Method for synthesizing bis (fluorosulfonyl) imide alkali metal salt by using bis (fluorosulfonyl) imide tertiary amine salt

Abstract

The invention relates to a method for synthesizing bis (fluorosulfonyl) imide alkali metal salt by using bis (fluorosulfonyl) imide tertiary amine salt. The method comprises the following steps: under the action of an external electric field, enabling alkali metal cations to pass through a cation exchange membrane to enter a product chamber (2), and enabling bis (fluorosulfonyl) imide anions in bis (fluorosulfonyl) imide tertiary amine salt to pass through an anion exchange membrane to enter the product chamber (2), alkali metal cations and bis (fluorosulfonyl) imide anions in the product chamber (2) are combined to form bis (fluorosulfonyl) imide alkali metal salt. The lithium bis (fluorosulfonyl) imide prepared by the method has extremely high purity and almost does not contain other water-soluble impurities, so that the subsequent purification step is greatly simplified.

Description

Technical Field

[0001] This invention relates to the fields of materials and chemical engineering, and specifically to a method for synthesizing alkali metal salts of bis(fluorosulfonyl)imide using tertiary amine salts of bis(fluorosulfonyl)imide. 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] A common method for synthesizing LiFSI uses thioyl fluoride as a raw material. Specifically, thioyl fluoride and ammonia are first used to synthesize a tertiary amine salt of bis(fluorosulfonyl)imide in the presence of a tertiary amine, which is then lithilated to obtain LiFSI. This method is characterized by its simple and efficient process and significant cost advantages. However, when triethylamine is used as an example of the tertiary amine, the reaction of the bis(fluorosulfonyl)imide triethylamine salt with lithium hydroxide produces LiFSI, triethylamine, and water. The triethylamine produced by this method is difficult to remove. More significantly, in the presence of triethylamine, the generated LiFSI is more prone to hydrolysis, producing various impurities such as hydrogen fluoride, sulfonamides, and sulfuric acid, which cannot meet the high purity requirements of lithium-ion battery electrolytes.

[0004] Patent CN116835539A reports a stepwise method for synthesizing high-purity lithium bis(fluorosulfonyl)imide. This method employs a stepwise reaction approach. In an ammonia-filled environment, triethylamine is used to slowly introduce sulfuryl fluoride, generating fluorosulfonamide triethylamine salt. This salt is then replaced with a strong acid to obtain fluorosulfonamide as an intermediate, which further reacts with sulfuryl fluoride to yield bis(fluorosulfonyl)imide triethylamine salt. In the lithiation process, potassium carbonate is first used to replace triethylamine to obtain KFSI, and then LiBF4 is used in a metathesis reaction with KFSI to obtain LiFSI. This avoids the introduction of anionic impurities, providing the necessary conditions for the synthesis of high-purity lithium bis(fluorosulfonyl)imide.

[0005] However, the current lithiation process for Et3NH·FSI is extremely cumbersome. Furthermore, a slight excess of alkali is generally required for complete reaction of Et3NH·FSI, but this excess alkali still promotes LiFSI decomposition. Therefore, subsequent purification requires a series of complex steps; otherwise, the product quality will not meet the high requirements of battery-grade applications. Thus, developing a strictly stoichiometric Et3NH·FSI lithiation process is essential for the one-step synthesis of LiFSI products.

[0006] This application is submitted in order to address the aforementioned issues. Summary of the Invention

[0007] This invention relates to a method for synthesizing alkali metal salts of bis(fluorosulfonyl)imide from tertiary amine salts of bis(fluorosulfonyl)imide. The method is based on electrochemical technology; one example is a three-membrane four-chamber electrolytic cell design and a two-electrode system, using alkali metal salts (e.g., lithium hydroxide) and tertiary amine salts of bis(fluorosulfonyl)imide (typically, triethylamine bis(fluorosulfonyl)imide Et3NH·FSI) as raw materials, to precisely synthesize alkali metal salts of bis(fluorosulfonyl)imide, such as lithium bis(fluorosulfonyl)imide (LiFSI), according to strict stoichiometric ratios.

[0008] The method includes the following steps:

[0009] Under the action of an external electric field, alkali metal cations pass through the cation exchange membrane and enter product chamber 2, while bisfluorosulfonylimide anions in the tertiary amine salt of bisfluorosulfonylimide pass through the anion exchange membrane and enter product chamber 2. In product chamber 2, alkali metal cations and bisfluorosulfonylimide anions combine to form bisfluorosulfonylimide alkali metal salt.

[0010] 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, a cation exchange membrane, a product chamber 2, a first anion exchange membrane, an alkalization chamber 3, a second anion exchange membrane, and a cathode chamber 4.

[0011] The raw material in the anode chamber 1 contains alkali metal cations;

[0012] The raw material in product chamber 2 is water or an aqueous solution of bis(fluorosulfonyl)imide alkali metal salt. More preferably, the concentration of the aqueous solution of bis(fluorosulfonyl)imide alkali metal salt is 0.001–0.1 mol / kg.

[0013] The raw material in the alkalization chamber 3 is water or an aqueous solution of a tertiary amine salt of difluorosulfonyl imide.

[0014] Preferably, the raw material in the cathode chamber 4 is an aqueous solution containing hydroxide ions, including but not limited to potassium hydroxide, sodium hydroxide, lithium hydroxide, etc.

[0015] In this system, the ion exchange membrane completely blocks the solution between the two chambers.

[0016] Preferably, the current density of the applied electric field is 10 mA / cm². 2 ~500mA / cm 2 .

[0017] Preferably, the raw materials in the anode chamber 1 contain alkali metal oxides, alkali metal hydroxides, alkali metal acetates, alkali metal sulfates, alkali metal methanesulfonates, or alkali metal chlorides. Examples include lithium oxide, lithium acetate, lithium methanesulfonate, lithium sulfate, and lithium carbonate. The raw materials are present in the form of an aqueous solution with a concentration of 0.1–5.3 mol / kg. For example, the raw materials in the anode chamber 1 can also be hydroxides, acetates, methanesulfonates, or chlorides of FSI alkali metal salts such as sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). This indicates that the method is versatile and can be used for the synthesis of FSI alkali metal salts such as sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).

[0018] The tertiary amines include, but are not limited to, triethylamine, trimethylamine, tri-n-butylamine, tri-n-propylamine, ethyl diisopropylamine, N,N-dimethylcyclohexylamine, pyridine, and other organic tertiary amine salts.

[0019] Preferably, the method employs intermittent or continuous operation.

[0020] Preferably, when the method is operated continuously, the raw material solution is continuously introduced into the anode chamber 1 and the alkalization chamber 3, the product chamber 2 continuously discharges the bis(fluorosulfonyl)imide alkali metal salt product, and the alkalization chamber 3 continuously discharges the tertiary amine product. Simultaneously, the anode chamber 1 and the alkalization chamber 3 also continuously discharge the reaction solution.

[0021] Preferably, the anode chamber 1 uses a catalytic electrode that has been proven to have excellent oxygen evolution reaction (OER) performance, including but not limited to nickel wire mesh, nickel foam, stainless steel mesh, ruthenium oxide, and titanium oxide-supported ruthenium, iridium, and other catalytic electrodes.

[0022] Preferably, the cathode chamber 4 uses a catalytic electrode that has been proven to have excellent hydrogen evolution reaction (HER) performance, including but not limited to nickel wire mesh, nickel foam, metallic platinum, and catalytic cathodes coated with catalyst.

[0023] Preferably, the raw material for the anode chamber 1 is lithium hydroxide (LiOH), including but not limited to lithium oxide, lithium acetate, lithium methanesulfonate, lithium sulfate, lithium carbonate, etc. More preferably, the concentration of the raw material is 0.1–5.3 mol / kg.

[0024] Preferably, the raw material for the product chamber 2 is a pure aqueous solution or an aqueous solution of 0.001-0.1 mol / kg concentration of bis(fluorosulfonyl)imide alkali metal salt.

[0025] Preferably, the tertiary amines include, but are not limited to, triethylamine, trimethylamine, tri-n-butylamine, tri-n-propylamine, ethyl diisopropylamine, N,N-dimethylcyclohexylamine, pyridine, and other organic tertiary amine salts.

[0026] The aqueous solution of the difluorosulfonyl imide tertiary amine salt is a water-saturated solution.

[0027] Preferably, the raw material for the cathode chamber 4 is an aqueous solution containing hydroxide ions, including but not limited to potassium hydroxide, sodium hydroxide, lithium hydroxide, etc.

[0028] Preferably, electrolysis is performed using a constant current method, with the operating current density set to 10–500 mA / cm². 2 The optimal operating conditions are 50–200 mA / cm. 2 The electrolysis voltage varies with the current.

[0029] Preferably, the operating pressure is set between atmospheric pressure (approximately 0 kPa gauge pressure) and 50 kPa gauge pressure.

[0030] Preferably, the operating temperature is controlled within the range of room temperature (usually 20℃±5℃, but the specific range is determined according to the experimental environment) to 80℃. For example, 15-80℃.

[0031] Preferably, the method is performed using an intermittent or continuous method.

[0032] In the continuous operation, the feed solution is continuously fed into the anode chamber 1 and the alkalization chamber 3, the product chamber 2 continuously discharges lithium difluorosulfonylimide product, and the alkalization chamber 3 continuously discharges tertiary amine product. More preferably, the feed molar ratio is Et3NH·FSI:LiOH = 1:(0.5~5). Of course, the reaction can be completed without following the above molar ratio.

[0033] Preferably, the anode chamber 1, cation exchange membrane, product chamber 2, first anion exchange membrane, alkalization chamber 3, second anion exchange membrane, and cathode chamber 4 form a three-membrane, four-chamber combination.

[0034] Preferably, the three-membrane four-chamber combination can be extended in series, that is, multiple identical three-membrane four-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 electrical and chemical equilibrium allows it. In practical applications, the recommended range of series stages is usually set to 1 to 20 stages. Its structure is (-)cathode|OH - (aq.)| - |Et3NH·FSI| - |LiFSI(aq.)| + |LiOH(aq.){ | - | Et3NH·FSI | - |LiFSI (aq.)| + |LiOH} n (aq.)|anode(+), where {} n For the extended part, where {} n左起 The first anion exchange membrane | - |Available|- |Water| - |Structure substitution; n represents the number of series connections, which theoretically has no upper limit, but in practice, n = 0 to 20 is appropriate.

[0035] Taking n=1 as an example, its structure is represented as (-)cathode|OH-(aq.)| - |Et3NH·FSI| - |LiFSI(aq.)| + |LiOH(aq.) | - | Et3NH·FSI | - |LiFSI(aq.)| + |LiOH If (aq.)|anode(+), then this extended series electrolyzer has two product chambers and two alkalization chambers. The two anode chambers 1 need to maintain alkalinity. Since extended series electrolyzers only require one pair of electrolytic reactions, the more stages connected in series, the lower the overall power consumption. However, because multi-stage extended series electrolyzers need to overcome higher resistance, there is an optimization limit to the equipment in practical operation.

[0036] Preferably, when more than one such combination is provided, the second anion exchange membrane of the previous combination is in contact with the anode chamber 1 of the next combination, or a buffer chamber 5 and a third anion exchange membrane are provided between the second anion exchange membrane of one combination and the anode chamber 1 of the next combination; the buffer chamber 5 contains water.

[0037] The function of buffer chamber 5 is to separate anode chamber 1 and alkalization chamber 3 to prevent the anions in anode chamber 1 and alkalization chamber 3 from mixing when there is no electric field.

[0038] The above technical solutions can be freely combined, provided they do not contradict each other.

[0039] The first anion exchange membrane, the second anion exchange membrane, and the third anion exchange membrane mentioned above may be the same or different.

[0040] The first anion exchange membranes in different combinations can be the same or different from each other.

[0041] The substances in the anode chamber 1 of different combinations can be the same or different from each other.

[0042] The substances in product chamber 2 in different combinations can be the same or different from each other.

[0043] The substances in alkalization chamber 3 in different combinations can be the same or different from each other.

[0044] The substances in the cathode chamber 4 in different combinations can be the same or different from each other.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The beneficial effects of this invention are as follows:

[0047] 1. This application innovatively proposes a method for synthesizing bis(fluorosulfonyl)imide alkali metal salts using an electrochemical approach. Utilizing the principle of electrodialysis, under the influence of an applied electric field, alkali metal cations pass through a cation exchange membrane into product chamber 2, while bis(fluorosulfonyl)imide anions pass through the anion exchange membrane into product chamber 2. In 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 the product purity generally reaches over 99%.

[0048] 2. In the method of this application, alkali metal cations and difluorosulfonamide anions are fed into the anode chamber 1 and the alkalization 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, since the alkali metal cations and difluorosulfonamide anions passing through the cation exchange membrane and the anion exchange membrane under the same applied electric field are strictly in accordance with the stoichiometric ratio, the alkali metal cations and difluorosulfonamide anions combine in the product chamber 2 in strict accordance with the stoichiometric ratio to form difluorosulfonamide alkali metal salt.

[0049] 3. The tertiary amine formed from the difluorosulfonylimide tertiary amine salt in the alkalization chamber after alkalization can be collected by azeotropic distillation after discharge. This tertiary amine has high purity and can be directly used as an industrial raw material. Under continuous operation, the remaining difluorosulfonylimide tertiary amine salt can be recycled back into the alkalization chamber through electrolysis to continue participating in the reaction.

[0050] 4. Preferably, when the anode chamber 1 contains an aqueous solution of lithium hydroxide, this application can synthesize LiFSI in stoichiometric ratio using lithium hydroxide and bis(fluorosulfonyl)imide tertiary amine salt (typically, Et3NH·FSI) as raw materials. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the reaction inside the electrolytic cell in Example 1.

[0052] Figure 2 This is a schematic diagram of the reaction inside the electrolytic cell in Example 15.

[0053] Figure 3 This is a schematic diagram of the reaction inside the electrolytic cell in Example 16.

[0054] 1. Anode chamber, 2. Product chamber, 3. Alkalization chamber, 4. Cathode chamber, 5. Buffer chamber. Detailed Implementation

[0055] 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.

[0056] The following example, using the synthesis of lithium bis(fluorosulfonyl)imide (LiFSI) from triethylamine bis(fluorosulfonyl)imide (Et3NH·FSI) and lithium hydroxide (LiOH), illustrates the principle of this application:

[0057] This invention employs an electrochemical method, a three-membrane, four-chamber electrolytic cell design, and a two-electrode system. The structure, from cathode to anode, is as follows: cathode chamber, cathode membrane (anion exchange membrane), alkalization chamber, anion exchange membrane, product chamber, anode membrane (cation exchange membrane), and anode chamber. A dilute alkaline solution is introduced into the cathode chamber for conductivity. Under energized conditions, hydrogen gas and hydroxide ions (eq. 1) are generated. The generated hydroxide ions pass through the cathode membrane into the alkalization chamber, where they react with a tertiary amine salt of difluorosulfonylimide (e.g., Et3NH·FSI) to generate free triethylamine and difluorosulfonylimide anions (FSI). - ); FSI - Under the influence of an electric field, lithium ions pass through the anion exchange membrane into the product chamber; an aqueous solution of alkali (represented by LiOH) is placed in the anode chamber, and an oxidation reaction occurs at the anode under energized conditions, where hydroxide ions are oxidized to oxygen (eq. 3). Lithium ions migrate through the cation exchange membrane to 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, in order to ensure electroneutrality in the product chamber, lithium ions and FSI anions combine strictly according to their stoichiometric ratio to form LiFSI (eq. 4).

[0058] The chemical reactions in each chamber are described below:

[0059] The reaction at the cathode is: 2H₂O + 2e⁻ - =H2 + 2OH - eq.1

[0060] The reaction in the alkalization chamber: Et3NH·FSI + OH - =Et3N+H2O+FSI - eq.2

[0061] The reaction at the anode: 2OH - -2e - = 1 / 2O2 + H2O eq.3

[0062] Product room reaction: FSI - +Li + =LiFSI eq.4

[0063] A typical method for synthesizing lithium bis(fluorosulfonyl)imide from a tertiary amine salt of bis(fluorosulfonyl)imide includes the following steps:

[0064] 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 bis(fluorosulfonyl)imide (LiFSI) solution is injected into product chamber 2; an aqueous solution of bis(fluorosulfonyl)imide triethylamine salt with a water content of 0–12% (water-saturated) is injected into alkalization chamber 3; and a potassium hydroxide aqueous solution with a concentration of 0.1–10 mol / kg is injected into cathode chamber 4.

[0065] Preferably, the raw material Et3NH·FSI is a water-saturated feed, i.e., the saturated water content is 12% by mass. Et3NH·FSI is a liquid under operating conditions.

[0066] Preferably, the Et3NH·FSI aqueous solution contains 0–12% water by mass, i.e., the Et3NH·FSI content is 88%–100%. The concentration of LiOH used is 1–5.3 mol / kg.

[0067] Preferably, the operating pressure is set between atmospheric pressure (approximately 0 kPa gauge pressure) and 50 kPa gauge pressure; while the operating temperature is controlled within the range of room temperature (usually 20℃ ± 5℃, depending on the experimental environment) to 80℃.

[0068] This technology is applicable to both batch and continuous processes. In batch processes, the reaction progress is detected by measuring the conductivity of the alkalization chamber. When the conductivity decreases, it indicates that the raw material Et3NH·FSI has been alkalized.

[0069] Preferably, this technology is applicable to the synthesis of LiFSI using a continuous process, namely, the feed solution is circulated into the anode chamber, free triethylamine is separated from the alkalization chamber, and fresh Et3NH·FSI is continuously added into the alkalization chamber; the product chamber continuously extracts the generated LiFSI aqueous solution.

[0070] Preferably, the free triethylamine can be collected by azeotropic distillation to obtain pure chemicals.

[0071] Preferably, when using 4.5–5 mol / kg LiOH, the mass concentration of LiFSI in the extracted LiFSI aqueous solution is 50–70%, and fresh pure water or low-concentration LiFSI aqueous solution is added to product chamber 2.

[0072] This method is also applicable to continuous reactions, i.e., continuous feeding of LiOH and Et3NH·FSI, with continuous production of LiFSI and alkalization solution from alkalization chamber 3. The mass fraction of Et3NH·FSI in the feed is 88%–100%, and the concentration of LiOH in the feed is 0.1–5.3 mol / kg. Because the aqueous solution of Et3NH·FSI has a low water content, a higher concentration of Et3NH·FSI is required in the feed.

[0073] Example 1

[0074] like Figure 1 A method for electrochemically synthesizing lithium bis(fluorosulfonyl)imide, 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, a first anion exchange membrane, an alkalization chamber 3, a second anion exchange membrane, and a cathode chamber 4.

[0075] The structure of the electrolytic cell is as follows: from cathode to anode, the structures are: (-) Cathode |OH-(aq)|-|Et3NH·FSI|-|LiFSI(aq.)| + |LiOH(aq.)| anode (+). Where the single vertical line | represents the interface, |-| represents the anion exchange membrane, and | + | indicates a cation exchange membrane.

[0076] Cathode 10*10cm 2 The platinum sheet electrode uses a 10*10cm anode. 2 Titanium oxide supported iridium oxide electrode.

[0077] The anode chamber 1 was initially filled with 250 ml of a 2.5 mol / kg lithium hydroxide aqueous solution, the cathode chamber 4 with a 1 mol / kg potassium hydroxide aqueous solution, the alkalization chamber 3 with 250 ml of an 88% (w / w) triethylamine bis(fluorosulfonyl)imide aqueous solution, and the product chamber 2 with 250 ml of a 0.001 mol / kg lithium(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 300 mA / cm². 2 The operating pressure is 0 kPa gauge pressure, and the operating temperature is 25℃.

[0078] After a reaction time of 1 hour, the conductivity of alkalization chamber 3 was measured by a conductivity meter, and the conductivity decreased by 2000 μS / cm.

[0079] Anode chamber 1 is continuously fed with a 2.5 mol / kg lithium hydroxide aqueous solution from the raw material chamber at a flow rate of 5 ml / min; cathode chamber 4 is continuously fed with a 1 mol / kg potassium hydroxide aqueous solution from the raw material chamber at a flow rate of 5 ml / min; alkalization chamber 3 is continuously fed with an 88% (w / w) triethylamine bis(fluorosulfonyl)imide aqueous solution from the raw material chamber at a flow rate of 0.25 ml / min; product chamber 2 is continuously fed with a 0.001 mol / kg lithium(fluorosulfonyl)imide (LiFSI) aqueous solution from the raw material chamber at a flow rate of 5 ml / min.

[0080] Anode chamber 1 to cathode chamber 4 simultaneously discharge material at the same flow rate as their feed.

[0081] The product from alkalization chamber 3 was collected by azeotropic distillation to obtain triethylamine, which was found to have a purity of 99.8% by gas chromatography.

[0082] The product discharged from product chamber 2 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.

[0083] Example 2

[0084] In addition to adding the solutions of anode chamber 1 and cathode chamber 4 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.

[0085] Table 1

[0086] Number of reaction groups 1 2 3 4 5 6 Lithium hydroxide / mol / kg 0.1 2 3 4 5 5.3 <![CDATA[Mass fraction of Et3NH·FSI / %]]> 88 90 92 94 96 100 Yield / % 98 96 94 81 70 69 purity / % 99.8 99.8 99.8 99.8 99.8 99.8

[0087] Example 3

[0088] Except for changing the temperature to 30, 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.

[0089] Table 2

[0090] Number of reaction groups 1 2 3 Reaction temperature / ℃ 15 50 80 Yield / % 98 98 98 purity / % 99.8 99.8 99.8

[0091] Example 4

[0092] In addition to setting the current density to 10, 50, 200, 300, and 500 mA / cm² 2 The same six reactions were carried out as in Example 1, and the yields and purities of lithium bis(fluorosulfonyl)imide are listed in Table 3 below.

[0093] Table 3

[0094] Number of reaction groups 1 2 3 4 5 6 <![CDATA[Current density / mA·cm -2 > 10 50 200 300 400 500 Yield / % 34 60 92 98 98 91 purity / % 99.8 99.8 99.8 99.8 99.8 99.8

[0095] Example 5

[0096] 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%.

[0097] Example 6

[0098] Besides changing the anode electrode to 10*10cm 2 The stainless steel mesh 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%.

[0099] Example 7

[0100] 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%.

[0101] Example 8

[0102] Besides changing the cathode electrode to 10*10cm 2 The nickel wire mesh 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%.

[0103] Example 9

[0104] Besides changing the cathode electrode to 10*10cm 2 The carbon cloth electrode with nickel foam catalyst was reacted in the same manner as in Example 1 to obtain lithium bis(fluorosulfonyl)imide in 98% yield and 99.8% purity.

[0105] Example 10

[0106] Except that the solution introduced into product chamber 2 was changed to 250 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%.

[0107] Example 11

[0108] Except that the solution introduced into product chamber 2 was replaced with 250 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%.

[0109] Example 12

[0110] 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.

[0111] Table 4

[0112] 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

[0113] Example 13

[0114] Except for changing the solution introduced into alkalization chamber 3 to the solution 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.

[0115] All of the solutions are saturated aqueous solutions.

[0116] Table 5

[0117]

[0118] Example 14

[0119] Except for changing the solution introduced into anode chamber 1 to the solution in Table 6 below, the solution introduced into product chamber 2 is also in Table 6 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 6 below.

[0120] Among them, NaFSI refers to sodium difluorosulfonamide, KFSI refers to potassium difluorosulfonamide, RbFSI refers to rubidium difluorosulfonamide, and CsFSI refers to cesium difluorosulfonamide.

[0121] Table 6

[0122]

[0123]

[0124] Example 15

[0125] like Figure 2 A method for electrochemically synthesizing lithium bis(fluorosulfonyl)imide, the method being 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, a first anion exchange membrane, an alkalization chamber 3, a second anion exchange membrane, and an anode chamber 1, a cation exchange membrane, a product chamber 2, a first anion exchange membrane, an alkalization chamber 3, and a second anion exchange membrane / cathode chamber 4.

[0126] In this embodiment, the anode chamber 1, cation exchange membrane, product chamber 2, first anion exchange membrane, alkalization chamber 3, and second anion exchange membrane constitute a combination, and the number of such combinations is n. In this embodiment, n = 1.

[0127] The structure of the electrolytic cell is represented as follows: its structure is (-) cathode |OH-(aq.)|-|Et3NH·FSI|-|LiFSI(aq.)| + |LiOH(aq.){|- | Et3NH·FSI | - |LiFSI(aq.)| + |LiOH} n (aq.)|Anode(+).

[0128] in{} n For the extended part, n represents the number of series connections, which theoretically has no upper limit; in this embodiment, n = 1. A single vertical line | represents an interface, |-| represents an anion exchange membrane, and | + | indicates a cation exchange membrane.

[0129] Cathode 10*10cm 2 The platinum sheet electrode uses a 10*10cm anode. 2 Titanium oxide supported iridium oxide electrode.

[0130] Initially, 250 ml of a 2.5 mol / kg lithium hydroxide aqueous solution was injected into each of the two anode chambers 1; 1 mol / kg potassium hydroxide aqueous solution was injected into each of the two cathode chambers 4; 250 ml of an 88% (w / w) triethylamine bis(fluorosulfonyl)imide aqueous solution was injected into each of the two alkalization chambers 3; and 250 ml of a 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) solution was injected into each of the two product chambers 2. A power supply was then connected, and electrolysis was performed using a constant voltage method with a current density set to 300 mA / cm². 2 The operating pressure is 0 kPa gauge pressure, and the operating temperature is 25℃.

[0131] After a reaction time of 1 hour, the conductivity of the two alkalization chambers 3 was measured by a conductivity meter, and the conductivity decreased by 2000 μS / cm.

[0132] Anode chamber 1 is continuously fed with a 2.5 mol / kg lithium hydroxide aqueous solution from the raw material chamber at a flow rate of 5 ml / min; cathode chamber 4 is continuously fed with a 1 mol / kg potassium hydroxide aqueous solution from the raw material chamber at a flow rate of 5 ml / min; alkalization chamber 3 is continuously fed with an 88% (w / w) triethylamine bis(fluorosulfonyl)imide aqueous solution from the raw material chamber at a flow rate of 0.25 ml / min; product chamber 2 is continuously fed with a 0.001 mol / kg lithium(fluorosulfonyl)imide (LiFSI) solution from the raw material chamber at a flow rate of 5 ml / min.

[0133] Anode chamber 1 to cathode chamber 4 are simultaneously discharged at the same flow rate as the feed.

[0134] The product from alkalization chamber 3 was collected by azeotropic distillation to obtain triethylamine, which was found to have a purity of 99.8% by gas chromatography.

[0135] The product from product room 2 was analyzed by ion chromatography, and the yield of lithium bis(fluorosulfonyl)imide was 98%, with a purity of 99.8%.

[0136] Example 16

[0137] like Figure 3 A method for electrochemically synthesizing lithium bis(fluorosulfonyl)imide, the method being 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, a first anion exchange membrane, an alkalization chamber 3, a second anion exchange membrane, a buffer chamber 5, a third anion exchange membrane, an anode chamber 1, a cation exchange membrane, a product chamber 2, a first anion exchange membrane, an alkalization chamber 3, a second anion exchange membrane, and a cathode chamber 4.

[0138] In this embodiment, the anode chamber 1, cation exchange membrane, product chamber 2, first anion exchange membrane, alkalization chamber 3, second anion exchange membrane, buffer chamber 5, and third anion exchange membrane constitute a combination, and the number of such combinations is n. In this embodiment, n = 1.

[0139] The structure of an electrolytic cell is represented as: (-) Cathode |OH-(aq.)| - |Et3NH·FSI| - |LiFSI(aq.)| + |LiOH(aq.) | - | Et3NH·FSI | - |LiFSI(aq.)| + |LiOH (aq.)|Anode(+),

[0140] The structure of an electrolytic cell is represented as: its structure is (-) cathode |OH-(aq.)| - |Et3NH·FSI| - |LiFSI(aq.)| + |LiOH(aq.){| - |Water| - |Et3NH·FSI | - |LiFSI(aq.)| + |LiOH} n (aq.)|Anode(+).

[0141] in{} n For the extended part, n represents the number of series connections, which theoretically has no upper limit. In this embodiment, n = 1.

[0142] The single vertical line | represents the interface. - | represents an anion exchange membrane,| + | indicates a cation exchange membrane.

[0143] Cathode 10*10cm 2 The platinum sheet electrode uses a 10*10cm anode. 2 Titanium oxide supported iridium oxide electrode.

[0144] Two anode chambers 1 are initially filled with 250 ml of 2.5 mol / kg lithium hydroxide aqueous solution, two cathode chambers 4 are initially filled with 1 mol / kg potassium hydroxide aqueous solution, two alkalization chambers 3 are initially filled with 250 ml of 88% triethylamine bisfluorosulfonyl imide aqueous solution, and two product chambers 2 are initially filled with 250 ml of 0.001 mol / kg lithium bisfluorosulfonyl imide (LiFSI) solution. Buffer chamber 5 is filled with 100 ml of pure aqueous solution.

[0145] Then, a power supply was connected, and electrolysis was performed using a constant voltage method with a current density set to 300 mA / cm². 2 The operating pressure is 0 kPa gauge pressure, and the operating temperature is 25℃.

[0146] After a reaction time of 1 hour, the conductivity of alkalization chamber 3 was measured by a conductivity meter, and the conductivity decreased by 2000 μS / cm.

[0147] Anode chamber 1 continuously feeds a 2.5 mol / kg lithium hydroxide aqueous solution from the raw material chamber at a flow rate of 5 ml / min; cathode chamber 4 continuously feeds a 1 mol / kg potassium hydroxide aqueous solution from the raw material chamber at a flow rate of 5 ml / min; alkalization chamber 3 continuously feeds an 88% (w / w) triethylamine bis(fluorosulfonyl)imide aqueous solution from the raw material chamber at a flow rate of 0.25 ml / min; product chamber 2 continuously feeds a 0.001 mol / kg lithium(fluorosulfonyl)imide (LiFSI) solution from the raw material chamber at a flow rate of 5 ml / min.

[0148] Anode chamber 1 to cathode chamber 4 are discharged at the same flow rate as the feed rate.

[0149] The product from alkalization chamber 3 was collected by azeotropic distillation to obtain triethylamine, which was found to have a purity of 99.8% by gas chromatography.

[0150] The product from product room 2 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 synthesizing a bisfluorosulfonimide alkali metal salt using a bisfluorosulfonimide tertiary amine salt, characterized by, The method comprises the following steps: Under the action of an applied electric field, alkali metal cations pass through a cation exchange membrane into a product chamber (2), bifluorosulfonylimide anions in a bifluorosulfonylimide tertiary amine salt pass through an anion exchange membrane into the product chamber (2), and the alkali metal cations and the bifluorosulfonylimide anions in the product chamber (2) combine to form a bifluorosulfonylimide alkali metal salt.

2. The method of claim 1, wherein, The method is performed using an electrolytic cell, and the electrolytic cell comprises an anode, a cathode, and, in sequence from the anode to the cathode, an anode chamber (1), a cation exchange membrane, a product chamber (2), a first anion exchange membrane, an alkalization chamber (3), a second anion exchange membrane, and a cathode chamber (4). The raw material in the anode chamber (1) contains alkali metal cations. The raw material in the product chamber (2) is water or an aqueous solution of a bifluorosulfonylimide alkali metal salt. The raw material in the alkalization chamber (3) is an aqueous solution containing a bifluorosulfonylimide tertiary amine salt. The raw material in the cathode chamber (4) is an aqueous solution containing hydroxide ions.

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 anode chamber (1) contains alkali metal oxides, alkali metal hydroxides, alkali metal acetates, alkali metal sulfates, alkali metal methanesulfonates, or alkali metal chlorides.

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

6. The method of claim 5, wherein, When there is more than one combination, the second anion exchange membrane of the previous combination is in contact with the anode chamber (1) of the next combination. Alternatively, a buffer chamber (5) and a third anion exchange membrane are arranged between the second anion exchange membrane of the previous combination and the anode chamber (1) of the next combination, and the buffer chamber (5) contains water.

7. The method of claim 2, wherein, The method is operated intermittently or continuously.

8. The method of claim 7, wherein, When the method is operated continuously, raw material liquid is continuously fed into the anode chamber (1) and the alkalization chamber (3), the product chamber (2) continuously discharges a bifluorosulfonylimide alkali metal salt product, and the alkalization chamber (3) continuously discharges a tertiary amine product.

9. The method of claim 7, wherein, The tertiary amine is selected from one or more of triethylamine, trimethylamine, tri-n-butylamine, tri-n-propylamine, ethyl diisopropylamine, N,N-dimethylcyclohexylamine, and pyridine.

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