Aqueous redox flow battery

Abstract

The invention provides an aqueous redox flow battery, and belongs to the technical field of energy storage systems. Comprising a positive electrode electrolyte, a diaphragm and a negative electrode electrolyte, the positive electrode electrolyte adopts HOTEMPO-SO3Na as an active substance, and the negative electrode electrolyte adopts (3-chloro-2-hydroxypropyl)-trimethyl ammonium chloride-4, 4 '-bipyridine as an active substance. Through cooperation of the positive electrode electrolyte and the negative electrode electrolyte, the HOTEMPO-SO3Na and (3-chloro-2-hydroxypropyl)-trimethyl ammonium chloride-4, 4 '-diketone with excellent oxidation-reduction performance and stability performance are combined, so that the lithium ion battery electrolyte is prepared from HOTEMPO-SO3Na and (3-chloro-2-hydroxypropyl)-trimethyl ammonium chloride-4, 4'-diketone. In the aspect of electrochemical performance, the redox flow battery is endowed with excellent redox performance and stable performance, the energy density of the battery is effectively improved, the cycle life of the battery is effectively prolonged, the active substance synthesis process of the positive electrolyte and the negative electrolyte is short, the synthesis method is simple, and the cost is low. And the production cost and the maintenance cost of the flow battery are effectively reduced.

Description

Technical Field

[0001] This application relates to an aqueous redox flow battery, belonging to the field of energy storage system technology. Background Technology

[0002] Flow batteries, as an emerging electrochemical energy storage system, mainly consist of a stack unit, electrolyte, electrolyte storage and supply unit, and external control unit. Their core working principle is as follows: the separate positive and negative electrode electrolytes circulate through the electrolyte storage and supply unit, while the dissolved active materials in the electrolyte undergo reversible redox reactions within the battery's stack unit, ultimately achieving the interconversion of electrical energy and chemical energy. This structure and working principle also allow for relatively independent design of the output power and capacity of flow batteries.

[0003] However, traditional flow batteries have many shortcomings in electrolyte composition and electrode material development, which greatly limit the performance optimization and application expansion of flow batteries. Summary of the Invention

[0004] In view of this, this application provides a low-cost, high-performance aqueous redox flow battery.

[0005] Specifically, this application is implemented through the following scheme: An aqueous redox flow battery includes a positive electrode electrolyte, a separator, a negative electrode electrolyte, and a supporting electrolyte. The positive electrode electrolyte uses HOTEMPO-SO3Na as the active material, the negative electrode electrolyte uses (3-chloro-2-hydroxypropyl)-trimethylammonium chloride-4,4'-pyridine as the active material, and the supporting electrolyte is a 2 M potassium chloride solution.

[0006] Furthermore, as a preferred option: The active material of the positive electrode electrolyte is prepared using the following steps: Step 1: 4-Epoxy-2,2',6,6'-Tetramethylpiperidine was added to an aqueous solution of sodium bisulfite. After stirring and reacting, the precipitate was collected by filtration and dried to obtain (4-hydroxy-2,2',6,6'-tetramethylpiperidine)-4-methanesulfonate. Step 2: Dissolve (4-hydroxy-2,2',6,6'-tetramethylpiperidine)-4-methanesulfonate in water, then add sodium bicarbonate and sodium tungstate. Add hydrogen peroxide in batches to the resulting aqueous solution, stir overnight, and separate to obtain (4-hydroxy-2,2',6,6'-tetramethylpiperidine-1-oxygen radical)-4-methanesulfonate, denoted as HOTEMPO-SO3Na.

[0007] The equivalent ratio of (4-hydroxy-2,2',6,6'-tetramethylpiperidine)-4-methanesulfonate, sodium bicarbonate and sodium tungstate is 1:0.5:0.01, and the equivalent ratio of hydrogen peroxide to aqueous solution is 1:2.

[0008] In step one, The 4-epoxy-2,2',6,6'-tetramethylpiperidine was added to the sodium bisulfite aqueous solution at an equivalent ratio of 1:1.2.

[0009] The stirring reaction refers to a stirring reaction at 80°C for 6 hours.

[0010] In step two, The equivalent ratio of (4-hydroxy-2,2',6,6'-tetramethylpiperidine)-4-methanesulfonate, sodium bicarbonate, and sodium tungstate is 1:0.5:0.01, and the equivalent ratio of hydrogen peroxide to aqueous solution is 1:2.

[0011] The overnight stirring was carried out at 40°C.

[0012] The active material of the above negative electrode electrolyte is prepared by the following method: 4,4'-bipyridine and (3-chloro-2-hydroxypropyl)-trimethylammonium chloride are added to a reaction vessel and reacted at 120°C for 24 h. After cooling overnight, ethanol and acetone are added to the reaction product sequentially, and the mixture is collected by filtration to obtain (3-chloro-2-hydroxypropyl)-trimethylammonium chloride-4,4'-bipyridine, denoted as Dex-vi. More preferably: The equivalent ratio of 4,4'-bipyridine to 3-chloro-2-hydroxypropyltrimethylammonium chloride is 1:3.

[0013] The volume ratio of the reaction product, ethanol, and acetone is 1:9:10.

[0014] The concentration of active material in the positive electrode electrolyte is 0.1~0.2 mol / L, with 0.1 mol / L being preferred.

[0015] The concentration of active material in the negative electrode electrolyte is 0.05~0.1 mol / L, with 0.05 mol / L being preferred.

[0016] The assembly process of the above-mentioned aqueous redox flow battery is as follows: HOTEMPO-SO3Na is dissolved in an aqueous potassium chloride solution to obtain the positive electrode electrolyte; (3-chloro-2-hydroxypropyl)-trimethylammonium chloride-4,4'-pyridine is dissolved in an aqueous potassium chloride solution to obtain the negative electrode electrolyte; the positive electrode electrolyte, negative electrode electrolyte, and stack unit are assembled sequentially to obtain the flow battery. More preferably, the concentration of the potassium chloride aqueous solution is 2~4 mol / L.

[0017] The battery stack mainly consists of plates, current collectors, and a separator, which is an anion exchange membrane, such as the Nature separator. This separator prevents direct contact between the positive and negative electrolytes while allowing the free movement of electrolyte ions to ensure charge balance between the two electrolytes.

[0018] This application utilizes the synergistic effect of the positive and negative electrolytes to enable HOTEMPO-SO3Na, which exhibits excellent redox performance and stability, to undergo a reversible redox reaction with (3-chloro-2-hydroxypropyl)-trimethylammonium chloride-4,4'-pyridine. In terms of electrochemical performance, this endows the flow battery with excellent redox performance and stability, effectively improving the battery's energy density and cycle life. The synthesis process of the active materials for both the positive and negative electrolytes is short and the synthesis method is simple, effectively reducing the production and maintenance costs of the flow battery. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The electrochemical properties of 5 mM HOTEMPO-SO3Na in 2 M potassium chloride aqueous solution were measured by cyclic voltammetry (CV). Part (a) of the figure is the current-voltage curve at different scan rates, and part (b) is the relationship between the oxidation peak current and the reduction peak current and the square root of the scan rate.

[0021] Figure 2 Electrochemical properties of 5 mM HOTEMPO-SO3Na in 2 M potassium chloride aqueous solution were obtained by electrochemical impedance spectroscopy (EIS).

[0022] Figure 3 The electrochemical properties of 5 mM HOTEMPO-SO3Na in 2 M potassium chloride aqueous solution were measured by rotating disk electrode-linear scanning voltammetry (RDE-LSV). Part (a) of the figure is the current-voltage curve at different scan rates, part (b) is the Levich curve of limiting current versus the square root of angular velocity, part (c) is the relationship between the reciprocal of limiting current and the reciprocal of the square root of angular velocity at different overpotentials, and part (d) is the Tafel curve obtained by the logarithm of overpotential and kinetic current value.

[0023] Figure 4 Image showing the redox potential difference between HOTEMPO-SO3Na and Dex-vi in ​​this application.

[0024] Figure 5 Images showing the rate performance of the flow battery of this application at different current densities.

[0025] Figure 6 The images show the charge-discharge curves of the flow battery of this application at different current densities.

[0026] Figure 7 25mA / cm 2 The image shows the long-cycle performance at current density. Part (a) of the image shows the long-cycle performance of the flow battery of this application, and part (b) shows the charge-discharge curves at different numbers of cycles.

[0027] Figure 8 Images showing the power density of the flow battery under different states of charge in this application.

[0028] Figure 9 For Comparative Example 1, the positive electrode electrolyte Bn is at 50 mA / cm 2 The following are the electrical performance diagrams. Part (a) of the diagram is the cycle stability performance diagram, and part (b) is the charge-discharge curve.

[0029] Figure 10 For Comparative Example 2, the positive electrode electrolyte 4-hydroxy-Tempo is at 50 mA / cm 2 The following are the electrical performance diagrams. Part (a) of the diagram is the cycle stability performance diagram, and part (b) is the charge-discharge curve. Detailed Implementation

[0030] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit the technical solutions of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application.

[0031] The batteries in the following embodiments and comparative examples need to be operated in a glove box, specifically an Etex single-sided workstation glove box, model Lab2000.

[0032] Example 1

[0033] This embodiment provides an aqueous redox flow battery, including a positive electrode electrolyte, a separator, and a negative electrode electrolyte. The positive electrode electrolyte uses HOTEMPO-SO3Na as the active material, and the negative electrode electrolyte uses (3-chloro-2-hydroxypropyl)-trimethylammonium chloride-4,4'-pyridine as the active material.

[0034] The assembly process of the above-mentioned aqueous redox flow battery is as follows: 1) Preparation of positive electrode electrolyte: 4-epoxy-2,2,6,6-tetramethylpiperidine was mixed with sodium bisulfite and stirred at 60°C for 6 hours to obtain (4-hydroxy-2,2',6,6'-tetramethylpiperidine)-4-methanesulfonate; (4-hydroxy-2,2',6,6'-tetramethylpiperidine)-4-methanesulfonate was mixed with sodium bicarbonate and sodium tungstate and stirred at 40°C overnight to obtain HOTEMPO-SO3Na.

[0035] HOTEMPO-SO3Na was added to 7 mL of 2M potassium chloride aqueous solution to obtain a positive electrode electrolyte with a HOTEMPO-SO3Na concentration of 0.1M.

[0036] 2) Preparation of negative electrode electrolyte: 4,4'-bipyridine and (3-chloro-2-hydroxypropyl)-trimethylammonium chloride were added to a reaction vessel and reacted at 120°C for 24 hours. After the reaction was completed, ethanol and acetone were added, and finally (3-chloro-2-hydroxypropyl)-trimethylammonium chloride-4,4'-bipyridine (Dex-vi) was obtained by filtration.

[0037] Add Dex-vi to 14 mL of 2M potassium chloride aqueous solution to obtain a negative electrode electrolyte with a Dex-vi concentration of 0.05M.

[0038] 3) Assemble the battery: Assemble the positive electrode electrolyte, negative electrode electrolyte and battery stack in sequence to obtain an aqueous redox flow battery.

[0039] The concentration of HOTEMPO-SO3Na used in the relevant electrochemical tests was 0.005 mol / L (i.e., 5 mM).

[0040] CV curve data were recorded using a ZIVE SP1 electrochemical workstation. Tests were conducted using a glassy carbon working electrode, an Ag / AgCl reference electrode, and a platinum wire electrode. The test results are as follows: Figure 1 As shown, HOTMEPO-SO3Na exhibits excellent reversible redox properties in aqueous systems. The redox potential of HOTMEPO-SO3Na does not change significantly with the rate of voltage change (see...). Figure 1 (part (a) in the text). Figure 1 Part (b) of the calculation yields an average median voltage of 566 mV for HOTMEPO-SO3Na and a potential difference of 67 mV. pc / i pa It has a redox potential of 1.07, exhibiting high redox potential and excellent electrochemical reversibility.

[0041] EIS curve data were recorded using a ZIVE SP1 electrochemical workstation. Tests were conducted using a glassy carbon working electrode, an Ag / AgCl reference electrode, and a platinum wire electrode. The test results are as follows: Figure 2 As shown: HOTMEPO-SO3Na exhibits low impedance in the aqueous system, and the electron transfer rate constant k 0 8.70×10 -3 cm 2 / s. This demonstrates that HOTMEPO-SO3Na exhibits excellent diffusion properties and superior electron transfer capabilities in aqueous systems.

[0042] RDE-LSV curve data were recorded using a SIN-RDE type rotating disk electrode apparatus and a ZIVE SP1 electrochemical workstation. Tests were conducted using a glassy carbon working electrode, an Ag / AgCl reference electrode, and a platinum wire electrode. The test results are as follows: Figure 3 As shown: RDE-LSV testing was conducted at a rate of 10 mV / s, with the rotation speed of the rotating disk electrode assembly gradually increasing from 400 rpm to 4000 rpm. At each rotation speed, the RDE-LSV curves showed a mass transfer-controlled limiting current and exhibited a distinct current plateau (see [link to RDE-LSV test]). Figure 3 (part (a) in the text).

[0043] The limiting current (I) of HOTMEPO-SO3Na in aqueous systems shows a clear linear relationship with the square root of the rotational speed (angular velocity) (see...). Figure 3 Part (b) of the equation conforms to the Levich equation. Under different voltages (e.g., Figure 3 In section (c), the limiting current (I) at 10mV, 20mV, 40mV, 60mV, 80mV, and 100mV all show a consistent trend with the rotational speed (angular velocity). Based on the Levich equation for HOTMEPO-SO3Na in the water system, with a slope of 7.94, the calculated diffusion coefficient D0 is 1.56 × 10⁻⁶. -6 cm 2 / s. To determine the rate constant during charge transfer, the overpotential (η) and logarithm of the kinetic current (Logi) of HOTMEPO-SO3Na in the aqueous system were further plotted. K Tafel curve () Figure 3 (d) of the text). The electron transfer rate constant k0 obtained from the fitted Tafel curve is 1.30 × 10⁻⁶. -3 cm 2 / s. LSV curve data show that HOTMEPO-SO3Na has excellent diffusion properties and excellent electron transfer capability in aqueous systems, making it a potential electrode material for flow batteries.

[0044] The applicant further tested and compared the differences between the active materials of the positive and negative electrolytes in this application, such as... Figure 4 As shown, the redox potential difference between the two is 793mV, indicating that the flow battery of the present invention can provide an output voltage of about 0.8V, demonstrating excellent battery performance.

[0045] The flow battery was tested for rate performance at different current densities, and the corresponding rate performance curves and charge-discharge curves were obtained, such as... Figure 5 , Figure 6 As shown: This flow battery operates at 150 mA / cm². 2 It can maintain a high energy density even under high current density.

[0046] From the long-cycle performance test data of this flow battery (see...) Figure 7 As can be seen from the data, the flow battery using HOTMEPO-SO3Na and Dex-vi as the positive and negative electrode active materials can still maintain 98% of its high battery capacity after 600 cycles, with a decay rate of 0.0066% per cycle and a daily decay rate of 0.457%.

[0047] Combination Figure 8 The flow battery exhibits 135 mW / cm² at 50% and 100% states of charge, respectively. 2 and 200mW / cm 2 The output power of the flow battery is demonstrated. This proves that the flow battery has excellent power density performance.

[0048] Comparative Example 1

[0049] CN120613419A is used as Comparative Example 1.

[0050] This comparative example provides five types of aqueous organic flow batteries.

[0051] The positive electrode electrolyte consists of 0.1 mol / L TEMPO electrolyte (C1~Bn), 1 mol / L potassium chloride, and 5 ml of water.

[0052] Negative electrode electrolyte: 0.1 mol / L of the negative electrode electrolyte Dex-Vi synthesized in Example 1, 1 mol / L potassium chloride, and 5 ml of solvent water.

[0053] The diaphragm is an anion exchange membrane (MTCP-50, 2.5*2.5 cm).

[0054] The testing method is the same as in Example 1. The test results are as follows: Figure 9 As shown: The initial capacity of the positive electrode electrolyte Bn is 2.35 Ah / L, which is less than 2.5 Ah / L in Example 1 (see...). Figure 9(as shown in part (a)); and after 1000 cycles, the capacity retention rate is 96.27%, lower than the high battery capacity of 98% maintained after 600 cycles in Example 1. Furthermore, the energy efficiency of the positive electrode electrolyte Bn is approximately 80%, lower than that of the TEMPO derivative of this application. The flow battery of this application exhibits excellent cycle stability and electrochemical performance, making it an excellent flow battery.

[0055] Comparative Example 2

[0056] This comparative example provides a conventional aqueous organic flow battery.

[0057] The positive electrode electrolyte consists of 0.1 mol / L 4-hydroxy-TEMPO, 1 mol / L potassium chloride, and 5 ml of water.

[0058] Negative electrode electrolyte: 0.1 mol / L of the negative electrode electrolyte Dex-Vi synthesized in Example 1, 1 mol / L potassium chloride, and 5 ml of solvent water.

[0059] The diaphragm is an anion exchange membrane (MTCP-50, 2.5*2.5 cm).

[0060] The testing method is the same as in Example 1. The test results are as follows: Figure 10 As shown: Although the initial capacity of 4-hydroxy-TEMPO was close to the theoretical capacity, the capacity retention rate was 85.77% after 50 cycles (see...). Figure 10 The 4-hydroxy-TEMPO exhibits a higher voltage plateau decay trend during cycling (see section (a) of Example 1), which is lower than the 98% high battery capacity maintained after 600 cycles in Example 1. Figure 10 The stability and energy efficiency of the TEMPO derivative series in this application are lower than those of the components in part (b). The flow battery of this application has excellent cycle stability and electrochemical performance, and is an excellent flow battery.

[0061] The above-described embodiments merely illustrate several feasible 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 present invention, nor are the embodiments intended to limit the scope of protection in the claims of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention. All equivalent implementations or changes that do not depart from the present invention should be included in the technology of the present invention.

Claims

1. An aqueous redox flow battery, comprising a positive electrode electrolyte, a separator, and a negative electrode electrolyte, characterized in that: The positive electrode electrolyte uses HOTEMPO-SO3Na as the active material, and the negative electrode electrolyte uses (3-chloro-2-hydroxypropyl)-trimethylammonium chloride-4,4'-pyridine as the active material.

2. The aqueous redox flow battery according to claim 1, characterized in that, The active material of the positive electrode electrolyte is prepared using the following steps: Step 1: 4-Epoxy-2,2',6,6'-Tetramethylpiperidine was added to an aqueous solution of sodium bisulfite. After stirring and reacting, the precipitate was collected by filtration and dried to obtain (4-hydroxy-2,2',6,6'-tetramethylpiperidine)-4-methanesulfonate. Step 2: Dissolve (4-hydroxy-2,2',6,6'-tetramethylpiperidine)-4-methanesulfonate in water, then add sodium bicarbonate and sodium tungstate. Add hydrogen peroxide in batches to the resulting aqueous solution, stir overnight, and separate to obtain HOTEMPO-SO3Na.

3. The aqueous redox flow battery according to claim 2, characterized in that: The equivalent ratio of 4-epoxy-2,2',6,6'-tetramethylpiperidine added to the sodium bisulfite aqueous solution was 1:1.2, the equivalent ratio of (4-hydroxy-2,2',6,6'-tetramethylpiperidine)-4-methanesulfonate, sodium bicarbonate and sodium tungstate was 1:0.5:0.01, and the equivalent ratio of hydrogen peroxide to the aqueous solution was 1:

2.

4. The aqueous redox flow battery according to claim 2, characterized in that: In step one, the reaction is carried out at 80°C for 6 hours with stirring. In step two, the reaction is carried out at 40°C overnight with stirring.

5. The aqueous redox flow battery according to claim 1, characterized in that, The active material of the negative electrode electrolyte is prepared by the following method: 4,4'-bipyridine and (3-chloro-2-hydroxypropyl)-trimethylammonium chloride are added to a reaction vessel, reacted at 120°C for 24 h, cooled overnight, and ethanol and acetone are added to the reaction product in sequence. The mixture is then filtered and collected to obtain (3-chloro-2-hydroxypropyl)-trimethylammonium chloride-4,4'-bipyridine.

6. The aqueous redox flow battery according to claim 5, characterized in that: The equivalent ratio of 4,4'-bipyridine to 3-chloro-2-hydroxypropyltrimethylammonium chloride is 1:3, and the volume ratio of the reaction product, ethanol, and acetone is 1:9:

10.

7. The aqueous redox flow battery according to claim 1, characterized in that: The concentration of active material in the positive electrode electrolyte is 0.1~0.2 mol / L, and the concentration of active material in the negative electrode electrolyte is 0.05~0.1 mol / L.

8. The aqueous redox flow battery according to claim 1, characterized in that: The diaphragm is an anion exchange membrane.

9. An aqueous redox flow battery according to any one of claims 1 to 8, characterized in that: HOTEMPO-SO3Na is dissolved in an aqueous potassium chloride solution to obtain the positive electrode electrolyte, and (3-chloro-2-hydroxypropyl)-trimethylammonium chloride-4,4'-pyridine is dissolved in an aqueous potassium chloride solution to obtain the negative electrode electrolyte. The positive electrode electrolyte, the negative electrode electrolyte, and the separator are assembled to obtain a flow battery.

10. An aqueous redox flow battery according to claim 9, characterized in that: The concentration of the potassium chloride aqueous solution is 2~4 mol / L.

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