A method for preparing sodium bisfluorosulfonimide

Abstract

This invention relates to a method for preparing sodium difluorosulfonylimide. First, crude difluorosulfonylimide is synthesized using dichlorosulfonylimide, a catalyst, and fluoroboric acid. Then, the difluorosulfonylimide is purified, and further, crude sodium difluorosulfonylimide is obtained through a reaction with a sodium source. This is then further purified into sodium difluorosulfonylimide. The resulting sodium difluorosulfonylimide has a high yield. No water is generated or the sodium difluorosulfonylimide is decomposed during its preparation, resulting in low acidity and low levels of sulfate, chloride, and fluoride ions, which meets the requirements of sodium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and specifically to a method for preparing sodium difluorosulfonylimide. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the market demand for batteries has increased. However, the scarcity of lithium resources and the continuous rise in the price of lithium raw materials have significantly impacted the development of the battery industry. Therefore, there is an urgent need to develop new energy storage systems that are abundant in resources, inexpensive, safe, environmentally friendly, high-performance, and suitable for large-scale applications to partially replace lithium-ion batteries and alleviate over-reliance on lithium resources.

[0003] Sodium is evenly and widely distributed globally, and related basic materials are inexpensive and environmentally friendly. More importantly, sodium and lithium ions, both belonging to Group I of the periodic table, have very similar electrochemical potentials: sodium is -2.71V, and lithium is -3.05V. Their charge-discharge plateau potentials in batteries are very close, indicating highly similar physicochemical properties. Therefore, developing sodium salts to replace lithium salts can reduce dependence on lithium resources and effectively lower raw material costs. Sodium difluorosulfonylimide has significant advantages in battery manufacturing: it is widely available and not easily decomposed, while also exhibiting better performance than lithium salts such as lithium hexafluorophosphate.

[0004] CN 115028146A discloses a method for preparing sodium difluorosulfonamide, comprising the following steps:

[0005] (1) Add aminosulfonic acid and fluorosulfonic acid to a reaction vessel and heat the mixture to 50-60℃. Pass carbonyl fluoride gas through the mixture. When all the solid aminosulfonic acid has reacted and dissolved until the reaction solution is clear, stop passing carbonyl fluoride gas. Raise the temperature to 70-120℃ and react. Discharge the gas to obtain a mixture. Obtain high-purity difluorosulfonyl imide by vacuum distillation. (2) Pass the alcohol solution of sodium alkoxide and difluorosulfonyl imide into a microchannel reactor and mix to form a salt to obtain an alcohol solution of sodium difluorosulfonyl imide. Then, filter, concentrate, back-extract crystallize, separate solid and liquid, wash, and dry to obtain sodium difluorosulfonyl imide crystals. However, this preparation method uses sodium alkoxide as the sodium source. Sodium alkoxide readily reacts with air to produce hydrogen gas, which is flammable and explosive, posing a high production risk. At the same time, the synthesized sodium difluorosulfonyl imide has a high content of fluoride and chloride ions.

[0006] CN 114572945A discloses a method for preparing sodium bis(fluorosulfonyl)imide and its application. The preparation method includes: mixing bis(fluorosulfonyl)imide, a sodium source, and a non-aqueous solvent uniformly in an inert atmosphere and then reacting them. After the reaction is completed, solid-liquid separation is performed to obtain sodium bis(fluorosulfonyl)imide. The non-aqueous solvent includes at least one selected from acetonitrile, valeronitrile, pyridine, chloroethanol, chloroform, n-propanol, toluene, diethyl ether, acetone, tetrahydrofuran, xylene, dimethyl sulfoxide, N,N-dimethylformamide, and methyl tert-butyl ether. The sodium source includes at least one selected from sodium hydroxide, sodium bicarbonate, and sodium carbonate. This preparation method obtains sodium bis(fluorosulfonyl)imide by reacting bis(fluorosulfonyl)imide and a sodium source in a non-aqueous solvent that can form an azeotrope with water. However, the purity of the obtained sodium bis(fluorosulfonyl)imide is low, which cannot meet the requirements of sodium-ion batteries. The synthesis process generates water and does not remove the water, resulting in easy decomposition and low yield.

[0007] Therefore, in view of the shortcomings of the existing technology, there is a need to provide a preparation method that does not generate water or decompose during the preparation process, has low content of sulfate ions, chloride ions and fluoride ions, and has a high yield of sodium difluorosulfonamide. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing sodium difluorosulfonyl imide. In the process of preparing sodium difluorosulfonyl imide, no water is generated and no decomposition occurs. Therefore, the acid content is low, and the content of sulfate ions, chloride ions and fluoride ions is low. In addition, the yield of sodium difluorosulfonyl imide is high.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] This invention provides a method for preparing sodium difluorosulfonamide, the method comprising the following steps:

[0011] (1) Dichlorosulfonamide, catalyst and fluoroboric acid are mixed and reacted. The resulting mixture is subjected to a first post-treatment to obtain crude dichlorosulfonamide.

[0012] (2) Mix the solid seed crystals of difluorosulfonyl imide, organic solvent and crude difluorosulfonyl imide obtained in step (1) uniformly, and perform solid-liquid separation on the obtained mixture. The solid phase is then subjected to a second post-treatment to obtain liquid difluorosulfonyl imide.

[0013] (3) The sodium source and the liquid difluorosulfonamide obtained in step (2) are uniformly mixed. The resulting melt is subjected to a third post-treatment to obtain crude difluorosulfonamide sodium.

[0014] (4) Mix the polar solvent with the crude sodium difluorosulfonamide obtained in step (3) and perform solid-liquid separation on the obtained solution to obtain filtrate; after the obtained filtrate undergoes a fourth post-treatment, add an unsuitable solvent for mixing, and after the obtained solid phase undergoes a fifth post-treatment, obtain the sodium difluorosulfonamide.

[0015] The method for preparing sodium difluorosulfonylimide provided by this invention first synthesizes crude difluorosulfonylimide using dichlorosulfonylimide, a catalyst, and fluoroboric acid. Then, the difluorosulfonylimide is purified, and crude sodium difluorosulfonylimide is obtained by further reacting it with a sodium source. Sodium difluorosulfonylimide is then purified again. The yield of sodium difluorosulfonylimide obtained is high. No water is generated or decomposed during the preparation of sodium difluorosulfonylimide. Therefore, the acid content is low, and the content of sulfate ions, chloride ions, and fluoride ions is low, which can meet the requirements of sodium-ion batteries.

[0016] Preferably, the specific steps of the mixing reaction in step (1) include: heating dichlorosulfonamide and catalyst, then adding fluoroboric acid and stirring continuously until no bubbles are generated, and then purging with nitrogen under heat preservation conditions.

[0017] Preferably, the mixing reaction is carried out in a PTFE flask.

[0018] Preferably, the heating process is carried out in an inert atmosphere.

[0019] Preferably, the temperature endpoint of the heating process is 50-120℃, for example, it can be 50℃, 60℃, 80℃, 100℃ or 120℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the nitrogen purging time is 5-15 hours, for example, 5 hours, 8 hours, 10 hours, 12 hours or 15 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the molar ratio of the catalyst to dichlorosulfonamide in step (1) is (0.0009-0.002):1, for example, it can be 0.0009:1, 0.001:1, 0.0013:1, 0.0017:1 or 0.002:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the catalyst in step (1) comprises any one or a combination of at least two of molybdenum pentachloride, antimony pentachloride, tin tetrachloride, acetonitrile, or titanium tetrachloride. Typical but non-limiting combinations include a combination of molybdenum pentachloride and antimony pentachloride, a combination of tin tetrachloride, acetonitrile, and titanium tetrachloride, or a combination of molybdenum pentachloride, antimony pentachloride, tin tetrachloride, acetonitrile, and titanium tetrachloride.

[0023] Preferably, the molar ratio of fluoroboric acid to dichlorosulfonamide in step (1) is (0.55-0.75):1, for example, it can be 0.55:1, 0.6:1, 0.65:1, 0.7:1 or 0.75:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the fluoroboric acid added in step (1) is added over a period of 6-10 hours, for example, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, step (1) the first post-processing includes sequential vacuum distillation and rectification.

[0026] Preferably, the temperature of the vacuum distillation is 30-70°C, for example, 30°C, 40°C, 50°C, 60°C or 70°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] The reduced pressure distillation can remove unreacted fluoroboric acid, facilitating subsequent rectification.

[0028] Preferably, the distillation temperature is 70-120°C, for example, 70°C, 80°C, 100°C, 110°C or 120°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the reflux time of the distillation is 0.5-2.5h, for example, it can be 0.5h, 1h, 1.5h, 2h or 2.5h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the specific steps of uniform mixing in step (2) include: dissolving the crude difluorosulfonamide obtained in step (1) in an organic solvent and mixing it evenly, and then adding it dropwise to a flask containing solid seed crystals of difluorosulfonamide to form a mixed solution.

[0031] Preferably, the temperature at which the organic solvent is dissolved is 18-39°C, for example, 18°C, 25°C, 30°C, 35°C or 39°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the organic solvent in step (1) includes dichloromethane and / or toluene.

[0033] Preferably, the temperature at which the bis(fluorosulfonyl)imide solid seed crystal is added to the flask is between -30°C and 17°C, for example, -30°C, -15°C, 0°C, 5°C, 10°C or 17°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0-10°C.

[0034] Preferably, the amount of the bis(fluorosulfonyl)imide solid seed crystal added is 0.1-1 wt% of the crude bis(fluorosulfonyl)imide, for example, it can be 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.8 wt% or 1 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the solid-liquid separation in step (2) is performed using a PP filter.

[0036] Preferably, step (2) the second post-processing includes vacuum distillation.

[0037] The purpose of vacuum distillation is to remove organic solvents.

[0038] Preferably, the temperature of the vacuum distillation is 30-70°C, for example, 30°C, 40°C, 50°C, 60°C or 70°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the sodium source in step (3) includes sodium fluoride and / or sodium hydrogen fluoride.

[0040] Preferably, the molar ratio of sodium source to liquid difluorosulfonamide in step (3) is (1-1.3):1, for example, it can be 1:1, 1.1:1, 1.2:1 or 1.3:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the specific steps of uniform mixing in step (3) include: heating the sodium source, then adding liquid difluorosulfonamide dropwise while continuously stirring, and continuing to stir after the addition is completed.

[0042] Preferably, the temperature of the heating process is 110-140℃, for example, it can be 110℃, 115℃, 120℃, 130℃ or 140℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the stirring time is 5-10 hours, for example, 5 hours, 6 hours, 8 hours, 9 hours or 10 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the third post-processing in step (3) includes vacuum distillation.

[0045] Preferably, the time for vacuum distillation is 2-5 hours, for example, 2 hours, 2.5 hours, 3 hours, 4 hours or 5 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] Preferably, the temperature of the vacuum distillation is 110-140°C, for example, 110°C, 115°C, 120°C, 130°C or 140°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Preferably, the process further includes a cooling step after the vacuum distillation.

[0048] Preferably, the polar solvent in step (4) includes any one or a combination of at least two of acetonitrile, diethyl ether, methyl tert-butyl ether, DMC, EMC, DEC or isopropyl ether. Typical but non-limiting combinations include a combination of acetonitrile and diethyl ether, a combination of methyl tert-butyl ether, DMC, EMC and DEC, or a combination of acetonitrile, diethyl ether, methyl tert-butyl ether, DMC, EMC, DEC and isopropyl ether.

[0049] Preferably, the mass ratio of the polar solvent to the crude sodium difluorosulfonamide in step (4) is (2-5):1, for example, it can be 2:1, 3:1, 4:1 or 5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] Preferably, an alkaline reagent is added during the uniform mixing in step (4).

[0051] Preferably, the alkaline reagent includes any one or a combination of at least two of triethylamine, hexamethyldisilazane, sodium carbonate, or sodium bicarbonate. Typical but non-limiting combinations include a combination of triethylamine and hexamethyldisilazane, a combination of hexamethyldisilazane, sodium carbonate, and sodium bicarbonate, or a combination of triethylamine, hexamethyldisilazane, sodium carbonate, and sodium bicarbonate.

[0052] Preferably, the mass ratio of acid to alkaline reagent in the crude sodium difluorosulfonamide in step (4) is 1:(5-15), for example, it can be 1:5, 1:8, 1:10, 1:12 or 1:15, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] Preferably, the solid-liquid separation in step (4) is performed using a PP filter membrane.

[0054] Preferably, the fourth post-processing in step (4) includes vacuum distillation.

[0055] Preferably, the temperature of the vacuum distillation is 30-60°C, for example, 30°C, 35°C, 40°C, 50°C or 60°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] Preferably, stirring is performed during the vacuum distillation process, and the vacuum distillation is stopped when stirring can no longer be performed.

[0057] Preferably, the undesirable solvent in step (4) includes any one or a combination of at least two of dichloromethane, dichloroethane, tetrachloroethane, or toluene. Typical but non-limiting combinations include a combination of dichloromethane and dichloroethane, a combination of dichloroethane, tetrachloroethane, and toluene, or a combination of dichloromethane, dichloroethane, tetrachloroethane, and toluene.

[0058] Preferably, the mass ratio of the undesirable solvent in step (4) to the filtrate after the fourth post-treatment is (2-4):1, for example, it can be 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] Preferably, the fifth post-processing in step (4) includes sequential washing with a poor solvent, vacuum distillation, and drying.

[0060] Preferably, the washing with the undesirable solvent is performed 2-4 times, for example, 2, 3 or 4 times.

[0061] Preferably, the drying temperature is 30-90℃, for example, it can be 30℃, 40℃, 50℃, 70℃ or 90℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] The method for preparing sodium difluorosulfonylimide provided by this invention first synthesizes crude difluorosulfonylimide using dichlorosulfonylimide, a catalyst, and fluoroboric acid. Then, the difluorosulfonylimide is purified and further reacted with a sodium source to obtain crude sodium difluorosulfonylimide. The sodium difluorosulfonylimide is then purified again. The yield of sodium difluorosulfonylimide obtained can reach over 95%. No water is generated or decomposed during the preparation of sodium difluorosulfonylimide, resulting in low acidity and low content of sulfate, chloride, and fluoride ions, which can meet the requirements of sodium-ion batteries. Detailed Implementation

[0064] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0065] Example 1

[0066] This embodiment provides a method for preparing sodium difluorosulfonamide, the method comprising the following steps:

[0067] (1) Dichlorosulfonamide and molybdenum pentachloride were heated to 80°C in a nitrogen atmosphere, and then fluoroboric acid was added dropwise for 8 hours while stirring continuously until no bubbles were generated. Then, nitrogen was used to purge the mixture for 10 hours under the heat preservation condition. The resulting mixture was then subjected to vacuum distillation at 50°C and rectification at 100°C. The reflux time of the rectification was 1.5 hours to obtain crude dichlorosulfonamide.

[0068] The molar ratio of molybdenum pentachloride to dichlorosulfonamide is 0.0013:1; the molar ratio of fluoroboric acid to dichlorosulfonamide is 0.65:1.

[0069] (2) At 30°C, the crude difluorosulfonamide obtained in step (1) is dissolved in dichloromethane and mixed evenly, and then dropped into a flask containing solid seed crystals of difluorosulfonamide to form a mixture; the mixture is filtered with a PP filter screen, and the solid phase is distilled under reduced pressure at 50°C to obtain liquid difluorosulfonamide.

[0070] The temperature at which the bis(fluorosulfonyl)imide solid seed crystals are added to the flask is 5°C; the amount of the bis(fluorosulfonyl)imide solid seed crystals added is 0.5 wt% of the crude bis(fluorosulfonyl)imide.

[0071] (3) Sodium fluoride was heated to 120°C, and then liquid difluorosulfonyl imide was added dropwise while stirring continuously. After the addition was completed, stirring was continued for 8 hours. The resulting melt was distilled under reduced pressure at 120°C for 3 hours, and after cooling, crude sodium difluorosulfonyl imide was obtained. The molar ratio of sodium fluoride to liquid difluorosulfonyl imide was 1.1:1.

[0072] (4) Acetonitrile and crude sodium difluorosulfonamide obtained in step (3) are mixed uniformly at a mass ratio of 3:1, and triethylamine is added at the same time. The mass ratio of acid in the crude sodium difluorosulfonamide to triethylamine is 1:10. The resulting solution is filtered through a PP filter membrane to obtain filtrate. The filtrate is then distilled under reduced pressure at 40°C and mixed with dichloromethane. The mass ratio of dichloromethane to the filtrate after reduced pressure distillation is 3:1. The resulting solid phase is washed three times with dichloromethane, distilled under reduced pressure, and dried at 50°C to obtain sodium difluorosulfonamide.

[0073] Example 2

[0074] This embodiment provides a method for preparing sodium difluorosulfonamide, the method comprising the following steps:

[0075] (1) Dichlorosulfonamide and tin tetrachloride were heated to 50°C in a nitrogen atmosphere, and then fluoroboric acid was added dropwise for 6 hours while stirring continuously until no bubbles were generated. Then, nitrogen was used to purge the mixture for 5 hours under the heat preservation condition. The resulting mixture was then subjected to vacuum distillation at 30°C and rectification at 70°C. The reflux time of the rectification was 0.5 hours to obtain crude dichlorosulfonamide.

[0076] The molar ratio of tin tetrachloride to dichlorosulfonamide is 0.0009:1; the molar ratio of fluoroboric acid to dichlorosulfonamide is 0.55:1.

[0077] (2) At 18°C, the crude difluorosulfonamide obtained in step (1) is dissolved in dichloromethane and mixed evenly, and then dropped into a flask containing solid seed crystals of difluorosulfonamide to form a mixture; the mixture is filtered with a PP filter screen, and the solid phase is distilled under reduced pressure at 30°C to obtain liquid difluorosulfonamide.

[0078] The temperature at which the bis(fluorosulfonyl)imide solid seed crystals are added to the flask is 0°C; the amount of the bis(fluorosulfonyl)imide solid seed crystals added is 0.1 wt% of the crude bis(fluorosulfonyl)imide.

[0079] (3) Sodium fluoride is heated to 110°C, then liquid difluorosulfonamide is added dropwise and stirred continuously. After the addition is completed, stirring is continued for 5 hours. The resulting melt is distilled under reduced pressure at 110°C for 5 hours. After cooling, crude sodium difluorosulfonamide is obtained. The molar ratio of sodium fluoride to liquid difluorosulfonamide is 1:1.

[0080] (4) Methyl tert-butyl ether and crude sodium difluorosulfonamide obtained in step (3) are mixed uniformly at a mass ratio of 2:1, and sodium carbonate is added at the same time. The mass ratio of acid in the crude sodium difluorosulfonamide to sodium carbonate is 1:5. The resulting solution is filtered using a PP filter membrane to obtain filtrate. After the filtrate is distilled under reduced pressure at 30°C, tetrachloroethane is added and mixed. The mass ratio of tetrachloroethane to the filtrate after reduced pressure distillation is 2:1. The resulting solid phase is washed twice with tetrachloroethane, distilled under reduced pressure, and dried at 30°C to obtain sodium difluorosulfonamide.

[0081] Example 3

[0082] This embodiment provides a method for preparing sodium difluorosulfonamide, the method comprising the following steps:

[0083] (1) Dichlorosulfonamide and titanium tetrachloride were heated to 120°C in a nitrogen atmosphere, and then fluoroboric acid was added dropwise for 10 h while stirring continuously until no bubbles were generated. Then, nitrogen was used to purge the mixture for 15 h under the heat preservation condition. The resulting mixture was then subjected to vacuum distillation at 70°C and rectification at 120°C. The reflux time of the rectification was 2.5 h to obtain crude dichlorosulfonamide.

[0084] The molar ratio of titanium tetrachloride to dichlorosulfonamide is 0.002:1; the molar ratio of fluoroboric acid to dichlorosulfonamide is 0.75:1.

[0085] (2) At 39°C, the crude difluorosulfonamide obtained in step (1) was dissolved in toluene and mixed evenly, and then dropped into a flask containing solid seed crystals of difluorosulfonamide to form a mixture; the mixture was filtered with a PP filter screen, and the solid phase was distilled under reduced pressure at 70°C to obtain liquid difluorosulfonamide.

[0086] The temperature at which the bis(fluorosulfonyl)imide solid seed crystals are added to the flask is 10°C; the amount of the bis(fluorosulfonyl)imide solid seed crystals added is 1 wt% of the crude bis(fluorosulfonyl)imide.

[0087] (3) Sodium hydrogen fluoride was heated to 140°C, and then liquid difluorosulfonyl imide was added dropwise while stirring continuously. After the addition was completed, stirring was continued for 10 hours. The resulting melt was distilled under reduced pressure at 140°C for 2 hours, and after cooling, crude sodium difluorosulfonyl imide was obtained. The molar ratio of sodium hydrogen fluoride to liquid difluorosulfonyl imide was 1.3:1.

[0088] (4) DMC and crude sodium difluorosulfonamide obtained in step (3) are mixed uniformly at a mass ratio of 5:1, and sodium bicarbonate is added at the same time. The mass ratio of acid in the crude sodium difluorosulfonamide to sodium bicarbonate is 1:15. The resulting solution is filtered using a PP filter membrane to obtain filtrate. The filtrate is then mixed with toluene after vacuum distillation at 60°C. The mass ratio of toluene to the filtrate after vacuum distillation is 4:1. The resulting solid phase is washed with toluene 4 times, vacuum distilled, and dried at 90°C to obtain sodium difluorosulfonamide.

[0089] Example 4

[0090] This embodiment provides a method for preparing sodium dichlorosulfonamide. The difference between this embodiment and Example 1 is that, except for adjusting the molar ratio of fluoroboric acid to dichlorosulfonamide in step (1) to 0.5:1, all other aspects are the same as in Example 1.

[0091] Example 5

[0092] This embodiment provides a method for preparing sodium dichlorosulfonamide. The difference between this embodiment and Example 1 is that, except for adjusting the molar ratio of fluoroboric acid to dichlorosulfonamide in step (1) to 0.8:1, all other aspects are the same as in Example 1.

[0093] Example 6

[0094] This embodiment provides a method for preparing sodium difluorosulfonylimide. The difference from Example 1 is that, except that the temperature when adding the difluorosulfonylimide solid seed crystal in step (1) to the flask is adjusted to -30°C, the rest is the same as in Example 1.

[0095] Example 7

[0096] This embodiment provides a method for preparing sodium difluorosulfonylimide. The difference from Example 1 is that, except that the temperature when adding the difluorosulfonylimide solid seed crystal in step (1) to the flask is adjusted to 17°C, the rest is the same as in Example 1.

[0097] Example 8

[0098] This embodiment provides a method for preparing sodium difluorosulfonylimide. The difference from Example 1 is that the sodium fluoride in step (3) is not subjected to a heating treatment, while the rest is the same as in Example 1.

[0099] Comparative Example 1

[0100] This comparative example provides a method for preparing sodium difluorosulfonylimide. The difference from Example 1 is that difluorosulfonylimide solid seed crystals are not added in step (2), while the rest are the same as in Example 1.

[0101] Comparative Example 2

[0102] This comparative example provides a method for preparing sodium bis(fluorosulfonyl)imide, which adopts the method for preparing sodium bis(fluorosulfonyl)imide disclosed in CN114572945A.

[0103] Sodium difluorosulfonamide was prepared using the methods provided in Examples 1-8 and Comparative Examples 1 and 2. The yield of sodium difluorosulfonamide was calculated based on the actual yield / theoretical yield. The contents of sulfate and chloride ions were determined by IC (ion chromatography), the contents of fluoride ions were determined by a fluoride ion meter, the contents of free acid were determined by titration, and the contents of moisture were determined by a moisture meter (for each component: main content ≥99.9%, free acid ≤100ppm, moisture ≤50ppm, sulfate ion ≤50ppm, chloride ion ≤10ppm, fluoride ion ≤100ppm). The color of sodium difluorosulfonamide was observed visually. The results are shown in Table 1.

[0104] Table 1

[0105]

[0106]

[0107] As can be seen from Table 1, the sodium difluorosulfonamide prepared by the preparation method provided by the present invention has a high yield, does not decompose, has low acidity, and low content of sulfate ions, chloride ions and fluoride ions, which can meet the requirements for sodium-ion batteries.

[0108] A comparison of Examples 1 with Examples 4 and 5 shows that exceeding the molar ratio of fluoroboric acid to dichlorosulfonamide will result in higher chloride or fluoride ion levels. A comparison of Examples 1 with Examples 6 and 7 shows that adding the dichlorosulfonamide solid seed crystal to the flask at a lower temperature will result in higher sulfate ion content, higher temperature, and lower yield. A comparison of Examples 1 with Example 8 shows that not heating the sodium fluoride will result in higher acid content.

[0109] As can be seen from the comparison between Example 1 and Comparative Example 1, without adding bis(fluorosulfonyl)imide solid seed crystals for bis(fluorosulfonyl)imide purification, it is impossible to obtain sodium bis(fluorosulfonyl)imide with good quality and high yield. As can be seen from the comparison between Example 1 and Comparative Example 2, the sodium bis(fluorosulfonyl)imide prepared by this prior art has low purity, which cannot meet the requirements of sodium-ion batteries. Water is generated during the synthesis process and is not removed, resulting in problems such as easy decomposition and low yield.

[0110] In summary, the method for preparing sodium difluorosulfonylimide provided by this invention first synthesizes crude difluorosulfonylimide using dichlorosulfonylimide, a catalyst, and fluoroboric acid. Then, the difluorosulfonylimide is purified, and further purified by reaction with a sodium source to obtain crude sodium difluorosulfonylimide. The yield of sodium difluorosulfonylimide obtained can reach over 95%. No water is generated or decomposed during the preparation of sodium difluorosulfonylimide, resulting in low acidity and low content of sulfate, chloride, and fluoride ions, which can meet the requirements of sodium-ion batteries.

[0111] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for producing sodium bisfluorosulfonimide, characterized by, The preparation method includes the following steps: (1) Dichlorosulfonamide, catalyst and fluoroboric acid are mixed and reacted. The resulting mixture is subjected to a first post-treatment to obtain crude dichlorosulfonamide. The molar ratio of fluoroboric acid to dichlorosulfonamide is (0.55-0.75):1; (2) Mix the solid seed crystals of difluorosulfonyl imide, organic solvent and crude difluorosulfonyl imide obtained in step (1) uniformly, and perform solid-liquid separation on the obtained mixture. The solid phase is then subjected to a second post-treatment to obtain liquid difluorosulfonyl imide. The specific steps of uniform mixing include: dissolving the crude difluorosulfonamide obtained in step (1) in an organic solvent and mixing it evenly, and then adding it dropwise to a flask containing solid seed crystals of difluorosulfonamide to form a mixed solution; The temperature at which the bis(fluorosulfonyl)imide solid seed crystals are added to the flask is 0-10°C. (3) The sodium source and the liquid difluorosulfonamide obtained in step (2) are uniformly mixed. The resulting melt is subjected to a third post-treatment to obtain crude sodium difluorosulfonamide. The specific steps of uniform mixing include: heating the sodium source, then adding liquid difluorosulfonamide dropwise while continuously stirring, and continuing to stir after the addition is completed; The temperature for the heating process is 110-140℃; (4) Mix the polar solvent with the crude sodium difluorosulfonamide obtained in step (3), and perform solid-liquid separation on the obtained solution to obtain filtrate; after the fourth post-treatment, add a poor solvent to the obtained filtrate and mix; after the fifth post-treatment, obtain the sodium difluorosulfonamide. An alkaline reagent is added during the uniform mixing process; The fourth post-processing includes vacuum distillation; The fifth post-processing includes sequential washing with undesirable solvents, vacuum distillation, and drying.

2. The production method according to claim 1, characterized by, The specific steps of the mixing reaction in step (1) include: heating dichlorosulfonamide and catalyst, then adding fluoroboric acid and stirring continuously until no bubbles are generated, and then purging with nitrogen under heat preservation conditions.

3. The production method according to claim 2, characterized by, The heating process is carried out in an inert atmosphere.

4. The production method according to claim 2, characterized by, The endpoint of the heating process is 50-120℃.

5. The preparation method according to claim 2, characterized in that, The nitrogen purging time is 5-15 hours.

6. The preparation method according to claim 1, characterized in that, The molar ratio of the catalyst to dichlorosulfonamide in step (1) is (0.0009-0.002):

1.

7. The preparation method according to claim 1, characterized in that, The catalyst in step (1) includes any one or a combination of at least two of molybdenum pentachloride, antimony pentachloride, tin tetrachloride, acetonitrile, or titanium tetrachloride.

8. The method of claim 1, wherein, The fluoroboric acid in step (1) is added over a period of 6-10 hours.

9. The method of claim 1, wherein, Step (1) The first post-processing includes sequential vacuum distillation and rectification.

10. The method of claim 9, wherein, The temperature for vacuum distillation is 30-70℃.

11. The preparation method according to claim 9, characterized in that, The distillation temperature is 70-120℃.

12. The method of claim 9, wherein, The reflux time for the distillation is 0.5-2.5 h.

13. The method of claim 1, wherein, The organic solvent in step (1) includes dichloromethane and / or toluene.

14. The method of claim 1, wherein, The amount of the bis(fluorosulfonyl)imide solid seed crystals added is 0.1-1 wt% of the crude bis(fluorosulfonyl)imide.

15. The method of claim 1, wherein, Step (2) The second post-processing includes vacuum distillation.

16. The method of claim 15, wherein, The temperature for vacuum distillation is 30-70℃.

17. The method of claim 1, wherein, The sodium source in step (3) includes sodium fluoride and / or sodium hydrogen fluoride.

18. The method of claim 1, wherein, The molar ratio of sodium source to liquid difluorosulfonamide in step (3) is (1-1.3):

1.

19. The method of claim 1, wherein, The stirring time is 5-10 hours.

20. The method of claim 1, wherein, The third post-processing step (3) includes vacuum distillation.

21. The method of claim 20, wherein, The vacuum distillation time is 2-5 hours.

22. The method of claim 20, wherein, The temperature for vacuum distillation is 110-140℃.

23. The method of claim 1, wherein, The polar solvent in step (4) includes any one or a combination of at least two of acetonitrile, diethyl ether, methyl tert-butyl ether, DMC, EMC, DEC or isopropyl ether.

24. The method of claim 1, wherein, The mass ratio of the polar solvent to crude sodium difluorosulfonamide in step (4) is (2-5):

1.

25. The method of claim 1, wherein, The alkaline reagent includes any one or a combination of at least two of triethylamine, hexamethyldisilazane, sodium carbonate, or sodium bicarbonate.

26. The method of claim 1, wherein, In step (4), the mass ratio of acid to alkaline reagent in the crude sodium difluorosulfonamide is 1:(5-15).

27. The method of claim 1, wherein, The temperature for vacuum distillation is 30-60℃.

28. The method of claim 1, wherein, The undesirable solvent in step (4) includes any one or a combination of at least two of dichloromethane, dichloroethane, tetrachloroethane, or toluene.

29. The method of claim 1, wherein, The mass ratio of the undesirable solvent in step (4) to the filtrate after the fourth post-treatment is (2-4):

1.

30. The method of claim 1, wherein, The number of times the unsuitable solvent is used for washing is 2-4 times.

31. The method of claim 1, wherein, The drying temperature is 30-90℃.

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