the value of D1 / D2 is preferably, for example, 1000 or less, more preferably 500 or less, and even more preferably 10 or more and 100 or less.

[0032] The particle size D1 of the main part is preferably, for example, 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.5 μm or more. On the other hand, D1 is preferably, for example, 20 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. Furthermore, the particle size D2 of the conductive part is preferably, for example, 1 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. On the other hand, D2 is preferably, for example, 500 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less.

[0033] The particle size of the main part is the cumulative particle size D at 50% of the cumulative volume, measured by laser diffraction scattering particle size distribution analysis. 50 On the other hand, the particle size of the conductive part is difficult to measure by laser diffraction scattering particle size distribution measurement when the conductive part is dispersed inside the particles of the main part. Therefore, the average particle size is measured by directly observing the conductive part dispersed inside the main part using SEM (scanning electron microscope) or TEM (transmission electron microscope). Note that, for example, when the conductive material is the carbon nanotube or carbon nanofiber mentioned above, the fiber diameter refers to the diameter in the cross-section of the fiber, or the average value of the major axis and minor axis.

[0034] In the positive electrode active material, the material is a composite material in which a main part and a conductive part are combined, that is, a composite material of particles containing an argyrodite-type compound that constitutes the main part and a conductive material that constitutes the conductive part. In the "composite" form, it is preferable that the conductive part is dispersed on the surface or inside the main part, in close and inseparable from the main part. In particular, from the viewpoint of further improving the performance of the battery of the present invention, it is preferable that the composite material is a material in which the positive electrode active material and the conductive material are combined by the application of mechanical energy.

[0035] Examples of "compounded" configurations include a configuration in which conductive material particles are inseparably dispersed on the surface and / or inside particles containing an argyrodite-type compound, and a configuration in which particles containing an argyrodite-type compound constituting the main part and conductive material particles constituting the conductive part chemically react and bond together.

[0036] "Conductive material particles are inseparably dispersed on the surface or inside the particles of the compound constituting the main part" means, for example, that when the active material of the present invention is observed using a scanning electron microscope (SEM-EDS) equipped with an energy-dispersive X-ray spectrometer, and the constituent elements of the compound constituting the main part (e.g., sulfur) are mapped to the constituent elements of the conductive material constituting the conductive part, it can be confirmed that the constituent elements of the compound constituting the main part (e.g., sulfur) and the constituent elements of the conductive material constituting the conductive part overlap. Alternatively, when observing a cross-section of the positive electrode layer of a battery made using the positive electrode active material of the present invention, it can be confirmed that the constituent elements of the compound constituting the main part (e.g., sulfur) and the constituent elements of the conductive material constituting the conductive part overlap on the surface or inside the active material. The chemical reaction and compounding of the main part and the conductive part can be confirmed, for example, by the presence or absence of CS bonding by Raman spectroscopy or photoelectron spectroscopy.

[0037] In the positive electrode active material, electron transfer between the outside of the active material and the main part is facilitated through the conductive part, thereby acquiring conductivity and lithium ion desorption function. Furthermore, by using a compound with an argyrodite-type crystal structure that has a high lithium content and high lithium ion conductivity in the main part, a battery having the active material of the present invention exhibits high capacity and high rate characteristics. In particular, the active material of the present invention is useful as a positive electrode active material for lithium-ion batteries. That is, it has superior conductivity compared to conventionally known sulfur-based positive electrode active materials such as elemental sulfur, lithium sulfide (Li2S) and its composite materials, or metal sulfides, and the desired battery performance can be obtained.

[0038] In the positive electrode active material, the amount of conductive material per 100 parts by mass of particles containing the argyrodite-type compound that constitutes the main part is preferably, for example, 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more. On the other hand, the amount of conductive material per 100 parts by mass of particles containing the argyrodite-type compound that constitutes the main part is preferably, for example, 50 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. With the main part and conductive part within this range, the battery of the present invention exhibits remarkably high capacity and high rate characteristics.

[0039] In the positive electrode active material, the lithium element content in the argyrodite-type compound is preferably, for example, 10% by mass or more, more preferably 12% by mass or more, and even more preferably 15% by mass or more. On the other hand, the aforementioned content is preferably, for example, 25% by mass or less, more preferably 23% by mass or less, and even more preferably 21% by mass or less. By setting the lithium element content within this range, the capacity of the battery of the present invention can be further increased.

[0040] In the positive electrode active material, the lithium ion conductivity of the argyrodite-type compound contained in the active material is, for example, 1 × 10⁻⁶. -5 Preferably, S / cm or higher, 1 × 10 -4 It is even more preferable that the ratio is 1 × 10⁻⁶ or higher. -3 It is even more preferable that the conductivity is S / cm or higher. The rate characteristics of the battery of the present invention can be further improved by increasing the conductivity of the argyrodite-type compound.

[0041] Next, a preferred method for producing the positive electrode active material used in the present invention will be described. This production method is broadly divided into two main steps: a first step of preparing particles containing the argyrodite-type compound that constitutes the main part, and a second step of mixing the argyrodite-type compound particles with a conductive material to composite them. Each step will be described below.

[0042] In the first step, particles containing an argyrodite-type compound are prepared. Argyrodite-type compounds can be produced by known methods. For example, particles of an argyrodite-type compound can be obtained by mixing lithium sulfide (Li2S) powder, phosphorus pentasulfide (P2S5) powder, lithium chloride (LiCl) powder, and lithium bromide (LiBr) powder, and then calcining them. For mixing these powders, it is preferable to use a ball mill, bead mill, homogenizer, etc.

[0043] After mixing as described above, the mixture is dried as necessary, then calcined under an inert atmosphere or under a flow of hydrogen sulfide gas (H2S), crushed or pulverized as necessary, and classified to obtain an argyrodite-type compound. When firing in an atmosphere containing hydrogen sulfide gas, the firing temperature is preferably, for example, 450°C or higher, and more preferably 550°C or higher. On the other hand, the firing temperature is preferably, for example, 700°C or lower, more preferably 650°C or lower, and even more preferably 600°C or lower. On the other hand, when firing in an inert atmosphere, the firing temperature is preferably, for example, 450°C or higher. On the other hand, the firing temperature is preferably, for example, 650°C or lower, more preferably 600°C or lower, and even more preferably 550°C or lower.

[0044] The particles of the argyrodite compound that constitute the main component can also be produced by amorphizing the raw material powder using a mechanical milling method, and then heat-treating the amorphized raw material powder to crystallize it as needed. In this case, there are no particular limitations on the processing apparatus and processing conditions, as long as the raw material powder can be sufficiently mixed and amorphized. In particular, when a planetary ball mill is used, the container in which the raw material powder is filled rotates on its own and around at high speed, generating high impact energy between the raw material powder and the balls, which are the grinding media placed in the container together, making it possible to amorphize the raw material powder efficiently and uniformly. The mechanical milling method may be either dry or wet.

[0045] The processing conditions for the mechanical milling method can be appropriately set according to the processing equipment used. For example, processing for a time of 0.1 hours to 100 hours can more efficiently and uniformly amorphousize the raw material powder. The balls used as the grinding media are preferably made of ZrO2, Al2O3, Si3N4 (silicon nitride), or WC (tungsten carbide), and the ball diameter is preferably between 0.2 mm and 10 mm.

[0046] Argyrodite-type compounds can be obtained by mechanically milling the amorphous raw material powder and then heat-treating it under the same firing conditions as described above to crystallize it. Since the raw material powder that has undergone mechanical milling is more uniformly mixed than the raw material powder obtained by conventional grinding and mixing, it is possible to further reduce the heat treatment temperature.

[0047] Furthermore, the particles of the argyrodite-type compound that constitute the main component can also be produced by a liquid-phase method using an organic solvent. For example, sulfides or halides that serve as raw materials for the argyrodite-type compound can be dissolved in a solvent such as tetrahydrofuran or ethanol, and the argyrodite-type compound can be precipitated using the solvent as a reaction field. Alternatively, the argyrodite-type compound can be obtained by synthesizing it beforehand using another method, dissolving it in a solvent such as ethanol, and then reprecipitation it. With such a liquid-phase method, it is possible to produce particles of the argyrodite-type compound in a shorter time and with less energy than other methods, and it is also relatively easy to reduce the particle size.

[0048] Once the main part, consisting of argyrodite-type compound particles, is obtained in this way, it is preferable to adjust the particle size of this main part to an appropriate size. The preferred particle size of the main part can be the same as described above, so the explanation is omitted here.

[0049] Next, the main component and the conductive material are mixed and compounded. The conductive material used can be the same as described above, so its explanation is omitted here.

[0050] The composite of the main component and the conductive material is achieved, for example, by applying mechanical energy to the particles of the argyrodite-type compound constituting the main component and the particles of the conductive material. For this purpose, it is preferable to apply compressive / impact forces or shear / frictional forces to the main component and the conductive material in their mixed state.

[0051] To compound the main component and conductive material in a mixed state by applying mechanical energy such as compressive / impact force or shear / frictional force, it is preferable to use equipment mainly used for stirring, mixing, kneading, granulating, grinding, dispersing, and / or surface modifying powders. For example, planetary ball mills, ball mills, jet mills, bead mills, agitator-type pulverizers, vibratory mills, hammer mills, roller mills, and atomizers can be used. The main types of mechanical energy that can be applied using these devices differ depending on the device. For example, when using a planetary ball mill, the main component and conductive material in a mixed state can be compounded by mainly applying compressive / impact force to them. The centrifugal acceleration obtained when the device rotates is not particularly limited as long as it is sufficient to compound the main component and conductive material, but for example, it is preferably 10G or more, more preferably 15G or more, and even more preferably 18G or more. Furthermore, the centrifugal acceleration is preferably 40G or less, more preferably 30G or less, and even more preferably 25G or less. Since the centrifugal acceleration is within the aforementioned range, the composite structure between the main body and the conductive material can be more effectively formed.

[0052] Furthermore, the aforementioned liquid-phase method can also be used in the compounding of the main component and the conductive material. In this case, the conductive material is first dispersed in an organic solvent, and then the raw material for the argyrodite compound particles, or the argyrodite compound itself, is added to the organic solvent. This allows the particles to precipitate on the surface or inside the conductive material, thereby achieving compounding. Compounding using this method makes it possible to further reduce the particle size of the compounded particles.

[0053] The positive electrode active material can be mixed with a solid electrolyte, conductive material, binder, etc., to form a positive electrode mixture. Details of the solid electrolyte will be described later.

[0054] The active material contained in the positive electrode mixture may consist solely of the positive electrode active material described above, or it may be used in combination with other active materials. Examples of other active materials include known elemental sulfur and active materials containing sulfur. The proportion of the positive electrode active material described above in the positive electrode mixture may be, for example, 20% by mass or more, 30% by mass or more, or 40% by mass or more. On the other hand, the proportion may be, for example, 70% by mass or less, or 60% by mass or less.

[0055] The battery of the present invention preferably has an interface in which the positive electrode active material and the solid electrolyte come into contact in order to make the desired effect more pronounced. Here, "the positive electrode active material and the solid electrolyte come into contact" includes both the contact between the positive electrode active material contained in the positive electrode and the solid electrolyte, and the contact between the positive electrode active material contained in the positive electrode and the solid electrolyte contained in the solid electrolyte layer.

[0056] The negative electrode in the battery of the present invention contains a negative electrode active material. The negative electrode active material can be the same as the negative electrode active material used in general solid-state batteries. Specific negative electrode active materials include known materials that intercept and deintercept lithium ions, such as Li metal, carbon materials, silicon, silicon oxide-based compounds such as SiO, tin-based compounds, and lithium titanate. Examples of carbon materials include sintered organic polymer compounds such as polyacrylonitrile, phenolic resin, phenol novolac resin, cellulose, artificial graphite, and natural graphite.

[0057] In the battery of the present invention, the solid electrolyte layer disposed between the positive electrode and the negative electrode is composed of a solid electrolyte. The solid electrolyte preferably has ion conductivity such as lithium ion conductivity. Specifically, for example, inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, halide solid electrolytes, hydride solid electrolytes, and organic polymer electrolytes such as polymer electrolytes can be mentioned. From the viewpoint of making the effects of the present invention more remarkable, the solid electrolyte is preferably a sulfide solid electrolyte. The sulfide solid electrolyte can be the same as the sulfide solid electrolyte used in general solid batteries. The sulfide solid electrolyte may contain, for example, Li element and S element and have lithium ion conductivity.

[0058] The sulfide solid electrolyte may be any of a crystalline material, glass ceramics, and glass. The sulfide solid electrolyte may contain a Li element, an S element, and a P element and may contain a crystal phase having an argyrodite-type crystal structure. Examples of such sulfide solid electrolytes include, for example, Li2S-P2S5, Li2S-P2S5-LiX (where "X" represents one or more halogen elements), Li2S-P2S5-P2O5, Li2S-Li3PO4-P2S5, Li3PS4, Li4P2S6, Li 10 GeP2S 12 、Li 3.25 Ge 0.25 P 0.75 S4、Li7P3S 11 、Li 3.25 P 0.95 S4、Li a PS b X c (where "X" represents one or more halogen elements; a represents a number of 3.0 or more and 9.0 or less; b represents a number of 3.5 or more and 6.0 or less; c represents a number of 0.1 or more and 3.0 or less), and compounds represented by the following formula can be mentioned. In addition, for example, the sulfide solid electrolytes described in International Publication No. 2013 / 099834 pamphlet and International Publication No. 2015 / 001818 pamphlet can be mentioned.

[0059] <000027%9>The battery of the present invention having the above configuration is preferably a lithium-ion battery, and more preferably a lithium-sulfur battery. The battery of the present invention is preferably a solid-state battery having a solid electrolyte layer, and more preferably an all-solid-state battery. The battery of the present invention may be a primary battery or a secondary battery, but is more preferably a secondary battery, and particularly preferably a lithium secondary battery. "Lithium secondary battery" broadly includes secondary batteries that perform charging and discharging by the movement of lithium ions between the positive and negative electrodes. "Solid-state battery" includes not only solid-state batteries that do not contain any liquid or gel-like substances as an electrolyte, but also embodiments that contain, for example, 50% by mass or less, 30% by mass or less, or 10% by mass or less of a liquid or gel-like substance as an electrolyte. [Examples]

[0060] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to these examples. Unless otherwise specified, "%" and "parts" mean "mass%" and "parts by mass," respectively.

[0061] [Example 1] The positive electrode active material was manufactured using the following method. Li 5.8 PS 4·8 Cl 1.2 To achieve the desired composition, lithium sulfide (Li2S) powder, phosphorus pentasulfide (P2S5) powder, and lithium chloride (LiCl) powder were used. Each powder was weighed to a total of 2g and placed in a ZrO2 container along with φ5mm ZrO2 balls. The mixture was then mixed and ground using a planetary ball mill (Fritsch, P-7) at 500 rpm for 20 hours to prepare a mixed powder. This mixed powder was filled into a carbon container and heated in a tubular electric furnace at a heating / cooling rate of 200°C / h while circulating hydrogen sulfide gas (H2S, 100% purity) at 1 L / min, and calcined at 500°C for 4 hours. Afterwards, the sample was crushed in a mortar, ground in a ball mill, and then sieved through a 53 μm mesh to obtain a particle size D 50A powdered compound with a particle size of 12 μm was obtained. Then, the sized powder, heptane as a solvent, and φ2 mm ZrO2 balls were placed in a ZrO2 container and milled at 150 revolutions per minute for 3 hours using a planetary ball mill (Fritsch, P-7) to obtain a particle size D 50 A 3.5 μm pulverized powder was prepared. As the conductive material, Ketjenblack® EC300, a conductive carbon black manufactured by Lion Specialty Chemicals, was used. This conductive material has a particle size of D 50 The particle size was 0.04 μm. 20 parts of conductive material were used for 100 parts of the compound, and the mixture was compounded using a planetary ball mill (Fritsch, P-7) at 500 revolutions / min (centrifugal acceleration 19.1 G) for 10 hours. Afterwards, the sample was crushed in a mortar and sieved through a 53 μm mesh sieve to obtain a particle size D 50 We obtained cathode active material particles with a diameter of 3.2 μm. XRD measurements using CuKα1 radiation confirmed that this compound has a crystalline phase with an argyrodite-type crystal structure. All of the above operations were performed inside a glove box that had been purged with thoroughly dried Ar gas (dew point below -60°C).

[0062] Next, a solid electrolyte was produced using the following method. Li 5.4 PS 4.4 Cl 0.8 Br 0.8 To achieve the desired composition, lithium sulfide (Li2S) powder, phosphorus pentasulfide (P2S5) powder, lithium chloride (LiCl) powder, and lithium bromide (LiBr) powder were used. Each was weighed to a total of 2g, and the mixture was mixed and ground using a planetary ball mill (Fritsch, P-7) at 100 revolutions per minute for 10 hours to prepare a mixed powder. This mixed powder was filled into a carbon container and heated in a tubular electric furnace at a heating / cooling rate of 200°C / h while circulating hydrogen sulfide gas (H2S, 100% purity) at 1 L / min, and calcined at 500°C for 4 hours. After that, the particles were sized using a sieve with a mesh size of 53 μm to obtain a particle size D 50A powdered compound with a particle size of 10 μm was obtained. The obtained sized powder was placed in a ZrO2 container with heptane as a solvent and φ2 mm ZrO2 balls, and milled using a planetary ball mill (Fritsch, P-7) at 100 revolutions / min for 3 hours until the particle size D 50 A 3.0 μm pulverized powder was prepared. Subsequently, the pulverized powder, heptane as a solvent, butyl acetate as a dispersant, and φ0.8 mm ZrO2 balls were placed in a ZrO2 container, and a planetary ball mill (Fritsch, P-7) was used to mill the mixture at 100 revolutions per minute for 3 hours until the particle size D 50 A 0.7 μm pulverized powder was prepared. XRD measurements using CuKα1 radiation confirmed that this compound has a crystalline phase with an argyrodite-type crystal structure.

[0063] As for the negative electrode active material, particle size D 50 Graphite with a thickness of 20 μm was used.

[0064] The positive electrode active material powder and the pulverized solid electrolyte powder described above were mixed in a mortar in a mass ratio of 60:40 to prepare the positive electrode mixture.

[0065] The aforementioned negative electrode active material powder and solid electrolyte pulverized powder were mixed in a mortar in a mass ratio of 50:50 to prepare the negative electrode mixture.

[0066] The preparation of the positive electrode mixture and negative electrode mixture described above was carried out in a glove box purged with thoroughly dried Ar gas (dew point below -60°C).

[0067] A solid electrolyte layer was formed by closing the lower opening of a polypropylene cylindrical container (opening diameter 10.5 mm, height 18 mm) with open top and bottom using a negative electrode (made of stainless steel), placing crushed solid electrolyte powder on top, closing it with a positive electrode (made of stainless steel), and then uniaxially pressing it at 100 MPa. Next, the positive electrode was removed, a positive electrode mixture was placed on top of the solid electrolyte layer, and the opening was closed again with the positive electrode. Then the cylindrical container was inverted to remove the negative electrode, a negative electrode mixture was placed on top of the solid electrolyte layer, and the opening was closed again with the negative electrode. Finally, a solid-state battery cell was fabricated by uniaxially pressing it at 560 MPa, resulting in a stacked positive electrode layer, solid electrolyte layer, and negative electrode layer. Lastly, the positive and negative electrodes were clamped together with a load of 6 N·m using a C-clamp to fabricate an all-solid-state battery cell with a stacked positive electrode layer, solid electrolyte layer, and negative electrode layer. The thickness of each layer was approximately 40 μm for the positive electrode layer, approximately 600 μm for the solid electrolyte layer, and approximately 60 μm for the negative electrode layer. The all-solid-state battery cells were fabricated in a glove box purged with argon gas at a dew point of -60°C. The fabricated all-solid-state batteries were designed to have a capacity of 2.0 mAh based on the positive electrode.

[0068] [Example 2] The positive electrode active material was manufactured using the following method. As the conductive material, carbon nanotubes (fiber diameter 150 nm) (Showa Denko, VGCF(registered trademark)-H) were used instead of Ketjenblack (registered trademark) used in Example 1. The cathode active material was obtained in the same manner as in Example 1, except for this difference.

[0069] The solid electrolyte was prepared using the following method. Li 5.8 PS 4.8 Cl 1.2To achieve the desired composition, lithium sulfide (Li2S) powder, phosphorus pentasulfide (P2S5) powder, and lithium chloride (LiCl) powder were used. Each was weighed to a total of 2g, and the mixture was mixed and ground using a planetary ball mill (Fritsch, P-7) at 100 revolutions per minute for 10 hours to prepare a mixed powder. This mixed powder was packed into a carbon container and heated in a tubular electric furnace at a heating / cooling rate of 200°C / h while circulating hydrogen sulfide gas (H2S, 100% purity) at 1 L / min, and calcined at 500°C for 4 hours. After that, the sample was crushed in a mortar and sieved through a 53 μm mesh sieve to obtain a particle size D 50 A powdered compound with a particle size of 11 μm was obtained. The obtained powder was granulated in the same manner as in Example 1, resulting in a particle size D 50 A 0.8 μm pulverized powder was prepared. XRD measurements using CuKα1 radiation confirmed that this compound has a crystalline phase with an argyrodite-type crystal structure.

[0070] As for the negative electrode active material, particle size D 50 Silicon with a thickness of 2.5 μm was used.

[0071] The positive electrode mixture was prepared in the same manner as in Example 1, except that the pulverized powders of the positive electrode active material and solid electrolyte described above were used.

[0072] The negative electrode active material powder, the pulverized solid electrolyte powder, and carbon nanotubes (fiber diameter 150 nm) (VGCF(registered trademark)-H) were mixed in a mortar in a mass ratio of 53:42:5 to prepare the negative electrode mixture.

[0073] Using the materials described above, an all-solid-state battery was manufactured in the same manner as in Example 1.

[0074] [Example 3] The positive electrode active material was manufactured using the following method. Li 5.4 PS 4.4 Cl 0.8 Br 0.8To achieve the desired composition, lithium sulfide (Li2S) powder, phosphorus pentasulfide (P2S5) powder, lithium chloride (LiCl) powder, and lithium bromide (LiBr) powder were used. Each powder was weighed to a total of 2g, and the mixture was mixed and ground using a planetary ball mill (Fritsch, P-7) at 100 revolutions per minute for 10 hours to prepare a mixed powder. This mixed powder was filled into a carbon container and heated in a tubular electric furnace at a heating / cooling rate of 200°C / h while circulating hydrogen sulfide gas (H2S, 100% purity) at 1 L / min, and calcined at 450°C for 4 hours. After that, the particles were sieved through a 53 μm mesh sieve to a particle size D 50 A powdered compound with a particle size of 9 μm was obtained. The obtained powder, heptane as a solvent, and a φ2 mm ZrO2 ball were placed in a ZrO2 container, and a planetary ball mill (Fritsch, P-7) was used to mill the mixture at 100 revolutions per minute for 3 hours until the particle size D 50 A 2.5 μm crushed powder was prepared. As the conductive material, carbon nanotubes (fiber diameter 150 nm) (manufactured by Showa Denko, VGCF(registered trademark)-H) used in Example 2 were used. 20 parts of the conductive material were used for every 100 parts of the compound. The cathode active material was obtained in the same manner as in Example 1, except for the above. XRD measurements using CuKα1 radiation confirmed that this compound has a crystalline phase with an argyrodite-type crystal structure.

[0075] The negative electrode active material is the graphite and particle size D used in Example 1. 50 SiO with a particle size of 5 μm was used in a mixture. The mass ratio of graphite to SiO was 85.5:14.5. The negative electrode mixture was prepared by mixing the negative electrode active material powder and the pulverized solid electrolyte powder used in Example 1 in a mortar and pestle in a mass ratio of 50:50.

[0076] The solid electrolyte and cathode mixture were prepared in the same manner as in Example 1. Furthermore, an all-solid-state battery was fabricated using these materials in the same manner as in Example 1.

[0077] [Example 4] The positive electrode active material was manufactured using the following method. To obtain the composition of Li7PS6, lithium sulfide (Li2S) powder and phosphorus pentasulfide (P2S5) powder were used. Each was weighed to a total of 2g, and the mixture was mixed and ground using a planetary ball mill (Fritsch, P-7) at 500 rpm for 20 hours to prepare a mixed powder. This mixed powder was filled into a carbon container and heated in a tubular electric furnace at a heating / cooling rate of 200°C / h while flowing Ar gas (100% purity) at 1 L / min, and calcined at 600°C for 4 hours. After that, the sample was crushed in a mortar and pestle, and sieved through a 53 μm mesh sieve to obtain a particle size D 50 A powdered compound with a particle size of 10 μm was obtained. The obtained powder, heptane as a solvent, and a φ2 mm ZrO2 ball were placed in a ZrO2 container, and the mixture was milled using a planetary ball mill (Fritsch, P-7) at 100 revolutions per minute for 3 hours to obtain a particle size of D 50 A 3.0 μm crushed powder was prepared. After grinding in a ball mill, the particles were sorted using a sieve with a mesh size of 53 μm to obtain a particle size D. 50 A powdered compound with a particle size of 4.8 μm was obtained. As the conductive material, Ketjenbrak® EC300, which was used in Example 1, was used. 20 parts of the conductive material were used for every 100 parts of the compound. The cathode active material was obtained in the same manner as in Example 1, except for the above. XRD measurements using CuKα1 radiation confirmed that this compound has a crystalline phase with an argyrodite-type crystal structure.

[0078] As the negative electrode active material, metallic lithium with a thickness of 100 μm was used.

[0079] The solid electrolyte and cathode mixture were prepared in the same manner as in Example 1.

[0080] Using these materials, an all-solid-state battery was fabricated as follows: A cylindrical polypropylene container (opening diameter 10.5 mm, height 18 mm) with open top and bottom was sealed at the bottom opening with a negative electrode (made of SUS), solid electrolyte powder was placed on top, and then sealed with a positive electrode (made of SUS). A solid electrolyte layer was then formed by uniaxial pressing at 200 MPa. Next, the positive electrode was removed, positive electrode mixture powder was placed on top of the solid electrolyte layer, and then sealed again with the positive electrode. Finally, the positive electrode layer and solid electrolyte layer were laminated by uniaxial pressing at 560 MPa. After that, the cylinder was inverted, the negative electrode was removed, Li foil was placed on top of the solid electrolyte layer, and then sealed again with the negative electrode. Finally, the positive and negative electrodes were clamped with a C-clamp under a load of 6 N·m to fabricate an all-solid-state battery cell in which the positive electrode layer, solid electrolyte layer, and negative electrode layer were laminated. The thickness of each layer was approximately 40 μm for the positive electrode layer, 600 μm for the solid electrolyte layer, and 100 μm for the negative electrode layer. The all-solid-state battery cells were fabricated in a glove box purged with argon gas at a dew point of -60°C. The capacity of the fabricated all-solid-state battery was set to 2.0 mAh based on the positive electrode.

[0081] [Example 5] 3LiBH4-LiI was used as the solid electrolyte. This solid electrolyte was prepared as follows. To obtain the composition 3LiBH4-LiI, lithium borohydride (LiBH4) powder and lithium iodide (LiI) powder were weighed to a total amount of 2g each. Mechanical milling was performed using a planetary ball mill (Fritsch, P-7) at 500 rpm for 10 hours to produce 3LiBH4-LiI powder. The sample was then crushed in a mortar and pestle and sieved to a particle size D using a 53 μm mesh sieve. 50 A powdered compound with a particle size of 12 μm was obtained. The obtained sized powder was placed in a ZrO2 container with heptane as a solvent and φ2 mm ZrO2 balls, and milled using a planetary ball mill (Fritsch, P-7) at 100 revolutions / min for 3 hours until the particle size D 50 A 6.4 μm crushed powder was prepared.

[0082] The same positive electrode active material as in Example 1 was used. The positive electrode mixture was prepared by mixing the positive electrode active material powder and the crushed solid electrolyte powder mentioned above in a mortar and pestle in a mass ratio of 75:25. Furthermore, the same negative electrode active material as in Example 4 was used. Using the materials described above, an all-solid-state battery was fabricated in the same manner as in Example 4.

[0083] [Example 6] An all-solid-state battery was fabricated in the same manner as in Example 1, except that the same positive electrode active material as in Example 2 was used.

[0084] [Example 7] Li 6.6 PS 5.6 Cl 0.4 To achieve the desired composition, lithium sulfide (Li2S) powder and phosphorus pentasulfide (P2S5) powder were used. Each was weighed to a total of 2g, and the mixture was mixed and ground using a planetary ball mill (Fritsch, P-7) at 500 rpm for 20 hours to prepare a mixed powder. This mixed powder was filled into a carbon container and heated in a tubular electric furnace at a heating / cooling rate of 200°C / h while flowing Ar gas (100% purity) at 1 L / min, and calcined at 550°C for 4 hours. After that, the sample was crushed in a mortar and pestle, and sieved through a 53 μm mesh sieve to obtain a particle size D 50 A powdered compound with a particle size of 9 μm was obtained. The obtained powder, heptane as a solvent, and a φ2 mm ZrO2 ball were placed in a ZrO2 container, and a planetary ball mill (Fritsch, P-7) was used to mill the mixture at 100 revolutions per minute for 3 hours until the particle size D 50 A 3.0 μm crushed powder was prepared. After grinding in a ball mill, the particles were sorted using a sieve with a mesh size of 53 μm to obtain a particle size D. 50 A powdered compound with a particle size of 4.8 μm was obtained. As the conductive material, Ketjenbrak® EC300, which was used in Example 1, was used. 20 parts of the conductive material were used for every 100 parts of the compound. The cathode active material was obtained in the same manner as in Example 1, except for the above. XRD measurements using CuKα1 radiation confirmed that this compound has a crystalline phase with an argyrodite-type crystal structure.

[0085] The same solid electrolyte, negative electrode active material, and negative electrode mixture were used as in Example 2. The positive electrode mixture was prepared in the same manner as in Example 2, and an all-solid-state battery was fabricated in the same manner as in Example 2.

[0086] [Comparative Example 1] In Example 1, instead of the positive electrode active material, LiNi coated with Nb material was used. 0.6 Co 0.2 Mn 0.2 O2 (hereinafter also referred to as "NCM") powder (D 50 A 4.2 μm (4.2 μm) was used. The positive electrode mixture powder for the positive electrode layer was prepared by mixing the positive electrode active material powder, the pulverized solid electrolyte powder used in Example 1, and carbon nanotubes (fiber diameter 150 nm) (Showa Denko, VGCF(registered trademark)-H) as a conductive material in a mass ratio of 60:37:3 using a mortar and pestle. A solid-state battery was obtained in the same manner as in Example 1, except for these factors.

[0087] [Comparative Example 2] In Example 1, instead of the positive electrode active material, a spinel-type lithium manganese nickel-containing composite oxide (LiMn) coated with Nb material was used. 1.5 Ni 0.5 O4, also referred to as "LMNO" below. ) Powder (D 50 A 4.1 μm (= 4.1 μm) was used. The positive electrode mixture powder for the positive electrode layer was prepared by mixing the positive electrode active material powder, the pulverized solid electrolyte powder used in Example 1, and carbon nanotubes (Showa Denko, VGCF(registered trademark)-H) as a conductive material in a mass ratio of 60:30:10 using a mortar and pestle. A solid-state battery was obtained in the same manner as in Example 1, except for these factors.

[0088] [Comparative Example 3] The same positive electrode active material as in Comparative Example 1 was used. The same solid electrolyte as in Example 1 was used, and the same negative electrode active material as in Example 2 was used. The positive electrode mixture was prepared in the same manner as in Comparative Example 1. Aside from these differences, an all-solid-state battery was obtained in the same manner as in Example 2.

[0089] [Comparative Example 4] Lithium sulfide (Li2S) powder and phosphorus pentasulfide (P2S5) powder were weighed to a total of 2g each, and mechanical milling was performed using a planetary ball mill (Fritsch, P-7) at 500 rpm for 30 hours to produce Li2S:P2S5=75:25 powder. The sample was then crushed in a mortar and pestle and sieved to a particle size D using a 53 μm mesh sieve. 50 A powdered compound with a particle size of 10 μm was obtained. The obtained powder, heptane as a solvent, and a φ5 mm ZrO2 ball were placed in a ZrO2 container, and the particle size D was obtained using a planetary ball mill (Fritsch, P-7) at 100 revolutions / min for 3 hours. 50 A 5.8 μm pulverized powder was prepared. As the conductive material, Ketjenbrak® EC300, which was used in Example 1, was used. 20 parts of the conductive material were used for every 100 parts of the compound. The positive electrode active material and positive electrode mixture were obtained in the same manner as in Example 2, except for the above.

[0090] The same solid electrolyte as in Example 2 was used. Furthermore, the same negative electrode active material as in Example 2 was used, and the negative electrode mixture was prepared in the same manner as in Example 2. Except for the use of the materials mentioned above, an all-solid-state battery was fabricated in the same manner as in Example 2.

[0091] 〔evaluation〕 The proportions of Ni, Co, and Mn elements in the positive electrode active materials obtained in the examples and comparative examples were measured. Furthermore, the all-solid-state batteries obtained in the examples and comparative examples were connected to a charge / discharge measuring device in an environmental test chamber maintained at 25°C or 120°C, and their initial capacity and cycle characteristics were measured using the following method. The results are shown in Table 1 below.

[0092] [Initial discharge voltage and capacity] In an all-solid-state battery using a positive electrode active material mainly composed of a compound having an argyrodite-type crystal structure, with a charge / discharge current of 2.0 mA as the 1C rate, the first charge / discharge (1st cycle) was performed using the CC-CV method at 0.03C and the CC method at 0.03C in order to efficiently de-absorb lithium ions contained in the positive electrode active material. From the second cycle onward, charging was performed using the CC-CV method at 0.1C and the CC method at 0.1C. On the other hand, in all-solid-state batteries using the positive electrode active materials used in Comparative Examples 1 to 3, since lithium ions contained in the positive electrode active material can be efficiently de-absorbed, charging was performed using the CC-CV method at 0.1C from the first cycle and the CC method at 0.1C. Note that the cutoff voltage differs depending on the combination of positive and negative electrode active materials used in the all-solid-state battery; therefore, as shown in Table 1, it was set according to the combination of positive and negative electrode active materials used in the all-solid-state batteries of each example and comparative example. Here, the average discharge voltage of the second cycle was defined as the initial discharge voltage, and the discharge capacity was defined as the initial discharge capacity. The initial charge-discharge curves of the all-solid-state batteries prepared in Examples 1, 2, and 6 and Comparative Examples 1 and 4 are shown in Figures 1 to 5.

[0093] [Cycle Characteristics] The above method was used to perform charge and discharge cycles up to 50 times, and the ratio of the discharge capacity at cycle 50 to the initial discharge capacity at cycle 2 was calculated as the capacity retention rate. Figure 6 shows the cycle characteristics of the all-solid-state batteries prepared in Examples 1, 2, and 6 and Comparative Examples 1 and 4.

[0094] [Table 1]

[0095] As is clear from the results shown in Table 1 and each figure, the all-solid-state batteries obtained in each example, despite not containing rare metals (excluding Li), exhibit comparable performance to the all-solid-state batteries of Comparative Examples 1 to 3, which contain positive electrode active materials containing rare metals. Although their initial discharge voltage is lower, their initial discharge capacity is larger, and their cycle characteristics are also better. In Comparative Example 4, the all-solid-state battery uses a sulfide positive electrode active material that does not contain rare metals (except for Li). The battery configuration is identical to that of Example 2, which uses an argyrodite-type compound (also a sulfide) as the positive electrode active material, except for the positive electrode active material. While the initial discharge voltage of Comparative Example 4 is almost the same as that of Example 2, the initial discharge capacity and cycle characteristics are lower. Therefore, although Comparative Example 4's all-solid-state battery does not contain rare metals (except for Li) and uses the same sulfide positive electrode active material as the argyrodite-type compound, it does not contain the argyrodite-type compound itself, thus failing to achieve good characteristics as an all-solid-state battery.

[0096] While the carbon material used as the conductive material differs between Example 1 and Example 6, it can be seen that using Ketjenblack as the conductive material, as in Example 1, results in even better initial capacity and cycle characteristics of the battery. Thus, among the carbon materials used as conductive materials, carbon black is preferable in terms of improving the initial capacity and discharge rate characteristics of the battery. From the viewpoint of making this advantage even more pronounced, it is preferable to use Ketjenblack as the carbon black, and among these, furnace black is preferable, and in particular, oil furnace black is preferable. [Industrial applicability]

[0097] The battery of the present invention uses as little rare metal as possible, including at least Ni and Co elements, and instead of rare metals, the positive electrode active material can be composed of raw materials that have a stable supply and low price fluctuations.

Claims

1. A battery having a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, The positive electrode includes a positive electrode active material, The positive electrode active material comprises lithium (Li), sulfur (S), phosphorus (P), and halogen elements, and includes a crystalline phase having an argyrodite-type crystal structure. The molar ratio of the halogen (X) element to the phosphorus (P) element is greater than 0 and less than 1.

0. The total amount of rare metals (excluding lithium (Li) element) contained in the positive electrode active material is 0.1% by mass or less. The rare metals are nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), and niobium (Nb), in a battery.

2. A battery having a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, The positive electrode contains a positive electrode active material, The positive electrode active material comprises a composite material containing a compound having a crystalline phase with an argyrodite-type crystal structure and lithium (Li), sulfur (S), and phosphorus (P), and a conductive material. In the composite material, the conductive material particles are inseparably dispersed on the surface and / or inside the particles containing the compound, or the particles containing the compound and the conductive material particles are chemically reacted and bonded together. A battery in which the total amount of nickel (Ni), cobalt (Co), and manganese (Mn) elements contained in the positive electrode active material is 0.1% by mass or less.

3. The battery according to claim 2, wherein the total amount of rare metals (excluding lithium (Li) element) contained in the positive electrode active material is 0.1% by mass or less.

4. The solid electrolyte layer has a solid electrolyte, The battery according to claim 1 or 2, wherein the solid electrolyte comprises lithium (Li), sulfur (S), and phosphorus (P), and includes a crystalline phase having an argyrodite-type crystal structure.

5. The battery according to claim 2, wherein the conductive material is a carbon material or a metallic material.

6. The battery according to claim 5, wherein the composite material is a material in which the compound and the conductive material are combined by the application of mechanical energy.

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