Device for electrochemical synthesis of bis (fluorosulfonyl) imide alkali metal salt
The combination of equal stoichiometric ratios of metal cations and difluorosulfonimide anions under the electrodialysis effect was achieved through electrochemical methods, which solved the complex problem of lithiation reaction operation, and realized the synthesis and simplified purification process of high-purity difluorosulfonimide alkali metal salt.
Patent Information
- Application Number
- CN202422195286.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-09
- Publication Date
- 2025-06-20
- Estimated Expiration
- 2034-09-09
AI Technical Summary
The operation process of the lithiation reaction is complicated and cumbersome, making it difficult to achieve accurate equimolar reaction conditions, resulting in the introduction of impurities and affecting the hydrolysis reaction and purification process of lithium bisfluorosulfonimide.
Electrochemical methods are used to achieve strict stoichiometric combination of metal cations and difluorosulfonimide anions through the electrodialysis effect of the cation and anion exchange membrane to form a difluorosulfonimide alkali metal salt.
The synthesis steps are simplified and the subsequent purification process is greatly simplified. The purity of the product is generally above 99%, meeting the high standards for battery-grade applications.
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Figure CN223003042U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the fields of materials and chemical engineering, and particularly relates to a device for electrochemically synthesizing alkali metal salts of bis(fluorosulfonyl)imide. Background Art
[0002] Lithium-ion batteries are currently one of the types with the highest energy density in the field of commercial secondary batteries. As a new component of lithium-ion battery electrolytes, lithium bis(fluorosulfonyl)imide (LiFSI) has the advantages of high stability (not decomposing below 200 °C), excellent low-temperature performance, good hydrolysis stability, and being more environmentally friendly. The development of its production process has received extensive attention and emphasis in the industry.
[0003] The synthesis of LiFSI generally has two-step and one-step methods, and the two-step process is more mature. The so-called "two-step method" is to first synthesize bis(fluorosulfonyl)imide (HFSI) by chemical synthesis and then lithiate it to obtain LiFSI. It is generally considered that the lithiation reaction is a simple acid-base reaction, so it has not received much more attention.
[0004] Among various LiFSI synthesis technologies, Li salts (such as LiF, Li2CO3) or Li bases (LiOH) can be used to react with HFSI to form LiFSI.
[0005] Patent CN117699748A discloses a method for preparing high-purity lithium bis(fluorosulfonyl)imide. Bis(chlorosulfonyl)imide is prepared by heating and stirring amino sulfonic acid, thionyl chloride, and chlorosulfonic acid under reflux. After fluorinating bis(chlorosulfonyl)imide, it is concentrated and refined with a benign solvent. After concentrating to a certain concentration, a poor solvent is added for crystallization, and the crude bis(fluorosulfonyl)imide is obtained by filtration. The crude product is lithiated with an alkaline lithium salt to form a salt and then slurried with dichloromethane solvent, filtered, and dried to obtain lithium bis(fluorosulfonyl)imide.
[0006] Patent CN116750733A discloses a method for preparing lithium bis(fluorosulfonyl)imide using sulfuryl fluoride; this application uses sulfuryl fluoride, ammonia, an organic base, a solvent, and lithium hydroxide to prepare lithium bis(fluorosulfonyl)imide; after preliminary purification by distillation and extraction, filtration is carried out first, and then after adsorption by a perfluorotail acid-based molecular sieve, trace impurity components in the crude product are further removed to obtain high-purity lithium bis(fluorosulfonyl)imide.
[0007] Patent CN110745795A discloses a method for electrochemically synthesizing lithium bis(fluorosulfonyl)imide. In this method, hydrofluoric acid is purified electrochemically to obtain high-purity colorless liquid bis(fluorosulfonyl)imide. Then, it is reacted with lithium hydroxide, and after filtration, recrystallization is carried out to obtain high-purity lithium bis(fluorosulfonyl)imide.
[0008] In the actual production process, we observed that the operation process of the lithiation reaction appears to be particularly complex and cumbersome, mainly due to the difficulty in achieving precise equimolar reaction conditions. Whether the bis(fluorosulfonyl)imide is in excess or the alkali metal salt is in excess, these non-ideal states will introduce impurities in the subsequent purification stage, and these impurities are very likely to promote the hydrolysis reaction of lithium bis(fluorosulfonyl)imide (LiFSI), thus requiring a series of cumbersome and delicate purification steps to ensure that the quality of the final product can meet the high standards set for battery-grade applications.
[0009] To solve the above problems, this application is proposed. Summary of the Utility Model
[0010] This application relates to a method for synthesizing an alkali metal salt of bis(fluorosulfonyl)imide. By using an electrochemical method, a reaction for generating an alkali metal salt of bis(fluorosulfonyl)imide with a strict stoichiometric molar ratio is achieved, which not only simplifies the synthesis steps but also greatly simplifies the subsequent purification process.
[0011] This application provides a device for electrochemically synthesizing an alkali metal salt of bis(fluorosulfonyl)imide, and the device includes: an anode and a cathode located at both ends;
[0012] From the anode to the cathode, there are sequentially arranged: an anode chamber 1, a cation exchange membrane, a product chamber 2, an anion exchange membrane, and a cathode chamber 3;
[0013] The cation exchange membrane is used to separate the anode chamber 1 and the product chamber 2 and only allows cations to pass through;
[0014] The anion exchange membrane is used to separate the product chamber 2 and the cathode chamber 3 and only allows anions to pass through;
[0015] The upper part of the anode chamber 1 is provided with an anode raw material inlet, and the lower part is provided with an anode raw material outlet;
[0016] The upper part of the product chamber 2 is provided with an inlet, and the lower part is provided with a product outlet;
[0017] The upper part of the cathode chamber 3 is provided with a cathode raw material inlet, and the lower part is provided with a cathode raw material outlet.
[0018] Preferably, the device further includes: a buffer chamber 4 located 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;
[0019] The second cation exchange membrane is used to separate the cathode chamber 3 and the buffer chamber 4 and only allows cations to pass through.
[0020] 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 in the device, one or more of this combination are provided.
[0021] Preferably, a bipolar membrane is provided between the cathode chamber 3 of the previous combination and the anode chamber 1 of the next combination.
[0022] Preferably, the anode chamber 1, the cation exchange membrane, the product chamber 2, the anion exchange membrane, the cathode chamber 3, the second cation exchange membrane, and the buffer chamber 4 form a combination, and one or more of such combinations are provided in the device.
[0023] Preferably, the device further includes: an alkalization chamber 03 located between the cathode chamber 3 and the cathode, and a second anion exchange membrane is provided between the alkalization chamber 03 and the cathode chamber 3;
[0024] The second anion exchange membrane is used to separate the cathode chamber 3 from the alkalization chamber 03 and only allows anions to pass through.
[0025] Preferably, the anode chamber 1, the cation exchange membrane, the product chamber 2, the anion exchange membrane, the alkalization chamber 03, and the second anion exchange membrane form a combination, and one or more of such combinations are provided in the device.
[0026] 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 second buffer chamber 05 and a third anion exchange membrane are provided between the second anion exchange membrane of the previous combination and the anode chamber 1 of the next combination.
[0027] The device further includes a power source connected to the cathode and the anode.
[0028] This application also provides a method for electrochemically synthesizing lithium bis(fluorosulfonyl)imide, and the method includes the following steps:
[0029] Under the action of an external electric field, metal cations pass through the cation exchange membrane and enter the product chamber 2, and the bis(fluorosulfonyl)imide anions pass through the anion exchange membrane and enter the product chamber 2, and metal cations and bis(fluorosulfonyl)imide anions in the product chamber 2 combine to form an alkali metal salt of bis(fluorosulfonyl)imide.
[0030] Preferably, the method is carried out using an electrolytic cell, and the electrolytic cell includes: an anode and a cathode, and sequentially arranged from the anode to the cathode are: 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 anions.
[0031] The solutions between the above-mentioned chambers do not flow, and only ions flow through the exchange membranes.
[0032] Preferably, electrolysis is carried out in a constant voltage mode, and the operating current density is controlled to be 10 mA / cm2 ~500 mA / cm 2 , more preferably, 50~200 mA / cm 2 .
[0033] Preferably, the operating pressure condition is set between atmospheric pressure (i.e., about 0 kPa gauge pressure) and 50 kPa gauge pressure.
[0034] The operating temperature is controlled within the range of room temperature (usually refers to 20℃±5℃, specifically determined according to the experimental environment) to 80℃. For example, 15~80℃.
[0035] Preferably, the metal cation is selected from alkali metal ions, such as one of lithium ions, Na ions, K ions, Rb ions, and Cs ions.
[0036] The raw materials of 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.
[0037] Preferably, the raw material of the cathode chamber 3 is an aqueous solution of bis(fluorosulfonyl)imide (HFSI) with a concentration of 0.1~10 mol / kg.
[0038] Preferably, the raw material of the product chamber 2 is water or an aqueous solution of alkali metal bis(fluorosulfonyl)imide salt. Preferably, the concentration of the aqueous solution of alkali metal bis(fluorosulfonyl)imide salt is 0.001~0.1 mol / kg. The role of adding a trace amount of alkali metal bis(fluorosulfonyl)imide salt is to pre-activate the electric field and promote electron transfer. The cation of the alkali metal bis(fluorosulfonyl)imide salt is the same as the metal cation in the anode chamber 1.
[0039] Preferably, a buffer chamber 4 is further provided between the cathode chamber 3 and the cathode, a second cation exchange membrane is provided between the cathode chamber 3 and the buffer chamber 4, and the buffer chamber 4 is filled with water.
[0040] Preferably, 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.
[0041] Preferably, the anode includes but is not limited to electrodes such as iridium oxide, ruthenium oxide, and ruthenium- and iridium-loaded oxides.
[0042] The cathode includes but is not limited to electrodes such as metal nickel, stainless steel, metal platinum, and platinum-loaded carbon catalysts.
[0043] The method adopts an intermittent process or a continuous process; when synthesizing an alkali metal salt of bis(fluorosulfonyl)imide using a continuous process, feed liquid is continuously added to the anode chamber 1 and the cathode chamber 3, and the generated solution of the alkali metal salt of bis(fluorosulfonyl)imide is continuously withdrawn from the product chamber 2.
[0044] Preferably, the gases generated in the anode chamber 1 and the cathode chamber 3 are respectively collected and utilized.
[0045] 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 such combinations are provided in the electrolytic cell. Theoretically, 1 - 20 such combinations can be provided.
[0046] That is, the above-mentioned two-membrane three-chamber combination can be expanded in series, that is, multiple identical two-membrane three-chamber combinations are provided in the same electrolytic cell, with the anode and the cathode at both ends respectively. Theoretically, the number of such series combinations is not absolutely limited as long as electrical and chemical equilibria are permitted. In practical applications, the recommended range of the series connection stages is usually set as 1 - 20 stages.
[0047] Preferably, the anode chamber 1, the product chamber 2, the cathode chamber 3, and the buffer chamber 4 form a combination, and one or more of such combinations are provided in the electrolytic cell.
[0048] Preferably, a buffer chamber 4 is further provided between the cathode chamber 3 of the previous series-connected two-membrane three-chamber combination and the anode chamber 1 of the next series-connected two-membrane three-chamber combination. A second cation exchange membrane is provided between the cathode chamber 3 and the buffer chamber 4, a second anion exchange membrane is provided between the buffer chamber 4 and the anode chamber 1, and the buffer chamber 4 contains a pure aqueous solution.
[0049] 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 is the expanded part, n represents the number of series connections, n = 0 - 20; "|-|water|+|" can be replaced by a bipolar membrane. A single vertical line | represents an interface, |-| represents an anion membrane, and |+| represents a cation membrane.
[0050] The above expression means:
[0051] The anode chamber 1, the product chamber 2, the cathode chamber 3, and the buffer chamber 4 form a combination, and when two such combinations are provided in the electrolytic cell, the structure is as follows:
[0052] From the anode to the cathode, the following are arranged in sequence: 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.
[0053] Alternatively: From the anode to the cathode, the following are arranged in sequence: 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.
[0054] On the premise of no contradiction, the above technical solutions can be freely combined.
[0055] Preferably, the method is carried out by an intermittent method or a continuous method. Among them, when synthesizing an alkali metal salt of bis(fluorosulfonyl)imide by a continuous method, raw materials are continuously added to the anode chamber 1 and the cathode chamber 3, and the generated alkali metal salt of bis(fluorosulfonyl)imide is continuously collected in the product chamber 2.
[0056] The beneficial effects of the present utility model are as follows:
[0057] An alkali metal salt of bis(fluorosulfonyl)imide can be electrochemically synthesized by using this device. Metal cations are added to the anode chamber 1, bis(fluorosulfonyl)imide anions are added to the cathode chamber 3. After applying a voltage between the cathode and the anode, the metal cations pass through the cation exchange membrane and enter the product chamber 2, and the bis(fluorosulfonyl)imide anions pass through the anion exchange membrane and enter the product chamber 2. In the product chamber 2, the metal cations and the bis(fluorosulfonyl)imide anions combine to form an alkali metal salt of bis(fluorosulfonyl)imide.
[0058] In addition, the method using this device has the following effects:
[0059] 1. This application creatively proposes a method for synthesizing an alkali metal salt of bis(fluorosulfonyl)imide by an electrochemical method. Driven by an external electric field, the electrodialysis effect promotes the alkali metal cations to cross the cation exchange membrane, and at the same time, the bis(fluorosulfonyl)imide anions pass through the anion exchange membrane and jointly migrate to the middle product chamber 2. In this product chamber 2, the alkali metal cations and the bis(fluorosulfonyl)imide anions combine strictly according to the stoichiometric ratio to form an alkali metal salt of bis(fluorosulfonyl)imide. There are no other water-soluble impurities in the product of the alkali metal salt of bis(fluorosulfonyl)imide in the product chamber 2, and the purity generally reaches more than 99%.
[0060] 2. In the method of the present application, the feeding of alkali metal cations and bis(fluorosulfonyl)imide anions is carried out in the anode chamber 1 and the cathode chamber 3 respectively. The alkali metal cations and bis(fluorosulfonyl)imide anions do not need to be fed in a stoichiometric ratio. That is, regardless of the feeding ratio, due to the action of the same external electric field, the alkali metal ions and bis(fluorosulfonyl)imide anions passing through the metal cation exchange membrane and the anion exchange membrane strictly conform to the stoichiometric ratio to directionally generate the product alkali metal bis(fluorosulfonyl)imide salt.
[0061] 3. Electrochemical methods are usually carried out under mild conditions (e.g., room temperature and atmospheric pressure), and electricity is used to replace environmentally harmful chemical reagents (such as stoichiometric oxidants and reductants), enabling electrochemistry to have the potential to improve the efficiency and sustainability of chemical reactions.
[0062] 4. Electrochemical technology makes this method for synthesizing alkali metal bis(fluorosulfonyl)imide salts continuous. Only continuous power supply is required, and continuous production can be carried out without adding any external oxidants and reductants. BRIEF DESCRIPTION OF THE DRAWINGS
[0063] Figure 1 It is a schematic diagram of the reaction in the electrolytic cell of Example 1.
[0064] Figure 2 It is a schematic diagram of the structure of the electrolytic cell of Example 1.
[0065] Figure 3 It is a schematic diagram of the reaction in the electrolytic cell of Example 2.
[0066] Figure 4 It is a schematic diagram of the structure of the electrolytic cell of Example 2.
[0067] Figure 5 It is a schematic diagram of the reaction in the electrolytic cell of Example 3.
[0068] Figure 6 It is a schematic diagram of the structure of the electrolytic cell of Example 3.
[0069] Figure 7 It is a schematic diagram of the reaction in the electrolytic cell of Example 4.
[0070] Figure 8 It is a schematic diagram of the structure of the electrolytic cell of Example 4.
[0071] Figure 9 It is a schematic diagram of the reaction in the electrolytic cell of Example 5.
[0072] Figure 10 It is a schematic diagram of the structure of the electrolytic cell of Example 5.
[0073] Figure 11 It is a schematic diagram of the reaction in the electrolytic cell of Example 6.
[0074] Figure 12 Schematic diagram of the electrolytic cell structure for Example 6.
[0075] List of reference numerals:
[0076] 1. Anode chamber, 2. Product chamber, 3. Cathode chamber, 4. Buffer chamber, 03. Alkalization chamber, 05. Second buffer chamber. Detailed implementation manners
[0077] The present invention will be further described below through examples, but not limited to these examples. For the experimental methods without specific conditions indicated in the examples, they are generally carried out according to the conventional conditions and the conditions described in the manuals, or according to the conditions recommended by the manufacturers. For the general equipment, materials, reagents, etc., they can be obtained from commercial channels without special instructions. The raw materials required in the following examples and comparative examples are all commercially available.
[0078] Taking the synthesis of lithium bis(fluorosulfonyl)imide (LiFSI) from bis(fluorosulfonyl)imide (HFSI) and lithium hydroxide (LiOH) as an example, the principle of this application will be described.
[0079] This application adopts an electrochemical method. Using a two-membrane three-chamber electrolytic cell design and a two-electrode system, the electrolytic cell is divided into three parts by an anion exchange membrane and a cation exchange membrane: the cathode chamber, the anode chamber, and the product chamber. An aqueous solution of an acid (i.e., HFSI) is placed in the cathode chamber and separated from the product chamber by an anion exchange membrane. An aqueous solution of a base (represented by LiOH) is placed in the anode chamber and separated from the product chamber by a cation exchange membrane. The intermediate region between the anion exchange membrane and the cation exchange membrane is the product chamber. When an electric current is applied to the anode and cathode, a reduction reaction occurs at the cathode, and hydrogen ions are reduced to hydrogen gas. The FSI anions migrate electrochemically through the anion exchange membrane into the product chamber. An oxidation reaction occurs at the anode, and hydroxide ions are oxidized to oxygen gas. 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, in order to ensure electrical neutrality in the product chamber, lithium ions and FSI anions combine strictly in their stoichiometric ratio to obtain LiFSI. The chemical reaction equations are described as follows:
[0080] Reaction at the cathode: 2H + + 2e - = H2↑
[0081] Reaction at the anode: 2OH - - 2e - = 1 / 2O2↑ + H2O
[0082] Reaction in the product chamber: FSI - + Li + = LiFSI
[0083] The technical solution of the present invention is as follows: Use a device that meets the above series of electrochemical processes, that is, an electrochemical synthesis reactor with a "two-membrane and three-chamber" structure including an anion exchange membrane, a cation exchange membrane, a cathode chamber, an anode chamber, and a product chamber. Using HFSI and LiOH as raw materials, through the electrolysis of water reaction, the strict stoichiometric synthesis of LiFSI is achieved.
[0084] A method for electrochemically synthesizing an alkali metal salt of bis(fluorosulfonyl)imide, comprising the following steps:
[0085] A platinum-containing electrode is used as the cathode, and an iridium oxide supported on titanium oxide electrode is used as the anode. An aqueous lithium hydroxide solution with a concentration of 0.1 - 5.3 mol / kg is injected into the anode chamber 1; an aqueous solution of lithium bis(fluorosulfonyl)imide (LiFSI) with a concentration of 0.001 mol / kg is injected into the product chamber 2; an aqueous solution of bis(fluorosulfonyl)imide (HFSI) with a concentration of 0.1 - 10 mol / kg is injected into the cathode chamber 3.
[0086] Preferably, to ensure production capacity, feed at a high concentration as much as possible. The concentration of HFSI used is 1 - 10 mol / kg, and the concentration of LiOH used is 1 - 5.3 mol / kg.
[0087] Preferably, the operating temperature of the electrolytic cell is room temperature, and the voltage is normal pressure.
[0088] The method of the present application is applicable to both batch and continuous processes.
[0089] Preferably, use the continuous method to synthesize LiFSI, that is, the feed liquid in the cathode chamber and the anode chamber is circulated, and the generated aqueous solution of LiFSI is continuously withdrawn from the product chamber.
[0090] Preferably, when using an aqueous solution of HFSI with a concentration of 4.5 - 5 mol / kg and an aqueous solution of LiOH with a concentration of 4.5 - 5 mol / kg as raw materials, the mass concentration of the withdrawn LiFSI is 60 - 70%, and corresponding pure water needs to be supplemented in the product chamber 2.
[0091] Example 1
[0092] As Figure 1-2 , a method for electrochemically synthesizing an alkali metal salt of bis(fluorosulfonyl)imide, the method is carried out using an electrolytic cell, the electrolytic cell includes: an anode, a cathode, and sequentially arranged from the anode to the cathode are: an anode chamber 1, a cation exchange membrane, a product chamber 2, an anion exchange membrane, and a cathode chamber 3.
[0093] The structure of the electrolytic cell is: from the cathode to the anode are (-) cathode|H-FSI|-|LiFSI(aq.)| + |Li(OH)(aq.)|anode(+). Where the single vertical line | represents the interface, |-| represents the anion membrane, and |+| represents the cation membrane.
[0094] The cathode uses a platinum sheet electrode of 10*10 cm 2 and the anode uses an iridium oxide supported on titanium oxide electrode of 10*10 cm 2 .
[0095] 300 ml of 2.5 mol / kg lithium hydroxide aqueous solution is initially injected into the anode chamber 1, 300 ml of 5 mol / kg bis(fluorosulfonyl)imide (HFSI) aqueous solution is initially injected into the cathode chamber 3, and 300 ml of 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) aqueous solution is initially injected into the product chamber 2. Then, a power supply is connected and electrolysis is carried out in a constant voltage mode, and the current density is set to 200 mA / cm 2 . The operating pressure is atmospheric pressure and the operating temperature is 25 °C.
[0096] After reacting for 1 h, the anode chamber 1 continuously feeds 2.5 mol / kg lithium hydroxide aqueous solution at a flow rate of 5 ml / min; the cathode chamber 3 continuously feeds 5 mol / kg bis(fluorosulfonyl)imide (HFSI) aqueous solution at a flow rate of 5 ml / min; the product chamber 2 continuously feeds 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) aqueous solution at a flow rate of 5 ml / min. The anode chamber 1 to the cathode chamber 3 continuously discharge at a flow rate of 5 ml / min.
[0097] The product of the discharge is detected by ion chromatography, and the yield of the product lithium bis(fluorosulfonyl)imide is 98% and the purity is 99.8%. When calculating the purity of lithium bis(fluorosulfonyl)imide in this application, water is not counted as an impurity.
[0098] Example 2
[0099] As Figure 3-4 , a method for electrochemically synthesizing an alkali metal salt of bis(fluorosulfonyl)imide, the method is carried out using an electrolytic cell, the electrolytic cell includes: an anode, a cathode, and sequentially arranged from the anode to the cathode are: 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, cathode chamber 3.
[0100] The cathode uses a platinum sheet electrode of 10*10 cm 2 and the anode uses a platinum sheet electrode of 10*10 cm 2The iridium oxide supported on titanium oxide electrode. 300 ml of 2.5 mol / kg lithium hydroxide aqueous solution is respectively introduced into the two anode chambers 1; 300 ml of 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) solution is respectively introduced into the two product chambers 2; 300 ml of 5 mol / kg bis(fluorosulfonyl)imide (HFSI) aqueous solution is respectively introduced into the two cathode chambers 3. Then, a power supply is connected, and electrolysis is carried out in a constant voltage mode, and the current density is set to 200 mA / cm 2 The operating pressure is atmospheric pressure, and the operating temperature is 25 °C.
[0101] After reacting for 1 h, 2.5 mol / kg lithium hydroxide aqueous solution is continuously fed into the anode chamber 1 from the raw material chamber at a flow rate of 5 ml / min; 5 mol / kg bis(fluorosulfonyl)imide (HFSI) aqueous solution is continuously fed into the cathode chamber 3 from the raw material chamber at a flow rate of 5 ml / min; 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) solution is continuously fed into the product chamber 2 from the raw material chamber at a flow rate of 5 ml / min.
[0102] The anode chamber 1 to the cathode chamber 3 are simultaneously discharged continuously at a flow rate of 5 ml / min.
[0103] The product of the discharge is detected by ion chromatography, and the yield of the product lithium bis(fluorosulfonyl)imide is 98%, and the purity is 99.8%.
[0104] Example 3
[0105] Such as Figure 5-6 , a method for electrochemically synthesizing an alkali metal salt of bis(fluorosulfonyl)imide, the method is carried out using an electrolytic cell, and the electrolytic cell includes: an anode, a cathode, and sequentially arranged from the anode to the cathode are: 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, cathode chamber 3.
[0106] The cathode uses a platinum sheet electrode of 10*10 cm 2 The anode uses an iridium oxide supported on titanium oxide electrode of 10*10 cm 2 300 ml of 2.5 mol / kg lithium hydroxide aqueous solution is respectively introduced into the two anode chambers 1; 300 ml of 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) solution is respectively introduced into the two product chambers 2; 300 ml of 5 mol / kg bis(fluorosulfonyl)imide (HFSI) aqueous solution is respectively introduced into the two cathode chambers 3.
[0107] 100 ml of pure aqueous solution is added to the buffer chamber 4.
[0108] Then connect to the power supply and perform electrolysis in a constant voltage mode, with the current density set at 200 mA / cm 2 . The operating pressure is atmospheric pressure and the operating temperature is 25 °C.
[0109] After reacting for 1 h, the anode chamber 1 continuously feeds a 2.5 mol / kg lithium hydroxide aqueous solution at a flow rate of 5 ml / min; the cathode chamber 3 continuously feeds a 5 mol / kg bis(fluorosulfonyl)imide (HFSI) aqueous solution at a flow rate of 5 ml / min; the product chamber 2 continuously feeds a 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) aqueous solution at a flow rate of 5 ml / min. The anode chamber 1 to the cathode chamber 3 continuously discharge at a flow rate of 5 ml / min simultaneously.
[0110] The product of the discharge is detected by ion chromatography, and the yield of the product lithium bis(fluorosulfonyl)imide is 98% and the purity is 99.8%.
[0111] The following takes the synthesis of lithium bis(fluorosulfonyl)imide (LiFSI) from triethylamine bis(fluorosulfonyl)imide (Et3NH·FSI) and lithium hydroxide (LiOH) as an example to illustrate the principle of this application:
[0112] This application adopts an electrochemical method, a three-membrane four-chamber electrolytic cell design and a two-electrode system. From the cathode to the anode, it is arranged in sequence as: cathode chamber, cathode membrane (anion exchange membrane), alkalization chamber, anion exchange membrane, product chamber, anode membrane (cation exchange membrane) and anode chamber. Dilute alkali solution is filled in the cathode chamber for conducting electricity. Under the condition of energization, hydrogen and hydroxide ions are generated (eq.1). The generated hydroxide ions pass through the cathode membrane and enter the alkalization chamber, where they react with the bis(fluorosulfonyl)imide tertiary amine salt (such as Et3NH·FSI) to generate free triethylamine and bis(fluorosulfonyl)imide anion (FSI - ); FSI- enters the product chamber through the anion membrane under the action of the electric field; an aqueous solution of alkali (represented by LiOH) is placed in the anode chamber. Under the condition of energization, an oxidation reaction occurs at the anode, and hydroxide is oxidized to oxygen (eq.3), and lithium ions migrate to the product chamber through the cation membrane. Since the anion membrane only allows anions to pass through and the cation membrane only allows cations to pass through, in order to ensure electrical neutrality in the product chamber, lithium ions and FSI anions combine strictly in their stoichiometric ratio to obtain LiFSI (eq.4).
[0113] The chemical reactions in each chamber are described as follows:
[0114] Reaction at the cathode: 2H2O + 2e - = H2 + 2OH- eq.1
[0115] Reaction in the alkalization chamber: Et3NH·FSI + OH- = Et3N + H2O + FSI- eq.2
[0116] Reaction on the anode: 2OH⁻ - 2e - = 1 / 2O₂ + H₂O eq.3
[0117] Reaction in the product chamber: FSI⁻ + Li + = LiFSI eq.4
[0118] A typical method for synthesizing lithium bis(fluorosulfonyl)imide using triethylamine salt of bis(fluorosulfonyl)imide includes the following steps:
[0119] A platinum-containing electrode is used as the cathode, and an iridium oxide supported on titanium oxide electrode is used as the anode. An aqueous lithium hydroxide solution with a concentration of 0.1 - 5.3 mol / kg is injected into the anode chamber 1; a 0.001 mol / kg solution of lithium bis(fluorosulfonyl)imide (LiFSI) is injected into the product chamber 2; an aqueous solution of triethylamine salt of bis(fluorosulfonyl)imide with a water content of 0 - 12% (saturated water state) is injected into the alkalization chamber 03; an aqueous potassium hydroxide solution with a concentration of 0.1 - 10 mol / kg is injected into the cathode chamber 3.
[0120] Preferably, the raw material Et₃NH·FSI is fed in a water-saturated state, that is, the saturated water content is 12%. Et₃NH·FSI is in a liquid state under the operating conditions.
[0121] Preferably, the water content in the aqueous solution of Et₃NH·FSI is 0 - 12%, that is, the content of Et₃NH·FSI is 88% - 100%. The concentration of LiOH used is 1 - 5.3 mol / kg.
[0122] Preferably, the operating pressure condition is set between atmospheric pressure (i.e., about 0 kPa gauge pressure) and 50 kPa gauge pressure; and the operating temperature is controlled in the range of room temperature (usually referring to 20°C ± 5°C, specifically determined according to the experimental environment) to 80°C.
[0123] This technology is applicable to batch processes and continuous processes. In the batch process, 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 completely.
[0124] Preferably, this technology is applicable to the synthesis of LiFSI using a continuous process, that is, the feed liquid is cyclically injected into the anode chamber, the free triethylamine is cyclically separated from the alkalization chamber, and at the same time, fresh Et₃NH·FSI is continuously added to the alkalization chamber; the aqueous solution of the generated LiFSI is continuously withdrawn from the product chamber.
[0125] Preferably, the free triethylamine can be collected by azeotropic distillation to obtain a pure chemical.
[0126] Preferably, when 4.5 - 5 mol / kg of LiOH is used, the mass concentration of LiFSI in the extracted aqueous LiFSI solution is 50 - 70%, and corresponding fresh pure water or a low-concentration aqueous LiFSI solution is replenished in the product chamber 2.
[0127] This method is also applicable to continuous reactions, that is, LiOH and Et3NH·FSI are continuously fed, and LiFSI and the alkalization liquid in the alkalization chamber 03 are continuously produced. The mass fraction of the fed Et3NH·FSI is 88% - 100%, and the concentration of the fed LiOH is 0.1 - 5.3 mol / kg. Since the water content in the aqueous Et3NH·FSI solution is relatively low, a higher concentration of Et3NH·FSI needs to be fed.
[0128] Example 4
[0129] As Figure 7-8 , a method for electrochemically synthesizing lithium bis(fluorosulfonyl)imide, the method is carried out using an electrolytic cell, and the electrolytic cell includes: an anode, a cathode, and are sequentially arranged 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 03, a second anion exchange membrane, and a cathode chamber 3.
[0130] The structure of the electrolytic cell is: (-) cathode | OH-(aq) | - | Et3NH·FSI | - | LiFSI(aq.) | + | LiOH(aq.) | anode (+) from the cathode to the anode. Where the single vertical line | represents the interface, | - | represents the anion membrane, and | + | represents the cation membrane.
[0131] The cathode uses a platinum sheet electrode of 10*10 cm 2 , and the anode uses an iridium oxide supported on titanium oxide electrode of 10*10 cm 2 .
[0132] 250 ml of an aqueous lithium hydroxide solution of 2.5 mol / kg is initially injected into the anode chamber 1, 1 mol / kg of an aqueous potassium hydroxide solution is initially injected into the cathode chamber 3, 250 ml of an aqueous solution of triethylammonium bis(fluorosulfonyl)imide with a mass concentration of 88% is initially injected into the alkalization chamber 03, and 250 ml of an aqueous solution of lithium bis(fluorosulfonyl)imide (LiFSI) of 0.001 mol / kg is initially injected into the product chamber 2. Then, a power supply is connected, and electrolysis is carried out in a constant voltage mode, and the current density is set to 300 mA / cm 2 . The operating pressure is normal pressure, and the operating temperature is 25°C.
[0133] After reacting for 1 h, the alkalization chamber 03 is detected by a conductivity meter, and the conductivity has decreased by 2000 μS / cm.
[0134] The anodic chamber 1 is continuously fed with an aqueous solution of lithium hydroxide at a concentration of 2.5 mol / kg at a flow rate of 5 ml / min from the raw material chamber; the cathodic chamber 3 is continuously fed with an aqueous solution of potassium hydroxide at a concentration of 1 mol / kg at a flow rate of 5 ml / min from the raw material chamber; the alkalization chamber 03 is continuously fed with an aqueous solution of triethylamine bis(fluorosulfonyl)imide with a mass concentration of 88% at a flow rate of 0.25 ml / min from the raw material chamber; the product chamber 2 is continuously fed with an aqueous solution of lithium bis(fluorosulfonyl)imide (LiFSI) at a concentration of 0.001 mol / kg at a flow rate of 5 ml / min from the raw material chamber.
[0135] The anodic chamber 1 to the cathodic chamber 3 are simultaneously discharged at the same flow rate as their feeding.
[0136] The product discharged from the alkalization chamber 03 is collected after being removed by azeotropic distillation to obtain a triethylamine product, and the purity is detected by gas chromatography to be 99.8%.
[0137] The product discharged from the product chamber 2 is detected by ion chromatography, and the yield of the product lithium bis(fluorosulfonyl)imide is 98% and the purity is 99.8%. Water is not counted as an impurity when calculating the purity of lithium bis(fluorosulfonyl)imide in this application.
[0138] Example 5
[0139] Such as Figure 9-10 , a method for electrochemically synthesizing lithium bis(fluorosulfonyl)imide, the method is carried out using an electrolytic cell, the electrolytic cell includes: an anode, a cathode, and sequentially arranged from the anode to the cathode are: an anodic chamber 1, a cation exchange membrane, a product chamber 2, a first anion exchange membrane, an alkalization chamber 03, a second anion exchange membrane, an anodic chamber 1, a cation exchange membrane, a product chamber 2, a first anion exchange membrane, an alkalization chamber 03, a second anion exchange membrane, and a cathodic chamber 3.
[0140] Among them, the anodic chamber 1, the cation exchange membrane, the product chamber 2, the first anion exchange membrane, the alkalization chamber 03, and the second anion exchange membrane are a combination, and the number of this combination is n. In this example, n = 1.
[0141] The structure of the electrolytic cell is represented as: its structure is (-) cathode|OH-(aq.)|-|Et3NH·FSI|-|LiFSI(aq.)|+|LiOH(aq.){| -|Et3NH·FSI|- |LiFSI(aq.)| + |LiOH} n (aq.)|anode(+).
[0142] Among them {} n is the extended part, n represents the number of series connections, theoretically there is no upper limit, and in this example, n = 1. A single vertical line | represents an interface, | - | represents an anion membrane, and | + | represents a cation membrane.
[0143] The cathode uses 10*10cm2 Platinum sheet electrode, with the anode being 10*10 cm 2 Iridium oxide supported on titanium oxide electrode.
[0144] Initially, 250 ml of 2.5 mol / kg lithium hydroxide aqueous solution was injected into each of the two anode chambers 1, 250 ml of 1 mol / kg potassium hydroxide aqueous solution was injected into each of the two cathode chambers 3, 250 ml of an aqueous solution of triethylamine bis(fluorosulfonyl)imide with a mass concentration of 88% was injected into each of the two alkalization chambers 03, and 250 ml of 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) solution was injected into each of the two product chambers 2. Then, a power supply was connected, and electrolysis was carried out in a constant voltage mode with the current density set at 300 mA / cm 2 . The operating pressure was atmospheric pressure, and the operating temperature was 25 °C.
[0145] After reacting for 1 h, the conductivity of the two alkalization chambers 03 was detected by a conductivity meter, and the conductivity decreased by 2000 μS / cm.
[0146] The anode chamber 1 continuously fed 2.5 mol / kg lithium hydroxide aqueous solution from the raw material chamber at a flow rate of 5 ml / min; the cathode chamber 3 continuously fed 1 mol / kg potassium hydroxide aqueous solution from the raw material chamber at a flow rate of 5 ml / min; the alkalization chamber 03 continuously fed an aqueous solution of triethylamine bis(fluorosulfonyl)imide with a mass concentration of 88% from the raw material chamber at a flow rate of 0.25 ml / min; the product chamber 2 continuously fed 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) solution from the raw material chamber at a flow rate of 5 ml / min.
[0147] The anode chamber 1 - cathode chamber 3 continuously discharged at the same flow rate as the feed.
[0148] The product discharged from the alkalization chamber 03 was collected after being removed by azeotropic distillation, and triethylamine product was obtained. The purity was detected by gas chromatography to be 99.8%.
[0149] The product discharged from the product chamber 2 was detected by ion chromatography, and the yield of the product lithium bis(fluorosulfonyl)imide was 98%, and the purity was 99.8%.
[0150] Example 6
[0151] As Figure 11-12, A method for electrochemically synthesizing lithium bis(fluorosulfonyl)imide, the method is carried out using an electrolytic cell, and the electrolytic cell includes: an anode and a cathode. From the anode to the cathode, there are sequentially arranged: an anode chamber 1, a cation exchange membrane, a product chamber 2, a first anion exchange membrane, an alkalization chamber 03, a second anion exchange membrane, a second buffer chamber 05, 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 03, a second anion exchange membrane, and a cathode chamber 3.
[0152] Among them, the anode chamber 1, the cation exchange membrane, the product chamber 2, the first anion exchange membrane, the alkalization chamber 03, the second anion exchange membrane, the second buffer chamber 05, and the third anion exchange membrane form a combination, and the number of this combination is n. In this embodiment, n = 1.
[0153] The structure of the electrolytic cell is represented as: (-) cathode|OH-(aq.)|-|Et3NH·FSI|-|LiFSI(aq.)|+|LiOH(aq.)|-|Et3NH·FSI|- |LiFSI(aq.)| + |LiOH (aq.)|anode(+),
[0154] The structure of the 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(+).
[0155] Among them, {} n is the extended part, n represents the number of series connections, and theoretically there is no upper limit. In this embodiment, n = 1 is taken.
[0156] Among them, the single vertical line | represents the interface, | - | represents the anion membrane, and | + | represents the cation membrane.
[0157] The cathode uses a platinum sheet electrode of 10*10 cm 2 and the anode uses an iridium oxide supported on titanium oxide electrode of 10*10 cm 2 .
[0158] Initially, 250 ml of 2.5 mol / kg lithium hydroxide aqueous solution is injected into the two anode chambers 1 respectively, 1 mol / kg potassium hydroxide aqueous solution is injected into the two cathode chambers 3 initially, 250 ml of 88% mass concentration triethylamine bis(fluorosulfonyl)imide aqueous solution is injected into the two alkalization chambers 03 initially, and 250 ml of 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) solution is injected into the two product chambers 2 initially. 100 ml of pure aqueous solution is injected into the second buffer chamber 05.
[0159] Then connect to the power supply and perform electrolysis in a constant voltage mode, with the current density set at 300 mA / cm 2 . The operating pressure is atmospheric pressure and the operating temperature is 25 °C.
[0160] After reacting for 1 h, the alkalization chamber 03 is detected by a conductivity meter, and the conductivity has decreased by 2000 μS / cm.
[0161] The 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; the cathode chamber 3 continuously feeds a 1 mol / kg potassium hydroxide aqueous solution from the raw material chamber at a flow rate of 5 ml / min; the alkalization chamber 03 continuously feeds a triethylamine bis(fluorosulfonyl)imide aqueous solution with a mass concentration of 88% from the raw material chamber at a flow rate of 0.25 ml / min; the product chamber 2 continuously feeds a 0.001 mol / kg lithium bis(fluorosulfonyl)imide (LiFSI) solution from the raw material chamber at a flow rate of 5 ml / min;
[0162] The anode chamber 1 to the cathode chamber 3 discharge at the same flow rate as the feeding speed at the same time.
[0163] The product discharged from the alkalization chamber 03 is removed and collected by azeotropic distillation to obtain a triethylamine product, and the purity is detected by gas chromatography to be 99.8%.
[0164] The product discharged from the product chamber 2 is detected by ion chromatography, and the yield of the product lithium bis(fluorosulfonyl)imide is 98% and the purity is 99.8%.
Claims
1. A device for electrochemically synthesizing bis(fluorosulfonyl)imide alkali metal salts, characterized in that: The device comprises: an anode and a cathode located at two ends; The following are arranged in sequence from the anode to the cathode: an anode chamber (1), a cation exchange membrane, a product chamber (2), an anion exchange membrane, and a cathode chamber (3); The cation exchange membrane is used to separate the anode chamber (1) and the product chamber (2) and only allows cations to pass through; The anion exchange membrane is used to separate the product chamber (2) and the cathode chamber (3) and only allows anions to pass through; The anode chamber (1) is provided with an anode raw material inlet at the top and an anode raw material outlet at the bottom; The product chamber (2) is provided with an inlet at the top and a product outlet at the bottom; The cathode chamber (3) is provided with a cathode raw material inlet at the top and a cathode raw material outlet at the bottom.
2. The device for electrochemically synthesizing bis(fluorosulfonyl)imide alkali metal salt according to claim 1, characterized in that: The device further comprises: a buffer chamber (4) located between the cathode chamber (3) and the cathode, wherein a second cation exchange membrane is arranged between the cathode chamber (3) and the buffer chamber (4); The second cation exchange membrane is used to separate the cathode chamber (3) from the buffer chamber (4) and allows only cations to pass through.
3. The device for electrochemically synthesizing bis(fluorosulfonyl)imide alkali metal salt according to claim 1, characterized in that: 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 in the device, one or more of the combination are provided.
4. The device for electrochemically synthesizing bis(fluorosulfonyl)imide alkali metal salt according to claim 3, characterized in that: A bipolar membrane is arranged between the cathode chamber (3) of the previous combination and the anode chamber (1) of the next combination.
5. The device for electrochemically synthesizing bis(fluorosulfonyl)imide alkali metal salt according to claim 2, characterized in that: The anode chamber (1), the cation exchange membrane, the product chamber (2), the anion exchange membrane, the cathode chamber (3), the second cation exchange membrane, and the buffer chamber (4) form a combination, and in the device, one or more of the combination are provided.
6. The device for electrochemically synthesizing bis(fluorosulfonyl)imide alkali metal salt according to claim 1, characterized in that: The device further comprises: an alkalization chamber (03) located between the product chamber (2) and the cathode chamber (3), wherein a second anion exchange membrane is arranged between the alkalization chamber (03) and the cathode chamber (3); The second anion exchange membrane is used to separate the alkalization chamber (03) from the cathode chamber (3) and allows only anions to pass through.
7. The device for electrochemically synthesizing bis(fluorosulfonyl)imide alkali metal salt according to claim 4, characterized in that: The anode chamber (1), cation exchange membrane, product chamber (2), anion exchange membrane, alkalization chamber (03), and second anion exchange membrane form a combination. In the device, one or more of the combination are provided.
8. The device for electrochemically synthesizing bis(fluorosulfonyl)imide alkali metal salt according to claim 4, characterized in that: When more than one 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 second buffer chamber (05) and a third anion exchange membrane are provided between the second anion exchange membrane of the previous combination and the anode chamber (1) of the next combination.