Lithium sulfide and a preparation method and application thereof

Abstract

The application provides lithium sulfide and a preparation method and application thereof. The preparation method comprises the following steps: spraying an atomized lithium source into a sulfur source to react, to obtain a crude product; and performing spray drying on the crude product, to obtain the lithium sulfide. The preparation method has high controllability, can prevent the problem of excessively fast reaction speed in the initial stage of the reaction, can obtain lithium sulfide with small particle size and capable of being directly used, does not need secondary grinding and refining, shortens the preparation time, and improves the conversion efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of compound preparation, and relates to lithium sulfide and a preparation method and application thereof. BACKGROUND

[0002] As a lithium sulfide, lithium sulfide is a white to yellow crystal with an inverse fluorite structure, has a melting point of 938 DEG C and a boiling point of 1372 DEG C, is easily soluble in water, can be dissolved in ethanol, can be dissolved in acid but not in alkali. Lithium sulfide is easy to absorb water vapor and hydrolyze in air, and release toxic hydrogen sulfide gas, so it is usually used in an atmosphere protection. Lithium sulfide is a potential electrolyte material used in rechargeable lithium ion batteries, and is also widely used in lithium-sulfur battery positive electrode materials, and has a very high theoretical capacity. At the same time, lithium sulfide can also be used as a basic material for synthesizing sulfide solid electrolytes in solid-state batteries to improve the ionic conductivity of solid-state batteries and improve the overall performance of solid-state batteries, so the excellent electrochemical performance of lithium sulfide determines its broad application prospects in the future development of lithium batteries.

[0003] At present, the preparation methods of lithium sulfide mainly include synthesis method and pyrolysis method. The synthesis method includes: reaction of metal lithium or organic lithium with sulfur in an organic solvent, such as CN 108190845A discloses a method for preparing high-purity lithium sulfide by using a pressure reaction kettle: high-purity metal lithium and high-purity sulfur are used as raw materials, and one or more of ether, cyclic ether, alkane, cycloalkane, aromatic hydrocarbon, heteroatom-substituted aromatic hydrocarbon and carbon disulfide are mixed as solvent, and the reaction is carried out in a high-pressure reaction kettle to prepare lithium sulfide. All the above operations are carried out in an inert atmosphere glove box, that is, lithium and sulfur are directly combined under high temperature and high pressure conditions in a pressure reaction kettle to obtain lithium sulfide which can be used as a raw material for synthesizing solid sulfide electrolyte. However, this method has high requirements for process control and has certain danger.

[0004] The pyrolysis method includes: sulfur source and lithium salt to generate lithium sulfide, such as patent CN 116917228A discloses a method for manufacturing lithium sulfide without by-products and with high ionic conductivity, which includes: reducing lithium sulfate put into a furnace under an atmosphere with a pressure of 0.05 MPa or less at a temperature of 700 DEG C or higher. However, the above method uses a high temperature for synthesis, and the lithium salt used is mostly high-priced lithium sulfate, and the reaction environment is mostly inert atmosphere or vacuum environment. At the same time, the above preparation methods are to mix or dissolve the reactants first, then add them at one time, and then react by changing the environmental conditions. This method will cause the reaction speed to be large at the beginning of the reaction, the particle size of the formed material is large, and the product cannot be directly used, and needs to be refined again.

[0005] Therefore, in the existing preparation process of lithium sulfide, the lithium source is mainly high-purity lithium metal, lithium hydroxide and other materials. Such materials have strict storage conditions and are prone to deterioration or explosion. At the same time, in the existing technology, the particle size of the produced lithium sulfide material is large (D50≥50 μm), and the material needs to be crushed, ground and processed, which increases the material preparation time and reduces the conversion efficiency.

[0006] Based on the above research, it is necessary to provide a preparation method of lithium sulfide, which can prepare lithium sulfide with small particle size at a low temperature and can be directly used. SUMMARY

[0007] The purpose of the present application is to provide a lithium sulfide and its preparation method and application. The preparation method has high controllability, can prevent the problem of too fast reaction speed at the beginning of the reaction, and can obtain lithium sulfide with small particle size and can be directly used without secondary grinding and refining, which shortens the preparation time and improves the conversion efficiency.

[0008] To achieve this purpose, the present application adopts the following technical solutions:

[0009] In a first aspect, the present application provides a preparation method of lithium sulfide, which comprises the following steps:

[0010] (1) Spray the atomized lithium source into the sulfur source for reaction to obtain a crude product;

[0011] (2) Spray drying the crude product of step (1) to obtain the lithium sulfide.

[0012] The present application avoids the problem of large particle size of the produced lithium sulfide by spray reaction and drying, and can obtain lithium sulfide with small particle size and can be directly used, which omits the crushing and grinding steps and shortens the preparation process. Moreover, the spray reaction can avoid the problem of too fast reaction at the beginning of the reaction, improve the controllability of the reaction, and reduce the required reaction temperature.

[0013] Preferably, the temperature of the reaction in step (1) is 120-150℃, for example, it can be 120℃, 130℃, 140℃ or 150℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0014] The present application controls the initial reaction speed and reduces the reaction temperature by spraying the atomized lithium source into the sulfur source, so that the reaction temperature is only 120-150℃. If the reaction temperature is too low, on the one hand, the lithium source sprayed into the tank at the early stage will not react fully, resulting in a decrease in conversion rate. On the other hand, the water produced by the reaction will condense into water droplets, causing water residue during the later vacuum stage. If the reaction temperature is too high, the gas pressure in the reaction tank will increase, increasing the burden on the reaction tank.

[0015] Preferably, the flow rate of the spraying is 10-50 mL / min, for example, it can be 10 mL / min, 20 mL / min, 30 mL / min, 40 mL / min or 50 mL / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0016] The flow rate of the lithium source sprayed in the present application affects the speed of the reaction, thereby affecting the quality of the product. If the flow rate of the spraying is too large, the amount of lithium source sprayed per unit time will be too large, and the reaction will not be sufficient. If the flow rate of the spraying is too small, in addition to significantly increasing the process reaction time, on the one hand, it will cause the molten lithium source to accumulate in the pipeline for a long time, making it more likely to form residue. On the other hand, it will require more detailed spraying process and more economic cost.

[0017] Preferably, the lithium source in step (1) is atomized by melting the lithium source.

[0018] The present application directly uses the molten lithium source for atomization, which can ensure that the lithium source reaches the reaction temperature directly and starts to react as soon as it comes into contact with the sulfur source in the tank. If the lithium source is dissolved in water and then sprayed, the water will prevent the temperature from exceeding 100℃ under normal pressure, and even if it is pressurized, it is difficult to reach above 750℃, which cannot cause the reaction to occur.

[0019] Preferably, the lithium source in step (1) is heated and melted at 750-900℃, for example, it can be 800℃, 850℃ or 900℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0020] Preferably, the lithium source in step (1) includes lithium carbonate.

[0021] The lithium source of the present application uses lithium carbonate to directly react with the sulfur source, which not only has low cost, but also has low sensitivity to the environment and strong compatibility.

[0022] Preferably, the sulfur source in step (1) includes hydrogen sulfide gas.

[0023] The hydrogen sulfide gas is first injected into the reaction tank, the inside of the reaction tank is heated to a reaction temperature of 120-150°C for standby, then the molten lithium carbonate is atomized and sprayed into the reaction tank for reaction.

[0024] Preferably, after the atomization of the lithium source in step (1) is completed, the system is vacuumed, then heated at a temperature above 100°C, for example, 110°C, 120°C, 150°C, 180°C or 200°C, for more than 1h, for example, 2h, 2.5h, 3h or 3.5h, then inert gas or dry air is introduced, and finally the crude product is collected.

[0025] After the atomization is completed, the inside of the reaction tank is vacuumed, the residual hydrogen sulfide gas and water vapor in the tank are sucked out, and the tank is heated at a temperature above 100°C for more than 1h, then inert gas or dry air is introduced, the tank is opened, and the product inside the tank is collected.

[0026] Preferably, the vacuuming time is more than 10min, for example, 15min, 25min, 35min or 45min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0027] Preferably, the obtained crude product is further purified before the spray drying in step (2).

[0028] Preferably, the purification includes dissolving the crude product in an organic solvent, then performing solid-liquid separation to remove solid impurities, and collecting the liquid.

[0029] Preferably, the organic solvent includes anhydrous ethanol.

[0030] Preferably, the molar ratio of the organic solvent, the sulfur source in step (1) and the lithium source in step (1) is (50-100):(2.05-2.4):1, for example, 60:2.2:1, 75:2.3:1 or 80:2.4:1, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0031] Preferably, the temperature for the spray drying in step (2) is 150-300°C, for example, 200°C, 250°C or 300°C, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0032] Preferably, the flow rate of the liquid spray during the spray drying in step (2) is 0.5-2L / min, for example, 1L / min, 1.5L / min or 2L / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0033] Preferably, the spray drying in step (2) is performed under vacuum.

[0034] Preferably, in the spray drying of step (2), the vacuum is maintained for 1h or more, for example, 1.5h, 2h, 2.5h or 3h, and then liquid is sprayed for drying.

[0035] The organic solvent obtained after the spray drying of the present application can be recycled.

[0036] As a preferred technical solution of the present application, the preparation method comprises the following steps:

[0037] (1) heating and melting a lithium source at 750-900℃ to obtain a molten lithium source, atomizing the molten lithium source, and then spraying it into a sulfur source at a flow rate of 10-50mL / min, and reacting at 120-150℃, after the atomization of the lithium source is completed, the system is vacuumized, and the temperature is maintained at 100℃ or above for 1h or more, then inert gas or dry air is introduced, and finally the crude product is collected;

[0038] (2) dissolving the crude product obtained in step (1) in an organic solvent, then performing solid-liquid separation to remove solid impurities, collecting the liquid, and then performing spray drying of the liquid at a flow rate of 0.5-2L / min under vacuum and at a temperature of 150-300℃ to obtain lithium sulfide.

[0039] In a second aspect, the present application provides a lithium sulfide prepared by the preparation method of the first aspect.

[0040] Preferably, the particle size D50 of the lithium sulfide is 6.0-10μm, for example, 6μm, 7μm, 8μm, 9μm or 10μm, but is not limited to the listed values, and other values not listed within the value range are also applicable.

[0041] Preferably, the yield of the lithium sulfide is 90-98.5%, for example, 91%, 93%, 95%, 97% or 98%, and the purity is 98-99.9%, for example, 98.2%, 98.5%, 99.0%, 99.5% or 99.9%, but is not limited to the listed values, and other values not listed within the value range are also applicable.

[0042] In a third aspect, the present application provides a battery comprising the lithium sulfide of the second aspect.

[0043] Compared with the prior art, the present application has the following beneficial effects:

[0044] The present application avoids large particle size of the produced lithium sulfide, and can obtain lithium sulfide with small particle size and capable of being directly used, thereby omitting the crushing and grinding steps and shortening the preparation process; and the spray reaction can avoid the problem of too fast reaction at the initial stage, improve the controllability of the reaction, and reduce the required reaction temperature. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 A flow chart of the preparation method according to Example 1 of the present application is shown in the figure.

[0046] Figure 2 XRD spectra of lithium sulfide standard and lithium sulfide obtained in Example 1 are shown in the figure.

[0047] Figure 3 A scanning electron microscope image of lithium sulfide obtained in Example 1 of the present application is shown in the figure. DETAILED DESCRIPTION

[0048] The technical solutions of the present application are further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations on the present application.

[0049] Example 1

[0050] The present embodiment provides a preparation method of lithium sulfide, and a flow chart of the preparation method is shown in the figure. Figure 1 First, lithium carbonate is calcined and melted into a liquid, then atomized and sprayed into a reaction tank containing hydrogen sulfide for reaction, the obtained crude product is dissolved with an organic solvent, after filtering impurities, the filtrate is atomized and sprayed into a spray drying tank, and spray drying is carried out under vacuum and high temperature conditions to obtain lithium sulfide product. The preparation method comprises the following steps:

[0051] (1) 2.05 mol of hydrogen sulfide gas (about 45.92 L) is injected into a vacuum reaction tank, and the reaction tank is heated to 120°C for standby;

[0052] 1 mol of lithium carbonate (about 73.9 g) is added into a furnace, heated to 750°C, and the lithium carbonate is melted into a liquid state. The molten lithium source is sprayed into the above reaction tank at a flow rate of 10 mL / min, and reacts with hydrogen sulfide gas at 120°C. After the atomization is completed, the reaction tank is vacuumed for 20 min, and then argon is introduced. After the tank body is opened, the crude product inside the tank body is collected;

[0053] (2) The crude product obtained in step (1) is dissolved in 100 mol (about 4670 g) of ethanol, then filtered to remove solid impurities, and the filtrate is collected;

[0054] The inside of the drying tank was heated to 150°C and vacuumized, then the filtrate was spray-dried at a flow rate of 0.5 L / min, after drying was completed, inert gas or dry air was introduced into the drying tank, the tank was opened, and lithium sulfide was obtained. The standard XRD spectrum of lithium sulfide and the XRD spectrum of lithium sulfide obtained in this example are shown in Figure 2 The scanning electron microscope image of lithium sulfide obtained in this example is shown in Figure 3

[0055] Example 2

[0056] This example provides a preparation method of lithium sulfide, which comprises the following steps:

[0057] (1) 12 moles of hydrogen sulfide gas (about 268.8 L) were injected into a vacuum reaction tank, and the reaction tank was heated to 150°C for standby;

[0058] 5 moles of lithium carbonate (about 370 g) were added into a furnace, and heated to 900°C to melt the lithium carbonate into a liquid state. The molten lithium source was sprayed into the above reaction tank at a flow rate of 30 mL / min, and reacted with hydrogen sulfide gas at 150°C. After the atomization was completed, the reaction tank was vacuumized for 10 min, and then heated at 100°C for 1 h. Dry air was introduced, and finally the tank was opened to collect the crude product inside the tank.

[0059] (2) The crude product obtained in step (1) was dissolved in 500 moles (about 23035 g) of ethanol, then filtered to remove solid impurities, and the filtrate was collected. The inside of the drying tank was heated to 300°C and vacuumized, then the filtrate was spray-dried at a flow rate of 2 L / min. After drying was completed, inert gas or dry air was introduced into the drying tank, the tank was opened, and lithium sulfide was obtained.

[0060] Example 3

[0061] This example provides a preparation method of lithium sulfide, which comprises the following steps:

[0062] (1) 44 moles of hydrogen sulfide gas (about 985.6 L) were injected into a vacuum reaction tank, and the reaction tank was heated to 150°C for standby;

[0063] 20 moles of lithium carbonate (about 1480 g) were added into a furnace, and heated to 850°C to melt the lithium carbonate into a liquid state. The molten lithium source was sprayed into the above reaction tank at a flow rate of 50 mL / min, and reacted with hydrogen sulfide gas at 150°C. After the atomization was completed, the reaction tank was vacuumized for 10 min, and then heated at 120°C for 1 h. Argon was introduced, and finally the tank was opened to collect the crude product inside the tank.

[0064] ​(2) The crude product obtained in step (1) is dissolved in 1000 mol (about 46070 g) of ethanol, and then filtered to remove solid impurities and collect the filtrate; the inside of the drying tank is heated to 220°C and vacuumized, and then the filtrate is spray-dried at a flow rate of 1 L / min, after drying is completed, inert gas or dry air is introduced into the drying tank, and the tank body is opened to obtain lithium sulfide.

[0065] Example 4

[0066] This example provides a preparation method of lithium sulfide, which is the same as example 1 except that the flow rate of the molten lithium source in step (1) is 3 mL / min.

[0067] Example 5

[0068] This example provides a preparation method of lithium sulfide, which is the same as example 1 except that the flow rate of the molten lithium source in step (1) is 70 mL / min.

[0069] Example 6

[0070] This example provides a preparation method of lithium sulfide, which is the same as example 1 except that the temperature of the reaction in step (1) is 80°C, and the adaptive reaction tank is heated to 80°C for standby.

[0071] Example 7

[0072] This example provides a preparation method of lithium sulfide, which is the same as example 1 except that the temperature of the reaction in step (1) is 180°C, and the adaptive reaction tank is heated to 180°C for standby.

[0073] Example 8

[0074] This example provides a preparation method of lithium sulfide, which is the same as example 1 except that the lithium carbonate in step (1) is not molten but dissolved in water to obtain a saturated lithium carbonate solution, which is then sprayed into the above-mentioned reaction tank at a flow rate of 10 mL / min.

[0075] Example 9

[0076] This example provides a preparation method of lithium sulfide, which is the same as example 1 except that the lithium carbonate in step (1) is replaced by lithium hydroxide in the same molar amount of lithium ions.

[0077] Comparative Example 1

[0078] The comparative example 1 provides a method for preparing lithium sulfide, which is the same as example 1 except that the lithium carbonate in step (1) is not melted and atomized, but directly placed in the reaction tank in solid form.

[0079] Comparative example 2

[0080] The comparative example 1 provides a method for preparing lithium sulfide, which is the same as example 1 except that the lithium carbonate in step (1) is not melted and atomized, but directly placed in the reaction tank in solid form.

[0081] The particle size D50, purity and reaction yield of the lithium sulfide obtained by the above examples and comparative examples are shown in Table 1 below:

[0082] Table 1

[0083] Particle size D 50 (μm) Purity (%) Yield (%) Example 1 7.46 99.4 93.34 Example 2 8.64 99.6 94.63 Example 3 6.57 99.6 95.04 Example 4 7.68 93.7 52.34 Example 5 8.27 96.2 72.38 Example 6 7.95 85.7 81.43 Example 7 8.17 99.1 64.45 Example 8 / 0 0 Example 9 7.61 43.5 35.81 Comparative Example 1 / 0 0 Comparative Example 2 Particles too large 99.04 92.26

[0084] From Table 1, the following can be seen:

[0085] (1) From example 1 and comparative examples 1-2, it can be seen that the present application can directly obtain lithium sulfide with small particle size, high yield and high purity. In comparative example 1, the lithium carbonate in the reaction tank cannot react with hydrogen sulfide without melting and atomization, and the product obtained in comparative example 2 has too large a particle size and needs to be further treated such as grinding before use. From example 1 and examples 4-7, it can be seen that the flow rate of the atomized molten lithium carbonate sprayed into the reaction tank and the reaction temperature will affect the reaction effect. Specifically, in example 4, the flow rate is too low, causing insufficient flow and pressure of the spray head, poor atomization effect, resulting in a decrease in yield and purity, and the low flow rate also leads to a long reaction time. In example 5, the flow rate is too high, causing large atomized particles, excess reaction raw materials and incomplete reaction. In example 6, the initial temperature is low, the reaction is incomplete, and the water generated in the early stage will be liquefied as water droplets due to the low temperature, falling down and reacting with the product to form LiOH. In example 7, the initial temperature is high, the reaction is violent, the temperature is too high in the later stage, the pressure of the tank body exceeds the safety value, causing the tank body to release pressure in the middle of the reaction, affecting the reaction and causing waste of the product.

[0086] (2) From example 1 and example 8, it can be seen that the present application preferably uses molten lithium carbonate for atomization to avoid introducing other impurities. If an aqueous lithium carbonate solution is used, the target product cannot be formed due to the influence of water. From example 1 and example 9, it can be seen that the present application preferably uses lithium carbonate for reaction, which has low cost, low sensitivity to the environment and strong compatibility, and is more suitable for the preparation method of the present application. Lithium hydroxide is extremely easy to decompose at a melting temperature of 750°C to form lithium oxide particles and hydrogen gas, and lithium oxide cannot react with hydrogen sulfide in the particle state.

[0087] In summary, the application provides a lithium sulfide and a preparation method and application thereof, the preparation method has high controllability, can prevent the problem of too fast reaction speed in the initial stage of reaction, obtains lithium sulfide with small particle size and capable of being directly used, does not need secondary grinding and refining, shortens the preparation time, and improves the conversion efficiency.

[0088] The above merely provides a specific implementation of the application, but the protection scope of the application is not limited thereto, and those skilled in the art should understand that any change or replacement within the technical scope disclosed by the application, which can be easily thought of by any person skilled in the art, falls within the protection scope and disclosure scope of the application.

Claims

1. A method for producing lithium sulfide, characterized by, The preparation method comprises the following steps: (1) atomizing a lithium source and spraying it into a sulfur source to react, to obtain a crude product; (2) spray drying the crude product of step (1) to obtain the lithium sulfide; The temperature of the reaction of step (1) is 120-150°C; the flow rate of the spraying is 10-50 mL / min; The atomization of the lithium source of step (1) comprises atomizing a molten lithium source; The lithium source of step (1) is heated and melted at 750-900°C.

2. The production method according to claim 1, characterized by, The lithium source of step (1) comprises lithium carbonate.

3. The preparation method according to claim 1, characterized in that, The sulfur source of step (1) comprises hydrogen sulfide gas.

4. The method of claim 1, wherein, After the atomization of the lithium source of step (1) is completed, the system is vacuumed, then kept at a temperature above 100°C for more than 1 hour, then inert gas or dry air is introduced, and finally the crude product is collected.

5. The production method according to claim 4, characterized by, The vacuuming time is more than 10 minutes.

6. The method of claim 1, wherein, Before the spray drying of step (2), the obtained crude product is also subjected to impurity removal.

7. The production method according to claim 6, characterized by, The impurity removal comprises dissolving the crude product in an organic solvent, then performing solid-liquid separation, removing solid impurities, and collecting the liquid.

8. The preparation method according to claim 7, characterized in that, The organic solvent comprises anhydrous ethanol.

9. The preparation method according to claim 7, characterized in that, The molar ratio of the organic solvent, the sulfur source of step (1), and the lithium source of step (1) is (50-100):(2.05-2.4):

1.

10. The method of claim 1, wherein, The temperature of the spray drying of step (2) is 150-300°C.

11. The method of claim 1, wherein, During the spray drying of step (2), the flow rate of the liquid spraying is 0.5-2 L / min.

12. The method of claim 1, wherein, The spray drying of step (2) is performed under vacuum.

13. The method of claim 1, wherein, During the spray drying of step (2), after vacuuming for more than 1 hour, liquid is sprayed for drying.

14. The method of claim 1, wherein, The preparation method comprises the following steps: (1) heating and melting a lithium source at 750-900°C to obtain a molten lithium source, atomizing the molten lithium source, then spraying it into a sulfur source at a flow rate of 10-50 mL / min, reacting at 120-150°C, after the atomization of the lithium source is completed, vacuuming the system, keeping it at a temperature above 100°C for more than 1 hour, then introducing inert gas or dry air, and finally collecting the crude product; (2) dissolving the crude product obtained in step (1) in an organic solvent, then performing solid-liquid separation, removing solid impurities, collecting the liquid, then under vacuum and at a temperature of 150-300°C, spraying the liquid at a flow rate of 0.5-2 L / min to perform spray drying, to obtain lithium sulfide.

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