JP2021150289A - Method for producing sulfide solid electrolyte material - Google Patents

Abstract

To provide a method for producing LGPS-based, Li-P-S-based and Li-P-S-O-based sulfide solid electrolytes that have excellent productivity.SOLUTION: Provided is a method for producing LGPS-based, Li-P-S-based and Li-P-S-O-based sulfide solid electrolyte materials, which includes a step of preparing a raw material powder, a step of mixing the raw material powder to yield a precursor powder, and a step of heating the precursor powder while circulating inert gas through the precursor powder. Here, setting the flow rate of the inert gas as F (mL/min), the weight of the precursor powder as M (g), and the internal volume of the heating vessel for heating the precursor powder as V (mL), F/M is 5 or more and 80 or less, V/F is 0.1 or more and 3.0 or less, the dew point of the inert gas is -30°C or lower, and the heating temperature is 250°C or more and 750°C or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a sulfide solid electrolyte, particularly a highly productive production method.

With the rapid spread of information-related devices such as personal computers, video cameras and mobile phones, and communication devices in recent years, the development of batteries used as their power sources has been emphasized. In addition, the automobile industry and the like are also developing high-output and high-capacity batteries for electric vehicles or hybrid vehicles. Currently, among various batteries, lithium batteries are attracting attention from the viewpoint of high energy density.

Lithium batteries currently on the market use an electrolytic solution containing a flammable organic solvent, so it is possible to install a safety device that suppresses the temperature rise during a short circuit and improve the structure and materials to prevent a short circuit. You will need it. On the other hand, a lithium battery in which the electrolyte is changed to a solid electrolyte layer and the battery is completely solidified does not use a flammable organic solvent in the battery, so that the safety device can be simplified, and the manufacturing cost and productivity can be improved. Is considered to be excellent.

A sulfide solid electrolyte material is known as a solid electrolyte material used in an all-solid-state lithium battery. For example, in Non-Patent Document _{1, Li (4-x)} Ge (1-x) Li ion conductor having a composition of P x _{S 4} (sulfide solid electrolyte material) is disclosed. Further, Patent Document 1 discloses a LiGePS-based sulfide solid electrolyte material having a high proportion of crystal phases having a specific peak in X-ray diffraction measurement. Further, Non-Patent Document 2 discloses a LiGePS-based sulfide solid electrolyte material having an excellent ionic conductivity of 12 mS / cm.
Further, Patent Document 2 discloses a solid electrolyte having high conductivity, including a Li-P-S-based and a Li-P-SO-based sulfide-based solid electrolyte.

International Publication No. 2011/118801 Japanese Patent No. 5787291

Ryoji Kanno et al., “Lithium Ionic Conductor Thio-LISICON The Li2S-GeS2-P2S5 System”, Journal of The Electrochemical Society, 148 (7) A742-A746 (2001) Noriaki Kamaya et al., “A lithium superionic conductor”, Nature Materials, Advanced online publication, 31 July 2011, DOI: 10.1038 / NMAT3066

However, LGPS-based, Li-PS-based, and Li-P-SO-based solid electrolytes are mainly manufactured on a small scale at the laboratory level for the purpose of developing new materials, and are put into practical use. The large-scale manufacturing method for the above has not been sufficiently studied.
As an example of a method for producing LGPS-based, Li-PS-based, and Li-P-SO-based solid electrolytes, in our laboratory, raw material compositions are mixed and pulverized (amorphized). , Molded (pelletized), and the pellets were vacuum-sealed in a quartz tube and heated and fired. In this case, since the quartz tube was vacuum-sealed on a laboratory scale, the amount that could be produced was only about 1 g.

The reason why the raw material composition is heated and fired in a closed system such as vacuum encapsulation is that sulfide solid electrolytes such as LGPS-based solid electrolytes, Li-PS-based and Li-PS-O-based solid electrolytes are used. itself is sulfide, also sulfide as its raw material is used the _{(LiS, P 2 S 5,} GeS 2 , etc.), such a high volatile sulfide, is due to easily react with moisture .. That is, when the sulfide is heated and calcined in an open system, there is a possibility that the composition of the raw material composition charged and the reaction product obtained may be different from each other. Therefore, a closed system is adopted.

However, in order to seal the quartz tube in a vacuum, after arranging the sample in the quartz tube, the quartz tube is burnt off while the inside of the quartz tube is evacuated, and the sample is enclosed in the vacuum tube. Therefore, in order to increase the size of the quartz tube and scale it up, it is necessary to burn off the huge quartz tube, and the reaction vessel (quartz tube) is disposable, which is extremely dangerous and costly. ..
Furthermore, the size of the reaction vessel (quartz tube, etc.) is relatively small, for example, a test tube size, in consideration of workability for sealing and disposable cost. The production amount per batch has also been limited to about 1 g.
When the sample to be reacted by encapsulating it in a quartz tube is a solid, the reaction is a solid-phase reaction, and the reaction rate is slow when the sample is in a powder state. Therefore, high pressure is applied during molding to pelletize the sample. Is being done. It is also desired to improve workability for this molding (pelletization).

The present invention has been made in view of the above problems, and is a method for producing an LGPS-based, Li-PS-based, and Li-P-SO-based sulfide solid electrolyte having excellent productivity. The purpose is to provide.

In order to solve the above problems, the inventor of the present application has conducted diligent studies and found that the invention is inert in the production of LGPS-based, Li-PS-based and Li-P-SO-based sulfide solid electrolyte materials. We have found that productivity can be improved by heating and firing the mixed raw material powder (precursor powder) while circulating the gas under specific conditions, and have completed the present invention.
The present invention provides the following means.

[1]
A method for producing an LGPS-based, Li-PS-based, and Li-P-SO-based sulfide solid electrolyte material.
Step of preparing raw material powder Step of mixing the raw material powder to obtain precursor powder,
The step of heating the precursor powder while flowing an inert gas through the precursor powder is included.
Here, it is assumed that the flow rate of the inert gas is F (mL / min), the weight of the precursor powder is M (g), and the internal volume of the heating container for heating the precursor powder is V (mL). , F / M is 5 or more and 80 or less, V / F is 0.1 or more and 3.0 or less,
The dew point of the inert gas is −30 ° C. or lower,
The heating temperature is 250 ° C. or higher and 750 ° C. or lower.
A method for producing a sulfide solid electrolyte material.
[2]
The inert gas is at least one selected from the group consisting of argon, dry air, nitrogen and helium.
The method for producing a sulfide solid electrolyte material according to [1].
[3]
The inert gas contains 1000 ppm or less of water.
The method for producing a sulfide solid electrolyte material according to [1] or [2].
[4]
The sulfide solid electrolyte material produced is characterized by an amount of more than 2 g per batch.
The method for producing a sulfide solid electrolyte material according to any one of [1] to [3].
Characterized by

In the method for producing an LGPS-based, Li-PS-based, and Li-P-SO-based sulfide solid electrolyte material according to the present invention, raw material powders are mixed to form a precursor powder, which is inert to the precursor powder. One of the features is that the precursor powder is heated while the gas is circulated. That is, in the present invention, it is not necessary to heat the precursor powder in a sealing system.
In order to make a quartz tube or the like a sealing system, it is necessary to burn off the quartz tube while evacuating, and since the quartz tube is disposable, there is a problem that it is very dangerous and costly. The manufacturing method according to the present invention can avoid the dangers and costs associated with forming a sealed system, and the productivity is improved.
Furthermore, in the sealing system, a relatively small size reaction vessel (quartz tube, etc.) is used in consideration of workability for sealing and disposable cost, and the production amount per batch is increased accordingly. It has been restricted. According to the production method according to the present invention, there is no limitation on the container size in principle, and the production amount per batch can be increased.
Further, according to the present invention, since the inert gas is circulated through the precursor powder, it is not necessary to mold (pelletize) the powder mixture. That is, the production method according to the present invention does not require the work of molding the powder at high pressure, and the workability can be significantly improved. In addition, since the process can be simplified, the possibility of unintended contamination is reduced, which is effective in improving product quality (purity, etc.).
Furthermore, the sulfide solid electrolyte material produced according to the present invention may have excellent water resistance.

FIG. 1 shows a schematic configuration example of an apparatus for heating while flowing an inert gas. FIG. 2 shows an XRD chart of a modified process with _{standard composition Li (4-x)} Ge _(1-x) PxS _{4 (x = 0.65).} FIG. 3 shows an XRD chart when the composition is changed under the same process conditions. FIG. 4 shows an XRD chart when the production amount is changed under the same process conditions. FIG. 5 shows an XRD chart of _{Li 9.81} Sn _0.81 P _2.19 S _12. FIG. 6 shows an XRD chart of _{Li 3} PS _4.

Hereinafter, a method for producing a sulfide solid electrolyte material, which is one aspect of the present invention, will be described in detail.

The sulfide-based solid electrolyte in the present invention is an LGPS-based, Li-PS-based, and Li-P-SO-based sulfide solid electrolyte material.

The LGPS-based sulfide-based solid electrolyte in the present invention contains M ₁ element, M ₂ element, and S element, and the above M ₁ is at least selected from the group consisting of Li, Na, K, Mg, Ca, and Zn. M ₂ is at least one selected from the group consisting of P, Sb, Si, Ge, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb, and is optionally additional. Contains at least one selected from the group consisting of Cl and O, has a peak at the position of 2θ = 29.58 ° ± 0.50 ° in X-ray diffraction measurement using CuKα ray, and has a peak at the position of 2θ = 29.58 ° ± 0.50 °. the diffraction intensity of the peak of .58 ° ± 0.50 ° and _{I a,} the diffraction intensity of the peak of 2θ = 27.33 ° ± 0.50 ° when the _{I B,} the value of I B / _{I a} It is less than 0.50.

Since the LGPS-based sulfide-based solid electrolyte has a high proportion of crystal phases having a peak near 2θ = 29.58 °, it can be used as a sulfide solid electrolyte material having good ionic conductivity. Therefore, a high output battery can be obtained by using the sulfide solid electrolyte material of the first embodiment.

In the present specification, the crystal phase having a peak near 2θ = 29.58 ° is referred to as “crystal phase A”, and the crystal phase having a peak near 2θ = 27.33 ° is referred to as “crystal phase B”. Sometimes referred to. Crystal phases A and B are both crystal phases exhibiting ionic conductivity, but their ionic conductivity is different. It is considered that the crystal phase A has significantly higher ionic conductivity than the crystal phase B. When the value of I B _/ I _A is less than 0.50, since it is possible to actively deposit the high crystal phase A of ion conductivity, it is possible to obtain a high ion conductivity sulfide solid electrolyte material ..

From the viewpoint of ionic conductivity, the LGPS-based sulfide-based solid electrolyte preferably has a high proportion of the crystal phase A having high ionic conductivity. _Therefore, it is preferable I value of B / _{I A} is smaller, it is preferable that in particular 0.45 or less, more preferably 0.25 or less, further to be 0.15 or less It is preferably 0.07 or less, and particularly preferably 0.07 or less. _Further, it is preferable that the value of I B / _{I A} is 0. In other words, the LGPS-based sulfide solid electrolyte material preferably does not have a peak near 2θ = 27.33 °, which is the peak of the crystal phase B.

The LGPS-based sulfide solid electrolyte material has a peak near 2θ = 29.58 °. As described above, this peak is one of the peaks of the crystal phase A having high ionic conductivity. Here, at 2θ = 29.58 °, the crystal lattice may change slightly depending on the material composition and the like, and the peak position may be slightly different from 2θ = 29.58 °. Therefore, the peak of the crystal phase A is defined as a peak at the position of 29.58 ° ± 0.50 °. The crystal phase A is usually 2θ = 17.38 °, 20.18 °, 20.44 °, 23.56 °, 23.96 °, 24.93 °, 26.96 °, 29.07 °, 29. It is considered to have peaks of .58 °, 31.71 °, 32.66 ° and 33.39 °. Note that these peak positions may also move back and forth within a range of ± 0.50 °.

On the other hand, the peak near 2θ = 27.33 ° is one of the peaks of the crystal phase B having low ionic conductivity, as described above. Here, when 2θ = 27.33 °, the crystal lattice may change slightly depending on the material composition and the like, and the peak position may be slightly different from 2θ = 27.33 °. Therefore, the peak of the crystal phase B is defined as a peak at a position of 27.33 ° ± 0.50 °. Crystal phase B usually has peaks of 2θ = 17.46 °, 18.12 °, 19.99 °, 22.73 °, 25.72 °, 27.33 °, 29.16 ° and 29.78 °. Is considered to have. Note that these peak positions may also move back and forth within a range of ± 0.50 °.

Further, the LGPS-based sulfide solid electrolyte material contains M ₁ element, M ₂ element and S element. The above M ₁ is preferably a monovalent or divalent element. Examples of the M ₁ include at least one selected from the group consisting of Li, Na, K, Mg, Ca, and Zn. All of these elements function as conduction ions. Above all, it is preferable that _{M 1 is Li.} This is because it can be used as a sulfide solid electrolyte material useful for lithium batteries. Further, M ₁ may be a monovalent element (for example, Li, Na, K), and a part thereof may be substituted with a divalent or higher element (for example, Mg, Ca, Zn). This facilitates the movement of monovalent elements and improves ionic conductivity.

On the other hand, the above M ₂ is preferably a trivalent, tetravalent or pentavalent element. Examples of the M ₂ include one selected from the group consisting of P, Sb, Si, Ge, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. Above all, in the first embodiment, the M ₂ is preferably at least one selected from the group consisting of P, Ge, Al, Zr, Sn, and B, and is at least one of P and Ge. More preferred. Further, the above M ₂ may be two or more kinds of elements.

Further, the LGPS-based sulfide solid electrolyte material contains at least one optionally additionally selected from the group consisting of Cl and O. That is, the LGPS-based sulfide solid electrolyte material may contain halides and oxides. Halides and / or oxides may be in the form of excellent chemical stability, which improves the chemical stability of the sulfide-based solid electrolyte in the present invention.

Therefore, as typical compositions of LGPS-based sulfide solid electrolytes, Li-Ge-PS composition (composition including Li, Ge, P, S) and Li-Sn-PS composition (Li, Sn, P) , S composition), Li-Si-Sn-PS composition (composition including Li, Si, Sn, P, S), Li-Si-PS-Cl-O composition (Li, Si, P) , S, Cl, O composition), Li-Si-P-S-Cl composition (composition including Li, Si, P, S, Cl), Li-Si-Sn-P-SO composition (Li , Si, Sn, P, S, O) and the like. Note that if these compositions are a composition that can obtain a value of a predetermined I _{B /} I _A, since the composition has a LGPS type crystal structure, the composition ratio of each element in the composition particularly limited It is not something that is done.

The composition of the sulfide solid electrolyte material LGPS system, but is not particularly limited as long as the composition can be obtained the value of a given _{I B / I A, Li (} 4-x) Ge (1-x ₎ P _x S ₄ (x satisfies 0 <x <1). This is because it can be used as a sulfide solid electrolyte material having high Li ion conductivity. _Here, the composition of _{Li (4-x) Ge (} 1-x) P x S 4 corresponds to the composition of the solid solution of _Li 3 PS ₄ and _Li 4 GeS _4. That is, this composition corresponds to the composition on the tie line of _{Li 3} PS ₄ and Li ₄ GeS _4. It should be _{noted that Li 3} PS ₄ and Li ₄ GeS ₄ both correspond to the ortho composition and have an advantage of high chemical stability. A sulfide solid electrolyte material having such a composition of Li _(4-x) Ge _(1-x) P _x S ₄ has been conventionally known as thiolysicon, and an LGPS-based sulfide solid electrolyte material has a composition. May be the same as the conventional thiolysicon.

_Also, x in _{Li (4-x) Ge (} 1-x) P x S 4 is not particularly limited as long as the value can be obtained the value of a given _I B / _{I A,} e.g. , 0.40 ≦ x, preferably 0.45 ≦ x, more preferably 0.50 ≦ x, more preferably 0.55 ≦ x, 0.60 It is more preferable to satisfy ≦ x. On the other hand, the above x preferably satisfies x ≦ 0.8, more preferably x ≦ 0.75, further preferably x ≦ 0.70, and x ≦ 0.75. It is more preferable, and it is further preferable to satisfy x ≦ 0.65. With such range of x, is because it smaller values of I B _/ I _A. This makes it possible to obtain a sulfide solid electrolyte material having further good Li ion conductivity. Further, the LGPS-based sulfide solid electrolyte material is preferably made by using Li ₂ S, P ₂ S ₅ and GeS ₂ .

Next, Li-P-S-O-based sulfide-based solid electrolyte in the present invention _is shown by _{Li 3 + 5x P 1-x} S 4-z O z, a 0.01 ≦ x ≦ 0.105, and It is preferable that 0.01 ≦ z ≦ 1.55. If the value of x is smaller than 0.01, _{the proportion of Li 7} PS ₆ and γ-Li ₃ PS ₄ contained in the sulfide-based solid electrolyte may increase, and the conductivity of the solid electrolyte may decrease. the value of x is, the larger than 1.55, the ratio of Li 2 _S contained in the sulfide-based solid electrolyte becomes high so that a conductivity of the solid electrolyte is reduced. Further, when the value of z becomes smaller than 0.01, _{the ratio of Li 7} PS ₆ , β-Li ₃ PS ₄ and γ-Li ₃ PS ₄ contained in the sulfide-based solid electrolyte becomes high, and the ratio of the solid electrolyte becomes high. The conductivity may decrease, and if the z value is larger than 1.55, _{the proportion of Li 7} PS ₆ contained in the sulfide-based solid electrolyte may increase, and the conductivity of the solid electrolyte may decrease. be. When the values of x and z are within the range of 0.01 ≦ x ≦ 0.105 and 0.01 ≦ z ≦ 1.55, the conductivity of the solid electrolyte becomes high.

Li-P-S-O-based sulfide-based solid _electrolyte, the case shown in _{Li 3 + 5x P 1-x} S 4-z O z, a 0.02 ≦ x ≦ 0.105, and 0.20 ≦ z It is more preferable that ≦ 1.20. When the values of x and z are 0.02 ≦ x ≦ 0.105 and 0.20 ≦ z ≦ 1.20, _{the ratio of Li 2} S and γ-Li ₃ PS ₄ becomes low, and the ratio of the solid electrolyte becomes low. The conductivity becomes high.

Li-P-S-O-based solid electrolyte, the case shown in _{Li 3 + 5x P 1-x} S 4-z O z, a 0.03 ≦ x ≦ 0.09, and 0.25 ≦ z ≦ It is more preferably 1.00. When the values of x and z are 0.03 ≦ x ≦ 0.09 and 0.25 ≦ z ≦ 1.00, _{the ratio of Li 2} S and γ-Li ₃ PS ₄ becomes low, and the ratio of the solid electrolyte becomes low. The conductivity becomes high.

Since the conductivity is as high as about 1 × 10 ^-4 S / cm or more, the Li-P—SO-based sulfide-based solid electrolyte is Li _{3 + 5x} P1 _-x S _{4-z Oz.} When x = 0.07, 0.20 ≦ z ≦ 1.00 is preferable, and when z = 50, 0.03 ≦ x ≦ 0.07 is preferable.

Since _{the ratio of Li 2} S and γ-Li ₃ PS ₄ is low and the conductivity of the sulfide-based solid electrolyte can be increased, the Li-P-SO-based sulfide solid electrolyte is Li _{3 + 5 x} P. shown in _{1-x S 4-z O} z, if an x = 0.07, further preferably 0.40 ≦ z ≦ 0.60.

The Li-PSO-based sulfide-based solid electrolyte in the present invention has at least 12.9 °, 14.4 °, in powder X-ray diffraction measurement with Cu—Kα rays having an X-ray wavelength of 1.5418 angstroms. Characteristic peaks near the diffraction angles (2θ) of 15.2 °, 18.0 °, 20.5 to 22.0 °, 24.2 °, 25.0 °, 28.0 °, and 30.6 °. Have. Therefore, the Li-PS-based and Li-P-SO-based sulfide-based solid electrolytes of the present invention have the above-mentioned characteristics in the powder X-ray diffraction measurement with Cu-Kα rays having an X-ray wavelength of 1.5418 angstroms. Has a target peak. From the diffraction angle (2θ) of the characteristic peak, it is presumed that it has a crystal structure similar _{to that of Li 3.33} Ge _0.33 P _0.66 S _4.

Further, the Li-PS-based sulfide-based solid electrolyte of the present invention _{does not contain P 2} O ₅ , is represented by Li _{3 + 5 x} P _1-x S ₄ , and is 0.06 ≦ x ≦ 0.08. Yes, in powder X-ray diffraction measurements with Cu-Kα rays with an X-ray wavelength of 1.5418 angstroms, at least 13.3 °, 14.75 °, 15.3 °, 18.0 °, 21.0-21. It is preferable to have a characteristic peak near the diffraction angle (2θ) of 7 °, 24.2 °, 25.4 °, 28.4 ° and 30.6 °. That is, the sulfide-based solid electrolyte of the present invention is represented by Li _{3 + 5x} P _1-x S ₄ , and is preferably 0.06 ≦ x ≦ 0.08. When the value of x is 0.06 ≦ x ≦ 0.08, the conductivity of the solid electrolyte becomes high.

The raw material powder of the LGPS-based, Li-PS-based, and Li-P-SO-based sulfide-based solid electrolytes in the present invention is particularly limited as long as the above-mentioned sulfide-based solid electrolyte can be obtained. It is possible to prepare a single element or a compound such as Li element, Ge element, Sn element, Si element, P element, S element, Cl element, O element, etc. Further, from the viewpoint of availability and the like, Li ₂ S, LiCl, LiOH, P ₂ S ₅ , P ₂ O ₃ , SCl ₂ , GeS _2, SnS ₂ , SiS _{2 and the} like may be prepared.

The raw material powders are mixed to obtain a precursor powder. Mixing may be done manually using an agate mortar and agate pestle. The mixing time may be appropriately adjusted in the range of several minutes to several hours depending on the amount of mixing and the degree of mixing.

In addition to or instead of manual mixing, mechanical milling may be used for mixing. Mechanical milling is a method of mixing raw material powders while pulverizing them while applying mechanical energy. Mechanical milling is preferable because a large amount of raw material powder can be mechanically mixed. Compared with manual mixing, mechanical milling is preferable because it is easier to make the raw material powder finer and it may increase the crystal purity of the product. Examples of such mechanical milling include a vibration mill, a ball mill, a turbo mill, a mechanofusion, a disc mill, and the like, and a vibration mill is particularly preferable. The conditions of the vibration mill are not particularly limited as long as the raw material powder can be mixed. The vibration amplitude of the vibration mill is preferably in the range of, for example, 5 mm to 15 mm, particularly preferably in the range of 6 mm to 10 mm. The vibration frequency of the vibration mill is preferably in the range of, for example, 500 rpm to 2000 rpm, particularly preferably in the range of 1000 rpm to 1800 rpm. The filling rate of the sample of the vibration mill is preferably in the range of, for example, 1% by volume to 80% by volume, particularly preferably in the range of 5% by volume to 60% by volume, and particularly preferably in the range of 10% by volume to 50% by volume. Further, it is preferable to use a vibrator (for example, an alumina vibrator) for the vibration mill. The mixing time may be appropriately adjusted in the range of several minutes to several hours depending on the amount of mixing and the degree of mixing.

The step of preparing the raw material powder and the step of mixing the raw material powder to obtain the precursor powder are inert to the raw material powder and the obtained precursor powder in order to prevent deterioration of the raw material powder and the obtained precursor powder due to moisture in the air. It is preferable to work in a glove box in a gas atmosphere.

By heating, the precursor powder is calcined into LGPS-based, Li-PS-based and Li-P-SO-based sulfide solid electrolyte materials. During this heating, an inert gas is passed through the precursor powder. The operation is not particularly limited as long as the inert gas can be heated while flowing. As an example, since the precursor powder is a powder, the precursor powder is placed in a dish-shaped container, and the precursor powder is placed in a dish-shaped container in which one side is closed and the other side is open. The precursor powder may be heated while the inert gas is circulated through the precursor powder by supplying and exhausting the inert gas from the open side of the pipe. The material of the dish-shaped container or tube is preferably one that does not react with the precursor powder, and alumina or the like can be used. FIG. 1 shows a schematic configuration example of an apparatus for heating while flowing an inert gas.

Conventionally, if the precursor is not heated and fired in a closed system, the composition of the precursor and the obtained reaction product may be different due to the volatilization of the sulfide contained in the precursor and the reaction with water. There was a possibility. However, according to the present invention, the LGPS system, Li-P-, which is a reaction product, does not cause such a deviation in composition by heating the inert gas while flowing into the precursor under specific conditions. S-based and Li-P-SO-based sulfide solid electrolyte materials can be obtained.

Further, conventionally, when the precursor powder is heated and fired as it is, the reaction rate is slow, so that the powder is compression-molded (pelletized) and then heated and fired. However, according to the present invention, under specific conditions. The reaction is accelerated by heating the inert gas while flowing into the precursor powder, and compression molding (pelletization) is not required. That is, in the present invention, the step of compression molding (pelletization) can be omitted, and the productivity is greatly improved. In addition, since the process can be simplified, the possibility of unintended contamination is reduced, which is effective in improving product quality (purity, etc.).

Details of the conditions for heating the precursor powder while allowing the inert gas to flow into the precursor powder will be described.

Assuming that the flow rate of the inert gas is F (mL / min) and the weight of the precursor powder is M (g), the F / m is 5 or more and 80 or less.
The heated and fired product obtained with F / M outside the above range may not sufficiently contain LGPS-based, Li-PS-based and Li-P-SO-based sulfide solid electrolyte materials. This can be confirmed by X-ray diffraction measurement.
More specifically, if the F / M is less than 5, the flow of the inert gas is stagnant, leaving excess volatile components excessively, and it is appropriate to keep the flow of the inert gas moderate under synthetic conditions. The effect of the present invention for obtaining a synthetic product having a surface condition is not obtained. On the other hand, if the F / M is more than 80, the volatile components are excessively removed from the compound to be calcined (precursor powder), and a synthetic product having an appropriate composition cannot be obtained. Preferably, the F / M may be 10 or more, and even more preferably, the F / M may be 20 or more. Further, preferably, the F / M may be 70 or less, and more preferably, the F / M may be 60 or less.

Further, assuming that the internal volume of the heating container for heating the precursor powder is V (mL), the V / F is 0.1 or more and 3.0 or less.
The heated and fired product obtained with V / F outside the above range may not sufficiently contain LGPS-based, Li-PS-based and Li-P-SO-based sulfide solid electrolyte materials. This can be confirmed by X-ray diffraction measurement.
More specifically, when the V / F is smaller than 0.1, the volatile components are excessively removed from the compound to be calcined (precursor powder), and a synthetic product having an appropriate composition cannot be obtained. On the other hand, if the V / F is larger than 3.0, the flow of the inert gas is stagnant, excessive residual volatile components are left excessively, and the flow of the inert gas is maintained at an appropriate level under synthetic conditions, so that the surface is appropriate. The effect of the present invention is not obtained, in which a synthetic product in which the state is obtained can be obtained. Preferably, the V / F may be 0.3 or more, and more preferably, the V / F may be 0.5 or more. Further, preferably, the V / F may be 2.7 or less, and more preferably, the V / F may be 2.5 or less.

The flow rate F (mL / min) of the inert gas, the weight M (g) of the precursor powder, and the heating vessel for heating the precursor powder so that the F / M and V / F in the above ranges can be obtained. The internal volume V (mL) of the (reaction vessel) may be adjusted as appropriate.

The dew point of the inert gas is −30 ° C. or lower.
When the dew point exceeds -30 ° C, the water contained in the inflowing gas reacts with the sulfide contained in the precursor powder, causing a deviation from the composition of the charged precursor, and the obtained heated and fired product is an LGPS system. , Li-P-S-based and Li-P-SO-based sulfide solid electrolyte materials may not be sufficiently contained. This can be confirmed by X-ray diffraction measurement.
The lower the dew point, the lower the water content, which is advantageous in suppressing the reaction with sulfide. Therefore, preferably, the dew point may be −35 ° C. or lower, and more preferably, the dew point may be −40 ° C. or lower. Even if the dew point is lowered excessively, the lower limit of the dew point may be −50 ° C. or higher in consideration of the saturation of the effect and the increase in cost. Preferably, the dew point may be −45 ° C. or higher.

The heating temperature is 250 ° C or higher and 750 ° C or lower.
The heated and fired product obtained at a heating temperature outside the above range may not sufficiently contain LGPS-based, Li-PS-based, and Li-P-SO-based sulfide solid electrolyte materials. This can be confirmed by X-ray diffraction measurement.
More specifically, when the heating temperature is less than 250 ° C., the reaction does not proceed and a large amount of unreacted material remains, and a synthetic product having the desired composition cannot be obtained. If there is, a synthetic product having a desired composition cannot be obtained due to thermal decomposition of the synthetic product or the like. Preferably, the heating temperature may be 300 ° C. or higher, and more preferably, the heating temperature may be 350 ° C. or higher. Further, preferably, the heating temperature may be 700 ° C. or lower, and more preferably, the heating temperature may be 650 ° C. or lower.
The heating time can be appropriately adjusted according to the heating temperature and the amount of the precursor powder charged. For example, the heating time may include the temperature raising time and the holding time, and each time may be in the range of 30 minutes to 48 hours.
Further, when the obtained heated and fired product is cooled to room temperature after the completion of heating, natural cooling may be adopted or annealing may be performed.

When the inert gas is circulated through the precursor powder, the pressure in the heating vessel (reaction vessel) may be normal pressure. Considering that the pressure fluctuates due to the flow of the inert gas, the normal pressure may be within the range of 1013 hPa ± 200 hPa. In the conventional sealing system, it is necessary to make the inside of the container substantially vacuum, but in this embodiment, normal pressure is sufficient, the operation is simple, and the productivity is improved.

In one aspect of the present invention, the inert gas to be circulated in the precursor powder is particularly limited as long as it does not react with the precursor powder, the sulfide contained therein, the reactor and the like to reduce the effect of the present invention. It may be at least one selected from the group consisting of argon, dry air, nitrogen and helium. The gas types listed here are preferable because they are easily available and easy to handle. The dry air contains about 20 vol% of oxygen, but if the oxygen content is about this level, the effect of the present invention can be sufficiently obtained.

In one aspect of the present invention, the water content of the inert gas may be 1000 ppm or less. This is because if the water content exceeds 1000 ppm, the action and effect of the present invention may be reduced by reacting with the precursor powder, the sulfide contained therein, the reactor and the like. Since the amount of water contained in the inert gas is preferably small, it may be 500 ppm or less, more preferably 100 ppm or less, and further preferably 10 ppm or less.

In one aspect of the present invention, the amount of LGPS-based, Li-PS-based, and Li-P-SO-based sulfide solid electrolyte material produced may exceed 2 g per batch. The production method of the present invention includes a step of heating the precursor powder while flowing an inert gas through the precursor powder, that is, the step can be performed in an open system instead of a closed system. Therefore, there is no restriction on the production amount as in the case of the conventional closed system, and in one aspect of the present invention, the production amount can be more than 2 g per batch. From the viewpoint of productivity, it is preferable that the production amount per batch is large. Therefore, the production amount per batch may be 3 g or more, or more than 3 g, more preferably 4 g or more, or more than 4 g, more preferably 5 g or more, or more than 5 g. The upper limit of the production amount per batch is not particularly limited, but it can be appropriately selected in consideration of equipment cost, operational workability, and the like. As an example, the upper limit of the production amount per batch may be 1000 g or less, 100 g or less, or 10 g or less.

In one aspect of the present invention, the precursor powder may be heated while being agitated by rotating the heating container for heating the precursor powder.
The container for heating the precursor powder is not particularly limited, but a container that can be rotated is preferable from the viewpoint of heating efficiency and stirring efficiency. It is preferable that the heating container has a substantially cylindrical shape as shown in FIG. 1 because it is easy to rotate the axis in the cylindrical axis direction.
The rotation speed can be appropriately adjusted in consideration of heating efficiency and the like, and may be 1 to 100 rotations / min. If it is less than 1 rotation / min, the effect of improving the heating efficiency and the stirring efficiency by rotation may not be sufficient. The upper limit of the rotation speed is not particularly limited, but 100 rotations / min may be the upper limit because the effect of increasing the rotation speed tends to be saturated and the equipment cost increases.

The sulfide solid electrolyte material produced by the present invention has a crystal structure of LGPS-based, Li-PS-based and Li-P-SO-based sulfide-based solid electrolytes, and has excellent ionic conduction. May have sex. From the viewpoint of application to batteries and the like, it is preferable that the ionic conductivity is high, and the ionic conductivity at 25 ° C. is 5.0 when the obtained powdered LGPS-based sulfide solid electrolyte material is made into sintered pellets. is preferably × ¹⁰ -3 S / cm or more, more preferably 6.0 × ¹⁰ -3 S / cm or more, more preferably may be 7.0 × ¹⁰ -3 S / cm or more.
The conductivity is the ionic conductivity of Li ions unless otherwise specified. The ionic conductivity of a sulfide-based solid electrolyte is measured, for example, by a well-known AC impedance method.

Further, it was confirmed that the sulfide solid electrolyte material produced by the present invention has excellent water resistance.

In general, sulfides are easily deteriorated by the moisture contained in the surrounding atmosphere, and harmful hydrogen sulfide may be generated accordingly. When the present inventors investigated this deterioration phenomenon in detail, the following findings were obtained. Specifically, the moisture in the atmosphere (H 2 _O), etc. are resulted and sulfur (S) elements present in and near the surface of the sulfide solid electrolyte, the physical adsorption, chemical adsorption reaction or a hydration reaction, some of these reactants is changed to hydrogen sulfide (H 2 _S). Hydrogen sulfide has a boiling point of −60.7 ° C. and is in a gaseous state except in a special environment, so that it irreversibly separates from the sulfide solid electrolyte. Single particle of the sulfide solid electrolyte, through the hydrogen sulfide (H 2 _S) leaving a portion of the tissue is collapsed, the single particle is divided, a plurality of smaller particles are formed. When a plurality of small crystal particles are formed, the interfacial contact between the small particles increases, the grain boundary resistance increases, and the ionic conductivity decreases. That is, when a sulfide solid electrolyte reacts with water contained in the surrounding atmosphere to generate hydrogen sulfide, the ionic conductivity is irreversibly deteriorated (decreased) due to the release of the hydrogen sulfide.

Based on the above findings, the present inventors have conceived to evaluate the degree of deterioration of the sulfide solid electrolyte by detecting hydrogen sulfide released from the sulfide solid electrolyte. In other words, it can be said that the sulfide solid electrolyte, which is evaluated to have a small amount of hydrogen sulfide detachment and a small degree of deterioration, has high water resistance. In the evaluation of the degree of deterioration of the sulfide solid electrolyte or the water resistance, it may be affected by the moisture contained in the surrounding atmosphere. Therefore, the sulfide solid electrolyte material is used as a glove box with a controlled dew point (dew point -40). Allow to stand in the air at ° C to −45 ° C for a predetermined time. During this period, the amount of hydrogen sulfide separated from the sulfide solid electrolyte was measured, and the ionic conductivity and crystal structure measured before and after standing or during the standing were compared to determine the deterioration between the sulfide solid electrolytes. Evaluate the degree or water resistance.

When the sulfide solid electrolyte material according to the present invention was placed in a glove box with a controlled dew point (atmosphere with a dew point of −40 ° C. to −45 ° C.), no hydrogen sulfide was generated, and subsequently, XRD measurement was performed over time. As a result, it was confirmed that the crystal structure was maintained for a longer period of time than the sulfide produced in the conventional closed system.

Furthermore, a battery using a sulfide solid electrolyte material was prepared, the battery was placed in a glove box in which the dew point was controlled in the same manner, and impedance measurement was performed over time. It was confirmed that the conductivity was higher than that of a real battery, and that the conductivity was maintained for a long period of time. In one example, the initial conductivity of the LGPS-based sulfide solid electrolyte obtained in the closed system was 6.6 ± 1.8 mS / cm, whereas the conductivity of the open system was 7.9 ± 1.9 mS / cm. there were. The conductivity of both the sulfide solid electrolytes obtained in the open system and the closed system after being allowed to stand in the glove box for a predetermined time was lower than the initial conductivity. However, when the initial value of the conductivity of the sulfide solid electrolyte obtained in the closed system is 100%, the degree of decrease in the conductivity reaches 80%, and the sulfide solid electrolyte obtained in the open system has the conductivity. The degree of decrease was 10%. That is, the sulfide solid electrolyte obtained in the open system had an extremely small degree of decrease in conductivity as compared with the closed system.

As described above, it was confirmed by the production method of the present invention that the sulfide solid electrolyte produced in the open system has excellent water resistance as compared with the sulfide solid electrolyte produced in the conventional closed system. rice field. Although it is not desired to be bound by a specific theory, according to the production method of the present invention, the surface of the obtained sulfide solid electrolyte is different from that of the conventional closed system due to the circulation of the inert gas. The reaction with water is suppressed and hydrogen sulfide is less likely to be generated, hydrogen sulfide does not separate from the solid electrolyte and the solid electrolyte structure is less likely to collapse or divide, and the resistance value at the grain boundary increases. It is considered that it is difficult to do so and high ionic conductivity is maintained.

In the series of steps included in the production method of the present invention, in order to prevent the raw material powder, the precursor powder, and the obtained solid electrolyte material from being deteriorated by the moisture in the air, the atmosphere of an inert gas such as argon is used. It is preferable to work with.

Hereinafter, the present invention will be described in more detail with reference to Examples. The following examples do not limit the present invention.

(Preparation of precursor powder)
Raw material powders were prepared and mixed to give precursor powders. A series of operations were performed in a glove box with a gas circulation purifier (DBO-1.5-T1000 manufactured by Miwa Seisakusho Co., Ltd.) having a dew point of −70 ° C. or lower.
As raw material powders, disulfide germanium (GeS ₂ produced by Kojundo Chemical Laboratory Co., Ltd. purity of 99.99%), lithium sulfide _(Li 2 S Mitsuwa Chemicals Co., Ltd. purity: 99.9%), lithium chloride (LiCl Fuji film Wako pure chemical Co., Ltd. purity 99.0%), lithium hydroxide (98% manufactured by pure LiOH Yoneyama Yakuhin Kogyo Co., Ltd.), diphosphorus pentasulfide _{(P 2 S 5 Sigma-Aldrich} Corporation , Ltd. purity: 99%), two Silicon sulfide (SiS ₂ manufactured by Mitsuwa Chemical Co., Ltd., purity 99%), tin disulfide (SnS ₂ manufactured by Mitsuwa Chemical Co., Ltd., purity 99%) and the like were prepared.
Depending on the test conditions, mixing was done manually or by manual and mechanical milling.
The above raw material powders are weighed in a predetermined amount at a stoichiometric ratio determined to give a solid electrolyte material of the desired composition, placed in an agate mortar, manually mixed with a spatula for 1 minute, and then mixed. The mixture was manually mixed for 15 minutes using an agate pestle. At that time, the adhered material was scraped off with a spatula once every 5 minutes so that the raw material mixed powder did not adhere to the inner wall of the agate mortar.
After manual mixing, vibration milling (VM: Vibration Milling) was performed for 30 minutes with a high-speed vibration crusher (TI-100 manufactured by CMT Co., Ltd.) as mechanical milling.

(Comparative example: Heating and firing in a sealed system)
Subsequently, in a glove box (DBO-1.5-T1000 manufactured by Miwa Seisakusho Co., Ltd.), about 1 g of precursor powder was placed in a powder molding die (inner diameter 13 mm), and a hydraulic press machine (RIKEN Seiki Co., Ltd. foot hydraulic pressure) was used. The pump P-6) was used to pressurize the display pressure to 20 MPa (molding pressure is about 433 MPa) to prepare pellets having a diameter of 10 mm and a thickness of about 1 cm.
The prepared pellets are placed in a Pyrex (registered trademark) tube with an outer diameter of 13 mm, an inner diameter of 11 mm, and a length of about 20 cm, which is closed on one side, and connected to a vacuum line (made of glass manufactured by Tojo Synthetic Chemical Laboratory Co., Ltd.) to be connected to Pyrex (registered). The inside of the pipe was reduced to 10 Pa.
Next, pellets were sealed in the Pyrex® tube while denting the glass wall of the Pyrex® tube from three directions (at intervals of about 120 °) with an LNG / O _{2 burner.}
A Pyrex (registered trademark) tube containing precursor pellets is placed in an alumina core tube tilted 5 to 10 ° from the horizontal direction, and a muffle furnace (300-Plus manufactured by Denken Hydental Co., Ltd.) is used to reach 550 ° C. 3 After raising the temperature in time, it was held for 8 hours.
After air cooling, the tube was opened in a glove box, the calcined product was taken out, and the calcined product was crushed with an agate mortar and an agate pestle for 10 minutes to obtain an LGPS-based sulfide solid electrolyte.

(Example of invention: heating and firing in an open system)
In a glove box (DBO-1.5-T1000 manufactured by Miwa Seisakusho Co., Ltd.), about 1.0 to 5.0 g of precursor powder was placed on an alumina boat and placed in an alumina tanman tube with one side closed. The opening of the Tanman tube was covered with a metal jig with an O-ring, and the inside of the tube was sealed by tightening the jig screw.
The Tanman tube containing the precursor powder was taken out from the glove box and installed in a tube furnace (VTDW-2R manufactured by Isuzu Seisakusho Co., Ltd.).
After injecting Ar gas at 0.2 L / min into a gas line connected to G1 grade (purity> 99.99995 vol.% Dew point <-80 ° C) Ar gas and replacing the inside of the gas line for about 1 minute. , The gas line and the metal jig of the Tanman tube were connected using a dedicated connector (Swagelock Miniature Quick Connect 1/8 SS-QM2-B (D) -200).
While the Ar gas was flowing in the Tanman tube (and the precursor in the tube), the temperature was raised to 550 ° C. for 3 hours and then maintained for 8 hours. The internal volume V of the Tanman tube, which is a heating container and a reaction container, was 180 mL. Assuming that the flow rate of the inert gas is F (mL / min) and the weight of the precursor powder is M (g), the F / M is 5 or more and 80 or less, and the V / F is 0.1 or more and 3.0 or less. It was controlled to be within the range of.
After air cooling, the metal jig is disassembled in the glove box, the seal is released, the calcined product is taken out from the Tanman tube, and the calcined product is crushed for 10 minutes with an agate mortar and an agate pestle to obtain an LGPS-based sulfide solid electrolyte. Obtained.

(Comparison of Invention Examples and Comparative Examples)
_{Li (4-x)} Ge _(1-x) PxS ₄ (x = 0.65), which is the standard composition for LGPS-based sulfide solid electrolytes _{, in other words Li (10 + δ)} Ge _{(1 + δ)} P _{2- After} fixing the composition at δ S ₁₂ (δ = 0.05), the mixing treatment conditions for the preparation of the precursor powder (either manually or by manual mechanical milling) and the precursor. Six types of LGPS-based sulfide solid electrolytes were prepared by changing the firing conditions (performed in a closed system or in an open system).
XRD measurement was performed on the obtained LGPS-based sulfide solid electrolyte, and the XRD pattern is shown in FIG.
"ICSD LGPS065" from the top in FIG. 2 first _is the XRD chart of the standard sample of _{Li 3.35 Ge 0.35 P 0.65 S 4} , the typical crystal structure of LGPS based sulfide-based solid electrolyte Is shown.
The second chart from the top is a manual mixing + firing in a closed system, and in addition to the LGPS type crystal peak as the main phase, the peak considered to be _{β-Li 3} PS _{4 as the impurity phase.} Was also confirmed.
Although the order of explanation is different, the fourth chart from the top is a manual mixing + firing in an open system (Ar inflow), and besides the LGPS type crystal peak as the main phase, A peak considered to be _{Li 4} P ₂ S ₆ as the impurity phase was also confirmed.
The third chart from the top is a sample of the fourth chart that was manually reground and then fired again in an open system (Ar inflow), showing the LGPS-type crystal peak as the main phase. Although the intensity increased (see, for example, the peak near 2θ = 12.5 °), a peak considered to be _{Li 4} P ₂ S _{6 as the impurity phase remained.}
The fifth chart from the top shows mixing in mechanical milling + firing in an open system (Ar inflow), and LGPS type crystal peaks are obtained in a single phase and do not contain impurities. Is suggested.
The sixth chart from the top shows mixing by mechanical milling + firing in a closed system, and like the fifth chart, LGPS type crystal peaks are obtained in a single phase, and impurities are It is suggested that it is not included.
The 7th chart from the top shows the mixing in mechanical milling + _{firing in an open system (O 2} inflow), and an uncertain XRD peak was obtained, and the LGPS phase could not be synthesized. Is suggested.

The XRD was measured as follows.
In order to identify the crystals contained in the prepared sample, powder X-ray diffraction measurement was performed using a powder X-ray diffractometer Ulima-IV (manufactured by Rigaku Co., Ltd.) and Smart Lab (manufactured by Rigaku Co., Ltd.). Cu-Kα rays with an X-ray wavelength of 1.5418 angstroms were used for the powder X-ray diffraction measurement. Powder X-ray diffraction measurement was performed at a diffraction angle (2θ) in 0.01 ° steps in the range of 10 to 35 °.

Table 1 summarizes the above results.

From the above manufacturing conditions, the conditions of mechanical milling + open firing (Ar) in which the LGPS type crystal peak was obtained in a single phase (fifth chart from the top) were adopted, and Li _{(4-x) was adopted.} Ge _(1-x) PxS ₄ x is changed from 0.45 to 0.70 in 0.05 increments, in other words Li _{(10 + δ)} Ge _{(1 + δ)} P _2-δ S ₁₂ δ It was changed from 0.65 to −0.10 in 0.15 increments. Here, XRD measurement is performed on the obtained fired product, and the XRD pattern is shown in FIG.
As the value of x increases, the peak shifts to a higher angle, which indicates that the LGPS type structure is maintained while the quantitative ratio of Ge and P changes. It is considered that x is 0.5 or more and 0.65 or less in the composition range generated by a single phase of the LGPS type structure.

Table 2 summarizes the conductivity of the fired product obtained by changing _{x in Li (4-x)} Ge _(1-x) PxS _{4 in the range 0.50 to 0.65.} For reference, the conductivity of the fired product obtained by firing in a closed system is also shown.

The conductivity was measured as follows.
The obtained sample was pulverized and placed in a cell for sintering pellets, and then a pressure of 169 MPa was applied to the cell for room temperature to prepare pellets. Then, sintering was carried out at 550 ° C. for 12 hours to obtain sintered pellets made of solid electrolyte materials having various compositions. A measurement sample was prepared with a pellet diameter of about 10 mm and a thickness of 1 to 2 mm. Au was used as the electrode, and this was attached to the measurement sample to obtain an Au / measurement sample / Au battery. A Frequency Response Analyzer manufactured by NF was used for measuring the conductivity of the sample for measurement. The AC impedance was measured under the conditions of a measurement range of 15 MHz to 100 Hz, a measurement temperature of 26 ° C. to 127 ° C., an AC voltage of 50 to 100 mV, and an integration time of 2 seconds, and the conductivity of the sample was measured.

Further, _{for a measurement sample using a solid electrolyte material in which x of Li (4-x)} Ge _(1-x) PxS ₄ is 0.55, a glove box with a controlled dew point (dew point −40 ° C. to −45). The conductivity was measured even after being allowed to stand in the air at ° C. for 12 hours. Assuming that the initial value of the conductivity of the sulfide solid electrolyte obtained in the closed system is 100%, the degree of decrease in conductivity reaches 80%, but the sulfide solid electrolyte obtained in the open system has a decrease in conductivity. The degree was 10%. Similar measurements were performed for other compositions, and it was confirmed that the degree of decrease in conductivity of the sulfide solid electrolyte obtained in the open system was extremely small as compared with that in the closed system.

Further, the production amount (fired amount) per batch was changed in the range of 1.0 to 5.0 g, and the obtained fired product was subjected to XRD measurement, and the XRD pattern thereof is shown in FIG.
The chart obtained by firing 5.0 g also shows a peak that is almost the same as the chart obtained by firing 1.0 g. Therefore, it is suggested that the present invention can scale up the productivity of the sulfide solid electrolyte material.

Further, the process conditions are appropriately adjusted according to the change in the production amount (firing amount), the flow rate of the inert gas is F (mL / min), the weight of the precursor powder is M (g), and the contents of the reaction vessel. When the product was V (mL), it was confirmed that the desired sulfide solid electrolyte material could be obtained in the range of F / M of 5 or more and 80 or less and V / F of 0.1 or more and 3.0 or less. .. The desired sulfide solid electrolyte material can be obtained when the dew point of the inert gas is changed in the range of -30 ° C or lower, and when dry air, nitrogen, or helium is used instead of Ar. It was confirmed.

(Example of invention: Spread of composition)
It was confirmed that a sulfide solid electrolyte material can be obtained when the composition is variously changed.
(1) LGPS system (composition including Li-Sn-PS composition Li, Sn, P, S))
Using tin disulfide (SnS _{2 ) instead of germanium disulfide (GeS 2} ) as the raw material powder, the composition of the obtained sulfide solid electrolyte is Li _9.81 Sn _0.81 P _2.19 S ₁₂ . A sulfide solid electrolyte was prepared under the same conditions as the above-mentioned mechanical milling + open system firing (Ar), except that the above-mentioned mechanical milling + open system firing (Ar) was performed. The obtained product, a sulfide solid electrolyte, was subjected to XRD measurement, and it was confirmed that the crystal structure was similar to that of a typical LGPS-based sulfide-based solid electrolyte. The XRD pattern is shown in FIG.
(2) LGPS system (Li-Si-Sn-PS composition (composition including Li, Si, Sn, P, S))
As the raw material powder, tin disulfide (SnS ₂ ) and silicon disulfide (SiS _{2 ) are used instead of germanium disulfide (GeS 2} ), and the composition of the obtained sulfide solid electrolyte is Li _3.45 Si _{0. A} sulfide solid electrolyte was prepared under the same conditions as the above-mentioned mechanical milling + open system firing (Ar) except that 36 Sn _0.09 P _0.55 S _{4 was set.} The obtained product, a sulfide solid electrolyte, was subjected to XRD measurement, and it was confirmed that the crystal structure was similar to that of a typical LGPS-based sulfide-based solid electrolyte. Furthermore, it was confirmed that the conductivity (initial value) was 7.1 mS / cm.
(3) LGPS system (Li-Si-PS-Cl-O composition (composition including Li, Si, Sn, P, S, Cl, O))
As the raw material powder in place of lithium sulfide _(Li 2 S), using lithium (LiCl) and lithium hydroxide chloride (LiOH), in place of the disulfide germanium (GeS _2), disulfide tin (SnS ₂₎ and secondary Using silicon sulfide (SiS ₂ ), the composition of the obtained sulfide solid electrolyte was _adjusted to Li 9.54 Si _1.74 P _1.44 S _11.4 Cl _0.3 O _0.3. Except for this, a sulfide solid electrolyte was prepared under the same conditions as the above-mentioned mechanical milling + open system firing (Ar). The obtained product, a sulfide solid electrolyte, was subjected to XRD measurement, and it was confirmed that the crystal structure was similar to that of a typical LGPS-based sulfide-based solid electrolyte. Furthermore, it was confirmed that the conductivity (initial value) was 10 mS / cm.
(4) The composition of the obtained sulfide solid electrolyte was set to Li ₃ PS _{4 without using germanium disulfide (GeS 2} ) as the Li-PS-based raw material powder, and the heating and firing temperature was adjusted. A sulfide solid electrolyte was prepared under the same conditions as the above-mentioned mechanical milling + open system firing (Ar) except that the temperature was set to 280 ° C. As a comparative example, production in a closed system (closed system) was also performed. The obtained sulfide solid electrolyte, which is a product, was subjected to XRD measurement and showed the same crystal structure _{as the typical β-Li 3} PS _{4 obtained in the conventional closed system (closed system).} It was confirmed. The XRD pattern is shown in FIG.

Claims (4)

A method for producing an LGPS-based, Li-PS-based, and Li-P-SO-based sulfide solid electrolyte material.
Step of preparing raw material powder Step of mixing the raw material powder to obtain precursor powder,
The step of heating the precursor powder while flowing an inert gas through the precursor powder is included.
Here, it is assumed that the flow rate of the inert gas is F (mL / min), the weight of the precursor powder is M (g), and the internal volume of the heating container for heating the precursor powder is V (mL). , F / M is 5 or more and 80 or less, V / F is 0.1 or more and 3.0 or less,
The dew point of the inert gas is −30 ° C. or lower,
The heating temperature is 250 ° C. or higher and 750 ° C. or lower.
A method for producing a sulfide solid electrolyte material. The method for producing a sulfide solid electrolyte material according to claim 1, wherein the inert gas is at least one selected from the group consisting of argon, dry air, nitrogen, and helium. The method for producing a sulfide solid electrolyte material according to claim 1 or 2, wherein the water content of the inert gas is 1000 ppm or less. The method for producing a sulfide solid electrolyte material according to any one of claims 1 to 3, wherein the amount of the sulfide solid electrolyte material to be produced is more than 2 g per batch.

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