阅读说明：本技术 硫化物固体电解质 (Sulfide solid electrolyte ) 是由 宇都野太 寺井恒太 梅木孝 中川将 山口展史 于 2017-08-08 设计创作，主要内容包括：一种硫化物固体电解质,包含锂、磷、硫、氯、溴,在使用了CuKα射线的粉末X射线衍射中,在2θ＝25.2±0.5deg具有衍射峰A,在29.7±0.5deg具有衍射峰B,衍射峰A以及衍射峰B满足下述式(A)：0.845＜S-A/S-B＜1.200…(A),式中,S-A表示所述衍射峰A的面积,S-B表示所述衍射峰B的面积,所述氯相对于磷的摩尔比c(Cl/P)与所述溴相对于磷的摩尔比d(Br/P),满足下述式(1)：1.2＜c+d＜1.9…(1)。(A sulfide solid electrolyte containing lithium, phosphorus, sulfur, chlorine, and bromine, and having a diffraction peak A at 2 theta of 25.2 + -0.5 deg and a diffraction peak B at 29.7 + -0.5 deg in powder X-ray diffraction using CuKalpha rays, wherein the diffraction peaks A and B satisfy the following formula (A): s is more than 0.845 A /S B < 1.200 … (A), wherein S A Represents the area of the diffraction peak A, S B And a molar ratio c (Cl/P) of chlorine to phosphorus to a molar ratio d (Br/P) of bromine to phosphorus, which represents the area of the diffraction peak B, and satisfies the following formula (1): 1.2 < c + d < 1.9 … (1).)

1. A sulfide solid electrolyte characterized in that,

comprises lithium, phosphorus, sulfur, chlorine and bromine,

the molar ratio c (Cl/P) of chlorine to phosphorus and the molar ratio d (Br/P) of bromine to phosphorus satisfy the following formula (1),

1.2＜c+d＜1.9…(1)，

comprising a thiogallate-type crystal structure having a lattice constant ofThe aboveThe following.

2. The sulfide solid electrolyte according to claim 1,

in powder X-ray diffraction using CuK alpha rays, the diffraction peak A is 25.2 +/-0.5 deg at 2 theta, the diffraction peak B is 29.7 +/-0.5 deg, the diffraction peak A and the diffraction peak B satisfy the following formula (A),

0.845＜S_A/S_B＜1.200…(A)，

in the formula, S_ADenotes the area of diffraction peak A, S_BThe area of diffraction peak B is shown.

3. The sulfide solid electrolyte according to claim 1 or 2, wherein a molar ratio d (Br/P) of bromine to phosphorus is 0.15 or more and 1.6 or less.

4. The sulfide solid electrolyte according to any one of claims 1 to 3,

the molar ratio c (Cl/P) of chlorine to phosphorus and the molar ratio d (Br/P) of bromine to phosphorus satisfy the following formula (2),

0.08＜d/(c+d)＜0.8…(2)。

5. the sulfide solid electrolyte according to any one of claims 1 to 4,

the molar ratio a of lithium to phosphorus (Li/P), the molar ratio b of sulfur to phosphorus (S/P), the molar ratio c of chlorine to phosphorus (Cl/P), and the molar ratio d of bromine to phosphorus (Br/P) satisfy the following formulas (3) to (5),

5.0≦a≦7.5…(3)，

6.5≦a+c+d≦7.5…(4)，

0.5≦a－b≦1.5…(5)，

wherein b >0 and c >0 and d >0 are satisfied.

6. The sulfide solid electrolyte according to any one of claims 1 to 5,

the powder X-ray diffraction using CuK alpha rays satisfies the following formula (B) without a diffraction peak of lithium halide or with a diffraction peak of lithium halide,

0＜I_C/I_A＜0.08…(B)，

in the formula I_CRepresents the intensity of the diffraction peak of lithium halide, I_AThe diffraction peak intensity was 25.2 ± 0.5 deg.

7. The sulfide solid electrolyte according to any one of claims 1 to 6,

in powder X-ray diffraction using CuK alpha rays, the powder X-ray diffraction has no diffraction peak or satisfies the following formula (C) when the powder X-ray diffraction has diffraction peaks at 14.4 + -0.5 deg and 33.8 + -0.5 deg,

0＜I_D/I_A＜0.09…(C)，

in the formula I_DRepresents a diffraction peak intensity of 14.4 + -0.5 deg.C, I_AThe diffraction peak intensity was 25.2 ± 0.5 deg.

8. The sulfide solid electrolyte according to any one of claims 2 to 7, wherein the diffraction peaks A and B are in the range of. + -. 0.3deg of the central value.

9. The sulfide solid electrolyte according to any one of claims 1 to 8, wherein the sulfide solid electrolyte is a solid³¹In P-NMR measurement, the peak has 81.5 to 82.5ppm, 83.2 to 84.7ppm, 85.2 to 86.7ppm and 87.2 to 89.4ppm respectively, and the ratio of the sum of the areas of the peak at 81.5 to 82.5ppm and the peak at 83.2 to 84.7ppm to the total area of all the peaks at 78 to 92ppm is 60% or more.

10. An electrode composite material comprising the sulfide solid electrolyte according to any one of claims 1 to 9 and an active material.

11. A lithium ion battery comprising at least one of the sulfide solid electrolyte according to any one of claims 1 to 9 and the electrode composite material according to claim 10.

12. A sulfide solid electrolyte characterized in that it is a solid³¹In P-NMR measurement, the peak has 81.5 to 82.5ppm, 83.2 to 84.7ppm, 85.2 to 86.7ppm and 87.2 to 89.4ppm respectively, and the ratio of the sum of the areas of the peak at 81.5 to 82.5ppm and the peak at 83.2 to 84.7ppm to the total area of all the peaks at 78 to 92ppm is 60% or more.

Technical Field

The present invention relates to a sulfide solid electrolyte.

Background

In recent years, as information-related devices such as computers, video cameras, and cellular phones, and communication devices have rapidly spread, the development of batteries used as power sources thereof has been attracting attention. Among such batteries, lithium ion batteries have attracted attention from the viewpoint of high energy density.

Since a lithium ion battery that is currently commercially available uses an electrolyte solution containing a flammable organic solvent, it is necessary to install a safety device for suppressing a temperature rise at the time of short circuit or to improve a structure and a material for preventing short circuit. In contrast, a lithium ion battery in which the electrolyte is changed to a solid electrolyte to completely solidify the battery is considered to be capable of simplifying a safety device and to be excellent in manufacturing cost or productivity because an organic solvent having combustibility is not used in the battery.

As a solid electrolyte used in a lithium ion battery, a sulfide solid electrolyte is known. As the crystal structure of the sulfide solid electrolyte, various structures are known, and one of them is an Argyrodite (Argyrodite) type crystal structure. Patent documents 1 to 5 and non-patent documents 1 to 3 disclose a thiogermorite-type crystal structure containing 1 halogen. Non-patent documents 4 and 5 report Li-containing compounds₆PS₅Cl_1-xBr_xAnd a thiogermite-type crystal structure containing 2 halogens is disclosed. Among the diglygeite-type crystal structures, there is a diglygeite-type crystal structure having a high lithium ion conductivity. However, further improvement in ion conductivity is required. In addition, the conventional sulfide-based solid electrolyte has a technical problem that hydrogen sulfide may be generated by a reaction with moisture in the atmosphere.

Documents of the prior art

Patent document

Patent document 1: japanese Kokai publication No. 2010-540396

Patent document 2: international publication WO2015/011937

Patent document 3: international publication WO2015/012042

Patent document 4: japanese patent laid-open publication No. 2016-24874

Patent document 5: international publication WO2016/104702

Non-patent document

Non-patent document 1: "applied chemistry in Germany (Angewandte Chemie International Edition)" at stage 47 (2008), No. 4, page 755-

Non-patent document 2: condensed physical Physica Status solidi, stage 208 (2011), No. 8, page 1804-

Non-patent document 3: solid State Ionics (Solid State ions) in 221 (2012), pages 1-5

Non-patent document 4: the institute of Electrical electrification 82, Back A set of talking essentials (2015), 2H08

Non-patent document 5: "Japanese society of chemistry, 94 spring annual meeting 2014 lecture preprint book II", page 474, 1H2-50

Disclosure of Invention

Technical problem to be solved by the invention

It is an object of the present invention to provide a novel sulfide solid electrolyte having higher ionic conductivity.

Another object of the present invention is to provide a novel sulfide solid electrolyte that suppresses the amount of hydrogen sulfide generated by a reaction with moisture in the atmosphere.

Solution to the above technical problem

According to one embodiment of the present invention, there is provided a novel sulfide solid electrolyte containing lithium, phosphorus, sulfur, chlorine, and bromine, having a diffraction peak a at 2 θ of 25.2 ± 0.5deg and a diffraction peak B at 2 θ of 29.7 ± 0.5deg in powder X-ray diffraction using CuK α rays, and satisfying the following formula (a) with respect to a mole ratio c (Cl/P) of chlorine to phosphorus and a mole ratio d (Br/P) of bromine to phosphorus, the following formula (1) being satisfied with respect to the diffraction peak a and the diffraction peak B,

1.2＜c+d＜1.9…(1)，

0.845＜S_A/S_B＜1.200…(A)，

in the formula, S_ARepresents the area of the diffraction peak A, S_BRepresents the area of the diffraction peak B.

Further, according to an embodiment of the present invention, there is provided an electrode composite material including the sulfide solid electrolyte and an active material.

In addition, according to an embodiment of the present invention, there is provided a lithium ion battery including at least one of the sulfide solid electrolyte and the electrode composite material.

Effects of the invention

According to one embodiment of the present invention, a sulfide solid electrolyte having high ionic conductivity can be provided.

Further, according to an embodiment of the present invention, it is possible to provide a sulfide solid electrolyte in which the amount of hydrogen sulfide generated by a reaction with moisture in the atmosphere is suppressed.

Drawings

Fig. 1 is a plan view of an example of a multi-shaft kneader for producing a sulfide solid electrolyte, the plan view being taken through the center of a rotating shaft.

Fig. 2 is a plan view of a part of a rotating shaft provided with blades, which is cut perpendicularly to the rotating shaft, in an example of a multi-shaft kneader for producing a sulfide solid electrolyte.

Fig. 3 is an X-ray diffraction pattern of the sulfide solid electrolyte obtained in example 1.

Fig. 4 is an X-ray diffraction pattern of the sulfide solid electrolyte obtained in comparative example 2.

Fig. 5 is an explanatory view of an apparatus for evaluating the amount of hydrogen sulfide generated from the sulfide solid electrolyte.

Fig. 6 shows the results of structural analysis of the sulfide solid electrolyte obtained in example 1 by using radiant light.

Detailed Description

The sulfide solid electrolyte according to one embodiment of the present invention contains lithium (Li), phosphorus (P), sulfur (S), chlorine (Cl), and bromine (Br) as constituent elements. And is characterized in that, in powder X-ray diffraction using CuK alpha rays, the diffraction peak A is 25.2 +/-0.5 deg at 2 theta, the diffraction peak B is 29.7 +/-0.5 deg, and the diffraction peak A and the diffraction peak B satisfy the following formula (A),

0.845＜S_A/S_B＜1.200…(A)，

in the formula, S_ADenotes the area of diffraction peak A, S_BThe area of diffraction peak B is shown.

Diffraction peaks A and B are peaks derived from a thiogermorite-type crystal structure. In addition to the diffraction peaks a and B, the diffraction peaks of the digermorite-type crystal structure may occur, for example, at 15.3 ± 0.5deg, 17.7 ± 0.5deg, 31.1 ± 0.5deg, 44.9 ± 0.5deg, or 47.7 ± 0.5deg, when 2 θ is equal to 15.3 ± 0.5 deg. The sulfide solid electrolyte of the present embodiment may have these peaks.

When the central value is a, the position of the diffraction peak is determined to be a ± 0.5deg in the present application, but is preferably a ± 0.3 deg. For example, in the case of the diffraction peak having a 2 θ of 25.2 ± 0.5deg, the median a is 25.2deg, and preferably, it is within a range of 25.2 ± 0.3 deg. The same is true for the determination of the positions of all other diffraction peaks in the present application.

The sulfide solid electrolyte of the present embodiment satisfies the formula (a), and thus has higher ion conductivity than a conventional solid electrolyte containing a geigrite crystal structure. The formula (A) is the area ratio (S) of diffraction peaks_A/S_B) Compared with the prior solid electrolyte containing the Geranite crystal structure, the electrolyte is larger. Preferably, the area ratio (S) of diffraction peaks_A/S_B) Is 0.850 to 1.150 inclusive, and more preferably 0.860 to 1.100 inclusive.

Area ratio (S)_A/S_B) It is considered that the larger the number of sites occupied by the halogen (the total of Cl and Br) in the thiogermite crystal structure, the higher the ratio. Among them, it is presumed that the site occupancy of Br is higher than that in the prior art. Generally, in a sulfide solid electrolyte, a plurality of crystal structures and non-crystal structures are mixed. Some of Cl and Br, which are added as constituent elements of the sulfide solid electrolyte, form a thiogermorite-type crystal structure, and other Cl and Br form crystal structures other than the thiogermorite-type crystal structure and amorphous structures. Further, it is also conceivable that Cl and Br are contained in the residual raw material. This implementationIt was found that the ratio of Br site occupancy, the area ratio (S), is increased in the ratio of halogen to Br sites in the Geranite-type crystal structure as compared with the prior art_A/S_B) Becomes large and thus the ion conductivity of the sulfide solid electrolyte becomes high.

A SiGe type crystal structure of PS₄ ^3-The structure is a unit structure of a main skeleton, and S surrounded by Li and halogen (Cl, Br) occupy sites around the unit structure.

The area ratio of the X-ray diffraction peaks of the crystal structure can be calculated from the coordinates of each element of the crystal structure (see "third edition of XRD diffraction manual, motors of science and chemistry, 2000, pages 14-15). The common germanite-type crystal structure is represented by space group F-43M and is volume G of international crystallography: definition and exchange of crystallographic data (ISBN:978-1-4020-3138-0) the crystal structure shown in No. 216 of the database. In the crystal structure shown in No. 216, in PS₄ ^3-The 4a site and the 4d site are present around the structure, and an element with a large ionic radius easily occupies the 4a site, and an element with a small ionic radius easily occupies the 4d site.

In the unit cell of the sigermorite-type crystal structure, the total number of 4a sites and 4d sites is 8. The area ratios of the X-ray diffraction peaks were calculated for the case where 4 Cl and 4S were arranged at these sites (case 1) and for the case where 4 Cl, 2 Br and 2S were arranged (case 2). As a result, it was found that in case 2, the area of the diffraction peak a (diffraction peak at 2 θ of 25 deg) was larger than that in case 1, while the area of the diffraction peak B (diffraction peak at 2 θ of 30 deg) was less changed. From the above calculation results, it is considered that the Br occupies the site and the area ratio (S)_A/S_B) Becomes larger.

In general, the area ratio or intensity ratio of X-ray diffraction peaks is proportional to the number of electrons of an element (refer to "guide to X-ray Crystal analysis", Shang Hua House, 1983). Since the number of electrons of Cl or S is approximately the same and the number of electrons of Br is large, it is considered that the site occupancy rate of Br becomes high in the crystal diffraction plane corresponding to the diffraction peak a. In addition, from the viewpoint of the size of the ionic radius, it can be estimated that the occupancy rate at the 4a site is high.

An increase in the amount of halogen occupying sites in the digermorite-type crystal structure means that the amount of S occupying sites in the digermorite-type crystal structure is relatively decreased. Halogen having a valence of-1 has a weaker ability to adsorb Li than sulfur having a valence of-2. In addition, the number of adsorbed Li is small. Therefore, it is considered that the density of Li around the site is decreased, and Li is easily moved, so that the ion conductivity of the digermorite-type crystal structure is increased.

In addition, in the case where the halogen is only Cl, the occupancy of S in the 4a site becomes high. By using Br having an ion radius equal to S together with Cl, the occupancy of Br in the 4a site becomes high, and as a result, the overall occupancy of halogen is increased. In addition, even when Cl occupies a part of the 4a site, Cl at the 4a site is unstable and may be released during the heat treatment. Therefore, it is considered preferable that the halogen having an appropriate ionic radius should occupy an appropriate site, while only increasing the halogen occupancy rate. In this embodiment, since 2 kinds of halogens (Cl and Br) occupy a large amount and appropriately sites in the digermorite-type crystal structure, it is presumed that the ion conductivity becomes high.

In the present embodiment, the molar ratio c (Cl/P) of chlorine to phosphorus and the molar ratio d (Br/P) of bromine to phosphorus satisfy the following formula (1),

1.2＜c+d＜1.9…(1)，

c + d is the molar ratio of chlorine and bromine relative to phosphorus. When c + d is in the above range, the effect of improving the ionic conductivity of the sulfide solid electrolyte is improved. c + d is preferably 1.4 to 1.8, more preferably 1.5 to 1.7.

In the sulfide solid electrolyte according to an embodiment of the present invention, the molar ratio d (Br/P) of bromine to phosphorus is preferably 0.15 to 1.6. The molar ratio d is more preferably 0.2 to 1.2, and still more preferably 0.4 to 1.0.

Further, the molar ratio c (Cl/P) of chlorine to phosphorus and the molar ratio d (Br/P) of bromine to phosphorus preferably satisfy the following formula (2),

0.08＜d/(c+d)＜0.8…(2)。

d/(c + d) is more preferably 0.15 to 0.6, and still more preferably 0.2 to 0.5.

The molar ratio of lithium to phosphorus a (Li/P), the molar ratio of sulfur to phosphorus b (S/P), the molar ratio of chlorine to phosphorus c (Cl/P), and the molar ratio of bromine to phosphorus d (Br/P) preferably satisfy the following formulae (3) to (5),

5.0≦a≦7.5…(3)，

6.5≦a+c+d≦7.5…(4)，

0.5≦a－b≦1.5…(5)，

(wherein b >0, c >0, and d >0 are satisfied).

By satisfying the above formulas (3) to (5), the thiogermite-type crystal structure can be easily formed.

The above formula (3) is preferably 5.0 ≦ a ≦ 6.8, more preferably 5.2 ≦ a ≦ 6.6.

The above formula (4) is preferably 6.6 ≦ a + c + d ≦ 7.4, more preferably 6.7 ≦ a + c + d ≦ 7.3.

The above formula (5) is preferably 0.6. ltoreq. a-b. ltoreq.1.3, more preferably 0.7. ltoreq. a-b. ltoreq.1.3.

The sulfide solid electrolyte of the present embodiment may contain Si, Ge, Sn, Pb, B, Al, Ga, As, Sb, Bi, O, Se, Te, and the like in addition to Li, P, S, Cl, and Br As described above, within a range not to impair the effects of the present invention. Further, the catalyst may be substantially composed of only Li, P, S, Cl, and Br. Consisting essentially of Li, P, S, Cl, and Br alone means: the sulfide solid electrolyte has, as constituent elements, only Li, P, S, Cl, and Br, except for inevitable impurities.

The molar ratio or composition of each element is not the molar ratio or composition in the raw material used in production, but the molar ratio or composition in the sulfide solid electrolyte as a product. The molar ratio of each element can be controlled by adjusting the content of each element in the raw material, for example.

In the present application, the molar ratio or composition of each element in the sulfide solid electrolyte is measured by ICP emission spectrometry, except for special reasons such as difficulty in analysis. The measurement method of the ICP emission spectrometry is described in examples.

In the sulfide solid electrolyte according to an embodiment of the present invention, when the powder X-ray diffraction using CuK α rays does not have a diffraction peak of lithium halide or has a diffraction peak of lithium halide, it is preferable that the following formula (B) is satisfied,

0＜I_C/I_A＜0.08…(B)，

(in the formula, I_CRepresents the intensity of the diffraction peak of lithium halide, I_AThe diffraction peak intensity was 25.2 ± 0.5 deg. ).

The above formula (B) shows that the amount of lithium halide is relatively small compared to the thiogermite type crystal structure. The presence of lithium halide is indicative of: among all halogens in the sulfide solid electrolyte, there are halogens that do not occupy sites in the digermorite-type crystal structure.

In the case where the lithium halide is LiCl, the diffraction peak intensity I of the lithium halide_CThe diffraction peak intensity is shown as occurring in the range of 34.0 deg.2 theta.35.5 deg. However, in the case where 2 or more diffraction peaks are present in this range, I_CThe diffraction peak intensity appearing on the side of the highest angle. In the case where the lithium halide is LiBr, I_CIs the intensity of a diffraction peak appearing in the range of 32.5 deg.f 2 theta 33.9 deg. However, in the case where 2 or more diffraction peaks are present in this range, I_CThe diffraction peak intensity appearing on the lowest side of the angle. The reason for this is that when a new crystal structure containing halogen described later is present, diffraction peaks appear at 14.4. + -. 0.5deg and 33.8. + -. 0.5 deg. Here, it is considered that, in the case where only one diffraction peak is observed in the range of 32.5 deg.C 2 θ 35.5deg, these diffraction peaks are derived from a new crystal structure containing halogen described later, regardless of whether or not a diffraction peak is observed in 14.4. + -. 0.5 deg. In this case, the diffraction peak was regarded as a diffraction peak in which no lithium halide was present. When diffraction peaks of LiCl and LiBr were observed, Ic was the total of the intensities of these diffraction peaks.

More preferably, formula (B) is 0 < I_C/I_A＜007, and more preferably 0 < I_C/I_A＜0.06。

In the sulfide solid electrolyte according to an embodiment of the present invention, it is preferable that the powder X-ray diffraction using CuK α rays does not have a diffraction peak or satisfies the following formula (C) when the powder X-ray diffraction has a diffraction peak at 2 θ of 14.4 ± 0.5deg and 33.8 ± 0.5deg,

0＜I_D/I_A＜0.09…(C)

(in the formula, I_DRepresents a diffraction peak intensity of 14.4 + -0.5 deg.C, I_AThe diffraction peak intensity was 25.2 ± 0.5 deg. ).

Although the crystal having diffraction peaks at 2 θ of 14.4 ± 0.5deg and 33.8 ± 0.5deg is a new crystal, it is presumed that it is a structure partially containing halogen. The above formula (C) shows that the new crystal structure is relatively small compared to the digermorite-type crystal structure. The presence of this new crystal structure indicates that: among all halogens in the sulfide solid electrolyte, there are halogens that do not occupy sites in the digermorite-type crystal structure.

More preferably, formula (C) is 0 < I_D/I_A< 0.06, more preferably 0 < I_D/I_A＜0.05。

In the sulfide solid electrolyte according to one embodiment of the present invention, the lattice constant of the thiogermite-type crystal structure is preferably set to be constantThe aboveThe following.

It is considered that the small lattice constant of the digermorite-type crystal structure means that the crystal structure contains a large amount of chlorine and bromine. If the lattice constant is insufficientBromine is difficult to incorporate into the crystal structure.

From the XRD pattern obtained in X-ray diffraction measurement (XRD), the lattice constant of the siganite-type crystal structure was calculated by performing full spectrum fitting (WPF) analysis using crystal structure analysis software. Details of the measurement are shown in the examples.

In the sulfide solid electrolyte according to one embodiment of the present invention, the solid electrolyte is a solid³¹In the P-NMR measurement, the peak is present at 81.5 to 82.5ppm (hereinafter referred to as region 1), 83.2 to 84.7ppm (hereinafter referred to as region 2), 85.2 to 86.7ppm (hereinafter referred to as region 3) and 87.2 to 89.4ppm (hereinafter referred to as region 4), respectively, and preferably, the ratio of the sum of the areas of the peak at 81.5 to 82.5ppm and the peak at 83.2 to 84.7ppm to the total area of all the peaks at 78 to 92ppm is 60% or more. It is presumed that a higher ratio of the sum of the areas of the 1 st peak and the 2 nd peak indicates a larger sum of the amount of chlorine and the amount of bromine incorporated into the thiogermorite-type crystal structure. As a result, the ion conductivity of the solid electrolyte becomes high.

In addition, the peak in the 1 st region is referred to as the 1 st peak (P)₁) The peak in the 2 nd region is referred to as the 2 nd peak (P)₂) The peak in the 3 rd region is referred to as the 3 rd peak (P)₃) The peak in the 4 th region is referred to as the 4 th peak (P)₄)。

The presence of a peak in a region means that a peak having a peak top is present in the region or that a peak is present in the region when separation is performed by the nonlinear least squares method.

A thiogermorite-type crystal structure (Li) in which chlorine is a halogen is reported₆PS₅Cl), due to PS in the crystal₄ ^3-Difference in distribution state of free chlorine (Cl) and free sulfur (S) around the structure, in the solid thereof³¹In the P-NMR spectrum, the resonance lines of a plurality of phosphors having different chemical shifts overlap (non-patent document 1). Based on these findings, the present inventors have found that a solid having a thiogermite crystal structure with a different ratio of free halogen to free S³¹P-NMR spectra were investigated. As a result, it was found that the NMR signal observed in the region of 78 to 92ppm can be separated into 4 PS species having different distribution states of the surrounding free S and free halogen₄ ^3-Peak of structure. In addition, it was found that, among the 4 kinds of peaks, in highWhen the area of the peak on the magnetic field side (the sum of the 1 st peak and the 2 nd peak) is relatively high, the ion conductivity of the solid electrolyte is high. The above-mentioned peak 1 and peak 2 are presumed to originate from PS in which the free elements around the peaks are mostly Cl or Br₄ ^3-And (5) structure. On the other hand, the 3 rd peak and the 4 th peak are assumed to originate from PS in which the free elements around the peaks are mostly S₄ ^3-And (5) structure.

The sulfide solid electrolyte according to an embodiment of the present invention can be produced, for example, by a production method including the steps of: producing an intermediate by applying a mechanical stress to the raw material mixture to cause a reaction; and a step of crystallizing the intermediate by heat treatment.

The raw material used is a combination of 2 or more compounds or monomers, and the whole contains elements that the sulfide solid electrolyte to be produced must contain, i.e., lithium, phosphorus, sulfur, and bromine.

As the raw material containing lithium, for example, lithium sulfide (Li) can be cited₂S), lithium oxide (Li)₂O), lithium carbonate (Li)₂CO₃) And lithium compounds and lithium metal monomers. Among these, lithium compounds are preferable, and lithium sulfide is more preferable.

Although the use of the above-mentioned lithium sulfide is not particularly limited, it is preferably high-purity lithium sulfide. For example, lithium sulfide can be produced by the methods described in Japanese patent application laid-open Nos. 7-330312, 9-283156, 2010-163356, and 2011-84438.

Specifically, lithium sulfide can be synthesized by reacting lithium hydroxide with hydrogen sulfide in a hydrocarbon organic solvent at 70 to 300 ℃ to produce lithium hydrosulfide, and then subjecting the reaction solution to a hydrogen sulfide removal treatment (jp 2010-163356 a).

Lithium sulfide can be synthesized by reacting lithium hydroxide with hydrogen sulfide in a water solvent at 10 to 100 ℃ to produce lithium hydrosulfide and then subjecting the reaction solution to a hydrogen sulfide removal treatment (jp 2011-84438 a).

As containing phosphorusExamples of the raw material include phosphorus trisulfide (P)₂S₃) Phosphorus pentasulfide (P)₂S₅) Phosphorus sulfide, sodium phosphate (Na) etc₃PO₄) And phosphorus compounds and phosphorus monomers. Among them, phosphorus sulfide is preferable, and phosphorus pentasulfide (P) is more preferable₂S₅). The phosphorus compound and the phosphorus monomer may be used without particular limitation as long as they are industrially produced and sold.

The raw material containing chlorine and/or bromine is preferably a raw material containing a halogen compound represented by the following formula (6), for example.

M_l-X_m…(6)

In formula (6), M represents 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 a combination of an oxygen element and a sulfur element with these elements, preferably lithium (Li) or phosphorus (P), more preferably lithium (Li).

X is chlorine (Cl) or bromine (Br).

In addition, 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 a plurality of xs are present, xs may be the same or different from each other. For example, SiBrCl described later₃Wherein m is 4 and X is composed of different elements such as Br and Cl.

Specific examples of the halogen compound represented by the formula (6) include NaCl, NaBr, LiCl, LiBr and BCl₃、BBr₃、AlBr₃、AlCl₃、SiCl₄、SiCl₃、Si₂Cl₆、SiBr₄、SiBrCl₃、SiBr₂Cl₂、PCl₃、PCl₅、POCl₃、PBr₃、POBr₃、P₂Cl₄、SCl₂、S₂Cl₂、S₂Br₂、GeCl₄、GeBr₄、GeCl₂、GeBr₂、AsCl₃、AsBr₃、SeCl₂、SeCl₄、Se₂Br₂、SeBr₄、SnCl₄、SnBr₄、SnCl₂、SnBr₂、SbCl₃、SbBr₃、SbCl₅、TeCl₂、TeCl₄、TeBr₂、TeBr₄、PbCl₄、PbCl₂、PbBr₂、BiCl₃、BiBr₃And the like.

Among them, lithium chloride (LiCl), lithium bromide (LiBr), and phosphorus pentachloride (PCl) can be preferably cited₅) Phosphorus trichloride (PCl)₃) Phosphorus pentabromide (PBr)₅) Or phosphorus tribromide (PBr)₃). Among them, LiCl, LiBr or PBr is preferable₃More preferably, LiCl and LiBr.

As the halogen compound, one of the above-mentioned compounds may be used alone, or two or more of the above-mentioned compounds may be used in combination. I.e. at least one of the above-mentioned compounds can be used.

In one embodiment of the present invention, the raw material contains a lithium compound, a phosphorus compound, and a halogen compound, and preferably at least one of the halogen compound and the phosphorus compound contains a sulfur element, and more preferably Li₂The combination of S and phosphorus sulfide with LiCl and LiBr is more preferably Li₂S、P₂S₅And combinations of LiCl and LiBr.

For example, in the reaction of Li₂S、P₂S₅When LiCl and LiBr are used as raw materials of a sulfide solid electrolyte, the molar ratio of the charged raw materials can be Li₂S∶P₂S₅The total ratio of LiCl to LiBr is 30-60: 10-25: 15-50.

In one embodiment of the present invention, the raw materials are reacted by applying a mechanical stress to the raw materials to form an intermediate. Here, "applying mechanical stress" means mechanically applying a shear force, an impact force, or the like. Examples of the method of applying mechanical stress include a pulverizer such as a planetary ball mill, a vibration mill, or a rotary mill, or a kneader.

In the prior art (for example, patent document 2) the raw material powder is pulverized and mixed to such an extent that the crystalline state of the raw material powder can be maintained. On the other hand, inIn the present embodiment, it is preferable that the raw materials are reacted by applying a mechanical stress, thereby forming an intermediate containing a glass component. That is, the raw material powder is pulverized and mixed by a mechanical stress stronger than that in the conventional art until at least a part of the raw material powder cannot maintain a crystalline state. Thus, PS, which is the basic skeleton of the Geranite crystal structure, can be generated in the intermediate stage₄ ^3-And a structure capable of highly dispersing halogen. It is presumed that the halogen highly dispersed in the intermediate is efficiently introduced to the site in the digermorite-type crystal structure by the heat treatment. From this, it is presumed that the sulfide solid electrolyte of the present embodiment exhibits high ion conductivity.

In addition, in XRD measurement, it can be confirmed that the intermediate contains a glass (amorphous) component from the presence of a broad peak (halo pattern) due to the amorphous component.

For example, when a planetary ball mill is used as the pulverizer, the pulverizing and mixing may be carried out for 0.5 to 100 hours at a rotation speed of several tens to several hundreds revolutions per minute. More specifically, in the case of the planetary ball mill (model P-7, manufactured by flight (flight) corporation) used in the examples of the present application, the rotation speed of the planetary ball mill is preferably 350rpm to 400rpm, and more preferably 360rpm to 380 rpm.

For example, when zirconia balls are used, the balls as the grinding medium preferably have a diameter of 0.2 to 20 mm.

The intermediate produced by pulverizing and mixing is subjected to heat treatment. The heat treatment temperature is preferably 350-480 ℃, more preferably 360-460 ℃, and further preferably 380-450 ℃. When the heat treatment temperature is slightly lower than the conventional one, the amount of halogen contained in the thiogermorite-type crystal structure tends to increase. This is presumably because, when the heat treatment temperature is high, the halogen is easily released from the site in the digermorite-type crystal structure.

Although the atmosphere for the heat treatment is not particularly limited, it is preferable to perform the heat treatment not under a hydrogen sulfide gas flow but under an inert gas atmosphere of nitrogen, argon, or the like. By suppressing the substitution of the free halogen in the crystal structure by sulfur, the amount of halogen in the crystal structure can be increased, and as a result, it is estimated that the ion conductivity of the obtained sulfide solid electrolyte is improved.

When a kneader is used as the device for applying mechanical stress, the kneader is not particularly limited, but a multi-shaft kneader having 2 or more shafts is preferable from the viewpoint of easy manufacturing.

The multi-shaft mixer is not particularly limited as long as, for example, the following is satisfied: the present invention relates to a rotary compressor including a housing and 2 or more rotary shafts, the rotary shafts being disposed so as to penetrate the housing in a longitudinal direction, and having blades (screws) provided along an axial direction, the housing including a raw material supply port at one end in the longitudinal direction and a discharge port at the other end, and two or more types of rotary motions being mutually acted to generate mechanical stress. By rotating 2 or more rotating shafts provided with blades of such a multi-shaft kneader, two or more types of rotational motions can be caused to interact with each other to generate mechanical stress, and the mechanical stress can be applied to a raw material moving in a direction from a supply port to a discharge port along the rotating shafts to cause the raw material to react.

A preferred example of a multi-shaft kneading machine that can be used in one embodiment of the present invention will be described with reference to fig. 1 and 2. Fig. 1 is a plan view of a multi-shaft mixer taken through the center of a rotating shaft. Fig. 2 is a plan view of a portion of the rotating shaft where the blades are provided, the portion being cut perpendicularly to the rotating shaft.

The multi-shaft kneader shown in fig. 1 is a twin-shaft kneader, and includes: a housing 1 having a supply port 2 at one end and a discharge port 3 at the other end; 2 rotation shafts 4a and 4b penetrating the housing 1 in the longitudinal direction. The rotating shafts 4a and 4b are provided with blades 5a and 5b, respectively. The raw material enters the housing 1 from the supply port 2, and is reacted by applying mechanical stress to the blades 5a and 5b, and the resultant reactant is discharged from the discharge port 3.

The number of the rotating shafts 4 is not particularly limited as long as it is 2 or more, and is preferably 2 to 4, and more preferably 2 in view of versatility. The rotation shafts 4 are preferably parallel shafts parallel to each other.

The blade 5 is provided to a rotating shaft for kneading the raw material, and is also called a screw. The cross-sectional shape is not particularly limited, and may be a shape having a cut-out portion in a part thereof, in addition to a substantially triangular shape in which each side of a regular triangle has the same convex arc shape as shown in fig. 2, a circular shape, an elliptical shape, a substantially quadrangular shape, or the like.

As shown in fig. 2, when a plurality of blades are provided, the blades may be provided on the rotary shaft at different angles. When further kneading effect is desired, the engaging type blade may be selected.

The number of rotations of the blades is not particularly limited, but is preferably 40 to 300rpm, more preferably 40 to 250rpm, and still more preferably 40 to 200 rpm.

In order to supply the raw materials into the kneading machine without stagnation, the multi-shaft kneading machine may be provided with a screw 6 on the side of the supply port 2 as shown in fig. 1, and may be provided with a reverse screw 7 on the side of the discharge port 3 as shown in fig. 1 in order to prevent the reaction product obtained by passing through the blade 5 from staying in the casing.

As the multi-shaft mixer, a commercially available mixer can be used. Examples of commercially available mixers include KRC kneaders (manufactured by Kikuchi Kogyo Co., Ltd.).

The kneading time of the raw materials may be appropriately adjusted depending on the kind and composition ratio of the elements constituting the desired sulfide solid electrolyte and the temperature during the reaction, and is preferably 5 minutes to 50 hours, more preferably 10 minutes to 15 hours, and still more preferably 1 to 12 hours.

The kneading temperature of the raw materials varies depending on the kind of the element constituting the desired sulfide solid electrolyte, the composition ratio, and the temperature during the reaction, and may be appropriately adjusted, and is preferably 0 ℃ or more, more preferably 25 ℃ or more, further preferably 100 ℃ or more, and most preferably 250 ℃ or more. The higher the temperature, the more the thiogermorite-type crystal structure can be precipitated at the kneading time. It is considered that the thiogenitic crystal structure is more likely to precipitate at 350 ℃ or higher. The upper limit of the kneading temperature may be less than 500 ℃ as long as the produced digermorite-type crystal structure is not decomposed.

Depending on the degree of progress of the reaction, the intermediate discharged from the discharge port of the multi-shaft kneader may be fed again from the supply port to further progress the reaction. The degree of progress of the reaction can be grasped from the increase and decrease in the peak of the obtained raw material derived from the intermediate.

The sulfide solid electrolyte can be obtained by heat-treating the intermediate obtained by kneading. The heat treatment temperature is preferably 350-480 ℃, more preferably 360-460 ℃, and further preferably 380-450 ℃. Although the atmosphere for the heat treatment is not particularly limited, it is preferable to perform the heat treatment not in a gas flow of hydrogen sulfide but in an inert gas atmosphere of nitrogen, argon, or the like.

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

[ electrode composite Material ]

An electrode composite material according to an embodiment of the present invention includes the sulfide solid electrolyte according to the present invention and an active material. Alternatively, it is produced from the sulfide solid electrolyte of the present invention. When the negative electrode active material is used as the active material, the negative electrode composite material is obtained. On the other hand, when a positive electrode active material is used, a positive electrode composite material is obtained.

Negative electrode composite material

An anode composite material is obtained by blending an anode active material to 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. A composite body composed of 2 or more of these materials can also be used. In addition, a negative electrode active material developed in the future can be used.

Preferably, the negative electrode active material has electron conductivity.

Examples of the carbon material include graphite (e.g., artificial graphite), graphitic carbon fiber, resin-fired carbon, thermally decomposed vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-fired carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon.

Examples of the metal material include a metal simple substance, an alloy, and a metal compound. Examples of the metal monomer include metal silicon, metal tin, metal lithium, metal indium, and metal aluminum. The metal alloy may be an alloy containing at least one of silicon, tin, lithium, indium, and aluminum. As the metal compound, a metal oxide can be cited. Examples of the metal oxide include silicon oxide, tin oxide, and aluminum oxide.

The blending ratio of the negative electrode active material to the solid electrolyte is preferably 95 wt% to 5 wt% to 95 wt%, more preferably 90 wt% to 10 wt% to 90 wt%, and still more preferably 85 wt% to 15 wt% to 85 wt%.

When the content of the negative electrode active material in the negative electrode composite material is too small, the capacitance decreases. In addition, when the negative electrode active material has electron conductivity and contains no or only a small amount of a conductive auxiliary agent, it is considered that the electron conductivity (electron conduction path) in the negative electrode is decreased to lower the rate capability, or the utilization rate of the negative electrode active material is decreased to lower the capacity. On the other hand, if the content of the negative electrode active material in the negative electrode composite is too large, it is considered that ion conductivity (ion conduction path) in the negative electrode is lowered to lower the rate capability, or the utilization rate of the negative electrode active material is lowered to lower the capacity.

The negative electrode composite material can also contain a conductive aid.

Preferably, the conductive aid is added when the electron conductivity of the negative electrode active material is low. The conductive assistant is only required to have conductivity, and the electron conductivity thereof is preferably 1 × 10³S/cm or more, more preferably 1X 10⁵And more than S/cm.

Specific examples of the conductive auxiliary agent include those containing at least one element selected from the group consisting of a carbon material, nickel, copper, aluminum, indium, silver, cobalt, magnesium, lithium, chromium, gold, ruthenium, platinum, beryllium, iridium, molybdenum, niobium, osmium, rhodium, tungsten, and zinc, and more preferably a carbon monomer having high conductivity, and a carbon material other than the carbon monomer; a metal monomer, mixture or compound comprising nickel, copper, silver, cobalt, magnesium, lithium, ruthenium, gold, platinum, niobium, osmium or rhodium.

Specific examples of the carbon material include carbon Black such as ketjen Black, acetylene Black, superconducting acetylene Black (Denka Black), thermal Black, and channel Black; graphite, carbon fiber, activated carbon, and the like, and they may be used alone or in combination of 2 or more. Among them, acetylene black having high electron conductivity, superconducting acetylene black, and ketjen black are preferable.

When the negative electrode composite material contains the conductive additive, the content of the conductive additive in the composite material is preferably 1 to 40 mass%, and more preferably 2 to 20 mass%. If the content of the conductive additive is too small, it is considered that the electron conductivity of the negative electrode is lowered to lower the rate capability, or the utilization rate of the negative electrode active material is lowered to lower the capacity. 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 decreases. It is estimated that the capacitance decreases when the amount of the negative electrode active material decreases. Further, it is considered that when the amount of the solid electrolyte is decreased, the ion conductivity of the negative electrode may be decreased to lower the rate capability, or the utilization rate of the negative electrode active material may be decreased to lower the capacity.

A binder may be further included to tightly bind the negative electrode active material and the solid electrolyte to each other.

As the adhesive, a fluorine-containing resin such as Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or fluororubber, a thermoplastic resin such as polypropylene or polyethylene, ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, or Natural Butyl Rubber (NBR) may be used alone or as a mixture of 2 or more kinds. In addition, a cellulose-based or Styrene Butadiene Rubber (SBR) aqueous dispersion or the like can be used as the aqueous binder.

The negative electrode composite material can be produced by mixing the solid electrolyte, the negative electrode active material, and any of the conductive additives and/or binders.

The mixing method is not particularly limited, and for example, the following methods can be applied: dry mixing using a mortar, ball mill, bead mill, jet mill, planetary ball mill, vibratory ball mill, sand mill, chopper; wet mixing, in which the raw materials are dispersed in an organic solvent, followed by mixing using a mortar, ball mill, bead mill, planetary ball mill, vibration ball mill, sand mill, or thin film gyrometer (Filmix), and then removing the solvent. Among them, wet mixing is preferable so as not to destroy the negative electrode active material particles.

Positive electrode composite material

A positive electrode composite material can be obtained by incorporating a positive electrode active material into the solid electrolyte of the present invention.

The positive electrode active material is a material capable of intercalating and deintercalating lithium ions, and a material known as a positive electrode active material in the field of batteries can be used. Further, a positive electrode active material developed in the future can be used.

Examples of the positive electrode active material include metal oxides and sulfides. The sulfide includes metal sulfide and nonmetal sulfide.

The metal oxide is, for example, a transition metal oxide. Specifically, V can be exemplified₂O₅、V₆O₁₃、LiCoO₂、LiNiO₂、LiMnO₂、LiMn₂O₄、Li(Ni_aCo_bMn_c)O₂(Here, 0)<a<1、0<b<1、0<c<1、a+b+c＝1)、LiNi_1-YCo_YO₂、LiCo_1-YMn_YO₂、LiNi_1-YMn_YO₂(Here, 0 ≦ Y<1)、Li(Ni_aCo_bMn_c)O₄(0<a<2、0<b<2、0<c<2、a+b+c＝2)、LiMn_2-ZNi_ZO₄、LiMn_2-ZCo_ZO₄(Here, 0)<Z<2)、LiCoPO₄、LiFePO₄、CuO、Li(Ni_aCo_bAl_c)O₂(Here, 0)<a<1、0<b<1、0<c<1. a + b + c ═ 1), and the like.

The metal sulfide includes titanium sulfide (TiS)₂) Molybdenum sulfide (MoS)₂) Iron sulfide (FeS )₂) Copper sulfide (CuS) and nickel sulfide (Ni)₃S₂) And the like.

In addition, as the metal oxide, bismuth oxide (Bi) can be mentioned₂O₃) Lead acid bismuth (Bi)₂Pb₂O₅) And the like.

Examples of the nonmetallic sulfide include organic disulfide compounds and carbon sulfide compounds.

In addition to the above, niobium selenide (NbSe)₃) Metal indium and sulfur can also be used for the positive electrode active material.

The positive electrode composite material may also further include a conductive auxiliary agent.

The conductive additive is the same as that used for the cathode composite material.

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

[ lithium ion Battery ]

A lithium ion battery according to an embodiment of the present invention includes at least one of the sulfide solid electrolyte and the electrode composite material of the present invention. Or is produced from at least one of the sulfide solid electrolyte and the electrode composite material of the present invention.

The lithium ion battery is not particularly limited in configuration, but generally has a structure in which a negative electrode layer, an electrolyte layer, and a positive electrode layer are stacked in this order. The layers of the lithium ion battery are explained below.

(1) Negative electrode layer

The negative electrode layer is preferably a layer made of the negative electrode composite material of the present invention.

Alternatively, the negative electrode layer is preferably a layer containing the negative electrode composite material of the present invention.

The thickness of the negative electrode layer is preferably 100nm to 5mm, more preferably 1 μm to 3mm, and still more preferably 5 μm to 1 mm.

The negative electrode layer can be produced by a known method, for example, by a coating method or an electrostatic method (electrostatic spraying method, electrostatic screen method, or the like).

(2) Electrolyte layer

The electrolyte layer is a layer containing a solid electrolyte or a layer made of a solid electrolyte. The solid electrolyte is not particularly limited, and is preferably the sulfide solid electrolyte of the present invention.

The electrolyte layer may be composed of only a solid electrolyte, or may further contain a binder. As the binder, the same binder as that of the negative electrode composite material of the present invention can be used.

The thickness of the electrolyte layer is preferably 0.001mm or more and 1mm or less.

The solid electrolyte of the electrolyte layer may be fused. The fusion means that a part of the solid electrolyte particles is dissolved and the dissolved part is integrated with other solid electrolyte particles. The electrolyte layer may be a solid electrolyte plate-like body, and the plate-like body also 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 or an electrostatic method (electrostatic spraying method, electrostatic screen method, or the like).

(3) Positive electrode layer

The positive electrode layer is a layer containing a positive electrode active material, and preferably a layer containing or made of the positive electrode composite material of the present invention.

The thickness of the positive electrode layer is preferably 0.01mm to 10 mm.

The positive electrode layer can be produced by a known method, for example, by a coating method or an electrostatic method (electrostatic spraying method, electrostatic screen method, or the like).

(4) Current collector

Preferably, the lithium ion battery of the present embodiment further includes a current collector. For example, the negative electrode current collector is provided on the opposite side of the negative electrode layer from the electrolyte layer side, and the positive electrode current collector is provided on the opposite side of the positive electrode layer from the electrolyte layer side.

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 or the like can be used.

The lithium ion battery of the present embodiment can be manufactured by bonding and joining the above members. As a method of joining, there are a method of laminating the respective members and pressing them, a method of passing between two rollers and pressing them (roller-to-roller), and the like.

The bonding surfaces may be bonded via an active material having ion conductivity or an adhesive material that does not inhibit ion conductivity.

In the joining, the fusion may be performed by heating in a range in which the crystal structure of the solid electrolyte does not change.

The lithium ion battery of the present embodiment can also be manufactured by sequentially forming the above-described members. The resin composition can be produced by a known method, for example, by a coating method or an electrostatic method (electrostatic spraying method, electrostatic screen method, or the like).

Examples

The present invention will be described in more detail below with reference to examples.

The evaluation method is as follows.

(1) Ion conductivity measurement and electron conductivity measurement

The sulfide solid electrolytes produced in the respective examples were filled in a tablet molding machine, and a compact was formed by applying a pressure of 407MPa (indicated by a pressure of 22MPa) using a small-sized press machine. Carbon was placed as an electrode on both surfaces of the molded article, and pressure was applied again by the sheet forming machine to produce a molded article (diameter about 10mm, thickness 0.1 to 0.2cm) for measurement. The ionic conductivity of the formed body was measured by means of an ac impedance measurement. The ionic conductivity was measured at 25 ℃.

In addition, in the method for measuring ion conductivity used in the present example, when the ion conductivity is less than 1.0X 10^-6In the case of S/cm, the ion conductivity cannot be measured accurately, and therefore, the measurement cannot be performed.

Further, the electronic conductivity of the formed body was measured by direct current measurement. The value of the electron conductivity was taken as a value at 25 ℃. Further, the electron conductivity when a voltage of 5V was applied was less than 1.0X 10^-6In the case of S/cm, the electron conductivity cannot be measured.

(2) X-ray diffraction (XRD) measurements

The powders of the sulfide solid electrolytes produced in the respective examples were molded into round pellets having a diameter of 10mm and a height of 0.1 to 0.3cm to prepare samples. The sample was measured using XRD with a gas-tight sample stage without contact with air. The 2 θ position of the diffraction peak was determined by the centroid method using XRD analysis program JADE.

The measurement was carried out under the following conditions using a SmartLab powder X-ray diffraction measuring apparatus manufactured by japan.

Tube voltage: 45kV

Tube current: 200mA

X-ray wavelength: Cu-K alpha ray

An optical system: parallel beam method

The slit is formed as follows: rope pulling slit 5 degrees, incident slit 1mm and light receiving slit 1mm

A detector: scintillation counter

Measurement range: 2 theta 10-60deg

Step width and scanning speed: 0.02deg, 1 deg/min

In the process of analyzing the peak position for confirming the presence of the crystal structure from the measurement results, the XRD analysis program JADE was used to draw a base line by 3-degree equation fitting, thereby finding the peak position.

The diffraction peak intensity and area of 25.2 ± 0.5deg (diffraction peak a) and 29.7 ± 0.5deg (diffraction peak B) were analyzed in the following order to calculate the area ratio.

Determining the maximum peak position of 23-27 deg 2 theta in XRD pattern, and using the intensity (height) of the peak top as diffraction peak intensity I_A. The integrated value of the measured intensities at 41 points located in the maximum peak position. + -. 0.4deg was defined as the area S of the diffraction peak A_A. Similarly, the maximum peak position of 28 to 32deg 2 θ is obtained, and the integrated value of the measured intensities at 41 points located within ± 0.4deg is taken as the area S of the diffraction peak B_B. According to S_AAnd S_BCalculating the area ratio (S)_A/S_B)。

In the case where the lithium halide is LiCl, the diffraction peak intensity I of the lithium halide_CDefining a peak at 2 theta of 34.0-35.5 deg, and defining the intensity of the peak top as diffraction peak intensity I_C. In addition, when 2 or more peaks exist in this range, the intensity of the peak limited to the side with the highest angle is used. When the lithium halide is LiBr, a peak at 2 theta of 32.5 to 33.9deg is defined, and the intensity of the peak top is defined as diffraction peak intensity I_C. In addition, when 2 or more peaks exist in this range, the intensity of the peak limited to the lowest angle side is used.

Furthermore, a peak at 2 theta of 14.0 to 15.0deg is defined, and the intensity of the peak top is taken as the diffraction peak intensity I_D。

(3) ICP measurement

Powders of the sulfide solid electrolytes produced in the respective examples were weighed and collected in a flask under an argon atmosphere. An alkaline aqueous KOH solution was added to the flask, and the sample was dissolved while paying attention to trapping sulfur components, and diluted appropriately to prepare a measurement solution. The composition thereof was determined by measuring it with an ICP-OES apparatus of paschen-longge type (plasma emission spectrometer (spectra ARCOS) manufactured by spieck, germany).

The standard curve solutions of Li, P and S were prepared by using 1000mg/L standard solution for ICP measurement, and the standard curve solutions of Cl and Br were prepared by using 1000mg/L standard solution for ion chromatography.

For each sample, 2 sets of measurement solutions were prepared, and each measurement solution was measured 5 times to calculate an average value. The composition was determined from the average of the measured values of the 2 groups of measurement solutions.

(4) Lattice constant of the Geranite-type crystal structure

XRD was measured under the same conditions as in the above (2). The obtained XRD pattern was subjected to full spectrum fit (WPF) analysis using the crystal structure analysis software JADE ver6 manufactured by MDI, to define each crystal component contained in the XRD pattern, and the lattice constant of each component was calculated.

Removing the background of the XRD pattern

In the XRD pattern after measurement, there is scattered light originating from the apparatus or a signal originating from the airtight holder on the low angle side. To remove such signals, a base line of the decay from the low angle side was calculated from the XRD pattern by fitting a 3-degree equation.

Identification of the Peak Components

Peak components were identified by superimposing XRD patterns with patterns calculated from structural information on an Inorganic Crystal Structure Database (ICSD) for each component contained in the sample. The structure information used is shown in table 1.

[ Table 1]

WPF analysis

The main parameter settings for the WFP analysis are as follows.

X-ray wavelength: cuk alpha ray

Fitting parameters: the peak shape is approximately a symmetrical peak. Simulating the temperature factorAnd (4) excluding in combination. In Li₂When crystals such as S remain as fine peaks, the fitting may not converge. In this case, the structure of the sigermorite-type crystal and the structure other than the lithium halide crystal are removed from the fitting target, the half width and the intensity are manually output, and the lattice constant of the sigermorite-type crystal structure is calculated by fitting.

Regarding the lattice constant, it was confirmed whether the peak position of the evaluated crystal structure sufficiently coincided with the fitting result. Regarding the area ratio, the result correctness was evaluated by setting the R value to 10% or less. The R value as a criterion of the fitting accuracy may be high when there are many unknown peaks or amorphous peaks remain.

(5) Solid body³¹P-NMR measurement

Approximately 60mg of the powder sample was charged into an NMR sample tube, and a solid was obtained using the following apparatus and conditions³¹P-NMR spectrum.

The device comprises the following steps: ECZ400R device (made by Japan electronic Co., Ltd.)

And (3) observing a nucleus:³¹P

observation frequency: 161.944MHz

Measuring the temperature: at room temperature

Pulse sequence: single pulse (using 90 degree pulse)

90 ° pulse width: 3.8 μm

Waiting time after FID measurement until next pulse application: 300s

Rotating speed of magic angle rotation: 12kHz

And (4) accumulating times: 16 times (twice)

Measurement range: 250ppm to-150 ppm

In the solid³¹In the measurement of P-NMR spectrum by using (NH)₄)₂HPO₄(chemical shift 1.33ppm) was used as an external reference to obtain a chemical shift.

Using a non-linear least squares method to remove the impurities in the solid³¹NMR signals in the range of 78-92 ppm of the P-NMR spectrum are separated into Gaussian functions or Pseudo-Voigt functions (linear sum of Gaussian and Lorentzian functions). Within the above range except that chlorine is contained toAnd bromine, and in addition to peaks due to the thiogermite-type crystal structure, Li may be observed at 88.5 to 90.5ppm₇PS₆Peak caused by Li in 86-87.6 ppm₃PS₄Overlap of peaks caused by β crystals. Therefore, in the case where these 2 peaks are not observed and in the case where these 2 peaks are observed, waveform separation is performed by a different method.

(5-1) No observation of Li₇PS₆And Li₃PS₄The peak caused by beta crystal of (2)

NMR signals in the range of 78-92 ppm were separated into 4 Gaussian functions or Pseudo-Voigt functions (linear sum of Gaussian and Lorentzian functions) over the range of positions and half widths shown in Table 2 using a nonlinear least squares method. From the area S of each of the obtained peaks A to C₁～S₄And their sum S_all(＝S₁+S₂+S₃+S₄) The area ratio (%) of each peak was calculated

[ Table 2]

(5-2) observation of Li₇PS₆And Li₃PS₄The peak caused by beta crystal of (2)

As shown in Table 3, in addition to 4 peaks due to the chlorine-containing thiogenitic crystal structure, Li was used₇PS₆(Peak I) or Li₃PS₄(Peak II) from the peaks, separating NMR signals of 78 to 92ppm by nonlinear least squares method, and obtaining the area S of the peaks A to C₁～S₄Area b of peak I and peak II₁And b₂And their sum S_all+b(＝S₁+S₂+S₃+S₄+b₁+b₂) The area ratio (%) of each peak was calculated.

[ Table 3]

Production example 1

(lithium sulfide (Li)₂S) manufacture)

A500 ml separable flask equipped with a stirrer was charged with 200g of an anhydrous LiOH (product of Kyowa chemical Co., Ltd.) dried under an inert gas. The temperature was raised under a stream of nitrogen and the internal temperature was maintained at 200 ℃. The nitrogen gas was changed to hydrogen sulfide gas (manufactured by Sumitomo Seiki Co., Ltd.), and the LiOH anhydride was reacted with hydrogen sulfide at a flow rate of 500 mL/min.

The moisture produced by the reaction is condensed and recovered by a condenser. 144ml of water were recovered at a time point after the reaction had proceeded for 6 hours. The reaction was continued for 3 hours, but no water was observed.

The resultant powder was recovered and purity and XRD were measured. As a result, the purity was 98.5%, and Li was confirmed by XRD₂Peak profile of S.

Example 1

Lithium sulfide (Li) produced in production example 1 was added₂S: purity 98.5%), phosphorus pentasulfide (P)₂S₅Manufactured by tianfu (thermophos) having a purity of 99.9% or more), lithium chloride (LiCl: manufactured by sigma aldrich, purity 99%) and lithium bromide (LiBr: manufactured by sigma aldrich, purity 99%) was used for the starting materials (hereinafter, in all examples, the purity of each starting material was the same). So that Li₂S、P₂S₅Molar ratio of LiCl to LiBr (Li)₂S∶P₂S₅LiCl: LiBr) in a ratio of 1.9: 0.5: 1.0: 0.6. Specifically, 0.447g of lithium sulfide, 0.569g of diphosphorus pentasulfide, 0.217g of lithium chloride, and 0.267g of lithium bromide were mixed to prepare a raw material mixture.

The raw material mixture and 30g of balls made of zirconia having a diameter of 10mm were put into a jar (45mL) made of zirconia by a planetary ball mill (model P-7, manufactured by Flight (FRITSCH)) and completely sealed. The inside of the tank was kept under an argon atmosphere. The treatment (mechanical grinding) was performed for 15 hours at 370rpm, which was the rotational speed of the planetary ball mill, to obtain glassy powder (intermediate).

Approximately 1.5g of the powder of the intermediate was charged into a carbon particle heating tube (PT2, manufactured by tokyo nit instruments) in a glove box under an argon (Ar) atmosphere, the orifice of the carbon particle heating tube was closed with quartz wool, and the carbon particle heating tube was sealed with a SUS-made sealing container so that air could not enter the carbon particle heating tube. Then, the sealed container was placed in an electric furnace (FUW243PA, manufactured by Mowa corporation) and heat-treated. Specifically, the temperature was raised from room temperature to 430 ℃ at 2.5 ℃/min (to 430 ℃ in about three hours), and the temperature was maintained at 430 ℃ for 8 hours. Then, it was slowly cooled and a sulfide solid electrolyte was obtained.

The ionic conductivity (. sigma.) of the sulfide solid electrolyte was 13.0 mS/cm.

The XRD pattern of the sulfide solid electrolyte is shown in fig. 3. Peaks derived from the digermorite-type crystal structure were observed at 2 θ of 15.5, 17.9, 25.4, 29.9, 31.3, 44.9, 47.8, 52.4, and 59.1 deg.

The sulfide solid electrolyte was subjected to ICP analysis, and the molar ratio of each element was measured. As a result, the molar ratio a (Li/P) was 5.35, the molar ratio b (S/P) was 4.33, the molar ratio c (Cl/P) was 1.102, and the molar ratio d (Br/P) was 0.62.

The blending of the raw materials and the production conditions are shown in table 4. The molar ratio of each element in the raw material and the molar ratio of each element in the sulfide solid electrolyte are shown in table 5. The areas, area ratios, and ion conductivities σ of diffraction peaks a and B in the XRD patterns of the sulfide solid electrolytes are shown in table 6. Diffraction peak intensities in the XRD pattern of the sulfide solid electrolyte and intensity ratio are shown in table 7. Lattice constant of sulfide solid electrolyte and³¹the area ratio of the peaks in P-NMR is shown in Table 8.

[ Table 4]

[ Table 5]

X is the sum of Cl and Br

[ Table 6]

In the table, S_AThe area of diffraction peak a (2 θ ═ 25.2 ± 0.5deg), S_BThe area of the diffraction peak B (2 θ: 29.7 ± 0.5deg) is shown.

[ Table 7]

In table I_AIntensity of diffraction peak a (2 θ ═ 25.2 ± 0.5deg), I_CIs the sum of the diffraction peak intensities of lithium halides, I_DThe intensity of the diffraction peak D (2 θ ═ 14.4 ± 0.5deg) was obtained.

[ Table 8]

Comparative example 1

The same raw materials as in example 1 were charged into a Schlenk bottle and mixed by shaking by hand. The obtained raw material mixture was heat-treated at 430 ℃ for 8 hours in the same manner as in example, to obtain a sulfide solid electrolyte.

The evaluation of the sulfide solid electrolyte was performed in the same manner as in example 1. The results are shown in tables 5 to 8.

In comparative example 1, it is presumed that the halogen is not dispersed even after the heat treatment because the raw materials are not sufficiently mixed before the heat treatment, and as a result, the halogen is not sufficiently introduced into the site in the germanite-type crystal structure.

Example 2

In example 2, a two-shaft kneader was used in place of the planetary ball mill of example 1 for the production of the intermediate. Specifically, kneading using a twin-screw kneader was carried out as follows.

A feeder (manufactured by Aishin Nano Technologies, Inc.) and a two-shaft kneading extruder (manufactured by Takara Shuzo, Inc., KRC kneader, impeller diameter. phi.8 mm) were provided in a glove box. 3.76g LiCl, 4.63g LiBr and 7.75g 7.75gLi were mixed by a feeder₂S and 9.87gP₂S₅The mixture (2) was fed from the feeding section at a constant speed, and kneaded at a rotation speed of 150rpm and a temperature of 250 ℃ (the outer surface of the casing of the biaxial kneading extruder was measured with a thermometer). The powder was discharged from the kneader outlet after about 120 minutes. The operation of returning the discharged powder to the supply part and kneading was repeated 5 times. The reaction time amounted to about 10 hours.

The obtained intermediate was subjected to heat treatment at 430 ℃ for 8 hours in the same manner as in example 1, to obtain a sulfide solid electrolyte.

The evaluation of the sulfide solid electrolyte was performed in the same manner as in example 1. The results are shown in tables 5 to 8.

Since a twin-screw kneading extruder used for mixing raw materials is an apparatus having a very high degree of mixing, it is considered that the constituent elements are highly dispersed in the intermediate. As a result, it is estimated that the ion conductivity is improved.

Examples 3 to 7 and comparative examples 2 to 4

Sulfide solid electrolytes were produced and evaluated in the same manner as in example 1, except that the raw material compositions were changed as shown in table 4. The results are shown in tables 5 to 8.

In comparative example 2, it is considered that the halogen occupying the site in the crystal structure is detached because the heat treatment temperature is high. Cl entering the 4a site or Br entering the 4d site is easily detached from the site.

The XRD spectrum of the sulfide solid electrolyte fabricated in comparative example 2 is shown in fig. 4.

It is presumed that, from the presence of a crystal of lithium halide or a new crystal having diffraction peaks at 2 θ ═ 14.4 ± 0.5deg and 33.8 ± 0.5deg, a part of Cl or Br occupying sites of the thiogermorite-type crystal structure is desorbed and formed.

In addition, as a result of XRD measurement of the sulfide solid electrolytes obtained in the respective examples, peaks derived from a germanite-type crystal structure were observed.

Examples 8 to 12 and comparative example 5

Sulfide solid electrolytes were produced and evaluated in the same manner as in example 1, except that the blending of raw materials and the production conditions were changed as shown in table 9. The results are shown in tables 10 to 12. In addition, as a result of XRD measurement of the sulfide solid electrolytes obtained in the respective examples, peaks derived from a germanite-type crystal structure were observed.

[ Table 9]

[ Table 10]

X is the sum of Cl and Br.

[ Table 11]

In the table, S_AThe area of diffraction peak a (2 θ ═ 25.2 ± 0.5deg), S_BThe area of the diffraction peak B (2 θ: 29.7 ± 0.5deg) is shown.

[ Table 12]

Example 13

Intermediates were prepared in the same manner as in example 1, except that the raw material composition and the preparation conditions were changed as shown in table 9.

Approximately 1.5g of intermediate powder was charged into a glass tube with a sealing function in a glove box under an argon (Ar) atmosphere, and the tip of the glass tube was sealed with a special jig so that air could not enter. Then, the glass tube was placed in an electric furnace. The special jig was inserted into a joint in an electric furnace, and a gas flow pipe was connected to conduct heat treatment while allowing hydrogen sulfide to flow at 0.5L/min. Specifically, the temperature was raised from room temperature to 500 ℃ at 3 ℃/min and maintained at 500 ℃ for 4 hours. Then, it was slowly cooled and a sulfide solid electrolyte was obtained.

The obtained sulfide solid electrolyte was evaluated in the same manner as in example 1. The results are shown in tables 10 to 12. In addition, the sulfide solid electrolyte obtained in example 13 also had an electron conductivity of less than 10^-6S/cm. Further, with respect to the results of XRD measurement, a peak derived from the digermorite-type crystal structure was observed.

Example 14

In the same manner as in example 2, kneading using a twin-screw kneader was carried out for the production of the intermediate. Kneading with the use of a biaxial kneader was carried out in addition to the feeding of 1.447gLiCl, 1.779gLiBr and 2.980gLi from the feeding part at a constant speed by the feeder₂S and 3.794gP₂S₅An intermediate was obtained in the same manner as in example 2 except for the mixture (2).

The obtained intermediate was subjected to heat treatment at 430 ℃ for 4 hours, thereby obtaining a sulfide solid electrolyte.

The evaluation results of the obtained sulfide solid electrolyte are shown in tables 10 to 12.

In addition, the sulfide solid electrolyte obtained in example 14 had an electron conductivity of less than 10^-6S/cm. In addition, as a result of XRD measurement, a peak derived from a digermorite-type crystal structure was observed.

Example 15

A sulfide solid electrolyte was produced and evaluated in the same manner as in example 14, except that the production conditions were changed to those shown in table 9. The results are shown in tables 10 to 12.

In addition, in practiceThe sulfide solid electrolyte obtained in example 15 also had an electron conductivity of less than 10^-6S/cm. Further, with respect to the results of XRD measurement, a peak derived from the digermorite-type crystal structure was observed.

[ amount of hydrogen sulfide production in sulfide solid electrolyte ]

The hydrogen sulfide generation amounts of the sulfide solid electrolytes produced in example 10 and comparative example 4 were evaluated by using the apparatus shown in fig. 5. The device is formed by sequentially connecting the following components through pipelines: flask 1, humidifying air; a flask 2 provided with a temperature/humidity meter 6 for measuring the temperature and humidity of the humidified air; a Schlang bottle 3 for putting the measurement sample 4; the hydrogen sulfide detector 7 measures the concentration of hydrogen sulfide contained in the air. The order of evaluation is as follows.

In a nitrogen glove box having a dew point of-80 ℃, about 0.1g of a powder sample prepared by sufficiently pulverizing a sample in a mortar was weighed and put into a 100ml schlenk bottle 3 and sealed (reference numeral 4 in fig. 5).

Next, air was flowed into flask 1 at 500 mL/min. The flow rate of the air is measured by the flow meter 5. In flask 1, air was humidified by passing it through water. Then, humidified air was flowed into the flask 2 and the temperature and humidity of the air were measured. The temperature of the air just after the circulation is 25 ℃ and the humidity is 80-90%. After that, humidified air is made to flow through the schlenk bottle 3 so as to be in contact with the measurement sample 4. The humidified air flowing through the schlenk bottle 3 was passed through a hydrogen sulfide meter 7 (Model 3000RS, manufactured by AMI corporation), and the amount of hydrogen sulfide contained in the humidified air was measured. The measurement time was set to 1 hour from immediately after the air was circulated until after the air was circulated. In addition, the amount of hydrogen sulfide was recorded at 15 second intervals.

The amount of hydrogen sulfide produced (mg/g) per 1g of the sample was calculated from the sum of the amounts of hydrogen sulfide observed over 2 hours. As a result, the amount of hydrogen sulfide generated in the sulfide solid electrolyte of example 10 was 26mg/g, and the amount of hydrogen sulfide generated in the sulfide solid electrolyte of comparative example 4 was 64 mg/g.

[ lithium ion Battery ]

Lithium ion batteries were produced using the sulfide solid electrolytes obtained in example 13 and comparative example 1, respectively, and rate performance was evaluated.

(A) Manufacture of lithium ion batteries

50mg of each of the sulfide solid electrolytes obtained in example 13 or comparative example 1 was put into a mold made of stainless steel having a diameter of 10mm, and the thickness of the electrolyte layer was uniformly flattened and pressed, and then a pressure of 185MPa was applied from the upper surface of the electrolyte layer by a hydraulic press to perform press molding.

Mixing Li₄Ti₅O₁₂Coating LiNi_0.8Co_0.15Al_0.05O₂As a positive electrode active material, the sulfide solid electrolyte obtained in example 13 or comparative example 1 was mixed as a solid electrolyte at a weight ratio of 70:30 to obtain a positive electrode material, 15mg of the positive electrode material was put on the upper surface of the electrolyte layer and was uniformly pressed flat to equalize the layer thickness of the positive electrode layer, and then pressure molding was performed by applying 407MPa pressure from the upper surface of the positive electrode layer by a hydraulic press.

Graphite powder as a negative electrode active material and the sulfide solid electrolyte obtained in example 13 or comparative example 1 were mixed in a weight ratio of 60:40 to prepare a negative electrode material. And (3) putting 12mg of the negative electrode material into the surface of the electrolyte layer opposite to the positive electrode layer, leveling and flattening the surface to ensure that the layer thickness of the negative electrode layer is uniform, and applying 555MPa pressure from the upper surface of the negative electrode layer by using a hydraulic press machine to perform compression molding so as to respectively manufacture the lithium ion battery with the three-layer structure of the positive electrode, the solid electrolyte layer and the negative electrode.

(B) Rate capability test

The lithium ion battery produced in the above (a) was allowed to stand in a thermostatic bath set at 25 ℃ for 12 hours, and then evaluated. The voltage was charged to 4.2V at 0.1C (0.189mA) and then discharged to 3.1V at 0.1C (0.189mA) in the 1 st cycle, to 4.2V at 0.5C (0.945mA) and then discharged to 3.1V at 0.5C (0.945mA) in the 2 nd to 10 th cycles. The capacity of the 10 th cycle was measured. Using a battery separately manufactured from the same sample, the capacity of the 10 th cycle at the time of charge and discharge at 0.1C in the 1 st cycle to the 10 th cycle was measured. The ratio of the capacity at the time of charge and discharge at 0.5C to the capacity at the time of charge and discharge at 0.1C was used as the evaluation value of the rate capability. The rate capability of the lithium ion battery using the sulfide solid electrolyte of example 13 was 73%. On the other hand, the rate performance in the lithium ion battery using the sulfide solid electrolyte of comparative example 1 was 50%.

[ evaluation examples ]

The sulfide solid electrolyte obtained in example 1 was subjected to structural analysis using radiant light and neutrons. Specifically, X-ray diffraction using radiant light was performed in accordance with SPring-8 BL19B 2. The measurement was performed on the sample enclosed in the glass capillary. From CeO₂The standard sample was subjected to correction of measurement data and to a specific woeld analysis (Rietveld analysis) based on a structural model of the germanite crystal. Neutron diffraction measurements were performed according to BL20 from J-PARC. In neutron diffraction, the occupancy of each site can be calculated by tewald structure analysis, and S and Cl at 4a and 4d sites can be distinguished. The existence ratio, which is the occupancy of the 4a and 4d sites, is calculated from a structural model satisfying both the radiation X-ray diffraction and neutron diffraction data.

Fig. 6 shows the results of structural analysis using radiated light. It can be confirmed that the difference between the actually measured data and the analyzed data is small and the fitting consistency is high. Regarding the site selectivity of halogen, it was confirmed from the analysis results that chlorine (Cl) easily occupies the 4d site and bromine (Br) easily occupies the 4a site.

Although several embodiments and/or examples of the present invention have been described in detail in the foregoing, those skilled in the art can easily make many modifications to these illustrated embodiments and/or examples without substantially departing from the novel teachings and effects of the present invention. Therefore, many of these modifications are also included in the scope of the present invention.

The entire contents of the japanese application specification, which is the basis of the paris convention priority of the present application, are incorporated herein by reference.