Method for preparing imidodisulfuryl fluoride lithium salt by one-pot method

Abstract

The invention discloses a method for preparing bis (fluorosulfonyl) imide lithium salt by a one-pot method. The preparation method comprises the following steps: mixing sulfuryl fluoride, ammonium fluoride, lithium hydroxide (lithium carbonate) and specific amine according to a certain proportion, synthesizing bis (fluorosulfonyl) imide lithium salt in an organic solvent, and then carrying out solid-liquid separation and purification to obtain the high-purity bis (fluorosulfonyl) imide lithium salt. The preparation method comprises the following steps: sequentially adding ammonium fluoride, organic amine and lithium hydroxide (lithium carbonate) under the condition of shielding gas, and stirring and reacting at a proper temperature; the method is simple to operate and is carried out in one reactor. The reaction conditions are mild, and the use of dangerous chemicals in the traditional method is avoided. The core of the invention is innovation of the synthesis method. The method is simpler to operate, and the reaction process is safer and more green.

Description

Technical Field

[0001] The invention relates to a method for preparing lithium bis(fluorosulfonyl)imide. The method can obtain lithium bis(fluorosulfonyl)imide in a one-pot process, has simpler operation, and a safer and greener reaction process. Background Art

[0002] Lithium salts, as a key component of lithium battery electrolytes, significantly influence the electrochemical properties of the electrolyte. Compared to traditional lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide (LiS2S2) offers high thermal stability, excellent electrochemical stability, high ionic conductivity, good compatibility with electrode materials, hydrolysis resistance, environmental friendliness, and long cycle life. It is a promising electrolyte lithium salt and a promising alternative to lithium hexafluorophosphate.

[0003] The current synthesis method of LiFSI is mainly divided into two steps: the first step is to synthesize bisfluorosulfonyl imide (HFSI) or bisfluorosulfonyl imide salt; the second step is to prepare lithium bisfluorosulfonyl imide through lithium exchange reaction.

[0004] U.S. Patents US8337797 and US9156692 disclose the use of urea and fluorosulfonic acid to react to prepare bisfluorosulfonyl imide. However, the fluorosulfonic acid used in this method and the bisfluorosulfonyl imide produced are both extremely acidic and corrosive, which results in relatively high requirements for the reactor. U.S. Patents US8377406, US4315935 and Chinese Patents CN101747242, CN102917979, CN103391896, etc. use chlorosulfonic acid, thionyl chloride and chlorosulfonyl isocyanate or aminosulfonic acid to react to obtain bischlorosulfonyl imide, which is then fluorinated with fluorination reagents such as potassium fluoride and hydrogen fluoride to obtain bisfluorosulfonyl imide. However, this method has many operating steps, and the catalysts and other chemicals used therein are difficult to remove cleanly, which will affect the final electrolyte effect.

[0005] Some patents also report the introduction of dehydration agents such as thionyl chloride and acid anhydride after lithiation, but the dehydration time is too long and the acid anhydride is difficult to remove.

[0006] Chinese patent CN110217764A discloses a method for preparing an organic alkaline salt of bisfluorosulfonyl imide, comprising reacting ammonia with sulfuryl fluoride in an organic solvent in the presence of an organic base, completely dissolving the resulting reaction mixture with a low-boiling-point ether solvent, washing the organic phase with water, and then distilling the resulting organic alkaline salt under reduced pressure to obtain the organic alkaline salt of bisfluorosulfonyl imide. However, this method uses ammonia gas and requires purification of the intermediate organic salt of bisfluorosulfonyl imide.

[0007] In order to overcome the defects of the existing LiFSI preparation method, such as harsh process conditions, inconvenient operation, and inability to effectively control impurity ions, a simple method for preparing lithium bis(fluorosulfonyl)imide is urgently needed in the field. Summary of the Invention

[0008] To address the shortcomings of the prior art, the present invention provides a one-pot method for preparing lithium bis(fluorosulfonyl)imide, which can avoid the introduction of impurity ions, obtain lithium bis(fluorosulfonyl)imide through simple operations, and is also relatively simple to purify.

[0009] The technical solution of the present invention is as follows

[0010] A lithium salt of bis(fluorosulfonyl)imide, characterized by having the following structure

[0011]

[0012] According to the present invention, the above-mentioned preparation method of lithium bis(fluorosulfonyl)imide comprises the following steps:

[0013] An ammonium salt is added to the reactor, and then the gas atmosphere in the reactor is replaced with an inert protective gas, an organic base and an organic solvent are added, and sulfuryl fluoride is introduced; after stirring for reaction, a lithium source is added for reaction; after the reaction is completed, the insoluble solid is filtered, and after removing the solvent, a poor solvent is added to the concentrated solution for crystallization to obtain a lithium salt of bis(fluorosulfonyl)imide.

[0014] The ammonium salt is one or more of ammonium fluoride, ammonium chloride, ammonium bromide, and ammonium bicarbonate; the concentration of the ammonium salt in the organic solvent is 15-25 mg / ml, preferably 18-23 mg / ml, and more preferably 20-22 mg / ml.

[0015] This reaction requires one or more of nitrogen or an inert gas (such as argon) as an inert protective gas.

[0016] The molar ratio of sulfuryl fluoride to ammonium salt is 2-2.5:1, preferably 2-2.3:1, and more preferably 2-2.2:1.

[0017] The molar ratio of the organic base to the ammonium salt is 2-3.5:1, preferably 2.8-3.2:1, more preferably 3-3.2:1;

[0018] The organic base is selected from trimethylamine, triethylamine, diisopropylethylamine, tri-n-propylamine, tributylamine, or N,N,N,N-tetramethylpropylenediamine, and another example is N,N,N,N-tetramethylpropylenediamine or triethylamine, 4-N,N-dimethylaminopyridine, pyridine or a mixture of two or more thereof.

[0019] The reaction temperature before adding the lithium source is 10-40°C, preferably 20-30°C, more preferably 25-28°C;

[0020] The reaction time is 3-7 hours, preferably 3-5 hours, more preferably 4-5 hours.

[0021] After adding the lithium source, the reaction temperature is 10-40°C, preferably 20-30°C, more preferably 25-28°C, and the reaction time is 2-4h, preferably 2.5-3.5h, more preferably 3-3.2h.

[0022] The molar ratio of the lithium source to the ammonium salt is 1-1.5:1, preferably 1-1.3:1, more preferably 1-1.2:1, and the lithium source is lithium hydroxide.

[0023] The organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0024] The temperature during the process of removing the solvent by distillation under reduced pressure is 40-60°C;

[0025] The poor solvent is dichloromethane, and the volume ratio of dichloromethane to the concentrated liquid is 1-5:1, preferably 2-3:1, and more preferably 2-2.5:1.

[0026] Preferably:

[0027] 1. Add ammonium fluoride into the reactor, replace the gas atmosphere in the reactor with protective gas, and then add organic base in sequence.

[0028] Organic solvent.

[0029] The preferred shielding gas is nitrogen.

[0030] The preferred organic base is triethylamine.

[0031] The preferred organic solvent is N,N-dimethylformamide.

[0032] 2. Stir at a suitable temperature for 30 minutes, then add sulfuryl fluoride.

[0033] The preferred temperature is 20-30°C

[0034] 3. Add lithium hydroxide into the reactor and stir to react.

[0035] 4. After the reaction is completed, filter the insoluble solid, remove the solvent by vacuum distillation at 50°C, and add dichloromethane to the concentrate.

[0036] The solid is precipitated and vacuum dried to obtain high-purity lithium bis(fluorosulfonyl)imide.

[0037] The reaction equation of the present invention is

[0038]

[0039] The beneficial effects of this application include:

[0040] 1. Compared with other reported reactions, the use of hazardous chemicals is reduced and the reaction process is greener.

[0041] 2. The method of the present invention has mild reaction conditions and low requirements for the reactor.

[0042] 3. The preparation method of the present invention has simple process, simple operation, easy to realize industrial production, and reduces costs.

[0043] This method is simple to operate and is carried out in a single reactor. The reaction conditions are mild and the use of hazardous chemicals in traditional methods is avoided. The core of this invention is an innovation in the synthesis method. This method is simpler to operate and the reaction process is safer and more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 LC-MS mass spectrum of lithium bis(fluorosulfonyl)imide. DETAILED DESCRIPTION

[0045] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0046] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0047] Example 1

[0048] 1. Add ammonium fluoride (102.6 mg, 2.77 mmol) into the reactor, replace the gas atmosphere in the reactor with nitrogen, and then add triethylamine (1.2 ml, 8.61 mmol) and N,N-dimethylformamide (5 ml, 64.83 mmol) in sequence;

[0049] 2. Stir at 25°C for 30 min to mix thoroughly, then add sulfuryl fluoride (6 mmol).

[0050] 3. After reacting for 5 h, lithium hydroxide (67 mg, 2.8 mmol) was added into the reactor, and then the gas atmosphere was replaced with nitrogen, and the reaction was stirred at 25° C. for 3 h.

[0051] 4. After the reaction is complete, filter the insoluble solids, remove the solvent by vacuum distillation at 50°C, add dichloromethane (twice the volume of the concentrate) to the concentrate to precipitate the solids, filter the solids, and then vacuum dry the solids to obtain high-purity lithium bis(fluorosulfonyl)imide. The yield is 95.6% and the purity is 99.6%.

[0052] 5. The reaction product was tested by LC-MC and its anion molecular weight was determined to be 180, which is consistent with the anion chemical structure of the target product lithium bis(fluorosulfonyl)imide. Figure 1

[0053] 6. The reaction product showed a single peak at 51 ppm by nuclear magnetic resonance (NMR) fluorine spectrum and a single peak at 0.16 ppm by lithium spectrum, consistent with the chemical structure reported in the literature and the standard sample. The structure of the reaction product was confirmed by LC-MS and NMR, confirming it to be lithium bis(fluorosulfonyl)imide. The yield and purity of the reaction product were calculated using NMR. (19F NMR (376 MHz, ACETONITRILE-D3) δ 51.17.7 Li NMR (155 MHz, ACETONITRILE-D3) δ 0.16.)

[0054] The lithium bis(fluorosulfonyl)imide salt has the following structure:

[0055]

[0056] Example 2

[0057] 1. Add ammonium fluoride (103.1 mg, 2.78 mmol) into the reactor, replace the gas atmosphere in the reactor with nitrogen, and then add triethylamine (1.2 ml, 8.61 mmol) and acetonitrile (5 ml, 96 mmol) in sequence.

[0058] 2. Stir at 25°C for 30 min, then add sulfuryl fluoride (6 mmol); react for 5 h;

[0059] 3. The reaction solution was distilled at 50°C to remove the solvent, and then 20 ml of water was added to wash the concentrate to obtain a white solid, which was identified as bis(fluorosulfonyl)imide triethylamine salt by nuclear magnetic resonance.

[0060] 4. Purified triethylammonium bis(fluorosulfonyl)imide (760 mg, 2.6 mmol) and lithium hydroxide (67 mg, 2.8 mmol) were added into the reactor, and then the gas atmosphere was replaced with nitrogen, and the reaction was stirred for 3 h.

[0061] 5. After the reaction is completed, the insoluble solid is filtered, and the solvent is removed by reduced pressure distillation at 50°C. Dichloromethane in an amount twice the volume of the concentrate is added to the concentrate to precipitate the solid, which is then filtered and vacuum dried to obtain high-purity lithium bis(fluorosulfonyl)imide. The reaction product is lithium bis(fluorosulfonyl)imide as determined by LC-MS and NMR, with a calculated yield of 80.5%.

[0062] The purity is 98.9%.

[0063] Example 3

[0064] The experimental process and conditions of the preparation method are the same as those of Example 1, except that the reaction solvent is adjusted and its effect on the product yield is tested, as shown in Table 1.

[0065] Table 1. Effect of different reaction solvents on reaction yield

[0066]

[0067] Example 4

[0068] The experimental process and conditions of the preparation method are the same as those of Example 1, except that the reaction temperature is adjusted and its effect on the product yield is detected, as shown in Table 2.

[0069] Table 2. Effect of different reaction temperatures on reaction yield

[0070] Serial number temperature time LiFSI yield purity Example 4-1 -10℃ 5h 71.1％ 99.4％ Example 4-2 10℃ 10h 73.8％ 98.2％ Example 4-3 15℃ 5h 92.6％ 97.9％ Example 4-4 10℃ 5h 89.7％ 99.0％ Examples 4-5 40℃ 5h 85.2％ 98.6％ Examples 4-6 50℃ 5h 79.5％ 98.3％ Examples 4-7 80℃ 5h 46.3％ 99.8％ Examples 4-8 25℃ 1h 45.9％ 99.4％ Examples 4-9 25℃ 10h 75.2％ 99.1％

[0071] High temperature and long reaction time will lead to the formation of by-products, thus reducing the yield. In Example 4-2, too long reaction time will lead to the formation of a large amount of by-products.

[0072] Example 5

[0073] The experimental process and conditions of the preparation method are the same as those of Example 1, except that the amount of ammonium fluoride added (2.8 mmol) is fixed, the ammonium fluoride, sulfuryl fluoride, triethylammonium, and lithium hydroxide are adjusted, and their effects on the product yield are detected, as shown in Table 3.

[0074] Table 3. Effect of adjusting ammonium fluoride, sulfuryl fluoride, triethylamine, and lithium hydroxide on reaction yield

[0075]

[0076]

[0077] After experiments, it was found that excess sulfuryl fluoride and lithium hydroxide had little effect on the reaction, but excess triethylamine would affect the lithiation process, making it difficult to convert the intermediate product into LiFSI.

[0078] Example 6

[0079] The experimental process and conditions of the preparation method are the same as those of Example 1, except that the selection and dosage of the ammonium salt are different, and the effect of the ammonium salt on the product yield is detected, as shown in Table 4.

[0080] Table 4. Effect of different ammonium salts on reaction yield

[0081] Serial number ammonium salt Dosage LiFSI yield purity Example 6-1 Ammonium chloride 2.77mmol 89.2％ 97.7％ Example 6-2 Ammonium bromide 2.77mmol 94.8％ 95.2％ Example 6-3 ammonium bicarbonate 2.77mmol 88.7％ 96.9％

[0082] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A one-pot method for preparing lithium bis(fluorosulfonyl)imide salt, characterized in that: The lithium bis(fluorosulfonyl)imide salt has the following structure: The one-pot preparation comprises the following steps: An ammonium salt is added to the reactor, and then the gas atmosphere in the reactor is replaced with an inert protective gas, an organic base and an organic solvent are added, and sulfuryl fluoride is introduced; after stirring for reaction, a lithium source is added for reaction; after the reaction is completed, the insoluble solid is filtered, and after removing the solvent, a poor solvent is added to the concentrated solution for crystallization to obtain a lithium salt of bis(fluorosulfonyl)imide.

2. The method according to claim 1, characterized in that The ammonium salt is one or more of ammonium fluoride, ammonium chloride, ammonium bromide, and ammonium bicarbonate; the concentration of the ammonium salt in the organic solvent is 15-25 mg / ml, preferably 18-23 mg / ml, and more preferably 20-22 mg / ml.

3. The method according to claim 1, characterized in that This reaction requires one or more of nitrogen or an inert gas (such as argon) as an inert protective gas.

4. The method according to claim 1, wherein The molar ratio of sulfuryl fluoride to ammonium salt is 2-2.5:1, preferably 2-2.3:1, and more preferably 2-2.2:

1.

5. The method according to claim 1, wherein The molar ratio of the organic base to the ammonium salt is 2-3.5:1, preferably 2.8-3.2:1, more preferably 3-3.2:1; The organic base is selected from trimethylamine, triethylamine, diisopropylethylamine, tri-n-propylamine, tributylamine, or N,N,N,N-tetramethylpropylenediamine, and another example is N,N,N,N-tetramethylpropylenediamine or triethylamine, 4-N,N-dimethylaminopyridine, pyridine or a mixture of two or more thereof.

6. The method according to claim 1, wherein The reaction temperature before adding the lithium source is 10-40°C, preferably 20-30°C, more preferably 25-28°C; The reaction time is 3-7 hours, preferably 3-5 hours, more preferably 4-5 hours.

7. The method according to claim 1, characterized in that After adding the lithium source, the reaction temperature is 10-40°C, preferably 20-30°C, more preferably 25-28°C, and the reaction time is 2-4h, preferably 2.5-3.5h, more preferably 3-3.2h.

8. The method according to claim 1, characterized in that The molar ratio of the lithium source to the ammonium salt is 1-1.5:1, preferably 1-1.3:1, more preferably 1-1.2:1, and the lithium source is lithium hydroxide.

9. The method according to claim 1, characterized in that The organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

10. The method according to claim 1, characterized in that The temperature during the process of removing the solvent by distillation under reduced pressure is 40-60°C; The poor solvent is dichloromethane, and the volume ratio of dichloromethane to the concentrated liquid is 1-5:1, preferably 2-3:1, and more preferably 2-2.5:1.

Images