Preparation method of alkali metal salt of difluoromethanesulfonimide

Abstract

The present application relates to a preparation method of an alkali metal salt of bis(fluorosulfonyl)imide, comprising the following steps: carrying out a metallization reaction on bis(fluorosulfonyl)imide, an alkali metal halide salt and an acid-binding agent at ≥65 °C without adding an additional solvent to prepare the alkali metal salt of bis(fluorosulfonyl)imide. The acidic gas generated by this method can directly react with the acid-binding agent to form a hydrogen halide organic salt. Through the synergistic effects in multiple aspects, the yield and purity of the alkali metal salt of bis(fluorosulfonyl)imide can be effectively improved; moreover, the raw materials are easily available, the operation is simple, no solvent is required, the reaction conditions are relatively mild, the requirements for equipment in the reaction process and the product are relatively low, and industrial production can be carried out.

Description

Technical Field

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

[0002] Lithium bis(fluorosulfonyl)imide, abbreviated as LiFSI, is a novel lithium-ion battery electrolyte with excellent performance and is currently used as an additive in lithium-ion electrolytes. Compared with the traditional lithium salt lithium hexafluorophosphate, the anion radius of LiFSI is larger, making it easier to dissociate lithium ions, which can improve the conductivity of the electrolyte; the decomposition temperature of LiFSI is higher, above 200 °C, with good thermal stability, which can improve the high-temperature resistance of the electrolyte; LiFSI can improve the discharge charge performance in low-temperature environments and maintain the capacitance retention rate in high-temperature environments, which can improve the high and low-temperature performance of lithium batteries. Using LiFSI in the electrolyte can significantly improve the cycle life, rate performance, and safety performance of the battery, and is expected to become the main component of the next-generation electrolyte.

[0003] Traditional methods for preparing lithium bis(fluorosulfonyl)imide include: 1) reacting bis(fluorosulfonyl)imide with LiOH or Li2CO3 at low temperature to prepare LiFSI; 2) performing cation exchange between ammonium bis(fluorosulfonyl)imide and LiOH to prepare LiFSI; 3) performing alkali metal exchange between potassium bis(fluorosulfonyl)imide and LiClO4 to prepare LiFSI. However, the purity of lithium bis(fluorosulfonyl)imide prepared by the above methods is relatively low and it is difficult to meet the usage standards of battery grade. Summary of the Invention

[0004] Based on this, this application provides a method for preparing alkali metal salts of bis(fluorosulfonyl)imide that can improve the yield and purity.

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

[0006] This application provides a method for preparing alkali metal salts of bis(fluorosulfonyl)imide, including the following steps:

[0007] Performing a metallization reaction on bis(fluorosulfonyl)imide, an alkali metal halide, and an acid-binding agent at ≥65 °C without adding an additional solvent to prepare an alkali metal salt of bis(fluorosulfonyl)imide.

[0008] In some embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the molar ratio of the alkali metal halide, the acid-binding agent to the bis(fluorosulfonyl)imide is (0.8 - 1.3):(0.3 - 1.5):1.

[0009] In some embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the acid-binding agent is selected from at least one of alkylamines and nitrogen heterocyclic organic bases.

[0010] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the alkylamine is selected from at least one of triethylamine and N,N - diisopropylethylamine.

[0011] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the nitrogen - containing heterocyclic organic base is selected from at least one of pyridine, 4 - dimethylaminopyridine, and 1,8 - diazabicyclo[5.4.0]undec - 7 - ene.

[0012] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the temperature of the metallization reaction is 65 °C to 150 °C.

[0013] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the metallization reaction is carried out under a protective atmosphere.

[0014] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the alkali metal halide salt is selected from at least one of lithium halide, sodium halide, and potassium halide.

[0015] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the lithium halide is selected from at least one of lithium fluoride, lithium chloride, and lithium bromide.

[0016] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the sodium halide is selected from at least one of sodium fluoride, sodium chloride, and sodium bromide.

[0017] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the potassium halide is selected from at least one of potassium fluoride, potassium chloride, and potassium bromide.

[0018] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, after the metallization reaction step, it further includes the steps of subjecting the reaction solution obtained from the metallization reaction to vacuum distillation and recrystallization in sequence.

[0019] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the temperature of the vacuum distillation is 30 °C to 100 °C, and the vacuum degree is - 0.08 MPa to - 0.1 MPa.

[0020] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, the recrystallization step includes:

[0021] In some of these embodiments, in the method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, a good solvent A is used to dissolve the crude product of the alkali metal salt of bis(fluorosulfonyl)imide obtained in the vacuum distillation step to obtain a mixed solution of the crude product of the alkali metal salt of bis(fluorosulfonyl)imide;

[0022] Perform solid-liquid separation on the crude mixture of the alkali metal salt of bis(fluorosulfonyl)imide, take the liquid phase, add poor solvent B to the liquid phase, and carry out distillation followed by static crystallization.

[0023] In some of these embodiments, in the preparation method of the alkali metal salt of bis(fluorosulfonyl)imide, the good solvent A is selected from at least one of methyl tert-butyl ether, anhydrous diethyl ether, tetrahydrofuran, n-heptane, cyclohexane, acetone, ethyl acetate, dimethyl carbonate, methyl ethyl carbonate, vinylene carbonate, 1,2-dichloroethane, dichloromethane, acetonitrile, methanol, and ethanol, and the poor solvent B is selected from at least one of 1,4-epoxyhexane, benzene, mesitylene, ethylbenzene, and toluene.

[0024] In some of these embodiments, in the preparation method of the alkali metal salt of bis(fluorosulfonyl)imide, the temperature of the static crystallization is -10°C to 80°C.

[0025] In some of these embodiments, in the preparation method of the alkali metal salt of bis(fluorosulfonyl)imide, the mass ratio of the good solvent A, the poor solvent B to the crude product of the alkali metal salt of bis(fluorosulfonyl)imide obtained in the vacuum distillation step is (0.15 - 0.5):(2 - 4):1.

[0026] Compared with the prior art, the preparation method of the alkali metal salt of bis(fluorosulfonyl)imide in this application has the following

[0027] Beneficial effects:

[0028] In the above preparation method of the alkali metal salt of bis(fluorosulfonyl)imide, bis(fluorosulfonyl)imide, alkali metal halide salt, and acid-binding agent are simultaneously added to the reaction system, and the metallization reaction is carried out at a specific temperature without adding other solvents additionally, increasing the contact concentration of the alkali metal halide salt and bis(fluorosulfonyl)imide, which is beneficial to the reaction of bis(fluorosulfonyl)imide and alkali metal halide salt to generate the alkali metal salt of bis(fluorosulfonyl)imide and acidic gas; while the acidic gas can directly react with the acid-binding agent to generate hydrogen halide organic salt. On the one hand, since the generated hydrogen halide is consumed in time, it can promote the metallization reaction to proceed in the forward reaction direction; on the other hand, by controlling the metallization reaction without adding other solvents, the generation of impurities in the system can be reduced, and the product alkali metal salt of bis(fluorosulfonyl)imide can be prevented from being dissolved by the solvent, which is not conducive to purification; at the same time, since the boiling points of the generated hydrogen halide organic salt and the target product alkali metal salt of bis(fluorosulfonyl)imide differ greatly, purification can be carried out by vacuum distillation. With the synergistic effect of multiple aspects, the yield and purity of the alkali metal salt of bis(fluorosulfonyl)imide can be effectively improved.

[0029] The above preparation method of the alkali metal salt of bis(fluorosulfonyl)imide has easily available raw materials, simple operation, does not require the use of solvents, has relatively mild reaction conditions, the reaction process and products have relatively low requirements for equipment, and can be industrially produced. Specific embodiments

[0030] Reference will now be made in detail to embodiments of the present invention, one or more examples of which are described below. Each example is provided to illustrate, not to limit, the present invention. Indeed, 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 invention. For example, features illustrated or described as part of one embodiment may be used in another embodiment to produce further embodiments.

[0031] Therefore, it is intended that the present invention covers such modifications and variations as come 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 skilled in the art will appreciate that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present invention.

[0032] 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 this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0033] The term "comprises", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment comprising 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 further restrictions, the elements limited by the sentence "comprising a ..." do not exclude the presence of other identical elements in the process, method, article or equipment comprising the elements. The indefinite articles "a" and "an" before the elements or components of the present invention have no restriction on the quantity requirements (i.e., the number of occurrences) of the elements or components. Therefore, "a" or "a" should be interpreted as including one or at least one, and elements or components in the singular also include plural forms, unless the quantity obviously refers only to the singular form. The meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0034] The weights 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 represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally increased or decreased 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 weights mentioned in the description of the embodiments of the present invention may be mass units known in the chemical industry, such as μg, mg, g, and kg.

[0035] Except as otherwise shown in the operating examples or otherwise indicated, all numbers used in the specification and claims to represent the amounts of ingredients, physical and chemical properties, etc. are understood to be adjusted by the term "about" in all cases. For example, thus, unless otherwise stated, the numerical parameters listed in the above specification and appended claims are approximate values, and those skilled in the art can appropriately change these approximate values to obtain the desired characteristics by using the teachings disclosed herein. The use of numerical ranges 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.

[0036] One embodiment of the present application provides a method for preparing an alkali metal bis(fluorosulfonyl)imide salt, comprising:

[0037] Step S10: Metallize bis(fluorosulfonyl)imide, an alkali metal halide salt, and an acid-binding agent at ≥65°C without adding an additional solvent to prepare an alkali metal bis(fluorosulfonyl)imide salt.

[0038] In the above method for preparing an alkali metal bis(fluorosulfonyl)imide salt, bis(fluorosulfonyl)imide, an alkali metal halide salt, and an acid-binding agent are simultaneously added to the reaction system, and a metallization reaction is carried out at a specific temperature without adding other solvents additionally, increasing the contact concentration of the alkali metal halide salt and bis(fluorosulfonyl)imide, which is beneficial to the reaction of bis(fluorosulfonyl)imide and the alkali metal halide salt to form an alkali metal bis(fluorosulfonyl)imide salt and an acidic gas; and the acidic gas can directly react with the acid-binding agent to form a hydrogen halide organic salt. On the one hand, since the generated hydrogen halide is consumed in time, it can promote the metallization reaction to proceed in the forward reaction direction; on the other hand, by controlling the metallization reaction without adding other solvents, the generation of impurities in the system can be reduced, and the product alkali metal bis(fluorosulfonyl)imide salt can be prevented from being dissolved by the solvent, which is not conducive to purification; at the same time, since the boiling points of the generated hydrogen halide organic salt and the target product alkali metal bis(fluorosulfonyl)imide salt differ greatly, purification can be carried out by vacuum distillation. With the synergistic effect of multiple aspects, the yield and purity of the alkali metal bis(fluorosulfonyl)imide salt can be effectively improved.

[0039] The above method for preparing an alkali metal bis(fluorosulfonyl)imide salt has easily available raw materials, simple operation, does not require the use of solvents, has relatively mild reaction conditions, the reaction process and products have low requirements for equipment, and can be industrially produced.

[0040] In some of these examples, in step S10, the molar ratio of the alkali metal halide salt, the acid-binding agent to bis(fluorosulfonyl)imide is (0.8~1.3):(0.3~1.5):1.

[0041] It is understood that the molar ratio of the alkali metal halide salt to bis(fluorosulfonyl)imide includes but is not limited to 0.8:1, 1:1, 1.1:1, 1.2:1, 1.3:1; the molar ratio of the acid-binding agent to bis(fluorosulfonyl)imide includes but is not limited to 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1.

[0042] Optionally, the molar ratio of lithium halide to bis(fluorosulfonyl)imide is (1 to 1.3):1.

[0043] Optionally, the molar ratio of the acid-binding agent to bis(fluorosulfonyl)imide is (0.3 to 1):1.

[0044] In some examples, in step S10, the molar ratio of the alkali metal halide salt, the acid-binding agent to bis(fluorosulfonyl)imide is (1 to 1.3):(0.3 to 1):1.

[0045] Furthermore, the molar ratio of the acid-binding agent to bis(fluorosulfonyl)imide is (0.5 to 1):1.

[0046] In some examples, in step S10, the molar ratio of the alkali metal halide salt, the acid-binding agent to bis(fluorosulfonyl)imide is (1 to 1.1):(0.5 to 1):1.

[0047] [[ID=]18]By controlling the molar ratio of the alkali metal halide salt, the acid-binding agent to bis(fluorosulfonyl)imide, the reaction can be accelerated and the product purity can be improved; if the addition amount of the acid-binding agent is too much, it will be unfavorable for the purification of the product; if the addition amount is less, it is unfavorable for the formation of the product.

[0048] In some examples, in step S10, the acid-binding agent is selected from at least one of alkylamines and nitrogen heterocyclic organic bases.

[0049] It is understood that the alkylamines include but are not limited to tripropylamine, n-propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, tert-butylamine, hexylamine, octylamine, aniline, cyclohexylamine, piperidine, triethylamine (TEA), N,N-diisopropylethylamine (diisopropylethylamine, DIPEA); the nitrogen heterocyclic organic bases include but are not limited to 1,8-diazabicycloundec-7-ene (DBU), methylpyridine, trimethylpyridine, pyridine (Py) and 4-dimethylaminopyridine (DMAP).

[0050] In some examples, in step S10, the alkylamine is selected from at least one of triethylamine and N,N-diisopropylethylamine.

[0051] In some examples, in step S10, the nitrogen heterocyclic organic base is selected from at least one of pyridine, 4-dimethylaminopyridine and 1,8-diazabicycloundec-7-ene.

[0052] Optionally, the acid-binding agent is selected from at least one of diisopropylethylamine, triethylamine, and pyridine.

[0053] In some examples, in step S10, the temperature of the metallization reaction is 65°C to 150°C.

[0054] It can be understood that the temperature of the metallization reaction includes but is not limited to 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°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 metallization reaction is 70°C to 140°C, 80°C to 130°C, 90°C to 125°C, 100°C to 120°C, 100°C to 110°C, etc.

[0055] Optionally, the temperature of the metallization reaction is 100°C to 120°C.

[0056] In some examples, in step S10, the time of the metallization reaction is 12 h to 24 h.

[0057] It can be understood that the time of the metallization reaction includes but is not limited to 12 h, 15 h, 18 h, 20 h, 22 h, 24 h.

[0058] It can be understood that the reaction time can be controlled by gas-phase monitoring of the reaction process.

[0059] In some examples, in step S10, the metallization reaction is carried out under a protective atmosphere.

[0060] 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.

[0061] Optionally, the lithiation reaction is carried out under a nitrogen or argon atmosphere.

[0062] In some examples, in step S10, the alkali metal halide salt is selected from at least one of lithium halide, sodium halide, and potassium halide.

[0063] It can be understood that when the alkali metal halide salt is lithium halide, the prepared alkali metal bis(fluorosulfonyl)imide salt is lithium bis(fluorosulfonyl)imide; when the alkali metal halide salt is sodium halide, the prepared alkali metal bis(fluorosulfonyl)imide salt is sodium bis(fluorosulfonyl)imide; when the alkali metal halide salt is potassium halide, the prepared alkali metal bis(fluorosulfonyl)imide salt is potassium bis(fluorosulfonyl)imide.

[0064] In some of these examples, in step S10, the alkali metal halide salt is selected from at least one of alkali metal fluoride salts, alkali metal chloride salts, and alkali metal bromide salts.

[0065] It can be understood that when the alkali metal halide salts are alkali metal fluoride salts, alkali metal chloride salts, and alkali metal bromide salts respectively, the products include alkali metal salts of bis(fluorosulfonyl)imide, and also include organic salts of hydrogen fluoride, organic salts of hydrogen chloride, and organic salts of hydrogen bromide respectively.

[0066] In some of these examples, in step S10, the lithium halide is selected from at least one of lithium fluoride, lithium chloride, and lithium bromide.

[0067] Optionally, the lithium halide is selected from at least one of lithium fluoride and lithium chloride.

[0068] Preferably, the lithium halide is lithium fluoride.

[0069] In some of these examples, in step S10, the sodium halide is selected from at least one of sodium fluoride, sodium chloride, and sodium bromide.

[0070] In some of these examples, in step S10, the potassium halide is selected from at least one of potassium fluoride, potassium chloride, and potassium bromide.

[0071] In some of these examples, in the method for preparing the alkali metal salt of bis(fluorosulfonyl)imide, after the metallization reaction step in step S10, it further includes:

[0072] Step S20: Subject the reaction solution obtained from the metallization reaction to vacuum distillation to obtain a crude product of the alkali metal salt of bis(fluorosulfonyl)imide.

[0073] The acidic gas generated by the reaction of bis(fluorosulfonyl)imide and the alkali metal halide salt reacts with the acid-binding agent to form an organic salt of hydrogen halide. The boiling point of this organic salt of hydrogen halide differs greatly from that of the target product, the alkali metal salt of bis(fluorosulfonyl)imide, and purification is carried out by vacuum distillation.

[0074] In some of these examples, in step S20, the temperature of the vacuum distillation is 30°C to 100°C, and the vacuum degree is -0.08 MPa to -0.1 MPa.

[0075] It can be understood that the temperature of the vacuum distillation can be selected from 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc., and the vacuum degree can be selected from -0.08 MPa, -0.09 MPa, -0.1 MPa, etc.

[0076] Furthermore, it can be understood that the temperature and vacuum degree of the vacuum distillation can be determined according to the boiling point of the generated organic salt of hydrogen halide.

[0077] Step S30: Recrystallize the crude product of the alkali metal salt of bis(fluorosulfonyl)imide obtained in step S20.

[0078] In some of these examples, step S30 includes:

[0079] Step S31: Dissolve the crude alkali metal bis(fluorosulfonyl)imide salt with a good solvent A to obtain a mixed solution of the crude alkali metal bis(fluorosulfonyl)imide salt;

[0080] Step S32: Perform solid-liquid separation on the mixed solution of the crude alkali metal bis(fluorosulfonyl)imide salt, take the liquid phase, add a poor solvent B to the liquid phase, and crystallize by distillation and then standing.

[0081] It can be understood that good solvents and poor solvents are for a specific compound. The object of this application is the alkali metal bis(fluorosulfonyl)imide salt. The good solvent has a good solubility for the alkali metal bis(fluorosulfonyl)imide salt, and the poor solvent has a low solubility for the alkali metal bis(fluorosulfonyl)imide salt; further, it can be understood that the good solvent and the poor solvent can be at least one of alkanes, ethers, alcohols, esters, benzenes, nitriles, halogenated alkanes, and ketones respectively and independently; further, they are at least one of ethers, esters, benzenes, and halogenated alkanes respectively and independently.

[0082] In some of these examples, the good solvent A is selected from at least one of methyl tert-butyl ether, anhydrous diethyl ether, tetrahydrofuran, n-heptane, cyclohexane, acetone, ethyl acetate, dimethyl carbonate, methyl ethyl carbonate, vinylene carbonate, 1,2-dichloroethane, dichloromethane, acetonitrile, methanol, and ethanol, and the poor solvent B is selected from at least one of 1,4-epoxyhexane, benzene, mesitylene, ethylbenzene, and toluene.

[0083] In some of these examples, the good solvent A is selected from at least one of anhydrous diethyl ether, n-heptane, and 1,2-dichloroethane, and the poor solvent B is toluene.

[0084] In some of these examples, the mass ratio of the good solvent A to the crude alkali metal bis(fluorosulfonyl)imide salt is (0.15 - 0.5):1.

[0085] It can be understood that the mass ratio of the good solvent A to the crude alkali metal bis(fluorosulfonyl)imide salt includes but is not limited to 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1.

[0086] In some of these examples, the mass ratio of the poor solvent B to the crude alkali metal bis(fluorosulfonyl)imide salt is (2 - 4):1.

[0087] It can be understood that the mass ratio of the poor solvent B to the crude alkali metal bis(fluorosulfonyl)imide salt includes but is not limited to 2:1, 2.5:1, 3:1, 3.2:1, 3.5:1, 4:1.

[0088] In some of these examples, in step S32, the distillation includes: first atmospheric distillation and then vacuum distillation.

[0089] Furthermore, in step S32, the vacuum degree of the vacuum distillation is -0.08 MPa to -0.1 MPa.

[0090] In some of these examples, in step S32, the temperature for static crystallization is -10°C to 80°C.

[0091] It can be understood that the temperature for static crystallization includes but is not limited to -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C.

[0092] It can be understood that in step S32, the solid-liquid separation step can remove insoluble substances, which can further improve the purity of the alkali metal bis(fluorosulfonyl)imide salt.

[0093] By dissolving the crude alkali metal bis(fluorosulfonyl)imide salt with a specific type of good solvent A, then adding a specific type of poor solvent B, controlling the ratios of the good solvent A, the poor solvent B and the crude alkali metal bis(fluorosulfonyl)imide salt, and combining distillation to crystallize the alkali metal bis(fluorosulfonyl)imide salt, with the interaction of multiple aspects, the purity of the alkali metal bis(fluorosulfonyl)imide salt can be further improved.

[0094] It can be understood that crystal seeding can also be used for crystallization.

[0095] In some of these examples, in the preparation method of the alkali metal bis(fluorosulfonyl)imide salt, after the recrystallization step in step S30, it further includes:

[0096] Step S40: Filtering, washing and drying the mixture containing the alkali metal bis(fluorosulfonyl)imide salt crystals obtained in step S30 in sequence.

[0097] In the preparation method of the alkali metal bis(fluorosulfonyl)imide salt of the present application, the alkali metal halide salt and the acid-binding agent are used in combination, and the hydrogen halide generated in the reaction is absorbed by chemical reaction, reducing the harm to equipment and personnel; the boiling point of the by-product hydrogen halide organic salt is quite different from that of the target product, and it can be removed by distillation, and the post-treatment is simple.

[0098] When the alkali metal halide salt is lithium fluoride, the by-product hydrogen halide organic salt is a fluorinating agent with relatively high added value, and it can also be used to prepare the raw material bis(fluorosulfonyl)imide; the preparation method is simple, no additional solvent needs to be added during the reaction, the reaction conditions are relatively mild, the requirements for equipment during the reaction process and for the product are lower than those of the previous methods, and industrial production can be carried out.

[0099] The preparation method of the alkali metal bis(fluorosulfonyl)imide salt of the present application can obtain an alkali metal bis(fluorosulfonyl)imide salt with relatively high purity.

[0100] It is understandable that the alkali metal salts of bis(fluorosulfonyl)imide can be lithium bis(fluorosulfonyl)imide, sodium bis(fluorosulfonyl)imide, and potassium bis(fluorosulfonyl)imide.

[0101] One embodiment of the present application provides an electrolyte comprising lithium bis(fluorosulfonyl)imide prepared by the preparation method of the above-mentioned alkali metal salts of bis(fluorosulfonyl)imide.

[0102] One embodiment of the present application provides a lithium battery comprising the above electrolyte.

[0103] Using lithium bis(fluorosulfonyl)imide prepared by the preparation method of the above-mentioned alkali metal salts of bis(fluorosulfonyl)imide as an electrolyte and further using it in a lithium battery, due to the high purity of lithium bis(fluorosulfonyl)imide prepared by the preparation method of the above-mentioned alkali metal salts of bis(fluorosulfonyl)imide, the cycle life, rate performance, and safety performance of the lithium battery can be significantly improved.

[0104] The following will further describe the present application in detail in conjunction with specific embodiments, but the embodiments of the present application are not limited thereto.

[0105] The preparation methods of bis(fluorosulfonyl)imide used in each example and comparative example are as follows:

[0106] Place thionyl chloride and sulfamic acid in a three-necked round-bottom flask that has been inert gas-displaced at least 3 times in advance through a Schleck device and equipped with a reflux condenser. Control the system temperature not exceeding 80 °C and add chlorosulfonic acid dropwise. The molar ratio of thionyl chloride, sulfamic acid, and chlorosulfonic acid is 2.4:1:1. After the dropwise addition, control the reaction system temperature at 110 °C - 120 °C for reaction. Hydrogen chloride and sulfur dioxide acidic gases are generated during the reaction, and the acidic gases are absorbed by a low-concentration sodium hydroxide solution. When the chlorosulfonic acid in the system is consumed, 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, and collect the distillate to obtain a colorless transparent liquid product, bis(chlorosulfonyl)imide (yield 99.5%). Place bis(chlorosulfonyl)imide and triethylamine trihydrofluoride (molar ratio 1:0.66) in a fluorine-lined reaction kettle that has been inert gas-displaced at least 3 times in advance and equipped with a reflux condenser for fluorination reaction. Maintain the reaction temperature at 100 °C and track the reaction progress by gas chromatography every about 2 hours. When the bis(chlorosulfonyl)imide in the system is consumed, 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, and collect the distillate to obtain a colorless transparent liquid product, bis(fluorosulfonyl)imide (yield 98%, purity 99.97%).

[0107] Example 1

[0108] 181.1 g (1.0 mol) of bis(fluorosulfonyl)imide, 26 g (1.0 mol) of lithium fluoride, and 33.73 g (0.33 mol) of triethylamine were placed in a 250 mL fluorine-lined reactor that had been purged with an inert gas at least three times in advance and equipped with a reflux condenser, and stirred for reaction. The reaction temperature was controlled at 100 °C to 110 °C, and the reaction progress was monitored by gas chromatography every about 2 hours. After the bis(fluorosulfonyl)imide in the system was consumed, the temperature of the reaction system was lowered to about 40 °C for vacuum distillation, maintaining a vacuum of not less than -0.08 MPa. The fraction of hydrogen fluoride organic salt (triethylamine hydrogen fluoride) was collected. After the light components were distilled off, the temperature of the remaining reaction system was lowered to room temperature, and 57 g of anhydrous ether was added to the remaining reaction system for dissolution. After stirring for 5 minutes, the insoluble matter was removed through a filter tube equipped with neutral filter paper. The filtrate was directly transferred to a 1000 mL three-in-one reactor that had been previously charged with 500 g of toluene, and concentrated by heating to 45 °C. First, atmospheric distillation was carried out until no distillate was obtained, and then vacuum distillation was carried out under a pressure of not less than -0.08 MPa. Distillation was stopped when the total mass of the distilled solvent was about 70% of the total mass of the crude product and the added solvent. The temperature was slowly lowered to about 30 °C for crystallization; then, at 20 °C to 35 °C, 100 g of toluene was added to wash the crystals. After washing at least 3 times, the crystals were dried under vacuum at 20 °C to 35 °C to obtain lithium bis(fluorosulfonyl)imide.

[0109] Example 2

[0110] It is basically the same as Example 1, except that in Example 2, the acid-binding agent triethylamine (0.33 mol) in Example 1 was replaced with 79 g (1.0 mol) of pyridine.

[0111] Example 3

[0112] It is basically the same as Example 1, except that in Example 3, the acid-binding agent triethylamine (0.33 mol) in Example 1 was replaced with 43.08 g (0.33 mol) of diisopropylethylamine.

[0113] Example 4

[0114] Place 181.1 g (1.0 mol) of bis(fluorosulfonyl)imide, 42.4 g (1.0 mol) of lithium chloride, and 33.73 g (0.33 mol) of triethylamine into a 250 mL fluorine-lined reaction kettle that has been purged with an inert gas at least 3 times in advance and equipped with a reflux condenser, and stir to react. Control the reaction temperature at 110 °C to 120 °C, and track the reaction progress by gas chromatography every about 2 hours. After the bis(fluorosulfonyl)imide in the system is consumed, lower the temperature of the reaction system to about 40 °C and perform vacuum distillation, maintaining the vacuum degree not lower than -0.08 MPa. Collect the fraction of hydrogen fluoride organic salt (triethylamine hydrogen fluoride). After the light components are distilled off, lower the temperature to room temperature, add 80 g of anhydrous ether, stir for 5 minutes, and remove the insoluble matter through a filter tube equipped with neutral filter paper. Transfer the filtrate directly to a 1000 mL three-in-one kettle that has been previously added with 550 g of toluene, heat up to 45 °C for concentration, first perform atmospheric distillation, and then change to vacuum distillation under a pressure not lower than -0.08 MPa. Stop distillation when the total mass of the distilled solvent is about 72% of the total mass of the crude product and the added solvent, and slowly cool down to about 30 °C for crystallization; then, at 20 °C to 35 °C, add 110 g of toluene to wash the crystals, wash at least 3 times, and then dry under vacuum at 20 °C to 35 °C to obtain lithium bis(fluorosulfonyl)imide.

[0115] Example 5

[0116] It is basically the same as Example 4, except that in Example 5, the acid-binding agent triethylamine (0.33 mol) in Example 4 is replaced with 79 g of pyridine (1.0 mol), and the good solvent A anhydrous ether in Example 4 is replaced with an equal mass of n-heptane.

[0117] Example 6

[0118] It is basically the same as Example 4, except that in Example 6, the acid-binding agent triethylamine (0.33 mol) in Example 4 is replaced with 43.08 g (0.33 mol) of diisopropylethylamine, and the good solvent A anhydrous ether in Example 4 is replaced with an equal mass of n-heptane.

[0119] Example 7

[0120] It is basically the same as Example 1, except that the good solvent A anhydrous ether in Example 1 is replaced with an equal mass of 1,2-dichloroethane.

[0121] Example 8

[0122] It is basically the same as Example 1, except that the reaction temperature is controlled at 140 °C to 150 °C, specifically as follows:

[0123] Place 181.1 g (1.0 mol) of bis(fluorosulfonyl)imide, 26 g (1.0 mol) of lithium fluoride, and 33.73 g (0.33 mol) of triethylamine into a 250 mL fluorine-lined reaction kettle that has been purged with an inert gas at least three times in advance and equipped with a reflux condenser, and stir to react. Control the reaction temperature at 140°C to 150°C, and track the reaction progress by gas chromatography every about 2 hours; the others are the same as in Example 1.

[0124] Example 9

[0125] It is basically the same as Example 1, except that in Example 9, the addition amount of triethylamine is increased to 67.46 g (0.66 mol).

[0126] Example 10

[0127] It is basically the same as Example 1, except that in Example 10, the addition amount of triethylamine is increased to 101.19 g (1 mol).

[0128] Comparative Example 1

[0129] It is basically the same as Example 1, except that 181.1 g (1.0 mol) of bis(fluorosulfonyl)imide, 26 g (1.0 mol) of lithium fluoride, 33.73 g (0.33 mol) of triethylamine, and 500 g of dichloromethane are placed into a 250 mL fluorine-lined reaction kettle that has been purged with an inert gas at least three times in advance and equipped with a reflux condenser, and stir to react.

[0130] Comparative Example 2

[0131] It is basically the same as Example 1, except that no acid-binding agent is added. Place 181.1 g (1.0 mol) of bis(fluorosulfonyl)imide and 26 g (1.0 mol) of lithium fluoride into a 250 mL fluorine-lined reaction kettle that has been purged with an inert gas at least three times in advance and equipped with a reflux condenser, and stir to react. Control the reaction temperature at 100°C to 110°C, and track the reaction progress by gas chromatography every about 2 hours; the others are the same as in Example 1.

[0132] Comparative Example 3

[0133] Basically the same as Example 1, the difference is that 181.1 g (1.0 mol) of bis(fluorosulfonyl)imide, 26 g (1.0 mol) of lithium fluoride and 500 g of dichloromethane are placed in a 250 mL fluorine-lined reaction kettle that has been purged with inert gas at least 3 times in advance and equipped with a reflux condenser, and stirred for reaction. The reaction temperature is controlled at 100 °C to 110 °C. After reacting for 12 hours, triethylamine is added dropwise to the reaction system until the pH value is 7 to 8. After continuing to stir for 30 min, filtration is carried out. The filter cake is rinsed with dichloroethane. The filter cake is taken and 57 g of anhydrous ether is added. After stirring for 5 minutes, the insoluble substances are removed through a filter tube equipped with neutral filter paper. The filtrate is directly transferred to a 1000 mL three-in-one kettle that has been previously added with 500 g of toluene. The temperature is raised to 45 °C for concentration. First, normal pressure distillation is carried out until no distillate is distilled out, and then reduced pressure distillation is carried out under a pressure of not less than -0.08 MPa. Distillation is stopped when the total mass of the distilled solvent is about 70% of the total mass of the crude product and the added solvent. It is slowly cooled to about 30 °C for crystallization; then at 20 °C to 35 °C, 100 g of toluene is added to wash the crystals. After washing at least 3 times, vacuum drying is carried out at 20 °C to 35 °C to obtain lithium bis(fluorosulfonyl)imide.

[0134] Comparative Example 4

[0135] Basically the same as Example 1, the difference is that the temperature of the lithiation reaction is controlled at 60 °C.

[0136] The lithium bis(fluorosulfonyl)imide prepared in each example and comparative example was detected. The yield is the mass yield, and the gas-phase normalization method is used; the purity is measured by the loss method; the chromaticity is measured by the platinum-cobalt colorimetric method; the water content is measured by the Karl Fischer coulometric method; the free acid content is measured by manual titration; the contents of chloride ions, sulfate ions and fluoride ions are measured by IC method, and the impurity metal ions are measured by ICP method. The results are shown in Table 1.

[0137] Table 1

[0138]

[0139]

[0140] As can be seen from Table 1, compared with the comparative examples, the lithium bis(fluorosulfonyl)imide prepared in the examples has higher yield and purity, and lower concentrations of moisture, free acid, chloride ions and fluoride ions; among them, in Comparative Example 1, an additional solvent was added to the system, resulting in a decrease in yield and purity and an increase in the concentrations of free acid and chloride ions; in Comparative Example 2, no acid-binding agent was added to the reaction system, and a trace amount of hydrogen fluoride generated during the reaction was entrapped in the product and difficult to remove, resulting in a decrease in yield and purity and an increase in the concentrations of free acid and chloride ions; in Comparative Example 3, when the organic base did not participate in the chemical reaction but was only used for adjusting the acid-base value in the subsequent purification reaction of the product, the final yield, purity, moisture, acid value and fluoride ion concentration of the product were not as good as those of the examples in which the organic base was directly used as an acid-binding agent to participate in the chemical reaction; in Comparative Example 4, the reaction could not proceed completely at a reduced reaction temperature, which had an impact on the yield, purity and fluoride ion concentration; compared with Example 8, appropriately reducing the reaction temperature within a certain range in Example 1 was more beneficial to the chromaticity; compared with Example 9 and Example 10, appropriately reducing the addition ratio of the acid-binding agent within a certain range in Example 1 would further improve the yield of the product and reduce the moisture content in the product. The purity, moisture, acid value, chloride ion and fluoride ion concentrations in lithium bis(fluorosulfonyl)imide all have an impact on the energy density, life, safety and cost of the battery, etc.; lithium bis(fluorosulfonyl)imide salts with high purity and low impurity content are the most desired products in the electrolyte market.

[0141] The technical features of the above-mentioned embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0142] The above-mentioned embodiments only represent several implementation manners of the present application, which are convenient for understanding the technical solutions 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 be made, and these all belong to 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 description can be used to explain the content of the claims.

Claims

1. A method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, characterized in that: The following steps are involved: Adding bisfluorosulfonyl imide, alkali metal halide and acid binding agent simultaneously to the reaction system, and performing metallization reaction at 65°C to 150°C without adding additional solvent to prepare bisfluorosulfonyl imide alkali metal salt; The molar ratio of the alkali metal halide, the acid binding agent and the bisfluorosulfonyl imide is (0.8-1.3):(0.3-1.5):1; The acid binding agent is selected from at least one of an alkylamine and a nitrogen heterocyclic organic base; After the metallization reaction step is completed, the method further includes sequentially performing reduced pressure distillation and recrystallization on the reaction solution obtained by the metallization reaction.

2. The preparation method according to claim 1, wherein The molar ratio of the alkali metal halide to the bis(fluorosulfonyl)imide is (1-1.3):1; The molar ratio of the acid binding agent to the bis(fluorosulfonyl)imide is (0.3-1):

1.

3. The preparation method according to claim 1, wherein The alkylamine is selected from at least one of triethylamine and N,N-diisopropylethylamine, and the nitrogen heterocyclic organic base is selected from at least one of pyridine, 4-dimethylaminopyridine and 1,8-diazabicycloundec-7-ene.

4. The preparation method according to claim 1, wherein The metallization reaction is carried out under a protective atmosphere.

5. The preparation method according to claim 1, wherein The alkali metal halide salt is selected from at least one of lithium halide, sodium halide and potassium halide.

6. The preparation method according to claim 5, wherein The lithium halide is selected from at least one of lithium fluoride, lithium chloride and lithium bromide, the sodium halide is selected from at least one of sodium fluoride, sodium chloride and sodium bromide, and the potassium halide is selected from at least one of potassium fluoride, potassium chloride and potassium bromide.

7. The preparation method according to claim 1, wherein The temperature of the reduced pressure distillation is 30° C. to 100° C., and the vacuum degree is -0.08 MPa to -0.1 MPa.

8. The preparation method according to claim 1, wherein The recrystallization step comprises: The crude bis(fluorosulfonyl)imide alkali metal salt obtained in the reduced pressure distillation step is dissolved in a good solvent A to obtain a crude bis(fluorosulfonyl)imide alkali metal salt mixed solution; The crude mixed liquid of the bisfluorosulfonyl imide alkali metal salt is subjected to solid-liquid separation, and the liquid phase is taken and a poor solvent B is added to the liquid phase. After distillation, the mixture is allowed to stand for crystallization.

9. The preparation method according to claim 8, wherein The good solvent A is selected from at least one of methyl tert-butyl ether, anhydrous ether, tetrahydrofuran, n-heptane, cyclohexane, dimethyl carbonate, ethyl methyl carbonate, vinylene carbonate and 1,2-dichloroethane, dichloromethane, acetonitrile, methanol and ethanol, and the poor solvent B is selected from at least one of 1,4-epoxyhexadecane, benzene, mesitylene, ethylbenzene and toluene.

10. The preparation method according to claim 8, characterized in that The temperature of the static crystallization is -10°C to 80°C.

11. The preparation method according to any one of claims 8 to 10, characterized in that The mass ratio of the good solvent A, the poor solvent B and the crude bisfluorosulfonyl imide alkali metal salt obtained in the reduced pressure distillation step is (0.15-0.5):(2-4):1.

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