Folding viologen, preparation method thereof and application of folding viologen in aqueous flow battery

Abstract

The invention relates to a folded viologen compound, a preparation method thereof and application of the folded viologen compound in an aqueous flow battery. The invention provides and synthesizes a class of double viologen compounds with'folding 'spatial conformation for the first time. The molecule is covalently connected with two viologen units through a flexible bridging group, so that the molecule can carry out efficient two-electron storage and also can carry out efficient reversible two-electron reaction, and the volume energy density of a battery is favorably improved. More importantly, in a two-electron reduction state, free radicals generated on the two viologen units can be subjected to intramolecular or intermolecular interaction (such as forming a free radical-free radical bond) through space approaching, so that the reaction activity of a substance in the reduction state is remarkably reduced, the reaction rate of the substance with oxygen is slowed down, and the oxygen-oxygen conversion efficiency is improved. And the stability of the electrolyte in the air is fundamentally improved. The preparation method provided by the invention has the advantages of simple steps, high yield, high product purity and good application prospect.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage and flow battery technology, and particularly to a folded violarin compound, its preparation method, and its application as a negative electrode active material in aqueous organic flow batteries. Background Technology

[0002] Energy storage technology is the "ballast" for the safe, efficient, and stable operation of new power systems, providing strategic support for achieving the "dual carbon" goal. Among them, electrochemical energy storage technology has the characteristics of high flexibility and fast response time, and has broad application prospects in the field of large-scale energy storage. In electrochemical energy storage, flow batteries have advantages such as capacity and power decoupling and high safety, and as a medium- to long-term safe energy storage technology, they have gradually begun commercial demonstrations in recent years. Among them, aqueous organic flow batteries have the advantages of widely available and inexpensive electroactive materials, easy energy level control, and good electrochemical reversibility, showing great commercial potential.

[0003] Viologen-based electroactive molecules have attracted widespread attention due to their good water solubility, high electrochemical reversibility, and suitability for near-neutral pH environments, making them a promising class of electroactive organic molecules. However, viologen, after reduction, becomes a highly reactive single / double radical, which is susceptible to attack by solvents and oxygen, threatening its stability and preventing flow batteries from operating stably in air. Therefore, developing air-tolerant viologen-based electrolytes is a crucial step in advancing viologen-based aqueous organic flow batteries towards practical applications. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a folded viologen, its preparation method, and its application in aqueous flow batteries. By covalently connecting two viologen units at both ends of a flexible bridging group (X), a "folded" spatial conformation is constructed. Through this molecular design, the reaction rate with oxygen is effectively slowed down, fundamentally improving the air stability of the electrolyte.

[0005] First aspect: A type of folded violane, with the following general structural formula:

[0006] In the formula, X represents a C3-C15 alkylene group and contains at most one first substituent, which is one of alkyl, alkoxy, hydroxy, carboxyl, quaternary ammonium or halogen; or, X represents a C3-C8 carbon chain and the carbon chain contains 1-6 ether groups or imino groups, the number of which is not more than the number of carbon atoms. R1-R 16 They are independently selected from hydrogen or C1-C6 alkyl groups; R 17 -R 18The components are independently selected from at least one of C1-C10 alkyl groups, C1-C10 alkyl groups whose terminals are substituted with a second substituent, or C1-C10 alkyl groups containing branches, wherein the second substituent is one of hydroxyl, carboxyl, quaternary ammonium, or sulfonic acid groups, and the branch is one of alkyl, hydroxyl, carboxyl, quaternary ammonium, or sulfonic acid groups. Y - The ion represents an anion selected from at least one of chloride, bromide, iodide, nitrate, hydrogen sulfate, and hexafluorophosphate, where b is an integer from 1 to 9. a is an integer from 1 to 9.

[0007] This invention is the first to propose and synthesize a class of bisvioren compounds with a "folded" spatial conformation. This molecule covalently connects two viologen units via a flexible bridging group (X), enabling efficient two-electron storage and reversible two-electron reactions, thus contributing to improved volumetric energy density of the battery. More importantly, in the two-electron reduced state, the free radicals generated on the two viologen units can interact intramolecularly or intermolecularly through spatial proximity (e.g., forming radical-radical bonds), significantly reducing the reactivity of the reduced substance and slowing its reaction rate with oxygen, fundamentally improving the stability of the electrolyte in air.

[0008] Based on this unique structure, the aqueous flow battery negative electrode electrolyte prepared with this folded viologen compound successfully solves the bottleneck problem of instability of traditional viologen-based electrolytes in air. This enables the battery to operate stably for a long time under non-strictly inert atmosphere conditions (such as air), reducing system packaging and maintenance costs. Therefore, this folded viologen compound, with its reversible two-electron reaction and excellent oxidation (air) resistance, provides an innovative solution for high-performance, high-stability flow battery electrolytes.

[0009] As a preferred embodiment, X represents a C3-C6 alkylene group and includes a first substituent, which is one of alkyl, alkoxy, hydroxy, carboxyl, quaternary ammonium, or halogen; or, X represents a C3-C6 carbon chain and the carbon chain includes 1-6 ether groups or imino groups, the number of which is not more than the number of carbon atoms.

[0010] In the folded viologen structure, C3-C6 alkylene groups or C3-C6 carbon chains have higher stability, especially the C3 structure, which is the most stable in folded viologen. If the carbon chain is too long, the stability of folded viologen will decrease.

[0011] As a preferred embodiment, the Y - It is selected from at least one of chloride ion, bromide ion, iodide ion, and nitrate ion. These anions have high water solubility, which is beneficial for increasing battery capacity in aqueous flow batteries.

[0012] As a preferred embodiment, the R 17 -R 18 Each can be independently selected from one of the following structures: , , , , , , , , , ,

[0013] Where n = 1-10, m = 0-5.

[0014] Appropriately increasing the content of water-soluble groups is beneficial to improving the solubility of folded viologen in aqueous solution, thereby increasing its capacity in aqueous flow batteries.

[0015] The second aspect: A method for preparing the folded violarite described in the first aspect includes the following steps: The 4,4-bipyridine derivative was added to an organic solvent, and then a bridging group was added to react and give the folded viologen intermediate. Then, a capping agent is added to the folded viologen intermediate, and the reaction is carried out to obtain the folded viologen; The capping agent is R. 17 -R 18 Halides of the structure; The structural formula of the 4,4-bipyridine derivative is shown below:

[0016] R1-R8 are independently selected from hydrogen or C1-C6 alkyl groups; The bridging group includes at least one of the following structures: , , , , , , , ,

[0017] Where d = 1-6, Y1 and Y2 are independently selected from chlorine, bromine and iodine atoms; The structural formula of the folded violarin intermediate is shown below:

[0018] Among them, R1-R 16They are independently selected from hydrogen or C1-C6 alkyl groups.

[0019] The method for preparing folded violarite provided by this invention is simple, has a high yield (up to 80% or more), and produces a product with good purity (>95%), making it suitable for large-scale preparation.

[0020] As a preferred embodiment, the folded viologen can be prepared into other anionic forms, namely the Y, by ion exchange. - It is selected from at least one of chloride ion, bromide ion, iodide ion, nitrate ion, hydrogen sulfate ion and hexafluorophosphate ion.

[0021] As a preferred embodiment, the organic solvent is at least one selected from acetonitrile, N,N-dimethylformamide, toluene, 1,4-dioxane, and dimethyl sulfoxide.

[0022] As a preferred embodiment, the reaction temperature of the 4,4-bipyridine derivative with the bridging group is 75-90℃, and the reaction time is 24-120h; the reaction temperature of the folded viologen intermediate with the capping agent is 80-150℃, and the reaction time is 24-120h.

[0023] If the reaction temperature is too low, the reaction will not be complete; if it is too high, it may cause long-chain polymerization, affecting the purity. If the purity cannot be guaranteed, it will affect the electrochemical performance.

[0024] Third aspect: A negative electrode electrolyte for an aqueous flow battery includes the folded violarin described in the first aspect. The folded violarin serves as the active material in the negative electrode electrolyte of the flow battery. Specifically, the folded violarin is uniformly mixed with a supporting electrolyte in deionized water. The supporting electrolyte includes potassium chloride, sodium chloride, cesium chloride, or ammonium chloride, with a concentration of 0.01-2.0 mol / L, and the concentration of the folded violarin is 0.01-1.0 mol / L.

[0025] Fourth aspect: An aqueous flow battery includes the negative electrode electrolyte described in the third aspect. Specifically, its positive electrode electrolyte is an aqueous solution of a soluble organic compound, a metal complex, or an inorganic compound, and the supporting electrolyte in the positive electrode electrolyte includes potassium chloride, sodium chloride, cesium chloride, or ammonium chloride. Attached Figure Description

[0026] Figure 1 The cyclic voltammetry curves are for the folded viologen prepared in Examples 1-8.

[0027] Figure 2 The cycling performance diagram of the Pr-foldaNV / FcNCl flow battery prepared in Example 10 is shown.

[0028] Figure 3The cycling performance diagram of the OH-foldaOV / FcNCl flow battery prepared in Example 11 is shown.

[0029] Figure 4 The image shows the cycle performance of the IS-foldaNV / FcNCl flow battery prepared in Example 12.

[0030] Figure 5 The rate performance diagram of the IS-foldaNV / FcNCl flow battery prepared in Example 12 is shown. Detailed Implementation

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0033] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe the methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0034] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0035] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0036] A type of folded violane, with the following general structural formula:

[0037] In the formula, X represents a C3-C15 alkylene group and contains at most one first substituent, which is one of alkyl, alkoxy, hydroxy, carboxyl, quaternary ammonium, or halogen; or, X represents a C3-C8 carbon chain and contains 1-6 ether groups or imino groups, the number of which is not more than the number of carbon atoms; in the embodiments of the present invention, the X group is a straight chain or a branched chain.

[0038] R1-R 16 They are independently selected from hydrogen or C1-C6 alkyl groups.

[0039] R 17 -R 18 The components are independently selected from at least one of C1-C10 alkyl groups, C1-C10 alkyl groups whose terminals are substituted with a second substituent, or C1-C10 alkyl groups containing branches, wherein the second substituent is one of hydroxyl, carboxyl, quaternary ammonium, or sulfonic acid groups, and the branch is one of alkyl, hydroxyl, carboxyl, quaternary ammonium, or sulfonic acid groups.

[0040] In an embodiment of the present invention, R 17 -R 18 Each can be independently selected from one of the following structures: , , , , , , , , , ,

[0041] Where n = 1-10, m = 0-5.

[0042] Y - The ion represents an anion selected from at least one of chloride, bromide, iodide, nitrate, hydrogen sulfate, and hexafluorophosphate, where b is an integer from 1 to 9. a is an integer from 1 to 9.

[0043] A method for preparing folded violarite includes the following steps: S1, the 4,4-bipyridine derivative was added to a flask, an organic solvent was added, and the bridging group was slowly added dropwise when the temperature was heated to 75-90℃. The reaction was carried out for 24-120 h. After the reaction was completed, the precipitate was filtered, washed, collected, and dried under vacuum to obtain the folded viologen intermediate.

[0044] S2, the folded violarin intermediate is put into a flask, an organic solvent and a capping agent are added. The amount of capping agent added is more than twice the molar amount of the folded violarin intermediate. The mixture is heated to 80-150℃ and reacted for 24-120h. After the reaction is completed, the mixture is filtered, washed, and the precipitate is collected and dried under vacuum to obtain folded violarin.

[0045] S3, through ion exchange, yields other anionic products, namely Y. - It is selected from at least one of chloride ion, bromide ion, iodide ion, nitrate ion, hydrogen sulfate ion and hexafluorophosphate ion.

[0046] The organic solvent includes at least one of acetonitrile, N,N-dimethylformamide, toluene, 1,4-dioxane, and dimethyl sulfoxide.

[0047] The structural formula of the 4,4-bipyridine derivative is shown below:

[0048] R1-R8 are independently selected from hydrogen or C1-C6 alkyl groups; The bridging group includes at least one of the following structures: , , , , , , , ,

[0049] Where d = 1-6, Y1 and Y2 are independently selected from chlorine, bromine and iodine atoms; The structural formula of the folded viologen intermediate is shown below:

[0050] Among them, R1-R 16 They are independently selected from hydrogen or C1-C6 alkyl groups.

[0051] The end-capping agent is R 17 -R 18 Halides of the structure.

[0052] An aqueous flow battery comprises the following components: (1) The positive and negative electrodes are made of graphite felt with a side length of 3×3cm and a thickness of 4mm.

[0053] (2) The diaphragm is a DSVN anion exchange membrane.

[0054] (3) The current collector is made of 2mm thick titanium plate.

[0055] (4) The active material of the positive electrode electrolyte is a TEMPO derivative (TMAP-TEMPO) or a ferrocene derivative FcNCl, and the concentration is 0.1-1.0 mol / L.

[0056] (5) The active substance of the negative electrode electrolyte is folded violane, and the concentration is 0.1-1.0 mol / L; the supporting electrolyte is 0.5-2 mol / L potassium chloride or sodium chloride aqueous solution.

[0057] Battery assembly: Assembling components such as end plates, current collectors, electrode frames, positive and negative electrodes, separators, supporting electrolytes, positive and negative electrolyte solutions, flow pipes, storage tanks, and peristaltic pumps according to a specific process.

[0058] Battery testing and electrochemical characterization: Charge-discharge cycle and rate testing were performed using a battery testing system, with a current density range of 20-120 mA / cm². 2 Its electrochemical properties were characterized by cyclic voltammetry (CV).

[0059] In this embodiment of the invention, the prepared folded viologen is shown below, corresponding to Examples 1-8 respectively: (1) Propyl-bridged folded viologen, with end capping group R 17 R 18 It is a quaternary ammonium salt chain -(CH2)3N(CH3)3 + The counter ion is Br - It was named Pr-foldaNV and prepared at concentrations ranging from 0.1 to 0.5 mol / L.

[0060] (2) Propyl-bridged folded viologen, with end capping group R 17 R 18 It is a methyl group, and its counterion is Br. - It was named Pr-foldaMV and prepared at a concentration of 0.1 mol / L.

[0061] (3) Hydroxypropyl-bridged folded viologen, with end capping group R 17 R 18 The hydroxyl chain is -(CH2)3OH, and the counterion is Br. - It was named OH-foldaOV and prepared at a concentration of 0.1-1.0 mol / L.

[0062] (4) Hydroxypropyl-bridged folded viologen, with end capping group R 17 R 18 It is a methyl group, and its counterion is Br. - It was named OH-foldaMV and prepared at a concentration of 0.1 mol / L.

[0063] (5) Hydroxypropyl-bridged folded viologen, with end capping group R17 R 18 It is a quaternary ammonium salt chain -(CH2)3N(CH3)3 + The counter ion is Br - It was named OH-foldaNV and prepared at a concentration of 0.1 mol / L.

[0064] (6) Isobutyl-bridged folded viologen, with end-capping group R 17 R 18 It is a quaternary ammonium salt chain -(CH2)3N(CH3)3 + The counter ion is Br - It was named IS-foldaNV and prepared at a concentration of 0.1 mol / L.

[0065] (7) Isobutyl-bridged folded viologen, with end-capping group R 17 R 18 It is a methyl group, and its counterion is Br. - It was named IS-foldaMV and prepared at a concentration of 0.1 mol / L.

[0066] (8) Isobutyl-bridged folded viologen, with end capping group R 17 R 18 The hydroxyl chain is -(CH2)3OH, and the counterion is Br. - It was named IS-foldaOV and prepared at a concentration of 0.1 mol / L.

[0067] Example 1 The preparation of propyl-bridged folded quaternary ammonium viologen Pr-foldaNV includes the following steps: (1) Weigh 10g (64mmol) of 4,4-bipyridine into a two-necked flask, add 100mL of acetonitrile, stir magnetically until completely dissolved to obtain solution A, and heat to 80℃.

[0068] (2) Weigh 4g (20mmol) of 1,3-dibromopropane into a beaker, add 50mL of acetonitrile, and obtain solution B.

[0069] (3) Transfer solution B to a constant pressure funnel and slowly add it dropwise to solution A. Stir the reaction for 24 hours.

[0070] (4) After the reaction is complete, filter, wash and collect the grayish-white precipitate, and dry it under vacuum to obtain the intermediate Pr-foldaBpy.

[0071] (5) Weigh 5.2g (10mmol) Pr-foldaBpy into a round-bottom flask, add 8g (30mmol) (3-bromopropyl) trimethylammonium bromide, add 200mL N,N-dimethylformamide, heat to 120℃, and react for 24h.

[0072] (6) After the reaction is complete, filter, wash and collect the yellow precipitate, and dry it under vacuum to obtain Pr-foldaNV.

[0073] Example 2 The preparation of propyl-bridged folded methyl viologen (Pr-foldaMV) includes the following steps: Steps (1)-(4) are exactly the same as in Example 1.

[0074] (5) Weigh 5.2g (10mmol) Pr-foldaBpy into a round-bottom flask, add 2.8g (30 mmol) chloroacetic acid, add 100mL N,N-dimethylformamide, heat to 150℃, and react for 24h.

[0075] (6) After the reaction is complete, filter, wash and collect the brown precipitate, and dry it under vacuum to obtain Pr-foldaMV.

[0076] Example 3 The preparation of hydroxypropyl-bridged folded hydroxyvioletin (OH-foldaOV) includes the following steps: (1) Weigh 10g (64mmol) of 4,4-bipyridine into a two-necked flask, add 100mL of acetonitrile, stir magnetically until completely dissolved, and obtain solution A. Heat to 85℃.

[0077] (2) Weigh 4.4g (20mmol) of 1,3-dibromo-2-propanol into a beaker, add 50mL of acetonitrile, and obtain solution B.

[0078] (3) Transfer solution B to a constant pressure funnel and slowly add it dropwise to solution A. Stir the reaction for 48 hours.

[0079] (4) After the reaction is complete, filter, wash and collect the grayish-white precipitate, and dry it under vacuum to obtain the intermediate OH-foldaBpy.

[0080] (5) Weigh 5.3g (10mmol) OH-foldaBpy into a round-bottom flask, add 4.17g (30mmol) 3-bromo-1-propanol, add 200mL N,N-dimethylformamide, heat to 100℃, and react for 48h.

[0081] (6) After the reaction is complete, filter, wash and collect the yellow precipitate, and dry it under vacuum to obtain OH-foldaOV.

[0082] Example 4 The preparation of hydroxypropyl-bridged folded methyl viologen (OH-foldaMV) includes the following steps: Steps (1)-(4) are exactly the same as in Example 3.

[0083] (5) Weigh 5.3g (10mmol) of OH-foldaBpy into a round-bottom flask, add 2.8g (30 mmol) of chloroacetic acid, add 200mL of N,N-dimethylformamide, heat to 150℃, and react for 24h.

[0084] (6) After the reaction is complete, filter, wash and collect the brown precipitate, and dry it under vacuum to obtain OH-foldaMV.

[0085] Example 5 The preparation of hydroxypropyl-bridged folded quaternary ammonium viologen (OH-foldaNV) includes the following steps: Steps (1)-(4) are exactly the same as in Example 3.

[0086] (5) Weigh 5.3g (10mmol) OH-foldaBpy into a round-bottom flask, add 8g (30mmol) (3-bromopropyl)trimethylammonium bromide, add 200mL N,N-dimethylformamide, heat to 120℃, and react for 24h.

[0087] (6) After the reaction is complete, filter, wash and collect the yellow precipitate, and dry it under vacuum to obtain OH-foldaNV.

[0088] Example 6 The preparation of isobutyl-bridged folded quaternary ammonium viologen IS-foldaNV includes the following steps: (1) Weigh 10g (64mmol) of 4,4-bipyridine into a two-necked flask, add 100mL of acetonitrile, stir magnetically until completely dissolved to obtain solution A, and heat to 80℃.

[0089] (2) Weigh 4.3g (20mmol) of 1,3-dibromo-2-methylpropane into a beaker, add 50mL of acetonitrile, and obtain solution B.

[0090] (3) Transfer solution B to a constant pressure funnel and slowly add it dropwise to solution A. Stir the reaction for 24 hours.

[0091] (4) After the reaction is complete, filter, wash and collect the grayish-white precipitate, and dry it under vacuum to obtain the intermediate IS-foldaBpy.

[0092] (5) Weigh 5.3g (10mmol) IS-foldaBpy into a round-bottom flask, add 8g (30mmol) (3-bromopropyl)trimethylammonium bromide, add 200mL N,N-dimethylformamide, heat to 120℃, and react for 24h.

[0093] (6) After the reaction is complete, filter, wash and collect the yellow precipitate, and dry it under vacuum to obtain IS-foldaNV.

[0094] Example 7 The preparation of isobutyl-bridged folded methyl viologen (IS-foldaMV) includes the following steps: Steps (1)-(4) are exactly the same as in Example 6.

[0095] (5) Weigh 5.3g (10mmol) IS-foldaBpy into a round-bottom flask, add 2.8g (30 mmol) chloroacetic acid, add 200mL N,N-dimethylformamide, heat to 150℃, and react for 24h.

[0096] (6) After the reaction is complete, filter, wash and collect the brown precipitate, and dry it under vacuum to obtain IS-foldaMV.

[0097] Example 8 The preparation of isobutyl-bridged folded hydroxyvioletin IS-foldaOV includes the following steps: Steps (1)-(4) are exactly the same as in Example 6.

[0098] (5) Weigh 5.3g (10mmol) IS-foldaBpy into a round-bottom flask, add 4.17g (30 mmol) 3-bromo-1-propanol, add 200mL N,N-dimethylformamide, heat to 100℃, and react for 48h.

[0099] (6) After the reaction is complete, filter, wash and collect the brown precipitate, and dry it under vacuum to obtain IS-foldaOV.

[0100] Example 9 The folded viologen prepared in Examples 1-8 was prepared into an aqueous solution, and 0.5 mol / L KCl was used as the supporting electrolyte. The scan rate was 100 mV s⁻¹. -1 A cyclic voltammetry test was then performed. The test results are as follows: Figure 1 The folded viologen prepared in Examples 1-8 has a reversible redox peak in the range of -0.4 to -0.6, with a peak potential difference of 30-35 mV, indicating that this redox peak corresponds to two electrons.

[0101] Example 10 The fabrication of the Pr-foldaNV / FcNCl flow battery includes the following steps: The Pr-folda NV folded viologen prepared in Example 1 was configured into a 0.1 mol / L aqueous solution as the negative electrode electrolyte for the flow battery. A 0.1 mol / L FcNCl aqueous solution was configured as the positive electrode electrolyte for the flow battery, and 1 mol / L KCl was used as the supporting electrolyte for both the positive and negative electrodes. A 3 × 3 cm² area was used. 2 Carbon felt electrodes are used as the positive and negative electrodes of the flow battery, titanium plates are used as the current collectors, and DSVN ion exchange membranes are used as the separators. Stainless steel end plates, current collectors, electrode frames, and carbon felt electrodes are assembled into a single cell in a specific order. The electrolyte is circulated between the external storage tank and the battery stack via pipelines delivered by a peristaltic pump. The positive and negative electrodes of the battery are connected to a battery testing system with a current density of 40 mA / cm². 2 Perform constant current charge and discharge tests on the battery.

[0102] like Figure 2 As shown, the flow battery based on 0.1 mol / L Pr-foldaNV exhibits good cycle performance.

[0103] Example 11 The preparation of an OH-foldaOV / FcNCl flow battery includes the following steps: The OH-foldaOV folded viologen prepared in Example 3 was used as a 1.0 mol / L aqueous solution as the negative electrode electrolyte for the flow battery. The remaining steps were exactly the same as in Example 10.

[0104] like Figure 3 As shown, the flow battery based on 1.0 mol / L OH-foldaOV exhibits good cycle performance.

[0105] Example 12 The fabrication of the IS-foldaNV / FcNCl flow battery includes the following steps: The IS-foldaNV folded viologen prepared in Example 6 was configured into an aqueous solution with a concentration of 0.5 mol / L and used as the negative electrode electrolyte for the flow battery. The remaining steps were exactly the same as in Example 10.

[0106] like Figure 4-5 As shown, the flow battery based on 0.5 mol / L IS-foldaNV exhibits good cycling performance in the range of 20–100 mA cm⁻¹. -2 It exhibits good rate performance.

[0107] Example 13 The fabrication of the Pr-foldaMV / FcNCl flow battery includes the following steps: The Pr-foldaMV folded viologen prepared in Example 2 was configured into an aqueous solution with a concentration of 0.1 mol / L and used as the negative electrode electrolyte for the flow battery. The remaining steps were exactly the same as in Example 10.

[0108] Example 14 The preparation of an OH-foldaMV / FcNCl flow battery includes the following steps: The OH-foldaMV folded viologen prepared in Example 4 was configured into an aqueous solution with a concentration of 0.1 mol / L and used as the negative electrode electrolyte for the flow battery. The remaining steps were exactly the same as in Example 10.

[0109] Example 15 The preparation of an OH-foldaNV / FcNCl flow battery includes the following steps: The OH-foldaNV folded viologen prepared in Example 5 was configured into an aqueous solution with a concentration of 0.1 mol / L and used as the negative electrode electrolyte for the flow battery. The remaining steps were exactly the same as in Example 10.

[0110] Example 16 The fabrication of an IS-foldaMV / TMAP-TEMPO flow battery includes the following steps: The IS-foldaMV folded viologen prepared in Example 7 was configured into a 0.1 mol / L aqueous solution as the negative electrode electrolyte for the flow battery. A 0.1 mol / L TMAP-TEMPO aqueous solution was configured as the positive electrode electrolyte for the flow battery. The remaining steps were exactly the same as in Example 10.

[0111] Example 17 The fabrication of an IS-foldaOVTMAP-TEMPO flow battery includes the following steps: The IS-foldaOV folded viologen prepared in Example 8 was configured into a 0.1 mol / L aqueous solution as the negative electrode electrolyte for the flow battery. A 0.1 mol / L TMAP-TEMPO aqueous solution was configured as the positive electrode electrolyte for the flow battery. The remaining steps were exactly the same as in Example 10.

[0112] Table 1 Electrochemical performance of the flow batteries prepared in Examples 10-17

[0113] As can be seen from Table 1, the folded viologen prepared in this invention has a high coulombic efficiency when applied to an aqueous flow battery, and still has a high capacity retention rate after 100 cycles.

[0114] The above embodiments are merely illustrative of several implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the invention patent. For those skilled in the art, any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments without departing from the concept of the present invention are all within the protection scope of the present invention.

Claims

1. A folded purple essence, characterized in that, The general formula for the structure is: In the formula, X represents a C3-C15 alkylene group and contains at most one first substituent, which is one of alkyl, alkoxy, hydroxy, carboxyl, quaternary ammonium or halogen; or, X represents a C3-C8 carbon chain and the carbon chain contains 1-6 ether groups or imino groups, the number of which is not more than the number of carbon atoms. R1-R 16 They are independently selected from hydrogen or C1-C6 alkyl groups; R 17 -R 18 The components are independently selected from at least one of C1-C10 alkyl groups, C1-C10 alkyl groups whose terminals are substituted with a second substituent, or C1-C10 alkyl groups containing branches, wherein the second substituent is one of hydroxyl, carboxyl, quaternary ammonium, or sulfonic acid groups, and the branch is one of alkyl, hydroxyl, carboxyl, quaternary ammonium, or sulfonic acid groups. Y - The ion represents an anion selected from at least one of chloride, bromide, iodide, nitrate, hydrogen sulfate, and hexafluorophosphate, where b is an integer from 1 to 9. a is an integer from 1 to 9.

2. The folded purple essence according to claim 1, characterized in that, X represents a C3-C6 alkylene group and contains a first substituent, which is one of alkyl, alkoxy, hydroxy, carboxyl, quaternary ammonium, or halogen; or, X represents a C3-C6 carbon chain and the carbon chain contains 1-6 ether groups or imino groups, the number of which is not more than the number of carbon atoms.

3. The folded purple essence according to claim 1, characterized in that, The Y - It is selected from at least one of chloride ion, bromide ion, iodide ion, and nitrate ion.

4. The folded purple essence according to claim 1, characterized in that, The R 17 -R 18 Each can be independently selected from one of the following structures: 、 、 、 、 、 、 、 、 、 、 Where n = 1-10, m = 0-5.

5. A method for preparing folded violarite as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The 4,4-bipyridine derivative was added to an organic solvent, and then a bridging group was added to react and give the folded viologen intermediate. Then, a capping agent is added to the folded viologen intermediate, and the reaction is carried out to obtain the folded viologen; The capping agent is R. 17 -R 18 Halides of the structure; The structural formula of the 4,4-bipyridine derivative is shown below: R1-R8 are independently selected from hydrogen or C1-C6 alkyl groups; The bridging group includes at least one of the following structures: 、 、 、 、 、 、 、 、 Where d = 1-6, Y1 and Y2 are independently selected from chlorine, bromine and iodine atoms; The structural formula of the folded violarin intermediate is shown below: Among them, R1-R 16 They are independently selected from hydrogen or C1-C6 alkyl groups.

6. The method for preparing folded violarite according to claim 5, characterized in that, The folded viologen can be used to prepare other anionic products, namely the Y... - It is selected from at least one of chloride ion, bromide ion, iodide ion, nitrate ion, hydrogen sulfate ion and hexafluorophosphate ion.

7. The method for preparing folded violarite according to claim 5, characterized in that, The organic solvent is at least one selected from acetonitrile, N,N-dimethylformamide, toluene, 1,4-dioxane, and dimethyl sulfoxide.

8. The method for preparing folded violarite according to claim 5, characterized in that, The reaction temperature of the 4,4-bipyridine derivative with the bridging group is 75-90℃, and the reaction time is 24-120h; the reaction temperature of the folded viologen intermediate with the capping agent is 80-150℃, and the reaction time is 24-120h.

9. A negative electrode electrolyte for an aqueous flow battery, characterized in that, Includes the folded purple essence as described in any one of claims 1 to 4.

10. An aqueous flow battery, characterized in that, Includes the negative electrode electrolyte as described in claim 9.

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