Solid electrolyte, and electrode mixture and battery including the same

Abstract

To provide a solid electrolyte having further excellent ion conductivity.SOLUTION: A solid electrolyte includes a lithium (Li) element, a phosphorus (P) element, a sulfur (S) element and an X element (X is at least one element selected from a chlorine (Cl) element, a bromine (Br) element and an iodine (I) element). The solid electrolyte has a peak attributed to the fluorine (F) element in a surface analysis by an X-ray photoelectron spectroscopy. Preferably, 0.01 to 0.34 is a ratio of a quantitative value (Atom%) of F1s and a quantitative value (Atom%) of P2p (the quantitative value of F1s / the quantitative value of P2p) calculated with a total amount of Li1s, C1s, O1s, F1s, P2p, S2p, Cl2p and Br3d as 100% by the X-ray photoelectron spectroscopy.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a solid electrolyte. The present invention also relates to an electrode mixture and a battery containing the solid electrolyte. [Background technology]

[0002] In recent years, solid electrolytes have been attracting attention as an alternative to the electrolytes used in many liquid batteries. Solid-state batteries using solid electrolytes are safer than liquid batteries that use flammable organic solvents, and are expected to be put to practical use as batteries with high energy density.

[0003] As a conventional technique related to solid electrolytes, for example, the technique described in Patent Document 1 is known. In recent years, research into such solid electrolytes has been actively conducted to obtain even better performance. For example, various studies have been conducted on solid electrolytes with high ionic conductivity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US2016 / 156064A1 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a solid electrolyte having superior ion conductivity. [Means for solving the problem]

[0006] The present invention relates to a compound semiconductor material comprising an element of lithium (Li), an element of phosphorus (P), an element of sulfur (S) and an element of X (X is at least one element selected from the group consisting of an element of chlorine (Cl), an element of bromine (Br) and an element of iodine (I)), The present invention provides a solid electrolyte having a peak attributable to fluorine (F) in surface analysis by X-ray photoelectron spectroscopy. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to its preferred embodiments. The solid electrolyte of the present invention contains at least lithium (Li), phosphorus (P), sulfur (S) and X elements.

[0008] The X element contained in the solid electrolyte of the present invention is a halogen element, more specifically, at least one element selected from chlorine (Cl), bromine (Br) and iodine (I) is used. The X element may be one of these elements or a combination of two or more of them. From the viewpoint of enhancing the lithium ion conductivity of the solid electrolyte of the present invention, the solid electrolyte preferably contains at least Cl element or Br element as the X element, and more preferably contains Br element and Cl element.

[0009] The solid electrolyte of the present invention containing the above-mentioned elements may be a crystalline compound. Alternatively, the solid electrolyte of the present invention may be a glassy compound. A crystalline compound is a substance in which a diffraction peak due to a crystalline phase is observed when measured by X-ray diffraction (hereinafter also referred to as "XRD").

[0010] The solid electrolyte of the present invention containing the above-mentioned elements has the composition formula Li a P.S. b X c (X is at least one halogen element; a is a number equal to or greater than 3.0 and equal to or less than 6.0; b is a number equal to or greater than 3.5 and equal to or less than 4.8; and c is a number equal to or greater than 0.1 and equal to or less than 3.0) is preferably contained in order to enhance the lithium ion conductivity of the solid electrolyte.

[0011] In the above composition formula, a, which indicates the molar ratio of Li element, is preferably, for example, a number of 3.0 or more and 6.0 or less, more preferably a number of 3.2 or more and 5.8 or less, and even more preferably a number of 3.4 or more and 5.4 or less. Note that a may be less than 5.4. In the above composition formula, b, which indicates the molar ratio of the S element, is preferably, for example, a number from 3.5 to 4.8, more preferably from 3.8 to 4.6, and even more preferably from 4.0 to 4.4. Note that b may be less than 4.4. In the above composition formula, c is, for example, preferably a number from 0.1 to 3.0, more preferably a number from 0.8 to 2.5, and even more preferably a number from 1.2 to 2.0. A compound in which a, b, and c fall within these ranges has sufficiently high lithium ion conductivity. The solid electrolyte of the present invention may contain only one type of compound represented by the above composition formula, or may contain two or more types of compound A.

[0012] In the present invention, the amount of Li a P.S. b X c The compound obtained in this way may contain elements other than Li, P, S, and halogen (X) elements. For example, it may be possible to replace a part of the Li element with another alkali metal element, to replace a part of the P element with another pnictogen element, or to replace a part of the S element with another chalcogen element.

[0013] The solid electrolyte of the present invention preferably contains a crystal phase having an argyrodite-type crystal structure, since this can enhance the lithium ion conductivity of the solid electrolyte. The argyrodite crystal structure is a crystal structure possessed by a group of compounds derived from a mineral represented by the chemical formula: Ag8GeS6. Whether or not the solid electrolyte of the present invention has a crystal phase of the argyrodite crystal structure can be confirmed by measurement using XRD. For example, in a diffraction pattern measured by XRD using CuKα1 radiation, the crystal phase of the argyrodite crystal structure shows characteristic diffraction peaks at 2θ=15.3°±1.0°, 17.7°±1.0°, 25.2°±1.0°, 30.0°±1.0°, 30.9°±1.0°, and 44.3°±1.0°. Depending on the elemental species constituting the solid electrolyte, in addition to the above diffraction peaks, characteristic diffraction peaks may be observed at 2θ=47.2°±1.0°, 51.7°±1.0°, 58.3°±1.0°, 60.7°±1.0°, 61.5°±1.0°, 70.4°±1.0°, and 72.6°±1.0°. For identification of the diffraction peaks derived from the argyrodite-type crystal structure, for example, the data of PDF No. 00-034-0688 can be used.

[0014] The solid electrolyte of the present invention is preferably made of a powder as an aggregate of particles. The particle size of the solid electrolyte of the present invention is measured by a volume cumulative particle size distribution measurement method using a laser diffraction scattering type particle size distribution measurement method. 50 The volume cumulative particle diameter D is preferably 2.0 μm or less, more preferably 1.8 μm or less, and particularly preferably 1.5 μm or less. 50 is preferably 0.45 μm or more, more preferably 0.50 μm or more, and particularly preferably 0.55 μm or more. By setting the particle size in this range, the contact points and contact area between the particles of the solid electrolyte are increased, and the lithium ion conductivity can be effectively improved.

[0015] The solid electrolyte of the present invention contains fluorine (F) element in addition to the above elements. Fluorine may be present as an element constituting the lithium ion conductive material constituting the solid electrolyte of the present invention, or may be present as an element constituting a material other than the material. In either case, fluorine is preferably contained in the surface region of the particles of the solid electrolyte of the present invention. In this specification, the "surface region" refers to the surface of the particles of the solid electrolyte and the area in the vicinity thereof. The present inventors have found that the presence of fluorine in the surface region of the particles of the solid electrolyte improves the ionic conductivity of the solid electrolyte as a whole. The reason for this is not clear at present, but the present inventors believe that the presence of fluorine in the surface region of the solid electrolyte increases the physical contact between the particles of the solid electrolyte, thereby improving the ionic conductivity.

[0016] Furthermore, the solid electrolyte of the present invention contains an X element (X is at least one element selected from chlorine (Cl), bromine (Br) and iodine (I). Both the X element and fluorine are group 17 elements and therefore tend to have a high affinity with each other. As a result, fluorine is easily adsorbed on the surface of the solid electrolyte, which acts to protect the surface and reduces the frequency of contact with moisture. As a result, it is presumed that this contributes to suppressing the decrease in ion conductivity.

[0017] In particular, when the solid electrolyte of the present invention is a crystalline compound, the solid electrolyte tends to have high hardness. Therefore, the physical contact between the particles of the solid electrolyte may be insufficient. In the present invention, it is presumed that the physical contact between the particles of the solid electrolyte can be sufficiently ensured by making fluorine exist in the surface region of the particles of the solid electrolyte, and as a result, the ion conductivity is improved. In particular, the crystal phase having an argyrodite type crystal structure has a higher hardness, and therefore the above-mentioned effect is more pronounced.

[0018] The presence of fluorine in the surface region of the solid electrolyte particles of the present invention can be confirmed by observing a peak attributable to fluorine (F) element in surface analysis by X-ray photoelectron spectroscopy (hereinafter also referred to as "XPS"). The measurement conditions of XPS will be described in the examples below.

[0019] In the present invention, it is sufficient that fluorine is present only in the surface region of the solid electrolyte particles, and it is not necessary that fluorine is present in the central region of the particles. Preferably, the absence of fluorine in the central region of the particles is advantageous from the viewpoint of further improving ion conductivity. When fluorine is present in the central region of the particles, it is advantageous from the viewpoint of further improving ion conductivity that the fluorine concentration in the central region is lower than the fluorine concentration in the surface region.

[0020] In the solid electrolyte of the present invention, the surface region of the particle refers to a region from the surface of the particle to a depth of less than 10 nm, which is a depth at which photoelectrons can be detected by XPS. On the other hand, the central region of the particle refers to a region located closer to the center of the particle than the surface region. The average fluorine concentration in the surface region and the central region of the particle can be measured by XPS.

[0021] In the solid electrolyte of the present invention, the form of fluorine present in the surface region of the particles is not particularly limited. In general, fluorine is preferably present in the form of a fluorine compound from the viewpoint of increasing the ionic conductivity of the solid electrolyte. In particular, fluorine is preferably present in the form of a fluoride solvent from the viewpoint of further increasing the ionic conductivity of the solid electrolyte.

[0022] The solvent for the fluoride may be a fluoride that is liquid at 20° C. Specific examples of the solvent include fluorine-containing chain hydrocarbons, fluorine-containing cyclic hydrocarbons, fluorine-containing alcohols, fluorine-containing ethers, fluorine-containing esters, and fluorine-containing ketones. The fluorine-containing chain hydrocarbons include chain alkanes in which some or all of the hydrogen atoms are substituted with fluorine. The fluorine-containing cyclic hydrocarbons include cyclic alkanes in which some or all of the hydrogen atoms are substituted with fluorine.

[0023] Examples of fluorine-containing ethers include alkyl fluoroalkyl ethers and difluoroalkyl ethers. From the viewpoint of further increasing the ionic conductivity of the solid electrolyte, alkyl fluoroalkyl ethers are preferred, and from the viewpoint of still further increasing the ionic conductivity of the solid electrolyte, alkyl perfluoroalkyl ethers are preferred. Examples of alkyl perfluoroalkyl ethers include methyl perfluorobutyl ether and ethyl perfluorobutyl ether.

[0024] Among the above-mentioned various solvents for fluorides, the preferred solvents are fluorine-containing ethers, from the viewpoint of further increasing the ionic conductivity of the solid electrolyte.

[0025] The amount of fluorine present in the surface region of the particles in the solid electrolyte of the present invention is preferably determined by a balance between the formation of a good conductive path due to the presence of fluorine and the ionic conductivity of the solid electrolyte itself. From this viewpoint, the amount of fluorine present in the surface region of the particles of the solid electrolyte is preferably such that the ratio of the quantitative value of F1s (Atom%) to the quantitative value of P2p (Atom%) calculated by X-ray photoelectron spectroscopy with the total amount of Li1s, C1s, O1s, F1s, P2p, S2p, Cl2p and Br3d as 100% (quantitative value of F1s / quantitative value of P2p) is 0.01 to 0.34, more preferably 0.01 to 0.25, and even more preferably 0.01 to 0.15. The quantitative value is calculated based on the sum of the peak areas derived from Li1s, C1s, O1s, F1s, P2p, S2p, Cl2p and Br3d observed by X-ray photoelectron spectroscopy.

[0026] From the same viewpoint as above, the amount of fluorine contained in the solid electrolyte of the present invention is preferably 0.1 atomic % or more and 5 atomic % or less, more preferably 0.1 atomic % or more and 3 atomic % or less, and even more preferably 0.1 atomic % or more and 1 atomic % or less, based on the total amount of the solid electrolyte.

[0027] Various methods can be used to make fluorine present on the surface of solid electrolyte particles. For example, a mixture containing solid electrolyte particles produced by a known method and a fluoride solvent can be subjected to wet grinding to make fluorine present on the surface produced by the wet grinding. Alternatively, fluorine can be made to exist on the surface of the particles by immersing solid electrolyte particles produced by a known method in a fluoride solvent. Alternatively, particles of a solid electrolyte produced by a known method can be subjected to plasma treatment in the presence of fluorine to cause fluorine to be present on the surfaces of the particles.

[0028] The solid electrolyte of the present invention is usually solid, but may contain a small amount of solvent depending on the manufacturing method. The amount of solvent contained in the solid electrolyte may be, for example, 5% by mass or less, 3% by mass or less, or 1% by mass or less. The amount of solvent contained in the solid electrolyte can be confirmed, for example, by ignition loss method.

[0029] The solid electrolyte of the present invention has lithium ion conductivity in a solid state. The solid electrolyte of the present invention preferably has a lithium ion conductivity of 0.5 mS / cm or more at room temperature, i.e., 25° C., and more preferably has a lithium ion conductivity of 1.0 mS / cm or more, and more preferably has a lithium ion conductivity of 1.5 mS / cm or more. The lithium ion conductivity can be measured using the method described in the Examples below.

[0030] The solid electrolyte of the present invention can be preferably manufactured by the method described below. A lithium source compound, a phosphorus source compound, a sulfur source compound, and a halogen source compound are used as raw materials. For example, lithium sulfide (Li2S) can be used as the lithium source compound. For example, diphosphorus pentasulfide (P2S5) can be used as the phosphorus source compound. When the lithium source compound and / or the phosphorus source compound is a sulfide, the sulfide can be used as the sulfur source compound. For the halogen source compound, compound B (LiX) can be used. These raw materials are mixed so that the lithium element, the phosphorus element, the sulfur element, and the halogen element are in a predetermined molar ratio. Then, the mixed raw materials are fired in an inert atmosphere or in an atmosphere containing hydrogen sulfide gas, thereby obtaining Li. a P.S. b X c A compound containing a crystal phase represented by the formula (I) and having an argyrodite crystal structure is obtained. The atmosphere containing hydrogen sulfide gas may be 100% hydrogen sulfide gas, or may be a mixed gas of hydrogen sulfide gas and an inert gas such as argon. The firing temperature is preferably, for example, 350° C. or higher and 550° C. or lower. The holding time at this temperature is preferably, for example, 0.5 hours or higher and 20 hours or lower.

[0031] The solid electrolyte thus obtained can be subjected to a predetermined pulverization process. The pulverization process can be performed by a wet or dry method. Various media mills can be used for the pulverization process. As the media mill, a ball mill, a bead mill, a paint shaker, a homogenizer, etc. can be used. As the dispersion media used in the media mill, balls and beads made of various ceramics including alumina and zirconia are used. The diameter of the dispersion media can be, for example, 0.1 mm or more and 50 mm or less.

[0032] When performing the grinding treatment by a wet method, it is preferable to use an organic solvent as a dispersion medium, since it can suppress the generation of hydrogen sulfide caused by the reaction between the solid electrolyte and water. Examples of the organic solvent include aromatic organic solvents such as toluene, xylene, benzene, and solvent naphtha, and aliphatic organic solvents such as heptane, decane, normal hexane, cyclohexane, and mineral spirits. These organic solvents can be used alone or in combination of two or more. In particular, by using the above-mentioned fluoride as the organic solvent, it is possible to make fluorine derived from the fluoride present on the surface generated by wet grinding.

[0033] The organic solvent and the solid electrolyte are mixed to form a slurry, and the slurry is subjected to wet pulverization. The concentration of the solid electrolyte contained in the slurry is preferably set to, for example, 5% by mass or more and 50% by mass or less, in order to successfully obtain a solid electrolyte with high lithium ion conductivity. In the wet pulverization using a media mill, the ratio of the dispersion medium to the slurry is preferably 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the slurry, in order to easily obtain a solid electrolyte with high lithium ion conductivity. The dispersion time by the media mill is generally preferably set to 0.5 hours or more and 60 hours or less, in order to easily obtain a solid electrolyte with high lithium ion conductivity.

[0034] The solid electrolyte of the present invention can be used as a material constituting a solid electrolyte layer, a positive electrode layer, or a negative electrode layer. Specifically, the solid electrolyte of the present invention can be used in a battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer. That is, the solid electrolyte can be used in a so-called solid battery. More specifically, it can be used in a lithium solid battery. The lithium solid battery may be a primary battery or a secondary battery. There is no particular restriction on the shape of the battery, and for example, a laminate type, a cylindrical type, a square type, or the like can be adopted. The term "solid battery" includes a solid battery that does not contain any liquid or gel substance as an electrolyte, as well as an embodiment that contains, for example, 50 mass % or less, 30 mass % or less, or 10 mass % or less of a liquid or gel substance as an electrolyte.

[0035] When the solid electrolyte layer contains the solid electrolyte of the present invention, the solid electrolyte layer can be produced by, for example, a method of dropping a slurry consisting of a solid electrolyte, a binder, and a solvent onto a substrate and scraping it off with a doctor blade or the like, a method of contacting the substrate with the slurry and then cutting it with an air knife, a method of forming a coating film by a screen printing method or the like and then removing the solvent by heating and drying, etc. Alternatively, the solid electrolyte can also be produced by forming a powdered solid electrolyte into a compressed powder by pressing or the like and then appropriately processing it. From the viewpoint of the balance between short circuit prevention and volumetric capacity density, the thickness of the solid electrolyte layer is typically preferably 5 μm or more and 300 μm or less, and more preferably 10 μm or more and 100 μm or less.

[0036] The solid electrolyte of the present invention is used together with an active material to form an electrode mixture. The ratio of the solid electrolyte in the electrode mixture is typically 10% by mass or more and 50% by mass or less. The electrode mixture may contain other materials such as a conductive assistant and a binder as necessary. The electrode mixture is mixed with a solvent to prepare a paste, which is then applied to a current collector such as aluminum foil and dried to prepare a positive electrode layer and a negative electrode layer.

[0037] As the positive electrode material constituting the positive electrode layer, a positive electrode material used as a positive electrode active material of a lithium ion battery can be appropriately used. For example, a positive electrode active material containing lithium, specifically, a spinel type lithium transition metal oxide and a lithium metal oxide having a layered structure, etc. can be mentioned. By using a high voltage positive electrode material as the positive electrode material, it is possible to improve the energy density. In addition to the positive electrode active material, the positive electrode material may contain a conductive material or other materials.

[0038] As the negative electrode material constituting the negative electrode layer, a negative electrode material used as a negative electrode active material in a lithium ion battery can be appropriately used. Since the solid electrolyte of the present invention is electrochemically stable, it can be used at a potential lower than lithium metal or a potential lower than lithium metal (about 0.1 V vs. Li + Carbonaceous materials such as graphite, artificial graphite, natural graphite, and non-graphitizable carbon (hard carbon), which are materials that are charged and discharged with a current of 0.1 wt. / Li, can be used as the negative electrode material. This can greatly improve the energy density of the solid-state battery. In addition, silicon or tin, which are promising high-capacity materials, can be used as the active material. In a battery using a general electrolyte, the electrolyte reacts with the active material during charging and discharging, causing corrosion on the active material surface, resulting in significant deterioration of the battery characteristics. In contrast to this, if the solid electrolyte of the present invention is used instead of the electrolyte and silicon or tin is used as the negative electrode active material, the above-mentioned corrosion reaction does not occur, and the durability of the battery can be improved. The negative electrode material may also contain a conductive material in addition to the negative electrode active material, or other materials. EXAMPLES

[0039] 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 such examples. Unless otherwise specified, "%" means "% by mass".

[0040] Example 1 (1) Preparation of solid electrolyte Li 5.4 P.S. 4.4 Cl 0.8 Br 0.8Li2S powder, P2S5 powder, LiCl powder, and LiBr powder were weighed out so as to obtain the composition. These powders were pulverized and mixed using a ball mill to obtain a mixed powder. The mixed powder was fired to obtain a fired product made of lithium ion conductive sulfide. The firing was performed using a tubular electric furnace. During the firing, 100% pure hydrogen sulfide gas was circulated through the electric furnace at 1.0 L / min. The firing temperature was set to 450°C, and firing was performed for 4 hours. As a result of XRD measurement, it was confirmed that this fired product had a crystal phase with an argyrodite crystal structure.

[0041] (2) Wet grinding of solid electrolyte The fired material was roughly crushed with a mortar and pestle, then crushed with a hammer crusher, and the crushed material was mixed with a solvent to form a slurry with a concentration of 10.8%. A mixture of ethyl nonafluorobutyl ether and ethyl nonafluoroisobutyl ether was used as the solvent. This slurry was subjected to wet grinding in a planetary ball mill (zirconia beads with a diameter of 0.8 mm). Wet grinding was performed for 1 hour using 30 parts by volume of beads (bead volume calculated from the packing density) per 100 parts by volume of the grinding container. After wet grinding, the slurry was separated into solid and liquid, and the solid content was dried. Drying was performed at 150°C for 20 minutes under a vacuum of -0.09 MPa relative to atmospheric pressure. The fired material after drying was sieved with a sieve with an opening of 53 μm to obtain the desired solid electrolyte.

[0042] Example 2 In the wet grinding of Example 1, a mixture of methyl nonafluorobutyl ether and methyl nonafluoroisobutyl ether was used as a solvent to prepare a slurry with a concentration of 10.3%. Except for this, the same procedure as in Example 1 was carried out to obtain the target solid electrolyte.

[0043] Comparative Example 1 In the wet grinding of Example 1, toluene was used as a solvent to prepare a slurry with a concentration of 16.7%. Except for this, the same procedure as in Example 1 was carried out to obtain the intended solid electrolyte.

[0044] 〔evaluation〕 The solid electrolytes obtained in the examples and comparative examples were subjected to XPS measurement by the method described below. 50 The results are shown in Table 1.

[0045] [XPS] The solid electrolyte after wet grinding was dried under the above-mentioned conditions, and then the particle surface of the solid electrolyte was analyzed using VersaProbeIII manufactured by ULVAC-PHI, Inc. The measurement conditions were as follows: Excitation X-ray: Monochromatic Al line (1486.7 eV) Output: 50W Acceleration voltage: 15 kV X-ray irradiation diameter: 200μmφ Measurement area: 1000μm x 300μm Take Angle: 45° Pass energy: 26.0 eV Energy step: 0.1 eV

[0046] The XPS data was analyzed using data analysis software (ULVAC-PHI "Multipack Ver. 9.0"). The background mode used was Iterated Shirley. The orbitals used for calculations were determined for each element as shown below. Li:1s C:1s O:1s F:1s P:2p S:2p Cl:2p Br:3d

[0047] [Particle size D 50 〕 Using an automatic sample feeder for laser diffraction particle size distribution measurement equipment (Microtrac SDC manufactured by Microtrac-Bell, Inc.), the solid electrolyte was put into toluene, and after irradiating it with 30W ultrasonic waves for 60 seconds at a flow rate of 50%, the particle size distribution was measured using a laser diffraction particle size distribution measurement equipment MT3000II manufactured by Microtrac-Bell, Inc. The particle size D was calculated from the obtained volumetric particle size distribution chart. 50 was measured.

[0048] [Lithium ion conductivity] The solid electrolyte was uniaxially pressed in a glove box filled with sufficiently dried Ar gas (dew point -60°C or less). It was further pressed at 200 MPa using a cold isostatic press to produce a pellet with a diameter of 10 mm and a thickness of about 4 to 5 mm. Carbon paste was applied to the top and bottom surfaces of the pellet as electrodes, and then heat treatment was performed at 180°C for 30 minutes to produce a sample for measuring ion conductivity. The lithium ion conductivity of the sample was measured using a Solartron 1255B manufactured by Toyo Corporation. The measurement was performed by an AC impedance method at a temperature of 25°C and a frequency of 0.1 Hz to 1 MHz.

[0049] [Table 1]

[0050] As is clear from the results shown in Table 1, in the solid electrolyte obtained in each Example, a peak attributed to fluorine was observed in the surface analysis by XPS, and as a result, the lithium ion conductivity was higher than that of the solid electrolyte of the comparative example. [Industrial Applicability]

[0051] According to the present invention, a solid electrolyte having higher ionic conductivity than ever before is provided.

Claims

1. A solid electrolyte containing lithium (Li), phosphorus (P), sulfur (S), and X (X is at least one element selected from chlorine (Cl), bromine (Br), and iodine (I), having a peak attributable to fluorine (F) in surface analysis by X-ray photoelectron spectroscopy; A solid electrolyte, wherein the amount of fluorine contained in the solid electrolyte is 0.1 atomic weight % or more and 5 atomic weight % or less with respect to the total amount of the solid electrolyte.

2. A solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), and X (X is at least one element selected from chlorine (Cl), bromine (Br), and iodine (I), having a peak attributable to fluorine (F) in surface analysis by X-ray photoelectron spectroscopy; A solid electrolyte, wherein the ratio of a quantitative value (Atom %) of F1s to a quantitative value (Atom %) of P2p, calculated by X-ray photoelectron spectroscopy with the total amount of Li1s, C1s, O1s, F1s, P2p, S2p, Cl2p, and Br3d defined as 100%, (quantitative value of F1s / quantitative value of P2p) is 0.01 or more and 0.34 or less.

3. 3. The solid electrolyte of claim 1, further comprising a fluoride solvent.

4. 2. The solid electrolyte according to claim 1, wherein the ratio of the quantitative value (Atom%) of F1s to the quantitative value (Atom%) of P2p calculated by X-ray photoelectron spectroscopy, where the total amount of Li1s, C1s, O1s, F1s, P2p, S2p, Cl2p, and Br3d is set to 100%, (quantitative value of F1s / quantitative value of P2p) is 0.01 or more and 0.34 or less.

5. 5. The solid electrolyte according to claim 1, comprising a crystalline phase having an argyrodite-type crystal structure.

6. An electrode mixture comprising the solid electrolyte according to claim 1 and an active material.

7. A battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, the battery containing the solid electrolyte according to claim 1 .