Preparation method of lithium fluorosulfonate

Abstract

The present invention provides a lithium fluorosulfonate preparation method, and relates to the technical field of chemical synthesis, the preparation method comprises: taking pyrosulfuric acid and lithium fluoride as raw materials, and carrying out a one-step reaction in a solvent to prepare the lithium fluorosulfonate. In the method, the lithium fluorosulfonate with high yield and purity is successfully prepared by precisely controlling the reaction molar ratio, temperature and other process conditions. Strong acid raw materials such as chlorosulfonic acid and fluorosulfonic acid are not used in the reaction process, and all the raw materials are solid, so that the preparation steps are relatively simple, the purity and yield of the product are high, the byproduct HF can be recycled to prepare lithium fluoride, the byproduct lithium sulfate can be recycled, and the total atom utilization rate is high, the environmental pollution is small, and the method is suitable for industrial production. And industrial production and application of the electrolyte for preparing the lithium battery are facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, and in particular to a method for preparing lithium fluorosulfonate. Background Art

[0002] Lithium fluorosulfonate is a new type of lithium salt that can be used as an electrolyte in lithium-ion battery electrolytes. Using lithium fluorosulfonate as a lithium-ion battery electrolyte can significantly improve the high-temperature charge-discharge cycle characteristics of lithium batteries and maintain a high battery capacity retention rate. Currently, known methods for producing lithium fluorosulfonate mostly involve reacting fluorosulfonic acid or chlorosulfonic acid with a lithium salt. This reaction produces large amounts of waste gas that is difficult to handle, and it also produces numerous side reactions, resulting in a high level of impurities that affect yield. Furthermore, the fluorosulfonic acid used as a raw material is difficult to obtain and readily reacts with moisture in the air to produce hydrogen fluoride, which is also difficult to handle. Fluorosulfonic acid and chlorosulfonic acid are prone to fuming, are highly corrosive, and are inconvenient to transport and use, severely limiting the production and use of lithium fluorosulfonate. Therefore, the existing technology needs further development. Summary of the Invention

[0003] In view of the various deficiencies of the existing technology, in order to solve the above problems, a preparation method of lithium fluorosulfonate is proposed, and the following technical solutions are provided: A method for preparing lithium fluorosulfonate comprises: using pyrosulfuric acid and lithium fluoride as raw materials to react in a solvent in one step to prepare lithium fluorosulfonate.

[0004] Furthermore, the molar ratio of the pyrosulfuric acid to lithium fluoride is 1.0:(3.0-3.5).

[0005] Furthermore, the molar ratio of pyrosulfuric acid to lithium fluoride is 1.0:3.1.

[0006] Furthermore, the reaction temperature of the pyrosulfuric acid and lithium fluoride is 10-150°C.

[0007] Furthermore, the reaction temperature of the pyrosulfuric acid and lithium fluoride is 25-80°C.

[0008] Furthermore, the reaction temperature of the pyrosulfuric acid and lithium fluoride is 40°C.

[0009] Furthermore, the mass ratio of the pyrosulfuric acid to the solvent is 1:(3-10).

[0010] Furthermore, the solvent is a non-aqueous solvent, and the non-aqueous solvent is one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, ethyl acetate, tetrahydrofuran, ethylene glycol dimethyl ether, ethyl ether, methyl tert-butyl ether, ethylene carbonate, and 1,4-dioxane.

[0011] Furthermore, the non-aqueous solvent is one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0012] Furthermore, inert gas protection is performed during the reaction of pyrosulfuric acid and lithium fluoride.

[0013] Beneficial effects: 1. In a preparation method of lithium fluorosulfonate of the present invention, pyrosulfuric acid is used as a raw material. By precisely controlling the reaction amount and condition parameters, lithium fluorosulfonate with high yield and purity is successfully prepared.

[0014] 2. No chlorosulfonic acid or fluorosulfonic acid is used in the reaction process of the present invention, the raw materials are all solid, the preparation steps are relatively simple, the by-product HF can be recycled to prepare lithium fluoride, and the by-product lithium sulfate can be recovered. Overall, the atomic utilization rate is high, the environmental pollution is small, and it is conducive to the industrial production and application of preparing lithium battery electrolytes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a reaction mechanism diagram of the present invention; Figure 2 It is the reaction mechanism diagram of Comparative Example 4; Figure 3 This is the reaction mechanism diagram of Comparative Example 5. DETAILED DESCRIPTION

[0016] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments in this application, other similar embodiments obtained by ordinary technicians in this field without making any creative work should fall within the scope of protection of this application.

[0017] According to an embodiment of the present invention, a method for preparing lithium fluorosulfonate is provided, comprising: using pyrosulfuric acid and lithium fluoride as raw materials in a solvent to react in a one-step manner to prepare lithium fluorosulfonate. In this method, lithium fluorosulfonate with high yield and purity is successfully prepared by precisely controlling process conditions such as the reaction molar ratio and temperature. Because no strongly acidic raw materials such as chlorosulfonic acid and fluorosulfonic acid are used in the reaction process, the raw materials are all solid, the preparation steps are relatively simple, the product has high purity and yield, the by-product HF can be recycled to prepare lithium fluoride, and the by-product lithium sulfate can be recovered. Overall, the atomic utilization rate is high, the environmental pollution is low, and it is conducive to the industrial production and application of lithium battery electrolytes.

[0018] This application selects pyrosulfuric acid as one of the raw materials. Pyrosulfuric acid is a solid material that avoids the strong corrosiveness of strong acids such as sulfuric acid and is convenient and easy to obtain. Pyrosulfuric acid and the by-product lithium sulfate obtained by the reaction can reduce the effect of moisture on the reaction and reduce the moisture requirement of the reaction system. Figure 1 As shown, pyrosulfuric acid decomposes into fluorosulfonic acid and lithium hydroxysulfonate under the action of lithium fluoride (Lewis base), fluorosulfonic acid and lithium fluoride continue to react to generate lithium fluorosulfonate and hydrogen fluoride, and lithium hydroxysulfonate and lithium fluoride continue to react to generate lithium sulfate.

[0019] During the reaction of pyrosulfuric acid and lithium fluoride, inert gas protection is performed. The inert gas protection is mainly to ensure anhydrous conditions, as moisture will cause lithium fluorosulfonate to decompose; the gas can also promote the discharge of generated HF from the reaction system.

[0020] Example 1 Add 178 g (1 mol) of pyrosulfuric acid into a constant pressure dropping funnel, add 712 g of dimethyl carbonate solvent, stir and dissolve, and record it as solution 1; Add 80.41 g (3.1 mol) of lithium fluoride to a three-necked flask, add 178 g of dimethyl carbonate solvent, stir evenly, introduce nitrogen to protect the reaction system, then slowly dropwise add solution 1 to the three-necked flask to react with stirring. The reaction temperature is set to 40°C to prevent the reaction from becoming violent. The gas generated by the reaction is introduced into the water through a reflux device. When no bubbles emerge from the gas inlet in the water, continue stirring for 3 hours, end the reaction, and naturally cool to room temperature.

[0021] The pH value of the reaction solution was tested, and then a regulating agent, pyrosulfuric acid, was added to adjust the pH value to about 7. The reaction solution was filtered to remove insoluble impurities, and the filtrate was concentrated under reduced pressure at 40°C. When no fraction was released, n-heptane was added for crystallization. After filtration, wet solid lithium fluorosulfonate was obtained, which was then dried in a vacuum drying oven at 50°C for 8 hours to obtain 96 g (0.5311 mol) of pure white powdery lithium fluorosulfonate solid with a yield of 90.5% and a purity of 99.8% (calculated as pyrosulfuric acid).

[0022] Example 2 Add 178 g (1 mol) of pyrosulfuric acid into a constant pressure dropping funnel, add 356 g of dimethyl carbonate solvent, stir and dissolve, and record it as solution 1; Add 78 g (3 mol) of lithium fluoride to a three-necked flask, add 178 g of dimethyl carbonate as solvent, stir evenly, introduce nitrogen to protect the reaction system, and then slowly dropwise add solution 1 to the three-necked flask for stirring reaction. The reaction temperature is set to 25°C to prevent the reaction from becoming violent. The gas generated by the reaction is introduced into the water through a reflux device. When no bubbles emerge from the gas inlet in the water, continue stirring for 3 hours, end the reaction, and naturally cool to room temperature.

[0023] The pH value of the reaction solution was tested, and sulfuric acid was added as a regulator to adjust the pH value to about 7. The reaction solution was filtered to remove insoluble impurities. The filtrate was concentrated under reduced pressure at 40°C. When no fraction was released, n-heptane was added for crystallization. After filtration, wet solid lithium fluorosulfonate was obtained, which was then dried in a vacuum drying oven at 50°C for 8 hours to obtain 91 g (0.858 mol) of pure white powdery lithium fluorosulfonate solid, with a yield of 85.8% and a purity of 99.7% (calculated as pyrosulfuric acid).

[0024] Example 3 Add 178 g (1 mol) of pyrosulfuric acid into a constant pressure dropping funnel, add 1424 g of dimethyl carbonate solvent, stir and dissolve, and record it as solution 1; Add 91 g (3.5 mol) of lithium fluoride to a three-necked flask, add 356 g of diethyl carbonate as solvent, stir evenly, introduce nitrogen to protect the reaction system, then slowly dropwise add solution 1 to the three-necked flask to react with stirring. Set the reaction temperature to 80°C to prevent the reaction from becoming violent. Pass the gas generated by the reaction into the water through a reflux device. When no bubbles emerge from the gas inlet in the water, continue stirring for 4 hours, terminate the reaction, and naturally cool to room temperature.

[0025] The pH value of the reaction solution was tested, and then a regulating agent, pyrosulfuric acid, was added to adjust the pH value to about 7. The reaction solution was filtered to remove insoluble impurities. The filtrate was concentrated under reduced pressure at 40°C. When no fraction was released, n-heptane was added for crystallization. After filtration, wet solid lithium fluorosulfonate was obtained, which was then dried in a vacuum drying oven at 50°C for 8 hours to obtain 94 g (0.887 mol) of pure white powdery lithium fluorosulfonate solid, with a yield of 88.7% and a purity of 99.6% (calculated as pyrosulfuric acid).

[0026] Example 4 Add 178 g (1.0 mol) of pyrosulfuric acid into a constant pressure dropping funnel, add 712 g of diethyl carbonate solvent, stir and dissolve, and record it as solution 1; Add 80.41 g (3.1 mol) of lithium fluoride to a three-necked flask, add 178 g of diethyl carbonate as solvent, stir evenly, introduce nitrogen to protect the reaction system, then slowly dropwise add solution 1 to the three-necked flask to react with stirring. The reaction temperature is set to 150°C to prevent the reaction from becoming violent. The gas generated by the reaction is introduced into the water through a reflux device. When no bubbles emerge from the gas inlet in the water, continue stirring for 4 hours, terminate the reaction, and naturally cool to room temperature.

[0027] The pH value of the reaction solution was tested, and then a regulating agent, pyrosulfuric acid, was added to adjust the pH value to about 7. The reaction solution was filtered to remove insoluble impurities. The filtrate was concentrated under reduced pressure at 40°C. When no fraction was released, n-heptane was added for crystallization. After filtration, wet solid lithium fluorosulfonate was obtained, which was then dried in a vacuum drying oven at 50°C for 8 hours to obtain 0.89 g (0.840 mol) of pure white powdery lithium fluorosulfonate solid with a yield of 84% and a purity of 99.2% (calculated as pyrosulfuric acid).

[0028] Example 5 Add 178 g (1.0 mol) of pyrosulfuric acid into a constant pressure dropping funnel, add 712 g of diethyl carbonate solvent, stir and dissolve, and record it as solution 1; Add 78 g (3.01 mol) of lithium fluoride to a three-necked flask, add 178 g of diethyl carbonate as solvent, stir evenly, introduce nitrogen to protect the reaction system, then slowly dropwise add solution 1 to the three-necked flask to react with stirring. Set the reaction temperature to 150°C to prevent the reaction from becoming violent. Pass the gas generated by the reaction into the water through a reflux device. When no bubbles emerge from the gas inlet in the water, continue stirring for 4 hours, terminate the reaction, and naturally cool to room temperature.

[0029] The pH value of the reaction solution was tested, and then a regulating agent, pyrosulfuric acid, was added to adjust the pH value to about 7. The reaction solution was filtered to remove insoluble impurities, and the filtrate was concentrated under reduced pressure at 40°C. When no fraction was released, n-heptane was added for crystallization. After filtration, wet solid lithium fluorosulfonate was obtained, which was then dried in a vacuum drying oven at 50°C for 8 hours to obtain 0.85 g (0.802 mol) of pure white powdery lithium fluorosulfonate solid, with a yield of 80.2% and a purity of 99.1% (calculated as pyrosulfuric acid).

[0030] Comparative Example 1 Add 178 g (1.0 mol) of pyrosulfuric acid into a constant pressure dropping funnel, add 712 g of dimethyl carbonate solvent, stir and dissolve, and record it as solution 1; Add 25.94 g (1 mol) of lithium fluoride to a three-necked flask, add 178 g of dimethyl carbonate solvent, stir evenly, introduce nitrogen to protect the reaction system, then slowly dropwise add solution 1 to the three-necked flask to react with stirring. The reaction temperature is set to 40°C to prevent the reaction from becoming violent. The gas generated by the reaction is introduced into the water through a reflux device. When no bubbles emerge from the gas inlet in the water, continue stirring for 3 hours, end the reaction, and naturally cool to room temperature.

[0031] The pH value of the reaction solution was tested, and then a regulating agent, pyrosulfuric acid, was added to adjust the pH value to about 7. The reaction solution was filtered to remove insoluble impurities. The filtrate was concentrated under reduced pressure at 40°C. When no fraction was released, n-heptane was added for crystallization. After filtration, wet solid lithium fluorosulfonate was obtained, which was then dried in a vacuum drying oven at 50°C for 8 hours to obtain 11 g (0.104 mol) of pure white powdery lithium fluorosulfonate solid with a yield of 10.4% and a purity of 47.1% (based on pyrosulfuric acid).

[0032] Comparative Example 2 Add 178 g (1.0 mol) of pyrosulfuric acid into a constant pressure dropping funnel, add 712 g of dimethyl carbonate solvent, stir and dissolve, and record it as solution 1; Add 129.7 g (5 mol) of lithium fluoride to a three-necked flask, add 356 g of dimethyl carbonate as solvent, stir evenly, introduce nitrogen to protect the reaction system, and then slowly dropwise add solution 1 to the three-necked flask for stirring reaction. The reaction temperature is set to 40°C to prevent the reaction from becoming violent. The gas generated by the reaction is introduced into the water through a reflux device. When no bubbles emerge from the gas inlet in the water, continue stirring for 3 hours, end the reaction, and naturally cool to room temperature.

[0033] The pH value of the reaction solution was tested, and then a regulating agent, pyrosulfuric acid, was added to adjust the pH value to about 7. The reaction solution was filtered to remove insoluble impurities, and the filtrate was concentrated under reduced pressure at 40°C. When no fraction was released, n-heptane was added for crystallization. After filtration, wet solid lithium fluorosulfonate was obtained, which was then dried in a vacuum drying oven at 50°C for 8 hours to obtain 0.66 g (0.623 mol) of pure white powdery lithium fluorosulfonate solid, with a yield of 62.3% and a purity of 66.6% (calculated as pyrosulfuric acid).

[0034] Comparative Example 3 Add 178 g (1.0 mol) of pyrosulfuric acid into a constant pressure dropping funnel, add 712 g of dimethyl carbonate solvent, stir and dissolve, and record it as solution 1; Add 78 g (3.01 mol) of lithium fluoride to a three-necked flask, add 178 g of dimethyl carbonate as solvent, stir evenly, introduce nitrogen to protect the reaction system, and then slowly dropwise add solution 1 to the three-necked flask to react with stirring. The reaction temperature is set to 180°C to prevent the reaction from becoming violent. The gas generated by the reaction is introduced into the water through a reflux device. When no bubbles emerge from the gas guide port in the water, continue stirring for 3 hours, end the reaction, and naturally cool to room temperature.

[0035] The pH value of the reaction solution was tested, and then a regulating agent, pyrosulfuric acid, was added to adjust the pH value to about 7. The reaction solution was filtered to remove insoluble impurities, and the filtrate was concentrated under reduced pressure at 40°C. When no fraction was released, n-heptane was added for crystallization. After filtration, wet solid lithium fluorosulfonate was obtained, which was then dried in a vacuum drying oven at 50°C for 8 hours to obtain 35 g (0.33 mol) of pure white powdery lithium fluorosulfonate solid, with a yield of 33% and a purity of 56.3% (calculated as pyrosulfuric acid).

[0036] Comparative Example 4 Add 57.34 g (0.716 mol) of sulfur trioxide into a constant pressure dropping funnel, add 712 g of dimethyl carbonate solvent, stir and dissolve, and record it as solution 1; Add 22.29 g (0.859 mol) of lithium fluoride and 20 g (1 mol) of anhydrous hydrogen fluoride into a three-necked flask, add 178 g of dimethyl carbonate as solvent, stir evenly, introduce nitrogen to protect the reaction system, then slowly dropwise add solution 1 into the three-necked flask to stir and react. The reaction temperature is set to 40°C to prevent the reaction from becoming violent. The gas generated by the reaction is introduced into the water through a reflux device. When no bubbles emerge from the gas inlet in the water, continue stirring for 3 hours, end the reaction, and naturally cool to room temperature.

[0037] The pH value of the reaction solution was tested, and sulfuric acid as a regulator was added to adjust the pH value to about 7. The reaction solution was filtered to remove insoluble impurities, and the filtrate was concentrated under reduced pressure at 40°C. When no fraction was released, n-heptane was added for crystallization. After filtration, wet solid lithium fluorosulfonate was obtained, which was then dried in a vacuum drying oven at 50°C for 8 hours to obtain 29 g (0.275 mol) of pure white powdery lithium fluorosulfonate solid with a yield of 38.4% and a purity of 97.8%.

[0038] Comparative Example 5 Add 70.17 g (0.716 mol) of sulfuric acid and 20 g (7 mol) of anhydrous hydrogen fluoride into a constant pressure dropping funnel, add 712 g of dimethyl carbonate solvent, stir and dissolve, and record it as solution 1; Add 22.29 g (0.859 mol) of lithium fluoride to a three-necked flask, add 178 g of dimethyl carbonate as solvent, stir evenly, introduce nitrogen to protect the reaction system, then slowly dropwise add solution 1 to the three-necked flask to react with stirring. The reaction temperature is set to 40°C to prevent the reaction from becoming violent. The gas generated by the reaction is introduced into the water through a reflux device. When no bubbles emerge from the gas inlet in the water, continue stirring for 3 hours, end the reaction, and naturally cool to room temperature.

[0039] The pH value of the reaction solution was tested, and sulfuric acid was added as a regulator to adjust the pH value to about 7. The reaction solution was filtered to remove insoluble impurities. The filtrate was concentrated under reduced pressure at 40°C. When no fraction was released, n-heptane was added for crystallization. The wet solid of lithium fluorosulfonate was obtained after filtration, and then dried in a vacuum drying oven at 50°C for 8 hours to obtain 21 g (0.198 mol) of pure white powdery lithium fluorosulfonate solid with a yield of 27.7% and a purity of 96.7%.

[0040] In the embodiment, pyrosulfuric acid is used as the raw material, and the molar ratio of lithium fluoride to pyrosulfuric acid and the reaction temperature and other parameters are reasonably controlled, so that the yield of the obtained lithium fluorosulfonate reaches more than 80% and the purity is more than 99%.

[0041] The reaction mechanism diagram of Comparative Example 4 is as follows Figure 2 As shown, the reaction mechanism diagram of Comparative Example 5 is as follows Figure 3 As shown. In Example 1, F - As a nucleophile (Lewis base), it attacks the sulfonyl group, causing the sulfonyl group of the pyrosulfuric acid to break and generate fluorosulfonic acid. Fluorosulfonic acid is neutralized with lithium fluoride to generate lithium fluorosulfonate, with essentially no side reactions occurring during the process. HF in Comparative Example 4 reacts with sulfur trioxide for an addition reaction. The amount of HF used during the reaction needs to be strictly controlled, otherwise it will cause over-fluorination and produce a large amount of polymer, and HF will remain in the fluorosulfonic acid, thereby inhibiting the next step of the reaction. The concentrated sulfuric acid in Comparative Example 5 is fluorinated by HF, and a substitution reaction occurs, generating water as a byproduct. Water will cause the fluorosulfonic acid to decompose, a reversible reaction that stops reacting after reaching a certain equilibrium. Furthermore, the reaction process is prone to decomposition, resulting in a large number of side reactions, making it difficult to control.

[0042] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing lithium fluorosulfonate, characterized in that: include: Lithium fluorosulfonate is prepared by using pyrosulfuric acid and lithium fluoride as raw materials through a one-step reaction in a solvent.

2. The method for preparing lithium fluorosulfonate according to claim 1, wherein: The molar ratio of the pyrosulfuric acid to the lithium fluoride is 1.0:(3.0-3.5).

3. The method for preparing lithium fluorosulfonate according to claim 1 or 2, characterized in that: The molar ratio of the pyrosulfuric acid to the lithium fluoride is 1.0:3.

1.

4. The method for preparing lithium fluorosulfonate according to claim 1, wherein: The reaction temperature of the pyrosulfuric acid and lithium fluoride is 10-150°C.

5. The method for preparing lithium fluorosulfonate according to claim 4, wherein: The reaction temperature of the pyrosulfuric acid and lithium fluoride is 25-80°C.

6. The method for preparing lithium fluorosulfonate according to claim 5, characterized in that: The reaction temperature of the pyrosulfuric acid and lithium fluoride is 40°C.

7. The method for preparing lithium fluorosulfonate according to claim 1, wherein: The mass ratio of the pyrosulfuric acid to the solvent is 1:(3-10).

8. The method for preparing lithium fluorosulfonate according to claim 1, wherein: The solvent is a non-aqueous solvent, and the non-aqueous solvent is one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, ethyl acetate, tetrahydrofuran, ethylene glycol dimethyl ether, ethyl ether, methyl tert-butyl ether, ethylene carbonate, and 1,4-dioxane.

9. The method for preparing lithium fluorosulfonate according to claim 1 or 8, characterized in that: The non-aqueous solvent is one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

10. The method for preparing lithium fluorosulfonate according to claim 1, wherein: Inert gas protection is carried out during the reaction between pyrosulfuric acid and lithium fluoride.

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