A preparation method of a bis(fluorosulfonyl)imide salt

Abstract

The present invention relates to a preparation method of a bis(fluorosulfonyl)imide salt, belonging to the field of lithium battery electrolytes. The method comprises the following steps: (1) reacting bis(fluorosulfonyl)imide acid with an alkali metal source in a poor solvent of the bis(fluorosulfonyl)imide salt to form the bis(fluorosulfonyl)imide salt; (2) when the alkali metal source in step (1) is an alkali metal hydroxide, or when the alkali metal source in step (1) is a carbonate and the molar ratio of the carbonate to the bis(fluorosulfonyl)imide acid < 1:1, adding a carbonate to the reaction system, then introducing carbon dioxide gas for reaction, and performing solid-liquid separation to obtain a crude bis(fluorosulfonyl)imide salt; when the alkali metal source in step (1) is a carbonate and the molar ratio of the carbonate to the bis(fluorosulfonyl)imide acid ≥ 1:1, directly introducing carbon dioxide gas into the reaction system for reaction, and performing solid-liquid separation to obtain a crude bis(fluorosulfonyl)imide salt. The present invention has good water removal effect and a simple process, and the obtained product meets the standard requirements.

Description

Technical Field

[0001] The present invention relates to a method for preparing difluorobis(sulfonyl)imide salts, belonging to the field of lithium battery electrolytes. Background Art

[0002] Lithium-ion batteries have been widely used due to their advantages such as high energy density and high working voltage. The lithium salts used in lithium-ion batteries mainly include lithium hexafluorophosphate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorobis(sulfonyl)imide, etc. Among them, lithium hexafluorophosphate has poor thermal stability, and lithium perchlorate has poor safety performance and is prone to safety hazards such as explosion. Lithium bis(trifluoromethanesulfonyl)imide has strong corrosiveness to aluminum current collectors. However, the decomposition temperature of lithium difluorobis(sulfonyl)imide is 200 °C, indicating its good thermal stability, thereby improving the safety performance of lithium-ion batteries; moreover, the large anion radius of lithium difluorobis(sulfonyl)imide makes the interaction force between it and lithium ions very weak. When in an organic solvent, lithium ions are easily dissociated from the molecule, showing high dissociation property and good conductivity, and can be used as the electrolyte of lithium secondary batteries; the electrolyte using lithium difluorobis(sulfonyl)imide (LIFSI) has good compatibility with the positive and negative electrode materials, and can significantly improve the high and low temperature performance of lithium-ion batteries. Therefore, lithium difluorobis(sulfonyl)imide has very important application prospects and values. Currently, lithium difluorobis(sulfonyl)imide has been considered as the best product that can replace other lithium salts.

[0003] Currently, most of the processes for producing LIFSI use difluorobis(sulfonyl)imide acid to react with lithium carbonate or lithium hydroxide monohydrate to obtain lithium difluorobis(sulfonyl)imide. However, a large amount of water is generated in this production. Currently, the more common water removal method is the thionyl chloride water removal method. After this method removes water, a large amount of hydrogen chloride and sulfur dioxide waste gases are generated, and the discharge of waste gases needs to be considered. At the same time, if the two gases are not discharged in time during the water removal process, the chloride ion content in the salt will be extremely high, and a large amount of chloride ions will also be introduced into the solvent, and dechlorination is required again, resulting in a series of complex operation steps. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing difluorobis(sulfonyl)imide salts, which solves the problems of difficult water removal and easy introduction of impurities in the prior art.

[0005] In order to achieve the above purpose, the technical solution adopted by the method for preparing difluorobis(sulfonyl)imide salts of the present invention is as follows:

[0006] A method for preparing difluorobis(sulfonyl)imide salts, comprising the following steps:

[0007] (1) React difluorobis(sulfonyl)imide acid with an alkali metal source in a poor solvent of difluorobis(sulfonyl)imide salt to form difluorobis(sulfonyl)imide salt; the alkali metal source is a carbonate or a hydroxide of an alkali metal;

[0008] (2) When the alkali metal source described in step (1) is a hydroxide of an alkali metal, or when the alkali metal source in step (1) is a carbonate and the molar ratio of the carbonate to the bis(fluorosulfonyl)imide acid < 1:1, a carbonate is added to the reaction system, and then carbon dioxide gas is introduced for reaction. After solid-liquid separation, a crude bis(fluorosulfonyl)imide salt is obtained; when the lithium source in step (1) is a carbonate and the molar ratio of the carbonate to the bis(fluorosulfonyl)imide acid ≥ 1:1, carbon dioxide gas is directly introduced into the reaction system for reaction, and after solid-liquid separation, a crude bis(fluorosulfonyl)imide salt is obtained; the carbonate is lithium carbonate or sodium carbonate; the hydroxide of the alkali metal is lithium hydroxide or sodium hydroxide.

[0009] The reaction equations involved in the present invention are as follows:

[0010] 2HN(SO2F)2 + Li2CO3 = 2LIN(SO2F)2 + H2O + CO2↑ or HN(SO2F)2 + LiOH = LIN(SO2F)2 + H2O

[0011] Li2CO3 + H2O + CO2 = 2LiHCO3

[0012] or

[0013] 2HN(SO2F)2 + Na2CO3 = 2NaN(SO2F)2 + H2O + CO2↑ or HN(SO2F)2 + NaOH = NaN(SO2F)2 + H2O

[0014] Na2CO3 + H2O + CO2 = 2NaHCO3

[0015] In the preparation method of the difluorosulfonylimide salt of the present invention, a carbonate or a hydroxide of an alkali metal reacts with difluorosulfonylimide acid in a poor solvent to generate a difluorosulfonylimide salt and water. Among them, the carbonate and the difluorosulfonylimide salt are insoluble in the poor solvent, and the hydroxide of the alkali metal and difluorosulfonylimide acid are soluble in the poor solvent. In order to remove water from the difluorosulfonylimide salt, in the present invention, a carbonate reacts with carbon dioxide gas and water to generate a bicarbonate, and the bicarbonate is dissolved in the poor solvent. Then, by separating the solid from the liquid, water, the poor solvent, and the substances dissolved in the poor solvent can be removed, obtaining a crude difluorosulfonylimide salt, reducing impurities and improving the purity of the product. And this water removal process is simple, the water removal is relatively thorough, the cost is low, the substances used are not corrosive, and it is green and economical. By detecting the obtained lithium difluorosulfonylimide salt product, it is found that the water content in the product is below 14 ppm, the acidity is below 22 ppm, and the chloride ion is below 3 ppm, meeting the standard requirements of the lithium difluorosulfonylimide product. It should be noted that the chloride ions contained in the product are introduced by difluorosulfonylimide acid; and by detecting the obtained sodium difluorosulfonylimide product, it is found that the water content in the product is below 15 ppm, the acidity is below 22 ppm, and the chloride ion is below 4 ppm.

[0016] Further, the poor solvent is a poor solvent of lithium carbonate or sodium carbonate.

[0017] Preferably, when the alkali metal source is lithium carbonate or lithium hydroxide, the poor solvent in step (1) is one or both of dichloromethane and dichloroethane; dichloromethane and dichloroethane meet the requirements of not dissolving lithium carbonate and lithium difluorosulfonylimide but dissolving lithium hydroxide, difluorosulfonylimide acid and lithium bicarbonate, and dichloromethane and dichloroethane have a certain hydrophobicity, and can effectively separate the solid from the liquid after the reaction to obtain a crude lithium difluorosulfonylimide salt with higher purity. Or when the alkali metal source is sodium carbonate or sodium hydroxide, the poor solvent in step (1) is one or any combination of halogenated hydrocarbons, aromatic hydrocarbons, and n-hexane. Halogenated hydrocarbons, aromatic hydrocarbons, and n-hexane meet the requirements of not dissolving sodium carbonate and sodium difluorosulfonylimide but dissolving difluorosulfonylimide acid and sodium bicarbonate.

[0018] More preferably, the halogenated hydrocarbon is one or any combination of dichloromethane, dichloroethane, chloroform, trichloroethane, and carbon tetrachloride. The aromatic hydrocarbon is one or both of benzene or benzyl methane.

[0019] More preferably, when the alkali metal source is sodium carbonate or sodium hydroxide, the poor solvent in step (1) is one or both of dichloromethane and dichloroethane.

[0020] To ensure the reaction efficiency of step (1) and the full progress of the reaction, preferably, the addition amount of the poor solvent is 2 to 10.5 times the theoretical value of the bis(fluorosulfonyl)imide salt, such as 2, 5, 6, 8, 10 or 10.3 times. The theoretical value of the bis(fluorosulfonyl)imide salt refers to the mass of the bis(fluorosulfonyl)imide salt obtained when either the alkali metal source or the bis(fluorosulfonium) acid reacts completely and is completely converted into the bis(fluorosulfonyl)imide salt.

[0021] Preferably, when the alkali metal source is the hydroxide of an alkali metal, the molar ratio of the hydroxide of the alkali metal to the bis(fluorosulfonyl)imide acid in step (1) is 1:0.5 to 1.1, such as 0.5, 0.6, 0.8, 0.9, 1.0 or 1.1.

[0022] Since the reaction of carbonate, carbon dioxide gas and water is not easy to proceed, to ensure the reaction efficiency and the full progress of the reaction, preferably, when the alkali metal source is the hydroxide of an alkali metal, the molar ratio of lithium carbonate added in step (2) to the bis(fluorosulfonyl)imide acid is 2 to 5:1, such as 2:1, 2.5:1, 2.8:1, 3:1, 3.3:1, 4:1 or 5:1.

[0023] Preferably, when the alkali metal source is carbonate, when the molar ratio of carbonate to bis(fluorosulfonyl)imide acid in step (1) < 1:1, the molar ratio of carbonate added in step (2) to the bis(fluorosulfonyl)imide acid is 2 to 5:1; more preferably 2.5 to 4:1; when the molar ratio of carbonate to bis(fluorosulfonyl)imide acid in step (1) is 1 to 6:1, it is further preferably 3.5 to 5:1, and carbon dioxide gas is directly introduced into the reaction system after step (1) for reaction.

[0024] Preferably, the temperature of the reaction in step (2) is 10 to 30 °C. If the temperature is too high, higher than 30 °C, it will cause the salt to appear in a sticky state and the reaction will stop. If the temperature is too low, lower than 10 °C, the reaction rate will be very slow, affecting the reaction efficiency.

[0025] To make the reaction of water more complete and reduce the interference of water in the product, preferably, the reaction time in step (2) is 10 to 20 h; carbon dioxide gas is continuously introduced during the reaction process.

[0026] Preferably, if the alkali metal source is lithium carbonate or lithium hydroxide, the reaction temperature in step (1) is 2 to 6 °C. More preferably 3 to 5 °C. If the alkali metal source is sodium carbonate or sodium hydroxide, the reaction temperature in step (1) is 10 to 30 °C. More preferably 30 °C. Detailed implementation mode

[0027] The preparation method of the bis(fluorosulfonyl)imide salt of the present invention comprises the following steps:

[0028] (1) React bis(fluorosulfonyl)imide acid with an alkali metal source in a poor solvent of bis(fluorosulfonyl)imide salt to form bis(fluorosulfonyl)imide salt; the alkali metal source is a carbonate or a hydroxide of an alkali metal;

[0029] (2) When the alkali metal source in step (1) is a hydroxide of an alkali metal, or when the alkali metal source in step (1) is a carbonate and the molar ratio of the carbonate to bis(fluorosulfonyl)imide acid < 1:1, add a carbonate to the reaction system, and then introduce carbon dioxide gas to react, and perform solid-liquid separation to obtain a crude bis(fluorosulfonyl)imide salt; when the alkali metal source in step (1) is a carbonate and the molar ratio of the carbonate to bis(fluorosulfonyl)imide acid ≥ 1:1, directly introduce carbon dioxide gas into the reaction system to react, and perform solid-liquid separation to obtain a crude bis(fluorosulfonyl)imide salt; the carbonate is lithium carbonate or sodium carbonate; the hydroxide of the alkali metal is lithium hydroxide or sodium hydroxide.

[0030] Further, the reaction of bis(fluorosulfonyl)imide acid with an alkali metal source in a poor solvent of bis(fluorosulfonyl)imide salt is specifically: first mix bis(fluorosulfonyl)imide acid, the alkali metal source and the poor solvent respectively, and then drop the mixed bis(fluorosulfonyl)imide acid into the mixed alkali metal source for reaction.

[0031] Further, the molar ratio of bis(fluorosulfonyl)imide acid to the poor solvent is (1 - 5):(1 - 2).

[0032] Further, bis(fluorosulfonyl)imide acid needs to be preheated to 5 - 10 °C before dropping, for example, 5, 6, 7, 8, 9 or 10 °C.

[0033] Further, the dropping is a slow dropping, and the dropping rate is 0.5 - 3.0 mL / min, preferably 1 mL / min.

[0034] Further, the preparation method of bis(fluorosulfonyl)imide salt further includes the following steps: dissolve the obtained crude product with an organic solvent, perform solid-liquid separation to obtain a bis(fluorosulfonyl)imide salt liquid.

[0035] Further, the preparation method of bis(fluorosulfonyl)imide salt further includes the following steps: add the bis(fluorosulfonyl)imide salt liquid to a poor solvent of bis(fluorosulfonyl)imide salt for concentration and crystallization, perform solid-liquid separation again, and dry.

[0036] Further, the organic solvent is a carbonate and / or an alkyl tert-butyl ether.

[0037] Further, the carbonate is dimethyl carbonate and / or ethyl methyl carbonate.

[0038] Further, the carbonate is a mixed solution of dimethyl carbonate and ethyl methyl carbonate.

[0039] Further, the mass ratio of dimethyl carbonate to ethyl methyl carbonate in the mixed solution is 1:1.

[0040] Further, the alkyl tert-butyl ether is methyl tert-butyl ether.

[0041] Further, the addition amount of methyl tert-butyl ether is 0.6 to 1.5 times the mass of lithium bis(fluorosulfonyl)imide, such as 0.6, 0.7, 0.8, 0.9, 1.0 or 1.5 times.

[0042] Further, the solvent used is a poor solvent for carbonates and a good solvent for bis(fluorosulfonyl)imide salts.

[0043] Further, the poor solvent used for concentration and crystallization is an alkane.

[0044] Further, the alkane is one or both of dichloroethane and dichloromethane.

[0045] Further, the addition amount of the alkane is 8 to 13 times the mass of the bis(fluorosulfonyl)imide salt, such as 8, 9, 10, 12 or 13 times.

[0046] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0047] Specific examples of the preparation method of the bis(fluorosulfonyl)imide salt of the present invention are as follows:

[0048] Example 1

[0049] The preparation method of lithium bis(fluorosulfonyl)imide salt in this example adopts the following steps:

[0050] (1) Clean the reaction kettle and check for leaks, then add 4 mol of lithium carbonate and dichloromethane to the reaction kettle, and adjust the temperature of the solution to 5 °C and stir evenly to obtain a mixed solution; wherein, the addition amount of dichloromethane is 10 times the mass of lithium bis(fluorosulfonyl)imide obtained when bis(fluorosulfonyl)imide acid completely reacts and is converted into lithium bis(fluorosulfonyl)imide;

[0051] (2) While stirring, slowly dropwise add a mixture of bis(fluorosulfonyl)imide acid and dichloromethane preheated to 10 °C to the mixed solution at 5 °C for reaction. The dropping rate of bis(fluorosulfonyl)imide acid is 1 mL / min, and the reaction temperature is controlled at 3 - 5 °C; wherein, the dropped mixture contains 1 mol of bis(fluorosulfonyl)imide acid, and the molar ratio of bis(fluorosulfonyl)imide acid to dichloromethane is 1:1;

[0052] (3) After the dropping is completed, continuously introduce carbon dioxide gas (≥99.999%) into the reaction solution at 18 °C for reaction, and the time for continuously introducing carbon dioxide gas is 16 h;

[0053] (4) Filter and remove the filtrate to obtain crude lithium bis(fluorosulfonyl)imide. The moisture content of this crude product is 14 ppm, the acidity is 19 ppm, and the chloride ion content is 3 ppm.

[0054] Example 2

[0055] The preparation method of lithium bis(fluorosulfonyl)imide salt in this example adopts the following steps:

[0056] (1) Clean the reaction kettle and check for leaks. Then add 1 mol of lithium hydroxide and dichloromethane to the reaction kettle, and adjust the temperature of the mixed solution to 3 °C and stir evenly to obtain a mixed solution. Among them, the added amount of dichloromethane is 8 times the mass of lithium bis(fluorosulfonyl)imide obtained when bis(fluorosulfonyl)imide acid completely reacts and is converted into lithium bis(fluorosulfonyl)imide.

[0057] (2) While stirring, slowly dropwise add a mixture of bis(fluorosulfonyl)imide acid and dichloromethane preheated to 10 °C to the mixed solution at 3 °C for reaction. The dropping rate of bis(fluorosulfonyl)imide acid is 1 mL / min, and the reaction temperature is controlled at 3 - 5 °C. Among them, the dropped mixture contains 1 mol of bis(fluorosulfonyl)imide acid, and the molar mass ratio of bis(fluorosulfonyl)imide acid to dichloromethane is 1:2.

[0058] (3) After the dropping is completed, add 3 mol of lithium carbonate to the reaction solution at 22 °C, and then start to continuously introduce carbon dioxide gas (≥99.999%) for reaction. The time for continuously introducing carbon dioxide gas is 12 h.

[0059] (4) Filter and remove the filtrate to obtain crude lithium bis(fluorosulfonyl)imide. The moisture content of this crude product is 5 ppm, the acidity is 8 ppm, and the chloride ion content is ND.

[0060] Example 3

[0061] The preparation method of lithium bis(fluorosulfonyl)imide salt in this example adopts the following steps:

[0062] (1) Clean the reaction kettle and check for leaks. Then add 3.5 mol of lithium carbonate and dichloromethane to the reaction kettle, and adjust the temperature of the mixed solution to 5 °C and stir evenly to obtain a mixed solution. Among them, the added amount of dichloromethane is 10 times the mass of lithium bis(fluorosulfonyl)imide obtained when bis(fluorosulfonyl)imide acid completely reacts and is converted into lithium bis(fluorosulfonyl)imide.

[0063] (2) While stirring, slowly add dropwise a mixture of difluorobis(sulfonyl)imide acid and dichloromethane preheated to 10 °C to the mixed solution at 5 °C for reaction. The dropping rate of difluorobis(sulfonyl)imide acid is 1 mL / min, and the reaction temperature is controlled at 3 - 5 °C. Among them, the dropped mixture contains 1 mol of difluorobis(sulfonyl)imide acid, and the molar mass ratio of difluorobis(sulfonyl)imide acid to dichloromethane is 2:1;

[0064] (3) After the dropping is completed, continuously introduce carbon dioxide gas (≥99.999%) into the reaction solution at 20 °C for reaction, and the time for continuously introducing carbon dioxide gas is 18 h;

[0065] (4) Filter to remove the filtrate to obtain a crude lithium difluorobis(sulfonyl)imide product. The moisture content of this crude product is 10 ppm, the acidity is 22 ppm, and the chloride ion content is 1 ppm;

[0066] (5) Dissolve this crude product with a mixed solution of dimethyl carbonate:ethyl methyl carbonate = 1:1 by mass ratio, filter the solid, and obtain a lithium difluorobis(sulfonyl)imide solution. The moisture content in this solution is 8 ppm, the acidity is 13 ppm, and the chloride ion content is 1 ppm. In order to obtain a pure lithium difluorobis(sulfonyl)imide product, recrystallization, filtration, and drying can be further carried out.

[0067] Example 4

[0068] The preparation method of lithium difluorobis(sulfonyl)imide salt in this example adopts the following steps:

[0069] (1) Clean the reaction kettle and check for leaks, then add 5 mol of lithium carbonate and dichloromethane to the reaction kettle, and adjust the temperature of the mixed solution to 5 °C and stir evenly to obtain a mixed solution. Among them, the added amount of dichloromethane is 5 times the mass of lithium difluorobis(sulfonyl)imide obtained when difluorobis(sulfonyl)imide acid completely reacts and is converted into lithium difluorobis(sulfonyl)imide;

[0070] (2) While stirring, slowly add dropwise a mixture of difluorobis(sulfonyl)imide acid and dichloromethane preheated to 10 °C to the mixed solution at 5 °C for reaction. The dropping rate of difluorobis(sulfonyl)imide acid is 1 mL / min, and the reaction temperature is controlled at 3 - 5 °C. Among them, the dropped mixture contains 1 mol of difluorobis(sulfonyl)imide acid, and the molar mass ratio of difluorobis(sulfonyl)imide acid to dichloromethane is 5:1;

[0071] (3) After the dropping is completed, continuously introduce carbon dioxide gas (≥99.999%) into the reaction solution at 28 °C for reaction, and the time for continuously introducing carbon dioxide gas is 10 h;

[0072] (4) Filter to remove the filtrate to obtain a crude lithium difluorobis(sulfonyl)imide product. The moisture content of this crude product is 2 ppm, the acidity is 15 ppm, and the chloride ion content is 1 ppm;

[0073] (5) Dissolve the crude lithium bis(fluorosulfonyl)imide in methyl tert-butyl ether with an addition amount of 0.8 times the mass of the crude product, filter off the insoluble matter, then add 10 times of dichloroethane and stir for crystallization, separate the solid and liquid, and dry the solvent with nitrogen to obtain the high-quality lithium bis(fluorosulfonyl)imide. The water content of this high-quality product is 1 ppm, the acidity is 3 ppm, and the chloride ion content is ND.

[0074] In other embodiments, the dichloroethane in step (5) can also be replaced by dichloromethane.

[0075] Example 5

[0076] The preparation method of sodium bis(fluorosulfonyl)imide in this example adopts the following steps:

[0077] (1) Clean the reaction kettle and check for leaks, then add 6 mol of sodium carbonate and dichloromethane to the reaction kettle, adjust the temperature of the mixed solution to 30 °C and stir evenly to obtain a mixed solution; among them, the addition amount of dichloromethane is 2 times the mass of the obtained sodium bis(fluorosulfonyl)imide when the bis(fluorosulfonyl)imide acid completely reacts and is converted into sodium bis(fluorosulfonyl)imide;

[0078] (2) While stirring, slowly dropwise add a mixture of bis(fluorosulfonyl)imide acid and dichloromethane to the mixed solution at 25 °C for reaction. The dropping rate of bis(fluorosulfonyl)imide acid is 10 mL / min, and the reaction temperature is controlled at 10-30 °C; among them, the dropped mixture contains 1 mol of bis(fluorosulfonyl)imide acid, and the molar mass ratio of bis(fluorosulfonyl)imide acid to dichloromethane is 8:1;

[0079] (3) After the dropping is completed, continuously introduce carbon dioxide gas (≥99.999%) into the reaction solution at 25 °C for reaction, and the continuous introduction time of carbon dioxide gas is 15 h;

[0080] (4) Filter to remove the filtrate to obtain the crude sodium bis(fluorosulfonyl)imide. The water content of this crude product is 15 ppm, the acidity is 35 ppm, and the chloride ion content is 4 ppm.

[0081] Example 6

[0082] The preparation method of sodium bis(fluorosulfonyl)imide in this example adopts the following steps:

[0083] (1) Clean the reaction kettle and check for leaks, then add 1 mol of sodium hydroxide and dichloroethane to the reaction kettle, adjust the temperature of the mixed solution to 10 °C and stir evenly to obtain a mixed solution; among them, the addition amount of dichloroethane is 1 times the mass of the obtained sodium bis(fluorosulfonyl)imide when the bis(fluorosulfonyl)imide acid completely reacts and is converted into sodium bis(fluorosulfonyl)imide;

[0084] (2) While stirring, a mixture of bis(fluorosulfonyl)imide acid and dichloroethane was slowly added dropwise to the mixed solution at 10 °C for reaction. The dropping rate of bis(fluorosulfonyl)imide acid was 5 mL / min, and the reaction temperature was controlled at 10 - 30 °C. Among them, in the added mixture, there was 1 mol of bis(fluorosulfonyl)imide acid, and the molar mass ratio of bis(fluorosulfonyl)imide acid to dichloroethane was 5:1;

[0085] (3) After the dropping was completed, 2 mol of sodium carbonate was added to the reaction solution at 20 °C, and then carbon dioxide gas (≥99.999%) was continuously introduced for reaction. The time for continuously introducing carbon dioxide gas was 15 h;

[0086] (4) The filtrate was removed by filtration to obtain a crude product of sodium bis(fluorosulfonyl)imide. The moisture content of this crude product was 8 ppm, the acidity was 25 ppm, and the chloride ion content was 2 ppm.

[0087] Example 7

[0088] The preparation method of sodium bis(fluorosulfonyl)imide in this example adopted the following steps:

[0089] (1) The reaction kettle was cleaned and leak-tested, and then 1 mol of sodium carbonate and dichloromethane were added to the reaction kettle. The temperature of this mixed solution was adjusted to 20 °C and stirred evenly to obtain a mixed solution. Among them, the added amount of dichloromethane was 2 times the mass of sodium bis(fluorosulfonyl)imide obtained when bis(fluorosulfonyl)imide acid completely reacted and was converted into sodium bis(fluorosulfonyl)imide;

[0090] (2) While stirring, a mixture of bis(fluorosulfonyl)imide acid and dichloromethane was slowly added dropwise to the mixed solution at 20 °C for reaction. The dropping rate of bis(fluorosulfonyl)imide acid was 10 mL / min, and the reaction temperature was controlled at 10 - 30 °C. Among them, in the added mixture, there was 1 mol of bis(fluorosulfonyl)imide acid, and the molar mass ratio of bis(fluorosulfonyl)imide acid to dichloroethane was 4:1;

[0091] (3) After the dropping was completed, carbon dioxide gas (≥99.999%) was continuously introduced into the reaction solution at 20 °C for reaction. The time for continuously introducing carbon dioxide gas was 15 h;

[0092] (4) The filtrate was removed by filtration to obtain a crude product of sodium bis(fluorosulfonyl)imide. The moisture content of this crude product was 3 ppm, the acidity was 8 ppm, and the chloride ion content was 1 ppm.

[0093] In other examples, the dichloromethane in step (1) can also be replaced by chloroform, trichloroethane, carbon tetrachloride, benzene or benzyl methane.

Claims

1. A preparation method of a bis(fluorosulfonyl)imide salt, characterized in that, It includes the following steps: (1) React difluoromethanesulfonimide acid with an alkali metal source in a poor solvent of difluoromethanesulfonimide salt to generate difluoromethanesulfonimide salt; the alkali metal source is a carbonate or a hydroxide of an alkali metal; (2) When the alkali metal source in step (1) is a hydroxide of an alkali metal, or when the alkali metal source in step (1) is a carbonate and the molar ratio of the carbonate to difluoromethanesulfonimide acid < 1:1, add a carbonate to the reaction system, then introduce carbon dioxide gas for reaction, and perform solid-liquid separation to obtain a crude product of difluoromethanesulfonimide salt; when the alkali metal source in step (1) is a carbonate and the molar ratio of the carbonate to difluoromethanesulfonimide acid ≥ 1:1, directly introduce carbon dioxide gas into the reaction system for reaction, and perform solid-liquid separation to obtain a crude product of difluoromethanesulfonimide salt; the carbonate is lithium carbonate or sodium carbonate; the hydroxide of the alkali metal is lithium hydroxide or sodium hydroxide; The addition amount of the poor solvent is 2 to 10.5 times the theoretical value of difluoromethanesulfonimide salt.

2. The preparation method of the bis(fluorosulfonyl)imide salt according to claim 1, characterized in that, When the alkali metal source is lithium carbonate or lithium hydroxide, the poor solvent in step (1) is one or both of dichloromethane and dichloroethane; or when the alkali metal source is sodium carbonate or sodium hydroxide, the poor solvent in step (1) is one or any combination of halogenated hydrocarbons, aromatic hydrocarbons, and n-hexane.

3. The preparation method of the bis(fluorosulfonyl)imide salt according to claim 1 or 2, characterized in that, When the alkali metal source is a hydroxide of an alkali metal, the molar ratio of the hydroxide of the alkali metal to difluoromethanesulfonimide acid in step (1) is 1:0.5 to 1.

1.

4. The preparation method of the bis(fluorosulfonyl)imide salt according to claim 3, wherein When the alkali metal source is a hydroxide of an alkali metal, the molar ratio of the carbonate added in step (2) to difluoromethanesulfonimide acid is 2 to 5:

1.

5. The preparation method of the bis(fluorosulfonyl)imide salt according to claim 1 or 2, characterized in that, When the alkali metal source is a carbonate, when the molar ratio of the carbonate to difluoromethanesulfonimide acid in step (1) < 1:1, the molar ratio of the carbonate added in step (2) to difluoromethanesulfonimide acid is 2 to 5:1; when the molar ratio of the carbonate to difluoromethanesulfonimide acid in step (1) is 1 to 6:1, directly introduce carbon dioxide gas into the reaction system after step (1) for reaction.

6. The preparation method of the bis(fluorosulfonyl)imide salt according to claim 1, characterized in that, The temperature of the reaction in step (2) is 10 to 30 °C.

7. The preparation method of the difluorosulfonylimide salt according to claim 1 or 2 or 6, characterized in that, The reaction time in step (2) is 10 to 20 h; carbon dioxide gas is continuously introduced during the reaction.

8. The preparation method of the difluoromethanesulfonimide salt according to claim 1 or 2, characterized in that, If the alkali metal source is lithium carbonate or lithium hydroxide, the reaction temperature in step (1) is 2 to 6 °C; if the alkali metal source is sodium carbonate or sodium hydroxide, the reaction temperature in step (1) is 10 to 30 °C.