Method for preparing lithium bis (fluorosulfonyl) imide through series connection method

Abstract

The invention discloses a method for preparing lithium bis (fluorosulfonyl) imide by a series method, which comprises the following steps: by taking sulfuryl chloride and potassium fluoride as raw materials, firstly carrying out fluorine-chlorine exchange in an aprotic polar solvent, then generating ammonium salt of bis (fluorosulfonyl) imide with ammonia gas under the action of a metal oxide or a non-metal oxide, removing gas in a reaction system, and finally obtaining the lithium bis (fluorosulfonyl) imide. And reacting with a metal lithium compound to prepare the lithium bis (fluorosulfonyl) imide. The method has the advantages of cheap and easily available raw materials, low cost, simple preparation process, low equipment requirements, mild reaction conditions and safe operation. A one-pot cascade reaction is adopted in the reaction process, so that a safe and environment-friendly green preparation technology is achieved, and side reaction caused by decomposition of bisulfimide is avoided; the post-treatment is simple, the yield of the target product is high, and the problem that moisture, chloride ions and sulfate ions in the product exceed the standard is solved.

Description

Technical Field

[0001] The invention relates to a method for preparing lithium bis(fluorosulfonyl)imide, in particular to a method for preparing lithium bis(fluorosulfonyl)imide from sulfuryl chloride. Background Art

[0002] Lithium bis(fluorosulfonyl)imide is a new type of electrolyte lithium salt in lithium battery electrolyte. Compared with the traditional electrolyte lithium hexafluorophosphate, lithium ions in lithium bis(fluorosulfonyl)imide are easier to dissociate, with higher conductivity and decomposition temperature, better chemical stability, thermal stability and safety performance. In addition, it also has unique effects in improving high-temperature storage and low-temperature discharge performance, and has the characteristics of long service life, high safety and environmental friendliness. Lithium bis(fluorosulfonyl)imide is currently considered to be a new generation of lithium-ion battery electrolyte that can replace lithium hexafluorophosphate and has good development prospects.

[0003] At present, the method commonly used at home and abroad is to fluorinate bis(chlorosulfonyl)imide to obtain bis(fluorosulfonyl)imide, and then bis(fluorosulfonyl)imide is reacted with alkali metal to prepare alkali metal salt. Bis(fluorosulfonyl)imide and alkaline lithium salts such as lithium hydroxide or lithium carbonate react in a low-polarity organic solvent to produce lithium bis(fluorosulfonyl)imide and water. In this step, dichlorothionyl is added to react with water to produce hydrogen chloride and sulfur dioxide gas to achieve the purpose of removing water. However, the dichlorothionyl water removal reaction is difficult to be thorough, the reaction time is long, and there are many wastes, which easily lead to excessive water, chloride ions and sulfate ions in the product. WO 2010113835 A1 patent uses SO2F2, NH3 and Et3N (triethylamine) in a molar ratio of 2:1:3, and reacts in an acetonitrile solvent under an ice-water bath to first obtain triethylamine bis(fluorosulfonyl)imide salt, and then the triethylamine bis(fluorosulfonyl)imide salt reacts with metal hydroxide to remove triethylamine to obtain a bis(fluorosulfonyl)imide metal salt product. The triethylamine salt of bisfluorosulfonyl imide is synthesized by using cheap raw materials such as SO2F2, NH3 and Et3N, which can efficiently exchange with metal ions to obtain the metal salt of bisfluorosulfonyl imide. This patent solves the problem of excessive chloride ions, but under aqueous conditions, triethylamine will promote the hydrolysis of SO2F2 to generate triethylamine salt of fluorosulfonic acid, which makes the purification cost of this process higher. In order to solve the deficiency of product purification, the patent CN 103664712 B uses concentrated sulfuric acid to acidify the metal salt of bisfluorosulfonyl imide, and then vacuum distills to obtain a bisfluorosulfonyl imide with a purity greater than 99%, and then obtains high-purity lithium bisfluorosulfonyl imide. Since this patent uses sulfuric acid acidification and vacuum distillation to improve purity, it has high equipment requirements and high energy consumption, which is not conducive to industrialization. Patent CN102459071 A found that SO2F2 first reacts with ammonia, and then reacts with 6 times the equivalent of fluoride salt at 60°C to directly generate a metal salt of bisfluorosulfonyl imide. Another good method is to use potassium bis(fluorosulfonyl imide) salt and lithium salt to exchange in a non-protonic organic solvent to generate lithium bis(fluorosulfonyl imide). However, the reaction is incomplete, potassium ions are easily left in the product, the purity of the product is difficult to improve, and the yield is not ideal (65% to 70%). Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a new preparation method of lithium bis(fluorosulfonyl)imide, which uses sulfuryl chloride, potassium fluoride and ammonia as main raw materials and utilizes a tandem reaction to prepare lithium bis(fluorosulfonyl)imide. The method has the advantages of simple operation, mild process conditions, good product quality, low cost, etc.

[0005] In order to solve the above technical problems, the present invention discloses a method for preparing lithium bis(fluorosulfonyl)imide by a tandem process. The method uses sulfuryl chloride and potassium fluoride as raw materials, first performs fluorine-chlorine exchange in a non-protonic polar solvent, then reacts with ammonia gas under the action of a metal oxide or a non-metal oxide to generate an ammonium salt of bis(fluorosulfonyl)imide, removes the gas from the reaction system, and then reacts with a metal lithium compound to obtain lithium bis(fluorosulfonyl)imide.

[0006] Further, the method comprises the following steps,

[0007] (1) Add a non-protonic polar solvent, potassium fluoride and sulfuryl chloride into a reaction vessel, start stirring, and react at a temperature of 10 to 50° C. for 1 to 8 hours;

[0008] (2) Add metal or non-metal oxide as a catalyst, then introduce ammonia gas, maintain the pressure in the reactor at 0.1-0.5 MPa, and continue the reaction at a temperature of -10-30°C for 1-8 hours;

[0009] (3) After replacing the gas in the reaction system with nitrogen, a metallic lithium compound is added and reacted at room temperature and normal pressure for 1 to 5 hours;

[0010] (4) Filter out insoluble matter, concentrate the filtrate, dissolve it in tetrahydrofuran or 2-methyltetrahydrofuran, add activated carbon and stir it thoroughly at room temperature, generally for 30 minutes, filter to remove activated carbon and insoluble matter, concentrate the filtrate with a rotary evaporator, and dry it in vacuum to obtain the target product.

[0011] Furthermore, the non-protonic polar solvent in step (1) is one or a mixture of two or more of an ester compound, a ketone compound, a nitrile compound or an ether compound; the ester compound is one or a mixture of two or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, methyl acetate, ethyl acetate, propyl acetate or isopropyl acetate; the ketone compound is one or a mixture of two or more of acetone, methyl ethyl ketone or butanone; the nitrile compound is one or a mixture of two of acetonitrile or propionitrile; the ether compound is one or a mixture of two or more of diethyl ether, isopropyl ether, methyl tert-butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, 1,4-dioxane, tetrahydrofuran or 2-methyltetrahydrofuran.

[0012] Furthermore, the aprotic polar solvent is one or a mixture of two or more of acetonitrile, dimethyl carbonate, diethyl carbonate, acetone, methyl ethyl ketone, methyl tert-butyl ether, 1,4-dioxane, tetrahydrofuran or 2-methyltetrahydrofuran.

[0013] Furthermore, in step (2), the metal or non-metal oxide is one or a mixture of two or more of magnesium oxide, calcium oxide, barium oxide, aluminum oxide or silicon dioxide.

[0014] Furthermore, in step (2), the metal or non-metal oxide is one or a mixture of two or more of calcium oxide, silicon oxide or magnesium oxide.

[0015] Furthermore, in step (3), the metallic lithium compound is one or a mixture of two or more of lithium oxide, lithium hydroxide, lithium carbonate, lithium tetrafluoroborate, lithium perchlorate, lithium chloride, lithium bromide and lithium phosphate.

[0016] Furthermore, in step (3), the metallic lithium compound is one or a mixture of two or more of lithium hydroxide, lithium carbonate and lithium phosphate.

[0017] Furthermore, the molar ratio of sulfuryl chloride to potassium fluoride is 1: 2-5, the molar ratio of sulfuryl chloride to ammonia is 1: 2-3; the molar ratio of sulfuryl chloride to metal or non-metal oxide is 1: 0.5-1.5; the molar ratio of sulfuryl chloride to metallic lithium compound is 1: 1-3.

[0018] Furthermore, the amount of the non-protonic polar solvent used in step (1) is 50-65% of the volume of the reaction container. A sufficient amount of solvent can prevent the raw materials from becoming sticky during stirring and prevent the introduced gas from escaping from the solvent and thus hindering the reaction.

[0019] Furthermore, the amount of tetrahydrofuran or 2-methyltetrahydrofuran used in step (4) is 2 to 3 times the weight of the concentrate. A sufficient amount of solvent used can fully dissolve the product and better remove inorganic matter in the concentrate.

[0020] The beneficial effects of the present invention are as follows:

[0021] 1) The raw materials used in the present invention are cheap and readily available, the cost is low, the preparation process is simple, the equipment requirements are low, the reaction conditions are mild, and the operation is safe.

[0022] 2) A one-pot tandem reaction is used during the reaction process, achieving a safe and environmentally friendly green preparation technology and avoiding the occurrence of side reactions caused by the decomposition of bissulfonylimide;

[0023] 3) The post-processing of the present invention is simple, the yield of the target product is high, and the problem of excessive moisture, chloride ions and sulfate ions in the product is solved. DETAILED DESCRIPTION

[0024] The present invention is further explained below in conjunction with the examples. The following examples are only used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0025] Example 1

[0026] In a 1000 ml reactor, add 500 ml acetonitrile, 116 g (2 mol) of potassium fluoride, and 135 g (1 mol) of sulfuryl chloride. Start stirring at a temperature of 10°C. After reacting for 8 hours, add 24 g (0.4 mol) of silicon dioxide and 4 g (0.1 mol) of magnesium oxide, and then introduce 34 g (2 mol) of ammonia. Keep the pressure in the reactor at 0.1 MPa and continue to react at -10°C for 5 hours. After replacing the gas in the reaction system with nitrogen, add 74 g (1 mol) of lithium carbonate. React at room temperature and normal pressure for 1 hour, filter out insoluble matter, concentrate the filtrate, dissolve it with 300 ml of tetrahydrofuran, add activated carbon and stir at room temperature for 30 minutes, filter, remove activated carbon and insoluble matter, concentrate the filtrate with a rotary evaporator, and vacuum dry to obtain 169.3 g of the target product with a yield of 91%, a purity of 99.9%, and a moisture content of ≤50 ppm, SO4 2- ≤50 ppm, Cl - ≤5 ppm, F - ≤50 ppm, various metal ions are ≤5 ppm.

[0027] Example 2

[0028] In a 1000 ml reactor, add 500 ml acetonitrile, 174 g (3 mol) of potassium fluoride, and 135 g (1 mol) of sulfuryl chloride, start stirring at a temperature of 50°C, react for 1 hour, add 60 g (1 mol) of silicon dioxide, 20 g (0.5 mol) of magnesium oxide, and then introduce 51 g (3 mol) of ammonia, maintain the pressure in the reactor at 0.3 MPa, and continue to react at 0°C for 5 hours. After replacing the gas in the reaction system with nitrogen, add 37 g (0.5 mol) of lithium carbonate and 24 g (1 mol) of lithium hydroxide, react at room temperature and normal pressure for 3 hours, filter out insoluble matter, concentrate the filtrate, dissolve it with 200 ml of tetrahydrofuran, add activated carbon and stir at room temperature for 30 minutes, filter, remove activated carbon and insoluble matter, concentrate with a rotary evaporator, and vacuum dry to obtain 171.1 g of the target product with a yield of 92%, a purity of 99.9%, and a moisture content of ≤50 ppm, SO4 2- ≤50 ppm,Cl - ≤5 ppm, F - ≤50 ppm, various metal ions are ≤5 ppm.

[0029] Example 3

[0030] In a 1000 ml reactor, add 600 ml acetonitrile, 290 g (5 mol) of potassium fluoride, and 135 g (1 mol) of sulfuryl chloride. Start stirring at a temperature of 20°C. After reacting for 5 hours, add 56 g (1 mol) of calcium oxide and 20 g (0.5 mol) of magnesium oxide, and then introduce 51 g (3 mol) of ammonia. Keep the pressure in the reactor at 0.5 MPa and the temperature at 10°C and continue to react for 8 hours. After replacing the gas in the reaction system with nitrogen, add 58 g (0.5 mol) of lithium phosphate and 12 g (0.5 mol) of lithium hydroxide. React at room temperature and normal pressure for 5 hours, filter out insoluble matter, concentrate the filtrate, dissolve it with 350 ml of 2-methyltetrahydrofuran, add activated carbon and stir at room temperature for 30 minutes, filter, remove activated carbon and insoluble matter, concentrate with a rotary evaporator, and vacuum dry to obtain 167.4 g of the target product with a yield of 90%, a purity of 99.9%, and a moisture content of ≤50 ppm, SO4 2- ≤50 ppm,Cl - ≤5 ppm, F - ≤50 ppm, various metal ions are ≤5 ppm.

[0031] Example 4

[0032] In a 1000 ml reactor, add 300 ml acetonitrile, 250 ml dimethyl carbonate, 290 g potassium fluoride (5 mol), 135 g sulfuryl chloride (1 mol), start stirring at a temperature of 20°C, react for 3 hours, add 56 g calcium oxide (1 mol), 20 g magnesium oxide (0.5 mol), and then introduce 51 g ammonia (3 mol), maintain the pressure in the reactor at 0.5 MPa, and continue to react at 10°C for 6 hours. After replacing the gas in the reaction system with nitrogen, add 58 g lithium phosphate (0.5 mol) and 12 g lithium hydroxide (0.5 mol), react at room temperature and normal pressure for 2 hours, filter out insoluble matter, concentrate the filtrate, dissolve it with 250 ml tetrahydrofuran, add activated carbon and stir at room temperature for 30 minutes, filter, remove activated carbon and insoluble matter, concentrate with a rotary evaporator, and vacuum dry to obtain 173 g of the target product with a yield of 93%, a purity of 99.9%, and a moisture content of ≤50 ppm, SO4 2- ≤50 ppm,Cl - ≤5 ppm, F - ≤50 ppm, various metal ions are ≤5 ppm.

[0033] Example 5

[0034] In a 1000 ml reactor, add 300 ml acetone, 350 ml dimethyl carbonate, 290 g potassium fluoride (5 mol), 135 g sulfuryl chloride (1 mol), start stirring at a temperature of 20°C, react for 3 hours, add 56 g calcium oxide (1 mol), 20 g magnesium oxide (0.5 mol), and then introduce 51 g ammonia (3 mol), maintain the pressure in the reactor at 0.5 MPa, and continue to react at 10°C for 8 hours. After replacing the gas in the reaction system with nitrogen, add 58 g lithium phosphate (0.5 mol) and 12 g lithium hydroxide (0.5 mol), react at room temperature and normal pressure for 1 hour, filter out insoluble matter, concentrate the filtrate, dissolve it with 400 ml tetrahydrofuran, add activated carbon and stir at room temperature for 30 minutes, filter, remove activated carbon and insoluble matter, concentrate with a rotary evaporator, and vacuum dry to obtain 169.3 g of the target product with a yield of 91%, a purity of 99.9%, and a moisture content of ≤50 ppm, SO4 2- ≤50 ppm,Cl - ≤5 ppm, F - ≤50 ppm, various metal ions are ≤5 ppm.

Claims

1. A method for preparing lithium bis(fluorosulfonyl)imide by a tandem process, characterized in that: The method uses sulfuryl chloride and potassium fluoride as raw materials, first performs fluorine-chlorine exchange in a non-protonic polar solvent, then reacts with ammonia gas under the action of metal oxide or non-metal oxide to generate ammonium salt of bisfluorosulfonyl imide, removes the gas in the reaction system, and then reacts with a metal lithium compound to obtain lithium bisfluorosulfonyl imide.

2. The method for preparing lithium bis(fluorosulfonyl)imide by a tandem process according to claim 1, characterized in that: The method comprises the following steps, (1) Add a non-protonic polar solvent, potassium fluoride and sulfuryl chloride into a reaction vessel, start stirring, and react at a temperature of 10 to 50° C. for 1 to 8 hours; (2) Add metal or non-metal oxides, then introduce ammonia gas, maintain the pressure in the reactor at 0.1-0.5 MPa, and continue the reaction at a temperature of -10-30°C for 1-8 hours; (3) After replacing the gas in the reaction system with nitrogen, a metallic lithium compound is added and reacted at room temperature and normal pressure for 1 to 5 hours; (4) Filter out insoluble matter, concentrate the filtrate, dissolve it in tetrahydrofuran or 2-methyltetrahydrofuran, add activated carbon, stir thoroughly at room temperature, filter, remove activated carbon and insoluble matter, concentrate the filtrate by rotary evaporator, and dry in vacuo to obtain the target product.

3. The method for preparing lithium bis(fluorosulfonyl)imide by a tandem process according to claim 1, characterized in that: The non-protonic polar solvent in step (1) is one or a mixture of two or more of an ester compound, a ketone compound, a nitrile compound or an ether compound; the ester compound is one or a mixture of two or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, methyl acetate, ethyl acetate, propyl acetate or isopropyl acetate; the ketone compound is one or a mixture of two or more of acetone, methyl ethyl ketone or butanone; the nitrile compound is one or a mixture of two of acetonitrile or propionitrile; the ether compound is one or a mixture of two or more of diethyl ether, isopropyl ether, methyl tert-butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, 1,4-dioxane, tetrahydrofuran or 2-methyltetrahydrofuran.

4. The method for preparing lithium bis(fluorosulfonyl)imide by a tandem process according to claim 3, characterized in that: The aprotic polar solvent is one or a mixture of two or more of acetonitrile, dimethyl carbonate, diethyl carbonate, acetone, methyl ethyl ketone, methyl tert-butyl ether, 1,4-dioxane, tetrahydrofuran or 2-methyltetrahydrofuran.

5. The method for preparing lithium bis(fluorosulfonyl)imide by a tandem process according to claim 1, characterized in that: In step (2), the metal or non-metal oxide is one or a mixture of two or more of magnesium oxide, calcium oxide, barium oxide, aluminum oxide or silicon dioxide.

6. The method for preparing lithium bis(fluorosulfonyl)imide by a tandem process according to claim 5, characterized in that: In step (2), the metal or non-metal oxide is one or a mixture of two or more of calcium oxide, silicon oxide or magnesium oxide.

7. The method for preparing lithium bis(fluorosulfonyl)imide by a tandem process according to claim 1, characterized in that: In step (3), the metallic lithium compound is one or a mixture of two or more of lithium oxide, lithium hydroxide, lithium carbonate, lithium tetrafluoroborate, lithium perchlorate, lithium chloride, lithium bromide and lithium phosphate.

8. The method for preparing lithium bis(fluorosulfonyl)imide by a tandem process according to claim 7, characterized in that: In step (3), the metallic lithium compound is one or a mixture of two or more of lithium hydroxide, lithium carbonate and lithium phosphate.

9. The method for preparing lithium bis(fluorosulfonyl)imide by a tandem process according to claim 1, characterized in that: The molar ratio of sulfuryl chloride to potassium fluoride is 1: 2-5, the molar ratio of sulfuryl chloride to ammonia is 1: 2-3; the molar ratio of sulfuryl chloride to metal or non-metal oxide is 1: 0.5-1.5; the molar ratio of sulfuryl chloride to metallic lithium compound is 1: 1-3.

10. The method for preparing lithium bis(fluorosulfonyl)imide by a tandem process according to claim 1, characterized in that: The amount of the aprotic polar solvent used in step (1) is 50-65% of the volume of the reaction container, and the amount of tetrahydrofuran or 2-methyltetrahydrofuran used in step (4) is 2-3 times the weight of the concentrate.