JP2024078896A - Method for producing SnS2 and its use - Google Patents

Abstract

[Problem] To provide a method for efficiently producing high-purity SnS2. [Solution] The method for producing SnS2 includes a filtration step in which a SnS2 dispersion containing SnS2, a solvent, and impurities is passed through a filter medium provided in a filtering means to form SnS2 aggregates on the filter medium, and a washing step in which a washing liquid is passed through the SnS2 aggregates formed on the filter medium to wash the SnS2 aggregates. [Selected Figure] Figure 1

Description

The present invention relates to a method for producing _SnS2 and a method for using it.

In recent years, _SnS2 (tin (IV) disulfide) has been attracting attention as a sintering aid and electrode catalyst material for CZTS compound semiconductors (compound semiconductors using Cu, Zn, Sn, and S instead of silicon) that can be used in solar cells. In addition, it has been proposed to use _SnS2 as a raw material for _{Li4SnS4 ,} which is preferably used as a solid electrolyte, and a method for producing _SnS2 has been studied.

Non-Patent Document 1 discloses a method for producing SnS2 by mixing an aqueous _Na2S solution and an aqueous _SnCl4 solution to obtain a _SnS2 dispersion containing _NaCl , and then washing the dispersion about five times using a centrifugal settler to remove NaCl.

Solid State Ionics, 2020, vol. 345, 115190

In the method described in Non-Patent Document 1, in order to improve the cleaning property, it is necessary to disintegrate the formed _SnS2 aggregates and disperse them in water. However, the present inventors have found that since _SnS2 after settling using a centrifugal settler forms strong aggregates, it cannot be dispersed by simply immersing it in water, and it is necessary to disintegrate the aggregates by applying a strong physical force, such as using a powerful disintegrator. Therefore, when mass-producing using the method described in Non-Patent Document 1, a process of disintegrating the aggregates is required, and it has been found that the method has a problem of low production efficiency.

Therefore, an object of the present invention is to provide a method for efficiently producing high-purity _SnS2 . Another object of the present invention is to provide a method for utilizing the _SnS2 obtained by the above method.

The present invention is a method for producing _SnS2 , comprising: a filtration step in which a _SnS2 dispersion containing SnS2, a solvent, and impurities is passed through a filter medium provided in a filtering means to form _SnS2 aggregates on the filter medium; and a washing step in which a washing liquid is passed through the _SnS2 aggregates formed on the filter medium to wash _{the SnS2} aggregates.

The present invention also relates to a method for using SnS ₂ , which comprises a step of contacting SnS ₂ produced by the above method with a sulfide containing an alkali metal to obtain a compound containing an alkali metal, tin, and sulfur.

According to the present invention, it is possible to efficiently produce high-purity SnS _2. Also, according to the present invention, it is possible to produce a compound containing an alkali metal, tin, and sulfur by using the SnS ₂ obtained by the above method.

FIG. 1 illustrates a reaction process according to one embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a filtration step according to one embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a filtration step according to one embodiment of the present invention. FIG. 4 is a schematic diagram illustrating a cleaning step according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing the structure of a filter medium portion of a filter press. FIG. 1 is a schematic diagram illustrating the manufacturing process of Na ₄ SnS ₄ and Na ₂ SnS ₃ according to one embodiment of the present invention.

<Method for producing _SnS2 >
The method for producing _SnS2 according to the present invention has the following steps: A filtration step in which a _SnS2 dispersion containing _SnS2 , a solvent, and impurities is passed through a filter medium provided in a filtering means to form _SnS2 aggregates on the filter medium; A washing step in which a washing liquid is passed through the _SnS2 aggregates formed on the filter medium to wash the _SnS2 aggregates. The method for producing _SnS2 according to the present invention may also have a drying step in which the washed _SnS2 aggregates obtained through the washing step are dried at a pressure preferably less than 5 kPa. Each step will be described in detail below.

[Filtration process]
In the filtration process, the _SnS2 dispersion containing _SnS2 , a solvent, and impurities is passed through a filter medium provided in the filtering means, whereby _SnS2 aggregates are formed on the filter medium.

( _SnS2 dispersion)
The _SnS2 dispersion contains at least _SnS2 , a solvent, and impurities. _{The SnS2} dispersion can be prepared by a known method. As an example, it can be prepared from _Na2S and _SnCl4 in a solvent based on the following reaction (see FIG. 1). Note that, instead of _Na2S , sulfides of other alkali metals such as _Li2S may be used, but _Na2S is preferred from the viewpoint of versatility.
_2Na2S + _SnCl4 → _SnS2 +4NaCl

Examples of the solvent include water; alcohols such as methanol and ethanol; water-soluble organic solvents such as acetone; and mixed solvents thereof. The solvent preferably contains water. Examples of water include pure water or ultrapure water. In addition, from the viewpoint of suppressing deterioration of the target product and a decrease in purity, the conductivity of the solvent (preferably water) is preferably less than 10 μS/cm, and the dissolved oxygen concentration in the solvent (preferably water) is preferably less than 10 mg-O/L. Each raw material used in the preparation of the SnS ₂ dispersion may be anhydrous or hydrated. Each raw material may be mixed in a solid form and then reacted by adding a solvent, or may be used in the reaction after adding a solvent to at least one of them to form a solution or dispersion, but it is preferable to use each raw material in the form of a solution dissolved in the above solvent. In this case, the concentration of each raw material in the solution is not particularly limited, but can be, for example, 1% by mass to 40% by mass.

The impurities contained in the _SnS2 dispersion prepared as described above are mainly, for example, NaCl, and also include unreacted raw materials (for example, _Na2S and _SnCl4 ), etc. In addition, when other raw materials are used instead of _Na2S and _SnCl4 as raw materials, salts derived from the other raw materials are obtained as impurities.

For example, when a Na ₂ S aqueous solution and a SnCl ₄ aqueous solution are mixed, the resulting SnS ₂ precipitates and disperses in the dispersion, and the impurity NaCl is dissolved in the aqueous solution. In the filtration process, the SnS ₂ dispersion thus obtained is passed through a filter provided in a filtering means. As a result, the SnS ₂ dispersed in the dispersion is deposited on the filter, forming SnS ₂ aggregates. Meanwhile, most of the impurities, including NaCl and the like, dissolved in the dispersion are discharged as filtrate. The concentration of SnS ₂ in the SnS ₂ dispersion is not particularly limited and can be set appropriately, for example, 1% by mass to 15% by mass.

(Filtering Means)
The filtering means is not particularly limited, and known means such as a centrifugal filter using heavy pressure filtration, a drum filter using vacuum filtration, and a filter press using pressure filtration can be used. Among these, in the present invention, it is preferable to use a filter press from the viewpoint of cleaning efficiency. When a filter press is used, the aggregates are less likely to break during filtration, and cleaning properties can be improved. When a filter press is used as the filtering means, examples of the filter material include filter cloth. When a drum filter is used as the filtering means, examples of the filter material include filter cloth. When a centrifugal filter is used as the filtering means, examples of the filter material include filter cloth and metal filters. In this specification, a centrifugal filter is a rotating body (basket) having a filter material and holes through which a liquid passes. In a centrifugal filter, a solid and a liquid in a processing liquid are separated by passing a processing liquid (dispersion liquid, etc.) through a filter material installed inside a basket having holes in the wall surface, and further, solid-liquid separation can be performed by discharging moisture smaller than the mesh of the filter material through the holes in the basket. On the other hand, the centrifugal sedimentation machine used in Non-Patent Document 1 has a rotor (basket) that does not have a filter medium (filter) or holes through which liquid passes, and performs solid-liquid separation or liquid-liquid separation without using a filter medium by forming and settling a heavy liquid (liquid or crystals (cake)) on the wall surface of the rotor and forming a light liquid thereon.

If the thickness of the _SnS2 aggregate formed on the filter medium in the filtration process is too large, the efficiency of the cleaning liquid in the cleaning process described below will decrease. Therefore, the thickness of the _SnS2 aggregate formed in the filtration process is preferably adjusted so that the thickness of the _SnS2 aggregate after cleaning is 1 to 100 mm in the vertical direction from the filtration surface of the filter medium, as described below. The difference between the _SnS2 aggregate after cleaning and the _SnS2 aggregate before cleaning (the _SnS2 aggregate formed in the filtration process) is the degree to which impurities have been removed, so the thickness of the _SnS2 aggregate after cleaning can be considered to be almost the same as the thickness of the _SnS2 aggregate before cleaning. If it is expected that the thickness of the _SnS2 aggregate after cleaning will exceed the above range, the _SnS2 dispersion can also be divided and filtered.

2 is a schematic diagram showing a filtration step according to one embodiment of the present invention. In this embodiment, the filtration step is carried out, for example, as follows. Step 1: Using a pump P, the _SnS2 dispersion is circulated or passed through the filter material 2 from the stock solution tank 1 storing the _SnS2 dispersion, forming _SnS2 aggregates on the filter material. In addition, a stirrer (not shown) is provided in the stock solution tank 1 storing the _SnS2 dispersion. In addition, the circulated or passed through the _SnS2 dispersion can be controlled by using a valve (not shown). When filtering the _SnS2 dispersion using a filter press, immediately after passing the _SnS2 dispersion through the filter material, a part of the _SnS2 dispersion (before forming the _SnS2 aggregates) in the _SnS2 dispersion may pass through the filter material (filter cloth) and flow to the filtrate side. This is because the mesh of the filter cloth provided in the filter press is slightly larger than the particle size of the _SnS2 dispersion. In the process of proceeding with the filtration, the particles of the _SnS2 dispersion gradually clog the mesh of the filter cloth, and finally, _SnS2 aggregates are formed on the filter material. Therefore, by circulating the _SnS2 dispersion, it is possible to recover _{the SnS2} that flowed out into the filtrate at the beginning of the filtration process. The _SnS2 dispersion may be passed through in one pass or through circulation, but the method of circulating the _SnS2 dispersion can recover almost the entire amount of the SnS2 aggregates. Step 2: After the recovery of the _SnS2 aggregates is completed, the filtrate (mainly containing NaCl) is recovered in the waste tank 3 and discharged as waste liquid. The filtrate may be discharged without passing through the filtration means by using a pipe not shown.

3 is a schematic diagram showing a filtration step according to another embodiment of the present invention. In this embodiment, the filtration step is carried out, for example, as follows. Step 1: The _SnS2 dispersion is passed from the stock solution tank 1 storing the _SnS2 dispersion onto the filter medium 2 in one pass using the pump P1, thereby forming _SnS2 aggregates on the filter medium. At this time, the filtrate is stored in the subsequent filtrate tank 4. In addition, a stirrer (not shown) is provided in the stock solution tank 1 storing the _SnS2 dispersion and in the filtrate tank 4 storing the filtrate. At this stage, a small amount of _SnS2 dispersion remains in the stock solution tank 1 and the filtrate tank 4. Step 2: Next, the filtrate is sent from the filtrate tank 4 to the stock solution tank 1 using the pump P2, and the remaining _SnS2 dispersion is collected in the stock solution tank 1. Step 3: The _SnS2 recovery liquid containing the recovered _SnS2 dispersion is circulated or passed through the filter medium 2 from the raw liquid tank 1 using the pump P1, and the _SnS2 dispersion is recovered as _SnS2 aggregates. According to this method, although the equipment is increased by adding steps 1 and 2, it is possible to recover almost all of the _SnS2 aggregates, and the filtration efficiency can be improved compared to the method shown in Figure 2. The circulation or one-pass passing of the _SnS2 recovery liquid can be controlled by using a valve not shown.

[Cleaning process]
Impurities such as NaCl are discharged as filtrate in the filtration process, but impurities such as NaCl still remain in the _SnS2 aggregates formed on the filter medium. Therefore, as shown in FIG. 4, in the washing process, the _SnS2 aggregates on the filter medium are washed by passing _{a washing liquid through them. This results in SnS2 aggregates} after washing with reduced impurities. The washing liquid may be supplied from the stock tank that contained the _SnS2 dispersion in the filtration process, or may be supplied from a separate pipe. In addition, the waste liquid may be stored in the filtrate tank or waste liquid tank in the filtration process, or may be discharged from a separate pipe.

Here, in the method described in Non-Patent Document 1, the following steps are carried out using a centrifugal settler to remove NaCl contained in the _SnS2 dispersion, thereby obtaining the target _SnS2 .
1. Place the _SnS2 dispersion in a centrifuge tube equipped with a centrifugal sedimenter;
2. Place the centrifuge tube in a centrifuge and rotate at 3,000 to 10,000 rpm for 5 minutes;
3. Discard the supernatant containing NaCl (leaving _SnS2 aggregates at the bottom of the centrifuge tube);
4. Add water to the centrifuge tube and immerse the _SnS2 aggregates;
5. The water in which the _SnS2 aggregates obtained in step 4 have been immersed is used as the _SnS2 dispersion in step 1, and steps 1 to 4 are repeated (about 5 times in total).

As described above, in the method described in Non-Patent Document 1, in steps 2 and 3, the _SnS2 aggregates are washed using a centrifugal settler, so the _SnS2 aggregates become strong lumps, and by simply repeating washing, such strong _SnS2 aggregates are not sufficiently dispersed, making it difficult to sufficiently wash out the impurities incorporated in the _SnS2 aggregates. Therefore, in order to remove the impurities incorporated in the _SnS2 aggregates, it is necessary to disintegrate the _SnS2 aggregates using, for example, an ultrasonic homogenizer, and then disperse them again in the dispersion liquid. On the other hand, in the present invention, the _SnS2 dispersion liquid is preferably filtered using a filter press, and the _SnS2 aggregates formed on the filter material are washed on the filter material. In the present invention, it is possible to reduce and remove impurities in the _SnS2 aggregates without going through a step of disintegrating the _SnS2 aggregates, and _SnS2 with high purity can be efficiently produced. That is, the washing step according to the present invention preferably does not include a step of disintegrating the _SnS2 aggregates.

(Cleaning solution)
The cleaning liquid is not particularly limited as long as it can remove impurities from the _SnS2 aggregates, and examples thereof include water; alcohols such as methanol and ethanol, water-soluble organic solvents such as acetone; and mixed solvents thereof. The cleaning liquid may be the same as the solvent contained in the _SnS2 dispersion, or may be different. However, from the viewpoint of simplifying the manufacturing method, the cleaning liquid is preferably the same as the solvent contained in the _SnS2 dispersion, and preferably contains water. Examples of water include pure water and ultrapure water. In addition, from the viewpoint of suppressing the deterioration of the target product and the decrease in purity, the electrical conductivity of the cleaning liquid (preferably water) is preferably less than 10 μS/cm, and the dissolved oxygen concentration in the cleaning liquid (preferably water) is preferably less than 10 mg-O/L.

The method of passing the cleaning liquid through the SnS ₂ aggregates on the filter medium is not limited. For example, a method of storing the cleaning liquid in a tank and pumping the cleaning liquid from the tank to the SnS ₂ aggregates, or a method of pressurizing the tank with an inert gas or the like to send the cleaning liquid to the SnS ₂ aggregates, etc. can be used. The flow rate of the cleaning liquid is not particularly limited as long as it can remove impurities from the SnS ₂ aggregates, and can be determined in consideration of pressure loss and cleaning time. The flow rate of the cleaning liquid is not particularly limited as long as it can remove impurities from the SnS ₂ aggregates, and can be determined in consideration of the purity of SnS ₂ and cleaning time. It is preferable to constantly measure the impurity concentration in the outflowing cleaning liquid during the flow of the cleaning liquid. The method of constantly measuring the impurity concentration in the outflowing cleaning liquid is not particularly limited. For example, a method of constantly measuring the impurity concentration in the outflowing cleaning liquid by connecting a conductivity meter to a pipe and measuring it can be mentioned.

In the present invention, the washing step may be performed only once or may be performed repeatedly. However, according to the present invention, impurities can be sufficiently removed from the _SnS2 aggregates by performing the washing step once.

The thickness of the _SnS2 aggregates after washing obtained through the washing process is preferably 1 to 100 mm in the vertical direction from the filtration surface of the filter medium from the viewpoint of washability. The filter medium may have not one but multiple filtration surfaces. When the filter medium has multiple filtration surfaces, it is preferable that the maximum thickness of the thicknesses in the vertical direction from the multiple filtration surfaces is in the above range. FIG. 5 is a schematic diagram showing the structure of the filter medium (filter cloth) part of the filter press. In FIG. 5, there is a slit-shaped groove (not shown) between the filter plate and the filter cloth, and the filtrate (washing liquid) flows through that part. Therefore, in the filter medium shown in FIG. 5, the left and right sides of the cake ( _SnS2 aggregates) on the paper surface are the filtration surfaces, and the thickness in the vertical direction from the filtration surface corresponds to the width of the cake (d in FIG. 5).

[Drying process]
The method for producing _SnS2 according to the present invention may have a drying step for drying the _SnS2 aggregate after washing obtained through the washing step. By carrying out the drying step, the solvent in the _SnS2 aggregate is removed, and _SnS2 can be isolated. The specific operation of the drying step is not particularly limited, and one or more of the conventionally known methods can be applied in combination. Specific examples of the drying method include vacuum drying (including freeze drying) and spray drying. Among these, vacuum drying is preferred. From the viewpoint of suppressing the deterioration of _SnS2 , the drying step is preferably carried out at a pressure of less than 5 kPa. In addition, the drying may be carried out under reduced pressure while heating, and in that case, the heating temperature can be, for example, 40 ° C to 80 ° C. In either case, it is preferable to set appropriate conditions according to the type of solvent contained in the _SnS2 aggregate.

The SnS ₂ obtained by the method according to the present invention can be identified, for example, by elemental analysis such as X-ray fluorescence analysis, X-ray diffraction measurement, and infrared absorption spectrum or Raman spectrum measurement.

<How to use _SnS2 >
The method for using SnS ₂ according to the present invention includes a step of obtaining a compound containing an alkali metal, tin, and sulfur by contacting SnS ₂ produced by the above method with a sulfide containing an alkali metal. That is, the method for using SnS ₂ according to the present invention can be said to be a method for producing a compound containing an alkali metal, tin, and sulfur from SnS ₂ and a sulfide containing an alkali metal. As the sulfide containing an alkali metal, a sulfide of an alkali metal is preferable, and as the alkali metal, Na, Li, and K are preferable. As the sulfide of an alkali metal, for example, Li ₂ S, Na ₂ S, and K ₂ S can be mentioned.

The method of contacting SnS ₂ with a sulfide containing an alkali metal is not particularly limited. SnS ₂ and a sulfide containing an alkali metal may be mixed in solid form and reacted by adding a solvent, or at least one of them may be used in the reaction in the form of a solution by adding a solvent. Examples of the solvent include water; alcohols such as methanol and ethanol, water-soluble organic solvents such as acetone; and mixed solvents thereof. The solvent may be the same as or different from the solvent contained in the SnS ₂ dispersion used in the SnS ₂ production method. However, when SnS ₂ is produced by the SnS ₂ production method and the obtained SnS ₂ is used as it is in this method, the solvent used in this method is preferably the same as the solvent contained in the SnS ₂ dispersion, and preferably contains water. Examples of water include pure water or ultrapure water. In addition, from the viewpoint of suppressing the deterioration of the target product and the decrease in purity, the conductivity of the solvent (preferably water) is preferably less than 10 μS/cm, and the dissolved oxygen concentration in the solvent (preferably water) is preferably less than 10 mg-O/L.

Examples of compounds containing an alkali metal, tin, and sulfur obtained by contacting SnS ₂ with a sulfide containing an alkali metal include the following compounds: compounds consisting of sodium, tin, and sulfur (e.g., Na ₄ SnS ₄ , Na ₂ SnS ₃ ), compounds consisting of lithium, tin, and sulfur (e.g., Li ₄ SnS ₄ , Li ₂ SnS ₃ ), etc. The obtained compounds containing an alkali metal, tin, and sulfur can be identified by, for example, elemental analysis such as X-ray fluorescence analysis, X-ray diffraction measurement, and infrared absorption spectrum or Raman spectrum measurement.

(Production _{of Na4SnS4} )
Hereinafter, as an embodiment, a case where Na ₄ SnS ₄ is produced by contacting SnS ₂ with Na ₂ S as a sulfide containing an alkali metal will be described with reference to FIG. 6. First, a Na ₂ S aqueous solution in which Na ₂ S is dissolved in water is prepared in a tank. The concentration of Na ₂ S in the Na ₂ S aqueous solution is not particularly limited and can be set appropriately, for example, 1% by mass to 20% by mass. Next, the Na 2 S aqueous solution is passed through the washed SnS ₂ aggregates on the filter medium produced by the method according to the present invention so that the molar ratio of SnS ₂ to Na ₂ S is 1:2. As a result, Na ₄ SnS ₄ is produced based on the following reaction formula. The resulting Na ₄ SnS ₄ aqueous solution is pale yellow. This reaction can be carried out, for example, directly in the filter press device in which _the SnS ₂ aggregates were produced.
_SnS2 + _{2Na2S → Na4SnS4}

In addition, Na ₄ SnS ₄ is produced by the above reaction, but it is presumed that Na ₂ SnS ₃ is actually produced until the molar ratio of SnS ₂ to Na ₂ S becomes 1:1. Since Na ₂ SnS ₃ is soluble in water, when SnS ₂ on the filter reacts with Na ₂ S to produce Na ₂ SnS ₃ , the Na ₂ SnS ₃ flows toward the filtrate. Therefore, when passing an amount of Na ₂ S aqueous solution that makes the molar ratio of SnS ₂ to Na ₂ S 1:2 through the SnS ₂ aggregates, it is preferable to circulate the filtrate (the filtrate is stored and circulated in the tank that contained the Na ₂ S aqueous solution) and use it again for the reaction with SnS ₂ (circulation liquid passing). As a result, the previously produced Na ₂ SnS ₃ is converted to Na ₄ SnS ₄ , and finally, when the molar ratio of consumed SnS ₂ to Na ₂ S becomes 1:2, Na ₄ SnS ₄ is obtained as the main product. In the apparatus shown in FIG. 6, the circulation of the filtrate can be appropriately controlled by using a valve (not shown).

It is also preferable to manufacture Na ₄ SnS ₄ in two steps according to the procedure shown below. First, in the first step, the Na ₂ S aqueous solution in the tank is circulated through the washed SnS ₂ aggregates on the filter medium so that the molar ratio of SnS ₂ to Na ₂ S is 1:1. As a result, a circulating liquid containing Na ₂ SnS ₃ as the main component is obtained in the tank in which the Na ₂ S aqueous solution was contained. Next, in the second step, the generated Na ₂ S is reacted again with the circulating liquid in the tank in an amount such that the molar ratio of Na ₂ SnS ₃ to Na ₂ S is 1:1. As a result, Na ₄ SnS ₄ is obtained from Na ₂ SnS ₃ .

(Production _{of Na2SnS3} )
In the above-mentioned production of Na ₄ SnS ₄ , Na ₂ S can be obtained by using _an amount of Na ₂ S such that the molar ratio of SnS ₂ to Na ₂ S is 1:1. That is, first, a Na ₂ S aqueous solution in which Na ₂ S is dissolved in water is prepared in a tank. Then, as shown in FIG. 6, the Na 2 S aqueous solution is circulated through the washed SnS ₂ aggregates on the filter medium produced by the method according to the present invention so that the molar ratio of SnS ₂ to Na ₂ S is 1:1. As a result, a Na ₂ SnS ₃ aqueous solution is obtained in the tank in which the Na ₂ S aqueous solution was contained _{. The obtained Na 2 SnS 3} aqueous solution is pale yellow.

In addition, when Na ₂ S is reacted with SnS ₂ in an amount exceeding 1:1 in molar ratio, Na ₄ SnS ₄ is generated _. Therefore, in the case of producing Na ₂ SnS ₃ , the amount of Na ₂ S used relative to SnS ₂ may be less than the theoretical amount of 1 molar amount in order to reliably suppress the production of Na ₄ SnS 4, and the reaction may be carried out so that unreacted SnS ₂ remains on the filter medium. Here, not limited to the production of Na ₂ SnS ₃ , immediately after passing a Na ₂ S aqueous solution through the washed SnS ₂ aggregates on the filter medium, the SnS ₂ aggregates may collapse and some of them may return to particles, passing through the filter medium and flowing into the filtrate. Therefore, particularly when the amount of Na ₂ S used relative to SnS ₂ is less than 1 molar amount, the unreacted SnS ₂ that flows into the filtrate may be recovered by filtering using a MF (microfilter) or UF (ultrafiltration) or the like.

As mentioned above, when the amount of _Na2S used relative to _SnS2 is adjusted to be less than the theoretical amount, unreacted _SnS2 aggregates remain on the filter medium. In this state where unreacted SnS2 aggregates remain, _{the SnS2 dispersion} in the _SnS2 manufacturing method can be passed through and the washing process (NaCl removal process) can be repeated. In addition, the unreacted _SnS2 aggregates remaining on the filter medium can be washed with a dissolving solution such as a _Na2S aqueous solution.

The above-mentioned manufacturing method of Na ₄ SnS ₄ and Na ₂ SnS ₃ can be similarly applied to the manufacturing of other compounds containing alkali metals, tin, and sulfur. The compound containing alkali metals, tin, and sulfur obtained in this manner can be used as a raw material for solid electrolytes, such as Li ₄ SnS ₄ , LGPS (lithium germanium phosphorus sulfur)-based solid electrolytes, and thio-LISICON.

[Example 1]
(Filtration process)
Na ₂ S.9H ₂ O was dissolved in water (dissolved oxygen concentration: less than 10 mg-O/L, electrical conductivity: less than 10 μS/cm) to prepare a 12 mass% Na ₂ S aqueous solution (A). Next, SnCl _{4.5H 2} O was dissolved in water (dissolved oxygen concentration: less than 10 mg-O/L, electrical conductivity: less than 10 μS/cm) to prepare a 28 mass% SnCl ₄ aqueous solution (B).
A was stirred while cooling, and B was added dropwise in small amounts and mixed until the molar ratio of Na ₂ S in A:SnCl ₄ in B became 2:1, thereby obtaining 8 mass% SnS ₂ dispersion (C) containing NaCl as an impurity.
C was passed through a filter press device with a filtration area of 0.1 ^m2 to deposit _SnS2 particles on the filter medium, thereby forming a pre-washed _SnS2 aggregate (D). The _SnS2 dispersion (C) was passed through the device shown in Figure 2 in a one-pass manner.
(Washing process)
Water (dissolved oxygen: less than 10 mg-O/L, conductivity: less than 10 μS/cm) was passed through D for 3 hours, and then squeezed to obtain washed _SnS2 aggregate (E). The thickness (d in FIG. 5) of the obtained washed _SnS2 aggregate (E) in the vertical direction from the filtration surface of the filter medium was 10 mm.

(analysis)
E was removed from the filter press device, water (dissolved oxygen: less than 10 mg-O/L, conductivity: less than 10 μS/cm) was added, and the mixture was disintegrated with an ultrasonic homogenizer (product name: LUH300, manufactured by Yamato Scientific Co., Ltd.) to obtain an 8 mass % _SnS2 dispersion (F) with a reduced amount of NaCl. F was filtered using a hydrophilic PVDF membrane filter with a pore size of 0.1 μm to prepare a filtrate (G), and the concentrations of Na and Cl in the filtrate (G) were analyzed using capillary electrophoresis.

[Example 2]
A washed _SnS2 aggregate (E) was obtained in the same manner as in Example 1.
E was dried at 80 ° C. and reduced pressure of less than 2 kPa to produce a dried _SnS2 body (H) (drying process).

[Example 3]
A washed _SnS2 aggregate (E) was obtained in the same manner as in Example 1.
E was dried at 80 ° C. and 7 kPa under reduced pressure to produce a dried _SnS2 body (H) (drying process).

[Example 4]
A washed _SnS2 aggregate (E) was obtained in the same manner as in Example 1.
A was prepared in an amount of A to give a molar ratio of E:Na ₂ S in A=1:2, and the filtrate was passed through the filter again in a circulating manner as shown in Fig. 6 to react SnS ₂ with Na ₂ S. In this way, a 15-20 mass% Na ₄ SnS ₄ aqueous solution (I) was prepared.

[Example 5]
A washed _SnS2 aggregate (E) was obtained in the same manner as in Example 1.
A was prepared in an amount of A to give a molar ratio of E:Na ₂ S in A=1:1, and the filtrate was passed through the filter again in a circulating manner as shown in Fig. 6 to react SnS ₂ with Na ₂ S. In this way, a 20-30 mass% Na ₂ SnS ₃ aqueous solution (J) was prepared.

[Comparative Example 1]
In the same manner as in Example 1, an 8% by mass _SnS2 dispersion (C) containing NaCl was prepared.
C was placed in a centrifuge tube and rotated at 3000 to 10000 rpm for 5 minutes using a centrifugal settler to settle the _SnS2 aggregates at the bottom of the centrifuge tube. The supernatant was discarded to obtain washed _SnS2 aggregates (E) (washing step).
Water (dissolved oxygen: less than 10 mg-O / L, conductivity: less than 10 μS / cm) was added to E, and the mixture was crushed with an ultrasonic homogenizer in the same manner as in Example 1 to obtain an 8 mass% _SnS2 dispersion (F) with a reduced amount of NaCl (crushing process).
F was filtered using a hydrophilic PVDF membrane filter having a pore size of 0.1 μm to prepare a filtrate (G). In the same manner as in Example 1, the concentrations of Na and Cl in the filtrate (G) were analyzed.

[Comparative Example 2]
The _SnS2 dispersion (F) obtained in Comparative Example 1 was placed in a centrifuge tube again, and the washing process using a centrifugal settler and the disintegration process using an ultrasonic homogenizer were repeated four times (a total of five disintegration processes were performed), to obtain an 8 mass% _SnS2 dispersion (F) with a reduced amount of NaCl.
F was filtered through a hydrophilic PVDF membrane filter having a pore size of 0.1 μm to prepare a filtrate (G), and the concentrations of Na and Cl in the filtrate (G) were analyzed in the same manner as in Example 1. In this Comparative Example 2, the total number of times of the crushing step was 5, but the last crushing step was for analyzing the concentrations of Na and Cl, so the number of times of the crushing step until the washed _SnS2 aggregate (E) was obtained was 4.

[Comparative Example 3]
A washed _SnS2 aggregate (E) was obtained by the same method as in Comparative Example 2 (washing step: 5 times).
E was mixed with A in a beaker until the molar ratio of E:Na ₂ S in A was 1:2, to prepare a 15 to 20 mass % Na ₄ SnS ₄ aqueous solution (I).

Table 1 shows the state of matter, hardness, color and _{thickness from the filtration surface, metallic luster, turbidity, and Na and Cl concentrations for the washed SnS2 agglomerate (E), filtrate (G), dried SnS2 (H), Na4SnS4 aqueous solution (I), and Na2SnS3 aqueous solution ( J} ) obtained in the examples and comparative examples.

As shown in Table 1, the purity of the washed SnS ₂ aggregate (E) can be relatively compared by comparing the concentrations of Na and Cl in the filtrate (G) obtained in Example 1, Comparative Example 1, and Comparative Example 2. From the comparison between Example 1 and Comparative Example 1, it can be seen that the manufacturing method of SnS ₂ according to the present invention is a manufacturing method with overwhelmingly superior cleaning properties compared to the conventional technology (Comparative Example 1). Furthermore, from the comparison between Example 1 and Comparative Example 2, it can be seen that according to the present invention, the amount of impurities can be reduced to 1/5 to 1/10 or less compared to the case where a process of crushing aggregates is performed every time washing is performed in the method described in Non-Patent Document 1, and the present invention is a method that can manufacture SnS ₂ with a higher purity than the conventional technology. If an attempt is made to manufacture SnS ₂ having the same purity as the present invention based on the conventional technology method, the five washing steps performed in Comparative Example 2 must be repeated at least six times, and the manufacturing efficiency will be further reduced.

In addition, from the comparison between Example 2 and Example 3, it can be seen that the state of the dried _SnS2 (H) changes significantly depending on the pressure during drying. That is, the H obtained in Example 2 was a yellowish brown dried solid, but the H obtained in Example 3 was a blackish brown dried solid with metallic luster, and the _SnS2 was partially altered during the drying process. Although the cause is unclear, it is speculated that in Example 2, the reaction between _SnS2 and oxygen was reduced by further reducing the pressure during drying, and the alteration of _SnS2 was suppressed. In any case, it can be seen that it is also possible to produce a dried _SnS2 with high purity by using the present invention.

From the comparison between Example 4 and Comparative Example 3, it can be seen that the SnS ₂ produced by the method according to the present invention can be used to produce Na ₄ SnS _4, which is a compound containing alkali metals, tin, and sulfur, in the same way as in the conventional technology. The Na ₄ SnS ₄ aqueous solutions (I) obtained in Example 4 and Comparative Example 3 are different in color, etc., and therefore contain essentially the same compound (Na ₄ SnS ₄ ), although the purity is different. That is, it can be seen that the SnS ₂ produced by the method of the present invention and the SnS ₂ produced by the conventional technology are the same compound except for the purity. However, as is clear from the presence or absence of a crushing step and the number of times, according to the present invention, high purity SnS ₂ can be efficiently produced without crushing the SnS ₂ aggregates, which was a problem in the conventional technology.

Furthermore, as shown in Example 5, it was found that the _SnS2 produced by the method according to the present invention can also be used to produce _Na2SnS3 by reacting with _Na2S in a molar ratio different from that in Example _{4. The Na2SnS3 obtained} by the present invention can be used as a raw material for solid _{electrolytes, similar to Na4SnS4 .}

The present invention includes the following configurations.
[Configuration 1]
A filtration process in which a _SnS2 dispersion containing _SnS2 , a solvent, and impurities is passed through a filter medium provided in a filtering means to form _SnS2 aggregates on the filter medium;
A washing step of passing a washing liquid through the _SnS2 aggregates formed on the filter medium to wash the _SnS2 aggregates;
A method for producing _SnS2 having the formula:
[Configuration 2]
_{2. The method of claim 1} , wherein the solvent comprises water.
[Configuration 3]
The method for producing _SnS2 according to configuration 1 or 2, wherein the conductivity of the solvent is less than 10 μS/cm.
[Configuration 4]
The method for producing _SnS2 according to any one of configurations 1 to 3, wherein the thickness of the _SnS2 aggregate after washing obtained through the washing step is 1 to 100 mm in a vertical direction from the filtration surface of the filter medium.
[Configuration 5]
The method for producing SnS ₂ according to any one of configurations 1 to 4, wherein the cleaning solution comprises water.
[Configuration 6]
The method for producing _SnS2 according to any one of configurations 1 to 5, wherein the electrical conductivity of the cleaning solution is less than 10 μS/cm.
[Configuration 7]
The method for producing _SnS2 according to any one of configurations 1 to 6, further comprising a drying step of drying the washed _SnS2 aggregates obtained through the washing step at a pressure of less than 5 kPa.
[Configuration 8]
A method for using SnS ₂ , comprising a step of contacting SnS 2 produced by the method according to any one of configurations 1 to ₇ with a sulfide containing an alkali metal to obtain a compound containing an alkali metal, tin, and sulfur.

1: Stock solution tank 2: Filter material 3: Waste liquid tank 4: Filtrate tank P, P1, P2: Pump

Claims (8)

A filtration process in which a _SnS2 dispersion containing _SnS2 , a solvent, and impurities is passed through a filter medium provided in a filtering means to form _SnS2 aggregates on the filter medium;
A washing step of passing a washing liquid through the _SnS2 aggregates formed on the filter medium to wash the _SnS2 aggregates;
A method for producing _SnS2 having the formula: The method for producing _SnS2 according to claim 1, wherein the solvent comprises water. The method for producing SnS2 according to claim ₂ , wherein the conductivity of the solvent is less than 10 μS/cm. The method for producing _SnS2 according to claim 1, wherein the thickness of the _SnS2 aggregate after washing obtained through the washing process is 1 to 100 mm in a vertical direction from the filtration surface of the filter medium. The method for producing _SnS2 according to claim 1, wherein the cleaning solution comprises water. The method for producing _SnS2 according to claim 5, wherein the electrical conductivity of the cleaning solution is less than 10 μS/cm. The method for producing _SnS2 according to any one of claims 1 to 6, further comprising a drying step of drying the washed _SnS2 aggregate obtained through the washing step at a pressure of less than 5 kPa. A method for using SnS ₂ , comprising the step of contacting SnS 2 produced by the method according to any one of claims 1 _to 6 with a sulfide containing an alkali metal to obtain a compound containing an alkali metal, tin, and sulfur.

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