Preparation method of high-purity low-water lithium bisfluorosulfonylimide

Abstract

The application discloses a preparation method of high-purity low-water lithium bisfluorosulfonimide, and the method comprises the following steps: S1, dissolving the lithium bisfluorosulfonimide crude product in an organic solvent to obtain solution A; S2, adding a water removal agent to the solution A to obtain solution B; S3, adding activated carbon to the solution B, stirring, filtering, concentrating the filtrate, crystallizing, and drying to obtain the high-purity low-water lithium bisfluorosulfonimide product; or the method comprises the following steps: S1, dissolving the lithium bisfluorosulfonimide crude product in an organic solvent to obtain solution C; S2, adding activated carbon powder to the solution C, stirring, filtering, pumping the filtrate into a lithium molecular sieve column, filtering the received solution again, concentrating the filtrate, adding anhydrous dichloromethane to crystallize, and drying to obtain the high-purity low-water lithium bisfluorosulfonimide product. The method is simple in operation and low in cost, the lithium bisfluorosulfonimide obtained by the method has a very low water content and is high in purity.

Description

Technical Field

[0001] This invention relates to the field of battery electrolyte materials technology, specifically to a method for preparing high-purity, low-water lithium difluorosulfonylimide. Background Technology

[0002] Most existing techniques for synthesizing lithium bis(fluorosulfonyl)imide involve first preparing bis(fluorosulfonyl)imide, then reacting it with lithium carbonate or lithium hydroxide to obtain lithium bis(fluorosulfonyl)imide. During this reaction, water is generated as a byproduct, and lithium bis(fluorosulfonyl)imide is highly hygroscopic, even forming complexes with water of crystallization. This often results in the final bis(fluorosulfonyl)imide product containing water, and further, due to hydrolysis, F... - SO4 2- Excessive content renders the product non-compliant with battery application standards. Furthermore, the thermal stability of water-containing lithium difluorosulfonamide deteriorates, making it prone to decomposition during high-temperature vacuum drying, while low-temperature vacuum drying is ineffective at removing moisture. Summary of the Invention

[0003] The purpose of this invention is to address the problem that lithium bisfluorosulfonylimide products prepared by existing processes contain water, which leads to product hydrolysis and causes the products to fail to meet battery usage standards. This invention provides a method for preparing high-purity, low-water lithium bisfluorosulfonylimide, thus solving the problem of water content in lithium bisfluorosulfonylimide products.

[0004] This invention is achieved through the following technical solution:

[0005] A method for preparing high-purity, low-water lithium difluorosulfonylimide includes the following steps:

[0006] S1. Dissolve crude lithium difluorosulfonylimide in an organic solvent to obtain solution A;

[0007] S2. Add a dehydrating agent to solution A to obtain solution B;

[0008] S3. Add activated carbon to the solution B, stir, filter, concentrate the filtrate, crystallize, and dry to obtain a high-purity, low-water lithium difluorosulfonylimide product.

[0009] Furthermore, a method for preparing high-purity, low-water lithium difluorosulfonylimide is provided: the organic solvent is selected from methyl tert-butyl ether or dimethyl carbonate; the molar volume ratio of crude lithium difluorosulfonylimide to the organic solvent in step S1 is 0.5–2.0 mol / L.

[0010] Furthermore, a method for preparing high-purity, low-water lithium difluorosulfonylimide: Step S2, when the temperature of solution A is 20-30°C, the dehydrating agent is added dropwise to obtain solution B;

[0011] Wherein: the dehydrating agent is hexamethyldisilazane; the amount of the dehydrating agent added is 1.0% to 5.0% of the crude weight of lithium bis(fluorosulfonyl)imide.

[0012] Furthermore, a method for preparing high-purity, low-water lithium difluorosulfonylimide is as follows: Step S3, add 1.0% to 10.0% of pretreated activated carbon powder by volume to the solution B, then stir at room temperature for 1 to 5 hours, then filter with ordinary filter paper, then pass the filtrate through a polytetrafluoroethylene microfiltration membrane, then concentrate the filtrate under reduced pressure, add anhydrous dichloromethane to crystallize, and then vacuum dry the crystals to obtain the high-purity, low-water lithium difluorosulfonylimide product.

[0013] Furthermore, a method for preparing high-purity, low-water lithium difluorosulfonyl imide: the polytetrafluoroethylene microfiltration membrane has a pore size of 0.1–0.45 μm;

[0014] The pretreatment process of the activated carbon powder includes the following steps: mixing the activated carbon powder with primary pure water, then boiling, cooling and filtering, rinsing with primary pure water, and then drying to complete the pretreatment of the activated carbon powder.

[0015] Another method for preparing high-purity, low-water lithium bis(fluorosulfonyl)imide is provided, comprising the following steps:

[0016] S1. Dissolve crude lithium difluorosulfonylimide in an organic solvent to obtain solution C;

[0017] S2. Add activated carbon powder to the solution C, stir, filter, pump the filtrate into a lithium molecular sieve column, filter the received solution a second time, concentrate the filtrate, add anhydrous dichloromethane to crystallize, dry, and obtain a high-purity, low-water lithium difluorosulfonylimide product.

[0018] Furthermore, a method for preparing high-purity, low-water-content lithium difluorosulfonylimide: a method for preparing lithium molecular sieves, comprising the following steps:

[0019] (1) Using 30% silica sol as the silicon source, lithium aluminate as the aluminum source, and lithium oxalate as the lithium source, the reaction was carried out under alkaline conditions at 90-120°C for 24-72 hours.

[0020] (2) Filter the reaction solution, wash and dry the filter cake to obtain lithium molecular sieve;

[0021] In use: The lithium molecular sieve is activated by vacuum calcination at 300-350°C, and then loaded into a molecular sieve adsorption column to form a lithium molecular sieve column.

[0022] Furthermore, a method for preparing high-purity, low-water lithium bis(fluorosulfonyl)imide is provided: the organic solvent is selected from methyl tert-butyl ether or dimethyl carbonate; the molar volume ratio of the crude lithium bis(fluorosulfonyl)imide to the organic solvent in step S1 is 0.5–2.0 mol / L.

[0023] Furthermore, a method for preparing high-purity, low-water lithium difluorosulfonylimide is as follows: Step S2, add 1.0% to 10.0% of pretreated activated carbon powder by volume to the solution C, then stir at room temperature for 1 to 5 hours, then filter with ordinary filter paper, and then pump the filtrate into a lithium molecular sieve column, controlling the receiving rate to 1 to 3 ml / min, then pass the received solution through a polytetrafluoroethylene microfiltration membrane, then concentrate the filtrate under reduced pressure, add anhydrous dichloromethane to crystallize, and then vacuum dry the crystals to obtain the high-purity, low-water lithium difluorosulfonylimide product.

[0024] Furthermore, a method for preparing high-purity, low-water lithium difluorosulfonyl imide: the polytetrafluoroethylene microfiltration membrane has a pore size of 0.1–0.45 μm;

[0025] The pretreatment process of the activated carbon powder includes the following steps: mixing the activated carbon powder with primary pure water, then boiling, cooling and filtering, rinsing with primary pure water, and then drying to complete the pretreatment of the activated carbon powder.

[0026] The beneficial effects of this invention are:

[0027] (1) The method of the present invention uses hexamethyldisilazane as a dehydrating agent, and the reaction is homogeneous, resulting in thorough dehydration. The hexamethyldisilazane and its hydrolysis product hexamethyldisilazane added in the present invention have low boiling points and can be easily removed by solvent distillation without residue.

[0028] (2) The process of the present invention is simple to operate and low in cost. The lithium difluorosulfonyl imide obtained by the method of the present invention has extremely low water content and high purity.

[0029] (3) In another method provided by the present invention, a lithium molecular sieve column is used to remove water from the lithium difluorosulfonylimide solution as a whole. It not only has a good water removal effect, but also is simple to operate. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] A method for preparing high-purity, low-water lithium difluorosulfonylimide includes the following steps:

[0033] S1. Dissolve crude lithium difluorosulfonylimide in pre-dried methyl tert-butyl ether with stirring to obtain solution A with a crude lithium difluorosulfonylimide concentration of 1.0 mol / L;

[0034] The parameters for the crude lithium bis(fluorosulfonyl)imide are: purity 99.5%, moisture content 0.1%, F... - Content 0.049%, SO4 2- Content 0.023%;

[0035] S2. Control the temperature of solution A to 20℃, then add hexamethyldisilazane (a dehydrating agent) dropwise to obtain solution B, and continue stirring for 2 hours;

[0036] The amount of hexamethyldisilazane (dehydrating agent) added is 1.0% of the crude weight of lithium bis(fluorosulfonyl)imide.

[0037] S3. Add 5.0% (by volume) of pretreated activated carbon powder to solution B above, then stir at room temperature for 4 hours. First, filter the solution using ordinary filter paper, then pass the filtrate through a polytetrafluoroethylene microfiltration membrane (0.1 μm pore size). Concentrate the filtrate under reduced pressure, add anhydrous dichloromethane to crystallize, filter, and then vacuum dry the crystals to obtain a high-purity, low-water lithium difluorosulfonylimide product; product purity 99.9%, moisture content 0.0011%, F - Content 0.0003%, SO4 2- Content 0.0002%;

[0038] The pretreatment process for activated carbon powder is as follows:

[0039] (1) Mix activated carbon powder with primary pure water at a volume ratio of 1:50, and then boil for 1 hour;

[0040] (2) After cooling and filtering, rinse with pure water and then vacuum dry at 120°C to complete the pretreatment of activated carbon powder.

[0041] The process by which the above-mentioned hexamethyldisilazane dehydrating agent removes moisture from the product is shown below:

[0042]

[0043] The hexamethyldisilazane and its hydrolysis product hexamethyldisilazane added in this invention have low boiling points and can be easily removed by solvent distillation without residue.

[0044] Example 2

[0045] A method for preparing high-purity, low-water lithium difluorosulfonylimide includes the following steps:

[0046] S1. Dissolve crude lithium difluorosulfonylimide in pre-dried dimethyl carbonate with stirring to obtain a solution C with a crude lithium difluorosulfonylimide concentration of 2.0 mol / L.

[0047] The parameters for the crude lithium bis(fluorosulfonyl)imide are: purity 99.5%, moisture content 0.1%, F... - Content 0.049%, SO4 2- Content 0.023%;

[0048] S2. Add 10.0% (by volume) of pretreated activated carbon powder to solution C above, then stir at room temperature for 1 hour. First, filter using ordinary filter paper, then pump the filtrate into a lithium molecular sieve column, controlling the receiving rate at 2 ml / min. Pass the received solution through a polytetrafluoroethylene microfiltration membrane (0.45 μm pore size), then concentrate the filtrate under reduced pressure, add anhydrous dichloromethane to crystallize, and vacuum dry the crystals to obtain a high-purity, low-water lithium difluorosulfonyl imide product; product purity 99.9%, moisture content 0.0012%, F - Content 0.00033%, SO4 2- Content 0.00021%;

[0049] The pretreatment process for activated carbon powder includes the following steps:

[0050] (1) Mix activated carbon powder with primary pure water at a volume ratio of 1:10, and then boil for 0.5 hours;

[0051] (2) After cooling and filtering, rinse with pure water and then vacuum dry at 100°C to complete the pretreatment of activated carbon powder.

[0052] The preparation method of lithium molecular sieves includes the following steps:

[0053] (1) Using 30% silica sol as the silicon source, lithium aluminate as the aluminum source, and lithium oxalate as the lithium source, the reaction was carried out at 100°C for 36 hours under alkaline conditions (specifically, lithium hydroxide or lithium carbonate can be used to adjust the system to be alkaline).

[0054] (2) Filter the reaction solution, wash the filter cake three times and then dry it to obtain lithium molecular sieve with a particle size of 1.0 to 2.0 mm;

[0055] In use: The lithium molecular sieve is activated by vacuum calcination at 350℃, and then loaded into the molecular sieve adsorption column to form a lithium molecular sieve column.

[0056] The moisture content and F of the obtained product -Content and SO4 2- The comparison of the content with the crude product clearly shows that the method of this invention can effectively remove the water content in the crude lithium difluorosulfonylimide, resulting in a product with extremely low water content and high purity, and avoiding the formation of F due to hydrolysis. - SO4 2- The excessive content of certain substances caused the product to fail to meet battery application standards.

[0057] The above-described preferred embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of the invention. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing high-purity, low-water lithium difluorosulfonylimide, characterized in that, The method includes the following steps: S1. Dissolve crude lithium difluorosulfonylimide in an organic solvent to obtain solution C; S2. Add pretreated activated carbon powder to the solution C, stir, filter, pump the filtrate into a lithium molecular sieve column, filter the received solution a second time, concentrate the filtrate, add anhydrous dichloromethane to crystallize, dry, and obtain a high-purity, low-water lithium difluorosulfonylimide product. The preparation method of lithium molecular sieves includes the following steps: (1) Using 30% silica sol as the silicon source, lithium aluminate as the aluminum source, and lithium oxalate as the lithium source, the reaction was carried out under alkaline conditions at 90-120°C for 24-72 hours. (2) Filter the reaction solution, wash and dry the filter cake to obtain lithium molecular sieve; In use: The lithium molecular sieve is activated by vacuum calcination at 300-350°C, and then loaded into a molecular sieve adsorption column to form a lithium molecular sieve column.

2. The method for preparing high-purity, low-water-content lithium difluorosulfonylimide according to claim 1, characterized in that, The organic solvent is selected from methyl tert-butyl ether or dimethyl carbonate; the molar volume ratio of the crude lithium bis(fluorosulfonyl)imide to the organic solvent in step S1 is 0.5 to 2.0 mol / L.

3. The method for preparing high-purity, low-water-content lithium difluorosulfonylimide according to claim 1, characterized in that, Step S2: Add 1.0% to 10.0% of the solution volume of pretreated activated carbon powder to the solution C, then stir at room temperature for 1 to 5 hours. Next, filter the solution with ordinary filter paper, then pump the filtrate into a lithium molecular sieve column, controlling the receiving rate to 1 to 3 ml / min. Pass the received solution through a polytetrafluoroethylene microfiltration membrane, then concentrate the filtrate under reduced pressure, add anhydrous dichloromethane to crystallize, and vacuum dry the crystals to obtain a high-purity, low-water lithium difluorosulfonylimide product.

4. The method for preparing high-purity, low-water-content lithium difluorosulfonylimide according to claim 3, characterized in that, The pore size of the polytetrafluoroethylene microfiltration membrane is 0.1–0.45 μm; The pretreatment process of activated carbon powder includes the following steps: mix activated carbon powder with primary pure water, then boil, cool and filter, rinse with primary pure water, and then dry to complete the pretreatment of activated carbon powder.

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