A method for preparing sodium bisfluorosulfonimide

Abstract

The application provides a preparation method of sodium bisfluorosulfonimide, which comprises the following steps: (1) sulfuryl fluoride and hexamethylsilazane are reacted in an inert atmosphere to obtain a crude product, and the crude product is subjected to gas phase separation to obtain bisfluorosulfonimide; (2) the bisfluorosulfonimide obtained in the step (1) is reacted with sodium fluoride to obtain the sodium bisfluorosulfonimide. The sulfuryl fluoride and the hexamethylsilazane are used as raw materials to prepare the bisfluorosulfonimide by one-step method, the cost is reduced, and the production safety is improved, then the sodium bisfluorosulfonimide is prepared by ion exchange reaction of the bisfluorosulfonimide and sodium fluoride, the three wastes and solvent use are reduced, the impurities are reduced, and the production safety and product quality are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of sodium ion batteries, and relates to a preparation method of sodium bisfluorosulfonimide. BACKGROUND

[0002] A sodium ion battery is a rechargeable battery, which mainly relies on the movement of sodium ions between a positive electrode and a negative electrode to work, and is similar to the working principle of a lithium ion battery. Compared with the lithium ion battery, the sodium ion battery has the following advantages: raw materials are easy to obtain, and production cost is low; charging time can be shortened to 1 / 5 of that of the lithium ion battery; the conductivity of sodium salt used in the sodium ion battery is about 20% higher than that of lithium salt used in the lithium ion battery, and the sodium ion battery has no over-discharge feature and allows the sodium ion battery to be discharged to zero volts. The disadvantage is that the energy density of the sodium ion battery is relatively low, but the energy density of the sodium ion can still be greater than 100 Wh / kg, which is comparable to that of a lithium iron phosphate battery, and is expected to replace the traditional lead-acid battery in the future.

[0003] At present, sodium salts mainly selected in the sodium ion battery are sodium hexafluorophosphate, sodium tetrafluorophosphate or sodium bisfluorosulfonimide. The fluorine content of sodium bisfluorosulfonimide is lower than that of sodium hexafluorophosphate, and the application of negative electrode materials shows that it helps to improve the cycle stability of the negative electrode materials, and is a good electrolyte material. Sodium bisfluorosulfonimide is a key high-performance electrolyte material in the sodium ion battery, and has high application value. The synthesis of sodium bisfluorosulfonimide from bisfluorosulfonimide is a common technical means in the field.

[0004] However, in the prior art, there are certain deficiencies in the preparation method of bisfluorosulfonimide, the water removal process is complex, impurities are introduced in the water removal process, and the yield is low. The current common means for synthesizing sodium bisfluorosulfonimide from bisfluorosulfonimide is to react bisfluorosulfonimide and a sodium source in a non-aqueous solvent that can form an azeotrope with water, but the synthesis of sodium bisfluorosulfonimide produces three wastes and introduces impurities.

[0005] The existing method for preparing sodium bisfluorosulfonimide is complicated, has high three wastes, low safety and high cost, therefore, how to prepare sodium bisfluorosulfonimide with low cost and high safety performance is an important research direction in the field. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a kind of sodium bisfluorosulfonimide. Bisfluorosulfonimide is prepared by one-step method at low cost, and sodium bisfluorosulfonimide is prepared by ion exchange reaction of bisfluorosulfonimide and sodium fluoride, which avoids the generation of by-product water.

[0007] To achieve this purpose, the following technical solutions are adopted in the present application:

[0008] The present application provides a preparation method of bisfluorosulfone imide, which comprises the following steps:

[0009] (1) reacting sulfuryl fluoride and hexamethylsilazane in an inert atmosphere to obtain a crude product, and performing gas phase separation on the crude product to obtain bisfluorosulfone imide;

[0010] (2) reacting the bisfluorosulfone imide obtained in step (1) with sodium fluoride to obtain sodium bisfluorosulfone imide.

[0011] In the present application, the structural formula of sulfuryl fluoride is shown as formula 1, Formula 1; the structural formula of hexamethylsilazane is shown as formula 2, In the present application, sulfuryl fluoride and hexamethylsilazane are used as raw materials to prepare bisfluorosulfone imide in one step, which reduces the cost and improves the production safety. In the present application, sodium fluoride has sufficient solubility in hydrogen fluoride, can fully exchange ions with bisfluorosulfone imide, and after the reaction is completed, hydrogen fluoride gas is evaporated to obtain sodium bisfluorosulfone imide. The preparation process is simple, no solvent is used, the three wastes are reduced, no water is generated in the salting process, the complex water removal process is avoided, impurities are reduced, the post-treatment process of sodium bisfluorosulfone imide is simplified, and the production safety and product quality are improved.

[0012] In the present application, the reaction of sulfuryl fluoride and hexamethylsilazane in step (1) is carried out under solvent-free conditions.

[0013] As a preferred technical solution of the present application, the molar ratio of sulfuryl fluoride to hexamethylsilazane in step (1) is (1.8-5):1, wherein the molar ratio can be 2:1, 2.4:1, 2.7:1, 3:1, 3.3:1, 3.7:1 or 4:1, etc., but is not limited to the listed values, and other values not listed in this range are also applicable, and preferably (1.8-3):1.

[0014] As a preferred technical solution of the present application, the inert atmosphere in step (1) includes argon atmosphere and / or nitrogen atmosphere.

[0015] Preferably, the temperature of the reaction in step (1) is 40-110℃, wherein the temperature can be 45℃, 50℃, 55℃, 60℃, 75℃, 80℃, 90℃, 100℃ or 110℃, etc., but is not limited to the listed values, and other values not listed in this range are also applicable, and further preferably 80-110℃.

[0016] Preferably, the reaction time of step (1) is 1-15 h, wherein the time can be 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h or 14 h, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable, and further preferably 3-15 h.

[0017] The reaction time of step (1) in the present application is preferably 1-15 h, and further preferably 3-15 h, so that the reaction is fully carried out, improving the conversion rate of raw materials and the yield of bisfluorosulfonylimide; if the reaction time is too long, the energy consumption is too large, increasing the probability of generating by-products; if the reaction time is too short, the reaction is incomplete, increasing the difficulty of post-treatment purification.

[0018] As a preferred technical solution of the present application, the crude product of step (1) comprises a combination of bisfluorosulfonylimide and trimethylfluorosilane; the crude product is subjected to gas phase separation to obtain liquid-phase bisfluorosulfonylimide.

[0019] Preferably, the gas phase separation temperature of step (1) is 17-80℃, for example, it can be 18℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 78℃, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0020] Preferably, the gas phase separation time of step (1) is 1-4 h, for example, it can be 1.5 h, 2 h, 2.5 h, 3 h or 3.5 h, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0021] The crude product includes liquid-phase bisfluorosulfonylimide, which is separated from trimethylfluorosilane, and the liquid-phase bisfluorosulfonylimide is subjected to rectification treatment to obtain the bisfluorosulfonylimide.

[0022] Preferably, the rectification treatment temperature is 90-160℃, wherein the temperature can be 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃ or 160℃, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0023] Preferably, the rectification treatment time is 2-6 h, wherein the time can be 2 h, 3 h, 4 h, 5 h or 6 h, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0024] In the present application, the reaction of the bis-fluorosulfonimide and sodium fluoride in step (2) is carried out under solvent-free conditions.

[0025] As a preferred technical solution of the present application, the molar ratio of the bis-fluorosulfonimide to sodium fluoride in step (2) is 1:(1.0-1.3), wherein the molar ratio can be 1:1, 1:1.1, 1:1.2, or 1:1.3, etc., but is not limited to the listed values, and other values not listed within this range are also applicable.

[0026] As a preferred technical solution of the present application, the temperature of the reaction in step (2) is 80-140°C, wherein the temperature can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, or 140°C, etc., but is not limited to the listed values, and other values not listed within this range are also applicable.

[0027] Preferably, the reaction in step (2) is carried out in a protective atmosphere.

[0028] Preferably, the protective atmosphere is an argon atmosphere and / or a nitrogen atmosphere.

[0029] Preferably, the reaction in step (2) is carried out for 0.1-24h, for example, 0.2h, 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, or 23h, etc., but is not limited to the listed values, and other values not listed within this range are also applicable, and further preferably 0.1-12h.

[0030] Preferably, after the reaction in step (2) is completed, the byproduct hydrogen fluoride (gas) is evaporated.

[0031] As a preferred technical solution of the present application, the preparation method specifically comprises the following steps:

[0032] (1) reacting sulfuryl fluoride and hexamethylsilazane in a molar ratio of (1.8-5):1 in an inert atmosphere at 40-110°C for 1-15h to obtain a crude product, and performing gas-phase separation on the crude product to obtain the bis-fluorosulfonimide;

[0033] (2) reacting the bis-fluorosulfonimide obtained in step (1) with sodium fluoride at 80-140°C for 0.1-24h to obtain the sodium bis-fluorosulfonimide.

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] The present application uses sulfonyl fluoride and hexamethylsilylamine as raw materials to prepare bisfluorosulfonylimide by one-step method, and then reacts bisfluorosulfonylimide with sodium fluoride to obtain bisfluorosulfonylimide sodium, which has a short preparation route, low production cost, no need to use organic solvents in the whole preparation process, less three wastes output, high yield and purity of the prepared bisfluorosulfonylimide sodium, the yield is ≥85.7%, and the purity can be ≥98.8% without complex post-treatment process. The prepared bisfluorosulfonylimide sodium can meet the performance requirements of sodium ion batteries for electrolyte sodium salt. DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application, and should not be regarded as specific limitations on the present application.

[0037] The terms "comprising", "including", "having" "with" or any other variant thereof, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or device that comprises a listed element does not necessarily limit to those elements only, but can include other elements not expressly listed or inherent to such composition, step, method, article, or device.

[0038] "Optional" or "any of" means that the matter or event described thereafter can occur or not occur, and the description includes the case where the event occurs and the case where the event does not occur.

[0039] The indefinite article "a" and "an" before an element or component of the present application does not have a quantitative requirement (i.e. occurrence frequency) on the number of the element or component. Therefore, "a" or "an" should be interpreted to include one or at least one, and the singular form of the element or component also includes the plural form, unless the number is obviously only singular.

[0040] The description of the terms "one embodiment", "some embodiments", "exemplarily", "specific examples" or "some examples" and the like described in the present application means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this paper, the illustrative description of the above terms is not necessarily for the same embodiment or example.

[0041] Moreover, the technical features involved in each embodiment of the present application can be combined with each other as long as there is no conflict between them.

[0042] Example 1

[0043] The present embodiment provides a preparation method of bisfluorosulfonylimide, which specifically comprises the following steps:

[0044] (1) the crude product is obtained by reacting sulfuryl fluoride and hexamethylsilazane in a molar ratio of 2:1 at 95°C for 6h under argon atmosphere; the liquid-phase bisfluorosulfonylimide is obtained by gas-phase separation of the crude product at 50°C to remove trimethylfluorosilane; the bisfluorosulfonylimide is obtained by rectification of the liquid-phase bisfluorosulfonylimide;

[0045] (2) the bisfluorosulfonylimide obtained in step (1) is added into a reactor, and sodium fluoride is added into the reactor, the molar ratio of the bisfluorosulfonylimide to the sodium fluoride being 1:1.1; the system is heated to 110°C for 6h to obtain sodium bisfluorosulfonylimide.

[0046] Example 2

[0047] The present embodiment provides a method for preparing bisfluorosulfonylimide, which specifically comprises the following steps:

[0048] (1) the crude product is obtained by reacting sulfuryl fluoride and hexamethylsilazane in a molar ratio of 2.2:1 at 105°C for 3h under argon atmosphere; the liquid-phase bisfluorosulfonylimide is obtained by gas-phase separation of the crude product at 60°C to remove trimethylfluorosilane; the bisfluorosulfonylimide is obtained by rectification of the liquid-phase bisfluorosulfonylimide;

[0049] (2) the bisfluorosulfonylimide obtained in step (1) is added into a reactor, and sodium fluoride is added into the reactor, the molar ratio of the bisfluorosulfonylimide to the sodium fluoride being 1:1.08; the system is heated to 120°C for 5h to obtain sodium bisfluorosulfonylimide.

[0050] Example 3

[0051] The present embodiment provides a method for preparing bisfluorosulfonylimide, which specifically comprises the following steps:

[0052] (1) the crude product is obtained by reacting sulfuryl fluoride and hexamethylsilazane in a molar ratio of 1.8:1 at 90°C for 8h under argon atmosphere; the liquid-phase bisfluorosulfonylimide is obtained by gas-phase separation of the crude product at 60°C to remove trimethylfluorosilane; the bisfluorosulfonylimide is obtained by rectification of the liquid-phase bisfluorosulfonylimide;

[0053] (2) the bisfluorosulfonylimide obtained in step (1) is added into a reactor, and sodium fluoride is added into the reactor, the molar ratio of the bisfluorosulfonylimide to the sodium fluoride being 1:1.15; the system is heated to 125°C for 4h to obtain sodium bisfluorosulfonylimide.

[0054] Example 4

[0055] The present embodiment provides a method for preparing bisfluorosulfonylimide, which specifically comprises the following steps:

[0056] (1) the crude product was obtained by reacting sulfuryl fluoride and hexamethylsilazane with a molar ratio of 3:1 at 100°C for 5h under argon atmosphere; the liquid-phase bisfluorosulfonyl imide was obtained by gas-phase separation of the crude product at 55°C to remove trimethylfluorosilane; and the bisfluorosulfonyl imide was obtained by rectification of the liquid-phase bisfluorosulfonyl imide;

[0057] (2) the bisfluorosulfonyl imide obtained in step (1) was added into a reactor, and sodium fluoride was added into the reactor, with a molar ratio of bisfluorosulfonyl imide to sodium fluoride being 1:1.2; the system was heated to 110°C and reacted for 8h to obtain sodium bisfluorosulfonyl imide.

[0058] Example 5

[0059] The present example provides a method for preparing bisfluorosulfonyl imide, which specifically comprises the following steps:

[0060] (1) the crude product was obtained by reacting sulfuryl fluoride and hexamethylsilazane with a molar ratio of 2.5:1 at 80°C for 10h under argon atmosphere; the liquid-phase bisfluorosulfonyl imide was obtained by gas-phase separation of the crude product at 60°C to remove trimethylfluorosilane; and the bisfluorosulfonyl imide was obtained by rectification of the liquid-phase bisfluorosulfonyl imide;

[0061] (2) the bisfluorosulfonyl imide obtained in step (1) was added into a reactor, and sodium fluoride was added into the reactor, with a molar ratio of bisfluorosulfonyl imide to sodium fluoride being 1:1.15; the system was heated to 120°C and reacted for 5h to obtain sodium bisfluorosulfonyl imide.

[0062] Example 6

[0063] The present example is identical to Example 1 except that the sulfuryl fluoride and hexamethylsilazane with a molar ratio of 2:1 are replaced by sulfuryl fluoride and hexamethylsilazane with a molar ratio of 1.5:1.

[0064] Example 7

[0065] The present example is identical to Example 4 except that the sulfuryl fluoride and hexamethylsilazane with a molar ratio of 3:1 are replaced by sulfuryl fluoride and hexamethylsilazane with a mass ratio of 4:1.

[0066] Example 8

[0067] The present example is identical to Example 5 except that the reaction at 80°C for 10h is replaced by the reaction at 70°C for 12h.

[0068] Example 9

[0069] The present example is identical to Example 5 except that the reaction at 80°C for 10h is replaced by the reaction at 70°C for 16h.

[0070] Comparative Example 1

[0071] The comparative example provides a preparation method of bisfluorosulfimide, specifically comprising the following steps:

[0072] (1) Bisfluorosulfimide is prepared according to the method of step (1) of Example 1;

[0073] (2) Sodium fluoride is dispersed in acetonitrile solvent, and the bisfluorosulfimide obtained in step (1) is added thereto, and the molar ratio of bisfluorosulfimide to sodium fluoride is 1:1.1; after the addition of bisfluorosulfimide, 90℃ is reacted for 12h to obtain a sodium bisfluorosulfimide solution; the sodium bisfluorosulfimide solution is concentrated by reduced pressure distillation and recrystallized to obtain sodium bisfluorosulfimide.

[0074] Comparative Example 2

[0075] The comparative example provides a preparation method of bisfluorosulfimide, specifically comprising the following steps:

[0076] (1) Into a reaction kettle, 150mL of anhydrous acetonitrile is added, then 76.5g of sulfonyl fluoride is added, then 40.35g of hexamethylsilazane is slowly added at room temperature with a pump, after the addition is completed, 90℃ is kept for 3h, then pressure distillation is used to recover unreacted sulfonyl fluoride and trimethylfluorosilane produced in the reaction, after the recovery of sulfonyl fluoride and trimethylfluorosilane is completed, reduced pressure distillation is used to recover the solvent and rectification treatment is performed to obtain the target product bisfluorosulfimide;

[0077] (2) The bisfluorosulfimide obtained in step (1) is added to the reactor, and sodium fluoride is added thereto, and the molar ratio of bisfluorosulfimide to sodium fluoride is 1:1.1; the system is heated to 110℃ and reacted for 6h to obtain sodium bisfluorosulfimide.

[0078] The purity and yield of the sodium bisfluorosulfimide prepared in Examples 1-9 and Comparative Examples 1-2 of the present application are tested, the purity is tested by ion chromatography, the yield of sodium bisfluorosulfimide (mass yield) is the total yield of the two-step reaction, and the test results are shown in Table 1.

[0079] Table 1

[0080] Purity (%) Yield (%) Example 1 99.2 86.5 Example 2 98.9 85.9 Example 3 99.1 86.2 Example 4 98.8 86.1 Example 5 99.3 85.7 Example 6 97.2 83.2 Example 7 98.3 82.1 Example 8 97.1 82.9 Example 9 97.6 83.6 Comparative Example 1 94.2 83.6 Comparative Example 2 97.2 82.7

[0081] As can be seen from Table 1, the sodium bisfluorosulfonimide prepared in Examples 1-5 has the characteristics of high purity and high yield, the yield is ≥85.7%, and the purity of the sodium bisfluorosulfonimide is ≥98.8% without a complicated post-treatment process; as compared with Example 1, Example 6 shows that the insufficient amount of sulfonyl fluoride leads to incomplete reaction, the bisfluorosulfonimide contains impurities that are difficult to remove, and the yield and purity of the sodium bisfluorosulfonimide are affected; as compared with Example 4, Example 7 shows that the excessive amount of sulfonyl fluoride leads to insufficient yield and purity of the bisfluorosulfonimide, and thus the yield and purity of the sodium bisfluorosulfonimide are reduced. As compared with Example 5, Examples 8-9 show that the excessively low reaction temperature of sulfonyl fluoride and hexamethylsilazane affects the reaction rate and degree, even if the reaction time is prolonged, the reaction cannot be completely performed, and the yield and purity of the bisfluorosulfonimide and the sodium bisfluorosulfonimide are reduced. As compared with Example 1, Comparative Examples 1-2 show that the preparation of the bisfluorosulfonimide (Comparative Example 2) and the sodium bisfluorosulfonimide (Comparative Example 1) by using the solvent method not only increases the three-waste output, but also produces by-products and brings in impurities in the preparation process, and thus the purity and yield of the final sodium bisfluorosulfonimide are reduced.

[0082] The applicant declares that the preparation method of the sodium bisfluorosulfonimide of the present application is illustrated by the above examples, but the present application is not limited to the above examples, i.e., it does not mean that the present application must rely on the above examples to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for producing sodium bisfluorosulfonimide, characterized by, The preparation method comprises the following steps: (1) sulfuryl fluoride and hexamethylsilazane are reacted under solvent-free conditions in an inert atmosphere to obtain a crude product, and the crude product is subjected to gas phase separation to obtain bisfluorosulfonylimide; the reaction temperature is 70-105 DEG C, and the reaction time is 3-15 h; the gas phase separation temperature is 50-60 DEG C; (2) the bisfluorosulfonylimide obtained in step (1) and sodium fluoride are reacted under solvent-free conditions to obtain the sodium bisfluorosulfonylimide; the reaction temperature is 110-125 DEG C, and the reaction time is 4-8 h.

2. The production method according to claim 1, characterized by, The molar ratio of the sulfuryl fluoride and hexamethylsilazane in step (1) is (1.8-5):

1.

3. The production method according to claim 2, characterized by, The molar ratio of the sulfuryl fluoride and hexamethylsilazane is (1.8-3):

1.

4. The production method according to claim 1, characterized by, The inert atmosphere in step (1) comprises an argon atmosphere and / or a nitrogen atmosphere.

5. The preparation method according to claim 1, characterized in that, The crude product in step (1) comprises a combination of bisfluorosulfonylimide and trimethylfluorosilane; the crude product is subjected to gas phase separation to obtain liquid-phase bisfluorosulfonylimide.

6. The method of claim 1, wherein, The gas phase separation time in step (1) is 1-4 h.

7. The preparation method according to claim 5, characterized in that, The liquid-phase bisfluorosulfonylimide is subjected to rectification treatment to obtain the bisfluorosulfonylimide.

8. The production method according to claim 7, characterized by, The rectification treatment temperature is 90-160 DEG C.

9. The preparation method according to claim 7, characterized in that, The rectification treatment time is 2-6 h.

10. The method of claim 1, wherein, The molar ratio of the bisfluorosulfonylimide and sodium fluoride in step (2) is 1:(1.0-1.3).

11. The method of claim 1, wherein, The reaction in step (2) is carried out in a protective atmosphere.

12. The method of claim 11, wherein, The protective atmosphere is an argon atmosphere and / or a nitrogen atmosphere.

13. The method of claim 1, wherein, After the reaction in step (2) is completed, the byproduct hydrogen fluoride is evaporated.

14. The method of claim 1, wherein, The preparation method specifically comprises the following steps: (1) sulfuryl fluoride and hexamethylsilazane in a molar ratio of (1.8-5):1 are reacted under solvent-free conditions in an inert atmosphere at 70-105 DEG C for 3-15 h to obtain a crude product, and the crude product is subjected to gas phase separation to obtain the bisfluorosulfonylimide; the gas phase separation temperature is 50-60 DEG C; (2) the bisfluorosulfonylimide obtained in step (1) and sodium fluoride are reacted under solvent-free conditions at 110-125 DEG C for 4-8 h to obtain the sodium bisfluorosulfonylimide.