A method for preparing sodium bisfluorosulfonimide

Abstract

The application relates to a preparation method of sodium bisfluorosulfonimide, which comprises the following steps: carrying out fluorination reaction on bischlorosulfonimide acid and sodium fluoride in a weak polar solvent under microwave-induced catalysis to generate sodium bisfluorosulfonimide, wherein the weak polar solvent is an ester solvent. In the application, sodium fluoride is used as a fluorination reagent and a sodium reagent, bischlorosulfonimide acid can be directly converted into sodium bisfluorosulfonimide, the synthesis steps and the discharge of three wastes are reduced, the production efficiency is improved, and the production cost is reduced.

Description

Technical Field

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

[0002] Sodium difluorosulfonamide (NaFSI) is a sodium salt electrolyte with moderate conductivity. Compared with sodium hexafluorophosphate (NaPF6), it has higher hydrolytic stability, thermal stability and electrochemical stability, which is beneficial to the improvement of battery cycle performance and high and low temperature performance. These advantages make NaFSI the most promising sodium salt electrolyte / additive for energy storage batteries.

[0003] The main methods for preparing NaFSI include the chlorosulfonic acid method, the ionic liquid method, and the cation exchange method. Among them, the chlorosulfonic acid method is the mainstream preparation process for NaFSI, which uses chlorosulfonic acid as a raw material.

[0004] Patent CN103935970A discloses a method for preparing bis(fluorosulfonyl)imide salts. First, chlorosulfonic acid reacts with aminosulfonic acid and sulfoxide to prepare bis(fluorosulfonyl)imide acid (HCSI); then, fluorination is performed to prepare bis(fluorosulfonyl)imide acid (HFSI); finally, reaction with a sodium reagent prepares NaFSI. Patent CN104671224A discloses a method for preparing NaFSI by fluorinating sodium(Na)(HCSI) with a fluorinating reagent, wherein NaFSI requires the preparation of HCSI from chlorosulfonic acid as a raw material, followed by sodium treatment. The preparation of NaFSI from NaFSI involves fluorine-chlorine exchange, which may result in excessively high chloride ion content in the product. All of the above chlorosulfonic acid methods suffer from problems such as multiple reaction steps, long reaction time, high cost, and low product quality.

[0005] Ionic liquid methods have many side reactions and poor reproducibility. Furthermore, the reaction involving ammonia is highly exothermic, leading to a rapid increase in pressure inside the reactor and posing an explosion risk. Cation exchange methods suffer from problems such as expensive raw materials and high levels of other cations and impurities in the product. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a method for preparing sodium difluorosulfonamide, which is characterized by high production efficiency, low waste, low energy consumption, high yield, and suitability for industrial production.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing sodium bis(fluorosulfonyl)imide, comprising: fluorination of dichlorosulfonylimide acid and sodium hydrogen fluoride (NaHF2) in a weakly polar solvent under microwave-induced catalysis to generate sodium bis(fluorosulfonyl)imide, wherein the weakly polar solvent is an ester solvent. This invention uses NaHF2 as both the fluorinating and sodium-ionizing reagents, enabling the direct conversion of HCSI to NaFSI, reducing the number of synthesis steps. While the sodium-ionization reaction of NaHF2 and HCSI is relatively easy under conventional heating conditions, the fluorination reaction requires a long time and involves numerous side reactions, including sodium fluorosulfonate, sodium aminosulfonate, and other unknown impurities. This invention utilizes microwave-induced catalytic fluorination, which significantly shortens the reaction time, improves the selectivity of the fluorination reaction, and reduces side reactions, including decomposition of HCSI due to excessive residence time in the reaction system and the generation of unknown impurities, thereby significantly improving product yield and quality. Furthermore, the preparation method of this invention does not require a phase transfer catalyst, further reducing costs and avoiding catalyst residue.

[0009] The microwave power of the present invention is 0-800W and the microwave time is 0.5-12h; preferably, the microwave power is 200-400W and the microwave time is 1-8h; more preferably, the microwave power is 200-300W and the microwave time is 1-2h.

[0010] Specifically, the preparation method of the present invention includes the following steps: first, sodium bifluoride is thoroughly mixed with a weakly polar solvent; then, dichlorosulfonyl imide acid is added to the reaction system, and a fluorination reaction is carried out under microwave-induced catalysis for 1-2 hours to obtain a reaction solution containing sodium dichlorosulfonyl imide; then, the reaction solution is post-treated to obtain a high-purity sodium dichlorosulfonyl imide product. Further, the post-treatment step specifically includes filtering the reaction solution to obtain a clear liquid, concentrating it, adding a poor solvent to stir and crystallize, filtering and drying to obtain the high-purity sodium dichlorosulfonyl imide product.

[0011] Since fluorination reactions commonly use highly polar solvents such as DMF and DMSO, these solvents can affect the microwave-induced catalysis in the reaction process described in this invention, resulting in a reaction rate at the same reaction temperature that is not significantly different from that of conventional heating. Non-polar solvents such as n-hexane are unsuitable as reaction solvents in this system. Therefore, this invention uses a weakly polar solvent instead of the commonly used highly polar solvent to further and effectively promote the increase in reaction rate. Specifically, the weakly polar solvent is an ester solvent; preferably, it is a carbonate solvent; more preferably, it is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0012] The microwave-induced catalytic reaction described in this invention does not require heating and can be carried out at room temperature.

[0013] The equivalent ratio of NaHF2 to HCSI is 4:1 to 1:1, preferably 3:1 to 1.5:1, and more preferably 2:1 to 1.5:1.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] 1. This invention uses NaHF2 as a fluorinating and sodium-ionizing reagent, which can directly convert HCSI into NaFSI, reducing synthesis steps and emissions of waste, improving production efficiency and reducing production costs.

[0016] 2. This invention utilizes microwave-induced catalytic fluorination, which can significantly shorten the reaction time, improve the selectivity of the reaction, and reduce the occurrence of side reactions, thereby fully improving the yield and quality of the product. Furthermore, the method described in this invention does not require a phase transfer catalyst, which can further reduce costs and avoid catalyst residue.

[0017] 3. In this invention, a weakly polar solvent is used instead of the strongly polar solvent commonly used in fluorination reactions, which effectively promotes the increase of reaction rate. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0019] Example 1

[0020] 9.3 g of sodium bifluoride (0.15 mol) and 50 g of dimethyl carbonate were mixed in a reaction vessel. 21.4 g of dichlorosulfonyl imide acid (0.1 mol) was slowly added dropwise with stirring. After the addition was complete, the microwave reactor (250 W) was turned on, and the reaction was refluxed for 2 hours. After the reaction was complete, the reaction solution was filtered to remove NaHF2, resulting in a clear solution. This solution was concentrated, and 30 g of dichloromethane was added with stirring to induce crystallization. The crystals were then filtered and dried to obtain 19.4 g of high-purity sodium dichlorosulfonyl imide.

[0021] Based on testing and calculations, the NaFSI product yield was 95.6% and the purity was 99.96%.

[0022] Example 2

[0023] The operation of Example 2 is the same as that of Example 1, except that the dimethyl carbonate is replaced with ethyl methyl carbonate, and the other operations remain unchanged, resulting in 19.3g of high-purity NaFSI product.

[0024] Based on testing and calculations, the NaFSI product yield was 95.1% and the purity was 99.94%.

[0025] Example 3

[0026] The operation of Example 3 is the same as that of Example 1, except that the dimethyl carbonate is replaced with ethyl acetate, and the other operations remain unchanged, to obtain 18.3g of high-purity NaFSI product.

[0027] Based on testing and calculations, the yield of the NaFSI product was 90.1%, and the purity was 99.95%.

[0028] Example 4

[0029] The operation of Example 5 is the same as that of Example 1, except that the microwave power is 200W and other operations remain unchanged, resulting in 18.9g of high-purity NaFSI product.

[0030] Based on testing and calculations, the yield of the NaFSI product was 93.1%, and the purity was 99.97%.

[0031] Example 5

[0032] The operation of Example 6 is the same as that of Example 1, except that the microwave power is 300W and other operations remain unchanged, resulting in 19.2g of high-purity NaFSI product.

[0033] Based on testing and calculations, the yield of the NaFSI product was 94.6%, and the purity was 99.95%.

[0034] Example 6

[0035] The operation of Example 7 is the same as that of Example 1, except that the amount of sodium bifluoride used is 18.6g (0.3mol), and other operations remain unchanged, resulting in 19.5g of high-purity NaFSI product.

[0036] Based on testing and calculations, the NaFSI product yield was 96.1% and the purity was 99.91%.

[0037] Example 7

[0038] The operation of Example 8 is the same as that of Example 1, except that the reaction time is 1 hour and other operations remain unchanged, resulting in 18.6g of high-purity NaFSI product.

[0039] Based on testing and calculations, the NaFSI product yield was 91.6% and the purity was 99.90%.

[0040] Comparative Example 1

[0041] 9.3 g of sodium bifluoride (0.15 mol) and 50 g of dimethyl carbonate were mixed in a reaction vessel. 21.4 g of dichlorosulfonylimide acid (HCSI) (0.1 mol) was slowly added dropwise with stirring. After the addition was complete, the mixture was heated in an oil bath and refluxed for 2 hours. After the reaction was complete, the reaction solution was filtered to remove NaHF2, resulting in a clear solution. This solution was concentrated, and 30 g of dichloromethane was added with stirring to induce crystallization. The crystals were then filtered and dried to obtain 10.8 g of high-purity sodium dichlorosulfonylimide.

[0042] Based on testing and calculations, the yield of the NaFSI product was 53.2%, and the purity was 99.30%.

[0043] Comparative Example 2

[0044] The operation of Comparative Example 2 was the same as that of Comparative Example 1, except that the reaction solvent was DMF and all other operations remained unchanged, resulting in 10.1g of high-purity NaFSI product.

[0045] Based on testing and calculations, the yield of the NaFSI product was 49.8%, and the purity was 99.23%.

[0046] Comparative Example 3

[0047] The procedure for Comparative Example 3 was the same as that for Comparative Example 1, except that the reaction solvent was ethyl acetate, and all other procedures remained unchanged, yielding 9.8g of high-purity NaFSI product.

[0048] Based on testing and calculations, the yield of the NaFSI product was 48.3%, and the purity was 99.09%.

[0049] Comparative Example 4

[0050] The operation of Comparative Example 4 was the same as that of Comparative Example 1, except that the reaction time was 24 hours and other operations remained unchanged, resulting in 9.8 g of high-purity NaFSI product.

[0051] Based on testing and calculations, the yield of the NaFSI product was 83.3%, and the purity was 95.47%.

[0052] Comparative Example 5

[0053] The operation of Comparative Example 1 was the same as that of Example 1, except that the reaction solvent was DMF and all other operations remained unchanged, resulting in 10.7g of high-purity NaFSI product.

[0054] Based on testing and calculations, the yield of the NaFSI product was 52.7%, and the purity was 99.13%.

[0055] Data from Examples 1-7 and Comparative Examples 1-5 show that, compared to conventional heating, the microwave-induced catalysis of this invention can significantly improve the product yield and quality. Furthermore, using low-polarity solvents such as esters as reaction solvents results in a product yield far higher than that of high-polarity solvents such as DMF. While conventional heating for NaFSI preparation can increase yield by extending the reaction time, the prolonged residence time of reactants and products in the reaction system easily leads to decomposition or the generation of other unknown impurities, significantly reducing product quality. Moreover, the purity of electrolytes typically needs to be at least 99.9%, which does not meet the quality requirements for sodium salt electrolyte products.

Claims

1. A process for the preparation of sodium bisfluorosulfonimide, characterized in that: The dichlorosulfonyl imide acid and sodium fluoride are subjected to fluorination reaction under microwave induction catalysis in a weak polar solvent, which is a carbonate solvent.

2. The process for the preparation of sodium bisfluorosulfonimide according to claim 1, characterized in that: The microwave power is 200-400 W, and the microwave time is 1-8 h.

3. The method of claim 1, wherein the sodium bisfluorosulfonimide is prepared by the process comprising: reacting a compound of formula (I) with sodium hydroxide in a solvent to form sodium bisfluorosulfonimide of formula (II). The microwave power is 200-300 W, and the microwave time is 1-2 h.

4. The method for preparing sodium difluorosulfonamide according to claim 1, characterized in that: The preparation method comprises the following steps: firstly, the sodium fluoride is fully mixed with a weak polar solvent, then the dichlorosulfonyl imide acid is added into the reaction system, and the fluorination reaction is carried out under microwave induction catalysis, the reaction time is 1-2 h, and a reaction liquid containing sodium difluorosulfonyl imide is obtained; and then the reaction liquid is subjected to post-treatment, and a high-purity sodium difluorosulfonyl imide product is obtained.

5. The process for the preparation of sodium bisfluorosulfonimide according to claim 4, characterized in that: The post-treatment step specifically comprises filtering the reaction liquid to obtain a clear liquid, adding a poor solvent for stirring and crystallization after concentration, filtering and drying, and obtaining a high-purity sodium difluorosulfonyl imide product.

6. The method for preparing sodium difluorosulfonamide according to claim 1, characterized in that: The weak polar solvent is at least one selected from dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate.

7. The method for preparing sodium difluorosulfonylimide according to claim 1, characterized in that: The equivalent ratio of sodium fluoride to dichlorosulfonyl imide acid is 4:1-1:

1.

8. The method for preparing sodium difluorosulfonamide according to claim 4, characterized in that: The equivalent ratio of sodium fluoride to dichlorosulfonyl imide acid is 3:1-1.5:1.