Alkali-soluble dihydroquinoline phenazine organic active substance, electrolyte containing the same and application of the electrolyte

Abstract

The invention discloses an alkali-soluble dihydroquinoline phenazine organic active substance, an electrolyte having the same and an application of the electrolyte. The alkali-soluble dihydroquinoline phenazine organic active substance has a molecular structure shown in formula (I), wherein R1, R2, R3, R4, R5, R6, R7 and R8 are independently selected from -H, -OH, -COOH, -SO3H, -Ar, -PO3H, -OC x H 2x COOH,‑OC y H 2y SO3H and ‑OC z H 2z PO3H, and contains at least one alkali-soluble group. This active material has the advantage of multi-electron transfer, and can transfer 4 equivalents of electrons cumulatively, and has the potential to build a high-energy density liquid flow battery.

Description

Technical Field

[0001] The invention relates to an alkali-soluble dihydroquinoline phenazine organic active substance, an electrolyte containing the same and application of the electrolyte, belonging to the technical field of electrochemical energy storage. Background Art

[0002] With the transformation of the global energy structure and the rapid development of renewable energy, the stability, reliability and efficiency of the power system are facing unprecedented challenges. Energy storage technology is a necessary support for addressing the bottlenecks of large-scale utilization such as intermittency and volatility of new energy. It is a key technology and infrastructure for building a new power system. It plays an irreplaceable role in improving the utilization rate of renewable energy, balancing power supply and demand, ensuring power quality, and improving the flexibility of the power system. Redox flow batteries store a large amount of energy in the electrolyte, have good scalability, variable modular design and reliable safety, and are an ideal solution for large-scale energy storage.

[0003] The electrolyte is the energy storage medium of the flow battery, and its stability has a great influence on the battery performance and cycle life. At the same time, the electrolyte is also the largest cost source of the flow battery, accounting for about 50%. Organic molecules have attracted much attention due to their abundant sources, low cost, environmental friendliness, batch synthesis, diverse structures, and adjustable physical and chemical properties and electrochemical properties. Compared with neutral and acidic flow batteries, alkaline organic flow batteries have more obvious advantages in open circuit voltage, energy density, stability and cycle life, material selection and cost, safety and environmental protection, as well as technical maturity and application prospects. Phenazine organics, as commonly used active substances in alkaline aqueous organic flow batteries, have a series of significant advantages, such as high electrochemical activity, good stability, environmental friendliness, high energy density, and easy synthesis and modification. However, phenazine organics usually do not have the ability to transfer multiple electrons (>2 electrons), and the potential for building high energy density flow batteries is insufficient. Summary of the invention

[0004] The purpose of the present invention is to provide an alkali-soluble dihydroquinoline phenazine organic active substance, an electrolyte having the same and the application of the electrolyte. The active substance has the advantage of multi-electron transfer, can transfer a total of 4 equivalents of electrons, and has the potential to construct a high-energy density liquid flow battery.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] An alkali-soluble dihydroquinoline phenazine organic active substance has the following molecular structure:

[0007] (I)

[0008] Wherein, R1, R2, R3, R4, R5, R6, R7, R8 are independently selected from -H, -OH, -COOH, -SO3H, -Ar, -PO3H, -OC x H 2x COOH, -OC y H 2y SO3H and -OC z H 2z PO3H, and contains at least one alkali-soluble group;

[0009] 1≤x≤24, 1≤y≤24, 1≤z≤24.

[0010] Preferably, R1, R3, R4, R5, R6, and R8 are -H, and R2 and R7 are -COOH or -SO3H or -PO3H.

[0011] Preferably, the preparation method of the active substance is: 2,5-dihydroxy-1,4-benzoquinone, the compound represented by formula (II) and glacial acetic acid are mixed and heated for reaction, and then cooled, separated, washed and dried to obtain the active substance;

[0012] (II);

[0013] In formula (II), R1, R2, R3, and R4 are independently selected from -H, -OH, -COOH, -SO3H, -Ar, -PO3H, -OC x H 2x COOH, -OC y H 2y SO3H and -OC z H 2z PO3H, and contains at least one alkali-soluble group; preferably -COOH or -SO3H; wherein 1≤x≤24, 1≤y≤24, 1≤z≤24.

[0014] Preferably, the molar ratio of 2,5-dihydroxy-1,4-benzoquinone, the compound represented by formula (II) and glacial acetic acid is 1:2-20:300-900.

[0015] Preferably, the compound represented by formula (II) is 3,4-diaminobenzoic acid or 3,4-diaminobenzenesulfonic acid or a mixture of the two.

[0016] Preferably, the heating reaction conditions are: 110-140° C., 12-48 h.

[0017] Preferably, the drying conditions are: under vacuum, 60-80° C., 12-48 h.

[0018] An alkaline aqueous organic liquid flow battery electrolyte comprises any of the above-mentioned alkaline-soluble dihydroquinoline phenazine organic active substances and an alkaline solution.

[0019] Preferably, in the electrolyte, the concentration of the alkaline-soluble dihydroquinoline phenazine organic active substance is 0.001-0.5M.

[0020] Use of any of the above-mentioned electrolytes in an asymmetric alkaline aqueous organic liquid flow battery and a symmetric alkaline aqueous organic liquid flow battery.

[0021] The beneficial effects of the present invention are:

[0022] Alkali-soluble dihydroquinoline phenazine organics have the advantage of multi-electron transfer, and can transfer 4 equivalents of electrons cumulatively. They have the potential to construct high-energy density flow batteries. Their synthesis method has the advantages of cheap raw materials, simple and green synthesis, etc. The alkaline-soluble dihydroquinoline phenazine organics have both oxidation centers and reduction centers, with a potential difference of nearly 0.8 V, and a ratio of oxidation electrons to reduction electrons of 1:1, which makes it possible for alkaline-soluble dihydroquinoline phenazine organics to be used as both positive and negative electrolyte active substances. The symmetric battery constructed by alkaline-soluble dihydroquinoline phenazine organics can transfer 2 equivalents of electrons. And because the positive and negative electrolyte active substances are the same substance, the cross-contamination between the positive and negative active substances can be greatly reduced, which makes it possible to use cheaper porous membranes instead of expensive ion exchange membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the cyclic voltammetry curve of DQPA electrolyte;

[0024] Figure 2 This is the charge and discharge curve of potassium ferrocyanide / potassium ferrocyanide||DQPA battery;

[0025] Figure 3 The structural changes of DQPA during the charge and discharge process in potassium ferrocyanide / potassium ferrocyanide||DQPA battery;

[0026] Figure 4 This is the rate performance diagram of potassium ferrocyanide / potassium ferrocyanide||DQPA battery;

[0027] Figure 5 This is the long cycle performance diagram of potassium ferrocyanide / potassium ferrocyanide||DQPA battery;

[0028] Figure 6 is the charge and discharge curve of DQPA||DQPA symmetric battery;

[0029] Figure 7 The structural changes of DQPA during the charge and discharge process in the DQPA||DQPA symmetric cell;

[0030] Figure 8 This is the long cycle performance diagram of DQPA||DQPA symmetric battery;

[0031] Fig. 9 The mass spectrum of the synthesized alkali-soluble dihydroquinoline phenazine organic compound (the left side is the test value, and the right side is the theoretical value);

[0032] Fig.10 The schematic diagram of the synthesis of alkali-soluble dihydroquinoline phenazine organic matter (active substance), wherein R is -COOH; the HOH in the product refers to H2O, and the reason for expressing it in this form is to explain the source of -OH in the generated water. DETAILED DESCRIPTION

[0033] The present application designs and synthesizes alkaline-soluble dihydroquinoline phenazine organic molecules (DQPA), which have the characteristics of four-electron step-by-step transfer and have doubled energy density compared to two-electron phenazine organics. The adjacent C=N and C-NH groups of DQPA exhibit two different chemical environments, resulting in both oxidation and reduction centers. In addition, due to the large LUMO energy gap between the oxidation state and the reduction state of DQPA, the two reactions have a considerable voltage difference, and a DQPA symmetric battery can be constructed to avoid cross-contamination of positive and negative active materials. The tested potassium ferrocyanide / potassium ferrocyanide||DQPA battery and DQPA symmetric battery can both operate stably.

[0034] Synthesis of alkali-soluble dihydroquinoline phenazine organic matter (active substance): Synthesis of dicarboxy dihydroquinoline phenazine by one-step method: 1 mol 2,5-dihydroxy-1,4-benzoquinone, 5 mol diaminobenzoic acid and 300 mol glacial acetic acid were added to a three-necked flask in sequence, and heated (140°C) to reflux overnight. After the reaction was completed and cooled to room temperature, the product was collected by vacuum filtration and washed with water and alcohol several times. Dry in a vacuum oven at 60°C overnight. The obtained product can be used without further purification (mass spectrum as shown in Fig. 9 The synthetic route is as follows:

[0035] .

[0036] The synthesis schematic diagram of the above dicarboxy dihydroquinoline phenazine is as follows Fig.10As shown, the process involves two condensation reactions. Since the solvents and reaction temperatures of the two condensation reactions are the same, there is no need to distribute the feed, and a one-step reaction can be selected. The use of excess diaminobenzoic acid (the ratio of the number of amino groups to the number of carbonyl groups in the reactants is 5:1) is to promote the reaction, because the condensation difficulty of amino groups with hydroxyl groups is greater than that of amino groups with carbonyl groups, and the excess amino compounds can be removed by subsequent water washing without affecting the purity of the product. The two products generated are isomers, and because of the same electrochemical properties, they can be used without purification and separation.

[0037] At the same time, since the heating temperature during the reaction needs to reach 140° C. (exceeding the boiling point of water), glacial acetic acid is used as a solvent to enable the condensation reaction to proceed successfully.

[0038] Preparation of alkaline-soluble dihydroquinoline phenazine organic electrolyte: The prepared dicarboxy dihydroquinoline phenazine is neutralized with an alkali according to the number of carboxyl groups, dissolved in a 1 M potassium hydroxide / sodium hydroxide solution, and prepared into a 0.002-0.1 M electrolyte.

[0039] Electrochemical performance test of alkaline-soluble dihydroquinoline phenazine organic electrolyte: The electrochemical performance test was carried out using an electrochemical workstation (Chenhua CHI660E) and a standard three-electrode device, in which a glassy carbon electrode was used as the working electrode, a platinum electrode was used as the counter electrode, and a saturated Ag / AgCl electrode was used as the reference electrode. Cyclic voltammetry was used to perform electrochemical tests on 0.002 M dicarboxy dihydroquinoline phenazine electrolyte, with a voltage range of -1.3 V to 0 V and a scan rate of 100 and 50 mV / s. Figure 1 It can be seen that DQPA has a set of reversible redox peaks near -1.0 V and -0.2 V, and the voltage difference is close to 0.8 V.

[0040] Potassium ferrocyanide / potassium ferrocyanide||DQPA alkaline aqueous organic flow battery test: The battery performance test was performed using the Xinwei constant current battery test system and a standard flow battery single cell module. A cation exchange membrane (including but not limited to perfluorosulfonic acid membrane and non-fluorinated membrane) was used as the diaphragm. The reaction area was based on the area of ​​the graphite felt electrode (4 cm 2 ). The volume of the negative electrode electrolyte was 8.0 mL, and the concentration of dicarboxydihydroquinolinephenazine was 0.1 molL -1 ; The volume of the positive electrode electrolyte is 32.0 mL, and the concentrations of potassium ferrocyanide and potassium ferrocyanide are 0.1 molL -1 The positive and negative electrolytes were pumped through a peristaltic pump (BT100-2J) at a rate of 100 mL min -1 The flow rate circulates between the battery and the tank.

[0041] 1. Battery rate performance test. Use the Xinwei constant current battery test system to test the single battery at 20-120 mAcm -2 Constant current charge and discharge rate test under current density. Figure 2 From the charge-discharge curves of the first and second cycles of DQPA, we can see that DQPA has two voltage platforms, and each platform transfers two electrons. At the same time, it can be proved that DQPA has oxidation centers and reduction centers, and they can be transformed into each other. The specific process is as follows Figure 3 shown.

[0042] 2. Battery constant current charge and discharge stability test. Use the Xinwei constant current battery test system to test the single battery at 80mAcm -2 Constant current charge and discharge test at current density.

[0043] Potassium ferrocyanide / potassium ferrocyanide||DQPA battery rate performance and potassium ferrocyanide / potassium ferrocyanide||DQPA battery long cycle performance are as follows Figure 4 , Figure 5 shown.

[0044] DQPA||DQPA Symmetric alkaline aqueous organic flow battery testing: Battery performance testing was performed using the Xinwei constant current battery testing system and a standard flow battery single cell module. A cation exchange membrane (including but not limited to perfluorosulfonic acid membrane and non-fluorinated membrane) was used as the diaphragm. The reaction area was based on the area of ​​the graphite felt electrode (4 cm 2 The active substances in the positive and negative electrolytes are both dicarboxy dihydroquinoline phenazine, the electrolyte volume is 8.0 mL, and the concentration is 0.1 molL -1 The positive and negative electrolytes were pumped through a peristaltic pump (BT100-2J) at a rate of 100 mL min -1 The flow rate circulates between the battery and the tank. The single cell is tested with a 20 mA cm flow rate using the Xinwei constant current battery test system. -2 Constant current charge and discharge test at current density.

[0045] The charge and discharge curves of the DQPA||DQPA symmetric battery, the structural changes of the DQPA in the DQPA||DQPA symmetric battery during the charge and discharge process, and the long cycle performance of the DQPA||DQPA symmetric battery are shown in Figure 2. Figure 6 , Figure 7 , Figure 8 shown.

[0046] In the potassium ferrocyanide / potassium ferrocyanide||DQPA alkaline aqueous organic liquid flow battery test and the DQPA||DQPA symmetric alkaline aqueous organic liquid flow battery test, dicarboxy dihydroquinoline phenazine can be used as both the negative electrode electrolyte active substance and the positive and negative electrode electrolyte active substance at the same time. The reason is that the alkali-soluble dihydroquinoline phenazine organic matter has both oxidation center and reduction center, and the ratio of oxidation electron number to reduction electron number is 1:1. Therefore, it can provide a basis for the alkali-soluble dihydroquinoline phenazine organic matter to be used as both the positive electrode electrolyte active substance and the negative electrode electrolyte active substance.

[0047] The above is only a preferred implementation of the patent of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the patent of the present invention. These improvements and modifications should also be regarded as the scope of protection of the patent of the present invention.

Claims

1. A positive and negative electrolyte for an alkaline aqueous organic flow battery, characterized in that: The electrolyte includes an alkali-soluble dihydroquinoline phenazine organic active substance and an alkali solution; wherein the alkali-soluble dihydroquinoline phenazine organic active substance has the following molecular structure formula: (I)， R1, R2, R3, R4, R5, R6, R7, and R8 are independently selected from -H, -COOH, and -SO3H, and contain at least one alkali-soluble group.

2. The positive and negative electrolytes for alkaline aqueous organic flow batteries according to claim 1, characterized in that: The preparation method of the alkaline-soluble dihydroquinoline phenazine active substance is as follows: 2,5-dihydroxy-1,4-benzoquinone, the compound represented by formula (II) and glacial acetic acid are mixed and heated for reaction, and then cooled, separated, washed and dried; (II); In formula (II), R1, R2, R3, and R4 are independently selected from -H, -COOH, and -SO3H, and contain at least one -COOH or -SO3H; 2,5-dihydroxy-1,4-benzoquinone, the molar ratio of the compound represented by formula (II) to glacial acetic acid is 1:2-20:300-900; The conditions for the heating reaction are: 110-140°C, 12-48h.

3. The positive and negative electrolytes for alkaline aqueous organic flow batteries according to claim 1, characterized in that: In the formula (I), R1, R2, R4, R5, and R8 are -H, R3 is -COOH, and R6 and R7 are -H or -COOH but not -H at the same time.

4. The positive and negative electrolytes for alkaline aqueous organic flow batteries according to claim 2, characterized in that: The compound represented by formula (II) is 3,4-diaminobenzoic acid.

5. The positive and negative electrolytes for alkaline aqueous organic flow batteries according to claim 1, characterized in that: In the electrolyte, the concentration of the alkaline-soluble dihydroquinoline phenazine organic active substance is 0.001-0.5M.

6. Use of the electrolyte according to claim 1 in an alkaline aqueous organic liquid flow battery.

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