阅读说明：本技术 具有硫银锗矿型晶体结构的硫化物固体电解质的制造方法 (Method for producing sulfide solid electrolyte having a thiogallate crystal structure ) 是由 菅原孝宜 千贺实 近藤德仁 增田直也 金原弘成 宇都野太 田村裕之 于 2019-03-01 设计创作，主要内容包括：一种具有硫银锗矿型晶体结构的硫化物固体电解质的制造方法,其特征在于,包括：以0.5kwh/kg以上的累积功率对含有单体磷的原料进行混合；对利用所述混合得到的前体以350～500℃进行热处理。(A method for producing a sulfide solid electrolyte having a thiogermorite-type crystal structure, comprising: mixing raw materials containing monomer phosphorus with the accumulated power of more than 0.5 kwh/kg; and performing heat treatment on the precursor obtained by the mixing at 350-500 ℃.)

1. A method for producing a sulfide solid electrolyte having a thiogermorite-type crystal structure, comprising:

mixing raw materials containing monomer phosphorus with the accumulated power of more than 0.5 kwh/kg;

and performing heat treatment on the precursor obtained by the mixing at 350-500 ℃.

2. The method for producing a sulfide solid electrolyte having a thiogenitic crystal structure according to claim 1,

the mixing is carried out with the cumulative power of 0.5kwh/kg or more and 20kwh/kg or less.

3. The method for producing a sulfide solid electrolyte having a thiogenitic crystal structure according to claim 1 or 2,

the feedstock also contains free sulfur.

4. The method for producing a sulfide solid electrolyte having a thiogermorite-type crystal structure according to any one of claims 1 to 3, wherein the sulfide solid electrolyte has a structure in which,

the raw material contains at least one halogen element selected from lithium, chlorine and bromine.

5. The method for producing a sulfide solid electrolyte having a thiogermorite-type crystal structure according to any one of claims 1 to 4, wherein the sulfide solid electrolyte has a structure in which,

the precursor contains P₂S₆ ^4-And (3) glass.

6. The method for producing a sulfide solid electrolyte having a thiogenitic crystal structure according to claim 5,

in the solid of the precursor³¹In P-NMR measurement, the maximum peak intensity of a peak observed in the range of 30 to 60ppm is higher than that of the P₂S₆ ^4-Of glassThe peak intensity is small.

7. The method for producing a sulfide solid electrolyte having a thiogenitic crystal structure according to claim 5 or 6,

the precursor also contains P₂S₇ ^4-Glass or PS₄ ^3-And (3) glass.

8. The method for producing a sulfide solid electrolyte having a thiogenitic crystal structure according to any one of claims 5 to 7,

in the solid of the precursor³¹In the P-NMR measurement, among peaks observed in the range of 30 to 120ppm, the P is₂S₆ ^4-Glass or the PS₄ ^3-The peak intensity of the glass is the greatest.

9. The method for producing a sulfide solid electrolyte having a thiogermorite-type crystal structure according to any one of claims 1 to 8, wherein the sulfide solid electrolyte has a structure in which,

the heat treatment is carried out under atmospheric pressure and in an inert gas atmosphere.

10. A method for producing a sulfide solid electrolyte having a thiogermorite-type crystal structure, comprising:

mixing raw materials containing monomer phosphorus to obtain a mixture containing P₂S₆ ^4-A precursor of glass;

and performing heat treatment on the precursor at 350-500 ℃.

11. The method for producing a sulfide solid electrolyte having a thiogermorite-type crystal structure according to any one of claims 1 to 10,

the weight loss rate at 600 ℃ in the thermogravimetric measurement of the precursor is 1.5% or less.

Technical Field

The present invention relates to a method for producing a sulfide solid electrolyte having a thiogenitic crystal structure.

Background

The development of batteries has been receiving attention as power sources for information-related devices, communication devices, automobiles, and the like. Among them, lithium ion batteries have attracted attention because of their high energy density.

Currently commercially available lithium ion batteries use an electrolyte solution containing a flammable organic solvent. On the other hand, a lithium ion battery (all-solid lithium ion battery) in which a battery is all-solid by using a solid electrolyte instead of an electrolytic solution has also been developed. The all-solid lithium ion battery is considered to be excellent in manufacturing cost and productivity because it is possible to simplify a safety device without using an organic solvent having flammability in the battery.

As a solid electrolyte used in a lithium ion battery, a sulfide solid electrolyte is known (for example, see patent documents 1 to 4). A sulfide solid electrolyte having an Argyrodite (Argyrodite) type crystal structure (hereinafter, also referred to as a geigrite type solid electrolyte) as one kind of sulfide solid electrolytes is stable in a wide temperature range, and therefore, it is expected that the use temperature range of a battery is expanded.

As a method for producing a digermorite-type solid electrolyte, for example, patent document 1 describes a method in which a raw material containing lithium sulfide, diphosphorus pentasulfide, lithium chloride or lithium bromide is mixed by a ball mill and then heat-treated.

Patent document 2 describes a method in which a raw material containing lithium sulfide and phosphorus pentasulfide is heated at 550 ℃ for 6 days and then gradually cooled.

Disclosure of Invention

As in patent documents 1 and 2, phosphorus pentasulfide is used as a raw material for a sulfide solid electrolyte. However, phosphorus pentasulfide is unstable to moisture, and therefore, attention is required for handling such as transportation and storage.

Therefore, the present inventors have studied to produce a digermorite-type solid electrolyte using a phosphorus monomer (monomeric phosphorus) instead of diphosphorus pentasulfide. Although there are examples of producing a solid electrolyte using phosphorus as a monomer as in patent documents 3 and 4, a solid electrolyte having high ionic conductivity cannot be obtained. As a result of the studies by the present inventors, it is known that when phosphorus is used as a monomer, the ion conductivity of the digermite-type solid electrolyte is low.

An object of the present invention is to provide a method for producing a digermorite-type solid electrolyte which uses elemental phosphorus as a raw material and has high ionic conductivity.

According to an aspect of the present invention, there is provided a method for producing a sulfide solid electrolyte having a sigermorite-type crystal structure, comprising: mixing raw materials containing monomer phosphorus with the accumulated power of more than 0.5 kwh/kg; and performing heat treatment on the precursor obtained by the mixing at 350-500 ℃.

Further, according to an aspect of the present invention, there is provided a method for producing a sulfide solid electrolyte having a sigermorite-type crystal structure, including: mixing raw materials containing monomer phosphorus to obtain a mixture containing P₂S₆ ^4-A precursor of glass; and performing heat treatment on the precursor at 350-500 ℃.

According to an aspect of the present invention, there is provided a method for producing a digermorite-type solid electrolyte having high ionic conductivity, using elemental phosphorus as a raw material.

Drawings

FIG. 1 shows the solid precursors obtained in example 1, example 2 and comparative example 1³¹P-NMR spectrum.

Fig. 2 is an XRD spectrum of the digermorite-type solid electrolyte obtained in example 1.

Fig. 3 is an XRD spectrum of the digermorite-type solid electrolyte obtained in example 2.

FIG. 4 shows the solid of the raw material used in comparative example 2³¹P-NMR spectrum.

Detailed Description

A method for producing a digermorite-type solid electrolyte according to an aspect of the present invention includes: mixing raw materials containing monomer phosphorus with the accumulated power of more than 0.5 kwh/kg; and performing heat treatment on the precursor obtained by the mixing at 350-500 ℃. The precursor obtained by mixing energy of a predetermined value or more is crystallized by heat treatment, and the ion conductivity of the finally produced digermorite-type solid electrolyte is increased.

The temperature for crystallizing the sigermorite-type solid electrolyte is relatively high, and thus the evaporation and sublimation of the raw material cause composition deviation. Phosphorus pentasulfide has a boiling point of about 515 ℃ and, for example, in Japanese Kokai publication No. 2010-540396, evaporation and sublimation are suppressed by sealing it in a quartz tube and performing heat treatment at 550 ℃.

On the other hand, in the case of using the monomer phosphorus, since the sublimation start temperature of the monomer phosphorus is around 430 ℃, the composition deviation is more likely to be caused. Particularly, in the case where the ionic conductivity of the solid electrolyte exceeds 7mS/cm, a slight compositional deviation has a large influence on the ionic conductivity. It is known that when a monomer phosphorus is used as a starting material in a solid electrolyte having high ionic conductivity, even if heat treatment is performed in a closed system, a composition distribution occurs in the treated material, and as a result, the ionic conductivity is lowered. In this embodiment, the precursor is prepared by mixing raw materials such as phosphorus monomer with a predetermined cumulative power and reacting the raw materials, whereby the composition variation in the subsequent heat treatment at high temperature can be suppressed. The desired precursor can be obtained with a relatively smaller cumulative power than in the case of using phosphorus pentasulfide, and therefore a digermite-type solid electrolyte having high ionic conductivity can be obtained more easily.

In the production method of this embodiment, a raw material containing phosphorus as a monomer is used. The phosphorus monomer may, for example, be yellow phosphorus or red phosphorus.

The compound or monomer other than phosphorus, which constitutes the raw material, can be appropriately selected so as to obtain a desired elemental composition of the digermorite-type solid electrolyte. The composition of the digermorite-type solid electrolyte may be as disclosed in patent document 1 or 2, for example. Examples of the composition formula include Li₆PS₅X、Li_7-xPS_6-xX_x(X ═ Cl, Br, I, X ═ 0.0 to 1.8), and the like. In the above examples, a compound or a monomer containing lithium element, sulfur element, and an element such as an optional halogen element as a constituent element can be used.

The lithium-containing compound may, for example, be lithium sulfide (Li)₂S), lithium oxide (Li)₂O), lithium carbonate (Li)₂CO₃). Among these, lithium compounds are preferable, and lithium sulfide is more preferable.

Although the above-mentioned lithium sulfide can be used without particular limitation, 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.

Examples of the phosphorus-containing compound which may contain a substance other than monomeric phosphorus include phosphorus trisulfide (P)₂S₃) Phosphorus pentasulfide (P)₂S₅) Phosphorus sulfide, sodium phosphate (Na) etc₃PO₄) And the like.

Examples of the sulfur-containing compound or monomer include Li₂S, free sulfur, H₂S、P₂S₅、P₄S₃、PSBr₃、PSCl₃、SOCl₂、SF₂、SF₄、SF₆、S₂F₁₀、SCl₂、S₂Cl₂、S₂Br₂. The sulfur-containing compound or monomer may be used in combination of 2 or more.

In this embodiment, since the phosphorus source is entirely or partially composed of phosphorus, it is preferable to use elemental sulfur as the sulfur source in view of easy composition adjustment.

Examples of the halogen-containing compound include compounds represented by the general formula (M)_l-X_m) The compound shown in the specification.

In the formula, 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 substance obtained by bonding an oxygen element or a sulfur element to these elements, preferably Li or P, more preferably Li.

X is a halogen element selected from F, Cl, Br and I.

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. 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 above formula include: sodium halides such as NaI, NaF, NaCl, and NaBr; LiF, and,Lithium halides such as LiCl, LiBr, and LiI; BCl₃、BBr₃、BI₃Boron halides, etc.; AlF₃、AlBr₃、AlI₃、AlCl₃And the like aluminum halides; SiF₄、SiCl₄、SiCl₃、Si₂Cl₆、SiBr₄、SiBrCl₃、SiBr₂Cl₂、SiI₄And the like silicon halides; PF (particle Filter)₃、PF₅、PCl₃、PCl₅、POCl₃、PSCl₃、PBr₃、PSBr₃、PBr₅、POBr₃、PI₃、PSI₃、P₂Cl₄、P₂I₄And the like phosphorus halides; SF₂、SF₄、SF₆、S₂F₁₀、SCl₂、S₂Cl₂、S₂Br₂And the like sulfur halides; GeF₄、GeCl₄、GeBr₄、GeI₄、GeF₂、GeCl₂、GeBr₂、GeI₂And the like germanium halides; AsF₃、AsCl₃、AsBr₃、AsI₃、AsF₅And the like arsenic halides; SeF₄、SeF₆、SeCl₂、SeCl₄、Se₂Br₂、SeBr₄And the like selenium halides; SnF₄、SnCl₄、SnBr₄、SnI₄、SnF₂、SnCl₂、SnBr₂、SnI₂Tin halides, etc.; SbF₃、SbCl₃、SbBr₃、SbI₃、SbF₅、SbCl₅Antimony halides, etc.; TeF₄、Te₂F₁₀、TeF₆、TeCl₂、TeCl₄、TeBr₂、TeBr₄、TeI₄And (3) tellurium halides; PbF₄、PbCl₄、PbF₂、PbCl₂、PbBr₂、PbI₂Lead halides, etc.; BiF₃、BiCl₃、BiBr₃、BiI₃And bismuth halides, etc.

Among these, lithium halide or phosphorus halide is preferable, and LiCl, LiBr, LiI or PBr is more preferable₃Further, it is preferableLiCl, LiBr or LiI, and LiCl or LiBr is particularly preferable.

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.

In addition, chlorine (Cl) may be used₂) And bromine (Br)₂) Such a halogen monomer.

Preferably, when the halogen element is C1 or Br, the raw material satisfies the composition represented by the following formula (1), for example.

Li_aPS_bCl_c1Br_c2(1)

(in the formula (1), a, b, C1 and C2 satisfy the following formulae (A) to (C))

5.0≤a≤6.5…(A)

6.1≤a+c1+c2≤7.5…(B)

0.5≤a-b≤1.5…(C)，

(wherein b >0 and c1+ c2>1.0 are satisfied.)

The above formula (A) is preferably 5.1. ltoreq. a + c. ltoreq.6.4, particularly preferably 5.2. ltoreq. a.ltoreq.6.3.

The above formula (B) is preferably 6.2. ltoreq. a + c1+ c 2. ltoreq.7.4, particularly preferably 6.3. ltoreq. a + c1+ c 2. ltoreq.7.3.

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

In the present application, the molar ratio and composition of each element in the sigermorite-type solid electrolyte are derived from the mixing ratio of the raw materials weighed out. In the present application, the molar ratio of the raw material is substantially equal to the molar ratio of the product, the digermorite-type solid electrolyte. In the production method of the present embodiment, since the composition variation in the production process can be suppressed, the variation in the molar ratio of each element of the raw material and the molar ratio of the diglygefite-type solid electrolyte is small.

In addition, the molar ratio and composition of each element in the digermorite-type solid electrolyte can be measured by ICP emission spectrometry.

The above-mentioned compound and monomer can be used without particular limitation as long as they are industrially produced and sold. The compounds and monomers are preferably high purity compounds and monomers.

In the production method of this embodiment, the raw materials containing phosphorus as a monomer are mixed at a cumulative power of 0.5kwh/kg or more to obtain a precursor. In one embodiment, P is preferably formed by thoroughly mixing raw materials containing a plurality of compounds or monomers₂S₆ ^4-And (3) glass. As described in patent document 4, P₂S₆ ^4-Crystals and P₂S₆ ^4-The ionic conductivity is significantly lower than that of glass. Therefore, it is considered that it is not preferable to contain P in general₂S₆ ^4-Glass serves as a precursor for the crystalline solid electrolyte. However, in this case, the raw material is reacted to P₂S₆ ^4-The glass is formed to such an extent that the solid electrolyte of the digermorite type having high ionic conductivity can be obtained by the subsequent heat treatment.

The mixing of the raw materials is performed in such a manner that a mechanical stress is applied to the raw materials to perform a vitrification reaction. In the case where the mixing of the raw materials is insufficient, the ion conductivity of the finally obtained digermorite-type solid electrolyte will not be sufficiently improved. The term "mechanically stressed" as used herein means that a shearing force, an impact force or the like is mechanically applied. Examples of the means for applying mechanical stress include a pulverizer such as a ball mill, a bead mill, a vibration mill, or a rotary mill, or a kneader. When mechanical stress is applied, heating may be performed to promote the reaction.

E.g. by solid bodies³¹Presence or absence of P-derived observation in P-NMR measurement₂S₆ ^4-Peak of glass to determine whether precursor contains P₂S₆ ^4-And (3) glass. Derived from P₂S₆ ^4-The peaks of the glass may be at the top of the solid³¹P-NMR spectrum was observed around 102 to 108 ppm.

In addition, cannot be based on solids³¹In the case where P-NMR spectrum is used to judge whether or not a peak is present at a specified position, the nonlinear least square method is used to determine the presence of a peak in the solid³¹The P-NMR spectrum was subjected to peak separation and it was determined whether or not a peak was present at the designated position.

For identification of the isolated peaks, reference can be made, for example, to h.eckert, z.zhang and h.kennedy "materials chemistry (chem.mater.) -2, 3, page 273 (1990).

In the production method of the present embodiment, the solid of the precursor is preferably used³¹The maximum peak intensity ratio P of peaks observed in the range of 30 to 60ppm in P-NMR measurement₂S₆ ^4-The peak intensity of the glass is small. Thus, it was confirmed whether or not the raw materials were sufficiently mixed and reacted to form P in the precursor₂S₆ ^4-And (3) glass. As a result, the ion conductivity of the finally obtained digermorite-type solid electrolyte is further improved. It is considered that the peak observed in the range of 30 to 60ppm is derived from the unreacted raw material.

In addition, the precursor contains P₂S₆ ^4-May contain P in addition to glass₂S₇ ^4-Glass or PS₄ ^3-And (3) glass. For example, by means of a solid³¹Whether or not the precursor contained P was determined by observing peaks derived from each glass in P-NMR measurement₂S₇ ^4-Glass or PS₄ ^3-And (3) glass. Derived from P₂S₇ ^4-The peaks of the glass may be at the top of the solid³¹P-NMR spectrum was observed around 91.4 ppm. Derived from PS₄ ^3-The glass has a peak top of 82.5 to 84.5 ppm. In the case of heating when mechanical stress is applied, the glass formed may also crystallize thermally. In this case, for example, PS may be contained₄ ^3-And (4) crystals. Derived from PS₄ ^3-The peak top of the peak of the crystal can be observed in the vicinity of 86-87 ppm.

Furthermore, it is preferable that the precursor is a solid³¹P-NMR measurement shows that among peaks observed in the range of 30 to 120ppm, P is present₂S₆ ^4-Glass or PS₄ ^3-The peak intensity of the glass is the greatest. Thus, P can be confirmed₂S₆ ^4-Glass or PS₄ ^3-The glass accounts for a higher proportion of the precursor. As a result, the ion conductivity of the finally obtained digermorite-type solid electrolyte is further improved. Warming up under mechanical stressIn this case, it is preferable that the precursor is a solid³¹P-NMR measurement shows that among peaks observed in the range of 30 to 120ppm, P is present₂S₆ ^4-Glass, PS₄ ^3-Glass or PS₄ ^3-The peak intensity of the crystals is maximal.

By "peak intensity" in this application is meant passing through a solid³¹P-NMR measures the distance (height) from the baseline to the peak of the resulting NMR spectrum.

Solids can also be replaced by weight loss in thermogravimetric measurements³¹P-NMR measurements were made to confirm whether the precursor was formed. A high weight loss rate means insufficient vitrification of the raw material, and as a result, the ion conductivity of the obtained digermite-type solid electrolyte tends to decrease. In this embodiment, the weight loss of the precursor at 600 ℃ is preferably 1.5% or less, more preferably 1.0% or less.

The mixing conditions of the raw materials need to be set appropriately according to the apparatus used for mixing. For example, when a planetary ball mill is used, the energy (cumulative power: kWh/kg) to be applied to the raw material may be controlled by adjusting the grinding medium, the rotational speed, the treatment time, the treatment temperature, and the like. The cumulative power is 0.5kWh/kg or more, preferably 1.0kWh/kg or more. The cumulative power is, for example, 20kWh/kg or less, preferably 10kWh/kg or less.

When the power consumption is known, the accumulated power can be obtained by dividing the amount of power obtained by subtracting the power when the sample is not put into the ball mill and rotated from the power when the ball mill is operated by the mass of the sample. When the power consumption is unknown, the kinetic energy obtained from the revolution radius, the rotation speed, the revolution ratio, the mass and number of balls, and the like of the ball mill is calculated as the kinetic energy applied to the sample.

In addition, the energy (power: kW/kg) to be imparted to the raw material needs to be appropriately set in consideration of the treatment apparatus and the treatment time. The energy is preferably 0.1kW/kg or more, and more preferably 0.3kW/kg or more. Further, it is preferably 7kW/kg or less, and more preferably 10kW/kg or less.

The shorter the heat treatment time is, the more preferable it is, but it is usually 10 minutes to 10 hours.

The precursor obtained by mixing the raw materials is subjected to a heat treatment to crystallize it, thereby producing a digermite-type solid electrolyte. The heat treatment temperature is 350-500 ℃, more preferably 360-500 ℃, and still more preferably 380-450 ℃.

The treatment time is adjusted depending on the temperature, and is usually 0.5 to 12 hours, preferably 1 to 8 hours.

Although the atmosphere of the heat treatment is not particularly limited, it is preferably performed under an inert gas atmosphere such as nitrogen or argon at atmospheric pressure.

For example, it can be confirmed that the solid electrolyte obtained by the present embodiment is a digermorite-type solid electrolyte by having diffraction peaks at 25.2 ± 0.5deg and 29.7 ± 0.5deg in powder X-ray diffraction measurement using CuK α rays. These diffraction peaks are peaks derived from a digermorite-type crystal structure.

Further, diffraction peaks of the digermorite-type crystal structure appear at, for example, 15.3 ± 0.5deg, 17.7 ± 0.5deg, 31.1.± 0.5deg, 44.9 ± 0.5deg, and 47.7 ± 0.5 deg. The solid electrolyte obtained by the present scheme may also have these peaks.

The solid electrolyte obtained by the present embodiment may contain elements such As Si, Ge, Sn, Pb, B, Al, Ga, As, Sb, and Bi in addition to the lithium element, the phosphorus element, the sulfur element, and any halogen element. Furthermore, chalcogens (oxygen (O), selenium (Se), tellurium (Te), etc.) may also be contained. In this embodiment, it is preferable that the halogen element contains at least one of lithium element, phosphorus element, sulfur element, chlorine and bromine.

According to this aspect, even if phosphorus pentasulfide is not used as a raw material, a digermite-type solid electrolyte having a high ionic conductivity can be obtained. For example, a digermite-type solid electrolyte having an ionic conductivity of 9mS/cm or more or 11mS/cm or more can be obtained. The digermorite-type solid electrolyte obtained by the present invention is preferably used as a constituent material of a lithium battery such as a solid electrolyte layer.

Another aspect of the present invention includes: mixing raw materials containing monomer phosphorus to obtain a mixture containing P₂S₆ ^4-A precursor of glass; heat treating the obtained precursor at 350-500 deg.C. Removing to obtain a solution containing P₂S₆ ^4-The same manufacturing method as described above is applied to the other glass precursors. Comprising P₂S₆ ^4-The glass precursor can be obtained by, for example, sufficiently mixing raw materials in the same manner as in the production method of the above embodiment.