Method for electrochemical synthesis of bis (fluorosulfonyl) imide alkali metal salt

Abstract

The invention relates to a method for electrochemical synthesis of bis (fluorosulfonyl) imide alkali metal salt. The method comprises the following steps that under the action of an external electric field, alkali metal cations penetrate through the cation exchange membrane to enter the product chamber (2), bis (fluorosulfonyl) imide anions penetrate through the anion exchange membrane to enter the product chamber (2), and the alkali metal cations and the bis (fluorosulfonyl) imide anions in the product chamber (2) are combined to form bis (fluorosulfonyl) imide alkali metal salt. The bis (fluorosulfonyl) imide alkali metal salt prepared by the method has extremely high purity and hardly contains other water-soluble impurities, so that the synthesis steps are simplified, and the subsequent purification process is greatly simplified.

Description

Technical Field

[0001] This invention relates to the field of materials and chemical engineering, specifically to a method for the precise synthesis of bis(fluorosulfonyl)imide alkali metal salts by direct isostoichiometry using an electrochemical method. Background Technology

[0002] Lithium-ion batteries are currently one of the highest energy density types in the commercial rechargeable battery field. Lithium bisfluorosulfonyl imide (LiFSI), as a new type of lithium-ion battery electrolyte component, has advantages such as high stability (does not decompose below 200℃), excellent low-temperature performance, good hydrolytic stability, and more environmentally friendly properties. The development of its production process has attracted widespread attention and importance from the industry.

[0003] The synthesis of LiFSI generally involves two-step and one-step methods, with the two-step method being more mature. The so-called "two-step method" involves first synthesizing bis(fluorosulfonyl)imide (HFSI) chemically, followed by lithiation to obtain LiFSI. The lithiation reaction is generally considered a simple acid-base reaction and therefore has not received much attention.

[0004] In various LiFSI synthesis techniques, Li salts (such as LiF, Li2CO3) or Li bases (LiOH) can be used to react with HFSI to generate LiFSI.

[0005] Patent CN117699748A discloses a method for preparing high-purity lithium difluorosulfonylimide. The method involves heating and stirring aminosulfonic acid, sulfonium chloride, and chlorosulfonic acid under reflux to obtain dichlorosulfonylimide. The dichlorosulfonylimide is then fluorinated and concentrated in a good solvent. After concentration to a certain level, a poor solvent is added for crystallization. The mixture is then filtered to obtain crude difluorosulfonylimide. The crude product is then lithiumized to form a salt using alkaline lithium, followed by pulping with dichloromethane solvent. After filtration and drying, lithium difluorosulfonylimide is obtained.

[0006] Patent CN116750733A discloses a method for preparing lithium bis(fluorosulfonyl)imide using thioyl fluoride. This invention uses thioyl fluoride, ammonia, organic base, solvent, and lithium hydroxide to prepare lithium bis(fluorosulfonyl)imide. This invention first purifies the product by distillation and extraction, then filters it, and finally adsorbs it through a fluoropeptide molecular sieve to further remove trace impurities from the crude product, thus obtaining high-purity lithium bis(fluorosulfonyl)imide.

[0007] Patent CN110745795A discloses a method for electrochemically synthesizing lithium bisfluorosulfonylimide. This method involves purifying hydrofluoric acid electrochemically to obtain a high-purity, colorless liquid of bisfluorosulfonylimide. Then, it is reacted with lithium hydroxide, filtered, and recrystallized to obtain high-purity lithium bisfluorosulfonylimide.

[0008] In actual production, we observed that the lithiation reaction process was particularly complex and cumbersome, mainly due to the difficulty in achieving precise equimolar ratio reaction conditions. Whether it's an excess of bis(fluorosulfonyl)imide or an excess of alkali metal salt, these non-ideal conditions introduce impurities into the subsequent purification stage. These impurities are highly likely to promote the hydrolysis of lithium bis(fluorosulfonyl)imide (LiFSI), thus requiring a series of tedious and meticulous purification steps to ensure that the final product meets the high standards set for battery-grade applications.

[0009] To address the above problems, this invention is proposed. Summary of the Invention

[0010] This invention relates to a method for synthesizing bis(fluorosulfonyl)imide alkali metal salts. An electrochemical method is employed to achieve a reaction with strictly stoichiometric molar ratios for the formation of bis(fluorosulfonyl)imide alkali metal salts, which not only simplifies the synthesis steps but also greatly simplifies the subsequent purification process.

[0011] This application provides a method for the electrochemical synthesis of lithium bis(fluorosulfonyl)imide, the method comprising the following steps:

[0012] Under the action of an external electric field, metal cations pass through the cation exchange membrane into product chamber 2, and bis(fluorosulfonyl)imide anions pass through the anion exchange membrane into product chamber 2. In product chamber 2, metal cations and bis(fluorosulfonyl)imide anions combine to form bis(fluorosulfonyl)imide alkali metal salt.

[0013] Preferably, the method is carried out in an electrolytic cell, which includes an anode and a cathode, and from the anode to the cathode are arranged the following in sequence: an anode chamber 1 containing metal cations, the cation exchange membrane, the product chamber 2, the anion exchange membrane, and a cathode chamber 3 containing bis(fluorosulfonyl)imide.

[0014] The solutions do not flow between the chambers; only ions flow through the exchange membrane.

[0015] Preferably, electrolysis is performed using a constant voltage method, with the operating current density controlled at 10 mA / cm². 2 ~500mA / cm 2 More preferably, it is 50–200 mA / cm 2 .

[0016] Preferably, the operating pressure is set to atmospheric pressure, approximately between 0 kPa gauge pressure and 50 kPa gauge pressure.

[0017] The operating temperature is controlled within room temperature, typically 20℃ ± 5℃, but the specific range is determined based on the experimental environment, up to 80℃. For example, 15~80℃.

[0018] Preferably, the metal cation is selected from alkali metal ions, such as lithium ions, Na ions, K ions, Rb ions, and Cs ions.

[0019] The raw materials for the anode chamber 1 include, but are not limited to, oxides, sulfates, hydroxides, acetates, methanesulfonates, or chlorides of alkali metals such as lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs), and the concentration of the raw materials is 0.1–5.3 mol / kg solution.

[0020] Preferably, the raw material for the cathode chamber 3 is an aqueous solution of bis(fluorosulfonyl)imide (HFSI) with a concentration of 0.1–10 mol / kg.

[0021] Preferably, the raw material for product chamber 2 is water or an aqueous solution of bis(fluorosulfonyl)imide alkali metal salt. Preferably, the concentration of the bis(fluorosulfonyl)imide alkali metal salt aqueous solution is 0.001–0.1 mol / kg. The purpose of adding a trace amount of bis(fluorosulfonyl)imide alkali metal salt is to pre-activate the electric field and promote electron transport. The cation of the bis(fluorosulfonyl)imide alkali metal salt is the same as the metal cation of the anode chamber 1.

[0022] Preferably, a buffer chamber 4 is further provided between the cathode chamber 3 and the cathode, and a second cation exchange membrane is provided between the cathode chamber 3 and the buffer chamber 4. The buffer chamber 4 contains water.

[0023] Preferably, the cathode is an electrode that catalyzes the hydrogen evolution reaction, and the anode is an electrode that catalyzes the oxygen evolution reaction.

[0024] Preferably, the anode includes, but is not limited to, electrodes made of iridium oxide, ruthenium oxide, and oxidized ruthenium and iridium.

[0025] Cathodes include, but are not limited to, electrodes made of metallic nickel, stainless steel, metallic platinum, and supported platinum-carbon catalysts.

[0026] The method employs either an intermittent or continuous process. When using a continuous process to synthesize bis(fluorosulfonyl)imide alkali metal salts, feed solution is continuously added to the anode chamber 1 and the cathode chamber 3, while the product chamber 2 continuously extracts the generated bis(fluorosulfonyl)imide alkali metal salt solution.

[0027] Preferably, the gases generated in the anode chamber 1 and the cathode chamber 3 are collected and utilized separately.

[0028] Preferably, the anode chamber 1, the cation exchange membrane, the product chamber 2, the anion exchange membrane, and the cathode chamber 3 form a combination, and one or more of this combination are provided in the electrolytic cell. Theoretically, 1 to 20 such combinations can be provided.

[0029] That is, the above-mentioned two-membrane three-chamber combination can be extended in series, that is, multiple identical two-membrane three-chamber combinations can be set in the same electrolytic cell, with the two ends being the anode and the cathode respectively. Theoretically, the number of such series combinations is not absolutely limited, provided that the electrical and chemical balance allows it. In practical applications, the recommended range of series levels is usually set to 1 to 20 levels.

[0030] Preferably, a buffer chamber 4 is provided between the cathode chamber 3 of the first series of two-membrane three-chamber combination and the anode chamber 1 of the second series of two-membrane three-chamber combination. A second cation exchange membrane is provided between the cathode chamber 3 and the buffer chamber 4, and a second anion exchange membrane is provided between the buffer chamber 4 and the anode chamber 1. The buffer chamber 4 contains a pure aqueous solution.

[0031] Preferably, the anode chamber 1, the product chamber 2, the cathode chamber 3, and the buffer chamber 4 are a combination, and one or more of this combination are provided in the electrolytic cell.

[0032] For example: its structure is (-) cathode |H-FSI| - |LiFSI(aq.)| + |Li(OH)(aq.){ | - |Water| + |H-FSI| - | LiFSI(aq.)| + |Li(OH)} n (aq.)|anode(+), where {} n For the extended part, n represents the number of cascaded elements, n = 0 to 20; "| - |Water| + | can be replaced by a bipolar film. A single vertical line | represents an interface. - | represents an anion exchange membrane,| + | indicates a cation exchange membrane.

[0033] The above expression means:

[0034] The anode chamber 1, the product chamber 2, the cathode chamber 3, and the buffer chamber 4 form a combination. When two of these combinations are installed in the electrolytic cell, the structure is as follows:

[0035] The following are arranged sequentially from anode to cathode: anode chamber 1, cation exchange membrane, product chamber 2, anion exchange membrane, cathode chamber 3, cation exchange membrane, buffer chamber 4, anion exchange membrane, anode chamber 1, cation exchange membrane, product chamber 2, anion exchange membrane, and cathode chamber 3.

[0036] Without buffer chamber 4, the scheme is as follows: from anode to cathode, the following are arranged in sequence: anode chamber 1, cation exchange membrane, product chamber 2, anion exchange membrane, cathode chamber 3, bipolar membrane, anode chamber 1, cation exchange membrane, product chamber 2, anion exchange membrane, and cathode chamber 3.

[0037] The above technical solutions can be freely combined, provided they do not contradict each other.

[0038] Preferably, the method is carried out using either an intermittent or continuous method. Specifically, when using a continuous method to synthesize bis(fluorosulfonyl)imide alkali metal salts, raw materials are continuously added to the anode chamber 1 and the cathode chamber 3, while the product chamber 2 continuously collects the generated bis(fluorosulfonyl)imide alkali metal salts.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The beneficial effects of this invention are as follows:

[0041] 1. This application innovatively proposes a method for synthesizing bis(fluorosulfonyl)imide alkali metal salts via electrochemical means. Driven by an applied electric field, the electrodialysis effect induces alkali metal cations to cross a cation exchange membrane, while bis(fluorosulfonyl)imide anions cross an anion exchange membrane, both migrating together to the intermediate product chamber 2. Within this product chamber 2, the alkali metal cations and bis(fluorosulfonyl)imide anions combine strictly according to a stoichiometric ratio to form the bis(fluorosulfonyl)imide alkali metal salt. The bis(fluorosulfonyl)imide alkali metal salt product in product chamber 2 contains no other water-soluble impurities, and its purity generally reaches over 99%.

[0042] 2. In the method of this application, alkali metal cations and difluorosulfonamide anions are fed into the anode chamber 1 and the cathode chamber 3, respectively. The alkali metal cations and difluorosulfonamide anions do not need to be fed according to the stoichiometric ratio. That is, regardless of the feeding ratio, under the action of the same external electric field, the alkali metal ions and difluorosulfonamide anions passing through the metal cation exchange membrane and the anion exchange membrane strictly conform to the stoichiometric ratio to generate the product difluorosulfonamide alkali metal salt.

[0043] 3. Electrochemical methods are usually carried out under mild conditions (e.g., ambient temperature and pressure), and the use of electricity to replace environmentally harmful chemical reagents (e.g., stoichiometric oxidants and reductants) gives electrochemistry the potential to improve the efficiency and sustainability of chemical reactions.

[0044] 4. Electrochemical technology enables the continuous production of this method for synthesizing alkali metal salts of bis(fluorosulfonyl)imide. It only requires a continuous supply of electricity and can be carried out continuously without the addition of any oxidizing or reducing agents. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the reaction inside the electrolytic cell in Example 1.

[0046] Figure 2 This is a schematic diagram of the reaction inside the electrolytic cell in Example 13.

[0047] Figure 3This is a schematic diagram of the reaction inside the electrolytic cell in Example 14.

[0048] List of reference numerals in the attached diagram:

[0049] 1. Anode chamber, 2. Product chamber, 3. Cathode chamber, 4. Buffer chamber. Detailed Implementation

[0050] The present invention will be further described below through embodiments, but is not limited to these embodiments. Experimental methods not specifically described in the embodiments generally use conventional conditions and conditions described in manuals, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified. The raw materials used in the following embodiments and comparative examples are all commercially available.

[0051] The principle of this application is as follows:

[0052] This application employs an electrochemical method. A two-membrane, three-chamber electrolytic cell design and a two-electrode system are used, dividing the electrolytic cell into three parts: a cathode chamber, an anode chamber, and a product chamber, separated by anion-exchange membranes and cation-exchange membranes. An acidic (HFSI) aqueous solution is placed in the cathode chamber, separated from the product chamber by anion-exchange membranes. An alkaline (LiOH-) aqueous solution is placed in the anode chamber, separated from the product chamber by cation-exchange membranes. The area between the anion-exchange membranes and cation-exchange membranes is the product chamber. When current is applied to the anode and cathode, a reduction reaction occurs at the cathode, reducing hydrogen ions to hydrogen gas, and FSI anions electromigrate through the anion-exchange membrane into the product chamber. An oxidation reaction occurs at the anode, oxidizing hydroxide ions to oxygen gas, and lithium ions pass through the cation-exchange membrane into the product chamber. Since the anion-exchange membrane only allows anions to pass through, and the cation-exchange membrane only allows cations to pass through, to ensure electroneutrality in the product chamber, lithium ions and FSI anions combine strictly in their stoichiometric ratio to form LiFSI. The chemical reaction equations are described below:

[0053] The reaction at the cathode: 2H + +2e - =H2↑

[0054] The reaction at the anode: 2OH - -2e - = 1 / 2O2↑ + H2O

[0055] Product room reaction: FSI - +Li + =LiFSI

[0056] The technical solution of the present invention is as follows: using an apparatus that satisfies the above-mentioned series of electrochemical processes, namely an electrochemical synthesis reactor with a "two-membrane three-chamber" structure including anion exchange membrane, cation exchange membrane, cathode chamber, anode chamber, and product chamber, using HFSI and LiOH as raw materials, and achieving the precise stoichiometric synthesis of LiFSI through water electrolysis reaction.

[0057] An electrochemical method for synthesizing alkali metal salts of bis(fluorosulfonyl)imide comprises the following steps:

[0058] The cathode uses a platinum-containing electrode, and the anode uses a titanium oxide-supported iridium oxide electrode. A lithium hydroxide aqueous solution with a concentration of 0.1–5.3 mol / kg is injected into anode chamber 1; a 0.001 mol / kg lithium bisfluorosulfonylimide (LiFSI) aqueous solution is injected into product chamber 2; and a bisfluorosulfonylimide (HFSI) aqueous solution with a concentration of 0.1–10 mol / kg is injected into cathode chamber 3.

[0059] Preferably, to ensure production capacity, the feed should be of high concentration, with HFSI concentration of 1-10 mol / kg and LiOH concentration of 1-5.3 mol / kg.

[0060] Preferably, the operating temperature of the electrolytic cell is room temperature and the voltage is atmospheric pressure.

[0061] The method described in this application is applicable to both intermittent and continuous methods.

[0062] Preferably, a continuous method is used to synthesize LiFSI, that is, the feed liquid is circulated between the cathode chamber and the anode chamber, and the generated LiFSI aqueous solution is continuously extracted from the product chamber.

[0063] Preferably, when using an HFSI aqueous solution with a concentration of 4.5–5 mol / kg and a LiOH aqueous solution with a concentration of 4.5–5 mol / kg as raw materials, the mass concentration of the extracted LiFSI is 60–70%, and corresponding pure water needs to be added to the product chamber 2.

[0064] Example 1

[0065] like Figure 1 A method for electrochemically synthesizing bis(fluorosulfonyl)imide alkali metal salts, wherein the method is carried out in an electrolytic cell, the electrolytic cell comprising: an anode and a cathode, and, from the anode to the cathode, sequentially arranged: an anode chamber 1, a cation exchange membrane, a product chamber 2, an anion exchange membrane, and a cathode chamber 3.

[0066] The structure of the electrolytic cell is as follows: from cathode to anode, the structures are: (-) Cathode |H-FSI|-|LiFSI(aq.)| + |Li(OH)(aq.)| anode (+). Where the single vertical line | represents the interface, |-| represents the anion exchange membrane, and | +| indicates a cation exchange membrane.

[0067] Cathode 10*10cm 2 The platinum sheet electrode uses a 10*10cm anode. 2 Titanium oxide supported iridium oxide electrode.

[0068] Anode chamber 1 was initially filled with 300 ml of 2.5 mol / kg lithium hydroxide aqueous solution, cathode chamber 3 was initially filled with 300 ml of 5 mol / kg lithium bis(fluorosulfonyl)imide (HFSI) aqueous solution, and product chamber 2 was initially filled with 300 ml of 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) aqueous solution. A power supply was then connected, and electrolysis was performed using a constant voltage method with a current density set to 200 mA / cm². 2 The operating pressure is 0 kPa gauge pressure, and the operating temperature is 25℃.

[0069] After a 1-hour reaction time, 2.5 mol / kg lithium hydroxide aqueous solution was continuously fed into anode chamber 1 at a flow rate of 5 ml / min; 5 mol / kg bis(fluorosulfonyl)imide (HFSI) aqueous solution was continuously fed into cathode chamber 3 at a flow rate of 5 ml / min; and 0.001 mol / kg lithium(fluorosulfonyl)imide (LiFSI) aqueous solution was continuously fed into product chamber 2 at a flow rate of 5 ml / min. Anode chambers 1 through cathode chamber 3 were simultaneously discharged continuously at a flow rate of 5 ml / min.

[0070] The product was analyzed by ion chromatography, and the yield of lithium bis(fluorosulfonyl)imide was 98%, with a purity of 99.8%. Water was not considered an impurity when calculating the purity of lithium bis(fluorosulfonyl)imide in this application.

[0071] Example 2

[0072] In addition to adding the solutions of anode chamber 1 and cathode chamber 3 according to the reaction concentrations in Table 1 below, six sets of reactions were carried out in the same manner as in Example 1, and the yields and purities of lithium difluorosulfonylimide are also listed in Table 1 below.

[0073] Table 1

[0074]

[0075] Example 3

[0076] Except for changing the temperature to 15, 50, and 80°C, the same three sets of reactions were carried out as in Example 1, and the yields and purities of lithium bis(fluorosulfonyl)imide are listed in Table 2 below.

[0077] Table 2

[0078] Number of reaction groups 1 2 3 Reaction temperature / ℃ 15 50 80 Yield / % 98 98 98 purity / % 99.8 99.8 99.8

[0079] Example 4

[0080] In addition to setting the current density to 10, 50, 200, 300, and 500 mA / cm² 2 Five sets of reactions were carried out in the same manner as in Example 1, and the yield and purity of lithium bis(fluorosulfonyl)imide are listed in Table 3 below.

[0081] Table 3

[0082] Number of reaction groups 1 2 3 4 5 <![CDATA[Current density / mA·cm -2 > 10 50 200 300 500 Yield / % 34 60 98 92 90 purity / % 99.8 99.8 99.8 99.8 99.8

[0083] Example 5

[0084] Except for changing the pressure to 50 kPa gauge pressure, the reaction was carried out in the same manner as in Example 1, yielding lithium bis(fluorosulfonyl)imide in 98% yield and with a purity of 99.8%.

[0085] Example 6

[0086] Besides changing the anode electrode to 10*10cm 2 The titanium oxide-supported ruthenium oxide electrode was reacted in the same manner as in Example 1 to obtain lithium bisfluorosulfonylimide with a yield of 98% and a purity of 99.8%.

[0087] Example 7

[0088] Besides changing the cathode electrode to 10*10cm 2 The nickel electrode was reacted in the same manner as in Example 1 to obtain lithium bis(fluorosulfonyl)imide with a yield of 98% and a purity of 99.8%.

[0089] Example 8

[0090] Besides changing the cathode electrode to 10*10cm 2 The carbon cloth electrode supported on platinum-carbon catalyst was reacted in the same manner as in Example 1 to obtain lithium bis(fluorosulfonyl)imide in 98% yield and 99.8% purity.

[0091] Example 9

[0092] Except that the solution introduced into product chamber 2 was changed to 300 ml of 0.1 mol / kg lithium bisfluorosulfonylimide (LiFSI) solution, the reaction was carried out in the same manner as in Example 1, and the yield of lithium bisfluorosulfonylimide was 98% and the purity was 99.8%.

[0093] Example 10

[0094] Except that the solution introduced into product chamber 2 was replaced with 300 ml of pure aqueous solution, the reaction was carried out in the same manner as in Example 1, and the yield of lithium bis(fluorosulfonyl)imide was 92% and the purity was 99.8%.

[0095] Example 11

[0096] Except for changing the solution introduced into anode chamber 1 to the solution in Table 4 below, the same six sets of reactions were carried out as in Example 1, and the yield and purity of lithium difluorosulfonylimide are also listed in Table 4 below.

[0097] Table 4

[0098] Number of reaction groups 1 2 3 4 Anode Chamber 1 Solution Lithium oxide Lithium acetate Lithium methanesulfonate Lithium sulfate Yield / % 95 91 92 96 purity / % 99.8 99.8 99.8 99.8

[0099] Example 12

[0100] Except for changing the solution introduced into anode chamber 1 to the solution in Table 5 below, the solution introduced into product chamber 2 is also in Table 5 below. The same 7 sets of reactions were carried out as in Example 1, and the yield and purity of the product are also listed in Table 5 below.

[0101] Among them, NaFSI refers to sodium difluorosulfonamide, KFSI refers to potassium difluorosulfonamide, RbFSI refers to rubidium difluorosulfonamide, and CsFSI refers to cesium difluorosulfonamide.

[0102] Table 5

[0103]

[0104] Example 13

[0105] like Figure 2 An electrochemical synthesis method for bis(fluorosulfonyl)imide alkali metal salts, wherein the method is carried out in an electrolytic cell, the electrolytic cell comprising: an anode and a cathode, and arranged sequentially from the anode to the cathode as: an anode chamber 1, a cation exchange membrane, a product chamber 2, an anion exchange membrane, a cathode chamber 3, a bipolar membrane, an anode chamber 1, a cation exchange membrane, a product chamber 2, an anion exchange membrane, and a cathode chamber 3.

[0106] Cathode 10*10cm 2 The platinum sheet electrode uses a 10*10cm anode. 2 A titanium oxide-supported iridium oxide electrode was used. Two anode chambers 1 were each purged with 300 ml of a 2.5 mol / kg lithium hydroxide aqueous solution; two product chambers 2 were each purged with 300 ml of a 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) solution; and two cathode chambers 3 were each purged with 300 ml of a 5 mol / kg bis(fluorosulfonyl)imide (HFSI) aqueous solution. A power supply was then connected, and electrolysis was performed using a constant voltage method with a current density set to 200 mA / cm². 2 The operating pressure is 0 kPa gauge pressure, and the operating temperature is 25℃.

[0107] After a reaction time of 1 hour, 2.5 mol / kg of lithium hydroxide aqueous solution was continuously fed from the feed chamber into the anode chamber 1 at a flow rate of 5 ml / min; 5 mol / kg of bis(fluorosulfonyl)imide (HFSI) aqueous solution was continuously fed from the feed chamber into the cathode chamber 3 at a flow rate of 5 ml / min; and 0.001 mol / kg of lithium(fluorosulfonyl)imide (LiFSI) solution was continuously fed from the feed chamber into the product chamber 2 at a flow rate of 5 ml / min.

[0108] Anode chamber 1 to cathode chamber 3 are simultaneously discharged continuously at a flow rate of 5 ml / min.

[0109] The product was analyzed by ion chromatography, and the yield of lithium bis(fluorosulfonyl)imide was 98%, with a purity of 99.8%.

[0110] Example 14

[0111] like Figure 3 An electrochemical synthesis method for bis(fluorosulfonyl)imide alkali metal salts, wherein the method is carried out in an electrolytic cell, the electrolytic cell comprising: an anode and a cathode, and arranged sequentially from the anode to the cathode as: an anode chamber 1, a cation exchange membrane, a product chamber 2, an anion exchange membrane, a cathode chamber 3, a cation exchange membrane, a buffer chamber 4, an anion exchange membrane, an anode chamber 1, a cation exchange membrane, a product chamber 2, an anion exchange membrane, and a cathode chamber 3.

[0112] Cathode 10*10cm 2 The platinum sheet electrode uses a 10*10cm anode. 2 The titanium oxide-supported iridium oxide electrode was used. 300 ml of 2.5 mol / kg lithium hydroxide aqueous solution was passed through each of the two anode chambers 1; 300 ml of 0.001 mol / kg lithium bisfluorosulfonylimide (LiFSI) solution was passed through each of the two product chambers 2; and 300 ml of 5 mol / kg bisfluorosulfonylimide (HFSI) aqueous solution was passed through each of the two cathode chambers 3.

[0113] Add 100ml of pure water solution to buffer chamber 4.

[0114] Then, a power supply was connected, and electrolysis was performed using a constant voltage method with a current density set to 200 mA / cm². 2 The operating pressure is 0 kPa gauge pressure, and the operating temperature is 25℃.

[0115] After a 1-hour reaction time, 2.5 mol / kg lithium hydroxide aqueous solution was continuously fed into anode chamber 1 at a flow rate of 5 ml / min; 5 mol / kg bis(fluorosulfonyl)imide (HFSI) aqueous solution was continuously fed into cathode chamber 3 at a flow rate of 5 ml / min; and 0.001 mol / kg lithium(fluorosulfonyl)imide (LiFSI) aqueous solution was continuously fed into product chamber 2 at a flow rate of 5 ml / min. Anode chambers 1 through cathode chamber 3 were simultaneously discharged continuously at a flow rate of 5 ml / min.

[0116] The product was analyzed by ion chromatography, and the yield of lithium bis(fluorosulfonyl)imide was 98%, with a purity of 99.8%.

Claims

1. A method for electrochemically synthesizing a bifluorosulfonylimide alkali metal salt, characterized by, The method comprises the following steps: Under the action of an applied electric field, the alkali metal cations pass through the cation exchange membrane into the product chamber (2), the bisfluorosulfonylimide anions pass through the anion exchange membrane into the product chamber (2), and the alkali metal cations and the bisfluorosulfonylimide anions in the product chamber (2) combine to form bisfluorosulfonylimide alkali metal salt.

2. The method of claim 1, wherein, The method is performed by using an electrolytic cell, and the electrolytic cell comprises an anode and a cathode, and is sequentially provided with an anode chamber (1) containing metal cations, the cation exchange membrane, the product chamber (2), the anion exchange membrane, and a cathode chamber (3) containing bisfluorosulfonylimide from the anode to the cathode.

3. The method of claim 1, wherein, The current density of the applied electric field is 10 mA / cm 2 ~ 500 mA / cm 2 .

4. The method of claim 1, wherein, The raw material in the product chamber (2) is water or an aqueous solution of bisfluorosulfonylimide alkali metal salt.

5. The method of claim 1, wherein, The raw material in the anode chamber (1) contains alkali metal oxide, alkali metal hydroxide, alkali metal acetate, alkali metal sulfate, alkali metal methane sulfonate or alkali metal chloride.

6. The method of claim 2, wherein, The cathode chamber (3) and the cathode are further provided with a buffer chamber (4), the cathode chamber (3) and the buffer chamber (4) are provided with a second cation exchange membrane, and the buffer chamber (4) contains water.

7. The method of claim 1, wherein, The anode chamber (1), the cation exchange membrane, the product chamber (2), the anion exchange membrane and the cathode chamber (3) form a combination, and one or more combinations are arranged in the electrolytic cell.

8. The method of claim 6, wherein, The anode chamber (1), the product chamber (2), the cathode chamber (3) and the buffer chamber (4) form a combination, and one or more combinations are arranged in the electrolytic cell.

9. The method of claim 2, wherein, The cathode uses an electrode with a catalytic function for the hydrogen evolution reaction, and the anode uses an electrode with a catalytic function for the oxygen evolution reaction. The method uses a batch process or a continuous process; when a continuous process is used to synthesize bisfluorosulfonylimide alkali metal salt, raw material liquid is continuously added to the anode chamber (1) and the cathode chamber (3), and an aqueous solution of bisfluorosulfonylimide alkali metal salt is continuously extracted from the product chamber (2).

Images