A preparation method of sodium bis(fluorosulfonyl)imide

Abstract

The invention discloses a method for preparing sodium bisfluorosulfonyl imide, in particular to a method for preparing sodium bisfluorosulfonyl imide by directly reacting an organic ammonium salt of bisfluorosulfonyl imide as a reaction raw material with an alkaline sodium reagent, belonging to the technical field of chemical synthesis and sodium ion batteries. The method is characterized in that in a polar solvent, the organic ammonium salt of bisfluorosulfonyl imide as a reaction raw material is directly reacted with an alkaline sodium reagent to obtain sodium bisfluorosulfonyl imide. The invention provides a method for preparing sodium bisfluorosulfonyl imide, wherein the reaction raw material is easily available, safe, easy to operate, the product has good purity, high yield, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to a method for preparing sodium bisfluorosulfonyl imide, in particular to a method for preparing sodium bisfluorosulfonyl imide by directly reacting trialkylammonium salt of bisfluorosulfonyl imide as a reaction raw material with an alkaline sodium reagent, and belongs to the technical field of chemical synthesis and sodium ion battery. Background Art

[0002] Sodium-ion battery, similar to lithium-ion battery, is a secondary battery that transfers charge by moving sodium ions between the positive and negative electrodes. Lithium-ion batteries are widely used in electronic products, electric vehicles, aerospace, military products, and renewable energy storage due to their high energy density, no memory effect, high operating voltage, wide operating temperature range, high number of cycles, and environmental friendliness. However, lithium resources are scarce, with the abundance of lithium resources in the earth's crust being only 0.0065%. According to the current rate of lithium resource consumption, the lithium resource reserves on Earth are estimated to last only about 65 years (J.-Y. Hwang, S.-T. Myung, Y.-K. Sun, Chem. Soc. Rev. 2017, 46, 3529-3614.). In addition, the geographical distribution of lithium resources is extremely uneven. China's lithium resource reserves account for less than 10% to 6% of the world's lithium resources, but the total amount of lithium materials processed in China reaches about 10% to 60%, of which more than 90% of lithium resources are imported. It is not difficult to understand that scarce lithium resources will become a bottleneck problem that hinders the sustainable and healthy development of my country's new energy lithium-ion batteries.

[0003] The abundance of sodium resources in the earth's crust reaches 2.75%, which is more than 420 times that of lithium resources, and its geographical distribution is relatively uniform. At the same time, the extraction of sodium resources is much easier than the corresponding extraction of lithium resources. Therefore, the production cost of sodium resources is much cheaper than that of lithium resources, which means that there is basically no material resource constraint problem for sodium-ion batteries! Since the mass and volume of sodium ions are larger than those of lithium ions, the energy density of sodium-ion batteries is relatively low, which limits its application in many fields such as electric vehicles. However, with the continuous improvement of sodium-ion battery technology, the energy density of sodium-ion batteries continues to increase, and sodium salts have higher conductivity than lithium salts, which can reduce the concentration of electrolytes and reduce the corresponding production costs. In addition, the internal resistance of sodium-ion batteries is also higher than that of corresponding lithium-ion batteries, resulting in less heat generation and lower temperature rise in dangerous moments such as short circuits. Therefore, the battery performance of sodium-ion batteries, such as safety performance, cycle life, high and low temperature performance, and rate, is more excellent, which can significantly improve the safety of transportation and operation of battery products. At -20°C, sodium-ion batteries can still guarantee an energy efficiency of ~90%, and at -40°C, they can also achieve an energy efficiency of ~70%. As new hard carbon electrode materials break through the bottleneck of low energy density of sodium-ion batteries, the development and industrialization of sodium-ion battery technology has been significantly accelerated (Yabuuchi, N., et al. Chem. Rev. 2014, 114, 11636-11682). Its application advantages in energy storage and low-power batteries have attracted more and more attention. Sodium-ion batteries will coexist with lithium-ion batteries!

[0004] The performance of sodium salt electrolyte will directly affect many important indicators of sodium ion batteries, such as storage capacity, electrochemical performance, and safety performance. It is a key factor in determining the performance of sodium ion batteries. 4 ) and sodium hexafluorophosphate (NaPF 6 ) is the most widely used electrolyte in sodium-ion batteries. Sodium perchlorate is a strong oxidant and is prone to safety risks. Sodium hexafluorophosphate has poor thermal and chemical stability, poor low-temperature cycle efficiency, and is easily decomposed by trace amounts of water to generate corrosive hydrogen fluoride (HF) gas. These disadvantages will not only cause further decomposition and loss of the electrolyte, but will also destroy the chemical structure of the electrolyte and electrodes, leading to battery capacity decay and safety hazards, posing a huge challenge to practical applications. Developing safer, more efficient electrolytes that can be used under harsh conditions such as low and high temperatures will be the most economical and effective way to improve the chemical performance of sodium-ion batteries. Sodium bisfluorosulfonylimide (Na + FSI -)'s comprehensive electrochemical properties, including electrical conductivity, stability to heat and trace water, and low and high temperature cycle efficiency, are superior to those of the corresponding sodium hexafluorophosphate. It has been recognized by domestic and foreign industry experts as the next generation sodium ion battery electrolyte to replace sodium hexafluorophosphate electrolyte and is currently the most ideal sodium salt electrolyte with the best industrial prospects.

[0005] The NH bond of bis(fluorosulfonyl)imide links two strong electron-withdrawing groups (FSO 2 -), so bis(fluorosulfonyl)imide has strong acidity (pK a =1.28), in organic solvents, its acidity is close to that of sulfuric acid. Public literature and patents have reported that bis(fluorosulfonyl)imide can be directly reacted with sodium carbonate to prepare sodium bis(fluorosulfonyl)imide (JK Ruff, M. Lustig, Inorg. Synth. 1968, 11, 138.; JK Ruff, Inorg. Chem. 1965, 4, 1446; Zhou Zhibin, Han Hongbo, Nie Jin, et al., CN102786451A). Sodium bis(fluorosulfonyl)imide can also be prepared by reacting bis(chlorosulfonyl)imide with excess anhydrous sodium fluoride (M. Beran, J. Prihoda, Z. Anorg. Allg. Chem. 2005, 631, 55; M. Beran, et. al., Polyhedron, 2006, 25, 1292-1298 and patent M. Cernik, et al., US Patent 7253317B2, FR. Patent PCT / FR01 / 04164 and WO02 / 053494, 2001). However, the reaction raw materials required for these methods of preparing sodium bis(fluorosulfonyl) electrolyte are highly acidic, highly corrosive and difficult to obtain, and the reaction product has low purity and is difficult to purify, so it is not suitable for large-scale industrial production. Summary of the invention

[0006] The present invention aims to provide a novel method for preparing sodium bis(fluorosulfonyl)imide with good synthesis purity, high product yield, safety, environmental protection and high efficiency.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing sodium bisfluorosulfonyl imide is characterized in that: in a polar solvent, bisfluorosulfonyl imide organic ammonium salt is used as a reaction raw material and directly reacts with an alkaline sodium reagent to obtain sodium bisfluorosulfonyl imide.

[0009] The chemical reaction equation involved in the present invention is as follows:

[0010]

[0011] Further settings are:

[0012] The polar solvent is selected from any one of water, alcohols such as methanol or ethanol, nitriles such as acetonitrile or propionitrile, ketones such as acetone or 2-butanone, esters such as dimethyl carbonate, diethyl carbonate, ethyl acetate, etc., ethers such as tetrahydrofuran, methyl tert-butyl ether, ethylene glycol dimethyl ether, etc., or mixed solvents prepared in different proportions, preferably ethanol or acetonitrile. The mass ratio of bis(fluorosulfonyl)imide triethylammonium salt to the solvent is preferably 1:1 to 1.5.

[0013] The alkaline sodium reagent is selected from any one of sodium hydroxide, sodium acetate, sodium alcoholate such as sodium methoxide or sodium ethoxide, sodium carbonate, sodium bicarbonate, sodium oxide, sodium sulfate and the like.

[0014] The molar ratio of the bisfluorosulfonyl imide organic ammonium salt to the alkaline sodium reagent is 1:0.5-10, preferably 1:0.5-1.1.

[0015] The reaction temperature is -40 to 120°C; preferably, the reaction temperature is 0 to 60°C.

[0016] After the reaction is completed, the insoluble inorganic matter is removed, and the reaction solvent and the organic alkaline acid-binding agent are recovered by vacuum distillation, and the obtained solid is purified to obtain a white solid of sodium bis(fluorosulfonyl)imide. The vacuum distillation temperature is 50-80°C.

[0017] Preferably, the series of operation processes such as collection, purification and storage of the sodium bis(fluorosulfonyl)imide product are all completed under dry, anhydrous and oxygen-free conditions.

[0018] The bisfluorosulfonyl imide organic ammonium salt of the present invention is prepared by the following method: sulfuryl fluoride is reacted with ammonia or ammonium salt in a high-sulfonyl reactor under the action of an organic amine acid-binding agent to obtain the bisfluorosulfonyl imide organic ammonium salt.

[0019] In order to save costs and be suitable for industrial production, the present invention also provides a bisfluorosulfonyl imide organic ammonium salt prepared using sulfuryl fluoride as a starting material, which can be purified by simple water washing, or can be directly used to prepare anhydrous bisfluorosulfonyl imide sodium salt, as follows:

[0020] A method for preparing sodium bis(fluorosulfonyl)imide, characterized in that it comprises the following steps:

[0021] (1) using sulfuryl fluoride and ammonia gas or ammonium salt as reaction raw materials, reacting in the presence of a non-protonic polar solvent and an organic alkaline acid-binding agent, removing insoluble inorganic matter after the reaction is completed, and removing the reaction solvent by vacuum distillation. The obtained bisfluorosulfonyl imide organic ammonium salt is purified by simple water washing, or is directly used for the chemical reaction of preparing anhydrous bisfluorosulfonyl imide sodium salt without further purification;

[0022]

[0023] In step (1):

[0024] The aprotic solvent is any one of acetonitrile, acetone, esters such as dimethyl carbonate, diethyl carbonate, ethyl acetate, etc., ethers such as tetrahydrofuran, methyl tert-butyl ether, ethylene glycol dimethyl ether, etc., preferably acetonitrile.

[0025] The molar ratio of the sulfuryl fluoride, the organic alkaline acid-binding agent and the ammonium salt is 1:1-10:0.2-1, preferably 1:1.5:0.5.

[0026] The organic alkaline acid-binding agent is any one of trimethylamine, triethylamine, N,N-diisopropylethylamine, tri-n-propylamine, tri-n-butylamine, pyridine, etc., preferably triethylamine.

[0027] The ammonium salt is selected from any one of the following ammonium salts: ammonium fluoride, ammonium chloride, ammonium bromide, ammonium bisulfate, ammonium bicarbonate, and ammonium bioxalate.

[0028] The reaction temperature is 0-60°C, preferably 10-30°C.

[0029] (2) dissolving the organic ammonium salt of bis(fluorosulfonyl)imide prepared in step (1) in water or a polar organic solvent, and directly reacting it with an alkaline sodium reagent. After the reaction is completed, removing the insoluble inorganic matter, and removing the reaction solvent by vacuum distillation to obtain a white solid product of sodium bis(fluorosulfonyl)imide.

[0030]

[0031] The reaction conditions of step (2) are as shown above.

[0032] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0033] 1. The present invention provides a method for preparing sodium salt of bis(fluorosulfonyl)imide, which has readily available reaction raw materials, is safe, easy to operate, has good product purity, high yield, and is suitable for large-scale industrial production.

[0034] 2. The present invention avoids the reaction step of generating a strongly acidic bis(fluorosulfonyl)imide intermediate by acidification, does not use strongly acidic materials such as chlorosulfonic acid, fluorosulfonic acid or concentrated sulfuric acid, has the advantages of high reaction safety, easy operation, and no stringent equipment requirements, and is suitable for green industrial production.

[0035] 3. The raw materials of the present invention are easily available, and the main reaction raw material ammonium salt can be added to the reaction system in the form of a simple powder solid or a solution with an accurate concentration, thereby avoiding the simultaneous use of multiple gas raw materials and effectively reducing the difficulty of reaction control and reaction risk.

[0036] 4. The white solid product of sodium bis(fluorosulfonyl)imide prepared by the present invention can be used for different applications without further purification, such as for preparing an electrolyte for sodium ion batteries.

[0037] The above contents disclosed in the present invention are further described in detail below through the implementation of specific embodiments, but are not limited to the following embodiments. The present invention includes various replacements or changes made according to the common technical knowledge and customary means in the above technical ideas, which should be included in the protection scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The bis(fluorosulfonyl)imide triethylammonium salt prepared by the present invention 1 HNMR spectrum.

[0039] Figure 2 The bis(fluorosulfonyl)imide triethylammonium salt prepared by the present invention 19 FNMR spectrum.

[0040] Figure 3 The sodium salt of bis(fluorosulfonyl)imide prepared by the present invention 19 FNMR spectrum. DETAILED DESCRIPTION

[0041] In the following examples, the bis(fluorosulfonyl)imide organic ammonium salt was prepared by the following method:

[0042] Under nitrogen atmosphere, add 9.3 g of ammonium fluoride to a 250 mL autoclave, control the temperature to 10°C, pump in 75.5 g of triethylamine and 60.0 g of acetonitrile, stir for 0.5 hour, control the temperature to 10°C and slowly introduce 51.0 g of sulfuryl fluoride gas, keep the temperature at 10°C for 4 hours, and terminate the reaction. The reaction solution was distilled under reduced pressure to recover the reaction solvent, and the concentrated solution was washed with water and dried to obtain 65.0 g of bis(fluorosulfonyl)imide triethylammonium salt, with a yield of 95% ( 1 HNMR spectrum Figure 1 Shown and 19 FNMR spectrum Figure 2 shown).

[0043] According to the above method, triethylamine is replaced by trimethylamine, tri-n-butylamine, and tripropylammonium to prepare bisfluorosulfonylimide trimethylammonium, bisfluorosulfonylimide tri-n-butylammonium, and bisfluorosulfonylimide tripropylammonium, respectively.

[0044] Example 1

[0045] In a nitrogen atmosphere, 56.4 g of triethylammonium bis(fluorosulfonyl)imide and 56.4 g of acetonitrile were added to a 250 mL three-necked reaction flask, and then 10.6 g of sodium carbonate was added, stirred and heated to 50°C until no carbon dioxide gas was generated. Insoluble inorganic matter was removed by filtration, and the reaction solution was distilled under reduced pressure at 50°C to recover the reaction solvent, to obtain 39.8 g of white solid, with a yield of 98.0% and a purity of 99.9%. The impurities were mainly 0.07% aminosulfonic acid and 0.03% fluorosulfonic acid.

[0046] Product Confirmation:

[0047] The reaction product was tested by LC / MS and the molecular weight (m / e) of the anion was 180, which was consistent with the chemical structure (II) of the bis(fluorosulfonyl)imide anion.

[0048]

[0049] The reaction product was further tested by negative ion chromatography, and the retention time and peak shape of the ion peak of the obtained product were consistent with those of the standard bis(fluorosulfonyl)imide salt. 19 FNMR spectrum Figure 3 As shown, it contains only one 51.90ppm fluorine resonance absorption peak, which is consistent with the chemical structure of sodium bis(fluorosulfonyl)sulfonate!

[0050] The reactants were tested by atomic absorption spectroscopy and the following results were obtained, proving that the reaction product was sodium salt

[0051] Serial number Test Items Test Methods Results 1 Sodium (Li, ppm) WI-24-19 126726.53 2 Lithium (Na, ppm) WI-24-16 0.08 3 Calcium (Ca, ppm) WI-24-16 1.54 4 Potassium (K, ppm) WI-24-16 2.83 5 Lead (Pb, ppm) WI-24-16 0.16 6 Iron (Fe, ppm) WI-24-16 0.56 7 Copper (Cu, ppm) WI-24-16 0.20 8 Zinc (Zn, ppm) WI-24-16 2.15 9 Magnesium (Mg, ppm) WI-24-16 0.14 10 Chromium (Cr, ppm) WI-24-16 0.05 11 Nickel (Ni, ppm) WI-24-16 ND 12 Manganese (Mn, ppm) WI-24-16 0.03 13 Barium, (Ba, ppm) WI-24-16 ND 14 Cadmium (Cd, ppm) WI-24-16 0.03 15 Aluminum (Al, ppm) WI-24-16 0.14 .

[0052] Replacement examples 1-1 to 1-7:

[0053] The preparation method is the same as that of Example 1, except that the reaction temperature and the type of sodium reagent are adjusted, and their effects on the yield and purity of the product are tested.

[0054] Table 1:

[0055] Serial number Sodium reagent type Reaction temperature Yield / % purity / % Aminosulfonic acid / % Fluorosulfonic acid / % Replacement Example 1-1 Sodium hydroxide 0 94.2 99.9 0.05 0.05 Replacement Example 1-2 Sodium oxide 10 94.8 99.9 0.05 0.05 Replacement Example 1-3 Sodium ethoxide -5 95.8 99.9 0.03 0.07 Replacement Example 1-4 Sodium carbonate 20 91.8 99.8 0.12 0.08 Replacement Example 1-5 Sodium carbonate 40 97.8 99.9 0.04 0.06 Replacement Example 1-6 Sodium carbonate 60 97.8 99.9 0.05 0.05 Replacement Example 1-7 Sodium carbonate 80 85.3 92.8 5.76 1.44 Replacement Example 1-8 Sodium carbonate 120 72.5 89.3 7.11 3.59

[0056] As shown in Table 1:

[0057] 1. The decomposition of the product increases with the increase of reaction temperature. Tests show that the by-products are mainly aminosulfonic acid and fluorosulfonic acid.

[0058] 2. Different alkaline sodium reagents have different optimal reaction temperatures. From the data in Table 1, the best alkaline sodium reagent should be sodium carbonate. When this sodium reagent is used, when the temperature exceeds 60°C, the product will accelerate decomposition, and when the temperature is too low, the yield will decrease. Therefore, the optimal temperature of the reaction should be 40°C to 60°C.

[0059] Replacement examples 1-9 to 1-15:

[0060] The preparation method is the same as that of Example 1, except that the amount of alkaline sodium reagent is adjusted, and its effect on the yield and purity of the product is tested.

[0061] Table 2:

[0062]

[0063] As shown in Table 2: when sodium carbonate is selected as the alkaline sodium reagent, the product yield and purity are optimal when the molar ratio of bis(fluorosulfonyl)imide triethylammonium salt to sodium carbonate is 1:0.5.

[0064] Replacement examples 1-16 to 1-22:

[0065] The preparation method is the same as that of Example 1, except that the reaction solvent and its amount are adjusted, and their effects on the yield and purity of the product are tested.

[0066] Table 3:

[0067]

[0068] As shown in Table 3:

[0069] 1. As shown in replacement examples 1-16 to 1-18, the amount of reaction solvent used has a significant negative impact when the mass ratio is lower than 1:1, and the product yield and purity are both reduced. When the mass ratio is higher than 1:1, there is no significant effect.

[0070] 2. As shown in replacement examples 1-19 to 1-23, different types of reaction solvents have different effects on product yield and purity, among which lipid solvents have a particularly significant effect on purity, and the best solvent is acetonitrile.

[0071] Replacement examples 1-24 to 1-29:

[0072] The preparation method is the same as that of Example 1, except that the vacuum distillation temperature is adjusted and its effect on the yield and purity of the product is tested.

[0073] Table 4:

[0074] Serial number Vacuum distillation Yield / % purity / % Aminosulfonic acid / % Fluorosulfonic acid / % Replacement Example 1-25 Vacuum distillation temperature 50℃ 98.0 99.9 0.07 0.03 Replacement Example 1-26 Vacuum distillation temperature 80℃ 98.0 99.9 0.08 0.02 Replacement Example 1-27 Vacuum distillation temperature 100℃ 91.3 99.1 0.57 0.33 Replacement Example 1-28 Vacuum distillation temperature 120℃ 68.3 86.5 11.21 2.29 Replacement Example 1-29 Vacuum distillation temperature 130℃ 65.4 83.3 12.79 3.91

[0075] As shown in Table 4:

[0076] As shown in Replacement Examples 1-25 to 1-29, the optimal vacuum distillation temperature is 50-80°C. Too low a temperature is not conducive to removing the reaction solvent and the acid binding agent, while too high a temperature will cause partial decomposition of the product.

Claims

1. A method for preparing sodium bis(fluorosulfonyl)imide, characterized in that , including the following steps: (1) Using sulfuryl fluoride and ammonia gas or ammonium salt as reaction materials, reacting in the presence of a non-protonic polar solvent and an organic alkaline acid-binding agent, removing insoluble inorganic matter after the reaction is completed, and removing the reaction solvent by vacuum distillation. The obtained bisfluorosulfonyl imide organic ammonium salt is purified by simple water washing, or is directly used in the chemical reaction of preparing anhydrous bisfluorosulfonyl imide sodium salt without further purification; (2) dissolving the organic ammonium salt of bis(fluorosulfonyl)imide prepared in step (1) in water or a polar organic solvent, and directly reacting it with an alkaline sodium reagent. After the reaction is completed, removing the insoluble inorganic matter, and removing the reaction solvent by vacuum distillation to obtain a white solid product of sodium bis(fluorosulfonyl)imide; In step (2): The polar solvent is ethanol or acetonitrile, and the mass ratio of bis(fluorosulfonyl)imide triethylammonium salt to the polar solvent is 1:1-1.5; The molar ratio of the bisfluorosulfonyl imide organic ammonium salt to the alkaline sodium reagent is 1:0.5; The alkaline sodium reagent is sodium carbonate; The reaction temperature is 50°C; After the reaction is completed, the insoluble inorganic matter is removed, and the reaction solvent and the organic alkaline acid-binding agent are recovered by vacuum distillation. The obtained solid is purified to obtain a white solid of sodium bis(fluorosulfonyl)imide, and the vacuum distillation temperature is 50-80°C.

2. The method for preparing sodium bis(fluorosulfonyl)imide according to claim 1, characterized in that: In step (1), the aprotic polar solvent is any one of acetonitrile, acetone, dimethyl carbonate, diethyl carbonate, ethyl acetate, tetrahydrofuran, methyl tert-butyl ether, and ethylene glycol dimethyl ether; the molar ratio of sulfuryl fluoride, organic alkaline acid binding agent, and ammonium salt is 1:1-10:0.2-1; the organic alkaline acid binding agent is trimethylamine, triethylamine, N,N - any one of diisopropylethylamine, tri-n-propylamine, tri-n-butylamine, and pyridine; the ammonium salt is selected from any one of the following ammonium salts: ammonium fluoride, ammonium chloride, ammonium bromide, ammonium hydrogen sulfate, ammonium hydrogen carbonate, and ammonium hydrogen oxalate; the reaction temperature is 0 to 60°C.

3. A method for preparing sodium bis(fluorosulfonyl)imide according to claim 1, characterized in that: In step (1), the aprotic polar solvent is acetonitrile, the molar ratio of sulfuryl fluoride, organic alkaline acid binding agent and ammonium salt is 1:1.5:0.5, the organic alkaline acid binding agent is triethylamine, the ammonium salt is ammonium fluoride, and the reaction temperature is 10-30°C.

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