Preparation method of lithium bis (fluorosulfonyl) imide

Abstract

The invention belongs to the technical field of preparation of lithium bis (fluorosulfonyl) imide, and particularly relates to a preparation method of lithium bis (fluorosulfonyl) imide, which comprises the following steps: step 1, reacting chlorosulfonic acid with chlorosulfonyl isocyanate under the action of a first catalyst to generate bis (fluorosulfonyl) imide; 2, hydrogen fluoride gas is introduced into the bis (chlorosulfonyl) imide generated in the step 1, and bis (fluorosulfonyl) imide is obtained under the action of a first catalyst; and 3, adding a first lithium salt into an organic solvent, adding the imidodisulfuryl fluoride obtained in the step 2 in the stirring process, and carrying out ion exchange to obtain the lithium imidodisulfuryl fluoride. According to the invention, the conversion rate is high, the usage amount of the catalyst is reduced, the steps are simplified, and the yield is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of lithium bis(fluorosulfonyl)imide, and specifically relates to a preparation method of 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 the electrolyte. 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, a large amount of corrosive gas HF will be produced. 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(fluorosulfonyl)amide, and finally performing a lithiation reaction to obtain lithium bis(fluorosulfonyl)amide. Most of the ammonia in this method is liquid or gas, which cannot be accurately measured in industrialization, and will generate unnecessary by-products. In addition, the lithium salt solution used in the lithiation reaction is super 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 easy to decompose in the aqueous solution, and the introduction of water makes desolventization and drying very difficult. Summary of the invention

[0004] The present invention provides a method for preparing lithium bis(fluorosulfonyl)imide to solve the defects pointed out in the above background technology.

[0005] According to a first aspect of an embodiment of the present invention, a method for preparing lithium bis(fluorosulfonyl)imide is provided, comprising the following steps: Step 1: Chlorosulfonic acid and chlorosulfonyl isocyanate react under the action of a first 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 a first catalyst; Step 3: adding the first lithium salt into an organic solvent, and adding the bisfluorosulfonyl imide obtained in step 2 during stirring to obtain the bisfluorosulfonyl imide lithium.

[0006] In one aspect of an embodiment of the present invention, the first catalyst includes a second catalyst and a third catalyst; the second catalyst is BCl3, and the third catalyst is any one of BeCl2, MgCl2, CaCl2 or SrCl2.

[0007] In one aspect of the embodiment of the present invention, the mass of the first catalyst is 1.5%-3.0% of the mass of the chlorosulfonic acid.

[0008] In one aspect of an embodiment of the present invention, the first catalyst includes BCl3 and BeCl2.

[0009] In another aspect of the embodiments of the present invention, the first catalyst includes BCl3 and MgCl2.

[0010] In another aspect of the embodiments of the present invention, the first catalyst includes BCl3 and CaCl2.

[0011] In one aspect of the embodiment of the present invention, the molar ratio of the second catalyst to the third catalyst is 1:(0.1-0.4).

[0012] In one aspect of the embodiment of the present invention, the molar ratio of the second catalyst to the third catalyst is 1:(0.2-0.35).

[0013] In one aspect of the embodiments of the present invention, the third catalyst is SrCl2.

[0014] In one aspect of the embodiment of the present invention, the second catalyst is BCl3; and the molar ratio of the second catalyst to the third catalyst is 1:(0.22-0.28).

[0015] In one aspect of the embodiments of the present invention, the first lithium salt includes a second lithium salt and a third lithium salt; the second lithium salt is LiCl, and the third lithium salt is at least one of Li2O, LiOH, LiHCO3 and Li2CO3.

[0016] In one aspect of the embodiments of the present invention, the first lithium salt includes a second lithium salt and a third lithium salt; the second lithium salt is LiCl, and the third lithium salt is at least one of Li2O, LiOH, LiHCO3 and Li2CO3; and, based on the total mass of the first lithium salt, the mass percentage of LiCl is 25%-55%.

[0017] In one aspect of the embodiments of the present invention, the first lithium salt includes a second lithium salt and a third lithium salt; the second lithium salt is LiCl, and the third lithium salt is any one of Li2O, LiOH, LiHCO3 or Li2CO3.

[0018] In one aspect of the embodiments of the present invention, the first lithium salt includes a second lithium salt and a third lithium salt; the second lithium salt is LiCl, and the third lithium salt is Li2CO3.

[0019] 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.

[0020] In one aspect of the embodiments of the present invention, the preparation method provided by the present invention comprises the following steps: Step 1a: adding a first catalyst and chlorosulfonic acid to a synthesis reactor that has been dried and replaced with an inert gas, and then slowly adding chlorosulfonyl isocyanate to the synthesis reactor under an inert gas environment, reacting at 85° C.-125° C. for 6-10 hours to generate a product containing bischlorosulfonyl imide; Step 2a: maintaining the temperature in the synthesis reactor at 95° C.-115° C., directly introducing hydrogen fluoride gas into the product containing bischlorosulfonyl imide generated in step 1a, reacting for 4-7 hours to obtain a product containing bisfluorosulfonyl imide, and distilling to obtain bisfluorosulfonyl imide; Step 3a: Add the first lithium salt to an organic solvent, slowly add the bis(fluorosulfonyl)imide obtained in step 2a during stirring, maintain the temperature at 0°C-15°C, react for 1-3h, obtain a product containing lithium bis(fluorosulfonyl)imide, and finally obtain the lithium bis(fluorosulfonyl)imide after filtering, separation, distillation and purification.

[0021] In one aspect of the embodiments of the present invention, the preparation method provided by the present invention comprises the following steps: Step 1b: adding the first catalyst and chlorosulfonic acid to the synthesis reaction kettle after being dried and replaced by inert gas, and then slowly adding the chlorosulfonyl isocyanate to the synthesis reaction kettle under an inert gas environment, reacting at 105° C. for 8 hours to generate a product containing bischlorosulfonyl imide; Step 2b: maintaining the temperature in the synthesis reactor at 105° C., directly introducing hydrogen fluoride gas into the product containing bischlorosulfonyl imide generated in step 1b, reacting for 5 hours to obtain a product containing bisfluorosulfonyl imide, and distilling to obtain bisfluorosulfonyl imide; Step 3b: Add the first lithium salt to an organic solvent, slowly add the bis(fluorosulfonyl)imide obtained in step 2b during stirring, maintain the temperature at 4° C., react for 2 hours, and obtain a product containing lithium bis(fluorosulfonyl)imide. After filtering, separation, distillation and purification, the lithium bis(fluorosulfonyl)imide is finally obtained.

[0022] In some embodiments of the present invention, step 1 further comprises ethylene dichloride as an organic solvent.

[0023] In one aspect of the embodiment of the present invention, in step 1, the inert gas is nitrogen.

[0024] In one aspect of the embodiment of the present invention, in step 1, the molar ratio of chlorosulfonic acid to chlorosulfonyl isocyanate is 1:(1.05-1.15).

[0025] In one aspect of the embodiment of the present invention, in step 1a, the molar ratio of chlorosulfonic acid to chlorosulfonyl isocyanate is 1:(1.05-1.15).

[0026] In one aspect of the embodiment of the present invention, in step 1b, the molar ratio of chlorosulfonic acid to chlorosulfonyl isocyanate is 1:(1.05-1.15).

[0027] In one aspect of the embodiment of the present invention, in step 2, the molar ratio of chlorosulfonic acid added in step 1 to hydrogen fluoride is 1:(1.15-1.25).

[0028] In one aspect of the embodiment of the present invention, in step 2a, the molar ratio of chlorosulfonic acid added in step 1 to hydrogen fluoride is 1:(1.15-1.25).

[0029] In one aspect of the embodiment of the present invention, in step 2b, the molar ratio of chlorosulfonic acid added in step 1 to hydrogen fluoride is 1:(1.15-1.25).

[0030] In one aspect of the embodiment of the present invention, in step 3, the molar ratio of the lithium element in the first lithium salt to bis(fluorosulfonyl)imide is 1:(0.55-0.95).

[0031] In one aspect of the embodiment of the present invention, in step 3a, the molar ratio of the lithium element in the first lithium salt to bis(fluorosulfonyl)imide is 1:(0.55-0.95).

[0032] In one aspect of the embodiment of the present invention, in step 3b, the molar ratio of the lithium element in the first lithium salt to bis(fluorosulfonyl)imide is 1:(0.8-0.95).

[0033] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses chlorosulfonic acid and chlorosulfonyl isocyanate as raw materials, uses a mixture of BCl3 and one of BeCl2, MgCl2, CaCl2 or SrCl2 as a catalyst, and prepares lithium bis(fluorosulfonyl)imide with a high conversion rate. In terms of chlorosulfonic acid, the conversion rates of step 1 and step 2 of the present invention are both 95% or more, and the overall conversion rate is also 85% or more; and, step 1 and step 2 of the present invention use the same catalyst, and there is no need to go through a separation process in the middle, which not only reduces the amount of catalyst used, but also simplifies the steps and further improves the yield.

[0034] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. DETAILED DESCRIPTION

[0035] 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.

[0036] 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.

[0037] 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.

[0038] In the description herein, unless otherwise specified, “above” and “below” include the number.

[0039] 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).

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The method provided by the present invention comprises the following steps: Step 1: Chlorosulfonic acid and chlorosulfonyl isocyanate react under the action of a first 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 a first catalyst; Step 3: adding the first lithium salt into an organic solvent, and adding the bisfluorosulfonyl imide obtained in step 2 during stirring to obtain the bisfluorosulfonyl imide lithium.

[0044] Specifically, the steps include: Step 1a: adding the first catalyst and chlorosulfonic acid to a synthesis reactor that has been dried and replaced with an inert gas, and then slowly adding chlorosulfonyl isocyanate to the synthesis reactor under an inert gas environment, reacting at 85° C.-125° C. for 6-10 hours to generate a product containing bischlorosulfonyl imide; Step 2a: maintaining the temperature in the synthesis reactor at 95° C.-115° C., directly introducing hydrogen fluoride gas into the product containing bischlorosulfonyl imide generated in step 1a, reacting for 4-7 hours to obtain a product containing bisfluorosulfonyl imide, and distilling to obtain bisfluorosulfonyl imide; Step 3a: Add the first lithium salt to an organic solvent, slowly add the bis(fluorosulfonyl)imide obtained in step 2a during stirring, maintain the temperature at 0°C-15°C, react for 1-3h, obtain a product containing lithium bis(fluorosulfonyl)imide, and finally obtain lithium bis(fluorosulfonyl)imide after filtering, separation, distillation and purification.

[0045] In the present invention, the chemical reaction formula of step 1 is as follows:

[0046] In some embodiments of the present invention, in step 1, the molar ratio of chlorosulfonic acid to chlorosulfonyl isocyanate is 1:(1.05-1.15); specifically, the molar ratio of chlorosulfonic acid to chlorosulfonyl isocyanate is 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09, 1:1.10, 1:1.11, 1:1.12, 1:1.13, 1:1.14 or 1:1.15; preferably, the molar ratio of chlorosulfonic acid to chlorosulfonyl isocyanate is 1:1.10.

[0047] In some embodiments of the present invention, in step 1, the mass of the first catalyst is 1.5%-3.0% of the mass of chlorosulfonic acid; specifically, the mass of the first catalyst is 1.5%, 2.0%, 2.2%, 2.5%, 2.7% or 3.0% of the mass of chlorosulfonic acid; preferably, the mass of the first catalyst is 2.0% of the mass of chlorosulfonic acid.

[0048] In some embodiments of the present invention, in step 1, the first catalyst includes a second catalyst and a third catalyst; the second catalyst is BCl3, and the second catalyst acts as a main catalyst; the third catalyst is one of BeCl2, MgCl2, CaCl2 or SrCl2, and the second catalyst acts as an auxiliary catalyst.

[0049] In some embodiments of the present invention, the molar ratio of the second catalyst to the third catalyst is 1:(0.1-0.4); specifically, the molar ratio of the second catalyst to the third catalyst is 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35 or 1:0.4; preferably, the molar ratio of the second catalyst to the third catalyst is 1:(0.2-0.35).

[0050] In some embodiments of the present invention, in step 1, the reaction temperature of step 1 is 85°C-125°C; specifically, the reaction temperature of step 1 is 85°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C or 125°C; preferably, the reaction temperature of step 1 is 105°C.

[0051] In some embodiments of the present invention, in step 1, the reaction time of step 1 is 6-10 h, specifically, the reaction time of step 1 is 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h or 10 h; preferably, the reaction time of step 1 is 8 h.

[0052] In some embodiments of the present invention, step 1 further comprises ethylene dichloride as an organic solvent.

[0053] In the present invention, the chemical reaction formula of step 2 is as follows:

[0054] In some embodiments of the present invention, in step 2, the molar ratio of chlorosulfonic acid added in step 1 to hydrogen fluoride is 1:(1.15-1.25); specifically, the molar ratio of chlorosulfonic acid added in step 1 to hydrogen fluoride is 1:1.15, 1:1.16, 1:1.17, 1:1.18, 1:1.19, 1:1.20, 1:1.21, 1:1.22, 1:1.23, 1:1.24 or 1:1.25; preferably, the molar ratio of chlorosulfonic acid added in step 1 to hydrogen fluoride is 1:1.20.

[0055] In some embodiments of the present invention, in step 2, the reaction temperature of step 2 is 95°C-115°C; specifically, the reaction temperature of step 2 is 95°C, 100°C, 105°C, 110°C or 115°C; preferably, the reaction temperature of step 2 is 105°C.

[0056] In some embodiments of the present invention, in step 2, the reaction time of step 2 is 4-7 h, specifically, the reaction time of step 2 is 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h or 7 h; preferably, the reaction time of step 2 is 5 h.

[0057] In the present invention, the chemical reaction formula of step 3 is as follows:

[0058] In some embodiments of the present invention, in step 3, LiM comprises LiCl and at least one of Li2O, LiOH, LiHCO3 and Li2CO3, wherein the mass percentage of LiCl accounts for 25%-55% of the mass of LiM.

[0059] In some embodiments of the present invention, in step 3, the molar ratio of lithium element in LiM to bis(fluorosulfonyl)imide is 1:(0.55-0.95); specifically, the molar ratio of lithium element to bis(fluorosulfonyl)imide is 1:0.8, 1:0.85, 1:0.9 or 1:0.95.

[0060] In some embodiments of the present invention, in step 3, the role of LiCl is to provide a lithium source while removing the water inevitably contained in the reaction system.

[0061] In some embodiments of the present invention, the reaction temperature of step 3 is 0°C-15°C; specifically, the reaction temperature of step 3 is 0°C, 4°C, 10°C or 15°C; preferably, the reaction temperature of step 3 is 4°C.

[0062] In some embodiments of the present invention, the reaction time of step 3 is 1-3 h, specifically, the reaction time of step 3 is 1 h, 1.5 h, 2 h, 2.5 h or 3 h; preferably, the reaction time of step 3 is 2 h.

[0063] In some embodiments of the present invention, step 3 is carried out in an organic solvent, and the organic solvent is any one of dichloromethane, dichloroethane, n-hexane, cyclohexane, toluene, xylene, ethyl acetate, methyl acetate, propyl acetate, diethyl ether, propyl ether, isopropyl ether or butyl ether. Preferably, the organic solvent is dichloromethane.

[0064] 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.

[0065] Embodiment 1 The following steps are involved: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.4g of BCl3 and 0.2g of BeCl2, add them to the synthesis reactor after nitrogen drying and replacement, then add the above-mentioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h to generate a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculation, the yield of Example 1 is 98.3% based on chlorosulfonic acid.

[0066] Embodiment 2 The following steps are involved: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.0g of BCl3 and 0.6g of BeCl2, add them to the synthesis reactor after nitrogen drying and displacement, then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h to generate a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculating, the yield of Example 2 is 91.4% based on chlorosulfonic acid.

[0067] Embodiment 3 The following steps are involved: 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 BCl3 and 0.1g of BeCl2, add them to the synthesis reactor after nitrogen drying and replacement, then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h to generate a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculation, the yield of Example 3 is 97.5% based on chlorosulfonic acid.

[0068] Embodiment 4 The following steps are involved: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.3g of BCl3 and 0.3g of MgCl2, add them to the synthesis reactor after nitrogen drying and replacement, then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h to generate a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculating, the yield of Example 4 is 89.5% based on chlorosulfonic acid.

[0069] Embodiment 5 The following steps are involved: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.0g of BCl3 and 0.6g of MgCl2, add them to the synthesis reactor after nitrogen drying and replacement, then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h to generate a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculating, the yield of Example 5 is 82.2% based on chlorosulfonic acid.

[0070] Embodiment 6 The following steps are involved: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.3g of BCl3 and 0.3g of CaCl2, add them to the synthesis reactor after nitrogen drying and replacement, then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h to generate a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculating, the yield of Example 6 is 85.5% based on chlorosulfonic acid.

[0071] Embodiment 7 The following steps are involved: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.2g of BCl3 and 0.4g of SrCl2, add them to the synthesis reactor after nitrogen drying and replacement, then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h to generate a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculation, the yield of Example 7 is 97.6% based on chlorosulfonic acid.

[0072] Embodiment 8 The following steps are involved: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.0g of BCl3 and 0.6g of SrCl2, add them to the synthesis reactor after nitrogen drying and replacement, then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h to generate a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculating, the yield of Example 8 is 95.6% based on chlorosulfonic acid.

[0073] Embodiment 9 The following steps are involved: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.4g of BCl3 and 0.2g of SrCl2, add them to the synthesis reactor after nitrogen drying and replacement, then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h to generate a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculation, the yield of Example 9 is 96.1% based on chlorosulfonic acid.

[0074] Comparative Example 1 The following steps are involved: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.4g of BCl3, add it to the synthesis reactor after nitrogen drying and replacement, then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h; obtain a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculation, the yield of comparative example 1 is 81.2% based on chlorosulfonic acid.

[0075] Comparative Example 2 The following steps are involved: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.6g of SrCl2, add it to the synthesis reactor after nitrogen drying and replacement, then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h to generate a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculation, the yield of comparative example 2 is 59.6% based on chlorosulfonic acid.

[0076] Comparative Example 3 The following steps are involved: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.6g of BeCl2, add it to the synthesis reactor after nitrogen drying and displacement, then add the aforementioned chlorosulfonic acid and dichloroethane, keep stirring and nitrogen protection; then weigh 77.84g of chlorosulfonyl isocyanate (48mL), slowly drop it into the synthesis reactor; after the dropwise addition is completed, react at 105°C for 8h to generate a product containing bischlorosulfonyl imide; after the reaction is completed, distill at 115°C-125°C to obtain pure bischlorosulfonyl imide. After weighing and calculation, the yield of comparative example 3 is 62.5% based on chlorosulfonic acid.

[0077] By comparing Examples 1 to 9 with Comparative Examples 1 to 3, it can be seen that the yield of preparing bischlorosulfonyl imide in Comparative Example 1 using only BCl3 as a catalyst is not as good as that in Examples 1 to 9 with the addition of an auxiliary catalyst (BeCl2, MgCl2, CaCl2, SrCl2); and the yield of preparing bischlorosulfonyl imide in Comparative Examples 2 and 3 using only an auxiliary catalyst is significantly poor. By comparing Examples 4 to 6 with Examples 1 to 3 and Examples 7 to 9, it can be seen that the yield of bischlorosulfonyl imide in the Examples using MgCl2 or CaCl2 as an auxiliary catalyst is not as good as that in the Examples using BeCl2 or SrCl2 as an auxiliary catalyst.

[0078] Embodiment 10 Embodiment 10 uses the catalyst ratio of embodiment 1, comprising the following steps: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.4g of BCl3 and 0.2g of BeCl2, add them 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 a product containing bischlorosulfonyl imide; After the reaction is completed, the temperature is kept at 105°C, and HF gas is directly 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 fraction of bis(fluorosulfonyl)imide. After weighing and calculation, the yield of Example 10 is 84.3% based on chlorosulfonic acid.

[0079] Embodiment 11 Example 11 uses the catalyst ratio of Example 3, and includes the following steps: 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 BCl3 and 0.1g of BeCl2, add them 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 a product containing bischlorosulfonyl imide; After the reaction is completed, the temperature is kept at 105°C, and HF gas is directly introduced into the synthesis reactor. The molar amount of HF gas is 1.2 times the molar amount of chlorosulfonic acid. The reaction is continued 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. After weighing and calculation, the yield of Example 11 is 83.9% based on chlorosulfonic acid.

[0080] Embodiment 12 Example 12 uses the catalyst ratio of Example 7, comprising the following steps: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.2g of BCl3 and 0.4g of SrCl2, add them 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 a product containing bischlorosulfonyl imide; After the reaction is completed, the temperature is kept at 105°C, and HF gas is directly 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 fraction of bis(fluorosulfonyl)imide. After weighing and calculation, the yield of Example 12 is 93.7% based on chlorosulfonic acid.

[0081] Embodiment 13 Example 13 uses the catalyst ratio of Example 9, comprising the following steps: Weigh 58g of chlorosulfonic acid (33mL), mix it with 100mL of dichloroethane, and place it in a sealed container after mixing; then weigh 1.4g of BCl3 and 0.2g of SrCl2, add them 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 a product containing bischlorosulfonyl imide; After the reaction is completed, the temperature is kept constant at 105°C, and HF gas is directly 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 fraction of bis(fluorosulfonyl)imide. After weighing and calculation, the yield of Example 13 is 90.6% based on chlorosulfonic acid.

[0082] It can be seen that although the yield of preparing bischlorosulfonyl imide in the embodiment using BeCl2 as an auxiliary catalyst is higher, the yield of preparing bisfluorosulfonyl imide is not as good as that in the embodiment using SrCl2 as an auxiliary catalyst.

[0083] Embodiment 14 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 1.2g of BCl3 and 0.4g of SrCl2, add them 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 a product containing bischlorosulfonyl imide; Step 2: After the reaction is completed, the temperature is maintained at 105°C, and HF gas is directly 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 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 bisfluorosulfonyl 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 (obtained after concentration and crystallization) to finally obtain a white anhydrous lithium bisfluorosulfonyl imide (LiFSI) solid product. After weighing and calculation, the yield of Example 14 is 90.3% based on chlorosulfonic acid.

[0084] 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 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 first catalyst to generate bischlorosulfonyl imide; the first catalyst includes a second catalyst and a third catalyst; the second catalyst is BCl3, and the third catalyst is any one of BeCl2, MgCl2, CaCl2 or SrCl2; Step 2: introducing hydrogen fluoride gas into the bischlorosulfonyl imide produced in step 1 to obtain bisfluorosulfonyl imide under the action of a first catalyst; Step 3: adding the first lithium salt into an organic solvent, and adding the bisfluorosulfonyl imide obtained in step 2 during stirring to obtain the bisfluorosulfonyl imide lithium.

2. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The molar ratio of the second catalyst to the third catalyst is 1:(0.1-0.4).

3. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 2, characterized in that: The molar ratio of the second catalyst to the third catalyst is 1:(0.2-0.35).

4. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The third catalyst is SrCl2.

5. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The second catalyst is BCl3; and the molar ratio of the second catalyst to the third catalyst is 1:(0.22-0.28).

6. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The first lithium salt includes a second lithium salt and a third lithium salt; the second lithium salt is LiCl, and the third lithium salt is at least one of Li2O, LiOH, LiHCO3 and Li2CO3.

7. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 6, 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.

8. The method for preparing lithium bis(fluorosulfonyl)imide according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1a: adding a first catalyst and chlorosulfonic acid to a synthesis reactor that has been dried and replaced with an inert gas, and then slowly adding chlorosulfonyl isocyanate to the synthesis reactor under an inert gas environment, reacting at 85° C.-125° C. for 6-10 hours to generate a product containing bischlorosulfonyl imide; Step 2a: maintaining the temperature in the synthesis reactor at 95° C.-115° C., directly introducing hydrogen fluoride gas into the product containing bischlorosulfonyl imide generated in step 1a, reacting for 4-7 hours to obtain a product containing bisfluorosulfonyl imide, and distilling to obtain bisfluorosulfonyl imide; Step 3a: adding the first lithium salt to an organic solvent, slowly adding the bis(fluorosulfonyl)imide obtained in step 2a during stirring, maintaining the temperature at 0°C-15°C, reacting to obtain a product containing lithium bis(fluorosulfonyl)imide, and finally obtaining the lithium bis(fluorosulfonyl)imide after filtering, separation, distillation and purification.

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