A method for preparing lithium bisfluorosulfonylimide from methylsilazane

Abstract

The present application relates to the technical field of lithium battery, and in particular to a method for preparing lithium bisfluorosulfonimide from methylsilazane; the method uses sulfuryl fluoride, methylsilazane, basic lithium, and resin-based diacid adsorbent as raw materials to synthesize lithium bisfluorosulfonimide, and has the advantages of easy availability, low price, simple operation, and high total yield; the method uses a low-temperature reaction when adding basic lithium, thereby avoiding the warming operation of the final product and ensuring the quality of the product; the method has the advantages of low production cost, few by-products, and simple post-treatment; the lithium bisfluorosulfonimide prepared by the method has a purity of 99.99% and a yield of 95.96%, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a method for preparing lithium bisfluorosulfonylimide from methylsilazane. Background Technology

[0002] With the depletion of traditional fossil fuel reserves and the increasing severity of air pollution, new energy vehicles, characterized by energy conservation and environmental protection, have emerged, and lithium batteries, as energy storage devices for these vehicles, are gradually being widely used. Key materials for lithium-ion batteries include: positive electrode, negative electrode, binder, separator, and electrolyte. Among these, the electrolyte plays a crucial role in transferring charge between the positive and negative electrodes, making it a critical component that significantly affects battery cycle life, safety performance, and energy output. Lithium bisfluorosulfonylimide (LiFSI) is a novel electrolyte lithium salt used in lithium battery electrolytes. It is environmentally friendly and has good safety performance, thus possessing the basic conditions for industrial application. Compared to traditional lithium salt lithium hexafluorophosphate (LiPF6), lithium ions in LiFSI are more easily dissociated, resulting in higher conductivity. LiFSI has a decomposition temperature above 200℃, exhibiting significantly better thermal stability and safety performance than LiPF6. Furthermore, it offers unique advantages in improving high-temperature storage and low-temperature discharge performance, and possesses excellent compatibility with electrodes. Therefore, LiFSI is a promising electrolyte for lithium-ion batteries.

[0003] Chinese Patent CN202211740521.1: Provides a method for preparing difluorosulfonylimide and a method for preparing difluorosulfonylimide salt. The method for preparing difluorosulfonylimide includes the following steps: (1) reacting sulfonyl chloride with NH3 to obtain dichlorosulfonylimide, wherein the pressure of the reaction is ≥0.7MPa; (2) reacting dichlorosulfonylimide with HF to obtain difluorosulfonylimide.

[0004] Chinese Patent CN202211652000.0: Provides a method for preparing lithium bis(fluorosulfonyl)imide and a lithium-ion battery. The preparation method includes the following steps: (1) adding lithium fluoride to liquid bis(fluorosulfonyl)imide to react, and mixing the generated product with an organic solvent to obtain a lithium bis(fluorosulfonyl)imide solution; (2) reacting the lithium bis(fluorosulfonyl)imide solution obtained in step (1) with lithium carbonate, and then performing solid-liquid separation to obtain the lithium bis(fluorosulfonyl)imide. This invention uses a lithium carbonate deacidification process to improve product quality while reducing costs, and prepares high-purity lithium bis(fluorosulfonyl)imide.

[0005] Chinese Patent CN202211139496.1 discloses a method for preparing lithium bis(fluorosulfonyl)imide, belonging to the field of lithium-ion battery chemical synthesis technology. The method includes the following steps: rinsing a primary or secondary amine ion exchange resin with a solvent having a water content of less than 10 ppm until the water content of the outflowing solvent is less than 10 ppm; preparing solution A; circulating solution A through the primary or secondary amine ion exchange resin to a mixing device A, and repeating the reaction until the concentration of the SuFEx reagent in the mixing device A no longer changes; forming a resin / lithium carbonate mixed bed; preparing solution B; introducing solution B into a resin reactor, keeping the resin reactor warm, and simultaneously venting the reaction tail gas; circulating solution B through the resin reactor to the mixing device B, and repeating the reaction until no reaction tail gas is emitted from the exhaust system; and obtaining a solution of lithium bis(fluorosulfonyl)imide in the mixing device B.

[0006] Lithium-ion batteries require extremely high purity of lithium bisfluorosulfonylimide, with impurity ions and moisture content controlled at the ppm level. Impurities in lithium bisfluorosulfonylimide include metal ions, which are difficult to separate using ordinary metal ion adsorbents, requiring steps such as vacuum distillation and recrystallization, thus increasing production costs. Summary of the Invention

[0007] Based on the above problems, the purpose of this invention is to provide a method for preparing lithium bisfluorosulfonylimide from methylsilazane. This invention uses thioyl fluoride, methylsilazane, basic lithium, and resin-based diacid adsorbent as raw materials to synthesize lithium bisfluorosulfonylimide. When adding basic lithium, this invention uses a low-temperature reaction to avoid heating the final product, thereby ensuring product quality and making it suitable for industrial production.

[0008] To achieve the above objectives, the first aspect of the present invention provides a method for preparing lithium bisfluorosulfonylimide from methylsilazane, the operation steps of which are as follows:

[0009] S1: Weigh 10-50 parts by weight of sulfuryl fluoride and 100-150 parts by weight of solvent, stir and mix, heat up, and slowly add 5-10 parts by weight of methylsilazane to react;

[0010] S2: After the reaction is complete, cool down and slowly add 15-20 parts of alkaline lithium to react. After the reaction is complete, add 0.02-0.5 parts of resin-based diacid adsorbent, stir for 20-40 minutes, and then filter to remove unreacted alkaline lithium and resin-based diacid adsorbent.

[0011] S3: After the filtrate is evaporated and concentrated, 100-150 parts of a weakly polar solvent or a non-polar solvent are added to precipitate solid lithium bisfluorosulfonylimide, which is then dried to obtain lithium bisfluorosulfonylimide.

[0012] Furthermore, the methylsilazane is octamethylcyclotetrasilazane, hexamethyldisilazane, or hexamethylcyclotrisilazane.

[0013] Furthermore, the solvent is an ester, amide, or nitrile.

[0014] Furthermore, esters include ethyl acetate and butyl acetate; further amides include N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0015] Furthermore, nitrile compounds include acetonitrile and propionitrile.

[0016] Preferably, the reaction temperature of S1 is 80-110℃ and the reaction time is 5-10h.

[0017] Preferably, the alkaline lithium is one or more of LiF, LiOH, LiHCO3 or Li2CO3.

[0018] Preferably, the reaction temperature of S2 is 0-20℃ and the reaction time is 5-10h.

[0019] Preferably, the weakly polar solvent or non-polar solvent is a halogenated hydrocarbon solvent, an alkane solvent, or a halogenated aromatic hydrocarbon solvent;

[0020] Furthermore, halogenated hydrocarbon solvents include dichloromethane and dichloroethane;

[0021] Furthermore, alkane solvents include n-hexane, cyclohexane, and n-heptane;

[0022] Furthermore, halogenated aromatic solvents include toluene, ethylbenzene, and chlorobenzene.

[0023] The second aspect of this invention provides a method for preparing a resin-based diacid adsorbent as follows:

[0024] S1: According to the mass percentage, nitrogen gas is introduced into a closed reaction vessel, and 2-5 parts of 2,3-dimercaptomalonic acid, 10-15 parts of 2,5-difluoro-3,6-dimercaptoterephthalic acid, and 100-200 parts of sodium hydroxide solution with a mass percentage concentration of 5-10% are added to the vessel. The mixture is stirred at 30-40℃ for 30-60 minutes, and the water is removed by vacuum distillation.

[0025] S2: Add 1000-1500 parts of ethanol, 100-130 parts of propylene-based adsorption resin, and 3-6 parts of triethylamine to a stirred tank. Stir at 60-72°C for 100-150 minutes, then filter to obtain resin-based sodium diacid.

[0026] S3: Ion exchange is performed to replace sodium ions with hydrogen ions. The process conditions are as follows: Sodium resin-based diacid is added to the ion exchange column, with the amount added being 30-60% of the ion exchange column volume. 100-200 parts of hydrochloric acid solution with a mass percentage concentration of 5-10% are added from the top of the column at a flow rate of 0.5-2 BV / h. The effluent is distilled to remove ethanol and dried to obtain the resin-based diacid adsorbent.

[0027] Furthermore, the preparation method of the propylene-based adsorption resin is as follows:

[0028] According to the mass fractions, nitrogen gas is introduced into a closed reaction vessel, and 12-15 parts of adsorption resin, 100-150 parts of acryloyl chloride, and 5-10 parts of anhydrous aluminum chloride are added to the vessel. The mixture is stirred at 40-50℃ for 10-20 hours, filtered, and dried to obtain allyl adsorption resin.

[0029] Furthermore, the adsorption resin includes one or more of styrene-divinylbenzene adsorption resin, styrene-divinylbenzene adsorption resin modified resin, polystyrene adsorption resin, polystyrene adsorption resin modified resin, polyacrylate adsorption resin, and polyacrylate adsorption resin modified resin.

[0030] Furthermore, the first macroporous adsorption resin includes non-polar D101, LX-100B, LX-T28, and weakly polar AB-8.

[0031] Reaction mechanism:

[0032] In this invention, sodium salts are first generated from 2,3-dimercaptomalonic acid and 2,5-difluoro-3,6-dimercaptoterephthalic acid; then, a thiol addition reaction is carried out with a propylene-based adsorption resin, followed by ion exchange to replace sodium ions with hydrogen ions, resulting in an adsorbent containing malonic acid and difluoroterephthalic acid functional groups.

[0033] Technical effects:

[0034] The present invention provides a method for preparing lithium bisfluorosulfonylimide from methylsilazane. Compared with the prior art, the present invention has the following significant advantages:

[0035] 1. This invention uses sulfuryl fluoride, methylsilane nitrogen, basic lithium, and resin-based diacid adsorbent as raw materials to synthesize lithium difluorosulfonylimide. The raw materials are readily available and inexpensive, the operation is simple, and the overall yield is high.

[0036] 2. This invention has low production costs, few by-products, and simple post-processing, making it suitable for industrial production;

[0037] 3. In this invention, the addition of alkaline lithium is carried out using a low-temperature reaction method, avoiding the heating operation of the final product, thereby ensuring the quality of the product. Detailed Implementation

[0038] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0039] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0040] Example 1

[0041] A method for preparing lithium bisfluorosulfonylimide from methylsilazane, comprising the following steps:

[0042] S1: Weigh 10g of sulfuryl fluoride and 100g of solvent, stir and mix, heat up, and slowly add 5g of methylsilazane to react;

[0043] S2: After the reaction is complete, cool down and slowly add 15g of alkaline lithium to react. After the reaction is complete, add 0.02g of resin-based diacid adsorbent, stir for 20 minutes, and then filter to remove unreacted alkaline lithium and resin-based diacid adsorbent.

[0044] S3: After the filtrate is evaporated and concentrated, 100g of a weakly polar solvent or a non-polar solvent is added to precipitate solid lithium bisfluorosulfonylimide, which is then dried to obtain lithium bisfluorosulfonylimide.

[0045] The methylsilazane mentioned is octamethylcyclotetrasilazane.

[0046] The solvent is ethyl acetate.

[0047] The reaction temperature of S1 is 80℃ and the reaction time is 5h.

[0048] The alkaline lithium is LiF.

[0049] The reaction temperature of S2 is 0℃ and the reaction time is 5h.

[0050] The weakly polar or non-polar solvent is dichloromethane.

[0051] The preparation method of the resin-based diacid adsorbent is as follows:

[0052] S1: In a closed reaction vessel, nitrogen gas is introduced, and 2g of 2,3-dimercaptomalonic acid, 10g of 2,5-difluoro-3,6-dimercaptoterephthalic acid and 100g of sodium hydroxide solution with a mass percentage concentration of 5% are added to the vessel. The mixture is stirred at 30°C for 30 minutes, and the water is removed by vacuum distillation.

[0053] S2: Add 1000g ethanol, 100g propylene-based adsorption resin, and 3g triethylamine to a stirred tank, stir at 60℃ for 100min, filter, and obtain resin-based sodium diacid.

[0054] S3: Ion exchange is performed to replace sodium ions with hydrogen ions. The process conditions are as follows: Sodium resin-based diacid is added to the ion exchange column at a volume of 30% of the column volume. 100g of 5% hydrochloric acid solution is added from the top of the column at a flow rate of 0.5 BV / h. The effluent is distilled to remove ethanol and then dried to obtain the resin-based diacid adsorbent.

[0055] The preparation method of the propylene-based adsorption resin is as follows:

[0056] Nitrogen gas was introduced into a closed reaction vessel, and 12g of adsorption resin, 100g of acryloyl chloride, and 5g of anhydrous aluminum chloride were added to the vessel. The mixture was stirred at 40°C for 10 hours, filtered, and dried to obtain allyl adsorption resin.

[0057] The adsorption resin is non-polar D101.

[0058] Example 2

[0059] A method for preparing lithium bisfluorosulfonylimide from methylsilazane, comprising the following steps:

[0060] S1: Weigh 20g of sulfuryl fluoride and 110g of solvent, stir and mix, heat up, and slowly add 6g of methylsilazane to react;

[0061] S2: After the reaction is complete, cool down and slowly add 16g of alkaline lithium to react. After the reaction is complete, add 0.2g of resin-based diacid adsorbent, stir for 25 minutes, and then filter to remove unreacted alkaline lithium and resin-based diacid adsorbent.

[0062] S3: After the filtrate is evaporated and concentrated, 110g of a weakly polar solvent or a non-polar solvent is added to precipitate solid lithium difluorosulfonylimide, which is then dried to obtain lithium difluorosulfonylimide.

[0063] The methylsilazane mentioned is hexamethyldisilazane.

[0064] The solvent is N,N-dimethylformamide.

[0065] The reaction temperature of S1 is 90℃ and the reaction time is 7h.

[0066] The alkaline lithium is LiOH.

[0067] The reaction temperature of S2 is 5℃ and the reaction time is 7h.

[0068] The weakly polar or non-polar solvent is n-hexane.

[0069] The preparation method of the resin-based diacid adsorbent is as follows:

[0070] S1: In a closed reaction vessel, nitrogen gas is introduced, and 3g of 2,3-dimercaptomalonic acid, 12g of 2,5-difluoro-3,6-dimercaptoterephthalic acid and 140g of sodium hydroxide solution with a mass percentage concentration of 6% are added to the vessel. The mixture is stirred at 35°C for 40 minutes, and the water is removed by vacuum distillation.

[0071] S2: Add 1200g ethanol, 110g propylene-based adsorption resin, and 4g triethylamine to a stirred tank, stir at 65℃ for 110min, filter, and obtain resin-based sodium diacid.

[0072] S3: Ion exchange is performed to replace sodium ions with hydrogen ions. The process conditions are as follows: Sodium resin-based diacid is added to the ion exchange column at a volume of 40% of the column volume. 140g of 6% hydrochloric acid solution is added from the top of the column at a flow rate of 1 BV / h. The effluent is distilled to remove ethanol and then dried to obtain the resin-based diacid adsorbent.

[0073] The preparation method of the propylene-based adsorption resin is as follows:

[0074] Nitrogen gas was introduced into a closed reaction vessel, and 13g of adsorption resin, 110g of acryloyl chloride, and 6g of anhydrous aluminum chloride were added to the vessel. The mixture was stirred at 45°C for 14 hours, filtered, and dried to obtain allyl adsorption resin.

[0075] The adsorption resin is non-polar LX-100B.

[0076] Example 3

[0077] A method for preparing lithium bisfluorosulfonylimide from methylsilazane, comprising the following steps:

[0078] S1: Weigh 40g of sulfuryl fluoride and 140g of solvent, stir and mix them, heat up, and slowly add 9g of methylsilazane to carry out the reaction;

[0079] S2: After the reaction is complete, cool down and slowly add 18g of alkaline lithium to react. After the reaction is complete, add 0.4g of resin-based diacid adsorbent, stir for 35 minutes, and then filter to remove unreacted alkaline lithium and resin-based diacid adsorbent.

[0080] S3: After the filtrate is evaporated and concentrated, 140g of a weakly polar solvent or a non-polar solvent is added to precipitate solid lithium bisfluorosulfonylimide, which is then dried to obtain lithium bisfluorosulfonylimide.

[0081] The methylsilazane mentioned is hexamethyldisilazane.

[0082] The solvent is acetonitrile.

[0083] The reaction temperature of S1 is 100℃ and the reaction time is 9h.

[0084] The alkaline lithium is LiHCO3.

[0085] The reaction temperature of S2 is 15℃ and the reaction time is 9h.

[0086] The weakly polar or non-polar solvent is toluene.

[0087] The preparation method of the resin-based diacid adsorbent is as follows:

[0088] S1: In a closed reaction vessel, nitrogen gas is introduced, and 4g of 2,3-dimercaptomalonic acid, 14g of 2,5-difluoro-3,6-dimercaptoterephthalic acid and 180g of sodium hydroxide solution with a mass percentage concentration of 9% are added to the vessel. The mixture is stirred at 35°C for 50 minutes, and the water is removed by vacuum distillation.

[0089] S2: Add 1400g ethanol, 120g propylene-based adsorption resin, and 5g triethylamine to a stirred tank, stir at 70℃ for 140min, filter, and obtain resin-based sodium diacid.

[0090] S3: Ion exchange is performed to replace sodium ions with hydrogen ions. The process conditions are as follows: Sodium resin-based diacid is added to the ion exchange column at a volume of 50% of the column volume. 180g of 9% hydrochloric acid solution is added from the top of the column at a flow rate of 1.5 BV / h. The effluent is distilled to remove ethanol and then dried to obtain the resin-based diacid adsorbent.

[0091] The preparation method of the propylene-based adsorption resin is as follows:

[0092] Nitrogen gas was introduced into a closed reaction vessel, and 14g of adsorption resin, 140g of acryloyl chloride, and 8g of anhydrous aluminum chloride were added to the vessel. The mixture was stirred at 45°C for 18 hours, filtered, and dried to obtain allyl adsorption resin.

[0093] The adsorption resin is non-polar LX-T28.

[0094] Example 4

[0095] A method for preparing lithium bisfluorosulfonylimide from methylsilazane, comprising the following steps:

[0096] S1: Weigh 50g of sulfuryl fluoride and 150g of solvent, stir and mix, heat up, and slowly add 10g of methylsilazane to react;

[0097] S2: After the reaction is complete, cool down and slowly add 0g of alkaline lithium to react. After the reaction is complete, add 0.5g of resin-based diacid adsorbent, stir for 40 minutes, and then filter to remove unreacted alkaline lithium and resin-based diacid adsorbent.

[0098] S3: After the filtrate is evaporated and concentrated, 150g of a weakly polar solvent or a non-polar solvent is added to precipitate solid lithium difluorosulfonylimide, which is then dried to obtain lithium difluorosulfonylimide.

[0099] The methylsilazane mentioned is hexamethylcyclotrisilazane.

[0100] The solvent is propionitrile.

[0101] The reaction temperature of S1 is 110℃ and the reaction time is 0h.

[0102] The alkaline lithium is Li2CO3.

[0103] The reaction temperature of S2 is 20℃ and the reaction time is 10h.

[0104] The weakly polar or non-polar solvent is ethylbenzene.

[0105] The preparation method of the resin-based diacid adsorbent is as follows:

[0106] S1: In a closed reaction vessel, nitrogen gas is introduced, and 5g of 2,3-dimercaptomalonic acid, 15g of 2,5-difluoro-3,6-dimercaptoterephthalic acid and 200g of sodium hydroxide solution with a mass percentage concentration of 10% are added to the vessel. The mixture is stirred at 40°C for 60 minutes, and the water is removed by vacuum distillation.

[0107] S2: Add 1500g ethanol, 30g propylene-based adsorption resin, and 6g triethylamine to a stirred tank, stir at 72℃ for 150min, filter, and obtain resin-based sodium diacid.

[0108] S3: Ion exchange is performed to replace sodium ions with hydrogen ions. The process conditions are as follows: Sodium resin-based diacid is added to the ion exchange column at a volume of 60% of the column volume. 200g of 10% hydrochloric acid solution is added from the top of the column at a flow rate of 2 BV / h. The effluent is distilled to remove ethanol and then dried to obtain the resin-based diacid adsorbent.

[0109] The preparation method of the propylene-based adsorption resin is as follows:

[0110] Nitrogen gas was introduced into a closed reaction vessel, and 15g of adsorption resin, 150g of acryloyl chloride, and 10g of anhydrous aluminum chloride were added to the vessel. The mixture was stirred at 50°C for 20 hours, filtered, and dried to obtain allyl adsorption resin.

[0111] The adsorption resin is weakly polar AB-8.

[0112] Comparative Example 1

[0113] A method for preparing lithium bisfluorosulfonylimide from methylsilazane, comprising the following steps:

[0114] S1: Weigh 10g of sulfuryl fluoride and 100g of solvent, stir and mix, heat up, and slowly add 5g of methylsilazane to react;

[0115] S2: After the reaction is complete, cool down and slowly add 15g of alkaline lithium. After the reaction is complete, filter to remove unreacted alkaline lithium.

[0116] S3: After the filtrate is evaporated and concentrated, 100g of a weakly polar solvent or a non-polar solvent is added to precipitate solid lithium bisfluorosulfonylimide, which is then dried to obtain lithium bisfluorosulfonylimide.

[0117] The methylsilazane mentioned is octamethylcyclotetrasilazane.

[0118] The solvent is ethyl acetate.

[0119] The reaction temperature of S1 is 80℃ and the reaction time is 5h.

[0120] The alkaline lithium is LiF.

[0121] The reaction temperature of S2 is 0℃ and the reaction time is 5h.

[0122] The weakly polar or non-polar solvent is dichloromethane.

[0123] Comparative Example 2

[0124] A method for preparing lithium bisfluorosulfonylimide from methylsilazane, comprising the following steps:

[0125] S1: Weigh 10g of sulfuryl fluoride and 100g of solvent, stir and mix, heat up, and slowly add 5g of methylsilazane to react;

[0126] S2: After the reaction is complete, cool down and slowly add 15g of alkaline lithium to react. After the reaction is complete, add 0.02g of resin-based diacid adsorbent, stir for 20 minutes, and then filter to remove unreacted alkaline lithium and resin-based diacid adsorbent.

[0127] S3: After the filtrate is evaporated and concentrated, 100g of a weakly polar solvent or a non-polar solvent is added to precipitate solid lithium bisfluorosulfonylimide, which is then dried to obtain lithium bisfluorosulfonylimide.

[0128] The methylsilazane mentioned is octamethylcyclotetrasilazane.

[0129] The solvent is ethyl acetate.

[0130] The reaction temperature of S1 is 80℃ and the reaction time is 5h.

[0131] The alkaline lithium is LiF.

[0132] The reaction temperature of S2 is 0℃ and the reaction time is 5h.

[0133] The weakly polar or non-polar solvent is dichloromethane.

[0134] The preparation method of the resin-based diacid adsorbent is as follows:

[0135] S1: In a closed reaction vessel, nitrogen gas is introduced, and 10g of 2,5-difluoro-3,6-dimercaptoterephthalic acid and 100g of sodium hydroxide solution with a mass percentage concentration of 5% are added to the vessel. The mixture is stirred at 30°C for 30 minutes, and the water is removed by vacuum distillation.

[0136] S2: Add 1000g ethanol, 100g propylene-based adsorption resin, and 3g triethylamine to a stirred tank, stir at 60℃ for 100min, filter, and obtain resin-based sodium diacid.

[0137] S3: Ion exchange is performed to replace sodium ions with hydrogen ions. The process conditions are as follows: Sodium resin-based diacid is added to the ion exchange column at a volume of 30% of the column volume. 100g of 5% hydrochloric acid solution is added from the top of the column at a flow rate of 0.5 BV / h. The effluent is distilled to remove ethanol and then dried to obtain the resin-based diacid adsorbent.

[0138] The preparation method of the propylene-based adsorption resin is as follows:

[0139] Nitrogen gas was introduced into a closed reaction vessel, and 12g of adsorption resin, 100g of acryloyl chloride, and 5g of anhydrous aluminum chloride were added to the vessel. The mixture was stirred at 40°C for 10 hours, filtered, and dried to obtain allyl adsorption resin.

[0140] The adsorption resin is non-polar D101.

[0141] Comparative Example 3

[0142] A method for preparing lithium bisfluorosulfonylimide from methylsilazane, comprising the following steps:

[0143] S1: Weigh 10g of sulfuryl fluoride and 100g of solvent, stir and mix, heat up, and slowly add 5g of methylsilazane to react;

[0144] S2: After the reaction is complete, cool down and slowly add 15g of alkaline lithium to react. After the reaction is complete, add 0.02g of resin-based diacid adsorbent, stir for 20 minutes, and then filter to remove unreacted alkaline lithium and resin-based diacid adsorbent.

[0145] S3: After the filtrate is evaporated and concentrated, 100g of a weakly polar solvent or a non-polar solvent is added to precipitate solid lithium bisfluorosulfonylimide, which is then dried to obtain lithium bisfluorosulfonylimide.

[0146] The methylsilazane mentioned is octamethylcyclotetrasilazane.

[0147] The solvent is ethyl acetate.

[0148] The reaction temperature of S1 is 80℃ and the reaction time is 5h.

[0149] The alkaline lithium is LiF.

[0150] The reaction temperature of S2 is 0℃ and the reaction time is 5h.

[0151] The weakly polar or non-polar solvent is dichloromethane.

[0152] The preparation method of the resin-based diacid adsorbent is as follows:

[0153] S1: In a closed reaction vessel, nitrogen gas is introduced, and 2g of 2,3-dimercaptomalonic acid and 100g of sodium hydroxide solution with a mass percentage concentration of 5% are added to the vessel. The mixture is stirred at 30°C for 30 minutes, and the water is removed by vacuum distillation.

[0154] S2: Add 1000g ethanol, 100g propylene-based adsorption resin, and 3g triethylamine to a stirred tank, stir at 60℃ for 100min, filter, and obtain resin-based sodium diacid.

[0155] S3: Ion exchange is performed to replace sodium ions with hydrogen ions. The process conditions are as follows: Sodium resin-based diacid is added to the ion exchange column at a volume of 30% of the column volume. 100g of 5% hydrochloric acid solution is added from the top of the column at a flow rate of 0.5 BV / h. The effluent is distilled to remove ethanol and then dried to obtain the resin-based diacid adsorbent.

[0156] The preparation method of the propylene-based adsorption resin is as follows:

[0157] Nitrogen gas was introduced into a closed reaction vessel, and 12g of adsorption resin, 100g of acryloyl chloride, and 5g of anhydrous aluminum chloride were added to the vessel. The mixture was stirred at 40°C for 10 hours, filtered, and dried to obtain allyl adsorption resin.

[0158] The adsorption resin is non-polar D101.

[0159] In a specific embodiment of the present invention, product purity and yield are calculated using the following method:

[0160] 1. Purity: The purity of lithium bis(fluorosulfonyl)imide = mass of lithium bis(fluorosulfonyl)imide in the mixture ÷ mass of the mixture × 100%;

[0161] 2. Yield: The yield of lithium bis(fluorosulfonyl)imide = actual amount of lithium bis(fluorosulfonyl)imide produced / theoretical amount of lithium bis(fluorosulfonyl)imide produced × 100%.

[0162] purity / % Yield / % Example 1 99.95 93.72 Example 2 99.97 94.53 Example 3 99.99 95.96 Example 4 99.98 95.03 Comparative Example 1 88.12 91.78 Comparative Example 2 91.35 92.85 Comparative Example 3 93.36 92.26

[0163] Compared with the comparative examples, the present invention is simple to operate, produces fewer by-products, has simple post-processing, high purity, and high total yield, making it suitable for industrial production.

[0164] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing lithium bisfluorosulfonylimide from methylsilazane, comprising the following steps: S1: Weigh 10-50 parts by weight of sulfuryl fluoride and 100-150 parts by weight of solvent, stir and mix, heat up, and slowly add 5-10 parts by weight of methylsilazane to react; S2: After the reaction is complete, cool down and slowly add 15-20 parts of alkaline lithium to react. After the reaction is complete, add 0.02-0.5 parts of resin-based diacid adsorbent, stir for 20-40 minutes, and then filter to remove unreacted alkaline lithium and resin-based diacid adsorbent. S3: After the filtrate is evaporated and concentrated, 100-150 parts of weakly polar solvent or non-polar solvent are added to precipitate solid lithium difluorosulfonylimide, which is then dried to obtain lithium difluorosulfonylimide. The preparation method of the resin-based diacid adsorbent is as follows: S1: According to the mass percentage, nitrogen gas is introduced into a closed reaction vessel, and 2-5 parts of 2,3-dimercaptomalonic acid, 10-15 parts of 2,5-difluoro-3,6-dimercaptoterephthalic acid, and 100-200 parts of sodium hydroxide solution with a mass percentage concentration of 5-10% are added to the vessel. The mixture is stirred at 30-40℃ for 30-60 minutes, and the water is removed by vacuum distillation. S2: Add 1000-1500 parts of ethanol, 100-130 parts of propylene-based adsorption resin, and 3-6 parts of triethylamine to a stirred tank. Stir at 60-72°C for 100-150 minutes, then filter to obtain resin-based sodium diacid. S3: Ion exchange is performed to replace sodium ions with hydrogen ions. The process conditions are as follows: Sodium resin-based diacid is added to the ion exchange column, with the amount added being 30-60% of the volume of the ion exchange column. 100-200 parts of hydrochloric acid solution with a mass percentage concentration of 5-10% are added from the top of the column at a flow rate of 0.5-2 BV / h. The effluent is distilled to remove ethanol and dried to obtain the resin-based diacid adsorbent. The preparation method of the propylene-based adsorption resin is as follows: According to the mass fraction, nitrogen gas is introduced into a closed reaction vessel, and 12-15 parts of adsorption resin, 100-150 parts of acryloyl chloride, and 5-10 parts of anhydrous aluminum chloride are added to the vessel. The mixture is stirred at 40-50℃ for 10-20 hours, filtered, and dried to obtain propylene-based adsorption resin. The adsorption resin includes one or more of the following: styrene-divinylbenzene adsorption resin, styrene-divinylbenzene modified adsorption resin, polystyrene adsorption resin, polystyrene modified adsorption resin, polyacrylate adsorption resin, and polyacrylate modified adsorption resin.

2. The method for preparing lithium bisfluorosulfonylimide from methylsilazane according to claim 1, characterized in that: The methylsilazane is octamethylcyclotetrasilazane, hexamethyldisilazane, or hexamethylcyclotrisilazane.

3. The method for preparing lithium bisfluorosulfonylimide from methylsilazane according to claim 1, characterized in that: The solvents are esters, amides, and nitriles; esters include ethyl acetate and butyl acetate; amides include N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; nitriles include acetonitrile and propionitrile.

4. The method for preparing lithium bisfluorosulfonylimide from methylsilazane according to claim 1, characterized in that: The reaction temperature of S1 is 80-110℃, and the reaction time is 5-10h.

5. The method for preparing lithium bisfluorosulfonylimide from methylsilazane according to claim 1, characterized in that: The alkaline lithium is one or more of LiF, LiOH, LiHCO3 or Li2CO3.

6. The method for preparing lithium bisfluorosulfonylimide from methylsilazane according to claim 1, characterized in that: The reaction temperature of S2 is 0-20℃, and the reaction time is 5-10h.

7. The method for preparing lithium bisfluorosulfonylimide from methylsilazane according to claim 1, characterized in that: The weakly polar or non-polar solvents mentioned are halogenated hydrocarbon solvents, alkane solvents, and halogenated aromatic hydrocarbon solvents; Halogenated hydrocarbon solvents include dichloromethane and dichloroethane; Alkane solvents include n-hexane, cyclohexane, and n-heptane; Halogenated aromatic solvents include chlorobenzene.