Solid electrolyte material and battery

Abstract

The present disclosure relates to a solid electrolyte material capable of suppressing a decrease in a fill rate. A solid electrolyte material containing a sulfide solid electrolyte and an organic compound, the sulfide solid electrolyte containing a lithium element, a sulfur element, and a phosphorus element, the organic compound having two or more benzene rings, and the melting point of the organic compound being 82 DEG C or less.

Description

Technical Field

[0001] This disclosure relates to solid electrolyte materials and batteries. Background Technology

[0002] Various techniques have been proposed for solid electrolytes, as disclosed in Japanese Patent Application Publication No. 2024-093769. Summary of the Invention

[0003] If the filling rate of the solid electrolyte material containing sulfide solid electrolyte and organic compound is low, there is a problem that the resistance of the electrode layer containing the solid electrolyte material increases.

[0004] This disclosure was made in view of the above-mentioned circumstances, and its main objective is to provide a solid electrolyte material capable of suppressing the reduction of filler content.

[0005] That is, this disclosure includes the following methods.

[0006] <1> A solid electrolyte material comprising a sulfide solid electrolyte and an organic compound.

[0007] The sulfide solid electrolyte contains lithium, sulfur, and phosphorus.

[0008] The organic compound has two or more benzene rings.

[0009] The organic compound has a melting point below 82°C.

[0010] <2> according to <1> The solid electrolyte material, wherein the organic compound has a melting point below 37°C.

[0011] <3> according to <1> or <2> The solid electrolyte material, wherein the organic compound has two benzene rings.

[0012] <4> According to the solid electrolyte material described in <1>, the organic compound is at least one selected from naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 1,4-dimethylnaphthalene, 1,5-dimethylnaphthalene and biphenyl.

[0013] <5> A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer.

[0014] The battery contains, in the positive electrode layer or the negative electrode layer, a... <1> ~ <4> The electrode mixture of the solid electrolyte material and the electrode active material described in any one of the above statements,

[0015] At least a portion of the organic compound is present between the electrode active material and the sulfide solid electrolyte.

[0016] In this disclosure, a solid electrolyte material is obtained that can suppress the decrease in fill rate. Attached Figure Description

[0017] The following description, with reference to the accompanying drawings, illustrates the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention, wherein like symbols denote like elements.

[0018] Figure 1 This is a schematic cross-sectional view illustrating the battery in this disclosure.

[0019] Figure 2 It is a coordinate graph showing the relationship between the melting point and the filling rate of the organic compounds in each solid electrolyte material obtained in Examples 1-9 and Comparative Examples 1-6.

[0020] Figure 3 It is a coordinate graph showing the relationship between the melting point and the filling rate of the organic compounds in each electrode layer obtained in Examples 10-12 and Comparative Examples 7-9. Detailed Implementation

[0021] In this disclosure, unless otherwise specified, the average particle size is the particle size at which the cumulative value of the particle size distribution of the volume reference, as determined by laser diffraction scattering particle size distribution measurement, is 50%, i.e., the median diameter (D50).

[0022] A. Solid electrolyte materials

[0023] This disclosure provides a solid electrolyte material comprising a sulfide solid electrolyte and an organic compound.

[0024] The sulfide solid electrolyte contains lithium, sulfur, and phosphorus.

[0025] The organic compound has two or more benzene rings.

[0026] The organic compound has a melting point below 82°C.

[0027] Solid electrolyte materials contain sulfide solid electrolytes and organic compounds.

[0028] Organic compounds are compounds that have two or more benzene rings.

[0029] Without organic compounds, the particles of sulfide solid electrolytes are difficult to slide against each other, resulting in a lower filling rate. However, by including organic compounds, the particles of sulfide solid electrolytes can slide against each other more easily, thus increasing the filling rate.

[0030] The organic compounds used in this disclosure are essentially nonpolar and hydrophobic molecules, which readily adsorb onto highly hydrophobic substances. The sulfide solid electrolytes used in this disclosure are low-polarity substances, and therefore have good compatibility with organic compounds.

[0031] Organic compounds increase the filling rate of solid electrolyte materials, thus reducing the voids in the electrode layer using the solid electrolyte material and suppressing the increase in resistance.

[0032] Organic compounds can have a melting point below 82°C, or even below 37°C.

[0033] In the organic compounds used in this disclosure, multiple molecules of the organic compound are stacked by intermolecular forces between aromatic π bonds. When the organic compound is used to press a solid electrolyte material, multiple particles of the sulfide solid electrolyte slide between the particles via the organic compound present between them, thus acting as a lubricant to lubricate the particles of the sulfide solid electrolyte. Therefore, in the case of organic compounds with strong stacking forces based on intermolecular forces between aromatic π bonds, i.e., high melting points (above 82°C), layer shift is difficult to occur, and therefore excellent lubrication effects cannot be expected. On the other hand, in the case of organic compounds with weak stacking forces based on intermolecular forces between aromatic π bonds, i.e., low melting points (below 82°C), layer shift is easy to occur during the pressing of the solid electrolyte material, thus exhibiting excellent lubrication function and increasing the filling rate of the solid electrolyte material.

[0034] Organic compounds can contain two or more benzene rings, but can also have three or fewer, or just two rings. For organic compounds to exert a lubricating effect, they need to stack due to intermolecular forces between aromatic π bonds. When there are two or more benzene rings, compared to when there is only one, the molecular planarity increases, making stacking easier and thus more likely to achieve a lubricating effect. When there are three or fewer benzene rings, it is assumed that the stacking force of the aromatic π bonds is not too strong, and the particles can easily slide between each other.

[0035] Examples of organic compounds include fused polycyclic hydrocarbons such as naphthalene, derivatives of fused polycyclic hydrocarbons, biphenyl and its derivatives, and compounds in which multiple benzene rings are linked by organic groups.

[0036] The organic compound may be at least one selected from naphthalene (melting point 80.2℃), 1-methylnaphthalene (melting point -22℃), 2-methylnaphthalene (melting point 37℃), 1,2-dimethylnaphthalene (melting point 1.6℃), 1,3-dimethylnaphthalene (melting point -6℃), 1,4-dimethylnaphthalene (melting point 7.6℃), 1,5-dimethylnaphthalene (melting point 82℃), 1,6-dimethylnaphthalene (melting point -13.9℃), 1,7-dimethylnaphthalene (melting point -6℃), 1-fluoronaphthalene (melting point -9℃), 1-chloronaphthalene (melting point -2.5℃), 1-bromonaphthalene (melting point -1.8℃), 1-iodonaphthalene (melting point 4.2℃), and biphenyl (melting point 69℃).

[0037] The organic compound can be more than 0% by mass relative to the solid electrolyte material, which can be more than 1% by mass, less than 5% by mass, or less than 2% by mass.

[0038] Raman analysis of solid electrolyte materials can confirm whether the aforementioned organic compounds are present in the solid electrolyte materials.

[0039] Sulfide solid electrolytes contain lithium, sulfur, and phosphorus. They may also contain metal (Me is at least one of As, Sb, Si, Ge, Sn, Bi, Al, Zn, Ga, and In). Additionally, sulfide solid electrolytes may contain halogens such as F, Cl, Br, and I.

[0040] Sulfide solid electrolytes can be glass-based (amorphous), glass-ceramic, or crystalline. They can possess a crystalline phase. Examples of such crystalline phases include the Thio-LISICON type, the argyrocerium sulfide type, and the LGPS type.

[0041] The composition of sulfide solid electrolytes is not particularly limited; examples include xLi₂S·(1-x)P₂S₅ (0.5≤x<1) and yLiI·zLiBr·(100-yz)(xLi₂S·(1-x)P₂S₅) (0.5≤x<1, 0≤y≤30, 0≤z≤30). In these compositions, x can satisfy 0.7≤x≤0.8. Other examples of sulfide solid electrolyte compositions include Li 7-x PS 6-x X x X is at least one of F, Cl, Br, and I, and x satisfies 0 ≤ x < 2. Other examples of sulfide solid electrolyte compositions include Li. 4-x Me 1-x P xS4 (0 < x < 1). The Me element is the same as defined above. Examples of the sulfide solid electrolyte include Li3PS4-LiI-LiBr, LiI-LiBr-Li2S-P2S5, LiI-Li2S-P2S5, LiI-Li2S-P2O5, and LiI-Li3PO4-P2S5, etc.

[0042] From the viewpoint of good operability, the shape of the sulfide solid electrolyte can be particulate.

[0043] In addition, the average particle diameter (D50) of the particles of the sulfide solid electrolyte is not particularly limited and can be 1 nm to 100 μm.

[0044] The proportion of the sulfide solid electrolyte relative to 100% by mass of the solid electrolyte material can be 95% by mass or more, or can be 98% by mass or more. The upper limit can be less than 100% by mass, or can be 99% by mass or less.

[0045] B. Battery

[0046] In the present disclosure, a battery is provided, which has a positive electrode layer, a negative electrode layer, and an electrolyte layer. The battery contains an electrode mixture in the positive electrode layer or the negative electrode layer. The electrode mixture contains the above solid electrolyte material containing the above sulfide solid electrolyte and the above organic compound and an electrode active material. The sulfide solid electrolyte contains lithium element, sulfur element, and phosphorus element.

[0047] At least a part of the organic compound exists between the electrode active material and the sulfide solid electrolyte.

[0048] The electrode mixture contains a solid electrolyte material and an electrode active material.

[0049] At least a part of the organic compound in the electrode mixture exists between the electrode active material and the sulfide solid electrolyte. Thus, it is speculated that the organic compound acts as a barrier and inhibits side reactions of the sulfide solid electrolyte (improves reduction resistance). Here, the benzene ring has a conjugated structure in which double bonds and single bonds are alternately connected and has a π electron cloud. Therefore, it is speculated that in an organic compound having two or more benzene rings, the region where the π electron cloud expands is wide and the chemical stability (oxidation resistance, reduction resistance) is good. As a result, the chemical stability is also improved in the sulfide solid electrolyte located near such an organic compound. It is speculated that through these mechanisms, an increase in resistance is inhibited in the battery using the electrode mixture in the present disclosure.

[0050] When the electrode mixture is contained in the positive electrode layer, the electrode mixture is a positive electrode mixture, and the positive electrode mixture contains the above solid electrolyte material and a positive electrode active material.

[0051] When the electrode mixture is contained in the negative electrode layer, the electrode mixture is a negative electrode mixture, which contains the aforementioned solid electrolyte material and negative electrode active material.

[0052] In the battery disclosed herein, as long as the positive electrode layer contains a positive electrode agent, the negative electrode layer may or may not contain the aforementioned solid electrolyte material.

[0053] The battery disclosed herein can contain either the aforementioned solid electrolyte material or not, provided that the negative electrode layer contains a negative electrode agent.

[0054] The battery disclosed herein may contain a positive electrode agent in the positive electrode layer and a negative electrode agent in the negative electrode layer.

[0055] The battery disclosed herein has a positive electrode layer, a negative electrode layer and an electrolyte layer, and typically has a positive electrode containing the positive electrode layer and a negative electrode containing the negative electrode layer.

[0056] Figure 1 This is a schematic cross-sectional view illustrating the battery in this disclosure. Figure 1 The battery 10 shown has a positive electrode layer 1, a negative electrode layer 2, an electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive current collector 4 for collecting current in the positive electrode layer 1, and a negative current collector 5 for collecting current in the negative electrode layer 2. In this disclosure, at least one of the positive electrode layer 1 and the negative electrode layer 2 comprises the solid electrolyte material described in "A. Solid Electrolyte Material" above.

[0057] According to this disclosure, by using the above-mentioned solid electrolyte material, a battery with high electrode layer fill rate and low resistance is obtained.

[0058] [positive electrode]

[0059] The positive electrode has a positive electrode layer and, if necessary, a positive electrode current collector.

[0060] The positive electrode layer is a layer that contains at least a positive electrode active material. The positive electrode layer may be a layer containing a positive electrode compound comprising the aforementioned solid electrolyte material and positive electrode active material. Additionally, the positive electrode layer may, as needed, contain at least one of a solid electrolyte, a conductive material, and a binder.

[0061] Examples of positive electrode active materials include oxide active materials. Examples of oxide active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other layered active substances in rock salt, LiMn2O4, Li4Ti5O 12 and Li(Ni 0.5 Mn 1.5Spinel-type active substances such as O4, and olivine-type active substances such as LiFePO4, LiMnPO4, LiNiPO4 and LiCoPO4.

[0062] A coating containing a Li-ion-conducting compound can be formed on the surface of the positive electrode active material. This inhibits the reaction between the positive electrode active material and the solid electrolyte. Examples of Li-ion-conducting compounds include B₂O₃, Li₂B₄O₇, LiBPO₄, Li₃PO₄, LiPO₃, and LiNbO₃. The coating thickness is, for example, 1 nm or more and 30 nm or less. The coverage of the positive electrode active material with the Li-ion-conducting compound is, for example, 70% or more, 90% or more, or 100%. There is no particular limitation on the coating method of the Li-ion-conducting compound; conventionally known methods can be appropriately used.

[0063] The positive electrode active material is usually in the form of particles. The positive electrode active material can be primary particles or secondary particles formed by the aggregation of primary particles.

[0064] The average particle size (D50) of the positive electrode active material is not particularly limited, for example, it can be 0.01 μm or more and 50 μm or less, or it can be 0.5 μm or more and 30 μm or less.

[0065] The proportion of positive electrode active material in the positive electrode layer can be, for example, 20% by mass or more. If the proportion of positive electrode active material is too low, sufficient energy density may not be obtained. On the other hand, the proportion of positive electrode active material in the positive electrode layer can be, for example, 80% by mass or less. If the proportion of positive electrode active material is too high, the ionic conductivity and electronic conductivity in the positive electrode layer may be relatively reduced.

[0066] The proportion of sulfide solid electrolyte in the positive electrode layer can be, for example, 10% by mass or more. If the proportion of sulfide solid electrolyte is too low, the ion conduction pathway in the positive electrode layer may be insufficient. On the other hand, the proportion of sulfide solid electrolyte in the positive electrode layer can be, for example, 60% by mass or less. If the proportion of sulfide solid electrolyte is too high, the proportion of positive electrode active material will be relatively low, and the energy density may be lower.

[0067] The positive electrode layer can contain conductive materials. By adding conductive materials, the electronic conductivity of the positive electrode layer is improved. Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), fibrous carbon materials such as vapor-phase carbon fiber (VGCF), carbon nanotubes (CNTs), and carbon nanofibers (CNFs).

[0068] The proportion of conductive material in the positive electrode layer can be, for example, 0.1% by mass or more. If the proportion of conductive material is too low, the electron conduction pathway in the positive electrode layer may be insufficient. On the other hand, the proportion of conductive material in the positive electrode layer can be, for example, 5% by mass or less. When the proportion of conductive material is too high, the proportion of positive electrode active material becomes relatively low, and the energy density may become lower.

[0069] The positive electrode layer may contain an adhesive. Examples of adhesives include styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butadiene rubber (BR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-isoprene-styrene block copolymer (SIS), and ethylene-propylene-diene copolymer (EPDM).

[0070] The proportion of binder in the positive electrode layer can be, for example, 0.5% by mass or more. If the proportion of binder is too low, it may not be able to sufficiently reduce the increase in resistance caused by charging and discharging. On the other hand, the proportion of binder in the positive electrode layer can be, for example, 5% by mass or less. If the proportion of binder is too high, the proportion of positive electrode active material becomes relatively low, and the energy density may become lower.

[0071] The thickness of the positive electrode layer can be, for example, greater than 0.1 μm and less than 1000 μm.

[0072] The manufacturing method of the positive electrode layer is not particularly limited. For example, the following method can be used: mixing the above-mentioned positive electrode agent with a solvent to obtain a positive electrode slurry, applying the above-mentioned positive electrode slurry to a positive electrode current collector and drying it to form a positive electrode layer. During the formation of the positive electrode layer, a pressing process can be performed to press the positive electrode layer in the thickness direction. Examples of pressing processes include roll forming and flat plate forming.

[0073] Examples of solvents include tetrahydronaphthalene, diisobutyl ketone, butyl butyrate, mesitylene, heptane, dibutyl ether, decane, dodecane, isodecane, and toluene, and may contain two or more of these components.

[0074] Materials used as positive current collectors include, for example, SUS, Cr, Au, Pt, Zn, aluminum, copper, nickel, iron, titanium, and carbon. The thickness of the positive current collector is, for example, 0.1 μm or more and 100 μm or less. The shape of the positive current collector can be foil-like or plate-like. The top view shape of the positive current collector is not particularly limited; for example, it can be circular, elliptical, rectangular, or any polygonal shape. The positive current collector can be a structure with a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on its surface.

[0075] [negative electrode]

[0076] The negative electrode has a negative electrode layer and, if necessary, a negative electrode current collector.

[0077] The negative electrode layer is a layer containing at least a negative electrode active material. The negative electrode layer may be a layer containing a negative electrode compound comprising the aforementioned solid electrolyte material and negative electrode active material. Additionally, the negative electrode layer may, as needed, contain at least one of a solid electrolyte, a conductive material, and a binder.

[0078] Examples of anode active materials include Si-based active materials, carbon-based active materials, oxide-based active materials, and Li-based active materials.

[0079] Examples of active materials in the Si system include elemental Si, Si alloys, Si oxides, and Si carbides. Examples of metals other than Si in Si alloys include Li, Sn, Fe, Co, Ni, Ti, Cr, Na, W, Mo, V, Nb, Zr, and Hf. Si alloys may contain only one metal other than Si, or they may contain two or more metals. Examples of Si oxides include SiO. Examples of Si carbides include SiC.

[0080] Examples of carbon-based active materials include graphite, hard carbon, and soft carbon.

[0081] Examples of active oxide-based materials include lithium titanate.

[0082] Examples of active materials in the Li-based system include elemental Li and Li alloys. Other metallic elements besides lithium contained in Li alloys include Mg, Ag, In, Sn, Si, Ga, Au, and Pt.

[0083] Regarding the conductive materials and adhesives used in the negative electrode layer, the same materials as those described in the positive electrode layer can be cited.

[0084] Materials used as negative current collectors include, for example, SUS, aluminum, copper, nickel, iron, titanium, and carbon. Furthermore, the thickness of the negative current collector varies depending on its shape, ranging from, for example, 1 μm to 50 μm. The shape of the negative current collector can be foil-like or plate-like. The top-view shape of the negative current collector is not particularly limited; examples include circular, elliptical, rectangular, and arbitrary polygonal shapes. The negative current collector can also have a structure with a buffer layer, elastic layer, or PTC thermistor layer disposed on its surface.

[0085] [Electrolyte layer]

[0086] The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and it contains at least an electrolyte. The electrolyte can be a solid electrolyte (sometimes called SE) or a liquid electrolyte (electrolyte).

[0087] Non-aqueous electrolytes can be used. A single non-aqueous electrolyte can be used alone, or two or more can be used in combination.

[0088] As a non-aqueous electrolyte, a non-aqueous electrolyte containing lithium salt and non-aqueous solvent is usually used.

[0089] Examples of lithium salts include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6; and organic lithium salts such as LiCF3SO3, LiN(SO2CF3)2(Li-TFSI), LiN(SO2C2F5)2, and LiC(SO2CF3)3.

[0090] Examples of non-aqueous solvents include ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), γ-butyrolactone, sulfolane, acetonitrile (AcN), dimethoxymethane, 1,2-dimethoxyethane (DME), 1,3-dimethoxypropane, diethyl ether, tetraethylene glycol dimethyl ether (TEGDME), tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide (DMSO), and mixtures thereof.

[0091] The concentration of lithium salt in non-aqueous electrolytes can be, for example, 0.3–5 M.

[0092] The electrolyte layer can be a membrane impregnated with the above-mentioned electrolyte solution and other electrolytes, which prevents the positive electrode layer from contacting the negative electrode layer.

[0093] The material used for the membrane is not particularly limited as long as it is a porous membrane. Examples include resins such as polyethylene (PE), polypropylene (PP), polyester, polyvinyl alcohol, cellulose, and polyamide, among which polyethylene and polypropylene are possible. Furthermore, the membrane can be a single-layer structure or a multi-layer structure. Examples of multi-layer membranes include a two-layer PE / PP structure, or a three-layer PP / PE / PP or PE / PP / PE structure.

[0094] The diaphragm can also be made of resin nonwoven fabric, glass fiber nonwoven fabric, or other nonwoven fabrics.

[0095] The electrolyte layer can be a solid electrolyte layer composed of solids.

[0096] The solid electrolyte layer contains a solid electrolyte and, if necessary, adhesives, etc.

[0097] The solid electrolyte layer contains the sulfide solid electrolyte described in "A. Solid Electrolyte Material" above as a solid electrolyte.

[0098] Solid electrolytes can be used alone or in combination with two or more types. Furthermore, when using two or more solid electrolytes, they can be mixed, or they can form two or more layers of solid electrolyte to create a multilayer structure.

[0099] The proportion of solid electrolyte in the solid electrolyte layer is not particularly limited; for example, it can be more than 50% by mass or 100% by mass. The solid electrolyte layer may contain less than 10% by mass of electrolyte relative to the total amount of solid electrolyte layer.

[0100] Examples of adhesives that can be contained in the above-mentioned positive electrode layer can be cited as examples.

[0101] The content of the binder in the solid electrolyte layer can be 0% to 10% by mass relative to the total amount of the solid electrolyte layer.

[0102] The thickness of the electrolyte layer can be, for example, greater than 0.1 μm and less than 1000 μm.

[0103] The battery disclosed herein may further include a constraint clamp that applies constraint pressure to the positive electrode layer, electrolyte layer, and negative electrode layer along the thickness direction. Particularly when the electrolyte layer is a solid electrolyte layer, constraint pressure can be applied to form good ion conduction and electron conduction pathways. The constraint pressure can be, for example, 0.1 MPa or more. On the other hand, the constraint pressure can be, for example, 100 MPa or less.

[0104] [Battery]

[0105] The type of battery disclosed herein is not particularly limited, but is typically a lithium-ion battery. Furthermore, the battery in this disclosure can be a liquid battery with an electrolyte layer containing an electrolyte solution, or a solid battery with an electrolyte layer containing a solid electrolyte. A solid battery can be a semi-solid battery or a fully solid battery. In this disclosure, a semi-solid battery is a battery whose electrolyte layer contains both a solid electrolyte and liquid components (e.g., solvent and electrolyte). In this disclosure, a fully solid battery is a battery whose electrolyte layer contains only a solid electrolyte. Additionally, the battery in this disclosure can be a primary battery or a secondary battery, and may also be a secondary battery. Because it can be repeatedly charged and discharged, it is useful, for example, as a vehicle battery.

[0106] There are no particular limitations on the shape of the battery; for example, it can be coin-shaped, cylindrical, square, sheet-shaped, button-shaped, flat, or stacked.

[0107] Batteries are used in various applications, including as power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. In particular, they can also be used as power sources for driving hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). Furthermore, batteries can be used as power sources for mobile bodies other than vehicles (such as railways, ships, and aircraft), and also as power sources for electrical appliances such as information processing devices.

[0108] <Example 1>

[0109] (Preparation of solid electrolyte materials)

[0110] 3000 mg of mesitylene and 20 mg of 1,5-dimethylnaphthalene (an organic compound) were added to a propylene container and dissolved. 1000 mg of glass-ceramic sulfide solid electrolyte particles were then added and stirred using an ultrasonic homogenizer to obtain a slurry. The slurry was then transferred to a petri dish and heated to dry, thereby removing the mesitylene and obtaining the solid electrolyte material.

[0111] <Example 2>

[0112] Except for replacing the organic compound with naphthalene, the solid electrolyte material was obtained using the same method as in Example 1.

[0113] <Example 3>

[0114] Except for replacing the organic compound with biphenyl, the solid electrolyte material was obtained using the same method as in Example 1.

[0115] <Example 4>

[0116] The solid electrolyte material was obtained using the same method as in Example 1, except that the organic compound was changed to 2-methylnaphthalene.

[0117] <Example 5>

[0118] The solid electrolyte material was obtained using the same method as in Example 1, except that the organic compound was changed to 1,4-dimethylnaphthalene.

[0119] <Example 6>

[0120] The solid electrolyte material was obtained using the same method as in Example 1, except that the organic compound was changed to 1-methylnaphthalene.

[0121] <Comparative Example 1>

[0122] 3000 mg of mesitylene was added to a propylene container, followed by 1000 mg of glass-ceramic sulfide solid electrolyte particles. The mixture was stirred using an ultrasonic homogenizer to obtain a slurry. The slurry was then transferred to a petri dish and heated to dry, thereby removing the mesitylene and obtaining the solid electrolyte material.

[0123] <Comparative Example 2>

[0124] The solid electrolyte material was obtained using the same method as in Example 1, except that the organic compound was replaced with decane.

[0125] <Comparative Example 3>

[0126] The solid electrolyte material was obtained using the same method as in Example 1, except that the organic compound was replaced with anthracene.

[0127] <Comparative Example 4>

[0128] The solid electrolyte material was obtained using the same method as in Example 1, except that the organic compound was changed to 2,3-dimethylnaphthalene.

[0129] <Example 7>

[0130] Except for changing the glass-ceramic sulfide solid electrolyte to a crystalline sulfide solid electrolyte, the solid electrolyte material was obtained using the same method as in Example 1.

[0131] <Example 8>

[0132] The glass-ceramic sulfide solid electrolyte was replaced with a crystalline sulfide solid electrolyte, and the organic compound was replaced with 1,4-dimethylnaphthalene. Otherwise, the solid electrolyte material was obtained by the same method as in Example 1.

[0133] <Example 9>

[0134] The glass-ceramic sulfide solid electrolyte was replaced with a crystalline sulfide solid electrolyte, and the organic compound was replaced with 1-methylnaphthalene. Otherwise, the solid electrolyte material was obtained by the same method as in Example 1.

[0135] <Comparative Example 5>

[0136] Except for changing the glass-ceramic sulfide solid electrolyte to a crystalline sulfide solid electrolyte, the solid electrolyte material was obtained using the same method as in Comparative Example 1.

[0137] <Comparative Example 6>

[0138] The glass-ceramic sulfide solid electrolyte was replaced with a crystalline sulfide solid electrolyte, and the organic compound was replaced with decane. Otherwise, the solid electrolyte material was obtained by the same method as in Example 1.

[0139] <Determination of Filling Ratio of Solid Electrolyte Materials>

[0140] 100 mg of each solid electrolyte material obtained in Examples 1-9 and Comparative Examples 1-6 was added to a φ11.28 mm barrel. The layers of solid electrolyte material were clamped together using SUS pins and pressed at 19.6 MPa. The volume of the pressed solid electrolyte material was taken as its apparent volume. The ratio of the total volume of the raw materials (organic compounds and sulfide solid electrolytes) to the apparent volume of the solid electrolyte material was taken as the filling rate and calculated using the following formula. The results are shown in Table 1.

[0141] Filling rate = (Total volume of raw materials for solid electrolyte material ÷ Apparent volume of solid electrolyte material) × 100

[0142] Table 1

[0143]

[0144] Figure 2 It is a coordinate graph showing the relationship between the melting point and the filling rate of the organic compounds in each solid electrolyte material obtained in Examples 1-9 and Comparative Examples 1-6.

[0145] Comparing Examples 1-6 and Comparative Examples 1-4, which used glass-ceramic sulfide solid electrolytes, it can be seen that Comparative Example 2, which used an organic compound without a benzene ring, had a lower filling rate than Comparative Example 1. Comparative Examples 2-3, which used an organic compound with a melting point exceeding 82°C, had a lower filling rate than Comparative Example 1. However, Examples 1-6, which used an organic compound with two benzene rings and a melting point below 82°C, had a higher filling rate than Comparative Example 1.

[0146] Comparing Examples 7-9 and Comparative Examples 5-6, which used crystalline sulfide solid electrolytes, it can be seen that Comparative Example 6, which used an organic compound without a benzene ring, had a lower filling rate than Comparative Example 5, while Examples 7-9, which used an organic compound with two benzene rings and a melting point of 82°C or less, had a higher filling rate than Comparative Example 5.

[0147] These results show that by using organic compounds with two or more benzene rings and a melting point below 82°C, the filling rate can be improved by utilizing the lubricant function of organic compounds.

[0148] <Comparative Example 7>

[0149] (Preparation of electrode mixture)

[0150] Mesitylene was added to a propylene container, along with nickel layered oxide (a layered active material containing nickel), a glass-ceramic sulfide solid electrolyte, and a conductive material, making their volume ratio 74 / 23 / 3%. The mixture was stirred using an ultrasonic homogenizer to obtain a slurry. The slurry was then transferred to a petri dish and heated to dry, thereby removing the mesitylene and obtaining an electrode mixture.

[0151] <Example 10>

[0152] (Preparation of electrode mixture)

[0153] Mesitylene was added to a propylene container, along with 20 mg of 1,5-dimethylnaphthalene (an organic compound), and dissolved. Then, nickel layered oxide (as the positive electrode active material), a glass-ceramic sulfide solid electrolyte, and a conductive material were added to achieve a volume ratio of 74 / 23 / 3%. The mixture was stirred using an ultrasonic homogenizer to obtain a slurry. The slurry was then transferred to a petri dish and heated to dry, thereby removing the mesitylene and obtaining the electrode mixture.

[0154] <Example 11>

[0155] The electrode mixture was obtained using the same method as in Example 10, except that the organic compound was changed to 1,4-dimethylnaphthalene.

[0156] <Example 12>

[0157] The electrode mixture was obtained using the same method as in Example 10, except that the organic compound was changed to 1-methylnaphthalene.

[0158] <Comparative Example 8>

[0159] The electrode mixture was obtained using the same method as in Example 10, except that the organic compound was replaced with decane.

[0160] <Comparative Example 9>

[0161] The electrode mixture was obtained using the same method as in Example 10, except that the organic compound was replaced with anthracene.

[0162] <Electrode layer filling rate determination>

[0163] 100 mg of each electrode mixture obtained in Examples 10-12 and Comparative Examples 7-9 was added to a φ11.28 mm barrel. The resulting electrode layer was clamped at the top and bottom with SUS pins and pressed at 19.6 MPa. The volume of the pressed electrode layer was taken as the apparent volume of the electrode layer. The ratio of the total volume of the raw materials of the electrode layer (organic compound, sulfide solid electrolyte, nickel layered oxide, and conductive material) to the apparent volume of the electrode layer was taken as the filling rate and calculated using the following formula. The results are shown in Table 2.

[0164] Electrode layer filling rate = (total volume of raw materials before electrode layer fabrication ÷ apparent volume of electrode layer) × 100

[0165] Table 2

[0166]

[0167] Figure 3 It is a coordinate graph showing the relationship between the melting point and the filling rate of the organic compounds in each electrode layer obtained in Examples 10-12 and Comparative Examples 7-9.

[0168] Comparative Example 8, which uses an organic compound without a benzene ring, has a lower filling rate than Comparative Example 7. Comparative Example 9, which uses an organic compound with a melting point exceeding 82°C, has a lower filling rate than Comparative Example 7. However, Examples 10-12, which use an organic compound with two benzene rings and a melting point below 82°C, have a higher filling rate than Comparative Example 7. Therefore, it is expected that the effect of reducing the voids in the electrode layer and lowering the resistance can be achieved.

Claims

1. A solid electrolyte material comprising a sulfide solid electrolyte and an organic compound, The sulfide solid electrolyte contains lithium, sulfur, and phosphorus. The organic compound has two or more benzene rings. The organic compound has a melting point below 82°C.

2. The solid electrolyte material according to claim 1, wherein the melting point of the organic compound is below 37°C.

3. The solid electrolyte material according to claim 1, wherein the organic compound has two benzene rings.

4. The solid electrolyte material according to claim 1, wherein the organic compound is at least one selected from naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 1,4-dimethylnaphthalene, 1,5-dimethylnaphthalene and biphenyl.

5. A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer, The battery contains an electrode mixture in the positive electrode layer or the negative electrode layer, the electrode mixture comprising the solid electrolyte material and electrode active material as described in any one of claims 1 to 4. At least a portion of the organic compound is present between the electrode active material and the sulfide solid electrolyte.

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