JP2021192375A - Sulfide solid electrolyte - Google Patents

Abstract

To provide a sulfide solid electrolyte containing a novel crystal structure and having high ionic conductivity.SOLUTION: A sulfide solid electrolyte includes lithium, phosphorus, sulfur and halogen elements, has an algyrodite crystal structure, and has diffraction peaks at 2θ=29.1±0.5deg and 33.8±0.5deg in powder X-ray diffraction measurements using CuKα rays.SELECTED DRAWING: None

Description

The present invention relates to a sulfide solid electrolyte, an electrode mixture and a lithium ion battery.

With the rapid spread of information-related devices such as personal computers, video cameras, and mobile phones and communication devices in recent years, the development of batteries used as power sources thereof has been regarded as important. Among the batteries, lithium ion batteries are attracting attention from the viewpoint of high energy density.
Lithium-ion batteries currently on the market use an electrolytic solution containing a flammable organic solvent, so installation of a safety device that suppresses temperature rise during a short circuit and improvements in structure and materials to prevent a short circuit Is required. On the other hand, a lithium-ion battery in which the electrolyte is changed to a solid electrolyte and the battery is completely solidified does not use a flammable organic solvent in the battery, so that the safety device can be simplified, and the manufacturing cost and productivity can be improved. Is considered to be excellent.

A sulfide solid electrolyte is known as a solid electrolyte used in a lithium ion battery. Various crystal structures of sulfide solid electrolytes are known, and one of them is an Argyrodite type crystal structure (Patent Documents 1 to 5 and Non-Patent Documents 1 to 3).
The algyrodite type crystal structure is a crystal having high stability, and some have high ionic conductivity. However, there is a need to develop a manufacturing method that can be mass-produced and to further improve the ionic conductivity.

Special Table 2010-540396 Gazette International release WO2015 / 01937 International release WO2015 / 012042 Japanese Unexamined Patent Publication No. 2016-24874 International release WO2016 / 104702

Angew. chem Vol. 47 (2008), No. 4, P. 755-758 Phys. Status. Solidi Vol. 208 (2011), No. 8, P.I. 1804-1807 Solid State Inics Vol. 221 (2012) P.I. 1-5

One of the objects of the present invention is to provide a novel sulfide solid electrolyte having high ionic conductivity.

According to one embodiment of the present invention, it contains lithium, phosphorus and sulfur, contains an algyrodite type crystal structure, and has 2θ = 14.4 ± 0.5 deg and 33.8 ± in powder X-ray diffraction measurements using CuKα rays. A sulfide solid electrolyte having a diffraction peak at 0.5 deg is provided.
Further, according to one embodiment of the present invention, the above-mentioned sulfide solid electrolyte and an electrode mixture containing an active material are provided.
Further, according to one embodiment of the present invention, there is provided a lithium ion battery containing at least one of the sulfide solid electrolyte and the electrode mixture.

According to one embodiment of the present invention, it is possible to provide a sulfide solid electrolyte containing a novel crystal structure and having high ionic conductivity.

It is a figure which shows the XRD pattern of the intermediate of Example 1. FIG. It is a figure which shows the XRD pattern of the sulfide solid electrolyte obtained in Example 1. FIG. It is a figure which shows ^{the solid 31} P-NMR measurement result of the sulfide solid electrolyte obtained in Example 1-3. It is a figure which shows the Raman measurement result of the sulfide solid electrolyte obtained in Example 1. FIG. It is a figure which shows the XRD pattern of the sulfide solid electrolyte obtained in Example 3. FIG. It is a figure which shows the XRD pattern of the sulfide solid electrolyte obtained in the comparative example 1. FIG. It is an XRD pattern of the mixed powder obtained in the comparative example 2.

The sulfide solid electrolyte according to the first aspect of the present invention contains lithium, phosphorus and sulfur, and contains an algyrodite type crystal structure. Then, it is a sulfide solid electrolyte having diffraction peaks at 2θ = 14.4 ± 0.5 deg and 33.8 ± 0.5 deg in the powder X-ray diffraction measurement using CuKα ray. The crystal structure specified by 2θ = 14.4 ± 0.5 deg and 33.8 ± 0.5 deg is considered to be a novel crystal structure. The novel crystal structure is for the unit structure of P ₂ S ₆ ^4-primary, as compared with Arujirodaito type crystal structure, is presumed that the element ratio S is small structures.

The novel crystal structure may appear in 29.1 ± 0.5 deg in addition to 14.4 ± 0.5 deg and 33.8 ± 0.5 deg. The sulfide solid electrolyte of the present invention may have these peaks.

Examples of the algyrodite-type crystal structure include those disclosed in Non-Patent Documents 1 to 3, JP-A-2010-540396, JP-A-2011-096630, and JP-A-2013-21171. can.

The sulfide solid electrolyte of this embodiment may contain a crystal structure other than the above crystal structure and the algyrodite type crystal structure. In this embodiment, the sulfide solid electrolyte containing a crystal structure is a sulfide solid electrolyte in which a peak derived from the sulfide solid electrolyte is observed in the X-ray diffraction pattern in the X-ray diffraction measurement. It does not matter whether or not there is a peak derived from the raw material. The sulfide solid electrolyte of the present invention may contain an amorphous solid electrolyte as a part thereof.

The sulfide solid electrolyte of this embodiment preferably has diffraction peaks at 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg in powder X-ray diffraction measurements using CuKα rays. By having these diffraction peaks, it can be determined that the sulfide solid electrolyte has an algyrodite type crystal structure.
The diffraction peaks of 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg are peaks derived from the algyrodite type crystal structure. Arujirodaito type crystal structure, and PS ₄ ^3- of the unit structure of the main skeleton, a structure surrounded by elemental sulfur lithium element (Li) around its (S) or halogen element (X) is arranged.
The diffraction peaks of the algyrodite type crystal structure are, for example, 2θ = 15.3 ± 0.5 deg, 17.7 ± 0.5 deg, 31.1. It may also appear at ± 0.5 deg, 44.9 ± 0.5 deg, and 47.7 ± 0.5 deg. The sulfide solid electrolyte of this embodiment may have these peaks.

In the present application, the position of the diffraction peak is determined by A ± 0.5 deg or A ± 0.4 deg when the median value is A, but it is preferably A ± 0.3 deg. For example, in the case of the above-mentioned diffraction peak of 2θ = 25.2 ± 0.5 deg, the median value A is 25.2 deg, and it is preferable that the median value is in the range of 2θ = 25.2 ± 0.3 deg. The same applies to the determination of all other diffraction peak positions in the present application.

The sulfide solid electrolyte of this embodiment preferably contains a chalcogen element or a halogen element other than sulfur. More preferably, it contains a halogen element, and most preferably chlorine or bromine.

In addition to the above-mentioned lithium, phosphorus and sulfur, the sulfide solid electrolyte of this embodiment may contain one or more elements X selected from the group consisting of chalcogen elements excluding sulfur and halogen elements. In this case, when the molar ratio of lithium to phosphorus is a (Li / P), the molar ratio of sulfur to phosphorus is b (S / P), and the molar ratio of element X to phosphorus is c (X / P), the following formula ( It is preferable to satisfy A) to (C).
5.0 ≤ a ≤ 7.5 ... (A)
6.5 ≤ a + c ≤ 7.5 ... (B)
0.5 ≤ a-b ≤ 1.5 ... (C)
(In the formula, b> 0 and c ≧ 0 are satisfied.)

Regarding the element X, examples of the chalcogen element excluding sulfur include oxygen (O), selenium (Se), tellurium (Te) and the like, and examples of halogen include F, Cl, Br, I and the like. The element X is preferably composed of only a halogen element.

The smaller the ionic radius of the element X, the more the element X contained in the algyrodite type crystal structure, and the higher the ionic conductivity. Therefore, the molar ratio a of lithium to phosphorus can be adjusted by the ionic radius of the element X. preferable. The element X can be classified into the following _{three groups (X 1} , X ₂ and X 3) according to the size of the ionic radius.
X ₁ : F, Cl, O
X ₂ : Br
X ₃ : I, Se, Te
In the element X, when _{the molar ratio occupied by the element X 1} is the largest, the above formula (A) is preferably 5.0 ≦ a ≦ 6.5, and 5.2 ≦ a ≦ 6.1. Is more preferable. Further, in the element X, when _{the molar ratio occupied by the element X 2} is the largest, the above formula (A) is preferably 5.2 ≦ a <≦ 6.8, and 5.3 ≦ a <≦ 6. 6 is more preferable. Further, in the element X, when _{the molar ratio occupied by the element X 3} is the largest, the above formula (A) is preferably 5.5 ≦ a ≦ 7.2, and 5.5 ≦ a ≦ 7.0. It is more preferable to have.

The above formula (B) preferably has 6.6 ≦ a + c ≦ 7.4, and more preferably 6.7 ≦ a + c ≦ 7.3.
In the above formula (C), 0.6 ≦ ab ≦ 1.3 is preferable, and 0.7 ≦ ab ≦ 1.3 is more preferable.

The molar ratio a (Li / P) of lithium to phosphorus, the molar ratio b (S / P) of sulfur to phosphorus, and the molar ratio c (X / P) of element X to phosphorus are the following formulas (A') to (C). ') Is more preferable.
5.0 ≤ a ≤ 7.1 ... (A')
6.5 ≤ a + c <7.1 ... (B')
1.0 <ab ≤ 1.5 ... (C')
(In the formula, b> 0 and c ≧ 0 are satisfied.)

The above formula (B') preferably has 6.6 ≦ a + c <7.1, and more preferably 6.8 ≦ a + c <7.1.
In the above formula (C'), 1.0 <ab ≦ 1.4 is preferable, and 1.0 <ab ≦ 1.3 is more preferable.
In the element X, when _{the molar ratio occupied by the element X 1} is the largest, the above formula (A') is preferably 5.2 ≦ a ≦ 6.5, and 5.25 ≦ a ≦ 6.4. Is more preferable. Further, in the element X, when _{the molar ratio occupied by the element X 2} is the largest, the above formula (A') is preferably 5.2 ≦ a ≦ 6.8, and 5.3 ≦ a ≦ 6.6. Is more preferable. Further, in the element X, when _{the molar ratio occupied by the element X 3} is the largest, the above formula (A') is preferably 5.5 ≦ a ≦ 7.0, and 5.5 ≦ a ≦ 6.8. Is more preferable.

In addition to the above lithium, phosphorus, sulfur and element X, elements such as Si, Ge, Sn, Pb, B, Al, Ga, As, Sb and Bi may be contained. When the sulfide solid electrolyte contains one or more elements M selected from the group consisting of Si, Ge, Sn, Pb, B, Al, Ga, As, Sb and Bi, the above (A) to (C) or The molar ratio of each element in (A') to (C') is the molar ratio to the total of the elements M and phosphorus. For example, the molar ratio a (Li / P) of lithium to phosphorus is Li / (P + M).

The sulfide solid electrolyte of this embodiment preferably satisfies, for example, the composition represented by the following formula (4).
Li _a (P _1-α M _α ) S _b X _c (4)
(In the formula, M is one or more elements selected from the group consisting of Si, Ge, Sn, Pb, B, Al, Ga, As, Sb and Bi, and X is F, Cl, Br, I. , O, Se and Te. One or more elements selected from the group. A to c satisfy the following formulas (1) to (3). Α is 0 ≦ α ≦ 0.3).
5.0 ≤ a ≤ 7.5 ... (1)
6.5 ≤ a + c ≤ 7.5 ... (2)
0.5 ≤ a-b ≤ 1.5 ... (3)
(In the formula, b> 0 and c ≧ 0 are satisfied.)

It is preferable that X in the formula (4) is one or more halogen elements selected from F, Cl, Br and I. As a result, the halogen element is incorporated into the algyrodite type crystal structure, and the ionic conductivity is enhanced. When two or more halogen elements are contained, the content ratio of each element is not particularly limited.
α is preferably 0.

The above formula (2) preferably has 6.6 ≦ a + c ≦ 7.4, and more preferably 6.7 ≦ a + c ≦ 7.3.
In the above formula (3), 0.6 ≦ ab ≦ 1.3 is preferable, and 0.7 ≦ ab ≦ 1.3 is more preferable.
In the element X, when _{the molar ratio occupied by the element X 1} is the largest, the above formula (1) is preferably 5.0 ≦ a ≦ 6.5, and 5.2 ≦ a ≦ 6.1. Is more preferable. Further, in the element X, when _{the molar ratio occupied by the element X 2} is the largest, the above formula (1) is preferably 5.2 ≦ a <≦ 6.8, and 5.3 ≦ a <≦ 6. 6 is more preferable. Further, in the element X, when _{the molar ratio occupied by the element X 3} is the largest, the above formula (1) is preferably 5.5 ≦ a ≦ 7.2, and 5.5 ≦ a ≦ 7.0. It is more preferable to have.

It is more preferable that a to c of the above formula (4) satisfy the following formulas (1') to (3').
5.0 ≤ a ≤ 7.1 ... (1')
6.5 ≤ a + c <7.1 ... (2')
1.0 <ab ≤ 1.5 ... (3')
(In the formula, b> 0 and c ≧ 0 are satisfied.)

The above formula (2') preferably has 6.6 ≦ a + c <7.1, and more preferably 6.8 ≦ a + c <7.1.
In the above formula (3'), 1.0 <ab ≦ 1.4 is preferable, and 1.0 <ab ≦ 1.3 is more preferable.
In the element X, when _{the molar ratio occupied by the element X 1} is the largest, the above formula (1') is preferably 5.2 ≦ a ≦ 6.5, and 5.25 ≦ a ≦ 6.4. Is more preferable. Further, in the element X, when _{the molar ratio occupied by the element X 2} is the largest, the above formula (1') is preferably 5.2 ≦ a ≦ 6.8, and 5.3 ≦ a ≦ 6.6. Is more preferable. Further, in the element X, when _{the molar ratio occupied by the element X 3} is the largest, the above formula (1') is preferably 5.5 ≦ a ≦ 7.0, and 5.5 ≦ a ≦ 6.8. Is more preferable.

The molar ratio and composition of each of the above-mentioned elements are not the molar ratio and composition of the input raw material used for production, but the sulfide solid electrolyte which is a product. For the molar ratio and composition of each element in the sulfide solid electrolyte, the values measured by the ICP emission spectrometry method shall be used except for special circumstances such as difficulty in analysis. The measurement method of the ICP emission spectrometry method will be described in Examples.
The molar ratio of each element can be controlled, for example, by adjusting the content of each element in the raw material.

The sulfide solid electrolyte of this embodiment has diffraction peaks (due to the argylodite-type crystal structure) at 2θ = 17.6 ± 0.4 deg and 2θ = 18.1 ± 0.4 deg in powder X-ray diffraction using CuKα rays. It is preferable not to have a diffraction peak), or if it has, it is preferable to satisfy the following formula (5).
_{0 <I A / I B <} 0.1 (5)
(Wherein, _{I A} represents the intensity of the diffraction peak but not the diffraction peak of Arujirodaito crystal structure of 2 [Theta] = 17.6 ± 0.4 deg and 2θ = 18.1 ± 0.4deg, _{I B} is 2 [Theta] = Represents the intensity of the diffraction peak of 29.7 ± 0.5 deg.)

Crystal structure identified by I _A (hereinafter. Referred to Li ₃ PS ₄ crystal structure) are the low ionic conductivity, lowering the ionic conductivity of the solid electrolyte. The above formula (5) represents that the amount of the _{Li 3} PS ₄ crystal structure is relatively small as compared with the algyrodite type crystal structure. Equation (5) _is, 0 _<more preferably _I is A / I B _<0.05, more preferably 0 _<I A / I B <0.02.
It should be noted that either 2θ = 17.6 ± 0.4 deg or 2θ = 18.1 ± 0.4 deg may not be able to be measured because it usually overlaps with the diffraction peak of the algyrodite type crystal structure having a relatively strong peak intensity. Therefore, of 2θ = 17.6 ± 0.4 deg and 2θ = 18.1 ± 0.4 deg, the one that is not the diffraction peak of the algyrodite type crystal structure is usually the weakest of these two peaks observed. Means one.

The sulfide solid electrolyte of this embodiment preferably satisfies the following formula (6) in powder X-ray diffraction using CuKα rays.
_{0 <I C / I B <} 0.100 ··· (6)
(Wherein, _{I C} represents the intensity of the diffraction peak of 2θ = 14.4 ± 0.5deg, _{I B} represents the intensity of the diffraction peak of 2θ = 29.7 ± 0.5deg.)

The diffraction peak of 2θ = 14.4 ± 0.5 deg is the diffraction peak of the above-mentioned novel crystal, and the diffraction peak of 2θ = 29.7 ± 0.5 deg is the diffraction peak of the algyrodite type crystal structure. The formula (6) represents that the number of new crystal structures is relatively small as compared with the algyrodite type crystal structure. In this embodiment, for example, a sulfide solid electrolyte containing an argylodite-type crystal structure is obtained by heat-treating an intermediate obtained by vitrifying the raw material mixture, but when the heat treatment temperature is raised, the formation of the argylodite-type crystal structure proceeds. Ion conductivity is improved because it is easy and the crystallinity is high. On the other hand, if the temperature of the heat treatment is too high, the formation of a new crystal structure increases, so that the formation of an argylodite type crystal structure is hindered. Therefore, it is preferable that a novel crystal structure is present in the sulfide solid electrolyte, but it is preferable that the ratio is low. Equation _(6), 0 _<more preferably I a C / I B <0.050, further _preferably a _{0.005 <I C / I B <} 0.030.

The sulfide solid electrolyte according to the second aspect of the present invention contains lithium, phosphorus and sulfur, and has an algyrodite type crystal structure. Then, in the solid ³¹ P-NMR measurement, it has a peak at 110 ± 5 ppm. The ^{structure identified by the peak of 110 ± 5 ppm in the solid 31} P-NMR measurement is considered to be a novel crystal structure. The novel crystal structure is for the unit structure of P ₂ S ₆ ^4-primary, as compared with Arujirodaito structure is presumed that the element ratio S is small structures.
The sulfide solid electrolyte according to the first aspect of the present invention also preferably has a peak at 110 ± 5 ppm in the ^{solid 31 P-NMR measurement.}

Novel crystalline structure contained in the sulfide solid electrolyte of the present embodiment, is constituted from a structure comprising a P ₂ S ₆ units. _Here, 380 cm having a novel crystalline structure of the present comprised of P 2 _{S 6} units, in addition to having a peak within a range of 110 ± 5 ppm in solid ³¹ P-NMR measurements, Raman spectroscopy ^- It can also be confirmed by having a peak in the range of ^{1 to} 395 cm ^{-1, and it is preferable that both are satisfied.} In the solid ³¹ P-NMR measurement, it is preferable to use the MAS (Magic Angle Spinning) method.
Sulfide solid electrolyte of the present embodiment, since the new crystalline structure is composed of a structure that includes a P ₂ S ₆ units, the less S defect structure of Arujirodaito type crystal structure is believed that the high ionic conductivity is obtained ..

The half width of the peak of 110 ± 5 ppm in the profile of the ^{solid 31 P-NMR measurement is preferably 5 ppm or less.} It is more preferably 4 ppm or less, still more preferably 3.5 ppm or less. The half-value width of the peak is related to the crystallinity of the crystal structure, and when the crystallinity is poor and the structure is greatly disturbed, the half-value width becomes wide. When the half width is greater than 5ppm is, P ₂ S ₆ units are not regularly arranged, it is inferred that does not constitute a novel crystalline structure.
The above half-value width can be confirmed by the method described in the examples.

Suitable requirements such as the composition of the sulfide solid electrolyte according to the second aspect of the present invention are the same as those of the sulfide solid electrolyte according to the first aspect of the present invention.
Hereinafter, the sulfide solid electrolyte according to the first aspect of the present invention and the sulfide solid electrolyte according to the second aspect of the present invention are collectively referred to as “the sulfide solid electrolyte of the present invention”.

The sulfide solid electrolyte of the present invention has a manufacturing method including a step of producing an intermediate by applying a mechanical stress to a mixture of raw materials described later and reacting the mixture, and a step of heat-treating the intermediate to crystallize it. It can be produced by one embodiment of the production method).

The raw materials used are two or more compounds containing the elements essential to the elemental sulfide solid electrolyte to be produced, that is, lithium, phosphorus, sulfur and any element X (chalcogen elements and halogen elements excluding oxygen and sulfur). Or use it in combination with a single substance.

Examples of the raw material containing lithium include _{lithium compounds such as lithium sulfide (Li 2} S), lithium oxide (Li ₂ O) and lithium carbonate (Li ₂ CO ₃ ), and lithium metal alone. Among them, a lithium compound is preferable, and lithium sulfide is more preferable.
The lithium sulfide can be used without particular limitation, but high-purity lithium sulfide is preferable. Lithium sulfide can be produced, for example, by the methods described in JP-A-7-330312, JP-A-9-283156, JP-A-2010-163356, and JP-A-2011-84438.
Specifically, lithium hydroxide and hydrogen sulfide are reacted at 70 ° C to 300 ° C in a hydrocarbon-based organic solvent to generate lithium hydrosulfide, and then this reaction solution is desulfided to hydrogen sulfide for sulfurization. Lithium can be synthesized (Japanese Patent Laid-Open No. 2010-163356).
Further, lithium hydroxide can be synthesized by reacting lithium hydroxide and hydrogen sulfide at 10 ° C. to 100 ° C. in an aqueous solvent to generate lithium hydrosulfide, and then dehydrosulfating this reaction solution (specially). Kai 2011-84438 (Ab. 2011).

Examples of the phosphorus-containing raw material include phosphorus sulfide such as diphosphorus trisulfide (P ₂ S ₃ ) and diphosphorus pentasulfide (P ₂ S ₅ ), phosphorus compounds such as sodium phosphate (Na ₃ PO ₄ ), and phosphorus compounds. Phosphorus alone and the like can be mentioned. Among these, preferred are phosphorus sulfides, phosphorus pentasulfide (P 2 _{S 5)} is more preferable. Phosphorus pentasulfide (P 2 _{S 5)} phosphorus compounds such as phosphorus alone is industrially produced, as long as that sold, it can be used without particular limitation.

As the raw material containing the element X, for example, it is preferable to contain a halogen compound represented by the following formula (7).
M _l- X _m (7)

In formula (7), M is sodium (Na), lithium (Li), boron (B), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), germanium (Ge), arsenic. (As), selenium (Se), tin (Sn), antimony (Sb), tellurium (Te), lead (Pb), bismuth (Bi), or these elements combined with an oxygen element or a sulfur element. , Lithium (Li) or phosphorus (P) is preferable, and lithium (Li) is more preferable.
X is preferably a halogen element selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).
Further, l is an integer of 1 or 2, and m is an integer of 1 to 10. When m is an integer of 2 to 10, that is, when there are a plurality of Xs, Xs may be the same or different. _{For example, SiBrCl 3} , which will be described later, has m of 4, and X is composed of different elements, Br and Cl.

Specific examples of the halogenated compound represented by the above formula (7) include sodium halides such as NaI, NaF, NaCl, and NaBr; lithium halides such as LiF, LiCl, LiBr, and LiI; BCl ₃ , BBr _{3 and the like.} , BI ₃ etc. Halogenated boron; AlF ₃ , AlBr ₃ , AlI ₃ , AlCl ₃ etc. Halogenated aluminum; SiF ₄ , SiCl ₄ , SiCl ₃ , Si ₂ Cl ₆ , SiBr ₄ , SiBrCl ₃ , SiBr ₂ Cl ₂ , SiI ₄ and halogenated _{silicon; PF 3, PF 5, PCl} 3, PCl 5, POCl 3, PBr 3, POBr 3, PI 3, P 2 Cl 4, P 2 I 4 halogenated such as phosphorus; SF ₂ , SF ₄ , SF ₆ , S ₂ F ₁₀ , SCl ₂ , S ₂ Cl ₂ , S ₂ Br _{2 and} other halogenated sulfur; GeF ₄ , GeCl ₄ , GeBr ₄ , GeI ₄ , GeF ₂ , GeCl ₂ , GeBr ₂ , GeI ₂ and halogenated _{germanium; AsF 3, AsCl 3, AsBr} 3, AsI 3, AsF 5 and halogenated _{arsenic; SeF 4, SeF 6, SeCl} 2, SeCl 4, Se 2 Br 2, SeBr 4 etc. halogenated _{selenium; SnF 4, SnCl 4, SnBr} 4, SnI 4, SnF 2, SnCl 2, SnBr 2, SnI 2 and halogenated _{tin; SbF 3, SbCl 3, SbBr} 3, SbI 3, SbF 5, SbCl 5 Halogenated antimonates such as TeF ₄ , Te ₂ F ₁₀ , TeF ₆ , TeCl ₂ , TeCl ₄ , TeBr ₂ , TeBr ₄ , TeI _4, etc. Halogenated tellurium; PbF ₄ , PbCl ₄ , PbF ₂ , PbCl ₂ . _2. Halogenated lead such as PbI ₂ ; Halogenated bismuth such as _{BiF 3} , BiCl ₃ , BiBr ₃ , BiI _{3 and the like.}

Among them, lithium halide such as lithium chloride (LiCl), lithium bromide (LiBr), lithium iodide (LiI), phosphorus pentachloride (PCl ₅ ), phosphorus trichloride (PCl ₃ ), phosphorus pentabromide (PBr _5). ), Phosphorus pentabromide (PBr ₃ ) and the like. Among them, lithium halide such as LiCl, LiBr, LiI and PBr ₃ are preferable, lithium halide such as LiCl, LiBr and LiI are more preferable, and LiCl and LiBr are more preferable.
As the halogen compound, one of the above compounds may be used alone, or two or more of them may be used in combination. That is, at least one of the above compounds can be used. Further, in this case, as the halogen element, one of the above halogen elements may be used alone, or two or more of them may be used in combination.

In the present embodiment, it contains a lithium compound, a phosphorus compound, and a halogen compound, and it is preferable that at least one of the lithium compound and the phosphorus compound contains a sulfur element, and a combination of lithium sulfide, phosphorus sulfide, and lithium halide is more suitable. A combination of lithium sulfide, diphosphorus pentasulfide and lithium halide is more preferred.
For example, when lithium sulfide, diphosphorus pentasulfide, or lithium halide is used as the raw material for the solid sulfide electrolyte of the present invention, the molar ratio of the input raw material is set to lithium sulfide: diphosphorus pentoxide: lithium halide =. It can be 37 to 88: 8 to 25: 0.1 to 50.

In the prior art (for example, Patent Document 2 and the like), the raw material powder is pulverized and mixed to the extent that the crystallinity can be maintained. On the other hand, in the present embodiment, it is preferable to apply mechanical stress to the raw material to react it to obtain an intermediate containing a glass component. That is, due to a stronger mechanical stress than in the prior art, at least a part of the raw material powder is pulverized and mixed until the crystallinity cannot be maintained. Thus, causing PS ₄ structure which is the basic skeleton of Arujirodaito type crystal structure at the stage of intermediates, and can be highly dispersed halogen. As a result, halogen is easily incorporated into the algyrodite-type crystal structure when the algyrodite-type crystal structure, which is a stable phase, is formed during the heat treatment in the next step. In addition, it is estimated that a low-ion conductive phase such as _{a Li 3} PS ₄ crystal structure is unlikely to occur because it does not pass through a different phase for each region. Therefore, it is estimated that the sulfide solid electrolyte of the present embodiment exhibits high ionic conductivity.
It should be noted that the inclusion of the glass (amorphous) component in the intermediate can be confirmed by the presence of a broad peak (halo pattern) due to the amorphous component in the XRD measurement.
Further, in the present embodiment, unlike Patent Document 1, it is not necessary to heat the raw material at 550 ° C. for 6 days, so that the mass productivity is high.

When a sulfide solid electrolyte containing an argylodite-type crystal structure is produced directly from a raw material without passing through an intermediate containing a glass component, it is difficult to obtain a sulfide solid electrolyte having high ionic conductivity. Halogen tends to stay in a stable phase, and when the sulfide solid electrolyte is produced directly from the raw material, the halogen changes to another stable phase while the algyrodite type crystal structure is being formed in the sulfide solid electrolyte. This is because they may be taken up or aggregated or reaggregated without being dispersed.
By producing an intermediate containing a glass component and mixing the material components at the atomic level, the halogen can smoothly enter the site of the algyrodite crystal structure during the heat treatment of the intermediate containing the glass component.

As the conditions for crushing and mixing, for example, when a planetary ball mill is used as the crusher, the rotation speed may be several tens to several hundreds of rotations / minute, and the treatment may be performed for 0.5 hours to 100 hours. More specifically, in the case of the planetary ball mill (manufactured by Fritsch, model number P-7) used in the examples of the present application, the rotation speed of the planetary ball mill is preferably 350 rpm or more and 400 rpm or less, and more preferably 360 rpm or more and 380 rpm or less.
As the ball as the crushing medium, for example, when a zirconia ball is used, the diameter thereof is preferably 0.2 to 20 mm.

The intermediate produced by pulverization and mixing is heat-treated under the atmosphere of an inert gas such as nitrogen or argon. The heat treatment temperature is preferably 350 to 650 ° C, more preferably 400 to 550 ° C.
In the present embodiment, the intermediate is heat-treated to obtain a sulfide solid electrolyte containing an algyrodite-type crystal structure, but when the heat-treated temperature is raised, the formation of the algyrodite-type crystal structure is likely to proceed and the crystallinity is increased. Therefore, the ionic conductivity is improved. On the other hand, if the temperature of the heat treatment is too high, the formation of a new crystal structure increases, so that the formation of an argylodite type crystal structure is hindered. In the present invention, it is preferable to adjust the heat treatment temperature within the above range to obtain appropriate conditions.
In the prior art (eg, Patent Documents 2-5), the raw material mixture is calcined under a hydrogen sulfide stream. It is thought that this will complement sulfur during firing. On the other hand, in the present invention, it is preferable to perform heat treatment in the absence of hydrogen sulfide. In this case, it is considered that a sulfide solid electrolyte having a lower sulfur content than the solid electrolyte of the prior art can be obtained. Novel crystalline structure in the present invention is to a P ₂ S ₆ ^4-main unit structure, since as compared with Arujirodaito structure is presumed that the element ratio S is small structure, the above conditions Is preferable.

For example, when lithium sulfide, diphosphorus pentasulfide, or lithium halide is used as the raw material for the solid sulfide electrolyte of the present invention, the molar ratio of the input raw material is set to lithium sulfide: diphosphorus pentasulfide: lithium halide =. It can be 37 to 88: 8 to 25: 0.1 to 50.

The sulfide solid electrolyte of the present invention can be used for a solid electrolyte layer such as a lithium ion secondary battery, a positive electrode, a negative electrode and the like.

[Electrode mixture]
The electrode mixture of one embodiment of the present invention includes the above-mentioned sulfide solid electrolyte of the present invention and an active material. Alternatively, it is produced by the sulfide solid electrolyte of the present invention. When a negative electrode active material is used as the active material, it becomes a negative electrode mixture. On the other hand, when a positive electrode active material is used, it becomes a positive electrode mixture.

-Negative electrode mixture A negative electrode mixture can be obtained by blending the negative electrode active material with the sulfide solid electrolyte of the present invention.
As the negative electrode active material, for example, a carbon material, a metal material, or the like can be used. Complexes consisting of two or more of these can also be used. Further, a negative electrode active material to be developed in the future can also be used.
Further, it is preferable that the negative electrode active material has electron conductivity.
Examples of carbon materials include graphite (for example, artificial graphite), graphite carbon fiber, resin calcined carbon, thermally decomposed vapor phase grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin calcined carbon, polyacene, and pitch-based carbon. Examples thereof include fibers, vapor-grown carbon fibers, natural graphite and non-graphitizable carbon.
Examples of the metal material include elemental metals, alloys, and metal compounds. Examples of the metal simple substance include metallic silicon, metallic tin, metallic lithium, metallic indium, and metallic aluminum. Examples of the alloy include alloys containing at least one of silicon, tin, lithium, indium and aluminum. Examples of the metal compound include metal oxides. The metal oxide is, for example, silicon oxide, tin oxide, or aluminum oxide.

The mixing ratio of the negative electrode active material and the solid electrolyte is preferably negative electrode active material: solid electrolyte = 95% by weight: 5% by weight to 5% by weight: 95% by weight, 90% by weight: 10% by weight to 10% by weight: 90% by weight. % Is more preferable, and 85% by weight: 15% by weight to 15% by weight: 85% by weight is even more preferable.
If the content of the negative electrode active material in the negative electrode mixture is too small, the electric capacity becomes small. Further, when the negative electrode active material has electron conductivity and does not contain a conductive auxiliary agent or contains only a small amount of the conductive auxiliary agent, the electron conductivity (electron conduction path) in the negative electrode is lowered and the rate is increased. It is considered that the characteristics may be lowered, the utilization rate of the negative electrode active material may be lowered, and the electric capacity may be lowered. On the other hand, if the content of the negative electrode active material in the negative electrode mixture is too large, the ionic conductivity (ion conduction path) in the negative electrode may decrease and the rate characteristics may decrease, or the utilization rate of the negative electrode active material may decrease, resulting in electricity. We think that the capacity may decrease.

The negative electrode mixture can further contain a conductive auxiliary agent.
When the electron conductivity of the negative electrode active material is low, it is preferable to add a conductive auxiliary agent. The conductive auxiliary agent may have conductivity, and its electronic conductivity is preferably 1 × 10 ³ S / cm or more, and more preferably 1 × 10 ⁵ S / cm or more.
Specific examples of the conductive additive include carbon materials, nickel, copper, aluminum, indium, silver, cobalt, magnesium, lithium, chromium, gold, ruthenium, platinum, beryllium, iridium, molybdenum, niobium, osnium, rhodium, etc. A substance containing at least one element selected from the group consisting of tungsten and zinc, more preferably a simple substance of carbon having high conductivity, a carbon material other than a simple substance of carbon; nickel, copper, silver, cobalt, magnesium, lithium, rhodium. Elementary substances, mixtures or compounds containing elemental metals, gold, platinum, niobium, osnium or rhodium.
Specific examples of the carbon material include carbon black such as Ketjen black, acetylene black, denka black, thermal black, and channel black; graphite, carbon fiber, activated carbon, etc., which may be used alone or in combination of two or more. It is possible. Of these, acetylene black, denka black, and ketjen black, which have high electron conductivity, are preferable.

When the negative electrode mixture contains a conductive auxiliary agent, the content of the conductive auxiliary agent in the mixture is preferably 1 to 40% by mass, more preferably 2 to 20% by mass. If the content of the conductive auxiliary agent is too small, the electron conductivity of the negative electrode may decrease and the rate characteristics may decrease, or the utilization rate of the negative electrode active material may decrease and the electric capacity may decrease. On the other hand, if the content of the conductive auxiliary agent is too large, the amount of the negative electrode active material and / or the amount of the solid electrolyte is small. It is presumed that the electric capacity decreases as the amount of the negative electrode active material decreases. Further, if the amount of the solid electrolyte is small, the ionic conductivity of the negative electrode may be lowered, the rate characteristics may be lowered, the utilization rate of the negative electrode active material may be lowered, and the electric capacity may be lowered.

In order to bind the negative electrode active material and the solid electrolyte tightly to each other, a binder may be further contained.
Examples of the binder include fluororesins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and fluororubber, thermoplastic resins such as polypropylene and polyethylene, ethylene-propylene-diene rubber (EPDM) and sulfonated. EPDM, natural butyl rubber (NBR) and the like can be used alone or as a mixture of two or more kinds. Further, an aqueous dispersion of cellulose-based binder or styrene-butadiene rubber (SBR), which is an aqueous binder, can also be used.

The negative electrode mixture can be produced by mixing a solid electrolyte, a negative electrode active material, and an arbitrary conductive auxiliary agent and / or a binder.
The mixing method is not particularly limited, but for example, dry mixing using a mortar, a ball mill, a bead mill, a jet mill, a planetary ball mill, a vibrating ball mill, a sand mill, or a cutter mill; and a mortar after dispersing the raw materials in an organic solvent. , Ball mills, bead mills, planetary ball mills, vibrating ball mills, sand mills, fill mixes can be used for mixing and then wet mixing to remove the solvent. Of these, wet mixing is preferable so as not to destroy the negative electrode active material particles.

-Positive electrode mixture A positive electrode mixture can be obtained by blending the positive electrode active material with the solid electrolyte of the present invention.
The positive electrode active material is a substance capable of inserting and removing lithium ions, and a substance known as a positive electrode active material in the battery field can be used. Further, a positive electrode active material to be developed in the future can also be used.

Examples of the positive electrode active material include metal oxides and sulfides. Sulfides include metallic sulfides and non-metallic sulfides.
The metal oxide is, for example, a transition metal oxide. Specifically, V ₂ O ₅ , V ₆ O ₁₃ , LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (here, 0 <a <1, _{0 <b <1,0 <c <} 1, a + b + c = 1), LiNi 1-Y Co Y O 2, LiCo 1-Y Mn Y O 2, LiNi 1-Y Mn Y O 2 ( where, 0 ≦ Y _{<1), Li (Ni a} Co b Mn c) O 4 (0 <a <2,0 <b <2,0 <c <2, a + b + c = 2), LiMn 2-Z Ni Z O 4, LiMn 2 _-Z Co _Z O _{4 (where, 0 <Z <2),} LiCoPO 4, LiFePO 4, CuO, Li (Ni a Co b Al c) O 2 ( where, 0 <a <1,0 <b < 1, 0 <c <1, a + b + c = 1) and the like.
As the metal sulfide, titanium sulfide _(TiS 2), molybdenum sulfide _(MoS 2), iron sulfide (FeS, _FeS 2), and the like of copper sulfide (CuS) and nickel sulfide _(Ni 3 _{S 2).}
Other examples of the metal oxide include bismuth oxide (Bi ₂ O ₃ ) and bismuth lead acid (Bi ₂ Pb ₂ O _5).
Examples of the non-metal sulfide include an organic disulfide compound and a carbon sulfide compound.
In addition to the above, niobium selenate (NbSe ₃ ), indium metal, and sulfur can also be used as the positive electrode active material.

The positive electrode mixture may further contain a conductive auxiliary agent.
The conductive auxiliary agent is the same as that of the negative electrode mixture.

The blending ratio of the solid electrolyte and the positive electrode active material of the positive electrode mixture, the content of the conductive auxiliary agent, and the method for producing the positive electrode mixture are the same as those of the negative electrode mixture described above.

[Lithium-ion battery]
The lithium ion battery of one embodiment of the present invention contains at least one of the above-mentioned sulfide solid electrolyte and electrode mixture of the present invention. Alternatively, it is produced by at least one of the sulfide solid electrolyte and the electrode mixture of the present invention.
The configuration of the lithium ion battery is not particularly limited, but generally has a structure in which a negative electrode layer, an electrolyte layer, and a positive electrode layer are laminated in this order. Hereinafter, each layer of the lithium ion battery will be described.

(1) Negative electrode layer The negative electrode layer is preferably a layer manufactured from the negative electrode mixture of the present invention.
Alternatively, the negative electrode layer is preferably a layer containing the negative electrode mixture of the present invention.
The thickness of the negative electrode layer is preferably 100 nm or more and 5 mm or less, more preferably 1 μm or more and 3 mm or less, and further preferably 5 μm or more and 1 mm or less.
The negative electrode layer can be manufactured by a known method, for example, by a coating method, an electrostatic method (electrostatic spray method, electrostatic screen method, etc.).

(2) Electrolyte layer The electrolyte layer is a layer containing a solid electrolyte or a layer manufactured from a solid electrolyte. The solid electrolyte is not particularly limited, but is preferably the sulfide solid electrolyte of the present invention.
The electrolyte layer may consist only of a solid electrolyte or may further contain a binder. As the binder, the same binder as the binder for the negative electrode mixture of the present invention can be used.

The thickness of the electrolyte layer is preferably 0.001 mm or more and 1 mm or less.
The solid electrolyte of the electrolyte layer may be fused. Fusing means that a part of the solid electrolyte particles is dissolved and the dissolved part is integrated with other solid electrolyte particles. Further, the electrolyte layer may be a plate-like body of a solid electrolyte, and the plate-like body includes a case where a part or all of the solid electrolyte particles are dissolved to form a plate-like body.
The electrolyte layer can be produced by a known method, for example, by a coating method, an electrostatic method (electrostatic spray method, electrostatic screen method, etc.).

(3) Positive Electrode Layer The positive electrode layer is a layer containing a positive electrode active material, preferably a layer containing the positive electrode mixture of the present invention or a layer manufactured from the positive electrode mixture of the present invention.
The thickness of the positive electrode layer is preferably 0.01 mm or more and 10 mm or less.
The positive electrode layer can be manufactured by a known method, for example, by a coating method, an electrostatic method (electrostatic spray method, electrostatic screen method, etc.).

(4) Current collector The lithium ion battery of the present embodiment preferably further includes a current collector. For example, the negative electrode current collector is provided on the side opposite to the electrolyte layer side of the negative electrode layer, and the positive electrode current collector is provided on the side opposite to the electrolyte layer side of the positive electrode layer.
As the current collector, a plate-like body or a foil-like body made of copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, indium, lithium, or an alloy thereof can be used.

The lithium ion battery of the present embodiment can be manufactured by laminating and joining the above-mentioned members. As a method of joining, there are a method of laminating each member and pressurizing / crimping, a method of pressurizing through between two rolls (roll to roll), and the like.
Further, the bonding surface may be bonded via an active material having ionic conductivity or an adhesive substance that does not inhibit the ionic conductivity.
In the bonding, heat fusion may be performed as long as the crystal structure of the solid electrolyte does not change.
Further, the lithium ion battery of the present embodiment can also be manufactured by sequentially forming each of the above-mentioned members. It can be manufactured by a known method, and for example, it can be manufactured by a coating method, an electrostatic method (electrostatic spray method, electrostatic screen method, etc.).

Hereinafter, the present invention will be described in more detail with reference to Examples.
The evaluation method is as follows.
(1) Ion conductivity measurement and electron conductivity measurement The sulfide solid electrolyte produced in each example was filled in a tablet molding machine, and a pressure of 407 MPa (press display value 22 MPa) was applied using a mini press machine to form a molded product. did. Carbon was placed on both sides of the molded product as electrodes, and pressure was applied again with the tablet molding machine to prepare a molded product (diameter about 10 mm, thickness 0.1 to 0.2 cm) for measurement. The ionic conductivity of this molded product was measured by AC impedance measurement. As the value of ionic conductivity, the value at 25 ° C. was adopted.
In the method for measuring the ionic conductivity used in this embodiment ^{, when the ionic conductivity is less than 1.0 × 10 -6} S / cm, the ionic conductivity cannot be measured accurately, so that the measurement is impossible. And said.
In addition, the electron conductivity of this molded product was measured by direct current electrical measurement. As the value of electron conductivity, the value at 25 ° C. was adopted. When the electron conductivity when a voltage of 5 V was applied was ^{less than 1.0 × 10 -6} S / cm, the electron conductivity was not measurable.

(2) X-ray diffraction (XRD) measurement From the sulfide solid electrolyte powder produced in each example, a circular pellet having a diameter of 10 mm and a height of 0.1 to 0.3 cm was formed into a sample. This sample was measured using an XRD airtight holder without contact with air. The 2θ position of the diffraction peak was determined by the center of gravity method using the XRD analysis program JADE.
It was carried out under the following conditions using a powder X-ray diffraction measuring device SmartLab of Rigaku Co., Ltd.
Tube voltage: 45kV
Tube current: 200mA
X-ray wavelength: Cu-Kα ray (1.5418 Å)
Optical system: Parallel beam method Slit configuration: Solar slit 5 °, incident slit 1 mm, light receiving slit 1 mm
Detector: Scintillation counter Measurement range: 2θ = 10-60deg
Step width, scan speed: 0.02 deg, 1 deg / min In the analysis of the peak position to confirm the existence of the crystal phase from the measurement results, the XRD analysis program JADE is used to draw a baseline by cubic approximation and the peak. I asked for the position.
In the intensity of the diffraction peak, 2θ = 29.7deg intensity of the diffraction peak of Arujirodaito type crystal structure present in _{± 0.5deg (I B), 2θ} = 17.6 ± 0.4deg and 18.1 ± 0.4 deg in _Li 3 PS ₄ the intensity of the diffraction peak of the crystal structure _(I a), and 2 [Theta] = 14.4 intensities of the diffraction peaks of the novel crystal structure present in ± 0.5deg _{(I C)} to the following procedure that exists Were determined.
Smoothing was performed by the moving average of the five points of the measured data, and the lowest intensity point between 17.5 to 18.5 deg was subtracted from the measured data as the background. After that, the maximum value of the measured data between the maximum values of the measured data of 17.0 to 17.8 deg and 17.9 to 18.5 deg is calculated, and the smaller peak intensity is the diffraction peak of the _{Li 3} PS _{4 crystal structure.} and the intensity _{(I a)} of the. Further, Arujirodaito type crystal structure was the maximum value of the measured data of 29.0~32.0deg the intensity of a diffraction peak _{(I B).} Further, 2 [Theta] = identify peaks in 14.0～15.0Deg, the intensity of the peak top was the intensity of a diffraction peak _{(I C).} From the intensity of the diffraction peak intensity ratio _(I A / I _B) and the intensity ratio _(I C / I _B) were calculated.

(3) ICP measurement The powder of the sulfide solid electrolyte produced in each example was weighed and collected in a vial in an argon atmosphere. A KOH alkaline aqueous solution was placed in a vial, and the sample was dissolved while paying attention to the collection of sulfur, and diluted appropriately to prepare a measurement solution. This was measured with a Paschen-Lunge type ICP-OES apparatus (SPECTOR RACOS manufactured by SPECTRO), and the composition was determined.
For the calibration curve solution, Li, P, S, Ge, Si are 1000 mg / L standard solutions for ICP measurement, Cl and Br are 1000 mg / L standard solutions for ion chromatograph, and I is potassium iodide (special grade reagent). Prepared using.
Two measurement solutions were prepared for each sample, and each measurement solution was measured 5 times to calculate the average value. The composition was determined by averaging the measured values of the two measuring solutions.

(4) NMR measurement About 60 mg of the sulfide solid electrolyte powder produced in each example was filled in an NMR sample tube, and a solid ³¹ PNMR spectrum was obtained under the following equipment and conditions.
Equipment: ECZ400R equipment (manufactured by JEOL RESONANCE Co., Ltd.)
Observation nucleus: ³¹ P
Observation frequency: 161.944MHz
Measurement temperature: Room temperature Pulse series: Single pulse (using 90 ° pulse)
90 ° pulse width: 3.8μ
Waiting time after FID measurement until the next pulse is applied 300 seconds Magic angle rotation speed 12 kHz
Number of integrations 64 times Measurement range: 250ppm to -150ppm
^{31 In} the measurement of the PNMR spectrum, the chemical shift was _{obtained by using (NH 4} ) ₂ HPO ₄ (chemical shift 1.33 ppm) as an external reference.

(5) Raman spectroscopic measurement About 100 mg of the sulfide solid electrolyte powder produced in each example was filled in a glass capillary, sealed with an ultraviolet curable resin, and microscopic Raman measurement was performed under the following equipment and conditions. For each sample, 5 measurements were made at different positions on the sample and the resulting profile was averaged using a profile.
Equipment: Almega (manufactured by Thermo Fisher Scientific Co., Ltd.)
Laser: 532 nm
Laser output level: 10%
Laser polarization: Parallel grating: 2400lines / mm
Spectrometer aperture: 25 μm pinhole Measurement range: 90 to 1300 cm ^-1
Exposure time: 10 seconds Number of exposures: 20
Background exposure count: 20
Number of measurements: 5

Production Example 1
(Production of lithium sulfide _(Li 2 S))
200 g of LiOH anhydrous (manufactured by Honjo Chemical Co., Ltd.) dried under an inert gas was charged into a 500 mL separable flask equipped with a stirrer. The temperature was raised under a nitrogen stream to maintain the internal temperature at 200 ° C. The nitrogen gas was switched to hydrogen sulfide gas (Sumitomo Seika Chemicals), the flow rate was 500 mL / min, and LiOH anhydride was reacted with hydrogen sulfide.
Moisture generated by the reaction was condensed and recovered by a condenser. When the reaction was carried out for 6 hours, 144 mL of water was recovered. The reaction was continued for another 3 hours, but no water was observed.
The product powder was recovered and the purity and XRD were measured. As a result, purity of 98.5%, a peak pattern of the XRD in Li ₂ S was confirmed.

Example 1
Lithium sulfide (purity 98.5%), diphosphorus pentasulfide (thermophos, purity 99.9% or more) and lithium chloride (Sigma-Aldrich, purity 99%) produced in Production Example 1 are used as starting materials. (Hereinafter, in all the examples, the purity of each starting material is the same). _{The mol ratio (Li 2} S: P ₂ S ₅ : LiCl) of lithium sulfide (Li ₂ S), diphosphorus pentasulfide (P ₂ S ₅ ), and lithium chloride (LiCl) is 46.8: 12.7: 40. Each raw material was mixed so as to be .5. Specifically, 0.483 g of lithium sulfide, 0.632 g of diphosphorus pentasulfide, and 0.385 g of lithium chloride were mixed to prepare a raw material mixture.

The raw material mixture and 30 g of zirconia balls having a diameter of 10 mm were placed in a planetary ball mill (Fritsch, model number P-7) zirconia pot (45 mL) and completely sealed. The inside of the pot had an argon atmosphere. A glass-like powder (intermediate) was obtained by processing (mechanical milling) for 15 hours at a rotation speed of 370 rpm with a planetary ball mill.
The XRD pattern of the intermediate of Example 1 is shown in FIG. By processing with a planetary ball mill, a halo pattern indicating that the raw material has been vitrified can be confirmed. Most of the raw material remained, but most of it was glass.
Approximately 1.5 g of the above intermediate powder is packed in a Tanman tube (PT2, manufactured by Tokyo Glass Equipment Co., Ltd.) in a glove box under an Ar atmosphere, the mouth of the Tanman tube is closed with quartz wool, and a SUS seal is used. The container was sealed to prevent air from entering. Then, the closed container was placed in an electric furnace (FUW243PA, manufactured by Advantech) and heat-treated. Specifically, the temperature was raised from room temperature to 500 ° C. at 2.5 ° C./min (the temperature was raised to 500 ° C. in 3 hours), and the temperature was maintained at 500 ° C. for 8 hours. Then, it was slowly cooled to obtain a sulfide solid electrolyte.
Table 1 shows the raw material composition, production conditions, and evaluation results.
The sulfide solid electrolyte was ICP analyzed and the molar ratio of each element was measured. The results are shown in Table 2.

The ionic conductivity (σ) of the obtained sulfide solid electrolyte was 7.4 mS / cm. The electron conductivity ^{was less than 10-6} S / cm.
The XRD pattern of the obtained sulfide solid electrolyte is shown in FIG. Peaks derived from the algyrodite type crystal structure were observed at 2θ = 15.6, 18.0, 25.6, 30.1, 31.5, 45.2, 48, 1 deg. In addition, peaks derived from the novel crystal structure were observed at 2θ = 14.4, 29.2, and 33.8 deg. On the other hand, no diffraction peak derived from the _{Li 3} PS _{4 crystal structure was observed.}

^{The solid 31} P-NMR measurement results of the obtained sulfide solid electrolyte are shown in FIG. A peak derived from the argylodite structure was observed around 81 ppm, and a peak derived from the novel crystal structure was observed around 108 ppm. Moreover, as a result of peak separation of the peak derived from the argilodite structure, no peak derived from the Li ₃ PS ₄ structure was observed.
The Raman measurement result of the obtained sulfide solid electrolyte is shown in FIG. A peak 430cm around ^-1 was derived from Arujirodaito structure, a peak derived from a novel crystalline structure was observed in the vicinity of 390cm ^-1.

Example 2
A sulfide solid electrolyte was prepared and evaluated in the same manner as in Example 1 except that the treatment time with the planetary ball mill was 60 hours. The results are shown in Tables 1 and 2.
As a result of XRD measurement, peaks derived from the algyrodite type crystal structure were observed at 2θ = 15.5, 18.0, 25.6, 30.1, 31.5, 45.1 and 48.1 deg. Peaks derived from the novel crystal structure were observed at 2θ = 14.4, 29.2, and 33.8 deg. On the other hand, no diffraction peak derived from the _{Li 3} PS _{4 crystal structure was observed.} The electron conductivity ^{was less than 10-6} S / cm.

^{The solid 31} P-NMR measurement results of the obtained sulfide solid electrolyte are shown in FIG. A peak derived from the argylodite structure was observed around 81 ppm, and a peak derived from the novel crystal structure was observed around 108 ppm. Moreover, as a result of peak separation of the peak derived from the argilodite structure, no peak derived from the Li ₃ PS ₄ structure was observed.

Examples 3 to 6, Comparative Example 1
A sulfide solid electrolyte was prepared in the same manner as in Example 2 except that the raw material composition, mechanical milling conditions, and heat treatment conditions were changed as shown in Table 1.
The heat treatment of Example 5 was carried out under Ar distribution. Specifically, the intermediate was packed in a glass tube with a sealing function in a glove box under an Ar atmosphere, and the tip of the glass tube was sealed with a special jig to prevent air from entering. After that, the glass tube was set in the electric furnace. A special jig was inserted into a joint in an electric furnace, connected to a gas flow pipe, and heat-treated while circulating Ar at 0.5 L / min. Specifically, the temperature was raised from room temperature to 500 ° C. at 3 ° C./min and maintained at 500 ° C. for 8 hours. Then, it was slowly cooled to obtain a sulfide solid electrolyte.

The evaluation results are shown in Tables 1 and 2. ^{Further, the solid 31} P-NMR measurement result of the sulfide solid electrolyte of Example 3 is shown in FIG. 3, and the XRD pattern is shown in FIG. The XRD pattern of the sulfide solid electrolyte of Comparative Example 1 is shown in FIG.

Regarding the XRD measurement results, in Example 3, peaks derived from the algyrodite type crystal structure were found at 2θ = 15.1, 18.0, 25.4, 29.9, 31.3, 44.9, and 47.8 deg. It was observed. In addition, peaks derived from the novel crystal structure were observed at 2θ = 14.4, 29.0, and 33.7 deg. On the other hand, no peak derived from the _{Li 3} PS _{4 crystal structure was observed.} The electron conductivity ^{was less than 10-6} S / cm.
In Examples 4 to 6, peaks derived from the algyrodite type crystal structure were observed at 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg, respectively, and 2θ = 14.4 ± 0.5 deg. Peaks derived from the novel crystal structure were observed at 33.8 ± 0.5 deg, respectively.
In Comparative Example 1, peaks derived from the algyrodite type crystal structure were observed at 2θ = 15.5, 25.6, 30.0, 30.4, 45.2, and 48.1 deg. On the other hand, no peak derived from the new crystal structure was observed. Furthermore, peaks derived from _Li 3 PS ₄ crystal structure 2θ = 17.6,18.2deg was observed _{was I A / I B = 0.16 (} I A is 2θ = 17.6 ± 0. represents the intensity of the diffraction peak but not a diffraction peak attributed to Arujirodaito crystal structure of 4deg and 2θ = 18.1 ± 0.4deg, _{I B} is the intensity of the diffraction peak of 2θ = 29.7 ± 0.5deg show.). The electron conductivity ^{was less than 10-6} S / cm.

Comparative Example 2
Regarding the treatment of the raw material powder, the raw materials shown in Table 1 were mixed with a planetary ball mill to the extent that the crystallinity of the raw materials could be maintained to obtain a mixed powder.
The XRD pattern of the obtained mixed powder is shown in FIG. The XRD pattern, which is a raw material _Li 2 _S, confirmed peaks of _P 2 S 5, LiCl, crystalline material powder was maintained.
Hydrogen sulfide was introduced during the heat treatment of the mixed powder. Specifically, in a glove box under an Ar atmosphere, about 1.5 g of mixed powder was packed in a glass tube with a sealing function, and the tip of the glass tube was sealed with a special jig to prevent air from entering. After that, the glass tube was set in the electric furnace. A special jig was inserted into a joint in an electric furnace, connected to a gas flow pipe, and heat-treated while circulating hydrogen sulfide at 0.5 L / min. Specifically, the temperature was raised from room temperature to 500 ° C. at 3 ° C./min and maintained at 500 ° C. for 4 hours. Then, it was slowly cooled to obtain a sulfide solid electrolyte.
Tables 1 and 2 show the production conditions and evaluation results of the sulfide solid electrolyte.

Example 7
Lithium sulfide, diphosphorus pentasulfide and lithium chloride used in Example 1 and lithium bromide (LiBr: manufactured by Sigma-Aldrich Co., Ltd., purity 99%) were used as starting materials. Each raw material was mixed so that the mol ratio (Li ₂ S: P ₂ S ₅ : LiCl: LiBr) was 46.8: 12.7: 35.4: 5.1. Specifically, 0.476 g of lithium sulfide, 0.594 g of diphosphorus pentasulfide, 0.332 g of lithium chloride, and 0.097 g of lithium bromide were mixed to prepare a raw material mixture.
A sulfide solid electrolyte was prepared in the same manner as in Example 1 except that the raw material mixture was changed.
The σ of the sulfide solid electrolyte was 9.8 mS / cm. The electron conductivity ^{was less than 10-6} S / cm.
As a result of the XRD measurement, a peak derived from the algyrodite type crystal structure was observed, and a peak derived from the novel crystal structure was observed. The peak intensity ratio was 0.006.
As a result of ICP analysis, the molar ratio a (Li / P) was 5.3, the molar ratio b (S / P) was 4.4, and the molar ratio c ((Cl + Br) / P) was 1.6.

Example 8
Lithium sulfide, diphosphorus pentasulfide, lithium chloride and lithium bromide used in Example 7 and lithium iodide were used as starting materials. Each raw material was mixed so that the mol ratio (Li ₂ S: P ₂ S ₅ : LiCl: LiBr: LiI) was 46.8: 12.7: 32.9: 5.1: 2.5. Specifically, 0.460 g of lithium sulfide, 0.575 g of diphosphorus pentasulfide, 0.298 g of lithium chloride, 0.094 g of lithium bromide, and 0.072 g of lithium iodide were mixed to prepare a raw material mixture.
A sulfide solid electrolyte was prepared in the same manner as in Example 1 except that the raw material mixture was changed.
The σ of the sulfide solid electrolyte was 9.0 mS / cm. The electron conductivity ^{was less than 10-6} S / cm.
As a result of the XRD measurement, a peak derived from the algyrodite type crystal structure was observed, and a peak derived from the novel crystal structure was observed. The peak intensity ratio was 0.009.
As a result of ICP analysis, the molar ratio a (Li / P) was 5.3, the molar ratio b (S / P) was 4.4, and the molar ratio c ((Cl + Br + I) / P) was 1.6.

Example 9
Lithium sulfide, diphosphorus pentasulfide and lithium chloride used in Example 1 and germanium sulfide (IV) (GeS ₂ : manufactured by High Purity Scientific Research Institute, 99% purity) were used as starting materials. Each raw material was mixed so that the mol ratio (Li ₂ S: P ₂ S ₅ : GeS ₂ : LiCl) was 46.9: 11.1: 2.5: 39.5. Specifically, 0.487 g of lithium sulfide, 0.558 g of diphosphorus pentasulfide, 0.076 g of germanium (IV) sulfide, and 0.378 g of lithium chloride were mixed to prepare a raw material mixture.
A sulfide solid electrolyte was prepared in the same manner as in Example 1 except that the raw material mixture was changed.
The σ of the sulfide solid electrolyte was 7.2 mS / cm. The electron conductivity ^{was less than 10-6} S / cm.
As a result of the XRD measurement, a peak derived from the algyrodite type crystal structure was observed, and a peak derived from the novel crystal structure was observed. The peak intensity ratio was 0.020.
As a result of ICP analysis, the molar ratio a (Li / (P + Ge)) was 5.3, the molar ratio b (S / (P + Ge)) was 4.3, and the molar ratio c (Cl / (P + Ge)) was 1.6. there were.

Example 10
Lithium sulfide, diphosphorus pentasulfide and lithium chloride used in Example 1 and silicon disulfide (SiS ₂ : manufactured by High Purity Scientific Research Institute) were used as starting materials. Each raw material was mixed so that the mol ratio (Li ₂ S: P ₂ S ₅ : SiS ₂ : LiCl) was 46.9: 11.1: 2.5: 39.5. Specifically, 0.495 g of lithium sulfide, 0.567 g of diphosphorus pentasulfide, 0.052 g of silicon disulfide, and 0.385 g of lithium chloride were mixed to prepare a raw material mixture.
A sulfide solid electrolyte was prepared in the same manner as in Example 1 except that the raw material mixture was changed.
The σ of the sulfide solid electrolyte was 7.1 mS / cm. The electron conductivity ^{was less than 10-6} S / cm.
As a result of the XRD measurement, a peak derived from the algyrodite type crystal structure was observed, and a peak derived from the novel crystal structure was observed. The peak intensity ratio was 0.021.
As a result of ICP analysis, the molar ratio a (Li / (P + Si)) was 5.3, the molar ratio b (S / (P + Si)) was 4.3, and the molar ratio c (Cl / (P + Si)) was 1.6. there were.

Claims (14)

Contains lithium, phosphorus, sulfur and halogen elements
Includes algyrodite-type crystal structure,
A sulfide solid electrolyte having diffraction peaks at 2θ = 29.1 ± 0.5 deg and 33.8 ± 0.5 deg in powder X-ray diffraction measurement using CuKα ray. The sulfide solid electrolyte according to claim 1, which has diffraction peaks at 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg in powder X-ray diffraction using CuKα rays. Furthermore, in powder X-ray diffraction using CuKα rays, 2θ = 15.3 ± 0.5 deg, 17.7 ± 0.5 deg, 31.1 ± 0.5 deg, 44.9 ± 0.5 deg and 47.7. The sulfide solid electrolyte according to claim 1 or 2, which has at least one of ± 0.5 deg diffraction peaks. The sulfide solid electrolyte according to any one of claims 1 to 3, wherein the range of the diffraction peak is ± 0.3 deg of the median value. The sulfide solid electrolyte according to any one of claims 1 to 4, wherein the halogen element is chlorine or bromine. It contains one or more elements X selected from the group consisting of chalcogen elements and halogen elements excluding sulfur, and has a molar ratio a (Li / P) of lithium to phosphorus, a molar ratio b (S / P) of sulfur to phosphorus, and The sulfide solid electrolyte according to any one of claims 1 to 5, wherein the molar ratio c (X / P) of the element X to phosphorus satisfies the following formulas (A) to (C).
5.0 ≤ a ≤ 7.5 ... (A)
6.5 ≤ a + c ≤ 7.5 ... (B)
0.5 ≤ a-b ≤ 1.5 ... (C)
(In the formula, b> 0 and c> 0 are satisfied.) The sulfide solid electrolyte according to claim 6, wherein the element X is one or more halogen elements selected from F, Cl, Br and I. The sulfide solid electrolyte according to any one of claims 1 to 5, which has a composition represented by the following formula (4).
Li _a (P _1-α M _α ) S _b X _c (4)
(In formula (4), M is one or more elements selected from the group consisting of Si, Ge, Sn, Pb, B, Al, Ga, As, Sb and Bi, and X is F, Cl, One or more elements selected from the group consisting of Br, I, O, Se and Te. A to c satisfy the following formulas (1) to (3). Α is 0 ≦ α ≦ 0.3. .)
5.0 ≤ a ≤ 7.5 ... (1)
6.5 ≤ a + c ≤ 7.5 ... (2)
0.5 ≤ a-b ≤ 1.5 ... (3)
(In the formula, b> 0 and c> 0 are satisfied.) The sulfide solid electrolyte according to claim 8, wherein X is one or more halogen elements selected from F, Cl, Br and I. In powder X-ray diffraction using CuKα ray, whether or not there is a diffraction peak (not a peak due to the argylodite type crystal structure) at 2θ = 17.6 ± 0.4 deg and 2θ = 18.1 ± 0.4 deg. The sulfide solid electrolyte according to any one of claims 1 to 9, which satisfies the following formula (5) when provided.
_{0 <I A / I B <} 0.1 (5)
(Wherein, _{I A} represents the intensity of the diffraction peak but not a diffraction peak attributed to Arujirodaito crystal structure of 2 [Theta] = 17.6 ± 0.4 deg and 2θ = 18.1 ± 0.4deg, _{I B} is 2θ = 29.7 ± 0.5deg represents the intensity of the diffraction peak.) Solid ³¹ The sulfide solid electrolyte according to any one of claims 1 to 10, which has a peak at 110 ± 5 ppm in P-NMR measurement. Having a peak within the range of ^{380cm -1 ~395cm} -1 in Raman spectroscopy, the sulfide solid electrolyte according to any one of claims 1 to 11. An electrode mixture containing the sulfide solid electrolyte according to any one of claims 1 to 12 and an active material. A lithium ion battery comprising at least one of the sulfide solid electrolyte according to any one of claims 1 to 12 and the electrode mixture according to claim 13.

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