Flow battery using saline water as electrolyte, and test system, operation method and application thereof

Abstract

The invention provides a flow battery taking saline water as electrolyte and a test system, an operation method and application of the flow battery. The flow battery comprises electrode chambers at two ends, and at least one flow battery module is arranged between the electrode chambers; the flow battery module comprises an anion selective film, an acid chamber, a bipolar film, a water chamber, a cation selective film, an alkali chamber and an anion selective film which are arranged in sequence; the acid chamber is communicated with an acid liquid storage tank, the alkali chamber is communicated with an alkali liquid storage tank, the water chamber is communicated with a saline liquid storage tank, and the electrode chamber is communicated with an electrode liquid storage tank; the whole battery is sealed; an inert electrode is arranged in the electrode chamber; the invention provides a novel flow battery taking saline water as electrolyte, the electrodialysis and reverse electrodialysis principles are combined, and an energy storage battery is constructed by utilizing a commercial ion selective film and a bipolar film, so that the cost of the flow battery is reduced, and the capacity expansion of the flow battery is realized; the system can be used for energy storage and power generation in high-salinity and high-acid-base environments; the environmental protection property of the energy storage battery is improved, and a new solution is provided for green and novel long-time energy storage.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage batteries, and in particular relates to a flow battery using salt water as an electrolyte, a test system, an operation method and an application thereof. Background Art

[0002] The installed capacity of renewable energy sources such as wind power and photovoltaic power is constantly increasing. However, due to the volatility of renewable energy generation, the "waste electricity" that cannot be connected to the grid is also increasing. Long-term energy storage can solve this problem well. Its advantage of storing electricity across days and months can meet the stable operation needs of the power system and help build a new power system in my country. As one of the stable and efficient energy storage methods, flow batteries have received widespread attention. Liquid flow batteries have the advantages of ultra-long cycle life, high safety and stability, and have obvious advantages in the context of the urgent need for large-scale long-term energy storage technology. The current research on liquid flow batteries focuses on the research of liquid flow batteries with all-vanadium, zinc-based, and iron-based electrolytes: all-vanadium is a relatively mature technical route with the most projects, but its cost is relatively high and its production capacity is limited. A 1GWh all-vanadium liquid flow battery requires 8,000 to 10,000 tons of vanadium pentoxide; the technical route represented by zinc-based has the problem of easy generation of zinc dendrites and puncturing the diaphragm, resulting in a short service life; the technical route represented by iron-based, although low in cost, has a low power density and also has the problem of hydrogen evolution during negative electrode charging. Therefore, it is crucial to develop new liquid flow batteries with low cost, good stability and high energy conversion efficiency for storing new energy such as solar energy and wind energy.

[0003] This section will talk about the basic principles of electrodialysis and reverse electrodialysis / the feasibility and benefits of developing flow batteries based on them, etc., rather than talking about their research progress. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a new electrodialysis flow battery with salt water as electrolyte for energy storage applications and a charging and discharging method thereof, so as to solve the problem of lack of stable, efficient and low-cost energy storage batteries in the current market.

[0005] In order to achieve the above-mentioned objectives, in the first aspect, the present invention provides a liquid flow battery, comprising electrode chambers at both ends, at least one liquid flow battery module is arranged between the electrode chambers, and the liquid flow battery module comprises an anion selective membrane, an acid chamber, a bipolar membrane, a water chamber, a cation selective membrane, an alkali chamber, and an anion selective membrane arranged in sequence; the acid chamber is connected to an acid liquid storage tank, the alkali chamber is connected to an alkali liquid storage tank, the water chamber is connected to a brine storage tank, and the electrode chamber is connected to an electrode liquid storage tank; the battery is sealed as a whole, and an inert electrode is arranged in the electrode chamber.

[0006] Furthermore, grooves are provided on both sides of the acid chamber, water chamber and alkali chamber, and sealing rings are arranged in the grooves; a groove is provided on the inner side of the electrode chamber, and a sealing ring is provided in the groove; through holes are evenly provided around the acid chamber, water chamber, alkali chamber and electrode chamber, and clamping devices are arranged in the through holes.

[0007] Furthermore, the clamping device adopts a double-headed stud or a single-headed stud and an easily dismantled assembly.

[0008] Furthermore, the acid chamber, water chamber, alkali chamber and electrode chamber all use plates with set thickness, and the acid chamber, water chamber, alkali chamber and electrode chamber are all provided with liquid inlets and liquid outlets, and the positions of the liquid inlets and liquid outlets are as far as possible.

[0009] Furthermore, the electrode liquid in the electrode chamber is FeCl 2 and FeCl 3 A mixed solution is prepared, and circulation pumps are provided at the inlets of the acid chamber, water chamber, alkali chamber and electrode chamber.

[0010] Furthermore, the brine storage tank contains sodium chloride solution, potassium chloride solution or lithium chloride solution, the alkali solution storage tank contains potassium hydroxide solution or sodium hydroxide solution, and the acid solution storage tank contains hydrochloric acid.

[0011] In a second aspect, the present invention provides a testing system for the liquid flow battery, comprising a liquid flow battery, a DC power supply, a variable resistor, an ammeter, a voltmeter, a flow meter and a thermometer; a brine storage tank, an acid storage tank, an alkali storage tank and an electrode liquid storage tank are connected to the liquid flow battery through pipelines to form a brine circulation path, an acid circulation path, an alkali circulation path and an electrode liquid circulation path respectively, and circulation pumps are arranged on the brine circulation path, the acid circulation path, the alkali circulation path and the electrode liquid circulation path, and flow meters and thermometers are arranged at the inlet and outlet of the liquid flow battery in the brine circulation path, the acid circulation path, the alkali circulation path and the electrode liquid circulation path respectively, the positive and negative poles of the liquid flow battery are connected in parallel with the voltmeter and the DC power supply, and at the same time, the ammeter and the variable resistor are connected in series and then in parallel with the positive and negative poles of the liquid flow battery, and a switch is arranged to control whether the DC power supply and the variable resistor are connected to the liquid flow battery.

[0012] In the third aspect, the present invention provides a test method based on the above test system. After the corresponding solutions are introduced into the acid chamber, water chamber, alkali chamber and electrode chamber and filled, a DC power supply is connected, and a set DC voltage is applied to both sides of the membrane assembly. The sodium ions and chloride ions in the high-concentration salt water enter the acid chamber and the alkali chamber through the ion selective membrane. When the voltage is applied, the bipolar membrane ionizes the water molecules into hydrogen ions and hydroxide ions, which enter the acid chamber and the alkali chamber respectively. The concentration of the outflowing salt water decreases, and the concentration of the hydrochloric acid and alkali solutions increases, and they flow back into the liquid storage tank to participate in the circulation; the electrode chamber is FeCl 2 and FeCl 3The mixed solution undergoes a reduction reaction at the cathode and an oxidation reaction at the anode. The electrode liquids at both ends circulate. After the charging process is completed, the variable resistor is connected to record the current meter and voltage display numbers. By changing the size of the external resistor, the maximum output power of the energy storage battery is calculated.

[0013] In a fourth aspect, the present invention provides a method for operating the above-mentioned flow battery, including a charging process: the electrode chamber is FeCl 2 and FeCl 3 The solution gains and loses electrons through the conversion between divalent iron and trivalent iron, and is transmitted through inert electrodes. Based on the principle of electrodialysis, a low-concentration acid solution is pre-flowed into the acid chamber, a low-concentration alkaline solution is pre-flowed into the alkaline chamber, and a high-concentration brine solution is flowed into the water chamber. Direct current is applied to both ends of the membrane assembly, and the bipolar membrane dissociates water, generating hydrogen ions and hydroxide ions on both sides of the cation selective membrane and the anion selective membrane, respectively. Chloride ions in the high-concentration salt water enter the acid chamber through the anion selective membrane, and cations enter the alkaline chamber through the cation selective membrane, thereby converting electrical energy into chemical energy of the acid and alkaline solutions and storing it. Discharge process: Based on the working principle of reverse electrodialysis, hydrogen ions and hydroxide ions undergo a neutralization reaction on the bipolar membrane. Under the action of concentration difference, chloride ions in the acid chamber enter the water chamber through the anion selective membrane, and sodium ions in the alkali chamber enter the water chamber through the cation selective membrane; a transmembrane voltage is formed, and the movement of ions on the inert electrodes at both ends is converted into the gain and loss of electrons, forming a current on the outside.

[0014] The present invention provides the application of the above-mentioned liquid flow battery as an energy storage battery of an energy storage power station.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention proposes a new type of liquid flow battery with salt water as electrolyte, combines the principles of electrodialysis and reverse electrodialysis, and uses commercial ion-selective membranes and bipolar membranes to construct energy storage batteries. Compared with traditional liquid flow batteries, the introduction of salt water greatly reduces the cost of liquid flow batteries and can achieve low-cost liquid flow battery expansion; it can be applied to energy storage and power generation in high-salinity and high-acid and high-base environments; the structure is simple, and the loading and unloading and cleaning of the membrane are convenient; the design of the feed inlet at the bottom and the discharge port at the top reduces concentration polarization; the environmental protection of the energy storage battery is improved, and a new solution is provided for green new long-term energy storage; the new type of liquid flow battery can convert the remaining wind and solar waste electricity from new energy power generation into acid-base chemical energy for storage, and release electrical energy through the acid-base neutralization reverse electrodialysis process to fill the peak electricity demand and achieve the effect of "peak shaving and valley filling". BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0017] Figure 1 It is a basic schematic diagram.

[0018] Figure 2 This is the schematic diagram of the multi-mode stack of liquid flow battery membrane components (Scheme 1).

[0019] Figure 3 This is the schematic diagram of a single membrane stack of a flow battery membrane assembly (Scheme 2).

[0020] Figure 4 It is a schematic diagram of the alkali chamber structure.

[0021] Figure 5 It is a schematic diagram of the acid chamber structure.

[0022] Figure 6 It is a schematic diagram of the water chamber structure.

[0023] Figure 7 It is a schematic diagram of the electrode chamber at the end of the membrane module.

[0024] Figure 8 Schematic diagram of the flow battery system. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention proposes a flow battery using salt water as electrolyte, combining the principles of electrodialysis and reverse electrodialysis, and using commercial ion selective membranes and bipolar membranes 23 to construct an energy storage battery. The present invention starts with electrodialysis desalination to produce acid and alkali, and acid and alkali neutralization and reverse electrodialysis power generation, finds the common points of battery components required for the two processes, and considers the characteristics of ion selective membranes to design and optimize the component structure and flow channel. During the charging process, salt water is ionized into acid and alkali; during the discharging process, the acid and alkali are neutralized, a transmembrane voltage is established, and power is output externally. Acid-base neutralization can reverse electrodialysis power generation by utilizing the concentration gradient of chloride ions between acid chamber 1 and salt chamber, the concentration gradient of sodium ions between alkali chamber 3 and salt chamber, and the acid-base gradient and hydrogen ion concentration gradient between acid chamber 1 and alkali chamber 3. This makes the theoretical voltage of acid-base neutralization reverse electrodialysis power generation much higher than the theoretical voltage between salt water and fresh water. Compared with the method of using concentration difference as energy storage battery, the desalination degree requirement during charging when acid and alkali are used as energy storage is lower, which is conducive to simplifying the electrodialysis device and is more suitable for industrial production and operation.

[0027] Example 1, the structure of the flow battery provided in this application is described as follows: the flow battery includes a membrane assembly, a feed pump, an acid storage tank, an alkali storage tank, a brine storage tank and an electrode liquid storage tank. The membrane assembly includes a plurality of membrane stacks, which are composed of an anion selective membrane 13, an alkali chamber 3, a bipolar membrane 23, an acid chamber 1, a cation selective membrane 33, and a water chamber 2, and are clamped by a holding device. The ends of the membrane assembly are electrode chambers 4, and ruthenium iridium titanium electrodes are arranged in the electrode chambers 4.

[0028] The working principle of the membrane assembly is as follows: (1) Charging process: a three-compartment reverse electrodialysis membrane stack configuration containing a bipolar membrane 23 is adopted, and the structure of "acid chamber 1 + alkali chamber 3 + water chamber 2" is composed of "anion selective membrane 13 + bipolar membrane 23 + cation selective membrane 33", and the electrode chamber 4 is FeCl 2 and FeCl 3solution, gaining and losing electrons through the conversion between ferrous and ferric iron, and transported through an inert ruthenium-iridium-titanium electrode. Using the principle of electrodialysis, an acid solution with a lower concentration is pre-introduced into the acid chamber 1, an alkaline solution with a lower concentration is pre-introduced into the alkaline chamber 3, and a sodium chloride solution with a higher concentration is introduced into the water chamber 2. Direct current is applied to both ends of the membrane assembly, and the bipolar membrane 23 can dissociate water, generating hydrogen ions and hydroxide ions on both sides of the cation selective membrane 33 and the anion selective membrane 13, respectively. Chloride ions in the high-concentration salt water enter the acid chamber 1 through the anion selective membrane 13, and sodium ions enter the alkaline chamber 3 through the cation selective membrane 33, that is, electrical energy is converted into chemical energy of the acid and alkaline solution and stored; (2) Discharge process: Using the working principle of reverse electrodialysis, hydrogen ions and hydroxide ions undergo a neutralization reaction on the bipolar membrane 23. Due to the concentration difference, chloride ions in the acid chamber 1 enter the water chamber 2 through the anion selective membrane 13, and sodium ions in the alkaline chamber 3 enter the water chamber 2 through the cation selective membrane 33; a transmembrane voltage is established, and the movement of ions on the ruthenium iridium titanium electrodes at both ends is converted into the gain and loss of electrons, forming a current externally.

[0029] In order to facilitate the understanding of this design, a more comprehensive and detailed description of the design is given below in conjunction with the drawings in the specification.

[0030] The basic working principle is as follows Figure 1 As shown, only a schematic diagram of the charge and discharge principle of a flow battery composed of a group of membrane stacks is shown. The electrodialysis flow battery for energy storage provided by the present invention comprises an electrode chamber 4 arranged at both ends, and a membrane stack composed of an alkali chamber 3, an acid chamber 1, and a water chamber 2. When the number of membrane stacks is one, such as Figure 3 As shown, the simplest electrodialysis flow battery assembly structure clamps four membranes, including an anion selective membrane 13, a cation selective membrane 33, a bipolar membrane 23 and an anion selective membrane 13. The device can be increased by increasing the number of membrane stacks, such as Figure 2 As shown, the battery capacity is expanded and the output voltage is increased.

[0031] The anion selective membrane 13, the bipolar membrane 23 and the cation selective membrane 33 are all commercially available mature products.

[0032] refer to Figure 3 The membrane assembly is fixed through the through holes at the four vertices, and the clamping device passes through the through holes and tightens and fixes. 2 +FeCl 3 The solution) is circulated and regenerated between the electrode chambers 4 at both ends. The feed liquid (alkali solution, acid solution, brine) enters the battery through the feed liquid inlet at one end, and when passing through the alkali chamber 3 / acid chamber 1 / water chamber 2, the alkali solution / acid solution / brine solution flows in and flows out from the upper outlet, and circulates again through the pump.

[0033] The specific structure of the alkali chamber 3 is referenced Figure 4Since a thinner two-dimensional material modified ion selective membrane needs to be clamped, grooves 12 are provided at the front and back for placing gaskets to press the ion selective membrane and play a sealing role. Alkali enters through the alkali liquid feed port 13 below, while acid and salt water will not enter, and there is only one alkali liquid discharge port 11 above. When the alkali liquid fills the alkali chamber 3, the excess alkali liquid can flow into the alkali liquid discharge port 11.

[0034] Specific structural reference of acid chamber 1 Figure 5 The acid enters through the acid feed port 22 below, while the alkali solution and the salt water do not enter, and there is only one acid discharge port 21 above. When the acid fills the acid chamber 1, the excess acid can flow into the acid discharge port 21.

[0035] Specific structural reference of water chamber 2 Figure 6 The salt water enters through the salt water feed port 32 at the bottom, while the alkaline solution and the acid solution will not enter, and there is only one salt water discharge port 31 at the top. When the salt water fills the water chamber 2, the excess salt water can flow into the salt water discharge port 31.

[0036] Membrane module end electrode chamber 4 structure reference Figure 7 The electrode liquid enters the electrode chamber 4 through the electrode liquid feed port 43, and the ruthenium iridium titanium electrode 42 provides a reaction site for the conversion of divalent iron and trivalent iron in the electrode liquid to gain and lose electrons, and transmits electrons. The excess electrode liquid enters the externally connected electrode liquid tank through the electrode liquid discharge port 41 and participates in the electrode liquid circulation at both ends.

[0037] Example 2, flow battery system The test of the membrane assembly is intended to test the performance of the liquid flow battery membrane assembly of this application to verify the rationality of the design, whether it can maintain stability under high salinity and high pH conditions, whether it can effectively increase the battery capacity by increasing the number of membrane stacks, whether it can meet the energy storage requirements and achieve higher energy efficiency and output power, and to overcome the concentration polarization phenomenon on the membrane surface, a larger feed rate is added and it is designed as a test system for feed-liquid circulation.

[0038] The schematic diagram of the flow battery system provided in this application is as follows Figure 8As shown, the charging capacity and power generation of a single membrane stack are tested first, and then the number of membrane stacks is increased, the output voltage and output current are recorded, and the optimal number of membrane stacks is calculated. Flow meters and thermometers are set at the feed inlet and outlet in the test device to ensure stable solution flow rate and solution temperature. The test system includes: DC power supply, variable resistor, ammeter, voltmeter, membrane assembly, four circulation pumps, eight flow meters and thermometers, brine storage tank, acid storage tank, alkali storage tank, electrode liquid storage tank and corresponding pipeline connection devices. The brine storage tank, the acid storage tank, the alkali storage tank, and the electrode liquid storage tank are connected to the flow battery through pipelines to form a brine circulation path, an acid circulation path, an alkali circulation path, and an electrode liquid circulation path, respectively. Circulation pumps are arranged on the brine circulation path, the acid circulation path, the alkali circulation path, and the electrode liquid circulation path. Flow meters and thermometers are arranged at the inlet and outlet of the flow battery in the brine circulation path, the acid circulation path, the alkali circulation path, and the electrode liquid circulation path, respectively. A voltmeter and a DC power supply are connected in parallel to the positive and negative electrodes of the flow battery. At the same time, an ammeter and a variable resistor are connected in series and then connected in parallel to the positive and negative electrodes of the flow battery. A double-throw switch controls whether the DC power supply and the variable resistor are connected to the flow battery; after the system test platform is built, the solution is first introduced to fill each compartment with the corresponding solution, and then the double-throw switch is turned to the DC power supply to apply a set DC voltage to both sides of the membrane assembly. The sodium ions and chloride ions in the high-concentration salt water enter the acid chamber 1 and the base chamber 3 through the ion selective membrane. When the voltage is applied, the bipolar membrane 23 ionizes the water molecules into hydrogen ions and hydroxide ions, which enter the acid chamber 1 and the base chamber 3 respectively, so that the concentration of the outflowing salt water is reduced, and the concentration of the hydrochloric acid and sodium hydroxide solutions is increased, and they flow back into the storage tank to participate in the cycle. The electrode chamber 4 contains FeCl 2 and FeCl 3 The mixed solution undergoes a reduction reaction at the cathode and an oxidation reaction at the anode, and the electrode liquid circulates at both ends. After the charging process is completed, the double-throw switch is turned to the variable resistor, and the current meter and voltage display values ​​are recorded. By changing the size of the external resistor, the maximum output power of the energy storage battery is calculated.

[0039] During the construction of the test system, since high-mass concentrations of brine, alkali and acid are all corrosive, there are certain requirements for the selection of pumps and pipelines, and the flow rate range of the pump should be large to ensure that the appropriate flow rate can be achieved when testing a single membrane stack or multiple membrane stacks.

[0040] Specific operation process (pre-test debugging stage) Charging process: ① Clean the flow battery, test pipeline and liquid storage tank with deionized water, install the ion selective membrane and bipolar membrane 23 in the flow battery in advance, and check the sealing of the flow battery.

[0041] ②Prepare NaCl solution of the required concentration for testing and test the conductivity. Place it in the brine tank. Prepare low-concentration NaOH solution and HCl solution of the required concentration for testing and place them in the alkali tank and acid tank respectively. Prepare FeCl 2 +FeCl 3 Solution, placed in the electrode solution tank.

[0042] ③ Start the circulation pump to pump the electrode solution, alkali solution, acid solution and brine into the flow battery and adjust the flow rate to a suitable level. When the flow battery is full of liquid and the inlet and outlet flow rates are stable, apply voltage to both ends of the flow battery to start electrolysis. After a period of time, record the conductivity of the brine in the brine tank.

[0043] ④After the test is completed, perform data processing.

[0044] Discharge process: ① Turn the switch from DC power supply to variable resistor.

[0045] ② Adjust the variable resistor to the maximum value and start the pump to pump the electrode liquid, alkali solution, acid solution and salt water into the flow battery, and adjust the flow rate to the appropriate rate. When the flow battery is full of liquid and the inlet and outlet flow rates are stable, start electrolysis and record the voltage of the voltmeter and the current of the ammeter. When testing the maximum output power, gradually reduce the resistance value, record the voltage of the voltmeter and the current of the ammeter, and Calculate the output power. When testing the battery capacity, fix the external resistance, record the voltage and current changes, and record the changes in the salt water conductivity.

[0046] ③After the test is completed, perform data processing.

[0047] In summary, the present invention provides an energy storage flow battery using the principle of electrodialysis / reverse electrodialysis and using a salt solution such as sodium chloride as an electrolyte. Using a salt solution represented by high-salinity sodium chloride as the electrolyte of the flow battery can greatly reduce the cost of the flow battery and achieve high returns. The flow battery couples the electrodialysis electrolysis process and the reverse electrodialysis power generation process: during the charging process, the salt water is ionized into acid and alkali; during the discharge process, the acid and alkali are neutralized, a transmembrane voltage is established, and power is output externally. The acid-base neutralization energy reverse electrodialysis power generation utilizes the concentration gradient of chloride ions between the acid chamber 1 and the salt chamber, the concentration gradient of sodium ions between the alkali chamber 3 and the salt chamber, and the acid-base gradient (i.e., the hydrogen ion concentration gradient) between the acid chamber 1 and the alkali chamber 3, which makes the theoretical voltage of the acid-base neutralization energy reverse electrodialysis power generation much higher than the theoretical voltage between the salt difference energy salt water and fresh water. Compared with the method of using concentration difference as an energy storage battery, the acid-base as energy storage has a lower requirement for the desalination degree during the charging process, which is conducive to simplifying the electrodialysis device and is more suitable for industrial production and operation.

[0048] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A liquid flow battery, characterized in that: The invention comprises electrode chambers (4) at both ends, at least one liquid flow battery module is arranged between the electrode chambers (4), and the liquid flow battery module comprises an anion selective membrane (13), an acid chamber (1), a bipolar membrane (23), a water chamber (2), a cation selective membrane (33), an alkali chamber (3), and an anion selective membrane (13) arranged in sequence; the acid chamber (1) is connected to an acid liquid storage tank, the alkali chamber (3) is connected to an alkali liquid storage tank, the water chamber (2) is connected to a salt water storage tank, and the electrode chamber (4) is connected to an electrode liquid storage tank; the battery is sealed as a whole, and an inert electrode is arranged in the electrode chamber (4).

2. The flow battery according to claim 1, characterized in that: The acid chamber (1), the water chamber (2), and the alkali chamber (3) are provided with grooves on both sides, and sealing rings are arranged in the grooves. The inner side surface of the electrode chamber (4) is provided with a groove, and a sealing ring is arranged in the groove. Through holes are evenly provided around the acid chamber (1), the water chamber (2), the alkali chamber (3), and the electrode chamber (4), and clamping devices are arranged in the through holes.

3. The flow battery according to claim 2, characterized in that: The clamping device adopts double-headed studs or single-headed studs and easily dismantled assemblies.

4. The flow battery according to claim 1, characterized in that: The acid chamber (1), the water chamber (2), the alkali chamber (3) and the electrode chamber (4) all use plates with a set thickness. The acid chamber (1), the water chamber (2), the alkali chamber (3) and the electrode chamber (4) are all provided with a liquid inlet and a liquid outlet, and the positions of the liquid inlet and the liquid outlet are as far as possible.

5. The flow battery according to claim 1, characterized in that: The electrode liquid in the electrode chamber (4) is a mixed solution of FeCl2 and FeCl3, and circulation pumps are provided at the inlets of the acid chamber (1), the water chamber (2), the alkali chamber (3) and the electrode chamber (4).

6. The flow battery according to claim 1, characterized in that: The brine storage tank contains sodium chloride solution, potassium chloride solution or lithium chloride solution, the alkali solution storage tank contains sodium hydroxide solution, potassium hydroxide or lithium hydroxide solution, and the acid solution storage tank contains hydrochloric acid.

7. The flow battery testing system according to any one of claims 1 to 6, characterized in that: It includes a liquid flow battery, a DC power supply, a variable resistor, an ammeter, a voltmeter, a flow meter and a thermometer; a brine storage tank, an acid storage tank, an alkali storage tank and an electrode liquid storage tank are connected to the liquid flow battery through pipelines to form a brine circulation path, an acid circulation path, an alkali circulation path and an electrode liquid circulation path respectively; circulation pumps are arranged on the brine circulation path, the acid circulation path, the alkali circulation path and the electrode liquid circulation path; flow meters and thermometers are arranged at the inlet and outlet of the liquid flow battery in the brine circulation path, the acid circulation path, the alkali circulation path and the electrode liquid circulation path respectively; the positive and negative poles of the liquid flow battery are connected in parallel with the voltmeter and the DC power supply; at the same time, the ammeter and the variable resistor are connected in series and then in parallel with the positive and negative poles of the liquid flow battery; a switch is arranged to control whether the DC power supply and the variable resistor are connected to the liquid flow battery.

8. A testing method based on the testing system according to claim 7, characterized in that: After the corresponding solutions are introduced into the acid chamber (1), the water chamber (2), the alkali chamber (3) and the electrode chamber (4) and filled, a DC power supply is connected and a set DC voltage is applied to both sides of the membrane assembly. The sodium ions and chloride ions in the high-concentration salt water enter the acid chamber (1) and the alkali chamber (3) through the ion selective membrane. When the voltage is applied, the bipolar membrane (23) ionizes the water molecules into hydrogen ions and hydroxide ions, which enter the acid chamber (1) and the alkali chamber (3) respectively. The concentration of the outflowing salt water decreases, and the concentration of the hydrochloric acid and alkali solutions increases, and they flow back into the storage tank to participate in the circulation. The electrode chamber (4) contains a mixed solution of FeCl2 and FeCl3. A reduction reaction occurs at the cathode and an oxidation reaction occurs at the anode. The electrode solutions at both ends circulate. After the charging process is completed, a variable resistor is connected to record the current meter and voltage display values. By changing the size of the external resistor, the maximum output power of the energy storage battery is calculated.

9. The method for operating a flow battery according to any one of claims 1 to 6, characterized in that: The charging process includes: the electrode chamber (4) contains FeCl2 and FeCl3 solutions, and electrons are gained and lost through the conversion between divalent iron and trivalent iron, and are transmitted through the inert electrode. Based on the principle of electrodialysis, an acid solution with a lower concentration is pre-flowed into the acid chamber (1), an alkali solution with a lower concentration is pre-flowed into the alkali chamber (3), and a salt solution with a higher concentration is flowed into the water chamber (2). Direct current is applied to both ends of the membrane assembly, and the bipolar membrane (23) dissociates water, generating hydrogen ions and hydroxide ions on both sides of the cation selective membrane (33) and the anion selective membrane (13), respectively. Chloride ions in the high-concentration salt water enter the acid chamber (1) through the anion selective membrane (13), and cations enter the alkali chamber (3) through the cation selective membrane (33), thereby converting electrical energy into chemical energy of the acid and alkali solutions and storing it. Discharge process: Based on the working principle of reverse electrodialysis, hydrogen ions and hydroxide ions undergo a neutralization reaction on the bipolar membrane (23). Under the action of the concentration difference, the chloride ions in the acid chamber (1) enter the water chamber (2) through the anion selective membrane (13), and the sodium ions in the alkali chamber (3) enter the water chamber (2) through the cation selective membrane (33); a transmembrane voltage is formed, and the movement of ions on the inert electrodes at both ends is converted into the gain and loss of electrons, forming an electric current on the outside.

10. The use of the flow battery according to any one of claims 1 to 5, characterized in that: As energy storage batteries in energy storage power stations.

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