Method for continuously preparing lithium bis (fluorosulfonyl) imide

Abstract

The invention relates to the technical field of preparation methods of lithium bis (fluorosulfonyl) imide, in particular to a method for continuously preparing lithium bis (fluorosulfonyl) imide, which comprises the following steps: reacting chlorosulfonic acid with chlorosulfonyl isocyanate under the action of a copper complex catalyst to generate bis (fluorosulfonyl) imide; the method comprises the following steps: introducing hydrogen fluoride gas into bis (chlorosulfonyl) imide, and obtaining bis (fluorosulfonyl) imide under the action of an iron complex catalyst; the preparation method comprises the following steps: adding lithium salt into an organic solvent, and adding imidodisulfuryl fluoride in a stirring process to obtain the product imidodisulfuryl fluoride lithium. According to the method, a reaction container does not need to be replaced in different steps, an intermediate product does not need to be separated and purified and then put into the next step of reaction, the product is obtained through direct continuous reaction, and the high yield is kept; in addition, due to the introduction of the copper complex catalyst and the iron complex catalyst, the temperature required by the reaction is further reduced, and the safety of the reaction process is improved while the energy is saved.

Description

Technical Field

[0001] The 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] With the rapid and high-quality development of the lithium-ion battery industry, higher requirements are placed on the safety and energy density of electrolytes. As a new type of electrolyte solute, lithium bis(fluorosulfonyl)imide (LiFSI) has better thermal stability and higher conductivity than traditional lithium hexafluorophosphate (LiPF6). Therefore, whether as a main salt additive or a core solute, LiFSI is likely to become the best substitute for LiPF6.

[0003] At present, the main LiFSI preparation technologies reported at home and abroad are as follows: (1) Using synthesized dichlorobenzene to directly react with LiF to prepare LiFSI will produce a large amount of corrosive gas HF. 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 sulfuryl chloride and other intermediates 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, which poses 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 mentioned above in the 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: Step 1: Chlorosulfonic acid and chlorosulfonyl isocyanate react under the action of a copper complex catalyst to generate bischlorosulfonyl imide; Step 2: introducing hydrogen fluoride gas into the bischlorosulfonyl imide generated in step 1 to obtain bisfluorosulfonyl imide under the action of an iron complex catalyst; Step 3: Add lithium salt into an organic solvent, and add the bisfluorosulfonyl imide obtained in step 2 during stirring to obtain the product of the lithium bisfluorosulfonyl imide.

[0006] 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.

[0007] In one aspect of the embodiments of the present invention, the iron complex catalyst is an iron porphyrin complex or an iron polypyridine complex.

[0008] In one aspect of the embodiments 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).

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

[0010] 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.

[0011] In one aspect of the embodiments of the present invention, the lithium salt is at least one of LiCl and Li2O, LiOH, LiHCO3 and Li2CO3.

[0012] 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.

[0013] In one aspect of an embodiment of the present invention, a method for continuously preparing lithium bis(fluorosulfonyl)imide comprises the following steps: Step 1: Add a copper complex catalyst and chlorosulfonic acid to a synthesis reactor that has been dried and replaced with an 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 1 containing bischlorosulfonyl imide; Step 2: raising the temperature in the synthesis reactor to 80-90° C., directly introducing hydrogen fluoride gas into the intermediate product 1 containing bischlorosulfonyl imide generated in step 1, reacting for 3-5 hours to obtain an intermediate product 2 containing bisfluorosulfonyl imide, and distilling to obtain bisfluorosulfonyl imide; Step 3: Add lithium salt to an organic solvent, slowly add the bis(fluorosulfonyl)imide obtained in step 2 during stirring, maintain the temperature at 0-15°C, react for 1-3h, and obtain an intermediate product 3 containing lithium bis(fluorosulfonyl)imide. After filtering, separating, distilling and purifying, the final product, the lithium bis(fluorosulfonyl)imide, is obtained.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention does not need to replace the reaction container in different steps, nor does it need to separate and purify the intermediate product before putting it into the next step of reaction. Instead, the product is directly obtained by continuous reaction and a high yield is maintained. In addition, the introduction of the copper complex catalyst and the iron complex catalyst further reduces the temperature required for the reaction, saves energy and improves the safety of the reaction process.

[0015] 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

[0016] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. The relevant 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.

[0017] For simplicity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0018] In this article, the terms "comprises", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device that includes the element.

[0019] In the description herein, unless otherwise specified, “above” and “below” include the number.

[0020] Unless otherwise specified, the terms used in the present invention have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in the present invention can be measured by various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of the present invention).

[0021] 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 range of variation 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 a range format is for convenience and simplicity, 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.

[0022] In the present invention, "slowly adding" may refer to adding dropwise, or adding the reactants in multiple batches in a manner that does not suddenly change the state of the reaction system or induce a violent reaction.

[0023] A list of items connected by the term "at least one of" or other similar terms may 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 may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0024] In the present invention, the iron polypyridine complex catalyst is prepared by the following method: 12.75 g of ferric nitrate is dissolved in 120 mL of ethanol solution, and then 21.36 g of 2,2':6',2"-terpyridine (CAS No. 1148-79-4) is added thereto, and 3 mol / L of NaOH solution is added successively under stirring until a dark yellow precipitate is precipitated, until the dark yellow precipitate no longer increases, the precipitate is collected by filtration, and after washing with acetone and drying, an iron polypyridine complex [Fe(tpy)(OH2)2] is obtained. 2+ (tpy=2,2':6',2''-terpyridine).

[0025] The present invention will be further described below in conjunction with the examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0026] Embodiment 1 The following steps are involved: Step 1: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.5g of tetra(acetonitrile)copper tetrafluoroborate (commercially available), add it to the synthesis reactor that has been dried and replaced with nitrogen, and then add the aforementioned chlorosulfonic acid and dichloroethane, keep 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 completed, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide; Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 85°C, and an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) 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 fraction of bis(fluorosulfonyl)imide; Step 3: Weigh 12.7g LiCl and 15.3g Li2CO3, add them to 150mL dichloromethane, stir to form a uniform suspension, keep stirring and control the temperature to 4°C, then add the bis(fluorosulfonyl)imide obtained in step 2 dropwise to carry out the 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 finally obtain a white anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculation, the yield of Example 1 is 92.5% based on chlorosulfonic acid.

[0027] Embodiment 2 The following steps are involved: Step 1: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.5g of tetra(acetonitrile)copper tetrafluoroborate (commercially available), add it to the synthesis reactor that has been dried and replaced with nitrogen, and then add the aforementioned chlorosulfonic acid and dichloroethane, keep 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 completed, react at 75°C for 8h to generate an intermediate product containing bischlorosulfonyl imide; Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 100° C., and an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) 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 fraction of bis(fluorosulfonyl)imide; Step 3: Weigh 12.7g LiCl and 15.3g Li2CO3, add them to 150mL dichloromethane, stir to form a uniform suspension, keep stirring and control the temperature to 4°C, then add the bis(fluorosulfonyl)imide obtained in step 2 dropwise to carry out the 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 finally obtain a white anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculation, the yield of Example 2 is 91.1% based on chlorosulfonic acid.

[0028] Embodiment 3 The following steps are involved: Step 1: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.5g of tetra(acetonitrile)copper tetrafluoroborate (commercially available), add it to the synthesis reactor that has been dried and replaced with nitrogen, and then add the aforementioned chlorosulfonic acid and dichloroethane, keep 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 completed, react at 105°C for 8h to generate an intermediate product containing bischlorosulfonyl imide; 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, 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, and 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 fraction of bis(fluorosulfonyl)imide; Step 3: Weigh 12.7g LiCl and 15.3g Li2CO3, add them to 150mL dichloromethane, stir to form a uniform suspension, keep stirring and control the temperature to 4°C, then add the bis(fluorosulfonyl)imide obtained in step 2 dropwise to carry out the 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 finally obtain a white anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculation, the yield of Example 3 is 89.5% based on chlorosulfonic acid.

[0029] Embodiment 4 The following steps are involved: Step 1: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.5g of tetra(acetonitrile)copper tetrafluoroborate (commercially available), add it to a synthesis reactor that has been dried and replaced with nitrogen, and then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), and slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 50°C for 8h to generate an intermediate product containing bischlorosulfonyl imide; Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 75°C, and an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) 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 fraction of bis(fluorosulfonyl)imide; Step 3: Weigh 12.7g LiCl and 15.3g Li2CO3, add them to 150mL dichloromethane, stir to form a uniform suspension, keep stirring and control the temperature to 4°C, then add the bis(fluorosulfonyl)imide obtained in step 2 dropwise to carry out the 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 finally obtain a white anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculation, the yield of Example 4 is 83.1% based on chlorosulfonic acid.

[0030] Embodiment 5 The following steps are involved: Step 1: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.5g of Cu-TMEDA catalyst (commercially available), add it to the synthesis reactor that has been dried and replaced with nitrogen, and then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), and slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide; Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 85°C, and an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) 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 fraction of bis(fluorosulfonyl)imide; Step 3: Weigh 12.7g LiCl and 15.3g Li2CO3, add them to 150mL dichloromethane, stir to form a uniform suspension, keep stirring and control the temperature to 4°C, then add the bis(fluorosulfonyl)imide obtained in step 2 dropwise to carry out the 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 finally obtain a white anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculation, the yield of Example 5 is 26.3% based on chlorosulfonic acid.

[0031] Embodiment 6 The following steps are involved: Step 1: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.5g of bis(tert-butylacetoacetate)copper(II) catalyst (commercially available), add it to the synthesis reactor that has been dried and replaced with nitrogen, and then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), and slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide; Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 85°C, and an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) 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 fraction of bis(fluorosulfonyl)imide; Step 3: Weigh 12.7g LiCl and 15.3g Li2CO3, add them to 150mL dichloromethane, stir to form a uniform suspension, keep stirring and control the temperature to 4°C, then add the bis(fluorosulfonyl)imide obtained in step 2 dropwise to carry out the 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 finally obtain a white anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculation, the yield of Example 6 is 21.5% based on chlorosulfonic acid.

[0032] Embodiment 7 The following steps are involved: Step 1: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.5g of bromotri(triphenylphosphine)copper(I) catalyst (commercially available), add it to a synthesis reactor that has been dried and replaced with nitrogen, and then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), and slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide; Step 2: After the reaction in step 1 is completed, the temperature in the synthesis reactor is raised to 85°C, and an iron polypyridine complex catalyst (1.75 g, the preparation process is as described above) 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 fraction of bis(fluorosulfonyl)imide; Step 3: Weigh 12.7g LiCl and 15.3g Li2CO3, add them to 150mL dichloromethane, stir to form a uniform suspension, keep stirring and control the temperature to 4°C, then add the bis(fluorosulfonyl)imide obtained in step 2 dropwise to carry out the 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 finally obtain a white anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculation, the yield of Example 7 is 18.9% based on chlorosulfonic acid.

[0033] Embodiment 8 The following steps are involved: Step 1: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.5g of tetra(acetonitrile)copper tetrafluoroborate (commercially available), add it to the synthesis reactor that has been dried and replaced with nitrogen, and then add the aforementioned chlorosulfonic acid and dichloroethane, keep 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 completed, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide; 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 fraction of bis(fluorosulfonyl)imide; Step 3: Weigh 12.7g LiCl and 15.3g Li2CO3, add them to 150mL dichloromethane, stir to form a uniform suspension, keep stirring and control the temperature to 4°C, then add the bis(fluorosulfonyl)imide obtained in step 2 dropwise to carry out the 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 finally obtain a white anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculation, the yield of Example 8 is 35.9% based on chlorosulfonic acid.

[0034] Comparative Example 1 The following steps are involved: Step 1: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.5g of cupric chloride catalyst (commercially available), add it to the synthesis reactor that has been dried and replaced with nitrogen, and then add the aforementioned chlorosulfonic acid and dichloroethane, keep 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 completed, react at 60°C for 8h to generate an intermediate product containing bischlorosulfonyl imide; 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 raised, 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, and 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 fraction of bis(fluorosulfonyl)imide; Step 3: Weigh 12.7g LiCl and 15.3g Li2CO3, add them to 150mL dichloromethane, stir to form a uniform suspension, keep stirring and control the temperature to 4°C, then add the bis(fluorosulfonyl)imide obtained in step 2 dropwise to carry out the 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 finally obtain a white anhydrous lithium bis(fluorosulfonyl)imide (LiFSI) solid product. After weighing and calculation, the yield of comparative example 1 is 68.8% based on chlorosulfonic acid.

[0035] It can be seen from Examples 1 to 4 that the present invention can reduce the reaction temperature of generating bischlorosulfonyl imide to 60°C (compared with the existing catalyst) by using tetrafluoroborate tetra(acetonitrile) copper catalyst and iron polypyridine complex catalyst; and reduce the reaction temperature of bisfluorosulfonyl imide to 85°C (compared with the existing catalyst). By comparing Example 1 with Examples 5 to 7, it can be seen that Examples 5 to 7 use other copper complex catalysts and iron complex catalysts, and their catalytic effects are poor; and the Lewis acid catalyst used in Comparative Example 1 has a large difference in yield compared with Example 1 at the lower temperature set in Example 1.

[0036] Those skilled in the art will readily appreciate other embodiments of the present invention 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 present invention and include common knowledge or customary technical means in the art that are not disclosed by the present invention.

Claims

1. A method for continuously preparing lithium bis(fluorosulfonyl)imide, characterized in that: The following steps are involved: Step 1: Chlorosulfonic acid and chlorosulfonyl isocyanate react under the action of a copper complex catalyst to generate bischlorosulfonyl imide; Step 2: introducing hydrogen fluoride gas into the bischlorosulfonyl imide generated in step 1 to obtain bisfluorosulfonyl imide under the action of an iron complex catalyst; Step 3: Add lithium salt into an organic solvent, and add the bisfluorosulfonyl imide obtained in step 2 during stirring to obtain the product of the lithium bisfluorosulfonyl imide.

2. The method for continuously preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The copper complex catalyst is Cu(NCMe)4BF4, Cu(NCMe)4PF6 or Cu(OAc)2.

3. The method for continuously preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The iron complex catalyst is an iron porphyrin complex or an iron polypyridine complex.

4. The method for continuously preparing lithium bis(fluorosulfonyl)imide according to claim 2 or 3, characterized in that: 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).

5. The method for continuously preparing lithium bis(fluorosulfonyl)imide according to claim 2, characterized in that: The copper complex catalyst is Cu(NCMe)4BF4.

6. The method for continuously preparing lithium bis(fluorosulfonyl)imide according to claim 3, characterized in that: 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.

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

8. 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.

9. The method for continuously preparing lithium bis(fluorosulfonyl)imide according to any one of claims 1 to 8, 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 an 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 1 containing bischlorosulfonyl imide; Step 2: raising the temperature in the synthesis reactor to 80-90° C., adding an iron complex catalyst, and then directly introducing hydrogen fluoride gas into the intermediate product 1 containing bischlorosulfonyl imide generated in step 1, reacting for 3-5 hours to obtain an intermediate product 2 containing bisfluorosulfonyl imide, and distilling to obtain bisfluorosulfonyl imide; Step 3: Add lithium salt to an organic solvent, slowly add the bis(fluorosulfonyl)imide obtained in step 2 during stirring, maintain the temperature at 0-15°C, react for 1-3h, and obtain an intermediate product 3 containing lithium bis(fluorosulfonyl)imide. After filtering, separating, distilling and purifying, the final product, the lithium bis(fluorosulfonyl)imide, is obtained.