Electrode mixture and manufacturing method thereof

Abstract

To provide an electrode mixture that has excellent electrical conductivity due to excellent contact between a solid electrolyte and an electrode active material, and that can exhibit high battery performance.SOLUTION: An electrode mixture contains a sulfide solid electrolyte and an electrode active material, and the electronic conductivity parameter X, expressed by a predetermined mathematical formula, satisfies 0.30≤X≤2.10.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrode mixture and a method for producing the same. [Background technology]

[0002] With the recent rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as their power sources has become increasingly important. Conventionally, batteries used for such applications have used electrolytes containing flammable organic solvents, but by making batteries all-solid-state, flammable organic solvents are not used in the battery, safety devices can be simplified, and manufacturing costs and productivity are excellent. Therefore, batteries in which the electrolyte is replaced with a solid electrolyte layer are being developed.

[0003] Electrodes in all-solid-state lithium batteries use electrode composites containing an active material and a solid electrolyte, and studies have been conducted to improve ionic conductivity by increasing interfacial contact between the active material and the solid electrolyte. For example, Patent Document 1 discloses a composite active material comprising active material particles containing a predetermined element and a sulfide solid electrolyte covering 76.0% or more of the surface of the active material particles. Patent Document 2 discloses a method of mixing an active material with a solution obtained by dissolving a solid electrolyte in an organic solvent. Non-Patent Document 1 discloses a method of producing a composite by mixing an active material with a sulfide solid electrolyte synthesized in ethanol. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-154407 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-191899 [Non-patent literature]

[0005] [Non-Patent Document 1] J. Jpn. Soc. Color Mater.,89[9],300-305(2016) Summary of the Invention [Problem to be solved by the invention]

[0006] However, it remains difficult to improve the dispersion and contact state between the solid electrolyte and the electrode active material, and there is room for further improvement. The present invention has been made in view of the above circumstances, and aims to provide an electrode mixture that has excellent conductivity due to an excellent dispersion and contact state between a solid electrolyte and an electrode active material, and that can exhibit high battery performance. [Means for solving the problem]

[0007] As a result of extensive research into solving the above problems, the present inventors have found that the problems can be solved by the following invention.

[0008] 1. An electrode composite containing a sulfide solid electrolyte and an electrode active material, wherein the electronic conductivity parameter X represented by the following formula (1) satisfies 0.30≦X≦2.10.

[0009]

number

[0010] According to the present invention, it is possible to provide an electrode mixture that has excellent conductivity due to the excellent dispersion and contact state between the solid electrolyte and the electrode active material, and that can exhibit high battery performance, and a method for producing the electrode mixture. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a flow diagram illustrating an example of a preferred embodiment of a method for producing a crystalline sulfide solid electrolyte. [Figure 2] FIG. 1 is a flow diagram illustrating an example of a preferred embodiment of a method for producing a crystalline sulfide solid electrolyte. [Figure 3] 1 shows X-ray diffraction spectra of an electrolyte precursor, an amorphous sulfide solid electrolyte, and a crystalline sulfide solid electrolyte obtained in an embodiment of the present invention. [Figure 4] 1 shows X-ray diffraction spectra of raw materials used in the examples. [Figure 5] 1 shows X-ray diffraction spectra of the crystalline sulfide solid electrolytes of Example 1 and Comparative Example 1. [Figure 6] 1 is a SEM (scanning electron microscope) photograph of the electrode mixture obtained in Example 1. [Figure 7] 1 is a SEM (scanning electron microscope) photograph of the electrode mixture obtained in Example 2. [Figure 8] 1 is a SEM (scanning electron microscope) photograph of the electrode mixture obtained in Comparative Example 1. [Figure 9] 1 is a graph showing the evaluation results of Examples and Comparative Examples. [Figure 10] 1 is an EDS image of nickel element constituting the electrode active material used in Example 1. [Figure 11] 1 is an EDS image of the phosphorus element constituting the sulfide solid electrolyte used in Example 1. [Figure 12] 1 is an EDS image of nickel element constituting the electrode active material used in Example 2. [Figure 13] 1 is an EDS image of the phosphorus element constituting the sulfide solid electrolyte used in Example 2. [Figure 14] 1 is a SEM (scanning electron microscope) photograph of the electrode mixture obtained in Example 3. [Figure 15] 1 is an EDS image of nickel element constituting the electrode active material used in Example 3. [Figure 16] 1 is an EDS image of the phosphorus element constituting the sulfide solid electrolyte used in Example 3. [Figure 17] 1 is a SEM (scanning electron microscope) photograph of the electrode mixture obtained in Example 4. [Figure 18] 1 is an EDS image of nickel element constituting the electrode active material used in Example 4. [Figure 19]1 is an EDS image of the phosphorus element constituting the sulfide solid electrolyte used in Example 4. [Figure 20] 1 is an EDS image of nickel element constituting the electrode active material used in Comparative Example 1. [Figure 21] 1 is an EDS image of the phosphorus element constituting the sulfide solid electrolyte used in Comparative Example 1. [Figure 22] 1 is a SEM (scanning electron microscope) photograph of the electrode mixture obtained in Comparative Example 2. [Figure 23] 1 is an EDS image of nickel element constituting the electrode active material used in Comparative Example 2. [Figure 24] 1 is an EDS image of the phosphorus element constituting the sulfide solid electrolyte used in Comparative Example 2. [Figure 25] 1 is a SEM (scanning electron microscope) photograph of the electrode mixture obtained in Comparative Example 3. [Figure 26] 1 is an EDS image of nickel element constituting the electrode active material used in Comparative Example 3. [Figure 27] 1 is an EDS image of the phosphorus element constituting the sulfide solid electrolyte used in Comparative Example 3. [Figure 28] 1 is a SEM (scanning electron microscope) photograph of the electrode mixture obtained in Example 5. [Figure 29] 1 is an EDS image of nickel element constituting the electrode active material used in Example 5. [Figure 30] 10 is an EDS image of the phosphorus element constituting the sulfide solid electrolyte used in Example 5. [Figure 31] 1 is a SEM (scanning electron microscope) photograph of the electrode mixture obtained in Example 6. [Figure 32] 1 is an EDS image of nickel element constituting the electrode active material used in Example 6. [Figure 33] 10 is an EDS image of the phosphorus element constituting the sulfide solid electrolyte used in Example 6. [Figure 34] 1 is a SEM (scanning electron microscope) photograph of the electrode mixture obtained in Example 7. [Figure 35] 1 is an EDS image of nickel element constituting the electrode active material used in Example 7. [Figure 36] 10 is an EDS image of the phosphorus element constituting the sulfide solid electrolyte used in Example 7. [Figure 37] 1 is a SEM (scanning electron microscope) photograph of the electrode mixture obtained in Comparative Example 4. [Figure 38] 1 is an EDS image of nickel element constituting the electrode active material used in Comparative Example 4. [Figure 39] 1 is an EDS image of the phosphorus element constituting the sulfide solid electrolyte used in Comparative Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") will be described. In this specification, the upper and lower limit values ​​of a range of values ​​expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values ​​in the examples can also be used as the upper and lower limit values.

[0013] In this specification, the term "solid electrolyte" refers to an electrolyte that maintains a solid state at 25° C. under a nitrogen atmosphere. The solid electrolyte in this embodiment contains lithium, sulfur, phosphorus, and a halogen element, and has ionic conductivity attributable to lithium. Because it contains sulfur, it is also called a "sulfide solid electrolyte."

[0014] The term "solid electrolyte" includes both crystalline solid electrolytes having a crystalline structure and amorphous solid electrolytes. In this specification, a crystalline solid electrolyte is a solid electrolyte in which a peak derived from the solid electrolyte is observed in the X-ray diffraction pattern in X-ray diffraction measurement, and is a material that does not require the presence or absence of peaks derived from the raw materials of the solid electrolyte. That is, a crystalline solid electrolyte includes a crystalline structure derived from the solid electrolyte, and a part of the crystalline structure may be derived from the solid electrolyte, or the entire crystalline structure may be derived from the solid electrolyte. Furthermore, as long as the crystalline solid electrolyte has the X-ray diffraction pattern described above, it may also include an amorphous solid electrolyte in part. Therefore, the crystalline solid electrolyte includes so-called glass ceramics obtained by heating an amorphous solid electrolyte to a temperature above the crystallization temperature. In addition, in this specification, the amorphous solid electrolyte refers to one in which the X-ray diffraction pattern in X-ray diffraction measurement is a halo pattern in which no peaks other than those derived from the material are observed, and it does not matter whether or not there are peaks derived from the raw materials of the solid electrolyte.

[0015] [Electrode composite material] The electrode mixture of this embodiment contains a sulfide solid electrolyte and an electrode active material, and the electronic conductivity parameter X represented by the following formula (1) satisfies 0.30≦X≦2.10.

[0016]

number

[0017] The composite active material described in Patent Document 1 has low electronic conductivity, and unless a conductive material is used, it cannot be said to be suitable for use as a positive electrode material or a negative electrode material. As a result of extensive research into this phenomenon, the inventors found that the composite active material described in Patent Document 1, for example, in Example 1, has a mixture ratio of active material particles to sulfide solid electrolyte (approximately 5:1 by mass), and the coverage rate of the active material particle surface with the sulfide solid electrolyte, which has low electronic conductivity, is extremely high at 82.3%, resulting in a decrease in the electronic conductivity of the composite active material. This shows that achieving an appropriate coverage state according to the mixture ratio is important for achieving excellent battery characteristics. Furthermore, even in the method described in Patent Document 2 and Non-Patent Document 1, in which an active material is mixed with an organic solvent such as ethanol, the resulting composite has low electronic conductivity, and again, unless a conductive material is used, it cannot be said to be suitable for use as a positive electrode material or a negative electrode material. The present inventors conducted an extensive investigation of these documents and found that, as shown in Comparative Example 3 of the present application described below, the solid electrolyte aggregates in the form of thin flakes and coats the electrode active material, so the dispersion state of the solid electrolyte on the surface of the electrode active material is not good and good contact between the two cannot be ensured, resulting in a composite with low electronic conductivity and inferior battery characteristics.

[0018] Based on the above findings, the present inventors have found that by setting the electronic conductivities of the electrode active material and the sulfide solid electrolyte, as well as the electrode composite obtained using these, and further the electronic conductivity parameter X derived from the fraction of the electrode active material, within specific ranges, it is possible to improve the coating state of the sulfide solid electrolyte on the electrode active material, i.e., to improve the contact state between the sulfide solid electrolyte and the electrode active material. The electronic conductivity of an electrode mixture containing a sulfide solid electrolyte and an electrode active material is theoretically expressed by the following formula (2).

[0019]

number

[0020] The measured value Σ(C) of the electronic conductivity of an electrode composite should essentially be the same as the theoretical value calculated by the above formula (2), but in reality it is not the same due to the influence of the state of the sulfide solid electrolyte and the electrode active material in the electrode composite, for example, the dispersion state of the sulfide solid electrolyte coating the surface of the electrode active material (hereinafter sometimes simply referred to as the "dispersion state"), the resulting contact state of the sulfide solid electrolyte with the surface of the electrode active material (hereinafter sometimes simply referred to as the "contact state"), particle size, etc. In other words, the electronic conductivity parameter X, which is the ratio between the measured value and the theoretical value, is not 1 but fluctuates around 1. The inventors believed that the electronic conductivity parameter X, which is the ratio of the measured electronic conductivity of an electrode mixture to the theoretical value, can be considered an indicator of the state of the sulfide solid electrolyte and the electrode active material in the electrode mixture, particularly the degree of dispersion and contact. Furthermore, by improving the dispersion and contact, the coverage of the sulfide solid electrolyte becomes appropriate depending on the electrode active material fraction, and therefore the electronic conductivity parameter X can also be considered an indicator of obtaining an appropriate coverage of the sulfide solid electrolyte depending on the fraction (hereinafter simply referred to as an "appropriate coverage depending on the fraction"). The inventors then determined that by setting the electronic conductivity parameter X within a specific range of 0.30≦X≦2.10, the sulfide solid electrolyte coated on the surface of the electrode mixture can be adjusted to a good dispersion state, ensuring excellent contact between the two. Furthermore, by achieving an appropriate coverage of the sulfide solid electrolyte depending on the electrode active material fraction, an electrode mixture with excellent conductivity and capable of exhibiting high battery performance can be obtained.

[0021] From the viewpoint of improving the dispersion and contact state of the sulfide solid electrolyte coated on the surface of the electrode active material, achieving a moderate coating state according to the fraction, and improving battery performance, the electronic conductivity parameter X is preferably 0.40 or more, more preferably 0.65 or more, even more preferably 0.80 or more, with the upper limit being preferably 2.05 or less, more preferably 1.90 or less, even more preferably 1.85 or less, still more preferably 1.80 or less, and particularly preferably 1.30 or less. As mentioned above, the upper and lower limits of X can be arbitrarily selected and combined from these numerical ranges, but from the viewpoint of improving the dispersion and contact state of the sulfide solid electrolyte coated on the surface of the electrode active material, achieving a moderate coating state according to the fraction, and improving battery performance, the combination of the upper and lower limits of X is preferably 0.40 or more and 2.05 or less, more preferably 0.65 or more and 1.90 or less, even more preferably 0.80 or more and 1.85 or less, still more preferably 0.80 or more and 1.80 or less, and particularly preferably 0.80 or more and 1.30 or less.

[0022] Regarding the calculation of the electronic conductivity parameter X, the electronic conductivity Σ(SE) of the sulfide solid electrolyte varies depending on the elements other than the sulfur element that constitute the sulfide solid electrolyte, the blending ratio, etc., so it cannot be generalized, but it is preferably 1.0 × 10 -7 S / cm or less, preferably 5.0×10 -8 S / cm or less, more preferably 1.0 × 10 -8 S / cm or less, and even more preferably 5.0×10 -9 S / cm or less, particularly preferably 2.25 × 10 -9 Within the above range, the electronic conductivity parameter X can be easily set within the range of 0.30≦X≦2.10. There is no particular lower limit, and the lower limit is usually 1.0×10 -10 S / cm or more. The electronic conductivity Σ(SE) of sulfide solid electrolytes that can be used for electrode composites is generally within the above range, but is less than 1.0 × 10 -8S / cm. Therefore, instead of the measured value of the electronic conductivity Σ(SE) of the sulfide solid electrolyte, the electronic conductivity parameter X can also be calculated using the above-mentioned general numerical value. Even if the above-mentioned general numerical value is used, as long as the calculated electronic conductivity parameter X is within the range of this embodiment, it is considered that the dispersion state and contact state of the sulfide solid electrolyte coating the surface of the electrode active material are in a favorable state or above a certain level.

[0023] In this specification, the electronic conductivity is a value measured by the following method. 0.2 g of sample (sulfide solid electrolyte, electrode active material, electrode composite) was weighed out and pressed at 20 MPa using a 10 mm diameter ceramic cylinder and pressing jig, rotated 120° and pressed again at 20 MPa, rotated 120° in the same direction and pressed again at 20 MPa to produce a pellet. The pellet was screwed at four points on both ends using blocking electrodes and fixed with a torque wrench to a pressure of 8 N·m to create a cell. Next, a predetermined voltage (4 points: 0.01 V, 0.1 V, 0.5 V, and 1 V) was applied to the cell for two hours, and the current and voltage values ​​after two hours were plotted. The resistance value R was calculated from the slope obtained by the least squares method. e Calculate the resistance value R and the pellet length L at the time of measurement. e , pellet cross-sectional area S e Using the above, the value σ is calculated using the following formula: e is the electronic conductivity. σ e =1 / R e ×L e / S e

[0024] The electronic conductivity Σ(A) of the electrode active material also varies depending on the elements constituting the electrode active material, so it cannot be generalized, but it is preferably 1.0 × 10 -6 S / cm or more, preferably 5.0×10 -6 S / cm or more, more preferably 1.0 × 10 -5 S / cm or more, and even more preferably 1.0×10 -4S / cm or more. Within the above range, the dispersion state and contact state are improved, and it becomes easier to achieve an appropriate coating state according to the fraction, that is, it becomes easier to set the electronic conductivity parameter X within the range of 0.30≦X≦2.10. There is no particular upper limit, and it is usually 1.0×10 -1 S / cm or less.

[0025] The electrode active material fraction α is the ratio of the electrode active material to the total amount of the sulfide solid electrolyte and electrode active material contained in the electrode mixture, and is preferably 0.4 or more, more preferably 0.5 or more, even more preferably 0.6 or more, still more preferably 0.7 or more, particularly preferably 0.8 or more, and even more particularly preferably 0.85 or more, with the upper limit being preferably 0.995 or less, more preferably 0.99 or less, even more preferably 0.98 or less, and still more preferably 0.95 or less. When the electrode active material fraction α is within this range, it is easy to achieve an electronic conductivity parameter X in the range of 0.30≦X≦2.10.

[0026] The electronic conductivity Σ(C) of the electrode mixture varies depending on the sulfide solid electrolyte and electrode active material constituting the electrode mixture and the blending ratio thereof, so it cannot be generalized, but is preferably 1.0 × 10 -6 S / cm or more, preferably 5.0×10 -6 S / cm or more, more preferably 1.0 × 10 -5 S / cm or more, and even more preferably 1.0×10 -4 S / cm or more, particularly preferably 1.0 × 10 -3 S / cm or more, more particularly preferably 3.5×10 -3 Within the above range, the electronic conductivity parameter X can be easily set within the range of 0.30≦X≦2.10. There is no particular upper limit, and it is usually 1.0×10 -1 S / cm or less, and considering the electronic conductivity parameter X, it is 1.0×10 -2 S / cm or less is preferable, and 6.50 × 10 -3 S / cm or less is more preferable, and 6.0×10 -3 S / cm or less is more preferable.

[0027] Further, in the elemental analysis of the electron microscope image by energy dispersive X-ray spectroscopy, the overlapping area ratio of the mapping of the elements constituting the sulfide solid electrolyte to the mapping of the elements constituting the electrode active material, which is binarized by a threshold value calculated by discriminant analysis, is represented as A×(1-α) / α (α: electrode active material fraction). It is preferable that 0.55 < A < 5.0.

[0028] The overlapping area ratio of the mapping of the elements constituting the sulfide solid electrolyte to the mapping of the elements constituting the electrode active material can grasp the positional relationship of the elements constituting each of the sulfide solid electrolytes covering the electrode active material. Therefore, it is an index of the contact state between the electrode active material and the sulfide solid electrolyte. Basically, the higher the overlapping area ratio, the better the contact state and the tendency for the battery performance to improve. From the viewpoint of improving the contact state between the electrode active material and the sulfide solid electrolyte and obtaining more excellent battery characteristics, the overlapping area ratio is preferably 0.060 or more, more preferably 0.080 or more, still more preferably 0.090 or more, and even more preferably 0.10 or more. As an upper limit, it is preferably 0.80 or less, more preferably 0.70 or less, still more preferably 0.60 or less, and even more preferably 0.50 or less. When the overlapping area ratio is within the above range, it becomes easier to make the electron conductivity parameter X within the range of 0.30 ≤ X ≤ 2.10. However, even within the above range, for example, in the case where the flaky sulfide solid electrolyte has aggregated as in Comparative Example 3 described later, the electron conductivity parameter X deviates from the range of 0.30 ≤ X ≤ 2.10, the contact state deteriorates, and excellent battery performance may not be obtained.

[0029] In this specification, the overlapping area ratio is a value that can be measured, for example, by the following method. A sample (sulfide solid electrolyte, electrode active material) is photographed using an electron microscope, such as a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM). The electron microscope image of the sample is subjected to elemental analysis using energy dispersive X-ray spectroscopy (EDS). This analysis is performed on the electron microscope image of the sample using an energy dispersive X-ray analyzer (EDS device). The resulting image (also referred to as an EDS image) of a specific element is then binarized using a threshold determined by discriminant analysis (known as "Otsu's binarization process") to map elements such as sulfur that constitute the sulfide solid electrolyte and nickel that constitute the electrode active material. The elements that constitute the sulfide solid electrolyte preferably include phosphorus for ease of measurement, and for similar reasons, the elements that constitute the electrode active material preferably include a transition element. The method for binarizing the image of the elements (EDS image) obtained by elemental analysis may be any known method and is not particularly limited. For example, processing using OpenCV (Open Source Computer Vision Library) in Python is easy. In this case, the binarized pixel data of the EDS image is extracted into a numerical matrix in which the absence of an element is represented by 0 and the presence of an element is represented by 255, and the image data is converted into a numerical matrix, and elements constituting the sulfide solid electrolyte, such as sulfur and phosphorus, and elements constituting the electrode active material, such as nickel, are mapped. The total number of 255s contained in the numerical matrix is ​​calculated as pixels where an element constituting the electrode active material is present, and the total number of overlapping 255s contained in these numerical matrices is calculated as pixels where an element constituting the electrode active material and an element constituting the sulfide solid electrolyte overlap. The value obtained by dividing these totals is used as the overlap area ratio.

[0030] In the electrode composite material of this embodiment, when the overlapping area ratio is expressed as A×(1-α) / α (α: electrode active material fraction), it is preferable that 0.55 < A < 5.0. As described above, since the overlapping area ratio can grasp the positional relationship of each element constituting the sulfide solid electrolyte covering the electrode active material, it is an index of the contact state. Since A calculated from the overlapping area ratio and the electrode active material fraction α takes into account the fraction α, it can be an index for grasping an appropriate coating state according to the fraction as well as the contact state. Therefore, when A is within the above range, an appropriate coating state of the sulfide solid electrolyte according to the electrode active material fraction α is likely to be obtained, so that the dispersion state and the contact state are improved, and more excellent battery performance can be obtained. From the same perspective, A is preferably 0.60 or more, more preferably 0.65 or more, still more preferably 0.7 or more, and even more preferably 0.75 or more. As the upper limit, it is preferably 4.8 or less, more preferably 4.7 or less, still more preferably 4.6 or less, and even more preferably 4.5 or less.

[0031] The electronic conductivity parameter X can be adjusted by the types of the sulfide solid electrolyte and the electrode active material contained in the electrode composite material, that is, the electronic conductivity according to these types, and the composition such as their blending ratios. The same applies to the overlapping area ratio, which is a preferable property. Hereinafter, a preferable configuration will be described in order to satisfy 0.30 ≤ X ≤ 2.10 for the electronic conductivity parameter X and to satisfy the overlapping area ratio, which is a preferable property.

[0032] (Sulfide solid electrolyte) First, the sulfide solid electrolyte used in this embodiment will be described. The sulfide solid electrolyte used in the electrode composite material of this embodiment may be either an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte, and a crystalline sulfide solid electrolyte is preferable from the viewpoint of battery characteristics.

[0033] The sulfide solid electrolyte used in the present embodiment contains at least sulfur element, and preferably contains lithium element as an element for exhibiting ionic conductivity, and preferably contains phosphorus element from the viewpoint of improving ionic conductivity, and more preferably contains a halogen element from the viewpoint of improving ionic conductivity.

[0034] The sulfide solid electrolyte used in this embodiment is preferably a crystalline sulfide solid electrolyte, and preferably includes a thiolicon region II crystal structure. If the sulfide solid electrolyte includes this crystal structure, it can become a solid electrolyte with high ionic conductivity, and therefore an electrode composite with excellent battery characteristics can be obtained.

[0035] The compounding ratios of these various elements will be described in detail in the method for producing a sulfide solid electrolyte described later, but the compounding ratio (molar ratio) of lithium element, sulfur element, phosphorus element, and halogen element is preferably 1.0-1.8:1.0-2.0:0.1-0.8:0.01-0.6, more preferably 1.1-1.7:1.2-1.8:0.2-0.6:0.05-0.5, and still more preferably 1.2-1.6:1.3-1.7:0.25-0.5:0.08-0.4. When bromine and iodine are used in combination as the halogen elements, the compounding ratio (molar ratio) of lithium, sulfur, phosphorus, bromine, and iodine is preferably 1.0-1.8:1.0-2.0:0.1-0.8:0.01-0.3:0.01-0.3, more preferably 1.1-1.7:1.2-1.8:0.2-0.6:0.02-0.25:0.02-0.25, more preferably 1.2-1.6:1.3-1.7:0.25-0.5:0.03-0.2:0.03-0.2, and even more preferably 1.35-1.45:1.4-1.7:0.3-0.45:0.04-0.18:0.04-0.18. By setting the compounding ratio (molar ratio) of lithium element, sulfur element, phosphorus element and halogen element within the above range, it becomes easier to obtain a solid electrolyte having a thiolithium region II type crystal structure and higher ionic conductivity.

[0036] The sulfide solid electrolyte used in this embodiment preferably has a volume-based average particle size (hereinafter, sometimes simply referred to as "average particle size") of 3 μm or more as measured by a laser diffraction particle size distribution measurement method, and a specific surface area (hereinafter, sometimes simply referred to as "specific surface area") of 20 m or more as measured by the BET method. 2 / g or more. Such properties make it easier to set the electronic conductivity parameter X within the range of 0.30≦X≦2.10, improve the dispersion and contact state of the sulfide solid electrolyte coating the surface of the electrode active material, and also make it easier to achieve an appropriate coating state according to the fraction, thereby making it easier to obtain high battery performance. In this way, the crystalline sulfide solid electrolyte used in this embodiment has an average particle size of at least a certain level and a particle size of 20 m 2 It is preferable that the sulfide solid electrolyte has a very large specific surface area of ​​1 / g or more. This indicates a structure in which small, highly crystalline primary particles aggregate to form secondary particles. This solid electrolyte structure forms good contact with the active material, making it easier to obtain an electrode composite that can exhibit high battery performance. That is, when the sulfide solid electrolyte used in this embodiment is mixed with the active material to form an electrode composite, it is easily crushed into primary particles at the crystal surface upon collision with the active material. It is believed that the necking between the primary particles is broken and new surfaces are formed, causing the primary particles to adhere to the active material. Because the sulfide solid electrolyte is a fine particle, it also has a strong van der Waals force, forming good contact with the active material. This is also evident from an SEM image of the sulfide solid electrolyte of this embodiment, where extremely small solid electrolyte particles are observed dispersed on the surface of the active material ( FIG. 6 ). As such, the sulfide solid electrolyte having the above properties does not aggregate into flaky sulfide solid electrolyte, as in Comparative Example 3 described below, and provides good contact with the electrode active material, resulting in excellent battery characteristics.

[0037] The sulfide solid electrolyte used in this embodiment preferably has a volume-based average particle size of 3 μm or more as measured by a laser diffraction particle size distribution measurement method. From the viewpoint of improving battery performance, the average particle size is more preferably 4 μm or more, even more preferably 5 μm or more, and even more preferably 7 μm or more. The upper limit is preferably 150 μm or less, more preferably 125 μm or less, even more preferably 100 μm or less, and even more preferably 50 μm or less. Sulfide solid electrolytes are prone to deterioration due to reaction with moisture in the air. In this embodiment, the solid electrolyte before crushing has a large average particle size, so that deterioration due to reaction with moisture, etc., can be prevented before being made into an electrode mixture. Furthermore, the bulk density can be increased, which is advantageous for transportation.

[0038] In this specification, the volume-based average particle size determined by a laser diffraction particle size distribution measurement method is the particle size at which 50% of the total particle size is reached when the particle size distribution cumulative curve is drawn and the cumulative total is calculated from the smallest particle size, and the volume distribution is the average particle size that can be measured using, for example, a laser diffraction / scattering particle size distribution measurement device. In this specification, the average particle size is referred to as the "average particle size (D 50 )" More specifically, the average particle size is measured, for example, as follows. First, 110 ml of dehydrated toluene (manufactured by Wako Pure Chemical Industries, product name: special grade) is placed in the dispersion tank of a laser diffraction particle size analyzer, and 6% of dehydrated tertiary butyl alcohol (manufactured by Wako Pure Chemical Industries, special grade) is added as a dispersant. After thoroughly mixing the mixture, dry sulfide solid electrolyte is added and the particle size is measured. The amount of dry sulfide solid electrolyte added is adjusted so that the laser scattering intensity corresponding to the particle concentration falls within a specified range (10-20%) on the measurement device's operation screen. If this range is exceeded, multiple scattering may occur, making it impossible to accurately determine the particle size distribution. If the amount is less than this range, the signal-to-noise ratio may deteriorate, making accurate measurements impossible. Depending on the measurement device, the laser scattering intensity will be displayed based on the amount of "dry sulfide solid electrolyte" added, so it is best to find the amount added that falls within the above laser scattering intensity. The optimum amount of "dried sulfide solid electrolyte" to be added varies depending on the type of metal salt, particle size, etc., but is generally about 0.005 g to 0.05 g.

[0039] In addition, the sulfide solid electrolyte has a specific surface area of ​​20 m2 measured by the BET method. 2 / g or more, and from the viewpoint of improving battery performance, it is more preferably 21m 2 / g or more, more preferably 23m 2 / g or more, and even more preferably 25m 2 / g or more, particularly preferably 27m 2 / g or more, and the upper limit is preferably 70m 2 / g or less, more preferably 60m 2 / g or less, more preferably 50m 2 / g or less, even more preferably 35m 2 / g or less. In this specification, the specific surface area is a value measured by the BET method (gas adsorption method), and either nitrogen (nitrogen method) or krypton (krypton method) may be used as the gas, and is measured by appropriately selecting the gas depending on the size of the specific surface area. The specific surface area can be measured using, for example, a commercially available gas adsorption measuring device (e.g., AUTOSORB6 (manufactured by Sysmex Corporation)).

[0040] Furthermore, the sulfide solid electrolyte used in this embodiment preferably has a half-width of the maximum peak, including the background at 2θ=10 to 40°, of Δ2θ=0.75° or less in X-ray diffraction measurement using CuKα radiation. Such properties result in higher ionic conductivity and improved battery performance. Furthermore, by increasing the crystallinity of the primary particles, when mixed with an active material to form an electrode composite, the particles are easily crushed into primary particles by their crystal planes upon collision with the active material, dispersing the solid electrolyte in the electrode composite. This facilitates achieving an electronic conductivity parameter X within the range of 0.30≦X≦2.10, improving the dispersion and contact of the sulfide solid electrolyte coated on the surface of the electrode active material and achieving an appropriate coating state according to the fraction, thereby facilitating high battery performance. The half-width will be described in detail in the description of the method for producing the sulfide solid electrolyte used in this embodiment.

[0041] (electrode active material) As the electrode active material contained in the electrode composite of this embodiment, a positive electrode active material or a negative electrode active material is adopted depending on whether the electrode composite is used for a positive electrode or a negative electrode. In this embodiment, from the viewpoint of improving battery performance, the sulfide solid electrolyte is preferably used as a positive electrode in combination with a positive electrode active material. That is, as the electrode active material contained in the electrode composite of this embodiment, a positive electrode active material is preferred.

[0042] The positive electrode active material can be any material that can promote a battery chemical reaction involving the movement of lithium ions due to the lithium element, which is preferably used as an element that exhibits ionic conductivity in this embodiment, in relation to the negative electrode active material. Examples of such positive electrode active materials that can insert and extract lithium ions include oxide-based positive electrode active materials and sulfide-based positive electrode active materials, and oxide-based positive electrode active materials are preferred.

[0043] The oxide-based positive electrode active material is preferably a lithium-containing transition metal composite oxide. That is, the electrode active material used in this embodiment preferably contains a transition element as a constituent element. Examples of transition metals that can be contained in the composite oxide include manganese, cobalt, nickel, iron, titanium, zirconium, tungsten, molybdenum, copper, chromium, tantalum, vanadium, and niobium. These can be used alone or in combination. In addition, preferred elements other than transition elements include Group 12 elements, which are typical elements, and zinc is particularly preferred. Preferred examples of the lithium-containing transition metal composite oxide include lithium-containing transition metal composite oxides such as LMO (lithium manganese oxide), LCO (lithium cobalt oxide), NMC (lithium nickel manganese cobalt oxide), NCA (lithium nickel cobalt aluminate), LNCO (lithium nickel cobalt oxide), and olivine-type compounds (LiMeNPO4, Me=Fe, Co, Ni, Mn).

[0044] Examples of sulfide-based positive electrode active materials include titanium sulfide (TiS2), molybdenum sulfide (MoS2), iron sulfide (FeS, FeS2), copper sulfide (CuS), and nickel sulfide (Ni3S2). In addition to the above positive electrode active materials, niobium selenide (NbSe3) and the like can also be used. In this embodiment, the positive electrode active material can be used alone or in combination of two or more types.

[0045] The negative electrode active material can be any material that can promote a battery chemical reaction involving the movement of lithium ions, such as an element that is preferably used in this embodiment as an element that exhibits ionic conductivity, preferably a metal that can form an alloy with lithium, an oxide thereof, an alloy of the metal with lithium, etc. As such a negative electrode active material that can insert and extract lithium ions, any material known in the battery field as a negative electrode active material can be used without any limitation. Examples of such negative electrode active materials include metallic lithium, metallic indium, metallic aluminum, metallic silicon, metallic tin, and other metallic lithium or metals capable of forming alloys with metallic lithium, oxides of these metals, and alloys of these metals with metallic lithium.

[0046] The electrode active material used in this embodiment may have a coating layer on its surface. The material for forming the coating layer may be an element that exhibits ionic conductivity in the sulfide solid electrolyte used in this embodiment, preferably an ion conductor such as a nitride or oxide of lithium element, or a composite thereof. Specifically, lithium nitride (LiN), LiGeO4, or other ion conductors having a main structure such as Li 4-2x Zn x Conductors with a lithiated crystal structure such as GeO4, and those with a Li3PO4-type framework structure such as Li 4-x Ge 1-x P x Conductors with thiolicon-type crystal structures such as S4, La 2 / 3-x Li 3x Examples include conductors having a perovskite crystal structure such as TiO3, and conductors having a NASICON crystal structure such as LiTi2(PO4)3. Also, Li y Ti 3-y O4(0 <y<3)、Li4Ti5O 12 Examples include lithium titanates such as (LTO), lithium metal oxides of metals belonging to Group 5 of the periodic table such as LiNbO3 and LiTaO3, and oxide-based conductors such as Li2O-B2O3-P2O5, Li2O-B2O3-ZnO, and Li2O-Al2O3-SiO2-P2O5-TiO2.

[0047] An electrode active material having a coating layer can be obtained, for example, by applying a solution containing various elements constituting the material forming the coating layer to the surface of the electrode active material, and then firing the electrode active material after application at a temperature preferably between 200°C and 400°C. Here, the solution containing various elements may be a solution containing alkoxides of various metals such as lithium ethoxide, titanium isopropoxide, niobium isopropoxide, tantalum isopropoxide, etc. In this case, the solvent may be an alcoholic solvent such as ethanol or butanol, an aliphatic hydrocarbon solvent such as hexane, heptane, or octane, or an aromatic hydrocarbon solvent such as benzene, toluene, or xylene. The above-mentioned attachment may be carried out by immersion, spray coating or the like.

[0048] From the viewpoint of improving production efficiency and battery performance, the firing temperature is preferably 200°C or higher and 400°C or lower, more preferably 250°C or higher and 390°C or lower, and the firing time is usually about 1 minute to 10 hours, preferably 10 minutes to 4 hours.

[0049] The coverage of the coating layer is preferably 90% or more, more preferably 95% or more, and even more preferably 100%, based on the surface area of ​​the electrode active material, i.e., the entire surface is coated. As described above, the electrode mixture of this embodiment has a large electrode active material fraction α and an appropriate coating state corresponding to this fraction α. ​​Furthermore, the dispersion and contact state of the sulfide solid electrolyte on the electrode active material surface are excellent, resulting in excellent battery characteristics. The thickness of the coating layer is preferably 1 nm or more, more preferably 2 nm or more, with an upper limit of preferably 30 nm or less, more preferably 25 nm or less. The thickness of the coating layer can be measured by cross-sectional observation using a transmission electron microscope (TEM), and the coverage can be calculated from the thickness of the coating layer, elemental analysis values, and BET surface area.

[0050] The sulfide solid electrolyte used in this embodiment may be a mechanically treated product thereof, and the electrode composite of this embodiment may contain the above-mentioned mechanically treated sulfide solid electrolyte and the above-mentioned electrode active material. That is, the sulfide solid electrolyte used in the electrode composite of this embodiment may be the above-mentioned sulfide solid electrolyte or a mechanically treated product thereof.

[0051] The volume-based average particle size of the mechanically treated sulfide solid electrolyte can be adjusted as desired, but is usually 0.05 μm or more, preferably 0.07 μm or more, more preferably 0.1 μm or more, and even more preferably 0.15 μm or more, with the upper limit usually being 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less, even more preferably 15 μm or less, and still more preferably 10 μm or less. In this embodiment, the mechanically treated sulfide solid electrolyte is preferably a crushed product of crystalline sulfide solid electrolyte having an average particle size smaller than that of the sulfide solid electrolyte before the mechanical treatment, i.e., the mechanical treatment is crushing. The specific surface area of ​​the mechanically treated sulfide solid electrolyte can be adjusted as desired, but is usually 0.1 m 2 / g or more, preferably 0.3m 2 / g or more, more preferably 0.5m 2 / g or more, more preferably 1m 2 / g or more, with the upper limit usually being 70m 2 / g or less, preferably 50m 2 / g or less, more preferably 45m 2 / g or less, more preferably 40m 2 / g or less.

[0052] The method for mechanically treating the sulfide solid electrolyte will be described in detail in the method for producing the sulfide solid electrolyte, which will be described later. The electrode composite of this embodiment, a mixture of a mechanically treated sulfide solid electrolyte and an electrode active material, is obtained by mixing the sulfide solid electrolyte with an electrode active material, or by mixing the mechanically treated sulfide solid electrolyte with an electrode active material. The method for mixing these will be described in detail in the method for producing an electrode composite described below.

[0053] (Other ingredients) The electrode mixture of this embodiment may contain other components such as a conductive material, a binder, etc. in addition to the sulfide solid electrolyte and the electrode active material. Examples of the conductive material, from the viewpoint of improving battery performance by improving electronic conductivity, include carbon-based materials such as artificial graphite, graphite carbon fiber, resin-baked carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads, furfuryl alcohol resin-baked carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon.

[0054] By using a binder, the strength of the positive electrode and the negative electrode when they are fabricated is improved. The binder is not particularly limited as long as it can impart functions such as binding property and flexibility, and examples thereof include fluorine-based polymers such as polytetrafluoroethylene and polyvinylidene fluoride, thermoplastic elastomers such as butylene rubber and styrene-butadiene rubber, and various resins such as acrylic resin, acrylic polyol resin, polyvinyl acetal resin, polyvinyl butyral resin, and silicone resin.

[0055] The blending ratio (mass ratio) of the electrode active material to the sulfide solid electrolyte in the electrode composite of this embodiment may be set to a blending ratio that results in the aforementioned electrode active material fraction α. ​​In the examples described below, this blending ratio is set to 90:10 (electrode active material fraction α of 0.90). This is because a relatively large amount of active material is more likely to cause changes in rate characteristics, and measurements were performed using this blending ratio at which differences in the properties of the solid electrolyte in the composite are particularly likely to appear. Therefore, the blending ratio is not limited to 90:10 (electrode active material fraction α of 0.90) and can be optimized within the above range. As described above, the electrode mixture of this embodiment has an extremely high coverage of 90% or more. However, the amount of sulfide solid electrolyte used is reduced, for example, by using a compounding ratio of the electrode active material to the sulfide solid electrolyte of 90:10 (electrode active material fraction α of 0.90) as employed in the examples. This provides a suitable coverage state according to the fraction. By providing a suitable coverage state according to the fraction, the dispersion and contact state of the sulfide solid electrolyte on the electrode active material surface are excellent, resulting in excellent battery characteristics. The fact that the electronic conductivity parameter X of the electrode mixture of this embodiment is within a predetermined range can also be said to mean that a suitable coverage state of the sulfide solid electrolyte on the electrode active material surface is obtained according to the electrode active material fraction, as described above.

[0056] When a conductive material is contained, the content of the conductive material in the electrode mixture is not particularly limited, but in consideration of improving battery performance and production efficiency, the content is preferably 0.5 mass% or more, more preferably 1 mass% or more, and even more preferably 1.5 mass% or more, and the upper limit is preferably 10 mass% or less, preferably 8 mass% or less, and even more preferably 5 mass% or less. Furthermore, when a binder is contained, the content of the binder in the electrode mixture is not particularly limited, but in consideration of improving battery performance and production efficiency, the content is preferably 1 mass % or more, more preferably 3 mass % or more, and even more preferably 5 mass % or more, with the upper limit being preferably 20 mass % or less, preferably 15 mass % or less, and even more preferably 10 mass % or less.

[0057] The electrode mixture of the present embodiment exhibits high battery performance and is suitable for use in forming the positive electrode layer, negative electrode layer, and electrolyte layer of an all-solid-state lithium battery, and is particularly suitable for use in the positive electrode layer and negative electrode layer. These layers can be produced by known methods. In addition, the all-solid-state lithium battery preferably includes a current collector in addition to the positive electrode layer, the negative electrode layer, and the electrolyte 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.

[0058] [Method for producing electrode mixture] The electrode mixture of this embodiment can be produced, for example, by a production method including mixing a sulfide solid electrolyte and an electrode active material. The sulfide solid electrolyte and electrode active material used in the method for producing an electrode mixture are as described above, and their compounding ratio (mass ratio) and other aspects are also as described above.

[0059] (Production of sulfide solid electrolytes) The sulfide solid electrolyte used in this embodiment can be produced, for example, by the following production method.

[0060] The method for producing the sulfide solid electrolyte used in the present embodiment preferably includes mixing raw material ingredients containing, in addition to elemental sulfur, preferably elemental lithium that exhibits ionic conductivity, elemental phosphorus that improves ionic conductivity, or more preferably elemental halogen, with a complexing agent. The method for producing a sulfide solid electrolyte preferably includes the following four embodiments, depending on whether a solid electrolyte such as Li3PS4 is used as a raw material and whether a solvent is used. Examples of preferred forms of these four embodiments are shown in Figures 1 (Embodiments A and B) and 2 (Embodiments C and D). Specifically, the present production method preferably includes: (Embodiment A) a production method using raw materials such as lithium sulfide and diphosphorus pentasulfide and a complexing agent; (Embodiment B) a production method using raw materials containing Li3PS4, which is the main structure of the electrolyte, and a complexing agent; (Embodiment C) a production method in which a solvent is added to raw materials such as lithium sulfide and a complexing agent in the above-mentioned embodiment A; and (Embodiment D) a production method in which a solvent is added to raw materials such as Li3PS4 and a complexing agent in the above-mentioned embodiment B. Hereinafter, embodiments A to D will be described in this order.

[0061] (Embodiment A) As shown in FIG. 1 , embodiment A is a manufacturing method characterized by mixing a raw material content containing lithium, sulfur, and phosphorus, preferably further containing a halogen, with a complexing agent, in which raw materials such as lithium sulfide and diphosphorus pentasulfide are used as the raw material content. Mixing the raw material content with the complexing agent typically produces an electrolyte precursor content in the form of a suspension, which is then dried to produce an electrolyte precursor. Further, heating the electrolyte precursor produces an amorphous or crystalline solid electrolyte. Although not shown, it is preferable to pulverize the electrolyte precursor before heating and then heat the pulverized electrolyte precursor obtained by pulverization. That is, this manufacturing method preferably includes mixing, pulverizing the electrolyte precursor obtained by mixing, and heating the pulverized electrolyte precursor obtained by pulverization. The following description will begin with embodiment A, but what is described as "of this embodiment" can also be applied to other embodiments.

[0062] (Raw material content) The raw material ingredients used in this embodiment contain lithium, sulfur, and phosphorus, and preferably further contain a halogen element. The raw material contained in the raw material-containing material may be, for example, a compound containing at least one of lithium, sulfur, and phosphorus, preferably further containing at least one halogen element. Specifically, lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; phosphorus sulfides such as diphosphorus trisulfide (P2S3) and diphosphorus pentasulfide (P2S5); phosphorus halides such as various phosphorus fluorides (PF3, PF5), various phosphorus chlorides (PCl3, PCl5, P2Cl4), various phosphorus bromides (PBr3, PBr5), and various phosphorus iodides (PI3, P2I4); thiophosphoryl fluoride (PSF3), thiophosphoryl chloride (PSCl3), thiophosphoryl bromide ( Representative examples of the starting material include raw materials consisting of at least two elements selected from the above four elements, such as thiophosphoryl halides, such as thiophosphoryl iodide (PSBr3), thiophosphoryl iodide (PSI3), thiophosphoryl fluoride dichloride (PSCl2F), and thiophosphoryl fluoride dibromide (PSBr2F); and elemental halogens, such as fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2), with chlorine (Cl2), bromine (Br2), and iodine (I2) being preferred, and bromine (Br2) and iodine (I2) being more preferred.

[0063] Examples of materials that can be used as raw materials other than those mentioned above include raw materials that contain at least one element selected from the above four elements and also contain an element other than the four elements, more specifically, lithium compounds such as lithium oxide, lithium hydroxide, and lithium carbonate; alkali metal sulfides such as sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide; metal sulfides such as silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, tin sulfide (SnS, SnS), aluminum sulfide, and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; halides of alkali metals other than lithium, 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; and phosphorus oxyhalides such as phosphorus oxychloride (POCl) and phosphorus oxybromide (POBr).

[0064] In embodiment A, from the viewpoint of more easily obtaining a solid electrolyte having a predetermined average particle size and specific surface area as well as high ionic conductivity, the raw materials are preferably lithium sulfide, phosphorus sulfide such as diphosphorus trisulfide (PS) or diphosphorus pentasulfide (PS), elemental halogens such as fluorine (F), chlorine (Cl), bromine (Br), or iodine (I), or lithium halides such as lithium fluoride, lithium chloride, lithium bromide, or lithium iodide. Preferred raw material combinations include, for example, a combination of lithium sulfide, diphosphorus pentasulfide, and a lithium halide, or a combination of lithium sulfide, diphosphorus pentasulfide, and an elemental halogen. Preferred lithium halides are lithium bromide and lithium iodide, and preferred elemental halogens are bromine and iodine.

[0065] The lithium sulfide used in embodiment A is preferably in the form of particles. The average particle size of lithium sulfide particles (D 50 ) is preferably 10 μm or more and 2000 μm or less, more preferably 30 μm or more and 1500 μm or less, and even more preferably 50 μm or more and 1000 μm or less. 50 ) is the particle size at which 50% of the total particle size is obtained by accumulating the particle size distribution curve from the smallest particle size, and the volume distribution is the average particle size that can be measured using, for example, a laser diffraction / scattering particle size distribution analyzer. Furthermore, among the above-mentioned examples of raw materials, solid raw materials preferably have an average particle size similar to that of the lithium sulfide particles, i.e., within the same range as that of the lithium sulfide particles.

[0066] When lithium sulfide, diphosphorus pentasulfide, and lithium halide are used as raw materials, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 70 to 80 mol%, more preferably 72 to 78 mol%, and even more preferably 74 to 76 mol%, from the viewpoint of obtaining higher chemical stability and higher ionic conductivity. When lithium sulfide, diphosphorus pentasulfide, lithium halide, and other raw materials used as needed are used, the content of lithium sulfide and diphosphorus pentasulfide relative to the total of these is preferably 60 to 100 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 80 mol%. Furthermore, when lithium bromide and lithium iodide are used in combination as the lithium halide, from the viewpoint of improving ionic conductivity, the proportion of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, still more preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0067] When using a halogen element as a raw material, for example, lithium sulfide and diphosphorus pentasulfide, the ratio of the number of moles of lithium sulfide (excluding the same number of moles of lithium sulfide as the halogen element) to the total number of moles of lithium sulfide and diphosphorus pentasulfide (excluding the same number of moles of lithium sulfide as the halogen element) is preferably within the range of 60 to 90%, more preferably within the range of 65 to 85%, even more preferably within the range of 68 to 82%, even more preferably within the range of 72 to 78%, and particularly preferably within the range of 73 to 77%. This is because these ratios result in higher ionic conductivity. From the same viewpoint, when lithium sulfide, diphosphorus pentasulfide, and a halogen element are used, the content of the halogen element relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and the halogen element is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%.

[0068] When lithium sulfide, diphosphorus pentasulfide, a halogen element, and a lithium halide are used, the content of the halogen element (α mol %) and the content of the lithium halide (β mol %) relative to the total amount thereof preferably satisfy the following formula (2), more preferably satisfy the following formula (3), even more preferably satisfy the following formula (4), and even more preferably satisfy the following formula (5). 2≦2α+β≦100…(2) 4≦2α+β≦80 …(3) 6≦2α+β≦50 …(4) 6≦2α+β≦30 …(5)

[0069] When two kinds of halogens are used as simple substances, the molar number of one halogen element in the substance is A1, and the molar number of the other halogen element in the substance is A2. 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.

[0070] Furthermore, when the two types of halogen atoms are bromine and iodine, where the number of moles of bromine is B1 and the number of moles of iodine is B2, the ratio B1:B2 is preferably 1 to 99:99 to 1, more preferably 15:85 to 90:10, even more preferably 20:80 to 80:20, still more preferably 30:70 to 75:25, and particularly preferably 35:65 to 75:25.

[0071] (complexing agent) In this embodiment, a complexing agent is used. In this specification, the complexing agent refers to a substance capable of forming a complex with lithium element, and has the property of reacting with sulfides, halides, etc. containing lithium element contained in the raw materials to promote the formation of an electrolyte precursor.

[0072] The complexing agent can be any agent having the above properties, and is preferably a compound containing an element having a high affinity with lithium, such as a hetero element such as nitrogen, oxygen, or chlorine, and more preferably a compound having a group containing such a hetero element, because such a hetero element or group containing such a hetero element can coordinate (bond) with lithium. The complexing agent is believed to have a property in which the heteroatom in its molecule has a high affinity for lithium, and thus is likely to bond with lithium-containing structures, such as Li3PS4, which typically contain a PS4 structure and is present as the main structure in the solid electrolyte obtained by this production method, as well as with lithium-containing raw materials, such as lithium halides, which are preferably used, to form aggregates. Therefore, by mixing the above-mentioned raw material contents with the complexing agent, lithium-containing structures, such as PS4 structures, or aggregates mediated by the complexing agent, and lithium-containing raw materials, such as lithium halides, or aggregates mediated by the complexing agent, are uniformly present, resulting in an electrolyte precursor in which the halogen elements are more dispersed and fixed. This is believed to result in a solid electrolyte with high ionic conductivity and suppressed hydrogen sulfide generation. It is also believed to be easier to obtain a desired average particle size and specific surface area. The reasons for using a complexing agent in the production method of this embodiment are as described above, but the reasons for using a halogen element are also similar: a solid electrolyte with high ionic conductivity and suppressed hydrogen sulfide generation is obtained, and a desired average particle size and specific surface area are more easily obtained.

[0073] Therefore, the complexing agent preferably has at least two heteroatoms capable of coordinating (bonding) in the molecule, and more preferably has a group containing at least two heteroatoms in the molecule. By having at least two groups containing heteroatoms in the molecule, a lithium-containing structure such as Li3PS4 containing a PS4 structure can be bonded to a lithium-containing raw material such as a preferred lithium halide via at least two heteroatoms in the molecule. This allows the halogen elements to be more dispersed and fixed in the electrolyte precursor, resulting in a solid electrolyte having a predetermined average particle size and specific surface area, high ionic conductivity, and suppressed hydrogen sulfide generation. From the above perspectives, among heteroatoms, nitrogen is preferred, and the nitrogen-containing group is preferably an amino group; that is, an amine compound is preferred as the complexing agent.

[0074] The amine compound is not particularly limited as long as it has an amino group in the molecule, as long as it can promote the formation of the electrolyte precursor, but a compound having at least two amino groups in the molecule is preferred. By having such a structure, a lithium-containing structure such as Li3PS4 containing a PS4 structure can be bonded to a lithium-containing raw material such as lithium halide via at least two nitrogen elements in the molecule, so that the halogen elements are more dispersed and fixed in the electrolyte precursor, resulting in a solid electrolyte having a predetermined average particle size and specific surface area and high ionic conductivity.

[0075] Examples of such amine compounds include aliphatic amines, alicyclic amines, heterocyclic amines, and aromatic amines, and these can be used alone or in combination.

[0076] More specifically, typical and preferred examples of the aliphatic amine include aliphatic primary diamines such as ethylenediamine, diaminopropane, and diaminobutane; aliphatic secondary diamines such as N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N'-dimethyldiaminopropane, and N,N'-diethyldiaminopropane; and aliphatic tertiary diamines such as N,N,N',N'-tetramethyldiaminomethane, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, N,N,N',N'-tetramethyldiaminopropane, N,N,N',N'-tetraethyldiaminopropane, N,N,N',N'-tetramethyldiaminobutane, N,N,N',N'-tetramethyldiaminopentane, and N,N,N',N'-tetramethyldiaminohexane. In the examples given in this specification, for example, in the case of diaminobutane, unless otherwise specified, all isomers of butane, such as linear and branched isomers, are included, in addition to isomers relating to the position of the amino group, such as 1,2-diaminobutane, 1,3-diaminobutane, and 1,4-diaminobutane. The number of carbon atoms in the aliphatic amine is preferably 2 or more, more preferably 4 or more, and even more preferably 6 or more, with the upper limit being preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. The number of carbon atoms in the hydrocarbon group of the aliphatic hydrocarbon group in the aliphatic amine is preferably 2 or more, and the upper limit being preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0077] Typical preferred examples of the alicyclic amine include alicyclic primary diamines such as cyclopropanediamine and cyclohexanediamine; alicyclic secondary diamines such as bisaminomethylcyclohexane; and alicyclic tertiary diamines such as N,N,N',N'-tetramethyl-cyclohexanediamine and bis(ethylmethylamino)cyclohexane. Typical preferred examples of the heterocyclic amine include heterocyclic primary diamines such as isophoronediamine; heterocyclic secondary diamines such as piperazine and dipiperidylpropane; and heterocyclic tertiary diamines such as N,N-dimethylpiperazine and bismethylpiperidylpropane. The number of carbon atoms in the alicyclic amine and heterocyclic amine is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0078] Representative preferred examples of the aromatic amine include aromatic primary diamines such as phenyldiamine, tolylenediamine, and naphthalenediamine; aromatic secondary diamines such as N-methylphenylenediamine, N,N'-dimethylphenylenediamine, N,N'-bismethylphenylphenylenediamine, N,N'-dimethylnaphthalenediamine, and N-naphthylethylenediamine; and aromatic tertiary diamines such as N,N-dimethylphenylenediamine, N,N,N',N'-tetramethylphenylenediamine, N,N,N',N'-tetramethyldiaminodiphenylmethane, and N,N,N',N'-tetramethylnaphthalenediamine. The aromatic amine preferably has 6 or more carbon atoms, more preferably 7 or more carbon atoms, and even more preferably 8 or more carbon atoms, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less carbon atoms.

[0079] The amine compound used in this embodiment may be substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, or a cyano group, or with a halogen atom. Although diamines have been given as specific examples, it goes without saying that the amine compounds that can be used in this embodiment are not limited to diamines, and examples thereof include aliphatic monoamines corresponding to various diamines such as trimethylamine, triethylamine, ethyldimethylamine, and the above-mentioned aliphatic diamines; piperidine compounds such as piperidine, methylpiperidine, and tetramethylpiperidine; pyridine compounds such as pyridine and picoline; morpholine compounds such as morpholine, methylmorpholine, and thiomorpholine; imidazole compounds such as imidazole and methylimidazole; and compounds corresponding to the above-mentioned alicyclic diamines. In addition to alicyclic monoamines such as monoamines corresponding to the above heterocyclic diamines; heterocyclic monoamines corresponding to the above heterocyclic diamines; and monoamines such as aromatic monoamines corresponding to the above aromatic diamines, polyamines having three or more amino groups such as diethylenetriamine, N,N',N''-trimethyldiethylenetriamine, N,N,N',N'',N''-pentamethyldiethylenetriamine, triethylenetetramine, N,N'-bis[(dimethylamino)ethyl]-N,N'-dimethylethylenediamine, hexamethylenetetramine, and tetraethylenepentamine can also be used.

[0080] Among the above, from the viewpoint of obtaining a predetermined average particle size and specific surface area as well as higher ionic conductivity, 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. Among the above amine compounds, the aliphatic tertiary diamine having tertiary amino groups at both ends is preferably tetramethylethylenediamine, tetraethylethylenediamine, tetramethyldiaminopropane, or tetraethyldiaminopropane, and in consideration of ease of availability, etc., tetramethylethylenediamine or tetramethyldiaminopropane is preferred.

[0081] Examples of complexing agents other than amine compounds include compounds having a group containing a hetero element such as oxygen, chlorine, or other halogen element, which have a high affinity with lithium. Compounds having a group other than an amino group that contains nitrogen as a hetero element, such as a nitro group or an amide group, also have similar effects.

[0082] Examples of the other complexing agents include alcohol solvents such as ethanol and butanol; ester solvents such as ethyl acetate and butyl acetate; aldehyde solvents such as formaldehyde, acetaldehyde and dimethylformamide; ketone solvents such as acetone and methyl ethyl ketone; ether solvents such as diethyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, dimethoxyethane, diethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether and anisole; 2-methoxyethyl acetate, 2-ethoxyethyl acetate (ethylene glycol acetate), 2-methoxy-1-methylethyl acetate (propylene glycol monomethyl ether acetate), 2-ethoxymethylethyl acetate, 2-( Examples of suitable solvents include glycol ester solvents such as (2-ethoxyethoxy)ethyl acetate, (2-acetoxyethoxy)methyl acetate, 1-methyl-2-ethoxyethyl acetate (propylene glycol monoethyl ether acetate), ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, and 2-methoxyethyl 3-(2-methoxyethoxy)propionate; halogen-containing aromatic hydrocarbon solvents such as trifluoromethylbenzene, nitrobenzene, chlorobenzene, chlorotoluene, and bromobenzene; nitrile solvents such as acetonitrile, methoxyacetonitrile, propionitrile, methoxypropionitrile, isobutyronitrile, and benzonitrile; and solvents containing carbon atoms and heteroatoms such as dimethyl sulfoxide and carbon disulfide. Among these, ether solvents are preferred, with diethyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, dimethoxyethane, and diethoxyethane being more preferred, diethyl ether, diisopropyl ether, dibutyl ether, and diethoxyethane being even more preferred, and diethoxyethane being even more preferred.

[0083] (mixture) As shown in the flow diagram of Fig. 1, the raw material inclusions and the complexing agent are mixed. In this embodiment, the raw material inclusions and the complexing agent may be mixed in either a solid or liquid form, but since the raw material inclusions usually contain a solid and the complexing agent is liquid, they are usually mixed in a form in which the solid raw material inclusions exists in the liquid complexing agent.

[0084] The amount of the raw material ingredients is preferably 5 g or more, more preferably 10 g or more, even more preferably 30 g or more, and even more preferably 50 g or more per liter of complexing agent, and the upper limit is preferably 500 g or less, more preferably 400 g or less, even more preferably 300 g or less, and even more preferably 250 g or less. When the amount of the raw material ingredients is within the above range, the raw material ingredients are easily mixed, the dispersion state of the raw materials is improved, and the reaction between the raw materials is promoted, making it easier to efficiently obtain an electrolyte precursor and further a solid electrolyte.

[0085] There is no particular limitation on the method of mixing the raw material inclusions and the complexing agent, and the raw material and the complexing agent contained in the raw material inclusions may be mixed in a device capable of mixing the raw material inclusions and the complexing agent. For example, it is preferable to supply the complexing agent into a tank, operate the stirring blade, and then gradually add the raw material, since this will result in a good mixing state of the raw material inclusions and improve the dispersibility of the raw material. Furthermore, when a halogen element is used as a raw material, the raw material may not be solid. Specifically, fluorine and chlorine are gaseous, and bromine is liquid, at room temperature and normal pressure. For example, if the raw material is liquid, it may be supplied into a tank together with a complexing agent separately from other solid raw materials. If the raw material is gaseous, it may be supplied by blowing it into a mixture of a complexing agent and a solid raw material.

[0086] This embodiment is characterized by including mixing the raw material inclusions with a complexing agent, and can be produced by a method that does not use equipment commonly referred to as a "pulverizer," such as a media-type pulverizer such as a ball mill or a bead mill, which is used for pulverizing solid raw materials. In this production method, the raw material inclusions and the complexing agent are mixed together to form an electrolyte precursor by simply mixing them. Furthermore, the mixture of the raw material inclusions and the complexing agent may be pulverized using a pulverizer, since this can shorten the mixing time required to obtain the electrolyte precursor and can achieve finer powder.

[0087] An example of a device for mixing the raw material ingredients and the complexing agent is a mechanical agitation mixer equipped with an agitator blade in a tank. Examples of mechanical agitation mixers include high-speed agitation mixers and double-arm mixers. High-speed agitation mixers are preferred in terms of improving the uniformity of the raw materials in the mixture of the raw material ingredients and the complexing agent, and achieving a predetermined average particle size, specific surface area, and higher ionic conductivity. Examples of high-speed agitation mixers include vertical-axis rotary mixers and horizontal-axis rotary mixers. Either type of mixer may be used.

[0088] Examples of the shape of the stirring blade used in the mechanical stirring mixer include blade type, arm type, anchor type, paddle type, full zone type, ribbon type, multi-stage blade type, double arm type, shovel type, double-shaft blade type, flat blade type, C-type blade type, etc., and from the viewpoint of increasing the uniformity of the raw material in the raw material content and obtaining a predetermined average particle size and specific surface area as well as higher ionic conductivity, the anchor type, paddle type, full zone type, shovel type, flat blade type, C-type blade type, etc. are preferred.

[0089] The temperature conditions when mixing the raw material ingredients and the complexing agent are not particularly limited and are, for example, −30 to 100° C., preferably −10 to 50° C., and more preferably about room temperature (23° C.) (for example, about room temperature ±5° C.). The mixing time is about 0.1 to 150 hours, and from the viewpoint of more uniform mixing and obtaining a predetermined average particle size, specific surface area, and higher ionic conductivity, it is preferably 1 to 120 hours, more preferably 4 to 100 hours, and even more preferably 8 to 80 hours.

[0090] By mixing the raw material ingredients with a complexing agent, the lithium, sulfur, and phosphorus elements, preferably a halogen element, contained in the raw materials are bonded directly to one another with or without the aid of a complexing agent through the action of the complexing agent. In other words, in this manufacturing method, the electrolyte precursor obtained by mixing the raw material ingredients with a complexing agent is composed of a complexing agent, lithium, sulfur, and phosphorus elements, preferably a halogen element. By mixing the raw material ingredients with a complexing agent, a substance containing an electrolyte precursor (hereinafter, sometimes referred to as an "electrolyte precursor-containing substance") is obtained. In this embodiment, the obtained electrolyte precursor is not completely dissolved in the liquid complexing agent, and typically a suspension containing a solid electrolyte precursor is obtained. Therefore, this manufacturing method corresponds to a heterogeneous system in a so-called liquid-phase method.

[0091] (to crush) The present production method preferably includes pulverizing the electrolyte precursor. By pulverizing the electrolyte precursor, a solid electrolyte with a small particle size can be obtained, and a decrease in ionic conductivity can be suppressed. Furthermore, by combining this with the mechanical treatment described below, a crystalline sulfide solid electrolyte having a desired average particle size and specific surface area can be more easily obtained. This makes it possible to easily produce a crystalline sulfide solid electrolyte suitable for the positive electrode layer, negative electrode layer, and electrolyte layer of an all-solid-state lithium battery, resulting in higher battery performance. Unlike mechanical milling using the so-called solid-phase method, the grinding of the electrolyte precursor does not involve mechanical stress to obtain an amorphous or crystalline solid electrolyte. As described above, the electrolyte precursor contains a complexing agent, and a lithium-containing structure such as a PS4 structure and a lithium-containing raw material such as a lithium halide are bonded (coordinated) via the complexing agent. It is believed that grinding the electrolyte precursor produces fine particles of the electrolyte precursor while maintaining the above-mentioned bonding (coordinated) and dispersion. By heating this electrolyte precursor, as described below, the complexing agent is removed and the components that were bonded (coordinated) via the complexing agent simultaneously bond, facilitating the reaction to form a crystalline sulfide solid electrolyte. Therefore, the large particle growth due to particle aggregation seen in the synthesis of conventional solid electrolytes is unlikely to occur, allowing for easy fine particle grinding and achieving higher battery performance.

[0092] The pulverizer used to pulverize the electrolyte precursor is not particularly limited as long as it can pulverize particles, and for example, a media-type pulverizer using a pulverizing medium can be used. Among media-type pulverizers, a wet pulverizer that can handle wet pulverization is preferred, considering that the electrolyte precursor is in a liquid state, mainly containing liquids such as a complexing agent and a solvent, or in a slurry state. Representative examples of wet mills include wet bead mills, wet ball mills, and wet vibration mills, with wet bead mills using beads as milling media being preferred because they allow for flexible adjustment of milling conditions and are suitable for smaller particle sizes. Alternatively, dry mills such as dry media mills (e.g., dry bead mills, dry ball mills, and dry vibration mills) and dry non-media mills (e.g., jet mills) can also be used.

[0093] The electrolyte precursor to be pulverized in the pulverizer is usually supplied as an electrolyte precursor-containing material obtained by mixing a raw material containing material and a complexing agent, and is supplied mainly in a liquid state or a slurry state. That is, the object to be pulverized in the pulverizer is mainly an electrolyte precursor-containing liquid or an electrolyte precursor-containing slurry. Therefore, the pulverizer used in this embodiment is preferably a flow-through pulverizer capable of circulating the electrolyte precursor-containing liquid or the electrolyte precursor-containing slurry as needed. More specifically, it is preferable to use a pulverizer in a form that circulates the slurry between a pulverizer (pulverizer mixer) that pulverizes the slurry and a temperature holding tank (reaction vessel), as described in JP 2010-140893 A.

[0094] The size of the beads used in the above-mentioned grinder may be selected appropriately depending on the desired particle size, processing amount, etc. For example, the diameter of the beads may be approximately 0.05 mmφ or more and 5.0 mmφ or less, preferably 0.1 mmφ or more and 3.0 mmφ or less, and more preferably 0.3 mmφ or more and 1.5 mmφ or less.

[0095] As the pulverizer used for pulverizing the electrolyte precursor, a machine capable of pulverizing an object using ultrasonic waves, such as a machine called an ultrasonic pulverizer, ultrasonic homogenizer, or probe ultrasonic pulverizer, can be used. In this case, various conditions such as the frequency of the ultrasonic waves may be appropriately selected depending on the average particle size of the desired electrolyte precursor, and the frequency may be, for example, about 1 kHz or more and 100 kHz or less, and from the viewpoint of more efficiently pulverizing the electrolyte precursor, the frequency is preferably 3 kHz or more and 50 kHz or less, more preferably 5 kHz or more and 40 kHz or less, and even more preferably 10 kHz or more and 30 kHz or less. The output of the ultrasonic crusher is usually about 500 to 16,000W, preferably 600 to 10,000W, more preferably 750 to 5,000W, and even more preferably 900 to 1,500W.

[0096] The average particle size of the electrolyte precursor obtained by grinding (D 50) is determined appropriately as desired, but is usually 0.01 μm or more and 50 μm or less, preferably 0.03 μm or more and 5 μm or less, and more preferably 0.05 μm or more and 3 μm or less. By setting the average particle size in this range, it is possible to meet the demand for a solid electrolyte having a small average particle size of 1 μm or less. Furthermore, higher battery performance can be obtained.

[0097] The grinding time is not particularly limited as long as it is a time that allows the electrolyte precursor to have a desired average particle size, and is usually from 0.1 hours to 100 hours. From the viewpoint of efficiently achieving a desired particle size, the grinding time is preferably from 0.3 hours to 72 hours, more preferably from 0.5 hours to 48 hours, and even more preferably from 1 hour to 24 hours.

[0098] The pulverization may be carried out after drying the electrolyte precursor-containing material such as the electrolyte precursor-containing liquid or the electrolyte precursor-containing slurry as described below to turn the electrolyte precursor into powder. In this case, it is preferable to use any of the dry grinders among the grinders exemplified above as grinders that can be used for grinding. Other matters related to grinding, such as grinding conditions, are the same as those for grinding an electrolyte precursor-containing liquid or an electrolyte precursor-containing slurry, and the average particle size of the electrolyte precursor obtained by grinding is also the same as those described above.

[0099] (Dry) The present manufacturing method may include drying the electrolyte precursor-containing material (usually a suspension), thereby obtaining a powder of the electrolyte precursor. By drying the material in advance, heating can be performed efficiently. The drying and subsequent heating may be performed in the same step.

[0100] Drying can be performed at a temperature appropriate for the type of remaining complexing agent (complexing agent not incorporated into the electrolyte precursor). For example, drying can be performed at a temperature equal to or higher than the boiling point of the complexing agent. Furthermore, drying can be performed by drying under reduced pressure (vacuum drying) using a vacuum pump or the like at a temperature typically between 5 and 100°C, preferably between 10 and 85°C, more preferably between 15 and 70°C, and even more preferably around room temperature (23°C) (for example, about room temperature ±5°C) to volatilize the complexing agent.

[0101] The drying may be performed by filtering the electrolyte precursor-containing material using a glass filter or the like, by solid-liquid separation by decantation, or by solid-liquid separation using a centrifuge, etc. In this embodiment, after the solid-liquid separation, the material may be dried under the above-mentioned temperature conditions. Specifically, solid-liquid separation can be easily performed by decantation, in which a substance containing an electrolyte precursor is transferred to a container, and after the electrolyte precursor has precipitated, the complexing agent and solvent that form the supernatant are removed, or by filtration using, for example, a glass filter with a pore size of about 10 to 200 μm, preferably 20 to 150 μm.

[0102] The electrolyte precursor is composed of a complexing agent, lithium, sulfur, and phosphorus, preferably further composed of a halogen. The X-ray diffraction pattern exhibits peaks distinct from those derived from the raw materials. The electrolyte precursor preferably contains a co-crystal composed of a complexing agent, lithium, sulfur, phosphorus, and a halogen. Simply mixing the raw material components results in peaks distinct from those derived from the raw materials. However, mixing the raw material components with a complexing agent results in peaks distinct from those derived from the raw materials. This indicates that the electrolyte precursor (co-crystal) has a structure distinct from that of the raw materials themselves. This is specifically confirmed in the Examples. Examples of X-ray diffraction patterns for the electrolyte precursor (co-crystal) and each raw material, such as lithium sulfide, are shown in Figures 3 and 4, respectively. The X-ray diffraction pattern indicates that the electrolyte precursor (co-crystal) has a specific crystal structure. Furthermore, the diffraction pattern does not include the diffraction patterns of any of the raw materials, such as lithium sulfide, shown in Figure 4, indicating that the electrolyte precursor (co-crystal) has a crystal structure distinct from that of the raw materials.

[0103] Furthermore, the electrolyte precursor (co-crystal) is characterized by having a structure different from that of the crystalline sulfide solid electrolyte. This is also specifically confirmed in the Examples. Figure 3 also shows the X-ray diffraction pattern of the crystalline solid electrolyte, which is different from the diffraction pattern of the electrolyte precursor (co-crystal). Note that the electrolyte precursor (co-crystal) has a specific crystalline structure and is different from the amorphous solid electrolyte having a broad pattern shown in Figure 3.

[0104] The cocrystal is composed of a complexing agent, lithium, sulfur, and phosphorus, and preferably further a halogen, and is typically presumed to form a complex structure in which lithium and other elements are directly bonded with and / or without the intervention of a complexing agent. Here, whether the complexing agent forms a co-crystal can be confirmed by, for example, gas chromatography analysis. Specifically, the powder of the electrolyte precursor is dissolved in methanol, and the resulting methanol solution is analyzed by gas chromatography, whereby the amount of the complexing agent contained in the co-crystal can be quantified. The content of the complexing agent in the electrolyte precursor varies depending on the molecular weight of the complexing agent, but is usually about 10% by mass to 70% by mass, preferably 15% by mass to 65% by mass.

[0105] In this production method, forming a co-crystal containing a halogen element is preferable in terms of achieving a predetermined average particle size, specific surface area, and improving ionic conductivity. By using a complexing agent, a lithium-containing structure such as a PS4 structure and a lithium-containing raw material such as a lithium halide are bonded (coordinated) via the complexing agent, making it easier to obtain a co-crystal in which the halogen element is more dispersed and fixed, thereby improving the predetermined average particle size, specific surface area, and ionic conductivity.

[0106] When using a raw material containing a halogen element, whether the halogen element in the electrolyte precursor forms a co-crystal can be confirmed by checking whether a predetermined amount of halogen element is contained in the electrolyte precursor even after solid-liquid separation of the electrolyte precursor-containing material. This is because halogen elements that do not form a co-crystal are more easily dissolved than halogen elements that form a co-crystal and are discharged into the liquid during solid-liquid separation. Furthermore, this can also be confirmed by checking whether the proportion of halogen element in the electrolyte precursor or sulfide solid electrolyte is not significantly reduced compared to the proportion of halogen element supplied by the raw material through composition analysis using ICP analysis (inductively coupled plasma atomic emission spectroscopy) of the electrolyte precursor or solid electrolyte. When using a raw material containing a halogen element, the amount of the halogen element remaining in the electrolyte precursor is preferably 30 mass % or more, more preferably 35 mass % or more, and even more preferably 40 mass % or more, based on the charged composition. The upper limit of the amount of the halogen element remaining in the electrolyte precursor is 100 mass %.

[0107] (heating) The present production method preferably includes heating the electrolyte precursor. Heating the electrolyte precursor includes, for example, heating the electrolyte precursor to obtain an amorphous sulfide solid electrolyte, heating the electrolyte precursor to obtain a crystalline sulfide solid electrolyte, or heating the electrolyte precursor to obtain an amorphous sulfide solid electrolyte and then heating the amorphous sulfide solid electrolyte to obtain a crystalline sulfide solid electrolyte. By including heating the electrolyte precursor, at least the complexing agent in the electrolyte precursor is removed, resulting in an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte containing lithium, sulfur, and phosphorus, and preferably further a halogen. The electrolyte precursor heated by this heating method may also be a pulverized electrolyte precursor obtained by the above-described pulverization. In the present production method, since a crystalline sulfide solid electrolyte is preferred as the sulfide solid electrolyte used in the electrode mixture, a crystalline sulfide solid electrolyte is preferred.

[0108] The removal of the complexing agent from the electrolyte precursor is supported by the fact that it is clear from the results of X-ray diffraction patterns, gas chromatography analysis, etc. that the complexing agent forms a co-crystal of the electrolyte precursor, and also by the fact that the solid electrolyte obtained by removing the complexing agent by heating the electrolyte precursor has the same X-ray diffraction pattern as the solid electrolyte obtained by a conventional method without using a complexing agent.

[0109] In this production method, the sulfide solid electrolyte is obtained by heating the electrolyte precursor to remove the complexing agent from the electrolyte precursor. The less complexing agent in the sulfide solid electrolyte, the better, but the sulfide solid electrolyte may contain a complexing agent to the extent that it does not impair the performance of the solid electrolyte. The content of the complexing agent in the sulfide solid electrolyte is usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0110] In this production method, to obtain the sulfide solid electrolyte, an electrolyte precursor may be heated to obtain an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte, or an electrolyte precursor may be heated to obtain an amorphous sulfide solid electrolyte, and then the amorphous sulfide solid electrolyte may be heated to obtain the crystalline sulfide solid electrolyte. In other words, in this production method, either an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte can be produced. Conventionally, to obtain a sulfide solid electrolyte with high ionic conductivity, for example, a sulfide solid electrolyte having a thiolisiconregion II crystal structure described below, it was necessary to prepare an amorphous sulfide solid electrolyte by mechanical pulverization such as mechanical milling, or other melt-quenching treatments, and then heat the amorphous sulfide solid electrolyte to obtain it. However, the present production method can be said to be superior to conventional production methods using mechanical milling or the like in that a crystalline sulfide solid electrolyte having a thiolisiconregion II crystal structure can be obtained by a method that does not involve mechanical pulverization or other melt-quenching treatments.

[0111] In the present production method, whether to obtain an amorphous sulfide solid electrolyte, a crystalline sulfide solid electrolyte, or an amorphous sulfide solid electrolyte and then a crystalline sulfide solid electrolyte, or a crystalline sulfide solid electrolyte directly from an electrolyte precursor is appropriately selected as desired, and can be adjusted by the heating temperature, heating time, etc. For example, when obtaining an amorphous sulfide solid electrolyte, the heating temperature of the electrolyte precursor may be determined depending on the structure of the crystalline sulfide solid electrolyte obtained by heating the amorphous sulfide solid electrolyte (or electrolyte precursor). Specifically, the amorphous sulfide solid electrolyte (or electrolyte precursor) is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA) at a temperature increase rate of 10°C / min. The heating temperature is preferably set to 5°C or lower, more preferably 10°C or lower, and even more preferably 20°C or lower, starting from the peak-top temperature of the exothermic peak observed at the lowest temperature. The lower limit is not particularly limited, but may be approximately -40°C or higher than the peak-top temperature of the exothermic peak observed at the lowest temperature. By setting the temperature range in this way, the amorphous sulfide solid electrolyte can be obtained more efficiently and reliably. The heating temperature for obtaining an amorphous sulfide solid electrolyte cannot be generally defined because it varies depending on the structure of the crystalline sulfide solid electrolyte to be obtained. However, it is generally preferably 135°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower. There is no particular lower limit, but it is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher.

[0112] Furthermore, when a crystalline sulfide solid electrolyte is obtained by heating an amorphous sulfide solid electrolyte or directly from an electrolyte precursor, the heating temperature can be determined depending on the structure of the crystalline sulfide solid electrolyte, and is preferably higher than the heating temperature for obtaining an amorphous sulfide solid electrolyte. Specifically, the amorphous sulfide solid electrolyte (or electrolyte precursor) 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 at the lowest temperature. There is no particular upper limit, but 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. The heating temperature for obtaining a crystalline sulfide solid electrolyte cannot be generally defined because it varies depending on the structure of the crystalline sulfide solid electrolyte to be obtained. However, it is generally preferably 130°C or higher, more preferably 135°C or higher, and even more preferably 140°C or higher. There is no particular upper limit, but it is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower.

[0113] The heating time is not particularly limited as long as it is a time that allows a desired amorphous sulfide solid electrolyte or crystalline sulfide solid electrolyte to be obtained, but is, for example, preferably 1 minute or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, and even more preferably 1 hour or more. The upper limit of the heating time is not particularly limited, but is preferably 24 hours or less, more preferably 10 hours or less, even more preferably 5 hours or less, and even more preferably 3 hours or less.

[0114] Furthermore, 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). This is because deterioration (e.g., oxidation) of the crystalline sulfide solid electrolyte can be prevented. The heating method is not particularly limited, and examples thereof include methods using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, and a calcination furnace. Furthermore, 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.

[0115] (Amorphous sulfide solid electrolyte) The amorphous sulfide solid electrolyte obtained by this production method contains lithium, sulfur, and phosphorus, and preferably also a halogen. Representative examples include solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr; and sulfide solid electrolytes further containing other elements such as oxygen and silicon, such as Li2S-P2S5-Li2O-LiI and Li2S-SiS2-P2S5-LiI. From the perspective of obtaining higher ionic conductivity, sulfide solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr, are preferred. The types of elements constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0116] When the amorphous sulfide solid electrolyte obtained by this production method contains at least Li2S-P2S5, the molar ratio of Li2S to P2S5 is preferably 65-85:15-35, more preferably 70-80:20-30, and even more preferably 72-78:22-28, from the viewpoint of obtaining higher ionic conductivity. When the amorphous sulfide solid electrolyte obtained by this production method is, for example, Li2S-P2S5-LiI-LiBr, the total content of lithium sulfide and diphosphorus pentasulfide is preferably 60 to 95 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 85 mol%. The ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, more preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0117] When a raw material containing a halogen element is used in the amorphous sulfide solid electrolyte obtained by the present production method, the compounding ratio (molar ratio) of lithium, sulfur, phosphorus, and halogen elements is preferably 1.0-1.8:1.0-2.0:0.1-0.8:0.01-0.6, more preferably 1.1-1.7:1.2-1.8:0.2-0.6:0.05-0.5, and even more preferably 1.2-1.6:1.3-1.7:0.25-0.5:0.08-0.4. When bromine and iodine are used in combination as the halogen elements, the compounding ratio (molar ratio) of lithium, sulfur, phosphorus, bromine, and iodine is preferably 1.0-1.8:1.0-2.0:0.1-0.8:0.01-0.3:0.01-0.3, more preferably 1.1-1.7:1.2-1.8:0.2-0.6:0.02-0.25:0.02-0.25, more preferably 1.2-1.6:1.3-1.7:0.25-0.5:0.03-0.2:0.03-0.2, and even more preferably 1.35-1.45:1.4-1.7:0.3-0.45:0.04-0.18:0.04-0.18. By setting the compounding ratio (molar ratio) of lithium element, sulfur element, phosphorus element, and halogen element within the above range, it becomes easier to obtain a sulfide solid electrolyte having a thiolithium region II type crystal structure described later and higher ionic conductivity. The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle diameter (D 50 ) can be, for example, in the range of 0.01 μm to 500 μm, or 0.1 to 200 μm.

[0118] The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle diameter (D 50 ) can be, for example, in the range of 0.01 μm to 500 μm, or 0.1 to 200 μm.

[0119] The volume-based average particle size of the amorphous sulfide solid electrolyte obtained by this manufacturing method is 3 μm or more, which is the same as the average particle size of the sulfide solid electrolyte used in the electrode composite of this embodiment. Furthermore, the specific surface area of ​​the amorphous sulfide solid electrolyte obtained by this manufacturing method, measured by the BET method, is 20 m or more, which is the same as the specific surface area of ​​the sulfide solid electrolyte used in the electrode composite of this embodiment. 2 / g or more. In this production method, the amorphous sulfide solid electrolyte is ultimately converted into a crystalline sulfide solid electrolyte by heating, and together with the electrode active material, constitutes the electrode mixture of this embodiment.

[0120] (Crystalline sulfide solid electrolyte) The crystalline sulfide solid electrolyte obtained by the present production method may be a so-called glass ceramic obtained by heating an amorphous sulfide solid electrolyte to a crystallization temperature or higher, and its crystal structure may be Li3PS4 crystal structure, Li4P2S6 crystal structure, Li7PS6 crystal structure, Li7P3S 11 Examples of such a crystal structure include a crystal structure having peaks at 2θ=approximately 20.2° and 23.6° (for example, JP 2013-16423 A).

[0121] Also, Li 4-x Ge 1-x P x S4-type thio-LISICON Region II crystal structure (Kanno et al., Journal of the Electrochemical Society, 148(7)A742-746(2001)), Li 4-x Ge 1-x P xExamples of such a crystal structure include a crystal structure similar to the S4-based thio-LISICON Region II type (see Solid State Ionics, 177 (2006), 2721-2725). The crystal structure of the crystalline sulfide solid electrolyte obtained by this production method is preferably the thio-LISICON Region II type crystal structure among the above, since it can provide higher ionic conductivity. Here, the "thio-LISICON Region II type crystal structure" refers to a structure in which Li 4-x Ge 1-x P x S4-type thio-LISICON Region II crystal structure, Li 4-x Ge 1-x P x This indicates that the crystalline sulfide solid electrolyte obtained by this production method has either the thio-LISICON Region II type or a crystal structure similar to that of the S4-based thio-LISICON Region II type. The crystalline sulfide solid electrolyte obtained by this production method may have the thio-LISICON Region II type crystal structure or may have it as the main crystal. However, from the viewpoint of obtaining higher ionic conductivity, it is preferable that it has it as the main crystal. In this specification, "having it as the main crystal" means that the proportion of the target crystal structure in the crystal structure is 80% or more, preferably 90% or more, and more preferably 95% or more. Furthermore, from the viewpoint of obtaining higher ionic conductivity, it is preferable that the crystalline sulfide solid electrolyte obtained by this production method does not contain crystalline Li3PS4 (β-Li3PS4).

[0122] In X-ray diffraction measurements using CuKα radiation, the diffraction peaks of the Li3PS4 crystal structure appear, for example, at 2θ = 17.5°, 18.3°, 26.1°, 27.3°, and 30.0°, the diffraction peaks of the Li4P2S6 crystal structure appear, for example, at 2θ = 16.9°, 27.1°, and 32.5°, and the diffraction peaks of the Li7PS6 crystal structure appear, for example, at 2θ = 15.3°, 25.2°, 29.6°, and 31.0°, and the diffraction peaks of the Li7P3S 11Diffraction peaks of the crystal structure appear, for example, at 2θ = 17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°. 4-x Ge 1-x P x The diffraction peaks of the S4 thio-LISICON Region II crystal structure appear, for example, at 2θ = 20.1°, 23.9°, and 29.5°. 4-x Ge 1-x P x Diffraction peaks of a crystal structure similar to the S4 thio-LISICON Region II type appear, for example, at 2θ = 20.2 and 23.6°. Note that these peak positions may vary within a range of ±0.5°.

[0123] As described above, when a thiolisiconregion II crystal structure is obtained in this embodiment, it is preferable that it does not contain crystalline Li3PS4 (β-Li3PS4). Figure 3 shows an example of X-ray diffraction measurement of the crystalline sulfide solid electrolyte obtained by this production method. Figure 4 shows an example of X-ray diffraction measurement of crystalline Li3PS4 (β-Li3PS4). As can be seen from Figures 3 and 4, the sulfide solid electrolyte of this embodiment does not have diffraction peaks at 2θ = 17.5° and 26.1° seen in crystalline Li3PS4, or even if it does have them, the peaks detected are extremely small compared to the diffraction peaks of the thiolisiconregion II crystal structure.

[0124] The compound has the structural skeleton of Li7PS6 and has the composition formula Li in which part of the P is replaced with Si. 7-x P 1-y Si y S6 and Li 7+x P 1-y Si yThe crystal structure represented by S6 (where x ranges from -0.6 to 0.6 and y ranges from 0.1 to 0.6) is cubic or orthorhombic, preferably cubic. In X-ray diffraction measurement using CuKα rays, it has peaks mainly appearing at the positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. The above composition formula Li 7-x-2y PS 6-x-y Cl x (where 0.8 ≤ x ≤ 1.7 and 0 < y ≤ -0.25x + 0.5) The crystal structure represented by is preferably cubic. In X-ray diffraction measurement using CuKα rays, it has peaks mainly appearing at the positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. Also, the above composition formula Li 7-x PS 6-x Ha x (where Ha is Cl or Br, and x is preferably 0.2 to 1.8) The crystal structure represented by is preferably cubic. In X-ray diffraction measurement using CuKα rays, it has peaks mainly appearing at the positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. Note that these peak positions may shift within the range of ±0.5°.

[0125] Also, the crystalline sulfide solid electrolyte obtained by this manufacturing method preferably has a full width at half maximum of the maximum peak including the background of 2θ = 10 to 40° in X-ray diffraction measurement using CuKα rays of Δ2θ = 0.75° or less. By having such properties, higher ionic conductivity can be obtained and the battery performance is improved. From the same perspective, as the full width at half maximum of the maximum peak, more preferably Δ2θ = 0.71° or less, and even more preferably Δ2θ = 0.66° or less. Having such a full width at half maximum indicates good crystallinity. As a result, when mixed with the active material, it is easily crushed into primary particles by the collision with the active material. Since it can be crushed with a small amount of energy, the decrease in ionic conductivity due to vitrification is less likely to occur. A typical example of a crystalline sulfide solid electrolyte having such properties is one having a thiolicon region II type crystal structure.

[0126] For example, Figure 5 shows an example of X-ray diffraction measurement of a crystalline sulfide solid electrolyte having a thiolicon region II crystal structure, which shows that the maximum peak, including the background of 2θ = 10 to 40°, is at 20.1°, and the half-width of this peak is a sharp Δ2θ = 0.59°. As such, the maximum peak has a sharp half-width of 0.75° or less, and the crystalline sulfide solid electrolyte exhibits extremely high ionic conductivity, enabling improved battery performance.

[0127] The shape of the crystalline sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle diameter (D 50 ) can be, for example, in the range of 0.01 μm to 500 μm, or 0.1 to 200 μm.

[0128] The volume-based average particle size of the crystalline sulfide solid electrolyte obtained by this production method is 3 μm or more, which is the same as the average particle size of the sulfide solid electrolyte used in the electrode mixture of this embodiment described later, and the specific surface area measured by the BET method is 20 m or more, which is the same as the specific surface area of ​​the sulfide solid electrolyte of this embodiment described above. 2 / g or more.

[0129] (Embodiment B) Next, embodiment B will be described. In embodiment B, the present production method is characterized by including mixing a raw material containing lithium, sulfur, and phosphorus, preferably further including a halogen, with a complexing agent, and the raw materials include a solid electrolyte such as Li3PS4, etc. In embodiment A, the lithium-containing structure such as Li3PS4, which is present as the main structure in the sulfide solid electrolyte obtained by the present production method, is synthesized by reaction between raw materials such as lithium sulfide to form an electrolyte precursor, and therefore the constituent ratio of the structure is likely to be small. Therefore, in embodiment B, a solid electrolyte containing the above structure is first prepared by manufacturing or the like and used as a raw material. This allows the structure to be bonded (coordinated) with a lithium-containing raw material such as lithium halide via a complexing agent, making it easier to obtain an electrolyte precursor in which the halogen element is dispersed and fixed. As a result, a sulfide solid electrolyte having a predetermined average particle size and specific surface area, high ionic conductivity, and suppressed generation of hydrogen sulfide is obtained.

[0130] Examples of raw materials containing lithium, sulfur, and phosphorus that can be used in embodiment B include amorphous solid electrolytes having a PS4 molecular structure or crystalline solid electrolytes, and from the viewpoint of suppressing hydrogen sulfide generation, amorphous solid electrolytes or crystalline solid electrolytes that do not contain a PS7 structure are preferred. These solid electrolytes can be produced by conventional production methods such as mechanical milling, slurry, and melt quenching, or commercially available products can also be used. In this case, the solid electrolyte containing lithium, sulfur, and phosphorus is preferably an amorphous solid electrolyte, which improves the dispersibility of the halogen element in the electrolyte precursor, making it easier for the halogen element to bond with the lithium, sulfur, and phosphorus in the solid electrolyte, thereby enabling a solid electrolyte having a predetermined average particle size and specific surface area as well as higher ionic conductivity to be obtained.

[0131] In embodiment B, the content of the amorphous sulfide solid electrolyte having a PS4 structure, etc., relative to the total amount of raw materials is preferably 60 to 100 mol %, more preferably 65 to 90 mol %, and even more preferably 70 to 80 mol %.

[0132] When an amorphous sulfide solid electrolyte having a PS4 structure or the like and a halogen element are used, the content of the halogen element relative to the amorphous sulfide solid electrolyte having a PS4 structure or the like is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%.

[0133] Other than that, the case where a halogen element and a lithium halide are used, and the case where two kinds of halogen elements are used are the same as those in embodiment A.

[0134] In embodiment B, other than the above raw materials, for example, the complexing agent, mixing, heating, drying, amorphous sulfide solid electrolyte, and crystalline sulfide solid electrolyte are the same as those described in embodiment A above. In addition, in embodiment B, it is preferable to pulverize the electrolyte precursor, the pulverizer used for pulverization, the fact that pulverization can be performed after mixing or after drying, and the conditions for pulverization are the same as those in embodiment A.

[0135] (Embodiments C and D) As shown in the flow diagram of FIG. 2, embodiments C and D differ from embodiments A and B above in that a solvent is added to the raw material ingredients and complexing agent. Embodiments C and D are heterogeneous solid-liquid processes, and in embodiments A and B, a solid electrolyte precursor is formed in a liquid complexing agent. If the electrolyte precursor is easily soluble in the complexing agent, component separation may occur. In embodiments C and D, a solvent in which the electrolyte precursor is insoluble is used, thereby preventing component elution from the electrolyte precursor.

[0136] (solvent) In the manufacturing methods of embodiments C and D, it is preferable to add a solvent to the raw material content and the complexing agent. By mixing the raw material content and the complexing agent using a solvent, the effect of using the complexing agent is promoted, that is, the formation of an electrolyte precursor that reacts with lithium, sulfur, and phosphorus, preferably also with a halogen element, and the lithium-containing structure such as the PS4 structure or an aggregate via the complexing agent, and the lithium-containing raw material such as lithium halide or an aggregate via the complexing agent are easily uniformly present, and an electrolyte precursor in which the halogen element is more dispersed and fixed is obtained. As a result, the effect of obtaining a predetermined average particle size and specific surface area as well as high ionic conductivity is easily achieved.

[0137] This production method is a so-called heterogeneous method, and it is preferable that the electrolyte precursor does not completely dissolve in the liquid complexing agent but precipitates. In embodiments C and D, the solubility of the electrolyte precursor can be adjusted by adding a solvent. In particular, halogen elements are easily eluted from the electrolyte precursor, so adding a solvent suppresses the elution of halogen elements to obtain the desired electrolyte precursor. As a result, through the electrolyte precursor in which components such as halogens are dispersed, a crystalline solid electrolyte having a predetermined average particle size and specific surface area, high ionic conductivity, and suppressed hydrogen sulfide generation, i.e., the sulfide solid electrolyte of the present embodiment described above, can be obtained.

[0138] A preferred example of a solvent having such properties is a solvent having a solubility parameter of 10 or less. In this specification, the solubility parameter is a value δ ((cal / cm)) calculated by the following formula (1), which is described in various documents, such as "Chemical Handbook" (published in 2004, 5th revised edition, Maruzen Co., Ltd.). 3 ) 1 / 2 ) and is also called the Hildebrand parameter or SP value.

[0139]

number

[0140] By using a solvent with a solubility parameter of 10 or less, the solvent is less likely to dissolve halogen elements, halogen-containing raw materials such as lithium halide, and even halogen-containing components constituting the co-crystal contained in the electrolyte precursor (e.g., an aggregate formed by bonding lithium halide and a complexing agent), compared to the complexing agent. This facilitates the fixation of halogen elements within the electrolyte precursor, resulting in a well-dispersed halogen element within the resulting electrolyte precursor and solid electrolyte, making it easier to obtain a sulfide solid electrolyte having a desired average particle size, specific surface area, and high ionic conductivity. In other words, the solvent used in this embodiment preferably does not dissolve the electrolyte precursor. From the same perspective, the solubility parameter of the solvent is preferably 9.5 or less, more preferably 9.0 or less, and even more preferably 8.5 or less.

[0141] More specifically, the solvent used in the production methods of embodiments C and D can be a wide variety of solvents that have conventionally been used in the production of sulfide solid electrolytes. Examples of such solvents include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents; and solvents containing carbon atoms such as alcohol-based solvents, ester-based solvents, aldehyde-based solvents, ketone-based solvents, ether-based solvents, nitrile-based solvents, and solvents containing carbon atoms and heteroatoms. Of these, solvents may be appropriately selected, preferably those having a solubility parameter within the above-mentioned range.

[0142] More specifically, aliphatic hydrocarbon solvents such as hexane (7.3), pentane (7.0), 2-ethylhexane, heptane (7.4), octane (7.5), decane, undecane, dodecane, and tridecane; alicyclic hydrocarbon solvents such as cyclohexane (8.2) and methylcyclohexane; aromatic hydrocarbon solvents such as benzene, toluene (8.8), xylene (8.8), mesitylene, ethylbenzene (8.8), tert-butylbenzene, trifluoromethylbenzene, nitrobenzene, chlorobenzene (9.5), chlorotoluene (8.8), and bromobenzene; alcohol-based solvents such as ethanol (12.7) and butanol (11.4); and ester-based solvents such as ethyl acetate (9.1) and butyl acetate (8.5). Examples of solvents include aldehyde solvents such as formaldehyde, acetaldehyde (10.3), and dimethylformamide (12.1); ketone solvents such as acetone (9.9) and methyl ethyl ketone; ether solvents such as diethyl ether (7.4), diisopropyl ether (6.9), dibutyl ether, tetrahydrofuran (9.1), dimethoxyethane (7.3), cyclopentyl methyl ether (8.4), tert-butyl methyl ether, and anisole; nitrile solvents such as acetonitrile (11.9), methoxyacetonitrile, propionitrile, methoxypropionitrile, isobutyronitrile, and benzonitrile; and solvents containing carbon atoms and heteroatoms such as dimethyl sulfoxide and carbon disulfide. Note that the numbers in parentheses in the above examples are SP values.

[0143] Among these solvents, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and ether-based solvents are preferred. From the viewpoint of obtaining a predetermined average particle size and specific surface area as well as more stable high ionic conductivity, heptane, cyclohexane, toluene, ethylbenzene, diethyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole are more preferred, diethyl ether, diisopropyl ether, and dibutyl ether are even more preferred, and dibutyl ether is particularly preferred. The solvent used in this embodiment is preferably an organic solvent exemplified above, and is an organic solvent different from the complexing agent. In this embodiment, these solvents may be used alone or in combination.

[0144] When a solvent is used, the content of the raw material in the raw material-containing mixture may be determined based on 1 L of the total amount of the complexing agent and the solvent.

[0145] In embodiments C and D, the electrolyte precursor-containing material can be dried at a temperature appropriate for the type of remaining complexing agent (complexing agent not incorporated into the electrolyte precursor) and solvent. For example, drying can be performed at a temperature equal to or higher than the boiling point of the complexing agent or solvent. Furthermore, drying can be performed under reduced pressure (vacuum drying) using a vacuum pump or the like at temperatures typically between 5 and 100°C, preferably between 10 and 85°C, more preferably between 15 and 70°C, and even more preferably around room temperature (23°C) (e.g., about room temperature ±5°C) to volatilize the complexing agent and solvent. Furthermore, heating in embodiments C and D also removes any remaining solvent in the electrolyte precursor. However, unlike the complexing agent that constitutes the electrolyte precursor, the solvent is less likely to form the electrolyte precursor. Therefore, the amount of solvent that may remain in the electrolyte precursor is typically 3% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less.

[0146] In embodiment C, apart from the points related to the solvent, for example, the complexing agent, mixing, heating, drying, amorphous sulfide solid electrolyte, crystalline sulfide solid electrolyte, etc. are the same as those described in embodiment A. Also, in embodiment D, apart from the points related to the solvent, they are the same as embodiment B. In addition, in embodiments C and D, it is preferable to pulverize the electrolyte precursor, the pulverizer used for pulverization, the fact that pulverization can be performed after mixing or after drying, and the conditions for pulverization are the same as those in embodiment A above.

[0147] (mechanical treatment) In the method for producing an electrode mixture of this embodiment, the crystalline sulfide solid electrolyte (hereinafter also referred to as "precursor for mechanical treatment") obtained in the above-described embodiments A to D may be further mechanically treated before use. The amorphous sulfide solid electrolyte and crystalline sulfide solid electrolyte, preferably the crystalline sulfide solid electrolyte, obtained in embodiments A to D are likely to have an electronic conductivity parameter X in the range of 0.30≦X≦2.10. The excellent contact between the solid electrolyte and the electrode active material results in excellent electrical conductivity, making it easier to obtain an electrode composite that can exhibit high battery performance. From a similar perspective, it is preferable to mechanically treat a mechanical treatment precursor that is an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte. A crystalline sulfide solid electrolyte having a desired average particle size and specific surface area, preferably the above-mentioned average particle size and specific surface area, can be easily obtained, improving the contact between the electrode active material and the sulfide solid electrolyte. Furthermore, it is possible to easily produce a crystalline sulfide solid electrolyte suitable for the positive electrode layer, negative electrode layer, and electrolyte layer of an all-solid-state lithium battery, resulting in an electrode composite that can exhibit high battery performance.

[0148] The method for mechanically treating the precursor for mechanical treatment is not particularly limited, but examples include methods using equipment such as a grinder or a stirrer. Examples of the agitator include a mechanical agitation mixer equipped with a stirring blade in a tank, which is exemplified as an apparatus that can be used in the above-mentioned method for producing a precursor for mechanical treatment. Examples of mechanical agitation mixers include high-speed agitation mixers and double-arm mixers, and any type can be used. However, from the viewpoint of more easily adjusting the desired average particle size, specific surface area, etc., high-speed agitation mixers are preferred. More specifically, as already mentioned, high-speed agitation mixers include vertical-axis rotary mixers, horizontal-axis rotary mixers, etc., as well as various other devices such as high-speed swirling thin-film agitators and high-speed shear agitators. Among these, from the viewpoint of more easily adjusting the desired average particle size, specific surface area, etc., high-speed swirling thin-film agitators (also referred to as thin-film swirling high-speed mixers, etc.) are preferred.

[0149] The pulverizer that can be used in this manufacturing method is a pulverizer having a volume-based average particle size of at least 3 μm as measured by a laser diffraction particle size distribution measurement method and a specific surface area of ​​at least 20 m as measured by the BET method. 2 The example includes a pulverizer having a rotor capable of stirring the sulfide solid electrolyte having a molecular weight of 1 / g or more, that is, the precursor for mechanical treatment. In this production method, the crushing (atomization) and granulation (particle growth) of the mechanical treatment precursor can be adjusted by adjusting the peripheral speed of the rotor of the pulverizer. That is, the average particle size can be reduced by crushing, and the average particle size can be increased by granulation. This allows the average particle size, specific surface area, and other properties of the sulfide solid electrolyte to be easily and freely adjusted. More specifically, crushing can be achieved by rotating the rotor at a low peripheral speed, and granulation can be achieved by rotating the rotor at a high peripheral speed. In this way, the average particle size, specific surface area, and other properties of the sulfide solid electrolyte can be easily adjusted simply by adjusting the peripheral speed of the rotor.

[0150] In this embodiment, when a precursor for mechanical treatment, which is an amorphous sulfide solid electrolyte and a crystalline sulfide solid electrolyte, preferably a crystalline sulfide solid electrolyte, obtained by the method of any one of the above-described embodiments A to D, is mechanically treated, from the viewpoint of obtaining higher battery performance, it is preferable to crush the precursor for mechanical treatment by mechanical treatment and use a finer crystalline sulfide solid electrolyte for the electrode mixture.

[0151] Regarding the peripheral speed of the rotating body, low and high peripheral speeds cannot be generally defined because they can vary depending on, for example, the particle size, material, and amount of the media used in the mill. For example, in the case of a device that does not use ball or bead milling media, such as a high-speed rotating thin-film mixer, even at relatively high peripheral speeds, mainly crushing occurs and granulation is difficult to occur. On the other hand, in the case of a device that uses milling media, such as a ball mill or bead mill, crushing can be performed at low peripheral speeds and granulation can be performed at high peripheral speeds, as described above. Therefore, if the specified conditions of the milling device, milling media, etc. are the same, the peripheral speed at which crushing is possible is lower than the peripheral speed at which granulation is possible. Therefore, for example, in the conditions under which granulation is possible at a peripheral speed of 6 m / s, a low peripheral speed means less than 6 m / s, and a high peripheral speed means 6 m / s or higher.

[0152] A more specific example of a grinder is a media-type grinder, which is broadly classified into a container-driven grinder and a media-agitation grinder. Examples of the container-driven grinding machine include a stirring tank, a grinding tank, or a combination of these, such as a ball mill or a bead mill. As the ball mill or bead mill, any of various types such as a rotary type, a rolling type, a vibrating type, or a planetary type can be used. Examples of media agitation type crushers include impact crushers such as cutter mills, hammer mills, and pin mills; tower-type crushers such as tower mills; agitation tank-type crushers such as tumbling mills, attritors, aquamizers, and sand grinders; flow tank-type crushers such as Viscomill and Pearl Mills; flow pipe-type crushers; annular-type crushers such as Coball Mills; and continuous dynamic crushers.

[0153] In this production method, from the viewpoint of more easily adjusting the desired average particle size, specific surface area, etc., a container-driven pulverizer is preferred, and a bead mill or a ball mill is particularly preferred. Container-driven pulverizers such as a bead mill or a ball mill are equipped with a container, such as a stirring tank or a pulverizing tank, that stores the mechanical treatment precursor as a rotating body capable of stirring the mechanical treatment precursor. Therefore, as described above, the average particle size, specific surface area, etc. of the sulfide solid electrolyte can be easily adjusted by adjusting the peripheral speed of the rotating body. Bead mills and ball mills can adjust the average particle size and specific surface area by adjusting the particle size, material, amount used, etc. of the beads and balls used, making it possible to adjust the morphology more finely and also to adjust the average particle size and specific surface area in a way that was not possible before. For example, a centrifugal type bead mill that can use so-called microbeads with extremely fine particles (φ0.015 to 1 mm or so) (e.g., Ultra Apex Mill (UAM)) can also be used.

[0154] Regarding the adjustment of the average particle size and specific surface area, the smaller the energy applied to the precursor for mechanical treatment, i.e., the lower the peripheral speed of the rotor, or the smaller the particle size of the beads, balls, etc., the smaller the average particle size (crushing) and the larger the specific surface area tends to be; on the other hand, the larger the energy, i.e., the higher the peripheral speed of the rotor, or the larger the particle size of the beads, balls, etc., the larger the average particle size (granulation) and the smaller the specific surface area tends to be. Furthermore, for example, the longer the time of mechanical treatment, the larger the average particle size tends to be (granulation). In this embodiment, as described above, it is preferable to produce a mechanically treated product (crushed product) crushed by mechanical treatment and mix it with an electrode active material. Therefore, it is preferable to reduce the energy imparted to the mechanical treatment precursor, that is, to reduce the peripheral speed of the rotor or reduce the particle size of the beads, balls, etc., and it is also preferable to shorten the time of mechanical treatment.

[0155] The particle size of the media used in a bead mill, ball mill, etc. may be determined appropriately taking into consideration the desired morphology as well as the type and scale of the equipment used, but is usually preferably 0.01 mm or more, more preferably 0.015 mm or more, even more preferably 0.02 mm or more, and still more preferably 0.04 mm or more, with the upper limit being preferably 3 mm or less, more preferably 2 mm or less, even more preferably 1 mm or less, and still more preferably 0.8 mm or less. Examples of the material of the medium include metals such as stainless steel, chrome steel, and tungsten carbide; ceramics such as zirconia and silicon nitride; and minerals such as agate.

[0156] The processing time for the mechanical treatment may be appropriately determined taking into consideration the desired average particle size, specific surface area, and the type and scale of the equipment used, but is usually preferably 5 seconds or more, more preferably 30 seconds or more, even more preferably 3 minutes or more, and even more preferably 15 minutes or more, with the upper limit being preferably 5 hours or less, more preferably 3 hours or less, even more preferably 2 hours or less, and even more preferably 1.5 hours or less. The peripheral speed of the rotating body in the mechanical treatment (the rotational speed in an apparatus such as a bead mill or ball mill) may be appropriately determined taking into consideration the desired average particle size, specific surface area, and the type and scale of the apparatus used, but is usually preferably 0.5 m / s or more, more preferably 1 m / s or more, even more preferably 2 m / s or more, and still more preferably 3 m / s or more, with the upper limit being preferably 55 m / s or less, more preferably 40 m / s or less, even more preferably 25 m / s, and still more preferably 15 m / s or less. The peripheral speed may be the same or may be changed during the treatment.

[0157] Mechanical treatment can be performed with a solvent. The solvent can be appropriately selected from those exemplified as solvents that can be used in the above-mentioned embodiments C and D of the method for producing a precursor for mechanical treatment. From the viewpoint of obtaining a predetermined average particle size and specific surface area as well as more stable high ionic conductivity, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and ether-based solvents are preferred. Heptane, cyclohexane, toluene, ethylbenzene, diethyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole are more preferred, heptane, toluene, and ethylbenzene are even more preferred, and heptane and toluene are even more preferred. In this embodiment, atomization can be easily achieved by crushing without using a dispersant. However, a dispersant may be used to further enhance dispersion and more efficiently atomize the particles. Of the above-mentioned solvents, for example, ether-based solvents can function as a dispersant. The amount of solvent used may be such that the content of the mechanical treatment precursor relative to the total amount of the mechanical treatment precursor and the solvent is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, with the upper limit being preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less.

[0158] (Mixing sulfide solid electrolyte and electrode active material) In this production method, when mixing a sulfide solid electrolyte, preferably a crystalline sulfide solid electrolyte, with an electrode active material, the mixing method is preferably a method using an apparatus such as a grinder or a stirrer, as described above as the method for mechanically treating the precursor for mechanical treatment. These apparatuses may be used alone or in combination as necessary, and from the viewpoint of efficiently obtaining an electrode mixture, they are preferably used alone, and mixing is preferably performed using an apparatus such as a grinder or a stirrer. As for the equipment such as a grinder or a stirrer, those explained as equipment that can be used in the mechanical treatment above can be preferably used, and among them, as the grinder, a stirring tank type grinder or a container-driven grinder is preferred, and a tumbling mill, a ball mill or a bead mill is more preferred, and as the stirrer, a high-speed stirring type mixer is preferred, and a high-speed rotating thin film type stirrer is preferred. In this mixing, particularly when a conductive material and a binder are used, an agitation tank type grinder is preferred, and a tumbling mill is particularly preferred.

[0159] In this mixture, the sulfide solid electrolyte, preferably the crystalline sulfide solid electrolyte, may or may not be mechanically treated. By using a mechanically treated material, a more uniform mixture can be obtained by mixing with the electrode active material, thereby improving battery performance. On the other hand, not using mechanical treatment improves manufacturing efficiency. Either method can be selected taking into consideration the desired performance of the electrode mixture, manufacturing efficiency, etc. In this embodiment, when a mechanically treated product is not used as the sulfide solid electrolyte, preferably a crystalline sulfide solid electrolyte, an electrode mixture containing the crystalline sulfide solid electrolyte and an electrode active material is obtained, or an electrode mixture containing a mechanically treated product in which at least a portion of the crystalline sulfide solid electrolyte is substantially mechanically treated by this mixing, and an electrode active material is obtained. Also, when a mechanically treated product is used as the crystalline sulfide solid electrolyte, an electrode mixture that is a mixture of the mechanically treated crystalline sulfide solid electrolyte and an electrode active material is obtained.

[0160] In this mixing, either dry mixing without using a solvent or wet mixing with a solvent may be employed. When a solvent is used, it may be appropriately selected from the various solvents exemplified as solvents that can be used in the mechanical treatment described above, i.e., aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, ether-based solvents, nitrile-based solvents, etc., and aromatic hydrocarbon solvents and nitrile-based solvents are preferred, with toluene and isobutyronitrile being more preferred. The amount of solvent used is the same as that used in the mechanical treatment. [Example]

[0161] 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.

[0162] (Production Example 1) 15.3 g of lithium sulfide and 24.7 g of diphosphorus pentasulfide were added to a 1 L reactor equipped with a stirring blade under a nitrogen atmosphere. After starting the stirring blade, 400 mL of tetrahydrofuran pre-cooled to -20 °C was added to the vessel. After allowing the temperature to rise naturally to room temperature (23 °C), stirring was continued for 72 h. The resulting reaction slurry was poured into a glass filter (pore size: 40-100 μm) to obtain the solid fraction. The solid fraction was then dried at 90 °C to obtain 38 g of Li3PS4 (purity: 90% by mass) as a white powder. Powder X-ray diffraction (XRD) analysis of the resulting powder using an X-ray diffraction (XRD) device (SmartLab, Rigaku Corporation) revealed a halo pattern, confirming that it was amorphous Li3PS4.

[0163] (Production Example 2) The bead mill used was a "Bead Mill LMZ015" (manufactured by Ashizawa Finetech Co., Ltd.) and was charged with 485 g of zirconia balls with a diameter of 0.5 mm. A 2.0-liter glass reactor equipped with a stirrer was used as the reaction vessel. 34.77 g of lithium sulfide and 45.87 g of diphosphorus pentasulfide were charged into a reaction vessel, and 1000 ml of dehydrated toluene was added to form a slurry. The slurry charged into the reaction vessel was circulated at a flow rate of 600 ml / min using the pump in the bead mill apparatus. After starting the operation of the bead mill at a peripheral speed of 10 m / s, 13.97 g of iodine (Wako Pure Chemical Industries, special grade) and 13.19 g of bromine (Wako Pure Chemical Industries, special grade) dissolved in 200 ml of dehydrated toluene were charged into the reaction vessel. After the addition of iodine and bromine, the peripheral speed of the bead mill was set to 12 m / s, and hot water (HW) was passed through the external circulation system, allowing the reaction to proceed while maintaining the pump discharge temperature at 70 °C. The supernatant of the resulting slurry was removed, and the slurry was placed on a hot plate and dried at 80 °C to obtain a powdered amorphous solid electrolyte. The resulting powdered amorphous solid electrolyte was heated at 195 °C for 3 hours using a hot plate installed in a glove box to obtain a crystalline solid electrolyte. Powder X-ray diffraction (XRD) analysis of the resulting crystalline solid electrolyte detected crystallization peaks at 2θ = 20.2 ° and 23.6 °, confirming that the electrolyte had a thiolithiform II crystal structure.

[0164] (Production Example 3: Preparation of Positive Electrode Active Material) LiNi 0.8 Co 0.15 Al 0.05 O2 (average particle size (D 50 ):6.2μm, BET specific surface area: 0.43m 2 / g, hereinafter sometimes referred to as "NCA.") was prepared with reference to a non-patent document (N. Ohta, K. Takada, L. Zhang, R. Ma, M. Osada, T. Sasaki, Adv. Mater. 18, 2226 (2006)). As a solution for forming the coating layer, a mixed solution of 208.9 g of titanium isopropoxide (TiOCHCH2CH3) with a purity of 99%, 4.1 g of Li metal, and 491.1 g of lithium ethoxide (LiOCH2CH3) solution prepared using 487 g of ethanol was used. The lithium ethoxide solution was spray-coated onto the NCA, and after drying to remove excess solvent, the NCA was baked at 300°C for 0.5 hours in a muffle furnace to form a layer of LTO (Li4Ti5O 12 A positive electrode active material having a coating layer of ) was prepared. The surface coverage of the obtained positive electrode active material was 92%, and the thickness of the coating layer was 4.2 nm.

[0165] Example 1 In a 100 mL Schlenk flask equipped with a stirrer, 1.70 g of the white powder obtained in Production Example 1 (1.53 g of Li3PS4), 0.19 g of lithium bromide, and 0.28 g of lithium iodide were introduced under a nitrogen atmosphere. After rotating the stirrer, 20 mL of the complexing agent tetramethylethylenediamine (TMEDA) was added, and stirring was continued for 12 hours. The resulting electrolyte precursor mixture was dried under vacuum (room temperature: 23°C) to obtain a powdered electrolyte precursor. The electrolyte precursor powder was then heated under vacuum at 120°C for 2 hours to obtain an amorphous sulfide solid electrolyte. The amorphous sulfide solid electrolyte was then heated under vacuum at 140°C for 2 hours to obtain a crystalline sulfide solid electrolyte. (The heating temperature (140°C in this example) required to obtain the crystalline sulfide solid electrolyte is sometimes referred to as the "crystallization temperature.")

[0166] The obtained powder electrolyte precursor and a portion of the crystalline sulfide solid electrolyte were dissolved in methanol, and the resulting methanol solution was analyzed by gas chromatography to measure the tetramethylethylenediamine content. The content of the complexing agent in the electrolyte precursor was 55.0 mass %, and the content of the complexing agent in the crystalline sulfide solid electrolyte was 1.2 mass %.

[0167] The obtained electrolyte precursor, amorphous sulfide solid electrolyte, and crystalline sulfide solid electrolyte were subjected to powder X-ray diffraction (XRD) measurement using a powder X-ray diffraction (XRD) device (D2 PHASER, manufactured by BRUKER Co., Ltd.) The X-ray diffraction spectrum of the crystalline sulfide solid electrolyte is shown in Figure 5.

[0168] In this example, X-ray diffraction (XRD) measurement was carried out as follows. The solid electrolyte powder for each example was used to create a sample by leveling a 20 mm diameter, 0.2 mm deep groove with glass. This sample was measured using a Kapton film for XRD without exposing it to air. The 2θ position of the diffraction peak was determined by Le Bail analysis using the XRD analysis program RIETAN-FP. The powder X-ray diffraction measurement was carried out under the following conditions using the above powder X-ray diffraction measurement device. Tube voltage: 30kV Tube current: 10mA X-ray wavelength: Cu-Kα ray (1.5418Å) Optical system: Concentration method Slit configuration: Soller slit 4°, divergence slit 1 mm, Kβ filter (Ni plate) Detector: Semiconductor detector Measurement range: 2θ=10-60deg Step width, scan speed: 0.05deg, 0.05deg / sec In addition, in analyzing the peak positions to confirm the presence of a crystalline structure from the measurement results, the XRD analysis program RIETAN-FP was used, and the baseline was corrected using an 11th-order Legendre orthogonal polynomial to determine the peak positions.

[0169] The composition of the obtained amorphous sulfide solid electrolyte was analyzed by inductively coupled plasma (ICP) analysis. The composition analysis results showed that the contents of Li, P, S, Br, and I were 10.1, 13.2, 55.2, 8.4, and 13.1 mass%, respectively. In the X-ray diffraction spectrum of the electrolyte precursor, peaks different from those derived from the raw materials used were observed, and the X-ray diffraction pattern was different from that of the amorphous sulfide solid electrolyte and the crystalline sulfide solid electrolyte. Powder X-ray diffraction (XRD) measurements were also performed on the raw materials used in Example 1 (amorphous Li3PS4, lithium bromide, and lithium iodide) and the raw materials used in other Examples (lithium sulfide, diphosphorus pentasulfide, and crystalline Li3PS4), and the resulting X-ray diffraction spectra are shown in Figure 4. The X-ray diffraction spectrum of the electrolyte precursor also showed an X-ray diffraction pattern different from that of the raw materials. The X-ray diffraction spectrum of the amorphous sulfide solid electrolyte confirmed that there were no peaks other than those derived from the raw materials. In addition, the X-ray diffraction spectrum of the crystalline sulfide solid electrolyte detected crystallization peaks mainly at 2θ = 20.2° and 23.6°, indicating that it has a thiolithiregion II crystal structure. When the ionic conductivity was measured, it was found to be 2.90 × 10 -3 (S / cm), confirming that the material has high ionic conductivity.

[0170] In the present example, the ionic conductivity was measured as follows. From the obtained crystalline sulfide solid electrolyte, a 10 mm diameter (cross-sectional area S i :0.785cm 2 ), height (L i ) Circular pellets of 0.1 to 0.3 cm were molded to prepare samples. Electrode terminals were attached to the top and bottom of the sample, and measurements were taken at 25°C using the AC impedance method (frequency range: 5 MHz to 0.5 Hz, amplitude: 10 mV). A Cole-Cole plot was obtained. 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 calculated as the bulk resistance R (Ω) of the electrolyte. i ) and calculate the ionic conductivity σ according to the following formula: i (S / cm) was calculated. R i =ρ(L i / S i ) σ=1 / ρ

[0171] The volume-based average particle size of the obtained crystalline sulfide solid electrolyte was 7.5 μm, and the specific surface area was 33 m 2 / g, and the half-width Δ2θ of the maximum peak (2θ=20.2°) including the background at 2θ=10 to 40° was 0.59°.

[0172] The half-value width was calculated by the following method. The half-width calculation uses a range of ±2° of the maximum peak. If the Lorentzian function ratio is A (0≦A≦1), the peak intensity correction value is B, the 2θ maximum peak is C, the peak position in the range used for calculation (C±2°) is D, the half-width parameter is E, the background is F, and the intensity of each peak in the peak range used for calculation is G, then when the variables are A, B, C, D, E, and F, calculate the following for each peak position. H=G-{B×{A / (1+(DC) 2 / E 2 )+(1-A)×exp(-1×(DC) 2 / E 2 )}+F} The H values ​​were summed within the range of the peak C ±2° to be calculated, and the sum was minimized with GRG nonlinearity using the solver function of the spreadsheet software Excel (Microsoft) to determine the half-width parameter. The half-width G was calculated using the obtained half-width parameters according to the following formula: G = E × 2 × (ln4) (1 / 2)

[0173] The average particle size was measured using a laser diffraction particle size analyzer (LA-920 (model number), manufactured by HORIBA). The specific surface area was measured by the BET flow method (three-point method) using nitrogen gas as the adsorbate in accordance with JIS R 1626:1996.

[0174] (Preparation of positive electrode mixture) Next, 0.1 g of the above crystalline sulfide solid electrolyte and 0.9 g of the positive electrode active material obtained in Production Example 3 were mixed for 1 hour at a rotation speed of 600 rpm using a tumbling mill ("Mini Ball Mill AV Type (Model No.)", manufactured by Asahi Rika Seisakusho) to obtain an electrode mixture (positive electrode mixture). The obtained electrode mixture (positive electrode mixture) was observed using a scanning electron microscope (SEM). A photograph taken with a scanning electron microscope (SEM) is shown in FIG. 6.

[0175] (Fabrication of half-cells using positive electrode composites) 60 mg of the 80(75Li2S / 25P2S5)-10LiBr-10LiI crystalline sulfide solid electrolyte obtained in Production Example 2 was placed in a ceramic cylinder having a diameter of 10 mm and pressure molded to form an electrolyte layer. A 23.6 mg portion of the cathode composite was placed on top of the electrolyte layer and pressure-molded to form the working electrode. An InLi alloy foil was attached to the surface of the electrolyte layer opposite the working electrode and pressure-molded to form the reference and counter electrodes. The cell was then screwed in four places at 90° intervals around the cell to create a three-layer half-cell. Note that the InLi alloy can be used as a reference electrode because the reaction potential for Li insertion and desorption is kept constant if the raw material ratio (Li / In) is 0.8 or less.

[0176] The cutoff voltage of the obtained half cell was set to 3.6 V during charging and 2.5 V during discharging, and the current density during charging and discharging was 0.24 mA cm -2 The charging capacity in the first cycle was 120 mAh / g, and in the second cycle, the current density was 0.48 mAcm. -2 The charge capacity at the second cycle was 113 mAh / g, and the current density at the third cycle was 2.4 mAcm -2 The charge capacity in the third cycle was 74 mAh / g, and the current density in the fourth cycle was 4.8 mAcm -2 The charge capacity after 4 cycles was 45 mAh / g. The current density was 9.6 mAcm for the 5th, 6th, and 7th cycles. -2 , 14.4mAcm -2 , 19.2mAcm -2 The cycle characteristics were evaluated, and the charge capacities at the 5th, 6th, and 7th cycles were 17 mAh / g, 6.3 mAh / g, and 2 mAh / g, respectively. The results are shown in Figure 9, with the C-rate on the horizontal axis and the charge capacity on the vertical axis.

[0177] The electronic conductivity of the crystalline sulfide solid electrolyte, the positive electrode active material, and the resulting positive electrode mixture was measured by the above-mentioned measurement method. The electronic conductivity Σ(C) of the electrode mixture was 5.70×10 -3 The electronic conductivity Σ(SE) of the crystalline sulfide solid electrolyte was 2.08×10 -9 The electron conductivity Σ(A) of the positive electrode active material was 2.45×10 -2 S / cm. In addition, since the electrode active material fraction α was 0.9, the electronic conductivity parameter X calculated by formula (1) was 1.18. These results are shown in Table 1. Note that the electronic conductivity parameter X was calculated using 1.0 × 10, which is a general value for the electronic conductivity of sulfide solid electrolytes. -8 When S / cm was used, X was 1.01.

[0178] Next, the overlap area ratio of the mapping of the elements constituting the electrode active material to the mapping of the elements constituting the sulfide solid electrolyte was measured using the above measurement method. For this measurement, the electrode active material and sulfide solid electrolyte were photographed using a scanning electron microscope (SEM), and the images were subjected to elemental analysis using an energy dispersive X-ray spectrometer (EDS). An image (EDS image) of nickel constituting the electrode active material is shown in Figure 10, and an image (EDS image) of phosphorus constituting the sulfide solid electrolyte is shown in Figure 11. Using the images of nickel and phosphorus, the overlap area ratio of the mapping of the elements constituting the electrode active material to the mapping of the elements constituting the sulfide solid electrolyte was measured using the above measurement method, and was found to be 0.45. Since the electrode active material fraction α was 0.9, A was 4.05. In measuring the overlap area ratio, the image obtained by elemental analysis was binarized using the OpenCV (Open Source Computer Vision Library) in Python. The results are shown in Table 1.

[0179] Example 2 In Example 1, in preparing the electrode mixture (cathode mixture), toluene and isobutyronitrile were added as solvents so that the total content of the crystalline sulfide solid electrolyte and the cathode active material was 10 mass %, and mixing was performed for 20 seconds at a rotation speed of 16,000 rpm using a high-speed rotating thin-film type mixer (product name: "FILMIX", manufactured by PRIMIX Corporation). An electrode mixture (cathode mixture) and a half-cell were prepared in the same manner as in Example 1. The resulting electrode mixture (positive electrode mixture) was observed using a scanning electron microscope (SEM). A photograph taken with the scanning electron microscope (SEM) is shown in FIG. The resulting half-cell was subjected to cycle evaluation in the same manner as in Example 1, and the cycle characteristics were evaluated in the same manner as in Example 1. The charge capacity at the first cycle was 178 mAh / g, the charge capacity at the second cycle was 136 mAh / g, the charge capacity at the third cycle was 124 mAh / g, and the charge capacity at the fourth cycle was 104 mAh / g. The charge capacities at the fifth, sixth, and seventh cycles were 63 mAh / g, 32 mAh / g, and 13 mAh / g, respectively. The results are shown in Figure 9, with the C-rate on the horizontal axis and the charge capacity on the vertical axis.

[0180] When the electronic conductivity was measured in the same manner as in Example 1, the electronic conductivity Σ(C) of the electrode mixture was 4.60 × 10 -3 S / cm. The electronic conductivity Σ(SE) of the crystalline sulfide solid electrolyte and the electronic conductivity Σ(A) of the positive electrode active material were the same as in Example 1. In addition, since the electrode active material fraction α was 0.9, the electronic conductivity parameter X calculated by formula (1) was 0.96. These results are shown in Table 1. When a general numerical value for the electronic conductivity of a sulfide solid electrolyte was used to calculate the electronic conductivity parameter X, X was 0.82. Furthermore, the overlap area ratio was measured in the same manner as in Example 1 and was found to be 0.13. Since the electrode active material fraction α was 0.9, A was found to be 1.17. These results are shown in Table 1. Furthermore, an image (EDS image) of the nickel element constituting the electrode active material is shown in FIG. 12, and an image (EDS image) of the phosphorus element constituting the sulfide solid electrolyte is shown in FIG. 13.

[0181] Example 3 An electrode composite (cathode composite) and a half cell were prepared in the same manner as in Example 1, except that a sulfide solid electrolyte was prepared by using 1,2-diethoxyethane (DEE) as the complexing agent instead of tetramethylethylenediamine (TMEDA) in Example 1. The obtained electrode mixture (positive electrode mixture) was observed using a scanning electron microscope (SEM). A photograph taken with the scanning electron microscope (SEM) is shown in FIG. The resulting half-cell was subjected to cycle evaluation in the same manner as in Example 1, and cycle characteristics were evaluated in the same manner as in Example 1. The charge capacity at the first cycle was 139 mAh / g, the charge capacity at the second cycle was 138 mAh / g, the charge capacity at the third cycle was 57 mAh / g, and the charge capacity at the fourth cycle was 27 mAh / g. The charge capacities at the fifth, sixth, and seventh cycles were 8.3 mAh / g, 0 mAh / g, and 0 mAh / g, respectively. Note that "0 mAh / g" at the sixth and seventh cycles means that the battery did not function and could not be measured.

[0182] When the electronic conductivity was measured in the same manner as in Example 1, the electronic conductivity Σ(C) of the electrode mixture was 6.93 × 10 -3 The electronic conductivity Σ(SE) of the crystalline sulfide solid electrolyte was 2.36×10 -9 S / cm. The electronic conductivity Σ(A) of the positive electrode active material was the same as in Example 1. In addition, since the electrode active material fraction α was 0.9, the electronic conductivity parameter X calculated by formula (1) was 1.42. These results are shown in Table 1. When a general numerical value for the electronic conductivity of a sulfide solid electrolyte was used to calculate the electronic conductivity parameter X, X was 1.23. Furthermore, the overlap area ratio was measured in the same manner as in Example 1 and was found to be 0.36. Since the electrode active material fraction α was 0.9, A was found to be 3.24. These results are shown in Table 1. Furthermore, an image (EDS image) of the nickel element constituting the electrode active material is shown in FIG. 15, and an image (EDS image) of the phosphorus element constituting the sulfide solid electrolyte is shown in FIG. 16.

[0183] Example 4 An electrode composite (cathode composite) and a half cell were prepared in the same manner as in Example 1, except that a sulfide solid electrolyte was prepared by using propylene glycol monomethyl ether acetate (PGMEA) instead of tetramethylethylenediamine (TMEDA) as the complexing agent. The resulting electrode mixture (positive electrode mixture) was observed using a scanning electron microscope (SEM). A photograph taken with the scanning electron microscope (SEM) is shown in FIG. The resulting half-cell was subjected to cycle evaluation in the same manner as in Example 1, and cycle characteristics were evaluated in the same manner as in Example 1. The charge capacity at the first cycle was 151 mAh / g, the charge capacity at the second cycle was 145 mAh / g, the charge capacity at the third cycle was 88 mAh / g, and the charge capacity at the fourth cycle was 43 mAh / g. The charge capacities at the fifth, sixth, and seventh cycles were 16 mAh / g, 5.5 mAh / g, and 0 mAh / g, respectively. Note that "0 mAh / g" at the seventh cycle means that the battery did not function and could not be measured.

[0184] When the electronic conductivity was measured in the same manner as in Example 1, the electronic conductivity Σ(C) of the electrode mixture was 5.13 × 10 -3 The electronic conductivity Σ(SE) of the crystalline sulfide solid electrolyte was 2.03×10 -9 S / cm. The electronic conductivity Σ(A) of the positive electrode active material was the same as in Example 1. Furthermore, since the electrode active material fraction α was 0.9, the electronic conductivity parameter X calculated by formula (1) was 1.07. These results are shown in Table 1. When a general numerical value for the electronic conductivity of a sulfide solid electrolyte was used to calculate the electronic conductivity parameter X, X was 0.91. Furthermore, the overlap area ratio was measured in the same manner as in Example 1 and was found to be 0.48. Since the electrode active material fraction α was 0.9, A was found to be 4.32. These results are shown in Table 1. Furthermore, an image (EDS image) of the nickel element constituting the electrode active material is shown in FIG. 18, and an image (EDS image) of the phosphorus element constituting the sulfide solid electrolyte is shown in FIG. 19.

[0185] Example 5 In Example 1, an electrode composite (cathode composite) and a half cell were prepared in the same manner as in Example 1, except that 0.2 g of the crystalline sulfide solid electrolyte and 0.8 g of the cathode active material were used to prepare the electrode composite (cathode composite). A half cell was prepared in the same manner as in Example 1. The obtained electrode composite (cathode composite) was observed using a scanning electron microscope (SEM). A photograph taken with a scanning electron microscope (SEM) is shown in FIG.

[0186] When the electronic conductivity was measured in the same manner as in Example 1, the electronic conductivity Σ(C) of the electrode mixture was 1.28 × 10 -3 S / cm. The electronic conductivity Σ(SE) of the crystalline sulfide solid electrolyte and the electronic conductivity Σ(A) of the positive electrode active material were the same as in Example 1. In addition, since the electrode active material fraction α was 0.8, the electronic conductivity parameter X calculated by formula (1) was 1.36. These results are shown in Table 1. When a general numerical value for the electronic conductivity of a sulfide solid electrolyte was used to calculate the electronic conductivity parameter X, X was 0.99. Furthermore, the overlap area ratio was measured in the same manner as in Example 1 and was found to be 0.21. Since the electrode active material fraction α was 0.8, A was found to be 0.84. These results are shown in Table 1. Furthermore, an image (EDS image) of the nickel element constituting the electrode active material is shown in FIG. 29, and an image (EDS image) of the phosphorus element constituting the sulfide solid electrolyte is shown in FIG. 30.

[0187] Example 6 The electrolyte precursor obtained in Example 1 was subjected to thermogravimetric analysis (TG) using a thermogravimetric analyzer (TG-DTA device, "TGA 2 (model number)," manufactured by Mettler-Toledo) at a temperature increase rate of 10°C / min. Considering that the entire mass loss was due to solvent, 0.24 g of electrolyte precursor and 0.9 g of positive electrode active material were mixed in the same manner as in Example 1 so that the powder ratio was 9:1 upon heating of the electrolyte precursor. After mixing, the mixture of active material and precursor was vacuum-heated at 160°C for 2 hours to obtain an electrode mixture. A half-cell was fabricated in the same manner as in Example 1. The obtained electrode mixture (positive electrode mixture) was observed using a scanning electron microscope (SEM). A scanning electron microscope (SEM) photograph is shown in FIG. 31. The resulting half-cell was subjected to cycle evaluation in the same manner as in Example 1, and the cycle characteristics were evaluated in the same manner as in Example 1. The charge capacity at the first cycle was 146 mAh / g, the charge capacity at the second cycle was 137 mAh / g, the charge capacity at the third cycle was 107 mAh / g, and the charge capacity at the fourth cycle was 77 mAh / g. The charge capacities at the fifth, sixth, and seventh cycles were 39.1 mAh / g, 18.2 mAh / g, and 7.10 mAh / g, respectively.

[0188] When the electronic conductivity was measured in the same manner as in Example 1, the electronic conductivity Σ(C) of the electrode mixture was 9.19 × 10 -3 S / cm. The electronic conductivity Σ(SE) of the crystalline sulfide solid electrolyte and the electronic conductivity Σ(A) of the positive electrode active material were the same as in Example 1. In addition, since the electrode active material fraction α was 0.9, the electronic conductivity parameter X calculated by formula (1) was 1.91. These results are shown in Table 1. When a general numerical value for the electronic conductivity of a sulfide solid electrolyte was used to calculate the electronic conductivity parameter X, X was 1.63. Furthermore, the overlap area ratio was measured in the same manner as in Example 1 and was found to be 0.21. Since the electrode active material fraction α was 0.9, A was found to be 1.89. These results are shown in Table 1. Furthermore, an image (EDS image) of the nickel element constituting the electrode active material is shown in FIG. 32, and an image (EDS image) of the phosphorus element constituting the sulfide solid electrolyte is shown in FIG. 33.

[0189] Example 7 The electrolyte precursor obtained in Example 1 was vacuum-heated at 120°C for 2 hours to obtain a glassy electrolyte precursor. Thermogravimetric analysis (TG) was performed in the same manner as in Example 6. Taking into account that the entire mass loss was due to the solvent, 0.11 g of the glassy electrolyte precursor and 0.9 g of the positive electrode active material were mixed in the same manner as in Example 1 so that the powder ratio was 9:1 when the glassy electrolyte precursor was heated. After mixing, the mixture of the active material and precursor was vacuum-heated at 160°C for 2 hours to obtain an electrode mixture. A half-cell was produced in the same manner as in Example 1. The obtained electrode mixture (cathode mixture) was observed using a scanning electron microscope (SEM). A scanning electron microscope (SEM) photograph is shown in FIG. 34. The resulting half-cell was subjected to cycle evaluation in the same manner as in Example 1, and the cycle characteristics were evaluated in the same manner as in Example 1. The charge capacity at the first cycle was 142 mAh / g, the charge capacity at the second cycle was 134 mAh / g, the charge capacity at the third cycle was 107 mAh / g, and the charge capacity at the fourth cycle was 74.4 mAh / g. The charge capacities at the fifth, sixth, and seventh cycles were 32.3 mAh / g, 13.3 mAh / g, and 3.88 mAh / g, respectively.

[0190] The electronic conductivity was measured in the same manner as in Example 1, and the electronic conductivity Σ(C) of the electrode mixture was 9.72 × 10 -3 S / cm. The electronic conductivity Σ(SE) of the crystalline sulfide solid electrolyte and the electronic conductivity Σ(A) of the positive electrode active material were the same as in Example 1. In addition, since the electrode active material fraction α was 0.9, the electronic conductivity parameter X calculated by formula (1) was 2.02. These results are shown in Table 1. When a general numerical value for the electronic conductivity of a sulfide solid electrolyte was used to calculate the electronic conductivity parameter X, X was 1.72. Furthermore, the overlap area ratio was measured in the same manner as in Example 1 and was found to be 0.26. Since the electrode active material fraction α was 0.9, A was found to be 2.34. These results are shown in Table 1. Furthermore, an image (EDS image) of the nickel element constituting the electrode active material is shown in FIG. 35, and an image (EDS image) of the phosphorus element constituting the sulfide solid electrolyte is shown in FIG. 36.

[0191] (Comparative Example 1) In Example 1, the crystalline sulfide solid electrolyte obtained in Production Example 2 (average particle size: 6.6 μm, BET specific surface area: 3.4 m) was used for producing the electrode mixture (positive electrode mixture). 2 A positive electrode composite and a half cell were produced in the same manner as in Example 1, except that 1000 sulphide / g was used. The crystalline sulfide solid electrolyte obtained in Production Example 2 was subjected to powder X-ray diffraction (XRD) measurement using an X-ray diffraction (XRD) device ("D2 PHASER (product number)" manufactured by BRUKER Co., Ltd.), and the X-ray diffraction spectrum is shown in FIG. 5. The half-width Δ2θ of the maximum peak (2θ = 20.2°) including the background in the 2θ = 10 to 40° range was 0.78°. The resulting electrode mixture (positive electrode mixture) was observed using a scanning electron microscope (SEM). A photograph taken with the scanning electron microscope (SEM) is shown in FIG. The cutoff voltage of the obtained half cell was set to 3.6 V during charging and 2.5 V during discharging, and the current density during charging and discharging was 0.24 mA cm -2 The charging capacity in the first cycle was 45.3 mAh / g, and in the second cycle, the current density was 1.2 mAcm. -2 The charge capacity at the second cycle was 12 mAh / g, and the current density at the third cycle was 2.4 mAcm -2 The charge capacity in the third cycle was 5.4 mAh / g, and the current density in the fourth cycle was 4.8 mAcm -2 The charge capacity after four cycles was 0.4 mAh / g. The current density was kept constant at 9.6 mAcm for the fifth cycle. -2 The charge rate was kept constant at 1000 kJ / s, and the charge capacity at the 5th cycle was 0 mAh / g. The results are shown in Figure 9, with the C rate on the horizontal axis and the charge capacity on the vertical axis. Note that the "0 mAh / g" at the 5th cycle means that the battery did not function as a battery and could not be measured.

[0192] When the electronic conductivity was measured in the same manner as in Example 1, the electronic conductivity Σ(C) of the electrode mixture was 1.23 × 10 -2The electronic conductivity Σ(SE) of the crystalline sulfide solid electrolyte was 2.07×10 -9 S / cm. The electronic conductivity Σ(A) of the positive electrode active material was the same as in Example 1. Furthermore, since the electrode active material fraction α was 0.9, the electronic conductivity parameter X calculated by formula (1) was 2.56. These results are shown in Table 1. When a general numerical value for the electronic conductivity of a sulfide solid electrolyte was used to calculate the electronic conductivity parameter X, X was 2.19. Furthermore, the overlap area ratio was measured in the same manner as in Example 1 and was found to be 0.059. Since the electrode active material fraction α was 0.9, A was found to be 0.531. These results are shown in Table 1. Furthermore, an image (EDS image) of the nickel element constituting the electrode active material is shown in FIG. 20, and an image (EDS image) of the phosphorus element constituting the sulfide solid electrolyte is shown in FIG. 21.

[0193] (Comparative Example 2) In Example 1, in preparing the electrode composite (cathode composite), tetramethylethylenediamine (TMEDA) was added as a solvent so that the total content of the crystalline sulfide solid electrolyte and the cathode active material was 10 mass %, and mixing was performed using a stirrer instead of a tumbling mill. An electrode composite (cathode composite) and a half cell were prepared in the same manner as in Example 1, except that: The obtained electrode mixture (positive electrode mixture) was observed using a scanning electron microscope (SEM). A photograph taken with the scanning electron microscope (SEM) is shown in FIG. The resulting half-cell was subjected to cycle evaluation in the same manner as in Example 1, and the cycle characteristics were evaluated in the same manner as in Example 1. The charge capacity at the first cycle was 72 mAh / g, the charge capacity at the second cycle was 51 mAh / g, the charge capacity at the third cycle was 9.4 mAh / g, and the charge capacity at the fourth cycle was 2.5 mAh / g. The charge capacities at the fifth, sixth, and seventh cycles were each 1.0 × 10 -4 mAh / g, 8.0×10 -5 mAh / g, 6.6×10 -5 It became mAh / g.

[0194] When the electronic conductivity was measured in the same manner as in Example 1, the electronic conductivity Σ(C) of the electrode mixture was 1.27 × 10 -4 S / cm. The electronic conductivity Σ(SE) of the crystalline sulfide solid electrolyte and the electronic conductivity Σ(A) of the positive electrode active material were the same as in Example 1. In addition, since the electrode active material fraction α was 0.9, the electronic conductivity parameter X calculated by formula (1) was 0.026. These results are shown in Table 1. When a general numerical value for the electronic conductivity of a sulfide solid electrolyte was used to calculate the electronic conductivity parameter X, X was 0.023. Furthermore, the overlap area ratio was measured in the same manner as in Example 1 and was found to be 0.21. Since the electrode active material fraction α was 0.9, A was found to be 1.89. These results are shown in Table 1. Furthermore, an image of the nickel element constituting the electrode active material is shown in FIG. 23, and an image of the phosphorus element constituting the sulfide solid electrolyte is shown in FIG. 24.

[0195] (Comparative Example 3) In Example 1, in preparing the electrode composite (cathode composite), ethanol was added as a solvent so that the total content of the crystalline sulfide solid electrolyte and the cathode active material was 10 mass %, and mixing was performed using a stirrer instead of a tumbling mill. An electrode composite (cathode composite) and a half cell were prepared in the same manner as in Example 1, except that The resulting electrode mixture (positive electrode mixture) was observed using a scanning electron microscope (SEM). A photograph taken with the scanning electron microscope (SEM) is shown in FIG. The resulting half-cell was subjected to cycle evaluation in the same manner as in Example 1, and cycle characteristics were evaluated in the same manner as in Example 1. The charge capacity at the first cycle was 1.3 mAh / g, the charge capacity at the second cycle was 0.030 mAh / g, the charge capacity at the third cycle was 0 mAh / g, and the charge capacity at the fourth cycle was 0 mAh / g. The charge capacities at the fifth, sixth, and seventh cycles were 0 mAh / g, 0 mAh / g, and 0 mAh / g, respectively. Note that "0 mAh / g" at the third to seventh cycles means that the battery did not function and could not be measured.

[0196] The electronic conductivity was measured in the same manner as in Example 1, and the electronic conductivity Σ(C) of the electrode mixture was 1.21 × 10 -3 S / cm. The electronic conductivity Σ(SE) of the crystalline sulfide solid electrolyte and the electronic conductivity Σ(A) of the positive electrode active material were the same as in Example 1. In addition, since the electrode active material fraction α was 0.9, the electronic conductivity parameter X calculated by formula (1) was 0.25. These results are shown in Table 1. When a general numerical value for the electronic conductivity of a sulfide solid electrolyte was used to calculate the electronic conductivity parameter X, X was 0.22. Furthermore, the overlap area ratio was measured in the same manner as in Example 1 and was found to be 0.26. Since the electrode active material fraction α was 0.9, A was found to be 2.34. These results are shown in Table 1. Furthermore, an image of the nickel element constituting the electrode active material is shown in FIG. 26, and an image of the phosphorus element constituting the sulfide solid electrolyte is shown in FIG. 27.

[0197] Comparative Example 4 In Comparative Example 1, an electrode mixture (cathode mixture) and a half cell were prepared in the same manner as in Comparative Example 1, except that 0.2 g of a crystalline sulfide solid electrolyte and 0.8 g of a cathode active material were used to prepare the electrode mixture (cathode mixture). The half cell was prepared in the same manner as in Example 1. The obtained electrode mixture (cathode mixture) was observed using a scanning electron microscope (SEM). A photograph taken with a scanning electron microscope (SEM) is shown in FIG. 37.

[0198] When the electronic conductivity was measured in the same manner as in Example 1, the electronic conductivity Σ(C) of the electrode mixture was 2.83 × 10 -3 The electronic conductivity Σ(SE) of the crystalline sulfide solid electrolyte was 2.07×10 -9 S / cm. The electronic conductivity Σ(A) of the positive electrode active material was the same as in Example 1. In addition, since the electrode active material fraction α was 0.8, the electronic conductivity parameter X calculated by formula (1) was 3.00. These results are shown in Table 1. When a general numerical value for the electronic conductivity of a sulfide solid electrolyte was used to calculate the electronic conductivity parameter X, X was 2.19. Furthermore, the overlap area ratio was measured in the same manner as in Example 1 and was found to be 0.056. Since the electrode active material fraction α was 0.8, A was found to be 0.22. These results are shown in Table 1. Furthermore, an image of the nickel element constituting the electrode active material is shown in FIG. 38, and an image of the phosphorus element constituting the sulfide solid electrolyte is shown in FIG. 39.

[0199] [Table 1]

[0200] From the above results, it was confirmed that the electrode composite of this embodiment has an electronic conductivity parameter that satisfies 0.30≦X≦2.10 and can exhibit high battery performance. Furthermore, a comparison between Examples 1 and 5 shows that when the electrode active material fraction α is set to 0.9 or 0.8 in the preparation of the electrode composite, the electronic conductivity parameter is approximately the same, and it is considered that the battery performance of each electrode composite is approximately the same. On the other hand, the electrode mixture of Comparative Example 1 did not satisfy the electronic conductivity parameter X of 0.30≦X≦2.10, and therefore did not exhibit high battery performance. The electrode mixture of Comparative Example 1 had an extremely small overlap area ratio and a small A, resulting in poor contact between the electrolyte and the active material, as well as poor coverage according to the fraction. The electrolyte and active material did not disperse but aggregated, resulting in an electronic conductivity parameter X greater than the range of 0.30≦X≦2.10, and therefore not exhibiting high battery performance. The SEM photograph of Comparative Example 1 ( FIG. 8 ) clearly shows that the amount of sulfide solid electrolyte on the electrode active material surface is small, confirming the small overlap area ratio. Furthermore, Comparative Example 4, which, like Comparative Example 1, has an electronic conductivity parameter X greater than the range of 0.30≦X≦2.10, also exhibits the same tendency as Comparative Example 1, and therefore is not considered to exhibit high battery performance. According to the SEM photograph (FIG. 25) of the electrode composite of Comparative Example 3, the solid electrolyte aggregated in a flaky state and coated the electrode active material, which resulted in poor dispersion of the sulfide solid electrolyte on the surface of the electrode active material and poor contact, resulting in low electronic conductivity of the composite and poor battery characteristics. Furthermore, for Comparative Example 2, as in Comparative Example 3, the parameter X was smaller than the range of 0.30≦X≦2.10, and a thick layer of electrolyte was present around the active material, lowering electronic conductivity. Furthermore, according to the SEM photograph (FIG. 22) of the electrode composite of Comparative Example 2, the same tendency as in Comparative Example 3 (FIG. 25) was confirmed, which suggests that the poor dispersion and contact conditions resulted in poor battery performance. [Industrial Applicability]

[0201] The electrode mixture of this embodiment can exhibit high battery performance. Furthermore, since the electrode mixture of this embodiment has excellent contact between the electrode active material and the sulfide solid electrolyte, the contact state between them is not reduced whether the electrode mixture is in the powder form or in the slurry form. Therefore, whether the battery is produced by any of various film-forming methods, such as an electrostatic coating method in which the powder is dry-coated, wet coating molding, or compression molding, or a molding method, the resulting battery can exhibit high battery performance. Therefore, the electrode mixture of this embodiment is suitable for use in all-solid-state lithium batteries, particularly in batteries used in information-related devices and communication devices such as personal computers, video cameras, and mobile phones.

Claims

1. The battery contains a sulfide solid electrolyte and an electrode active material, and an electronic conductivity parameter X represented by the following formula (1) satisfies 0.30≦X≦2.10, the sulfide solid electrolyte contains lithium, sulfur, phosphorus, and a halogen element; the element constituting the electrode active material is at least one metal element selected from manganese, cobalt, nickel, iron, titanium, zirconium, tungsten, molybdenum, copper, chromium, tantalum, zinc, vanadium, and niobium; In elemental analysis of an electron microscope image by energy dispersive X-ray spectroscopy, polarization is performed using a threshold determined by discriminant analysis. When the overlap area ratio of a mapping of elements constituting the sulfide solid electrolyte to a mapping of elements constituting the electrode active material is expressed as A×(1−α) / α (α: electrode active material fraction), A satisfies 0.55<A<5.

0. [Equation 1]

2. 2. The electrode mixture according to claim 1, wherein the element constituting the electrode active material includes a transition element, and the element constituting the sulfide solid electrolyte includes a phosphorus element.

3. 3. The electrode mixture according to claim 1, wherein the electrode active material is an oxide-based positive electrode active material.

4. The electrode mixture according to any one of claims 1 to 3, wherein the electrode active material fraction α is 0.6 or more and 0.99 or less.

5. The electronic conductivity Σ(C) is 1.0 × 10 －６ The electrode mixture according to any one of claims 1 to 4, having a viscosity of 250 S / cm or more.

6. The electronic conductivity Σ(A) of the electrode active material is 1.0 × 10 －５ The electrode mixture according to any one of claims 1 to 5, having a viscosity of 250 S / cm or more.

7. The electronic conductivity Σ(SE) of the sulfide solid electrolyte is 1.0 × 10 －７ The electrode mixture according to any one of claims 1 to 6, wherein the electrical conductivity is 0.5 S / cm or less.

8. The electronic conductivity Σ(SE) of the sulfide solid electrolyte in the electronic conductivity parameter X is 1.0 × 10 －８ The electrode mixture according to any one of claims 1 to 7, calculated as S / cm.

9. The electrode mixture according to any one of claims 1 to 8, wherein the sulfide solid electrolyte is a crystalline sulfide solid electrolyte.

10. The electrode mixture according to any one of claims 1 to 9, wherein the sulfide solid electrolyte comprises a thiolicon region II type crystal structure.

11. The sulfide solid electrolyte has a specific surface area of ​​20 m as measured by the BET method. ２ The electrode mixture according to any one of claims 1 to 10, wherein the electrode mixture has a viscosity of 1 / g or more.

12. The electrode mixture according to any one of claims 1 to 11, wherein the sulfide solid electrolyte has a volume-based average particle size measured by a laser diffraction particle size distribution measurement method of 3 µm or more.

13. The electrode mixture according to any one of claims 1 to 12, wherein the sulfide solid electrolyte is a mechanically treated product.

14. The sulfide solid electrolyte has a maximum peak half width including a background of 2θ = 10 to 40 ° in X-ray diffraction measurement using CuKα rays. The electrode mixture according to any one of claims 1 to 13, wherein Δ2θ = 0.75 ° or less.

Images