Synthesis method of bis(fluorosulfonyl)imide

Abstract

The present application relates to a method for synthesizing bis(fluorosulfonyl)imide, comprising the following steps: reacting dichlorosulfonylimide with a nitrogen-containing organic salt of hydrogen fluoride at 80°C to 125°C under solvent-free conditions to obtain bis(fluorosulfonyl)imide. Controlling the fluorination reaction to proceed under solvent-free conditions can avoid the nitrogen-containing organic salt of hydrogen chloride by-product being dissolved by the solvent, so that the nitrogen-containing organic salt of hydrogen chloride by-product is in a solid form at a specific reaction temperature, promoting the fluorination reaction to proceed in the positive direction and effectively improving the reaction yield; moreover, the melting point and boiling point of the nitrogen-containing organic salt of hydrogen chloride by-product and the target product bis(fluorosulfonyl)imide differ greatly, the purification is simple, and the purity is relatively high.

Description

Technical Field

[0001] This application relates to the technical field of chemical synthesis, and particularly to a method for synthesizing bis(fluorosulfonyl)imide. Background Art

[0002] Bis(fluorosulfonyl)imide, with the chemical formula (FSO 2 ) 2 NH, abbreviated as HFSI, has a melting point of 17 °C and a boiling point of 170 °C. It is a strong acid, and its salts have wide applications in catalysis, electrolytes, fluorinating agents, etc.; especially the lithium salt of bis(fluorosulfonyl)imide, LiFSI, due to its large anion structure and the strong electronegativity of fluoride ions and sulfonyl groups, makes the interaction force between it and lithium ions very weak. When LiFSI is dissolved in organic solvents or in the molten state, lithium ions are in a highly free state, having excellent electrical conductivity, and can be applied in the electrolytes of lithium secondary batteries, supercapacitors, ionic liquid catalysts and other fields; and LiFSI does not decompose below 200 °C, has high thermal stability, and is superior to the commonly used lithium battery electrolyte lithium hexafluorophosphate (LiPF 6 ), and is very likely to become a new type of fluorinated lithium salt as the main component of the next-generation electrolyte. As an important synthetic intermediate of LiFSI, its synthesis method and production process have received extensive attention.

[0003] Traditional synthesis methods of bis(fluorosulfonyl)imide include: 1) First synthesize bis(chlorosulfonyl)imide or chlorosulfonylphosphazene trichloride, and then carry out a fluorochloride exchange reaction with a fluorinating reagent such as HF, AsF 3 or SbF 3 to obtain HFSI. Its disadvantages are that the fluorinating reagents AsF 3 , SbF 3 are highly toxic, and the by-products generated have boiling points close to that of HFSI, making it difficult to purify; while HF has strong corrosiveness and high requirements for equipment, it is difficult to select equipment, and the industrial production threshold is relatively high; 2) Synthesize HFSI by reacting fluorosulfonyl isocyanate or urea with fluorosulfonic acid. In this method, HFSI is easily contaminated by excessive fluorosulfonic acid, and the boiling points of HFSI and fluorosulfonic acid are 170 °C and 165 °C respectively, with close boiling points, making purification difficult and costly. Summary of the Invention

[0004] Based on this, this application provides a method for synthesizing bis(fluorosulfonyl)imide with simple purification and high purity.

[0005] The technical solution for this application to solve the above technical problems is as follows.

[0006] A method for synthesizing bis(fluorosulfonyl)imide, comprising the following steps:

[0007] Perform a fluorination reaction on bis(chlorosulfonyl)imide and a nitrogen-containing organic salt of hydrogen fluoride at 80 °C to 125 °C under solvent-free conditions to obtain bis(fluorosulfonyl)imide.

[0008] In some of these embodiments, in the synthesis method of bis(fluorosulfonyl)imide, the temperature of the fluorination reaction is 80°C to 115°C.

[0009] In some of these embodiments, in the synthesis method of bis(fluorosulfonyl)imide, the nitrogen-containing hydrogen fluoride organic salt is selected from at least one of tertiary amine hydrofluorides and nitrogen heterocyclic hydrofluorides.

[0010] In some of these embodiments, in the synthesis method of bis(fluorosulfonyl)imide, the tertiary amine hydrofluoride is selected from at least one of triethylamine trihydrofluoride and diisopropylethylamine trihydrofluoride.

[0011] In some of these embodiments, in the synthesis method of bis(fluorosulfonyl)imide, the nitrogen heterocyclic hydrofluoride is selected from at least one of pyridine hydrofluoride, 4-methylaminopyridine hydrofluoride, and melamine hydrofluoride.

[0012] In some of these embodiments, in the synthesis method of bis(fluorosulfonyl)imide, the molar ratio of dichlorosulfonylimide to the nitrogen-containing hydrogen fluoride organic salt is 1:(0.5 to 2.8).

[0013] In some of these embodiments, in the synthesis method of bis(fluorosulfonyl)imide, the fluorination reaction is carried out under a protective atmosphere.

[0014] In some of these embodiments, in the synthesis method of bis(fluorosulfonyl)imide, after the fluorination reaction step, it further includes the steps of successively performing a first vacuum distillation and re-purification on the reaction solution obtained from the fluorination reaction. The temperature of the first vacuum distillation is 30°C to 80°C, and the vacuum degree is -0.08 MPa to -0.1 MPa.

[0015] In some of these embodiments, in the synthesis method of bis(fluorosulfonyl)imide, the re-purification includes the following steps:

[0016] Perform a second vacuum distillation on the reaction solution remaining after the first vacuum distillation. The temperature of the second vacuum distillation is 80°C to 120°C, and the vacuum degree is -0.08 MPa to -0.1 MPa.

[0017] In some of these embodiments, in the synthesis method of bis(fluorosulfonyl)imide, the re-purification includes the following steps:

[0018] Perform solid-liquid separation on the reaction solution remaining after the first vacuum distillation at 30°C to 80°C.

[0019] In some of these embodiments, in the synthesis method of bis(fluorosulfonyl)imide, the preparation of dichlorosulfonylimide includes the following steps:

[0020] While maintaining the temperature of the feeding system at <80°C, thionyl chloride, sulfamic acid, and chlorosulfonic acid are added in sequence, and then a series reaction is carried out at 80°C to 150°C to obtain bis(chlorosulfonyl)imide.

[0021] In some of these embodiments, in the method for synthesizing bis(fluorosulfonyl)imide, the molar ratio of the sulfamic acid, the chlorosulfonic acid, and the thionyl chloride is 1:(1 to 1.1):(2 to 2.8).

[0022] In some of these embodiments, in the method for synthesizing bis(fluorosulfonyl)imide, after the step of the series reaction is completed, it further includes a step of performing a third vacuum distillation on the reaction solution obtained from the series reaction.

[0023] In some of these embodiments, in the method for synthesizing bis(fluorosulfonyl)imide, the temperature of the third vacuum distillation is 60°C to 100°C, and the vacuum degree is -0.08 MPa to -0.1 MPa.

[0024] Compared with the prior art, the method for synthesizing bis(fluorosulfonyl)imide of the present application has the following beneficial effects:

[0025] In the above method for synthesizing bis(fluorosulfonyl)imide, at the above specific temperature, both bis(chlorosulfonyl)imide and the nitrogen-containing organic salt of hydrogen fluoride are in a liquid phase. At this specific temperature, bis(chlorosulfonyl)imide and the nitrogen-containing organic salt of hydrogen fluoride undergo a fluorination reaction through halogen substitution to generate the target product bis(fluorosulfonyl)imide and the by-product nitrogen-containing organic salt of hydrogen chloride; among them, the fluorination reaction is controlled to be carried out under solvent-free conditions to avoid the target product bis(fluorosulfonyl)imide and the by-product nitrogen-containing organic salt of hydrogen chloride being dissolved by the solvent, so that the by-product nitrogen-containing organic salt of hydrogen chloride is in a solid form at the specific temperature, promoting the fluorination reaction to proceed in the positive direction and effectively improving the reaction yield; and the melting point of the target product bis(fluorosulfonyl)imide is much lower than that of the by-product nitrogen-containing organic salt of hydrogen chloride. At the specific temperature, the target product bis(fluorosulfonyl)imide is in a liquid form and the by-product nitrogen-containing organic salt of hydrogen chloride is in a solid form. The fluorination reaction is controlled to be carried out under solvent-free conditions to avoid the target product bis(fluorosulfonyl)imide and the by-product nitrogen-containing organic salt of hydrogen chloride being dissolved by the solvent, so that solid-liquid separation can be controlled at the specific temperature; and the boiling point of the by-product nitrogen-containing organic salt of hydrogen chloride is relatively high, with a large difference from the boiling point of the target product bis(fluorosulfonyl)imide, and it can also be purified by distillation, so that the purity of bis(fluorosulfonyl)imide is relatively high.

[0026] The fluorination reagent used in the present application is a nitrogen-containing organic salt of hydrogen fluoride. Compared with metal fluorination reagents, it has less toxicity and is easy to purify later; compared with pure hydrogen fluoride gas, it has a higher safety factor and lower requirements for equipment. Detailed implementation manners

[0027] References to embodiments of the present invention will now be provided in detail, one or more examples of which are described below. Each example is provided as an explanation rather than a limitation of the present invention. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made to the present invention without departing from the scope or spirit of the present invention. For example, a feature illustrated or described as part of one embodiment may be used in another embodiment to produce a further embodiment.

[0028] Therefore, it is intended that the present invention covers such modifications and variations that fall within the scope of the appended claims and their equivalents. Other objects, features and aspects of the present invention are disclosed in or are obvious from the following detailed description. Those of ordinary skill in the art will appreciate that this discussion is only a description of exemplary embodiments and is not intended to limit the broader aspects of the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0030] The term "comprises", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "comprising one..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements. The indefinite articles "a kind of" and "an" before the elements or components of the present invention are not restrictive to the quantity requirements (i.e., the number of occurrences) of the elements or components. Therefore, "a" or "a kind of" should be interpreted as including one or at least one, and the elements or components in the singular form also include the plural form, unless the number clearly refers only to the singular form. The meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0031] The weight of the relevant components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also indicate the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the description of the embodiments of the present invention, it is within the scope disclosed in the description of the embodiments of the present invention. Specifically, the weight described in the description of the embodiments of the present invention may be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0032] Except as otherwise indicated or shown in the operating examples, all numbers used in the specification and claims to indicate amounts of ingredients, physical and chemical properties, etc. are to be understood as being adjusted in all instances by the term "about". For example, thus, unless otherwise stated, the numerical parameters set forth in the foregoing specification and the appended claims are approximations, and those skilled in the art can seek to obtain the desired properties using the teachings disclosed herein and appropriately vary these approximations. The use of a numerical range expressed with endpoints includes all numbers within that range and any range within that range. For example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, etc.

[0033] One embodiment of the present application provides a method for synthesizing bis(fluorosulfonyl)imide, comprising:

[0034] Step S10: React dichlorosulfonylimide with a nitrogen-containing organic salt of hydrogen fluoride at 80°C to 125°C under solvent-free conditions to obtain bis(fluorosulfonyl)imide.

[0035] In the above method for synthesizing bis(fluorosulfonyl)imide, at the above specific temperature, both dichlorosulfonylimide and the nitrogen-containing organic salt of hydrogen fluoride are in the liquid phase. At this specific temperature, the dichlorosulfonylimide and the nitrogen-containing organic salt of hydrogen fluoride undergo a fluorination reaction through halogen substitution to generate the target product bis(fluorosulfonyl)imide and the by-product nitrogen-containing organic salt of hydrogen chloride; wherein, the fluorination reaction is controlled to be carried out under solvent-free conditions to avoid the target product bis(fluorosulfonyl)imide and the by-product nitrogen-containing organic salt of hydrogen chloride being dissolved by the solvent, so that the by-product nitrogen-containing organic salt of hydrogen chloride is in a solid form at the specific temperature, promoting the fluorination reaction to proceed in the forward direction and effectively improving the reaction yield; and the melting point of the target product bis(fluorosulfonyl)imide is much lower than that of the by-product nitrogen-containing organic salt of hydrogen chloride. At the specific temperature, the target product bis(fluorosulfonyl)imide is in a liquid form and the by-product nitrogen-containing organic salt of hydrogen chloride is in a solid form. Controlling the fluorination reaction to be carried out under solvent-free conditions can avoid the target product bis(fluorosulfonyl)imide and the by-product nitrogen-containing organic salt of hydrogen chloride being dissolved by the solvent, thereby enabling solid-liquid separation to be carried out at a specific temperature; and the boiling point of the by-product nitrogen-containing organic salt of hydrogen chloride is relatively high, with a large difference from the boiling point of the target product bis(fluorosulfonyl)imide, and it can also be purified by distillation, thereby making the purity of bis(fluorosulfonyl)imide relatively high.

[0036] The fluorination reagent used in the present application is a nitrogen-containing organic salt of hydrogen fluoride, which has relatively low toxicity compared with metal fluorination reagents and is easy to purify subsequently; compared with pure hydrogen fluoride gas, it has a higher safety factor and lower requirements for equipment; the reaction conditions are mild and the process operation is simple.

[0037] Meanwhile, the present application adopts a solvent-free reaction system, which can not only avoid the by-product hydrogen chloride nitrogenous organic salt being dissolved by the solvent, making the by-product hydrogen chloride nitrogenous organic salt in a solid form at a specific reaction temperature, promoting the fluorination reaction to proceed in the positive direction, effectively improving the reaction yield, but also does not require a solvent removal step in the post-treatment process, simplifies the process, is economical and practical, has less three wastes, causes less pollution to the environment, and is suitable for industrial production.

[0038] It can be understood that the temperature of the fluorination reaction includes but is not limited to 80 °C, 82 °C, 85 °C, 88 °C, 90 °C, 92 °C, 95 °C, 98 °C, 100 °C, 102 °C, 105 °C, 108 °C, 110 °C, 112 °C, 115 °C, 118 °C, 120 °C, 122 °C, 125 °C. In some examples, it can be within the range formed by any two of these point values as the end values, and the same applies hereinafter. For example, the temperature of the fluorination reaction is 80 °C to 120 °C, 80 °C to 115 °C, 80 °C to 110 °C, 90 °C to 120 °C, 90 °C to 110 °C, 100 °C to 110 °C.

[0039] Optionally, the temperature of the fluorination reaction is 80 °C to 115 °C.

[0040] By controlling the temperature of the fluorination reaction and conducting the fluorination reaction under solvent-free conditions, the two cooperate to make the by-product hydrogen chloride nitrogenous organic salt in a solid form at a specific reaction temperature, thereby promoting the fluorination reaction to proceed in the positive direction.

[0041] In some of these examples, in step S10, the hydrogen fluoride nitrogenous organic salt is selected from at least one of tertiary amine hydrofluorides and nitrogen heterocyclic hydrofluorides.

[0042] It can be understood that the tertiary amine hydrofluorides include but are not limited to triethylamine trihydrofluoride, tri-n-propylamine trihydrofluoride, diisopropylethylamine trihydrofluoride, tri-n-butylamine trihydrofluoride, tri-n-pentylamine trihydrofluoride.

[0043] Optionally, the tertiary amine hydrofluoride is selected from at least one of triethylamine trihydrofluoride and diisopropylethylamine trihydrofluoride.

[0044] Preferably, the tertiary amine hydrofluoride is triethylamine trihydrofluoride.

[0045] It can be understood that the nitrogen heterocycle in the nitrogen heterocyclic hydrofluoride can be a cyclic amine with 4 to 9 carbon atoms.

[0046] Further, the azacycles in the azacycle hydrofluorides include, but are not limited to, pyridine, 2-methylpyridine, 4-methylaminopyridine, pyrazine, triazine, and melamine; correspondingly, the azacycle hydrofluorides include, but are not limited to, pyridine hydrofluoride, 2-methylpyridine hydrofluoride, 4-methylaminopyridine hydrofluoride, pyrazine hydrofluoride, triazine hydrofluoride, and melamine hydrofluoride.

[0047] Optionally, the azacycle hydrofluoride is selected from at least one of pyridine hydrofluoride, 4-methylaminopyridine hydrofluoride, and melamine hydrofluoride.

[0048] Preferably, the azacycle hydrofluoride is pyridine hydrofluoride.

[0049] In some examples, in step S10, the molar ratio of dichlorosulfonylimide to the nitrogen-containing organic salt of hydrogen fluoride is 1:(0.5 - 2.8).

[0050] It can be understood that the molar ratio of dichlorosulfonylimide to the nitrogen-containing organic salt of hydrogen fluoride includes, but is not limited to, 1:0.5, 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.8.

[0051] Optionally, the molar ratio of dichlorosulfonylimide to the nitrogen-containing organic salt of hydrogen fluoride is 1:(0.6 - 2).

[0052] By controlling the molar ratio of dichlorosulfonylimide to the nitrogen-containing organic salt of hydrogen fluoride, the fluorine-chlorine substitution is effectively promoted.

[0053] In some examples, in step S10, the nitrogen-containing organic salt of hydrogen fluoride is added to the system of dichlorosulfonylimide for the fluorination reaction.

[0054] In some examples, in step S10, the fluorination reaction is carried out under a protective atmosphere.

[0055] It can be understood that the protective atmosphere includes a neutral gas or an inert gas; further, the neutral gas includes nitrogen, and the inert gases include helium, neon, argon, krypton, xenon, etc.

[0056] Optionally, the fluorination reaction is carried out under a nitrogen or argon atmosphere.

[0057] In some examples, in the synthesis method of difluorosulfonylimide, after the fluorination reaction step in step S10, it further includes:

[0058] Step S20: Perform the first reduced-pressure distillation on the reaction solution obtained from the fluorination reaction.

[0059] In some of these examples, in step S20, the temperature of the first reduced-pressure distillation is 30°C to 80°C, and the vacuum degree is -0.08 MPa to -0.1 MPa.

[0060] It can be understood that the temperature of the first reduced-pressure distillation includes but is not limited to 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, and the vacuum degree includes but is not limited to -0.08 MPa, -0.09 MPa, -0.1 MPa.

[0061] It can be understood that by subjecting the reaction solution obtained from the fluorination reaction to the first reduced-pressure distillation and controlling the temperature and vacuum degree of the first reduced-pressure distillation, the residual hydrogen fluoride nitrogen-containing organic salt in the reaction system is removed in the distillate, while the target product bis(fluorosulfonyl)imide and the by-product hydrogen chloride nitrogen-containing organic salt remain in the remaining reaction solution.

[0062] Step S30: Subject the reaction solution remaining after the first reduced-pressure distillation in step S20 to further purification.

[0063] In some of these examples, step S30 includes:

[0064] Subject the reaction solution remaining after the first reduced-pressure distillation to a second reduced-pressure distillation, where the temperature of the second reduced-pressure distillation is 80°C to 120°C, and the vacuum degree is -0.08 MPa to -0.1 MPa.

[0065] It can be understood that the temperature of the second reduced-pressure distillation includes but is not limited to 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, and the vacuum degree of the second reduced-pressure distillation includes but is not limited to -0.08 MPa, -0.09 MPa, -0.1 MPa.

[0066] It can be understood that the temperature of the second reduced-pressure distillation is higher than that of the first reduced-pressure distillation.

[0067] The boiling point of the by-product hydrogen chloride nitrogen-containing organic salt is relatively high, and there is a large difference in boiling point from the target product bis(fluorosulfonyl)imide. By performing purification through reduced-pressure distillation and controlling the temperature and vacuum degree of the second reduced-pressure distillation, the purity of bis(fluorosulfonyl)imide can be further improved.

[0068] It can be understood that the distillate obtained from the second reduced-pressure distillation is bis(fluorosulfonyl)imide.

[0069] In some other examples, step S30 includes:

[0070] Perform solid-liquid separation on the reaction solution remaining after the first reduced-pressure distillation at 30°C to 80°C.

[0071] It is understandable that the solid-liquid separation is carried out while controlling the reaction solution at a specific temperature; further, it is understandable that when performing the solid-liquid separation, the temperature of the reaction solution includes but is not limited to 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, and 80 °C.

[0072] Optionally, the reaction solution remaining after the first vacuum distillation is subjected to solid-liquid separation at 40 °C to 70 °C.

[0073] The melting point of the target product bis(fluorosulfonyl)imide is much lower than that of the by-product nitrogen-containing hydrochloride salt. At a specific temperature, the target product bis(fluorosulfonyl)imide is in a liquid form, and the by-product nitrogen-containing hydrochloride salt is in a solid form. By controlling the solid-liquid separation at a specific temperature, the target product bis(fluorosulfonyl)imide and the by-product nitrogen-containing hydrochloride salt can be effectively separated, thereby effectively improving the purity of bis(fluorosulfonyl)imide.

[0074] It is understandable that the solid phase is the nitrogen-containing hydrochloride salt of hydrogen chloride, and the liquid phase is bis(fluorosulfonyl)imide.

[0075] Furthermore, the methods of solid-liquid separation include but are not limited to filtration and centrifugation.

[0076] Optionally, filtration is used for solid-liquid separation.

[0077] Furthermore, the material used for filtration is a polymer membrane material, and the pore size shall not be greater than 0.1 micrometer.

[0078] It is understandable that the materials used for filtration include but are not limited to filter membranes and filter bags.

[0079] In some examples, in the synthesis method of bis(fluorosulfonyl)imide, the preparation of bis(chlorosulfonyl)imide includes:

[0080] Step S100: Perform a tandem reaction on sulfamic acid, thionyl chloride, and chlorosulfonic acid to obtain bis(chlorosulfonyl)imide.

[0081] It is understandable that the tandem reaction refers to a reaction in which two or more consecutive reactions occur for the reactants added without performing new operations in the same reaction environment, that is, a one-pot tandem reaction is carried out.

[0082] In some examples, in step S100, under the condition that the temperature of the feeding system is maintained at <80 °C, thionyl chloride, sulfamic acid, and chlorosulfonic acid are sequentially added, and then a tandem reaction is carried out.

[0083] Furthermore, the temperature of the tandem reaction is 80 °C to 150 °C.

[0084] It is understandable that the temperature of the tandem reaction includes but is not limited to 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, and 150 °C.

[0085] Optionally, the temperature of the tandem reaction is 90 °C to 130 °C.

[0086] By controlling the temperature of the system during feeding, the conversion rate of the raw materials can be effectively increased and the occurrence of side reactions can be effectively reduced, thereby effectively increasing the yield of the product.

[0087] In some of these examples, in step S100, the time of the tandem reaction is 12 h to 24 h.

[0088] It can be understood that the time of the tandem reaction includes but is not limited to 12 h, 15 h, 18 h, 20 h, 22 h, 24 h; further, it can be understood that the reaction time can be controlled by gas-phase monitoring of the reaction process.

[0089] In some of these examples, in step S100, the tandem reaction is carried out under a protective atmosphere.

[0090] Similarly, the protective atmosphere includes a neutral gas or an inert gas; further, the neutral gas includes nitrogen, and the inert gases include helium, neon, argon, krypton, xenon, etc.

[0091] Optionally, the tandem reaction is carried out under a nitrogen or argon atmosphere.

[0092] In some of these examples, in step S100, the molar ratio of sulfamic acid, chlorosulfonic acid and thionyl chloride is 1:(1 to 1.1):(2 to 2.8).

[0093] It can be understood that when the amount of substance of sulfamic acid is defined as 1 part, the amount of substance of chlorosulfonic acid includes but is not limited to 1, 1.02, 1.05, 1.08, 1.1 parts; the amount of substance of thionyl chloride includes but is not limited to 2, 2.2, 2.4, 2.5, 2.6, 2.8. In some examples, it can be within the range formed by any two of these point values as the end values.

[0094] Optionally, the molar ratio of sulfamic acid, chlorosulfonic acid and thionyl chloride is 1:(1 to 1.1):(2 to 2.4).

[0095] In some of these examples, in step S100, after the tandem reaction step, it further includes:

[0096] Step S110: A step of subjecting the reaction solution obtained from the tandem reaction to a third vacuum distillation.

[0097] In some of these examples, in step S100, the temperature of the third vacuum distillation is 60 °C to 100 °C, and the vacuum degree is -0.08 MPa to -0.1 MPa.

[0098] It is understandable that the temperature of the third vacuum distillation includes but is not limited to 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C; the vacuum degree of the third vacuum distillation includes but is not limited to -0.08 MPa, -0.09 MPa, -0.1 MPa.

[0099] By performing the third vacuum distillation under specific temperature and vacuum conditions, the excessive thionyl chloride in the system can be effectively removed, and the components at a specific temperature are collected, which is the pure product of bis(chlorosulfonyl)imide.

[0100] One embodiment of the present application provides a method for synthesizing an alkali metal salt of bis(fluorosulfonyl)imide, in which the bis(fluorosulfonyl)imide obtained by the above-mentioned method for synthesizing bis(fluorosulfonyl)imide and an alkali metal halide salt are mixed for a metallization reaction.

[0101] It is understandable that the alkali metal salt of bis(fluorosulfonyl)imide can be lithium bis(fluorosulfonyl)imide, sodium bis(fluorosulfonyl)imide, or potassium bis(fluorosulfonyl)imide.

[0102] Another embodiment of the present application provides a method for synthesizing lithium bis(fluorosulfonyl)imide, in which the bis(fluorosulfonyl)imide obtained by the above-mentioned method for synthesizing bis(fluorosulfonyl)imide and a lithiated salt are mixed for a lithiation reaction.

[0103] One embodiment of the present application provides an electrolyte containing lithium bis(fluorosulfonyl)imide obtained by the above-mentioned method for synthesizing lithium bis(fluorosulfonyl)imide.

[0104] One embodiment of the present application provides a lithium battery containing the above electrolyte.

[0105] Using lithium bis(fluorosulfonyl)imide obtained by the above-mentioned method for synthesizing lithium bis(fluorosulfonyl)imide as an electrolyte and further using it in a lithium battery, due to the high purity of lithium bis(fluorosulfonyl)imide obtained by the above-mentioned method for synthesizing lithium bis(fluorosulfonyl)imide, the cycle life, rate performance, and safety performance of the lithium battery can be significantly improved. Specific embodiments

[0107] The following further describes the present application in detail in conjunction with specific embodiments, but the embodiments of the present application are not limited thereto.

[0108] Example 1

[0109] (1) Place 249.9 g (2.1 mol) of thionyl chloride and 97.0 g (1.0 mol) of sulfamic acid into a 500 mL three-necked round-bottom flask that has been inert gas replaced at least 3 times in advance through a Schleck apparatus and is equipped with a reflux condenser. While controlling the system temperature not exceeding 80 °C, add dropwise 116.5 g (1.0 mol) of chlorosulfonic acid. After the addition is complete, control the reaction system temperature at 110 °C - 120 °C for the reaction. During the reaction, hydrogen chloride and sulfur dioxide acidic gases are generated, and the acidic gases are absorbed by a low-concentration sodium hydroxide solution. Gas chromatography is used to track the reaction progress every about 2 hours. When the chlorosulfonic acid in the system is consumed (about 20 h), lower the reaction system temperature to 50 °C - 60 °C for vacuum distillation. The light component thionyl chloride can be recycled. Raise the temperature to 60 °C - 80 °C and continue vacuum distillation, maintaining the vacuum degree at -0.08 MPa - -0.1 MPa. Collect the distillate to obtain 212.9 g of a colorless transparent liquid product, bis(chlorosulfonyl)imide, with a yield of 99.5%.

[0110] (2) Place 107 g (0.5 mol) of bis(chlorosulfonyl)imide and 53.7 g (0.33 mol) of triethylamine trihydrofluoride into a 250 mL fluorine-lined reaction kettle that has been inert gas replaced at least 3 times in advance and is equipped with a reflux condenser for the fluorination reaction. Maintain the reaction temperature at 100 °C, and use gas chromatography to track the reaction progress every about 2 hours. When the bis(chlorosulfonyl)imide in the system is consumed (about 10 h), lower the reaction system temperature to 40 °C - 50 °C for vacuum distillation. After removing the unreacted hydrofluoride salts, take the remaining reaction system and continue vacuum distillation at 90 °C - 100 °C and -0.08 MPa - -0.1 MPa conditions. Collect the distillate to obtain 88.7 g of a colorless transparent liquid product, bis(fluorosulfonyl)imide.

[0111] Example 2

[0112] Place 107 g (0.5 mol) of bis(chlorosulfonyl)imide prepared in step (1) of Example 1 and 99.1 g (1.0 mol) of pyridine hydrofluoride into a 250 mL fluorine-lined reaction kettle that has been inert gas replaced at least 3 times in advance and is equipped with a reflux condenser for reaction. Maintain the reaction temperature at 110 °C, and use gas chromatography to track the reaction progress every about 2 hours. When the bis(chlorosulfonyl)imide in the system is consumed (about 12 h), lower the reaction system temperature to 40 °C - 50 °C for vacuum distillation. After removing the unreacted hydrofluoride salts, take the remaining reaction system and continue vacuum distillation at 90 °C - 100 °C and -0.08 MPa - -0.1 MPa conditions. Collect the distillate to obtain 88.1 g of a colorless transparent liquid product, bis(fluorosulfonyl)imide.

[0113] Example 3

[0114] 107 g (0.5 mol) of dichlorosulfonylimide prepared in step (1) of Example 1 and 59.7 g (0.4 mol) of diisopropylethylamine trihydrofluoride were placed in a 250 mL fluorine-lined reaction kettle that had been purged with an inert gas at least three times in advance and equipped with a reflux condenser, and reacted while maintaining the reaction temperature at 90 °C. The reaction progress was tracked by gas chromatography every about 2 hours. After the dichlorosulfonylimide in the system was consumed (about 14 h), the temperature of the reaction system was lowered to 40 °C - 50 °C for vacuum distillation. After removing the unreacted hydrofluoride salt, the remaining reaction system was further subjected to vacuum distillation at 90 °C - 100 °C and -0.08 MPa to -0.1 MPa, and the distillate was collected to obtain 87.1 g of a colorless transparent liquid product, bis(fluorosulfonyl)imide.

[0115] Example 4

[0116] 107 g (0.5 mol) of dichlorosulfonylimide prepared in step (1) of Example 1 and 128.14 g (1.0 mol) of 4-methylaminopyridine hydrofluoride were placed in a 250 mL fluorine-lined reaction kettle that had been purged with an inert gas at least three times in advance and equipped with a reflux condenser, and reacted while maintaining the reaction temperature at 120 °C. The reaction progress was tracked by gas chromatography every about 2 hours. After the dichlorosulfonylimide in the system was consumed (about 16 h), the temperature of the reaction system was lowered to 40 °C - 50 °C for vacuum distillation. After removing the unreacted hydrofluoride salt, the remaining reaction system was subjected to vacuum distillation at 80 °C - 90 °C and -0.09 MPa to -0.1 MPa, and the distillate was collected to obtain 86.6 g of a colorless transparent liquid product, bis(fluorosulfonyl)imide.

[0117] Example 5

[0118] 107 g (0.5 mol) of dichlorosulfonylimide prepared in step (1) of Example 1 and 146.13 g (1.0 mol) of melamine hydrofluoride were placed in a 250 mL fluorine-lined reaction kettle that had been purged with an inert gas at least three times in advance and equipped with a reflux condenser, and reacted while maintaining the reaction temperature at 120 °C. The reaction progress was tracked by gas chromatography every about 2 hours. After the dichlorosulfonylimide in the system was consumed (about 20 h), the temperature of the reaction system was lowered to 40 °C - 50 °C for vacuum distillation. After removing the unreacted hydrofluoride salt, the remaining reaction system was subjected to vacuum distillation at 80 °C - 90 °C and -0.09 MPa to -0.1 MPa, and the distillate was collected to obtain 86.7 g of a colorless transparent liquid product, bis(fluorosulfonyl)imide.

[0119] Example 6

[0120] It is basically the same as Example 1, except that the fluorination reaction temperature in Example 6 is 125 °C.

[0121] Example 7

[0122] It is basically the same as Example 1, except that the fluorination reaction temperature in Example 7 is 80 °C.

[0123] Example 8

[0124] It is basically the same as Example 1, except that the addition amount of triethylamine trihydrofluoride in Example 8 is 0.5 mol, that is, the molar ratio of dichlorosulfonylimide to nitrogen-containing organic salt of hydrogen fluoride is 1:1.

[0125] Example 9

[0126] It is basically the same as Example 1, except that the addition amount of triethylamine trihydrofluoride in Example 9 is 1.4 mol, that is, the molar ratio of dichlorosulfonylimide to nitrogen-containing organic salt of hydrogen fluoride is 1:2.8.

[0127] Example 10

[0128] 107 g (0.5 mol) of dichlorosulfonylimide and 53.7 g (0.33 mol) of triethylamine trihydrofluoride prepared in step (1) of Example 1 were placed in a 250 mL fluorine-lined reaction kettle that had been replaced with inert gas at least 3 times and equipped with a reflux condenser for fluorination reaction. The reaction temperature was maintained at 100 °C, and the reaction process was tracked by gas chromatography every about 2 hours. After the dichlorosulfonylimide in the system was consumed (about 10 h), the temperature of the reaction system was lowered to 40 °C - 50 °C for vacuum distillation. After removing the unreacted hydrofluoride salt, the remaining reaction system was filtered at 60 °C, and the filtrate was taken to obtain 88.7 g of a colorless transparent liquid product, bis(fluorosulfonyl)imide.

[0129] Comparative Example 1

[0130] It is basically the same as Example 1, except that the fluorination reaction temperature in Comparative Example 1 is 50 °C.

[0131] Comparative Example 2

[0132] It is basically the same as Example 1, except that the fluorination reaction temperature in Comparative Example 2 is 150 °C.

[0133] Comparative Example 3

[0134] 107 g (0.5 mol) of dichlorosulfonylimide prepared in step (1) of Example 1, 53.7 g (0.33 mol) of triethylamine trihydrofluoride and 100 mL of dimethyl carbonate were placed in a 250 mL fluorine-lined reaction kettle that had been purged with an inert gas at least three times in advance and equipped with a reflux condenser for fluorination reaction. The reaction temperature was maintained at 100 °C, and the reaction progress was tracked by gas chromatography every about 2 hours. When the dichlorosulfonylimide in the system was consumed completely (about 10 h), the temperature of the reaction system was lowered to 50 °C - 60 °C for vacuum distillation. After removing the unreacted hydrofluoride salt and dimethyl carbonate, the remaining reaction system was subjected to vacuum distillation at 90 °C - 100 °C and -0.08 MPa to -0.1 MPa to collect the distillate, and 86.4 g of colorless transparent liquid product bis(fluorosulfonyl)imide was obtained.

[0135] The main different parameters for preparing bis(fluorosulfonyl)imide in each example and comparative example are shown in Table 1:

[0136] Table 1

[0137]

[0138] The bis(fluorosulfonyl)imide prepared in each example and comparative example was detected. The yield was the mass yield, and the gas phase normalization method was used; the purity was measured by the loss-on-drying method; the water content was measured by the Karl Fischer coulometric method; the free acid content was measured by manual titration; the contents of chloride ion, sulfate ion and fluoride ion were measured by IC method, and the impurity metal ions were measured by ICP method. The results are shown in Table 2.

[0139] Table 2

[0140]

[0141]

[0142] It can be seen from Table 2 that, compared with the comparative examples, the yield and purity of the bis(fluorosulfonyl)imide prepared in the examples are higher; among them, it can be seen from Example 1, Examples 6 - 7 and Comparative Examples 1 - 2 that the lower temperature of the fluorination reaction in Comparative Example 1 is not conducive to the reaction, and its yield and purity are both lower, and the contents of chloride ion and free acid are on the high side; the temperature in Comparative Example 2 is higher, and other side reactions are likely to occur, resulting in lower purity; in Comparative Example 3, an additional solvent was added to the reaction system, which had an adverse effect on the yield, purity and water content of the product.

[0143] The technical features of the above-described examples can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above examples are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0144] The above-described embodiments merely represent several implementation manners of the present application, which are convenient for understanding the technical solution of the present application specifically and in detail, but should not be construed as a limitation on the protection scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all fall within the protection scope of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments based on the technical solutions provided by the present application are all within the protection scope of the appended claims of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for synthesizing bis(fluorosulfonyl)imide, characterized in that, it comprises the following steps: Performing a fluorination reaction on dichlorosulfonylimide and a nitrogen-containing organic salt of hydrogen fluoride at 80°C to 115°C under solvent-free conditions to obtain bis(fluorosulfonyl)imide; the dichlorosulfonylimide and the nitrogen-containing organic salt of hydrogen fluoride are in a liquid phase at the temperature of the fluorination reaction, and the nitrogen-containing organic salt of hydrogen fluoride is selected from at least one of tertiary amine hydrofluorides and nitrogen heterocyclic hydrofluorides, the tertiary amine hydrofluorides are selected from at least one of triethylamine trihydrofluoride and diisopropylethylamine trihydrofluoride, and the nitrogen heterocyclic hydrofluorides are selected from at least one of pyridine hydrofluoride, 4-methylaminopyridine hydrofluoride, and melamine hydrofluoride.

2. The method for synthesizing bis(fluorosulfonyl)imide according to claim 1, characterized in that, the molar ratio of the dichlorosulfonylimide to the nitrogen-containing organic salt of hydrogen fluoride is 1:(0.5 - 2.8).

3. The method for synthesizing bis(fluorosulfonyl)imide according to claim 1, characterized in that, the fluorination reaction is carried out under a protective atmosphere.

4. The method for synthesizing bis(fluorosulfonyl)imide according to any one of claims 1 to 3, characterized in that, after the fluorination reaction step is completed, it further comprises the steps of successively performing a first vacuum distillation and re-purification on the reaction solution obtained from the fluorination reaction, the temperature of the first vacuum distillation is 30°C to 80°C, and the vacuum degree is -0.08 MPa to -0.1 MPa.

5. The method for synthesizing bis(fluorosulfonyl)imide according to claim 4, characterized in that, the re-purification comprises the following steps: Performing a second vacuum distillation on the reaction solution remaining after the first vacuum distillation, the temperature of the second vacuum distillation is 80°C to 120°C, and the vacuum degree is -0.08 MPa to -0.1 MPa.

6. The method for synthesizing bis(fluorosulfonyl)imide according to claim 4, characterized in that, the re-purification comprises the following steps: Performing solid-liquid separation on the reaction solution remaining after the first vacuum distillation at 30°C to 80°C.

7. The method for synthesizing bis(fluorosulfonyl)imide according to any one of claims 1 to 3, 5 to 6, characterized in that, the preparation of the dichlorosulfonylimide comprises the following steps: While maintaining the temperature of the feeding system at <80°C, successively adding thionyl chloride, sulfamic acid, and chlorosulfonic acid, and then performing a series reaction at 80°C to 150°C to obtain dichlorosulfonylimide.

8. The method for synthesizing bis(fluorosulfonyl)imide according to claim 7, characterized in that, the molar ratio of the sulfamic acid, the chlorosulfonic acid, and the thionyl chloride is 1:(1 - 1.1):(2 - 2.8).

9. The method for synthesizing bis(fluorosulfonyl)imide according to claim 7, characterized in that, after the series reaction step is completed, it further comprises the step of performing a third vacuum distillation on the reaction solution obtained from the series reaction.

10. The method for synthesizing bis(fluorosulfonyl)imide according to claim 9, characterized in that, the temperature of the third vacuum distillation is 60°C to 100°C, and the vacuum degree is -0.08 MPa to -0.1 MPa.

Images