Synthesis method of lithium fluorosulfonate

Abstract

The invention provides a synthesis method of lithium fluorosulfonate, which comprises the following steps of: reacting sulfates and a lithium source which are used as raw materials, and reacting a product obtained after the reaction of the sulfates and the lithium source with water to obtain the lithium fluorosulfonate, the sulfate is dimethyl sulfate, diethyl sulfate, monoethyl sulfate or monomethyl sulfate; the lithium source is fluorine-containing lithium salt; the molar ratio of the sulfates to the lithium source is (0.6-1.1): 1. According to the method, sulfates, a lithium source and water are selected as raw materials, other solvents do not need to be added in the whole reaction process, purification is not needed in the middle process, the reaction process is simple, operation is convenient, the sulfates are wide in source and easy to transport, and therefore the route is very suitable for industrial production. The synthesized lithium fluorosulfonate does not introduce chloride ions, the service life of the battery can be prolonged, and the highest yield of the lithium fluorosulfonate can reach 91.7%.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion batteries, and in particular to a method for synthesizing lithium fluorosulfonate. Background Art

[0002] As a key component of lithium-ion batteries, the performance of the electrolyte directly affects the overall performance of the battery, such as energy density, charge and discharge efficiency, cycle life and safety. As a lithium salt with unique physical and chemical properties, lithium fluorosulfonate (LiFSI) is gradually emerging in the battery field. It has the advantages of high ionic conductivity, good thermal stability and chemical stability, which enable it to significantly improve the electrochemical performance of the battery, such as improving the energy density and power density of the battery, and improving the low temperature performance and cycle life of the battery. In the research and development of high-energy-density lithium-ion batteries and fast-charging batteries, lithium fluorosulfonate has shown great application potential and is expected to meet the growing demand for battery performance in modern electronic devices and electric vehicles.

[0003] Although lithium fluorosulfonate has such important potential value in the field of batteries and catalysis, there are still many deficiencies in the current research on its preparation method. Traditional preparation methods often face problems such as harsh reaction conditions, many side reactions, low product purity, and raw material corrosion equipment. Not only does it increase the maintenance cost of the equipment and reduce its service life, it also produces a large amount of hazardous waste, pollutes the environment, and limits the industrial application of lithium fluorosulfonate. In the known lithium fluorosulfonate process routes, most of them use chlorosulfonic acid and lithium fluoride to react to synthesize lithium fluorosulfonate, or obtain fluorosulfonic acid by fluorination of chlorosulfonic acid, and then react fluorosulfonic acid with lithium salt to obtain lithium fluorosulfonate. However, this type of method uses chlorosulfonic acid as a reaction raw material, which will introduce chloride ions, resulting in a high chloride ion content in the final lithium fluorosulfonate. Chloride ions are a harmful element in batteries and will have a serious impact on battery life.

[0004] Therefore, the prior art needs to be further developed. Summary of the invention

[0005] In view of the various deficiencies of the prior art, in order to solve the above problems, a synthesis method of lithium fluorosulfonate is proposed, and the following technical solution is provided: A method for synthesizing lithium fluorosulfonate, comprising reacting a sulfate ester and a lithium source as raw materials, and reacting a product of the reaction of the sulfate ester and the lithium source with water to obtain lithium fluorosulfonate; The sulfate ester is dimethyl sulfate, diethyl sulfate, monoethyl sulfate or monomethyl sulfate; The lithium source is a fluorine-containing lithium salt; The molar ratio of the sulfate to the lithium source is (0.6-1.1):1.

[0006] Furthermore, the reaction temperature of the sulfate ester and the lithium source is 30-60° C., and the reaction time is 5-10 hours.

[0007] Furthermore, the temperature for the reaction between the product after the reaction of the sulfate ester and the lithium source and water is -20 to -10°C, and the time for adding water when the product after the reaction of the sulfate ester and the lithium source and water reacts is 2-3h.

[0008] Furthermore, the reaction time of the product after the reaction of the sulfate ester and the lithium source with water is 6-24 hours.

[0009] Furthermore, the fluorine-containing lithium salt is lithium fluoride, lithium hexafluorophosphate, lithium trifluoromethanesulfonate or lithium perfluorobutylsulfonate.

[0010] Furthermore, the reaction between the sulfate ester and the lithium source and the reaction between the product after the reaction between the sulfate ester and the lithium source and water are both carried out under an inert gas atmosphere.

[0011] Furthermore, the product of the reaction between the sulfate and the lithium source is reacted with water and then post-treated to obtain lithium fluorosulfonate, and the post-treatment includes adding a polar aprotic solvent and then filtering, distilling under reduced pressure, and stirring and crystallizing with a poor solvent.

[0012] Furthermore, the polar aprotic solvent can be selected from ethyl methyl carbonate, dimethyl carbonate or carbonic acid diester, and the poor solvent is dichloromethane, dichloroethane, n-hexane or isopropane.

[0013] Beneficial effects: 1. The present invention selects sulfates, lithium sources and water as raw materials. No other solvents need to be added during the entire reaction process, and no purification is required during the intermediate process. The reaction process is simple and easy to operate. Sulfates are widely available and easy to transport, so this route is very suitable for industrial production.

[0014] 2. The lithium fluorosulfonate synthesized by the present invention will not introduce chloride ions, and can increase the life of the battery.

[0015] 3. The yield of lithium fluorosulfonate in the synthesis method of lithium fluorosulfonate of the present invention can reach 91.7%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a reaction mechanism diagram of a synthesis method of lithium fluorosulfonate of the present invention. DETAILED DESCRIPTION

[0017] 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 all fall within the scope of protection of this application.

[0018] According to an embodiment of the present invention, a method for synthesizing lithium fluorosulfonate is provided. Figure 1 , including: reacting with sulfate esters and lithium source as raw materials, and reacting the product after the reaction of sulfate esters and lithium source with water to obtain lithium fluorosulfonate. The present invention selects sulfate esters, lithium source and water as raw materials, and the whole reaction process does not need to add other solvents, and the intermediate process does not need to be purified. The reaction process is simple and easy to operate. Sulfate esters are widely available and easy to transport. Therefore, this route is very suitable for industrial production. In addition, the lithium fluorosulfonate synthesized by the present invention will not introduce chloride ions, which can increase the life of the battery. Among them Figure 1 R and R' in can be an alkyl chain or H, respectively.

[0019] The sulfates are dimethyl sulfate, diethyl sulfate, monoethyl sulfate and monomethyl sulfate.

[0020] The temperature of the reaction between the product of the reaction of the sulfate and the lithium source and water is -20 to -10°C, the water is added for 2-3 hours, and the reaction is continued for 6-24 hours after the addition is completed, which is conducive to the full reaction. Controlling the water addition time is conducive to controlling the occurrence of side reactions.

[0021] After the reaction is completed, pure lithium fluorosulfonate is obtained by post-treatment operations such as filtration, reduced pressure distillation, and crystallization with a poor solvent.

[0022] Example 1 (1) Under nitrogen protection, 37.8 g (0.5 mol) of dimethyl sulfate and 13 g (0.5 mol) of lithium fluoride were added to a flask at a reaction temperature of 50° C. for 10 h.

[0023] (2) Under a nitrogen atmosphere, the temperature was controlled at -20°C, and water was added dropwise to the flask in step (1). The addition time was 2.6 hours, and the reaction was kept at -10°C for 24 hours. After the reaction, 60 mL of ethyl methyl carbonate was added to dissolve the crude lithium fluorosulfonate and the mixture was filtered to remove unreacted lithium fluoride. The mixture was concentrated under reduced pressure to remove part of the ethyl methyl carbonate, and a lithium fluorosulfonate concentrate was obtained. 60 mL of dichloromethane was added to the concentrate to obtain pure lithium fluorosulfonate. The lithium fluorosulfonate yield was 64.4%.

[0024] Example 2 (1) Under nitrogen protection, 37.8 g (0.3 mol) of dimethyl sulfate and 13 g (0.5 mol) of lithium fluoride were added to a flask at a reaction temperature of 60° C. for 5 h.

[0025] (2) Under a nitrogen atmosphere, the temperature was controlled at -15°C, and water was added dropwise to the flask in step (1). The addition time was 2.6 hours, and the reaction was kept at -10°C for 12 hours. After the reaction, 60 mL of ethyl methyl carbonate was added to dissolve the crude lithium fluorosulfonate and the mixture was filtered to remove unreacted lithium fluoride. The mixture was concentrated under reduced pressure to remove part of the ethyl methyl carbonate, and a lithium fluorosulfonate concentrate was obtained. 60 mL of dichloromethane was added to the concentrate to obtain pure lithium fluorosulfonate. The lithium fluorosulfonate yield was 74%.

[0026] Example 3 (1) Under nitrogen protection, 63 g (0.5 mol) of dimethyl sulfate and 13 g (0.5 mol) of lithium fluoride were added to a flask at a reaction temperature of 35° C. for 6 h.

[0027] (2) Under a nitrogen atmosphere, the temperature was controlled at -10°C, and water was added dropwise to the flask in step (1). The addition time was 2 hours, and the reaction was kept at -10°C for 6 hours. After the reaction, 60 mL of ethyl methyl carbonate was added to dissolve the crude lithium fluorosulfonate and the mixture was filtered to remove unreacted lithium fluoride. The mixture was concentrated under reduced pressure to remove part of the ethyl methyl carbonate, and a lithium fluorosulfonate concentrate was obtained. 60 mL of dichloromethane was added to the concentrate to obtain pure lithium fluorosulfonate. The lithium fluorosulfonate yield was 81.3%.

[0028] Example 4 (1) Under nitrogen protection, 63 g (0.55 mol) of dimethyl sulfate and 13 g (0.5 mol) of lithium fluoride were added to a flask at a reaction temperature of 45° C. for 6 h.

[0029] (2) Under a nitrogen atmosphere, the temperature was controlled at -10°C, and water was added dropwise to the flask in step (1). The addition time was 2 hours, and the reaction was kept at -10°C for 6 hours. After the reaction, 60 mL of ethyl methyl carbonate was added to dissolve the crude lithium fluorosulfonate and the mixture was filtered to remove unreacted lithium fluoride. The mixture was concentrated under reduced pressure to remove part of the ethyl methyl carbonate, and a lithium fluorosulfonate concentrate was obtained. 60 mL of dichloromethane was added to the concentrate to obtain pure lithium fluorosulfonate. The lithium fluorosulfonate yield was 87%.

[0030] Example 5 (1) Under nitrogen protection, 63 g (0.55 mol) of dimethyl sulfate and 13 g (0.5 mol) of lithium fluoride were added to a flask at a reaction temperature of 50° C. for 6 h.

[0031] (2) Under a nitrogen atmosphere, the temperature was controlled at -15°C, and water was added dropwise to the flask in step (1). The addition time was 2.6 hours, and the reaction was kept at -10°C for 12 hours. After the reaction, 60 mL of ethyl methyl carbonate was added to dissolve the crude lithium fluorosulfonate and the mixture was filtered to remove unreacted lithium fluoride. The mixture was concentrated under reduced pressure to remove part of the ethyl methyl carbonate, and a lithium fluorosulfonate concentrate was obtained. 60 mL of dichloromethane was added to the concentrate to obtain pure lithium fluorosulfonate. The lithium fluorosulfonate yield was 91.7%.

[0032] Example 6 (1) Under nitrogen protection, 77 g (0.5 mol) of diethyl sulfate and 13 g (0.5 mol) of lithium fluoride were added to a flask at a reaction temperature of 40° C. for 8 h.

[0033] (2) Under a nitrogen atmosphere, the temperature was controlled at -10°C, and water was added dropwise to the flask in step (1). The addition time was 3 hours, and the temperature was kept at -10°C for 6 hours. After the reaction, 60 mL of ethyl methyl carbonate was added to dissolve the crude lithium fluorosulfonate and the mixture was filtered to remove unreacted lithium fluoride. The mixture was concentrated under reduced pressure to remove part of the dimethyl carbonate, and a lithium fluorosulfonate concentrate was obtained. 60 mL of dichloromethane was added to the concentrate to obtain pure lithium fluorosulfonate. The lithium fluorosulfonate yield was 75.8%.

[0034] Example 7 (1) Under nitrogen protection, 56 g (0.5 mol) of monomethyl sulfate and 13 g (0.5 mol) of lithium fluoride were added to a flask at a reaction temperature of 30° C. for 6 h.

[0035] (2) Under a nitrogen atmosphere, the temperature was controlled at -10°C, and water was added dropwise to the flask in step (1). The addition time was 3 hours, and the reaction was kept at -10°C for 6 hours. After the reaction, 60 mL of ethyl methyl carbonate was added to dissolve the crude lithium fluorosulfonate and the mixture was filtered to remove unreacted lithium fluoride. The mixture was concentrated under reduced pressure to remove part of the dimethyl carbonate, and a lithium fluorosulfonate concentrate was obtained. 60 mL of dichloromethane was added to the concentrate to obtain pure lithium fluorosulfonate. The lithium fluorosulfonate yield was 80.7%.

[0036] Comparative Example 1 (1) Under nitrogen protection, 63 g (0.5 mol) of dimethyl sulfate and 13 g (0.5 mol) of lithium fluoride were added to a flask at a reaction temperature of 75° C. for 6 h.

[0037] (2) Under a nitrogen atmosphere, the temperature was controlled at -10°C, and water was added dropwise to the flask in step (1). The addition time was 2 hours, and the reaction was kept at -10°C for 6 hours. After the reaction, 60 mL of ethyl methyl carbonate was added to dissolve the crude lithium fluorosulfonate and the mixture was filtered to remove unreacted lithium fluoride. The mixture was concentrated under reduced pressure to remove part of the ethyl methyl carbonate, and a lithium fluorosulfonate concentrate was obtained. 60 mL of dichloromethane was added to the concentrate to obtain pure lithium fluorosulfonate. The lithium fluorosulfonate yield was 44.6%.

[0038] Comparative Example 2 (1) Under nitrogen protection, 63 g (0.5 mol) of dimethyl sulfate and 13 g (0.5 mol) of lithium fluoride were added to a flask at a reaction temperature of 45° C. for 2 h.

[0039] (2) Under a nitrogen atmosphere, the temperature was controlled at -10°C, and water was added dropwise to the flask in step (1). The addition time was 2 hours, and the reaction was kept at -10°C for 6 hours. After the reaction, 60 mL of ethyl methyl carbonate was added to dissolve the crude lithium fluorosulfonate and the mixture was filtered to remove unreacted lithium fluoride. The mixture was concentrated under reduced pressure to remove part of the ethyl methyl carbonate, and a lithium fluorosulfonate concentrate was obtained. 60 mL of dichloromethane was added to the concentrate to obtain pure lithium fluorosulfonate. The lithium fluorosulfonate yield was 43.2%.

[0040] Comparative Example 3 (1) Under nitrogen protection, 63 g (0.5 mol) of dimethyl sulfate and 13 g (0.5 mol) of lithium fluoride were added to a flask at a reaction temperature of 45° C. for 6 h.

[0041] (2) Under a nitrogen atmosphere, the temperature was controlled at -10°C, and water was added dropwise to the flask in step (1). The addition time was 2 hours, and the reaction was kept at -10°C for 2 hours. After the reaction, 60 mL of ethyl methyl carbonate was added to dissolve the crude lithium fluorosulfonate and the mixture was filtered to remove unreacted lithium fluoride. The mixture was concentrated under reduced pressure to remove part of the ethyl methyl carbonate, and a lithium fluorosulfonate concentrate was obtained. 60 mL of dichloromethane was added to the concentrate to obtain pure lithium fluorosulfonate. The lithium fluorosulfonate yield was 40.7%.

[0042] As can be seen from the above-mentioned Examples 1-5, the present invention provides a new method for synthesizing lithium fluorosulfonate, with a yield of up to 91.7%, wherein dimethyl sulfate first reacts with lithium fluoride at a certain temperature and time to generate methoxy lithium and methyl fluorosulfonate; the generated methoxy lithium and methyl fluorosulfonate react with water to generate lithium fluorosulfonate, and the entire reaction process does not require the addition of other solvents, the operation is simple, and the intermediate process does not require purification, which is similar to a one-pot direct synthesis, and is very suitable for industrial production. The sulfuric acid esters used in Examples 6-7 are diethyl sulfate and monomethyl sulfate, respectively. Compared with the use of dimethyl sulfate in Example 3, the yield of lithium fluorosulfonate is relatively reduced. Specifically, dimethyl sulfate will generate lithium methoxide during the reaction, and lithium methoxide has a strong alkalinity and a faster reaction rate.

[0043] Compared with Example 3, in Comparative Example 1, since the reaction temperature in step (1) in Comparative Example 1 is too high, the raw material dimethyl sulfate is decomposed in large quantities, resulting in a decrease in the yield of the final product lithium fluorosulfonate.

[0044] Compared with Example 3, in Comparative Example 2, due to the short reaction time in step (1) in Comparative Example 2, the reaction between the raw material dimethyl sulfate and lithium fluoride is incomplete, resulting in a lower yield of the final product lithium fluorosulfonate.

[0045] Compared with Example 3, in Comparative Example 3, after the addition of water in step (2) in Comparative Example 3 was completed, the insulation time was too short, resulting in incomplete reaction of the intermediate products methoxylithium and methyl fluorosulfonate with water, resulting in a reduced yield of the final product lithium fluorosulfonate.

[0046] The lithium fluorosulfonate prepared in the present application does not contain chloride ions, while the chloride ion content of lithium fluorosulfonate prepared in the prior art is generally 10-30 ppm. In addition, the yield of lithium fluorosulfonate in the present application can reach 91.7%, while the yield of lithium fluorosulfonate in the prior art is generally around 87%.

[0047] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description 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 may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for synthesizing lithium fluorosulfonate, characterized in that: A sulfate ester and a lithium source are used as raw materials for reaction, and a product after the reaction of the sulfate ester and the lithium source reacts with water to obtain lithium fluorosulfonate; The sulfate ester is dimethyl sulfate, diethyl sulfate, monoethyl sulfate or monomethyl sulfate; The lithium source is a fluorine-containing lithium salt; The molar ratio of the sulfate to the lithium source is (0.6-1.1):

1.

2. The method for synthesizing lithium fluorosulfonate according to claim 1, characterized in that: The reaction temperature of the sulfate ester and the lithium source is 30-60° C., and the reaction time is 5-10 hours.

3. The method for synthesizing lithium fluorosulfonate according to claim 1, characterized in that: The temperature for the reaction between the product of the reaction between the sulfate and the lithium source and water is -20 to -10°C, and the time for adding water is 2-3 hours.

4. The method for synthesizing lithium fluorosulfonate according to claim 1, characterized in that: The reaction time of the product after the reaction of the sulfate ester and the lithium source with water is 6-24 hours.

5. The method for synthesizing lithium fluorosulfonate according to claim 1, characterized in that: The fluorine-containing lithium salt is lithium fluoride, lithium hexafluorophosphate, lithium trifluoromethanesulfonate or lithium perfluorobutylsulfonate.

6. The method for synthesizing lithium fluorosulfonate according to claim 1, characterized in that: The reaction between the sulfate ester and the lithium source and the reaction between the product after the reaction between the sulfate ester and the lithium source and water are both carried out under an inert gas atmosphere.

7. The method for synthesizing lithium fluorosulfonate according to claim 1, characterized in that: The product of the reaction between the sulfate and the lithium source is reacted with water and then post-treated to obtain lithium fluorosulfonate. The post-treatment includes adding a polar aprotic solvent, filtering, distilling under reduced pressure, and stirring and crystallizing with a poor solvent.

8. The method for synthesizing lithium fluorosulfonate according to claim 7, characterized in that: The polar aprotic solvent can be selected from ethyl methyl carbonate, dimethyl carbonate or carbonic acid diester, and the poor solvent is dichloromethane, dichloroethane, n-hexane or isopropane.

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