Oxadiazole viologen compounds, their preparation methods and their applications in flow batteries

Abstract

This invention proposes an oxadiazole viologen compound, its preparation method, and its application in flow batteries, belonging to the field of electrochemical battery energy storage technology. The oxadiazole viologen compound of this invention can be used as a negative electrode material in organic flow batteries. It can accept two electrons, significantly improving the charge-discharge capacity and cycle stability of flow batteries, reducing the permeability of both positive and negative electrodes, and broadening the selection range of negative electrode active materials for neutral organic flow batteries. Furthermore, the preparation method of the aforementioned two-electron oxadiazole viologen compound provided by this invention is simple, time-efficient, and easy to operate.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical battery energy storage technology, and particularly relates to an oxadiazole viologen compound, its preparation method, and its application in flow batteries. Background Technology

[0002] Due to severe environmental burdens and the overuse of fossil fuels, renewable energy is receiving increasing attention. The increasingly severe ecological and environmental protection situation has greatly accelerated the shift from fossil fuels to new energy sources, making the arrival of the new energy era inevitable. Wind and solar power generation are developing rapidly. However, these two power generation methods are significantly limited by natural factors, exhibiting intermittency and randomness. Therefore, we need to seek better energy storage methods. The development of energy storage technology is driving the development and popularization of renewable energy. Energy storage technology is key to transforming randomly fluctuating energy into energy-friendly energy, and its technological advancements are of great significance in promoting the energy revolution.

[0003] Flow batteries (AORFB), as one of the most promising large-scale energy storage technologies, possess advantages such as high safety, high efficiency, comprehensive tunability of organic molecules, low cost, and long cycle life. In recent years, extensive research has been conducted on the molecular engineering of AORFB active materials with different structures, achieving significant progress in their application across various battery systems. Existing technologies have revealed that AORFB active materials with structures such as quinone, ferrocene, TEMPO (tetramethylpiperidine), viologen, phenazine, and phenothiazine possess excellent performance and a large application market. Among these, quinone, viologen, phenazine, and phenothiazine are mainly used as anode materials, while ferrocene and TEMPO are mainly used as cathode materials. Most organic materials achieve energy transfer through single-electron and double-electron discharge. However, current organic flow batteries still have many shortcomings, such as degradation, capacity issues, and electrolyte cross-contamination. Based on this, this invention proposes oxadiazole viologen compounds that can be applied to flow batteries. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes an oxadiazole viologen compound, its preparation method, and its application in flow batteries. The prepared oxadiazole viologen compound can be used as a negative electrode material in organic flow batteries. It can accept two electrons, significantly improving the charge-discharge capacity and cycle stability of flow batteries, and reducing the permeability of both positive and negative electrodes.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One of the technical solutions of the present invention:

[0007] An oxadiazole viologen compound, wherein the structural formula of the oxadiazole viologen compound is as follows:

[0008]

[0009] Wherein, R is selected from CH2CH2CH2N + (CH3)3、CH2CH2CH2SO3 - Or CH2CH2CH2CH2SO3 - .

[0010] The second technical solution of the present invention:

[0011] A method for preparing the aforementioned oxadiazole viologen compound includes the following steps: adding isoniazid and isonicotinic acid to a solvent, mixing and stirring, heating under reflux for 5 hours to obtain a mixture, neutralizing the mixture with an aqueous sodium hydroxide solution to neutral, cooling, filtering, washing, and drying to obtain a two-electron oxadiazole viologen (2,5-bis(4-pyridyl)-1,3,4-oxadiazole), the reaction equation of which is as follows:

[0012]

[0013] Subsequently, the two-electron oxadiazole viologen was mixed and stirred with 3-bromopropyltrimethylammonium bromide, 1,3-propanesulfonate lactone or 1,4-butanesulfonate lactone in an organic solvent, heated under reflux for 24 h, cooled, filtered, washed and dried to obtain the oxadiazole viologen compound.

[0014] When the two-electron oxadiazole viologen reacts with 3-bromopropyltrimethylammonium bromide, the reaction equation is:

[0015]

[0016] When the two-electron oxadiazole viologen reacts with 1,3-propanesulfonate lactone, the reaction equation is as follows:

[0017]

[0018] When the two-electron oxadiazole viologen reacts with 1,4-butyryl lactone, the reaction equation is as follows:

[0019]

[0020] Furthermore, the molar ratio of isoniazid to isonicotinic acid is 1:2.

[0021] Furthermore, the molar ratio of the two-electron oxadiazole viologen to 3-bromopropyltrimethylammonium bromide, 1,3-propanesulfonate lactone, or 1,4-butanesulfonate lactone is 1:2.5, that is, the molar ratio of two-electron oxadiazole viologen to 3-bromopropyltrimethylammonium bromide, two-electron oxadiazole viologen to 1,3-propanesulfonate lactone, or two-electron oxadiazole viologen to 1,4-butanesulfonate lactone is 1:2.5.

[0022] Furthermore, the solvent for mixing isoniazid and isonicotinic acid is phosphorus oxychloride, and the organic solvent for mixing the dielectron oxadiazole viologen with 3-bromopropyltrimethylammonium bromide, 1,3-propanesulfonate lactone or 1,4-butanesulfonate lactone is dimethyl sulfoxide (DMSO) or dimethylformamide (DMF).

[0023] Furthermore, the temperature of the heating reflux reaction is 120°C.

[0024] The third technical solution of the present invention:

[0025] The application of the oxadiazole viologen compounds in neutral organic flow batteries, wherein the oxadiazole viologen compounds are used as negative electrode active materials in neutral organic flow batteries.

[0026] The fourth technical solution of the present invention:

[0027] A neutral organic flow battery, wherein the negative electrode active material of the neutral organic flow battery is the aforementioned oxadiazole viologen compound, the positive electrode material is ferrocene or potassium ferricyanide, and the electrolyte is sodium chloride, potassium chloride, or sodium sulfate.

[0028] The oxadiazole viologen compounds of this invention possess electron-donating properties, which reduce the redox potential of the battery, increase the voltage energy density, and significantly broaden the operating voltage range of the flow battery. The reversible chemical equations for the gain and loss of two electrons by the oxadiazole viologen compounds are as follows:

[0029]

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] (1) This invention provides a two-electron oxadiazole viologen compound, which is prepared by adding an oxadiazole to the middle of 4,4-bipyridine, allowing it to accept two electrons. Furthermore, by grafting a quaternary ammonium salt, 1,3-propanesulfonate lactone, or 1,4-butanesulfonate lactone onto the two-electron oxadiazole-bridged viologen structure, the water solubility of the resulting two-electron oxadiazole-bridged viologen derivative is improved, further enhancing the energy density of the flow battery. Using it as the negative electrode active material in a neutral organic flow battery, compared to 4,4-bipyridine (viologen molecule), it can improve the battery's cycle stability and energy density, enhance cycle stability, and reduce the battery's redox potential. This not only significantly broadens the operating voltage range of the flow battery but also increases the voltage energy density. Using the two-electron oxadiazole viologen compound of this invention as the negative electrode active material in an organic flow battery, and assembling it with a positive electrode active material to form an organic flow battery, broadens the selection range of negative electrode active materials for organic flow batteries, and has broad application prospects in large-scale renewable energy storage.

[0032] (2) The preparation method of the above-mentioned two-electron oxadiazole viologen compounds provided by the present invention is simple, time-saving and easy to operate. Attached Figure Description

[0033] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0034] Figure 1 The cyclic voltammetry curve of the oxadiazole viologen compound prepared in Example 2 of this invention as a negative electrode active material is shown.

[0035] Figure 2 This is a graph showing the relationship between peak current and the square root of scan rate for the oxadiazole viologen compound prepared in Example 2 of this invention as the negative electrode active material.

[0036] Figure 3 This is a battery window test diagram of an organic flow battery composed of oxadiazole viologen compounds prepared in Example 2 of the present invention and potassium ferricyanide;

[0037] Figure 4 This is a partial charge-discharge curve of an organic flow battery composed of oxadiazole viologen compounds prepared in Example 2 of the present invention and potassium ferricyanide.

[0038] Figure 5 The coulombic efficiency diagram shows the organic flow battery composed of oxadiazole viologen compounds prepared in Example 2 of this invention and potassium ferricyanide. Detailed Implementation

[0039] 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.

[0040] 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. Every smaller range between any stated value or intermediate value within a stated range, and 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.

[0041] 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 have been 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 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.

[0042] 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 readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0043] 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.

[0044] All raw materials used in the embodiments of this invention were obtained through commercial purchase.

[0045] In this embodiment of the invention, room temperature refers to 25±2℃.

[0046] The technical solution of the present invention will be further illustrated by the following embodiments.

[0047] Example 1

[0048] Preparation of two-electron oxadiazole viologen:

[0049]

[0050] 6.86 g of isoniazid and 12.3 g of isonicotinic acid (molar ratio of isoniazid to isonicotinic acid 1:2) were added to a 250 mL round-bottom flask. Then, 25 mL of phosphorus oxychloride (solvent) was added and stirred. The mixture was heated under reflux at 120 °C for 5 h to obtain a mixture. The mixture was neutralized to neutral with sodium hydroxide aqueous solution and then cooled to 0 °C with ice water. The precipitate was filtered, washed with water, recrystallized with methanol, and dried to obtain white crystals of 2,5-bis(4-pyridyl)-1,3,4-oxadiazole, which is the dielectron oxadiazole viologen. 1 H NMR (400MHz, DMSO-d6, ppm): δ8.89(d,4H), 8.09(d,4H).

[0051] Example 2: Preparation of Oxadiazole Viologen Compound-1

[0052] Using 3-bromopropyltrimethylammonium bromide and the two-electron oxadiazole viologen prepared in Example 1 as raw materials, two-electron oxadiazole viologen compound-1 was prepared. The reaction equation is as follows:

[0053]

[0054] 0.8 g of the two-electron oxadiazole viologen prepared in Example 1, 2.30 g of 3-bromopropyltrimethylammonium bromide, and 20 mL of DMF were added to a 100 mL round-bottom flask and stirred (the molar ratio of oxadiazole viologen to 3-bromopropyltrimethylammonium bromide was 1:2.5). The mixture was heated under reflux at 120 °C for 24 h, cooled to room temperature, filtered, washed with DMF, and dried to obtain the product, which is the two-electron oxadiazole viologen compound-1. 1 H NMR (400MHz, D2O, ppm): δ9.25(d,4H),8.85(d,4H),4.91-4.81(m,4H),3.63-3.53(m,4H),3.17(s,18H),2.74-2.61(m,4H). 13 C NMR (101MHz, D2O, ppm): δ162.94, 146.35, 137.92, 126.07, 62.41, 58.67, 53.31, 24.68.

[0055] Example 3: Preparation of Oxadiazole Viologen Compound-2

[0056] Using 1,3-propanesulfonate lactone and the dielectron oxadiazole viologen prepared in Example 1 as raw materials, dielectron oxadiazole viologen compound-2 was prepared. The reaction equation is as follows:

[0057]

[0058] 0.8 g of the dielectron oxadiazole viologen prepared in Example 1, 1.1 g of 1,3-propanesulfonate lactone, and 20 mL of LDMF were added to a 100 mL round-bottom flask and stirred (the molar ratio of oxadiazole viologen to 1,3-propanesulfonate lactone was 1:2.5). The mixture was heated under reflux at 120 °C for 24 h, cooled to room temperature, filtered, washed with DMSO, and dried to obtain the product, which is the dielectron oxadiazole viologen compound-2. 1 H NMR (400MHz, D2O, ppm): δ9.18(d,4H),8.77(d,4H),4.86(t,4H),2.98(t,4H),2.49(p,4H). 13 C NMR (101MHz, D2O): δ162.94,146.32,137.52,125.74,60.62,47.02,26.17

[0059] Example 4: Preparation of Oxadiazole Viologen Compound-3

[0060] Using 1,4-butyryl lactone and the two-electron oxadiazole viologen prepared in Example 1 as raw materials, two-electron oxadiazole viologen compound-3 was prepared. The reaction equation is as follows:

[0061]

[0062] 0.8 g of the two-electron oxadiazole-bridged viologen prepared in Example 1, 1.23 g of 1,4-butanesulfonate lactone, and 20 mL of LDMF were added to a 100 mL round-bottom flask and stirred (the molar ratio of oxadiazole viologen to 1,4-butanesulfonate lactone was 1:2.5). The mixture was heated under reflux at 120 °C for 24 h, cooled to room temperature, filtered, washed with DMSO, and dried to obtain the product, which is the two-electron oxadiazole viologen compound-3. 1 H NMR (400MHz, D2O, ppm): δ9.16(d,4H),8.76(d,4H),4.75(t,4H),2.98-2.89(m,4H),2.20(p,4H),1.79(p,4H). 13 C NMR (101MHz, D2O): δ162.94, 146.11, 137.36, 125.67, 61.92, 49.91, 29.36, 20.89.

[0063] Example 5 Cyclic Voltmeter Curve Test

[0064] Using sodium chloride aqueous solutions with concentrations of 0.1M, 0.2M, 0.3M, 0.4M, and 0.5M as electrolytes, the two-electron oxadiazole viologen compound-1 prepared in Example 2 was sequentially added to them, with its concentration controlled at 0.02 mol / L. Ferrocene or potassium ferricyanide was used as the positive electrode material to form an organic flow battery. A three-electrode system was employed: a 3 mm diameter glassy carbon electrode as the working electrode, a platinum sheet electrode as the auxiliary electrode, and a saturated silver chloride electrode (with a reference electrode potential of 0.2 V) as the reference electrode. The scan rate was 2 mV / s. The cyclic voltammetry curve of the two-electron oxadiazole viologen compound-1 prepared in Example 2 of this invention as the negative electrode active material is shown in [Figure number missing]. Figure 1 ,Depend on Figure 1It can be seen that the flow battery exhibits two pairs of reversible redox peaks in sodium chloride aqueous solutions of different concentrations, and the reproducibility is good under different electrolyte concentrations. This indicates that the two-electron oxadiazole viologen compound-1 prepared in Example 2 of this invention has good electrochemical reversibility. When silver / silver chloride is used as the reference electrode, it reduces the redox potential of the battery (-0.608V vs. silver / silver chloride and -0.78V vs. silver / silver chloride), increases the voltage energy density, and significantly broadens the operating voltage range of the flow battery.

[0065] Example 6: Test of the relationship between peak current and the square root of scan rate

[0066] A 0.5 M sodium chloride aqueous solution was used as the electrolyte. The two-electron oxadiazole viologen compound-1 prepared in Example 2 was added as the negative electrode material, with its concentration controlled at 0.01 mol / L. The positive electrode material was ferrocene or potassium ferricyanide, forming a neutral organic flow battery. The peak current versus the square root of the scan rate for this neutral organic flow battery is shown in the figure. Figure 2 ,Depend on Figure 2 It can be seen that the redox peak potential is related to the square root of the scan rate (V). 1 / 2 Linear fitting was performed, and the slopes were on the same order of magnitude, proving that the two-electron oxadiazole viologen compounds of the present invention have reversible electrochemical properties, and that the diffusion coefficients of their oxidation and reduction reactions are approximately the same, on the same order of magnitude.

[0067] Example 7 Charge and Discharge Test

[0068] The two-electron oxadiazole viologen compound-1 prepared in Example 2 was added to a 0.5M sodium chloride aqueous solution as the negative electrode electrolyte, with its concentration controlled at 0.05 mol / L. Potassium ferricyanide was added to the sodium chloride aqueous solution as the positive electrode electrolyte, with its concentration controlled at 0.05 mol / L. The above positive and negative electrode electrolytes were loaded into positive and negative electrode storage tanks, respectively. A Nafion 212 membrane was used as the separator, and graphite felt was used as the working electrode. The batteries were assembled into a flow battery using clamps. A constant current of 10 mA and a voltage of 1.35 V were set for charge-discharge testing.

[0069] Figure 3 This is a battery window test diagram of an organic flow battery composed of a two-electron oxadiazole viologen compound-1 prepared in Example 2 of this invention and potassium ferricyanide. Figure 3 It can be seen that the open-circuit voltages of the positive and negative electrodes are 0.86758V and 1.04221V, respectively, which are at a good level for a neutral flow battery, and the electronic discharge can be controlled by controlling the voltage.

[0070] Figure 4This is a partial charge-discharge curve of the organic flow battery composed of the two-electron oxadiazole viologen compound-1 prepared in Example 2 of this invention and potassium ferricyanide. Figure 4 It can be seen that the charge and discharge of this flow battery is relatively regular, with no side reactions occurring and a clear charge and discharge plateau, which is consistent with the characteristics of a battery.

[0071] Figure 5 The coulombic efficiency diagram of the organic flow battery composed of the two-electron oxadiazole viologen compound-1 prepared in Example 2 of this invention and potassium ferricyanide is shown in the figure. Figure 5 It can be seen that the flow battery obtained by the present invention maintains a stable coulombic efficiency of up to 93% after 28 cycles, and remains stable throughout the cycle, indicating good battery performance.

[0072] The compounds prepared in Examples 3 and 4 also have the same electrochemical properties because an oxadiazole is added to the middle of 4,4-bipyridine, which can accept two electrons.

[0073] In summary, this invention provides a two-electron oxadiazole viologen compound, which incorporates an oxadiazole molecule at the center of a 4,4-bipyridine, allowing it to accept two electrons and significantly increasing the energy density of the flow battery compared to a single viologen molecule. Furthermore, the increased molecular size of this compound compared to a single viologen molecule reduces permeability between the positive and negative electrodes, preventing cross-contamination of the electrolytes and increasing battery life. The compound exhibits strong redox peak reproducibility, improving cycle stability. The introduction of quaternary ammonium salt and sulfonate structures into the two-electron oxadiazole viologen compound of this invention lowers the redox potential of the battery, increases the voltage energy density, and significantly widens the operating voltage range of the flow battery. Its derivatives are readily soluble in aqueous solutions, further enhancing the energy density of the flow battery, making it a preferred material for flow batteries. As a negative electrode active material in organic flow batteries, the two-electron oxadiazole viologen compound of this invention, when assembled with positive electrode active materials to form organic flow batteries, has broad application prospects in large-scale renewable energy storage and grid peak shaving.

[0074] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An oxadiazole viologen compound, characterized by, The structural formula of the oxadiazole viologen compound is: 。 2. A method of preparing the oxadiazole purpurin compound according to claim 1, characterized by, Includes the following steps: Isoniazid and isonicotinic acid were added to a solvent, mixed and stirred, and heated under reflux to obtain a mixture. The mixture was neutralized, cooled, filtered, washed, and dried to obtain a two-electron oxadiazole viologen. The two-electron oxadiazole viologen was mixed with 3-bromopropyltrimethylammonium bromide in an organic solvent, stirred and heated under reflux to obtain the oxadiazole viologen compound.

3. The method for preparing oxadiazole viologen compounds according to claim 2, characterized in that, The molar ratio of isoniazid to isonicotinic acid is 1:

2.

4. The method for preparing oxadiazole viologen compounds according to claim 2, characterized in that, The molar ratio of the two-electron oxadiazole viologen to 3-bromopropyltrimethylammonium bromide is 1:2.

5.

5. The method for preparing oxadiazole viologen compounds according to claim 2, characterized in that, The solvent for mixing isoniazid and isonicotinic acid is phosphorus oxychloride, and the organic solvent for mixing the dielectron oxadiazole viologen and 3-bromopropyltrimethylammonium bromide is dimethylformamide.

6. The method for preparing oxadiazole viologen compounds according to claim 2, characterized in that, The temperature of the heating reflux reaction was 120°C.

7. The application of the oxadiazole viologen compound of claim 1 in a neutral organic flow battery, characterized in that, The oxadiazole viologen compounds are used as negative electrode active materials in neutral organic flow batteries.

8. A neutral organic flow battery, characterized in that, The negative electrode active material of the neutral organic flow battery is the oxadiazole viologen compound as described in claim 1, the positive electrode material is ferrocene or potassium ferricyanide, and the electrolyte is sodium chloride, potassium chloride, or sodium sulfate.

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