Modified sulfide solid electrolyte and method for producing same

Abstract

Provided are: a modified sulfide solid electrolyte which has excellent coating applicability when being coated in the form of a paste and can exhibit battery performance having excellent efficiency even when a sulfide solid electrolyte having a large specific surface area is used, the modified sulfide solid electrolyte comprising a sulfide solid electrolyte having a BET specific surface area of 10 m2 / g or more and containing a lithium atom, a sulfur atom, a phosphorus atom and a halogen atom and an epoxy compound, and the modified sulfide solid electrolyte having a peak in a region of 2800 to 3000 cm-1 in an infrared ray absorption spectrum obtained by a FT-IR analysis (ATR method); and a method for producing the modified sulfide solid electrolyte.

Description

[Technical Field]

[0001] The present invention relates to a modified sulfide solid electrolyte and a method for producing the same. [Background technology]

[0002] With the recent rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as power sources for these devices has become increasingly important. Among these, lithium-ion batteries have attracted attention due to their high energy density. Conventionally, batteries used for such applications have used electrolytes containing flammable organic solvents, which necessitates the installation of safety devices to suppress temperature rises during short circuits, as well as improvements in the structure and materials to prevent short circuits.In response to this, development is underway to replace the electrolyte with a solid electrolyte and make the battery all-solid, which eliminates the use of flammable organic solvents in the battery, simplifies the safety devices, and is superior in terms of manufacturing cost and productivity.

[0003] Sulfide solid electrolytes have been known as solid electrolytes used in solid electrolyte layers, and the primary goal of sulfide solid electrolytes is to improve their ionic conductivity. For example, in order to improve ionic conductivity, a method for producing a composite solid electrolyte has been proposed in which the surface of a sulfide-based solid electrolyte is coated with a predetermined halogenated hydrocarbon compound as a coating material (see, for example, Patent Document 1). As a surface coating technique, for example, Patent Document 2 discloses a solid electrolyte composition in which a coating film is formed on the surface of a sulfide solid electrolyte with a compound having a C═O bond or a compound having an S═O bond, in order to enhance the affinity between the active material used in the negative electrode, positive electrode, etc., when manufacturing a lithium-ion battery and the sulfide solid electrolyte, thereby improving cycle characteristics. Patent Document 3 also discloses that in a sulfide solid electrolyte containing lithium, phosphorus, and sulfur, and also containing an ester compound of a carboxylic acid and an alcohol, the ester compound is bound or adsorbed to the surface of the conductive sulfide, thereby improving the cycle characteristics of the solid battery. It also discloses that the sulfide solid electrolyte can be obtained by a manufacturing method including a step of wet-pulverizing a slurry containing a lithium-ion conductive sulfide, an organic solvent, and an ester compound. Thus, in recent years, toward the practical application of lithium-ion batteries, there has been a diversification of demands for not only simply improving the ionic conductivity of the sulfide solid electrolyte itself, but also for other performance improvements. To address these demands, surface coating techniques have been applied. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-87633 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-147173 [Patent Document 3] International Publication No. 2020 / 203231 Brochure Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and aims to provide a modified sulfide solid electrolyte and a method for producing the same, which have excellent applicability when applied as a paste and can efficiently exhibit excellent battery performance, even for sulfide solid electrolytes with a large specific surface area. Another aim of the present invention is to provide an electrode composite and a lithium-ion battery that exhibit excellent battery performance. [Means for solving the problem]

[0006] The modified sulfide solid electrolyte according to the present invention comprises: BET specific surface area is 10m 2 / g or more, and comprising a sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and an epoxy compound; In the infrared absorption spectrum by FT-IR analysis (ATR method), -1 modified sulfide solid electrolyte with a peak at is. Further, the method for producing a modified sulfide solid electrolyte according to the present invention includes the steps of: BET specific surface area is 10m 2 / g or more and containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, an epoxy compound, and an organic solvent; removing the organic solvent. is.

[0007] The modified sulfide solid electrolyte according to the present invention comprises: BET specific surface area is 10m 2 / g or more, and comprising a sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and an epoxy compound, modified sulfide solid electrolyte, is.

[0008] The electrode mixture according to the present invention is An electrode mixture comprising the modified sulfide solid electrolyte according to the present invention and an electrode active material; is. The lithium ion battery according to the present invention is A lithium ion battery comprising at least one of the modified sulfide solid electrolyte according to the present invention and the electrode composite according to the present invention; is. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a modified sulfide solid electrolyte and a method for producing the same that have excellent applicability when applied as a paste and can efficiently exhibit excellent battery performance. Furthermore, according to the present invention, it is possible to provide an electrode composite and a lithium ion battery that exhibit excellent battery performance. [Brief explanation of the drawings]

[0010] [Figure 1] 1 shows CV curves of the modified sulfide solid electrolytes of Examples 23 and 24 and the sulfide solid electrolyte of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") will be described. In this specification, the upper and lower limit values ​​of a range of values ​​expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values ​​in the examples can also be used as the upper and lower limit values.

[0012] (Findings gained by the inventors to arrive at the present invention) As a result of extensive research aimed at solving the above problems, the present inventors have discovered the following and have completed the present invention. There have been existing techniques for coating the surface of a sulfide solid electrolyte with some kind of compound, as described in Patent Documents 1 to 3. Patent Documents 1 to 3 address the issue of using the techniques to improve battery performance, such as improving ionic conductivity and increasing the affinity between the sulfide solid electrolyte and active materials used in the negative electrode, positive electrode, etc. when manufacturing a lithium-ion battery, thereby improving cycle characteristics.

[0013] In the manufacturing process of lithium-ion batteries (also called "all-solid-state batteries"), a paste is prepared by mixing a solid electrolyte, other predetermined components, and a solvent, and the paste is then applied to form a separator layer and an electrode mixture layer. To improve the performance of these layers, it is necessary to increase the density of the solid electrolyte that constitutes these layers, and using a solid electrolyte with a large specific surface area is effective for increasing the density.

[0014] Thus, there is a demand for a solid electrolyte with a large specific surface area. However, if the specific surface area of ​​the solid electrolyte is large, the viscosity of the paste increases, causing a manufacturing problem of significantly reducing the coating suitability. On the other hand, it is possible to improve the coating suitability of the paste by using a large amount of solvent to reduce the viscosity of the paste, but this causes problems such as a longer drying time and a decrease in the density of the solid electrolyte constituting the layer, resulting in a decrease in battery performance. Therefore, there is a trade-off between the coating suitability of the paste and obtaining high battery performance. Furthermore, if the specific surface area is 10 m or less, the paste will not be able to be applied. 2 / g or more, when made into a paste, the viscosity of the sulfide solid electrolyte increases, resulting in a significant decrease in coating suitability. In addition, a large amount of solvent is required to lower the viscosity of the paste, which results in a longer drying time and a significant decrease in battery performance due to a decrease in density.

[0015] As in Patent Documents 1 to 3, many studies have been conducted on the subject of improving ionic conductivity and battery performance. However, in a situation where the practical application of lithium ion batteries is rapidly progressing, we have noticed that no studies have been conducted on methods for improving performance in the manufacturing process, such as paste coating suitability, with a focus on mass production. The present inventors have been conducting intensive research into the compounds to be coated on the surface of sulfide solid electrolytes, while following the techniques disclosed in Patent Documents 1 to 3, and have discovered a compound having a specific surface area of ​​10 m 2We have found that even sulfide solid electrolytes with a specific surface area of ​​10 m or more can be made into sulfide solid electrolytes that have excellent applicability when applied as a paste and can efficiently exhibit excellent battery performance by attaching lithium halide to their surfaces. Lithium halide has been used as a raw material for sulfide solid electrolytes, but by attaching it to the surface of a sulfide solid electrolyte, it is possible to increase the specific surface area to 10 m. 2 / g or more, it is a surprising phenomenon that has not been recognized until now that a sulfide solid electrolyte can have the effect of excellent coatability when applied as a paste.

[0016] In this specification, the term "solid electrolyte" refers to an electrolyte that remains solid at 25° C. under a nitrogen atmosphere. The "sulfide solid electrolyte" obtained by the production method of this embodiment is a solid electrolyte that contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms and has ionic conductivity due to the lithium atoms.

[0017] The term "sulfide solid electrolyte" includes both crystalline sulfide solid electrolytes having a crystalline structure and amorphous sulfide solid electrolytes. In this specification, a crystalline sulfide solid electrolyte is a solid electrolyte in which peaks derived from the solid electrolyte are observed in the X-ray diffraction pattern in powder X-ray diffraction (XRD) measurement, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present. That is, a crystalline sulfide solid electrolyte includes a crystalline structure derived from the solid electrolyte, and the crystalline structure may be partially or entirely derived from the solid electrolyte. Furthermore, as long as the crystalline sulfide solid electrolyte has the X-ray diffraction pattern described above, it may also partially contain an amorphous sulfide solid electrolyte (also referred to as a "glass component"). Therefore, the crystalline sulfide solid electrolyte includes so-called glass ceramics obtained by heating an amorphous solid electrolyte (glass component) above its crystallization temperature.

[0018] In addition, in this specification, the amorphous sulfide solid electrolyte (glass component) refers to one in which the X-ray diffraction pattern in powder X-ray diffraction (XRD) measurement is a halo pattern in which no peaks other than those derived from the material are observed, and it does not matter whether or not there are peaks derived from the raw materials of the solid electrolyte. In this embodiment, the distinction between crystalline and amorphous applies to both the sulfide solid electrolyte and the modified sulfide solid electrolyte.

[0019] The modified sulfide solid electrolyte according to the first aspect of the present embodiment has: BET specific surface area is 10m 2 / g or more, and comprising a sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and an epoxy compound; In the infrared absorption spectrum by FT-IR analysis (ATR method), -1 modified sulfide solid electrolyte with a peak at is.

[0020] Typical sulfide solid electrolytes containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms include sulfide solid electrolytes obtained by conventional methods, for example, using lithium sulfide, diphosphorus pentasulfide, lithium halides, elemental halogens, etc. That is, the modified sulfide solid electrolyte of this embodiment has a BET specific surface area of ​​10 m by conventional methods. 2 The solid electrolyte contains a sulfide solid electrolyte having a large specific surface area of ​​0.1g / g or more, and an epoxy compound.

[0021] Conventional BET specific surface area is 10m 2In sulfide solid electrolytes with a large specific surface area of ​​1 / g or more, pastes containing the electrolyte at a content required to ensure the density of the solid electrolyte in the layer to achieve the desired battery performance suffer from significantly reduced coating performance, making it extremely difficult to efficiently form positive electrodes, negative electrodes, and electrolyte layers. The sulfide solid electrolyte of this embodiment dramatically improves coating suitability, i.e., is "modified," by incorporating an epoxy compound into a conventional sulfide solid electrolyte, and therefore should be called a "modified sulfide solid electrolyte."

[0022] In addition, the modified sulfide solid electrolyte according to the first embodiment has a peak at 2800 to 3000 cm in an infrared absorption spectrum by FT-IR analysis (ATR method). -1 This peak is not detected in the sulfide solid electrolyte, and is therefore thought to be a peak derived from the epoxy compound contained in the modified sulfide solid electrolyte.

[0023] The modified sulfide solid electrolyte according to the second embodiment of the present invention has a peak at 2800 to 3000 cm in an infrared absorption spectrum by FT-IR analysis (ATR method). -1 The peak detected in the graph is due to the C—H stretching vibration of the alkyl chain in the epoxy compound. As mentioned above, this peak is not detected in sulfide solid electrolytes prepared by conventional methods, and is a peak that appears when the epoxy compound is contained, and it is believed that the epoxy compound exists while maintaining its structure.

[0024] Although it is unclear how the epoxy compound is contained in the modified sulfide solid electrolyte of this embodiment, it is presumed that the epoxy compound adheres to the surface of the sulfide solid electrolyte while maintaining its structure. This is because, according to the examples described below, the above peaks are clearly detected, and therefore it is believed that the epoxy compound is present in a form that is easily detectable.

[0025] Furthermore, a comparison between the examples and comparative examples described below confirms that the modified sulfide solid electrolyte of this embodiment has a lower oil absorption than a sulfide solid electrolyte that does not contain an epoxy compound. It is natural to consider that the reduction in oil absorption is due to the epoxy compound adhering to the surface of the sulfide solid electrolyte and blocking at least a portion of the pores of the sulfide solid electrolyte. It is generally known that the oil absorption, like the specific surface area, is related to the improvement of coatability. It is presumed that the adhesion of the epoxy compound to the surface of the sulfide solid electrolyte reduces the oil absorption, thereby improving coatability.

[0026] Regarding the adhesion of the epoxy compound to the surface of the sulfide solid electrolyte, the details of how the adhesion occurs, i.e., whether it is physical or chemical, are unknown. However, because heteroatoms such as oxygen atoms have the property of easily bonding with lithium atoms, halogen atoms, etc., it is highly likely that the oxygen atoms contained in the epoxy compound bond with the lithium atoms, halogen atoms, etc. that constitute the sulfide solid electrolyte and adhere to the surface, i.e., chemical adhesion. Regardless of the type of adhesion, it is believed that the modified sulfide solid electrolyte of the present embodiment is likely to have a reduced oil absorption amount as long as an epoxy compound is attached to its surface, thereby improving its coatability and battery performance.

[0027] The modified sulfide solid electrolyte according to the third aspect of the present embodiment is 1 In the H-NMR spectrum, a peak at 0.0 to 5.0 ppm is present that is derived from the alkyl chain. The modified sulfide solid electrolyte according to this embodiment has this peak, and it is believed that the epoxy compound exists in the modified sulfide solid electrolyte while maintaining its structure.

[0028] A modified sulfide solid electrolyte according to a fourth aspect of this embodiment is specified to use, as the epoxy compound, at least one compound selected from epoxy compound 1 represented by general formula (1), epoxy compound 2 represented by general formula (2), and epoxy compound 3 represented by general formula (3). A detailed description of the epoxy compounds represented by general formulas (1) to (3) will be given later.

[0029] The modified sulfide solid electrolyte of this embodiment has excellent coatability if it contains an epoxy compound, but excellent coatability can be easily obtained and the coatability itself can be improved by using specific epoxy compounds, namely, epoxy compounds 1 to 3. It is believed that by using epoxy compounds having a molecular size of at least a certain level as represented by general formulas (1) to (3), the effect of reducing oil absorption can be easily obtained, and coatability can be easily improved.

[0030] In a modified sulfide solid electrolyte according to a fifth aspect of the present embodiment, the content of the epoxy compound is 0.03 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the sulfide solid electrolyte. When the content of the epoxy compound is within the above range, the epoxy compound is dispersed and adhered to the surface of the sulfide solid electrolyte in an appropriate amount, reducing oil absorption and maintaining appropriate lithium ion conductivity, which tends to improve coating suitability and efficiently achieve excellent battery performance. The "epoxy compound content" refers to the amount of epoxy compound used in producing the modified sulfide solid electrolyte, and if the amount used is known, this amount is the content.

[0031] In a modified sulfide solid electrolyte according to a sixth aspect of the present embodiment, the molecular weight of the epoxy compound is 60 or more. As described above, by using an epoxy compound having a molecular size of a certain level or more, the effect of reducing oil absorption can be easily obtained, and the coating suitability can be easily improved.

[0032] The modified sulfide solid electrolyte according to the seventh aspect of the present embodiment is the modified sulfide solid electrolyte according to the fourth aspect, wherein the epoxy compound 1 in the general formula (1) is 11 is a monovalent hydrocarbon group having 3 to 24 carbon atoms or a monovalent halogenated hydrocarbon group having 3 to 24 carbon atoms, and X 12 and X 13 is a compound in which is a hydrogen atom. Among the epoxy compounds 1 represented by general formula (1), those defined in the seventh embodiment are likely to adhere to the surface of the sulfide solid electrolyte and reduce the oil absorption, which in turn tends to improve the coating suitability and efficiently achieve excellent battery performance.

[0033] The modified sulfide solid electrolyte according to the eighth aspect of the present embodiment is the same as that according to the fourth aspect, except that the epoxy compound 2 in the general formula (2) is 21 is a group represented by general formula (2a), and X 22 and X 23 is a hydrogen atom, and in general formula (2a), R 21 is a divalent hydrocarbon group having 1 to 4 carbon atoms, and R 22 is a monovalent hydrocarbon group having 2 to 24 carbon atoms. Among the epoxy compounds 2 represented by general formula (2), those specified in the eighth embodiment are likely to adhere to the surface of the sulfide solid electrolyte and reduce the oil absorption, which in turn tends to improve the coating suitability and efficiently facilitate the development of excellent battery performance.

[0034] In the modified sulfide solid electrolyte according to the ninth aspect of the present embodiment, the epoxy compound 3 in the fourth aspect is a compound represented by the general formula (3), wherein X 31 is a group represented by general formula (3a), and X 32 and X 33 is a hydrogen atom, and in general formula (3a), R 31 is a divalent hydrocarbon group having 1 to 4 carbon atoms, and R 32 is a divalent hydrocarbon group having 2 to 8 carbon atoms, and X 34 and X 36 is a group represented by general formula (3b), and X 35is a monovalent hydrocarbon group having 1 to 4 carbon atoms, and in general formula (3b), R 34 ~R 36 is a monovalent hydrocarbon group having 1 to 4 carbon atoms. Among the epoxy compounds 3 represented by general formula (3), those specified in the ninth embodiment are easily attached to the surface of the sulfide solid electrolyte to reduce the oil absorption, which makes it easy to improve the coating suitability and efficiently realize excellent battery performance.

[0035] In the modified sulfide solid electrolyte according to a tenth aspect of the present embodiment, the epoxy compound 3 in the fourth aspect is a compound represented by the general formula (3), wherein X 31 is a group represented by general formula (3a), and X 22 and X 23 is a hydrogen atom, and in general formula (3a), R 31 is a divalent hydrocarbon group having 1 to 4 carbon atoms, and R 32 is a single bond, and X 34 ~X 36 is a monovalent hydrocarbon group having 1 to 8 carbon atoms. Among the epoxy compounds 3 represented by general formula (3), those specified in the tenth embodiment, like the compounds specified in the ninth embodiment, adhere to the surface of the sulfide solid electrolyte and tend to reduce the oil absorption, which tends to improve the coating suitability and also tends to efficiently achieve excellent battery performance.

[0036] A method for producing a modified sulfide solid electrolyte according to an eleventh aspect of the present embodiment includes: BET specific surface area is 10m 2 / g or more and containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, an epoxy compound, and an organic solvent; removing the organic solvent. That is it. As described above, the modified sulfide solid electrolyte of the present embodiment is not particularly limited by its manufacturing method as long as it contains an epoxy compound. However, according to the manufacturing method of the modified sulfide solid electrolyte of the eleventh aspect of the present embodiment, the epoxy compound can be present so as to adhere to the surface of the sulfide solid electrolyte in view of its characteristics, and therefore the modified sulfide solid electrolyte has excellent coating suitability and efficiently exhibits excellent battery performance, making it possible to more efficiently manufacture such a modified sulfide solid electrolyte of the present embodiment.

[0037] By mixing the sulfide solid electrolyte, the epoxy compound, and the organic mixture, a solution or slurry mixture is obtained. However, since the modified sulfide solid electrolyte cannot be used as is, the organic solvent must be removed from the solution or slurry.

[0038] A twelfth aspect of the present embodiment is a method for producing a modified sulfide solid electrolyte, wherein the organic solvent used in the method for producing a modified sulfide solid electrolyte of the eleventh aspect is at least one solvent selected from aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, ester-based solvents, nitrile-based solvents, and ether-based solvents. By using the above solvent as the organic solvent, adhesion of the epoxy compound to the surface of the sulfide solid electrolyte can be promoted, and the coating suitability can be easily improved.

[0039] An electrode mixture according to a thirteenth aspect of the present embodiment includes the modified sulfide solid electrolyte of the first aspect and an electrode active material. That is it. Further, a lithium ion battery according to a fourteenth aspect of the present embodiment includes at least one of the modified sulfide solid electrolyte etc. of the first aspect and the electrode active material of the thirteenth aspect, That is it.

[0040] As described above, the modified sulfide solid electrolyte of this embodiment has excellent coatability when applied as a paste and can efficiently achieve excellent battery performance. Therefore, since the electrode composite containing the modified sulfide solid electrolyte of this embodiment also has excellent coatability, lithium ion batteries can be efficiently manufactured, and the resulting lithium ion batteries have excellent battery performance.

[0041] The modified sulfide solid electrolyte according to a fifteenth aspect of the present embodiment is BET specific surface area is 10m 2 / g or more, and comprising a sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and an epoxy compound, That is it. The modified sulfide solid electrolyte having such a configuration also exhibits the same effects as the modified sulfide solid electrolyte of the first embodiment, that is, excellent applicability when applied as a paste and the ability to efficiently exhibit excellent battery performance. The modified sulfide solid electrolyte of the first embodiment is the modified sulfide solid electrolyte of the fifteenth embodiment, which has a peak at 2800 to 3000 cm in an infrared absorption spectrum by FT-IR analysis (ATR method). -1 However, as described above, this peak is derived from the epoxy compound contained in the modified sulfide solid electrolyte, and this indicates that this peak appears due to the inclusion of the epoxy compound.

[0042] The electrode mixture according to the sixteenth aspect of this embodiment is The modified sulfide solid electrolyte of the fifteenth form and an electrode active material, That is it. Further, a lithium ion battery according to a seventeenth aspect of the present embodiment includes at least one of the modified sulfide solid electrolyte etc. of the fifteenth aspect and the electrode active material of the sixteenth aspect, That is it. The electrode mixture and the lithium ion battery are the same as those described for the electrode mixture of the thirteenth embodiment and the lithium ion battery of the fourteenth embodiment.

[0043] [Modified sulfide solid electrolyte] The modified sulfide solid electrolyte of this embodiment has a BET specific surface area of ​​10 m 2 / g or more, and the solid electrolyte contains a sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and an epoxy compound, and the infrared absorption spectrum by FT-IR analysis (ATR method) has a peak density of 2800 to 3000 cm -1 This peak is not detected in the sulfide solid electrolyte that does not contain an epoxy compound, and is therefore a peak derived from the epoxy compound.

[0044] In this specification, FT-IR analysis refers to analysis using a Fourier transform infrared spectrophotometer, and means measurement using attenuated total reflectance (ATR) method, and the infrared absorption spectrum is a spectrum measured using an FT-IR device under the following conditions: Measurement method: Total reflection measurement method (ATR method) Measurement wavenumber range: 650 to 4000 cm -1 Light source: Globar lamp (SiC) Detector: DTGS detector Resolution: 4cm -1 Measurement time: 1 second / time Accumulation count: 256 times

[0045] In the infrared absorption spectrum, 2800 to 3000 cm -1 It is known that the peak at is derived from C-H stretching vibration. As mentioned above, this peak is considered to be derived from an epoxy compound, and more specifically, it is derived from a C-H bond in the epoxy compound. Furthermore, when the epoxy compound has an alkyl chain, this peak is derived from a C-H bond (C-H stretching vibration) of the alkyl chain in the epoxy compound. In the modified sulfide solid electrolyte of this embodiment, the peak is clearly detected, and therefore it is believed that the epoxy compound is contained in a form that is easily detectable, i.e., that it is present so as to adhere to the surface of the sulfide solid electrolyte. This presence is believed to reduce the oil absorption of the sulfide solid electrolyte and provide excellent coatability.

[0046] The modified sulfide solid electrolyte of this embodiment has: 1 In the 1 H-NMR spectrum, it is preferable that the epoxy compound has a peak at 0.0 to 5.0 ppm that is derived from the alkyl chain of the epoxy compound. In this specification, 1 The peaks in the H-NMR spectrum were measured using a nuclear magnetic resonance (NMR) apparatus under the following conditions: Observation kernel: 1 H Resonance frequency: 500MHz Probe: 5mmφ TCI cryoprobe Measurement temperature: 25℃ Accumulation count: 16 times

[0047] As described above, the modified sulfide solid electrolyte of this embodiment has an infrared absorption spectrum of 2800 to 3000 cm -1 It is believed that the peak is clearly detectable, that is, that the sulfide solid electrolyte is present in such a manner that it adheres to the surface of the sulfide solid electrolyte. 1 The detection of peaks derived from the alkyl chains in the H-NMR spectrum also means that the alkyl chains are present in a manner that they are attached to the surface of the sulfide solid electrolyte, as in the infrared absorption spectrum, and it is believed that excellent coating suitability can be obtained.

[0048] Furthermore, as will be shown in the examples described later, a modified sulfide solid electrolyte obtained by mixing a sulfide solid electrolyte and an epoxy compound in an organic solvent is added to a solvent such as toluene to form a slurry, and then allowed to stand. When the supernatant is analyzed by gas chromatography mass spectrometry (GC / MS), no epoxy compound is detected. On the other hand, when the precipitated powder is dried to remove the solvent, it is dissolved in deuterated methanol, and 1 When H-NMR measurement is performed, the chemical shift of groups (such as alkyl groups) derived from the epoxy compound is detected. From this phenomenon, it is believed that in the modified sulfide solid electrolyte, the epoxy compound adheres strongly to the surface of the sulfide solid electrolyte, and this adhesion reduces the oil absorption amount and results in excellent coatability.

[0049] When the epoxy compound is attached to the surface of the sulfide solid electrolyte, it may be attached so as to cover the entire surface of the sulfide solid electrolyte, or it may be attached to only a part of the surface.

[0050] The epoxy compound is not particularly limited as long as it is a compound having an epoxy ring. From the viewpoint of more efficiently improving the coating suitability and improving the battery performance, preferred examples include epoxy compounds 1 to 3 represented by the following general formulas (1) to (3), respectively.

[0051] (Epoxy compound 1) Epoxy compound 1 is a compound represented by the following general formula (1).

[0052] [ka]

[0053] In general formula (1), X 11 ~X 13 are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, or a monovalent halogenated hydrocarbon group, and X 11 ~X 13At least one of the groups is a monovalent hydrocarbon group or a monovalent halogenated hydrocarbon group.

[0054] X 11 ~X 13 Examples of the monovalent hydrocarbon group include monovalent aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups, with aliphatic hydrocarbon groups and alicyclic hydrocarbon groups being preferred, and aliphatic hydrocarbon groups being more preferred. Preferred examples of the aliphatic hydrocarbon group include alkyl groups and alkenyl groups, with alkyl groups being preferred. The number of carbon atoms in the aliphatic hydrocarbon group, in the case of an alkyl group, is preferably 1 or more, more preferably 2 or more, even more preferably 4 or more, and even more preferably 6 or more, with the upper limit being preferably 24 or less, more preferably 20 or less, and even more preferably 16 or less. In the case of an alkenyl group, the number of carbon atoms is 2 or more, preferably 4 or more, and the upper limit is preferably 24 or less, more preferably 20 or less, and even more preferably 16 or less. X 11 ~X 13 The aliphatic hydrocarbon group X may be either linear or branched, with linear being preferred. The aliphatic hydrocarbon group X may be partially substituted with a hydroxyl group or the like. 11 ~X 13 When a plurality of the groups are aliphatic hydrocarbon groups, the aliphatic hydrocarbon groups may be the same or different.

[0055] X 11 ~X 13 The monovalent alicyclic hydrocarbon group is preferably a cycloalkyl group or a cycloalkenyl group, and more preferably a cycloalkyl group. The number of carbon atoms in the alicyclic hydrocarbon group is 3 or more, preferably 4 or more, and preferably 12 or less, more preferably 8 or less, and even more preferably 6 or less. X 11 ~X 13 The alicyclic hydrocarbon group may be partially substituted with a hydroxyl group, the above-mentioned monovalent aliphatic hydrocarbon group (for example, an alkyl group, an alkenyl group), etc. 11 ~X 13 When a plurality of the groups are alicyclic hydrocarbon groups, the plurality of alicyclic hydrocarbon groups may be the same or different.

[0056] X 11 ~X 13 Examples of the monovalent aromatic hydrocarbon group include a phenyl group, a naphthyl group, a biphenyl group, a diphenylmethyl group, a trityl group, an anthranyl group, a perylenyl group, and a pyrenyl group. X 11 ~X 13 The monovalent aromatic hydrocarbon group may be partially substituted with a hydroxyl group, the above-mentioned monovalent aliphatic hydrocarbon group (for example, an alkyl group, an alkenyl group), or the like. 11 ~X 13 When a plurality of the aromatic hydrocarbon groups are aromatic hydrocarbon groups, the aromatic hydrocarbon groups may be the same or different.

[0057] X 11 ~X 13 The monovalent halogenated hydrocarbon group of X 11 ~X 13 Examples of the hydrocarbon group include groups in which a part of the hydrocarbon groups exemplified above is substituted with a halogen atom. Of the monovalent hydrocarbon groups listed above, the hydrocarbon group substituted with a halogen atom is preferably an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, more preferably an aliphatic hydrocarbon group, and even more preferably an alkyl group.

[0058] X 11 ~X 13 The halogen atom contained in the monovalent halogenated hydrocarbon group is preferably fluorine, chlorine, bromine or iodine, more preferably fluorine, chlorine or bromine, and even more preferably fluorine. The number of halogen atoms in the halogenated hydrocarbon group cannot be generalized because it varies depending on the number of carbon atoms in the hydrocarbon group, but is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and still more preferably 6 or more, and the upper limit is preferably 16 or less, more preferably 12 or less, and even more preferably 9 or less.

[0059] X 11 ~X 13As the halogen atom, fluorine, chlorine, bromine and iodine are preferred, as with the halogen atoms that can be contained in the above halogenated hydrocarbon groups, with fluorine, chlorine and bromine being more preferred, and fluorine being even more preferred.

[0060] X 11 ~X 13 At least one of X is a monovalent hydrocarbon group or a monovalent halogenated hydrocarbon group, i.e., X 11 ~X 13 One, two, or three of these may be monovalent hydrocarbon groups or monovalent halogenated hydrocarbon groups, and from the viewpoint of improving coating suitability, it is preferred that one of them is a monovalent hydrocarbon group or a monovalent halogenated hydrocarbon group.

[0061] The epoxy compound 1 represented by the general formula (1) is, among others, X 11 is a monovalent hydrocarbon group having 1 to 24 carbon atoms or a monovalent halogenated hydrocarbon group having 1 to 24 carbon atoms, and X 12 and X 13 is preferably a hydrogen atom, and the hydrocarbon group is preferably an aliphatic hydrocarbon group as described above, more preferably an alkyl group or an alkenyl group, and even more preferably an alkyl group. The number of carbon atoms is also as described above, and in the case of an alkyl group, it is preferably 1 or more, more preferably 2 or more, even more preferably 4 or more, and still more preferably 6 or more, and the upper limit is preferably 24 or less, more preferably 20 or less, and even more preferably 16 or less.

[0062] (Epoxy compound 2) The epoxy compound 2 is a compound represented by the following general formula (2).

[0063] [ka]

[0064] In general formula (2), X 21 ~X 23 are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, or a group represented by general formula (2a), and X21 ~X 23 At least one of R is a group represented by general formula (2a). 21 is a divalent hydrocarbon group, and R 22 is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, or a monovalent halogenated hydrocarbon group.

[0065] X 21 ~X 23 The monovalent hydrocarbon group of X 11 ~X 13 Examples of the monovalent hydrocarbon group include the same monovalent aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups as exemplified above, with aliphatic hydrocarbon groups and alicyclic hydrocarbon groups being preferred, and aliphatic hydrocarbon groups being more preferred. Among the aliphatic hydrocarbon groups, alkyl groups and alkenyl groups are more preferred, and alkyl groups are even more preferred.

[0066] X 21 ~X 23 The monovalent halogenated hydrocarbon group of X 11 ~X 13 The halogen atom may also be any of the above X 11 ~X 13 Examples of the monovalent hydrocarbon group include those exemplified above.

[0067] X 21 ~X 23 At least one of them is a group represented by general formula (2a). 21 ~X 23 Among these, one, two or three may be groups represented by general formula (2a), and preferably one.

[0068] X 21 ~X 23 Regarding the group represented by general formula (2a), R 21 As the divalent hydrocarbon of the above X 21 ~X 23 A hydrocarbon group obtained by removing one hydrogen atom from a monovalent hydrocarbon group such as R 21Examples of the divalent hydrocarbon include divalent aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups, with aliphatic hydrocarbon groups and alicyclic hydrocarbon groups being preferred, and aliphatic hydrocarbon groups being more preferred. The divalent aliphatic hydrocarbon group is preferably an alkylene group or an alkenylene group, more preferably an alkylene group. In the case of an alkylene group, the number of carbon atoms is preferably 1 or more, with the upper limit being preferably 8 or less, more preferably 6 or less, even more preferably 4 or less, and still more preferably 2 or less. In the case of an alkenylene group, the number of carbon atoms is preferably 2 or more, with the same upper limit as that of an alkylene group.

[0069] X 21 ~X 23 Regarding the group represented by general formula (2a), R 22 As the monovalent hydrocarbon of the formula X 21 ~X 23 Examples of the monovalent hydrocarbon groups include the same as the monovalent hydrocarbon groups in the above, that is, monovalent aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups, and aliphatic hydrocarbon groups and aromatic hydrocarbon groups are preferred. The aliphatic hydrocarbon group is preferably an alkyl group or an alkenyl group, more preferably an alkyl group, and the aliphatic hydrocarbon group may be linear or branched. When the aliphatic hydrocarbon group is an alkyl group, the number of carbon atoms is preferably 1 or more, more preferably 2 or more, and even more preferably 4 or more, and the upper limit is preferably 24 or less, more preferably 16 or less, even more preferably 12 or less, and even more preferably 10 or less.

[0070] Among the aromatic hydrocarbon groups, phenyl, biphenyl, diphenylmethyl, and trityl groups are preferred, with phenyl, diphenylmethyl, and trityl groups being more preferred, and phenyl and trityl groups being even more preferred. These aromatic hydrocarbon groups may be substituted with a halogen atom, a hydroxyl group, a monovalent aliphatic hydrocarbon group (an alkyl group, an alkenyl group), or the like.

[0071] R 22 As the monovalent halogenated hydrocarbon, the above R 22Examples of the monovalent hydrocarbon group include a group in which a portion of the group is substituted with a halogen atom. 22 The halogen atoms contained in the monovalent halogenated hydrocarbons, and R 22 The halogen atom is preferably fluorine, chlorine, bromine or iodine, more preferably fluorine, chlorine or bromine, and even more preferably fluorine.

[0072] The epoxy compound 2 represented by the general formula (2) is, among others, X 21 is a group represented by general formula (2a), and X 22 and X 23 is a hydrogen atom, and in general formula (2a), R 21 is a divalent hydrocarbon group having 1 to 8 carbon atoms, and R 22 is preferably a monovalent hydrocarbon group having 1 to 24 carbon atoms, and R 21 a divalent hydrocarbon group, R 22 The monovalent hydrocarbon group is as described above. Also, R 22 When the monovalent hydrocarbon group is a phenyl group, it is preferably substituted with a monovalent aliphatic hydrocarbon group, and more preferably with an alkyl group. The alkyl group preferably has 1 or more carbon atoms, more preferably 2 or more, and even more preferably 4 or more, and the upper limit is preferably 24 or less, more preferably 12 or less, even more preferably 8 or less, and even more preferably 6 or less. In this case, the aliphatic hydrocarbon group may be either linear or branched, and is preferably branched. 22 Among these, an aliphatic hydrocarbon group having a quaternary carbon atom is preferred, and a tert-butyl group is particularly preferred.

[0073] (Epoxy compound 3) The epoxy compound 3 is a compound represented by the following general formula (3).

[0074] [ka]

[0075] In general formula (3), X 31~X 33 are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, or a group represented by general formula (3a), and X 31 ~X 33 At least one of R is a group represented by general formula (3a). 31 and R 32 are each independently a single bond or a divalent hydrocarbon group, and X 34 ~X 36 each independently represents a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, -OR 33 or a group represented by general formula (3b). 33 ~R 36 are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, or a monovalent halogenated hydrocarbon group.

[0076] X 31 ~X 33 The monovalent hydrocarbon group of X 11 ~X 13 Examples of the monovalent hydrocarbon group include the same monovalent aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups as exemplified above, with aliphatic hydrocarbon groups and alicyclic hydrocarbon groups being preferred, and aliphatic hydrocarbon groups being more preferred. Among the aliphatic hydrocarbon groups, alkyl groups and alkenyl groups are more preferred, and alkyl groups are even more preferred.

[0077] X 31 ~X 33 The monovalent halogenated hydrocarbon group of X 11 ~X 13 The halogen atom may also be any of the above X 11 ~X 13 Examples of the monovalent hydrocarbon group include those exemplified above.

[0078] X 31 ~X 33 At least one of them is a group represented by general formula (3a). 31 ~X 33Among these, one, two or three may be groups represented by general formula (3a), and preferably one.

[0079] X 31 ~X 33 Regarding the group represented by general formula (3a), R 31 and R 32 As the divalent hydrocarbon of the above X 31 ~X 33 A hydrocarbon group obtained by removing one hydrogen atom from a monovalent hydrocarbon group such as R 31 Examples of the divalent hydrocarbon include divalent aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups, with aliphatic hydrocarbon groups and alicyclic hydrocarbon groups being preferred, and aliphatic hydrocarbon groups being more preferred. The divalent aliphatic hydrocarbon group is preferably an alkylene group or an alkenylene group, more preferably an alkylene group. In the case of an alkylene group, the number of carbon atoms is preferably 1 or more, with the upper limit being preferably 8 or less, more preferably 6 or less, even more preferably 4 or less, and still more preferably 2 or less. In the case of an alkenylene group, the number of carbon atoms is preferably 2 or more, with the same upper limit as that of an alkylene group.

[0080] X 34 ~X 36 The monovalent hydrocarbon group and the monovalent halogenated hydrocarbon group are the above-mentioned X 31 ~X 33 Examples of the monovalent hydrocarbon group and halogenated hydrocarbon include the same as those exemplified above. X 34 ~X 36 -OR 33 R in 33 , R in general formula (3b) 34 ~R 36 The monovalent hydrocarbon group and the monovalent halogenated hydrocarbon group are also 34 ~X 36 The monovalent hydrocarbon group and the monovalent halogenated hydrocarbon group are the same as those mentioned above.

[0081] The epoxy compound 3 represented by the general formula (3) is, among others, X 31is a group represented by general formula (3a), and X 32 and X 33 is a hydrogen atom, and in general formula (3a), R 31 is a divalent hydrocarbon group having 1 to 8 carbon atoms, and R 32 is a divalent hydrocarbon group having 1 to 8 carbon atoms, and X 34 and X 36 is a group represented by general formula (3b), and X 35 is a monovalent hydrocarbon group having 1 to 24 carbon atoms, and in general formula (3b), R 34 ~R 36 is preferably a monovalent hydrocarbon group having 1 to 24 carbon atoms. In this case, R 31 and R 32 The divalent hydrocarbon group is as described above, but R 31 The number of carbon atoms in the divalent hydrocarbon group is preferably 1 or more, and the upper limit is preferably 8 or less, more preferably 6 or less, even more preferably 4 or less, and even more preferably 2 or less. 32 The number of carbon atoms in the divalent hydrocarbon group X is preferably 1 or more, more preferably 2 or more, and the upper limit is preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less. 35 , R 34 ~R 36 The monovalent hydrocarbon group is as described above, but X 35 The number of carbon atoms in the monovalent hydrocarbon group is preferably 1 or more, and the upper limit is preferably 24 or less, more preferably 12 or less, even more preferably 8 or less, still more preferably 4 or less, and particularly preferably 2 or less. 34 ~R 36 The number of carbon atoms in the monovalent hydrocarbon group is also 35 The number of carbon atoms in the monovalent hydrocarbon group is the same as that of the

[0082] In addition, the epoxy compound 3 represented by the general formula (3) is, among others, X 31 is a group represented by general formula (3a), and X 22 and X 23 is a hydrogen atom, and in general formula (3a), R 31 is a divalent hydrocarbon group having 1 to 8 carbon atoms, and R32 is a single bond, and X 34 ~X 36 is preferably a monovalent hydrocarbon group having 1 to 24 carbon atoms. In this case, R 31 The divalent hydrocarbon group is as described above, but R 31 The number of carbon atoms in the divalent hydrocarbon group X is preferably 1 or more, and the upper limit is preferably 8 or less, more preferably 6 or less, even more preferably 4 or less, and still more preferably 2 or less. 34 ~X 36 The monovalent hydrocarbon group is as described above, but X 34 , X 36 The number of carbon atoms in the monovalent hydrocarbon group is preferably 1 or more, and the upper limit is preferably 24 or less, more preferably 12 or less, even more preferably 8 or less, still more preferably 4 or less, and particularly preferably 2 or less. 35 The number of carbon atoms in the monovalent hydrocarbon group is preferably 1 or more, more preferably 2 or more, and even more preferably 4 or more, and the upper limit is preferably 24 or less, more preferably 12 or less, even more preferably 8 or less, and even more preferably 6 or less. 35 The hydrocarbon group may be either linear or branched, preferably branched, and is preferably an aliphatic hydrocarbon group having a quaternary carbon atom, particularly preferably a tert-butyl group.

[0083] The molecular weight of the epoxy compound contained in the modified sulfide solid electrolyte of this embodiment is preferably 60 or more, more preferably 70 or more, and the upper limit is preferably 400 or less, more preferably 380 or less, and even more preferably 350 or less. Use of an epoxy compound with such a molecular weight makes it possible to efficiently improve the coatability.

[0084] Although the content of the epoxy compound cannot be generalized because it varies depending on the type of epoxy compound used, it is preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass, even more preferably 0.1 parts by mass or more, and still more preferably 0.5 parts by mass, relative to 100 parts by mass of the sulfide solid electrolyte, and the upper limit is preferably 25 parts by mass or less, more preferably 20 parts by mass or less. By using the epoxy compound so as to satisfy such a content, it becomes possible to efficiently improve the coatability.

[0085] (Production of sulfide solid electrolyte) Next, the sulfide solid electrolyte that forms the modified sulfide solid electrolyte of this embodiment will be described. The sulfide solid electrolyte that can be used in this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and has a BET specific surface area of ​​10 m 2 Any material having a saturation of 1 / g or more can be used without any particular limitation, and commercially available products can be used as they are, or they can be manufactured and used. A method for producing a sulfide solid electrolyte that can be used in this embodiment will be described below. The sulfide solid electrolyte that can be used in this embodiment can be obtained by a production method that includes mixing two or more raw materials selected from compounds containing at least one atom of a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom, for example.

[0086] (raw materials) As the raw materials, two or more compounds selected from compounds containing at least one atom of lithium atom, sulfur atom, phosphorus atom, and halogen atom can be used. Compounds that can be used as raw materials contain at least one atom of a lithium atom, a sulfur atom, a phosphorus atom, or a halogen atom, and more specifically, lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; alkali metal halides such as sodium iodide, sodium fluoride, sodium chloride, and sodium bromide; phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5); various phosphorus fluorides (PF3, PF5), various phosphorus chlorides (PCl3, PCl5, P2Cl4), and various phosphorus bromides (PBr3, PB Representative examples of the starting material include raw materials consisting of at least two atoms selected from the above four types of atoms, such as phosphorus halides such as thiophosphoryl fluoride (PSF3), thiophosphoryl chloride (PSCl3), thiophosphoryl bromide (PSBr3), thiophosphoryl iodide (PSI3), thiophosphoryl fluoride dichloride (PSCl2F), and thiophosphoryl fluoride dibromide (PSBr2F); and elemental halogens such as fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2), preferably bromine (Br2) and iodine (I2).

[0087] Examples of compounds that can be used as raw materials other than those mentioned above include compounds containing at least one atom selected from the above four types of atoms and also containing atoms other than the four types of atoms, more specifically lithium compounds such as lithium oxide, lithium hydroxide, and lithium carbonate; alkali metal sulfides such as sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide; metal sulfides such as silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, tin sulfide (SnS, SnS), aluminum sulfide, and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; metal halides such as aluminum halides, silicon halides, germanium halides, arsenic halides, selenium halides, tin halides, antimony halides, tellurium halides, and bismuth halides; and phosphorus oxyhalides such as phosphorus oxychloride (POCl3) and phosphorus oxybromide (POBr3).

[0088] In this embodiment, from the viewpoint of more easily obtaining a sulfide solid electrolyte having high ionic conductivity, among halogen atoms, chlorine atoms, bromine atoms, and iodine atoms are preferred, and bromine atoms and iodine atoms are more preferred. These atoms may be used alone or in combination. For example, in the case of lithium halide, lithium bromide may be used alone, lithium iodide may be used alone, or lithium bromide and lithium iodide may be used in combination. From the same viewpoint, preferred compounds that can be used as raw materials include, among the above, lithium sulfide; phosphorus sulfides such as diphosphorus trisulfide (P2S3) and diphosphorus pentasulfide (P2S5); elemental halogens such as fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2); and lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; and among the phosphorus sulfides, diphosphorus pentasulfide is preferred; among the elemental halogens, chlorine (Cl2), bromine (Br2), and iodine (I2) are preferred; and among the lithium halides, lithium chloride, lithium bromide, and lithium iodide are preferred.

[0089] Preferred combinations of compounds that can be used as raw materials include, for example, a combination of lithium sulfide, phosphorus pentasulfide, and a lithium halide, and a combination of lithium sulfide, phosphorus pentasulfide, and an elemental halogen. Preferred lithium halides include lithium bromide, lithium iodide, and lithium chloride, and preferred elemental halogens include chlorine, bromine, and iodine.

[0090] In the present embodiment, when lithium sulfide is used as the compound containing lithium atoms, the lithium sulfide is preferably in the form of particles. The average particle size of lithium sulfide particles (D 50 ) is preferably 10 μm or more and 2000 μm or less, more preferably 30 μm or more and 1500 μm or less, and even more preferably 50 μm or more and 1000 μm or less. 50) is the particle size at which 50% of the total particle size is obtained by accumulating the particle size distribution curve from the smallest particle size, and the volume distribution is the average particle size that can be measured using, for example, a laser diffraction / scattering particle size distribution analyzer. Furthermore, among the above-mentioned examples of raw materials, solid raw materials preferably have an average particle size similar to that of the lithium sulfide particles, i.e., within the same range as that of the lithium sulfide particles.

[0091] When lithium sulfide, diphosphorus pentasulfide, and lithium halide are used as raw materials, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 60 mol% or more, more preferably 65 mol% or more, and even more preferably 68 mol% or more, from the viewpoint of obtaining higher chemical stability and obtaining high ionic conductivity by improving the PS4 fraction, and the upper limit is preferably 80 mol% or less, more preferably 78 mol% or less, and even more preferably 76 mol% or less.

[0092] When lithium sulfide, diphosphorus pentasulfide, lithium halide, and other raw materials used as needed are used, the content of lithium sulfide and diphosphorus pentasulfide relative to the total of these is preferably 60 mol% or more, more preferably 65 mol% or more, and even more preferably 70 mol% or more, and the upper limit is preferably 100 mol% or less, more preferably 90 mol% or less, and even more preferably 80 mol% or less.

[0093] Furthermore, when lithium bromide and lithium iodide are used in combination as the lithium halide, from the viewpoint of improving the PS4 fraction and obtaining high ionic conductivity, the proportion of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 mol% or more, more preferably 20 mol% or more, even more preferably 40 mol% or more, still more preferably 50 mol% or more, with the upper limit being preferably 99 mol% or less, more preferably 90 mol% or less, even more preferably 80 mol% or less, and still more preferably 70 mol% or less.

[0094] When using a halogen element as a raw material, for example, lithium sulfide and diphosphorus pentasulfide, the ratio of the number of moles of lithium sulfide (excluding the same number of moles of lithium sulfide as the halogen element) to the total number of moles of lithium sulfide and diphosphorus pentasulfide (excluding the same number of moles of lithium sulfide as the halogen element) is preferably within the range of 60 to 90%, more preferably within the range of 65 to 85%, even more preferably within the range of 68 to 82%, even more preferably within the range of 72 to 78%, and particularly preferably within the range of 73 to 77%. This is because these ratios result in higher ionic conductivity. From the same viewpoint, when lithium sulfide, diphosphorus pentasulfide, and a halogen element are used, the content of the halogen element relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and the halogen element is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%.

[0095] When lithium sulfide, diphosphorus pentasulfide, a halogen element, and a lithium halide are used, the content of the halogen element (α mol %) and the content of the lithium halide (β mol %) relative to the total amount of these elements preferably satisfy the following formula (1), more preferably satisfy the following formula (2), even more preferably satisfy the following formula (3), and even more preferably satisfy the following formula (4). 2≦2α+β≦100…(1) 4≦2α+β≦80 …(2) 6≦2α+β≦50 …(3) 6≦2α+β≦30 …(4)

[0096] (mixture) The mixing of two or more raw materials selected from compounds containing at least one atom of a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom can be carried out, for example, by using a mixer. Alternatively, the mixing can be carried out by using a stirrer, a grinder, or the like. This is because the use of a stirrer can cause mixing of the raw materials, and the use of a pulverizer causes pulverization of the raw materials but also causes mixing at the same time. In other words, it can be said that the sulfide solid electrolyte used in this embodiment can be produced by stirring, mixing, pulverizing, or a combination of these processes, two or more raw materials selected from compounds containing at least one atom of a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom.

[0097] Examples of the stirrer or mixer include a mechanical stirring mixer that is equipped with stirring blades in a reaction vessel and can stir (also referred to as mixing by stirring or stirring mixing). Examples of the mechanical stirring mixer include a high-speed stirring mixer and a double-arm mixer. Examples of the high-speed stirring mixer include a vertical-axis rotary mixer and a horizontal-axis rotary mixer, and either type of mixer may be used.

[0098] Examples of the shape of the stirring blade used in the mechanical stirring mixer include blade type, arm type, anchor type, paddle type, full zone type, ribbon type, multi-stage blade type, double arm type, shovel type, double blade type, flat blade type, C-type blade type, etc., and from the viewpoint of promoting the reaction of the raw materials more efficiently, the shovel type, flat blade type, C-type blade type, anchor type, paddle type, full zone type, etc. are preferred, with the anchor type, paddle type, and full zone type being more preferred.

[0099] When a mechanically agitated mixer is used, the rotation speed of the agitator blades can be adjusted appropriately depending on the volume of the fluid in the reaction tank, the temperature, the shape of the agitator blades, etc., and is not particularly limited. However, it is usually set to about 5 rpm or more and 400 rpm or less. From the viewpoint of more efficiently promoting the reaction of the raw materials, the rotation speed is preferably 10 rpm or more and 300 rpm or less, more preferably 15 rpm or more and 250 rpm or less, and even more preferably 20 rpm or more and 200 rpm or less.

[0100] The temperature conditions when mixing is performed using a mixer are not particularly limited, and are, for example, usually −30 to 120° C., preferably −10 to 100° C., more preferably 0 to 80° C., and even more preferably 10 to 60° C. The mixing time is usually 0.1 to 500 hours, and from the viewpoint of dispersing the raw materials more uniformly and promoting the reaction, is preferably 1 to 450 hours, more preferably 10 to 425 hours, even more preferably 20 to 400 hours, and still more preferably 40 to 375 hours.

[0101] The method of mixing with pulverization using a pulverizer has been conventionally adopted as a solid-phase method (mechanical milling method). As the pulverizer, for example, a media-type pulverizer using pulverization media can be used. Media-type mills are broadly classified into vessel-driven mills and media-agitation mills. Examples of vessel-driven mills include agitation tanks, grinding tanks, and combinations thereof, such as ball mills and bead mills. Examples of media-agitation mills include impact mills such as cutter mills, hammer mills, and pin mills; tower mills and other tower-type mills; agitation tank mills such as attritors, aquamizers, and sand grinders; flow-tank mills such as Viscomill and pearl mills; flow-tube mills; annular mills such as Coball mills; continuous dynamic mills; and single- or multi-shaft kneaders. Among these, considering the ease of adjusting the particle size of the resulting sulfide, the ball mills and bead mills exemplified as vessel-driven mills are preferred, and planetary mills are particularly preferred.

[0102] These pulverizers can be appropriately selected depending on the desired scale, etc. For relatively small scales, container-driven pulverizers such as ball mills and bead mills can be used, while for large scales or mass production, other types of pulverizers may be used.

[0103] Furthermore, as will be described later, when the materials are in a liquid state involving a liquid such as a solvent or in a slurry state during mixing, it is preferable to use a wet mill that can handle wet milling. Representative examples of wet mills include wet bead mills, wet ball mills, and wet vibration mills, with wet bead mills using beads as milling media being preferred because they allow for flexible adjustment of milling conditions and are suitable for smaller particle sizes. Alternatively, dry mills such as dry media mills (e.g., dry bead mills, dry ball mills, and dry vibration mills) and dry non-media mills (e.g., jet mills) can also be used.

[0104] Furthermore, when the material to be mixed is in a liquid or slurry state, a flow-through mill that can be operated to circulate as needed can also be used. Specifically, a mill that circulates the material between a mill (milling mixer) that pulverizes the slurry and a temperature holding tank (reaction vessel) can be used.

[0105] The size of the beads or balls used in the ball mill or bead mill may be appropriately selected depending on the desired particle size, processing amount, etc. For example, the diameter of the beads is usually 0.05 mm or more, preferably 0.1 mm or more, more preferably 0.3 mm or more, with the upper limit being usually 5.0 mm or less, preferably 3.0 mm or less, more preferably 2.0 mm or less. The diameter of the balls is usually 2.0 mm or more, preferably 2.5 mm or more, more preferably 3.0 mm or more, with the upper limit being usually 20.0 mm or less, preferably 15.0 mm or less, more preferably 10.0 mm or less. Examples of materials include metals such as stainless steel, chrome steel, and tungsten carbide; ceramics such as zirconia and silicon nitride; and minerals such as agate.

[0106] Furthermore, when a ball mill or bead mill is used, the rotation speed varies depending on the scale of the treatment and cannot be generalized, but is usually 10 rpm or more, preferably 20 rpm or more, and more preferably 50 rpm or more, with the upper limit being usually 1,000 rpm or less, preferably 900 rpm or less, more preferably 800 rpm or less, and even more preferably 700 rpm or less. The grinding time in this case varies depending on the scale of the treatment and cannot be generalized, but is usually 0.5 hours or more, preferably 1 hour or more, more preferably 5 hours or more, and even more preferably 10 hours or more, with the upper limit being usually 100 hours or less, preferably 72 hours or less, more preferably 48 hours or less, and even more preferably 36 hours or less.

[0107] By selecting the size and material of the media (beads, balls) used, the rotor rotation speed, time, etc., it is possible to perform mixing, stirring, pulverization, or a combination of these processes, and it is possible to adjust the particle size, etc. of the resulting sulfide.

[0108] (solvent) In the above mixing, a solvent may be added to the raw materials and mixed in. As the solvent, various solvents widely known as organic solvents may be used.

[0109] As the solvent, a wide variety of solvents that have conventionally been used in the production of solid electrolytes can be used, and examples thereof include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents.

[0110] Examples of aliphatic hydrocarbons include hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane. Examples of alicyclic hydrocarbons include cyclohexane and methylcyclohexane. Examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, trifluoromethylbenzene, and nitrobenzene.

[0111] In addition to the above hydrocarbon solvents, solvents containing heteroatoms such as atoms other than carbon and hydrogen atoms, such as nitrogen, oxygen, sulfur, and halogen atoms, are also suitable. Such solvents have the property of easily forming complexes with compounds containing lithium, phosphorus, sulfur, and halogen atoms, which are used as raw materials (hereinafter, such solvents are also referred to as "complexing agents"). These solvents are useful in that they facilitate the retention of halogen atoms within the structure of the sulfide solid electrolyte, thereby achieving higher ionic conductivity. Preferred examples of such complexing agents include ether solvents, ester solvents, and alcohol solvents, aldehyde solvents, and ketone solvents, which contain oxygen atoms as heteroatoms.

[0112] Preferred examples of the ether solvent include aliphatic ethers such as dimethyl ether, diethyl ether, tert-butyl methyl ether, dimethoxymethane, dimethoxyethane, diethylene glycol dimethyl ether (diglyme), triethylene oxide glycol dimethyl ether (triglyme), diethylene glycol, and triethylene glycol; alicyclic ethers such as ethylene oxide, propylene oxide, tetrahydrofuran, tetrahydropyran, dimethoxytetrahydrofuran, cyclopentyl methyl ether, and dioxane; heterocyclic ethers such as furan, benzofuran, and benzopyran; and aromatic ethers such as methyl phenyl ether (anisole), ethyl phenyl ether, dibenzyl ether, and diphenyl ether.

[0113] Preferred examples of the ester solvent include methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, and isopropyl acetate; aliphatic esters such as methyl propionate, ethyl propionate, dimethyl oxalate, diethyl oxalate, dimethyl malonate, diethyl malonate, dimethyl succinate, and diethyl succinate; alicyclic esters such as methyl cyclohexanecarboxylate, ethyl cyclohexanecarboxylate, and dimethyl cyclohexanedicarboxylate; heterocyclic esters such as methyl pyridinecarboxylate, methyl pyrimidinecarboxylate, acetolactone, propiolactone, butyrolactone, and valerolactone; and aromatic esters such as methyl benzoate, ethyl benzoate, dimethyl phthalate, diethyl phthalate, butyl benzyl phthalate, dicyclohexyl phthalate, trimethyl trimellitate, and triethyl trimellitate.

[0114] Preferred examples of the solvent include alcohol solvents such as ethanol and butanol; aldehyde solvents such as formaldehyde, acetaldehyde and dimethylformamide; and ketone solvents such as acetone and methyl ethyl ketone.

[0115] Examples of solvents containing a nitrogen atom as a heteroatom include solvents having a group containing a nitrogen atom, such as an amino group, an amide group, a nitro group, or a nitrile group. Preferred examples of solvents having an amino group include aliphatic amines such as ethylenediamine, diaminopropane, dimethylethylenediamine, diethylethylenediamine, dimethyldiaminopropane, tetramethyldiaminomethane, tetramethylethylenediamine (TMEDA), and tetramethyldiaminopropane (TMPDA); alicyclic amines such as cyclopropanediamine, cyclohexanediamine, and bisaminomethylcyclohexane; heterocyclic amines such as isophoronediamine, piperazine, dipiperidylpropane, and dimethylpiperazine; and aromatic amines such as phenyldiamine, tolylenediamine, naphthalenediamine, methylphenylenediamine, dimethylnaphthalenediamine, dimethylphenylenediamine, tetramethylphenylenediamine, and tetramethylnaphthalenediamine. Preferred examples include nitrile solvents such as acetonitrile and acrylonitrile; and solvents containing a nitrogen atom such as dimethylformamide and nitrobenzene.

[0116] Preferred examples of the solvent containing a halogen atom as a hetero atom include dichloromethane, chlorobenzene, trifluoromethylbenzene, chlorobenzene, chlorotoluene, and bromobenzene. Preferred examples of the solvent containing a sulfur atom include dimethyl sulfoxide and carbon disulfide.

[0117] When a solvent is used, the amount of solvent used is preferably 100 mL or more, more preferably 200 mL or more, even more preferably 250 mL or more, and even more preferably 300 mL or more per kg of the total amount of raw materials, and the upper limit is preferably 3000 mL or less, more preferably 2500 mL or less, even more preferably 2000 mL or less, and even more preferably 1550 mL or less. When the amount of solvent used is within the above range, the raw materials can be reacted efficiently.

[0118] (Dry) When mixing is performed using a solvent, the method may include drying the fluid (usually a slurry) obtained by mixing after the mixing. When a complexing agent is used as the solvent, the complexing agent is removed from a complex containing the complexing agent. When a complexing agent and a solvent are used in combination, the complexing agent is removed from a complex containing the complexing agent and the solvent is removed. When a solvent other than a complexing agent is used, the solvent is removed to obtain a sulfide solid electrolyte. The obtained sulfide solid electrolyte exhibits ionic conductivity due to lithium atoms.

[0119] The fluid obtained by mixing can be dried at a temperature that depends on the type of solvent, for example, at a temperature equal to or higher than the boiling point of the complexing agent. Alternatively, the complexing agent and the solvent used as needed can be evaporated by drying under reduced pressure (vacuum drying) using a vacuum pump or the like at typically 5 to 100°C, preferably 10 to 85°C, more preferably 15 to 70°C, and even more preferably at about room temperature (23°C) (for example, about room temperature ±5°C).

[0120] Drying may be performed by filtering the fluid using a glass filter or the like, by solid-liquid separation by decantation, or by solid-liquid separation using a centrifuge or the like. When a solvent other than a complexing agent is used, a sulfide solid electrolyte is obtained by solid-liquid separation. When a complexing agent is used as the solvent, after solid-liquid separation, drying is performed under the above-mentioned temperature conditions to remove the complexing agent incorporated into the complex. Specifically, solid-liquid separation can be easily performed by transferring the fluid to a container, allowing the sulfide (or a complex if a complexing agent is contained (which can also be called a precursor of a sulfide solid electrolyte)) to precipitate, followed by decantation to remove the supernatant complexing agent and solvent, or by filtration using, for example, a glass filter with a pore size of about 10 to 200 μm, preferably 20 to 150 μm.

[0121] Drying may be carried out after mixing and before the hydrogen treatment described below, or may be carried out after the hydrogen treatment.

[0122] The sulfide solid electrolyte obtained by the above-mentioned mixing, or, when a solvent is used, the sulfide solid electrolyte obtained by removing the solvent by the above-mentioned drying, exhibits ionic conductivity due to lithium atoms. The sulfide solid electrolyte obtained by the above mixing is basically an amorphous sulfide solid electrolyte (glass component) unless it is mixed by pulverizing using a pulverizer to the extent that it crystallizes, for example.

[0123] The sulfide solid electrolyte obtained by the above mixing may be an amorphous sulfide solid electrolyte (glass component) or a crystalline sulfide solid electrolyte, and can be appropriately selected as desired. When producing a crystalline sulfide solid electrolyte, the amorphous sulfide solid electrolyte obtained by the above mixing can be heated to form a crystalline sulfide solid electrolyte. The sulfide solid electrolyte may also include a crystalline sulfide solid electrolyte having an amorphous component (glass component) formed on its surface as a result of being subjected to a process such as pulverization described below in order to adjust the particle size of the powder of the crystalline sulfide solid electrolyte. Thus, the sulfide solid electrolyte having an amorphous component includes an amorphous sulfide solid electrolyte and a crystalline sulfide solid electrolyte having an amorphous component formed on its surface.

[0124] (heating) When a crystalline sulfide solid electrolyte is produced, heating may be further included. When an amorphous sulfide solid electrolyte (glass component) is obtained by the above mixing, a crystalline sulfide solid electrolyte can be obtained by heating, and when a crystalline sulfide solid electrolyte is obtained, a crystalline sulfide solid electrolyte with improved crystallinity can be obtained. Furthermore, when a complexing agent is used as a solvent during mixing, a complex containing the complexing agent is formed. However, the complexing agent can also be removed from the complex by heating without performing the drying process described above, thereby obtaining a sulfide solid electrolyte, and the sulfide solid electrolyte can be made amorphous or crystalline depending on the heating conditions.

[0125] For example, when obtaining an amorphous sulfide solid electrolyte, the heating temperature can be determined depending on the structure of the crystalline sulfide solid electrolyte obtained by heating the amorphous sulfide solid electrolyte. Specifically, the amorphous sulfide solid electrolyte is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA) at a temperature increase rate of 10°C / min. The heating temperature is preferably set to 5°C or less, more preferably 10°C or less, and even more preferably 20°C or less, starting from the temperature of the exothermic peak observed at the lowest temperature. There is no particular lower limit, but the heating temperature can be set to about -40°C or more, which is the temperature of the exothermic peak observed at the lowest temperature. By setting the temperature range, the amorphous sulfide solid electrolyte can be obtained more efficiently and reliably. The heating temperature for obtaining an amorphous sulfide solid electrolyte cannot be generally defined because it varies depending on the structure of the crystalline sulfide solid electrolyte to be obtained. However, it is generally preferably 135°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower. There is no particular lower limit, but it is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 105°C or higher.

[0126] Furthermore, when an amorphous sulfide solid electrolyte is heated to obtain a crystalline sulfide solid electrolyte, the heating temperature can be determined depending on the structure of the crystalline sulfide solid electrolyte, and is preferably higher than the heating temperature for obtaining an amorphous sulfide solid electrolyte. Specifically, the amorphous sulfide solid electrolyte is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA) at a temperature increase rate of 10°C / min. The temperature is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, starting from the peak top temperature of the exothermic peak observed at the lowest temperature. There is no particular upper limit, but it should be about 40°C or lower. By using such a temperature range, a crystalline sulfide solid electrolyte can be obtained more efficiently and reliably. The heating temperature for obtaining a crystalline sulfide solid electrolyte cannot be generally defined because it varies depending on the composition and structure of the resulting crystalline sulfide solid electrolyte. However, it is generally preferably 130°C or higher, more preferably 135°C or higher, and even more preferably 140°C or higher. There is no particular upper limit, but it is preferably 600°C or lower, more preferably 550°C or lower, and even more preferably 500°C or lower.

[0127] The heating time is not particularly limited as long as it is a time that allows a desired amorphous sulfide solid electrolyte or crystalline sulfide solid electrolyte to be obtained, but is, for example, preferably 1 minute or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, and even more preferably 1 hour or more. The upper limit of the heating time is not particularly limited, but is preferably 24 hours or less, more preferably 10 hours or less, even more preferably 5 hours or less, and even more preferably 3 hours or less.

[0128] Furthermore, the heating is preferably carried out in an inert gas atmosphere (e.g., a nitrogen atmosphere or an argon atmosphere) or a reduced pressure atmosphere (particularly in a vacuum). An inert gas atmosphere containing hydrogen at a certain concentration, for example, the concentration of hydrogen in the hydrogen treatment described below, may also be used. This is because deterioration (e.g., oxidation) of the crystalline sulfide solid electrolyte can be prevented. The heating method is not particularly limited, and examples thereof include a method using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, a baking furnace, etc. Furthermore, industrially, a horizontal dryer having a heating means and a feeding mechanism, a horizontal vibration fluidized dryer, etc. may also be used, and the method may be selected depending on the amount of processing to be heated.

[0129] (Sulfide solid electrolyte) As described above, the sulfide solid electrolyte used in this embodiment may be a commercially available product or may be manufactured. The sulfide solid electrolyte obtained by the above method is an amorphous (glass component), crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and is suitably used as the sulfide solid electrolyte in this embodiment.

[0130] (BET specific surface area) The specific surface area of ​​the sulfide solid electrolyte used in this embodiment is a BET specific surface area of ​​10 m 2 / g or more. Despite having such a large specific surface area, the modified sulfide solid electrolyte of this embodiment has excellent applicability when applied as a paste and exhibits the effect of efficiently achieving excellent battery performance. The higher the BET specific surface area of ​​the sulfide solid electrolyte, the more advantageous this effect can be. From this perspective, the BET specific surface area is set to 12 m 2 / g or more is preferable, and 15m 2 / g or more is more preferable, and 20m 2 From the same viewpoint, there is no particular upper limit, but in reality, it is preferable that the upper limit is 100 m 2 / g or less, preferably 75m 2 / g or less, more preferably 50m 2 / g or less. In this specification, the BET specific surface area is a specific surface area measured in accordance with JIS Z 8830:2013 (Method for measuring the specific surface area of ​​powder (solid) by gas adsorption) using krypton as the adsorbate.

[0131] (Amorphous sulfide solid electrolyte) The amorphous sulfide solid electrolyte obtained by the above method contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. Representative examples include solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr; and solid electrolytes further containing other atoms such as oxygen atoms and silicon atoms, such as Li2S-P2S5-Li2O-LiI and Li2S-SiS2-P2S5-LiI. From the viewpoint of obtaining higher ionic conductivity, preferred examples include solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr. The types of atoms constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0132] The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle diameter (D 50 ) can be, for example, in the range of 0.01 μm to 500 μm, or 0.1 to 200 μm.

[0133] (Crystalline sulfide solid electrolyte) The crystalline sulfide solid electrolyte obtained by the above method may be a so-called glass ceramic obtained by heating an amorphous solid electrolyte to a crystallization temperature or higher, and its crystal structure may be Li3PS4 crystal structure, Li4P2S6 crystal structure, Li7PS6 crystal structure, Li7P3S 11 Examples of such a crystal structure include a crystal structure having peaks at 2θ=approximately 20.2° and 23.6° (for example, JP 2013-16423 A).

[0134] Also, Li 4-x Ge 1-x P xS4-type thio-LISICON Region II crystal structure (Kanno et al., Journal of the Electrochemical Society, 148(7)A742-746(2001)), Li 4-x Ge 1-x P x Examples of such a crystal structure include a crystal structure similar to the S4-based thio-LISICON Region II type (see Solid State Ionics, 177 (2006), 2721-2725). The crystal structure of the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is preferably the thio-LISICON Region II type crystal structure among the above, since it can provide higher ionic conductivity. Here, the "thio-LISICON Region II type crystal structure" refers to a structure in which Li 4-x Ge 1-x P x S4-type thio-LISICON Region II crystal structure, Li 4-x Ge 1-x P x This indicates that the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment has either the thio-LISICON Region II type or a crystal structure similar to that of the S4-based thio-LISICON Region II type. The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may have the thio-LISICON Region II type crystal structure or may have it as the main crystal. However, from the viewpoint of obtaining higher ionic conductivity, it is preferable that it has it as the main crystal. In this specification, "having it as the main crystal" means that the proportion of the target crystal structure in the crystal structure is 80% or more, preferably 90% or more, and more preferably 95% or more. Furthermore, from the viewpoint of obtaining higher ionic conductivity, it is preferable that the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment does not contain crystalline Li3PS4 (β-Li3PS4).

[0135] In X-ray diffraction measurements using CuKα radiation, the diffraction peaks of the Li3PS4 crystal structure appear, for example, at 2θ = 17.5°, 18.3°, 26.1°, 27.3°, and 30.0°, the diffraction peaks of the Li4P2S6 crystal structure appear, for example, at 2θ = 16.9°, 27.1°, and 32.5°, and the diffraction peaks of the Li7PS6 crystal structure appear, for example, at 2θ = 15.3°, 25.2°, 29.6°, and 31.0°, and the diffraction peaks of the Li7P3S 11 Diffraction peaks of the crystal structure appear, for example, at 2θ = 17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°. 4-x Ge 1-x P x The diffraction peaks of the S4 thio-LISICON Region II crystal structure appear, for example, at 2θ = 20.1°, 23.9°, and 29.5°. 4-x Ge 1-x P x Diffraction peaks of a crystal structure similar to the S4 thio-LISICON Region II type appear, for example, at 2θ = 20.2 and 23.6°. Note that these peak positions may vary within a range of ±0.5°.

[0136] As described above, when a thiolisiconregion II crystal structure is obtained in this embodiment, it is preferable that the thiolisiconregion II crystal structure does not contain crystalline Li3PS4 (β-Li3PS4). The sulfide solid electrolyte obtained by the production method of this embodiment does not have diffraction peaks at 2θ = 17.5° and 26.1° seen in crystalline Li3PS4, or even if it does have such peaks, the detected peaks are extremely small compared to the diffraction peaks of the thiolisiconregion II crystal structure.

[0137] The compound has the structural skeleton of Li7PS6 and has the composition formula Li in which part of the P is replaced with Si. 7-x P 1-y Si y S6 and Li 7+x P 1-y Si yThe crystal structure represented by S6 (where x ranges from -0.6 to 0.6 and y ranges from 0.1 to 0.6) is cubic or orthorhombic, preferably cubic, and in X-ray diffraction measurement using CuKα radiation, it mainly has peaks appearing at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. The above composition formula Li 7-x-2y PS 6-x-y Cl x (where 0.8 ≤ x ≤ 1.7 and 0 < y ≤ -0.25x + 0.5) is preferably cubic, and in X-ray diffraction measurement using CuKα radiation, it mainly has peaks appearing at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. Also, the above composition formula Li 7-x PS 6-x Ha x (where Ha is Cl or Br, and x is preferably from 0.2 to 1.8) is preferably cubic, and in X-ray diffraction measurement using CuKα radiation, it mainly has peaks appearing at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. The crystal structures basically having the structural framework of these Li7PS6 are also referred to as the argyrodite-type crystal structure. Note that these peak positions may shift within a range of ±0.5°.

[0138] The shape of the crystalline sulfide solid electrolyte is not particularly limited, and for example, particulate form can be mentioned. The average particle size (D 50 ) of the particulate crystalline sulfide solid electrolyte can be exemplified within a range of, for example, 0.01 μm to 500 μm, 0.1 to 200 μm.

[0139] (Properties of the modified sulfide solid electrolyte) The modified sulfide solid electrolyte of this embodiment has a BET specific surface area of 10 m 2 / g or more and has a large specific surface area. From the viewpoint that the higher the BET specific surface area of the sulfide solid electrolyte, the more the superiority of the effect can be shown, the BET specific surface area is 12 m 2 / g or more is preferable, and 15m 2 / g or more is more preferable, and 20m 2 From the same viewpoint, there is no particular upper limit, but in reality, it is preferable that the upper limit is 100 m 2 / g or less, preferably 75m 2 / g or less, more preferably 50m 2 / g or less. Even if lithium halide adheres to the surface, it does not have a significant effect on the BET specific surface area of ​​the sulfide solid electrolyte, and the BET specific surface area of ​​the sulfide solid electrolyte used in this embodiment is substantially the same as the BET specific surface area of ​​the modified sulfide solid electrolyte. 2 / g or more, the BET specific surface area of ​​the modified sulfide solid electrolyte will naturally be 10m 2 / g or more.

[0140] Although the BET specific surface area of ​​the modified sulfide solid electrolyte of this embodiment is large as described above, the oil absorption is typically small, less than 0.9 mL / g, and even less than 0.85 mL / g, or even less than 0.80 mL / g, due to the effect of the lithium halide attached to the surface. Because the modified sulfide solid electrolyte of this embodiment has a small oil absorption despite its large BET specific surface area, it is possible to suppress an increase in the viscosity of the paste when it is made into a paste, resulting in excellent coatability. Furthermore, since there is no need to use a solvent or the like to suppress an increase in the viscosity of the paste, excellent battery performance is more likely to be achieved. In this specification, the oil absorption was measured by adding one drop of butyl butyrate to 1 g of a modified sulfide solid electrolyte sample in a mortar or the like, stirring with a spatula, and repeating this process until the sample became paste-like. The total amount of butyl butyrate added was taken as the oil absorption (mL / g). Here, "paste-like" refers to a state in which the sample "can be spread without breaking or crumbling and can be lightly adhered to a measurement plate," as defined in "7.2 Measurement" of JIS K5101-13-1:2004 (Testing methods for pigments - Part 13: Oil absorption - Section 1: Refined linseed oil method).

[0141] Furthermore, the ionic conductivity of the modified sulfide solid electrolyte of this embodiment is usually 0.5 mS / cm or more, and further, 1.0 mS / cm or more, 1.5 mS / cm or more, 2.0 mS / cm or more, or 2.5 mS / cm or more, and has extremely high ionic conductivity, resulting in a lithium battery with excellent battery performance.

[0142] (Application) The modified sulfide solid electrolyte of the present embodiment has excellent coating suitability and can be used in the manufacture of batteries without using a solvent, etc., and therefore can efficiently exhibit excellent battery performance. In addition, the modified sulfide solid electrolyte has high ionic conductivity and excellent battery performance, making it suitable for use in batteries. The modified sulfide solid electrolyte of this embodiment may be used in a positive electrode layer, a negative electrode layer, or an electrolyte layer. Each layer may be produced by a known method.

[0143] The battery preferably includes a current collector in addition to the positive electrode layer, electrolyte layer, and negative electrode layer, and a known current collector can be used. For example, a layer of a material that reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu, coated with Au or the like can be used.

[0144] [Method for producing modified sulfide solid electrolyte] The method for producing a modified sulfide solid electrolyte of this embodiment is to produce a modified sulfide solid electrolyte having a BET specific surface area of ​​10 m 2 / g or more and containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, an epoxy compound, and an organic solvent, and removing the organic solvent. According to the production method of this embodiment, the modified sulfide solid electrolyte of this embodiment can be efficiently produced, that is, the modified sulfide solid electrolyte of this embodiment is preferably produced by the production method of this embodiment.

[0145] The BET specific surface area used in the manufacturing method of this embodiment is 10 m 2The sulfide solid electrolyte having a densitometric value of 0.1 to 1.0 μm and containing lithium, sulfur, phosphorus, and halogen atoms is the same as the sulfide solid electrolyte described above as being usable in the modified sulfide solid electrolyte of this embodiment. Therefore, the sulfide solid electrolyte may be a commercially available product, or may be one produced by the above-described sulfide solid electrolyte method.

[0146] Examples of organic solvents used in the production method of this embodiment include the solvents described above as being usable in the method for producing a sulfide solid electrolyte. From the viewpoint of promoting mixing of the sulfide solid electrolyte with the epoxy compound and efficiently obtaining a modified sulfide solid electrolyte containing the sulfide solid electrolyte and the epoxy compound, and further from the viewpoint of promoting adhesion of the epoxy compound to the sulfide solid electrolyte, among the above solvents, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and ether solvents, ester solvents, and nitrile solvents exemplified as complexing agents are preferred, with aromatic hydrocarbon solvents being more preferred. In the production method of this embodiment, the organic solvent may be one of these, or a combination of two or more of them.

[0147] In the production method of this embodiment, the method of mixing the sulfide solid electrolyte, the epoxy compound, and the organic solvent can be the same as the “mixing” method in the method of producing the sulfide solid electrolyte described above.

[0148] The organic solvent can be removed by the same method as the "drying" in the method for producing the sulfide solid electrolyte. In addition, in the production method of this embodiment, the "heating" step in the method for producing the sulfide solid electrolyte may be carried out.

[0149] [Another modified sulfide solid electrolyte] The modified sulfide solid electrolyte according to another embodiment of the present invention (the modified sulfide solid electrolyte according to the fifteenth embodiment of the present invention) has a BET specific surface area of ​​10 m 2 / g or more and containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and an epoxy compound. As described above, such modified sulfide solid electrolytes in other forms also have excellent coatability when applied as a paste, as does the modified sulfide solid electrolyte of the present embodiment, and exhibit the effect of being able to efficiently achieve excellent battery performance.

[0150] The BET specific surface area, epoxy compound, sulfide solid electrolyte and its manufacturing method, and method for manufacturing the modified sulfide solid electrolyte in the modified sulfide solid electrolyte of the above-mentioned different form are the same as those described for the modified sulfide solid electrolyte of the above-mentioned embodiment.

[0151] [Electrode composite material] The electrode composite of this embodiment is an electrode composite containing the modified sulfide solid electrolyte of this embodiment and an electrode active material, or an electrode composite containing the modified sulfide solid electrolyte of another form and an electrode active material.

[0152] (electrode active material) As the electrode active material, a positive electrode active material or a negative electrode active material is adopted depending on whether the electrode mixture is used for the positive electrode or the negative electrode.

[0153] The positive electrode active material can be any material that can promote a battery chemical reaction involving the movement of lithium ions due to atoms that are used to exhibit ionic conductivity, preferably lithium atoms, in relation to the negative electrode active material. Examples of such positive electrode active materials that can insert and extract lithium ions include oxide-based positive electrode active materials and sulfide-based positive electrode active materials.

[0154] Preferred examples of oxide-based positive electrode active materials include lithium-containing transition metal composite oxides such as LMO (lithium manganese oxide), LCO (lithium cobalt oxide), NMC (lithium nickel manganese cobalt oxide), NCA (lithium nickel cobalt aluminate), LNCO (lithium nickel cobalt oxide), and olivine-type compounds (LiMeNPO4, Me=Fe, Co, Ni, Mn). Examples of sulfide-based positive electrode active materials include titanium sulfide (TiS2), molybdenum sulfide (MoS2), iron sulfide (FeS, FeS2), copper sulfide (CuS), and nickel sulfide (Ni3S2). In addition to the above positive electrode active materials, niobium selenide (NbSe3) and the like can also be used. The positive electrode active material can be used alone or in combination of two or more kinds.

[0155] The negative electrode active material can be any material that can promote a battery chemical reaction involving the movement of lithium ions originating from lithium atoms, such as an atom that is used as an atom to exhibit ionic conductivity, preferably a metal that can form an alloy with lithium atoms, an oxide thereof, an alloy of the metal with lithium atoms, etc. As such a negative electrode active material capable of inserting and extracting lithium ions, any material known in the field of batteries as a negative electrode active material can be used without any limitation. Examples of such negative electrode active materials include metallic lithium, metallic indium, metallic aluminum, metallic silicon, metallic tin, and other metallic lithium or metals capable of forming alloys with metallic lithium, oxides of these metals, and alloys of these metals with metallic lithium.

[0156] The electrode active material used in this embodiment may have a coating layer on its surface. The material for forming the coating layer is an ion conductor such as an atom that exhibits ionic conductivity in the sulfide solid electrolyte, preferably a nitride or oxide of lithium atoms, or a composite thereof. Specifically, lithium nitride (Li3N), Li4GeO4, and the like, which have a main structure, for example, Li 4-2x Zn x Conductors with a lithiated crystal structure such as GeO4, and those with a Li3PO4-type framework structure such as Li 4-x Ge 1-x P x Conductors with thiolicon-type crystal structures such as S4, La 2 / 3-x Li 3xExamples include conductors having a perovskite crystal structure such as TiO3, and conductors having a NASICON crystal structure such as LiTi2(PO4)3. Also, Li y Ti 3-y O4(0 <y<3)、Li4Ti5O 12 Examples include lithium titanates such as (LTO), lithium metal oxides of metals belonging to Group 5 of the periodic table such as LiNbO3 and LiTaO3, and oxide-based conductors such as Li2O-B2O3-P2O5, Li2O-B2O3-ZnO, and Li2O-Al2O3-SiO2-P2O5-TiO2.

[0157] An electrode active material having a coating layer can be obtained, for example, by applying a solution containing various atoms constituting the material that forms the coating layer to the surface of the electrode active material, and then firing the electrode active material after application at a temperature preferably between 200°C and 400°C. Here, the solution containing various atoms may be a solution containing alkoxides of various metals such as lithium ethoxide, titanium isopropoxide, niobium isopropoxide, tantalum isopropoxide, etc. In this case, the solvent may be an alcoholic solvent such as ethanol or butanol, an aliphatic hydrocarbon solvent such as hexane, heptane or octane, or an aromatic hydrocarbon solvent such as benzene, toluene or xylene. The above-mentioned attachment may be carried out by immersion, spray coating or the like.

[0158] From the viewpoint of improving production efficiency and battery performance, the firing temperature is preferably 200°C or higher and 400°C or lower, more preferably 250°C or higher and 390°C or lower, and the firing time is usually about 1 minute to 10 hours, preferably 10 minutes to 4 hours.

[0159] The coverage of the coating layer is preferably 90% or more, more preferably 95% or more, and even more preferably 100% of the surface area of ​​the electrode active material, i.e., the entire surface is covered. The thickness of the coating layer is preferably 1 nm or more, more preferably 2 nm or more, and the upper limit is preferably 30 nm or less, more preferably 25 nm or less. The thickness of the coating layer can be measured by cross-sectional observation using a transmission electron microscope (TEM), and the coverage rate can be calculated from the thickness of the coating layer, elemental analysis values, and BET specific surface area.

[0160] (Other ingredients) The electrode mixture of this embodiment may contain, in addition to the modified sulfide solid electrolyte and electrode active material, other components such as a conductive material, a binder, etc. That is, the method for producing an electrode mixture of this embodiment may use, in addition to the modified sulfide solid electrolyte and electrode active material, other components such as a conductive material, a binder, etc. The conductive material, binder, etc. may be added to and mixed with the modified sulfide solid electrolyte and electrode active material when mixing the modified sulfide solid electrolyte and electrode active material. Examples of the conductive material, from the viewpoint of improving battery performance by improving electronic conductivity, include carbon-based materials such as artificial graphite, graphite carbon fiber, resin-baked carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads, furfuryl alcohol resin-baked carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon.

[0161] By using a binder, the strength of the positive electrode and the negative electrode when they are fabricated is improved. The binder is not particularly limited as long as it can impart functions such as binding property and flexibility, and examples thereof include fluorine-based polymers such as polytetrafluoroethylene and polyvinylidene fluoride, thermoplastic elastomers such as butylene rubber and styrene-butadiene rubber, and various resins such as acrylic resin, acrylic polyol resin, polyvinyl acetal resin, polyvinyl butyral resin, and silicone resin.

[0162] The compounding ratio (mass ratio) of the electrode active material to the modified sulfide solid electrolyte in the electrode mixture is preferably 99.5:0.5 to 40:60, more preferably 99:1 to 50:50, and even more preferably 98:2 to 60:40, in order to improve battery performance and in consideration of production efficiency.

[0163] When a conductive material is contained, the content of the conductive material in the electrode mixture is not particularly limited, but in consideration of improving battery performance and production efficiency, the content is preferably 0.5 mass% or more, more preferably 1 mass% or more, and even more preferably 1.5 mass% or more, and the upper limit is preferably 10 mass% or less, preferably 8 mass% or less, and even more preferably 5 mass% or less. Furthermore, when a binder is contained, the content of the binder in the electrode mixture is not particularly limited, but in consideration of improving battery performance and production efficiency, the content is preferably 1 mass % or more, more preferably 3 mass % or more, and even more preferably 5 mass % or more, with the upper limit being preferably 20 mass % or less, preferably 15 mass % or less, and even more preferably 10 mass % or less.

[0164] [Lithium-ion battery] The lithium ion battery of this embodiment is a lithium ion battery that includes at least one selected from the modified sulfide solid electrolyte of this embodiment described above and the electrode composite described above, and also includes at least one selected from the modified sulfide solid electrolyte of another form described above and the electrode composite described above.

[0165] The lithium ion battery of this embodiment is not particularly limited in its configuration as long as it contains either the modified sulfide solid electrolyte of this embodiment, an electrode composite containing the same, or a different form of modified sulfide solid electrolyte or an electrode composite containing the same, and may have the configuration of a commonly used lithium ion battery.

[0166] The lithium ion battery of this embodiment preferably includes, for example, a positive electrode layer, a negative electrode layer, an electrolyte layer, and a current collector. The positive electrode layer and the negative electrode layer preferably use the electrode mixture of this embodiment, and the electrolyte layer preferably uses the modified sulfide solid electrolyte of this embodiment or another modified sulfide solid electrolyte.

[0167] The current collector may be a known material, for example, a layer of Au or the like coated with a material that reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu. [Example]

[0168] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0169] Production Example 1: Preparation of sulfide solid electrolyte 1 A Schlenk flask (volume: 100 mL) equipped with a stirrer was charged with 0.59 g of lithium sulfide, 0.95 g of diphosphorus pentasulfide, 0.19 g of lithium bromide, and 0.28 g of lithium iodide under a nitrogen atmosphere. After rotating the stirrer, 20 mL of the complexing agent tetramethylethylenediamine (TMEDA) was added, and stirring was continued for 12 hours. The resulting complex was dried under vacuum (room temperature: 23 °C) to obtain a powdered complex. The complex powder was then heated under vacuum at 120 °C for 2 hours to obtain an amorphous sulfide solid electrolyte. The amorphous sulfide solid electrolyte was then heated under vacuum at 140 °C for 2 hours to obtain a crystalline sulfide solid electrolyte 1 (the heating temperature (140 °C in this example) to obtain a crystalline sulfide solid electrolyte is sometimes referred to as the "crystallization temperature"). The BET specific surface area of ​​the obtained amorphous sulfide solid electrolyte and crystalline sulfide solid electrolyte was measured, and both were 40 m 2 / g.

[0170] Production Example 2: Preparation of sulfide solid electrolyte 2 In a reaction vessel equipped with an agitator (volume: 500 mL), 30.0 g of the sulfide solid electrolyte powder obtained in Production Example 1 and 470 g of toluene were placed under a nitrogen atmosphere. After rotating the agitator, the mixture was pulverized for 30 minutes using a microbead mill capable of circulating (model UAM-015, manufactured by Hiroshima Metal & Machinery Co., Ltd.) under specified conditions (bead material: zirconia, bead diameter: 0.1 mm, bead amount: 391 g, pump flow rate: 150 mL / min, peripheral speed: 8 m / s, mill jacket temperature: 20°C). The resulting slurry was dried under vacuum (room temperature: 23°C) to obtain a white powder of amorphous solid electrolyte. This white powder was crystallized at 160°C for 2 hours to obtain crystalline sulfide solid electrolyte 2. The BET specific surface area of ​​the resulting crystalline sulfide solid electrolyte 2 was measured and found to be 10 m 2 / g.

[0171] Production Example 3: Preparation of sulfide solid electrolyte 3 In a reaction vessel equipped with an agitator (volume: 500 mL), 30.0 g of the sulfide solid electrolyte powder obtained in Production Example 1 and 470 g of toluene were charged under a nitrogen atmosphere. After rotating the agitator, a microbead mill capable of circulating (model UAM-015, manufactured by Hiroshima Metal & Machinery Co., Ltd.) was used to carry out a first pulverization treatment for 30 minutes under specified conditions (bead material: zirconia, bead diameter: 0.05 mm, bead amount: 391 g, pump flow rate: 150 mL / min, peripheral speed: 8 m / s, mill jacket temperature: 20°C). The peripheral speed was then changed to 12.5 m / s, and a second pulverization treatment was carried out for 10 minutes. The resulting slurry was dried under vacuum (room temperature: 23°C) to obtain a white powder of amorphous solid electrolyte. This white powder was crystallized at 160°C for 2 hours to obtain crystalline sulfide solid electrolyte 3. The BET specific surface area of ​​the resulting crystalline sulfide solid electrolyte 3 was measured and found to be 8 m 2 / g.

[0172] Production Example 4: Preparation of sulfide solid electrolyte 4 In a glove box under a nitrogen atmosphere, a total of 110.0 g of a mixture having a molar ratio of Li2S:P2S5:LiBr:LiCl=47.5:12.5:15.0:25.0 was weighed out and roughly mixed by shaking in a glass container. The coarsely mixed raw materials were dispersed in a mixed solvent of 1140 mL of dehydrated toluene (manufactured by Wako Pure Chemical Industries) and 7 mL of dehydrated isobutyronitrile (manufactured by Kishida Chemical Co., Ltd.) under a nitrogen atmosphere to form a slurry (slurry concentration: 10% by mass). The slurry was mixed and ground for 1 hour using a circulating bead mill (model number "LMZ015", manufactured by Ashizawa Finetech Co., Ltd.) (bead material: zirconia, bead diameter: 0.5 mmφ, bead amount: 456 g, pump flow rate: 500 mL / min, peripheral speed: 12 m / s). Next, the slurry was dried under reduced pressure, and 30.0 g of the resulting raw material mixture was dispersed in 300 mL of ethylbenzene (manufactured by Wako Pure Chemical Industries, Ltd.). The slurry was dried under reduced pressure to remove the solvent, and the resulting mixture was fired at 380°C for at least 1 hour using an electric furnace ("F-1404-A (model number)", manufactured by Tokyo Glass Instruments Co., Ltd.) in a glove box under a nitrogen atmosphere, to obtain a crystalline sulfide solid electrolyte 4 having an argyrodite-type crystal structure. The BET specific surface area of ​​the resulting crystalline sulfide solid electrolyte 4 was measured and found to be 12 m 2 / g.

[0173] Example 1 In a nitrogen atmosphere, 3 g of the crystalline sulfide solid electrolyte 1 obtained in Production Example 1 was weighed and added to a Schlenk tube (volume: 100 mL) equipped with a stirrer, and 22 g of toluene was added and stirred to form a slurry fluid. 0.05 g of butylene oxide (5 parts by mass relative to 100 parts by mass of the crystalline sulfide solid electrolyte) was further added to the slurry fluid as an epoxy compound, and after stirring for 10 minutes, the toluene was distilled off by vacuum drying to obtain a modified sulfide solid electrolyte. The oil absorption and ionic conductivity of the obtained modified sulfide solid electrolyte were measured according to the following methods. The reduction rate of the oil absorption was calculated according to the following methods. The measurement results and calculation results are shown in Table 1. Furthermore, FT-IR analysis (ATR method) was carried out according to the following method, and the infrared absorption spectrum showed a peak at 2800 to 3000 cm-1 It was confirmed that there was a peak at . 1 1 H-NMR measurement confirmed that the compound had a peak at 0.0 to 5.0 ppm derived from alkyl chains.

[0174] Examples 2 to 19 A modified sulfide solid electrolyte was prepared in the same manner as in Example 1, except that the type of crystalline sulfide solid electrolyte and the type and amount of epoxy compound used were changed to those shown in Table 1. The oil absorption and ionic conductivity of the obtained modified sulfide solid electrolyte were measured according to the following methods. The reduction rate of the oil absorption was calculated according to the following methods. The measurement results and calculation results are shown in Table 1. Furthermore, FT-IR analysis (ATR method) was carried out according to the following method, and the infrared absorption spectrum showed a peak at 2800 to 3000 cm -1 It was confirmed that there was a peak at . 1 1 H-NMR measurement confirmed that the compound had a peak at 0.0 to 5.0 ppm derived from alkyl chains.

[0175] Comparative Examples 1 to 3 The oil absorption and ionic conductivity of sulfide solid electrolytes 1 to 3 obtained in Production Examples 1 to 3 were measured according to the following methods. The reduction rate of oil absorption was also calculated according to the following method. The measurement and calculation results are shown in Table 1. The oil absorption of sulfide solid electrolytes 1 to 3 was 1.03 mL / g, 0.93 mL / g, and 0.66 mL / g, respectively. In addition, FT-IR analysis (ATR method) was performed based on the following method. In the infrared absorption spectrum, -1 No peak was observed at this point. 1 When H-NMR measurement was carried out, no peaks at 0.0 to 5.0 ppm due to alkyl chains were confirmed.

[0176] (Measurement of oil absorption) 1 g of the solid electrolyte obtained in each of the examples and comparative examples was used as a sample, and in an agate mortar, one drop of butyl butyrate was added using a dropper and stirred with a spatula, and this operation was repeated until the sample became a paste, and the total amount of butyl butyrate added was taken as the oil absorption (mL / g). The measured oil absorption was evaluated according to the following criteria. A. Less than 0.8 mL / g B. 0.8 mL / g or more and less than 0.9 mL / g C. 0.9 mL / g or more

[0177] (Decrease rate of oil absorption) The oil absorptions of sulfide solid electrolytes 1 to 4 obtained in Production Examples 1 to 4 were measured in the same manner as described above (oil absorption measurement). Using the oil absorption A of sulfide solid electrolytes 1 to 4 and the oil absorption B of the sulfide solid electrolytes obtained in the Examples and Comparative Examples by the above (oil absorption measurement), the value calculated by the following formula was used as the oil absorption reduction rate. Here, the oil absorption A is taken to be the oil absorption of any of sulfide solid electrolytes 1 to 4 used in the Examples and Comparative Examples. For example, the oil absorption reduction rate of Example 1 is calculated by defining the oil absorption of sulfide solid electrolyte 1 as oil absorption A and the oil absorption of the modified sulfide solid electrolyte of Example 1 as oil absorption B. Decrease rate of oil absorption = (Oil absorption A - Oil absorption B) / Oil absorption A x 100 (%)

[0178] (Measurement of ionic conductivity) In this example, the ionic conductivity was measured as follows. From the sulfide solid electrolyte, a 10 mm diameter (cross-sectional area S: 0.785 cm 2 ) and a height (L) of 0.1 to 0.3 cm were molded into circular pellets to serve as samples. Electrode terminals were attached to the top and bottom of the samples, and measurements were made at 25°C using the AC impedance method (frequency range: 1 MHz to 100 Hz, amplitude: 10 mV) to obtain a Cole-Cole plot. The real part Z' (Ω) at the point where -Z'' (Ω) is minimum near the right end of the arc observed in the high-frequency region was taken as the bulk resistance R (Ω) of the electrolyte, and the ionic conductivity σ (S / cm) was calculated according to the following equation: R=ρ(L / S) σ=1 / ρ The measured ionic conductivity was evaluated according to the following criteria. A.2.5mS / cm or more B. 0.5 mS / cm or more and less than 2.5 mS / cm C. Less than 0.5 mS / cm

[0179] (FT-IR analysis (ATR method)) Measurement equipment: FR-IR spectrometer "VERTEX70v (model number)" manufactured by Bruker Measurement method: Total reflection measurement method (ATR method) Measurement wavenumber range: 650 to 4000 cm -1 Light source: Globar lamp (SiC) Detector: DTGS detector Resolution: 4cm -1 Measurement time: 1 second / time Accumulation count: 256 times Measurement conditions: Using a diamond prism, irradiating at an incident angle of 45°

[0180] ( 1 H-NMR measurement) Nuclear magnetic resonance spectrometer (NMR spectrometer): AVANCE III HD (Beuker) Observation kernel: 1 H Resonance frequency: 500MHz Probe: 5mmφ TCI cryoprobe Measurement temperature: 25℃ Accumulation count: 16 times

[0181] [Table 1]

[0182] From the examples, the modified sulfide solid electrolyte of this embodiment was rated A or B in terms of oil absorption, and the reduction rate of the oil absorption was 15% or more in both cases. 2 / g or more, it was confirmed that the oil absorption was small and the coating suitability was excellent. It was also confirmed that the ionic conductivity was high, with an A or B rating. On the other hand, the sulfide solid electrolytes of Comparative Examples 1 to 3, which were not mixed with an epoxy compound and did not contain an epoxy compound, were sulfide solid electrolytes 1 to 3 prepared in Production Examples 1 to 3, respectively, and were the conventional sulfide solid electrolytes themselves. 2 / g or more, sulfide solid electrolytes 1 and 2 were rated C in terms of oil absorption, confirming that they were poor in coatability. Furthermore, sulfide solid electrolyte 3 of Comparative Example 3 was rated A in both oil absorption and ionic conductivity, confirming that there was little need for modification. That is, the method for producing a modified sulfide solid electrolyte of this embodiment was 2 It has been confirmed that a high molecular weight of 1 / g or more is suitable because it can reduce the oil absorption amount and improve the coatability.

[0183] Example 20 The modified sulfide solid electrolyte obtained in the above example was examined as follows to confirm whether or not the epoxy compound was attached to the sulfide solid electrolyte. First, the modified sulfide solid electrolyte obtained in Example 6, containing 1 mass% 1,2-epoxyoctadecane (1 part by mass of 1,2-epoxyoctadecane per 100 mass parts of sulfide solid electrolyte), was slurried with toluene (slurry concentration: 12 mass%) and allowed to stand for 12 hours. The supernatant resulting from the settling of the sulfide solid electrolyte was collected and analyzed by gas chromatography-mass spectrometry (GC / MS). The quantification in this analysis was carried out by analyzing the feed solution (a 1 mass% toluene solution of 1,2-epoxyoctadecane) in the same manner as the supernatant, and the peak area of ​​1,2-epoxyoctadecane in the feed solution was set to 1 and compared with the peak area of ​​1,2-epoxyoctadecane remaining in the supernatant (the closer the peak area of ​​the supernatant is to 1, the more epoxy compounds are liberated from the sulfide solid electrolyte and dissolved in toluene). According to this analysis, no epoxy compounds were detected in the supernatant, and therefore it is believed that all of the epoxy compounds were attached to the sulfide solid electrolyte.

[0184] (Gas chromatography mass spectrometry conditions) Gas chromatograph: 6890B (Agient) Analytical column: HP-5ms (Agilent) GC oven temperature rise conditions: initial temperature 50℃ 50℃~300℃, temperature rise at 10℃ / min Hold at 300℃ for 5 minutes Sample injection volume: 1 μL

[0185] The precipitated sulfide solid electrolyte was washed by adding toluene to the precipitated sulfide solid electrolyte, stirring the mixture, leaving it to stand for 12 hours, and removing the supernatant. This process was repeated three times. After washing, the sulfide solid electrolyte obtained by drying the toluene was dissolved in deuterated methanol and purified by the above method. 1 H-NMR measurements revealed the chemical shifts of groups (such as alkyl groups) derived from epoxy compounds.

[0186] Example 21 A modified sulfide solid electrolyte was obtained in the same manner as in Example 6, except that the content of 1,2-epoxyoctadecane in Example 6 was 3 mass % (the amount of 1,2-epoxyoctadecane used was 3 mass parts per 100 mass parts of the sulfide solid electrolyte). The oil absorption of the obtained modified sulfide solid electrolyte was measured according to the oil absorption measurement method described above. The reduction rate of the oil absorption was calculated according to the following method. The measurement and calculation results are shown in Table 1. The supernatant of the obtained modified sulfide solid electrolyte was analyzed by gas chromatography mass spectrometry (GC / MS) in the same manner as in Example 20. According to this analysis, although a small amount of epoxy compound was detected in the supernatant (peak area: 0.25), it was confirmed that the epoxy compound was attached to the sulfide solid electrolyte. The settled powder was also treated in the same manner as in Example 20. 1 H-NMR measurements revealed the chemical shifts of groups (such as alkyl groups) derived from epoxy compounds.

[0187] Example 22 A modified sulfide solid electrolyte was obtained in the same manner as in Example 6, except that the content of 1,2-epoxyoctadecane in Example 6 was 10 mass% (10 parts by mass of 1,2-epoxyoctadecane per 100 parts by mass of sulfide solid electrolyte). The oil absorption of the obtained modified sulfide solid electrolyte was measured according to the oil absorption measurement method described above. The reduction rate of the oil absorption was calculated according to the following method. The measurement and calculation results are shown in Table 1. The supernatant of the obtained modified sulfide solid electrolyte was analyzed by gas chromatography mass spectrometry (GC / MS) in the same manner as in Example 20. According to this analysis, although a small amount of epoxy compound was detected in the supernatant (peak area: 0.43), it was confirmed that the epoxy compound was attached to the sulfide solid electrolyte. The settled powder was also treated in the same manner as in Example 20. 1 H-NMR measurements revealed the chemical shifts of groups (such as alkyl groups) derived from epoxy compounds. From the results of Examples 20 to 22, it was confirmed that the epoxy compound in the modified sulfide solid electrolyte is contained in such a way that it adheres to the sulfide solid electrolyte, and that most of the epoxy compound remains in the modified sulfide solid electrolyte even after washing with toluene. 1 H-NMR measurements confirmed that the epoxy compounds remained in the modified sulfide solid electrolyte.

[0188] Examples 23 to 28 A modified sulfide solid electrolyte was prepared in the same manner as in Example 1, except that the type of crystalline sulfide solid electrolyte and the type and amount of epoxy compound used were changed to those shown in Table 2. The oil absorption and ionic conductivity of the resulting modified sulfide solid electrolyte were measured according to the above-mentioned methods. The reduction rate of the oil absorption was also calculated according to the above-mentioned methods. The measurement and calculation results are shown in Table 2.

[0189] Comparative Example 4 For each sulfide solid electrolyte 4 obtained in Production Example 4, the oil absorption and ionic conductivity were measured according to the following methods. The reduction rate of oil absorption was also calculated according to the above methods. The measurement results and calculation results are shown in Table 2. The oil absorption of sulfide solid electrolyte 4 was 1.06 mL / g. In addition, FT-IR analysis (ATR method) was performed based on the above method, and the infrared absorption spectrum showed a peak at 2800-3000 cm -1 No peak was observed at this point. 1 When H-NMR measurement was carried out, no peaks at 0.0 to 5.0 ppm due to alkyl chains were confirmed.

[0190] (CV measurement (irreversible capacity) To evaluate the irreversible capacity, the following CV measurement cell was used. A total of 100 mg of the sulfide solid electrolyte obtained in the examples and granular Denka Black (particle size: 35 nm, manufactured by Denka Co., Ltd.) (sulfide solid electrolyte: Denka Black (mass ratio) = 85:15) were mixed in a mortar for 10 minutes to obtain powder (1) for measurement. 100 mg of electrolyte for the separator layer was added to a 10 mm diameter battery cell, and the cell was pressurized in a stainless steel mold at 10 MPa / cm 2 After pressing three times while rotating by 120° at a pressure of 20 MPa / cm, 50 mg of powder (1) was added. 2 Then, the powder (1) was pressed three times with a pressure of 20 MPa / cm from the opposite side of the powder (1). 2 The press was performed three times, rotating the press by 120° each time.

[0191] The electrolyte for the separator was synthesized under the following conditions. A 1-L reactor equipped with an impeller was charged with 20.5 g of L2S, 33.1 g of P2S5, 10.0 g of LiI, and 6.5 g of LiBr under a nitrogen atmosphere. After rotating the impeller, 630 g of toluene was added, and the resulting slurry was stirred for 10 minutes. The reactor was connected to a recirculating bead mill ("Star Mill LMZ015" (product name), manufactured by Ashizawa Finetech Co., Ltd., zirconia bead material: zirconia, bead diameter: 0.5 mm, bead amount: 456 g), and milling was performed for 45 hours (pump flow rate: 650 mL / min, bead mill peripheral speed: 12 m / s, mill jacket temperature: 45 °C). The obtained slurry was dried under vacuum at room temperature (25°C) and then heated (80°C) to obtain a white powder of amorphous solid electrolyte. The obtained white powder was further heated under vacuum at 195°C for 2 hours to obtain a white powder of crystalline solid electrolyte. In the XRD spectrum of the crystalline solid electrolyte, crystallization peaks were detected at 2θ = 20.2° and 23.6°, confirming that it had a thiolicon region II crystal structure. In addition, the average particle size (D 50 ) was 4.5 μm and the ionic conductivity was 5.0 mS / cm.

[0192] An InLi foil (having a layered structure, " / " indicates the space between each layer. In: 10mmφ×0.1mm / Li: 9mmφ×0.08mm / SUS: 10mmφ×0.1mm) was placed on the opposite side of the electrolyte measurement powder (1) for the separator layer, and a pressure of 6 MPa / cm was applied. 2The cell was fixed with four screws with an insulator between them to prevent a short circuit between the powder (1) and the InLi foil, and the screws were fixed with a torque of 8 N m to obtain the measurement cell.

[0193] The obtained measurement cell was connected to a measuring device ("VSP-3 (model number)", manufactured by Biologic), and a CV curve was obtained under the following conditions. Measurement temperature: 25℃ Sweep speed: 0.1mV / s Potential measurement range: Open circuit voltage (+2.7V) → +5.0V → +2.7V Number of cycles: 5

[0194] [Table 2]

[0195] From Examples 23 to 28, the modified sulfide solid electrolyte of this embodiment was rated A or B in terms of oil absorption, and the reduction rate of the oil absorption was 17% or more in all cases. 2 / g or more, it was confirmed that the oil absorption was small and the coating suitability was excellent. It was also confirmed that the ionic conductivity was high, with an A or B rating.

[0196] CV measurements were performed on the modified sulfide solid electrolytes of Examples 23 and 24 and the sulfide solid electrolyte of Comparative Example 1 based on the above method. The CV curves for the first cycle are shown in FIG. 1. The CV curves in FIG. 1 confirm a decrease in oxidation current for the modified sulfide solid electrolytes of Examples 23 and 24, indicating that the epoxy compound coating can suppress the oxidation reaction occurring at the interface between the electrolyte and the conductive material. On the other hand, the sulfide solid electrolyte of Comparative Example 1 was found to have a poorer effect on suppressing the oxidation reaction than Examples 23 and 24. [Industrial Applicability]

[0197] The modified sulfide solid electrolyte of this embodiment, even if it is a sulfide solid electrolyte with a large specific surface area, has excellent applicability when applied as a paste and can efficiently exhibit excellent battery performance. Furthermore, since the modified sulfide solid electrolyte of this embodiment has high ionic conductivity, it is suitable for use in batteries, particularly batteries used in information-related devices and communication devices such as personal computers, video cameras, and mobile phones.

Claims

1. BET specific surface area is 10m ２ / g or more, and comprising a sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms; and an epoxy compound; In the infrared absorption spectrum by FT-IR analysis (ATR method), －１ has a peak at The epoxy compound is at least one compound selected from the group consisting of epoxy compound 1 represented by the following general formula (1), epoxy compound 2 represented by the following general formula (2), and epoxy compound 3 represented by the following general formula (3): Modified sulfide solid electrolyte. 【Chemistry 1】 In general formula (1), X 11 to X 13 each independently represent a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, or a monovalent halogenated hydrocarbon group, and at least one of X 11 to X 13 is a monovalent hydrocarbon group or a monovalent halogenated hydrocarbon group. In general formula (2), X 21 to X 23 are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, or a group represented by general formula (2a), and at least one of X 21 to X 23 is a group represented by general formula (2a). In general formula (2a), R 21 is a divalent hydrocarbon group, and R 22 is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, or a monovalent halogenated hydrocarbon group. In general formula (3), X 31 is a group represented by general formula (3a), X 32 and X 33 are hydrogen atoms, in general formula (3a), R 31 is a divalent hydrocarbon group having 1 to 8 carbon atoms, R 32 is a divalent hydrocarbon group having 1 to 8 carbon atoms, X 34 and X 36 are groups represented by general formula (3b), X 35 is a monovalent hydrocarbon group having 1 to 24 carbon atoms, and in general formula (3b), R 34 to R 36 are monovalent hydrocarbon groups having 1 to 24 carbon atoms.

2. The modified sulfide solid electrolyte according to claim 1, wherein the peak is derived from C-H stretching vibration of an alkyl chain in the epoxy compound.

3. １ The modified sulfide solid electrolyte according to claim 2, wherein the H-NMR spectrum has a peak at 0.0 to 5.0 ppm derived from the alkyl chain.

4. The epoxy compound 1 is a compound represented by the general formula (1), wherein X １１ is a monovalent hydrocarbon group having 1 to 24 carbon atoms or a monovalent halogenated hydrocarbon group having 1 to 24 carbon atoms, and X １２ and X １３ The modified sulfide solid electrolyte according to any one of claims 1 to 3, wherein is a compound in which is a hydrogen atom.

5. The epoxy compound 2 is a compound represented by the general formula (2), wherein X ２１ is a group represented by general formula (2a), and X ２２ and X ２３ is a hydrogen atom, and in general formula (2a), R ２１ is a divalent hydrocarbon group having 1 to 8 carbon atoms, and R ２２ The modified sulfide solid electrolyte according to any one of claims 1 to 4, wherein is a compound in which is a monovalent hydrocarbon group having 1 to 24 carbon atoms.

6. The epoxy compound 3 is a compound represented by the general formula (3), wherein X ３１ is a group represented by general formula (3a), and X ２２ and X ２３ is a hydrogen atom, and in general formula (3a), R ３１ is a divalent hydrocarbon group having 1 to 8 carbon atoms, and R ３２ is a single bond, and X ３４ ~X ３６ The modified sulfide solid electrolyte according to any one of claims 1 to 5, wherein is a compound in which is a monovalent hydrocarbon group having 1 to 24 carbon atoms.

7. The content of the epoxy compound is 0.03 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the sulfide solid electrolyte. Modified sulfide solid electrolyte according to any one of claims 1 to 6.

8. The modified sulfide solid electrolyte according to any one of claims 1 to 7, wherein the molecular weight of the epoxy compound is 60 or more.

9. The modified sulfide solid electrolyte according to any one of claims 1 to 8, wherein the molecular weight of the epoxy compound is 60 or more and 400 or less.

10. The content of the epoxy compound is 0.03 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the sulfide solid electrolyte. Modified sulfide solid electrolyte according to any one of claims 1 to 9.

11. BET specific surface area is 10m ２ / g or more and containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, an epoxy compound, and an organic solvent; removing the organic solvent.

12. 12. The method for producing a modified sulfide solid electrolyte according to claim 11, wherein the organic solvent is at least one solvent selected from the group consisting of an aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, an aromatic hydrocarbon solvent, an ether solvent, an ester solvent, and a nitrile solvent.

13. An electrode mixture comprising the modified sulfide solid electrolyte according to any one of claims 1 to 10 and an electrode active material.

14. A lithium ion battery comprising at least one of the modified sulfide solid electrolyte according to any one of claims 1 to 10 and the electrode mixture according to claim 13.

15. BET specific surface area is 10m ２ / g or more, and the solid electrolyte contains a sulfide containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and an epoxy compound. fruit, The epoxy compound is at least one compound selected from the group consisting of epoxy compound 1 represented by the following general formula (1), epoxy compound 2 represented by the following general formula (2), and epoxy compound 3 represented by the following general formula (3): Modified sulfide solid electrolyte. 【Chemistry 1】 In general formula (1), X 11 to X 13 each independently represent a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, or a monovalent halogenated hydrocarbon group, and at least one of X 11 to X 13 is a monovalent hydrocarbon group or a monovalent halogenated hydrocarbon group. In general formula (2), X 21 to X 23 are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, or a group represented by general formula (2a), and at least one of X 21 to X 23 is a group represented by general formula (2a). In general formula (2a), R 21 is a divalent hydrocarbon group, and R 22 is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, or a monovalent halogenated hydrocarbon group. In general formula (3), X 31 is a group represented by general formula (3a), X 32 and X 33 are hydrogen atoms, in general formula (3a), R 31 is a divalent hydrocarbon group having 1 to 8 carbon atoms, R 32 is a divalent hydrocarbon group having 1 to 8 carbon atoms, X 34 and X 36 are groups represented by general formula (3b), X 35 is a monovalent hydrocarbon group having 1 to 24 carbon atoms, and in general formula (3b), R 34 to R 36 are monovalent hydrocarbon groups having 1 to 24 carbon atoms.

16. An electrode mixture comprising the modified sulfide solid electrolyte according to claim 15 and an electrode active material.

17. A lithium ion battery comprising at least one of the modified sulfide solid electrolyte according to claim 15 and the electrode mixture according to claim 16.

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