A method for preparing anhydrous lithium bisfluorosulfonylimide

Abstract

The present application provides a preparation method of anhydrous lithium bisfluorosulfonimide, comprising the steps of: reacting bisfluorosulfonimide with lithium salt in the presence of a mixed solvent and an inhibitor by passing high-pressure carbon dioxide, and then separating and purifying the product by an anti-solvent crystallization method. The method of the present application can directly obtain almost anhydrous lithium bisfluorosulfonimide product, saves the drying process, greatly improves the product quality, and saves the production cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrolyte, and particularly relates to a preparation method of anhydrous lithium bisfluorosulfonylimide. BACKGROUND

[0002] As a new electrolyte additive, lithium bisfluorosulfonylimide is increasingly recognized by the market, and is widely used in the preparation of ionic liquids and catalysts, and the market demand is increasing day by day. Electric cars are replacing oil cars, and with the increasing maturity of lithium battery technology, electric cars will be further developed. The demand for batteries, especially lithium batteries, is increasing, and the supporting electrolyte is also rising. In addition, whether the battery has excellent performance is not only dominated by design and electrode, but also the performance of the electrolyte is also decisive, so the research on the electrolyte is a long way to go.

[0003] Nowadays, lithium batteries dominate the battery industry, and various preparation methods of electrolyte are emerging in an endless stream. The synthesis of lithium hexafluorophosphate and lithium bisfluorosulfonylimide is in full swing. At present, the performance of lithium bisfluorosulfonylimide in all aspects is very good, and it has great development prospects.

[0004] Patent CN106365132A provides a preparation method of lithium bisfluorosulfonylimide. First, lithium bisfluorosulfonylimide is prepared, and then it is reacted with lithium carbonate to obtain lithium bisfluorosulfonylimide. A large amount of water is generated in the reaction process. Because lithium bisfluorosulfonylimide has strong water absorption, it is very difficult to separate.

[0005] And patent US2004097757 provides a preparation method of lithium bisfluorosulfonylimide. Lithium fluoride is directly reacted with dichlorosulfonylimide. Although no water is generated in the reaction process, a large amount of hydrogen fluoride is generated, which requires high material quality of the reaction equipment and a large amount of acid residue in the later stage, which is also difficult to remove.

[0006] Therefore, it is desired in the art to develop an economical and efficient preparation method of lithium bisfluorosulfonylimide to improve the deficiencies in the existing synthesis method. SUMMARY

[0007] In view of the above problems in the prior art, the present application provides a new preparation method. The method can directly produce anhydrous lithium bisfluorosulfonylimide solid salt, and the preparation steps are less, and the drying step is omitted, solving the problem of long production time in the traditional process. The whole process is low-temperature reaction, which greatly reduces the decomposition of the product in the drying process, and the product quality is improved.

[0008] To achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows:

[0009] A preparation method of anhydrous bisfluorosulfone imide, comprising the steps of: reacting bisfluorosulfone imide with lithium salt in the presence of mixed solvents and inhibitors by passing high-pressure carbon dioxide; and separating and purifying the product by anti-solvent crystallization after the reaction is completed.

[0010] In some specific embodiments, the inhibitor is a sodium alkyl benzene sulfonate surfactant, such as sodium dodecyl benzene sulfonate, sodium tetradecyl benzene sulfonate, sodium hexadecyl benzene sulfonate, sodium octadecyl benzene sulfonate, sodium eicosyl benzene sulfonate, etc., preferably at least one of sodium dodecyl benzene sulfonate, sodium tetradecyl benzene sulfonate, sodium hexadecyl benzene sulfonate, and sodium octadecyl benzene sulfonate.

[0011] The mixed solvents are selected from two or more of carbonates, benzene compounds, and / or ether compounds.

[0012] Preferably, the carbonates are selected from one or more of EMC, DMC, DEC, and EC; the benzene compounds are selected from at least one of toluene, xylene, and mesitylene; and the ether compounds are one or more of MTBE, diethylene glycol dimethyl ether, dioxane, and tetrahydrofuran.

[0013] More preferably, the mass ratio of the carbonates to the remaining solvents is 0.1-5:1, such as 0.2:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, etc., preferably 0.5-3:1.

[0014] In some specific embodiments, the purity of the raw bisfluorosulfone imide is 99wt% or higher, such as 99.5wt% or higher, etc.

[0015] In some specific embodiments, the lithium salt is selected from at least one of lithium carbonate, lithium phosphate, lithium fluoride, and lithium sulfate, preferably at least one of lithium carbonate and lithium phosphate.

[0016] In some specific embodiments, the molar ratio of bisfluorosulfone imide to lithium in the lithium salt is 0.9-1.3:1, such as 1:1, 1.1:1, 1.2:1, etc., preferably 1-1.1:1; specifically, for example, the molar ratio of bisfluorosulfone imide to lithium in the lithium salt is 0.9-1.2:1, preferably 1-1.1:1.

[0017] In some specific embodiments, the amount of the inhibitor added is 5wt%-20wt% of the mass of the lithium salt, such as 5wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%, 20wt%, etc., preferably 8wt%-15wt%.

[0018] In the present application, the solvent needs to be dehydrated, and the specific dehydration form is not limited, for example, molecular sieve adsorption dehydration, etc. It can also be directly purchased, only the water content is controlled below 5ppm, and the total amount of metal ions is not more than 20ppm.

[0019] In some specific embodiments, the mixed solvent contains a carbonate compound solvent, and the remaining solvent, the amount of the remaining solvent added is 10-100wt% of the mass of bisfluorosulfonylimide, for example, 20%,

[0020] 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc., preferably 30-60%; the remaining solvent can be a single benzene solvent or an ether solvent, or an arbitrary ratio combination of benzene and ether solvents.

[0021] In some specific embodiments, the purity of the high-pressure carbon dioxide is 90.0% or more, preferably 95% or more, for example, 96%, 98%, 99%, etc., and the remaining impurities in the used carbon dioxide can be inert gases such as helium and nitrogen, and the water content is less than 0.1ppm; the pressure in the reactor after the carbon dioxide is introduced is 15-30MPa, for example, 16MPa, 17MPa, 18MPa, 19MPa, 18MPa, 20MPa, 21MPa, 22MPa, 23MPa, 24MPa, 25MPa, 28MPa, 30MPa, etc., preferably 20-25Mpa.

[0022] In some specific embodiments, the reaction temperature of the reaction is -50-100℃, for example, -40℃, -30℃, -20℃, -10℃, -5℃, 0℃, 5℃, 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, etc., preferably -40-30℃.

[0023] In some specific embodiments, the reaction time of the reaction is 5-120min, for example, 10min, 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, etc., preferably 20-60min.

[0024] In the present application, the gas phase space of the reaction kettle in the reaction process is kept above one-third of the total volume to ensure sufficient carbon dioxide and buffer the reaction pressure fluctuation to ensure safety; the reaction kettle can be a self-suction stirring paddle, and the stirring rate can be adjusted according to the actual working conditions to achieve effective self-suction effect.

[0025] In some specific embodiments, the anti-solvent is an organic solvent having a solubility of less than 0.5 wt% for the product, such as dichloromethane, trichloromethane, acetonitrile, or the like, preferably dichloromethane and / or acetonitrile.

[0026] In some specific embodiments, the mass ratio of the anti-solvent to the good solvent (e.g., a carbonate compound solvent) is 1-10:1, such as 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or the like, preferably 3-5:1; and the crystallization time of the anti-solvent is 0.5-12 h, such as 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, or the like, preferably 1-3 h.

[0027] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0028] The preparation method of the present application can directly obtain almost anhydrous lithium bisfluorosulfonylimide product, and all indexes can reach the standard, without generating a large amount of water as in the traditional lithium carbonate method, causing difficult removal; meanwhile, there is no problem of generating a large amount of HF as in the lithium fluoride salt formation method, causing strong corrosion to the reaction equipment, and the product acid value is difficult to reach the standard.

[0029] The preparation method of the present application is simple in operation, the product purity is high, can reach more than 99.9%, the product impurities are few, the water content is extremely low, and the acid value is low, and the product prepared by the method has strong market competitiveness. DETAILED DESCRIPTION

[0030] In order to better understand the technical scheme of the present application, the content of the present application will be further described below in combination with examples, but the content of the present application is not limited to the following examples.

[0031] The main raw material source information used in the examples of the present application is as follows, and other ordinary commercially available raw materials are used unless otherwise specified.

[0032] The experimental operations involved in the following examples or comparative examples are the conventional experimental methods in the art unless otherwise specified.

[0033] Analysis method:

[0034] Moisture determination: The analysis process should be carried out in a glove box, about 0.5 g of the sample is weighed to 0.001 g, the sample is placed in a full-automatic moisture determination instrument measuring bottle, and after complete dissolution and uniform stirring, the moisture is determined. The arithmetic mean of the parallel determination results is the determination result, and the absolute difference of the two parallel determination results is not more than 20% of the arithmetic mean; the equipment is selected as: Kyoto Electronics KEM coulomb charge method full-automatic moisture determination instrument MKC-710S.

[0035] The product purity is determined by ion chromatography for anions, which can refer to GB / T 19282-2014.

[0036] The acid value is determined by the following method: about 10 g of the sample is weighed to 0.0002 g, and then quickly poured into a beaker containing 100 ml of ice water. The sample is completely dissolved by shaking the beaker. 10 drops of 1 g / L bromine thymol blue indicator solution are added, and the solution is quickly titrated to light blue with 0.01 mol / L NaOH standard titration solution. The titration end point is determined by maintaining the light blue color for 10 s. The solution temperature is still maintained at ≤4 ℃ at the end point. The arithmetic mean of the parallel determination results is the determination result. The absolute difference between the two parallel determination results is not more than 20% of the arithmetic mean.

[0037] Example 1

[0038] The lithium bisfluorosulfonylimide is prepared by the following steps:

[0039] bisfluorosulfonylimide (purity: 99.5%): 1000 g, sodium dodecyl sulfonate: 23.4 g, toluene: 500 g, EMC: 500 g, the reaction temperature is adjusted to -20 ℃, carbon dioxide (purity: 99.9%) is passed, the pressure is adjusted to 23 Mpa, the stirring speed is 2000 rpm / min, then lithium carbonate: 194.7 g is slowly added, after 30 min of reaction, dichloromethane 2000 g is added, crystallization is performed for 2 h, after filtration, the product is obtained by nitrogen blowing and drying, the purity is 99.99%, the water content is 5 ppm, and the acid value is 26 ppm.

[0040] Example 2

[0041] The lithium bisfluorosulfonylimide is prepared by the following steps:

[0042] bisfluorosulfonylimide (purity: 99.5%): 1000 g, sodium dodecyl sulfonate: 23.4 g, toluene: 500 g, EMC: 500 g, the reaction temperature is adjusted to -20 ℃, carbon dioxide (purity: 99.9%) is passed, the pressure is adjusted to 23 Mpa, the stirring speed is 2000 rpm / min, then lithium carbonate: 194.7 g is slowly added, after 30 min of reaction, dichloromethane 2000 g is added, crystallization is performed for 2 h, after filtration, the product is obtained by nitrogen blowing and drying, the purity is 99.99%, the water content is 5 ppm, and the acid value is 26 ppm.

[0043] Example 3

[0044] Take difluorosulfone (purity: 99.5%): 1000g, sodium octadecyl sulfonate: 18.3g, mesitylene: 100g, DEC: 1000g, adjust the reaction temperature to: -50℃, pass carbon dioxide (purity: 99.9%), adjust the pressure to 25Mpa, stirring speed: 800rpm / min, then slowly add lithium sulfate: 303.9g, after reaction for 20min, add acetonitrile 5000g, crystallize for 12h, after filtration, dry by nitrogen blowing to obtain the product, purity: 99.91%, water content 10ppm, acid value 33ppm.

[0045] Example 4

[0046] Preparation of lithium difluorosulfone, the steps are:

[0047] Take difluorosulfone (purity: 99.1%): 1000g, sodium tetradecyl sulfonate: 8.8g, toluene: 600g, EC: 200g, adjust the reaction temperature to: 0℃, pass carbon dioxide (purity: 99.8%), adjust the pressure to 30Mpa, stirring speed: 1200rpm / min, then slowly add lithium fluoride: 110.5g, after reaction for 60min, add n-hexane 600g, crystallize for 3h, after filtration, dry by nitrogen blowing to obtain the product, purity: 99.85%, water content 7ppm, acid value 49ppm.

[0048] Example 5

[0049] Preparation of lithium difluorosulfone, the steps are:

[0050] Take difluorosulfone (purity: 99.5%): 1000g, sodium dodecyl sulfonate: 25.6g, xylene: 500g, dioxane: 500g, EMC: 250g, adjust the reaction temperature to: 10℃, pass carbon dioxide (purity: 99.2%), adjust the pressure to 25Mpa, stirring speed: 1500rpm / min, then slowly add lithium carbonate: 170.3g, after reaction for 120min, add dichloromethane 2000g, diethyl ether: 500g, crystallize for 8h, after filtration, dry by nitrogen blowing to obtain the product, purity: 99.89%, water content 7ppm, acid value 29ppm.

[0051] Example 6

[0052] Preparation of lithium difluorosulfone, the steps are:

[0053] Take difluorosulfone imine (purity: 99.5%): 1000g, sodium octadecyl sulfonate: 57.6g, diethylene glycol dimethyl ether: 800g, DEC: 160g, the reaction temperature is raised to: 60°C, carbon dioxide (purity: 99.0%) is passed, the pressure is adjusted to 28Mpa, the stirring speed is: 2100rpm / min, then lithium sulfate: 319.9g is slowly added, after 90min of reaction, dichloromethane 1440g is added, crystallization is carried out for 1h, after filtration, nitrogen is blown dry to obtain the product, purity: 99.97%, water content 12ppm, acid value 35ppm.

[0054] Example 7

[0055] Preparation of lithium difluorosulfone imine, the steps are:

[0056] Take difluorosulfone imine (purity: 99.5%): 1000g, sodium octadecyl sulfonate: 57.6g, diethylene glycol dimethyl ether: 800g, DEC: 160g, the reaction temperature is raised to: 60°C, carbon dioxide (purity: 99.0%) is passed, the pressure is adjusted to 28Mpa, the stirring speed is: 2100rpm / min, then lithium sulfate: 319.9g is slowly added, after 90min of reaction, dichloromethane 1440g is added, crystallization is carried out for 1h, after filtration, nitrogen is blown dry to obtain the product, purity: 99.97%, water content 12ppm, acid value 35ppm.

[0057] Example 8

[0058] Preparation of lithium difluorosulfone imine, the steps are:

[0059] Take difluorosulfone imine (purity: 99.5%): 1000g, sodium octadecyl sulfonate: 57.6g, diethylene glycol dimethyl ether: 800g, DEC: 160g, the reaction temperature is raised to: 60°C, carbon dioxide (purity: 99.0%) is passed, the pressure is adjusted to 28Mpa, the stirring speed is: 2100rpm / min, then lithium sulfate: 319.9g is slowly added, after 90min of reaction, dichloromethane 1440g is added, crystallization is carried out for 1h, after filtration, nitrogen is blown dry to obtain the product, purity: 99.97%, water content 12ppm, acid value 35ppm.

[0060] Comparative Example 1

[0061] Compared with Example 1, no inhibitor sodium dodecyl sulfonate is added, and other conditions are exactly the same. The purity of the final product is: 99.99%, the water content is 8726ppm, and the acid value is 135ppm.

[0062] Comparative Example 2

[0063] The same conditions as in Example 1, except that no carbon dioxide was passed. Purity of final product: 99.99%, water content: 7944 ppm, acid value: 89 ppm.

[0064] It will be understood by those skilled in the art that modifications or improvements can be made to the present application under the teachings of the present specification. Such modifications or improvements should also fall within the scope of the present application as defined by the claims.

Claims

1. A process for the preparation of anhydrous lithium bisfluorosulfonylimide, characterized in that, The method comprises the steps of: reacting difluorosulfimine and lithium salt in a mixed solvent in the presence of an inhibitor under high-pressure carbon dioxide; and separating and purifying the product by anti-solvent crystallization after the reaction is completed. The mixed solvent contains a carbonate compound solvent and a remaining solvent; the remaining solvent is a benzene solvent or an ether solvent alone or a combination of benzene and ether solvents in any proportion. The inhibitor is any one of sodium dodecyl sulfonate, sodium tetradecyl sulfonate, sodium hexadecyl sulfonate, and sodium octadecyl sulfonate. The pressure of the high-pressure carbon dioxide introduced into the reactor is 15-30 MPa. The anti-solvent crystallization method uses an organic solvent having a solubility of less than 0.5 wt% for the lithium bisfluorosulfimide product.

2. The production method according to claim 1, characterized by, The carbonate compound is any one or more of EMC, DMC, DEC, and EC; the benzene compound is any one or more of toluene, xylene, and mesitylene; and the ether compound is any one or more of MTBE, diethylene glycol dimethyl ether, dioxane, and tetrahydrofuran.

3. The production method according to claim 2, characterized by, The mass ratio of the remaining solvent to the carbonate compound in the mixed solvent is 0.1-5:

1.

4. The production method according to claim 3, characterized by, The mass ratio of the remaining solvent to the carbonate compound in the mixed solvent is 0.5-3:

1.

5. The preparation method according to claim 1, characterized in that, The molar ratio of lithium in the lithium salt to the difluorosulfimine is 0.9-1.3:

1.

6. The production method according to claim 5, wherein The molar ratio of lithium in the lithium salt to the difluorosulfimine is 1-1.1:

1.

7. The preparation method according to claim 5, characterized in that, The amount of the inhibitor added is 5 wt% to 20.0 wt% of the mass of the lithium salt.

8. The preparation method according to claim 7, characterized in that, The amount of the inhibitor added is 8.0 wt% to 15.0 wt% of the mass of the lithium salt.

9. The method of any one of claims 1 to 5, wherein, The purity of the difluorosulfimine is greater than 99 wt%; and / or The lithium salt is any one or more of lithium carbonate, lithium phosphate, lithium sulfate, and lithium fluoride.

10. The preparation method according to claim 9, characterized in that, The lithium salt is any one or both of lithium carbonate and lithium phosphate.

11. The method of any one of claims 1 to 5, wherein, The amount of the remaining solvent added is 10-100 wt% of the mass of the difluorosulfimine.

12. The method of claim 11, wherein, The amount of the remaining solvent added is 30-60 wt% of the mass of the difluorosulfimine.

13. The method of any one of claims 1 to 5, wherein the method is carried out in the presence of a reducing agent. The purity of the high-pressure carbon dioxide is greater than 90.0%.

14. The method of claim 13, wherein, The purity of the high-pressure carbon dioxide is greater than 99.5%.

15. The preparation method according to claim 13, characterized in that, The pressure of the high-pressure carbon dioxide introduced into the reactor is 20-25 MPa.

16. The method of any one of claims 1 to 5, wherein, The temperature of the reaction is -50-100°C.

17. The method of claim 16, wherein, The temperature of the reaction is -40-30°C.

18. The method of any one of claims 1 to 5, wherein, The time of the reaction is 5-120 min.

19. The method of claim 18, wherein, The time of the reaction is 20-60 min.

20. The method of any one of claims 1-5, wherein, The anti-solvent is any one or more of dichloromethane, trichloromethane, acetonitrile, n-hexane, diethyl ether, iodomethane, dichloroethane, and trichloroethane.

21. The method of claim 20, wherein, The anti-solvent is dichloromethane and / or acetonitrile.

22. The method of claim 20, wherein, The mass ratio of the amount of the anti-solvent added to the carbonate compound solvent is 1-10:

1.

23. The preparation method according to claim 22, characterized in that, The mass ratio of the amount of the anti-solvent added to the carbonate compound solvent is 3-5:

1.

24. The method of claim 22, wherein, The crystallization time of the anti-solvent is 0.5-12 h.

25. The method of claim 24, wherein, The crystallization time of the anti-solvent is 1-3 h.