A method for continuously preparing lithium bis(fluorosulfonyl)imide

Abstract

The present invention relates to the technical field of preparation methods of lithium bisfluorosulfonyl imide, and in particular to a method for continuously preparing lithium bisfluorosulfonyl imide, comprising the following steps: chlorosulfonic acid and chlorosulfonyl isocyanate react under the action of a copper complex catalyst to generate bischlorosulfonyl imide; hydrogen fluoride gas is introduced into the bischlorosulfonyl imide to obtain bisfluorosulfonyl imide under the action of an iron complex catalyst; a lithium salt is added to an organic solvent, and bisfluorosulfonyl imide is added during stirring to obtain the product lithium bisfluorosulfonyl imide. The present invention does not require changing the reaction vessel in different steps, nor does it require separating and purifying the intermediate product before putting it into the next reaction step, but directly obtains the product by continuous reaction, and maintains a high yield; in addition, the introduction of the copper complex catalyst and the iron complex catalyst further reduces the temperature required for the reaction, saving energy while improving the safety of the reaction process.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation methods of lithium bis(fluorosulfonyl)imide, and in particular to a method for continuously preparing lithium bis(fluorosulfonyl)imide. Background Art

[0002] The rapid and high-quality development of the lithium-ion battery industry places higher demands on the safety and energy density of electrolytes. As a new electrolyte solute, lithium bis(fluorosulfonyl)imide (LiFSI) offers superior thermal stability and higher conductivity than traditional lithium hexafluorophosphate (LiPF6). Therefore, whether used as a primary salt additive or a core solute, LiFSI has the potential to become the best alternative to LiPF6.

[0003] At present, the main LiFSI preparation technologies reported at home and abroad are as follows: (1) Using synthesized dichlorodiphenylamine to directly react with LiF to prepare LiFSI, a large amount of corrosive gas HF will be generated. At the same time, the excess LiF and LiFSI are not easy to separate, and the residual HF will have adverse effects on lithium batteries. (2) Using ammonia water, ammonium salt or other organic ammonia as the source of ammonia, then adding intermediates such as sulfuryl chloride to synthesize lithium bis(fluorosulfonylamide), and finally performing a lithiation reaction to obtain lithium bis(fluorosulfonylamide). The ammonia in this method is mainly liquid or gas, which cannot be accurately measured and will generate unnecessary by-products. In addition, the lithium salt solution used in the lithiation reaction is strongly alkaline and flammable and explosive, posing a safety hazard. (3) Using purified difluoro acid to react with lithium carbonate and deionized water to form a suspension, the reaction solution is spray-dried to obtain the product. This reaction is a neutralization exothermic reaction. The product is prone to decomposition in the aqueous solution, and the introduction of water makes desolventization and drying more difficult. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for continuously preparing lithium bis(fluorosulfonyl)imide to solve the problems raised in the above background technology.

[0005] According to a first aspect of an embodiment of the present invention, a method for continuously preparing lithium bis(fluorosulfonyl)imide comprises the following steps:

[0006] Step 1: Chlorosulfonic acid reacts with chlorosulfonyl isocyanate in the presence of a copper complex catalyst to generate bischlorosulfonyl imide;

[0007] Step 2: introducing hydrogen fluoride gas into the bischlorosulfonyl imide produced in step 1 to obtain bisfluorosulfonyl imide under the action of an iron complex catalyst;

[0008] Step 3: adding a lithium salt to an organic solvent, and adding the bisfluorosulfonyl imide obtained in step 2 during stirring to obtain the product, the lithium bisfluorosulfonyl imide.

[0009] In one aspect of an embodiment of the present invention, the copper complex catalyst is Cu(NCMe)4BF4, Cu(NCMe)4PF6 or Cu(OAc)2.

[0010] In one aspect of the embodiments of the present invention, the iron complex catalyst is an iron porphyrin complex or an iron polypyridine complex.

[0011] In one aspect of the embodiment of the present invention, in the copper complex catalyst and the iron complex catalyst, the molar ratio of copper atoms to iron atoms is 1:(0.75-1.5).

[0012] In one aspect of an embodiment of the present invention, the copper complex catalyst is Cu(NCMe)4BF4.

[0013] In one aspect of the embodiments of the present invention, the iron complex catalyst is an iron polypyridine complex, and the iron polypyridine complex is obtained by reacting iron ions with 2,2':6',2"-terpyridine.

[0014] In one aspect of the embodiments of the present invention, the lithium salt is LiCl and at least one of Li2O, LiOH, LiHCO3 and Li2CO3.

[0015] In one aspect of the embodiments of the present invention, the organic solvent is any one of dichloromethane, dichloroethane, n-hexane, cyclohexane, toluene, xylene, ethyl acetate, methyl acetate, propyl acetate, ethyl ether, propyl ether, isopropyl ether or butyl ether.

[0016] In one aspect of an embodiment of the present invention, a method for continuously preparing lithium bis(fluorosulfonyl)imide comprises the following steps:

[0017] Step 1: Add a copper complex catalyst and chlorosulfonic acid to a synthesis reactor that has been dried and replaced with inert gas, then slowly add chlorosulfonyl isocyanate to the synthesis reactor under an inert gas environment, and react at 55-65° C. for 3-6 hours to generate an intermediate product containing bischlorosulfonyl imide;

[0018] Step 2: Raise the temperature in the synthesis reactor to 80-90° C., directly introduce hydrogen fluoride gas into the intermediate product 1 containing bischlorosulfonyl imide generated in step 1, and react for 3-5 hours to obtain the intermediate product 2 containing bisfluorosulfonyl imide, which is then distilled to obtain bisfluorosulfonyl imide;

[0019] Step 3: Add the lithium salt to the organic solvent, slowly add the bis(fluorosulfonyl)imide obtained in step 2 during stirring, maintain the temperature at 0-15°C, react for 1-3 hours, and obtain the intermediate product 3 containing lithium bis(fluorosulfonyl)imide. After filtration, separation, distillation and purification, the final product, the lithium bis(fluorosulfonyl)imide, is obtained.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention does not require replacement of reaction vessels in different steps, nor does it require separation and purification of intermediate products before feeding into the next reaction. Instead, the product is directly obtained by continuous reaction while maintaining a relatively high yield. In addition, the introduction of copper complex catalysts and iron complex catalysts further reduces the temperature required for the reaction, thereby saving energy and improving the safety of the reaction process.

[0022] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. The embodiments described herein are illustrative and are used to provide a basic understanding of the present invention. The embodiments of the present invention should not be interpreted as limiting the present invention.

[0024] For the sake of clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0025] As used herein, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0026] In the description herein, unless otherwise specified, “above” and “below” include the number itself.

[0027] Unless otherwise specified, the terms used herein have the commonly understood meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned herein can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods described in the examples of the present invention).

[0028] The term "about" is used to describe and illustrate small changes. When used in conjunction with an event or situation, the term may refer to an example in which the event or situation occurs precisely and an example in which the event or situation occurs very approximately. For example, when used in conjunction with a numerical value, the term may refer to a variation range of less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. In addition, amounts, ratios, and other numerical values ​​are sometimes presented in this article in a range format. It should be understood that such range formats are for convenience and brevity, and should be flexibly understood to include not only numerical values ​​explicitly designated as range limits, but also all individual numerical values ​​or subranges encompassed within the range, as if each numerical value and subrange were explicitly designated.

[0029] In the present invention, "slowly adding" may refer to adding dropwise, or adding the reactants in multiple batches in a manner that does not abruptly change the state of the reaction system or trigger a violent reaction.

[0030] A list of items linked by the term "at least one of" or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can contain a single component or multiple components. Item B can contain a single component or multiple components. Item C can contain a single component or multiple components.

[0031] In the present invention, an iron polypyridine complex catalyst is prepared by dissolving 12.75 g of ferric nitrate in 120 mL of ethanol solution, then adding 21.36 g of 2,2':6',2"-terpyridine (CAS No. 1148-79-4), and adding dropwise a 3 mol / L NaOH solution under stirring until a dark yellow precipitate is precipitated. The precipitate is collected by filtration, washed with acetone, and dried to obtain an iron polypyridine complex [Fe(tpy)(OH2)2]. 2+(tpy=2,2':6',2''-terpyridine).

[0032] The present invention will be further described below with reference to the following examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0033] Example 1

[0034] The following steps are involved:

[0035] Step 1: Weigh 58g of chlorosulfonic acid (33mL) and mix it with 100mL of dichloroethane. After mixing, seal and place. Then weigh 1.5g of tetrakis(acetonitrile)copper tetrafluoroborate (commercially available) and add it to a synthesis reactor that has been dried and replaced with nitrogen. Then add the aforementioned chlorosulfonic acid and dichloroethane, maintain stirring and nitrogen protection. Then weigh 77.84g of chlorosulfonyl isocyanate (48mL) and slowly add it dropwise to the synthesis reactor. After the addition is complete, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide.

[0036] Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 85°C. While the temperature is rising, an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) is added, and HF gas is introduced into the synthesis reactor. The molar amount of HF gas is 1.2 times the molar amount of chlorosulfonic acid. The reaction is carried out for 5 hours. After the reaction is completed, the liquid after the reaction is subjected to reduced pressure distillation to collect the bis(fluorosulfonyl)imide fraction;

[0037] Step 3: Weigh 12.7g of LiCl and 15.3g of Li₂CO₃ into 150mL of dichloromethane and stir to form a uniform suspension. Maintain stirring and control the temperature at 4°C. Then, add the bis(fluorosulfonyl)imide obtained in Step 2 dropwise to carry out an ion exchange process. After the reaction is completed, filter, separate the solid and liquid, distill and recover the reaction solvent, and purify (concentrate and crystallize) to obtain a white, anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. Weighing and calculation show that the yield of Example 1 is 92.5% based on chlorosulfonic acid.

[0038] Example 2

[0039] The following steps are involved:

[0040] Step 1: Weigh 58g of chlorosulfonic acid (33mL) and mix it with 100mL of dichloroethane. After mixing, seal and place. Then weigh 1.5g of tetrakis(acetonitrile)copper tetrafluoroborate (commercially available) and add it to a synthesis reactor that has been dried and replaced with nitrogen. Then add the aforementioned chlorosulfonic acid and dichloroethane, maintain stirring and nitrogen protection. Then weigh 77.84g of chlorosulfonyl isocyanate (48mL) and slowly add it dropwise to the synthesis reactor. After the addition is complete, react at 75°C for 8h to generate an intermediate product containing bischlorosulfonyl imide.

[0041] Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 100° C., and while the temperature is rising, an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) is added, and HF gas is introduced into the synthesis reactor. The molar amount of HF gas is 1.2 times the molar amount of chlorosulfonic acid. The reaction is carried out for 5 hours. After the reaction is completed, the liquid after the reaction is subjected to reduced pressure distillation to collect the difluorosulfonyl imide fraction;

[0042] Step 3: Weigh 12.7g of LiCl and 15.3g of Li₂CO₃ into 150mL of dichloromethane and stir to form a uniform suspension. Maintain stirring and control the temperature at 4°C. Then, add the bis(fluorosulfonyl)imide obtained in Step 2 dropwise to carry out an ion exchange process. After the reaction is completed, filter, separate the solid and liquid, distill and recover the reaction solvent, and purify (concentrate and crystallize) to obtain a white, anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculating, the yield of Example 2 is 91.1% based on chlorosulfonic acid.

[0043] Example 3

[0044] The following steps are involved:

[0045] Step 1: Weigh 58g of chlorosulfonic acid (33mL) and mix it with 100mL of dichloroethane. After mixing, seal and place. Then weigh 1.5g of tetrakis(acetonitrile)copper tetrafluoroborate (commercially available) and add it to a synthesis reactor that has been dried and replaced with nitrogen. Then add the aforementioned chlorosulfonic acid and dichloroethane, maintain stirring and nitrogen protection. Then weigh 77.84g of chlorosulfonyl isocyanate (48mL) and slowly add it dropwise to the synthesis reactor. After the addition is complete, react at 105°C for 8h to generate an intermediate product containing bischlorosulfonyl imide.

[0046] Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is maintained at 105°C, and an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) is added while the temperature is increased. HF gas is introduced into the synthesis reactor, and the molar amount of HF gas is 1.2 times the molar amount of chlorosulfonic acid. The reaction is carried out for 5 hours. After the reaction is completed, the liquid after the reaction is subjected to reduced pressure distillation to collect the difluorosulfonyl imide fraction;

[0047] Step 3: Weigh 12.7g of LiCl and 15.3g of Li₂CO₃ into 150mL of dichloromethane and stir to form a uniform suspension. Maintain stirring and control the temperature at 4°C. Then, add the bis(fluorosulfonyl)imide obtained in Step 2 dropwise to carry out an ion exchange process. After the reaction is completed, filter, separate the solid and liquid, distill and recover the reaction solvent, and purify (concentrate and crystallize) to obtain a white, anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculating, the yield of Example 3 is 89.5% based on chlorosulfonic acid.

[0048] Example 4

[0049] The following steps are involved:

[0050] Step 1: Weigh 58g of chlorosulfonic acid (33mL) and mix it with 100mL of dichloroethane. After mixing, seal and place. Then weigh 1.5g of tetrakis(acetonitrile)copper tetrafluoroborate (commercially available) and add it to a synthesis reactor that has been dried and replaced with nitrogen. Then add the aforementioned chlorosulfonic acid and dichloroethane, maintain stirring and nitrogen protection. Then weigh 77.84g of chlorosulfonyl isocyanate (48mL) and slowly add it dropwise to the synthesis reactor. After the addition is complete, react at 50°C for 8h to generate an intermediate product containing bischlorosulfonyl imide.

[0051] Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 75°C. While the temperature is rising, an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) is added, and HF gas is introduced into the synthesis reactor. The molar amount of HF gas is 1.2 times the molar amount of chlorosulfonic acid. The reaction is carried out for 5 hours. After the reaction is completed, the liquid after the reaction is subjected to reduced pressure distillation to collect the difluorosulfonyl imide fraction;

[0052] Step 3: Weigh 12.7g of LiCl and 15.3g of Li₂CO₃ into 150mL of dichloromethane and stir to form a uniform suspension. Maintain stirring and control the temperature at 4°C. Then, add the bis(fluorosulfonyl)imide obtained in Step 2 dropwise to carry out an ion exchange process. After the reaction is completed, filter, separate the solid and liquid, distill and recover the reaction solvent, and purify (concentrate and crystallize) to obtain a white, anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculating, the yield of Example 4 is 83.1% based on chlorosulfonic acid.

[0053] Example 5

[0054] The following steps are involved:

[0055] Step 1: Weigh 58g of chlorosulfonic acid (33mL) and mix it with 100mL of dichloroethane. After mixing, place it in a sealed container. Then, weigh 1.5g of Cu-TMEDA catalyst (commercially available) and add it to a synthesis reactor that has been dried and replaced with nitrogen. Then, add the aforementioned chlorosulfonic acid and dichloroethane, maintain stirring and nitrogen protection. Next, weigh 77.84g of chlorosulfonyl isocyanate (48mL) and slowly add it dropwise to the synthesis reactor. After the addition is complete, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide.

[0056] Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 85°C. While the temperature is rising, an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) is added, and HF gas is introduced into the synthesis reactor. The molar amount of HF gas is 1.2 times the molar amount of chlorosulfonic acid. The reaction is carried out for 5 hours. After the reaction is completed, the liquid after the reaction is subjected to reduced pressure distillation to collect the bis(fluorosulfonyl)imide fraction;

[0057] Step 3: Weigh 12.7g of LiCl and 15.3g of Li₂CO₃ into 150mL of dichloromethane and stir to form a uniform suspension. Maintain stirring and control the temperature at 4°C. Then, add the bis(fluorosulfonyl)imide obtained in Step 2 dropwise to carry out an ion exchange process. After the reaction is completed, filter, separate the solid and liquid, distill and recover the reaction solvent, and purify (concentrate and crystallize) to obtain a white, anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculating, the yield of Example 5 is 26.3% based on chlorosulfonic acid.

[0058] Example 6

[0059] The following steps are involved:

[0060] Step 1: Weigh 58g of chlorosulfonic acid (33mL) and mix it with 100mL of dichloroethane. After mixing, seal and place. Then, weigh 1.5g of bis(tert-butylacetoacetate)copper(II) catalyst (commercially available) and add it to a synthesis reactor that has been dried and replaced with nitrogen. Then, add the aforementioned chlorosulfonic acid and dichloroethane, maintaining stirring and nitrogen protection. Next, weigh 77.84g of chlorosulfonyl isocyanate (48mL) and slowly add it dropwise to the synthesis reactor. After the dropwise addition is complete, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide.

[0061] Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 85°C. While the temperature is rising, an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) is added, and HF gas is introduced into the synthesis reactor. The molar amount of HF gas is 1.2 times the molar amount of chlorosulfonic acid. The reaction is carried out for 5 hours. After the reaction is completed, the liquid after the reaction is subjected to reduced pressure distillation to collect the bis(fluorosulfonyl)imide fraction;

[0062] Step 3: Weigh 12.7g of LiCl and 15.3g of Li2CO3 into 150mL of dichloromethane and stir to form a uniform suspension. Maintain stirring and control the temperature at 4°C. Then, add the bis(fluorosulfonyl)imide obtained in Step 2 dropwise to carry out an ion exchange process. After the reaction is completed, filter, separate the solid and liquid, distill and recover the reaction solvent, and purify (concentrate and crystallize) to obtain a white, anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculating, the yield of Example 6 is 21.5% based on chlorosulfonic acid.

[0063] Example 7

[0064] The following steps are involved:

[0065] Step 1: Weigh 58g of chlorosulfonic acid (33mL) and mix it with 100mL of dichloroethane. After mixing, seal and place. Then, weigh 1.5g of bromotris(triphenylphosphine)copper(I) catalyst (commercially available) and add it to a synthesis reactor that has been dried and replaced with nitrogen. Then, add the aforementioned chlorosulfonic acid and dichloroethane, maintaining stirring and nitrogen protection. Next, weigh 77.84g of chlorosulfonyl isocyanate (48mL) and slowly add it dropwise to the synthesis reactor. After the dropwise addition is complete, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide.

[0066] Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 85°C. While the temperature is rising, an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) is added, and HF gas is introduced into the synthesis reactor. The molar amount of HF gas is 1.2 times the molar amount of chlorosulfonic acid. The reaction is carried out for 5 hours. After the reaction is completed, the liquid after the reaction is subjected to reduced pressure distillation to collect the bis(fluorosulfonyl)imide fraction;

[0067] Step 3: Weigh 12.7g of LiCl and 15.3g of Li2CO3 into 150mL of dichloromethane and stir to form a uniform suspension. Maintain stirring and control the temperature at 4°C. Then, add the bis(fluorosulfonyl)imide obtained in Step 2 dropwise to carry out an ion exchange process. After the reaction is completed, filter, separate the solid and liquid, distill and recover the reaction solvent, and purify (concentrate and crystallize) to obtain a white, anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculating, the yield of Example 7 is 18.9% based on chlorosulfonic acid.

[0068] Example 8

[0069] The following steps are involved:

[0070] Step 1: Weigh 58g of chlorosulfonic acid (33mL) and mix it with 100mL of dichloroethane. After mixing, seal and place. Then weigh 1.5g of tetrakis(acetonitrile)copper tetrafluoroborate (commercially available) and add it to a synthesis reactor that has been dried and replaced with nitrogen. Then add the aforementioned chlorosulfonic acid and dichloroethane, maintain stirring and nitrogen protection. Then weigh 77.84g of chlorosulfonyl isocyanate (48mL) and slowly add it dropwise to the synthesis reactor. After the addition is complete, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide.

[0071] Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 85°C, and n-butylferrocene catalyst (1.75 g, commercially available) is added while the temperature is raised. HF gas is introduced into the synthesis reactor, and the molar amount of HF gas is 1.2 times the molar amount of chlorosulfonic acid. The reaction is carried out for 5 hours. After the reaction is completed, the liquid after the reaction is subjected to reduced pressure distillation to collect the difluorosulfonyl imide fraction;

[0072] Step 3: Weigh 12.7g of LiCl and 15.3g of Li₂CO₃ into 150mL of dichloromethane and stir to form a uniform suspension. Maintain stirring and control the temperature at 4°C. Then, add the bis(fluorosulfonyl)imide obtained in Step 2 dropwise to carry out an ion exchange process. After the reaction is completed, filter, separate the solid and liquid, distill and recover the reaction solvent, and purify (concentrate and crystallize) to obtain a white, anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculating, the yield of Example 8 is 35.9% based on chlorosulfonic acid.

[0073] Comparative Example 1

[0074] The following steps are involved:

[0075] Step 1: Weigh 58g of chlorosulfonic acid (33mL) and mix it with 100mL of dichloroethane. After mixing, seal and place it. Then weigh 1.5g of copper chloride catalyst (commercially available) and add it to the synthesis reactor that has been dried and replaced with nitrogen. Then add the above-mentioned chlorosulfonic acid and dichloroethane, maintain stirring and nitrogen protection. Then weigh 77.84g of chlorosulfonyl isocyanate (48mL) and slowly add it dropwise to the synthesis reactor. After the dropwise addition is completed, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide.

[0076] Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 85°C, and while the temperature is rising, ferric chloride catalyst (1.75 g, commercially available) is added, and HF gas is introduced into the synthesis reactor. The molar amount of HF gas is 1.2 times the molar amount of chlorosulfonic acid. The reaction is carried out for 5 hours. After the reaction is completed, the liquid after the reaction is subjected to reduced pressure distillation to collect the difluorosulfonyl imide fraction;

[0077] Step 3: Weigh 12.7g of LiCl and 15.3g of Li2CO3 into 150mL of dichloromethane and stir to form a uniform suspension. Maintain stirring and control the temperature at 4°C. Then, add the bis(fluorosulfonyl)imide obtained in Step 2 dropwise to carry out an ion exchange process. After the reaction is completed, filter, separate the solid and liquid, distill and recover the reaction solvent, and purify (concentrate and crystallize) to obtain a white, anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculating, the yield of Comparative Example 1 is 68.8% based on chlorosulfonic acid.

[0078] As can be seen from Examples 1 to 4, the present invention, by using tetrakis(acetonitrile)copper tetrafluoroborate catalyst and iron polypyridine complex catalyst, can reduce the reaction temperature for the formation of bischlorosulfonyl imide to 60°C (compared to existing catalysts); and reduce the reaction temperature for bisfluorosulfonyl imide to 85°C (compared to existing catalysts). Comparison of Example 1 with Examples 5 to 7 shows that Examples 5 to 7 use other copper complex catalysts and iron complex catalysts, which have poor catalytic effects. Furthermore, the Lewis acid catalyst used in Comparative Example 1, at the lower temperature set in Example 1, exhibits a significantly lower yield than that of Example 1.

[0079] Other embodiments of the present invention will readily occur to those skilled in the art after considering the specification and practicing the disclosure disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein.

Claims

1. A method for continuously preparing lithium bis(fluorosulfonyl)imide, characterized in that: The following steps are involved: Step 1: Chlorosulfonic acid reacts with chlorosulfonyl isocyanate in the presence of a copper complex catalyst to generate bischlorosulfonyl imide; Step 2: introducing hydrogen fluoride gas into the bischlorosulfonyl imide produced in step 1 to obtain bisfluorosulfonyl imide under the action of an iron complex catalyst; Step 3: adding a lithium salt to an organic solvent, and adding the bisfluorosulfonyl imide obtained in step 2 during stirring to obtain the product, the lithium bisfluorosulfonyl imide; Wherein, the copper complex catalyst is Cu(NCMe)4BF4, and the iron complex catalyst is an iron polypyridine complex; The iron polypyridine complex catalyst is prepared by dissolving 12.75 g of ferric nitrate in 120 mL of ethanol solution, then adding 21.36 g of 2,2':6',2"-terpyridine thereto, and dropwise adding 3 mol / L NaOH solution under stirring until a dark yellow precipitate is precipitated, until the dark yellow precipitate no longer increases, collecting the precipitate by filtration, washing with acetone, and drying to obtain the iron polypyridine complex.

2. The method for continuously preparing lithium bis(fluorosulfonyl)imide according to claim 1, wherein: In the copper complex catalyst and the iron complex catalyst, the molar ratio of copper atoms to iron atoms is 1:(0.75-1.5).

3. The method for continuously preparing lithium bis(fluorosulfonyl)imide according to claim 1, wherein: The lithium salt is at least one of LiCl and Li2O, LiOH, LiHCO3 and Li2CO3.

4. The method for continuously preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The organic solvent is any one of dichloromethane, dichloroethane, n-hexane, cyclohexane, toluene, xylene, ethyl acetate, methyl acetate, propyl acetate, ethyl ether, propyl ether, isopropyl ether or butyl ether.

5. The method for continuously preparing lithium bis(fluorosulfonyl)imide according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Add a copper complex catalyst and chlorosulfonic acid to a synthesis reactor that has been dried and replaced with inert gas, then slowly add chlorosulfonyl isocyanate to the synthesis reactor under an inert gas environment, and react at 55-65° C. for 3-6 hours to generate an intermediate product containing bischlorosulfonyl imide; Step 2: Raise the temperature in the synthesis reactor to 80-90°C, add an iron complex catalyst, and then directly introduce hydrogen fluoride gas into the intermediate product 1 containing bischlorosulfonyl imide generated in step 1, react for 3-5 hours to obtain an intermediate product 2 containing bisfluorosulfonyl imide, and then distill to obtain bisfluorosulfonyl imide; Step 3: Add the lithium salt to the organic solvent, slowly add the bis(fluorosulfonyl)imide obtained in step 2 during stirring, maintain the temperature at 0-15°C, react for 1-3 hours, and obtain the intermediate product 3 containing lithium bis(fluorosulfonyl)imide. After filtration, separation, distillation and purification, the final product, the lithium bis(fluorosulfonyl)imide, is obtained.