Crystalline sulfide solid electrolyte and method for manufacturing same

Abstract

The present invention provides: a crystalline sulfide solid electrolyte which contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, is excellent in battery lifetime characteristics and voltage resistance, also has excellent coatability, and has an elastic dissipation energy, calculated from a focus curve measured by an atomic force microscopy, of 5.0×10-18 J or more; and a method for manufacturing the same.

Description

Crystalline sulfide solid electrolyte and its manufacturing method

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

[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 for use as their power sources has become increasingly important. Traditionally, batteries used for such applications have used electrolytes containing flammable organic solvents. However, because the electrolytes are liquid and flammable, safety concerns regarding leakage, fire, and the like have arisen when used in batteries. In particular, for automotive applications, high capacity and high output are required, and safety concerns regarding batteries using conventional electrolytes are becoming increasingly serious. Therefore, development of batteries in which the electrolyte is replaced with a solid electrolyte layer is underway, as solid-state batteries eliminate the use of flammable organic solvents, simplify safety devices, and offer superior manufacturing costs and productivity.

[0003] Various types of solid electrolytes have been developed for use in the solid electrolyte layer. For example, Patent Document 1 describes a Li ２ S-P ２ S ５ Patent Document 2 describes a solid electrolyte containing Li, as well as a solid electrolyte containing halogen atoms. ２ S-P ２ S ５ -LiI-based sulfide solid electrolyte, Patent Documents 3 and 4 disclose Li ２ S-P ２ S ５ -LiI-LiBr-based sulfide solid electrolytes are disclosed. Furthermore, Patent Document 5 discloses a solid electrolyte having an argyrodite-type crystal structure as a solid electrolyte. Patent Document 6 discloses a sulfide-based solid electrolyte in which the surface of a compound having a cubic argyrodite-type crystal structure is coated with a compound having a non-argyrodite-type crystal structure.

[0004] Furthermore, Patent Document 7 discloses a method for producing a solid having a crystal peak of XRD at a predetermined position. ３１Patent Document 8 discloses a sulfide solid electrolyte containing an argyrodite-type crystal structure, in which the half-width of a peak observed in P-NMR measurement is within a predetermined range. Patent Document 8 discloses a sulfide solid electrolyte containing (A) a sulfide solid electrolyte having an argyrodite-type crystal structure, and (B) a sulfide solid electrolyte having a crystal structure different from that of (A). Patent Document 9 discloses a sulfide compound for solid electrolytes having a crystalline phase with a cubic argyrodite-type crystal structure and a predetermined composition.

[0005] Japanese Patent Application Laid-Open No. 2005-228570 Japanese Patent Application Laid-Open No. 2013-201110 International Publication No. 2014 / 208180 Pamphlet International Publication No. 2014 / 208239 Pamphlet International Publication No. 2018 / 047566 Pamphlet International Publication No. 2018 / 003333 Pamphlet International Publication No. 2018 / 216730 Pamphlet International Publication No. 2019 / 003986 Pamphlet International Publication No. 2019 / 009228 Pamphlet

[0006] The present invention has been made in view of the above circumstances, and aims to provide a sulfide solid electrolyte that is excellent in battery life characteristics and voltage resistance, as well as in coatability.

[0007] The crystalline sulfide solid electrolyte according to the present invention contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and has an elastic dissipation energy of 5.0×10 calculated from a focus curve measured by atomic force microscopy. －１８ J or more.

[0008] The present invention also provides a method for producing a crystalline sulfide solid electrolyte, the method comprising: mixing, in a solvent, a raw material-containing material including a plurality of solid electrolyte raw materials each including at least one atom selected from lithium, phosphorus, sulfur, and halogen atoms to obtain a raw material mixture; heat-treating the raw material mixture to obtain a heat-treated product; pulverizing the heat-treated product to obtain a pulverized heat-treated product; and drying the pulverized heat-treated product, the method comprising at least one of the following processes (1) and (2): (1) in obtaining the pulverized heat-treated product, pulverization is performed with a pulverization energy of 0.50 Wh / kg or more; and (2) in drying, drying is performed by flash drying.

[0009] According to the present invention, it is possible to provide a sulfide solid electrolyte that is excellent in battery life characteristics and voltage resistance, as well as in coatability.

[0010] 1 is an AFM focus curve for calculating the elastic dissipation energy of the crystalline sulfide solid electrolytes of Examples and Comparative Examples; FIG. 2 is a graph for evaluating the life characteristics of the crystalline sulfide solid electrolytes of the batteries of Examples and Comparative Examples; FIG. 3 is an X-ray diffraction spectrum of the powder obtained in Example 1; FIG. 4 is an X-ray diffraction spectrum of the powder obtained in Example 2; FIG. 5 is an X-ray diffraction spectrum of the powder obtained in Example 3; and FIG. 6 is an X-ray diffraction spectrum of the powder obtained in Comparative Example 1.

[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 numerical range expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values ​​of the examples can also be used as the upper and lower limit values. Furthermore, preferred specifications can be arbitrarily adopted. In other words, one preferred specification can be adopted in combination with one or more other preferred specifications. It can be said that a combination of preferred items is more preferable.

[0012] (Findings Obtained by the Inventors to Achieve the Present Invention) The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found the following, which has led to the completion of the present invention.

[0013] Among the various solid electrolytes mentioned above, sulfide solid electrolytes containing halogen atoms have attracted attention due to their high ionic conductivity. However, while sulfide solid electrolytes containing halogen atoms have the great advantage of high ionic conductivity, when used in lithium-ion batteries, they can exhibit a rapid decrease in capacity midway through charge-discharge tests. This tendency has been found to be particularly pronounced in sulfide solid electrolytes with an argyrodite-type crystal structure.

[0014] Sulfide solid electrolytes can be used in the positive electrode layer, negative electrode layer, and solid electrolyte layer of lithium-ion batteries, and are used in combination with electrode active materials (positive electrode active material, negative electrode active material) in the electrodes (positive electrode, negative electrode). Because both the sulfide solid electrolyte and the electrode active material are solids, forming a contact interface between the sulfide solid electrolyte and the electrode active material is important for achieving good battery performance. Therefore, even if the sulfide solid electrolyte has high ionic conductivity, if the contact interface is not sufficiently formed, sufficient performance may not be achieved when it is applied to a battery.

[0015] Focusing on these characteristics, Patent Documents 7 to 9 have investigated the improvement of adhesion between sulfide solid electrolytes having an argyrodite-type crystal structure and electrode active materials by focusing on their crystallite size and elastic modulus (Young's modulus). Sulfide solid electrolytes having an argyrodite-type crystal structure are generally known to have a high elastic modulus (Young's modulus), i.e., a high hardness. The sudden capacity decrease during cycling may be due to the high elastic modulus (Young's modulus), which makes it difficult to form a contact interface with the electrode active material. However, it has been discovered that sulfide solid electrolytes having an argyrodite-type crystal structure have excellent battery life characteristics, which do not exhibit the sudden capacity decrease during cycling despite having an elastic modulus (Young's modulus) comparable to that of conventional sulfide solid electrolytes having an argyrodite-type crystal structure. This phenomenon means that the elastic modulus (Young's modulus) may not contribute to the formation of a contact interface with the electrode active material, a phenomenon that could not be predicted from the contents of Patent Documents 7 to 9.

[0016] As a result of further research into sulfide solid electrolytes with excellent battery life characteristics, it was discovered that the elastic dissipation energy calculated from the focus curve measured by atomic force microscopy significantly contributes to the expression of the performance. Based on this discovery, the inventors have developed a crystalline sulfide solid electrolyte having the above-mentioned configuration, i.e., a sulfide solid electrolyte having an elastic dissipation energy of 5.0 × 10 －１８ By using a crystalline sulfide solid electrolyte having a solubility of 0.1 J or more and having such a configuration, the effects of excellent battery life characteristics, voltage resistance, and coatability have been achieved.

[0017] (Regarding various aspects of the present embodiment) A crystalline sulfide solid electrolyte according to a first aspect of the present embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and has an elastic dissipation energy of 5.0 × 10 calculated from a focus curve measured by atomic force microscopy. －１８ J or more.

[0018] The crystalline sulfide solid electrolyte of this embodiment has an elastic dissipation energy of 5.0 × 10 －１８ It is believed that the property of being J or more promotes the formation of a contact interface with the electrode active material, resulting in excellent battery life characteristics and voltage resistance.

[0019] As will be understood from the measurement method described later, the elastic dissipation energy is a value calculated from the stress-displacement characteristics when a measurement probe is pressed into a powder of the crystalline sulfide solid electrolyte to a predetermined stress and then pulled out, and serves as an index for evaluating plastic deformation. In other words, the larger the elastic dissipation energy, the easier the plastic deformation. Therefore, when the elastic dissipation energy of the crystalline sulfide solid electrolyte of this embodiment is 5.0 × 10 －１８ The fact that the hardness is J or more means that the material has a property that is easily plastically deformed.

[0020] Since the crystalline sulfide solid electrolyte of this embodiment has an elastic dissipation energy within the above range, it is easy to form a contact interface with the electrode active material, and the contact interface can be sufficiently secured. As a result, it is possible to secure a larger number of contact interfaces than with conventional crystalline sulfide solid electrolytes, and therefore it is thought that the current does not concentrate locally, making it easier to suppress rapid degradation.

[0021] Furthermore, since a contact interface with the electrode active material can be easily formed, the crystalline sulfide solid electrolyte of the present embodiment has high compatibility with the electrode active material, and when a paste-like electrode mixture is mixed with the electrode active material during the battery manufacturing process, the coating properties are improved. This is also thought to be due to the elastic dissipation energy of the crystalline sulfide solid electrolyte of the present embodiment.

[0022] The crystalline sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. While the inclusion of halogen atoms increases the ionic conductivity of the crystalline sulfide solid electrolyte itself, it is also known that the crystalline sulfide solid electrolyte generally becomes a hard powder. The inclusion of halogen atoms in the crystalline sulfide solid electrolyte of this embodiment increases the ionic conductivity of the solid electrolyte itself. Furthermore, by setting the elastic dissipation energy within the above range, excellent coatability can be obtained when using the crystalline sulfide solid electrolyte, more specifically, when using it together with an electrode active material to manufacture a battery. Furthermore, after manufacture, a larger contact interface can be ensured, thereby improving the battery's life characteristics and voltage resistance. Thus, the crystalline sulfide solid electrolyte of this embodiment not only has the property of high ionic conductivity itself, but also has excellent coatability during the battery manufacturing process and the life characteristics and voltage resistance of the manufactured battery.

[0023] The crystalline sulfide solid electrolyte according to a second aspect of the present embodiment is the crystalline sulfide solid electrolyte according to the first aspect, wherein the crystallite size is 5 nm or more and 60 nm or less. By setting the crystallite size of the crystalline sulfide solid electrolyte according to the present embodiment within the above range, the conductivity can be maintained at a practical level while the elastic dissipation energy is large, so that a large contact interface with the electrode active material can be secured, resulting in excellent battery life characteristics, voltage resistance, and coatability.

[0024] A crystalline sulfide solid electrolyte according to a third aspect of the present embodiment is the crystalline sulfide solid electrolyte according to the first or second aspect, wherein the halogen atoms include at least two selected from chlorine atoms, bromine atoms, and iodine atoms. By including at least two selected from chlorine atoms, bromine atoms, and iodine atoms as halogen atoms, higher ionic conductivity can be obtained.

[0025] The crystalline sulfide solid electrolyte according to a fourth aspect of this embodiment is any one of the first to third aspects, wherein the volume-based average particle size measured by a laser diffraction particle size distribution measurement method is 0.1 μm or more and 10 μm or less. When the average particle size is within this range, a contact interface with the electrode active material is easily formed, resulting in good paths for ionic conduction and electronic conduction. Furthermore, when the crystalline sulfide solid electrolyte is made into a paste-like electrode mixture together with the electrode active material during the battery manufacturing process, good thixotropy is obtained, and coatability is improved.

[0026] A crystalline sulfide solid electrolyte according to a fifth aspect of the present embodiment is any one of the first to fourth aspects, wherein the specific surface area measured by the BET method is 12 m ２ / g or more.

[0027] Generally, the larger the specific surface area, the higher the viscosity of the electrode mixture, which tends to result in a decrease in coatability. Since the crystalline sulfide solid electrolyte of the present embodiment has a specific surface area within the above range, when it is made into a paste-like electrode mixture together with an electrode active material, good thixotropy is obtained, so that the coatability does not decrease and the crystalline sulfide solid electrolyte has excellent coatability.

[0028] A crystalline sulfide solid electrolyte according to a sixth aspect of the present embodiment is any one of the first to fifth aspects, further comprising: ３１ The ratio of the total area of ​​all peaks attributable to glass components to the total area of ​​all peaks in the range of 60 to 120 ppm observed in P-NMR measurement is 5% or more in terms of phosphorus atoms.

[0029] The crystalline sulfide solid electrolyte of this embodiment preferably contains a glass component. When the crystalline sulfide solid electrolyte contains a glass component as a part thereof, the elastic dissipation energy tends to fall within the above range. Therefore, a large contact interface with the electrode active material can be secured, resulting in excellent battery life characteristics, voltage resistance, and coatability.

[0030] The crystalline sulfide solid electrolyte according to a seventh aspect of the present embodiment is any one of the first to sixth aspects, wherein the Young's modulus is 1 GPa or more and 50 GPa or less.

[0031] The crystalline sulfide solid electrolyte of this embodiment has a Young's modulus comparable to that of conventional products, making it suitable for use as a solid electrolyte. Although the Young's modulus is comparable to that of conventional products, the crystalline sulfide solid electrolyte has a predetermined elastic dissipation energy, ensuring a large contact interface with the electrode active material, resulting in excellent battery life characteristics, voltage resistance, and coatability.

[0032] The crystalline sulfide solid electrolyte according to an eighth aspect of the present embodiment is any one of the first to seventh aspects, wherein the crystalline sulfide solid electrolyte has an argyrodite-type crystal structure.

[0033] Crystalline sulfide solid electrolytes having an argyrodite-type crystal structure are known to have hard properties among crystalline sulfide solid electrolytes containing halogen atoms. The crystalline sulfide solid electrolyte of the present embodiment, even though having such hard properties, has a predetermined elastic dissipation energy, so that a large contact interface with the electrode active material can be secured, resulting in excellent battery life characteristics, voltage resistance, and coatability.

[0034] A ninth aspect of this embodiment of the present invention relates to a method for producing a crystalline sulfide solid electrolyte, the method comprising: mixing, in a solvent, a raw material-containing material including a plurality of solid electrolyte raw materials each including at least one atom selected from lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a raw material mixture; heat-treating the raw material mixture to obtain a heat-treated product; pulverizing the heat-treated product to obtain a pulverized heat-treated product; and drying the pulverized heat-treated product, and the method comprises performing at least one of the following processes (1) and (2): (1) in obtaining the pulverized heat-treated product, pulverization is performed with a pulverization energy of 0.50 Wh / kg or more; and (2) in drying, drying is performed by flash drying.

[0035] According to the manufacturing method of this embodiment, the crystalline sulfide solid electrolyte of this embodiment can be easily manufactured, and therefore, is suitably employed when manufacturing the crystalline sulfide solid electrolyte of this embodiment. By mixing the raw material ingredients in a solvent to form a raw material mixture, the solid electrolyte raw material can be made more uniform. By heat-treating the more uniform raw material mixture to obtain a heat-treated product, a crystalline sulfide solid electrolyte containing halogen atoms can be more easily obtained by heat treatment for a shorter period of time. Furthermore, by performing heat treatment for a shorter period of time, not only can aggregation and sintering between particles of the heat-treated product be suppressed, but deterioration due to thermal history can also be suppressed. Therefore, the heat-treated product obtained by heat-treating the above raw material mixture can be called a crystalline sulfide solid electrolyte having high quality.

[0036] The heat-treated product is then pulverized to obtain a pulverized heat-treated product. The heat-treated product is a crystalline sulfide solid electrolyte in which aggregation and sintering between particles are suppressed, so that the particle size can be adjusted while suppressing the energy involved in the pulverization. The elastic dissipation energy can be reduced to 5.0 × 10 －１８ Here, in the manufacturing method of this embodiment, in the above (1) obtaining the pulverized heat-treated product, the pulverization treatment is performed with a pulverization energy of 0.50 Wh / kg or more, thereby adjusting the particle size by pulverizing the heat-treated product (crystalline sulfide solid electrolyte) and reducing the elastic dissipation energy to 5.0 × 10 －１８It becomes easier to get J or above.

[0037] The manufacturing method of this embodiment further includes drying the pulverized heat-treated product. For example, if a solvent is used in pulverizing the heat-treated product, the solvent can be removed. Even if a solvent is not used, the solvent used in obtaining the raw material mixture may remain, so the remaining solvent can be removed. In this case, by performing a process of drying by air flow drying in the drying step (2), not only can the solvent be removed, but also the elastic dissipation energy can be reduced to 5.0 × 10 －１８ It becomes easier to get J or above.

[0038] In the manufacturing method of this embodiment, by performing at least one of the processes of (1) obtaining the pulverized heat-treated product by pulverizing with a pulverization energy of 0.50 Wh / kg or more, and (2) drying by flash drying, the elastic dissipation energy of the resulting crystalline sulfide solid electrolyte can be increased to 5.0 × 10 －１８ In the manufacturing method of this embodiment, it is sufficient to carry out either one of the processes (1) and (2), or both of the processes (1) and (2). By carrying out both the processes (1) and (2), the elastic dissipation energy can be increased to 5.0 × 10 －１８ It becomes easier to get J or above.

[0039] A tenth aspect of the present embodiment is the method for producing a crystalline sulfide solid electrolyte of the ninth aspect, wherein the flash drying is performed using at least one device selected from a flash dryer and a spray dryer.

[0040] In drying the pulverized heat-treated product, air flow drying is used to not only remove the solvent but also reduce the elastic dissipation energy of the resulting crystalline sulfide solid electrolyte to 5.0 × 10 －１８ In particular, by performing flash drying using at least one device selected from a flash dryer and a spray dryer, the elastic dissipation energy of the resulting crystalline sulfide solid electrolyte can be increased to 5.0 × 10 －１８ It becomes easier to get J or above.

[0041] The method for producing a crystalline sulfide solid electrolyte according to an eleventh aspect of the present embodiment is the method for producing a crystalline sulfide solid electrolyte according to the ninth or tenth aspect, wherein the heat treatment is carried out at a heating temperature T １ the first heat treatment at the heating temperature T １ Heating temperature T higher than °C ２ and a second heat treatment at 100°C.

[0042] By performing the heat treatment in two steps, the first heat treatment and the second heat treatment, the elastic dissipation energy of the resulting crystalline sulfide solid electrolyte can be increased to 5.0 × 10 －１８ J or more, deterioration due to thermal history is suppressed, and a higher quality crystalline sulfide solid electrolyte can be obtained.

[0043] Hereinafter, the crystalline sulfide solid electrolyte of this embodiment will be described in more detail in accordance with the above embodiment.

[0044] In this specification, the term "solid electrolyte" refers to an electrolyte that maintains a solid state under a nitrogen atmosphere at 25° C. The sulfide solid electrolyte in this embodiment is a solid electrolyte that contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, uses lithium atoms as conductive species, and has ionic conductivity due to the lithium atoms.

[0045] The term "sulfide solid electrolyte" includes both a crystalline sulfide solid electrolyte having the crystal structure according to this embodiment and an amorphous sulfide solid electrolyte. In this specification, a crystalline sulfide solid electrolyte refers to a sulfide solid electrolyte in which a peak derived from the sulfide solid electrolyte is observed in an X-ray diffraction pattern obtained by X-ray diffraction measurement, regardless of whether or not a peak derived from the raw materials of the sulfide solid electrolyte is present. That is, a crystalline sulfide solid electrolyte includes a crystal structure derived from the sulfide solid electrolyte, and a portion of the crystal structure may be derived from the sulfide solid electrolyte, or the entire crystal structure may be derived from the sulfide solid electrolyte. Furthermore, as long as the crystalline sulfide solid electrolyte has the X-ray diffraction pattern described above, it may also include an amorphous sulfide solid electrolyte in part. Therefore, the crystalline sulfide solid electrolyte includes so-called glass ceramics obtained by heating an amorphous sulfide solid electrolyte to a temperature equal to or higher than the crystallization temperature. In this specification, the amorphous sulfide solid electrolyte refers to an X-ray diffraction pattern in X-ray diffraction measurement that has a halo pattern in which no peaks other than those derived from the material are substantially observed, regardless of whether or not there are peaks derived from the raw materials of the sulfide solid electrolyte.

[0046] [Crystalline sulfide solid electrolyte] The crystalline sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and has an elastic dissipation energy of 5.0 × 10 calculated from a focus curve measured by atomic force microscopy. －１８ J or more.

[0047] The elastic dissipation energy is a value calculated from a focus curve measured by atomic force microscopy, and more specifically, a value that can be measured by the method described in the Examples. As described above, the elastic dissipation energy is a value that serves as an index for evaluating plastic deformation, and the elastic dissipation energy of the crystalline sulfide solid electrolyte of this embodiment is 5.0 × 10 －１８ From the viewpoint of improving the life characteristics, voltage resistance, and coatability of the battery, the elastic dissipation energy is preferably 6.0 × 10 －１８J or more, more preferably 7.0 × 10 －１８ J or more, more preferably 8.0 × 10 －１８ There is no particular upper limit, but it is usually 25.0 × 10 －１８ J or below.

[0048] The crystallite diameter of the crystalline sulfide solid electrolyte of this embodiment is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more, with the upper limit being preferably 60 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less. When the crystallite diameter is within the above range, the ionic conductivity of the crystalline sulfide solid electrolyte itself is improved, and the life characteristics, voltage resistance, and coatability of the battery are also improved.

[0049] The average particle size of the crystalline sulfide solid electrolyte of this embodiment is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more, with the upper limit being preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less. When the average particle size is within the above range, a contact interface with the electrode active material is easily formed, and paths for ionic conduction and electronic conduction are improved. Furthermore, when the crystalline sulfide solid electrolyte is made into a paste-like electrode mixture together with the electrode active material during the battery manufacturing process, good thixotropy is obtained and coatability is improved. The average particle size can be measured, for example, using a laser diffraction / scattering particle size distribution measuring device. When a particle size distribution integration curve is drawn, the particle size (D ５０ )

[0050] The specific surface area of ​​the crystalline sulfide solid electrolyte of this embodiment is preferably 12 m ２ / g or more, more preferably 14m ２ / g or more, more preferably 15m ２ There is no particular upper limit, but from the viewpoint of improving thixotropy and achieving excellent coating properties when the electrode active material is used in a paste-like electrode mixture, it is preferably 40 m / g or more. ２ / g or less, more preferably 30m ２ / g or less, more preferably 25m ２The specific surface area is the specific surface area measured by the BET method, and is determined by measuring the nitrogen (N ２ ) is the specific surface area measured by the BET method by adsorption.

[0051] The solid state of the crystalline sulfide solid electrolyte of this embodiment ３１ The ratio of the total area of ​​all peaks derived from glass components to the total area of ​​all peaks in the range of 60 to 120 ppm observed in P-NMR measurement (hereinafter also referred to as "degree of vitrification") is preferably 5% or more, more preferably 7% or more, and even more preferably 9% or more. The upper limit is preferably 30% or less, more preferably 25% or less, and even more preferably 20% or less. As described above, this ratio (degree of vitrification) means the ratio of glass components contained in the crystalline sulfide solid electrolyte. When the crystalline sulfide solid electrolyte of this embodiment has a glass component within the above range, the elastic dissipation energy is 5.0 × 10 －１８ As a result, a large contact interface with the electrode active material can be secured, resulting in excellent battery life characteristics and voltage resistance.

[0052] solid ３１ The ratio of the total area of ​​all peaks attributable to glass components to the total area of ​​all peaks in the range of 60 to 120 ppm observed in P-NMR measurement is the ratio of the total area of ​​all peaks attributable to glass components to the total area of ​​all peaks. ４ ３－ It is the ratio of the total area of ​​all peaks derived from the glass component (corresponding to the ratio of phosphorus atoms contained in the glass component to all phosphorus atoms contained in the crystalline sulfide solid electrolyte), and is a ratio indicating the content of the glass component in the crystalline sulfide solid electrolyte (molar ratio based on phosphorus atoms).

[0053] The degree of vitrification can be measured, for example, by the following method. ３１ NMR (solid state) ３１ From the P-NMR spectrum, the PS relative to the total area ４ ３－ The percentage is the total area of ​​the peak of the glass component (peak: 82-85 ppm). ３１The P-NMR measurement may be carried out in accordance with a conventional method, for example, using a nuclear magnetic resonance apparatus under the conditions described in the Examples.

[0054] The Young's modulus (elastic modulus) of the crystalline sulfide solid electrolyte of this embodiment is preferably 1 GPa or more, more preferably 5 GPa or more, and even more preferably 10 GPa or more, with the upper limit being preferably 50 GPa or less, more preferably 40 GPa or less, and even more preferably 30 GPa or less. The Young's modulus of the crystalline sulfide solid electrolyte of this embodiment can be said to be comparable to that of conventional products, and is suitable for use as a solid electrolyte.

[0055] (Constituent Atoms) The crystalline sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. By containing halogen atoms, the ionic conductivity is improved compared to sulfide solid electrolytes containing lithium atoms, phosphorus atoms, and sulfur atoms. Preferred examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, and among these, chlorine atoms, bromine atoms, and iodine atoms are preferred. In the crystalline sulfide solid electrolyte of this embodiment, the halogen atoms may be any of the above halogen atoms alone or in combination.

[0056] The halogen atoms can be adopted depending on the crystal structure to be obtained. For example, when a crystalline sulfide solid electrolyte having a thiolicon region II crystal structure described later is to be obtained, the halogen atoms preferably contain at least one of a bromine atom and an iodine atom, more preferably a bromine atom and an iodine atom. When a crystalline sulfide solid electrolyte having an argyrodite crystal structure is to be obtained, the halogen atoms preferably contain at least one of a chlorine atom and a bromine atom, more preferably a chlorine atom and a bromine atom.

[0057] In the crystalline sulfide solid electrolyte of this embodiment, the composition ratio (molar ratio) of lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms is preferably 1.0 to 1.8: 0.1 to 0.8: 1.0 to 2.0: 0.01 to 0.6, more preferably 1.1 to 1.7: 0.2 to 0.6: 1.2 to 1.8: 0.05 to 0.5, and even more preferably 1.2 to 1.6: 0.25 to 0.5: 1.3 to 1.7: 0.08 to 0.4. Here, the types and composition ratios (molar ratios) of atoms constituting the crystalline sulfide solid electrolyte of this embodiment can be confirmed, for example, by an ICP emission spectrometer. The atomic composition ratio (molar ratio) of the crystalline sulfide solid electrolyte of this embodiment is substantially the same as the atomic composition ratio (molar ratio) calculated from the solid electrolyte raw material contained in the raw material content used during production. Therefore, the atomic composition ratio (molar ratio) calculated from the amount of the solid electrolyte raw material used can be used as the atomic composition ratio (molar ratio) without checking with the above-mentioned analyzer.

[0058] When bromine and iodine, or bromine and chlorine are used in combination as halogen atoms, the composition ratio (molar ratio) of lithium atoms, phosphorus atoms, sulfur atoms, bromine, and iodine (or chlorine) is preferably 1.0 to 1.8: 0.1 to 0.8: 1.0 to 2.0: 0.01 to 0.3: 0.01 to 0.3, more preferably 1.1 to 1.7: 0.2 to 0.6: 1.2 to 1.8: 0.02 to 0.25: 0.02 to 0.25, even more preferably 1.2 to 1.6: 0.25 to 0.5: 1.3 to 1.7: 0.03 to 0.2: 0.03 to 0.2, and still more preferably 1.35 to 1.45: 0.3 to 0.45: 1.4 to 1.7: 0.04 to 0.18: 0.04 to 0.18. By setting the composition ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms within the above range, it becomes easier to obtain a solid electrolyte having a higher ionic conductivity and a crystal structure described below, particularly a thiolicon region II crystal structure or an argyrodite crystal structure.

[0059] (Crystal Structure) The crystal structure of the crystalline sulfide solid electrolyte of this embodiment is not particularly limited as long as it is a crystal structure composed of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and preferably includes a thiolicon region II type (also referred to as "R-II type") crystal structure and an argyrodite type (also referred to as "ARG type") crystal structure. The crystalline sulfide solid electrolyte of this embodiment generally has higher ionic conductivity and is harder, and preferably has an argyrodite type crystal structure that makes it difficult to ensure a contact interface with the electrode active material. This is because the presence of elastic dissipation energy ensures a contact interface with the electrode active material, allowing the characteristic of high ionic conductivity to be effectively utilized.

[0060] The thiolicon region II crystal structure is Li ４－ｘ Ge １－ｘ P ｘ S ４ 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 S ４ Representative examples include crystal structures similar to the thio-LISICON Region II type (see Solid State Ionics, 177 (2006), 2721-2725).

[0061] The above Li ４－ｘ Ge １－ｘ P ｘ S ４ The diffraction peaks of the 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 S ４Diffraction peaks of a crystal structure similar to that of 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°.

[0062] The crystalline sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. ４－ｘ Ge １－ｘ P ｘ S ４ However, when the crystalline sulfide solid electrolyte of the present embodiment has the same diffraction peaks as the "thiolisiconregion II type crystal structure" and a crystal structure similar to the thiolisiconregion II type crystal structure, it can be said that the crystalline sulfide solid electrolyte of the present embodiment has a thiolisiconregion II type crystal structure formed by lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. This also applies to the argyrodite type crystal structure described later.

[0063] The argyrodite crystal structure is ７ P.S. ６ The argyrodite-type crystal structure has a structural skeleton basically as shown in the figure, with some of the P substituted with Si. The composition formula of the argyrodite-type crystal structure is, for example, Li ７－ｘ P １－ｙ Si ｙ S ６ , Li ７＋ｘ P １－ｙ Si ｙ S ６ (x is −0.6 to 0.6, y is 0.1 to 0.6) The argyrodite-type crystal structure represented by these composition formulas is a cubic or orthorhombic crystal, preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°.

[0064] The composition formula of the argyrodite crystal structure is Li ７－ｘ－２ｙ P.S. ６－ｘ－ｙ Cl ｘ(0.8≦x≦1.7, 0<y≦−0.25x+0.5). The argyrodite-type crystal structure represented by this composition formula is preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, it has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. The composition formula of the argyrodite-type crystal structure is preferably Li ７－ｘ P.S. ６－ｘ Ha ｘ (Ha is Cl or Br, and x is preferably 0.2 to 1.8) The argyrodite-type crystal structure represented by this composition formula is preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, it has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°.

[0065] [Method for producing crystalline sulfide solid electrolyte] The method for producing a crystalline sulfide solid electrolyte of the present embodiment includes: mixing, in a solvent, a raw material-containing material including a plurality of solid electrolyte raw materials each including at least one atom selected from lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a raw material mixture; heat-treating the raw material mixture to obtain a heat-treated product; pulverizing the heat-treated product to obtain a pulverized heat-treated product; and drying the pulverized heat-treated product, and also includes performing at least one of the following treatments (1) and (2): (1) in obtaining the pulverized heat-treated product, pulverization is performed with a pulverization energy of 0.50 Wh / kg or more; and (2) in drying, drying is performed by flash drying.

[0066] (Obtaining a raw material mixture) The method for producing a crystalline sulfide solid electrolyte of this embodiment will be described by first obtaining a raw material mixture. The production method of this embodiment includes mixing, in a solvent, raw material-containing materials including multiple solid electrolyte raw materials each containing at least one atom selected from lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a raw material mixture.

[0067] (Raw Material Content) The raw material content used in the present embodiment contains a plurality of solid electrolyte raw materials containing at least one atom selected from a lithium atom, a phosphorus atom, a sulfur atom, and a halogen atom, and preferably contains two or more solid electrolyte raw materials (substances) containing at least one atom selected from these atoms.

[0068] Examples of the solid electrolyte raw material (substance) contained in the raw material content include lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ) and other phosphorus sulfides; raw materials containing at least two atoms selected from the above-mentioned atoms, and fluorine (F ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ Representative examples of the raw material include a halogen element such as halogen, phosphorus, sulfur, and the like; and a raw material consisting of one atom selected from the above-mentioned elements.

[0069] Among the above, examples of the solid electrolyte raw material containing lithium atoms, sulfur atoms, and phosphorus atoms include lithium sulfide; diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ Among the phosphorus sulfides, diphosphorus pentasulfide is preferred.

[0070] Among the above, lithium sulfide, diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ) and other phosphorus sulfides, fluorine (F ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ and lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide are preferred. When oxygen atoms are introduced into the solid electrolyte, lithium oxide, lithium hydroxide, and phosphate compounds such as lithium phosphate are preferred.

[0071] Among the above, either a halogen element or a lithium halide can be preferably used as a solid electrolyte raw material containing a halogen atom. The halogen atoms contained in the raw material inclusions are as described above as halogen atoms that may be contained in the crystalline sulfide solid electrolyte of this embodiment, and it is preferable to use a solid electrolyte raw material containing such halogen atoms. As the lithium halide, lithium chloride, lithium bromide, and lithium iodide are more preferable. When attempting to obtain a crystalline sulfide solid electrolyte having a thiolicon region II crystal structure, it is preferable to use at least one of lithium bromide and lithium iodide, and it is more preferable to use lithium bromide and lithium iodide in combination. Furthermore, when attempting to obtain a crystalline sulfide solid electrolyte having an argyrodite crystal structure, it is preferable to use at least one of lithium chloride and lithium bromide, and it is more preferable to use lithium chloride and lithium bromide in combination.

[0072] The halogen element is chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ ) is more preferred. When attempting to obtain a crystalline sulfide solid electrolyte having a thiolicon region II type crystal structure, it is preferable to use at least one of bromine and iodine, and it is more preferred to use bromine and iodine in combination. When attempting to obtain a crystalline sulfide solid electrolyte having an argyrodite type crystal structure, it is preferable to use at least one of chlorine and bromine, and it is more preferred to use chlorine and bromine in combination.

[0073] Preferred examples of the combination of solid electrolyte raw materials contained in the raw material inclusions include a combination of lithium sulfide, phosphorus sulfide, and lithium halide, a combination of lithium sulfide, phosphorus sulfide, and a simple halogen, and a combination of lithium sulfide, phosphorus sulfide, lithium halide, and a simple halogen. More preferred examples include a combination of lithium sulfide, phosphorus pentasulfide, and a lithium halide, and a combination of lithium sulfide, phosphorus pentasulfide, and a simple halogen. In the above combinations, preferred lithium halides are lithium chloride, lithium bromide, and lithium iodide, and preferred simple halogens are chlorine, bromine, and iodine. As mentioned above, the solid electrolyte raw material containing halogen atoms can be selected depending on the type of sulfide solid electrolyte to be obtained.

[0074] The raw material contains a solid electrolyte raw material containing at least two kinds of atoms selected from the above-mentioned atoms. Examples of solid electrolyte raw materials other than the above include various phosphorus fluorides (PF ３ , P.F. ５ ), various phosphorus chlorides (PCl ３ , PCl ５ , P ２ Cl ４ ), various phosphorus bromides (PBr ３ , PBr ５ ), various phosphorus iodides (PI ３ , P ２ I ４ ) and the like; phosphorus halides such as thiophosphoryl fluoride (PSF ３ ), thiophosphoryl chloride (PSCl ３ ), thiophosphoryl bromide (PSBr ３ ), thiophosphoryl iodide (PSI ３ ), thiophosphoryl fluoride dichloride (PSCl ２ F), thiophosphoryl fluoride dibromide (PSBr ２ F) and the like.

[0075] Examples of solid electrolyte raw materials other than those mentioned above that are contained in the raw material inclusion include solid electrolyte raw materials that contain at least one atom selected from the above atoms and also contain atoms other than the atoms mentioned above, 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; silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, and tin sulfide (SnS, SnS ２ metal sulfides such as aluminum sulfide and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; halides of alkali metals other than lithium such as sodium halides such as sodium iodide, sodium fluoride, sodium chloride and sodium bromide; metal halides such as aluminum halides, silicon halides, germanium halides, arsenic halides, selenium halides, tin halides, antimony halides, tellurium halides and bismuth halides; phosphorus oxychloride (POCl ３ ), phosphorus oxybromide (POBr ３ When oxygen atoms are introduced into the solid electrolyte, phosphoric acid compounds such as lithium oxide, lithium hydroxide and lithium phosphate are preferred.

[0076] In this embodiment, PS ４ Li containing structure ３ P.S. ４ can also be used as a solid electrolyte raw material. ３ P.S. ４ In this case, the combination of the solid electrolyte raw materials contained in the raw material contents may be Li, ３ P.S. ４ and the lithium halide, Li ３ P.S. ４ and the above-mentioned elemental halogens, Li ３ P.S. ４ and the lithium halide and the elemental halogen.

[0077] The solid electrolyte raw material such as lithium sulfide used in this embodiment is preferably in the form of particles. ５０ ) is preferably 0.1 to 1000 μm, more preferably 0.5 to 100 μm, and even more preferably 1 to 20 μm. 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, that is, within the same range as that of the lithium sulfide particles. In the production method of this embodiment, the particle size of the solid electrolyte raw material may be adjusted using a pulverizer such as a pin mill, as necessary, before use.

[0078] When the raw material contains lithium sulfide, diphosphorus pentasulfide, and lithium halide, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is, from the viewpoint of obtaining higher chemical stability and higher ionic conductivity, preferably 60 mol% or more, more preferably 65 mol% or more, even more preferably 70 mol% or more, and even more preferably 74 mol% or more, with the upper limit being preferably 85 mol% or less, more preferably 83 mol% or less, and even more preferably 80 mol% or less. The range is typically preferably 60 to 85 mol%, more preferably 65 to 83 mol%, even more preferably 70 to 80 mol%, and even more preferably 74 to 80 mol%. Furthermore, when attempting to obtain a sulfide solid electrolyte having a thiolicon region II type crystal structure, in addition to the above ranges, particularly 74 to 78.5 mol%, 74 to 78 mol%, and 74 to 76 mol% are preferred, and when attempting to obtain a sulfide solid electrolyte having an argyrodite type crystal structure, in addition to the above ranges, particularly 76 to 83 mol%, 77 to 80 mol%, and 78 to 80 mol% are preferred.

[0079] When the raw material content includes lithium sulfide, diphosphorus pentasulfide, lithium halide, and other raw materials used as needed, the content of lithium sulfide and diphosphorus pentasulfide relative to the total is preferably 50 mol% or more, more preferably 55 mol% or more, and even more preferably 60 mol% or more, with the upper limit being preferably 100 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less, and still more preferably 80 mol% or less. The range is typically preferably 50 to 100 mol%, more preferably 55 to 90 mol%, even more preferably 60 to 85 mol%, and even more preferably 60 to 80 mol%. Furthermore, when attempting to obtain a sulfide solid electrolyte having a thiolicon region II type crystal structure, in addition to the above ranges, particularly 65 to 90 mol%, 70 to 85 mol%, and 75 to 83 mol% are preferred, and when attempting to obtain a sulfide solid electrolyte having an argyrodite type crystal structure, in addition to the above ranges, particularly 50 to 78 mol%, 55 to 70 mol%, and 55 to 65 mol% are preferred.

[0080] When the raw material contains a combination of lithium bromide and lithium iodide as lithium halides, from the viewpoint of improving ionic conductivity, the ratio 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 35 mol% or more, and even more preferably 45 mol% or more, with the upper limit being preferably 99 mol% or less, more preferably 90 mol% or less, even more preferably 75 mol% or less, and even more preferably 60 mol% or less. The range is typically preferably 1 to 99 mol%, more preferably 20 to 90 mol%, even more preferably 35 to 75 mol%, and even more preferably 45 to 60 mol%. Furthermore, when attempting to obtain a sulfide solid electrolyte having a thiolicon region II crystal structure, in addition to the above range, 40 to 75 mol%, 40 to 65 mol%, and 45 to 55 mol% are particularly preferred.

[0081] Furthermore, when the raw material contains a combination of lithium bromide and lithium chloride as the lithium halide, from the viewpoint of improving ionic conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium chloride is preferably 1 mol% or more, more preferably 15 mol% or more, even more preferably 25 mol% or more, and even more preferably 35 mol% or more, with the upper limit being preferably 99 mol% or less, more preferably 75 mol% or less, even more preferably 60 mol% or less, and even more preferably 45 mol% or less. The range is typically preferably 1 to 99 mol%, more preferably 15 to 75 mol%, even more preferably 25 to 60 mol%, and even more preferably 35 to 45 mol%. Furthermore, when attempting to obtain a sulfide solid electrolyte having an argyrodite-type crystal structure, in addition to the above range, 25 to 45 mol% or 35 to 40 mol% is particularly preferred.

[0082] When the raw material inclusions include elemental halogens as raw materials, including 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 elemental halogen to the total number of moles of lithium sulfide and diphosphorus pentasulfide excluding the same number of moles of lithium sulfide as the elemental halogen 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.

[0083] From the same viewpoint, when the raw material contains lithium sulfide, diphosphorus pentasulfide, and an elemental halogen, the content of the elemental halogen relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and the elemental halogen is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and still more preferably 3 to 15 mol%.

[0084] When the raw material contains lithium sulfide, diphosphorus pentasulfide, an elemental halogen, and a lithium halide, the content of the elemental halogen (α mol %) and the content of the lithium halide (β mol %) relative to the total amount of lithium sulfide, diphosphorus pentasulfide, the elemental halogen, and the lithium halide preferably satisfy the following formula (1), more preferably satisfy the following formula (2), even more preferably satisfy the following formula (3), and still 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)

[0085] When the raw material contains two types of halogen as simple substances, the mole number of one halogen atom in the substance is A1, and the mole number of the other halogen atom in the substance is A2, and the ratio A1:A2 is preferably 1 to 99:99 to 1, more preferably 10:90 to 90:10, even more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30.

[0086] When the raw material contains two kinds of halogen atoms, and the two kinds of halogen atoms are bromine and iodine, then, if the number of moles of bromine is A1 and the number of moles of iodine is A2, the ratio A1:A2 is preferably 1:99 to 99:1, more preferably 20:80 to 80:20, even more preferably 35:65 to 80:20, and even more preferably 45:55 to 70:30. When the two kinds of halogen atoms are bromine and chlorine, then, if the number of moles of bromine is B1 and the number of moles of chlorine is B2, the ratio B1:B2 is preferably 1:99 to 99:1, more preferably 15:85 to 75:25, even more preferably 25:75 to 60:40, and even more preferably 35:45 to 65:55.

[0087] In addition, the raw material contains Li ３ P.S. ４ If the raw material contains Li, the total amount of the raw material contained in the raw material ３ P.S. ４ The content of Li is preferably 60 to 100 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 80 mol%. ３ P.S.４ Li may be prepared by manufacturing, and in this case, it can be obtained by reacting lithium sulfide with diphosphorus pentasulfide in a molar ratio of 3:1. ３ P.S. ４ When using lithium sulfide and diphosphorus pentasulfide, the compounding ratio with other raw materials such as lithium halide and elemental halogen may be the same as that when lithium sulfide and diphosphorus pentasulfide are used. For example, when lithium sulfide and diphosphorus pentasulfide are reacted in a molar ratio of 3:1, 2 moles of Li ３ P.S. ４ Therefore, 2 moles of Li ３ P.S. ４ corresponds to a total of 4 moles of lithium sulfide and diphosphorus pentasulfide. Therefore, in the compounding ratio when using the above lithium sulfide and diphosphorus pentasulfide, the number of moles of lithium sulfide and diphosphorus pentasulfide is ３ P.S. ４ It can be applied as twice the amount of Li ３ P.S. ４ When using a halogen atom, Li ３ P.S. ４ The amount of the halogen element to be used is preferably 1 to 50 mol %, more preferably 10 to 40 mol %, even more preferably 20 to 30 mol %, and even more preferably 22 to 28 mol %.

[0088] (Solvent) As the solvent used when mixing the raw material ingredients, a wide range 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.

[0089] Examples of aliphatic hydrocarbons include hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, tridecane, etc. Examples of alicyclic hydrocarbons include cyclohexane, methylcyclohexane, etc. Examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, etc. Among the above hydrocarbon solvents, aromatic hydrocarbon solvents are preferred.

[0090] Other examples include solvents containing heteroatoms such as nitrogen atoms, oxygen atoms, sulfur atoms, and halogen atoms. Heteroatoms have a high affinity for lithium atoms and tend to bond with the solid electrolyte raw materials contained in the raw material inclusions to form complexes (hereinafter also referred to as "electrolyte precursors"). Therefore, solvents containing heteroatoms are compounds (hereinafter also referred to as "complexing agents") that can coordinate (bond) with the lithium atoms contained in the raw material inclusions to form complexes. Mixing the solid electrolyte raw materials with the complexing agent forms a complex, which makes it easier to maintain the uniform dispersion of the solid electrolyte raw materials, particularly the dispersion of the halogen atoms. As a result, it is believed that a sulfide solid electrolyte with high ionic conductivity can be obtained.

[0091] 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.

[0092] Preferred examples of solvents having an amino group include aliphatic amines such as ethylenediamine, diaminopropane, dimethylethylenediamine, diethylethylenediamine, dimethyldiaminopropane, tetramethyldiaminomethane, tetramethylethylenediamine (TMEDA), tetramethyldiaminopropane (TMPDA), tetraethylethylenediamine, and tetraethyldiaminopropane; 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. Also preferred are nitrile solvents such as acetonitrile, acrylonitrile, and isobutyronitrile; and nitrogen-containing solvents such as dimethylformamide, nitrobenzene, and dimethylacetamide.

[0093] As the solvent containing a nitrogen atom, from the viewpoint of obtaining higher ionic conductivity, a solvent having an amino group is preferred, and among them, an aliphatic amine is preferred. Furthermore, among the aliphatic amines having an amino group, a polyamine having two or more amino groups is preferred, and a diamine having two amino groups is preferred. From the same viewpoint, a tertiary amine having a tertiary amino group as the amino group is preferred, a tertiary diamine having two tertiary amino groups is more preferred, a tertiary diamine having two tertiary amino groups at both ends is even more preferred, and an aliphatic tertiary diamine having tertiary amino groups at both ends is even more preferred. As the aliphatic tertiary diamine, the above-mentioned tetramethylethylenediamine, tetraethylethylenediamine, tetramethyldiaminopropane, and tetraethyldiaminopropane are preferred, and tetramethylethylenediamine and tetraethylethylenediamine are more preferred.

[0094] Preferred examples of the solvent containing an oxygen atom include those containing an oxygen atom as a heteroatom, such as ether solvents and ester solvents, as well as alcohol solvents, aldehyde solvents and ketone solvents.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] Preferred examples of solvents containing a halogen atom as a heteroatom include chloroform, carbon tetrachloride, dichloromethane, chlorobenzene, dichlorobenzene, trifluoromethylbenzene, chlorotoluene, bromobenzene, etc. Preferred examples of solvents containing a sulfur atom include dimethyl sulfoxide, carbon disulfide, etc.

[0099] As described above, typical examples of solvents containing heteroatoms include the above-mentioned solvents containing nitrogen atoms, solvents containing oxygen atoms, solvents containing halogen atoms, and solvents containing sulfur atoms. From the viewpoint of obtaining higher ionic conductivity, solvents containing nitrogen atoms and solvents containing oxygen atoms are more preferred, and solvents containing nitrogen atoms are even more preferred. It is also preferable to use a hydrocarbon solvent in combination with a solvent containing a heteroatom. In this case, it is preferable to use the above-mentioned aromatic hydrocarbon solvent as the hydrocarbon solvent, and a solvent containing a nitrogen atom is preferred as the solvent containing a heteroatom. Among them, amine solvents and nitrile solvents are preferred, and nitrile solvents are more preferred.

[0100] The amount of solvent used is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, relative to 10 parts by mass of the raw material content, and the upper limit is preferably 150 parts by mass or less, more preferably 130 parts by mass or less. Therefore, when a solvent is used, the pulverized heat-treated product is in the form of a slurry containing the pulverized heat-treated product and the solvent.

[0101] When the amount of solvent used is within the above range, the raw material contents in the raw material mixture are more easily made uniform, and when a complexing agent is used, complexes can be formed more efficiently, so that the atoms in the heat-treated product obtained by the heat treatment can be more uniformly dispersed, and the ionic conductivity of the resulting crystalline sulfide solid electrolyte can be improved. Furthermore, as described above, the heat treatment can be performed for a shorter period of time, which not only prevents aggregation and sintering between particles in the heat-treated product but also prevents deterioration due to thermal history.

[0102] (Mixing) The mixing of the raw material ingredients in the solvent is not particularly limited as long as the raw material ingredients can be mixed, and can be performed using equipment such as a stirrer, mixer, or pulverizer. Mixing of the raw material ingredients can occur using a stirrer, and using a pulverizer will result in pulverization of the raw material ingredients, but mixing also occurs at the same time. In other words, in the production method of this embodiment, the solid electrolyte raw materials can be mixed by stirring, mixing, pulverization, or a combination of these processes, as long as they are at least mixed.

[0103] In the manufacturing method of this embodiment, the mixing for obtaining the raw material content is preferably performed using a pulverizer among the above-mentioned devices. By using a pulverizer, the particle size of the raw material mixture can be adjusted, so the heat treatment time can be further shortened and a crystalline sulfide solid electrolyte can be more easily obtained as a heat-treated product. In addition, the elastic dissipation energy of the resulting crystalline sulfide solid electrolyte can be reduced to 5.0 × 10 －１８ It becomes easier to get J or above.

[0104] As the pulverizer, for example, a media-type pulverizer using a pulverizing medium can be used. Media-type pulverizers are broadly classified into container-driven pulverizers and media-agitation pulverizers. Examples of container-driven pulverizers include agitation tanks, grinding tanks, and combinations thereof, such as ball mills and bead mills. Examples of media-agitation pulverizers include impact pulverizers such as cutter mills, hammer mills, and pin mills; tower-type pulverizers such as tower mills; agitation tank pulverizers such as attritors, aquamizers, and sand grinders; flow-tank pulverizers such as Viscomills and pearl mills; flow-tube pulverizers; annular pulverizers such as Coball mills; continuous dynamic pulverizers; and single- or multi-shaft kneaders. Among these, considering the ease of adjusting the particle size of the resulting raw material mixture, the ball mills and bead mills exemplified as container-driven pulverizers are preferred, and planetary pulverizers are particularly preferred.

[0105] 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.

[0106] In the production method of this embodiment, since the mixture is mixed in a solvent, the mixture is in a liquid state or a slurry state accompanied by the solvent, and therefore a wet mill that can handle wet milling is preferred. Typical wet mills include a wet bead mill, a wet ball mill, and a wet vibration mill, and a wet bead mill that uses beads as milling media is preferred because it allows for free adjustment of the milling operation conditions and is easily adaptable to smaller particle sizes.

[0107] Since the material to be mixed is in a liquid or slurry state, a flow-through mill that can be operated to circulate the material 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.

[0108] When a ball mill or a bead mill is used, the rotation speed varies depending on the scale of the treatment and cannot be generalized, but is usually 10 to 1000 rpm, preferably 20 to 900 rpm. The milling time varies depending on the scale of the treatment and cannot be generalized, but is usually 0.5 to 100 hours, preferably 1 to 72 hours, and more preferably 5 to 48 hours.

[0109] By selecting the size and material of the medium (beads or 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 raw material mixture.

[0110] (Obtaining a Heat-Treated Product) The manufacturing method of this embodiment includes heat-treating the raw material mixture obtained by obtaining the raw material mixture to obtain a heat-treated product. The raw material mixture is a mixture containing a solid electrolyte raw material and a solvent. When a complexing agent is used as the solvent, at least a portion of the solid electrolyte raw material forms a complex with the complexing agent, resulting in a mixture containing a complex, a solid electrolyte raw material that does not contribute to the formation of the complex, and the complex. Regardless of the form of the raw material mixture, a heat-treated product is obtained by heat-treating it, and the heat-treated product can be called a crystalline sulfide solid electrolyte.

[0111] In the manufacturing method of this embodiment, the heat treatment may be performed by heating to a desired heating temperature all at once, or by heating stepwise in a plurality of stages up to a predetermined heating temperature. In the manufacturing method of this embodiment, stepwise heating is preferable, and in consideration of ease of operation, heating is performed by heating while increasing the temperature in two stages, specifically, at a heating temperature T １ First heat treatment at a temperature T １ Heating temperature T higher than °C ２ In this way, after calcining in the first heat treatment to obtain a calcined product, the calcined product is then fired in the second heat treatment, thereby promoting crystallization of the sulfide solid electrolyte and reducing the elastic dissipation energy of the crystalline sulfide solid electrolyte to 5.0 × 10 －１８J or more, and deterioration due to thermal history can be suppressed, making it possible to obtain a crystalline sulfide solid electrolyte of higher quality.

[0112] As will be described later, when the raw material mixture is heat-treated, a solvent may be added to form a slurry before the heat treatment in order to make the raw material mixture more uniform. In this case, the solvent used is removed by a first heat treatment to obtain a calcined product while removing the solvent, and then crystallization is promoted by a second heat treatment, thereby increasing the elastic dissipation energy of the crystalline sulfide solid electrolyte to 5.0 × 10. －１８ J or more, and deterioration due to thermal history can be suppressed, making it possible to obtain a crystalline sulfide solid electrolyte of higher quality.

[0113] The heating temperature cannot be generalized because it varies depending on the crystal structure to be obtained, but when a 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 set to 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 on the lowest temperature side, and although there is no particular upper limit, it should be about 40°C or lower. By setting the temperature range in this way, a crystalline sulfide solid electrolyte can be obtained more efficiently and reliably.

[0114] When heating is performed in a stepwise manner, the final heating temperature may be set to the above temperature range. ２ ° C. is the heating temperature T of the first heat treatment １ There is no particular limitation on the heating temperature as long as it is higher than 100° C., but it may be selected from the above temperature range.

[0115] Heating temperature T of the first heat treatment １The temperature is preferably in the range of 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 when the 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. There is no particular restriction on the lower limit, but it is preferably about −40°C or more, which is the temperature of the exothermic peak observed at the lowest temperature.

[0116] In the first heat treatment, the temperature range is set as described above to obtain an amorphous sulfide solid electrolyte, and then, in the subsequent second heat treatment, heat treatment for obtaining a crystalline sulfide solid electrolyte is performed. If the heating temperature in the second heat treatment is set within the temperature range described above as the final heating temperature in the case of the above-mentioned stepwise heating, a crystalline sulfide solid electrolyte can be obtained.

[0117] In the production method of this embodiment, the heating temperature for obtaining the heat-treated product cannot be generalized because it varies depending on the crystal structure to be obtained as described above, but is usually 110° C. or higher, preferably 120° C. or higher, more preferably 130° C. or higher, and even more preferably 140° C. or higher, with the upper limit being preferably 600° C. or lower, more preferably 550° C. or lower, and even more preferably 500° C. or lower. When the heat treatment is performed in stages, it is sufficient that the heating temperature in the final heat treatment stage is within the above range.

[0118] For example, when the crystal structure to be obtained is a thiolicon region II crystal structure, the heating temperature T １ The heating temperature T of the second heat treatment is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 105°C or higher, and the upper limit is preferably 135°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower. ２ °C is the heating temperature T １ ° C. or higher, and is preferably 110° C. or higher, more preferably 120° C. or higher, even more preferably 135° C. or higher, and still more preferably 140° C. or higher, with the upper limit being preferably 240° C. or lower, more preferably 220° C. or lower, and even more preferably 200° C. or lower.

[0119] When the crystal structure to be obtained is an argyrodite-type crystal structure, the heating temperature T １ The heating temperature T of the second heat treatment is preferably 100°C or higher, more preferably 125°C or higher, and even more preferably 150°C or higher, and the upper limit is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower. ２ °C is the heating temperature T １ ° C. or higher, and preferably 300° C. or higher, more preferably 330° C. or higher, and even more preferably 350° C. or higher, with the upper limit being preferably 600° C. or lower, more preferably 550° C. or lower, and even more preferably 500° C. or lower.

[0120] As described above, in obtaining the heat-treated product, a solvent may be added to the raw material mixture before the heat treatment. By making the raw material mixture more uniform, a more uniform heat-treated product can be obtained, and the ionic conductivity of the resulting crystalline sulfide solid electrolyte can be improved.

[0121] The solvent used in the heat treatment can be appropriately selected from the solvents exemplified as solvents that can be used in obtaining the raw material mixture, and hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents are preferred, with aromatic hydrocarbon solvents being more preferred. The amount of solvent used is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, per 10 parts by mass of the raw material content, with the upper limit being preferably 150 parts by mass or less, more preferably 130 parts by mass or less, and even more preferably 110 parts by mass or less. Therefore, when a solvent is used, the raw material mixture to be heat treated is in the form of a slurry containing the solid electrolyte raw material and the solvent.

[0122] The heating time is not particularly limited as long as it is a time that allows the desired 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. When heating stepwise, the total time should be within the above range.

[0123] 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). For example, an inert gas atmosphere containing a certain concentration of hydrogen may 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 include methods using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, and a firing furnace. In addition, industrially, a horizontal dryer or a horizontal vibration fluidized dryer having a heating means and a feeding mechanism can also be used, and the method may be selected depending on the amount of heat to be processed.

[0124] (Obtaining a pulverized heat-treated product) The manufacturing method of this embodiment includes pulverizing the heat-treated product obtained by obtaining the heat-treated product. As described above, the time required for heat treatment to obtain the heat-treated product can be shortened, and therefore aggregation and sintering between particles of the obtained heat-treated product can be suppressed. Therefore, the energy required for pulverization can be suppressed, and the elastic dissipation energy of the resulting crystalline sulfide solid electrolyte can be reduced to 5.0 × 10 －１８ It can be J or more.

[0125] In obtaining the pulverized heat-treated product (1), it is preferable to pulverize the pulverized material with a pulverization energy of 0.50 Wh / kg or more. By setting the pulverization energy to 0.50 Wh / kg or more, the elastic dissipation energy of the obtained crystalline sulfide solid electrolyte can be kept within the above range, i.e., 5.0 × 10 －１８In the drying of the pulverized heat-treated product described below, if drying by air flow drying is not performed in the drying step (2), the treatment (1) above must be performed.

[0126] The pulverization energy in the pulverization is set to 5.0 × 10 elastic dissipation energy of the resulting crystalline sulfide solid electrolyte. －１８ From the viewpoint of facilitating the attainment of a value of 5.0×10 or more, the elastic dissipation energy is preferably 0.60 Wh / kg or more, more preferably 0.70 Wh / kg or more, and the upper limit is preferably 3.0 Wh / kg or less, more preferably 2.5 Wh / kg or less, and even more preferably 2.3 Wh / kg or less. By pulverizing the crystalline sulfide solid electrolyte while suppressing the pulverization energy in this manner, the particle size of the resulting crystalline sulfide solid electrolyte can be adjusted, and the elastic dissipation energy can be reduced to 5.0×10 －１８ It becomes easier to get J or above.

[0127] The heat-treated product may be pulverized to obtain the pulverized heat-treated product, for example, using a pulverizer described as a pulverizer that can be used to obtain the raw material mixture.

[0128] A solvent may also be used to obtain the pulverized heat-treated product. That is, the heat-treated product may be pulverized together with the solvent using a pulverizer. The solvent may be appropriately selected from the solvents described as being usable in obtaining the raw material mixture. When a solvent is used, the amount of solvent used is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, per 10 parts by mass of the heat-treated product, with the upper limit being preferably 150 parts by mass or less, more preferably 120 parts by mass or less. Therefore, when a solvent is used, the pulverized heat-treated product is in the form of a slurry containing the pulverized heat-treated product and the solvent.

[0129] (Drying the pulverized and heat-treated product) The production method of this embodiment includes drying the pulverized and heat-treated product. As described above, drying is performed to remove a solvent if one is used in obtaining the pulverized and heat-treated product, or to remove the remaining solvent if one is used in obtaining the raw material mixture.

[0130] The drying of the pulverized and heat-treated product is preferably carried out by flash drying in the above-mentioned (2) drying. By flash drying, not only can the solvent be removed but also the elastic dissipation energy of the resulting crystalline sulfide solid electrolyte can be reduced to 5.0 × 10 －１８ In obtaining the pulverized heat-treated product, if the treatment (1) is not carried out, the treatment (2) must be carried out.

[0131] The flash drying method can be any method that uses a flash current and is not particularly limited. For example, the method can be performed using at least one device selected from a flash dryer and a spray dryer.

[0132] When flash drying is performed, any commercially available flash dryer may be used, such as a static dryer that blows hot air onto a stationary object to be dried (pulverized heat-treated object) to dry it, a fluidized dryer that dries the object to be dried (pulverized heat-treated object) while fluidizing it with hot air, or a flash dryer that supplies the object to be dried (pulverized heat-treated object) into a pipe through which a heated airflow is supplied, thereby heating the object to be heated with the heated airflow. A direct hot air type flash dryer, in which the heated airflow comes into direct contact with the object to be dried (pulverized heat-treated object), is preferred.

[0133] The drying temperature when using the above-mentioned static dryer or the like cannot be generally specified because it varies depending on the boiling point of the solvent used, etc., but is usually 0 to 180°C, preferably 10 to 150°C, more preferably 15 to 125°C, and even more preferably room temperature (23°C) to 100°C.

[0134] Furthermore, a medium fluidized dryer using a medium such as media particles can be used as the airflow dryer. A medium fluidized dryer is a dryer of a type in which a heated airflow is blown into the dryer to heat and fluidize the medium such as media particles, thereby drying the material to be dried (pulverized heat-treated material) with the heated airflow and the medium such as heated media particles.

[0135] The spray dryer may be a commercially available device such as a spray dryer or spray drier, and is a type of dryer in which the material to be dried (pulverized heat-treated material) is sprayed from a spray nozzle using gas and dried by contacting it with heated gas supplied from a separate line.

[0136] The drying temperature can be set according to the type of solvent, etc. contained in the pulverized heat-treated product to be dried, and can be set at a temperature equal to or higher than the boiling point of the solvent, etc. As described above, the drying temperature varies depending on the boiling point, etc. of the solvent, etc. used, and therefore cannot be generally specified. However, when drying is performed by flash drying using the above-mentioned spray dryer or the like, the drying temperature is usually about 50 to 250°C, preferably 100 to 240°C, more preferably 150 to 230°C, and even more preferably 180 to 220°C.

[0137] Furthermore, after drying the pulverized heat-treated product, classification may be carried out to adjust the particle size. Classification can be carried out, for example, using an air classifier. Examples of air classifiers include conventional classifiers that rotate powder at high speed to separate it into fine powder and coarse powder by centrifugation, such as rotor-type air rotation classifiers that employ a classification rotor, and rotorless cyclone classifiers.

[0138] As described above, the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and has an elastic dissipation energy of 5.0 × 10 calculated from a focus curve measured by atomic force microscopy. －１８ J or more. Therefore, the crystalline sulfide solid electrolyte of this embodiment can be easily obtained by the manufacturing method of this embodiment. The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is as described above for the crystalline sulfide solid electrolyte of this embodiment.

[0139] (Applications) The crystalline sulfide solid electrolyte of this embodiment and the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment are excellent in battery life characteristics, voltage resistance, and coatability. In addition, due to their high ionic conductivity, they are suitable for use in electrode mixtures and batteries. The crystalline sulfide solid electrolyte of this embodiment may be used in a positive electrode layer, a negative electrode layer, or an electrolyte layer. Each layer can be manufactured by a known method.

[0140] (Electrode active material) When the crystalline sulfide solid electrolyte of the present embodiment is used as an electrode mixture, it can be used as an electrode mixture containing the crystalline sulfide solid electrolyte of the present embodiment (or the crystalline sulfide solid electrolyte obtained by the production method of the present embodiment) and an electrode active material.

[0141] 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 a positive electrode or a negative electrode. As the positive electrode active material or the negative electrode active material, materials conventionally used as these active materials can be used. In addition to the sulfide solid electrolyte and the electrode active material, other components such as a conductive material and a binder may also be included.

[0142] (Lithium ion battery) When the crystalline sulfide solid electrolyte of this embodiment is used as a battery, it can be used as a lithium ion battery containing at least one selected from the crystalline sulfide solid electrolyte of this embodiment (or the crystalline sulfide solid electrolyte obtained by the production method of this embodiment) and the electrode mixture.

[0143] The battery preferably includes a current collector in addition to the positive electrode layer, the electrolyte layer, and the 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] 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.

[0145] (Measurement of Elastic Modulus (Young's Modulus) and Elastic Dissipation Energy) Elastic modulus was calculated by measuring the focus curve (AFM focus curve) measured by atomic force microscopy. Using the following measuring device, AFM force curve measurements were performed on the measurement objects obtained in the Examples and Comparative Examples. From the obtained force curve (test force-displacement characteristics), the elastic modulus (Young's modulus) of the sample was calculated using the DMT model, and the elastic dissipation energy was calculated from the difference between the test force-displacement characteristics during indentation and pull-out. Measurements were performed on 10 particles for one measurement object, and the maximum and minimum values ​​were excluded from the obtained elastic dissipation energy values, and the average value of the remaining eight points was taken as the elastic dissipation energy of the measurement object.

[0146] Measurement equipment: Nanoscope V and Dimension ICON (manufactured by Bruker AXS) AFM probe: silicon cantilever Measurement conditions: Ramp mode (force curve measurement mode), focus curves of 10 particles were obtained for each measurement object. Measurement environment: argon atmosphere Sample form: Sample powder was fixed on a Si substrate with epoxy resin to serve as the measurement sample Displacement speed: 85 nm / sec Maximum test force: 1.0 μN

[0147] (Evaluation of battery life characteristics) 1. Preparation of positive electrode mixture LiNi was used as the positive electrode active material. ０．５ Co ０．２ Mn ０．３ O ２ (hereinafter also referred to as "NCM") coated with lithium niobate was used. 76 mg of NCM, 19 mg of the solid electrolyte of each of the examples and comparative examples, and 5 mg of a conductive additive ("Denka Black Li Li-400 (model number)", manufactured by Denka Co., Ltd.) were weighed and mixed in a mortar for 10 minutes to prepare a positive electrode mixture.

[0148] 2. Assembling the Test Cell For battery evaluation, a test cell assembled with a 10 mm diameter ceramic cylinder and a metal piston was used. 150 mg of argyrodite-type solid electrolyte (d50: 4.0 μm) was placed in the cylinder and pressed three times at 180 MPa to form a separator layer (solid electrolyte layer). Next, 33 mg of the prepared positive electrode composite was placed on one side of the separator layer and pressed three times at 360 MPa. The separator was then inverted and pressed once more at 180 MPa, 360 MPa, and 550 MPa to form a positive electrode composite layer. Furthermore, Li metal foil and Ti foil as a current collector were sequentially placed on the side of the separator layer opposite the side on which the positive electrode composite layer was formed, to prepare a battery pellet. The upper and lower metal pistons were restrained with M8 bolts and nuts at a tightening torque of 2 N·m (the actual pressure applied to the battery pellet was approximately 40 MPa), and the battery pellets were sealed in a sealed container for measurement.

[0149] 3. Evaluation Battery performance evaluation was carried out in a 60°C environment. The evaluation conditions were a 1C current value of 4.5 mA and a voltage range of 4.3 V to 2.5 V. First, two cycles of CCCV charge-CC discharge were performed at 0.1 C. Next, 100 cycles of CCCV charge-CC discharge test were performed at 0.5 C. The ratio of the initial discharge capacity C1 at 0.5 C to the discharge capacity C2 at the 100th cycle (100 × C2 / C1) was used as an index of battery performance.

[0150] (Evaluation of voltage resistance) A trickle charge test was conducted based on the following method to evaluate voltage resistance. The measurement objects obtained in the Examples and Comparative Examples were used to form the following positive electrode layers to prepare lithium ion batteries, and a trickle charge test was conducted under the following test conditions to calculate the post-trickle resistance. The smaller the post-trickle resistance, the better the voltage resistance. (Lithium ion battery) Electrode area: Φ10 mm (0.785 cm ２) Positive electrode layer: 9 mg of electrode mixture obtained by mixing NCM811, the object to be measured (solid electrolyte) and a conductive additive (mixing ratio (mass ratio): 60 / 35 / 5) Solid electrolyte layer: ARG type solid electrolyte (d50: 4.0 μm, σ: 7.9 mS / cm) 150 mg Counter electrode / reference electrode: InLi (Test conditions) Potential range: 4.25 V - 2.5 V vs Li + / Li After charging and discharging at 0.1 C at room temperature (23 ° C), 0.1 C charge - 1 C discharge, and further discharge at 0.1 C (discard discharge), and then charged at 0.1 C. Then, trickle charging was performed at 4.25 V for 48 hours at 60 ° C. After the trickle charge test, the AC impedance was measured again at room temperature, and the post-trickle resistance was calculated.

[0151] (Powder X-ray Diffraction (XRD) Measurement) Powder X-ray diffraction (XRD) measurement was carried out as follows. The sulfide solid electrolyte powder obtained in the Examples and Comparative Examples was filled into a groove 20 mm in diameter and 0.2 mm deep, and leveled with glass to prepare a sample. This sample was sealed with Kapton film for XRD and measured under the following conditions without being exposed to air. Measurement device: D2 PHASER, manufactured by Bruker Corporation Tube voltage: 30 kV Tube current: 10 mA X-ray wavelength: Cu-Kα ray (1.5418 Å) Optical system: focusing method Slit configuration: Soller slit 4°, divergence slit 1 mm, Kβ filter (Ni plate) used Detector: semiconductor detector Measurement range: 2θ = 10-60 deg Step width, scan speed: 0.05 deg, 0.05 deg / sec

[0152] (Measurement of Crystallite Size) The crystallite size (L) was determined according to the method of P. Scherrer et al. Specifically, using the results of the above (powder X-ray diffraction (XRD) measurement), it was determined by calculation using the following formula. Crystallite size (L) = Kλ / (β × cos θ) K: constant, 0.9 was used. λ: 1.5418 Å (Cu-Kα radiation) β: calculated from β = w−B. w: half-width of the 25.5° peak obtained by measurement B: instrument constant (a standard material (silicon) was measured in the same manner as above (powder X-ray diffraction (XRD) measurement), and B = 0.1497° was determined from the peak at 2θ = 28.5°.)

[0153] For w (half width obtained by measurement), a linear baseline was set on the peak shape obtained by XRD measurement, and the difference between the intensity at each point and the baseline was calculated to obtain an XRD curve. The XRD curve was set as an equation consisting of a Lorentz function L(x) and a Gaussian function G(x) (f(x) = (1 - α) × L(x) + α × G(x)), and the parameters A, w, and x were calculated by curve fitting. ０ and α were determined.

[0154]

[0155] (Measurement of average particle diameter) A laser diffraction particle size distribution measuring device ("LA-950 (product name)" (manufactured by Horiba, Ltd.) was used to measure the particle diameter (D ５０ ) was measured and used as the average particle size.

[0156] (Measurement of specific surface area) Nitrogen (N ２ The specific surface area was measured by the BET method using adsorption.

[0157] (solid ３１ P-NMR measurement) Measurement was performed using the following equipment under the following conditions: Equipment: ECZ400R (manufactured by JEOL Ltd.) Observation nuclei: ３１ P Observation frequency: 161.994 MHz Measurement temperature: room temperature Pulse sequence: single pulse 90° pulse width: 3.2 μs Waiting time after FID measurement until next pulse application: 60 s MAS (magic angle spinning) rotation speed: 11 kHz Number of accumulations: 64 Measurement range: 250 ppm to -150 ppm Sample amount: 100 mg External standard: NH ４ H ２ P.O. ４ (chemical shift 1.00 ppm)

[0158] Peak separation: When peak separation is required, the obtained solid ３１The P-NMR spectrum is analyzed using the software "FT-NMR" (software included in "FT-NMR Data Processing by Personal Computer," Revised Edition (Second Edition) (Sankyo Publishing)) to determine the separated peaks. The software calculates the separated peaks, calculated NMR signal values, and the residual sum of squares R2 from the NMR signals (experimental values) using the nonlinear least squares method. Peak separation is considered complete when the residual sum of squares R2 within the analysis range between the experimental and calculated values, assuming the maximum peak height to be 1, is 0.007 or less and the number of separated peaks is the smallest.

[0159] solid ３１ Based on the data obtained by P-NMR measurement, PS ４ ３－ Based on the peak areas due to glass components and other structures, PS ４ ３－ The phosphorus ratio (mol%) contained in the glass components was calculated. ４ ３－ PS relative to the total area of ​​peaks due to other structures including glass components ４ ３－ From the area ratio of the peak due to the glass component (peak: 82-85 ppm), PS ４ ３－ The phosphorus ratio (mol %) contained in the glass component was calculated. This phosphorus ratio (mol %) is the ratio of phosphorus atoms in the glass component, and is defined as the ratio of the total area of ​​all peaks derived from the glass component ("degree of vitrification").

[0160] (Measurement of Ion Conductivity) In this example, the measurement of ion conductivity was carried out as follows. A 10 mm diameter (cross-sectional area S: 0.785 cm ) sample was taken from the measurement object obtained in the examples and comparative examples. ２) and a height (L) of 0.1 to 0.3 cm were molded into a circular pellet to prepare a sample. Electrode terminals were attached to the top and bottom of the sample, and measurements were made at 25°C using an AC impedance method (frequency range: 5 MHz to 0.5 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 formula. Here, if the curve does not form an arc, the intercept of the real part Z' (Ω) axis was taken as the bulk resistance R (Ω): R = ρ(L / S) σ = 1 / ρ

[0161] (Example 1) Li ２ S, P ２ S ５ LiBr and LiCl were separately pulverized under a nitrogen atmosphere using a pin mill equipped with a constant feeder (model number 100UPZ, manufactured by Hosokawa Micron Corporation). ２ S, P ２ S ５ , LiBr and LiCl in a molar ratio of Li ２ S:P ２ S ５ The mixture was weighed so that the ratio of LiBr:LiCl was 47.5:12.5:15.0:25.0, and the mixture was placed in a glass container, and the container was shaken to roughly mix.

[0162] The crude mixture was dispersed in a mixed solvent of dehydrated toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and dehydrated isobutyronitrile (manufactured by Kishida Chemical Co., Ltd.) under a nitrogen atmosphere to obtain a slurry of approximately 15% by mass. While maintaining the slurry in a nitrogen atmosphere, mixing was carried out for 1 hour using a bead mill (model number "LMZ015", manufactured by Ashizawa Finetech Co., Ltd.) (milling medium: 456 g of 0.5 mm diameter zirconia beads, peripheral speed: 12 m / s, circulation flow rate: 500 mL / min).

[0163] The obtained slurry was placed in an autoclave (1000 mL capacity, made of SUS316) equipped with a stirrer and a heating oil bath, and heat-treated at 180°C for 2 hours while stirring at a rotation speed of 70 rpm to obtain a calcined product. The calcined product was dried in a planetary mixer ("Nauta Mixer (registered trademark)" manufactured by Hosokawa Micron Corporation) and then mixed with Al. ２ O ３ The mixture was transferred to a sagger ("999-60S (model number)", manufactured by Tokyo Glass Instruments Co., Ltd.), placed in an electric furnace ("F-1404-A (model number)", manufactured by Tokyo Glass Instruments Co., Ltd.), and subjected to heat treatment at 430°C (heating time: 2 hours) to obtain a heat-treated product.

[0164] The obtained heat-treated product was dispersed in a mixed solvent of dehydrated toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and dehydrated isobutyronitrile (manufactured by Kishida Chemical Co., Ltd.) under a nitrogen atmosphere to obtain an approximately 8 wt % slurry. The slurry was pulverized using a bead mill (model "LMZ015", manufactured by Ashizawa Finetech Co., Ltd.) while maintaining the nitrogen atmosphere, to obtain a slurry containing the pulverized heat-treated product. The pulverization energy required at this time was 0.74 kWh / kg.

[0165] The obtained slurry containing the pulverized heat-treated material was dried using a spray dryer (model CNL-3, manufactured by Okawahara Chemical Engineering Co., Ltd.) to obtain a crystalline sulfide solid electrolyte. The spraying conditions and heated airflow conditions were as follows: (Spraying conditions) Spray pressure: 0.35 MPa Drying temperature (inlet): 200°C Drying temperature (outlet): 110°C Airflow rate: 300 Nm ３ / time

[0166] The obtained crystalline sulfide solid electrolyte was subjected to the measurement of elastic dissipation energy, evaluation of battery life characteristics, evaluation of voltage resistance, and evaluation of coatability by the above-mentioned methods. ５０The following were measured: specific surface area, ratio of the glass component in terms of phosphorus atoms (shown as "glass component ratio" in Table 1), Young's modulus (elastic modulus), and ionic conductivity. The measurement results and evaluation results are shown in Table 1. Furthermore, the obtained crystalline sulfide solid electrolyte was subjected to powder XRD diffraction measurement by the above-mentioned method. The X-ray diffraction spectrum is shown in FIG. 3.

[0167] Furthermore, the crystalline sulfide solid electrolyte and binder obtained in Example 1 were weighed out in a ratio of 98:2 (mass ratio), and dehydrated butyl butyrate was gradually added to the mixture while mixing with a medicine spoon to prepare a slurry with a solids concentration of approximately 40-60%. The slurry was processed in a planetary centrifugal mixer ("Awatori Rentaro (ARE-310) (trade name)" manufactured by THINKY) at 2000 rpm for 5 minutes and 2200 rpm for 30 seconds to prepare a slurry for coatability evaluation. The above slurry was dripped onto the deepest groove side of a grind gauge (0-100 μm, manufactured by BYK-Gardner) and pulled toward the shallower groove side with a scraper to form a film. The groove depth was read where streaks began to appear. Coatability was evaluated based on the groove depth, and streaks were observed at 20 μm or less, confirming that the shallow grooves provided excellent coatability.

[0168] Example 2 A crystalline sulfide solid electrolyte was obtained in the same manner as in Example 1, except that the pulverization energy used in pulverizing the heat-treated product to obtain the pulverized heat-treated product was set to 2.25 kWh / kg. The obtained crystalline sulfide solid electrolyte was subjected to measurement of elastic dissipation energy, evaluation of battery life characteristics, and evaluation of voltage resistance by the above-mentioned methods. In addition, the crystallite size and average particle size (D ５０ The glass composition was measured for its specific surface area, phosphorus atom ratio, Young's modulus (elastic modulus), and ionic conductivity. The measurement and evaluation results are shown in Table 1.

[0169] The obtained crystalline sulfide solid electrolyte was subjected to powder XRD diffraction measurement using the method described above. The X-ray diffraction spectrum is shown in Figure 4. Furthermore, when the coatability was evaluated using the same method as in Example 1, it was confirmed that streaks of 20 μm or less were present, and that the grooves were shallow, providing excellent coatability.

[0170] (Example 3) A crystalline sulfide solid electrolyte was obtained in the same manner as in Example 2, except that in drying the slurry containing the pulverized heat-treated product in Example 2, vacuum drying was performed at 100°C in a Schlenk bottle instead of using a spray dryer, and coarse particles were removed by dry classification using a centrifugal airflow classifier ("50ATP (model number)", manufactured by Hosokawa Micron Corporation). The elastic dissipation energy of the obtained crystalline sulfide solid electrolyte was measured by the above-mentioned methods, and the battery life characteristics and voltage resistance were evaluated. Furthermore, the crystallite size and average particle size (D ５０ The glass composition was measured for its specific surface area, phosphorus atom ratio, Young's modulus (elastic modulus), and ionic conductivity. The measurement and evaluation results are shown in Table 1.

[0171] The obtained crystalline sulfide solid electrolyte was subjected to powder XRD diffraction measurement using the method described above. The X-ray diffraction spectrum is shown in Figure 5. Furthermore, when the coatability was evaluated using the same method as in Example 1, it was confirmed that streaks of 20 μm or less were present, and that the grooves were shallow, providing excellent coatability.

[0172] Comparative Example 1 A crystalline sulfide solid electrolyte was obtained in the same manner as in Example 3, except that the pulverization energy when pulverizing the heat-treated product to obtain a pulverized heat-treated product was set to 0.3 kWh / kg. The obtained crystalline sulfide solid electrolyte was subjected to measurement of elastic dissipation energy, evaluation of battery life characteristics, and evaluation of voltage resistance by the above-mentioned methods. In addition, the crystallite size and average particle size (D ５０ The following were measured: specific surface area, ratio of glass components in terms of phosphorus atoms, Young's modulus (elastic modulus), and ionic conductivity. The measurement and evaluation results are shown in Table 1. The obtained crystalline sulfide solid electrolyte was also subjected to powder XRD diffraction measurement using the method described above. The X-ray diffraction spectrum is shown in FIG.

[0173]

[0174] FIG. 1 shows the AFM focus curves measured in Examples 1 and 2 and Comparative Example 1. The elastic dissipation energy is the area of ​​the region surrounded by the focus curve (the red region in the figure). The elastic dissipation energy of the crystalline sulfide solid electrolytes of Examples 1 and 2 is 20×10 －１８ J and 9 x 10 －１８ J and 5.0 x 10 －１８ The elastic dissipation energy of the crystalline sulfide solid electrolyte of Example 3 was also measured in the same manner as in Examples 1 and 2, and was found to be 11×10 －１８ J and 5.0 x 10 －１８ Here, the evaluation of voltage resistance based on the resistance after trickle measured by the above method and the evaluation of coatability show that the voltage resistance and coatability are excellent, and the elastic dissipation energy is 5.0 × 10 －１８ It was confirmed that the crystalline sulfide solid electrolytes of Examples 1 to 3 also had excellent life characteristics, as shown in FIG. 2. The elastic dissipation energy of the crystalline sulfide solid electrolyte of Comparative Example 1 was 3×10 －１８ J and 5.0 x 10 －１８ 2, it was confirmed that the crystalline sulfide solid electrolyte of Comparative Example 1 was also inferior in life characteristics.

[0175] According to the X-ray diffraction spectrum, it was confirmed that the crystalline sulfide solid electrolytes of Examples 1 to 3 had diffraction peaks at 2θ = 25.5° and 29.9°, etc., which were derived from an argyrodite-type crystal structure. It was also found that the ionic conductivity was slightly lower than that of the comparative example. This is thought to be because a portion of the crystalline sulfide solid electrolyte became a glass component. However, considering that other performance characteristics such as coatability, voltage resistance, and life characteristics were excellent, it can be said that the decrease was not so great as to cause practical problems.

[0176] The crystalline sulfide solid electrolyte of the present embodiment has excellent battery life characteristics, voltage resistance, and coatability, and is therefore suitable for use in batteries, particularly in batteries used in information-related devices and communication devices such as personal computers, video cameras, and mobile phones.

Claims

1. A material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and having an elastic dissipation energy of 5.0 x 10 calculated from a focus curve measured by atomic force microscopy. －１８ J or more.

2. The crystalline sulfide solid electrolyte according to claim 1, having a crystallite size of 5 nm or more and 60 nm or less.

3. The crystalline sulfide solid electrolyte according to claim 1 or 2, wherein the halogen atoms include at least two types selected from the group consisting of chlorine atoms, bromine atoms and iodine atoms.

4. The crystalline sulfide solid electrolyte according to any one of claims 1 to 3, wherein the volume-based average particle size measured by a laser diffraction particle size distribution measuring method is 0.1 µm or more and 10 µm or less.

5. The specific surface area measured by the BET method is 12 m ２ The crystalline sulfide solid electrolyte according to any one of claims 1 to 4, wherein the SrO2 content is 1 / g or more.

6. Solid ３１ The ratio of the total area of ​​all peaks derived from glass components to the total area of ​​all peaks at 60 to 120 ppm observed in P-NMR measurement is 5% or more in terms of phosphorus atoms. The crystalline sulfide solid electrolyte according to any one of claims 1 to 5.

7. The crystalline sulfide solid electrolyte according to any one of claims 1 to 6, having a Young's modulus of 1 GPa or more and 50 GPa or less.

8. A crystalline sulfide solid electrolyte according to any one of claims 1 to 7, having an argyrodite-type crystal structure.

9. A method for producing a crystalline sulfide solid electrolyte, comprising: mixing, in a solvent, a raw material-containing material including a plurality of solid electrolyte raw materials each including at least one atom selected from lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a raw material mixture; heat-treating the raw material mixture to obtain a heat-treated product; pulverizing the heat-treated product to obtain a pulverized heat-treated product; and drying the pulverized heat-treated product, and comprising at least one of the following processes (1) and (2): (1) in obtaining the pulverized heat-treated product, pulverization is performed with a pulverization energy of 0.50 Wh / kg or more; and (2) in drying, drying is performed by flash drying.

10. The method for producing a crystalline sulfide solid electrolyte according to claim 9, wherein the flash drying is carried out using at least one device selected from a flash dryer and a spray dryer.

11. The heat treatment is performed at a heating temperature T １ ℃, then the heating temperature T １ Heating temperature T higher than °C ２ The method for producing a crystalline sulfide solid electrolyte according to claim 9 or 10, further comprising a second heat treatment at 200° C.

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