Sulfide solid electrolyte and method for producing sulfide solid electrolyte

Abstract

Provided is a sulfide solid electrolyte that has high ionic conductivity and high water resistance, while also being cost-effective. The sulfide solid electrolyte contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, wherein the molar ratio (MO / MS) of the oxygen atoms (MO) to the sulfur atoms (MS) is 0.0050 or more. The sulfide solid electrolyte has diffraction peaks at 2θ = 17.8 ± 0.3°, 18.2 ± 0.3°, 19.8 ± 0.3°, 21.8 ± 0.3°, 23.8 ± 0.3°, 25.9 ± 0.3°, 29.5 ± 0.3°, and 30.0 ± 0.3° in X-ray diffraction measurement using CuKα rays.

Description

Sulfide solid electrolyte and method for producing sulfide solid electrolyte

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

[0002] With the recent rapid spread of information-related and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries for use as their power sources has become increasingly important. Lithium-ion batteries, in particular, have attracted attention due to their high energy density. Traditionally, batteries used for these applications have employed 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 particular, automotive applications demand higher capacity and higher power output, raising safety concerns about batteries using conventional liquid electrolytes. In response to these issues, development of batteries using solid electrolyte layers is underway, as this eliminates the use of flammable organic solvents, simplifies safety devices, and improves 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. Patent Document 2 discloses a lithium ion conductive sulfide-based crystallized glass containing lithium, phosphorus, and sulfur elements and having a predetermined diffraction peak in X-ray diffraction, and a lithium ion conductive sulfide-based crystallized glass containing Li, ２ S and P ２ S ５ Patent Document 3 discloses a method for producing lithium ion conductive sulfide-based crystallized glass, which comprises firing a sulfide-based glass having the following composition at a predetermined temperature: ３１A solid electrolyte is disclosed, the PNMR spectrum of which has a peak at a predetermined position attributable to crystals, and which has a predetermined ratio of the crystals.

[0004] JP 2018-174130 A JP 2005-228570 A International Publication No. 2007-68539 Pamphlet

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sulfide solid electrolyte that has high ionic conductivity and high water resistance, and that is manufactured at low cost.

[0006] The sulfide solid electrolyte according to the present invention contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and the oxygen atoms (M Ｏ ) and the sulfur atom (M Ｓ ) and the molar ratio (M Ｏ / M Ｓ ) is 0.0050 or more, and in X-ray diffraction measurement using CuKα rays, the sulfide solid electrolyte has diffraction peaks at 2θ=17.8±0.3°, 18.2±0.3°, 19.8±0.3°, 21.8±0.3°, 23.8±0.3°, 25.9±0.3°, 29.5±0.3°, and 30.0±0.3°.

[0007] The method for producing a sulfide solid electrolyte according to the present invention includes mixing raw material ingredients containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and heating the mixture obtained by the mixing to crystallize the mixture, and the oxygen atoms (M Ｏ ) and the sulfur atom (M Ｓ ) and the molar ratio (M Ｏ / M Ｓ ) is 0.0050 or more.

[0008] It is possible to provide a sulfide solid electrolyte that has high ionic conductivity and high water resistance, and that is manufactured at low cost.

[0009] 1 is a schematic diagram of an apparatus used to measure the amount of hydrogen sulfide generated in the examples. 2 is an X-ray diffraction pattern of the sulfide solid electrolyte obtained in the examples and comparative examples. 3 is a solid of the sulfide solid electrolyte obtained in Example 2. ３１P-NMR spectrum.

[0010] 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.

[0011] (Discoveries Obtained by the Inventors to Achieve the Present Invention) Patent Document 1 discloses a solid electrolyte material containing, in addition to lithium atoms, phosphorus atoms, and sulfur atoms, hydroxyl groups or halogen atoms so as to exhibit a predetermined composition formula, and the inclusion of halogen atoms aims to improve ionic conductivity. However, the diffraction peaks of the solid electrolyte material described in Patent Document 1 obtained by powder X-ray diffraction are different from the diffraction peaks of the sulfide solid electrolyte of the present embodiment, and it is believed that the solid electrolyte material has a crystal structure different from that of the sulfide solid electrolyte of the present embodiment. Furthermore, no attention is paid to properties such as water resistance, and improvements in these properties are desired.

[0012] The lithium ion conductive sulfide-based crystallized glass described in Patent Document 2 has an ionic conductivity of 1.0 to 2.1 × 10 －３ S / cm, and further improvement in ionic conductivity is desired. Furthermore, no attention is paid to properties such as water resistance. The crystallized glass described in Patent Document 2 contains oxygen atoms derived from the sulfur oxides of lithium sulfite, lithium sulfate, and lithium thiosulfate, which are contained as impurities in the lithium sulfide used as a raw material. However, these oxygen atoms are contained only as impurities, and are not intentionally used, so the content of oxygen atoms is low. Therefore, properties such as ionic conductivity and water resistance are low, and further improvement is desired.

[0013] The solid electrolyte described in Patent Document 3 has a viscosity of 2.3 to 5.0 × 10 －３In addition to a high ionic conductivity of 2.5 S / cm, the material can achieve heat resistance that does not deteriorate in performance even at high solder reflow temperatures of 260 to 280°C in the case of lead-free solder. However, no attention has been paid to properties such as water resistance, and improvements in these properties are desired.

[0014] As described above, the inventions described in the above Patent Documents 1 to 3 did not pay any attention to the property of water resistance. In order to improve these properties, the present inventors have used Li, which is a solid electrolyte containing lithium atoms, phosphorus atoms, and sulfur atoms and is known to have high ionic conductivity. ７ P ３ S １１ We focused on sulfide solid electrolytes with a crystalline structure. ７ P ３ S １１ As a result of conducting research and development into replacing some of the sulfur atoms in a solid electrolyte with a crystalline structure with oxygen atoms, it was discovered that replacing sulfur atoms with oxygen atoms improves water resistance and reduces the amount of hydrogen sulfide generated.

[0015] By replacing some of the sulfur atoms with oxygen elements, it is possible to eliminate the use of halogen atoms or to minimize the amount of raw materials containing halogen atoms used, thereby reducing costs, and furthermore, it is possible to simultaneously achieve high water resistance. This is a surprising phenomenon that has not been recognized at all until now, and is not disclosed at all in Patent Documents 1 to 3.

[0016] In this specification, the term "solid electrolyte" refers to an electrolyte that maintains a solid state at 25° C. under a nitrogen atmosphere. The "sulfide solid electrolyte" of this embodiment is a solid electrolyte that contains oxygen atoms in addition to at least lithium atoms, sulfur atoms, and phosphorus atoms, and may also contain halogen atoms, and has ionic conductivity attributable to lithium atoms.

[0017] The term "sulfide solid electrolyte" includes both crystalline sulfide solid electrolytes having a crystalline structure and amorphous sulfide solid electrolytes. In this specification, a crystalline sulfide solid electrolyte is a solid electrolyte in which 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.

[0018] 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.

[0019] (Various aspects of the present embodiment) A sulfide solid electrolyte according to a first aspect of the present embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and the oxygen atoms (M Ｏ ) and the sulfur atom (M Ｓ ) and the molar ratio (M Ｏ / M Ｓ ) is 0.0050 or more, and in X-ray diffraction measurement using CuKα rays, the sulfide solid electrolyte has diffraction peaks at 2θ=17.8±0.3°, 18.2±0.3°, 19.8±0.3°, 21.8±0.3°, 23.8±0.3°, 25.9±0.3°, 29.5±0.3°, and 30.0±0.3°.

[0020] As described above, the sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and by setting the molar ratio of oxygen atoms to sulfur atoms within a predetermined range and having the above-mentioned predetermined diffraction peak, it has high ionic conductivity, high water resistance, and low cost. The mechanism by which the sulfide solid electrolyte of this embodiment has high ionic conductivity, high water resistance, and low cost is not clear, but can be thought of as follows.

[0021] The sulfide solid electrolyte of this embodiment contains oxygen atoms among the various atoms constituting it, and it is thought that some of the sulfur atoms are substituted with oxygen atoms. More specifically, the diffraction peaks of the sulfide solid electrolyte of this embodiment are ７ P ３ S １１ It is thought that this is the same as the diffraction peak that appears in the crystal structure, but by containing a certain amount of oxygen atoms, ７ P ３ S １１ It is believed that some of the sulfur atoms in the crystal structure are replaced with oxygen atoms. Although oxygen atoms have a smaller ionic radius than sulfur atoms, Li ７ P ３ S １１ It is believed that the lattice spacing of the crystal structure is extended, causing a unique distortion of the crystal lattice, which in turn changes the distance between lithium atoms in the crystal structure, thereby improving ionic conductivity. Furthermore, by substituting some of the sulfur atoms with oxygen atoms, the amount of sulfur atoms in the sulfide solid electrolyte is reduced, which is thought to reduce the amount of hydrogen sulfide generated at low dew points, i.e., improve water resistance.

[0022] Since the sulfide solid electrolyte of this embodiment has the above-mentioned predetermined diffraction peak, Li ７ P ３ S １１ It is thought that the Li has a crystalline structure as a basic skeleton. ７ P ３ S１１ A part of the sulfur atoms constituting the crystal structure is replaced with oxygen atoms, and the ７ P ３ S １１ It is believed that the compound has a crystalline structure. The substitution of some sulfur atoms with oxygen atoms is discussed in the solid ３１ PSO observed by P-NMR measurement ３ ３－ The peak due to PO ４ ３－ The peak due to P ２ O ７ ４－ This can be confirmed by the presence of a peak due to the above. Thus, it is considered that the sulfide solid electrolyte of this embodiment has high ionic conductivity and high water resistance, and is manufactured at low cost.

[0023] The sulfide solid electrolyte according to a second aspect of the present embodiment is the sulfide solid electrolyte according to the first aspect, wherein the molar ratio (M Ｏ / M Ｓ ) is equal to or greater than 0.0050 and equal to or less than 0.25.

[0024] As described above, it is believed that oxygen atoms substitute for some of the sulfur atoms in the sulfide solid electrolyte of this embodiment. When the ratio of oxygen atoms to sulfur atoms is within the above range, not only is ionic conductivity improved more efficiently, but water resistance is also improved.

[0025] The sulfide solid electrolyte according to a third aspect of the present embodiment is the first or second aspect described above, and has a composition represented by the following composition formula (1): (100-y)(aLi ２ S.b.P. ２ (S １－ｃ O ｃ ) ５ )+(y)LiX (1) (In composition formula (1), a, b, and c satisfy 0.680<a<0.730, 0.270<b<0.320, and 0.0050≦c≦0.200, respectively, and y satisfies 0.0≦y<20.0. X represents a halogen atom.)

[0026] The sulfide solid electrolyte of this embodiment has a composition represented by the composition formula (1), which facilitates improved ionic conductivity and water resistance. Since y in the composition formula (1) is 0 or greater, the sulfide solid electrolyte according to the third embodiment also contains halogen atoms. For example, as described in Patent Document 1, the inclusion of halogen atoms is expected to improve ionic conductivity. However, to supply halogen atoms to the sulfide solid electrolyte, a halogen-containing material, such as lithium halide or an elemental halogen, is used as a raw material, but lithium halide is particularly expensive. As described above, the sulfide solid electrolyte of this embodiment can improve ionic conductivity by containing oxygen atoms. Therefore, even if the amount of halogen atoms used is relatively small, such as 0.0≦y<20 as represented by the composition formula (1), the improvement in ionic conductivity, which is the main effect of halogen atoms, is easily achieved. Furthermore, when the solid electrolyte is represented by the composition formula (1), the lithium atoms, phosphorus atoms, sulfur atoms, oxygen atoms, and halogen atoms constituting the solid electrolyte are contained in a balanced manner, which facilitates the effects of using oxygen atoms and halogen atoms. As a result, it becomes easier to obtain high ionic conductivity and water resistance while reducing raw material costs.

[0027] A sulfide solid electrolyte according to a fourth aspect of the present embodiment is the sulfide solid electrolyte of the third aspect, wherein the halogen atom of X is at least one halogen atom selected from a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0028] 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.

[0029] A sulfide solid electrolyte according to a fifth aspect of the present embodiment is any one of the first to fourth aspects, wherein the oxygen atoms are selected from the group consisting of P ２ O ５The theory is that it originates from

[0030] When producing the 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 oxygen atoms can be easily incorporated into the structure of the solid electrolyte. As a result, the sulfide solid electrolyte of this embodiment has the above-mentioned diffraction peak, and also has improved ionic conductivity and water resistance.

[0031] The sulfide solid electrolyte according to a sixth aspect of the present embodiment is any one of the first to fifth aspects, further comprising: ３１ P-NMR measurement revealed that P was present at -5.0±5.0 ppm. ２ O ７ ４－ A peak due to this is observed.

[0032] solid ３１ The observation of the above peaks in the P-NMR measurement indicates that some of the sulfur atoms in the sulfide solid electrolyte of this embodiment are substituted with oxygen atoms, and that Li ７ P ３ S １１ This means that the crystal structure is substituted with oxygen atoms, which makes it easier to obtain the effects of including oxygen atoms, improving ionic conductivity and water resistance.

[0033] A sulfide solid electrolyte according to a seventh aspect of the present embodiment is any one of the first to sixth aspects, wherein the sulfide solid electrolyte has an ionic conductivity of 1.75 mS / cm or more.

[0034] The sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms and has a predetermined diffraction peak, and therefore has high ionic conductivity within the above range.

[0035] The sulfide solid electrolyte according to an eighth aspect of the present embodiment is any one of the first to seventh aspects, wherein the sulfide solid electrolyte is a glass ceramic.

[0036] Glass ceramics are obtained by heating an amorphous solid electrolyte (glass component) above its crystallization temperature. The sulfide solid electrolyte thus obtained is a Li-based solid electrolyte in which some of the sulfur atoms are replaced with oxygen atoms. ７ P ３ S １１ The resulting crystalline sulfide solid electrolyte has a crystalline structure and exhibits the above-mentioned diffraction peaks, resulting in improved ionic conductivity and water resistance.

[0037] A method for producing a sulfide solid electrolyte according to a ninth aspect of the present embodiment includes mixing raw material contents containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and heating the mixture obtained by the mixing to crystallize the mixture, and the oxygen atoms (M Ｏ ) and the sulfur atom (M Ｓ ) and the molar ratio (M Ｏ / M Ｓ ) is 0.0050 or more.

[0038] The sulfide solid electrolyte of this embodiment can be easily produced by the production method according to the ninth embodiment.

[0039] A tenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte of the ninth aspect, wherein the raw material contents contain diphosphorus pentoxide.

[0040] When diphosphorus pentasulfide is included as a raw material ingredient, some of the sulfur atoms are easily replaced with oxygen atoms, which facilitates the incorporation of oxygen atoms into the structure of the solid electrolyte. As a result, the sulfide solid electrolyte obtained by the manufacturing method of this embodiment has the above-mentioned diffraction peak, and also has improved ionic conductivity and water resistance.

[0041] [Sulfide Solid Electrolyte] The sulfide solid electrolyte of the present embodiment is a sulfide solid electrolyte having the oxygen atom (M Ｏ ) and the sulfur atom (M Ｓ ) and the molar ratio (M Ｏ / M Ｓ) is 0.0050 or more, and in X-ray diffraction measurement using CuKα rays, it has diffraction peaks at 2θ=17.8±0.3°, 18.2±0.3°, 19.8±0.3°, 21.8±0.3°, 23.8±0.3°, 25.9±0.3°, 29.5±0.3°, and 30.0±0.3°.

[0042] (Diffraction Peaks) The sulfide solid electrolyte of this embodiment has diffraction peaks at 2θ = 17.8 ± 0.3 °, 18.2 ± 0.3 °, 19.8 ± 0.3 °, 21.8 ± 0.3 °, 23.8 ± 0.3 °, 25.9 ± 0.3 °, 29.5 ± 0.3 °, and 30.0 ± 0.3 ° in X-ray diffraction measurement using CuKα radiation, and is therefore a "crystalline" sulfide solid electrolyte. The peak positions of the diffraction peaks possessed by the sulfide solid electrolyte of this embodiment vary depending on the peak position, but as described above, may vary within a range of ± 0.3 °, further ± 0.2 °, or ± 0.1 °. The measurement method for X-ray diffraction measurement using CuKα radiation in this specification will be described in the Examples.

[0043] The above diffraction peaks are ７ P ３ S １１ It is thought that this is the same as the diffraction peak that appears in the crystal structure, but by containing a certain amount of oxygen atoms, ７ P ３ S １１ It is believed that some of the sulfur atoms in the crystal structure are replaced with oxygen atoms. ３１ PSO observed by P-NMR measurement ３ ３－ The peak due to PO ４ ３－ The peak due to P ２ O ７ ４－ This can be confirmed by the presence of peaks due to

[0044] (Constituent Atoms) The sulfide solid electrolyte of this embodiment contains a lithium atom, a phosphorus atom, a sulfur atom, and an oxygen atom. The sulfide solid electrolyte of this embodiment may also contain a halogen atom. Preferred examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Of these halogen atoms, a chlorine atom, a bromine atom, and an iodine atom are preferred, with a bromine atom and an iodine atom being more preferred. The halogen atom may contain any of these atoms alone or multiple types of atoms.

[0045] The oxygen atoms in the sulfide solid electrolyte of this embodiment are P ２ O ５ The method for producing a sulfide solid electrolyte of the present embodiment is not particularly limited as long as it contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, the molar ratio of oxygen atoms to sulfur atoms is within a predetermined range, and the above-mentioned diffraction peak is exhibited. 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 sulfide solid electrolyte with oxygen atoms, P is preferably used as a raw material containing oxygen atoms. ２ O ５ It is preferable to use diphosphorus pentoxide.

[0046] Furthermore, the 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 sulfide solid electrolyte of this embodiment is more likely to exhibit the above-mentioned diffraction peaks as diffraction peaks. As a result, ionic conductivity and water resistance are improved. Here, "not containing metal atoms" not only literally means that no metal atoms are contained (i.e., 0% by mass), but also includes cases where metal atoms are unavoidably mixed in. In this case, the content is 3% by mass or less, 2% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.1% by mass or less, based on the total amount of the crystalline sulfide solid electrolyte.

[0047] (Composition) As described above, the sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, has a molar ratio of oxygen atoms to sulfur atoms within a predetermined range, and has the above-mentioned diffraction peaks. The composition of the sulfide solid electrolyte of this embodiment will be described below.

[0048] The sulfide solid electrolyte of this embodiment contains oxygen atoms (M Ｏ ) sulfur atom (M Ｓ ) to the ratio (M Ｏ / M Ｓ ) is 0.0050 or more. Ｏ / M Ｓ If the ratio (M ) is less than 0.0050, the effect of using oxygen atoms cannot be obtained, and the effect of improving ionic conductivity and water resistance is difficult to obtain. Ｏ / M Ｓ The ratio (M) is preferably 0.0080 or more, more preferably 0.010 or more, and the upper limit is preferably 0.25 or less, more preferably 0.22 or less, and even more preferably 0.20 or less. Ｏ / M Ｓ ) is preferably 0.0050 or more and 0.25 or less, 0.0080 or more and 0.25 or less, 0.010 or more and 0.25 or less, 0.0050 or more and 0.22 or less, 0.0080 or more and 0.22 or less, 0.010 or more and 0.22 or less, 0.0050 or more and 0.20 or less, 0.0080 or more and 0.20 or less, and 0.010 or more and 0.20 or less.

[0049] The sulfide solid electrolyte of this embodiment preferably has a composition represented by the following composition formula (1): By having the composition represented by the following composition formula (1), the above-mentioned predetermined diffraction peak is more likely to appear, resulting in improved ionic conductivity and improved water resistance. The type and composition of atoms constituting the sulfide solid electrolyte of this embodiment can be confirmed, for example, by an ICP optical emission spectrometer.

[0050] (100-y) (aLi ２ S.b.P. ２ (S １－ｃ Oｃ ) ５ )+(y)LiX (1)

[0051] In composition formula (1), a, b, and c satisfy the following relations: 0.680<a<0.730, 0.270<b<0.320, and 0.0050≦c≦0.200, respectively; y satisfies the following relation: 0.0≦y<20.0; and X represents a halogen atom.

[0052] a is Li in which some of the sulfur atoms are substituted with oxygen atoms, which is the basic structure of the sulfide solid electrolyte of this embodiment. ７ P ３ S １１ The amount of raw materials containing lithium atoms and sulfur atoms used to form the crystal structure was determined by the following formula: lithium sulfide (Li ２ S). a satisfies 0.680<a<0.730. From the viewpoint of making it easier for the diffraction peak to appear and thereby improving ionic conductivity and water resistance, a is preferably 0.685 or more, more preferably 0.690 or more, and even more preferably 0.695 or more, and the upper limit is preferably 0.725 or less, more preferably 0.720 or less, and even more preferably 0.715 or less.

[0053] Representative preferred numerical ranges for a include more than 0.680 and 0.725 or less, more than 0.680 and 0.720 or less, more than 0.680 and 0.715 or less, 0.685 or more and less than 0.730, 0.685 or more and 0.725 or less, 0.685 or more and 0.720 or less, 0.685 or more and 0.715 or less, 0.690 or more and less than 0.730, 0.690 or more and 0.725 or less, 0.690 or more and 0.720 or less, 0.690 or more and 0.715 or less, 0.695 or more and less than 0.730, 0.695 or more and 0.725 or less, 0.695 or more and 0.720 or less, and 0.695 or more and 0.715 or less.

[0054] b is Li in which some of the sulfur atoms are substituted with oxygen atoms, which is the basic structure of the sulfide solid electrolyte of this embodiment. ７ P ３ S １１ The amount of raw material containing sulfur atoms and phosphorus atoms used to form the crystal structure was determined by the following formula: ２ S ５) is calculated. b satisfies 0.270<b<0.320. From the viewpoint of making it easier for the diffraction peak to appear and, as a result, improving ionic conductivity and water resistance, b is preferably 0.275 or more, more preferably 0.280 or more, and even more preferably 0.285 or more, and the upper limit is preferably 0.315 or less, more preferably 0.310 or less, and even more preferably 0.305 or less.

[0055] Representative preferred numerical ranges for b include more than 0.270 and 0.315 or less, more than 0.270 and 0.310 or less, more than 0.270 and 0.305 or less, 0.275 or more and less than 0.320, 0.275 or more and 0.315 or less, 0.275 or more and 0.310 or less, 0.275 or more and 0.305 or less, 0.280 or more and less than 0.320, 0.280 or more and 0.315 or less, 0.280 or more and 0.310 or less, 0.280 or more and 0.305 or less, 0.285 or more and less than 0.320, 0.285 or more and 0.315 or less, 0.285 or more and 0.310 or less, and 0.285 or more and 0.305 or less.

[0056] c denotes the substitution rate of oxygen atoms when some sulfur atoms are replaced with oxygen atoms. c satisfies 0.0050≦c≦0.200. From the viewpoint of making it easier to exhibit the above diffraction peak and thereby improving ionic conductivity and water resistance, c is preferably 0.0070 or more, more preferably 0.0085 or more, and even more preferably 0.010 or more, with the upper limit being preferably 0.180 or less, more preferably 0.170 or less, and even more preferably 0.160 or less.

[0057] Representative numerical ranges of c include 0.0050 or more and 0.180 or less, 0.0050 or more and 0.170 or less, 0.0050 or more and 0.160 or less, 0.0070 or more and 0.200 or less, 0.0070 or more and 0.180 or less, 0.0070 or more and 0.170 or less, 0.0070 or more and 0.160 or less, 0.0085 or more and 0.200 or less, 0.0085 or more and 0.180 or less, 0.0085 or more and 0.170 or less, 0.0085 or more and 0.160 or less, 0.010 or more and 0.200 or less, 0.010 or more and 0.180 or less, 0.010 or more and 0.170 or less, and 0.010 or more and 0.160 or less.

[0058] y means the content of halogen atoms. In the composition formula (1), for convenience, it is expressed in the form of LiX (lithium halide), but the raw material containing halogen atoms is not limited to lithium halide, and as will be described later, for example, elemental halogen may also be used. y satisfies 0.0≦y<20.0. Even if y=0.0 and no halogen atoms are contained, the inclusion of oxygen atoms makes it easier to exhibit the above diffraction peak, thereby improving ionic conductivity and water resistance. From the same viewpoint, it is preferably greater than 0.0, more preferably 1.0 or more, and even more preferably 3.0 or more, with the upper limit being preferably 15.0 or less, more preferably 10.0 or less, and even more preferably 5.0 or less.

[0059] Representative preferred numerical ranges for y include 0 or more and 15.0 or less, 0 or more and 10.0 or less, 0 or more and 5.0 or less, more than 0 and 15.0 or less, more than 0 and 10.0 or less, more than 0 and 5.0 or less, 1.0 or more and less than 20.0, 1.0 or more and 15.0 or less, 1.0 or more and 10.0 or less, 1.0 or more and 5.0 or less, 3.0 or more and less than 20.0, 3.0 or more and 15.0 or less, 3.0 or more and 10.0 or less, and 3.0 or more and 5.0 or less.

[0060] 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 sulfide solid electrolyte of this embodiment.

[0061] (solid ３１ P-NMR spectrum) The sulfide solid electrolyte of this embodiment is a solid ３１ P-NMR measurement revealed that P was present at -5.0±5.0 ppm. ２ O ７ ４－ It is preferable that a peak due to PSO be observed at 34.0±5.0 ppm. ３ ３－ Furthermore, there is a peak at 6.0±5.0 ppm due to PO ４ ３－ In this specification, a peak due to the solid 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.

[0062] P ２ O ７ ４－ Peaks due to PSO ３ ３－ Peaks due to and PO ４ ３－ The peak due to Li indicates that at least the sulfide solid electrolyte of this embodiment has oxygen atoms in its structure, and indicates that some of the sulfur atoms have been substituted with oxygen atoms. ７ P ３ S １１ This means that the crystal structure is substituted with oxygen atoms, resulting in improved ionic conductivity and water resistance.

[0063] (Ionic Conductivity) The ionic conductivity of the sulfide solid electrolyte of this embodiment can be 1.75 mS / cm or more, and even 1.80 mS / cm or more. Thus, the sulfide solid electrolyte of this embodiment has high ionic conductivity.

[0064] For example, when the amount of raw material containing a halogen atom 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 1.75 mS / cm or more, or even 1.80 mS / cm or more, 2.0 mS / cm or more, or 2.3 mS / cm or more.

[0065] (Other Crystal Structures) The sulfide solid electrolyte of this embodiment has a Li crystalline structure in which some of the sulfur atoms are substituted with oxygen atoms, which can exhibit the above-mentioned diffraction peak. ７ P ３ S １１ Although it is considered that the α-phase has a crystalline structure, it may have other crystalline structures. As other crystalline structures, for example, Li-based α-phases such as the thiolicon region II crystalline structure and the LGPS crystalline structure are also available. ３ P.S. ４ A preferred example is a crystal structure having the following basic structure:

[0066] 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 such a crystal structure include a crystal structure similar to the thio-lisicon region II type (see Solid State Ionics, 177 (2006), 2721-2725). Diffraction peaks of the thio-lisicon region II type crystal structure appear, for example, at 2θ=20.1°, 23.9°, and 29.5°, and diffraction peaks of a crystal structure similar to the thio-lisicon region II type crystal structure appear, for example, at 2θ=20.2° and 23.6°. The sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and may further contain halogen atoms, and Li ４－ｘ Ge １－ｘ P ｘ S ４ However, if a compound has the same diffraction peak as these thiolisicon region II type crystal structures, it can be said to have a thiolisicon region II type crystal structure formed by atoms other than the above atoms, i.e., Li, Ge, P, and S. Furthermore, the thiolisicon region II type crystal structure and a crystal structure similar to the thiolisicon region II type crystal structure are similar to each other, and in this specification, these are collectively referred to as the thiolisicon region II type crystal structure. Since the thiolisicon region II type crystal structure and the similar crystal structure have similar diffraction peaks, they are very close to each other, so it is technically reasonable to treat the "thiolisicon region II type crystal structure" as including the thiolisicon region II type crystal structure and the similar crystal structure.

[0067] In addition, the LGPS type crystal structure is 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”).

[0068] The sulfide solid electrolyte of this embodiment has a Li in which some of the sulfur atoms are substituted with oxygen atoms. ７ P ３ S １１ The crystalline structure 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 crystallinity and thereby obtaining higher ionic conductivity, the sulfide solid electrolyte of this embodiment is preferably a glass ceramic. The same applies to the thiolicon region II crystalline structure and the LGPS crystalline structure.

[0069] The sulfide solid electrolyte of the present embodiment has high ionic conductivity, high water resistance, and low cost, and has excellent battery performance. Therefore, it is suitable for use in, for example, an electrode mixture in combination with an electrode active material, or in a lithium ion battery (including an all-solid-state battery).

[0070] 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 mixture containing the 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 mixture containing the sulfide solid electrolyte of this embodiment and a negative electrode active material. Furthermore, the sulfide solid electrolyte may be used as it is in the electrolyte layer.

[0071] [Electrode Mixture] As described above, the electrode mixture contains the 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] (Other Components) The electrode mixture may contain other components such as a conductive material, a binder, etc. in addition to the 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 sulfide solid electrolyte and electrode active material of the present embodiment. The other components such as a conductive material, a binder, etc. may be added to and mixed with the sulfide solid electrolyte and the electrode active material when mixing them. 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.

[0080] 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.

[0081] The compounding ratio (mass ratio) of the electrode active material to the sulfide solid electrolyte in the electrode mixture is preferably 99.5:0.5 to 40:60, more preferably 99:1 to 50:50, and even more preferably 98:2 to 60:40, in order to improve battery performance and in consideration of production efficiency.

[0082] 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.

[0083] [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.

[0084] The lithium ion battery is not particularly limited in its configuration as long as it contains the sulfide solid electrolyte of the present embodiment and an electrode composite containing the sulfide solid electrolyte, and has the configuration of a commonly used lithium ion battery.

[0085] 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 sulfide solid electrolyte of the present embodiment, and the electrolyte layer preferably uses the sulfide solid electrolyte of the present embodiment.

[0086] 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.

[0087] [Method for producing sulfide solid electrolyte] A method for producing the sulfide solid electrolyte of this embodiment will be described. The method for producing the sulfide solid electrolyte of this embodiment includes mixing raw material ingredients containing lithium atoms, sulfur atoms, phosphorus atoms, and oxygen atoms, and heating the mixture obtained by the mixing to crystallize the mixture, and the oxygen atoms (M Ｏ ) and the sulfur atom (M Ｓ ) and the molar ratio (M Ｏ / M Ｓ ) is 0.0050 or more.

[0088] (Raw material containing substance) The raw material containing substance contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen 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.

[0089] 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, ...

[0090] 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.

[0091] The raw material may further contain a halogen atom, and examples of the raw material include substances containing a halogen atom. 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.

[0092] 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.

[0093] As the raw material, a substance containing at least one atom selected from the group consisting of lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and further halogen atoms, can be used. For example, 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 ２Thiophosphoryl 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 ２ metal sulfides such as aluminum sulfide and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; halides of alkali metals other than lithium such as sodium halides such as sodium iodide, sodium fluoride, sodium chloride and sodium bromide; metal halides such as aluminum halides, silicon halides, germanium halides, arsenic halides, selenium halides, tin halides, antimony halides, tellurium halides and bismuth halides; phosphorus oxychloride (POCl ３ ), phosphorus oxybromide (POBr ３ and the like.

[0094] 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.

[0095] 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.

[0096] In the method for producing a 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 ) is used. In addition, it is preferable to appropriately select from the above raw materials so as to obtain a composition represented by the above composition formula (1). By using raw materials in this way, a material containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms and having a predetermined molar ratio (M Ｏ / M Ｓ ) and having the above-described diffraction peak. Therefore, the sulfide solid electrolyte of this embodiment can be easily produced by the sulfide solid electrolyte of this embodiment.

[0097] The composition of the sulfide solid electrolyte of this embodiment can be confirmed by an ICP atomic emission spectrometer as described above, but 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, so the composition can also be considered to be a composition calculated from the substances used as raw materials and their blending ratios.

[0098] 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 is, from the viewpoint of making the diffraction peak more likely to appear and thereby improving ionic conductivity and water resistance, preferably more than 68.0 mol%, more preferably 68.5 mol% or more, even more preferably 69.0 mol% or more, still more preferably 69.5 mol% or more, based on a in the above composition formula (1), with the upper limit being preferably less than 73.0 mol%, more preferably 72.5 mol% or less, even more preferably 72.0 mol% or less, still more preferably 71.5 mol% or less. As the numerical range, the numerical range described above as the numerical range of a can be converted into mol%.

[0099] 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 is, based on c in the above composition formula (1), preferably 0.50 mol% or more, more preferably 0.70 mol% or more, even more preferably 0.85 mol% or more, and still more preferably 1.0 mol% or more, from the viewpoint of making the above diffraction peak more likely to appear and thereby improving ionic conductivity and water resistance, with the upper limit being preferably 20.0 mol% or less, more preferably 18.0 mol% or less, even more preferably 17.0 mol% or less, and even more preferably 16.0 mol% or less. As the numerical range, the numerical range described above as the numerical range of c can be converted into mol% and applied.

[0100] 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 more than 80.0 mol%, more preferably 85.0 mol% or more, even more preferably 90.0 mol% or more, and still more preferably 95.0 mol% or more, with the upper limit being preferably less than 100 mol%, more preferably 99.0 mol% or less, and even more preferably 97.0 mol% or less. Representative preferred numerical ranges include more than 80.0 mol% and less than 100 mol%, more than 80.0 mol% and 99.0 mol% or less, more than 80.0 mol% and 97.0 mol% or less, 85.0 mol% or more and less than 100 mol%, 85.0 mol% or more and 99.0 mol% or less, 85.0 mol% or more and 97.0 mol% or less, 90.0 mol% or more and less than 100 mol%, 90.0 mol% or more and 99.0 mol% or less, 90.0 mol% or more and 97.0 mol% or less, 95.0 mol% or more and less than 100 mol%, 95.0 mol% or more and 99.0 mol% or less, and 95.0 mol% or more and 97.0 mol% or less.

[0101] Furthermore, when lithium sulfide, diphosphorus pentasulfide, lithium halide, a raw material containing an oxygen atom, and other raw materials used as needed 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, based on y in the above composition formula (1), preferably more than 0.0 mol%, more preferably 1.0 mol% or more, and even more preferably 3.0 mol% or more, with the upper limit being preferably less than 20.0 mol%, more preferably 15.0 mol% or less, even more preferably 10.0 mol% or less, and still more preferably 5.0 mol% or less. As the numerical range, the numerical range described above as the numerical range of y can be converted into mol% and applied.

[0102] (Mixing) The mixing of raw material containing lithium atoms, sulfur atoms, phosphorus atoms, and oxygen atoms, and raw material containing 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 sulfide solid electrolyte of this embodiment can be preferably produced by stirring, mixing, pulverizing, or a combination of these processes, of 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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 sulfide solid electrolyte.

[0113] (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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] (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.

[0124] 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.

[0125] 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.

[0126] Drying may be carried out after mixing and before the hydrogen treatment described below, or may be carried out after the hydrogen treatment.

[0127] 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.

[0128] 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.

[0129] (Heating) When producing the sulfide solid electrolyte of this embodiment, heating may be further included. If an amorphous sulfide solid electrolyte (glass component) is obtained by the above 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. In other words, the heating can be considered an operation performed for crystallization. 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 drying, a sulfide solid electrolyte can be obtained. Depending on the heating conditions, the resulting sulfide solid electrolyte can be either amorphous or crystalline.

[0130] The heating temperature may be determined depending on the structure of the 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) at a temperature increase rate of 10 ° C. / min. The temperature of the peak top of the exothermic peak observed at the lowest temperature can be determined as the starting point. By setting the temperature range as such, 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 200 ° C. or higher, more preferably 250 ° C. or higher, and even more preferably 280 ° C. or higher. There is no particular upper limit, but it is preferably 400 ° C. or lower, more preferably 370 ° C. or lower, and even more preferably 350 ° C. or lower.

[0131] The heating time is not particularly limited as long as it is a time that allows a sulfide solid electrolyte of desired crystallinity 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.

[0132] 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.

[0133] 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.

[0134] (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

[0135] (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: Concentration method Slit configuration: Soller slit 4° (both 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

[0136] (solid ３１ P-NMR measurement) Measurement was performed using the following equipment under the following conditions: Equipment: ECZ400R (manufactured by JEOL Ltd.) Observation nuclei: ３１P 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)

[0137] 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.

[0138] (Evaluation of Water Resistance (Measurement of Amount of Hydrogen Sulfide Generated)) The solid electrolyte powders produced in each Example and Comparative Example were subjected to the following exposure test, and the amount of hydrogen sulfide generated was measured. First, the test apparatus (exposure test apparatus 1) used in the exposure test will be described with reference to FIG. 1 . The exposure test apparatus 1 mainly comprises a flask 10 for humidifying nitrogen, a static mixer 20 for mixing humidified nitrogen and non-humidified nitrogen, a dew point meter 30 (M170 / DMT152 manufactured by VAISALA) for measuring the moisture content of the mixed nitrogen, a double reaction tube 40 in which a measurement sample is placed, a dew point meter 50 for measuring the moisture content of nitrogen discharged from the double reaction tube 40, and a hydrogen sulfide meter 60 (Model 3000RS manufactured by AMI) for measuring the hydrogen sulfide concentration in the discharged nitrogen, and these components are connected by pipes (not shown). The temperature of the flask 10 is set to 10°C by a cooling tank 11. The tubes connecting the components were made of Teflon (registered trademark) tubing with a diameter of 6 mm. In this figure, the tubes are not shown, and instead, the flow of nitrogen is indicated by arrows.

[0139] The evaluation procedure was as follows. Approximately 1.5 g of powder sample 41 obtained in each of the Examples and Comparative Examples was weighed out in a nitrogen glove box with a dew point of -80°C, and the sample was placed inside reaction tube 40 and sealed, sandwiched between quartz wool 42. The evaluation was carried out at room temperature (20°C). Nitrogen was supplied to apparatus 1 at 0.02 MPa from a nitrogen source (not shown). The supplied nitrogen passed through a bifurcated branch pipe BP, with a portion being supplied to flask 10 and humidified. The remainder was supplied directly to static mixer 20 as unhumidified nitrogen. The amount of nitrogen supplied to flask 10 was adjusted with needle valve V. The dew point was controlled by adjusting the flow rates of unhumidified and humidified nitrogen with a needle valve-equipped flow meter FM. Specifically, unhumidified nitrogen was supplied to the static mixer 20 at a flow rate of 800 mL / min and humidified nitrogen at a flow rate of 10 to 30 mL / min, and mixed. The dew point of the mixed gas (a mixture of unhumidified nitrogen and humidified nitrogen) was confirmed using the dew point meter 30.

[0140] After adjusting the dew point to -30°C, the three-way cock 43 was rotated to allow the mixed gas to flow through the reaction tube 40 for two hours. The amount of hydrogen sulfide contained in the mixed gas that had passed through the sample 41 was measured with a hydrogen sulfide meter 60. The amount of hydrogen sulfide was recorded at 15-second intervals. For reference, the dew point of the mixed gas after exposure was also measured with a dew point meter 50. The cumulative amount of hydrogen sulfide generated (cc / g-solid electrolyte) for 120 minutes from the start of measurement is shown in Table 1. In addition, the nitrogen was passed through an alkali trap 70 to remove hydrogen sulfide from the nitrogen after measurement.

[0141] Example 1 A raw material containing lithium sulfide, diphosphorus pentasulfide, and diphosphorus pentoxide weighed out to a molar ratio of 70.0:29.7:0.3 (total: 1.5 g) was 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. The obtained powdered product (amorphous sulfide solid electrolyte) was heated for 2 hours at a heating temperature of 300 ° C. under an inert atmosphere (nitrogen atmosphere), to obtain a crystalline sulfide solid electrolyte.

[0142] In the composition formula (1) of the obtained crystalline sulfide solid electrolyte, a, b, and c are 70, 30, and 0.01, respectively. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured and found to be 2.5 mS / cm. In addition, when the obtained crystalline sulfide solid electrolyte was subjected to X-ray diffraction measurement using CuKα radiation, diffraction peaks were confirmed at 2θ = 17.9 °, 18.4 °, 19.7 °, 21.7 °, 23.6 °, 25.8 °, 29.6 °, and 29.9 °, and diffraction peaks corresponding to 2θ = 17.8 ± 0.3 °, 18.2 ± 0.3 °, 19.8 ± 0.3 °, 21.8 ± 0.3 °, 23.8 ± 0.3 °, 25.9 ± 0.3 °, 29.5 ± 0.3 °, and 30.0 ± 0.3 ° were confirmed. The X-ray diffraction pattern is shown in FIG. 2.

[0143] Examples 2 to 10 Crystalline sulfide solid electrolytes of Examples 2 to 10 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 changed to those shown in Table 1. The heating temperature of the product (amorphous sulfide solid electrolyte) in these examples was 300°C. For the crystalline sulfide solid electrolyte obtained in each example, a, b, c, and y in the composition formula (1) are shown in Table 1. 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 Table 1, and the X-ray diffraction patterns of Examples 2 to 10 are shown in FIG. 2.

[0144] Comparative Example 1 A sulfide solid electrolyte of Comparative Example was produced 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 1. The ionic conductivity, thermogravimetric differential calorimetry, and powder XRD diffraction measurement were performed on the obtained crystalline sulfide solid electrolyte. The results are shown in Table 1, and the X-ray diffraction pattern of Comparative Example 1 is shown in FIG.

[0145]

[0146] From FIG. 2 and Table 1, it was confirmed that the sulfide solid electrolyte of this embodiment had diffraction peaks at 2θ = 17.8 ± 0.3°, 18.2 ± 0.3°, 19.8 ± 0.3°, 21.8 ± 0.3°, 23.8 ± 0.3°, 25.9 ± 0.3°, 29.5 ± 0.3°, and 30.0 ± 0.3°. That is, the sulfide solid electrolyte obtained in the examples can be said to be a crystalline sulfide solid electrolyte. It was confirmed that the ionic conductivity of the sulfide solid electrolyte of this embodiment was 1.8 to 3.2 mS / cm, which was higher than the ionic conductivity of the sulfide solid electrolyte of Comparative Example 1, 1.7 mS / cm. Furthermore, with regard to the water resistance of the sulfide solid electrolyte of this embodiment, the amount of hydrogen sulfide generated was at most 5.79 (cc / g), which was as low as 6.00 (cc / g) or less, confirming that the sulfide solid electrolyte had excellent water resistance. From the above results, it is considered that the sulfide solid electrolyte of Comparative Example 1 did not use a raw material containing oxygen atoms, and therefore did not achieve high ionic conductivity and was also poor in water resistance.

[0147] The sulfide solid electrolytes of Examples 8 and 9 contain halogen atoms. It can be seen that the sulfide solid electrolytes containing halogen atoms have ionic conductivity and water resistance comparable to the sulfide solid electrolytes of other Examples that do not contain halogen atoms. This confirms that the sulfide solid electrolyte of this embodiment has high ionic conductivity and high water resistance even when the content of halogen atoms is low, i.e., even when it is low cost.

[0148] Regarding the sulfide solid electrolyte of Example 2, solid ３１ P-NMR measurement was carried out. ３１ The P-NMR spectrum is shown in Figure 3. ３１ Using 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 2. The calculated phosphorus ratio (mol%) of each structure is shown in Table 2.

[0149]

[0150] As shown in Table 2, the sulfide solid electrolyte of Example 2 has a P ２ O ７ ４－ 2 and Table 1, the sulfide solid electrolyte of Example 2 is a Li2O3 solid electrolyte in which some of the sulfur atoms are substituted with oxygen atoms. ７ P ３ S １１ It can be seen that the sulfide solid electrolyte of Example 2 has a crystalline structure. ３１ The results of P-NMR measurements and the results of P-NMR measurements have confirmed that the sulfide solid electrolytes of other examples also have the same crystal structure. ７ P ３ S １１In comparison with the sulfide solid electrolyte of Comparative Example 1 having a Li-type crystalline structure, the sulfide solid electrolyte of the Example has a Li-type crystalline structure in which some of the sulfur atoms are substituted with oxygen atoms. ７ P ３ S １１ It is believed that the presence of this type of crystal structure results in high ionic conductivity and high water resistance.

[0151] From the above results, it can be seen that the sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and has a molar ratio (M Ｏ / M Ｓ ) is within a predetermined range and has a predetermined diffraction peak, and it has been confirmed that by having such a configuration, it is possible to reduce costs while having high ionic conductivity and high water resistance. ７ P ３ S １１ It is believed that by substituting oxygen atoms for some of the sulfur atoms in the crystalline structure, high ionic conductivity and high water resistance can be achieved while achieving low costs.

[0152] The sulfide solid electrolyte of this embodiment has high ionic conductivity and high water resistance, and therefore has 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, as well as in automotive applications.

Claims

1. A compound containing a lithium atom, a phosphorus atom, a sulfur atom, and an oxygen atom, wherein the oxygen atom (M Ｏ ) and the sulfur atom (M Ｓ ) and the molar ratio (M Ｏ / M Ｓ ) is 0.0050 or more, and in X-ray diffraction measurement using CuKα radiation, the sulfide solid electrolyte has diffraction peaks at 2θ = 17.8 ± 0.3°, 18.2 ± 0.3°, 19.8 ± 0.3°, 21.8 ± 0.3°, 23.8 ± 0.3°, 25.9 ± 0.3°, 29.5 ± 0.3°, and 30.0 ± 0.3°.

2. The molar ratio (M Ｏ / M Ｓ 2. The sulfide solid electrolyte according to claim 1, wherein σ is 0.0050 or more and 0.25 or less.

3. The sulfide solid electrolyte according to claim 1 or 2, having a composition represented by the following composition formula (1): (100-y)(aLi ２ S.b.P. ２ (S １－ｃ O ｃ ) ５ )+(y)LiX (1) (In composition formula (1), a, b, and c satisfy 0.680<a<0.730, 0.270<b<0.320, and 0.0050≦c≦0.200, respectively, and y satisfies 0.0≦y<20.

0. X represents a halogen atom.) 4. The sulfide solid electrolyte according to claim 3, wherein the halogen atom of X is at least one halogen atom selected from the group consisting of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

5. The oxygen atom is P ２ O ５ The sulfide solid electrolyte according to any one of claims 1 to 4, which is derived from 6. Solid ３１ P-NMR measurement revealed that P was present at -5.0±5.0 ppm. ２ O ７ ４－ The sulfide solid electrolyte according to any one of claims 1 to 5, in which a peak due to 7. The sulfide solid electrolyte according to any one of claims 1 to 6, having an ionic conductivity of 1.75 mS / cm or more.

8. The sulfide solid electrolyte according to any one of claims 1 to 7, which is a glass ceramic.

9. A method for producing a crystallized material, comprising: mixing raw material components containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms; and heating the mixture obtained by the mixing to crystallize the mixture, wherein the oxygen atoms (M Ｏ ) and the sulfur atom (M Ｓ ) and the molar ratio (M Ｏ / M Ｓ ) is 0.0050 or more.

10. The method for producing a sulfide solid electrolyte according to claim 9, wherein the raw material contains diphosphorus pentoxide.

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