Crystalline sulfide solid electrolyte

Abstract

The present invention provides a crystalline sulfide solid electrolyte which comprises a novel structure having α-Li3PS4, which has room temperature stability, as a basic structure, and which contains a lithium atom, a phosphorus atom, a sulfur atom, an oxygen atom, and a halogen atom, wherein the crystalline sulfide solid electrolyte has a diffraction peak at 2θ1 = 17.8 ± 0.5° in an X-ray diffraction measurement using a CuKα ray, and the difference between the position 2θ1 of the diffraction peak and the position 2θ2 of another diffraction peak closest to the diffraction peak (|2θ1 - 2θ2|) is less than 0.5°.

Description

Crystalline sulfide solid electrolyte

[0001] The present invention relates to a crystalline sulfide solid electrolyte.

[0002] In recent years, the rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones has placed great importance on the development of batteries for use as their power sources. Lithium-ion batteries, in particular, have attracted attention due to their high energy density. Traditionally, batteries used for such applications have used electrolytes containing flammable organic solvents, necessitating the installation of safety devices to suppress temperature rise during short circuits, as well as improvements in the structure and materials to prevent short circuits. In response to this issue, development is underway to develop batteries that use solid electrolytes, eliminating the need for flammable organic solvents, simplifying safety devices, and improving manufacturing costs and productivity.

[0003] Various types of solid electrolytes have been developed for use in the solid electrolyte layer. For example, Patent Document 1 describes a solid electrolyte having the composition formula Li ４－４ｙ－ｘ－ｚ P １＋ｙ S ４－ｚ X ｚ (0.2≦x≦1.0, 0<z≦0.2, 0≦y≦0.075, X is at least one of F, Cl, N, and OH), and has a peak at a predetermined position in X-ray diffraction measurement using CuKα rays. ３ P.S. ４－ｘ O ｘ Disclosed are solid electrolyte materials having a composition of (1≦x≦3) and crystalline phases A and B with peaks at predetermined positions in X-ray diffraction measurement using CuKα rays, and solid electrolyte materials further containing LiX (X is F, Cl, Br or I). Patent Document 3 also discloses a solid electrolyte material comprising an ion conductor having a Li element and an anion structure containing at least a P element, wherein the main component of the anion structure is PS. ４ ３－ and the ionic conductor has an anionic structure of PS ４ ３－ and P.S. ３ O ３－and PS ２ O ２ ３－ and PSO ３ ３－ A sulfide solid electrolyte material characterized by not having PO as an anion structure, and ４ ３－ A sulfide solid electrolyte material is disclosed, further comprising:

[0004] JP 2018-174130 A JP 2017-33859 A JP 2017-152352 A

[0005] The present invention has been made in view of the above circumstances, and provides an α-Li alloy having room temperature stability. ３ P.S. ４ The object of the present invention is to provide a crystalline sulfide solid electrolyte having a novel structure having the following basic structure:

[0006] The crystalline sulfide solid electrolyte according to the present invention contains lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms, and has a 2θ １ = 17.8 ± 0.5°, and the diffraction peak is at the position 2θ １ and the position 2θ of the diffraction peak closest to the diffraction peak. ２ The difference between (|2θ １ -2θ ２ |) is less than 0.5°.

[0007] According to the present invention, α-Li having room temperature stability is ３ P.S. ４ It is possible to provide a crystalline sulfide solid electrolyte having a novel structure having the following basic structure:

[0008] 1 is an X-ray diffraction pattern of a crystalline sulfide solid electrolyte obtained in an example; 2 is an X-ray diffraction pattern of a crystalline sulfide solid electrolyte obtained in an example; 3 is an X-ray diffraction pattern of a crystalline sulfide solid electrolyte obtained in a comparative example; 4 is an X-ray diffraction pattern of a crystalline sulfide solid electrolyte obtained in an example; ３１ P-NMR spectrum.

[0009] 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 expressed by "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.

[0010] (Findings Obtained by the Inventors to Achieve the Present Invention) As a result of intensive research to solve the above-mentioned problems, the inventors have found the following and have completed the present invention. ３ P.S. ４ The crystal structure based on the basic skeleton includes α-Li ３ P.S. ４ (hereinafter simply referred to as "α phase (high temperature phase)" or "α phase"), β-Li ３ P.S. ４ (hereinafter simply referred to as "β phase (medium temperature phase)" or "β phase"), γ-Li ３ P.S. ４ It is known that crystal structures such as the α phase (room temperature phase) and the γ phase (hereinafter also referred to simply as "γ phase" or "γ phase") exist. The α phase (high temperature phase) is known to have higher ionic conductivity than other phases, and the inventors focused on a crystalline sulfide solid electrolyte having the α phase (high temperature phase). Although the α phase (high temperature phase) can be expressed by heating at a high temperature of 400 to 500 ° C., it is known to undergo a phase transition to the stable β phase (intermediate temperature phase) and γ phase (room temperature phase) in the process of returning to room temperature. In other words, the α phase (high temperature phase) is known to lack stability. Therefore, it is difficult to produce a crystalline sulfide solid electrolyte having the α phase (high temperature phase) unless a special production method such as rapid cooling is used.

[0011] As described above, in Patent Documents 1 to 3, the basic skeleton of lithium atoms, phosphorus atoms, and sulfur atoms is Li ３ P.S. ４In addition to atoms capable of forming α-type cations, solid electrolytes containing atoms such as halogen atoms and oxygen atoms are disclosed. These patent documents disclose the technical idea of ​​improving ionic conductivity and stability such as thermal stability and chemical stability by using atoms such as halogen atoms and oxygen atoms. However, there is no disclosure that the use of these atoms can produce an α-phase (high-temperature phase) or further impart room temperature stability to the α-phase (high-temperature phase). Furthermore, the stabilities such as thermal stability and chemical stability in these patent documents all refer to stability against exothermic heating due to an oxidation-reduction reaction with oxygen contained in the positive electrode active material, and do not mean that room temperature stability can be imparted to a crystalline phase that is inherently poorly stable at room temperature.

[0012] As described above, in the prior art, special production methods such as rapid cooling have been known for focusing on the α phase (high-temperature phase) and producing a crystalline sulfide solid electrolyte having this phase, but methods that allow for easy production are not widely known and have not received much attention.

[0013] While developing methods for more easily stabilizing crystalline sulfide solid electrolytes having an α-phase (high-temperature phase), the inventors focused on replacing some of the sulfur atoms with oxygen atoms. Further development led to the discovery that a crystalline sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms and having a specific diffraction peak due to the α-phase (high-temperature phase) has a novel structure called an α-phase (high-temperature phase) that is stable at room temperature and has high ionic conductivity. The use of halogen atoms and the substitution of some of the sulfur atoms with oxygen atoms to provide a specific diffraction peak can impart room temperature stability to a crystalline phase that is inherently unstable at room temperature. This is a surprising phenomenon that has not been recognized at all until now, as previously mentioned, and is not disclosed in Patent Documents 1 to 3.

[0014] In this specification, the term "solid electrolyte" refers to an electrolyte that maintains a solid state under a nitrogen atmosphere at 25° C. The "sulfide solid electrolyte" of this embodiment is a solid electrolyte that contains oxygen atoms in addition to lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and has ionic conductivity due to the lithium atoms.

[0015] The term "sulfide solid electrolyte" includes both crystalline sulfide solid electrolytes having a crystalline structure and amorphous sulfide solid electrolytes. In this specification, a crystalline sulfide solid electrolyte is a solid electrolyte in which a peak derived from the solid electrolyte is observed in the X-ray diffraction pattern in powder X-ray diffraction (XRD) measurement, regardless of whether or not a peak derived from the raw material of the solid electrolyte is present. That is, a crystalline sulfide solid electrolyte includes a crystalline structure derived from the solid electrolyte, and a portion 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 sulfide solid electrolyte has the X-ray diffraction pattern described above, it may also include an amorphous sulfide solid electrolyte (also referred to as a "glass component") as a portion of the crystalline sulfide solid electrolyte. Therefore, the crystalline sulfide solid electrolyte includes so-called glass ceramics obtained by heating an amorphous solid electrolyte (glass component) above its crystallization temperature.

[0016] In this specification, the amorphous sulfide solid electrolyte (glass component) refers to a solid electrolyte in which the X-ray diffraction pattern in powder X-ray diffraction (XRD) measurement is a halo pattern in which no peaks other than those derived from the material are observed, and it does not matter whether or not there are peaks derived from the raw materials of the solid electrolyte.

[0017] (Regarding various aspects of the present embodiment) The sulfide solid electrolyte according to a first aspect of the present embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms, and has a 2θ １ = 17.8 ± 0.5°, and the diffraction peak is at the position 2θ １ and the position 2θ of the diffraction peak closest to the diffraction peak. ２ The difference between (|2θ １ -2θ２ |) is less than 0.5°.

[0018] As described above, the crystalline sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms, and has the above-mentioned predetermined diffraction peaks, thereby providing a novel structure called an α-phase (high-temperature phase) that is stable at room temperature and exhibiting high ionic conductivity. The crystalline sulfide solid electrolyte of this embodiment contains oxygen atoms and halogen atoms, among the various constituent atoms, to thereby exhibit a diffraction peak at 2θ = 17.8 ± 0.5°, and the diffraction peak position 2θ １ and the position 2θ of the diffraction peak closest to the diffraction peak. ２ The difference between (|2θ １ -2θ ２ By making the angle | less than 0.5°, a novel structure called an α phase (high temperature phase) that is stable at room temperature is provided.

[0019] The reason why the crystalline sulfide solid electrolyte of this embodiment has a novel structure called an α-phase (high-temperature phase) that is stable at room temperature is thought to be largely due to the fact that oxygen atoms are incorporated into part of the structure of the sulfide solid electrolyte by substituting some of the sulfur atoms, since this novel structure would not be realized if oxygen atoms were not contained. Furthermore, it is thought that the inclusion of halogen atoms also enables high ionic conductivity.

[0020] Usually, Li ３ P.S. ４The α-phase (high-temperature phase) of the composition appears in the high-temperature region and transitions to the β-phase (intermediate-temperature phase) and γ-phase (room-temperature phase) at room temperature. This is because, when heated, thermal expansion results in a crystal lattice size that stabilizes the α-phase (high-temperature phase). However, when the temperature is returned to room temperature, the crystal lattice size decreases, making it impossible to maintain the α-phase (high-temperature phase), and transitions to the β-phase (intermediate-temperature phase) and γ-phase (room-temperature phase). According to the research of the present researchers, it has been confirmed that the use of oxygen atoms shifts the diffraction peak angle of a crystalline sulfide solid electrolyte having a thiolicon region II crystal structure to a higher angle, i.e., the entire crystal lattice becomes smaller. This is because oxygen atoms with a small ionic radius are substituted for some of the sulfur atoms, resulting in the PS lattice, which forms the basic skeleton of the thiolicon region II crystal structure. ４ This means that the crystal lattice size of the skeleton is small. From this, it is thought that oxygen atoms with a small ionic radius replace some of the sulfur atoms. By replacing some of the sulfur atoms with oxygen atoms with a small ionic radius, the entire crystal lattice becomes smaller, and by heating to high temperatures, the α-phase (high-temperature phase), which is difficult to appear and exist unless the crystal lattice size is expanded, can be adjusted to a crystal lattice size that is more likely to be stabilized. Therefore, the room temperature stability of the α-phase (high-temperature phase) is improved. Furthermore, the inclusion of halogen atoms is thought to facilitate the skeletal arrangement of the α-phase (high-temperature phase) and also contribute to improving ionic conductivity.

[0021] When there are diffraction peaks other than those due to the novel structure of the α phase (high-temperature phase) that is stable at room temperature, the difference in the positions of these diffraction peaks (|2θ １ -2θ ２ If the angle | is less than 0.5°, it means that a novel structure called an α-phase (high temperature phase) that is stable at room temperature is more stably present, and other structures such as a β-phase (intermediate temperature phase) are not present, or even if they are present, they are present in trace amounts. Therefore, the crystalline sulfide solid electrolyte of this embodiment has higher ionic conductivity. Thus, it is considered that the crystalline sulfide solid electrolyte of this embodiment has a novel structure called an α-phase (high temperature phase) that is stable at room temperature and has high ionic conductivity.

[0022] The crystalline sulfide solid electrolyte according to a second aspect of the present embodiment is the crystalline sulfide solid electrolyte according to the first aspect, wherein the oxygen atom (M Ｏ ) the sulfur atom (M Ｓ ) to the ratio (M Ｏ / M Ｓ ) is equal to or greater than 0.0025 and equal to or less than 0.25.

[0023] As described above, in the crystalline sulfide solid electrolyte of this embodiment, oxygen atoms are considered to substitute for some of the sulfur atoms. When the ratio of oxygen atoms to sulfur atoms is within the above range, that is, when the ratio of sulfur atoms substituted with oxygen atoms is within the above range, a novel structure called an α-phase (high-temperature phase) that is stable at room temperature is easily formed, and ionic conductivity is improved.

[0024] The crystalline sulfide solid electrolyte according to a third aspect of the present embodiment is the crystalline sulfide solid electrolyte of the first or second aspect, which has a composition represented by the following composition formula (1): (100-y)(0.5)(Li ３＋２ｚ P (S １－ｘ O ｘ ) ４＋ｚ )+(y)LiX (1) (In the composition formula (1), x, y, and z each satisfy 0.0025≦x≦0.15, 0.010≦y<25.0, and −0.17≦z≦1.5, and X represents a halogen atom.)

[0025] The crystalline sulfide solid electrolyte of this embodiment, having the composition represented by the composition formula (1), is likely to exhibit a novel structure called an α-phase (high-temperature phase) that is stable at room temperature, thereby facilitating the attainment of high ionic conductivity. The halogen atoms contained in the crystalline sulfide solid electrolyte of this embodiment are supplied by a halogen-atom-containing raw material, such as lithium halide or an elemental halogen, but lithium halide is particularly expensive. Because the lithium, phosphorus, sulfur, oxygen, and halogen atoms that constitute the solid electrolyte are contained in a balanced manner, even if the halogen atom content is low, i.e., even if the amount of halogen-atom-containing raw material used is reduced, the main effect of halogen atoms, which is the improvement in ionic conductivity, is likely to be obtained. As a result, high ionic conductivity is likely to be obtained while reducing raw material costs.

[0026] The crystalline sulfide solid electrolyte according to a fourth aspect of the present embodiment is any one of the first to third aspects, wherein: ３１ P-NMR measurement revealed that PSO was 34.0±5.0 ppm. ３ ３－ A peak due to the above is observed. The crystalline sulfide solid electrolyte according to a fifth aspect is the crystalline sulfide solid electrolyte according to any one of the first to fourth aspects, ３１ P-NMR measurement revealed that PO was present at 6.0±5.0 ppm. ４ ３－ A peak due to this is observed.

[0027] solid ３１ When the above peaks are observed by P-NMR measurement, the crystalline sulfide solid electrolyte of this embodiment has a 2θ １ As a result, the crystalline silicon has a novel structure called the α phase (high-temperature phase) that is stable at room temperature, and high ionic conductivity is easily obtained.

[0028] The crystalline sulfide solid electrolyte according to a sixth aspect of the present embodiment is any one of the first to fifth aspects, wherein at least two exothermic peaks are measured in thermogravimetric differential calorimetry (measured at a heating rate of 10°C / min), and the temperature difference between the peak tops of the two exothermic peaks is 30.0°C or more and 130.0°C or less.

[0029] When the above two exothermic peaks are observed in the thermogravimetric differential calorimetry, the crystalline sulfide solid electrolyte of the present embodiment has a 2θ １ As a result, the crystalline silicon has a novel structure called the α phase (high-temperature phase) that is stable at room temperature, and high ionic conductivity is easily obtained.

[0030] A crystalline sulfide solid electrolyte according to a seventh aspect of the present embodiment is any one of the first to sixth aspects, wherein the halogen atom is at least one halogen atom selected from a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0031] Higher ionic conductivity is more easily obtained by employing, as the halogen atom, at least one halogen atom selected from a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, that is, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom alone, or two or more halogen atoms selected from these atoms.

[0032] The crystalline sulfide solid electrolyte according to an eighth aspect of the present embodiment is any one of the first to seventh aspects, wherein the ionic conductivity is 0.85 mS / cm or more.

[0033] The crystalline sulfide solid electrolyte of the present embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms and has a predetermined diffraction peak, and therefore has high ionic conductivity as in the above range.

[0034] A crystalline sulfide solid electrolyte according to a ninth aspect of the present embodiment is any one of the first to eighth aspects, wherein the oxygen atoms are P ２ O ５The theory is that it originates from

[0035] When producing the crystalline sulfide solid electrolyte of this embodiment, P ２ O ５ By adopting this, some of the sulfur atoms can be easily replaced with oxygen atoms, and therefore oxygen atoms can be easily incorporated into the structure of the solid electrolyte. １ As a result, the crystalline silicon has a novel structure called an α phase (high-temperature phase) that is stable at room temperature, and high ionic conductivity is easily obtained.

[0036] The crystalline sulfide solid electrolyte according to a tenth aspect of the present embodiment is any one of the first to ninth aspects, wherein the crystalline sulfide solid electrolyte is a glass ceramic.

[0037] As described above, glass ceramics are obtained by heating an amorphous solid electrolyte (glass component) to a temperature equal to or higher than the crystallization temperature. The crystalline sulfide solid electrolyte thus obtained has a 2θ １ As a result, the crystalline silicon has a novel structure called an α phase (high-temperature phase) that is stable at room temperature, and high ionic conductivity is easily obtained.

[0038] [Crystalline sulfide solid electrolyte] The crystalline sulfide solid electrolyte of the present embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms, and has a 2θ １ = 17.8 ± 0.5°.

[0039] (Diffraction Peak) The crystalline sulfide solid electrolyte of the present embodiment has a 2θ diffraction peak in X-ray diffraction measurement using CuKα rays. １= 17.8 ± 0.5°, it is a "crystalline" sulfide solid electrolyte. The peak position of the diffraction peak of the crystalline sulfide solid electrolyte of this embodiment varies depending on the peak position, but as already described, may vary within a range of ± 0.5°, further ± 0.4°, or ± 0.3°. Furthermore, the measurement method for X-ray diffraction measurement using CuKα radiation in this specification will be described in the Examples.

[0040] 2θ １ The crystal structure exhibiting a diffraction peak at 2θ = 17.8 ± 0.5° is a novel structure called an α phase (high temperature phase) having room temperature stability in a crystalline sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms. １ The diffraction peak at θ = 17.8 ± 0.5 ° is a diffraction peak specific to the crystalline sulfide solid electrolyte of this embodiment in the crystalline sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms.

[0041] (Diffraction Peak Split Width) The crystalline sulfide solid electrolyte of the present embodiment has a 2θ １ = 17.8 ± 0.5 °, the crystalline sulfide solid electrolyte of this embodiment can be said to be a solid electrolyte that mainly has a crystalline structure resulting from this diffraction peak, i.e., a novel structure called the α phase (high-temperature phase) that is stable at room temperature. Here, the criterion for determining "mainly" is, for example, if the ratio of a certain crystalline structure to the total crystalline structure is 60% or more, it can be said that the certain crystalline structure (the above-mentioned novel structure) is mainly present, and if it is in between, i.e., more than 40% but less than 60%, it can be said that other crystalline structures are mixed in.

[0042] In the crystalline sulfide solid electrolyte of this embodiment, the position 2θ of the diffraction peak １ and 2θ １ The position 2θ of the diffraction peak closest to the diffraction peak ２ The difference between the diffraction peak splitting width and the diffraction peak splitting width (|2θ １ -2θ ２|) is less than 0.5°. If the diffraction peak splitting width is less than 0.5°, a novel structure called the α phase (high temperature phase) which is stable at room temperature is more stably present, and other structures such as the β phase (medium temperature phase) are not present, or even if they are present, they are in trace amounts. １ In some cases, a diffraction peak due to a structure other than the α phase (high temperature phase), for example, a β phase (medium temperature phase), appears near the diffraction peak of 2θ １ Even if structures other than the α phase (high-temperature phase) are included, if the diffraction peaks due to the other structures are small, the 2θ １ The diffraction peaks are difficult to observe as if they are split, and the diffraction peak split width (|2θ １ -2θ ２ That is, the diffraction peak split width (|2θ １ -2θ ２ If the diffraction peak splitting width (|2θ) is small, the proportion of a novel structure called the α phase (high temperature phase) that is stable at room temperature in the crystalline sulfide solid electrolyte increases. １ -2θ ２ |) is preferably 0.4° or less, more preferably 0.3° or less, even more preferably 0.2° or less, and still more preferably 0.1° or less, since the proportion of the α phase (high temperature phase) which is stable at room temperature increases as the | is smaller.

[0043] Also, 2θ １ The position 2θ of the diffraction peak closest to the diffraction peak ２ The diffraction peak split width (|2θ １ -2θ ２ |) is within the above range, and from the viewpoint of making it easier to make the peak split width less than 0.5°, the diffraction angle is preferably 17.4° or more, more preferably 17.6° or more, and even more preferably 17.7° or more, with the upper limit being preferably 18.2° or less, more preferably 18.1° or less.

[0044] When the crystalline sulfide solid electrolyte of the present embodiment has a crystal structure including an α phase (high-temperature phase) and another crystal structure, the diffraction peak split width (|2θ １ -2θ ２It is also possible to determine the type of crystal structure a substance has by using the diffraction peak split width (|2θ １ -2θ ２ |) is 0.5° or more, the diffraction peak is １ and 2θ ２ Since it is observed that the diffraction peak is clearly split into α phase (high temperature phase) and β phase (medium temperature phase), it has β phase (medium temperature phase) as the main crystal structure (the proportion of β phase (medium temperature phase) is 60% or more), and it can be judged that it cannot be said that the main crystal structure is α phase (high temperature phase). On the other hand, the diffraction peak split width (|2θ １ -2θ ２ When the diffraction peak splitting width (|2θ) is greater than 0.3° and less than 0.5°, it can be determined that the α phase (high temperature phase) is mixed with the β phase, and the proportion of the α phase (high temperature phase) is greater than 40% and less than 60%. １ -2θ ２ If the difference |) is 0.3° or less, it can be determined that the α phase (high-temperature phase) is the main crystal structure.

[0045] The crystalline sulfide solid electrolyte of this embodiment preferably has at least one peak at 2θ = 26.0°, 29.2°, or 29.9° as a peak other than the above diffraction peak. Further improvement in crystallinity results in the appearance of these peaks, resulting in higher ionic conductivity. As mentioned above, the positions of these diffraction peaks fluctuate within a range of ±0.5°, further ±0.4°, or ±0.3°.

[0046] (Constituent Atoms) The crystalline sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. Among these halogen atoms, fluorine atoms, chlorine atoms, and bromine atoms are preferred, and fluorine atoms and chlorine atoms are more preferred. The halogen atoms may contain these atoms alone or multiple types of atoms.

[0047] The oxygen atoms in the crystalline sulfide solid electrolyte of this embodiment are P ２ O ５The method for producing the crystalline sulfide solid electrolyte of this embodiment is not particularly limited as long as it contains lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms and has the above-mentioned diffraction peak. There are also no particular limitations on the raw materials used, but in consideration of the ease of replacing some of the sulfur atoms in the structure of the crystalline sulfide solid electrolyte with oxygen atoms, P is preferably used as a raw material containing oxygen atoms. ２ O ５ It is preferred to use

[0048] Furthermore, the crystalline sulfide solid electrolyte of this embodiment preferably does not contain at least one metal atom selected from sodium atoms, boron atoms, aluminum atoms, silicon atoms, germanium atoms, arsenic atoms, selenium atoms, antimony atoms, tellurium atoms, lead atoms, and bismuth atoms. By not containing these atoms, the crystalline sulfide solid electrolyte of this embodiment has a 2θ １ = 17.8 ± 0.5° diffraction peak is likely to appear. As a result, it has a novel structure called an α phase (high temperature phase) that is stable at room temperature, and high ionic conductivity is likely to be obtained. Here, not containing metal atoms literally means not containing any metal atoms at all (i.e., 0 mass%), but also includes cases where metal atoms are unavoidably mixed in. In this case, the content is 3 mass% or less, 2 mass% or less, 1 mass% or less, 0.5 mass% or less, 0.3 mass% or less, or 0.1 mass% or less based on the total amount of the crystalline sulfide solid electrolyte.

[0049] (Composition) As described above, the crystalline sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms, and has the above-mentioned diffraction peak, i.e., 2θ １ = 17.8 ± 0.5 °. From the viewpoint of having such a diffraction peak, it is preferable to have a predetermined composition. Hereinafter, a preferred embodiment of the composition of the crystalline sulfide solid electrolyte of this embodiment will be described.

[0050] The crystalline sulfide solid electrolyte of this embodiment has an oxygen atom (M Ｏ ) sulfur atom (M Ｓ ) to the ratio (M Ｏ / MＳ ) is preferably 0.0025 or more and 0.25 or less. With such a ratio, a novel structure called an α phase (high temperature phase) that is stable at room temperature is easily developed, and ionic conductivity is improved. From the same viewpoint, the ratio (M Ｏ / M Ｓ ) is preferably 0.0050 or more, more preferably 0.010 or more, even more preferably 0.015 or more, and still more preferably 0.020 or more, and the upper limit is preferably 0.20 or less, more preferably 0.175 or less, even more preferably 0.15 or less, and still more preferably 0.125 or less.

[0051] The crystalline sulfide solid electrolyte of the present embodiment preferably has a composition represented by the following composition formula (1): １ The type and composition of atoms constituting the crystalline sulfide solid electrolyte of this embodiment can be confirmed, for example, by an ICP optical emission spectrometer.

[0052] (100-y)(0.5)(Li ３＋２ｚ P (S １－ｘ O ｘ ) ４＋ｚ )+(y)LiX (1)

[0053] In the composition formula (1), x, y, and z satisfy the following conditions: 0.0025≦x≦0.15, 0.010≦y<25.0, and −0.17≦z≦1.5, respectively. X represents a halogen atom.

[0054] x represents the substitution rate of oxygen atoms when some sulfur atoms are replaced with oxygen atoms. x satisfies 0.0025≦x≦0.15, and from the viewpoint of easily exhibiting the above-mentioned diffraction peak and thus having a novel structure called an α-phase (high-temperature phase) that is stable at room temperature and obtaining high ionic conductivity, x is preferably 0.0050 or more, more preferably 0.010 or more, and even more preferably 0.015 or more, with the upper limit being preferably 0.12 or less, more preferably 0.10 or less, even more preferably 0.090 or less, and still more preferably 0.080 or less.

[0055] Representative numerical ranges of x are 0.0025 or more and 0.15 or less, 0.0025 or more and 0.12 or less, 0.0025 or more and 0.10 or less, 0.0025 or more and 0.090 or less, 0.0025 or more and 0.080 or less, 0.0050 or more and 0.15 or less, 0.0050 or more and 0.12 or less, 0.0050 or more and 0.10 or less, 0.0050 or more and 0.090 or less, 0.0050 or more and 0.080 or less, Preferred examples thereof include 0.080 or less, 0.010 to 0.15, 0.010 to 0.12, 0.010 to 0.10, 0.010 to 0.090, 0.010 to 0.080, 0.015 to 0.15, 0.015 to 0.12, 0.015 to 0.10, 0.015 to 0.090, and 0.015 to 0.080.

[0056] The symbol y represents the content of halogen atoms. For convenience, the composition formula (1) is expressed in the form of LiX (lithium halide), but the raw material containing halogen atoms is not limited to lithium halide, and may be, for example, a simple halogen, as will be described later.

[0057] y satisfies 0.010≦y<25.0, and makes it easier for the above-mentioned diffraction peaks to appear. As a result, from the viewpoint of having a novel structure called an α-phase (high-temperature phase) that is stable at room temperature and obtaining high ionic conductivity, y is preferably 0.050 or more, more preferably 0.10 or more, even more preferably 0.30 or more, and still more preferably 0.50 or more, with the upper limit being preferably 22.0 or less, more preferably 20.0 or less, even more preferably 15.0 or less, still more preferably 10.0 or less, and particularly preferably 7.5 or less.

[0058] Representative numerical ranges for y are 0.010 or more and less than 25.0, 0.010 or more and less than 22.0, 0.010 or more and less than 20.0, 0.010 or more and less than 15.0, 0.010 or more and less than 10.0, 0.010 or more and less than 7.5, 0.050 or more and less than 25.0, 0.050 or more and less than 22.0, 0.050 or more and less than 20.0, 0.050 or more and less than 15.0, 0.050 or more and less than 10.0, 0.050 or more and less than 7.5, 0.10 or more and less than 25.0, 0.10 or more and less than 22.0, 0.10 Preferred examples thereof include 0.50 or less than 25.0, 0.50 or less than 22.0, 0.50 or less than 20.0, 0.10 or more and 15.0, 0.10 or more and 10.0, 0.10 or more and 7.5, 0.30 or more and less than 25.0, 0.30 or more and 22.0, 0.30 or more and 20.0, 0.30 or more and 15.0, 0.30 or more and 10.0, 0.30 or more and 7.5, 0.50 or more and less than 25.0, 0.50 or more and 22.0, 0.50 or more and 20.0, 0.50 or more and 15.0, 0.50 or more and 10.0, and 0.50 or more and 7.5.

[0059] z is α-Li ３ P.S. ４ z satisfies −0.17≦z≦1.5, and from the viewpoint of easily exhibiting the above-mentioned diffraction peak and, as a result, having a novel structure called an α-phase (high-temperature phase) that is stable at room temperature and obtaining high ionic conductivity, it is preferably −0.15 or more, more preferably −0.10 or more, and even more preferably −0.050 or more, with the upper limit being preferably 1.0 or less, more preferably 0.80 or less, even more preferably 0.40 or less, and still more preferably 0.20 or less.

[0060] Representative numerical ranges of z include -0.17 or more and 1.5 or less, -0.17 or more and 1.0 or less, -0.17 or more and 0.80 or less, -0.17 or more and 0.40 or less, -0.17 or more and 0.20 or less, -0.15 or more and 1.5 or less, -0.15 or more and 1.0 or less, -0.15 or more and 0.80 or less, -0.15 or more and 0.40 or less, and -0.15 or more and 0.20 or less. Preferred examples include -0.10 or more and 1.5 or less, -0.10 or more and 1.0 or less, -0.10 or more and 0.80 or less, -0.10 or more and 0.40 or less, -0.10 or more and 0.20 or less, -0.050 or more and 1.5 or less, -0.050 or more and 1.0 or less, -0.050 or more and 0.80 or less, -0.050 or more and 0.40 or less, and -0.050 or more and 0.20 or less.

[0061] The product of x and y (x × y) is preferably 0.0010 or more, more preferably 0.0050 or more, even more preferably 0.010 or more, and even more preferably 0.025 or more, with the upper limit being preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and even more preferably 1.25 or less. As mentioned above, x and y can each take any value selected from the above range, but by adopting x and y such that the product of x and y (x × y) falls within the above range, the above x and y will take well-balanced values, making it easier to express the diffraction peak, and as a result, it becomes easier to obtain a novel structure called an α-phase (high-temperature phase) that is stable at room temperature, and it becomes easier to obtain high ionic conductivity.

[0062] Representative preferred numerical ranges for the product of x and y (x × y) include 0.0010 or more and 2.5 or less, 0.0010 or more and 2.0 or less, 0.0010 or more and 1.5 or less, 0.0010 or more and 1.25 or less, 0.0050 or more and 2.5 or less, 0.0050 or more and 2.0 or less, 0.0050 or more and 1.5 or less, 0.0050 or more and 1.25 or less, 0.010 or more and 2.5 or less, 0.010 or more and 2.0 or less, 0.010 or more and 1.5 or less, 0.010 or more and 1.25 or less, 0.025 or more and 2.5 or less, 0.025 or more and 2.0 or less, 0.025 or more and 1.5 or less, and 0.025 or more and 1.25 or less.

[0063] In the composition formula (1), X represents a halogen atom. The halogen atom is the same as the halogen atom described as a constituent atom of the crystalline sulfide solid electrolyte of this embodiment.

[0064] (solid ３１ P-NMR spectrum) The crystalline sulfide solid electrolyte of this embodiment is a solid ３１ P-NMR measurement revealed that PSO ３ ３－ It is preferable that a peak due to PO is observed at 6.0±5.0 ppm. ４ ３－ It is preferable that a peak due to the above is observed. ３１ The method for P-NMR measurement will be explained in the examples. ３１ The peaks measured by P-NMR may fluctuate within a range of ±5.0 ppm, and further within a range of ±4.0 ppm, ±3.0 ppm, or ±2.0 ppm.

[0065] PSO ３ ３－ Peaks due to and PO ４ ３－ The peak due to indicates that at least the crystalline sulfide solid electrolyte of this embodiment has oxygen atoms in its structure. ３１ The crystalline sulfide solid electrolyte having the above peak in the P-NMR spectrum has oxygen atoms incorporated into its structure, that is, some of the sulfur atoms are replaced by oxygen atoms, and therefore the above 2θ １ = 17.8 ± 0.5°. As a result, a novel structure called an α phase (high temperature phase) that is stable at room temperature is easily obtained, and high ionic conductivity is easily obtained.

[0066] (Exothermic Peak) The crystalline sulfide solid electrolyte of this embodiment preferably exhibits at least two exothermic peaks in thermogravimetric differential calorimetry (measured at a heating rate of 10° C. / min), with the temperature difference between the peak tops of the two exothermic peaks being 30.0° C. or more and 130.0° C. or less. The method for thermogravimetric differential calorimetry in this specification will be described in the examples.

[0067] When the above two exothermic peaks are observed in the thermogravimetric differential calorimetry, the crystalline sulfide solid electrolyte of the present embodiment has a 2θ １ = 17.8 ± 0.5° is likely to appear. In this case, when the temperature of the lower peak top of the two exothermic peaks is Tc1 and the temperature of the higher peak top is Tc2, the temperature difference between the peak tops (ΔTc = Tc2 - Tc1) is preferably 30.0 °C or more and 130.0 °C or less, as described above. The lower limit of the temperature difference is preferably 35.0 °C or more, more preferably 40.0 °C or more, and the upper limit is preferably 125 °C or less.

[0068] In thermogravimetric differential calorimetry, the peak top temperature (Tc1) of the exothermic peak on the low temperature side is not particularly limited in terms of its lower limit, but 2θ １ Considering the ease with which a diffraction peak of 17.8±0.5° appears, the temperature is preferably 180° C. or higher, more preferably 190° C. or higher, and even more preferably 200° C. or higher, with the upper limit being preferably 330° C. or lower, more preferably 300° C. or lower, and even more preferably 275° C. or lower. The peak top temperature (Tc2) of the exothermic peak on the higher temperature side is preferably 190° C. or higher, more preferably 200° C. or higher, even more preferably 220° C. or higher, and even more preferably 240° C. or higher.

[0069] 2θ １It can be said that a crystalline sulfide solid electrolyte having a diffraction peak at 2θ = 17.8 ± 0.5° is one in which the above two exothermic peaks are easily observed. The observation of these two exothermic peaks means that a crystalline sulfide solid electrolyte, particularly a crystalline sulfide solid electrolyte having an α phase (high-temperature phase) that exhibits high ionic conductivity, is easily obtained. Therefore, when the above two exothermic peaks are observed in thermogravimetric differential calorimetry, the above 2θ １ = 17.8 ± 0.5°, and as a result, a novel structure called an α phase (high temperature phase) that is stable at room temperature is easily obtained, and high ionic conductivity is easily obtained.

[0070] (Ionic Conductivity) The ionic conductivity of the crystalline sulfide solid electrolyte of this embodiment can be 0.85 mS / cm or more, further 0.90 mS / cm or more, or 1.0 mS / cm or more. Thus, the crystalline sulfide solid electrolyte of this embodiment has high ionic conductivity.

[0071] For example, when the amount of raw material containing halogen atoms used is small, more specifically, even when y in the above composition formula (1) is as small as 10.0 or less, the ionic conductivity can be 0.85 mS / cm or more, or even 1.0 mS / cm or more, 1.1 mS / cm or more, 1.3 mS / cm or more, or 1.5 mS / cm or more. On the other hand, when the amount of raw material containing halogen atoms used is large, more specifically, even when y in the above composition formula (1) is as large as more than 10.0, the ionic conductivity can be 0.85 mS / cm or more, or even 1.0 mS / cm or more, 1.1 mS / cm or more, or 1.2 mS / cm or more.

[0072] (Other Crystal Structures) The crystalline sulfide solid electrolyte of this embodiment has a 2θ １ The α-phase (high temperature phase) has a novel structure that can exhibit a diffraction peak at 17.8±0.5° and is stable at room temperature, but other crystal structures may also be used. Examples of other crystal structures include the thiolicon region II crystal structure, the LGPS crystal structure, and other α-phases (high temperature phases) that have the same structure as the Li- ３ P.S. ４ A preferred example is a crystal structure having the following basic structure:

[0073] The thiolicon region II crystal structure is, for example, Li ４－ｘ Ge １－ｘ P ｘ S ４ Thio-LISICON Region II crystal structure (Kanno et al., Journal of the Electrochemical Society, 148(7)A742-746(2001)), Li ４－ｘ Ge １－ｘ P ｘ S ４ Examples of the LGPS type crystal structure include those having a crystal structure similar to the thio-LISICON Region II type (see Solid State Ionics, 177 (2006), 2721-2725). ３＋ｘ P.S. ４－ｙ O ｙ (x satisfies −1≦x≦1, and y satisfies 0<y<4) (also referred to as “Li—P—S—O-based sulfide solid electrolyte”).

[0074] The α phase (high temperature phase) of the crystalline sulfide solid electrolyte of this embodiment can be formed without using an amorphous solid electrolyte (glass component), or can be formed as a so-called glass ceramic obtained by heating an amorphous solid electrolyte (glass component) to a temperature above its crystallization temperature. From the viewpoint of further improving the crystallinity and thereby obtaining higher ionic conductivity, the crystalline sulfide solid electrolyte of this embodiment is preferably a glass ceramic. The same applies to the above-mentioned thiolisilicon region II crystal structure and LGPS crystal structure. Here, the above-mentioned "Li ４－ｘ Ge １－ｘ P ｘ S ４The notation of the crystal structure "thio-LISICON Region II type" means that the crystal structure was found in the above document to be composed of Li, Ge, P, and S atoms. The sulfide solid electrolyte obtained by the production method of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and therefore, is not a "Li ４－ｘ Ge １－ｘ P ｘ S ４ "Li in thio-LISICON Region II type" ４－ｘ Ge １－ｘ P ｘ S ４ However, when the sulfide solid electrolyte obtained by the manufacturing method of this embodiment has the same diffraction peak as the above-mentioned "thiolisiconregion II type crystal structure" (including the above-mentioned "similar crystal structure"), it can be said that the sulfide solid electrolyte obtained by the manufacturing method of this embodiment has a thiolisiconregion II type crystal structure formed by lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms.

[0075] [Applications] The crystalline sulfide solid electrolyte of the present embodiment has high ionic conductivity while reducing raw material costs, and has excellent battery performance. Therefore, it is suitable for use in, for example, an electrode composite in combination with an electrode active material, or in a lithium ion battery.

[0076] When the sulfide solid electrolyte of this embodiment is used in a lithium ion battery, it may be used in the positive electrode layer, the negative electrode layer, or the electrolyte layer. When used in the positive electrode layer, it can be used as an electrode composite containing the crystalline sulfide solid electrolyte of this embodiment and a positive electrode active material, and when used in the negative electrode layer, it can be used as an electrode composite containing the crystalline sulfide solid electrolyte of this embodiment and a negative electrode active material. Furthermore, the crystalline sulfide solid electrolyte may be used as it is in the electrolyte layer.

[0077] [Electrode Mixture] As described above, the electrode mixture contains the crystalline sulfide solid electrolyte of the present embodiment and an electrode active material. Depending on whether the electrode mixture is used for a positive electrode or a negative electrode, a positive electrode active material or a negative electrode active material is adopted as the electrode active material.

[0078] The positive electrode active material can be any material that can promote a battery chemical reaction involving the movement of lithium ions due to atoms that are used to exhibit ionic conductivity, preferably lithium atoms, in relation to the negative electrode active material. Examples of such positive electrode active materials that can insert and extract lithium ions include oxide-based positive electrode active materials and sulfide-based positive electrode active materials.

[0079] Oxide-based positive electrode active materials include 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 (LiMeNPO ４ , Me=Fe, Co, Ni, Mn) and other lithium-containing transition metal composite oxides are preferred. Examples of sulfide-based positive electrode active materials include titanium sulfide (TiS ２ ), molybdenum sulfide (MoS ２ ), iron sulfide (FeS, FeS ２ ), copper sulfide (CuS), nickel sulfide (Ni ３ S ２ In addition to the above positive electrode active materials, niobium selenide (NbSe) ３ The positive electrode active material may be used alone or in combination of two or more.

[0080] The negative electrode active material can be any atom capable of exhibiting ionic conductivity, preferably a metal capable of forming an alloy with lithium atoms, its oxide, or an alloy of the metal with lithium atoms, as long as it can promote the battery chemical reaction involving the transfer of lithium ions due to lithium atoms. As such a negative electrode active material capable of intercalating and deintercalating lithium ions, any material known in the battery field as a negative electrode active material can be used without limitation. For example, when constructing a lithium-ion battery, such a negative electrode active material can be used. Examples of such a negative electrode active material include silicon-based active materials such as Si, Si alloys, and silicon oxide; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metals capable of forming alloys with metallic lithium or metallic lithium, such as metallic lithium, metallic indium, metallic aluminum, metallic silicon, and metallic tin, oxides of these metals, and alloys of these metals with metallic lithium.

[0081] The electrode active material may have a coating layer on its surface. Examples of materials for forming the coating layer include ion conductors such as nitrides, oxides, or composites of atoms that exhibit ionic conductivity in the sulfide solid electrolyte, preferably lithium atoms. Specifically, lithium nitride (Li ３ N), Li ４ GeO ４ The main structure is, for example, Li ４－２ｘ Zn ｘ GeO ４ Conductors having a lysicone-type crystal structure such as Li ３ P.O. ４ For example, Li ４－ｘ Ge １－ｘ P ｘ S ４ Conductors having a thiolicon-type crystal structure such as La ２／３－ｘ Li ３ｘ TiO ３ Conductors having a perovskite crystal structure such as LiTi ２ (P.O. ４ ) ３ Conductors having a NASICON type crystal structure such as Li ｙTi ３－ｙ O ４ (0<y<3), Li ４ Ti ５ O １２ Lithium titanate (LTO), LiNbO ３ , LiTaO ３ Lithium metal oxides of metals belonging to Group 5 of the periodic table, such as Li ２ Alumni ２ O ３ -P ２ O ５ system, Li ２ Alumni ２ O ３ -ZnO-based, Li ２ O-Al ２ O ３ -SiO ２ -P ２ O ５ -TiO ２ Examples of suitable conductors include oxide-based conductors such as those based on ZnO.

[0082] An electrode active material having a coating layer can be obtained, for example, by applying a solution containing various atoms constituting the material forming the coating layer to the surface of the electrode active material and then baking the electrode active material after application, preferably at 200°C to 400°C. Here, the solution containing various atoms may be, for example, a solution containing alkoxides of various metals such as lithium ethoxide, titanium isopropoxide, niobium isopropoxide, or tantalum isopropoxide. 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 application may be performed by immersion, spray coating, or the like.

[0083] 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.

[0084] 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 preferably covered. The thickness of the coating layer is preferably 1 nm or more, more preferably 2 nm or more, and the upper limit is preferably 30 nm or less, more preferably 25 nm or less. The thickness of the coating layer can be measured by cross-sectional observation using a transmission electron microscope (TEM), and the coverage can be calculated from the thickness of the coating layer, elemental analysis value, and BET specific surface area.

[0085] (Other Components) The electrode mixture may contain other components such as a conductive material, a binder, etc. in addition to the crystalline sulfide solid electrolyte and electrode active material of the present embodiment. That is, the electrode mixture may contain other components such as a conductive material, a binder, etc. in addition to the crystalline sulfide solid electrolyte and electrode active material of the present embodiment. When mixing the crystalline sulfide solid electrolyte and the electrode active material, the other components such as a conductive material, a binder, etc. may be added to and mixed with the crystalline sulfide solid electrolyte and the electrode active material. From the viewpoint of improving battery performance by improving electronic conductivity, examples of the conductive material include carbon-based materials such as artificial graphite, graphite carbon fiber, resin-calcined carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads, furfuryl alcohol resin-calcined carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon.

[0086] The use of a binder improves the strength of the produced positive and negative electrodes. 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, acrylic resins, acrylic polyol resins, polyvinyl acetal resins, polyvinyl butyral resins, and silicone resins.

[0087] The blending ratio (mass ratio) of the electrode active material to the crystalline sulfide solid electrolyte in the electrode mixture is preferably 99.5:0.5 to 40:60, more preferably 99:1 to 50:50, and even more preferably 98:2 to 60:40, in consideration of improving battery performance and production efficiency.

[0088] 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 manufacturing efficiency, it is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, with the upper limit being preferably 10% by mass or less, preferably 8% by mass or less, and even more preferably 5% by 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 manufacturing efficiency, it is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, with the upper limit being preferably 20% by mass or less, preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0089] [Lithium-ion battery] The crystalline sulfide solid electrolyte of this embodiment can also be used in a lithium-ion battery as described above. For example, the lithium-ion battery can include at least one selected from the sulfide solid electrolyte of this embodiment and the electrode composite.

[0090] The lithium ion battery is not particularly limited in its configuration as long as it contains the crystalline sulfide solid electrolyte of the present embodiment described above and an electrode composite containing the same, and has the configuration of a commonly used lithium ion battery. It may be any.

[0091] The lithium ion battery preferably includes, for example, a positive electrode layer, a negative electrode layer, an electrolyte layer, and a current collector. The positive electrode layer and the negative electrode layer preferably use an electrode mixture containing the crystalline sulfide solid electrolyte of the present embodiment, and the electrolyte layer preferably uses the crystalline sulfide solid electrolyte of the present embodiment.

[0092] The current collector may be a known material, for example, a layer of Au or the like coated with a material that reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu.

[0093] (Method for producing crystalline sulfide solid electrolyte) A method for producing the crystalline sulfide solid electrolyte of this embodiment will be described. The crystalline sulfide solid electrolyte of this embodiment can be obtained by a production method including mixing raw material components containing, for example, lithium atoms, sulfur atoms, phosphorus atoms, oxygen atoms, and halogen atoms.

[0094] (Raw material containing substance) The raw material containing substance contains lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms. More specifically, the raw material containing substance contains one or more kinds of atoms selected from the group consisting of these atoms (hereinafter also referred to as "raw material"), and preferably contains two or more kinds of raw materials.

[0095] The raw materials include, for example, lithium sulfide; diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ and phosphorus sulfides such as methyl phosphate, ...

[0096] Among the above, lithium sulfide and diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ Among phosphorus sulfides, phosphorus pentasulfide (P ２ S ５ ) is preferred.

[0097] Preferred examples of the raw material include substances containing halogen atoms. For example, lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; fluorine (F ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２) and other simple halogen atoms are typically preferred.

[0098] Furthermore, preferable raw materials include substances containing oxygen atoms. For example, diphosphorus pentoxide (P ２ O ５ ), lithium oxide (Li ２ Representative examples of preferred cations include diphosphorus pentoxide (P ２ O ５ ) is preferred.

[0099] The raw material is a substance containing at least one atom selected from lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms, such as various phosphorus fluorides (PF ３ , P.F. ５ ), various phosphorus chlorides (PCl ３ , PCl ５ , P ２ Cl ４ ), various phosphorus bromides (PBr ３ , PBr ５ ), various phosphorus iodides (PI ３ , P ２ I ４ ) and the like; phosphorus halides such as thiophosphoryl fluoride (PSF ３ ), thiophosphoryl chloride (PSCl ３ ), thiophosphoryl bromide (PSBr ３ ), thiophosphoryl iodide (PSI ３ ), thiophosphoryl fluoride dichloride (PSCl ２ F), thiophosphoryl fluoride dibromide (PSBr ２ Thiophosphoryl halides such as lithium oxide, lithium hydroxide, lithium carbonate, and the like; alkali metal sulfides such as sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide; silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, and tin sulfide (SnS, SnS ２metal sulfides such as aluminum sulfide and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; halides of alkali metals other than lithium such as sodium halides such as sodium iodide, sodium fluoride, sodium chloride and sodium bromide; metal halides such as aluminum halides, silicon halides, germanium halides, arsenic halides, selenium halides, tin halides, antimony halides, tellurium halides and bismuth halides; phosphorus oxychloride (POCl ３ ), phosphorus oxybromide (POBr ３ and the like.

[0100] Also, P.S. ４ Li containing structure ３ P.S. ４ , Li ７ P ３ S １１ It is also possible to use as a raw material substances that act as solid electrolytes, such as Li ３ P.S. ４ When using as a raw material, for example, Li is first obtained by using lithium sulfide and diphosphorus pentasulfide. ３ P.S. ４ This can be prepared by manufacturing or the like and used as a raw material.

[0101] The raw materials such as lithium sulfide are preferably in the form of particles. This facilitates mixing of the raw materials, which makes it easier to produce a crystalline sulfide solid electrolyte. The average particle size (D ５０ In consideration of the reaction of the raw materials, handling, etc., the average particle size (D) is preferably, for example, 0.1 μm or more and 1000 μm or less, 0.5 μm or more and 100 μm or less, or 1 μm or more and 20 μm or less. ５０ ) is the particle size at which 50% (volume basis) of the total particle size is reached when the particle sizes are sequentially added together starting from the smallest particle size when an integrated particle size distribution curve is drawn, and the volume distribution refers to an average particle size that can be measured using, for example, a laser diffraction / scattering particle size distribution measuring device.

[0102] In the method for producing a crystalline sulfide solid electrolyte of this embodiment, the above raw materials may be used in appropriate combination. For example, Ｏ ) sulfur atom (M Ｓ ) to the ratio (M Ｏ / M Ｓ ), and for example, to have a composition represented by the above composition formula (1). １ = 17.8 ± 0.5°. As a result, it has a novel structure called an α-phase (high-temperature phase) that is stable at room temperature, making it easier to obtain high ionic conductivity. Note that, as already described, the composition of the crystalline sulfide solid electrolyte of this embodiment can be confirmed using an ICP optical emission spectrometer; however, since it contains oxygen atoms, there may be a discrepancy between the actual composition and the measured value. In such cases, it has been confirmed that there is almost no discrepancy between the substances used as raw materials and their blending ratios and the composition calculated from the substances and their blending ratios. Therefore, it can also be considered as a composition calculated from the substances used as raw materials and their blending ratios.

[0103] When lithium sulfide and diphosphorus pentasulfide are used as raw materials, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide makes it easier to exhibit the above-mentioned diffraction peaks, and as a result, from the viewpoint of having a novel structure called an α-phase (high-temperature phase) that is stable at room temperature and obtaining high ionic conductivity, is preferably 45.0 mol% or more, more preferably 60.0 mol% or more, even more preferably 67.0 mol% or more, still more preferably 70.0 mol% or more, and particularly preferably 73.0 mol% or more, with the upper limit being preferably 85.0 mol% or less, more preferably 80.0 mol% or less, even more preferably 78.0 mol% or less, and still more preferably 77.5 mol% or less. Representative numerical ranges are preferably 45.0 to 85.0 mol%, 55.0 to 85.0 mol%, 65.0 to 85.0 mol%, 67.0 to 85.0 mol%, 70.0 to 85.0 mol%, 73.0 to 85.0 mol%, 55.0 to 78.0 mol%, 65.0 to 78.0 mol%, 67.0 to 78.0 mol%, 70.0 to 78.0 mol%, and 73.0 to 78.0 mol%.

[0104] When the raw material content includes diphosphorus pentoxide as a raw material containing diphosphorus pentasulfide and oxygen atoms, the ratio of diphosphorus pentoxide to the total of these makes it easier to express the above-mentioned diffraction peaks, and as a result, has a novel structure called an α-phase (high-temperature phase) that is stable at room temperature, and from the viewpoint of obtaining high ionic conductivity, is preferably 0.1 mol% or more, more preferably 0.5 mol% or more, even more preferably 1.0 mol% or more, still more preferably 2.5 mol% or more, with the upper limit being preferably 20.0 mol% or less, more preferably 16.0 mol% or less, even more preferably 12.0 mol% or less, and still more preferably 10.0 mol% or less. Representative numerical ranges are preferably 0.1 to 20.0 mol%, 0.1 to 16.0 mol%, 0.1 to 12.0 mol%, 0.1 to 10.0 mol%, 0.5 to 20.0 mol%, 0.5 to 16.0 mol%, 0.5 to 12.0 mol%, 0.5 to 10.0 mol%, 1.0 to 20.0 mol%, 1.0 to 16.0 mol%, 1.0 to 12.0 mol%, 1.0 to 10.0 mol%, 2.5 to 20.0 mol%, 2.5 to 16.0 mol%, 2.5 to 12.0 mol%, and 2.5 to 10.0 mol%.

[0105] When the raw material content includes lithium sulfide, diphosphorus pentasulfide, lithium halide, a raw material containing an oxygen atom, and other raw materials used as needed, the content of lithium sulfide and diphosphorus pentasulfide relative to the total of these is preferably 70.0 mol% or more, more preferably 80.0 mol% or more, even more preferably 85.0 mol% or more, and still more preferably 90.0 mol% or more, with the upper limit being preferably less than 100 mol%, more preferably 99.0 mol% or less, and even more preferably 98.0 mol% or less.

[0106] Furthermore, in a case where lithium sulfide, diphosphorus pentasulfide, lithium halide, a raw material containing an oxygen atom, and other raw materials used as necessary are included, the content of lithium halide relative to the total of lithium sulfide, diphosphorus pentasulfide, lithium halide, and the raw material containing an oxygen atom is preferably 0.010 mol% or more, more preferably 0.050 mol% or more, even more preferably 0.10 mol% or more, still more preferably 0.30 mol% or more, and particularly preferably 0.50 mol% or more, and the upper limit is preferably 25.0 mol% or less, more preferably 22.0 mol% or less, even more preferably 20.0 mol% or less, still more preferably 15.0 mol% or less, particularly preferably 10.0 mol% or less, and still more particularly preferably 7.5 mol% or less.

[0107] (Mixing) The mixing of raw material containing lithium atoms, sulfur atoms, phosphorus atoms, oxygen atoms, and halogen atoms is not particularly limited as long as the raw materials can be mixed. For example, the mixing can be performed using a pulverizer, mixer, stirrer, etc. Using a pulverizer will result in pulverization of the raw materials, but mixing will also occur at the same time. Mixing of the raw materials can also occur using a mixer or stirrer. Therefore, it can be said that the crystalline sulfide solid electrolyte of this embodiment can be preferably produced by stirring, mixing, pulverizing, or a combination of any of these processes using two or more raw materials selected from substances containing at least one atom of lithium atoms, sulfur atoms, phosphorus atoms, oxygen atoms, and halogen atoms.

[0108] Examples of the stirrer or mixer include a mechanical stirring mixer that is equipped with stirring blades in a reaction vessel and can stir (also referred to as mixing by stirring or stirring and mixing). Examples of the mechanical stirring mixer include a high-speed stirring mixer and a double-arm mixer. Examples of the high-speed stirring mixer include a vertical-axis rotary mixer and a horizontal-axis rotary mixer, and either type of mixer may be used.

[0109] 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 promoting the reaction of the raw materials more efficiently, the shovel type, flat blade type, C-type blade type, anchor type, paddle type, full zone type, etc. are preferred, with the anchor type, paddle type, and full zone type being more preferred.

[0110] When a mechanical stirring mixer is used, the rotation speed of the stirring blades can be adjusted appropriately depending on the volume of the fluid in the reaction vessel, the temperature, the shape of the stirring blades, etc., and is not particularly limited. However, it is usually sufficient to set the rotation speed at about 5 rpm or more and 400 rpm or less. From the viewpoint of more efficiently promoting the reaction of the raw materials, the rotation speed is preferably 10 rpm or more and 300 rpm or less, more preferably 15 rpm or more and 250 rpm or less, and even more preferably 20 rpm or more and 200 rpm or less.

[0111] The temperature conditions when mixing is performed using a mixer or the like are not particularly limited, and are, for example, usually −30 to 120° C., preferably −10 to 100° C., more preferably 0 to 80° C., and even more preferably 10 to 60° C. The mixing time is usually 0.1 to 500 hours, and from the viewpoint of achieving a more uniform dispersion state of the raw materials and promoting the reaction, is preferably 1 to 450 hours, more preferably 10 to 425 hours, even more preferably 20 to 400 hours, and still more preferably 40 to 375 hours.

[0112] The method of mixing with pulverization using a pulverizer has traditionally been adopted as a solid-phase method (mechanical milling method). As the pulverizer, for example, a media-type pulverizer using a pulverization medium can be used. Media-type pulverizers are broadly classified into container-driven pulverizers and media-agitation pulverizers. Examples of container-driven pulverizers include agitation tanks, pulverization tanks, or combinations thereof, such as ball mills and bead mills. Examples of media-agitation pulverizers include impact pulverizers such as cutter mills, hammer mills, and pin mills; tower-type pulverizers such as tower mills; agitation tank pulverizers such as attritors, aquamizers, and sand grinders; flow-through tank pulverizers such as Viscomill and pearl mills; flow-through pipe pulverizers; annular pulverizers such as Coball mills; continuous dynamic pulverizers; and various pulverizers such as single-shaft or multi-shaft kneaders. Among these, considering the ease of adjusting the particle size of the resulting sulfide, the ball mills and bead mills exemplified as container-driven pulverizers are preferred, and planetary pulverizers are particularly preferred.

[0113] These pulverizers can be appropriately selected depending on the desired scale, etc. For relatively small scales, container-driven pulverizers such as ball mills and bead mills can be used, while for large scales or mass production, other types of pulverizers may be used.

[0114] Furthermore, as will be described later, when the mixture is in a liquid state involving a liquid such as a solvent or in a slurry state during mixing, a wet mill that can handle wet milling is preferred. Typical examples of wet mills include wet bead mills, wet ball mills, and wet vibration mills. Wet bead mills that use beads as milling media are preferred because they allow for free adjustment of milling conditions and are easily adaptable to smaller particle sizes. 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.

[0115] Furthermore, when the material to be mixed is in a liquid state or a slurry state, a flow-through mill that can perform a circulation operation to circulate the material as needed can also be used. Specifically, a mill that circulates the material between a mill (pulverizing mixer) that pulverizes the slurry and a temperature holding tank (reaction vessel) can be used.

[0116] When using a ball mill or bead mill, the rotation speed varies depending on the scale of the treatment and cannot be generalized, but is usually 10 rpm or more, preferably 20 rpm or more, more preferably 50 rpm or more, and even more preferably 100 rpm or more. The upper limit is usually 1,000 rpm or less, preferably 900 rpm or less, more preferably 800 rpm or less, even more preferably 700 rpm or less, and even more preferably 500 rpm or less. The milling time varies depending on the scale of the treatment and cannot be generalized, but is usually 0.5 hours or more, preferably 1 hour or more, more preferably 5 hours or more, even more preferably 10 hours or more, even more preferably 20 hours or more, and particularly preferably 25 hours or more. The upper limit is usually 100 hours or less, preferably 72 hours or less, and more preferably 48 hours or less. When the milling time is within the above range, the atoms contained in the raw material, especially oxygen atoms and halogen atoms, are more efficiently and uniformly dispersed, making it easier to obtain high ionic conductivity.

[0117] By selecting the size and material of the medium (beads or balls) used, the rotor rotation speed, time, and the like, it is possible to perform mixing, stirring, pulverization, or a combination of these processes, and it is possible to adjust the particle size, etc. of the resulting crystalline sulfide solid electrolyte.

[0118] (Solvent) When mixing the raw materials, a solvent may be added to the raw materials and mixed in. As the solvent, various solvents widely known as organic solvents may be used.

[0119] As the solvent, a wide variety of solvents that have conventionally been used in the production of solid electrolytes can be used, and examples thereof include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents.

[0120] Examples of aliphatic hydrocarbons include hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane. Examples of alicyclic hydrocarbons include cyclohexane and methylcyclohexane. Examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, trifluoromethylbenzene, and nitrobenzene.

[0121] In addition to the above hydrocarbon solvents, solvents containing heteroatoms such as atoms other than carbon and hydrogen atoms, for example, nitrogen, oxygen, sulfur, and halogen atoms, are also suitable. Such solvents have the property of easily forming complexes with raw materials containing lithium, phosphorus, sulfur, oxygen, and halogen atoms (hereinafter, such solvents are also referred to as "complexing agents"), and are useful in that they facilitate the retention of halogen atoms within the structure of the sulfide solid electrolyte, thereby achieving higher ionic conductivity. Preferred examples of such complexing agents include ether solvents, ester solvents, and alcohol solvents, aldehyde solvents, and ketone solvents containing oxygen atoms as heteroatoms. Furthermore, when using such complexing agents, it is possible to proceed with the reaction of the raw materials using a mixer or agitator without using a mill.

[0122] Preferred examples of the ether solvent include aliphatic ethers such as dimethyl ether, diethyl ether, tert-butyl methyl ether, dimethoxymethane, dimethoxyethane, diethylene glycol dimethyl ether (diglyme), triethylene oxide glycol dimethyl ether (triglyme), diethylene glycol, and triethylene glycol; alicyclic ethers such as ethylene oxide, propylene oxide, tetrahydrofuran, tetrahydropyran, dimethoxytetrahydrofuran, cyclopentyl methyl ether, and dioxane; heterocyclic ethers such as furan, benzofuran, and benzopyran; and aromatic ethers such as methyl phenyl ether (anisole), ethyl phenyl ether, dibenzyl ether, and diphenyl ether.

[0123] Preferred examples of the ester solvent include methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, and isopropyl acetate; aliphatic esters such as methyl propionate, ethyl propionate, dimethyl oxalate, diethyl oxalate, dimethyl malonate, diethyl malonate, dimethyl succinate, and diethyl succinate; alicyclic esters such as methyl cyclohexanecarboxylate, ethyl cyclohexanecarboxylate, and dimethyl cyclohexanedicarboxylate; heterocyclic esters such as methyl pyridinecarboxylate, methyl pyrimidinecarboxylate, acetolactone, propiolactone, butyrolactone, and valerolactone; and aromatic esters such as methyl benzoate, ethyl benzoate, dimethyl phthalate, diethyl phthalate, butyl benzyl phthalate, dicyclohexyl phthalate, trimethyl trimellitate, and triethyl trimellitate.

[0124] Preferred examples of the solvent include alcohol solvents such as ethanol and butanol; aldehyde solvents such as formaldehyde, acetaldehyde and dimethylformamide; and ketone solvents such as acetone and methyl ethyl ketone.

[0125] Examples of solvents containing a nitrogen atom as a heteroatom include solvents having a nitrogen atom-containing group such as an amino group, an amide group, a nitro group, or a nitrile group. For example, preferred examples of solvents having an amino group include aliphatic amines such as ethylenediamine, diaminopropane, dimethylethylenediamine, diethylethylenediamine, dimethyldiaminopropane, tetramethyldiaminomethane, tetramethylethylenediamine (TMEDA), and tetramethyldiaminopropane (TMPDA); alicyclic amines such as cyclopropanediamine, cyclohexanediamine, and bisaminomethylcyclohexane; heterocyclic amines such as isophoronediamine, piperazine, dipiperidylpropane, and dimethylpiperazine; and aromatic amines such as phenyldiamine, tolylenediamine, naphthalenediamine, methylphenylenediamine, dimethylnaphthalenediamine, dimethylphenylenediamine, tetramethylphenylenediamine, and tetramethylnaphthalenediamine. Preferred examples of solvents containing a nitrogen atom include nitrile solvents such as acetonitrile and acrylonitrile; and solvents containing a nitrogen atom such as dimethylformamide, nitrobenzene, and dimethylacetamide.

[0126] Preferred examples of solvents containing a halogen atom as a heteroatom include chloroform, carbon tetrachloride, dichloromethane, chlorobenzene, dichlorobenzene, trifluoromethylbenzene, chlorotoluene, bromobenzene, etc. Preferred examples of solvents containing a sulfur atom include dimethyl sulfoxide, carbon disulfide, etc.

[0127] When a solvent is used, the amount of the solvent used is preferably 100 mL or more, more preferably 200 mL or more, even more preferably 250 mL or more, and still more preferably 300 mL or more per kg of the total amount of the raw materials, and the upper limit is preferably 3000 mL or less, more preferably 2500 mL or less, even more preferably 2000 mL or less, and still more preferably 1550 mL or less. When the amount of the solvent used is within the above range, the raw materials can be reacted efficiently.

[0128] (Drying) When mixing is performed using a solvent, the method may include drying the fluid (usually a slurry) obtained by mixing. When a complexing agent is used as a solvent, the sulfide solid electrolyte is obtained by removing the complexing agent from a complex containing the complexing agent. When a complexing agent and a solvent are used in combination, the complexing agent is removed from a complex containing the complexing agent and the solvent is removed. When a solvent other than a complexing agent is used, the solvent is removed to obtain the sulfide solid electrolyte.

[0129] The fluid obtained by mixing can be dried at a temperature depending on the type of solvent. 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 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 (e.g., 23°C) (e.g., about room temperature ±5°C), thereby volatilizing the complexing agent and any solvent used as needed.

[0130] Drying may be performed by filtering the fluid using a glass filter or the like, by solid-liquid separation by decantation, or by solid-liquid separation using a centrifuge or the like. When a solvent other than a complexing agent is used, a sulfide solid electrolyte can be obtained by solid-liquid separation. When a complexing agent is used as the solvent, solid-liquid separation is performed, and then drying is performed under the above-mentioned temperature conditions to remove the complexing agent incorporated into the complex. Specifically, solid-liquid separation is performed by transferring the fluid to a container, and after the sulfide (or the complex if a complexing agent is included (which may also be referred to as a precursor of the sulfide solid electrolyte)) is precipitated, decantation is performed to remove the supernatant complexing agent and solvent, or filtration using a glass filter with a pore size of about 10 to 200 μm, preferably 20 to 150 μm, for example.

[0131] Drying may be carried out after mixing and before the hydrogen treatment described below, or may be carried out after the hydrogen treatment.

[0132] The sulfide solid electrolyte obtained by the above mixing, or the sulfide solid electrolyte obtained by removing the solvent by the above drying when a solvent is used, exhibits ionic conductivity due to lithium atoms. The sulfide solid electrolyte obtained by the above mixing is basically an amorphous sulfide solid electrolyte (glass component) unless it is mixed by pulverizing using a pulverizer to the extent that it crystallizes, for example.

[0133] The sulfide solid electrolyte obtained by the above-mentioned mixing may be an amorphous sulfide solid electrolyte (glass component) or a crystalline sulfide solid electrolyte, and can be appropriately selected as desired. When producing a crystalline sulfide solid electrolyte, the amorphous sulfide solid electrolyte obtained by the above-mentioned mixing can be heated to produce a crystalline sulfide solid electrolyte. The sulfide solid electrolyte may also include a crystalline sulfide solid electrolyte in which an amorphous component (glass component) is formed on the surface thereof as a result of performing a process such as pulverization described below to adjust the particle size of the crystalline sulfide solid electrolyte powder. Therefore, sulfide solid electrolytes containing an amorphous component include amorphous sulfide solid electrolytes and crystalline sulfide solid electrolytes in which an amorphous component is formed on the surface thereof.

[0134] (Heating) When producing the crystalline sulfide solid electrolyte of this embodiment, heating may be further included. If an amorphous sulfide solid electrolyte (glass component) is obtained by the above-mentioned mixing, a crystalline sulfide solid electrolyte can be obtained by heating. Also, if a crystalline sulfide solid electrolyte is obtained, a crystalline sulfide solid electrolyte with improved crystallinity can be obtained. In either case, heating can convert the resulting sulfide solid electrolyte into a crystalline sulfide solid electrolyte, thereby improving ionic conductivity. Furthermore, if a complexing agent is used as a solvent during mixing, a complex containing the complexing agent is formed. However, even if the complexing agent is removed from the complex by heating without the above-mentioned drying, a sulfide solid electrolyte can be obtained. Depending on the heating conditions, the sulfide solid electrolyte can be made amorphous or crystalline.

[0135] The heating temperature may be determined depending on the structure of the crystalline sulfide solid electrolyte. Specifically, an amorphous sulfide solid electrolyte corresponding to the crystalline sulfide solid electrolyte to be obtained is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA device) at a temperature increase condition of 10 ° C. / min. The temperature is preferably set to 5 ° C. or higher, more preferably 10 ° C. or higher, and even more preferably 20 ° C. or higher, starting from the peak top temperature of the exothermic peak observed on the lowest temperature side. The upper limit is not particularly limited, but may be about 40 ° C. or lower. By setting the temperature range as described above, 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 specified because it varies depending on the composition and structure of the crystalline sulfide solid electrolyte to be obtained, but is typically preferably 130 ° C. or higher, more preferably 135 ° C. or higher, and even more preferably 140 ° C. or higher. The upper limit is not particularly limited, but is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, and even more preferably 200 ° C. or lower.

[0136] 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.

[0137] 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). For example, an inert gas atmosphere containing a certain concentration of hydrogen may be used. This is because deterioration (e.g., oxidation) of the crystalline sulfide solid electrolyte can be prevented. The heating method is not particularly limited, and examples include methods using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, and a firing furnace. 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.

[0138] 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.

[0139] (Measurement of Ion Conductivity) In the present example, the measurement of ion conductivity was carried out as follows. A 10 mm diameter (cross-sectional area S: 0.785 cm ) sample was taken from the crystalline solid electrolyte obtained in the examples and comparative examples. ２ ), and a height (L) of 0.1 to 0.3 cm were molded into a circular pellet to prepare a sample. Electrode terminals were attached to the top and bottom of the sample, and measurements were made at 25°C using an AC impedance method (frequency range: 7 MHz to 0.1 Hz, amplitude: 10 mV) to obtain a Cole-Cole plot. The real part Z' (Ω) at the point where -Z'' (Ω) is minimum near the right end of the arc observed in the high-frequency region was taken as the bulk resistance R (Ω) of the electrolyte, and the ionic conductivity σ (S / cm) was calculated according to the following formula: R = ρ (L / S) σ = 1 / ρ

[0140] (X-ray Diffraction Measurement (Powder XRD Diffraction Measurement)) Powder X-ray diffraction (XRD) measurement was carried out as follows. The powder of the solid electrolyte produced in each Example and Comparative Example was filled into a groove with a diameter of 20 mm and a depth of 0.2 mm, and leveled with glass to prepare a sample. This sample was sealed with a Kapton film for XRD and measured without being exposed to air. Measurement was carried out using a powder X-ray diffractometer ("D2 PHASER (model number)", manufactured by BRUKER Japan Co., Ltd.) under the following conditions. Tube voltage: 30 kV Tube current: 10 mA X-ray wavelength: Cu-Kα ray (1.5418 Å) Optical system: focusing method Slit configuration: Soller slit 4° (on both the incident and receiving sides), divergence slit 1 mm, Kβ filter (Ni plate 0.5%), air scatter screen 3 mm) Detector: semiconductor detector Measurement range: 2θ = 10-60 deg Step width, scan speed: 0.05 deg, 0.05 deg / sec From the obtained XRD pattern, a peak appearing at 2θ = 20.3° and a peak appearing at 2θ = 29.6° were identified.

[0141] (Thermogravimetric Differential Thermal Analysis (TG-DTA)) Thermogravimetric Differential Thermal Analysis (TG-DTA) was performed using a thermogravimetric differential thermal analyzer (TG-DTA) ("TGA / DSC3+ (model number)" manufactured by METTLER TOLEDO). The measurement was carried out by packing a sample (approximately 10 mg to 20 mg) in an Al pan and heating it under N ２ The temperature was raised from 30°C at a rate of 10°C / min in an atmosphere, and for the temperatures at which exothermic peaks were observed in the DTA curve, the peak top temperature of the lower exothermic peak was designated Tc1 (°C), and the peak top temperature of the higher exothermic peak was designated Tc2 (°C). The temperature difference ΔTc (=Tc2-Tc1) between the peak tops of these two exothermic peaks was calculated.

[0142] (solid ３１ P-NMR measurement) Measurement was performed using the following equipment under the following conditions: Equipment: ECZ400R (manufactured by JEOL Ltd.) Observation nuclei: ３１ P Observation frequency: 161.994 MHz Measurement temperature: room temperature Pulse sequence: single pulse 90° pulse width: 3.2 μs Waiting time after FID measurement until next pulse application: 60 s MAS (magic angle spinning) rotation speed: 11 kHz Number of accumulations: 64 Measurement range: 250 ppm to -150 ppm Sample amount: 100 mg External standard: NH ４ H ２ P.O. ４ (chemical shift 1.00 ppm)

[0143] Peak separation: When peak separation is required, the obtained solid ３１ The P-NMR spectrum is analyzed using the software "FT-NMR" (software included in "FT-NMR Data Processing by Personal Computer," Revised Edition (Second Edition) (Sankyo Publishing)) to determine the separated peaks. The software calculates the separated peaks, calculated NMR signal values, and the residual sum of squares R2 from the NMR signals (experimental values) using the nonlinear least squares method. Peak separation is considered complete when the residual sum of squares R2 within the analysis range between the experimental and calculated values, assuming the maximum peak height to be 1, is 0.007 or less and the number of separated peaks is the smallest.

[0144] Example 1 Lithium sulfide, diphosphorus pentasulfide, diphosphorus pentoxide, and lithium chloride were weighed to a molar ratio of 67.50:21.60:0.90:10.00 (total: 1.5 g), and placed in a 45 ml zirconia pot of a planetary ball mill (manufactured by Fritsch: model number P-7) together with 10 zirconia balls having a diameter of 10 mm (approximately 32 g) under a nitrogen atmosphere, completely sealed, and the pot was placed under an inert atmosphere (nitrogen atmosphere). Without heating or cooling (room temperature), the planetary ball mill was rotated at 370 rpm and mechanical milling was performed for 40 hours. Thermogravimetric differential calorimetry of the obtained powdered product (amorphous sulfide solid electrolyte) was performed, and the peak top temperature Tc1 of the low-temperature exothermic peak was 219 ° C., and the peak top temperature Tc2 of the high-temperature exothermic peak was 250 ° C., and ΔTc was 31 ° C. The above product was heated in an inert atmosphere (nitrogen atmosphere) at 219°C (Tc1) for 2 hours to obtain a crystalline sulfide solid electrolyte.

[0145] In the composition formula (1) of the obtained crystalline sulfide solid electrolyte, x, y, and z are 0.02500, 10.0000, and 0.0000, respectively, and x × y is 0.25000. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured and found to be 1.2 mS / cm. Furthermore, when the obtained crystalline sulfide solid electrolyte was subjected to X-ray diffraction measurement using CuKα radiation, 2θ １ = 17.8 ± 0.5° and a diffraction peak at 17.6°. １ The diffraction peak closest to ２ A diffraction peak at 2θ = 18.0° was confirmed. １ and 2θ ２ Difference between the diffraction peak splitting width and the １ -2θ ２ The X-ray diffraction pattern is shown in Figure 1.

[0146] Examples 2 to 14 Crystalline sulfide solid electrolytes of Examples 2 to 14 were prepared in the same manner as in Example 1, except that the types and blending ratios of the raw materials in Example 1 were as shown in Tables 1-1 and 1-2. The heating temperature of the product (amorphous sulfide solid electrolyte) in these examples was the temperature Tc1 for each example. For the crystalline sulfide solid electrolyte obtained in each example, x, y, and z in the composition formula (1) are shown in Tables 1-1 and 1-2. The obtained crystalline sulfide solid electrolytes were subjected to ionic conductivity measurement, thermogravimetric differential calorimetry, and powder XRD diffraction measurement. The results are shown in Tables 1-1 and 1-2. The X-ray diffraction patterns for Examples 2 to 12 are shown in FIG. 1, and the X-ray diffraction patterns for Examples 13 and 14 are shown in FIG. 2.

[0147] Comparative Examples 1 to 10 Comparative sulfide solid electrolytes were prepared in the same manner as in Example 1, except that the types and blending ratios of raw materials and the pulverization conditions (production method) in Example 1 were changed to those shown in Table 2. The ionic conductivity, thermogravimetric differential calorimetry, and powder XRD diffraction measurement were performed on the obtained crystalline sulfide solid electrolytes. The results are shown in Table 2, and the X-ray diffraction patterns of Comparative Examples 1 to 10 are shown in FIG.

[0148]

[0149]

[0150]

[0151] The crystal structures shown in Tables 1-1, 1-2 and 2 are as follows: α: The main crystal structure is α-Li ３ P.S. ４ (α phase (high temperature phase)) β: The main crystal structure is β-Li ３ P.S. ４ (β phase (medium temperature phase)). R: The main crystal structure has a thiolicon region II type crystal structure. α+β: α-Li ３ P.S. ４ (α phase (high temperature phase)) and β-Li ３ P.S. ４ (β phase (medium temperature phase)) α+R: α-Li ３ P.S. ４(α phase (high temperature phase)) and thiolicon region II type crystal structure. α+L: α-Li ３ P.S. ４ (α phase (high temperature phase)) and LGPS type crystal structure. β+4141: β-Li ３ P.S. ４ (β phase (medium temperature phase)) and crystalline Li ４ P.S. ４ I have.

[0152] The milling conditions for Manufacturing Methods 1 to 3 shown in Tables 1-1, 1-2, and 2 are as follows. Manufacturing Method 1: The milling conditions in Example 1 were as follows: a total of 1.5 g of raw material was placed in a 45 ml zirconia pot together with 10 10 mm diameter zirconia balls (approximately 32 g) under a nitrogen atmosphere, completely sealed, and the pot was placed under an inert atmosphere (nitrogen atmosphere). Mechanical milling was performed using a planetary ball mill (manufactured by Fritsch: model number P-7) at the rotation speed and time shown in the table without heating or cooling (room temperature). Manufacturing Method 2: In Manufacturing Method 1, a total of 10 g of raw material was placed in a 500 ml zirconia pot, and a planetary ball mill (manufactured by Fritsch: model number P-5) was used as the milling device. The same procedure was followed as in Manufacturing Method 1, except that the total of 10 g of raw material was placed in a 500 ml zirconia pot with 600 g of 10 mm diameter zirconia balls. The milling apparatus was a planetary ball mill (manufactured by Fritsch: model number P-5). The milling conditions were as shown in the table. Production method 3: The same grinding conditions as in Production method 1 were used, except that the total amount of raw materials contained was 2.35 g.

[0153] From the examples, it was confirmed that the ionic conductivity of the crystalline sulfide solid electrolyte of this embodiment is 1.0 to 1.5 mS / cm, which is higher than the ionic conductivity of the crystalline sulfide solid electrolyte of the comparative example, which is 0.1 to 0.8 mS / cm. １ = 17.8 ± 0.5°, and the diffraction peak split width (| 2θ １ -2θ ２ It was also confirmed that the α phase (high temperature phase) having room temperature stability was the main crystalline structure, since the α-phase | was less than 0.5°.

[0154] Regarding the comparative examples, the crystalline sulfide solid electrolytes of Comparative Examples 1 to 4, which used raw materials containing oxygen atoms but did not use raw materials containing halogen atoms, were confirmed to have an α phase (high temperature phase) that is stable at room temperature in Comparative Examples 2 and 3, but because they did not contain halogen atoms, their ionic conductivity was not high. Furthermore, the crystalline sulfide solid electrolytes of Comparative Examples 5 to 7, which used raw materials containing halogen atoms but did not use raw materials containing oxygen atoms, mainly exhibited a β phase (medium temperature phase), and even though they contained halogen atoms, their ionic conductivity was not high. Thus, it was found that when neither oxygen atoms nor halogen atoms are contained, the α phase (high temperature phase) is unlikely to be exhibited, and even if the α phase (high temperature phase) is exhibited, the ionic conductivity is not high.

[0155] For the crystalline sulfide solid electrolytes of Comparative Examples 8 and 10, the diffraction peak split width (|2θ １ -2θ ２ |) was 0.5° or more, the sulfide solid electrolyte of Comparative Example 9 did not have the α phase (high temperature phase) having room temperature stability as its main crystalline structure, and the ionic conductivities were low at 0.6 and 0.1 mS / cm, respectively. In addition, the sulfide solid electrolyte of Comparative Example 9 had a halo pattern as shown in FIG. 3, and was confirmed to have no crystalline structure. Thus, even if the sulfide solid electrolyte contained lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms, 2θ １ = 17.8 ± 0.5°, and the diffraction peak split width (| 2θ １ -2θ ２ It was confirmed that there were also some crystalline sulfide solid electrolytes in which the angle of curvature | was less than 0.5°. Such an event may be more likely to occur depending on the conditions (e.g., grinding conditions and heating conditions) used in producing the crystalline sulfide solid electrolyte, the composition used, the type of halogen atom, and the like.

[0156] Regarding the crystalline sulfide solid electrolyte of Example 6, ３１ P-NMR measurement was carried out. ３１ The P-NMR spectrum is shown in Figure 4. ３１Using the data obtained by P-NMR measurement, the phosphorus ratio (mol%) contained in each structure was calculated based on the peak area attributable to each structure. Specifically, the phosphorus ratio (mol%) contained in each structure was calculated from the ratio of the peak area of ​​each structure to the total area of ​​the peaks attributable to each structure shown in Table 3. The calculated phosphorus ratio (mol%) of each structure is shown in Table 3.

[0157]

[0158] As shown in Table 3, all of the crystalline sulfide solid electrolytes of Example 6 were PSO ３ ３－ A peak due to PO was observed. ４ ３－ Peaks due to the incorporation of oxygen atoms into the crystal structure were also observed, indicating that oxygen atoms were incorporated into the crystal structure. Furthermore, it was confirmed that the crystalline sulfide solid electrolyte of Example 6 stabilized the α-phase (high-temperature phase) and exhibited a high ionic conductivity of 1.5 mS / cm even when a trace amount of raw material containing halogen atoms, 5.0 mol%, was added. This demonstrates that by incorporating oxygen atoms into the crystal structure, a sulfide solid electrolyte having an α-phase (high-temperature phase) that exhibits high ionic conductivity can be obtained, even with a small content of halogen atoms.

[0159] The crystalline sulfide solid electrolyte of this embodiment has high ionic conductivity and excellent battery performance, and is therefore suitable for use, for example, in combination with an electrode active material to form an electrode composite, or in lithium ion batteries, which are suitable for use in information-related devices and communication devices such as personal computers, video cameras, and mobile phones.

Claims

1. Contains lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms, and has a 2θ １ = 17.8 ± 0.5°, and the position of the diffraction peak is 2θ １ and the position 2θ of the diffraction peak closest to the diffraction peak. ２ Difference from (|2θ １ −2θ ２ |) is less than 0.5°.

2. The oxygen atom (M Ｏ The sulfur atom (M Ｓ ) to the ratio (M Ｏ / M Ｓ 2. The crystalline sulfide solid electrolyte according to claim 1, wherein the crystalline sulfide solid electrolyte is 0.0025 or more and 0.25 or less.

3. The crystalline sulfide solid electrolyte according to claim 1 or 2, having a composition represented by the following composition formula (1): (100-y)(0.5)(Li ３＋２ｚ P (S １－ｘ O ｘ ) ４＋ｚ )+(y)LiX (1) (In the composition formula (1), x, y, and z each satisfy 0.0025≦x≦0.15, 0.010≦y<25.0, and −0.17≦z≦1.

5. X represents a halogen atom.) 4. Solid ３１ P-NMR measurement showed PSO at 34.0±5.0 ppm. ３ ３－ The crystalline sulfide solid electrolyte according to any one of claims 1 to 3, in which a peak due to is observed.

5. Solid ３１ P-NMR measurement revealed that PO was present at 6.0±5.0 ppm. ４ ３－ The crystalline sulfide solid electrolyte according to any one of claims 1 to 4, in which a peak due to is observed.

6. A crystalline sulfide solid electrolyte according to any one of claims 1 to 5, in which at least two exothermic peaks are measured in a thermogravimetric differential calorimetry (measured at a heating rate of 10°C / min), and the temperature difference between the peak tops of the two exothermic peaks is 30.0°C or more and 130.0°C or less.

7. The crystalline sulfide solid electrolyte according to any one of claims 1 to 6, wherein the halogen atom is at least one type of halogen atom selected from the group consisting of fluorine atom, chlorine atom, bromine atom and iodine atom.

8. The crystalline sulfide solid electrolyte according to any one of claims 1 to 7, having an ionic conductivity of 0.85 mS / cm or more.

9. The oxygen atom is P ２ O ５ The crystalline sulfide solid electrolyte according to any one of claims 1 to 8, which is derived from 10. The crystalline sulfide solid electrolyte according to any one of claims 1 to 9, which is a glass ceramic.

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