JP2016225033A - Method for producing sulfide solid electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a sulfide solid electrolyte from an amorphous sulfide solid electrolyte where, in the step of heat treatment for producing a crystallized sulfide solid electrolyte from an amorphous sulfide solid electrolyte, by reducing the precipitation of sulfur and a sulfur compound on a wiring or the like, the clogging of the wiring is prevented, and the productive efficiency of the crystallized sulfide solid electrolyte is improved.SOLUTION: Provided is a method for producing a crystallized sulfide solid electrolyte having a process where an amorphous sulfide solid electrolyte is crystallized by heating treatment to produce a crystallized sulfide solid electrolyte, in which the process is performed using equipment having a reaction tank of performing crystallization, capture part for capturing sulfur and/or a sulfur compound in a gas made to flow out from the reaction tank; and a flow passage between the reaction tank and the capture part, and the flow passage is heated to 150°C.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a sulfide solid electrolyte.

  In recent years, all-solid-state batteries in which the electrolytic solution is replaced with a solid electrolyte have attracted attention. Compared to a secondary battery using an electrolytic solution, an all-solid battery does not use an electrolytic solution, so that it does not cause decomposition of the electrolytic solution due to overcharging, and further has high cycle durability and energy density. doing.

  A sulfide solid electrolyte is known as a kind of solid electrolyte used in an all-solid battery. As one method for producing a sulfide solid electrolyte, for example, a method of synthesizing an amorphous solid electrolyte by a method described in Patent Document 1 is known. Also known is a method for producing a crystallized sulfide solid electrolyte with improved ionic conductivity by heat-treating an amorphous sulfide solid electrolyte at a temperature above the crystallization temperature to form a glass ceramic. .

  Also, in the step of synthesizing the amorphous sulfide solid electrolyte, by adding an oxygen-containing organic compound to the raw material, the ionic conductivity of the synthesized amorphous sulfide solid electrolyte is maintained and the recovery rate is improved. The method is known.

  However, in the step of synthesizing the amorphous sulfide solid electrolyte, when a method of adding an oxygen-containing organic compound to the raw material is used, in the step of crystallizing the amorphous sulfide solid electrolyte by heat treatment, Among them, there is a problem that the amorphous sulfide solid electrolyte and the oxygen-containing organic compound undergo a chemical reaction, and the performance of the produced crystallized sulfide solid electrolyte is deteriorated.

  On the other hand, a method for suppressing the reaction between the amorphous sulfide solid electrolyte and the oxygen-containing organic compound by reducing the concentration of the organic compound in the reaction vessel in the atmosphere is disclosed (Patent Document 2).

  In addition, in the step of heat-treating the amorphous sulfide solid electrolyte, the sulfur component in the amorphous sulfide solid electrolyte evaporates and adheres to and adheres to the inside of the container, so that the reaction vessel is clogged and corroded. there were.

  For this, a method is disclosed in which the step of heat-treating the amorphous sulfide solid electrolyte is performed in a solvent, thereby preventing the reaction tank from being blocked or corroded due to adhesion or fixation inside the container. (Patent Document 3).

  In addition, in the method of treating exhaust gas such as combustion gas by adding ammonia to remove nitrogen oxides and sulfur oxides in the exhaust gas, there is a problem that the exhaust duct is blocked by adhering ammonium nitrate or ammonium sulfate to the inner wall of the pipe. there were.

  On the other hand, as a method of preventing the exhaust duct from being blocked, the temperature in the duct is maintained at 80 ° C. to 150 ° C., whereby ammonium nitrate and ammonium sulfate are thermally decomposed to prevent adhesion to the wall (patent) Reference 4) exists.

JP 2012-48973 A Japanese Patent Laying-Open No. 2015-50042 JP 2014-96391 A JP-A-7-31844

  As a method for efficiently performing the step of heat-treating the amorphous sulfide solid electrolyte, the methods of Patent Documents 1 and 2 are disclosed. However, in the method of Patent Document 1, sulfur is deposited on the pipes and clogged. There is a problem of end.

  On the other hand, the method of Patent Document 2 can solve the problem that sulfur is deposited on a pipe and is blocked, but in order to carry out the method, a sealed container such as an autoclave is required, and an oxygen-containing organic compound is required. Such impurities cannot be removed, and the ionic conductivity of the electrolyte decreases. In addition, it has been found that the use of an organic solvent increases the production cost and deteriorates the production efficiency. Further, it has been found that depending on the selected solvent, the quality caused by the desorbed sulfur component mixed into the sulfide solid electrolyte is lowered.

  Therefore, the object of the present invention is to reduce the precipitation of sulfur and sulfur compounds on the piping while removing the organic compounds added in the process of producing the crystallized sulfide solid electrolyte in the heat treatment step. It is intended to provide a method for producing a sulfide solid electrolyte that can prevent clogging, increase the production efficiency of the crystallized sulfide solid electrolyte, and maintain the quality of the crystallized sulfide solid electrolyte. .

The present inventors have found that the above problems can be solved by the following means.
A method for producing a crystallized sulfide solid electrolyte, comprising a step of crystallizing an amorphous sulfide solid electrolyte by heat treatment to produce a crystallized sulfide solid electrolyte, and this step is performed for crystallization. Using a reaction tank, a trap for capturing sulfur and / or sulfur compounds in the gas flowing out of the reaction tank, and a facility having a flow path between the reaction tank and the trap; A method for producing a crystallized sulfide solid electrolyte, which is heated to 150 ° C. or higher.

  According to the method of the present invention, in the heat treatment step for producing a crystallized sulfide solid electrolyte from an amorphous sulfide solid electrolyte, precipitation of sulfur and sulfur compounds on the pipe is reduced and the pipe is blocked. This makes it possible to efficiently produce a crystallized sulfide solid electrolyte.

FIG. 1 is a schematic view when a vacuum pump is used in a process for producing a crystallized sulfide solid electrolyte by crystallizing an amorphous sulfide solid electrolyte by heat treatment in the method of the present invention. FIG. 2 shows the results of the reference example. FIG. 3 compares the occlusion frequencies of the example and the comparative example.

  Hereinafter, embodiments of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist of the present invention.

  The present invention is a method for producing a crystallized sulfide solid electrolyte, comprising a step of crystallizing an amorphous sulfide solid electrolyte by a heat treatment to produce a crystallized sulfide solid electrolyte. Performing using a reaction tank for crystallization, a trapping part for trapping sulfur and / or sulfur compounds in the gas flowing out of the reaction tank, and a facility having a flow path between the reaction tank and the trapping part, This is a method for producing a crystallized sulfide solid electrolyte in which a flow path is heated to 150 ° C. or higher.

  In general, sulfur is considered to have a boiling point of 444 ° C. or higher. As a result of the study by the present inventors, in the process of heat-treating an amorphous sulfide solid electrolyte to obtain a crystallized sulfide solid electrolyte, around 50 ° C. However, it was confirmed that the volatilization of sulfur compounds occurred. And when the temperature of the flow path was heated to 150 ° C. and an experiment was conducted to confirm whether the flow path could be blocked, the frequency of blockage was greatly reduced.

  As a result, the present inventors have found that heating the flow path to 150 ° C. or more can reduce the precipitation of sulfur and sulfur compounds in the flow path and prevent the blockage of the flow path.

<Amorphous sulfide solid electrolyte>
The amorphous sulfide solid electrolyte is, for example, lithium sulfide and one or more sulfides selected from the group consisting of boron sulfide, silicon sulfide, phosphorus sulfide, gallium sulfide, germanium sulfide, tin sulfide, and antimony sulfide, It is preferably synthesized by reacting with one or more lithium halides selected from the group consisting of LiCl, LiBr, and LiI.

  Although a specific synthesis method is not particularly limited, it can be synthesized by a known method. For example, the description of Patent Document 1 can be referred to.

<Crystalline sulfide solid electrolyte>
The crystallized sulfide solid electrolyte is a glass ceramic sulfide solid electrolyte produced by crystallizing an amorphous sulfide solid electrolyte by heat treatment.

  The temperature of the heat treatment is not particularly limited as long as it is a temperature capable of crystallizing the amorphous sulfide solid electrolyte, but it is preferably 130 ° C. or higher and 250 ° C. or lower, more preferably 160 ° C. or higher and 220 ° C. or lower, Preferably it is 170 degreeC or more and 200 degrees C or less.

  The heat treatment time is not particularly limited as long as the amorphous sulfide solid electrolyte can be crystallized, but it is preferably 5 minutes to 50 hours, more preferably 2 hours to 40 hours.

  Although the apparatus used for heat processing is not specifically limited, For example, a hot plate, a drying furnace, an electric furnace etc. are mentioned.

<Reaction tank>
The reaction tank refers to a container in which an amorphous sulfide solid electrolyte is installed in order to perform heat treatment in a process for producing a crystallized sulfide solid electrolyte by heat treatment of an amorphous sulfide solid electrolyte.

  The mechanism by which gas flows out from the reaction tank is not particularly limited. Examples include a method of reducing the pressure of the reaction tank using a vacuum pump (see FIG. 1), a method of circulating gas in the reaction tank, and the like. In addition, a method that does not use a device for causing gas to flow out, such as utilizing the fact that the gas in the reaction vessel is heated in the heat treatment step and thermally expanded to push the gas out of the reaction vessel, is also conceivable.

<Sulfur compounds>
A sulfur compound refers to a molecule that contains elemental sulfur. In the present invention, a sulfur compound refers to a substance that may be deposited in a flow path and clog the flow path in the heat treatment step.

<Capture part>
The capturing unit captures sulfur and / or sulfur compounds in the gas. The substance to be trapped is considered to be mainly a sulfur compound having a boiling point between the trapping part temperature and the channel heating temperature, but is not particularly limited.

<Flow path>
The flow path is a pipe connected to the reaction tank and the capture unit, and gas flowing out from the reaction tank flows. Pipe seals in the flow path (parts and materials that prevent leakage of liquids and gases to the outside, rainwater, dust, etc. in machinery and equipment) are not particularly limited, but from the standpoint of solvent resistance, Viton-based It is preferred to use a seal.

<Flow path temperature>
The method for heating the channel is not particularly limited as long as the channel can be heated to 150 ° C. or higher. The temperature of the flow path is heated to 150 ° C. or higher. Although there is no particular upper limit to the temperature for suppressing clogging, the sulfur component is completely volatilized at a temperature lower than 600 ° C., and is preferably 150 ° C. or higher and 600 ° C. or lower from the viewpoint of efficiency. Furthermore, it is preferable to use a Viton-based (fluororubber) seal from the viewpoint of solvent resistance for the pipe seal in the flow path. Since the heat-resistant temperature of the Viton-based seal is 200 ° C. or lower, the temperature is 150 ° C. As mentioned above, it is more preferable that it is 200 degrees C or less.

  Hereinafter, although the manufacturing method which concerns on this invention is explained in full detail based on an Example, this invention is not limited to the following specific forms.

<Example>
1. Step of synthesizing amorphous sulfide solid electrolyte As starting materials, lithium sulfide (Li ₂ S), diphosphorus pentasulfide (P ₂ S ₅ ) and lithium iodide (LiI) were used. Next, in a glove box with Ar atmosphere (dew point −70 ° C.), Li ₂ S and P ₂ S ₅ are converted to a molar ratio of 75Li ₂ S · 25P ₂ S ₅ (Li ₃ PS ₄ , ortho composition). Weighed so that Next, LiI was weighed so that LiI was 10 mol% with respect to the total of Li ₂ S, P ₂ S ₅ , and LiI.

A total of 2 g of Li ₂ S, P ₂ S ₅ , and LiI weighed above is charged into a planetary ball mill container (45 cc, made of ZrO ₂ ), dehydrated heptane (moisture content of 30 ppm or less, 4 g) is charged, and ZrO _Two balls (diameter = 5 mm, 53 g) were charged, and the container was completely sealed (Ar atmosphere).

  This container was attached to a planetary ball mill (P7 manufactured by Fritsch), and mechanical milling was performed 40 times at a base plate rotation speed of 500 rpm for 1 hour and 15 minutes.

Thereafter, the obtained sample was dried so as to remove heptane on a hot plate (120 ° C., 2 hours) to obtain an amorphous sulfide solid electrolyte. The composition of the obtained amorphous sulfide solid electrolyte was 10LiI · 90 (0.75Li ₂ S · 0.25P ₂ S ₅ ).

2. Heat treatment process of amorphous sulfide solid electrolyte material The amorphous sulfide solid electrolyte obtained by the above method was weighed and sealed in a container. And baking (crystallization) was performed using the apparatus shown in FIG. 1, and the crystallized sulfide solid electrolyte of the Example was obtained. In this step, the flow channel contact temperature was set to 150 ° C.

<Comparative example>
In the amorphous solid electrolyte heat treatment step described in the examples, a crystallized sulfide solid electrolyte of a comparative example was obtained in the same manner as in the example except that the flow path was not heated.

<Evaluation>
About the Example and the comparative example, the blockage frequency of the flow path was compared. In the method of the comparative example, occlusion occurred twice in 26 times (7.7%), but in the method of the example, occlusion occurred only once in 76 times (1.3%) (see FIG. 3).

  In addition, the blockage which generate | occur | produced once in the Example generate | occur | produced in the junction part of piping and a capture part in a flow path. The cause of the blockage may be that the heating is insufficient, and if the heating is performed appropriately, it is considered that the blockage did not occur.

<Reference example>
In the step of producing a crystallized sulfide solid electrolyte by applying heat treatment to the amorphous sulfide solid electrolyte, the temperature at which the sulfur compound is generated was measured under the following conditions.

  As a thermal analysis device, a TPD-MS device (heating device: TRC special heating device Small-2, MS device: Shimadzu GC / MS QP5050A (4)) was used. As the data processing system, a thermal analysis data processing system “THADAP-TGGC / MS” (not for sale) manufactured by Toray Research Center was used.

  Before starting the measurement, the data was set in the apparatus, and the measurement was started after flowing the carrier gas for 15 minutes or more. The heating conditions were room temperature to 500 ° C. (temperature increase rate: 10 ° C./min). The MS sensitivity was Gain 1.4 kV. The mass range was 10 to 300. The atmosphere was a helium flow (50 mL / min). The standard substances were sodium tungstate dihydrate, 1-butene and carbon dioxide.

  The sample is 3.24 mg of LiI, LiBr, (0.75Li2S + 0.25P2S5) mixed at 10:15:75 (molar fraction), mechanically milled and synthesized in a hydrocarbon solvent and an ether dispersant. What was processed was used.

  The result of the experiment is shown in FIG. As shown in FIG. 2, under the conditions of the reference example, a substance having a molecular weight of 64 starts to evaporate from around 50 ° C., and shows a peak around 180 ° C. From this, it is considered that in the reference example, the sulfur compound starts to volatilize around 50 ° C., and the volatilization amount becomes the highest around 180 ° C. Therefore, in order to achieve the object of the present invention to prevent the precipitation of sulfur compounds, it is conceivable that the temperature of the flow path is set to 50 ° C. or higher. In particular, the temperature of the flow path is set between 150 ° C. and 200 ° C. If so, it is considered to be the most efficient.

DESCRIPTION OF SYMBOLS 1 Vacuum pump 2 Capture part 3 Flow path 4 Heater 5 Reaction tank

Claims (1)

A method for producing a crystallized sulfide solid electrolyte, comprising:
Crystallization of the amorphous sulfide solid electrolyte by heat treatment to produce the crystallized sulfide solid electrolyte,
The process includes a reaction tank for performing crystallization, a trap for capturing sulfur and / or a sulfur compound in gas flowing out of the reaction tank, and a flow path between the reaction tank and the trap. Using equipment, and
Heating the flow path to 150 ° C. or higher;
A method for producing a crystallized sulfide solid electrolyte.

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