A method for preparing lithium perfluoroalkyl disulfonylimide

Abstract

This invention discloses a method for preparing lithium perfluoroalkyl disulfonylimide, belonging to the field of chemical synthesis technology. The method involves cooling an acetonitrile solution containing triethylenetetramine formate ionic liquid to -50°C to -30°C, then introducing ammonia gas, followed by the sequential addition of anhydrous lithium hydroxide, triethylsilane, and 1-hydroxybenzotriazole, and then adding perfluoroalkyl disulfonyl fluoride as shown in Formula 1. A two-stage heating reaction is then carried out to obtain lithium perfluoroalkyl disulfonylimide as shown in Formula 2. This invention provides a highly selective and simple one-step synthetic route, simultaneously achieving high purity, low moisture content, and high yield of the product, providing strong technical support for the efficient industrial production and high-end electrochemical applications of lithium perfluoroalkyl disulfonylimide.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis technology, and particularly relates to a method for preparing lithium perfluoroalkyl disulfonylimide. Background Technology

[0002] Lithium perfluoroalkyl disulfonylimide is a class of electrolyte salts that simultaneously contain a perfluoroalkyl chain, a cyclic sulfonylimide anion, and a lithium cation. Its unique cyclic sulfonylimide anion structure endows this class of compounds with excellent thermal stability, a wide electrochemical window, and good ionic conductivity, making it a promising candidate for applications in novel electrochemical energy storage devices such as lithium-ion batteries, lithium-sulfur batteries, and all-solid-state lithium batteries.

[0003] In the prior art, methods for synthesizing lithium salts containing a cyclic perfluoroalkyl disulfonylimide skeleton have been reported in the literature. The most classic route employs a two-step method: first, perfluoroalkyl disulfonyl fluoride reacts with ammonia to obtain a sulfonamide ammonium salt intermediate; second, the intermediate undergoes a neutralization and metathesis reaction with an inorganic base (such as lithium hydroxide) to obtain the lithium salt product. The reaction of perfluoroalkyl disulfonyl fluoride with ammonia is typically carried out by adding an organic solution of the sulfonyl fluoride to liquid ammonia or a mixture of liquid ammonia and an organic solvent. For example, CN1212688A discloses first condensing ammonia into liquid ammonia, adding tetrahydrofuran to prepare a liquid ammonia / tetrahydrofuran mixed solution, then slowly adding a tetrahydrofuran solution of perfluoroalkyl-di-sulfonyl fluoride to the above mixed solution to carry out a cyclization reaction to obtain a sulfonamide ammonium salt intermediate, and then reacting the intermediate with lithium hydroxide under reflux in tetrahydrofuran to obtain the lithium salt. In this patent, the yield of ammonium salt in the first step is 70%–86%, and the yield of lithium salt in the second step is 96%–97%, with a total yield of approximately 67%–83%. Furthermore, the patent states that the separation of byproducts and impurities mixed in with the product is extremely difficult and will further reduce the yield.

[0004] It is evident that the separation and purification of sulfonamide ammonium salt intermediates is the technical bottleneck of the entire process. This is because the intermediates have poor solubility in organic solvents, requiring multiple solid-liquid separation operations such as filtration, washing, and drying for purification. The process is cumbersome, and material entrainment and mechanical losses during separation further reduce the overall yield. Perfluoroalkyl disulfonyl fluoride is prone to side reactions such as hydrolysis under alkaline conditions. In the existing two-step method, the amination reaction and the alkali salt formation reaction are carried out step by step, each requiring independent temperature control and solvent systems. The process is complex and difficult to scale up industrially. When the intermediates are not completely separated, residual sulfonamide impurities are difficult to remove effectively. These impurities have been proven to corrode aluminum current collectors in lithium-ion batteries, severely affecting the electrochemical performance of the electrolyte salt.

[0005] Therefore, developing a preparation method with mild and controlled reaction conditions, no need for intermediate separation and purification, simple operation, high product purity and high yield is of great significance for realizing the efficient and low-cost industrial production of lithium perfluoroalkyl disulfonylimide and its application in high-end electrochemical energy storage devices. Summary of the Invention

[0006] The purpose of this invention is to overcome the technical problems of existing methods for preparing lithium perfluoroalkyl disulfonylimide, such as cumbersome steps, the need for separation and purification of intermediates, low yield, and difficulty in meeting the requirements of electrochemical applications. This invention provides a method for preparing lithium perfluoroalkyl disulfonylimide by in-situ preparation of an acetonitrile solution containing triethylenetetramine formate ionic liquid, optimization of the feeding sequence, and introduction of a catalytic system. This integrates the three-step reaction of amination, cyclization, and salt formation into one step, achieving the technical effects of no need for separation and purification of intermediates, mild and controlled reaction conditions, simple operation, and high product purity and high yield.

[0007] The technical solution adopted in this invention is: A method for preparing lithium perfluoroalkyl disulfonyl imide, the key point of which is to cool the acetonitrile solution containing triethylenetetramine formate ionic liquid to -50℃~-30℃ and then introduce ammonia gas, followed by the sequential addition of anhydrous lithium hydroxide, triethylsilane and 1-hydroxybenzotriazole, and then the addition of perfluoroalkyl disulfonyl fluoride, and carry out a two-stage heating reaction to obtain the above-mentioned lithium perfluoroalkyl disulfonyl imide; The above-mentioned perfluoroalkyl disulfonyl fluoride is shown in Formula 1. Formula 1 The above-mentioned perfluoroalkyl disulfonylimide lithium is shown in Formula 2. Formula 2 In Equation 1, n is an integer from 1 to 5.

[0008] Specifically, the aforementioned lithium perfluoroalkyl disulfonylimide is one of the following compounds: .

[0009] Specifically, the two-stage heating reaction is to first raise the temperature to -5℃ to 5℃ and react for 45 min to 90 min, then continue to raise the temperature to 20℃ to 30℃ and continue to react for 90 min to 150 min.

[0010] Preferably, the molar ratio of perfluoroalkyl disulfonyl fluoride, triethylenetetramine, and formic acid is 1:(0.8–1.2):(3.6–5.4).

[0011] Preferably, the molar ratio of perfluoroalkyl disulfonyl fluoride, anhydrous lithium hydroxide, triethylsilane and 1-hydroxybenzotriazole is 1:(1.3-1.7):(1.0-1.2):(0.08-0.12).

[0012] Furthermore, the triethylenetetramine formate ionic liquid is prepared in situ by reacting triethylenetetramine with formic acid via an acid-base neutralization reaction.

[0013] Furthermore, the specific process of the acid-base neutralization reaction between triethylenetetramine and formic acid is as follows: triethylenetetramine is dissolved in acetonitrile, the temperature is lowered to 0℃~5℃, formic acid is added dropwise to carry out the acid-base neutralization reaction, and after the addition is completed, the mixture is stirred for 10min~15min, and after drying, an acetonitrile solution containing triethylenetetramine formate ionic liquid is obtained.

[0014] Furthermore, the above drying process involves adding molecular sieves for dehydration.

[0015] Specifically, the amount of ammonia introduced is such that for every 0.1 mol of perfluoroalkyl disulfonyl fluoride, the ammonia weight increases by 8 g to 12 g.

[0016] More specifically, after the reaction was completed, the mixture was extracted with petroleum ether, the organic phases were combined, and the solvent was evaporated to obtain the above-mentioned perfluoroalkyl disulfonylimide lithium.

[0017] Compared with the prior art, the present invention has the following advantages: First, this invention uses an acetonitrile solution containing triethylenetetramine formate ionic liquid as the solvent system, and combines the synergistic catalysis of 1-hydroxybenzotriazole and triethylsilane to design a highly efficient one-step reaction pathway for amination, cyclization, and salt formation. Specifically, the triethylenetetramine formate ionic liquid effectively activates ammonia molecules and enhances their effective concentration in the liquid phase through multiple hydrogen bonds formed between the ammonium group site on its cation and the formate anion. Simultaneously, the polar microenvironment provided by the ionic liquid helps stabilize the ionic intermediates generated during the reaction, suppressing the hydrolysis side reaction of perfluoroalkyl sulfonyl fluoride under alkaline conditions from the source. The active catalytic intermediate generated in situ by 1-hydroxybenzotriazole and triethylsilane can effectively activate the SF bond of sulfonyl fluoride, significantly improving the selectivity and conversion efficiency of the amination reaction. The synergistic effect of the above mechanisms fundamentally solves the technical problem of separating and purifying intermediates in the traditional two-step method, enabling the amination, cyclization and salt formation reactions to be completed continuously in one pot. The intermediates can be directly converted into the target product without separation, achieving a simultaneous improvement in reaction selectivity and process efficiency.

[0018] Secondly, this invention employs a specific feeding sequence of "adding alkali first, then catalyst," ensuring that the substrate is activated only after a sufficiently established low-temperature alkaline environment is established. This guarantees that the catalytically active species exert their efficient effects at the optimal time, avoiding the ineffective consumption of the catalyst under alkaline-free conditions. Combined with a staged heating strategy—completing the main transformation at low temperature to suppress side reactions and then driving the reaction to completion at room temperature—this achieves broad applicability to substrates with varying carbon chain lengths. After the reaction, only petroleum ether extraction is required for efficient separation of the product from the ionic liquid and inorganic salts. Post-processing is simple, eliminating the need for cumbersome purification steps such as column chromatography.

[0019] Third, the preparation method of this invention has a wide process window and high substrate versatility. By reasonably adjusting the process parameters, this invention exhibits excellent applicability to perfluoroalkyl disulfonyl fluoride substrates with different carbon chain lengths. The products prepared by this invention have high purity, low moisture content, and stable yield, which can meet the stringent quality requirements of electrolyte salts for high-end electrochemical energy storage devices such as lithium-ion batteries.

[0020] In summary, this invention provides a highly selective and simple one-step synthesis route through a technical solution using an acetonitrile solvent system containing triethylenetetramine formate ionic liquid, synergistic catalysis of 1-hydroxybenzotriazole and triethylsilane, a specific feeding sequence, and a staged heating strategy. This simultaneously achieves high product purity, low moisture content, and high yield, providing strong technical support for the efficient industrial production and high-end electrochemical applications of lithium perfluoroalkyl disulfonylimide. Attached Figure Description

[0021] Figure 1 This is the high-performance liquid chromatogram of sample 1 of the present invention.

[0022] Figure 2 This is the high performance liquid chromatography-mass spectra of sample 1 of the present invention.

[0023] Figure 3 It is sample 1 of the present invention. 1 H nuclear magnetic resonance spectrum ( 1 H NMR).

[0024] Figure 4 It is sample 1 of the present invention. 19 F nuclear magnetic resonance spectrum ( 19 F NMR). Detailed Implementation

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0028] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0029] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0030] Unless otherwise specified in the examples, the standard conditions can be followed; unless the manufacturer of the reagents or instruments used is specified, they are all commercially available products.

[0031] Example 1 This embodiment provides a method for preparing a lithium perfluoroalkyl disulfonylimide compound, the structural formula of which is shown in Formula 3. The specific process is as follows: Formula 3 S1. Preparation of proton-type amine ionic liquids: Under nitrogen protection, 80 mL of acetonitrile and 0.10 mol of triethylenetetramine were added to a dry reaction flask, the temperature was lowered to 2 °C, and 20 mL of formic acid solution (a 22.5 mol / L aqueous solution containing 0.45 mol of formic acid) was slowly added dropwise at 300 r / min. The molar ratio of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, triethylenetetramine, and formic acid added subsequently is 1:1:4.5. After the addition was complete, stirring was continued for 12 minutes. Then, 18 g of activated 4A molecular sieve was added. The mixture was stirred at room temperature for 22 minutes while maintaining the stirring speed to remove water. The molecular sieve was removed by filtration to obtain a dry acetonitrile solution containing triethylenetetramine formate ionic liquid (abbreviated as acetonitrile solution containing [TETA][HCOO] ionic liquid).

[0032] S2, Cooling down and introducing ammonia: The acetonitrile solution containing the [TETA][HCOO] ionic liquid was cooled to -40°C, and ammonia gas was introduced while maintaining the stirring speed until the reaction flask gained 10g in weight.

[0033] S3. Add catalyst and reaction substrate: 0.15 mol of anhydrous lithium hydroxide, 0.11 mol of triethylsilane, and 0.010 mol of 1-hydroxybenzotriazole were added sequentially to the system. Maintain the temperature at -40℃ and stir at 300r / min for 7min to ensure the catalyst is fully dispersed; Slowly add 0.1 mol of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride; The molar ratio of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, anhydrous lithium hydroxide, triethylsilane, and 1-hydroxybenzotriazole is 1:1.5:1.1:0.10.

[0034] S4. Heating reaction and post-treatment: After the addition of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, the system was heated to 0°C and reacted for 65 min. Continue heating to 25°C and continue the reaction for 120 minutes; After the reaction was completed, 250 mL of petroleum ether was added to the reaction solution for extraction. After thorough shaking, the mixture was allowed to stand and separated. The upper organic phase was retained, and the lower phase was extracted twice more with petroleum ether. All organic phases were combined and the solvent was evaporated to obtain lithium perfluoroalkyl disulfonylimide as shown in Formula 3, namely lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide, denoted as Sample 1.

[0035] Example 2 This embodiment prepares a perfluoroalkyl disulfonylimide lithium compound, and the specific process is as follows: S1. Preparation of proton-type amine ionic liquids: Under nitrogen protection, 90 mL of acetonitrile and 0.12 mol of triethylenetetramine were added to a dry reaction flask, the temperature was lowered to 5 °C, and 24 mL of formic acid solution (a 22.5 mol / L aqueous solution containing 0.54 mol of formic acid) was slowly added dropwise at 400 r / min. The molar ratio of the subsequently added 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, triethylenetetramine, and formic acid is 1:1.2:5.4. After the addition was complete, stirring was continued for 10 minutes. Then, 22 g of activated 4A molecular sieve was added. The mixture was stirred at room temperature for 15 minutes while maintaining the stirring speed to perform dehydration. The molecular sieve was removed by filtration to obtain a dry acetonitrile solution containing [TETA][HCOO] ionic liquid.

[0036] S2, Cooling down and introducing ammonia: The acetonitrile solution containing the [TETA][HCOO] ionic liquid was cooled to -30°C, and ammonia gas was introduced while maintaining the stirring speed until the reaction flask gained 12g in weight.

[0037] S3. Add catalyst and reaction substrate: 0.17 mol of anhydrous lithium hydroxide, 0.12 mol of triethylsilane, and 0.012 mol of 1-hydroxybenzotriazole were added sequentially to the system. Maintain the temperature at -30℃ and stir at 400r / min for 5min to ensure the catalyst is fully dispersed; Slowly add 0.1 mol of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride; The molar ratio of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, anhydrous lithium hydroxide, triethylsilane and 1-hydroxybenzotriazole is 1:1.7:1.2:0.12.

[0038] S4. Heating reaction and post-treatment: After the addition of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, the system was heated to 5°C and reacted for 45 min. Continue heating to 30°C and continue the reaction for 90 minutes; After the reaction was completed, 300 mL of petroleum ether was added to the reaction solution for extraction. After thorough shaking, the mixture was allowed to stand and separated. The upper organic phase was retained, and the lower phase was extracted twice more with petroleum ether. All organic phases were combined and the solvent was evaporated to obtain lithium perfluoroalkyl disulfonylimide as shown in Formula 3, namely lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide, denoted as Sample 2.

[0039] Example 3 This embodiment prepares a perfluoroalkyl disulfonylimide lithium compound, and the specific process is as follows: S1. Preparation of proton-type amine ionic liquids: Under nitrogen protection, 70 mL of acetonitrile and 0.08 mol of triethylenetetramine were added to a dry reaction flask, the temperature was lowered to 0 °C, and 16 mL of formic acid solution (a 22.5 mol / L aqueous solution containing 0.36 mol of formic acid) was slowly added dropwise at 200 r / min. The molar ratio of the subsequently added 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, triethylenetetramine, and formic acid is 1:0.8:3.6. After the addition is complete, continue stirring for 15 minutes, add 15 g of activated 4A molecular sieve, maintain the stirring speed at room temperature for 30 minutes to perform dehydration treatment, filter to remove the molecular sieve, and obtain a dry acetonitrile solution containing [TETA][HCOO] ionic liquid.

[0040] S2, Cooling down and introducing ammonia: The acetonitrile solution containing the [TETA][HCOO] ionic liquid was cooled to -50°C, and ammonia gas was introduced while maintaining the stirring speed until the reaction flask gained 8g in weight.

[0041] S3. Add catalyst and reaction substrate: 0.13 mol of anhydrous lithium hydroxide, 0.10 mol of triethylsilane, and 0.008 mol of 1-hydroxybenzotriazole were added sequentially to the system. Maintain the temperature at -50℃ and stir at 200r / min for 10min to ensure the catalyst is fully dispersed; Slowly add 0.1 mol of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride; The molar ratio of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, anhydrous lithium hydroxide, triethylsilane and 1-hydroxybenzotriazole is 1:1.3:1.0:0.08.

[0042] S4. Heating reaction and post-treatment: After the addition of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, the system was heated to -5°C and reacted for 90 min. Continue heating to 20°C and continue the reaction for 150 minutes; After the reaction was completed, 200 mL of petroleum ether was added to the reaction solution for extraction. After thorough shaking, the mixture was allowed to stand and separated. The upper organic phase was retained, and the lower phase was extracted three times with petroleum ether. All organic phases were combined and the solvent was evaporated to obtain lithium perfluoroalkyl disulfonylimide as shown in Formula 3, namely lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide, denoted as Sample 3.

[0043] Example 4 In this embodiment, lithium perfluoroalkyl disulfonylimide was prepared using the same process as in Example 1, except that in step S3, an equal amount of perfluoroethanedisulfonyl fluoride was used instead of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride. The subsequent steps were the same, and lithium perfluoroalkyl disulfonylimide as shown in Formula 4 was prepared, which was designated as Sample 4.

[0044] Formula 4 Example 5 This embodiment prepares a perfluoroalkyl disulfonylimide lithium compound. The specific process is the same as in Example 1, except that: in step S2, the acetonitrile solution containing [TETA][HCOO] ionic liquid is cooled to -30°C; in step S3, an equal amount of perfluorobutanedisulfonyl fluoride is used instead of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, the temperature is maintained at -30°C, and the perfluorobutanedisulfonyl fluoride is dissolved in 30 mL of acetonitrile and diluted before being slowly added dropwise; in step S4, the system is heated to 5°C and reacted for 90 min, then heated to 30°C and reacted for another 150 min; the subsequent steps are the same, and the perfluoroalkyl disulfonylimide lithium compound shown in Formula 5 is prepared, which is designated as Sample 5.

[0045] Formula 5 Comparative Example 1 This comparative example provides a comparative preparation method, the specific implementation of which is the same as in Example 1, except that: in step S1, the preparation of an acetonitrile solution containing [TETA][HCOO] ionic liquid is not carried out, that is, triethylenetetramine and formic acid solution are not added, and 80 mL of acetonitrile is directly used as the reaction solvent; molecular sieve dehydration treatment is not carried out; the remaining operations remain unchanged, and the subsequent steps are the same as in Example 1, and the product obtained is recorded as control 1.

[0046] Comparative Example 2 This comparative example provides a comparative preparation method, the specific implementation of which is the same as in Example 1, except that in step S1, 80 mL of acetonitrile is replaced with an equal volume of tetrahydrofuran; the rest of the operations remain unchanged, and the subsequent steps are the same as in Example 1. The product obtained is recorded as control 2.

[0047] Comparative Example 3 This comparative example provides a comparative preparation method, the specific implementation of which is the same as in Example 1, except that: in step S3, triethylsilane and 1-hydroxybenzotriazole are not added, only 0.15 mol of anhydrous lithium hydroxide is added, the temperature is kept at -40℃, and after stirring at 300 r / min for 7 min, 0.1 mol of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride is slowly added dropwise; the rest of the operation remains unchanged, and the subsequent steps are the same as in Example 1. The product obtained is designated as control 3.

[0048] Comparative Example 4 This comparative example provides a comparative preparation method, the specific implementation of which is the same as in Example 1, except that: in step S3, the amount of 1-hydroxybenzotriazole is adjusted from 0.010 mol to 0.020 mol, that is, the molar ratio of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, anhydrous lithium hydroxide, triethylsilane and 1-hydroxybenzotriazole is adjusted from 1:1.5:1.1:0.10 to 1:1.5:1.1:0.20; the remaining operations remain unchanged, and the subsequent steps are the same as in Example 1, and the product obtained is designated as control 4.

[0049] Comparative Example 5 This comparative example provides a comparative preparation method, the specific implementation of which is the same as in Example 1, except that: in step S3, the order of adding materials is adjusted to add 0.010 mol of 1-hydroxybenzotriazole, 0.11 mol of triethylsilane and 0.15 mol of anhydrous lithium hydroxide in sequence; the rest of the operation remains unchanged, and the subsequent steps are the same as in Example 1. The product obtained is recorded as control 5.

[0050] Analysis and Testing The purity of each sample or reference standard was analyzed using high performance liquid chromatography (HPLC), and the moisture content of the sample or reference standard was determined. The product yield was also calculated. The results are shown in Table 1.

[0051] Product yield = Actual weight of the product obtained (g) / Theoretical yield (g) calculated based on the amount of perfluoroalkyl disulfonyl fluoride used × 100%.

[0052] In addition, the structure was confirmed using high-performance liquid chromatography-mass spectrometry and nuclear magnetic resonance analysis. The relevant test chromatograms for sample 1 are shown below. Figures 1-4 .

[0053] Table 1: Summary Table of Product Yield and Quality Analysis As shown in Table 1, the purity of the samples prepared in Examples 1-5 of this invention was consistently 99.6% or higher, reaching a maximum of 99.9%; the moisture content was effectively controlled within 80 ppm, with a minimum of 62 ppm; and the product yield was consistently above 93%, reaching a maximum of 96.5%. It is evident that the preparation method of this invention, using an acetonitrile solution containing triethylenetetramine formate ionic liquid as the solvent system, combined with the synergistic catalysis of 1-hydroxybenzotriazole and triethylsilane, exhibits excellent reaction selectivity and conversion efficiency for perfluoroalkyl disulfonyl fluoride substrates of different carbon chain lengths. It effectively suppresses side reactions such as hydrolysis, which is beneficial for subsequent impurity removal and trace moisture control, ensuring that the product quality meets the high-end application requirements of lithium-ion battery electrolyte salts.

[0054] Examples 1-3, using 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride as the substrate, yielded products with a purity of over 99.6% and a yield of over 93%, fully demonstrating the wide process window, flexible parameter adjustment, and good process controllability and reproducibility of the present invention. Example 4, using perfluoroethanedisulfonyl fluoride as the substrate, achieved the highest product yield of 96.5% and a purity of 99.6% among all samples, showcasing the excellent adaptability of the method to five-membered ring substrates. Example 5, using perfluorobutanedisulfonyl fluoride as the substrate, represents a substrate type with longer carbon chains and reduced solubility. The present invention improved substrate dispersibility by diluting with acetonitrile before addition and appropriately increased the reaction temperature, achieving a yield of 94.4%. It is evident that the preparation method of the present invention can obtain products with high purity and high yield for substrates of different carbon chain lengths, demonstrating broad substrate applicability.

[0055] In contrast, reference standard 1 did not involve the preparation of an ionic liquid; only pure acetonitrile was used as the solvent. Although an equal amount of ammonia gas was introduced, the lack of the hydrogen bonding activation of NH3 and the inhibition of the hydrolysis side reaction of sulfonyl fluoride by the triethylenetetraminecarbamate ionic liquid resulted in a decrease in the selectivity of the amination-cyclization reaction, and some substrates underwent hydrolysis and other side reactions, leading to a decrease in purity to 98.2% and a yield to 78.5%. Therefore, the acetonitrile solution containing triethylenetetraminecarbamate ionic liquid used in this invention plays a crucial role in activating NH3, inhibiting side reactions, and ensuring high selectivity of the reaction.

[0056] In the preparation of reference standard 2, acetonitrile was replaced with tetrahydrofuran, resulting in a decrease in both product purity and yield. This is because tetrahydrofuran has poorer synergistic compatibility with ionic liquids than acetonitrile, affecting the dispersion state of the ionic liquid and the NH3 absorption efficiency.

[0057] Reference standard 3 was prepared without the addition of triethylsilane and 1-hydroxybenzotriazole, using only LiOH as the base, thus omitting the catalytic activation system. This resulted in the ineffective activation of the SF bond of the sulfonyl fluoride, reducing the reactivity and consequently causing the purity to drop to 97.3%, the yield to plummet to 73.6%, and the moisture content to increase significantly. This demonstrates that the synergistic catalytic system of 1-hydroxybenzotriazole and triethylsilane is essential for achieving high conversion and high yield.

[0058] In the preparation of reference standard 4, the amount of 1-hydroxybenzotriazole was increased, which led to a decrease in purity to 98.0% and a decrease in yield to 82.3%. This is because the excess 1-hydroxybenzotriazole competes with the substrate for side reactions. Therefore, controlling the amount of 1-hydroxybenzotriazole within a reasonable range is the key to balancing catalytic efficiency and side reaction inhibition.

[0059] Reference standard 5 was prepared with a modified feeding order: 1-hydroxybenzotriazole and triethylsilane were added first, followed by anhydrous lithium hydroxide. This reversal of the feeding order resulted in 1-hydroxybenzotriazole being in an alkaline environment initially, preventing timely deprotonation and the formation of an activated catalytic intermediate with the silicon additive. After the addition of LiOH, an alkaline environment gradually established, but catalyst activation was delayed. The catalytic system had not yet reached its optimal activity state when the substrate was added, leading to a partial loss of catalytic efficiency and a yield reduction to 87.1%. This clearly demonstrates the necessity of this specific feeding order for the efficient operation of the catalytic system.

[0060] In summary, this invention integrates the three-step reaction of amination, cyclization, and salt formation into a single step through multiple technical means, including an acetonitrile solvent system containing triethylenetetramine formate ionic liquid, synergistic catalysis of 1-hydroxybenzotriazole and triethylsilane, a specific feeding sequence, and post-treatment by extraction. This achieves the technical advantages of eliminating the need for intermediate separation and purification, mild and controlled reaction conditions, and simple operation. It effectively solves the technical problems of existing two-step methods, such as cumbersome steps, difficulty in intermediate separation, low yield, and product purity that cannot meet the requirements of electrochemical applications.

[0061] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for producing lithium perfluoroalkyldisulfonimide, characterized by, In an acetonitrile solution containing triethylenetetraminecarbamate ionic liquid, after cooling to -50℃ to -30℃, ammonia gas is introduced, followed by the sequential addition of anhydrous lithium hydroxide, triethylsilane and 1-hydroxybenzotriazole, and then perfluoroalkyl disulfonyl fluoride, to carry out a two-stage heating reaction to obtain the perfluoroalkyl disulfonyl imide lithium. The perfluoroalkyl disulfonyl fluoride is as shown in Formula 1. Formula 1 The perfluoroalkyl disulfonylimide lithium is as shown in Formula 2. Formula 2 In Equation 1, n is an integer from 1 to 5.

2. The production method according to claim 1, characterized by, The lithium perfluoroalkyl disulfonylimide is one of the following compounds: 。 3. The preparation method according to claim 1, characterized in that, The two-stage heating reaction specifically involves first heating to -5℃ to 5℃ and reacting for 45 min to 90 min, then continuing to heat to 20℃ to 30℃ and reacting for another 90 min to 150 min.

4. The preparation method according to claim 1, characterized in that, The molar ratio of perfluoroalkyl disulfonyl fluoride, triethylenetetramine, and formic acid is 1:(0.8–1.2):(3.6–5.4).

5. The preparation method according to claim 1, characterized in that, The molar ratio of perfluoroalkyl disulfonyl fluoride, anhydrous lithium hydroxide, triethylsilane and 1-hydroxybenzotriazole is 1:(1.3-1.7):(1.0-1.2):(0.08-0.12).

6. The preparation method according to claim 1, characterized in that, Triethylenetetramine formate ionic liquid is prepared in situ by reacting triethylenetetramine with formic acid via an acid-base neutralization reaction.

7. The preparation method according to claim 6, characterized in that, The specific process of the acid-base neutralization reaction between triethylenetetramine and formic acid is as follows: triethylenetetramine is dissolved in acetonitrile, the temperature is lowered to 0℃~5℃, formic acid is added dropwise to carry out the acid-base neutralization reaction, and after the addition is completed, the mixture is stirred for 10min~15min. After drying, an acetonitrile solution containing triethylenetetramine formate ionic liquid is obtained.

8. The preparation method according to claim 7, characterized in that, The drying process involves adding molecular sieves for dehydration.

9. The preparation method according to claim 1, characterized in that, The amount of ammonia introduced is such that for every 0.1 mol of perfluoroalkyl disulfonyl fluoride, the corresponding increase in ammonia weight is 8 g to 12 g.

10. The preparation method according to claim 1, characterized in that, After the reaction was completed, the mixture was extracted with petroleum ether, the organic phases were combined, and the solvent was evaporated to obtain the lithium perfluoroalkyl disulfonylimide.

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