An aqueous redox flow battery and its preparation method

Abstract

The present invention discloses an aqueous redox flow battery and a preparation method thereof, relating to the technical field of flow batteries, including a positive electrolyte, a negative electrolyte, and a separator. Among them: the positive electrolyte uses a complex of ferric chloride and crown ether as an active substance, the negative electrolyte uses disodium anthraquinone-2,7-disulfonate as an active substance, and the separator is used to isolate the positive electrolyte and the negative electrolyte to prevent direct contact, while allowing ions in the electrolyte to freely shuttle. For the aqueous redox flow battery of the present invention, the positive electrolyte uses a complex of ferric chloride and crown ether as an active substance, and the negative electrolyte uses disodium anthraquinone-2,7-disulfonate as an active substance, which has excellent redox performance and stability, and improves the energy density and cycle life of the battery.

Description

Technical Field

[0001] The present disclosure relates to the field of energy storage systems, and particularly to an aqueous redox flow battery and a preparation method thereof. Background Art

[0002] With the rapid development of fields such as electronic products, electric vehicles, smart grids, and aerospace, the demand for various energy sources by humans has also increased accordingly. At the same time, the gradual depletion of fossil energy has made energy and environmental issues one of the most important challenges for the sustainable development of human society. Therefore, the efficient utilization of renewable energy has become the primary issue to be faced in energy development. However, most renewable energies cannot be used alone as stable energy sources and cannot be directly used after being obtained. Due to the above problems, there is an urgent need for scientists to find efficient energy conversion devices and reliable energy storage systems.

[0003] A flow battery is a new type of electrochemical energy storage technology and has received extensive attention due to its unique performance advantages. A flow battery consists of key components such as a stack unit, electrolytes, an electrolyte storage and supply unit, and a management and control unit. Its core working principle is to separate the positive and negative electrolytes and circulate them separately, and through the reversible redox reaction of the active substances in the positive and negative electrolyte solutions, the mutual conversion between electrical energy and chemical energy is realized.

[0004] Flow batteries have characteristics such as high capacity, wide application fields, and long cycle service life. Its active substances are stored in the electrolytes and have fluidity, which makes the design of the battery power and capacity relatively independent and is particularly suitable for large-scale electricity storage needs. According to different electrode active substances, flow batteries can be divided into various types, such as all-vanadium flow batteries, lithium-ion flow batteries, and lead-acid flow batteries. Among them, all-vanadium flow batteries have broad application prospects in the energy storage field due to their advantages such as high safety, fast start-up speed, and long battery life.

[0005] In recent years, with the accelerated promotion of the global energy transformation and the rapid development of renewable energy, energy storage technology, as a key bridge connecting renewable energy power generation with the power grid and users, has become increasingly prominent. As an efficient and reliable energy storage technology, flow batteries have made remarkable progress in terms of technological innovation, industrial upgrading, market demand, and policy support, injecting strong impetus into the optimization and adjustment of the global energy structure and the green and low-carbon transformation.

[0006] Traditional flow batteries still have many deficiencies in aspects such as electrode materials and electrolyte compositions, which limit the improvement of their performance and the expansion of their application scope. Therefore, it is of great significance to develop a flow battery with excellent performance and low cost. Summary of the Invention

[0007] The first aspect of the present invention aims to provide an aqueous redox flow battery.

[0008] The technical solution adopted by the present invention is as follows:

[0009] An aqueous redox flow battery includes a positive electrolyte, a negative electrolyte, and a separator. Among them: the positive electrolyte uses a complex of ferric chloride and crown ether as the active substance, the negative electrolyte uses disodium anthraquinone-2,7-disulfonate as the active substance, and the separator is used to isolate the positive electrolyte and the negative electrolyte to prevent direct contact, while allowing the ions in the electrolyte to shuttle freely.

[0010] In the aqueous redox flow battery of the present invention, the positive electrolyte uses a complex of ferric chloride and crown ether as the active substance, and this metal complex has excellent redox performance and stability; the negative electrolyte uses disodium anthraquinone-2,7-disulfonate as the active substance, and this material can undergo a redox reaction with the positive active substance. The flow battery using the above materials has excellent redox performance and stability, and improves the energy density and cycle life of the battery.

[0011] The further settings are as follows:

[0012] The complex of ferric chloride and crown ether is obtained in the following way: put ferric chloride and crown ether into water in proportion, stir and react, after the reaction is completed, carry out vacuum rotary evaporation, and then place it in an oven to dry to obtain the complex of ferric chloride and crown ether.

[0013] The crown ether is selected from any one of 12-crown-4, 15-crown-5, and 18-crown-6.

[0014] The molar ratio of the crown ether to ferric chloride is 1:0.1 to 1:1, preferably 1:1.

[0015] Dissolve the complex of ferric chloride and crown ether in an ammonium chloride aqueous solution to serve as the positive electrolyte of the flow battery.

[0016] Dissolve the disodium anthraquinone-2,7-disulfonate in an ammonium chloride aqueous solution, and then carry out a charging treatment to obtain the negative electrolyte of the flow battery.

[0017] The charging method is as follows: configure 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radical in an ammonium chloride aqueous solution as the positive electrolyte, use the disodium anthraquinone-2,7-disulfonate electrolyte as the negative electrolyte, assemble the above positive electrolyte, negative electrolyte and separator in sequence to form a flow battery, and carry out charging.

[0018] The second aspect of the present invention aims to provide a preparation method of an aqueous redox flow battery, including the following steps:

[0019] (1) Preparation of positive electrode electrolyte:

[0020] Put crown ether and ferric chloride into water according to the molar ratio of 1:0.1 - 1:1, stir and react. After the reaction is completed, perform vacuum rotary evaporation, and then place it in an oven for drying to obtain a complex of ferric chloride and crown ether. Dissolve the complex of ferric chloride and crown ether in an ammonium chloride aqueous solution as the positive electrode electrolyte of the flow battery.

[0021] (2) Preparation of negative electrode electrolyte:

[0022] Dissolve disodium anthraquinone-2,7-disulfonate in an ammonium chloride aqueous solution to obtain a disodium anthraquinone-2,7-disulfonate electrolyte solution, and then perform charging treatment on it. After the charging is completed, obtain the negative electrode electrolyte.

[0023] The charging treatment is as follows: Prepare 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radical in an ammonium chloride aqueous solution as the positive electrode electrolyte, use the disodium anthraquinone-2,7-disulfonate electrolyte solution as the negative electrode electrolyte, assemble the above positive electrode electrolyte, negative electrode electrolyte and separator in sequence to form a flow battery, and perform charging.

[0024] (3) Assembly of the battery:

[0025] Assemble the positive electrode electrolyte prepared in step (1), the negative electrode electrolyte prepared in step (2), and the separator in sequence to obtain an aqueous redox flow battery.

[0026] The beneficial effects of the present invention are as follows:

[0027] Compared with the prior art, the present invention has the following advantages: Using the complex of crown ether and ferric chloride as the positive electrode active material and disodium anthraquinone-2,7-disulfonate as the negative electrode active material, it has excellent redox performance and stability, improves the energy density and cycle life of the battery; and the preparation process is simple, easy to realize large-scale production, and reduces the cost of the battery.

[0028] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Description of the Drawings

[0029] Figure 1 It is the schematic diagram of an aqueous redox flow battery of the present invention.

[0030] Figure 2 It is the electrochemical property diagram measured by cyclic voltammetry (CV) of the 5 mM complex of 12-crown-4 and ferric chloride prepared in Example 1 in a 1 M potassium chloride aqueous solution.

[0031] Figure 3Electrochemical property diagram measured by cyclic voltammetry (CV) of the 5 mM complex of 15-crown-5 and iron chloride prepared for Example 2 in 1 M aqueous potassium chloride solution.

[0032] Figure 4 Electrochemical property diagram measured by cyclic voltammetry (CV) of the 5 mM complex of 18-crown-6 and iron chloride prepared for Example 3 in 1 M aqueous potassium chloride solution.

[0033] Figure 5 Electrochemical property diagram measured by linear sweep voltammetry (LSV) of the 5 mM complex of 12-crown-4 and iron chloride prepared for Example 1 in 1 M aqueous potassium chloride solution.

[0034] Figure 6 Levich curve of the limiting current and the square root of the rotation rate of the complex of 12-crown-4 and iron chloride prepared for Example 1.

[0035] Figure 7 Tafel curve obtained from the overpotential and the logarithm of the kinetic current value of the complex of 12-crown-4 and iron chloride prepared for Example 1.

[0036] Figure 8 Electrochemical property diagram measured by linear sweep voltammetry (LSV) of the 5 mM complex of 15-crown-5 and iron chloride prepared for Example 2 in 1 M aqueous potassium chloride solution.

[0037] Figure 9 Levich curve of the limiting current and the square root of the rotation rate of the complex of 15-crown-5 and iron chloride prepared for Example 2.

[0038] Figure 10 Tafel curve obtained from the overpotential and the logarithm of the kinetic current value of the complex of 15-crown-5 and iron chloride prepared for Example 2.

[0039] Figure 11 Electrochemical property diagram measured by linear sweep voltammetry (LSV) of the 5 mM complex of 18-crown-6 and iron chloride prepared for Example 3 in 1 M aqueous potassium chloride solution.

[0040] Figure 12 Levich curve of the limiting current and the square root of the rotation rate of the complex of 18-crown-6 and iron chloride prepared for Example 3.

[0041] Figure 13 Tafel curve obtained from the overpotential and the logarithm of the kinetic current value of the complex of 18-crown-6 and iron chloride prepared for Example 3.

[0042] Figure 14 Long cycle data graph of the aqueous redox flow battery prepared in Example 1.

[0043] Figure 15 Long cycle data graph of the aqueous redox flow battery prepared in Example 2.

[0044] Figure 16 Long cycle data graph of the aqueous redox flow battery prepared in Example 3. Detailed implementation manners

[0045] As Figure 1 shown, the aqueous redox flow battery described in the embodiments of the present invention includes a positive electrolyte, a negative electrolyte, and a separator. Among them: the positive electrolyte uses a complex of ferric chloride and crown ether as the active substance, and this metal complex has excellent redox performance and stability; the negative electrolyte uses disodium anthraquinone-2,7-disulfonate as the active substance. Disodium anthraquinone-2,7-disulfonate needs to obtain electrons first before it can be used as the negative electrolyte of the present invention, and this material can undergo a redox reaction with the positive active substance; the separator uses an ion exchange membrane. In this embodiment, the Nature membrane is used to isolate the positive electrolyte and the negative electrolyte to prevent direct contact, and at the same time allow the ions in the electrolyte to shuttle freely; the flow battery of the present invention needs to operate in a glove box. Specifically, an Itrex single-sided working station glove box is selected, and the equipment model is Lab2000.

[0046] The implementation effects of the present invention will be further described in detail below in combination with examples under different process conditions.

[0047] Example 1

[0048] A preparation method of an aqueous redox flow battery includes the following steps:

[0049] (1) Prepare the positive electrolyte:

[0050] Put 12-crown-4 and ferric chloride into water in a molar ratio of 1:1, stir and react. After the reaction is completed, perform vacuum rotary evaporation, and then place it in an oven to dry to obtain the metal complex. Configure a 0.1M concentration of this metal complex in 8 mL of 1M ammonium chloride aqueous solution, and this solution is used as the positive electrolyte of the flow battery.

[0051] (2) Prepare the negative electrolyte:

[0052] Prepare a 0.05 M solution of disodium anthraquinone-2,7-disulfonate in 10 mL of 1 M aqueous ammonium chloride. This material needs to obtain electrons first to be used as the negative electrolyte of a flow battery. Specifically, prepare a 0.1 M solution of tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl radical) in 12 mL of 1 M aqueous ammonium chloride. Use the previously prepared tempol electrolyte as the positive electrode of the flow battery, and the prepared disodium anthraquinone-2,7-disulfonate electrolyte as the negative electrode. Assemble the positive electrode electrolyte, negative electrode electrolyte, and separator in sequence to form a flow battery, and perform charging. After the charging is completed, the obtained disodium anthraquinone-2,7-disulfonate electrolyte is used as the negative electrolyte of the present invention.

[0053] (3)Assemble the battery:

[0054] Use the complex solution of 12-crown-4 and iron chloride prepared in step (1) as the positive electrode electrolyte, and use the disodium anthraquinone-2,7-disulfonate electrolyte after the charging in step (2) is completed as the negative electrode electrolyte. Assemble the positive electrode electrolyte, negative electrode electrolyte, and separator in sequence to form a flow battery, and obtain the first aqueous redox flow battery of the present invention.

[0055] Example 2

[0056] A method for preparing an aqueous redox flow battery includes the following steps:

[0057] (1)Prepare the positive electrode electrolyte:

[0058] Put 15-crown-5 and iron chloride into water in a molar ratio of 1:1, stir and react. After the reaction is completed, perform vacuum rotary evaporation, and then place it in an oven to dry to obtain a metal complex. Prepare a 0.1 M solution of this metal complex in 8 mL of 1 M aqueous ammonium chloride. This solution is used as the positive electrode electrolyte of the flow battery.

[0059] (2)Prepare the negative electrode electrolyte:

[0060] Prepare a 0.05 M solution of disodium anthraquinone-2,7-disulfonate in 10 mL of 1 M aqueous ammonium chloride. This material needs to obtain electrons first to be used as the negative electrolyte of a flow battery. Specifically, prepare a 0.1 M solution of tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl radical) in 12 mL of 1 M aqueous ammonium chloride. Use the previously prepared tempol electrolyte as the positive electrode of the flow battery, and the prepared disodium anthraquinone-2,7-disulfonate electrolyte as the negative electrode. Assemble the positive electrode electrolyte, negative electrode electrolyte, and separator in sequence to form a flow battery, and perform charging. After the charging is completed, the obtained disodium anthraquinone-2,7-disulfonate electrolyte is used as the negative electrolyte of the present invention.

[0061] (3) Assembling the battery:

[0062] Take the complex solution of 15-crown-5 and iron chloride prepared in step (1) as the positive electrolyte, take the electrolyte solution of disodium anthraquinone-2,7-disulfonate after charging in step (2) as the negative electrolyte, and assemble the positive electrolyte, negative electrolyte and diaphragm in sequence to form a flow battery, thus obtaining the second aqueous redox flow battery of the present invention.

[0063] Example 3

[0064] A preparation method of an aqueous redox flow battery, comprising the following steps:

[0065] (1) Preparing the positive electrolyte:

[0066] Put 18-crown-6 and iron chloride into water in a molar ratio of 1:1, stir and react. After the reaction is completed, perform vacuum rotary evaporation, and then place it in an oven to dry to obtain a metal complex. Prepare a 0.1M solution of this metal complex in 8 mL of 1M ammonium chloride aqueous solution, and this solution is used as the positive electrolyte of the flow battery.

[0067] (2) Preparing the negative electrolyte:

[0068] Prepare a 0.05M solution of disodium anthraquinone-2,7-disulfonate in 10 mL of 1M ammonium chloride aqueous solution. This material needs to obtain electrons first to be used as the negative electrolyte of the flow battery. Specifically, prepare a 0.1M solution of tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl radical) in 12 mL of 1M ammonium chloride aqueous solution. Take the aforementioned prepared tempol electrolyte as the positive electrode of the flow battery, and the prepared electrolyte solution of disodium anthraquinone-2,7-disulfonate as the negative electrode. Assemble the positive electrolyte, negative electrolyte and diaphragm in sequence to form a flow battery, and perform charging. After the charging is completed, the obtained electrolyte solution of disodium anthraquinone-2,7-disulfonate is used as the negative electrolyte of the present invention.

[0069] (3) Assembling the battery:

[0070] Take the complex solution of 18-crown-6 and iron chloride prepared in step (1) as the positive electrolyte, take the electrolyte solution of disodium anthraquinone-2,7-disulfonate after charging in step (2) as the negative electrolyte, and assemble the positive electrolyte, negative electrolyte and diaphragm in sequence to form a flow battery, thus obtaining the third aqueous redox flow battery of the present invention.

[0071] Performance test:

[0072] Performance tests were conducted on the positive electrode active materials (complexes of crown ethers and iron chloride) prepared in Examples 1-3 and the aqueous redox flow battery, using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and long cycle performance tests:

[0073] The CV curve data was recorded using a ZIVE SP1 electrochemical workstation. Tests were carried out using a glassy carbon working electrode, an Ag / AgCl reference electrode, and a platinum wire counter electrode. The test results are as Figures 2 - 4 shown.

[0074] As Figures 2 - 4 shown, the complexes of crown ethers and iron chloride exhibit excellent reversible redox performance in aqueous systems. The redox potential of the complexes of crown ethers and iron chloride does not change with the scanning rate. Data can be obtained from the figure that the average median voltage of the complex of 12-crown-4 and iron chloride is 474.31 mV ( Figure 2 ), the average median voltage of the complex of 15-crown-5 and iron chloride is 468.35 mV ( Figure 3 ), and the average median voltage of the complex of 18-crown-6 and iron chloride is 469.21 mV ( Figure 4 ). The CV data shows that the complexes of crown ethers and iron chloride have a relatively high redox potential and are potential positive electrode materials for flow batteries.

[0075] The LSV curve data was recorded using a SIN-RRDE type rotating ring-disk electrode device. Tests were carried out using an Ag / AgCl reference electrode and a platinum wire counter electrode. The test results are as Figures 5 - 13 shown.

[0076] Combined with Figures 5 - 7 shown, the LSV scans were carried out at a rate of 10 mV s -1 , and the rotation speed was increased from 400 rpm to 4000 rpm. At all rotation speeds, the LSV curves showed a limiting current controlled by mass transfer and presented a distinct plateau shape. The limiting currents ( I ) of the complexes of crown ether iron chloride were all linearly dependent on the square root of the rotation speed ( ω 1 / 2 ), in line with the Levich equation. Based on the slope of the Levich plot of the complex of 12-crown-4 and iron chloride being -15.48 ( Figure 6 ), the diffusion coefficient D value was calculated to be 6.47×10 -6 cm 2 s -1 . To determine the rate constant of the charge transfer process, a plot of the overpotential (η) of the oxidation of the complex of 12-crown-4 and iron chloride versus the logarithm of the kinetic current (Logi K ) was plotted (Figure 7 ). The electron transfer rate obtained from the fitted Tafel plot is 1.27×10 -3 cm 2 s -1 . The LSV curve data shows that the complex of 12-crown-4 and iron chloride has excellent diffusion performance and excellent electron transfer ability in aqueous solution, and is a potential electrode material for flow batteries.

[0077] Combined with Figures 8 - 10 as shown, the LSV scan was carried out at a rate of 10 mV s -1 . The rotation speed was increased from 400 rpm to 4000 rpm. At all rotation speeds, the LSV curves showed a limiting current controlled by mass transfer and presented a distinct plateau shape. The limiting current ( I ) of the complex of crown ether iron chloride was linearly dependent on the square root of the rotation speed ( ω 1 / 2 ), in line with the Levich equation. According to the slope of the Levich plot of the complex of 15-crown-5 and iron chloride being -15.85 ( Figure 9 ), the diffusion coefficient D value was calculated to be 6.37×10 -6 cm 2 s -1 . To determine the rate constant of the charge transfer process, a plot of the overpotential (η) of the oxidation of the complex of 15-crown-5 and iron chloride against the logarithm of the kinetic current (Logi K ) was plotted ( Figure 10 ). The electron transfer rate obtained from the fitted Tafel plot is 6.71×10 -3 cm 2 s -1 . The LSV curve data shows that the complex of 15-crown-5 and iron chloride has excellent diffusion performance and excellent electron transfer ability in aqueous solution, and is a potential electrode material for flow batteries.

[0078] Combined with Figures 11 - 13 as shown, the LSV scan was carried out at a rate of 10 mV s -1 . The rotation speed was increased from 400 rpm to 4000 rpm. At all rotation speeds, the LSV curves showed a limiting current controlled by mass transfer and presented a distinct plateau shape. The limiting current ( I ) of the complex of crown ether iron chloride was linearly dependent on the square root of the rotation speed ( ω 1 / 2 ), in line with the Levich equation. According to the slope of the Levich plot of the complex of 18-crown-6 and iron chloride being -21.42 ( Figure 12), the calculated diffusion coefficient D value is 5.21×10 -6 cm 2 s -1 . To determine the rate constant of the charge transfer process, a plot of the overpotential (η) of the oxidation of the complex of 18-crown-6 and iron chloride versus the logarithm of the kinetic current (Logi K ) was plotted ( Figure 13 ). The electron transfer rate obtained from the fitted Tafel plot is 3.28×10 -6 cm 2 s -1 . The LSV curve data shows that the complex of 18-crown-6 and iron chloride has excellent diffusion performance and excellent electron transfer ability in an aqueous system, and is a potential electrode material for flow batteries.

[0079] The long cycle performance data of the flow battery was recorded using BTSDA software. The test results are as Figures 14 - 16 shown.

[0080] Combined with Figures 14 - 16 shown, the long cycle data of the flow battery shows that the complex of crown ether and iron chloride exhibits excellent charge-discharge efficiency, always maintaining at 100%. The flow battery using the complex of 12-crown-4 and iron chloride still maintains 100% battery capacity after 200 cycles, showing excellent cycle performance. The flow battery using the complex of 15-crown-5, 18-crown-6 and iron chloride does not show excellent cycle performance compared with the flow battery using the complex of 12-crown-4 and iron chloride. The long cycle performance data shows that the flow battery using the complex of 12-crown-4 and iron chloride has more excellent charge-discharge efficiency and cycle performance, and is an excellent positive electrode material for flow batteries.

Claims

1. An aqueous redox flow battery comprising a positive electrode electrolyte, a negative electrode electrolyte, and a diaphragm, characterized in that: The positive electrode electrolyte uses a complex of ferric chloride and crown ether as an active substance, and the negative electrode electrolyte uses anthraquinone-2,7-disulfonic acid disodium salt as an active substance. The separator is used to isolate the positive electrode electrolyte and the negative electrode electrolyte to prevent direct contact, while allowing ions in the electrolyte to shuttle freely; The complex of ferric chloride and crown ether is obtained by the following method: ferric chloride and crown ether are added into water in proportion, stirred for reaction, and after the reaction is completed, vacuum rotary evaporation is performed, and then placed in an oven for drying to obtain the complex of ferric chloride and crown ether; The crown ether is selected from any one of 12-crown-4, 15-crown-5, and 18-crown-6; The molar ratio of the crown ether to ferric chloride is 1:0.1 to 1:1; The anthraquinone-2,7-disulfonic acid disodium salt is dissolved in an ammonium chloride aqueous solution and then charged to obtain a negative electrode electrolyte for a liquid flow battery; the charging process is as follows: 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxy free base is configured in an ammonium chloride aqueous solution as a positive electrode electrolyte, anthraquinone-2,7-disulfonic acid disodium salt solution is used as a negative electrode electrolyte, and then a liquid flow battery is assembled for charging.

2. An aqueous redox flow battery according to claim 1, characterized in that: The molar ratio of the crown ether to ferric chloride is 1:

1.

3. The aqueous redox flow battery according to claim 1, characterized in that: The complex of ferric chloride and crown ether is dissolved in an aqueous ammonium chloride solution and used as the positive electrode electrolyte of the liquid flow battery.

4. A method for preparing an aqueous redox flow battery, characterized in that: The following steps are involved: (1) Preparation of positive electrode electrolyte: The crown ether and ferric chloride are added into water in a molar ratio of 1:0.1 to 1:1, and stirred for reaction. After the reaction is completed, vacuum rotary evaporation is performed, and then the complex of ferric chloride and crown ether is dried in an oven to obtain the complex of ferric chloride and crown ether. The complex of ferric chloride and crown ether is dissolved in an aqueous ammonium chloride solution as a positive electrode electrolyte of a liquid flow battery; The crown ether is selected from any one of 12-crown-4, 15-crown-5, and 18-crown-6; (2) Preparation of negative electrode electrolyte: Dissolving anthraquinone-2,7-disulfonic acid disodium salt in an aqueous solution of ammonium chloride to obtain an anthraquinone-2,7-disulfonic acid disodium salt electrolyte, and then performing a charging process to obtain a negative electrode electrolyte after the charging is completed; In step (2), the anthraquinone-2,7-disulfonic acid disodium salt electrolyte is charged, and the charging process is as follows: 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxy free base is prepared in an ammonium chloride aqueous solution as a positive electrode electrolyte, and the anthraquinone-2,7-disulfonic acid disodium salt electrolyte is used as a negative electrode electrolyte, and then assembled into a liquid flow battery for charging; (3) Assembling the battery: The positive electrode electrolyte prepared in step (1), the negative electrode electrolyte prepared in step (2), and the diaphragm are assembled in sequence to obtain an aqueous redox flow battery.

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