A method for preparing a bisfluorosulfimide

Abstract

The application relates to a preparation method of an imide compound, in particular to a preparation method of a bifluorosulfone imide. The preparation method comprises the following steps: step 1: mixing fluorides with sulfur trioxide, then heating to 120 DEG C-250 DEG C to react, and then cooling to -30 DEG C-0 DEG C; step 2: adding a mixture of sulfur trioxide and a reaction medium into the product formed in step 1, finally adding ammonia, and post-treating, so that the bifluorosulfone imide is obtained, wherein the fluorides at least comprise calcium fluoride, and the reaction medium is a compound with a freezing point lower than 10 DEG C and a boiling point lower than 120 DEG C under normal pressure. In the preparation method, the fluorides, sulfur trioxide and ammonia are used as starting materials, so that no chloride ion is mixed in the reaction system, the reaction condition is relatively mild and reliable, and the bifluorosulfone imide can be obtained at a high yield.

Description

Technical Field

[0001] This invention relates to a method for preparing an imide compound, specifically a method for preparing bis(fluorosulfonyl)imide. Background Technology

[0002] The fluoride ions in lithium difluorosulfonylimide have strong electron-withdrawing properties, which weakens the coordination between the cations and anions of the lithium salt and enhances the activity of the lithium ions. Therefore, compared with lithium hexafluorophosphate, lithium difluorosulfonylimide has better performance in terms of low temperature resistance, high temperature performance, conductivity, safety, and compatibility. Lithium difluorosulfonylimide has far superior physicochemical properties to lithium hexafluorophosphate and is a next-generation lithium salt electrolyte for lithium-ion batteries that can replace lithium hexafluorophosphate.

[0003] In the existing technology, the most commonly used method for preparing lithium bisfluorosulfonylimide is to first prepare bischlorosulfonylimide using thioyl chloride and ammonia, then obtain bisfluorosulfonylimide using a fluorinating agent, and finally lithiate it using an alkali metal salt to generate lithium bisfluorosulfonylimide.

[0004] However, the above method for preparing bisfluorosulfonyl imide inevitably results in chloride ion impurities in the product, reducing product quality; in addition, the reaction requires high pressure, resulting in high energy consumption and low safety performance. Summary of the Invention

[0005] This invention is made to solve the above-mentioned problems, and aims to provide a method for preparing bisfluorosulfonylimide with simple and readily available raw materials that does not contain chlorine atoms.

[0006] This invention provides a method for preparing bis(fluorosulfonyl)imide, comprising the following steps:

[0007] Step 1: Mix the fluoride with sulfur trioxide and heat to 120℃-250℃ to react, then cool to -30℃-0℃;

[0008] Step 2: Add a mixture of sulfur trioxide and reaction medium to the product formed in Step 1, and finally add ammonia. After post-treatment, bis(fluorosulfonyl)imide is obtained. The fluoride includes at least calcium fluoride, and the reaction medium is a compound with a freezing point below 10°C and a boiling point below 120°C under normal pressure.

[0009] Another aspect of the present invention provides a method for preparing a bis(fluorosulfonyl)imide salt, comprising preparing a bis(fluorosulfonyl)imide using the method for preparing a bis(fluorosulfonyl)imide as described in the first aspect of the present invention, and reacting the bis(fluorosulfonyl)imide with an alkali metal salt to obtain the bis(fluorosulfonyl)imide salt.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] According to the method for preparing bis(fluorosulfonyl)imide of the present invention, since fluoride, sulfur trioxide, and ammonia are used as starting materials, chloride ions are not introduced into the reaction system. Furthermore, the reaction conditions are relatively mild and reliable, allowing for the high yield of bis(fluorosulfonyl)imide. Specifically, the bis(fluorosulfonyl)imide obtained using the method of the present invention has a yield as high as 97.1% and a content of 95.5%. Attached Figure Description

[0012] Figure 1 This is the fluorine spectrum of Example 1 of the present invention. Detailed Implementation

[0013] The following describes in detail the embodiments of the preparation method of bis(fluorosulfonyl)imide specifically disclosed in this invention.

[0014] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this document; "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer greater than or equal to 2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0015] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0016] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0017] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0018] Preparation method of bis(fluorosulfonyl)imide

[0019] The first aspect of this invention provides a method for preparing bis(fluorosulfonyl)imide, comprising the following steps:

[0020] Step 1: Mix the fluoride with sulfur trioxide and heat to 120℃-250℃ to react, then cool to -30℃-0℃;

[0021] Step 2: Add a mixture of sulfur trioxide and reaction medium to the product formed in Step 1, and finally add ammonia. After post-treatment, bis(fluorosulfonyl)imide is obtained. The fluoride includes at least calcium fluoride, and the reaction medium is a compound with a freezing point below 10°C and a boiling point below 120°C under normal pressure.

[0022] The method for preparing bis(fluorosulfonyl)imide provided by this invention may further include the following feature: In step 1, the fluoride comprises a major fluoride and a minor fluoride. In some embodiments, the major fluoride is calcium fluoride and / or strontium fluoride. The minor fluoride is any one or more of boron fluoride, iron fluoride, ferrous fluoride, zinc fluoride, or copper fluoride. Preferably, the major fluoride in the fluoride is calcium fluoride, and the minor fluoride is iron fluoride or boron fluoride.

[0023] The method for preparing bis(fluorosulfonyl)imide provided by this invention may also have the following feature: in step 1, the molar ratio of the primary fluoride to the secondary fluoride is 1:(0.02-0.5). In some embodiments, the molar ratio of the primary fluoride to the secondary fluoride may be 1:(0.02-0.08), 1:(0.08-0.4), 1:(0.4-0.5), 1:(0.08-0.2), or 1:(0.2-0.4), etc. Preferably, the molar ratio of the primary fluoride to the secondary fluoride is 1:(0.08-0.4).

[0024] The method for preparing bis(fluorosulfonyl)imide provided by the present invention may also have the following feature: in step 1, the molar ratio of sulfur trioxide to fluoride is (4-10):1. In some embodiments, the molar ratio of sulfur trioxide to fluoride may also be (4-6):1, (6-8):1, or (8-10):1, etc.

[0025] The method for preparing bis(fluorosulfonyl)imide provided by this invention may also have the following characteristics: in step 1, the temperature may be first raised to 120℃-150℃, 150℃-200℃, or 200℃-250℃, etc., and then lowered to -30℃-0℃, -30℃--20℃, -20℃--10℃, or -10℃-0℃, etc.

[0026] The method for preparing bis(fluorosulfonyl)imide provided by this invention may also have the following feature: in step 2, the reaction medium is a low-boiling-point compound. Preferably, the reaction medium is selected from any one or more of acetonitrile, tetrahydrofuran, methyl tert-butyl ether, etc.

[0027] The method for preparing bis(fluorosulfonyl)imide provided by this invention may also have the following characteristic: the molar mass ratio of the fluoride to the mixture of sulfur trioxide and the reaction medium is 1 mol:(300-1000) g. In some embodiments, the molar mass ratio of the fluoride to the mixture of sulfur trioxide and the reaction medium may also be 1 mol:(300-500) g, 1 mol:(500-800) g, or 1 mol:(800-1000) g, etc.

[0028] The method for preparing bis(fluorosulfonyl)imide provided by this invention may also have the following feature: the mass ratio of sulfur trioxide to the reaction medium in the mixture of sulfur trioxide and the reaction medium is 1:(1-5). In some embodiments, the mass ratio of sulfur trioxide to the reaction medium is 1:(1-3), or 1:(3-5), etc. The mixture of sulfur trioxide and the reaction medium can be obtained by slowly adding sulfur trioxide to the reaction medium while maintaining stirring, with the temperature controlled between 0℃-5℃, 0℃-1℃, 1℃-3℃, or 3℃-5℃. Before use, the mixture of sulfur trioxide and the reaction medium is stored at 0℃-5℃. During the reaction, when the compound of sulfur trioxide and the reaction medium is added, the temperature needs to be controlled between 0℃-5℃ and stirring for a period of time, for example, 2h-4h.

[0029] The method for preparing bis(fluorosulfonyl)imide provided by the present invention may also have the following feature: wherein the ammonia is selected from ammonia gas or liquid ammonia.

[0030] The method for preparing bis(fluorosulfonyl)imide provided by this invention may further include the following feature: the molar ratio of the fluoride to the ammonia is 1:(3-10). For example, the molar ratio of the fluoride to the ammonia may be 1:(3-5), 1:(5-8), or 1:(8-10). In some embodiments, the molar ratio of the fluoride to the ammonia is 1:(3-10). In some embodiments, the molar ratio of the fluoride to the ammonia may be, for example, 1:(3-5), 1:(5-8), or 1:(8-10).

[0031] In the preparation method of bis(fluorosulfonyl)imide provided by the present invention, ammonia is added and stirred at a controlled temperature of 0℃-5℃ for a period of time, for example, 4h-6h. In some embodiments, ammonia is added and stirred at a controlled temperature of 0℃-5℃ for a period of time, for example, 4h-6h.

[0032] The method for preparing bis(fluorosulfonyl)imide provided by this invention may also include the following feature: the post-processing step includes: a first filtration, taking the filtrate, distilling to remove the reaction medium (e.g., a low-boiling-point compound), a second filtration, taking the filtrate, and thus obtaining bis(fluorosulfonyl)imide. Preferably, the first filtration step is carried out at 0℃-20℃. More preferably, the first filtration step is carried out at 0℃-10℃ or 0℃-5℃. The second filtration step can be carried out at a temperature above the melting point of bis(fluorosulfonyl)imide (17℃), generally around 30℃ is preferred.

[0033] Preparation method of bis(fluorosulfonyl)imide salt

[0034] The second aspect of the present invention provides a method for preparing a bis(fluorosulfonyl)imide salt, comprising preparing a bis(fluorosulfonyl)imide using the method for preparing a bis(fluorosulfonyl)imide as described in the first aspect of the present invention, and reacting the bis(fluorosulfonyl)imide with an alkali metal salt to obtain the bis(fluorosulfonyl)imide salt.

[0035] The method for preparing the bis(fluorosulfonyl)imide salt provided by this invention may further include the following feature: the molar ratio of bis(fluorosulfonyl)imide to the alkali metal salt is 1:(1-1.5). In specific embodiments, the molar ratio of bis(fluorosulfonyl)imide to the alkali metal salt may also be 1:(1-1.2) or 1:(1.2-1.5), etc. Preferably, the molar ratio of bis(fluorosulfonyl)imide to the alkali metal salt is 1:1.

[0036] The method for preparing bis(fluorosulfonyl)imide salt provided by the present invention may also have the following feature: wherein the alkali metal salt is selected from one or more of potassium fluoride, lithium fluoride, sodium fluoride, potassium hydroxide, sodium hydroxide, lithium hydroxide, potassium carbonate, sodium carbonate, and lithium carbonate.

[0037] The method for preparing bisfluorosulfonyl imide salt provided by the present invention may also have the following feature: wherein the bisfluorosulfonyl imide salt may be, for example, lithium bisfluorosulfonyl imide.

[0038] The technical solution of this application will be clearly and completely described below with reference to embodiments of the present invention. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention still fall within the scope of protection of the present invention.

[0039] In the following embodiments, the mixture of sulfur trioxide and the reaction medium is prepared by slowly adding sulfur trioxide to the reaction medium while maintaining a temperature between 0°C and 5°C and stirring. Before use, the mixture of sulfur trioxide and the reaction medium is stored between 0°C and 5°C.

[0040] In the following examples, all reagents are commercially available products unless otherwise stated.

[0041] In this embodiment of the invention, the method for detecting the content of bis(fluorosulfonyl)imide is as follows: High-performance liquid chromatography-diode array detector-evaporative light detector (HPLC-DAD-ELSD) is used to detect the content, and the specific conditions are as follows:

[0042] Chromatographic column: Waters ShieldRP18 4.6×1510mm×3.5μm

[0043] Mobile phase A: 0.1% triethylamine acetate (Preparation method: Accurately transfer 1 mL of acetic acid and 1 mL of triethylamine into 2 L of water, mix well and sonicate)

[0044] Mobile phase B: Acetonitrile

[0045] Elution gradient:

[0046] 0.0 95 5 4.0 10 90 6.0 10 90 6.1 95 5 10 95 5

[0047] Flow rate: 1.0 mL / min

[0048] Column temperature: 40℃

[0049] Wavelength: 210nm

[0050] Diluent: Water-acetonitrile (50 / 50, v / v)

[0051] Injection volume: 5 μL

[0052] Needle washing solution: acetonitrile

[0053] ELSD parameters:

[0054] Nebulizer Temperature 60℃ Gas Flow Rate 1.5SLM LED Intensity 100％ Date Rate 80Hz Smothing 50 (50 seconds) PMT Gain 2.0

[0055] Calculation method: The content results were calculated using the logarithmic linear external standard method.

[0056] <Example 1>

[0057] A method for preparing difluorosulfonyl imide

[0058] This embodiment provides a method for preparing bis(fluorosulfonyl)imide, comprising the following steps:

[0059] Step 1: Add 39.0g calcium fluoride (0.5mol, 1.0eq), 11.3g iron fluoride (0.1mol, 0.2eq), and 280.2g sulfur trioxide (3.5mol, 7.0eq) to a 1L sealed reaction vessel and heat to 150℃ for 16h.

[0060] Step 2: Cool to -15℃, and introduce 600g of a mixture of sulfur trioxide and acetonitrile (mass ratio of sulfur trioxide to acetonitrile is 1:1.5) at 0℃-5℃ into the reaction system. Maintain the temperature at 0℃-5℃ and stir for 3 hours. Then introduce 29.8g of ammonia gas (1.75mol, 3.5eq), and continue stirring at 0℃-5℃ for another 5 hours. After the reaction is complete, filter at 0℃-5℃. Collect the filtrate, remove acetonitrile and other low-boiling-point materials by vacuum distillation, and filter again to obtain 86.2g of difluorosulfonyl imide, with a yield of 95.2% and a purity of 95.5%. The yield is calculated based on calcium fluoride; in this example, the theoretical product is 0.5mol. Therefore, the yield of difluorosulfonyl imide = [86.2g / (0.5mol*181.13)]*100% = 95.2%. The calculation method for other examples is the same as in Example 1.

[0061] Fluorine spectrum Figure 1 . 18 F NMR(376MHZ, Methanol-d4)δ50.50

[0062] <Example 2>

[0063] Screening of fluorides

[0064] This embodiment screens fluorides based on Example 1. The screening method includes the following steps:

[0065] Step 1: Add 0.5 mol of the main fluoride, the minor fluoride and 280.2 g of sulfur trioxide (3.5 mol, 7.0 eq) to a 1 L sealed reaction vessel, heat to 150 °C and react for 16 h.

[0066] Step 2: Cool to -15℃, and introduce 600g of a mixture of sulfur trioxide and acetonitrile (mass ratio of sulfur trioxide to acetonitrile is 1:1.5) at 0℃-5℃ into the reaction system. Stir and react for 3 hours at 0℃-5℃, then introduce 29.8g of ammonia gas (1.75mol, 3.5eq), and continue stirring and reacting at 0℃-5℃ for another 5 hours. After the reaction is complete, filter at 0℃-5℃, collect the filtrate, remove acetonitrile and other low-boiling-point materials by vacuum distillation, and then filter again to obtain difluorosulfonyl imide.

[0067] In the embodiments listed in the table below, all reaction conditions are the same as those described in the screening method above, except for the screening conditions listed in the table. The screening results are shown in Table 1.

[0068] Table 1 Screening table for fluorides

[0069]

[0070] a. The reaction time in step 1 is extended to 36 hours;

[0071] b. Increase the reaction temperature in step 1 to 200°C.

[0072] As shown in Table 1, copper fluoride, iron fluoride, and boron trifluoride can all produce certain catalytic effects in the reaction system of this embodiment, which can shorten the reaction time from at least 36 hours to about 16 hours. Furthermore, this application also found that even when the amount of iron fluoride is reduced to 0.04 mol, the reaction can still achieve a good yield.

[0073] <Example 3>

[0074] Screening of reaction media

[0075] Based on Example 1, this embodiment screened the reaction medium. The screening method includes the following steps:

[0076] Step 1: Add 39.0g calcium fluoride (0.5mol, 1.0eq), 11.3g iron fluoride (0.1mol, 0.2eq), and 280.2g sulfur trioxide (3.5mol, 7.0eq) to a 1L sealed reaction vessel and heat to 150℃ for 16h.

[0077] Step 2: Cool down to -15℃, introduce a mixture of sulfur trioxide and reaction medium at 0℃-5℃ into the reaction system, and stir the reaction at 0℃-5℃ for 3 hours. Then introduce 29.8g of ammonia gas (1.75mol, 3.5eq), and continue stirring the reaction at 0℃-5℃ for 5 hours. After the reaction is complete, filter at 0℃-5℃, take the filtrate, remove acetonitrile and other low-boiling-point materials by vacuum distillation, and then filter again to obtain difluorosulfonyl imide.

[0078] In the embodiments listed in the table below, all reaction conditions are the same as those described in the screening method above, except for the screening conditions listed in the table. The screening results are shown in Table 2.

[0079] Table 2 Screening of reaction media

[0080]

[0081] As shown in Table 2, the reaction can proceed successfully when methyl tert-butyl ether and tetrahydrofuran are used as reaction media, but fuming sulfuric acid cannot make the reaction proceed smoothly.

[0082] <Example 4>

[0083] Screening of ammonia usage

[0084] This embodiment, based on Embodiment 1, further refines the dosage of ammonia. The refinement method includes the following steps:

[0085] Step 1: Add 39.0g calcium fluoride (0.5mol, 1.0eq), 11.3g iron fluoride (0.1mol, 0.2eq), and 280.2g sulfur trioxide (3.5mol, 7.0eq) to a 1L sealed reaction vessel and heat to 150℃ for 16h.

[0086] Step 2: Cool to -15℃, and introduce 600g of a mixture of sulfur trioxide and acetonitrile (mass ratio of sulfur trioxide to acetonitrile is 1:1.5) at 0℃-5℃ into the reaction system. Stir and react for 3 hours at 0℃-5℃, then introduce ammonia gas and continue stirring and reacting at 0℃-5℃ for another 5 hours. After the reaction is complete, filter at 0℃-5℃, collect the filtrate, remove acetonitrile and other low-boiling-point materials by vacuum distillation, and then filter again to obtain difluorosulfonyl imide.

[0087] In the embodiments listed in the table below, all reaction conditions are the same as those described in the screening method above, except for the screening conditions listed in the table. The screening results are shown in Table 3.

[0088] Table 3 Screening of Ammonia Dosage

[0089] 1 1mol 36.7％ 33.2g Not detected 2 2.5mol 95.9％ 86.9g 92.1％ 3 5mol 97.1％ 87.9g 94.6％

[0090] As shown in Table 3, when the amount of ammonia is only 2 eq, the reaction yield is low. When the amount of ammonia is greater than 5 eq, the reaction yield and content are not significantly different.

[0091] <Example 5>

[0092] Preparation method of lithium bis(fluorosulfonyl)imide:

[0093] 19.1 g of bis(fluorosulfonyl)imide (95% purity) and 260 mg of lithium fluoride were added to a reaction vessel, the temperature was lowered to 0-10℃, 30 g of hydrogen fluoride was added, and the reaction was carried out at 0-10℃ for 5-10 h. After the reaction was completed, the mixture was filtered, the solid was collected, and dried at 35℃ for 8 h to obtain 18 g of lithium(bis(fluorosulfonyl)imide), with a yield of 96.2%.

[0094] The role and effect of the embodiments

[0095] According to the preparation method of bis(fluorosulfonyl)imide involved in the above embodiments, since fluoride, sulfur trioxide and ammonia are used as starting materials, chloride ions are not introduced into the reaction system. At the same time, the reaction conditions are relatively mild and reliable, and bis(fluorosulfonyl)imide can be obtained in high yield.

[0096] Furthermore, the applicant unexpectedly discovered that when a mixed fluoride consisting of calcium fluoride and other fluorides was used as a reaction raw material, the reaction yield was improved to a certain extent.

[0097] Furthermore, the applicant unexpectedly discovered that the reaction yield could also be improved to some extent when acetonitrile or tert-butyl methyl ether was used as the reaction medium.

[0098] The applicant declares that the present invention illustrates the preparation method of bis(fluorosulfonyl)imide through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0099] The above embodiments are preferred examples of the present invention and are not intended to limit the scope of protection of the present invention. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0100] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for preparing difluorosulfonyl imide, characterized in that, Includes the following steps: Step 1: Mix the fluoride with sulfur trioxide and heat to 120℃-250℃ to react, then cool to -30℃-0℃; Step 2: Add a mixture of sulfur trioxide and reaction medium to the product formed in Step 1, and finally add ammonia. After post-treatment, difluorosulfonyl imide is obtained. The fluorides include major fluorides and minor fluorides. The primary fluoride is selected from calcium fluoride. The minor fluoride is selected from any one or more of boron fluoride, iron fluoride, ferrous fluoride, zinc fluoride, or copper fluoride. The reaction medium is selected from any one or more of acetonitrile, tetrahydrofuran, and methyl tert-butyl ether.

2. The method for preparing bis(fluorosulfonyl)imide according to claim 1, characterized in that, in, The molar ratio of the primary fluoride to the secondary fluoride is 1:(0.02-0.5).

3. The method for preparing bis(fluorosulfonyl)imide according to claim 1, characterized in that, in, In step 1, the molar ratio of sulfur trioxide to fluoride is (4-10):

1.

4. The method for preparing bis(fluorosulfonyl)imide according to claim 1, characterized in that, in, The molar mass ratio of the fluoride and the mixture of sulfur trioxide and reaction medium is 1 mol: (300-1000) g.

5. The method for preparing bis(fluorosulfonyl)imide according to claim 1, characterized in that, in, In step 2, the mass ratio of sulfur trioxide to the reaction medium in the mixture of sulfur trioxide and reaction medium is 1:(1-5). And / or, add the mixture of sulfur trioxide and reaction medium at a controlled temperature of 0℃-5℃.

6. The method for preparing bis(fluorosulfonyl)imide according to claim 1, characterized in that, in, The molar ratio of the fluoride to the ammonia is 1:(3-10). And / or, add ammonia while controlling the temperature at 0℃-5℃; And / or, the ammonia is selected from ammonia gas or liquid ammonia.

7. The method for preparing bis(fluorosulfonyl)imide according to claim 1, characterized in that, in, The post-processing steps include: first filtration, taking the filtrate, distilling to remove the reaction medium, and second filtration to obtain difluorosulfonamide.

8. A method for preparing a difluorosulfonyl imide salt, characterized in that, The method includes preparing bisfluorosulfonylimide using the preparation method of bisfluorosulfonylimide as described in any one of claims 1 to 7, and reacting the bisfluorosulfonylimide with an alkali metal salt to obtain a bisfluorosulfonylimide salt.

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