Lithium sulfide and preparation method thereof

Abstract

The invention relates to lithium sulfide and a preparation method thereof.The preparation method includes the following steps that sublimed sulfur powder and a lithium source are mixed and subjected to a heating reaction, and the lithium source comprises at least one of anhydrous lithium hydroxide, lithium hydroxide monohydrate, lithium oxide, lithium hydride and lithium carbonate; a reducing gas is introduced while the heating reaction is performed, or the reducing gas is introduced after the heating reaction is finished, and a reduction reaction is performed; and after the reaction is finished, introducing protective gas for calcining to prepare the lithium sulfide. The preparation method provided by the invention can realize low-cost and high-purity production of lithium sulfide, and ensures the safety and environmental protection of the production process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium sulfide preparation, in particular to a kind of lithium sulfide and preparation method thereof. BACKGROUND

[0002] As an important inorganic compound, lithium sulfide has a wide range of applications in various fields. In the field of new energy, lithium sulfide is one of the key materials for lithium-sulfur batteries. Lithium-sulfur batteries have attracted much attention due to their high theoretical energy density and are expected to become the mainstream of next-generation high-performance battery technology. In addition, lithium sulfide is also used in the electronic industry to prepare some special electronic components and semiconductor materials, such as in the process of preparing some photoresistors, capacitors and other electronic devices, which plays an important role in improving the performance and stability of the devices. At the same time, in the field of chemical synthesis, lithium sulfide can be used as a sulfurizing agent for some organic synthesis reactions to introduce sulfur atoms and synthesize sulfur-containing organic compounds, which has a wide application prospect.

[0003] Currently, the main preparation processes for lithium sulfide are carbon thermal reduction method and gas-solid reaction method. Among them, carbon thermal reduction method is to use carbon to react with lithium-containing compounds at high temperature to prepare lithium sulfide. This method usually requires a high reaction temperature of about 800-1000℃, which consumes a lot of energy. Moreover, in order to remove the impurities generated during the reaction, organic solvents are often used for purification, which not only increases the production cost but also may cause environmental pollution.

[0004] Gas-solid reaction method is to prepare lithium sulfide by reacting gaseous hydrogen sulfide with solid lithium-containing compounds such as lithium hydroxide under certain conditions. Although this method can reduce the reaction temperature to some extent, hydrogen sulfide gas is highly toxic and easily leaks, posing a serious safety hazard. The production equipment and operating environment have very high requirements. Moreover, the reaction conversion rate of gas-solid reaction method is relatively low, the reaction time is long, and the production efficiency needs to be improved, which is difficult to meet the demand of large-scale industrial production. At the same time, due to incomplete reaction, lithium hydroxide is easily left, and organic solvents are difficult to effectively distinguish between lithium sulfide and lithium hydroxide, resulting in a complex impurity removal process and difficulty in obtaining high-purity lithium sulfide. SUMMARY

[0005] Therefore, it is necessary to provide a kind of lithium sulfide and preparation method thereof to solve the above problems. The preparation method can realize low-cost and high-purity production of lithium sulfide, while ensuring the safety and environmental protection of the production process.

[0006] A preparation method of lithium sulfide, comprising the following steps:

[0007] mixing sublimed sulfur powder with a lithium source, and performing a heating reaction, wherein the lithium source includes at least one of anhydrous lithium hydroxide, monohydrate lithium hydroxide, lithium oxide, lithium hydride, and lithium carbonate;

[0008] performing a reduction reaction by introducing a reducing gas while the heating reaction is being performed, or after the heating reaction is completed;

[0009] performing calcination by introducing a protective gas after the reaction is completed, thereby producing lithium sulfide.

[0010] In one embodiment, the molar ratio of the sublimed sulfur powder to the lithium source is 1: (0.3-2).

[0011] In one embodiment, the reducing gas includes at least one of hydrogen, carbon monoxide, hydrogen sulfide, and methane.

[0012] In one embodiment, the flow rate of the reducing gas is 50 mL / min-500 mL / min.

[0013] In one embodiment, when the reducing gas is introduced while the heating reaction is being performed, the heating reaction and the reduction reaction are simultaneously performed at a temperature of 100°C-700°C, a pressure of 0.1 KPa-1 KPa, and a time of 8 h-15 h.

[0014] In one embodiment, when the reducing gas is introduced after the heating reaction is completed, the heating reaction and the reduction reaction are performed in steps, and the temperature of the heating reaction and the reduction reaction is independently selected from 100°C-700°C, the pressure is independently selected from 0.1 KPa-1 KPa, and the time is independently selected from 8 h-15 h.

[0015] In one embodiment, when the lithium source is anhydrous lithium hydroxide, the molar ratio of the sublimed sulfur powder to the anhydrous lithium hydroxide is 1: (1-1.5), the reducing gas is hydrogen, and the temperature of the heating reaction and the reduction reaction is independently selected from 100°C-300°C.

[0016] or, when the lithium source is monohydrate lithium hydroxide, the molar ratio of the sublimed sulfur powder to the anhydrous lithium hydroxide is 1: (1.2-1.8), the reducing gas is hydrogen, and the temperature of the heating reaction and the reduction reaction is independently selected from 100°C-500°C.

[0017] or, when the lithium source is lithium oxide, the molar ratio of the sublimed sulfur powder to the lithium oxide is 1: (0.3-0.5), the reducing gas is hydrogen, and the temperature of the heating reaction and the reduction reaction is independently selected from 120°C-350°C.

[0018] Or, when the lithium source is selected from lithium hydride, the molar ratio of sublimed sulfur powder to lithium hydride is 1:(1.3~2), the reducing gas is selected from hydrogen, and the temperature of the heating reaction and the reducing reaction is independently selected from 100℃~350℃;

[0019] Or, when the lithium source is selected from lithium carbonate, the molar ratio of sublimed sulfur powder to lithium carbonate is 1:(0.5~0.8), the reducing gas is selected from hydrogen, and the temperature of the heating reaction and the reducing reaction is independently selected from 150℃~700℃.

[0020] In one of the embodiments, the temperature of the calcination is 400℃~600℃, and the time is 6h~10h.

[0021] A lithium sulfide prepared by the method for preparing lithium sulfide as described above.

[0022] In one of the embodiments, the purity of the lithium sulfide is greater than 99%, the carbon content is less than 1%, the impurity content is less than 50ppm, and the moisture content is less than 50ppm.

[0023] The method for preparing lithium sulfide provided by the present application uses sublimed sulfur powder and a specific lithium source to react, and the synergistic effect of the reducing gas can not only reduce the impurities such as lithium per-sulfate, lithium thiosulfate and lithium sulfite into lithium sulfide, but also can reduce the impurity content of lithium sulfide and improve the purity of lithium sulfide, and the quality is far superior to that of the traditional method. Moreover, the reaction rate can be significantly improved, so that the efficient and green synthesis of lithium sulfide is realized, and the technical problems such as incomplete reaction and difficult impurity removal in the traditional method are overcome, the technical bottleneck of the traditional method is broken, and the market demand can be better met. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0025] Figure 1 The X-ray diffraction pattern of the lithium sulfide prepared in Example 1 of the present application, wherein A is the X-ray diffraction peak of the lithium sulfide prepared in Example 1 of the present application;

[0026] Figure 2 The X-ray photoelectron spectrogram of the heating reaction product in Example 4 of the present application;

[0027] Figure 3 The X-ray photoelectron spectrogram of the lithium sulfide prepared in Example 4 of the present application. DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present application, the present application will be described in more detail below. However, it should be understood that the present application can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided so that the disclosure of the present application can be more thoroughly and completely understood.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein is for the purpose of describing particular embodiments or examples only and is not intended to be limiting of the present application. As used herein, the term "and / or," used in the

[0030] In the present application, when a numerical range is involved, unless otherwise specified, the numerical range is considered to be continuous and includes the minimum value and the maximum value of the range, and every value between the minimum value and the maximum value. Further, when the range refers to an integer, every integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0031] The present application provides a method for preparing lithium sulfide, comprising the following steps:

[0032] Mixing sublimed sulfur powder with a lithium source and performing a heating reaction, wherein the lithium source includes at least one of anhydrous lithium hydroxide, monohydrate lithium hydroxide, lithium oxide, lithium hydride, and lithium carbonate;

[0033] Simultaneously with the heating reaction, a reducing gas is introduced, or after the heating reaction is completed, a reducing gas is introduced to perform a reduction reaction;

[0034] After the reaction is completed, a protective gas is introduced to perform calcination, thereby obtaining lithium sulfide.

[0035] The preparation method has the advantages that: the low-cost sublimed sulfur powder is used to react with a specific lithium source in combination with the synergistic effect of a reducing gas, so that the lithium persulfate, lithium thiosulfate, lithium sulfite and other impurities can be reduced to lithium sulfide, which is beneficial to reduce the impurity content in the lithium sulfide and improve the purity of the lithium sulfide, and the quality is far superior to that of the traditional method, and the reaction rate can be significantly improved, so that the efficient and green synthesis of the lithium sulfide is realized, the technical problems such as incomplete reaction and difficult impurity removal in the traditional method are overcome, the technical bottleneck of the traditional method is broken, and the market demand can be better met.

[0036] In an embodiment of the present application, the molar ratio of the sublimed sulfur powder to the lithium source is 1:(0.3-2), and by adjusting the molar ratio of the sublimed sulfur powder to the lithium source, the reaction of the lithium source can be ensured, and incomplete reaction to form residues can be avoided.

[0037] It can be understood that the molar ratio of the sublimed sulfur powder to the lithium source includes but is not limited to any one value or a range value between any two values in 1:2, 1:1.8, 1:1.5, 1:1.2, 1:1, 1:0.8, 1:0.5, 1:0.3, and as a preferred, the molar ratio of the sublimed sulfur powder to the lithium source is 1:(0.3-1.5).

[0038] In an embodiment of the present application, the lithium source preferably includes at least one of anhydrous lithium hydroxide, lithium hydroxide monohydrate, lithium oxide and lithium hydride, which is more beneficial to reduce the influence of impurities and improve the reaction efficiency.

[0039] It can be understood that the sublimed sulfur powder of the present application mainly includes nanoscale elemental sulfur, and a conventional commercial product can be used, and the present application does not limit this.

[0040] In an embodiment of the present application, the mixing method of the sublimed sulfur powder and the lithium source includes but is not limited to stirring, ball milling or sieving.

[0041] In an embodiment of the present application, the reducing gas includes at least one of hydrogen, carbon monoxide, hydrogen sulfide and methane, and as a preferred, the reducing gas includes at least one of hydrogen, carbon monoxide and methane.

[0042] It should be noted that, considering that the heating reaction of sublimed sulfur powder and lithium source is usually carried out in a protective atmosphere, when the reducing gas is introduced at the same time as the heating reaction, the reducing gas can be mixed with the protective gas and introduced; when the reducing gas is introduced after the heating reaction is completed, at least part of the protective gas is replaced by the reducing gas, which is beneficial to reduce the explosion limit and improve safety, and the protective gas does not react with the raw materials, can carry away the generated water vapor or gas, and accelerate the forward reaction rate. Specifically, hydrogen can be mixed with argon, carbon monoxide can be mixed with argon, methane can be mixed with argon, and the like. Further, when a mixed gas is used for the reduction reaction, the volume ratio of the reducing gas in the mixed gas is preferably 5% to 10%.

[0043] In an embodiment of the present application, when the lithium source is selected from anhydrous lithium hydroxide and the reducing gas is selected from hydrogen, the specific reaction process of the heating reaction and the reduction reaction includes the following reaction equations (formula 1-1) to (formula 1-6) shown below:

[0044] 3S+6LiOH→2Li2S+Li2SO3+3H2O (formula 1-1);

[0045] 4S+6LiOH→2Li2S+Li2S2O3+3H2O (formula 1-2);

[0046] Li2S+S→Li2S2 (formula 1-3);

[0047] Li2S2+H2→Li2S+H2S↑ (formula 1-4);

[0048] Li2SO3+H2→Li2S+H2O+SO2↑ (formula 1-5);

[0049] Li2S2O3+H2→Li2S+H2S↑+H2O (formula 1-6).

[0050] In an embodiment of the present application, when the lithium source is selected from lithium oxide and the reducing gas is selected from hydrogen, the specific reaction process of the heating reaction and the reduction reaction includes the following reaction equations (formula 2-1) to (formula 2-3) shown below:

[0051] 2Li2O+3S→2Li2S+SO2↑ (formula 2-1);

[0052] Li2S+S→Li2S2 (formula 2-2);

[0053] Li2S2+H2→Li2S+H2S↑ (formula 2-3).

[0054] In an embodiment of the present application, when the lithium source is selected from lithium hydride and the reducing gas is selected from hydrogen, the specific reaction process of the heating reaction and the reduction reaction includes the following reaction equations (formula 3-1) to (formula 3-3) as shown:

[0055] 2LiH + S → Li2S + H2↑ (formula 3-1);

[0056] Li2S + S → Li2S2 (formula 4-2);

[0057] Li2S2 + H2→ Li2S + H2S↑ (formula 4-3).

[0058] In an embodiment of the present application, when the lithium source is selected from lithium carbonate and the reducing gas is selected from hydrogen, the specific reaction process of the heating reaction and the reduction reaction includes the following reaction equations (formula 4-1) to (formula 4-3) as shown:

[0059] 2Li2CO3 + 3S → 2Li2S + 2CO2↑ + SO2↑ (formula 4-1);

[0060] Li2S + S → Li2S2 (formula 4-2);

[0061] Li2S2 + H2→ Li2S + H2S↑ (formula 4-3).

[0062] It should be noted that the gases such as water, carbon dioxide, sulfur dioxide and hydrogen sulfide generated in the above reaction will be discharged from the reactor with the gas flow, which is conducive to promoting the forward reaction and further improving the reaction efficiency. In the present application, the gas is continuously introduced and discharged. It can be understood that although a small amount of hydrogen sulfide gas may be generated in the reaction process of the present application, compared with the traditional gas-solid reaction method, the use and emission of the highly toxic gas hydrogen sulfide are significantly reduced, which is more friendly to the operators and the environment, and is conducive to improving the safety and environmental protection of the preparation process.

[0063] In an embodiment of the present application, the flow rate of the reducing gas is 50 mL / min to 500 mL / min. When the flow rate of the reducing gas is too low, the water, carbon dioxide, sulfur dioxide and hydrogen sulfide generated in the reaction will accumulate in the reactor, hindering the forward reaction and thus affecting the reaction efficiency. When the flow rate of the reducing gas is too high, the sublimed sulfur powder and the lithium source will be carried out of the reactor by the gas flow, wasting raw materials and increasing the cost of raw materials. Therefore, by adjusting the flow rate of the reducing gas within a suitable range, the present application is conducive to maximizing the reaction efficiency and preparation benefit.

[0064] It can be understood that the flow rate of the reducing gas includes but is not limited to any one value or a range value between any two values of 50 mL / min, 100 mL / min, 200 mL / min, 300 mL / min, 400 mL / min, 500 mL / min. When the reducing gas is a mixed gas of the reducing gas and the protective gas, the flow rate at this time refers to the total flow rate of the mixed gas of the reducing gas and the protective gas.

[0065] In an embodiment of the present application, when the reducing gas is introduced while the heating reaction is carried out, the heating reaction and the reduction reaction are simultaneously carried out, the reaction temperature is 100℃-700℃, including but not limited to any one value or a range value between any two values of 100℃, 200℃, 400℃, 600℃, 700℃; the pressure is 0.1KPa-1KPa, including but not limited to any one value or a range value between any two values of 0.1KPa, 0.2KPa, 0.5KPa, 0.8KPa, 1KPa; the time is 8h-15h, including but not limited to any one value or a range value between any two values of 8h, 10h, 11h, 12h, 13h, 14h, 15h, preferably 10h-15h.

[0066] In an embodiment of the present application, when the reducing gas is introduced after the heating reaction is completed, the heating reaction and the reduction reaction are carried out step by step, the temperature of the heating reaction and the temperature of the reduction reaction are respectively and independently selected from 100℃-700℃, including but not limited to any one value or a range value between any two values of 100℃, 200℃, 400℃, 600℃, 700℃; the pressure is 0.1KPa-1KPa, including but not limited to any one value or a range value between any two values of 0.1KPa, 0.2KPa, 0.5KPa, 0.8KPa, 1KPa; the time is 8h-15h, including but not limited to any one value or a range value between any two values of 8h, 10h, 11h, 12h, 13h, 14h, 15h, preferably 10h-15h.

[0067] It can be understood that when the heating reaction and the reduction reaction are carried out step by step, the temperature, the pressure and the time of the heating reaction can be the same as or different from the temperature, the pressure and the time of the reduction reaction, which is not limited by the present application.

[0068] In an embodiment of the present application, when the lithium source is selected from anhydrous lithium hydroxide, the molar ratio of the sublimed sulfur powder to the anhydrous lithium hydroxide is preferably 1:(1-1.5), the reducing gas is preferably hydrogen, and the temperature of the heating reaction and the temperature of the reduction reaction can be respectively and independently selected from 100℃-300℃. By carrying out the reaction at a relatively low temperature, high-temperature and high-pressure conditions are not required, which is conducive to further reducing energy consumption and improving the safety and environmental protection of the preparation process.

[0069] In an embodiment of the present application, when the lithium source is selected from lithium hydroxide monohydrate, the molar ratio of sublimed sulfur powder to anhydrous lithium hydroxide is preferably 1: (1.2-1.8), the reducing gas is preferably hydrogen, and the temperature of the heating reaction and the temperature of the reduction reaction can be independently selected from 100-500°C, respectively.

[0070] In an embodiment of the present application, when the lithium source is selected from lithium oxide, the molar ratio of sublimed sulfur powder to lithium oxide is preferably 1: (0.3-0.5), the reducing gas is preferably hydrogen, and the temperature of the heating reaction and the temperature of the reduction reaction can be independently selected from 120-350°C, respectively.

[0071] In an embodiment of the present application, when the lithium source is selected from lithium hydride, the molar ratio of sublimed sulfur powder to lithium hydride is preferably 1: (1.3-2), the reducing gas is preferably hydrogen, and the temperature of the heating reaction and the temperature of the reduction reaction can be independently selected from 100-350°C, respectively.

[0072] In an embodiment of the present application, when the lithium source is selected from lithium carbonate, the molar ratio of sublimed sulfur powder to lithium carbonate is preferably 1: (0.5-0.8), the reducing gas is preferably hydrogen, and the temperature of the heating reaction and the temperature of the reduction reaction can be independently selected from 150-700°C, respectively.

[0073] By performing calcination in a protective atmosphere, it is beneficial to remove excess sublimed sulfur powder in the reaction product, so that the reaction product changes from light yellow to pure white, thereby further improving the purity of the lithium sulfide.

[0074] In an embodiment of the present application, the temperature of the calcination is 400-600°C, including but not limited to any one value or a range value between any two values selected from 400°C, 450°C, 500°C, 550°C, and 600°C, and is preferably 400-500°C; the time of the calcination is 6-10h, including but not limited to any one value or a range value between any two values selected from 6h, 7h, 8h, 9h, and 10h.

[0075] The present application also provides a lithium sulfide prepared by the method for preparing lithium sulfide as described above. The lithium sulfide prepared by the method provided by the present application has high purity and low impurity content, and the quality is far superior to that of lithium sulfide prepared by a traditional method.

[0076] In an embodiment of the present application, the purity of the lithium sulfide is greater than 99%, and more preferably greater than 99.9%; the carbon content is less than 1%, the impurity content is less than 50ppm, and the moisture content is less than 50ppm.

[0077] It can be understood that the impurities in the lithium sulfide include but are not limited to lithium carbonate, lithium peroxide, lithium thiosulfate, and lithium sulfite.

[0078] The following will be further illustrated by the following specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. The specific conditions not noted in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments not noted by the manufacturer are all the conventional products which can be obtained by market purchase.

[0079] Example 1

[0080] 100 g of sublimed sulfur powder and 100 g of anhydrous lithium hydroxide were stirred and mixed uniformly, placed in a reactor, and reacted at a temperature of 195°C for 15 h, during which a mixed gas of hydrogen and argon (wherein the volume of hydrogen was 5% of the total volume of the mixed gas) was continuously introduced, and the total flow rate of the mixed gas was 300 mL / min.

[0081] After the reaction was completed, the reaction product was calcined in a muffle furnace at 460°C for 10 h to prepare lithium sulfide.

[0082] The lithium sulfide prepared in this example was subjected to X-ray diffraction (XRD) test, and the results are shown in FIG. 1. Figure 1 As compared with the XRD standard card (Li2S-PDF#00-023-0369), it can be proved that the product prepared in this example is lithium sulfide.

[0083] Example 2

[0084] 150 g of sublimed sulfur powder and 120 g of anhydrous lithium hydroxide were stirred and mixed uniformly, placed in a reactor, and reacted at a temperature of 200°C for 14 h, during which a mixed gas of carbon monoxide and argon (wherein the volume of carbon monoxide was 10% of the total volume of the mixed gas) was continuously introduced, and the total flow rate of the mixed gas was 200 mL / min.

[0085] After the reaction was completed, the reaction product was calcined in a muffle furnace at 480°C for 8 h to prepare lithium sulfide.

[0086] Example 3

[0087] 200 g of sublimed sulfur powder and 150 g of anhydrous lithium hydroxide were stirred and mixed uniformly, placed in a reactor, and reacted at a temperature of 255°C for 15 h, during which a mixed gas of methane and argon (wherein the volume of methane was 8% of the total volume of the mixed gas) was continuously introduced, and the total flow rate of the mixed gas was 250 mL / min.

[0088] After the reaction was completed, the reaction product was calcined in a muffle furnace at 500°C for 6 h to prepare lithium sulfide.

[0089] Example 4

[0090] 50 g of sublimed sulfur powder was mixed with 90 g of lithium hydroxide monohydrate, and the mixture was stirred and placed in a reactor. Argon was introduced into the reactor, and the mixture was reacted at 195°C for 12 hours. The reaction product was subjected to X-ray photoelectron spectroscopy (XPS) test, and the results are shown in FIG. 1. As shown in FIG. 1, it was found from the XPS test that lithium sulfide was successfully synthesized by the preparation method, but the characteristic peaks of lithium sulfide were relatively weak in the XPS spectrum, and the presence of lithium thiosulfate and lithium sulfite was also detected. Figure 2

[0091] After the reaction was completed, the argon gas was replaced with hydrogen gas, and the reaction was continued at 480°C for 13 hours with a flow rate of 350 mL / min.

[0092] After the reaction was completed, the reaction product was calcined in a muffle furnace at 550°C for 8 hours to obtain lithium sulfide.

[0093] The lithium sulfide obtained in this example was subjected to XPS test, and the results are shown in FIG. 3. As shown in FIG. 3, it was found from the XPS test that the characteristic peaks of lithium sulfide were strong in the XPS spectrum, and the presence of lithium thiosulfate and lithium sulfite was not detected. Figure 3

[0094] Example 5

[0095] 280 g of sublimed sulfur powder was mixed with 30 g of lithium hydride and 20 g of lithium oxide, and the mixture was stirred and placed in a reactor. Argon was introduced into the reactor, and the mixture was reacted at 330°C for 8 hours. After the reaction was completed, the argon gas was replaced with hydrogen gas, and the reaction was continued at 305°C for 15 hours with a flow rate of 300 mL / min.

[0096] After the reaction was completed, the reaction product was calcined in a muffle furnace at 535°C for 7 hours to obtain lithium sulfide.

[0097] Example 6

[0098] 63 g of sublimed sulfur powder was mixed with 65 g of lithium carbonate, and the mixture was stirred and placed in a reactor. Argon was introduced into the reactor, and the mixture was reacted at 530°C for 11 hours. After the reaction was completed, the argon gas was replaced with hydrogen gas, and the reaction was continued at 290°C for 9 hours with a flow rate of 200 mL / min.

[0099] After the reaction was completed, the reaction product was calcined in a muffle furnace at 600°C for 6 hours to obtain lithium sulfide.

[0100] Comparative Example 1

[0101] 100 g of sublimed sulfur powder was mixed with 100 g of anhydrous lithium hydroxide, and the mixture was stirred and placed in a reactor. The mixture was reacted at 195°C for 15 hours with continuous introduction of argon gas at a flow rate of 10 mL / min.

[0102] ​​After the reaction, the reaction product was calcined in a muffle furnace at 460°C for 10h to obtain lithium sulfide.

[0103] Comparative Example 2

[0104] 100g of sublimed sulfur powder was mixed with 100g of lithium amide and stirred to be uniform, and then was placed in a reactor to react at a temperature of 195°C for 15h, during which a mixed gas of hydrogen and argon (the volume of hydrogen was 5% of the total volume of the mixed gas) was continuously introduced at a flow rate of 10mL / min.

[0105] After the reaction, the reaction product was calcined in a muffle furnace at 460°C for 10h to obtain lithium sulfide.

[0106] Comparative Example 3

[0107] 100g of sublimed sulfur powder was mixed with 100g of lithium nitride and stirred to be uniform, and then was placed in a reactor to react at a temperature of 195°C for 15h, during which a mixed gas of hydrogen and argon (the volume of hydrogen was 5% of the total volume of the mixed gas) was continuously introduced at a flow rate of 10mL / min.

[0108] After the reaction, the reaction product was calcined in a muffle furnace at 460°C for 10h to obtain lithium sulfide.

[0109] The purity, moisture content and carbon content of the lithium sulfide obtained in all the examples and comparative examples were tested, and the results are shown in Table 1.

[0110] Table 1

[0111]

[0112] As can be seen from Table 1, the lithium sulfide prepared according to the preparation method provided in the present application has high purity, low impurity content and moisture content. In Comparative Example 1, since no reducing gas was introduced, lithium thiosulfate and lithium sulfite could not be reduced to lithium sulfide, and part of the sulfur element reacted with the lithium sulfide that had been generated to form stable lithium persulfide. In Comparative Examples 2 and 3, since lithium amide and lithium nitride were used as the lithium source, the raw materials were difficult to purify and were expensive, which led to an increase in side reactions and impure products.

[0113] The technical features of the above-described examples can be combined in any manner. In order to make the description brief, all possible combinations of the technical features in the above-described examples are not described, however, as long as the combinations of the technical features do not contradict each other, they should be considered to be within the scope of the present disclosure.

[0114] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing lithium sulfide, characterized in that, Includes the following steps: Sublimed sulfur powder is mixed with a lithium source and heated to react, wherein the lithium source includes at least one of anhydrous lithium hydroxide, lithium hydroxide monohydrate, lithium oxide, lithium hydride, and lithium carbonate. A reduction reaction is carried out by introducing a reducing gas during the heating reaction, or by introducing a reducing gas after the heating reaction is completed. After the reaction is complete, a protective gas is introduced for calcination to obtain lithium sulfide.

2. The method for preparing lithium sulfide according to claim 1, characterized in that, The molar ratio of the sublimed sulfur powder to the lithium source is 1:(0.3~2).

3. The method for preparing lithium sulfide according to claim 1, characterized in that, The reducing gas includes at least one of hydrogen, carbon monoxide, hydrogen sulfide, and methane.

4. The method for preparing lithium sulfide according to claim 1, characterized in that, The flow rate of the reducing gas is 50 mL / min to 500 mL / min.

5. The method for preparing lithium sulfide according to claim 1, characterized in that, When a reducing gas is introduced during the heating reaction, the heating reaction and the reduction reaction proceed simultaneously. The reaction temperature is 100℃~700℃, the pressure is 0.1KPa~1KPa, and the time is 8h~15h.

6. The method for preparing lithium sulfide according to claim 1, characterized in that, When the reducing gas is introduced after the heating reaction is completed, the heating reaction and the reduction reaction are carried out in separate steps. The temperature of the heating reaction and the reduction reaction are independently selected from 100℃ to 700℃, the pressure is independently selected from 0.1KPa to 1KPa, and the time is independently selected from 8h to 15h.

7. The method for preparing lithium sulfide according to claim 1, characterized in that, When the lithium source is selected from anhydrous lithium hydroxide, the molar ratio of sublimed sulfur powder to anhydrous lithium hydroxide is 1:(1~1.5), the reducing gas is selected from hydrogen, and the heating reaction and reduction reaction temperatures are independently selected from 100℃~300℃. Alternatively, when the lithium source is selected from lithium hydroxide monohydrate, the molar ratio of sublimed sulfur powder to anhydrous lithium hydroxide is 1:(1.2~1.8), the reducing gas is selected from hydrogen, and the temperatures of the heating reaction and the reduction reaction are independently selected from 100℃~500℃. Alternatively, when the lithium source is lithium oxide, the molar ratio of sublimed sulfur powder to lithium oxide is 1:(0.3~0.5), the reducing gas is hydrogen, and the temperatures of the heating reaction and the reduction reaction are independently selected from 120℃~350℃. Alternatively, when the lithium source is lithium hydride, the molar ratio of sublimed sulfur powder to lithium hydride is 1:(1.3~2), the reducing gas is hydrogen, and the heating reaction and reduction reaction temperatures are independently selected from 100℃~350℃. Alternatively, when the lithium source is lithium carbonate, the molar ratio of sublimed sulfur powder to lithium carbonate is 1:(0.5~0.8), the reducing gas is hydrogen, and the temperatures of the heating reaction and the reduction reaction are independently selected from 150℃~700℃.

8. The method for preparing lithium sulfide according to claim 1, characterized in that, The calcination temperature is 400℃~600℃, and the time is 6h~10h.

9. A lithium sulfide, characterized in that, The lithium sulfide is prepared by the method for preparing lithium sulfide as described in any one of claims 1 to 8.

10. The lithium sulfide according to claim 9, characterized in that, The lithium sulfide has a purity greater than 99%, a carbon content of less than 1%, an impurity content of less than 50 ppm, and a moisture content of less than 50 ppm.

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