A viologen polymer and its preparation method and application

Abstract

The present invention discloses a viologen polymer and a preparation method and application thereof, belonging to the technical field of organic liquid flow batteries. 1-Methyl-[4,4'-bipyridine]-1-iodide and 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione containing negative electrode active molecules undergo a substitution reaction to generate a monomer HMPB; (2) the monomer HMPB is subjected to a Grubbs third-generation catalyst-catalyzed ring-opening polymerization to obtain a viologen polymer. The viologen polymer prepared by the present invention adopts Grubbs controlled ring-opening polymerization to increase the solubility of the viologen polymer and improve the energy density of the battery. The prepared aqueous organic liquid flow battery system has the advantages of low cost, stable charge and discharge performance, high solubility of active materials, and is easy to achieve large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of aqueous organic liquid flow batteries, and specifically relates to a viologen polymer and a preparation method thereof, as well as application of the viologen polymer as a negative active electrode material in polymer-based aqueous organic liquid flow batteries. Background Art

[0002] The continuous depletion of fossil fuels in recent years has led to severe global resource shortages and environmental pollution, necessitating the development of green, renewable energy. However, renewable energy sources such as wind, solar, and tidal power suffer from discontinuity and uncontrollability, making the integration of renewable resources and energy storage systems imperative. Flow batteries, with their ability to independently regulate power and energy, freedom from geographical constraints, and safety and reliability, have become the most promising large-scale energy storage technology.

[0003] All-vanadium redox flow batteries are a relatively mature energy storage technology. However, as a rare metal, vanadium presents challenges such as high cost and limited resources. In contrast, aqueous organic flow batteries utilize diverse organic molecules as electrochemically active materials. This not only significantly reduces the cost of the redox couple but also allows for the regulation of the electrode potential, solubility, and stability of the organic active electrolyte through rational molecular design. This represents an effective approach to developing the next generation of highly safe, low-cost, and high-capacity energy storage technologies.

[0004] Organic polymers have received widespread attention as electrode materials for flow batteries in recent years. Organic polymers have stable structures and are easy to design with multiple redox sites. Most importantly, when assembling flow batteries, dialysis membranes can be used instead of expensive ion exchange membranes. This can effectively prevent cross-contamination between ions and greatly reduce the cost of the flow battery system. Summary of the Invention

[0005] The first aspect of the present invention is to provide a viologen polymer having the following chemical structure:

[0006]

[0007] Wherein: n is 10 to 1000.

[0008] A second aspect of the present invention is to provide a method for preparing a viologen polymer, characterized in that it comprises the following steps:

[0009] (1) 1-methyl-[4,4'-bipyridyl]-1-iodide containing the negative electrode active molecule and 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione undergo a substitution reaction to generate monomer HMPB (Formula 1);

[0010] (2) The monomer HMPB is subjected to ring-opening polymerization catalyzed by Grubbs' third-generation catalyst to obtain viologen polymer (Formula 2).

[0011] The reaction equations involved are as follows:

[0012]

[0013] Further:

[0014] A method for preparing a viologen polymer, characterized in that it comprises the following steps:

[0015] (1) Using acetonitrile as solvent, 1-methyl-[4,4'-bipyridyl]-1-iodide and 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione were subjected to a substitution reaction. After the reaction, a yellow solid polymer monomer HMPB was obtained by filtration.

[0016] (2) The HMPB monomer is dissolved in a mixed solution of methanol and deionized water, the pH of the solution is adjusted to 2 with hydrochloric acid, sodium chloride and Grubbs third-generation catalyst are added, and the reaction is carried out under a nitrogen atmosphere; after the reaction is completed, a vinyl isobutyl ether polymerization terminator is added, the mixture is stirred at room temperature, distilled under reduced pressure, and precipitated in ether three times to obtain a viologen polymer.

[0017] In the step (1):

[0018] The molar ratio of 1-methyl-[4,4'-bipyridyl]-1-iodide to 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione is 1:1.2.

[0019] The substitution reaction was carried out at 110° C. under condensation reflux for 2 hours.

[0020] In the step (2):

[0021] The molar ratio of the monomer HMPB to the Grubbs third-generation catalyst is 10-100 / 1.

[0022] The polymerization reaction was stirred at 40° C. for 24 hours.

[0023] The third aspect of the present invention is to provide a viologen polymer as a negative active electrode material in an aqueous organic liquid flow battery, specifically as follows:

[0024] An aqueous organic liquid flow battery system includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte includes a positive electrode electrolyte and a negative electrode electrolyte, and is characterized in that the electrolyte in the positive electrode electrolyte is potassium sulfonate TEMPO, and the electrolyte in the negative electrode electrolyte is a viologen derivative.

[0025] Preferably, the positive electrode is carbon felt, the negative electrode is a graphite plate, and the diaphragm is a dialysis membrane or a cationic diaphragm.

[0026] In the positive electrode electrolyte, the concentration of potassium sulfonate TEMPO is a solution ranging from 0.1 mol / L to its saturation concentration.

[0027] In the negative electrode electrolyte, the concentration of the viologen polymer is a solution ranging from 0.1 mol / L to its saturation concentration.

[0028] Preferably, the positive electrode electrolyte and the negative electrode electrolyte further include a supporting electrolyte, wherein the supporting electrolyte includes one or more of sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, sodium nitrate, and sodium nitrate. The molar concentration of the supporting electrolyte is preferably 0.1-3 mol / L.

[0029] The beneficial effects of the present invention are as follows:

[0030] (1) The present invention prepares a new type of viologen polymer, which adopts Grubbs ring-opening polymerization to precisely control the molecular weight of the polymer. By controlling the molecular weight of the polymer, the viscosity of the negative electrode active material electrolyte can be adjusted, the solubility of the viologen polymer can be increased, and the energy density of the battery can be improved.

[0031] (2) The present invention provides a novel method for preparing a viologen polymer, which has low cost of polymerization raw materials, a simple and efficient polymerization method, and a high yield. It can be polymerized in water and directly used as the negative electrode active material of a liquid flow battery, greatly reducing the cost of the battery system.

[0032] (3) The present invention provides a novel application of viologen polymer in aqueous organic liquid flow batteries.

[0033] This invention provides an aqueous organic flow battery based on a novel viologen polymer, aiming to address the challenges faced by traditional flow batteries. The novel viologen polymer is designed and synthesized and used as the negative active electrolyte in the aqueous organic flow battery. Through Grubbs ring-opening catalytic polymerization, the molecular weight of the viologen polymer can be precisely controlled, thereby maximizing the electrochemical performance of the viologen polymer flow battery. Experimental testing has shown that this battery, utilizing a viologen polymer with excellent redox properties as the active material and a water-based electrolyte as the medium for energy storage and release, exhibits high efficiency, long cycle life, and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The water-soluble monomer HMPB prepared in Example 1 1 H NMR spectrum.

[0035] Figure 2 is the viologen polymer prepared in Example 1 1 H NMR spectrum.

[0036] Figure 3 The cyclic voltammetry curves of the potassium sulfonate TEMPO positive electrode electrolyte and the viologen polymer negative electrode electrolyte of Example 2 at a scan rate of 100 mv / s.

[0037] Figure 4 This is a graph showing the charge and discharge cycle stability of the aqueous organic liquid flow battery prepared in Example 3 at a current density of 50 mA.

[0038] Figure 5 This is the charge and discharge platform curve of the aqueous organic liquid flow battery prepared in Example 3 at a current density of 50 mA. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to specific embodiments.

[0040] Example 1: Preparation of Viologen Polymer

[0041] (1) 1-Methyl-[4,4'-bipyridyl]-1-iodide (4.0 g, 13.42 mol, 1 equiv) was placed in a 500 ml round-bottom flask, 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione (4.58 g, 16.10 mol, 1.2 equiv) was added, and 400 ml of acetonitrile was added. The mixture was stirred under reflux at 110°C for 24 hours. The reaction was stopped, cooled to room temperature, and filtered to obtain 6.09 g of HMPB monomer as a yellow solid. The yield was 78%.

[0042] (2) HMPB (0.2 g, 0.343 mmol, 10 equiv) was placed in a small glass bottle, and 0.8 ml of methanol and 0.4 ml of water were added to dissolve it. Hydrochloric acid was added to adjust the pH of the solution to 2, and then 0.5 M NaCl (0.029 g) was added. N2 gas was purged for 15 min. 30.35 mg of Grubbs' third-generation catalyst (dissolved in 0.5 ml of THF) was added. The monomer:initiator equivalent ratio was 10:1, and the reaction was stirred at 40°C for 1 hour. After the reaction was completed, the mixture was cooled to room temperature, and 100 μl of vinyl isobutyl ether was added to terminate the polymerization. The mixture was rotated at room temperature for one hour. The mixture was evaporated under reduced pressure, and the solid was dissolved in trifluoroethanol and then precipitated twice in diethyl ether to obtain a viologen polymer with a polymer conversion rate of 97%.

[0043] Product Confirmation:

[0044] Monomeric HMPB 1 H NMR spectrum Figure 1 As shown, 1 H NMR (400 MHz, D2O) δ9.11 (dd, J=21.2, 5.8 Hz, 4H), 8.58 (dd, J=16.4, 5.7 Hz, 4H), 6.23 (s, 2H), 4.70 (s, 2H), 4.54 (s, 3H), 3.56 (s, 2H), 3.51 (s, 2H), 3.43 (s, 2H), 2.29 (s, 2H), 1.77 (s, 1H), 1.68 (s, 1H). The figure shows that the synthesized HMPB monomer has high purity. Its H NMR spectrum contains 11 different hydrogen species with an area ratio of 4:4:2:2:3:2:2:2:2:1:1, which matches that of HMPB.

[0045] Figure 2 To obtain the H NMR spectrum of the prepared viologen polymer, we added a terminal group to the polymer chain in order to see the number of monomers in the polymer. Figure 2 We can see that each molecular chain of the polymer contains 17 monomer molecules.

[0046] Replacement examples 1-2 to 1-5:

[0047] The preparation method is the same as that of Example 1, except that the molar ratio of the reaction materials in step (1), i.e., 1-methyl-[4,4'-bipyridyl]-1-iodide and 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione, is adjusted, and its effect on the reaction yield is tested, as shown in Table 1.

[0048] Table 1

[0049] Serial number Reaction material ratio Monomer yield Example 1 1:1.2 78％ Replacement Example 1-2 1:0.1 10％ Replacement Example 1-3 1:0.5 35％ Replacement Example 1-4 1:5 78％ Replacement Example 1-5 1:10 78％

[0050] As shown in Table 1, when the molar ratio of 1-methyl-[4,4'-bipyridyl]-1-iodide to 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione is 1:0.1, the monomer yield is 10%. As the molar ratio increases, the reaction yield gradually increases. When the molar ratio is 1:1.2, the yield is optimal. As the amount of 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione is further increased to an excess, the reaction yield does not increase significantly.

[0051] Replacement examples 1-6 to 1-9:

[0052] The preparation method is the same as that of Example 1, except that the reaction temperature of step (1) is adjusted, and its effect on the reaction yield is tested, as shown in Table 2.

[0053] Table 2

[0054] Serial number Reaction temperature Monomer yield Example 1 110 78％ Replacement Example 1-6 50 10％ Replacement Example 1-7 80 30％ Replacement Example 1-8 100 55％ Replacement Example 1-9 115 77％

[0055] As shown in Table 2: When the reaction temperature of 1-methyl-[4,4'-bipyridyl]-1-iodide and 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione is 50°C, the monomer yield is only 10%. As the temperature increases, the monomer yield gradually increases. When the reaction temperature reaches 110°C, the monomer yield is the highest.

[0056] Replacement examples 1-10 to 1-13:

[0057] The preparation method is the same as that of Example 1, except that the reaction time of step (1) is adjusted and its effect on the reaction yield is tested, as shown in Table 3.

[0058] Table 3

[0059] Serial number Reaction time Monomer yield Example 1 24h 78％ Replacement Example 1-10 6h 20％ Replacement Example 1-11 12h 30％ Replacement Example 1-12 20h 70％ Replacement Example 1-13 30h 78％

[0060] As shown in Table 3: The reaction time of 1-methyl-[4,4'-bipyridyl]-1-iodide and 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione is 6 hours, and the monomer yield is only 20%. As the reaction time increases, the monomer yield gradually increases. When the reaction time reaches 24 hours, the monomer yield is the highest. As the reaction time further increases, the reaction yield does not increase significantly.

[0061] Replacement examples 1-14 to 1-17:

[0062] The preparation method is the same as that of Example 1, except that the reaction material ratio in step (2) (the molar ratio of monomer HMPB to Grubbs' third-generation catalyst) is adjusted, and its effect on the reaction yield is tested, as shown in Table 4.

[0063] Table 4

[0064] Serial number Reaction material ratio Polymer conversion Example 1 10:1 97％ Replacement Example 1-14 5:1 97％ Replacement Example 1-15 20：1 95％ Replacement Example 1-16 50:1 93％ Replacement Example 1-17 100:1 90％

[0065] As shown in Table 4, when the molar ratio of monomer HMPB to Grubbs third-generation catalyst is 5:1, the polymer conversion rate can reach 97%. As the molar ratio increases, the polymer conversion rate decreases slightly.

[0066] Replacement examples 1-18 to 1-21:

[0067] The preparation method is the same as that of Example 1, except that the polymerization reaction temperature in step (2) is adjusted, and its effect on the reaction yield is tested, as shown in Table 5.

[0068] Table 5

[0069] Serial number Polymerization temperature ℃ Polymer conversion Example 1 60 97％ Replacement Example 1-18 25 50％ Replacement Example 1-19 40 70％ Replacement Example 1-20 50 80％ Replacement Example 1-21 70 95％

[0070] As shown in Table 5: When the polymerization reaction temperature is 25°C, the polymer conversion rate is only 50%. As the reaction temperature increases, the polymer conversion rate gradually increases. When the reaction temperature reaches 60°C, the polymer conversion rate is the highest.

[0071] Replacement examples 1-22 to 1-25:

[0072] The preparation method is the same as that of Example 1, except that the polymerization reaction time of step (2) is adjusted, and its effect on the reaction yield is tested, as shown in Table 6.

[0073] Table 6

[0074] Serial number Reaction time Polymer conversion Example 1 1h 97％ Replacement Example 1-22 0.5h 50％ Replacement Example 1-23 0.8h 80％ Replacement Example 1-24 1.5h 97％ Replacement Example 1-25 2h 97％

[0075] As shown in Table 6, the polymer conversion rate was only 50% at a polymerization reaction time of 0.5 h. As the reaction time increased, the polymer conversion rate gradually increased, reaching its highest value at a reaction time of 1 h. Further increases in reaction time did not significantly increase the polymer conversion rate.

[0076] Example 2:

[0077] The viologen polymer prepared in Example 1 was dissolved in 10 ml of a 0.5 mol / L supporting electrolyte sodium sulfate solution to a concentration of 5 mmol / L. This solution was exposed to nitrogen gas to remove oxygen while conducting a three-electrode cyclic voltammetry test. A glassy carbon electrode served as the working electrode, an Ag / AgCl reference electrode, and a platinum electrode served as the counter electrode. The scan rate was 100 mV / s over a voltage range of -0.8 to 0 V.

[0078] Potassium TEMPO sulfonate was dissolved in 10 ml of a 0.5 mol / L supporting electrolyte sodium sulfate solution to a controlled concentration of 5 mmol / L. This solution was then exposed to nitrogen to remove oxygen while conducting three-electrode cyclic voltammetry. A glassy carbon electrode served as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum electrode as the counter electrode. The scan rate was 100 mV / s over a voltage range of 0-1 V.

[0079] analyze: Figure 3 The cyclic voltammetry curves of the potassium sulfonate TEMPO positive electrolyte and the viologen polymer negative electrolyte in Example 2 at a scan rate of 100 mv / s are shown. Figure 3 It can be seen that both materials have reversible redox and have a potential difference that matches the aqueous electrolyte, with a high potential difference of 1.1V. Therefore, the aqueous liquid flow battery we constructed has a high output voltage higher than 1V, which greatly improves the energy density and power density of the aqueous organic liquid flow battery.

[0080] Example 3: Construction of an aqueous organic flow battery based on a novel viologen polymer

[0081] The positive electrolyte tank was filled with 0.5 mol / L potassium sulfonate TEMPO, 0.1 mol / L supporting electrolyte sodium sulfate, and 50 ml of aqueous solution. The negative electrolyte tank was filled with 0.1 mol / L viologen polymer, 0.5 mol / L supporting electrolyte sodium sulfate, and 50 ml of aqueous solution. A cationic separator (Fumasep E-620, 2.5 x 2.5 cm) was used as the separator. The above electrolytes were introduced into a flow battery device as the positive and negative electrolytes. The battery was assembled in the following order: graphite current collector - carbon paper / graphite felt electrode - cation exchange membrane - carbon paper / graphite felt electrode - graphite current collector. A peristaltic pump was used to drive the liquid for charging and discharging.

[0082] During the test, the battery was first left to stand for 30 minutes, and then a constant current charge (current 50mA, voltage upper limit 1.6V) and constant current discharge (current 50mA, voltage lower limit 0.6V) cycle test was performed 50 times. The flow rate of the peristaltic pump was 50rpm, and the test was finally terminated. The charge and discharge cycle stability diagram of the aqueous flow battery at a current density of 50mA was obtained as shown in the figure below. Figure 4As shown, the charge and discharge platform curve of the aqueous liquid flow battery at a current density of 50mA is obtained as follows Figure 5 shown.

[0083] Combine Figure 4 、 Figure 5 It can be seen that the aqueous organic flow battery based on the viologen polymer and potassium sulfonate TEMPO of the present invention has charge and discharge cycle stability, a coulombic efficiency close to 100% and a stable output voltage of 1.1V.

[0084] Summarize:

[0085] The present invention prepares a new type of viologen polymer. The aqueous organic liquid flow battery constructed based on the above-mentioned new viologen polymer has the characteristics of low cost, high safety, stable charging and discharging; the polymer material has high solubility, controllable molecular weight, easy preparation, and excellent electrochemical performance, and is promising for large-scale production and commercialization.

[0086] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A viologen polymer, characterized in that The chemical structure is as follows: Wherein: n is 10 to 1000.

2. A method for preparing the viologen polymer according to claim 1, characterized in that: The following steps are involved: (1) 1-Methyl-[4,4'-bipyridyl]-1-iodide containing the negative electrode active molecule and 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione undergo a substitution reaction to generate the monomer HMPB; (2) The monomer HMPB was ring-opening polymerized by Grubbs' third-generation catalyst to obtain viologen polymer.

3. The method for preparing a viologen polymer according to claim 2, wherein: The following steps are involved: (1) Using acetonitrile as solvent, 1-methyl-[4,4'-bipyridyl]-1-iodide and 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione were subjected to a substitution reaction. After the reaction, a yellow solid polymer monomer HMPB was obtained by filtration. (2) The HMPB monomer is dissolved in a mixed solution of methanol and deionized water, the pH of the solution is adjusted to 2 with hydrochloric acid, sodium chloride and Grubbs third-generation catalyst are added, and the reaction is carried out under a nitrogen atmosphere; after the reaction is completed, a vinyl isobutyl ether polymerization terminator is added, the mixture is stirred at room temperature, distilled under reduced pressure, and precipitated in ether three times to obtain a viologen polymer.

4. The method for preparing a viologen polymer according to claim 2, wherein: In the step (1), the molar ratio of 1-methyl-[4,4'-bipyridyl]-1-iodide to 2-(3-bromopropyl)-3a,4,7,7a-tetrahydro-1H-4,7-methylisoindole-1,3(2H)-dione is 1:1.

2.

5. The method for preparing a viologen polymer according to claim 2, wherein: In the step (1), the substitution reaction is carried out under condensation reflux at 110° C. for 2 hours.

6. The method for preparing a viologen polymer according to claim 2, wherein: In the step (2), the molar ratio of the monomer HMPB to the Grubbs third-generation catalyst is 10 to 100 / 1.

7. The method for preparing a viologen polymer according to claim 2, wherein: In the step (2), the polymerization reaction is stirred at 40° C. for 24 hours.

8. Application of a viologen polymer as a negative active electrode material in an aqueous organic liquid flow battery.

9. The use of a viologen polymer as a negative active electrode material in an aqueous organic flow battery according to claim 8, characterized in that: The aqueous organic liquid flow battery system includes a positive electrode, a negative electrode, a diaphragm, and an electrolyte, wherein the electrolyte includes a positive electrode electrolyte and a negative electrode electrolyte, and is characterized in that the electrolyte in the positive electrode electrolyte is potassium sulfonate TEMPO, and the concentration of potassium sulfonate TEMPO is a solution ranging from 0.1 mol / L to its saturation concentration; the electrolyte in the negative electrode electrolyte is a viologen derivative, and the concentration of the viologen polymer is a solution ranging from 0.1 mol / L to its saturation concentration.

10. Use of a viologen polymer as a negative active electrode material in an aqueous organic liquid flow battery according to claim 9, characterized in that: The positive electrode electrolyte and the negative electrode electrolyte further include a supporting electrolyte, which includes one or more of sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, sodium nitrate, and sodium nitrate, and the molar concentration of the supporting electrolyte is 0.1-3 mol / L.

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