JP2018133227A - Method for manufacturing solid sulfide electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid sulfide electrolyte which can suppress the generation of hydrogen sulfide during exposure to the air, and the lowering of ion conductivity.SOLUTION: A method for manufacturing a solid sulfide electrolyte comprises: a ball-milling step of performing, by a ball-mill, a first mechanical milling process on a raw material composition including LiS, PS, LiI and LiBr to synthesize sulfide glass; a particle size-controlling step of adding BiSand an ether compound to the sulfide glass, and performing, by the ball-mill, a second mechanical milling process on the resultant mixture in such a condition that a total crushing energy E per unit weight, defined by a predetermined formula becomes smaller than that in the first mechanical milling process, thereby making the sulfide glass corpuscles while modifying the quality of the sulfide glass with BiS; and a baking step of baking the sulfide glass subjected to quality modification by BiSand atomization into corpuscles at a temperature equal to or higher than a crystallization temperature to obtain a solid sulfide electrolyte, which is a glass ceramic. In the method, these steps are implemented in this order.SELECTED DRAWING: Figure 2

Description

  The present application discloses a method for producing a sulfide solid electrolyte.

  A metal ion secondary battery having a solid electrolyte layer using a flame retardant solid electrolyte (for example, a lithium ion secondary battery, etc., hereinafter sometimes referred to as “all solid battery”) is used for ensuring safety. It has advantages such as easy to simplify the system.

  As a technique related to such an all solid state battery, for example, Patent Document 1 discloses a sulfide solid electrolyte material that contains Li, P, Bi and suppresses the generation of hydrogen sulfide that occurs when it comes into contact with moisture in the atmosphere. It is disclosed.

Patent Document 2 discloses a method for producing a Li ₂ S—P ₂ S ₅ —LiI—LiBr-based sulfide solid electrolyte containing at least Li ₂ S, P ₂ S _5, LiI, and LiBr. . Patent Document 3 includes a compound selected from Fe ₂ O ₃ , ZnO and Bi ₂ O ₃ in a Li ₂ S—P ₂ S ₅ -based sulfide solid electrolyte, and is intended to suppress the generation of hydrogen sulfide when exposed to the atmosphere. A sulfide solid electrolyte is disclosed.

JP 2014-154376 A Japanese Patent Laid-Open No. 2015-011898 International Publication No. 2011/118799

  In the sulfide solid electrolyte described in Patent Document 1, there is a problem that the Bi component is dispersed in the bulk of the sulfide fixed electrolyte to inhibit bulk ionic conduction and the ionic conductivity is lowered.

  Then, this indication makes it a subject to provide the sulfide solid electrolyte which can suppress generation | occurrence | production of hydrogen sulfide at the time of atmospheric exposure, and can suppress the fall of ion conductivity.

In order to solve the above problems, the present disclosure takes the following means.
In the present disclosure, a ball mill process for synthesizing a sulfide glass by performing a first mechanical milling using a ball mill on a raw material composition containing Li ₂ S, P ₂ S ₅ , LiI, and LiBr; Bi ₂ S ₃ and an ether compound are added, and the second mechanical milling using a ball mill is performed under the condition that the total grinding energy E per unit weight defined by the following formula (1) is smaller than that of the first mechanical milling. Performing a particle size adjustment step of atomizing the sulfide glass while reforming the sulfide glass with Bi ₂ S ₃ , and firing the sulfide glass modified and atomized with Bi ₂ S ₃ at a temperature equal to or higher than the crystallization temperature; And a firing step for obtaining a sulfide solid electrolyte, which is a ceramic, in this order.
E = 1/2 nmv ² / s · t Formula (1)
(N is the number of media (pieces), m is the weight (kg) per media, v is the speed of the media (m / s), s is (i) the weight of the raw material composition in the ball mill process (g) (Ii) In the particle size adjustment step, the weight (g) of sulfide glass and t is the processing time (seconds).

  According to the present disclosure, it is possible to provide a sulfide solid electrolyte capable of suppressing the generation of hydrogen sulfide during exposure to the atmosphere and suppressing the decrease in ionic conductivity.

FIG. 1A is a flow chart showing an example of a method for producing a sulfide solid electrolyte according to the prior art, and a diagram conceptually showing a bulk cross section of the sulfide solid electrolyte obtained by the production method. (B) is a flow chart showing an example of the manufacturing method of the present disclosure, and a diagram conceptually showing a bulk cross section of a sulfide solid electrolyte obtained by the manufacturing method. Is a graph showing measurement results of the initial conductivity and H _{2 S} evolution rate of Example 1 and Comparative Example 1.

  Hereinafter, the present disclosure will be described. In addition, the form shown below is an illustration of this indication and this indication is not limited to the form shown below. Unless otherwise specified, the notation “A to B” for the numerical values A and B means “A to B”. In this notation, when a unit is attached to only the numerical value B, the unit is also applied to the numerical value A.

FIG. 1A is a conceptual diagram showing a flowchart showing an example of a conventional method for producing a sulfide solid electrolyte and a bulk cross section of the sulfide solid electrolyte obtained by the production method. FIG. 2 is a diagram conceptually showing a flowchart showing an example of the manufacturing method of the present disclosure and a bulk cross section of a sulfide solid electrolyte obtained by the manufacturing method.
As shown in FIG. 1A, in the prior art, in order to suppress the generation of hydrogen sulfide during exposure to the atmosphere, Bi ₂ S ₃ is added from the raw material stage, and a sulfide glass is synthesized by a ball mill process. The sulfide solid electrolyte was synthesized through the adjustment process and the firing process. In the sulfide solid electrolyte obtained by such a method, Bi ₂ S ₃ diffuses into the bulk and exists in a uniformly dispersed state as shown in the right diagram of FIG. There was a problem that ₂ S ₃ hindered lithium ion conduction in the bulk and the ionic conductivity was lowered. In addition, if the amount of Bi ₂ S ₃ added is reduced to maintain ionic conductivity, the probability that the outermost surface is exposed increases, so that the water resistance decreases and a large amount of hydrogen sulfide is generated when exposed to the atmosphere. was there.
On the other hand, in the technique of the present disclosure, as shown in FIG. 1B, after the sulfide glass is synthesized from the raw material by the ball mill step (S1), Bi ₂ S ₃ is added to the sulfide glass, The sulfide solid electrolyte is synthesized through the adjustment step (S2) and the firing step (S3). According to the manufacturing method of the present disclosure, as shown in the right drawing of FIG. 1 (b), the selectively modified bulk surface by Bi ₂ S _3, it is concentrated Bi ₂ S ₃ in a bulk surface A sulfided solid electrolyte can be obtained. According to such a sulfide solid electrolyte, the bulk ion conductivity can be maintained, and the particle surface as a reaction site can be protected and the function can be enhanced, so that the generation rate of hydrogen sulfide is further reduced. be able to.
Hereinafter, the ball mill process (S1), the particle size adjustment process (S2), and the firing process (S3) included in the manufacturing method of the present disclosure will be described in order.

1. Ball mill process (S1)
In the ball mill process (hereinafter sometimes referred to as “S1”), first mechanical milling using a ball mill is performed on a raw material composition containing Li ₂ S, P ₂ S ₅ , LiI, and LiBr to obtain sulfide. It is a process of synthesizing glass.

(1) the raw material composition material composition in the present disclosure _is intended to contain _{Li 2 S, P 2 S 5} , LiI and LiBr. The ratio of each raw material in the raw material composition is not particularly limited. Among them, 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%, more preferably in the range of 72mol% ~78mol%, 74mol More preferably, it is in the range of% to 76 mol%. This is because a sulfide solid electrolyte having an ortho composition or a composition in the vicinity thereof can be obtained, and a sulfide solid electrolyte 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 disclosure, the crystal composition to which Li ₂ S is most added in the sulfide is referred to as an ortho composition. In the Li ₂ S—P ₂ S ₅ system, Li ₃ PS ₄ corresponds to the ortho composition. In the case of Li ₂ S—P ₂ S ₅ based sulfide solid electrolyte, 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: 25 on a molar basis. .

  Further, the total ratio of LiI and LiBr in the raw material composition is not particularly limited as long as a desired sulfide solid electrolyte can be obtained. For example, it is in the range of 10 mol% to 35 mol%. Preferably, it is in the range of 10 mol% to 30 mol%, more preferably in the range of 15 mol% to 25 mol%.

(2) First mechanical milling In S1, sulfide glass is synthesized by performing first mechanical milling using a ball mill on the raw material composition. Sulfide glass is a material synthesized by amorphizing the raw material composition. It is not only a strict “glass” in which periodicity as a crystal is not observed in X-ray diffraction measurement etc., but also amorphous by mechanical milling. It means all materials synthesized by synthesis. Therefore, even in the case where, for example, a peak derived from a raw material (LiI or the like) is observed in X-ray diffraction measurement or the like, any material synthesized by amorphization corresponds to sulfide glass. The first mechanical milling needs to be performed under conditions where the total grinding energy E per unit weight defined by the formula (1) described later is larger than the second mechanical milling in the particle size adjustment step (S2). The first mechanical milling may be performed wet or dry. Wet mechanical milling can be performed by introducing a liquid together with the raw material into a ball mill.

  The first mechanical milling is a process of making the material composition amorphous while imparting mechanical energy to the raw material composition. In the present disclosure, it is preferable to use a planetary ball mill from the viewpoint of obtaining a desired sulfide glass efficiently using a ball mill.

The various conditions of the first mechanical milling are set so that the raw material composition can be made amorphous and sulfide glass can be obtained. For example, when a planetary ball mill is used, raw materials and grinding balls are added to the container, and processing is performed at a predetermined rotation speed and time. Generally, the higher the number of rotations, the faster the generation rate of sulfide glass, and the longer the treatment time, the higher the conversion rate to sulfide glass. The rotation speed of the base plate when performing the planetary ball mill is preferably in the range of, for example, 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. In addition, examples of the material of the container and ball for pulverization used in the ball mill include ZrO ₂ and Al ₂ O ₃ . Moreover, the diameter of the ball for grinding | pulverization exists in the range of 1 mm-20 mm, for example.

  The liquid used when the first mechanical milling is performed in a wet manner is preferably an aprotic liquid that does not generate hydrogen sulfide by the reaction with the raw material composition. Aprotic liquids can be roughly 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.

  As an example of the nonpolar aprotic liquid, a linear or cyclic alkane that is liquid at room temperature (25 ° C.) can be given. The number of carbon atoms of the chain alkane is preferably 5 or more, for example, and the upper limit is not particularly limited as long as it is liquid at room temperature. Specific examples of the chain alkane include heptane. The chain alkane may have a branch. On the other hand, specific examples of cyclic alkanes include cyclopentane and the like.

  Other examples of nonpolar aprotic liquids include aromatic hydrocarbons such as toluene; chain ethers such as diethyl ether; cyclic ethers such as tetrohydrofuran; alkyl halides such as methyl chloride. And the like; esters such as ethyl acetate; and fluorine compounds such as heptane fluoride. In addition, the addition amount of the said liquid is not specifically limited, What is necessary is just the quantity which can obtain desired sulfide glass.

2. Particle size adjustment step (S2)
In the particle size adjusting step (hereinafter sometimes referred to as “S2”), Bi ₂ S ₃ and an ether compound are added to the sulfide glass, and the total grinding energy E per unit weight defined by the following formula (1) is This is a step of performing second mechanical milling using a ball mill under conditions smaller than those of the first mechanical milling and atomizing the sulfide glass while reforming the sulfide glass with Bi ₂ S ₃ .
E = 1/2 nmv ² / s · t Formula (1)
(N is the number of media (pieces), m is the weight (kg) per media, v is the speed of the media (m / s), s is the weight of the raw material composition in the (i) ball mill step (S1). (G), (ii) In the particle size adjustment step (S2), the weight (g) of sulfide glass, and t is the processing time (seconds).

In S2, it is preferable to prepare a mixture containing sulfide glass, Bi ₂ S ₃ and an ether compound. This mixture may contain a solvent if necessary. Further, this mixture is preferably a dispersion or slurry in which sulfide glass and Bi ₂ S ₃ are dispersed in an ether compound (and a solvent). On the other hand, an ether compound (and a solvent if necessary) is added to the mixture obtained by mixing sulfide glass and Bi ₂ S ₃ without preparing a mixed solution when performing the second mechanical milling. Also good.

(1) Bi ₂ S ₃
In S2, by adding Bi ₂ S ₃ to the sulfide glass, the sulfide glass modified by Bi ₂ S ₃ and atomized after S2 (hereinafter simply referred to as “Bi-modified microsulfide glass”) There is.) Further, it is possible after the firing step described later (S3), to obtain a sulfide solid electrolyte modified with Bi ₂ S _3.

The amount of Bi ₂ S ₃ added is preferably in the range of 0.5 mol% to 5 mol%, for example, with respect to the total 100 mol% of sulfide glass and Bi ₂ S ₃ . If the amount of Bi ₂ S ₃ added is too small, it may be difficult to suppress the generation of hydrogen sulfide during exposure to the atmosphere. If the amount of Bi ₂ S ₃ added is too large, the lithium ion conductivity of the solid electrolyte will be reduced. This is because there is a possibility that the performance may be lowered.

(2) Ether Compound The ether compound in the present disclosure is not particularly limited as long as it has an ether group (C—O—C). Among these, the ether compound preferably has two hydrocarbon groups bonded to an oxygen atom. This is because the reactivity with sulfide glass is low. Moreover, it is preferable that carbon number of the said hydrocarbon group is 10 or less, respectively. This is because if the carbon number is too large, it may be difficult to remove the ether compound by drying.

  The hydrocarbon group may be chain-like or cyclic. The hydrocarbon group is preferably a saturated hydrocarbon group or an aromatic hydrocarbon group. Examples of the hydrocarbon group include an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group, a cycloalkyl group such as a cyclopentyl group and a cyclohexyl group, and an aromatic hydrocarbon group such as a phenyl group and a benzyl group. Can be mentioned. Specific examples of the ether compound include dimethyl ether, ethyl methyl ether, dipropyl ether, dibutyl ether, cyclopentyl methyl ether, anisole and the like. The molecular weight of the ether compound is preferably in the range of 46 to 278, for example, and more preferably in the range of 74 to 186.

Further, the addition amount of the ether compound is preferably in the range of 0.01% by weight to 100% by weight, for example, 0.1% by weight to 100% by weight with respect to the total of sulfide glass and Bi ₂ S _3. % Is more preferable, and it is further preferable to be in the range of 1% by weight to 50% by weight. If the amount of the ether compound added is too small, granulation of the sulfide glass or Bi modified microsulfide glass in S2 and adhesion of the sulfide glass, Bi ₂ S ₃ or Bi modified microsulfide glass to the media This is because it is difficult to prevent the removal of the ether compound, and if the amount of the ether compound added is too large, it may be difficult to remove the ether compound.

(3) Solvent In the present disclosure, a solvent may be added in addition to the ether compound. By performing wet mechanical milling using a solvent as the second mechanical milling, granulation of the sulfide glass or Bi-modified microsulfide glass in S2, and sulfide glass to the medium, Bi ₂ S ₃ Alternatively, the Bi-modified microsulfide glass can be prevented from adhering. Examples of the solvent include alkanes such as heptane, hexane, and octane, and aromatic hydrocarbons such as benzene, toluene, and xylene. In addition, the addition amount of the said liquid is not specifically limited, What is necessary is just the quantity which can obtain desired Bi modified | denatured micro sulfide glass. Moreover, it is preferable that the said solvent is a thing with little water content. This is because generation of hydrogen sulfide (deterioration of Bi-modified microsulfide glass) can be suppressed.

(4) Second mechanical milling The second mechanical milling is a process of atomizing the sulfide glass while reforming it with Bi ₂ S ₃ . In the present disclosure, it is preferably performed using a ball mill, and from the viewpoint of efficiently obtaining a desired Bi-modified microsulfide glass, it is preferably performed using a planetary ball mill.

The various conditions of the second mechanical milling are set so that the sulfide glass can be modified by Bi ₂ S ₃ while being pulverized to a desired particle size. For example, when a planetary ball mill is used, a sulfide glass, Bi ₂ S ₃ , an ether compound, a solvent and a grinding ball are added, and the treatment is performed at a predetermined rotation speed and time. The ball diameter (φ) of the grinding balls is preferably in the range of 0.05 mm to 2 mm, for example, and more preferably in the range of 0.3 mm to 1 mm. If the ball diameter is too small, handling of the grinding balls is difficult and may cause contamination.If the ball diameter is too large, the sulfide glass is ground to a desired particle diameter, This is because it may be difficult to modify with Bi ₂ S ₃ . In addition, the rotation speed of the base plate when performing the planetary ball mill is, for example, preferably within a range of 100 rpm to 400 rpm, and more preferably within a range of 150 rpm to 300 rpm. Further, the treatment time when performing the planetary ball mill is, for example, preferably in the range of 0.5 hours to 5 hours, and more preferably in the range of 1 hour to 4 hours.

In S2, the second mechanical milling using the ball mill may be performed under the condition that the total grinding energy E per unit weight defined by the following formula (1) is smaller than that of the first mechanical milling. is important. By satisfying these conditions, the bulk surface of the sulfide glass can be selectively modified with Bi ₂ S ₃ while atomizing the sulfide glass, and Bi ₂ S ₃ is concentrated on the bulk surface. Quality microsulfide glass can be obtained.
In addition, the total grinding energy E per unit weight in S2 is preferably in the range of 50 J · sec / g to 450 J · sec / g, while satisfying such conditions, 100 J · sec / g to 300 J · sec / g. More preferably, it is within the range of g. This is because a more refined Bi-modified microsulfide glass can be obtained.
E = 1/2 nmv ² / s · t Formula (1)
In equation (1), n is the number of media (pieces), m is the weight (kg) per media, v is the speed of the media (m / s), and s is (i) in the ball mill step (S1). Weight (g) of raw material composition, (ii) In the particle size adjustment step (S2), the weight (g) of sulfide glass, and t is the treatment time (seconds). Formula (1) shows the total grinding energy when it is assumed that the kinetic energy of the media (for example, beads and balls) is all used for grinding the raw material composition or sulfide glass.
The media speed v can be determined as appropriate according to the type of media-type grinding process. For example, in the case of a planetary ball mill, the velocity v of the medium can be obtained by Expression (2).
v = dπRα / 1000/60 Formula (2)
In formula (2), d is the diameter (mm) of the pot (container), R is the number of rotations of the base plate (rpm), and α is the revolution ratio.

In the present disclosure, since an ether compound is used when performing the second mechanical milling, the ether compound functions as a dispersant for sulfide glass and Bi ₂ S ₃ , and sulfide glass, Bi ₂ S ₃ or Bi. Adhesion and granulation of the modified microsulfide glass can be prevented. As a result, Bi-modified microsulfide glass can be obtained with a high recovery rate. The recovery rate of the Bi-modified microsulfide glass is preferably 90% or more, and more preferably 95% or more, for example. The recovery rate can be calculated by (recovered amount of Bi-modified microsulfide glass) / (input amount of sulfide glass and Bi ₂ S ₃ ).

  In the present disclosure, it is preferable to have a drying step for removing the ether compound (and the solvent) after S2. It is necessary to perform drying at a temperature lower than the crystallization temperature. The drying time can be, for example, 10 minutes to 24 hours.

The average particle diameter (D ₅₀ ) of the Bi-modified microsulfide glass obtained by S2 is not particularly limited as long as it is smaller than that of the sulfide glass. For example, it is within the range of 0.1 μm to 5 μm. Is preferable, and it is more preferable that it is in the range of 0.5 μm to 4 μm. In addition, the said average particle diameter can be determined with a particle size distribution meter, for example.

3. Firing step (S3)
The firing step (hereinafter sometimes referred to as “S3”) involves firing a sulfide glass modified with Bi ₂ S ₃ and atomized (Bi-modified microsulfide glass) at a temperature equal to or higher than the crystallization temperature. This is a step of obtaining a sulfide solid electrolyte which is a glass ceramic.

  The crystallization temperature of the Bi-modified microsulfide glass can be determined by differential thermal analysis (DTA). The crystallization temperature of the Bi-modified microsulfide glass varies depending on the composition of the Bi-modified microsulfide glass, but is, for example, in the range of 130 ° C. or higher and 250 ° C. or lower. The time for firing at a temperature equal to or higher than the crystallization temperature is not particularly limited as long as the Bi-modified microsulfide glass is crystallized, and can be, for example, 5 minutes to 5 hours.

  The upper limit of the firing temperature in S3 is not particularly limited, but if the temperature is too high, the sulfide solid electrolyte, which is a glass ceramic, has a low Li ion conductivity (referred to as a low Li ion conduction phase). )) Is preferably generated at a temperature lower than the generation temperature of the low Li ion conductive phase. The generation temperature of the low Li ion conducting phase can be specified by X-ray diffraction measurement using CuKα rays. The generation temperature of the low Li ion conducting phase varies depending on the composition of the Bi-modified microsulfide glass, but is, for example, in the range of 230 ° C. or higher and 500 ° C. or lower.

Since the sulfide solid electrolyte obtained by the production method of the present disclosure is modified by Bi ₂ S _{3, the} water resistance is improved, and suppression of generation of hydrogen sulfide during exposure to the atmosphere can be suppressed. In addition, according to the present disclosure, Bi ₂ S ₃ is not uniformly dispersed in the bulk of the sulfide solid electrolyte and is concentrated on the bulk surface, so that it is difficult to inhibit bulk ion conduction. That is, according to the present disclosure, it is possible to achieve both improvement in water resistance and maintenance of ionic conductivity, both of which have been difficult in the past.

  In the sulfide solid electrolyte obtained by the production method of the present disclosure, specifically, maintaining ionic conductivity is preferably 50% or more, more preferably 70% or more, relative to the ionic conductivity of sulfide glass. It means that the ionic conductivity is more preferably 80% or more, particularly preferably 90% or more. In addition, the ionic conductivity of the sulfide solid electrolyte can be determined by, for example, an AC impedance method.

In the sulfide solid electrolyte obtained by the production method of the present disclosure, Li ₂ S—P ₂ S ₅ − in which the Bi existing ratio on the bulk surface is 0.0066 or more and 0.07 or less with respect to the total of Bi and P (Bi + P). A LiBr—LiI—Bi ₂ S ₃ -based sulfide solid electrolyte is preferable. Note that the ratio of Bi to the sum of Bi and P on the bulk surface (Bi + P) can be determined by, for example, X-ray photoelectric spectroscopy (XPS).

[Synthesis of sulfide solid electrolyte]
<Example 1>
(Ball mill process)
Li ₂ S (manufactured by Furuuchi Chemical Co., Ltd.) 0.5503 g, P ₂ S ₅ (manufactured by Aldrich) 0.8874 g, LiI (manufactured by Nichiho Chemical) 0.2850 g, LiBr (manufactured by High Purity Chemical Research Laboratory) 0.2773 g (Total 2 g of raw material composition) is put into a zirconia pot (capacity 45 ml) containing 5 mm diameter zirconia balls (total 53 g) as a medium, and then 4 g of dehydrated heptane (manufactured by Kanto Chemical Co., Ltd.) is put into the lid. did. This was set in a planetary ball mill apparatus (Fritsch P-7), and sulfide glass was obtained by mechanical milling (first mechanical milling) for 20 hours at a base plate rotation speed of 500 rpm.
(Granularity adjustment process)
1.9465 g of this sulfide glass and 0.0535 g of Bi ₂ S ₃ (manufactured by Aldrich) (amount corresponding to 0.5 mol% with respect to 100 mol% in total of sulfide glass and Bi ₂ S ₃ ) were used as media. The zirconia pot containing 3 mm diameter zirconia balls (total of 40 g) was charged again, 2 g of dibutyl ether (manufactured by Kishida Chemical) and 6 g of heptane were put on the lid. This is again set in the planetary ball mill apparatus, and is subjected to mechanical milling (second mechanical milling) for 20 hours at a base plate rotation speed of 200 rpm, whereby the sulfide glass modified and atomized by Bi ₂ S ₃ ( Bi-modified microsulfide glass) was obtained.
(Baking process)
The obtained Bi-modified microsulfide glass was baked by heating for 3 h at a temperature equal to or higher than the crystallization temperature in an inert atmosphere to obtain a sulfide solid electrolyte according to Example 1.

<Comparative Example 1>
Li ₂ S (manufactured by Furuuchi Chemical) 0.5356 g, P ₂ S ₅ (manufactured by Aldrich) 0.8636 g, LiI (manufactured by Nichibo Chemical) 0.2773 g, and LiBr (manufactured by High-Purity Chemical Laboratory) 0.2699 g And 0.055 g of Bi ₂ S ₃ (manufactured by Aldrich) (amount corresponding to 0.5 mol% with respect to the total of 100 mol% of each raw material and Bi ₂ S ₃ ) as media, 5 mm diameter zirconia balls (53 g in total) Was put in a zirconia pot (capacity 45 ml), and then 4 g of dehydrated heptane (manufactured by Kanto Chemical Co., Ltd.) was put on the lid. This was set in a planetary ball mill apparatus (Fritsch P-7), and sulfide glass was obtained by mechanical milling for 20 hours under the same conditions as in the ball mill process of Example 1.
2 g of this sulfide glass was again put into the zirconia pot containing 0.3 mm diameter zirconia balls (total of 40 g) as media, and 2 g of dibutyl ether (manufactured by Kishida Chemical) and 6 g of heptane were put on the lid. This was set again in the planetary ball mill apparatus and stirred for 20 hours under the same conditions as in the particle size adjustment step of Example 1 to obtain atomized sulfide glass.
The atomized sulfide glass was fired in the same manner as in Example 1 to obtain a sulfide solid electrolyte according to Comparative Example 1.

[Measurement item]
1. Bi surface abundance ratio By XPS, the Bi abundance ratio on the surface of the sulfide solid electrolyte obtained in Example 1 and Comparative Example 1 was determined as the ratio of Bi to the sum of Bi and P (Bi + P). The results are shown in Table 1.

2. Conductivity measurement 100 mg of the sulfide solid electrolyte obtained in Example 1 and Comparative Example 1 was weighed and subjected to a 4t press with a pellet molding machine to produce a conductivity cell. The initial conductivity was calculated from the resistance obtained by AC impedance measurement for the conductivity cell and the pellet thickness. The results are shown in FIG.

3. Measurement of H ₂ S generation amount A ₂ L sealed desiccator was prepared, and a container containing 10 cc of water, an H ₂ S sensor, and a circulation fan were placed in the container and left until the atmospheric temperature and humidity were stabilized. After the temperature and humidity have stabilized, place the petri dish containing 100 mg of the sulfide solid electrolyte powder obtained in Example 1 and Comparative Example 1 in a desiccator, and monitor the amount of generated H ₂ S with a sensor. Was used to calculate the H ₂ S generation rate. The results are shown in FIG.

From the comparison of the measurement results of Example 1 and Comparative Example 1 in Table 1 and FIG. 2, according to the manufacturing method of the present disclosure, it is possible to produce a sulfide solid electrolyte having Bi ₂ S ₃ concentrated on the surface. Was confirmed. Further, it was confirmed that the sulfide solid electrolyte can suppress generation of hydrogen sulfide when exposed to the atmosphere while maintaining high ionic conductivity.

Claims (1)

A ball mill step of performing a first mechanical milling using a ball mill on a raw material composition containing Li ₂ S, P ₂ S ₅ , LiI and LiBr to synthesize sulfide glass;
Bi ₂ S ₃ and an ether compound were added to the sulfide glass, and a ball mill was used under the condition that the total grinding energy E per unit weight defined by the following formula (1) was smaller than that of the first mechanical milling. A particle size adjusting step of performing second mechanical milling and atomizing the sulfide glass while reforming the sulfide glass with Bi ₂ S ₃ ;
Firing the sulfide glass modified and atomized with Bi ₂ S ₃ at a temperature equal to or higher than the crystallization temperature to obtain a sulfide solid electrolyte which is a glass ceramic;
A method for producing a sulfide solid electrolyte, comprising:
E = 1/2 nmv ² / s · t Formula (1)
(N is the number of media (pieces), m is the weight (kg) per media, v is the speed of the media (m / s), s is (i) the weight of the raw material composition in the ball mill process ( g), (ii) In the particle size adjusting step, the weight (g) of the sulfide glass and t is the processing time (seconds).