JP2014038755A - Manufacturing method of sulfide solid electrolytic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a sulfide solid electrolytic material having a high Li ion conductivity.SOLUTION: A manufacturing method of a sulfide solid electrolytic material comprises: an amorphization step for synthesizing sulfide glass by amorphization of a raw material composition including LiS, a sulfide of A (A is at least one of P, Si, Ge, Al and B), and LiX (X is halogen); and a synthesis step for heating the sulfide glass at a crystallization temperature or higher, cooling the sulfide glass at a cooling rate of 1K sor faster to synthesize a glass ceramic having peaks at 2θ=20.2° and 23.6° in X-ray diffraction measurement by use of Cu Kα rays. The proportion of the LiX included in the raw material composition, and the heating temperature and a heating time in the synthesis step are controlled so that the glass ceramic can be obtained.

Description

  The present invention relates to a method for producing a sulfide solid electrolyte material having high Li ion conductivity.

  With the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones in recent years, development of batteries that are used as power sources has been regarded as important. Also in the automobile industry and the like, development of high-power and high-capacity batteries for electric vehicles or hybrid vehicles is being promoted. Currently, lithium batteries are attracting attention among various batteries from the viewpoint of high energy density.

  Since lithium batteries currently on the market use an electrolyte containing a flammable organic solvent, it is possible to install safety devices that suppress the temperature rise during short circuits and to improve the structure and materials to prevent short circuits. Necessary. In contrast, a lithium battery in which the electrolyte is changed to a solid electrolyte layer to make the battery completely solid does not use a flammable organic solvent in the battery, so the safety device can be simplified, and manufacturing costs and productivity can be reduced. It is considered excellent. Furthermore, a sulfide solid electrolyte material is known as a solid electrolyte material used for such a solid electrolyte layer.

Since the sulfide solid electrolyte material has a high Li ion conductivity, it is useful for increasing the output of the battery, and various studies have been made heretofore. For example, Patent Document 1 discloses a sulfide solid electrolyte material, which is a glass having an ionic conductor having an ortho composition and LiI and having a glass transition point.
Further, as a method for obtaining a sulfide solid electrolyte material having high Li ion conductivity, a method for obtaining a sulfide solid electrolyte material having a high temperature stable phase by performing a solid-phase reaction at a crystallization temperature or higher and then rapidly cooling, A method of obtaining a sulfide solid electrolyte material by performing a heat treatment at a glass transition temperature or higher, quenching to a temperature lower than the above temperature to obtain a sulfide glass, and further performing a heat treatment again is disclosed (Patent Document 2 and 3).

JP 2012-048773 A JP 2001-250580 A JP 2008-103229 A

As shown in the above patent documents and the like, a sulfide solid electrolyte material having high Li ion conductivity is required.
As a result of intensive research, the inventors have made a limited LiX addition range when synthesizing glass ceramics by applying heat treatment to a sulfide glass doped with LiX as a method for synthesizing a sulfide electrolyte material, It has been found that glass ceramics with extremely high Li ion conductivity can be obtained by performing heat treatment in a heating temperature range and a heating time. It has also been found that the reason why the Li ion conductivity is increased is due to a novel crystal phase that has not been conventionally known.
However, the glass ceramics found by the present inventors do not improve the crystallinity (ratio) of the new crystal phase after cooling despite the high possibility that many new crystal phases are formed during the heat treatment. There is a problem that Li ion conductivity is lowered.

  The present invention has been made in view of the above circumstances, and its main object is to provide a method for producing a sulfide solid electrolyte material having high Li ion conductivity.

  As a result of further intensive studies, the present inventors have found that the cause of the above problem is the process of cooling after heat treatment. The present inventors found that the new crystal phase with high Li ion conductivity formed during the heat treatment is thermodynamically slightly unstable (metastable phase), and in the process of cooling after the heat treatment, the new crystal phase is Since a phase transition occurs in another crystalline phase or glass that is thermodynamically stable, the crystallinity (ratio) of the new crystalline phase does not improve, and the glass ceramics cannot have high Li ion conductivity after cooling. Estimated. Accordingly, the present inventors maintain a new crystal phase with high Li ion conductivity without causing a phase transition to another crystal phase that is thermodynamically stable by performing heat treatment and cooling at a predetermined rate. The present invention has been completed by finding that a glass ceramic sulfide solid electrolyte material can be obtained.

That is, in the present invention, a raw material composition containing a sulfide of Li ₂ S, A (A is at least one of P, Si, Ge, Al and B), and LiX (X is a halogen) Amorphization step of synthesizing sulfide glass, heating the sulfide glass at a temperature higher than the crystallization temperature, cooling at a cooling rate of ¹ K · s ⁻¹ or more, A synthesis step of synthesizing glass ceramics having peaks at 2θ = 20.2 ° and 23.6 ° in the X-ray diffraction measurement used, and the proportion of LiX contained in the raw material composition, and Provided is a method for producing a sulfide solid electrolyte material, wherein the heating temperature and heating time in the synthesis step are adjusted so that the glass ceramic is obtained.

According to the present invention, the heating temperature and the heating time until the sulfide glass synthesized by adjusting the ratio of LiX by the amorphization process has a specific peak in the X-ray diffraction measurement using CuKα rays. By performing heat treatment while adjusting the temperature, and further cooling at a cooling rate of ¹ K · s ⁻¹ or more, it is possible to prevent a phase transition from a crystalline phase exhibiting high Li ion conductivity to a stable crystalline phase, etc. The crystallinity (ratio) of the crystal phase exhibiting high Li ion conductivity can be improved. This makes it easy to obtain a single phase of the crystalline phase, and it is possible to synthesize a glass ceramic sulfide solid electrolyte material having high Li ion conductivity even after cooling.

  In the said invention, it is preferable that the ratio of LiX contained in the said sulfide solid electrolyte material is more than 13 mol% and less than 30 mol%. This is because the sulfide solid electrolyte material in which the ratio of LiX is within the above range can have a crystal phase with high Li ion conductivity.

  In the said invention, it is preferable that the said heating temperature exists in the range of 160 to 200 degreeC. This is because the sulfide glass obtained in the amorphization step is heat-treated at the above heating temperature, thereby having a crystal phase having a specific peak in X-ray diffraction measurement using CuKα rays.

  In the present invention, a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte formed between the positive electrode active material layer and the negative electrode active material layer A sulfide solid electrolyte in which at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte material layer is obtained by the above-described production method. Provided is a method for producing a lithium solid state battery, characterized by being formed using a material.

  According to the present invention, by using the sulfide solid electrolyte material obtained by the manufacturing method described above, a lithium solid battery having high Li ion conductivity can be obtained, and the battery can have high output. Become.

In the present invention, the sulfide glass is heat-treated at a temperature equal to or higher than the crystallization temperature of the sulfide glass while adjusting the heating temperature and the heating time, and cooled at a cooling rate of ¹ K · s ⁻¹ or more. Therefore, it is possible to suppress the crystal phase exhibiting high Li ion conductivity from causing a phase transition and improve the crystallinity (ratio) of the crystal phase. Therefore, there is an effect that a sulfide solid electrolyte material having high Li ion conductivity can be obtained even after cooling.

It is a flowchart which shows an example of the manufacturing method of the sulfide solid electrolyte material of this invention. It is a result of the X-ray-diffraction measurement using the CuK alpha ray with respect to the sample for evaluation obtained in Examples 1-2 and Comparative Examples 1-2. It is Li ion conductivity in 25 degreeC with respect to the sample for evaluation obtained in Examples 1-2 and Comparative Examples 1-2. It is a result of the X-ray diffraction measurement with respect to the glass ceramic obtained by reference example A1-A5. It is a result of the X-ray-diffraction measurement with respect to the glass ceramic obtained by reference example B2-B4. It is a measurement result of Li ion conductivity with respect to the sample obtained by reference example A1-A5 and reference example B1-B9.

  Hereinafter, a method for producing a sulfide solid electrolyte material and a method for producing a lithium solid battery of the present invention will be described in detail.

A. First, a method for producing a sulfide solid electrolyte material of the present invention will be described. The method for producing a sulfide solid electrolyte material of the present invention includes a sulfide of Li ₂ S, A (A is at least one of P, Si, Ge, Al and B), and LiX (X is a halogen). An amorphizing step for amorphizing a raw material composition containing sulphide and synthesizing a sulfide glass, and heating the sulfide glass at a temperature equal to or higher than a crystallization temperature, and at a cooling rate of ¹ K · s ⁻¹ or higher. And a synthesis step of synthesizing a glass ceramic having a peak at 2θ = 20.2 ° and 23.6 ° in an X-ray diffraction measurement using CuKα rays, and is included in the raw material composition The ratio of LiX, and the heating temperature and heating time in the synthesis step are adjusted so that the glass ceramic is obtained.

A method for producing a sulfide solid electrolyte material of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an example of a method for producing a sulfide solid electrolyte material of the present invention.
First, a raw material composition containing LiI, Li ₂ S and P ₂ S ₅ is prepared. At this time, the ratio of LiI contained in the raw material composition is adjusted to be a desired glass ceramic composition. Next, as an amorphization process, the raw material composition is subjected to mechanical milling to contain an ion conductor having Li, P and S (for example, Li ₃ PS ₄ ) and LiI. Synthesize sulfide glass. Next, the sulfide glass obtained by the amorphization process is heated at a temperature equal to or higher than the crystallization temperature, and the heating temperature and the heating time are adjusted (heat treatment), whereby the sulfide glass exhibits CuKα rays. In the X-ray diffraction measurement used, a crystal phase having peaks at 2θ = 20.2 ° and 23.6 ° is obtained, and further, the crystal phase having the above peaks is retained by cooling at a predetermined rate (cooling treatment). Thus obtained sulfide solid electrolyte material can be obtained (synthesis process). The sulfide solid electrolyte material obtained by the present invention is a glass ceramic, and in the following description, the “sulfide solid electrolyte material” may be referred to as “glass ceramic”. In addition, the sulfide solid electrolyte material in the present invention will be described in detail in the section of “A. Method for producing sulfide solid electrolyte material 5. Sulfide solid electrolyte material”, and thus the description thereof is omitted here.

Here, in the present invention, “the peak at 2θ = 20.2 ° in the X-ray diffraction measurement using CuKα ray” means not only a strict peak at 2θ = 20.2 ° but also 2θ = 20.2. A peak in the range of ± 0.5 °. Depending on the crystal state, the position of the peak may slightly move back and forth, so it is defined as above. Similarly, the peak at 2θ = 23.6 ° is not only a strict peak at 2θ = 23.6 °, but also a peak within a range of 2θ = 23.6 ° ± 0.5 °.
In the following description, “peaks at 2θ = 20.2 ° and 23.6 ° in X-ray diffraction measurement using CuKα rays” may be abbreviated as “two specific peaks”.

In our study, sulfides of Li ₂ S, A (A is at least one of P, Si, Ge, Al and B), and LiX having a desired ratio (X is a halogen) The sulfide glass obtained by amorphizing the raw material composition containing Cu was subjected to heat treatment so as to be within a specific temperature range above the crystallization temperature while adjusting the heating time, thereby using CuKα rays. In the X-ray diffraction measurement, the crystal phase has peaks at 2θ = 20.2 ° and 23.6 °. These two specific peaks are peaks of a novel crystal phase that has not been conventionally known, and it has been found that the novel crystal phase exhibits high Li ion conductivity. That is, the glass ceramic obtained by the above-described method is considered to be a sulfide solid electrolyte material having a high Li ion conductivity having the above novel crystal phase. In the following description, the above novel crystal phase is converted to a high Li ion conductivity. May be referred to as a crystalline crystal phase.

However, the glass ceramics found by the present inventors improve the crystallinity (ratio) of the new crystal phase after cooling despite the high possibility that many of the new crystal phases described above are formed during the heat treatment. However, it was found that there was a problem that the Li ion conductivity was lowered.
On the other hand, the present inventors have found that the cause of the decrease in Li ion conductivity of the glass ceramic is in the process of cooling after the heat treatment.
In glass ceramics at the time of heat treatment, there is a high possibility that many crystal phases exhibiting high Li ion conductivity are formed. However, the above crystal phases are thermally unstable crystal phases (hereinafter referred to as metastable phases). Therefore, during the slow cooling after the heat treatment, the high Li ion conductive crystal phase which is a metastable phase is a thermodynamically stable crystal phase (hereinafter sometimes referred to as a stable phase). Or a phase transition to glass occurs. As a result, after cooling, the glass ceramic has a reduced metastable phase and has a lot of stable phase or glass, and the crystallinity (ratio) of the high Li ion conductive crystal phase does not improve, so the Li ion conductivity decreases. I estimated.
Therefore, the present inventors heated the sulfide glass at a temperature equal to or higher than the crystallization temperature, and after performing the heat treatment while adjusting the heating temperature and the heating time so that the two specific peaks appear, By cooling at the cooling rate, the crystal phase of the glass ceramic is prevented from phase transition from the high Li ion conductive crystal phase to the stable phase or glass, and the crystallinity (ratio) of the high Li ion conductive crystal phase is improved. I found out. Thereby, a single phase of a high Li ion conductive crystal phase can be easily obtained, and a glass ceramic sulfide solid electrolyte material having high Li ion conductivity even after cooling can be obtained.

The method for producing a sulfide solid electrolyte material of the present invention comprises at least an amorphization step and a synthesis step.
Hereinafter, each process is demonstrated in order.

1. Amorphization process
First, the amorphization process in the present invention will be described. The amorphizing step in the present invention contains a sulfide of Li ₂ S, A (A is at least one of P, Si, Ge, Al and B), and LiX (X is a halogen). This is a step of making the raw material composition amorphous to synthesize sulfide glass. Moreover, this process adjusts the ratio of the said LiX contained in the said raw material composition so that desired glass ceramics may be obtained.

(1) Raw material composition The raw material composition in this step is a sulfide of Li ₂ S, A (A is at least one of P, Si, Ge, Al and B), and LiX (X is a halogen). ).

The Li ₂ S contained in the raw material composition preferably has few impurities. This is because side reactions can be suppressed. Examples of the method for synthesizing Li ₂ S include the method described in JP-A-7-330312. Furthermore, Li ₂ S is preferably purified using the method described in WO2005 / 040039.
On the other hand, examples of the sulfide A contained in the raw material composition include P ₂ S ₃ , P ₂ S ₅ , SiS ₂ , GeS ₂ , Al ₂ S ₃ , and B ₂ S ₃ .

The raw material composition is, when containing Li ₂ S and _P 2 _{S 5,} the proportion of Li ₂ S to the total of Li ₂ S and _P 2 _{S 5} is preferably in the range of 70 mol% 80 mol% 72 mol% to 78 mol% is more preferable, and 74 mol% to 76 mol% is more preferable. Incidentally, the raw material composition is, when containing Li ₂ S and _Al 2 _{S 3,} which is the same when containing Li ₂ S and _B 2 _{S 3.} On the other hand, the raw material composition is, when containing Li ₂ S and SiS _2, the ratio of Li ₂ S to the total of Li ₂ S and SiS ₂ is in the range of 62.5mol% ~70.9mol% Is preferable, it is more preferable that it is in the range of 63 mol% to 70 mol%, and it is more preferable that it is in the range of 64 mol% to 68 mol%. The same applies when the raw material composition contains Li ₂ S and GeS ₂ .

In the raw material composition, X in LiX is halogen, and specific examples include F, Cl, Br, and I. This is because glass ceramics having high Li ion conductivity can be obtained. Of these, Cl, Br, and I are preferable, and I is particularly preferable.
Further, the ratio of LiX in the raw material composition is adjusted to a ratio capable of synthesizing a desired glass ceramic and is slightly different depending on the synthesis conditions, but within a range of more than 13 mol% and less than 30 mol%, The ratio is preferably such that glass ceramics can be synthesized.

(2) Amorphization process In this process, as a method of amorphizing the raw material composition, for example, mechanical milling and melt quenching can be mentioned, and among these, mechanical milling is preferable. This is because processing at room temperature is possible, and the manufacturing process can be simplified. In addition, although the melt quench method has limitations on the reaction atmosphere and reaction vessel, mechanical milling has an advantage that a sulfide glass having a desired composition can be easily synthesized. The mechanical milling may be dry mechanical milling or wet mechanical milling, but the latter is preferred. This is because the raw material composition can be prevented from adhering to the wall surface of a container or the like, and a more amorphous sulfide glass can be obtained.

  Mechanical milling is not particularly limited as long as the raw material composition is mixed while applying mechanical energy, and examples thereof include a ball mill, a vibration mill, a turbo mill, a mechanofusion, and a disk mill. Among these, a ball mill is preferable, and a planetary ball mill is particularly preferable. This is because the desired sulfide glass can be obtained efficiently.

Various conditions of mechanical milling are set so that a desired sulfide glass can be obtained. For example, when a planetary ball mill is used, the raw material composition and grinding balls are added to the container, and the treatment is performed at a desired rotation speed and time. In general, the larger the number of revolutions, the faster the generation rate of sulfide glass, and the longer the treatment time, the higher the conversion rate from the raw material composition to sulfide glass. Specifically, the rotation speed of the base plate when performing the planetary ball mill is, for example, preferably in the range of 200 rpm to 500 rpm, and more preferably in the range of 250 rpm to 400 rpm. Further, the treatment time when performing the planetary ball mill is preferably in the range of 1 hour to 100 hours, and more preferably in the range of 1 hour to 50 hours. Examples of the material of the container used for the ball mill and the ball for grinding include ZrO ₂ and Al ₂ O _3. The diameter of the ball for grinding is within a range of 1 mm to 20 mm, for example. It is preferably within the range of 10 g to 100 g.

  The liquid used for wet mechanical milling preferably has a property of not generating hydrogen sulfide by the reaction with the raw material composition. Hydrogen sulfide is generated when protons dissociated from liquid molecules react with the raw material composition or sulfide glass. Therefore, it is preferable that the liquid has an aprotic property that does not generate hydrogen sulfide. In addition, aprotic liquids can be broadly classified into polar aprotic liquids and nonpolar aprotic liquids.

  Although it does not specifically limit as a polar aprotic liquid, For example, Ketones, such as acetone; Nitriles, such as acetonitrile; Amides, such as N, N- dimethylformamide (DMF); Dimethyl sulfoxide (DMSO) And the like.

  An example of a nonpolar aprotic liquid is alkane that is liquid at room temperature (25 ° C.). The alkane may be a chain alkane or a cyclic alkane. The chain alkane preferably has, for example, 5 or more carbon atoms. On the other hand, the upper limit of the carbon number of the chain alkane is not particularly limited as long as it is liquid at room temperature. Specific examples of the chain alkane include pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, and paraffin. The chain alkane may have a branch. On the other hand, specific examples of the cyclic alkane include cyclopentane, cyclohexane, cycloheptane, cyclooctane, and cycloparaffin.

  Other examples of nonpolar aprotic liquids include aromatic hydrocarbons such as benzene, toluene and xylene; chain ethers such as diethyl ether and dimethyl ether; cyclic ethers such as tetrohydrofuran; chloroform Alkyl halides such as methyl chloride and methylene chloride; esters such as ethyl acetate; fluorinated benzene, heptane fluoride, 2,3-dihydroperfluoropentane, 1,1,2,2,3,3 Fluorine compounds such as 4-heptafluorocyclopentane can be exemplified. The amount of the liquid added is not particularly limited.

  When the raw material composition is amorphized by wet mechanical milling, the obtained sulfide glass is preferably dried. This is for removing the liquid used in the mechanical milling remaining in the sulfide glass. The drying temperature is preferably lower than the crystallization temperature of the sulfide glass, and is preferably in the range of 100 ° C to 150 ° C, for example.

(3) Sulfide glass The sulfide glass obtained in this step refers to a material synthesized by amorphizing the above raw material composition. Strict “No periodicity as a crystal is observed in X-ray diffraction measurement etc. It means not only “glass” but also all materials synthesized by amorphization by mechanical milling or the like. Therefore, in the X-ray diffraction measurement using CuKα rays, for example, even if a peak derived from a raw material (LiI, etc.) is observed, if it is a material synthesized by amorphization, the sulfide glass Applicable.

2. Synthesis Step Next, the synthesis step in the present invention will be described. In the synthesis step of the present invention, the sulfide glass is heated at a temperature equal to or higher than the crystallization temperature, cooled at a cooling rate of ¹ K · s ⁻¹ or higher, and in X-ray diffraction measurement using CuKα rays, 2θ = 20. In this step, glass ceramics having peaks at 2 ° and 23.6 ° are synthesized.
Moreover, this process is characterized by adjusting the heating temperature and the heating time so that a desired glass ceramic is obtained.
In the following description, this process is divided into “(1) heat treatment” and “(2) cooling treatment”, and will be described in order.

(1) Heat treatment The heat treatment in this step is a treatment for heating the sulfide glass at a temperature higher than the crystallization temperature. In the heat treatment, the heating temperature and the heating time are adjusted so as to obtain a desired glass ceramic.

The heating temperature is equal to or higher than the crystallization temperature of the sulfide glass, and is a temperature at which glass ceramics having peaks at 2θ = 20.2 ° and 23.6 ° are obtained in the X-ray diffraction measurement using CuKα rays. is there. In addition, the crystallization temperature of sulfide glass can be determined by differential thermal analysis (DTA).
The range of the heating temperature is a temperature range in which the two specific peaks appear in the X-ray diffraction measurement using CuKα rays, and is slightly different depending on the composition of the sulfide glass. It is preferable that it is in the range of ° C to 200 ° C, and among them, the heating temperature is preferably in the range of 170 ° C to 190 ° C, and particularly preferably in the range of 180 ° C to 190 ° C. This is because when the heating temperature is not within the above range, the high Li ion conductive crystal phase having the two specific peaks may not be formed.

  The specific heating time is appropriately selected according to the heating temperature described above, but is preferably in the range of 1 minute to 24 hours, for example, and more preferably in the range of 30 minutes to 3 hours. In particular, it is preferably in the range of 1 hour to 3 hours. More specifically, when the heating temperature is 160 ° C., which is the lower limit of the heating temperature range described above, it is preferably within a range of 1 hour to 10 hours, and when the heating temperature is 200 ° C., it is 1 hour to 3 hours. It is preferable to be within the range. If the heating time is too short, the two specific peak intensities do not become the desired intensity, and the glass ceramic obtained through the cooling treatment may not have a high Li ion conductive crystal phase, This is because if the heating time is too long, the above two specific peak intensities are lowered, and there is a possibility that the high Li ion conductive crystal phase changes to a stable phase or glass.

  The heat treatment in this step is preferably performed in an inert gas atmosphere (for example, an Ar gas atmosphere). This is because deterioration (for example, oxidation) of the sulfide glass can be prevented. Although the method of heat processing is not specifically limited, For example, the method using a baking furnace can be mentioned.

(2) Cooling process Next, the cooling process in this process is demonstrated. The cooling process in this step is a process of performing cooling at a cooling rate of ¹ K · s ⁻¹ or more after the above-described heat treatment.

Usually, when the sulfide glass is heat-treated and cooled, a method in which the sulfide glass is placed in a heat-treatment environment, for example, left in a furnace in which heat treatment is performed and cooled is used. For this reason, the cooling rate becomes slower in accordance with the rate of decrease in the furnace temperature. When the cooling rate is slow, the high Li ion conductive crystalline phase of the metastable phase formed by heat treatment undergoes a phase transition to the stable phase or glass during cooling, and the crystallinity (ratio of the high Li ion conductive crystalline phase) ) Does not improve, it is estimated that the Li-ion conductivity of the glass ceramic after the cooling treatment is lowered.
On the other hand, in the present invention, since the phase transition from the metastable phase to the stable phase or the like is suppressed by cooling at a predetermined cooling rate, the glass ceramic after cooling may retain a high Li ion conductive crystal phase. And the crystallinity (ratio) of the high Li ion conductive crystal phase is improved. Thereby, the glass ceramic can easily obtain a single phase of a high Li ion conductive crystal phase, and can have high Li ion conductivity even after cooling.

The cooling rate is preferably a rate at which a high Li ion conductive crystal phase is maintained during cooling, and is preferably 1 K · s ⁻¹ or more, and more preferably 10 K · s ^{−1 to} 1000 K · s ^−. It is preferable to be within the range of ¹ . If the cooling rate is slower than the above range, the high Li ion conductive crystal phase undergoes a phase transition to the stable phase or glass, and the crystallinity (ratio) of the high Li ion conductive crystal phase does not improve. This is because ceramics may not have high Li ion conductivity.

  The cooling method is not particularly limited as long as it can be cooled at a predetermined cooling rate. For example, it may be allowed to cool at room temperature, that is, it may be air-cooled. Alternatively, ice cooling, air cooling, cooling by blowing an inert gas, or the like may be used. Among these, cooling in ice water is preferable. By using the above cooling method, it is possible to suppress the phase transition from the high Li ion conductive crystal phase to the stable phase or glass and to improve the crystallinity (ratio) of the high Li ion conductive crystal phase. It is.

  The cooling treatment in this step is preferably performed without placing a certain time or more from the heat treatment, specifically, the time from the heat treatment to the start of the cooling treatment is preferably within 10 seconds. It is preferably within 1 second. If the transition time from the heat treatment to the cooling treatment is longer than the above range, the high Li ion conductive crystal phase undergoes a phase transition to a stable phase or glass, and the crystallinity (ratio) of the high Li ion conductive crystal phase does not improve. Therefore, the glass ceramic after cooling may not have high Li ion conductivity.

It is preferable to cool until the temperature of the glass ceramic is 100 ° C. or lower by the cooling treatment in this step, and it is particularly preferable that the glass ceramic is cooled to 50 ° C. or lower, particularly 25 ° C. or lower. It is preferable. When the temperature of the glass ceramic after cooling is higher than the above range, a phase transition from a high Li ion conductive crystal phase to a stable phase or glass occurs, and the crystallinity (ratio) of the high Li ion conductive crystal phase is improved. Because there is a possibility of not.
The cooling environment temperature is appropriately selected depending on the cooling method, and is preferably 25 ° C. or less, for example, preferably 10 ° C. or less, and particularly preferably 0 ° C. or less. preferable. When the cooling environment temperature is higher than the above range, the predetermined cooling rate is not achieved, and the crystal phase undergoes a phase transition from the high Li ion conductive crystal phase to the stable phase or glass during the cooling process, and the high Li ion conductive crystal This is because the crystallinity (ratio) of the phase may not be improved.

  The cooling treatment time is appropriately selected according to the cooling method and the cooling rate described above, and is preferably lowered to room temperature as soon as possible. This is because the crystal phase may undergo a phase transition from the high Li ion conductive crystal phase to the stable phase or glass during the cooling treatment, and the crystallinity (ratio) of the high Li ion conductive crystal phase may not be improved.

  The cooling treatment in this step is preferably performed in an environment where the glass ceramic is not in direct contact with moisture. This is because glass ceramics may cause deterioration such as oxidation due to direct contact with moisture. As water content in the implementation environment of a cooling process, it is preferable to carry out in the environment of 10 ppm or less, for example, and it is preferable to carry out in an environment of 0.5 ppm or less especially. Specifically, the environment having the above conditions is preferably performed in a closed container filled with an inert gas atmosphere (for example, an Ar gas atmosphere).

3. Other Steps The present invention has at least the above-described amorphization step and synthesis step, but may have other steps as necessary. Examples of other processes include a atomization process.

4). Sulfide solid electrolyte material The sulfide solid electrolyte material obtained by the present invention includes Li, A (A is at least one of P, Si, Ge, Al, and B), X (X is a halogen), S The glass ceramics are characterized by having peaks at 2θ = 20.2 ° and 23.6 ° in the X-ray diffraction measurement using CuKα rays. Since the sulfide solid electrolyte material has the two specific peaks, it can have a high Li ion conductivity.

  The sulfide solid electrolyte material obtained by the present invention has peaks at 2θ = 20.2 ° and 23.6 ° in the X-ray diffraction measurement using CuKα ray. Although the peak pattern in depends on the crystal structure, it does not depend greatly on the type of atoms constituting the crystal structure. Therefore, the same pattern can be obtained if the same crystal structure is formed regardless of the types of A and X. That is, regardless of the types of A and X, the same pattern can be obtained if a high Li ion conductive crystal phase is formed. Note that the position of this pattern may slightly move back and forth. From this point, it is preferable to define the peaks at 2θ = 20.2 ° and 23.6 ° within a range of ± 0.5 °. .

  The sulfide solid electrolyte material obtained by the present invention preferably has a high Li ion conductive crystal phase as a main component, and specifically, the high Li ion conductive crystal phase in the entire crystal phase of the sulfide solid electrolyte material. The ratio is preferably 50 mol% or more, and it is particularly preferable that all the crystal phases of the sulfide solid electrolyte material are high Li ion conductive crystal phases.

  In addition, the sulfide solid electrolyte material obtained by the present invention is not limited to the high Li ion conductive crystal phase having peaks of 2θ = 20.2 ° and 23.6 ° in the X-ray diffraction measurement using CuKα ray. 2θ = 21.0 °, having a peak at 28.0 °, that is, one forming a low Li ion conductive crystal phase may be included. These peaks are peaks of a novel crystal phase that has not been conventionally known, but are peaks of a crystal phase having a lower Li ion conductivity than a high Li ion conductive crystal phase. A crystal phase having peaks at 2θ = 21.0 ° and 28.0 ° may be referred to as a low Li ion conductive crystal phase. Further, the peak at 2θ = 21.0 ° indicating the low Li ion conductive crystal phase is not limited to the exact peak at 2θ = 21.0 °, but within the range of 2θ = 21.0 ° ± 0.5 °. The peak at. Depending on the crystal state, the position of the peak may slightly move back and forth, so it is defined as above. Similarly, the peak at 2θ = 28.0 ° is not only a strict peak at 2θ = 28.0 ° but also a peak within a range of 2θ = 28.0 ° ± 0.5 °.

The sulfide solid electrolyte material obtained by the present invention preferably has a low proportion of low Li ion conductive crystal phase. Specifically, the peak intensity at 2θ = 20.2 ° with respect to the peak intensity at 2θ = 21.0 ° is I _20.2 / I _21.0, and 2θ = 23 with respect to the peak intensity at 2θ = 21.0 °. When the peak intensity at .6 ° is I _23.6 / I _21.0 , I _20.2 / I _21.0 and I _23.6 / I _21.0 are each 0.1 or more Among them, it is preferable that each is 0.2 or more, and it is particularly preferable that I _20.2 / I _21.0 is 1 or more. When the ratio of I _20.2 / I _21.0 and I _23.6 / I _21.0 is not in the above range, the ratio of the low Li ion conductive crystal phase is increased and the Li ion conductivity is not high. This is because there is a possibility of becoming a sulfide solid electrolyte material.

  In addition, the sulfide solid electrolyte material obtained by the present invention includes an ion conductor having Li, A (A is at least one of P, Si, Ge, Al, and B), and S, and LiX (X is And is preferably a halogen. At this time, at least a part of LiX is usually present in a state of being taken into the structure of the ionic conductor as a LiX component.

The ion conductor in the present invention has Li, A (A is at least one of P, Si, Ge, Al and B), and S. The ionic conductor is not particularly limited as long as it has Li, A, and S. Among them, it is preferable to have an ortho composition. This is because a sulfide solid electrolyte material having high chemical stability can be obtained. Here, ortho generally refers to one having the highest degree of hydration among oxo acids obtained by hydrating the same oxide. In the present invention, the crystal composition in which Li ₂ S is added most in the sulfide is called the ortho composition. For example, Li ₃ PS ₄ corresponds to the ortho composition in the Li ₂ S—P ₂ S ₅ system, Li ₃ AlS ₃ corresponds to the ortho composition in the Li ₂ S—Al ₂ S ₃ system, and Li ₂ S—B _2. In the S ₃ system, Li ₃ BS ₃ corresponds to the ortho composition, in the Li ₂ S—SiS ₂ system, Li ₄ SiS ₄ corresponds to the ortho composition, and in the Li ₂ S—GeS ₂ system, Li ₄ GeS _{4 corresponds} to the ortho composition. Applicable.

Here, “having an ortho composition” includes not only a strict ortho composition but also a composition in the vicinity thereof. Specifically, the main component is an anion structure having an ortho composition (PS ₄ ³⁻ structure, SiS ₄ ⁴⁻ structure, GeS ₄ ⁴⁻ structure, AlS ₃ ³⁻ structure, BS ₃ ³⁻ structure). The ratio of the anion structure of the ortho composition is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, based on the total anion structure in the ion conductor, 90 mol % Or more is particularly preferable. The ratio of the anion structure of the ortho composition can be determined by Raman spectroscopy, NMR, XPS, or the like.

It is preferable that the sulfide solid electrolyte material obtained by the present invention does not substantially contain Li ₂ S. It is because it can be set as the sulfide solid electrolyte material with little hydrogen sulfide generation amount. Li ₂ S reacts with water to generate hydrogen sulfide. For example, when the proportion of Li ₂ S contained in the raw material composition is large, Li ₂ S tends to remain. “Substantially free of Li ₂ S” can be confirmed by X-ray diffraction using CuKα rays. Specifically, when it does not have a Li ₂ S peak (2θ = 27.0 °, 31.2 °, 44.8 °, 53.1 °), it is determined that it does not substantially contain Li ₂ S. can do.

Moreover, it is preferable that the said sulfide solid electrolyte material does not contain bridge | crosslinking sulfur substantially. It is because it can be set as the sulfide solid electrolyte material with little hydrogen sulfide generation amount. “Bridged sulfur” refers to bridged sulfur in a compound obtained by reacting Li ₂ S with the sulfide of A described above. For example, Li ₂ S and _P 2 _{S 5} is bridging sulfur reactions to become _{S 3} PS-PS 3 structure corresponds. Such bridging sulfur easily reacts with water and easily generates hydrogen sulfide. Furthermore, “substantially free of bridging sulfur” can be confirmed by measurement of a Raman spectrum. For example, in the case of a Li ₂ S—P ₂ S ₅ sulfide solid electrolyte material, the peak of the S ₃ P—S—PS ₃ structure usually appears at 402 cm ⁻¹ . Therefore, it is preferable that this peak is not detected. Moreover, the peak of PS ₄ ³⁻ structure usually appears at 417 cm ⁻¹ . In the present invention, the intensity _{I 402} at 402 cm ^-1 is preferably smaller than the intensity _{I 417} at 417 cm ^-1. More specifically, the strength I ₄₀₂ is preferably 70% or less, more preferably 50% or less, and even more preferably 35% or less with respect to the strength I ₄₁₇ . As for the sulfide solid electrolyte material other than Li 2 _{S-P 2} S ₅ based, to identify the unit containing the crosslinking sulfur, by measuring the peak of the unit, are substantially free of bridging sulfur It can be judged that there is no.

In the case of a Li ₂ S—P ₂ S ₅ -based sulfide solid electrolyte material, the ratio of Li ₂ S and P ₂ S ₅ to obtain the ortho composition is Li ₂ S: P ₂ S ₅ = 75 on a molar basis. : 25. The same applies to the Li ₂ S—Al ₂ S ₃ -based sulfide solid electrolyte material and the Li ₂ S—B ₂ S ₃ -based sulfide solid electrolyte material. On the other hand, in the case of a Li ₂ S—SiS ₂ -based sulfide solid electrolyte material, the ratio of Li ₂ S and SiS ₂ to obtain the ortho composition is Li ₂ S: SiS ₂ = 66.7: 33.3 on a molar basis. It is. The same applies to the case of a Li ₂ S—GeS ₂ -based sulfide solid electrolyte material.

  Further, the ratio of LiX in the sulfide solid electrolyte material is not particularly limited as long as it is a glass ceramic having a high Li ion conductive crystal phase. For example, it is preferably more than 13 mol% and less than 30 mol%. Especially, it is preferable that it exists in the range of 15 mol%-25 mol%.

Examples of the shape of the sulfide solid electrolyte material obtained by the present invention include particles. The average particle diameter (D ₅₀ ) of the particulate sulfide solid electrolyte material is preferably in the range of 0.1 μm to ₅₀ μm, for example. The sulfide solid electrolyte material preferably has a high Li ion conductivity, and the Li ion conductivity at room temperature is preferably 1 × 10 ⁻⁴ S / cm or more, for example, 1 × 10 ⁻³ S. / Cm or more is more preferable.

Since the sulfide solid electrolyte material obtained by the present invention is a glass ceramic, it has an advantage of higher heat resistance than sulfide glass. For example, as a conventional manufacturing method, Li ion conductivity can be further increased by doping LiI into Li ₂ S—P ₂ S ₅ -based sulfide glass. However, when LiI is doped, the crystallization temperature of sulfide glass may decrease. When sulfide glass having a low crystallization temperature is used for a battery, for example, when the battery temperature reaches or exceeds the crystallization temperature of sulfide glass, heat is generated due to crystallization of the sulfide glass. There are problems in that each material constituting the material is altered (deteriorated) or the battery case or the like is damaged. On the other hand, in this invention, the bad influence of the heat_generation | fever accompanying crystallization can be prevented by setting it as the glass ceramic crystallized previously. Further, there is an advantage that the battery cooling mechanism and the safety mechanism can be simplified.

  The sulfide solid electrolyte material obtained by the present invention can be used for any application requiring Li ion conductivity. Especially, it is preferable that the said sulfide solid electrolyte material is what is used for a battery.

B. Next, a method for manufacturing a lithium solid state battery will be described. The method for producing a lithium solid state battery of the present invention is formed between a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and the positive electrode active material layer and the negative electrode active material layer. And a solid state electrolyte layer, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer is obtained by the above-described production method. It is formed using a solid electrolyte material.

According to the present invention, by using the sulfide solid electrolyte material obtained by the manufacturing method described above, a lithium solid battery having high Li ion conductivity can be obtained, and the output of the battery can be increased.
The method for producing a lithium solid state battery of the present invention includes at least a solid electrolyte layer forming step, a positive electrode active material layer forming step, and a negative electrode active material layer forming step.
Hereafter, the manufacturing method of the lithium solid battery of this invention is demonstrated for every process.

1. Solid electrolyte layer forming step The solid electrolyte layer forming step in the present invention is a layer formed between a positive electrode active material layer and a negative electrode active material layer, which will be described later, and is a step of forming a layer containing at least a solid electrolyte material. .

(1) Solid electrolyte material The solid electrolyte material used in this step is not particularly limited as long as it has Li ion conductivity, and examples thereof include a sulfide solid electrolyte material and an oxide solid electrolyte material. be able to. The sulfide solid electrolyte material is preferable in that it has a higher ionic conductivity than the oxide solid electrolyte material, and the oxide solid electrolyte material has higher chemical stability than the sulfide solid electrolyte material. This is preferable.
The solid electrolyte material may be an amorphous material or a crystalline material. The amorphous material can be obtained, for example, by applying a mechanical milling method or a melt quenching method to the raw material composition. The crystalline material can be obtained, for example, by applying a solid phase method to the raw material composition.
Among these, the solid electrolyte material used in this step is preferably the sulfide solid electrolyte material described in the above-mentioned section “A. Method for producing sulfide solid electrolyte material”.

  The content of the sulfide solid electrolyte material is not particularly limited as long as a desired insulating property is obtained. For example, the content is in the range of 10% by volume to 100% by volume. It is preferable to be within the range of 100% by volume. In particular, in the present invention, it is preferable that the solid electrolyte layer is composed only of the sulfide solid electrolyte material.

(2) Other materials The solid electrolyte layer formed in this step may contain a binder in addition to the solid electrolyte material. This is because a solid electrolyte layer having flexibility can be obtained by containing a binder. Examples of the binder include fluorine-containing binders such as PTFE and PVDF.

(3) Solid electrolyte layer formation process As a formation method of the solid electrolyte layer in this process, the press method etc. can be mentioned, for example. In addition, the thickness of the solid electrolyte layer formed in this step is, for example, preferably in the range of 0.1 μm to 1000 μm, and more preferably in the range of 0.1 μm to 300 μm.

2. Positive electrode active material layer forming step The positive electrode active material layer forming step in the present invention is a step of forming a positive electrode active material layer containing at least a positive electrode active material.

(1) Positive electrode active material The positive electrode active material used in this step is not particularly limited. For example, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _{1 / 3} O ₂ rock salt layered type active material, LiMn ₂ O ₄ , spinel type active material such as Li (Ni _0.5 Mn _1.5 ) O ₄ , LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCuPO _4, etc. An olivine type active material etc. can be mentioned. Si-containing oxides such as Li ₂ FeSiO ₄ and Li ₂ MnSiO ₄ may be used as the positive electrode active material.

  Examples of the shape of the positive electrode active material used in this step include a particle shape, and among them, a true spherical shape or an elliptical spherical shape is preferable. Moreover, when a positive electrode active material is a particle shape, it is preferable that the average particle diameter exists in the range of 0.1 micrometer-50 micrometers, for example. Further, the content of the positive electrode active material in the positive electrode active material layer formed in this step is preferably in the range of 10% by volume to 99% by volume, for example, in the range of 20% by volume to 99% by volume. It is more preferable.

(2) Other materials The positive electrode active material layer formed in this step preferably contains a solid electrolyte material in addition to the positive electrode active material described above. This is because the positive electrode active material is in contact with the solid electrolyte material, and the ionic conductivity of the positive electrode active material layer can be improved.
As the solid electrolyte material used in this step, the same materials as those described in the above-mentioned section “1. Solid electrolyte layer forming step” can be used. The sulfide solid electrolyte material described in the section “Material production method” is preferable.
The detailed description of the sulfide solid electrolyte material is the same as the content described in the above-mentioned section “A. Method for producing sulfide solid electrolyte material”, and thus the description thereof is omitted here.

  The content of the sulfide solid electrolyte material is, for example, in the range of 0.1% by volume to 80% by volume, particularly in the range of 1% by volume to 60% by volume, in particular, with respect to the positive electrode active material layer to be formed. It is preferably within the range of 10% by volume to 50% by volume.

  The positive electrode active material layer formed in this step may further contain at least one of a conductive material and a binder in addition to the positive electrode active material and the solid electrolyte material described above. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. As the binder, the same materials as those described in the above-mentioned section “1. Solid electrolyte layer forming step” can be used.

(3) Positive electrode active material layer forming step The positive electrode active material layer forming method in this step may be a method capable of forming a positive electrode active material layer having the above material on a solid electrolyte layer or a positive electrode current collector. For example, a press method, a sputtering method, a PVD method, a CVD method, an electrolytic plating method, an electroless plating method, or the like can be used.
Moreover, it is preferable that the thickness of the positive electrode active material layer formed at this process exists in the range of 0.1 micrometer-1000 micrometers, for example.

When the solid electrolyte material contained in the positive electrode active material layer formed in this step is a sulfide solid electrolyte material having an ionic conductor having an ortho composition and using LiI, the positive electrode active material is It preferably has a potential of 2.8 V (vs Li) or higher, and more preferably has a potential of 3.0 V (vs Li) or higher.
Conventionally, since LiI was considered to decompose near 2.8 V, a sulfide solid electrolyte material having LiI has not been used for the positive electrode active material layer. On the other hand, since the above-described sulfide solid electrolyte material has an ionic conductor having an ortho composition, it is considered that LiI is stabilized by interaction with the ionic conductor and oxidative decomposition of LiI can be suppressed.

3. Negative electrode active material layer forming step The negative electrode active material forming step in the present invention is a step of forming a negative electrode active material layer containing at least a negative electrode active material.

(1) Negative electrode active material As a negative electrode active material used at this process, a metal active material and a carbon active material can be mentioned, for example. Examples of the metal active material include In, Al, Si, and Sn. On the other hand, examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Further, the content of the negative electrode active material in the negative electrode active material layer formed in this step is preferably in the range of, for example, 10% by volume to 99% by volume, and in the range of 20% by volume to 99% by volume. It is more preferable. The conductive material and the binder are the same as those used for the positive electrode active material layer described above. The thickness of the negative electrode active material layer is preferably in the range of 0.1 μm to 1000 μm, for example.

(2) Other materials The negative electrode active material layer formed in this step preferably contains a solid electrolyte material in addition to the negative electrode active material described above. This is because the negative electrode active material and the solid electrolyte material are in contact with each other, and the ionic conductivity of the negative electrode active material layer can be improved.
As the solid electrolyte material used in this step, the same materials as those described in the above-mentioned section “1. Solid electrolyte layer forming step” can be used. The sulfide solid electrolyte material described in the section “Material production method” is preferable. The detailed description of the sulfide solid electrolyte material is the same as the content described in the above-mentioned section “A. Method for producing sulfide solid electrolyte material”, and thus the description thereof is omitted here.

  The content of the sulfide solid electrolyte material is, for example, in the range of 0.1% by volume to 80% by volume, particularly in the range of 1% by volume to 60% by volume, in particular, with respect to the negative electrode active material layer to be formed. It is preferably within the range of 10% by volume to 50% by volume.

  The negative electrode active material layer formed in this step may further contain at least one of a conductive material and a binder in addition to the negative electrode active material and the solid electrolyte material described above. As the conductive material, the same materials as those described in the above-mentioned section “B. Manufacturing method of lithium solid battery 2. Positive electrode active material layer forming step (2) Other materials” can be used. As the depositing material, the same materials as those described in the above-mentioned section “B. Manufacturing method of lithium solid battery 1. Solid electrolyte layer forming step” can be used.

(3) Negative electrode active material layer forming step The negative electrode active material layer forming method in this step may be a method capable of forming a negative electrode active material layer having the above material on a solid electrolyte layer or a negative electrode current collector. For example, a press method, a sputtering method, a PVD method, a CVD method, an electrolytic plating method, an electroless plating method, or the like can be used.
Moreover, it is preferable that the thickness of the negative electrode active material layer formed at this process exists in the range of 0.1 micrometer-1000 micrometers, for example.

4). Other Steps In the present invention, in addition to the steps described above, a step of disposing a positive electrode current collector on the surface of the positive electrode active material layer, a step of disposing a negative electrode current collector on the surface of the negative electrode active material layer, power generation You may have the process of accommodating an element in a battery case.
Examples of the material for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. Among them, SUS is preferable. On the other hand, examples of the material for the negative electrode current collector include SUS, copper, nickel, and carbon. Among them, SUS is preferable.
In addition, the thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably appropriately selected according to the use of the lithium solid state battery. Moreover, the battery case used for this invention can use the battery case of a common lithium solid battery, for example, the battery case made from SUS etc. can be mentioned.

5. Lithium Solid Battery The lithium solid battery obtained by the method for producing a lithium solid battery of the present invention may be a primary battery or a secondary battery, but among them, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful, for example, as a vehicle-mounted battery. Furthermore, examples of the shape of the lithium solid state battery obtained by the present invention include a coin type, a laminate type, a cylindrical type, and a square type.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  The present invention will be described more specifically with reference to the following examples and comparative examples. Unless otherwise specified, each operation such as weighing, synthesis, and drying was performed in an Ar atmosphere.

[Example 1]
(Amorphization process)
As starting materials, lithium sulfide (Li ₂ S, manufactured by Nippon Chemical Industry Co., Ltd.), diphosphorus pentasulfide (P ₂ S ₅ , manufactured by Aldrich) and lithium iodide (LiI, manufactured by Aldrich) were used. Next, 0.606 g of Li ₂ S, 0.978 g of P ₂ S ₅ and 0.416 g of LiI were weighed and mixed for 5 minutes in an agate mortar. 2 g of the obtained mixture is put into a planetary ball mill container (45 cc, made of ZrO ₂ ), dehydrated heptane (moisture content of 30 ppm or less, 4 g) is added, and further ZrO ₂ balls (φ = 5 mm, 53 g) are added. The container was completely sealed. This container was attached to a planetary ball mill (P7 made by Fritsch), and mechanical milling was performed for 20 hours at a base plate rotation speed of 500 rpm. Then, heptane was removed by drying at 100 ° C. to obtain a sulfide glass.

(Synthesis process)
1 g of the sulfide glass obtained by the above amorphization process was placed in a quartz tube and then vacuum-sealed. The quartz tube was placed in a tabletop muffle furnace and heat treated at 185 ° C. for 3 hours to obtain a sample.

After the heat treatment, the quartz tube containing the sample was subjected to a cooling treatment (air cooling) at room temperature in the atmosphere and crystallized to obtain glass ceramics. The molar composition of the obtained glass ceramics corresponded to x = 15 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ). The cooling rate of air cooling at this time was ^{1K · s -1 ~10K · s -1} , cooling time was 10 minutes.

[Example 2]
In the cooling treatment, glass ceramics were obtained in the same manner as in Example 1 except that the quartz tube containing the sample was put into water and subjected to a cooling treatment (water cooling). The molar composition of the obtained glass ceramics corresponded to x = 15 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ). The cooling rate of water cooling at this time was 10 K · s ⁻¹ to 10 ² K · s ⁻¹ , and the cooling time was 3 seconds (0.05 minutes).

[Comparative Example 1]
After putting 1 g of sulfide glass into a quartz tube, it is sealed in a heat treatment vessel made of SUS filled with Ar atmosphere and heat-treated in a desktop muffle furnace, and the sample in the heat treatment vessel is placed on the table as a cooling treatment. A glass ceramic was obtained in the same manner as in Example 1 except that it was cooled to room temperature in a muffle furnace. The molar composition of the obtained glass ceramics corresponded to x = 15 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ). In addition, the cooling rate in the furnace cooling at this time was about 10 ⁻² K · S ⁻¹ , and the cooling time was 60 minutes.

[Comparative Example 2]
The above-mentioned sulfide glass was used as a comparative sample without performing the synthesis step on the sulfide glass obtained in the amorphization step of Example 1.

  Table 1 shows a summary of cooling rates according to differences in heating temperature and cooling method in Examples 1-2 and Comparative Examples 1-2.

[Evaluation 1]
(XRD measurement)
Powder XRD measurement was performed on the samples for evaluation obtained in Examples 1 and 2 and Comparative Examples 1 and 2 using an XRD apparatus (Rigaku, RINT-UltimaIII). In addition, the said measurement measured the sample for evaluation in the jig on a dome, and measured it in the range of 2 (theta) = 10 degrees-60 degrees under the inert atmosphere of Ar gas. The result is shown in FIG.
As shown in FIG. 2, the intensity of the peaks appearing at 2θ = 20.2 ° and 23.6 ° is increased by performing the cooling process by air cooling or water cooling rather than cooling in the furnace. From this, by setting a predetermined cooling rate, the phase transition from the high Li ion conductive crystal phase to the stable phase or glass is suppressed, and the crystallinity (ratio) of the high Li ion conductive crystal phase is improved. it is conceivable that.

(Li ion conductivity measurement)
For the samples for evaluation obtained in Examples 1 and 2 and Comparative Examples 1 and 2, Li ion conductivity (normal temperature) was measured by the AC impedance method. Li ion conductivity was measured as follows. First, the glass ceramic powder or sulfide glass powder synthesized in each Example and Comparative Example was cold-pressed at a pressure of 4.3 ton / cm ² to obtain a pellet of φ = 11.99 mm and a thickness of about 500 μm. Was made. Next, the pellets were placed in an inert atmosphere container filled with Ar gas, and measurement was performed. For the measurement, Solartron (SI1260) manufactured by Toyo Corporation was used. Moreover, the measurement temperature was adjusted to 25 ° C. in a thermostatic bath. The result is shown in FIG.
From FIG. 3, the glass ceramics of Examples 1 and 2 subjected to the cooling treatment at a predetermined cooling rate are the glass ceramics of Comparative Example 1 subjected to the cooling treatment by cooling, and those of Comparative Example 2 where the synthesis process was not performed. Compared with sulfide glass, it showed high Li ion conductivity.

[Reference Example A1]
As starting materials, lithium sulfide (Li ₂ S, manufactured by Nippon Chemical Industry Co., Ltd.), diphosphorus pentasulfide (P ₂ S ₅ , manufactured by Aldrich) and lithium iodide (LiI, manufactured by Aldrich) were used. Next, Li ₂ S and P ₂ S ₅ were weighed so as to have a molar ratio of 75Li ₂ S · 25P ₂ S ₅ (Li ₃ PS ₄ , ortho composition). Next, LiI was weighed so that the LiI ratio was 14 mol%. The weighed starting materials were mixed in an agate mortar for 5 minutes, 2 g of the mixture was put into a planetary ball mill container (45 cc, made of ZrO ₂ ), dehydrated heptane (moisture content of 30 ppm or less, 4 g) was added, and ZrO _{2 was} further added. A ball (φ = 5 mm, 53 g) was charged, and the container was completely sealed. This container was attached to a planetary ball mill (P7 made by Fritsch), and mechanical milling was performed for 40 hours at a base plate rotation speed of 500 rpm. Then, heptane was removed by drying at 100 ° C. to obtain a sulfide glass.

0.5 g of the obtained sulfide glass was placed in a glass tube, and the glass tube was placed in a SUS sealed container. The sealed container was heat-treated at 190 ° C. for 10 hours to obtain glass ceramics. The molar composition of the obtained glass ceramic corresponds to x = 14 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ).

[Reference Examples A2 to A5]
The ratio of LiI was changed to x = 15, ₂₀ , 24, 25 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ), respectively, and the heating temperature was changed to a table. A glass ceramic was obtained in the same manner as in Reference Example A1, except that the temperature was changed to the temperature described in 2.

[Reference Examples B1 to B4]
The ratio of LiI was changed to x = 0, 10, 13, and 30 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ), respectively, and the heating temperature was expressed respectively. A glass ceramic was obtained in the same manner as in Reference Example A1, except that the temperature was changed to the temperature described in 2.

[Reference Examples B5 to B9]
Reference examples except that the ratio of LiI was changed to x = 0, 10, 20, 30, 40 in xLiI. (100-x) (0.75Li ₂ S.0.25P ₂ S ₅ ), respectively. A sulfide glass was obtained in the same manner as A1. Then, without performing heat treatment, sulfide glass was used as a comparative sample.

[Evaluation 2]
(X-ray diffraction measurement)
X-ray diffraction (XRD) measurement using CuKα rays was performed on the glass ceramics obtained in Reference Examples A1 to A5 and B2 to B4. For XRD measurement, RINT Ultimate III manufactured by Rigaku was used. The results are shown in FIGS. As shown in FIG. 4, it was confirmed that the glass ceramics obtained in Reference Examples A1 to A5 have peaks of a high Li ion conductive crystal phase at 2θ = 20.2 ° and 23.6 °. On the other hand, as shown in FIG. 5, in the glass ceramics obtained in Reference Examples B2 to B4, the peak of the high Li ion conductive crystal phase was not confirmed, and 2θ = 21.0 ° and 28.0 °. Only the peak of the low Li ion conductive crystal phase was confirmed. Further, from the obtained XRD chart, the peak intensity ratio (I _20.2 / I _21.0 ) of 2θ = 20.2 ° with respect to 2θ = 21.0 ° and 2θ = 23 with respect to 2θ = 21.0 ° A peak intensity ratio (I _23.6 / I _21.0 ) of .6 ° was determined. The results are shown in Table 3. In Reference Example A1, since the peaks at 2θ = 21.0 ° and 28.0 ° were not confirmed, the above peak intensity ratio was not obtained.

(Li ion conductivity measurement)
For the samples obtained in Reference Examples A1 to A5 and Reference Examples B1 to B9, Li ion conductivity (normal temperature) was measured by the AC impedance method. Li ion conductivity was measured using the same method as in the above-described example except that the pressure of the cold press was 4 ton / cm ² . The results are shown in Table 4 and FIG.

  As shown in Table 4 and FIG. 6, the glass ceramics obtained in Reference Examples A1 to A5 all exhibited high Li ion conductivity. This is considered to be because the samples obtained in Reference Examples A1 to A5 have a high Li ion conductive crystal phase having peaks of 2θ = 20.2 ° and 23.6 °. Reference Example B1 and Reference Example B5, Reference Example B2 and Reference Example B6, and Reference Example B4 and Reference Example B8 each have the same LiI content x. Thus, when the sulfide glass doped with LiI is heat-treated, the Li ion conductivity usually decreases. In contrast, the glass ceramics after heat treatment obtained in Reference Examples A1 to A5 exhibit a heterogeneous behavior that Li ion conductivity is improved by heat-treating sulfide glass. The degree was extremely high as glass ceramics.

The glass ceramic obtained in Reference Example A2 had a molar composition of xLiI · (100−x) (0.75Li ₂ S · 0.25P), similar to the glass ceramic obtained in Examples 1 and 2 described above. ₂ S ₅ ) indicates x = 15. In Examples 1 and 2, heat treatment was performed at a shorter heating time at a lower heating temperature than in Reference Example A2, but the obtained glass ceramic had Li ion conductivity equivalent to that of the glass ceramic of Reference Example A2. It was confirmed to have.
That is, it can be seen that by performing the cooling treatment at a predetermined cooling rate after the heat treatment, the crystallinity (ratio) of the high Li ion conductive crystal phase is improved, and the glass ceramic exhibits high Li ion conductivity.

Claims (4)

A raw material composition containing a sulfide of Li ₂ S, A (A is at least one of P, Si, Ge, Al, and B) and LiX (X is halogen) is made amorphous and sulfided An amorphization step of synthesizing the glass,
The sulfide glass is heated at a temperature equal to or higher than the crystallization temperature, cooled at a cooling rate of ¹ K · s ⁻¹ or higher, and in X-ray diffraction measurement using CuKα rays, 2θ = 20.2 °, 23.6 °. A synthesis step of synthesizing a glass ceramic having a peak at
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A method for producing a sulfide solid electrolyte material, wherein the ratio of LiX contained in the raw material composition, and the heating temperature and heating time in the synthesis step are adjusted so that the glass ceramic is obtained.   The method for producing a sulfide solid electrolyte material according to claim 1, wherein the ratio of LiX contained in the sulfide solid electrolyte material is more than 13 mol% and less than 30 mol%.   The method for producing a sulfide solid electrolyte material according to claim 1 or 2, wherein the heating temperature is in a range of 160 ° C to 200 ° C. Lithium having a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte material layer formed between the positive electrode active material layer and the negative electrode active material layer A method for producing a solid state battery comprising:
The sulfide solid electrolyte material obtained by the manufacturing method according to any one of claims 1 to 3, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte material layer. A method for producing a lithium solid state battery, characterized in that it is formed using

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