Solid electrolyte materials and batteries

Abstract

The present invention provides a solid electrolyte material that can suppress the decrease in ionic conductivity. [Solution] A solid electrolyte material comprising a sulfide solid electrolyte containing lithium, sulfur, and phosphorus, and an organic compound, wherein the organic compound contains a halogen element and has two or more benzene rings, and the ratio of the organic compound to 100% by mass of the solid electrolyte material is 5.37% by mass or less.

Description

[Technical Field]

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

[0002] Various technologies have been proposed for solid electrolytes, such as those disclosed in Patent Documents 1 and 2. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-093769 [Patent Document 2] Japanese Patent Publication No. 2020-087633 [Overview of the project] [Problems that the invention aims to solve]

[0004] From the perspective of suppressing the degradation of sulfide solid electrolytes, the addition of organic compounds to sulfide solid electrolytes is being considered. However, solid electrolyte materials containing sulfide solid electrolytes and organic compounds have the problem that the ionic conductivity decreases due to the organic compounds.

[0005] This disclosure has been made in view of the above circumstances, and its main purpose is to provide a solid electrolyte material that can suppress the decrease in ionic conductivity. [Means for solving the problem]

[0006] In other words, this disclosure includes the following aspects: <1> A solid electrolyte material containing a sulfide solid electrolyte containing lithium, sulfur, and phosphorus, and an organic compound, The aforementioned organic compound contains a halogen element and has two or more benzene rings. A solid electrolyte material in which the proportion of the organic compound to 100% by mass of the solid electrolyte material is 5.37% by mass or less.

[0007] <2> The proportion of the organic compound to 100% by mass of the solid electrolyte material is 2.26% by mass or less. <1> The solid electrolyte material described above.

[0008] <3> The aforementioned organic compound is at least one selected from the group consisting of 1,5-dibromonaphthalene, 1,5-difluoronaphthalene, 1,5-diiodonaphthalene, 1-bromo-2-iodonaphthalene, 2-bromo-1-iodonaphthalene, and 2,3-dibromonaphthalene. <1> or <2> The solid electrolyte material described above.

[0009] <4> The aforementioned organic compound is 1,5-dibromonaphthalene. <1> or <2> The solid electrolyte material described above.

[0010] <5> A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer, The aforementioned battery is <1> ~ <4> An electrode composite material comprising a solid electrolyte material described in any one of the above and an electrode active material is included in the positive electrode layer or the negative electrode layer. A battery in which at least a portion of the organic compound is present between the electrode active material and the sulfide solid electrolyte. [Effects of the Invention]

[0011] This disclosure offers the advantage of obtaining a solid electrolyte material that can suppress the decrease in ionic conductivity. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic cross-sectional view illustrating a battery in this disclosure. [Figure 2] Figure 2 is a graph showing the relationship between the organic compound content and ionic conductivity of each solid electrolyte material obtained in Examples 1-5 and Comparative Examples 1-7.

Mode for Carrying Out the Invention

[0013] In the present disclosure, unless otherwise specified, the average particle diameter of the particles is the value of the median diameter (D50), which is the particle diameter at 50% of the integrated value in the volume-based particle size distribution measured by laser diffraction / scattering particle size distribution measurement.

[0014] A. Solid Electrolyte Material In the present disclosure, a solid electrolyte material containing a sulfide solid electrolyte containing a lithium element, a sulfur element, and a phosphorus element, and an organic compound, wherein the organic compound contains a halogen element and has two or more benzene rings, and provides a solid electrolyte material in which the ratio of the organic compound to 100% by mass of the solid electrolyte material is 5.37% by mass or less.

[0015] The solid electrolyte material contains a sulfide solid electrolyte and an organic compound.

[0016] The organic compound is a compound containing a halogen element and having two or more benzene rings. Since the organic compound contains a halogen element, the polarity within the molecule becomes large, and it can attract and easily move Li ions present in the solid electrolyte material and in the electrode layer, etc., improving the ionic conductivity. Since the organic compound improves the ionic conductivity of the solid electrolyte material, an effect of improving the ionic conductivity of the electrode layer using the solid electrolyte material can be expected. The organic compound used in the present disclosure is basically a nonpolar and hydrophobic molecule, and is likely to adsorb to a highly hydrophobic substance. The sulfide solid electrolyte used in the present disclosure is a substance with low polarity, and thus has good compatibility with the organic compound. The halogen element is at least one selected from the group consisting of F, Cl, Br, and I. The organic compound may contain two or more benzene rings, six or fewer, or just two. In the organic compound used in this disclosure, multiple molecules of the organic compound are stacked via intermolecular forces between aromatic π bonds. When a solid electrolyte material is pressed, the organic compound functions as a lubricant, causing multiple particles of the sulfide solid electrolyte to slide between them like shearing layers via the organic compound present between the particles. For the organic compound to exert its lubricating effect, it is necessary for the particles to stack via intermolecular forces between aromatic π bonds. It is presumed that when there are two or more benzene rings rather than one, the flatness of the molecules increases, making stacking easier and thus facilitating the lubricating effect. When there are six or fewer benzene rings, it is presumed that the stacking force of the aromatic π bonds does not become too large, and the particles slide more easily between each other. Examples of organic compounds include halogen element derivatives of condensed polycyclic hydrocarbons such as naphthalene, anthracene, fluorene, phenalene, tetracene, and pentacene, halogen element derivatives of biphenyl, and compounds in which multiple benzene rings containing halogen elements are linked by organic groups. The organic compound may be at least one selected from the group consisting of 1,5-dibromonaphthalene, 1,5-difluoronaphthalene, 1,5-diiodonaphthalene, 1-bromo-2-iodonaphthalene, 2-bromo-1-iodonaphthalene, and 2,3-dibromonaphthalene. The proportion of the organic compound relative to 100% by mass of the solid electrolyte material may be 5.37% by mass or less, or 2.26% by mass or less, and the lower limit may be greater than 0% by mass or greater than 0.38% by mass. By performing Raman analysis on a solid electrolyte material, it is possible to confirm whether the above-mentioned organic compound is present in the solid electrolyte material.

[0017] The sulfide solid electrolyte contains lithium element, sulfur element and phosphorus element. The sulfide solid electrolyte may further contain a Me element (Me is at least one of As, Sb, Si, Ge, Sn, Bi, Al, Zn, Ga, and In). Further, the sulfide solid electrolyte may contain halogen elements such as F, Cl, Br, and I.

[0018] The sulfide solid electrolyte may be a glass-based (amorphous) sulfide solid electrolyte, a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. The sulfide solid electrolyte may have a crystalline phase. Examples of the crystalline phase include, for example, Thio-LISICON type crystalline phase, argyrodite type crystalline phase, and LGPS type crystalline phase.

[0019] The composition of the sulfide solid electrolyte is not particularly limited, and examples thereof include, for example, xLi2S·(1-x)P2S5 (0.5≦x<1), and yLiI·zLiBr·(100-y-z)(xLi2S·(1-x)P2S5) (0.5≦x<1, 0≦y≦30, 0≦z≦30). In these compositions, x may satisfy 0.7≦x≦0.8. Further, as another example of the composition of the sulfide solid electrolyte, Li x PS 6-x X x is mentioned. X is at least one of F, Cl, Br, I, and x satisfies 0≦x<2. Further, as another example of the composition of the sulfide solid electrolyte, Li 4-x Me 1-x P x S4 (0<x<1) is mentioned. The Me element is the same as the above definition. Examples of the sulfide solid electrolyte include Li3PS4-LiI-LiBr, LiI-LiBr-Li2S-P2S5, LiI-Li2S-P2S5, LiI-Li2S-P2O5, and LiI-Li3PO4-P2S5.

[0020] The shape of the sulfide solid electrolyte may be particulate from the viewpoint of good handleability. Furthermore, the average particle size (D50) of the sulfide solid electrolyte particles is not particularly limited and may range from 1 nm to 100 μm. The ratio of sulfide solid electrolyte to 100% by mass of solid electrolyte material may be 94.63% by mass or more, 97.74% by mass or more, and the upper limit may be less than 100% by mass or 99.62% by mass or less.

[0021] B.Battery This disclosure relates to a battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer, The battery includes an electrode composite material in the positive electrode layer or the negative electrode layer, which comprises the sulfide solid electrolyte containing lithium, sulfur, and phosphorus, the organic compound, and an electrode active material. The present invention provides a battery in which at least a portion of the organic compound is present between the electrode active material and the sulfide solid electrolyte.

[0022] The electrode composite material includes a solid electrolyte material and an electrode active material. At least a portion of the organic compounds in the electrode mixture are present between the electrode active material and the sulfide solid electrolyte. It is presumed that the organic compounds function as a barrier, suppressing side reactions of the sulfide solid electrolyte (improving reduction resistance). Here, the benzene ring has a conjugated structure in which double bonds and single bonds are alternately linked, and has a π electron cloud. Therefore, in organic compounds having multiple benzene rings, the region where the π electron cloud extends is wide, resulting in good chemical stability (oxidation resistance, reduction resistance), and as a result, it is presumed that the chemical stability of the sulfide solid electrolyte located near such organic compounds is also improved. Due to these mechanisms, it is presumed that resistance increase is suppressed in batteries using the electrode mixture of this disclosure. When the electrode mixture is included in the positive electrode layer, the electrode mixture is a positive electrode mixture, and the positive electrode mixture includes the above-mentioned solid electrolyte material and a positive electrode active material. When the electrode mixture is included in the negative electrode layer, the electrode mixture is a negative electrode mixture, and the negative electrode mixture includes the solid electrolyte material and the negative electrode active material. In the battery of the present disclosure, if the positive electrode layer contains a positive electrode composite material, the negative electrode layer may or may not contain the above solid electrolyte material. In the battery of the present disclosure, if the negative electrode layer contains a negative electrode composite material, the positive electrode layer may or may not contain the above solid electrolyte material. The battery of the present disclosure may contain a positive electrode composite material in the positive electrode layer and a negative electrode composite material in the negative electrode layer.

[0023] The battery in the present disclosure has a positive electrode layer, a negative electrode layer, and an electrolyte layer, and usually has a positive electrode including the positive electrode layer and a negative electrode including the negative electrode layer. FIG. 1 is a schematic cross-sectional view illustrating the battery in the present disclosure. The battery 10 shown in FIG. 1 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 electrode current collector 4 for collecting current from the positive electrode layer 1, and a negative electrode current collector 5 for collecting current from the negative electrode layer 2. In the present disclosure, at least one of the positive electrode layer 1 or the negative electrode layer 2 contains the solid electrolyte material described in the above "A. Solid Electrolyte Material". According to the present disclosure, by using the above-described solid electrolyte material, a battery having high ion conductivity and low resistance in the electrode layer can be obtained.

[0024] [Positive Electrode] The positive electrode has a positive electrode layer and may further have a positive electrode current collector as needed. The positive electrode layer is a layer containing at least a positive electrode active material. The positive electrode layer may be a layer containing a positive electrode composite material including the above solid electrolyte material and the positive electrode active material. Further, the positive electrode layer may contain at least one of a solid electrolyte, a conductive material, and a binder as needed.

[0025] Examples of the positive electrode active material include oxide active materials. Examples of the oxide active material include rock salt layer-type active materials such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and the like, LiMn2O4, Li4Ti5O 12 , and Li(Ni 0.5 Mn 1.5Examples include spinel-type active materials such as O4, and olivine-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. A coating layer containing a Li-ion conductive compound may be formed on the surface of the positive electrode active material. This is because it can suppress the reaction between the positive electrode active material and the solid electrolyte. Examples of Li-ion conductive compounds include B2O3, Li2B4O7, LiBPO4, Li3PO4, LiPO3, and LiNbO3. The thickness of the coating layer is, for example, 1 nm to 30 nm. The coverage rate of the Li-ion conductive compound coating the positive electrode active material is, for example, 70% or more, may be 90% or more, or may be 100%. The method of coating with the Li-ion conductive compound is not particularly limited, and conventionally known methods can be used as appropriate.

[0026] The positive electrode active material is usually particulate. The positive electrode active material may be primary particles or secondary particles formed by aggregation of primary particles. The average particle size (D50) of the positive electrode active material is not particularly limited, but for example, it may be 0.01 μm or more and 50 μm or less, or 0.5 μm or more and 30 μm or less.

[0027] The proportion of positive electrode active material in the positive electrode layer may be, for example, 20% by mass or more. If the proportion of positive electrode active material is too low, a sufficient energy density may not be obtained. On the other hand, the proportion of positive electrode active material in the positive electrode layer may 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 relatively decrease.

[0028] The proportion of sulfide solid electrolyte in the positive electrode layer may be, for example, 10% by mass or more. If the proportion of sulfide solid electrolyte is too low, there may be insufficient ion conduction paths in the positive electrode layer. On the other hand, the proportion of sulfide solid electrolyte in the positive electrode layer may 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, which may result in a lower energy density.

[0029] The positive electrode layer may contain a conductive material. Adding a conductive material improves the electronic conductivity of the positive electrode layer. 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 Ketjenblack (KB), and fibrous carbon materials such as vapor-processed carbon fiber (VGCF), carbon nanotubes (CNT), and carbon nanofibers (CNF).

[0030] The proportion of conductive material in the positive electrode layer may be, for example, 0.1% by mass or more. If the proportion of conductive material is too low, there may be insufficient electron conduction paths in the positive electrode layer. On the other hand, the proportion of conductive material in the positive electrode layer may be, for example, 5% by mass or less. If the proportion of conductive material is too high, the proportion of positive electrode active material will be relatively low, which may result in a lower energy density.

[0031] The positive electrode layer may contain a binder. Examples of binders 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).

[0032] The proportion of binder in the positive electrode layer may be, for example, 0.5 mass% or more. If the proportion of binder is too low, the increase in resistance due to charging and discharging may not be sufficiently reduced. On the other hand, the proportion of binder in the positive electrode layer may be, for example, 5 mass% or less. If the proportion of binder is too high, the proportion of positive electrode active material will be relatively low, which may result in a lower energy density.

[0033] The thickness of the positive electrode layer may be, for example, 0.1 μm or more and 1000 μm or less.

[0034] The method for manufacturing the positive electrode layer is not particularly limited, but for example, it may involve mixing the positive electrode mixture with a solvent to obtain a positive electrode slurry, coating the positive electrode slurry onto a positive electrode current collector, drying it, and forming a positive electrode layer. When forming the positive electrode layer, a pressing process may be performed to press the positive electrode layer in the thickness direction. Examples of pressing processes include roller pressing and flat plate pressing. Examples of solvents include tetralin, diisobutyl ketone, butyl butyrate, mesitylene, heptane, dibutyl ether, decane, dodecane, isodecane, and toluene, and may contain two or more of these components.

[0035] Examples of materials for the positive electrode current collector include SUS, Cr, Au, Pt, Zn, aluminum, copper, nickel, iron, titanium, and carbon. The thickness of the positive electrode current collector is, for example, 0.1 μm or more and 100 μm or less. The shape of the positive electrode current collector may be foil-like or plate-like. The planar shape of the positive electrode current collector is not particularly limited, but examples include circular, elliptical, rectangular, and any polygonal shape. The positive electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer on its surface.

[0036] [Negative electrode] The negative electrode has a negative electrode layer and, if necessary, further has a negative electrode current collector. The negative electrode layer is a layer containing at least a negative electrode active material. The negative electrode layer may also contain a negative electrode composite material comprising the solid electrolyte material and the negative electrode active material. Furthermore, the negative electrode layer may optionally contain at least one of a solid electrolyte, a conductive material, and a binder. Examples of negative electrode active materials include Si-based active materials, carbon-based active materials, oxide-based active materials, and Li-based active materials. Examples of Si-based active materials 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 two or more. An example of a Si oxide is SiO. An example of a Si carbide is SiC. Examples of carbon-based active materials include graphite, hard carbon, and soft carbon. Examples of oxide-based active materials include lithium titanate. Examples of lithium-based active materials include elemental lithium and lithium alloys. Other metallic elements contained in lithium alloys include Mg, Ag, In, Sn, Si, Ga, Au, and Pt. The conductive material and binder used in the negative electrode layer are the same as those described for the positive electrode layer above.

[0037] Examples of materials for the negative electrode current collector include SUS, aluminum, copper, nickel, iron, titanium, and carbon. The thickness of the negative electrode current collector varies depending on its shape, but may be in the range of, for example, 1 μm to 50 μm. The shape of the negative electrode current collector may be foil-like or plate-like. The planar shape of the negative electrode current collector is not particularly limited, but examples include circular, elliptical, rectangular, and any polygonal shape. The negative electrode current collector may have a buffer layer, an elastic layer, or a PTC thermistor layer on its surface.

[0038] [Electrolyte layer] The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and contains at least an electrolyte. The electrolyte may be a solid electrolyte (sometimes referred to as SE) or a liquid electrolyte (electrolyte solution). Non-aqueous electrolytes can be used as the electrolyte. One type of non-aqueous electrolyte may be used alone, or two or more types may be used in combination.

[0039] As a non-aqueous electrolyte, one containing a lithium salt and a non-aqueous solvent is typically used. 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. Examples of non-aqueous solvents include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl 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. The concentration of the lithium salt in the non-aqueous electrolyte may be, for example, 0.3 to 5 M.

[0040] The electrolyte layer may be impregnated with an electrolyte such as the aforementioned electrolyte solution, and a separator may be used to prevent contact between the positive electrode layer and the negative electrode layer. The material for the separator is not particularly limited as long as it is a porous membrane. Examples include polyethylene (PE), polypropylene (PP), polyester, polyvinyl alcohol, cellulose, and polyamide resins, with polyethylene and polypropylene being particularly preferred. The separator may have a single-layer structure or a multi-layer structure. Examples of multi-layer separators include a PE / PP two-layer separator, or a PP / PE / PP or PE / PP / PE three-layer separator. The separator may be made of nonwoven fabrics such as resin nonwoven fabric or glass fiber nonwoven fabric.

[0041] The electrolyte layer may be a solid electrolyte layer composed of solids. The solid electrolyte layer contains a solid electrolyte and, if necessary, a binder, etc. The solid electrolyte layer contains the sulfide solid electrolyte described in "A. Solid Electrolyte Material" above as the solid electrolyte. Solid electrolytes can be used individually or in combination of two or more types. When using two or more types of solid electrolytes, they may be mixed together, or two or more layers of solid electrolytes may be formed to create a multilayer structure. The proportion of solid electrolyte in the solid electrolyte layer is not particularly limited, but may be, for example, 50% by mass or more, or 100% by mass. The solid electrolyte layer may contain less than 10% by mass of electrolyte relative to the total amount of the solid electrolyte layer. Examples of binders include those that can be incorporated into the positive electrode layer as described above. The binder content in the solid electrolyte layer may be 0% to 10% by mass relative to the total amount of the solid electrolyte layer.

[0042] The thickness of the electrolyte layer may be, for example, 0.1 μm or more and 1000 μm or less.

[0043] The battery in this disclosure may further include a restraining jig that applies restraining pressure along the thickness direction to the positive electrode layer, electrolyte layer, and negative electrode layer. In particular, if the electrolyte layer is a solid electrolyte layer, restraining pressure may be applied to form good ion conduction paths and electron conduction paths. The restraining pressure may be, for example, 0.1 MPa or more. On the other hand, the restraining pressure may be, for example, 100 MPa or less.

[0044] [battery] The type of battery in this disclosure is not particularly limited, but is typically a lithium-ion battery. Furthermore, the battery in this disclosure may be a liquid battery in which the electrolyte layer contains an electrolyte solution, or a solid battery in which the electrolyte layer contains a solid electrolyte. The solid battery may be a semi-solid battery or a fully solid battery. In this disclosure, a semi-solid battery is a battery in which the electrolyte layer has a solid electrolyte and a liquid component (e.g., solvent and electrolyte solution). In this disclosure, a fully solid battery is a battery in which the electrolyte layer has only a solid electrolyte as the electrolyte. Furthermore, the battery in this disclosure may be a primary battery or a secondary battery, but is particularly favored as a secondary battery because it can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery. The shape of the battery is not particularly limited and may be, for example, coin-type, cylindrical, prismatic, sheet-type, button-type, flat-type, or stacked-type.

[0045] Applications of batteries include, for example, powering vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline cars, and diesel cars. In particular, they may be used as power sources for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). Batteries may also be used as power sources for mobile devices other than vehicles (e.g., trains, ships, aircraft), and as power sources for electrical products such as information processing devices. [Examples]

[0046] <Comparative Example 1> (Preparation of solid electrolyte materials) 3000 mg of mesitylene was placed in a propylene container, and 1000 mg of sulfide solid electrolyte particles were added to it. A slurry was obtained by stirring with an ultrasonic homogenizer. The slurry was placed in a petri dish, and then the mesitylene was removed by heating and drying to obtain a solid electrolyte material.

[0047] <Comparative Example 2> (Preparation of solid electrolyte materials) 3000 mg of mesitylene was placed in a propylene container, and 10 mg of 1,5-dimethylnaphthalene was added as an organic compound so that the ratio of the organic compound to the resulting solid electrolyte material was 0.58% by mass, and the mixture was dissolved. 1000 mg of sulfide solid electrolyte particles were then added, and the mixture was stirred with an ultrasonic homogenizer to obtain a slurry. The slurry was placed in a petri dish, and then the mesitylene was removed by heating and drying to obtain the solid electrolyte material.

[0048] <Comparative Example 3> A solid electrolyte material was obtained in the same manner as in Comparative Example 2, except that 20 mg of the organic compound was added so that the ratio of the organic compound to 100% by mass of the resulting solid electrolyte material was 1.42% by mass.

[0049] <Comparative Example 4> A solid electrolyte material was obtained in the same manner as in Comparative Example 2, except that 40 mg of the organic compound was added so that the ratio of the organic compound to 100% by mass of the resulting solid electrolyte material was 3.10% by mass.

[0050] <Comparative Example 5> A solid electrolyte material was obtained in the same manner as in Comparative Example 2, except that 60 mg of the organic compound was added so that the ratio of the organic compound to 100% by mass of the resulting solid electrolyte material was 4.53% by mass.

[0051] <Comparative Example 6> A solid electrolyte material was obtained in the same manner as in Comparative Example 2, except that 80 mg of the organic compound was added so that the proportion of the organic compound to 100% by mass of the resulting solid electrolyte material was 7.13% by mass.

[0052] <Example 1> (Preparation of solid electrolyte materials) 3000 mg of mesitylene was placed in a propylene container, and 10 mg of 1,5-dibromonaphthalene was added as an organic compound so that the ratio of the organic compound to the resulting solid electrolyte material was 0.38% by mass. 1000 mg of sulfide solid electrolyte particles were then added, and the mixture was stirred with an ultrasonic homogenizer to obtain a slurry. The slurry was placed in a petri dish, and then the mesitylene was removed by heating and drying to obtain the solid electrolyte material.

[0053] <Example 2> A solid electrolyte material was obtained in the same manner as in Example 1, except that 20 mg of the organic compound was added so that the ratio of the organic compound to 100% by mass of the resulting solid electrolyte material was 1.49% by mass.

[0054] <Example 3> A solid electrolyte material was obtained in the same manner as in Example 1, except that 30 mg of the organic compound was added so that the ratio of the organic compound to 100% by mass of the resulting solid electrolyte material was 2.26% by mass.

[0055] <Example 4> A solid electrolyte material was obtained in the same manner as in Example 1, except that 40 mg of the organic compound was added so that the ratio of the organic compound to 100% by mass of the resulting solid electrolyte material was 3.53% by mass.

[0056] <Example 5> A solid electrolyte material was obtained in the same manner as in Example 1, except that 60 mg of the organic compound was added so that the ratio of the organic compound to 100% by mass of the resulting solid electrolyte material was 5.37% by mass.

[0057] <Comparative Example 7> A solid electrolyte material was obtained in the same manner as in Example 1, except that 80 mg of the organic compound was added so that the ratio of the organic compound to 100% by mass of the resulting solid electrolyte material was 6.80% by mass.

[0058] <Thermogravimetry (TG)> For each solid electrolyte material obtained in Examples 1-5 and Comparative Examples 2-7, TG measurements were performed in an inert atmosphere at a heating rate of 5°C / min and an upper temperature limit of 300°C. From the obtained results, the mass loss of the solid electrolyte material at 200°C was defined as the content of the organic compound contained in the solid electrolyte material. From the content of the organic compound contained in the solid electrolyte material, the ratio of the organic compound to 100% by mass of the solid electrolyte material was calculated. The results are shown in Table 1.

[0059] <Measurement of ionic conductivity of solid electrolyte materials> A cylinder with a diameter of φ11.28 mm was used. 100 mg of each solid electrolyte material obtained in Examples 1-5 and Comparative Examples 1-7 was placed in the cylinder, and an evaluation cell was fabricated by sandwiching the layers of solid electrolyte material between SUS pins and press molding at 58.8 MPa. The ionic conductivity of the solid electrolyte material was calculated using the resistance value obtained from the AC impedance measured at 25°C, the thickness of the solid electrolyte material, and the area. The results are shown in Table 1. The ionic conductivity shown in Table 1 is a relative value with Comparative Example 1 set to 1.

[0060] <Measurement of filling density of solid electrolyte materials> 100 mg of each solid electrolyte material obtained in Examples 1-5 and Comparative Examples 1-7 was placed in a φ11.28 mm cylinder, the layers of solid electrolyte material were clamped between SUS pins, and pressed at 19.8 MPa. The volume of the solid electrolyte material after pressing was taken as the apparent volume of the solid electrolyte material. The ratio of the total volume of the raw materials (organic compounds and sulfide solid electrolytes) of the solid electrolyte material to the apparent volume of the solid electrolyte material was calculated as the packing rate using the following formula. The results are shown in Table 1. Packing rate = (Total volume of raw materials for solid electrolyte material ÷ Apparent volume of solid electrolyte material) × 100

[0061] [Table 1]

[0062] Figure 2 is a graph showing the relationship between the organic compound content and ionic conductivity of each solid electrolyte material obtained in Examples 1-5 and Comparative Examples 1-7. Examples 1-3 have higher ionic conductivity than Comparative Examples 2-7. Example 4 has higher ionic conductivity than Comparative Example 4, which contains a similar amount of organic compound. Example 5 has higher ionic conductivity than Comparative Example 5, which contains a similar amount of organic compound. The presence of halogen elements in organic compounds increases their intramolecular polarity. Examples in which the halogen-containing organic compound is present in 5.37% by mass or less show increased ionic conductivity compared to comparative examples containing a similar proportion of halogen-free organic compounds. Examples 1-5 have lower ionic conductivity than Comparative Example 1, but the presence of organic compounds is expected to suppress degradation associated with charging and discharging of the sulfide solid electrolyte and reduce resistance increase. In particular, Examples 1-2 have a higher packing density than Comparative Example 1, and are expected to have lower electrode layer resistance when used in the electrode layer than Comparative Example 1.

[0063] <Comparative Example 8> (Preparation of electrode composite material) Mesitylene was placed in a propylene container, and Si as the negative electrode active material, a sulfide solid electrolyte, and a conductive material were added in a ratio of 38 / 58 / 4 vol%. A slurry was obtained by stirring with an ultrasonic homogenizer. The slurry was placed in a petri dish, and then the mesitylene was removed by heating and drying to obtain an electrode mixture.

[0064] <Comparative Example 9> (Preparation of electrode composite material) Mesitylene was placed in a propylene container, and 1,5-dimethylnaphthalene was added as an organic compound so that the ratio of the organic compound to the resulting solid electrolyte material was 1% by mass. Si as the negative electrode active material, sulfide solid electrolyte, and conductive material were then added in 38 / 58 / 4 vol% proportions, and the mixture was stirred with an ultrasonic homogenizer to obtain a slurry. The slurry was placed in a petri dish, and then the mesitylene was removed by heating and drying to obtain an electrode mixture.

[0065] <Example 6> An electrode composite was obtained in the same manner as in Comparative Example 9, except that the organic compound was changed to 1,5-dibromonaphthalene.

[0066] <Measurement of ionic conductivity of electrode layers> Using 50 mg of each electrode mixture obtained in Example 6 and Comparative Examples 8-9, a cell was prepared using a φ11.28 mm cylinder, with the layers arranged in the following order: Li metal, sulfide solid electrolyte layer (100 mg sulfide solid electrolyte), electrode mixture (electrode layer), sulfide solid electrolyte layer (100 mg sulfide solid electrolyte), and Li metal. The ionic conductivity of the electrode layer was calculated by the DC method at 25°C. The results are shown in Table 2. The ionic conductivity shown in Table 2 is a relative value with Comparative Example 8 set to 1.

[0067] <Measurement of electrode layer filling density> 100 mg of each electrode mixture obtained in Example 6 and Comparative Examples 8-9 was placed in a φ11.28 mm cylinder, the resulting electrode layer was clamped between SUS pins, and pressed at 19.8 MPa. The volume of the electrode layer after pressing was taken as the apparent volume of the electrode layer. The packing efficiency, calculated as the ratio of the total volume of the electrode layer's raw materials (organic compound, sulfide solid electrolyte, Si as negative electrode active material, and conductive material) to the apparent volume of the electrode layer, was calculated using the following formula. The results are shown in Table 2. Electrode layer packing efficiency = (Total volume of raw materials before electrode layer fabrication ÷ Apparent volume of electrode layer) × 100

[0068] [Table 2]

[0069] Example 6 exhibits higher ionic conductivity than Comparative Example 9, which contains a similar amount of organic compound. Although Example 6 and Comparative Example 9 have lower ionic conductivity than Comparative Example 8, the presence of organic compounds results in a higher packing density, which is expected to reduce resistance by decreasing voids in the electrode layer. [Explanation of symbols]

[0070] 1 ... Positive electrode layer 2 ... Negative electrode layer 3 …electrolyte layer 4 …Positive current collector 5 … Negative current collector 10 … batteries

Claims

1. A solid electrolyte material containing a sulfide solid electrolyte containing lithium, sulfur, and phosphorus, and an organic compound, The aforementioned organic compound contains a halogen element and has two or more benzene rings. A solid electrolyte material in which the proportion of the organic compound to 100% by mass of the solid electrolyte material is 5.37% by mass or less.

2. The solid electrolyte material according to claim 1, wherein the proportion of the organic compound to 100% by mass of the solid electrolyte material is 2.26% by mass or less.

3. The solid electrolyte material according to claim 1, wherein the organic compound is at least one selected from the group consisting of 1,5-dibromonaphthalene, 1,5-difluoronaphthalene, 1,5-diiodonaphthalene, 1-bromo-2-iodonaphthalene, 2-bromo-1-iodonaphthalene, and 2,3-dibromonaphthalene.

4. The solid electrolyte material according to claim 1, wherein the organic compound is 1,5-dibromonaphthalene.

5. A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer, The battery includes an electrode composite material comprising a solid electrolyte material according to any one of claims 1 to 4 and an electrode active material in the positive electrode layer or the negative electrode layer. A battery in which at least a portion of the organic compound is present between the electrode active material and the sulfide solid electrolyte.

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