Solid electrolyte, electrode binder containing the same, and battery

Abstract

This solid electrolyte contains: elemental lithium (Li); elemental phosphorus (P); elemental sulfur (S); and an element X (X being at least one selected from elemental chlorine (Cl), elemental bromine (Br), and elemental iodine (I)). The solid electrolyte has a peak belonging to elemental fluorine (F), in surface analysis by X-ray photoelectron spectroscopy. It is preferable for the ratio (quantitative value of F1s / quantitative value of P2p) of the quantitative value of F1s (Atom%) and the quantitative value of P2p (Atom%), calculated by X-ray photoelectron spectroscopy where the total amount of Li1s, C1s, O1s, F1s, P2p, S2p, Cl2p, and Br3d is 100%, to be 0.01 to 0.34.

Description

Technical Field

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

Background Art

[0002] In recent years, solid electrolytes have attracted attention as an alternative to electrolytes used in many liquid batteries. A solid battery using a solid electrolyte is expected to be put into practical use as a battery with higher safety than a liquid battery using a flammable organic solvent and further having a high energy density.

[0003] As a conventional technique related to a solid electrolyte, for example, the one described in Patent Document 1 is known. Regarding such solid electrolytes, in recent years, research for obtaining more excellent performance has been active. For example, various studies have been made on solid electrolytes having high ionic conductivity.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] An object of the present invention is to provide a solid electrolyte having more excellent ionic conductivity.

[0006] The present invention 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.), and provides a solid electrolyte having a peak attributed to a fluorine (F) element in surface analysis by X-ray photoelectron spectroscopy.

Modes for Carrying Out the Invention

[0007] The present invention will be described based on its preferred embodiments. The solid electrolyte of the present invention contains at least lithium (Li) element, phosphorus (P) element, sulfur (S) element, and X element.

[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) element, bromine (Br) element, and iodine (I) element is used. The X element may be one of these elements, or may be 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, it is preferable that the solid electrolyte contains at least Cl element or Br element as the X element, and it is more preferable to contain both Br element and Cl element.

[0009] The solid electrolyte of the present invention containing the above-described 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 diffraction peaks attributable to a crystal phase are observed when measurement is performed by an X-ray diffraction method (hereinafter also referred to as "XRD").

[0010] The solid electrolyte of the present invention containing the above-described elements has a composition formula Li a PS b X c (X is at least one halogen element. a represents a number of 3.0 or more and 6.0 or less. b represents a number of 3.5 or more and 4.8 or less. c represents a number of 0.1 or more and 3.0 or less.) It is preferable from the viewpoint of enhancing the lithium ion conductivity of the solid electrolyte to contain a compound represented by.

[0011] In the above composition formula, a indicating the molar ratio of the 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 compositional formula, b representing the molar ratio of the S element is preferably, for example, a number of 3.5 or more and 4.8 or less, more preferably a number of 3.8 or more and 4.6 or less, and still more preferably a number of 4.0 or more and 4.4 or less. Note that b may be less than 4.4. In the above compositional formula, c is preferably, for example, a number of 0.1 or more and 3.0 or less, more preferably a number of 0.8 or more and 2.5 or less, and still more preferably a number of 1.2 or more and 2.0 or less. Compounds in which a, b, and c are within this range will have a sufficiently high lithium ion conductivity. In the solid electrolyte of the present invention, there may be a case where only one kind of the compound represented by the above compositional formula is contained, or there may be a case where two or more kinds of compounds A are contained.

[0012] In the present invention, the charged amount is Li a PS b X c The compound obtained so as to be may contain elements other than the Li element, P element, S element, and halogen (X) element. For example, a part of the Li element may be replaced with another alkali metal element, a part of the P element may be replaced with another pnictogen element, or a part of the S element may be replaced with another chalcogen element.

[0013] It is preferable that the solid electrolyte of the present invention contains a crystal phase having a particularly argyrodite-type crystal structure from the viewpoint of enhancing the lithium ion conductivity of the solid electrolyte. The argyrodite-type crystal structure is a crystal structure possessed by a group of compounds derived from minerals represented by the chemical formula: Ag8GeS6. Whether the solid electrolyte of the present invention has a crystal phase of the argyrodite-type crystal structure can be confirmed by measurement using XRD or the like. For example, in the diffraction pattern measured by XRD using CuKα1 radiation, the crystal phase of the argyrodite-type 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°. Further, depending on the elemental species constituting the solid electrolyte, in addition to the above diffraction peaks, there may be cases where characteristic diffraction peaks are shown 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 the 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 preferably consists of powder as an aggregate of particles. The particle size of the solid electrolyte of the present invention, represented by the volume median diameter D at a cumulative volume of 50% by volume measured by the laser diffraction scattering particle size distribution measurement method 50 is, for example, preferably 2.0 μm or less, more preferably 1.8 μm or less, and particularly preferably 1.5 μm or less. On the other hand, the volume median diameter D 50 is, for example, 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 within this range, the contact points and contact areas between the particles of the solid electrolyte increase, and the improvement of lithium ion conductivity can be effectively achieved.

[0015] The solid electrolyte of the present invention contains a fluorine (F) element in addition to the above-described elements. Fluorine may exist as an element constituting a lithium-ion conductive substance that constitutes the solid electrolyte of the present invention, or may exist as an element constituting a substance different from the said substance. In any case, it is preferable that fluorine is contained in the surface region in 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 sites in the vicinity thereof. As a result of the inventor's study, it has been found that the presence of fluorine in the surface region of the particles of the solid electrolyte improves the ionic conductivity of the entire solid electrolyte. Although the reason for this is not clear at present, the inventor believes 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 element X (X is at least one element selected from the group consisting of a chlorine (Cl) element, a bromine (Br) element, and an iodine (I) element).) Since both the element X and fluorine are Group 17 elements, they tend to have a high affinity, and fluorine is likely to adsorb on the surface of the solid electrolyte, thereby exerting an action of protecting the surface and reducing the frequency of contact with moisture. As a result, it is presumed that it contributes to suppressing the decrease in ionic conductivity.

[0017] In particular, when the solid electrolyte of the present invention is a crystalline compound, the solid electrolyte tends to have a high hardness. Therefore, the physical contact between the particles of the solid electrolyte may be insufficient. In the present invention, by causing fluorine to exist in the surface region of the particles of the solid electrolyte, it is possible to sufficiently ensure the physical contact between the particles of the solid electrolyte, and as a result, it is presumed that the ionic conductivity is improved. Especially, when the crystal phase has an alluaudite-type crystal structure, the above effect becomes remarkable because its hardness is even higher.

[0018] The presence of fluorine in the surface region of the particles of the solid electrolyte of the present invention can be confirmed by observing a peak attributed to the 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 particles of the solid electrolyte, and it is not necessary for fluorine to be 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 ionic conductivity. When fluorine is present in the central region of the particles, it is advantageous from the viewpoint of further improving ionic conductivity that the concentration of fluorine in the central region is lower than the concentration of fluorine in the surface region.

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

[0021] There is no particular limitation on the form of existence of fluorine present in the surface region of the particles in the solid electrolyte of the present invention. Generally, it is preferable from the viewpoint of enhancing the ionic conductivity of the solid electrolyte that fluorine exists in the form of a fluorine compound. In particular, it is preferable from the viewpoint of further enhancing the ionic conductivity of the solid electrolyte that fluorine exists in the form of a fluoride solvent.

[0022] Examples of the fluoride solvent include fluorides that are liquid at 20°C. Specifically, fluorine-containing chain hydrocarbons, fluorine-containing cyclic hydrocarbons, fluorine-containing alcohols, fluorine-containing ethers, fluorine-containing esters, and fluorine-containing ketones can be mentioned. Examples of the fluorine-containing chain hydrocarbons include chain alkanes in which some or all of the hydrogen atoms are substituted with fluorine. Examples of the fluorine-containing cyclic hydrocarbons include cyclic alkanes in which some or all of the hydrogen atoms are substituted with fluorine.

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

[0024] Among the solvents of the above various fluorides, particularly, the solvent preferred from the viewpoint of further enhancing the ionic conductivity of the solid electrolyte is fluorine-containing ether.

[0025] In the solid electrolyte of the present invention, the amount of fluorine present in the surface region of the particles is preferably determined by the 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 (quantitative value of F1s / quantitative value of P2p) of the quantitative value of F1s (Atom%) to the quantitative value of P2p (Atom%) calculated with the total amount of Li1s, C1s, O1s, F1s, P2p, S2p, Cl2p and Br3d being 100% by X-ray photoelectron spectroscopy is 0.01 or more and 0.34 or less, more preferably 0.01 or more and 0.25 or less, and still more preferably 0.01 or more and 0.15 or less. The above quantitative value is calculated based on the total peak area 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 weight% or more and 5 atomic weight% or less, more preferably 0.1 atomic weight% or more and 3 atomic weight% or less, and still more preferably 0.1 atomic weight% or more and 1 atomic weight% or less with respect to the total amount of the solid electrolyte.

[0027] Various methods can be employed to introduce fluorine onto the surface of solid electrolyte particles. For example, a mixed solution containing solid electrolyte particles produced by a known method and a fluoride solvent can be subjected to wet grinding, thereby introducing fluorine onto the surface generated by the wet grinding. Alternatively, solid electrolyte particles produced by a known method can be immersed in a fluoride solvent to introduce fluorine onto the surface of the particles. Alternatively, solid electrolyte particles produced by a known method can be subjected to plasma treatment in the presence of fluorine to introduce fluorine onto the surface of the particles.

[0028] The solid electrolyte of the present invention is usually solid, but may contain a small amount of solvent depending on its 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 the loss on ignition method.

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

[0030] The solid electrolyte of the present invention can preferably be produced by the method described below. As raw materials, a lithium source compound, a phosphorus source compound, a sulfur source compound, and a halogen source compound are used. As the lithium source compound, for example, lithium sulfide (Li2S) can be used. As the phosphorus source compound, for example, diphosphorus pentasulfide (P2S5) can be used. When the lithium source compound and / or the phosphorus source compound is a sulfide as the sulfur source compound, the sulfide can be used as the sulfur source compound. As the halogen source compound, compound B (LiX) can be used. These raw materials are mixed so that the lithium element, phosphorus element, sulfur element, and halogen element have a predetermined molar ratio. Then, the mixed raw materials are fired in an inert atmosphere or fired in an atmosphere containing hydrogen sulfide gas to obtain a compound represented by Li a PS b X c and containing a crystal phase having an argyrodite-type crystal structure. The atmosphere containing hydrogen sulfide gas may be 100% hydrogen sulfide gas, or 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 longer and 20 hours or shorter.

[0031] The solid electrolyte thus obtained can be subjected to a predetermined grinding treatment. The grinding treatment can be performed wet or dry. Various media mills can be used for the grinding treatment. 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, various ceramics balls and beads such as 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 wet grinding, it is preferable to use an organic solvent as the dispersion medium because 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 spirit. These organic solvents can be used alone or in combination of two or more. Particularly, by using the above-mentioned fluoride as the organic solvent, fluorine derived from the fluoride can be present on the surface generated by wet grinding.

[0033] The organic solvent and the solid electrolyte are mixed to form a slurry, and this slurry is subjected to wet grinding. The concentration of the solid electrolyte contained in the slurry is preferably set, for example, at 5% by mass or more and 50% by mass or less from the viewpoint of successfully obtaining a solid electrolyte with high lithium ion conductivity. In wet grinding using a media mill, the ratio of the dispersion medium to the slurry is preferably such that 5 parts by mass or more and 50 parts by mass or less of the dispersion medium is used with respect to 100 parts by mass of the slurry, from the viewpoint of easily obtaining a solid electrolyte with high lithium ion conductivity. The dispersion time by the media mill is generally preferably set at 0.5 hour or more and 60 hours or less, from the viewpoint of easily obtaining 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 limitation on the shape of the battery, and for example, shapes such as laminate type, cylindrical type, and rectangular type can be adopted. The "solid battery" includes not only a solid battery that does not contain any liquid substance or gel substance as an electrolyte, but also, for example, a mode in which a liquid substance or gel substance of 50% by mass or less, 30% by mass or less, or 10% by mass or less is contained as an electrolyte.

[0035] When the solid electrolyte of the present invention is contained in the solid electrolyte layer, the solid electrolyte layer can be produced, for example, by dropping a slurry composed of a solid electrolyte, a binder, and a solvent onto a substrate and scraping it with a doctor blade or the like, a method of cutting with an air knife after bringing the substrate into contact with the slurry, a method of forming a coating film by screen printing or the like, and then removing the solvent through heat drying. Alternatively, it can also be produced by pressing a powdery solid electrolyte into a compact by pressing or the like and then appropriately processing it. The thickness of the solid electrolyte layer is preferably typically 5 μm or more and 300 μm or less, and more preferably 10 μm or more and 100 μm or less, in view of the balance between short-circuit prevention and volumetric capacity density.

[0036] The solid electrolyte of the present invention is also used with an active material to constitute an electrode binder. The proportion of the solid electrolyte in the electrode binder is typically 10% by mass or more and 50% by mass or less. The electrode binder may contain other materials such as a conductive aid and a binder as required. The positive electrode layer and the negative electrode layer can be produced by mixing the electrode binder and a solvent to prepare a paste, applying it onto a current collector such as an aluminum foil, and drying it.

[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, a lithium metal oxide having a layered structure, and the like can be mentioned. By using a high-voltage positive electrode material as the positive electrode material, the energy density can be improved. The positive electrode material may contain a conductive material in addition to the positive electrode active material, or may contain other materials.

[0038] As the negative electrode material constituting the negative electrode layer, a negative electrode material used as a negative electrode active material of a lithium ion battery can be appropriately used. Since the solid electrolyte of the present invention is electrochemically stable, carbon-based materials such as graphite, artificial graphite, natural graphite, and non-graphitizable carbon (hard carbon), which are materials that charge and discharge at a low potential (about 0.1 V vs. Li + / Li) comparable to lithium metal or lithium metal, can be used as the negative electrode material. Thereby, the energy density of the solid battery can be greatly improved. Also, silicon or tin, which is promising as a high-capacity material, can be used as the active material. In a battery using a general electrolyte solution, the electrolyte solution reacts with the active material during charge and discharge, and the battery characteristics deteriorate significantly due to corrosion occurring on the surface of the active material. In contrast, when the solid electrolyte of the present invention is used instead of the electrolyte solution and silicon or tin is used as the negative electrode active material, the above-described corrosion reaction does not occur, so that the durability of the battery can be improved. Regarding the negative electrode material, a conductive material may be included in addition to the negative electrode active material, or other materials may be included.

Example

[0039] Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “mass%”.

[0040] 〔Example 1〕 (1) Preparation of solid electrolyte Li 5.4 PS 4.4 Cl 0.8 Br 0.8Li2S powder, P2S5 powder, LiCl powder, and LiBr powder were weighed so as to have the following 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 composed of a lithium ion conductive sulfide. The firing was carried out using a tubular electric furnace. During the firing, hydrogen sulfide gas with a purity of 100% was circulated through the electric furnace at a rate of 1.0 L / min. The firing temperature was set at 450 °C and the firing was carried out for 4 hours. As a result of XRD measurement, it was confirmed that this fired product had a crystal phase with an argyrodite-type crystal structure.

[0041] (2) Wet pulverization of the solid electrolyte After the fired product was roughly pulverized with a mortar and pestle, it was pulverized with a hammer crusher, and the pulverized product was mixed with a solvent to form a slurry with a concentration of 10.8%. As the solvent, a mixture of ethyl nonafluorobutyl ether and ethyl nonafluoroisobutyl ether was used. This slurry was subjected to wet pulverization using a planetary ball mill apparatus (zirconia beads with a diameter of 0.8 mm). 30 parts by volume of beads (the bead volume was calculated from the packing density) were used for 100 parts by volume of the pulverization container, and wet pulverization was carried out for 1 hour. After wet pulverization, the slurry was subjected to solid-liquid separation, and the solid content was dried. The drying was carried out at 150 °C for 20 minutes under a vacuum of -0.09 MPa with respect to atmospheric pressure. The fired product after drying was sieved through a sieve with an opening of 53 μm to obtain the target solid electrolyte.

[0042] 〔Example 2〕 In the wet pulverization of Example 1, a mixture of methyl nonafluorobutyl ether and methyl nonafluoroisobutyl ether was used as the solvent to form a slurry with a concentration of 10.3%. Otherwise, the target solid electrolyte was obtained in the same manner as in Example 1.

[0043] 〔Comparative Example 1〕 In the wet pulverization of Example 1, toluene was used as the solvent to form a slurry with a concentration of 16.7%. Otherwise, the target solid electrolyte was obtained in the same manner as in Example 1.

[0044] 〔Evaluation〕 For the solid electrolytes obtained in the examples and comparative examples, XPS measurements were carried out by the method described below. Also, the particle size D 50 and the lithium ion conductivity were measured. The results are shown in Table 1.

[0045] 〔XPS〕 After drying the solid electrolyte after wet grinding under the above conditions, surface analysis of the solid electrolyte particles was performed using VersaProbeIII manufactured by ULVAC-PHI, Inc. The conditions used for the measurement are as follows. Excitation X-ray: Monochromatic Al line (1486.7 eV) Output: 50 W Acceleration voltage: 15 kV X-ray irradiation diameter: 200 μmφ Measurement area: 1000 μm × 300 μm Take of Angle: 45° Pass energy: 26.0 eV Energy step: 0.1 eV

[0046] XPS data was analyzed using data analysis software (MultiPak Ver9.0 manufactured by ULVAC-PHI, Inc.). The background mode used was Iterated Shirley. Next, the orbitals used in the calculation 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 a laser diffraction particle size distribution measuring device (Microtrac SDC manufactured by Microtrac Bell Co., Ltd.), a solid electrolyte was put into toluene, and ultrasonic waves of 30 W were irradiated multiple times for 60 seconds at a flow rate of 50%. After that, the particle size distribution was measured using a laser diffraction particle size distribution measuring machine "MT3000II" manufactured by Microtrac Bell Co., Ltd. From the chart of the obtained volume-based particle size distribution, the particle size D 50 was measured.

[0048] 〔Lithium Ion Conductivity〕 The solid electrolyte was uniaxially pressure-molded in a glove box replaced with sufficiently dried Ar gas (dew point -60°C or lower). Further, it was molded at 200 MPa using a cold isostatic pressing device to produce pellets with a diameter of 10 mm and a thickness of about 4 mm to 5 mm. After applying carbon paste as an electrode on both upper and lower surfaces of the pellet, 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 Solatron 1255B of Toyo Technica Co., Ltd. The measurement was performed by the alternating current impedance method under the conditions of 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 electrolytes obtained in each example, peaks attributed to fluorine were 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 ion conductivity than ever is provided.

Claims

1. Lithium (Li) element, phosphorus (P) element, sulfur (S) element, and X element (X is at least one element selected from chlorine (Cl) element, bromine (Br) element, and iodine (I) element), and a fluorine-containing ether, fluorine (F) element exists only in the surface region of particles containing the lithium (Li) element, phosphorus (P) element, sulfur (S) element, and X element (X is at least one element selected from chlorine (Cl) element, bromine (Br) element, and iodine (I) element), and fluorine (F) element does not exist in the central region of the particles, the surface region is a region with a depth of less than 10 nm from the surface of the particles, and the central region is a region located closer to the center of the particles than the surface region, including a crystal phase having an argyrodite-type crystal structure, a solid electrolyte having a peak attributed to fluorine (F) element in surface analysis by X-ray photoelectron spectroscopy.

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

3. An electrode binder containing the solid electrolyte according to Claim 1 or 2 and an active material.

4. 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 or 2.

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